@article{abdelkader_2018,
title = {Robust H ∞ gain neuro-adaptive observer design for nonlinear uncertain systems},
author = {Abdelkader, K.; Krais, B.},
journal = {Transactions of the Institute of Measurement and Control},
year = {2108},
institution = {Higher Institute of Computer Science of Mahdia, Tunisia},
abstract = {To guarantee convergent state estimates and exact approximations, it is highly desirable that observers can independently dominate the effects of unmodelled dynamics. Based on adaptive nonlinear approximation, this paper presents a robust H∞ gain neuro-adaptive observer (RH∞GNAO) design methodology for a large class of uncertain nonlinear systems in the presence of time-varying unknown parameters with bounded external disturbances on the state vector and on the output of the original system. The proposed RH∞GNAO incorporates radial basis function neural networks (RBFNNs) to approximate the unknown nonlinearities in the uncertain system. The weight dynamics of every RBFNN are adjusted online by using an adaptive projection algorithm. The asymptotic convergence of the state and parameter estimation errors is achieved by using Lyapunov cogitation under a well-defined persistent excitation condition, and without recourse to the strictly positive real condition. The repercussions of unknown disturbances are reduced by integrating an H∞ gain performance criterion into the proposed estimation approach. The condition imposed by this proposed observer approach, such that all estimated signals are uniformly ultimately bounded, is expressed in the form of the linear matrix inequality problem and warrants the demanded performances. To evaluate the performance of the proposed observer, various simulations are presented. },
keywords = {Uncertain nonlinear systems, Lyapunov stability, disturbances, neural networks, adaptive observer, H-infinity, linear matrix inequality},
language = {English},
publisher = {SAGE}
}

To guarantee convergent state estimates and exact approximations, it is highly desirable that observers can independently dominate the effects of unmodelled dynamics. Based on adaptive nonlinear approximation, this paper presents a robust H∞ gain neuro-adaptive observer (RH∞GNAO) design methodology for a large class of uncertain nonlinear systems in the presence of time-varying unknown parameters with bounded external disturbances on the state vector and on the output of the original system. The proposed RH∞GNAO incorporates radial basis function neural networks (RBFNNs) to approximate the unknown nonlinearities in the uncertain system. The weight dynamics of every RBFNN are adjusted online by using an adaptive projection algorithm. The asymptotic convergence of the state and parameter estimation errors is achieved by using Lyapunov cogitation under a well-defined persistent excitation condition, and without recourse to the strictly positive real condition. The repercussions of unknown disturbances are reduced by integrating an H∞ gain performance criterion into the proposed estimation approach. The condition imposed by this proposed observer approach, such that all estimated signals are uniformly ultimately bounded, is expressed in the form of the linear matrix inequality problem and warrants the demanded performances. To evaluate the performance of the proposed observer, various simulations are presented.

@article{wang_2019,
title = {A computationally efficient dynamical model of fluidic soft actuators and its experimental verification},
author = {Wang, T.; Zhang, Y.; Zhu, Y.; Zhu, S.},
journal = {Mechatronics},
year = {2019},
month = {04},
volume = {58},
institution = {Zhejiang University, China},
abstract = {This work develops a computationally efficient dynamical model for fluidic bending soft actuators in consideration of distributed-mass effect. The model in universal form is based on the Lagrangian approach and the constant curvature assumption. Since the model parameters are dependent on actuator type, a case study on the soft actuator with fiber-reinforced structure is carried out due to its convenience in manufacture and resistance to trivial deformation. The expressions of strain energy, gravitational potential energy, kinetic energy and generalized force are derived with respect to a generalized coordinate defined by the bending angle of the soft actuator. Material deformation and fluidic volume variation are also considered and derived in the model. Additionally, Taylor series expansions are employed to reduce the model complexity by neglecting the high-order terms reasonably. Finally, an experimental setup for the soft actuator is built and a curvature sensor is utilized to detect the bending angle. Experiments under typical operating conditions are implemented to verify the model and the results show that the measured data are in good accordance with the predicted responses. The proposed dynamical model can serve as a basis for further model-based control algorithm design for fluidic soft actuators. },
keywords = {Dynamical model Bending actuators Computationally efficient Fluidic power Soft robotics},
language = {English},
publisher = {Elsevier Ltd.}
}

This work develops a computationally efficient dynamical model for fluidic bending soft actuators in consideration of distributed-mass effect. The model in universal form is based on the Lagrangian approach and the constant curvature assumption. Since the model parameters are dependent on actuator type, a case study on the soft actuator with fiber-reinforced structure is carried out due to its convenience in manufacture and resistance to trivial deformation. The expressions of strain energy, gravitational potential energy, kinetic energy and generalized force are derived with respect to a generalized coordinate defined by the bending angle of the soft actuator. Material deformation and fluidic volume variation are also considered and derived in the model. Additionally, Taylor series expansions are employed to reduce the model complexity by neglecting the high-order terms reasonably. Finally, an experimental setup for the soft actuator is built and a curvature sensor is utilized to detect the bending angle. Experiments under typical operating conditions are implemented to verify the model and the results show that the measured data are in good accordance with the predicted responses. The proposed dynamical model can serve as a basis for further model-based control algorithm design for fluidic soft actuators.

@article{blondin_2019,
title = {A holistic optimization approach for inverted cart-pendulum control tuning},
author = {Blondin, M.J.; Pardalos, P.M.},
journal = {Soft Computing},
year = {2019},
institution = {University of Florida, USA},
abstract = {The inverted cart-pendulum (ICP) is a nonlinear underactuated system, which dynamics are representative of many applications. Therefore, the development of ICP control laws is important since these laws are suitable to other systems. Indeed, many nonlinear control strategies have emerged from the control of the ICP. For these reasons, the ICP remains a canonical and fundamental benchmark problem in control theory and robotics that is of interest to the scientific community. Till now, the trial-and-error method is still widely applied for ICP controller tuning as well as the sequential tuning referring to tune the swing-up controller and thereafter, the stabilization controller. Therefore, the aim of this paper is to automate and facilitate the ICP control in one step. Thus, this paper proposes to holistically optimize ICP controllers. The holistic optimization is performed by a simplified Ant Colony Optimization method with a constrained Nelder–Mead algorithm (ACO-NM). Holistic optimization refers to a simultaneous tuning of the swing-up, stabilization and switching mode parameters. A new cost function is designed to minimize swing-up time, achieve high stabilization performance and consider system constraints. The holistic approach optimizes four controller structures, which include controllers that have never been tuned by a specific method besides by the trial-and-error method. Simulation results on a ICP nonlinear model show that ACO-NM in the holistic approach is effective compared to other algorithms. In addition, contrary to the majority of work on the subject, all the optimized controllers are validated experimentally. The simulation and experimental results obtained confirm that the holistic approach is an efficient optimization tool and specifically responds to the need of optimization technique for the potential-well controller structure and for the Q [diagonal of the matrix and the full matrix] in the linear–quadratic regulator (LQR) technique. Moreover, ICP experimental response analysis demonstrates that using the full Q provides greater experimental stabilization performance than using its diagonal terms in the LQR technique. },
issn = {1432-7643},
keywords = {Inverted cart-pendulum system, Nonlinear control, Optimization, Holistic approach, Swing-up, Stabilization },
language = {English},
publisher = {Springer Berlin Heidelberg}
}

The inverted cart-pendulum (ICP) is a nonlinear underactuated system, which dynamics are representative of many applications. Therefore, the development of ICP control laws is important since these laws are suitable to other systems. Indeed, many nonlinear control strategies have emerged from the control of the ICP. For these reasons, the ICP remains a canonical and fundamental benchmark problem in control theory and robotics that is of interest to the scientific community. Till now, the trial-and-error method is still widely applied for ICP controller tuning as well as the sequential tuning referring to tune the swing-up controller and thereafter, the stabilization controller. Therefore, the aim of this paper is to automate and facilitate the ICP control in one step. Thus, this paper proposes to holistically optimize ICP controllers. The holistic optimization is performed by a simplified Ant Colony Optimization method with a constrained Nelder–Mead algorithm (ACO-NM). Holistic optimization refers to a simultaneous tuning of the swing-up, stabilization and switching mode parameters. A new cost function is designed to minimize swing-up time, achieve high stabilization performance and consider system constraints. The holistic approach optimizes four controller structures, which include controllers that have never been tuned by a specific method besides by the trial-and-error method. Simulation results on a ICP nonlinear model show that ACO-NM in the holistic approach is effective compared to other algorithms. In addition, contrary to the majority of work on the subject, all the optimized controllers are validated experimentally. The simulation and experimental results obtained confirm that the holistic approach is an efficient optimization tool and specifically responds to the need of optimization technique for the potential-well controller structure and for the Q [diagonal of the matrix and the full matrix] in the linear–quadratic regulator (LQR) technique. Moreover, ICP experimental response analysis demonstrates that using the full Q provides greater experimental stabilization performance than using its diagonal terms in the LQR technique.

@conference{sousa_2019,
title = {A Learning Controller Design Approach for a 3-DOF Helicopter System with Online Optimal Control},
author = {Sousa, G.B.; Lima, J.V.R.; Rego, P.H.M.; Souza, A.G.; Fonseca Neto, J.V.},
year = {2019},
institution = {State University of Maranhão, Brazil; Technological Institute of Aeronautics, Brazil; Federal University of Maranhão, Brazil},
abstract = {This paper presents the design and investigation of performance of a 3-DOF Quanser helicopter system using a learning optimal control approach that is grounded on approximate dynamic programming paradigms, specifically action-dependent heuristic dynamic programming (ADHDP). This approach results in an algorithm that is embedded in the actor-critic reinforcement learning architecture, that characterizes this design as a model-free structure. The developed methodology aims at implementing an optimal controller that acts in real-time in the plant control, using only the input and output signals and states measured along the system trajectories. The feedback control design technique is capable of an online tuning of the controller parameters according to the plant dynamics, which is subject to the model uncertainties and external disturbances. The experimental results demonstrate the desired performance of the proposed controller implemented on the 3-DOF Quanser helicopter. },
keywords = {Action-Dependent Heuristic Dynamic Programming, Actor-Critic Reinforcement Learning, Real-Time Control, 3-DOF Helicopter},
language = {English}
}

This paper presents the design and investigation of performance of a 3-DOF Quanser helicopter system using a learning optimal control approach that is grounded on approximate dynamic programming paradigms, specifically action-dependent heuristic dynamic programming (ADHDP). This approach results in an algorithm that is embedded in the actor-critic reinforcement learning architecture, that characterizes this design as a model-free structure. The developed methodology aims at implementing an optimal controller that acts in real-time in the plant control, using only the input and output signals and states measured along the system trajectories. The feedback control design technique is capable of an online tuning of the controller parameters according to the plant dynamics, which is subject to the model uncertainties and external disturbances. The experimental results demonstrate the desired performance of the proposed controller implemented on the 3-DOF Quanser helicopter.

@article{harmanci_2019,
title = {A Novel Approach for 3D-Structural Identification through Video Recording: Magnified Tracking},
author = {Harmanci, Y.E.; Gülan, U.; Holzner, M.; Chatzi, E. },
journal = {Sensors},
year = {2019},
volume = {19},
number = {5},
institution = {ETH Zürich, Switzerland},
abstract = {Advancements in optical imaging devices and computer vision algorithms allow the exploration of novel diagnostic techniques for use within engineering systems. A recent field of application lies in the adoption of such devices for non-contact vibrational response recordings of structures, allowing high spatial density measurements without the burden of heavy cabling associated with conventional technologies. This, however, is not a straightforward task due to the typically low-amplitude displacement response of structures under ambient operational conditions. A novel framework, namely Magnified Tracking (MT), is proposed herein to overcome this limitation through the synergistic use of two computer vision techniques. The recently proposed phase-based motion magnification (PBMM) framework, for amplifying motion in a video within a defined frequency band, is coupled with motion tracking by means of particle tracking velocimetry (PTV). An experimental campaign was conducted to validate a proof-of-concept, where the dynamic response of a shear frame was measured both by conventional sensors as well as a video camera setup, and cross-compared to prove the feasibility of the proposed non-contact approach. The methodology was explored both in 2D and 3D configurations, with PTV revealing a powerful tool for the measurement of perceptible motion. When MT is utilized for tracking “imperceptible” structural responses (i.e., below PTV sensitivity), via the use of PBMM around the resonant frequencies of the structure, the amplified motion reveals the operational deflection shapes, which are otherwise intractable. The modal results extracted from the magnified videos, using PTV, demonstrate MT to be a viable non-contact alternative for 3D modal identification with the benefit of a spatially dense measurement grid. },
keywords = {vibration-based measurement; SHM; structural identification; motion magnification; particle tracking velocimetry},
language = {English},
publisher = {MDPI}
}

Advancements in optical imaging devices and computer vision algorithms allow the exploration of novel diagnostic techniques for use within engineering systems. A recent field of application lies in the adoption of such devices for non-contact vibrational response recordings of structures, allowing high spatial density measurements without the burden of heavy cabling associated with conventional technologies. This, however, is not a straightforward task due to the typically low-amplitude displacement response of structures under ambient operational conditions. A novel framework, namely Magnified Tracking (MT), is proposed herein to overcome this limitation through the synergistic use of two computer vision techniques. The recently proposed phase-based motion magnification (PBMM) framework, for amplifying motion in a video within a defined frequency band, is coupled with motion tracking by means of particle tracking velocimetry (PTV). An experimental campaign was conducted to validate a proof-of-concept, where the dynamic response of a shear frame was measured both by conventional sensors as well as a video camera setup, and cross-compared to prove the feasibility of the proposed non-contact approach. The methodology was explored both in 2D and 3D configurations, with PTV revealing a powerful tool for the measurement of perceptible motion. When MT is utilized for tracking “imperceptible” structural responses (i.e., below PTV sensitivity), via the use of PBMM around the resonant frequencies of the structure, the amplified motion reveals the operational deflection shapes, which are otherwise intractable. The modal results extracted from the magnified videos, using PTV, demonstrate MT to be a viable non-contact alternative for 3D modal identification with the benefit of a spatially dense measurement grid.

@article{perez-alcocer_2019,
title = {A novel Lyapunov-based trajectory tracking controller for a quadrotor: Experimental analysis by using two motion tasks},
author = {Perez-Alcocer, R.; Moreno-Valenzula, J.},
journal = {Mechatronics},
year = {2019},
month = {08},
volume = {61},
institution = {Instituto Politécnico Nacional-CITEDI, Mexico},
abstract = {A novel model-based controller for quadrotor trajectory tracking is presented in this paper. The closed-loop stability is studied by Lyapunov’s theory guaranteeing local asymptotical stability of the resulting equilibrium point. The performance of the proposed scheme is compared in real time with respect to three known trajectory tracking controllers having different structures. Besides, two desired trajectories encoding different motion tasks are specified. The gains of the tested controllers are selected so that the mean value of the total thrust is the same. An analysis by using different performance indexes is employed in order assess the tracking performance of each scheme. The proposed controller presents the best experimental execution for the two implemented motion tasks. },
keywords = {Quadrotor, Trajectory tracking, Model-based controller, Lyapunov theory, Real–time experiments},
language = {English},
publisher = {Elsevier Ltd.}
}

A novel model-based controller for quadrotor trajectory tracking is presented in this paper. The closed-loop stability is studied by Lyapunov’s theory guaranteeing local asymptotical stability of the resulting equilibrium point. The performance of the proposed scheme is compared in real time with respect to three known trajectory tracking controllers having different structures. Besides, two desired trajectories encoding different motion tasks are specified. The gains of the tested controllers are selected so that the mean value of the total thrust is the same. An analysis by using different performance indexes is employed in order assess the tracking performance of each scheme. The proposed controller presents the best experimental execution for the two implemented motion tasks.

@article{huang_2019,
title = {A PSO-tuned Fuzzy Logic System for Position Tracking of Mobile Robot},
author = {Huang, C.; Farooq, U.; Liu, H.; Gu, J.; Luo, J.},
journal = {International Journal of Robotics and Automation},
year = {2019},
volume = {206},
abstract = {In this paper, we proposed a simple but practical fuzzy logic position tracking controller for a wheeled mobile robot. Certain mobile robot with symmetric or ignorable body shape may focus on its position precision on a path tracking task. In this case, we assigned its position errors as input of our fuzzy logic controller and its linear and angular velocities as outputs. Then, we optimized it by tuning the parameters of scaling and membership functions using a particle swarm optimization. Our fuzzy logic system was optimized and simulated in Matlab and Simulink and was experimentally tested on Quanser’s Qbot2 robot with Quarc control system. After optimization, the values of Fitness Function (cumulative position errors) have distinctly decreased from 35.9642 to 5.8246 in simulation and from 37.4041 to 7.3935 experimentally. These results had shown that the optimized system outperformed the same system without optimization. },
language = {English},
publisher = {Acta Press}
}

In this paper, we proposed a simple but practical fuzzy logic position tracking controller for a wheeled mobile robot. Certain mobile robot with symmetric or ignorable body shape may focus on its position precision on a path tracking task. In this case, we assigned its position errors as input of our fuzzy logic controller and its linear and angular velocities as outputs. Then, we optimized it by tuning the parameters of scaling and membership functions using a particle swarm optimization. Our fuzzy logic system was optimized and simulated in Matlab and Simulink and was experimentally tested on Quanser’s Qbot2 robot with Quarc control system. After optimization, the values of Fitness Function (cumulative position errors) have distinctly decreased from 35.9642 to 5.8246 in simulation and from 37.4041 to 7.3935 experimentally. These results had shown that the optimized system outperformed the same system without optimization.

@article{arabi_2019,
title = {A set-theoretic model reference adaptive control architecture with dead-zone effect},
author = {Arabi, E.; Yucelen, T.},
journal = {Control Engineering Practice},
year = {2019},
month = {08},
volume = {89},
institution = {University of Michigan, USA; University of South Florida, USA},
abstract = {A new set-theoretic model reference adaptive control architecture with dead-zone effect is presented. The key feature of our approach utilizes a new generalized restricted potential function, where it not only provides a user-defined uncertain dynamical system performance but also has the capability to stop the adaptation when system errors are small (i.e., inside dead-zone) — a practice adopted in adaptive control applications. The stability of the proposed technique is analyzed through showing the boundedness of an energy function in all possible variations and its experimental validation is also given through an aerospace testbed. },
keywords = {Uncertain dynamical systems, Set-theoretic model reference adaptive control, Dead-zone effect, User-defined worst-case performance guarantees, Stability analysis Experiments},
language = {English},
publisher = {Elsevier Ltd.},
pages = {12-29}
}

A new set-theoretic model reference adaptive control architecture with dead-zone effect is presented. The key feature of our approach utilizes a new generalized restricted potential function, where it not only provides a user-defined uncertain dynamical system performance but also has the capability to stop the adaptation when system errors are small (i.e., inside dead-zone) — a practice adopted in adaptive control applications. The stability of the proposed technique is analyzed through showing the boundedness of an energy function in all possible variations and its experimental validation is also given through an aerospace testbed.

@article{chan_2019,
title = {A smart mechatronic base isolation system using earthquake early warning},
author = {Chan, R.W.K.; Lin, Y.-S.; Tagawa, H.},
journal = {Soil Dynamics and Earthquake Engineering},
year = {2019},
month = {04},
volume = {119},
institution = {RMIT University, Australia; Hiroshima University, Japan},
abstract = {In earthquake-prone countries such as Japan, effects of earthquakes are one of the major design objectives in buildings and infrastructures. Recent advances in earthquake engineering have improved the safety and reliability of buildings and infrastructures. Better understanding of geomorphology of earthquakes also enables us to better predict and estimate propagation of such natural hazard. For example, the Earthquake Early Warning (EEW) system in Japan provides advanced warnings using the different arrival times of P and S waves. On the other hand, techniques and methods in passive, semi-active and active vibration control have flourished. Base-isolation is a proven technique which enhances earthquake resilience of buildings and bridges. In general, this technique involves decoupling a superstructure from its foundation and lengthens its natural period of vibration. This technique is mature and commercialization has taken place worldwide. However, wind-resistance of base-isolated structures is generally a concern as the lateral stiffness of a base-isolated structure is low and serviceability wind effects may induce unacceptable lateral movement and/or vibration of the structure. This paper presents a new concept which the base-isolation system is activated by EEW system through a mechatronic system. In other times the structure is not base-isolated and provides strong lateral resistance against wind loads. As a backup design, the proposed system also equips with its own network of accelerometers which can trigger base isolation system independent from EEW system. The smart mechatronic base isolation system is fully automated, and resets itself after each ground motion. The paper describes the conceptual framework of proposed system and presents laboratory-scaled proof-of-concept experiments. Four historical earthquake time histories were used as ground excitations. Structural responses are compared between the two triggering mechanisms and results are discussed. Finally, the concept of Internet of Things (IoT) which make use of EEW is discussed, allowing connectivity between a single control unit and a network of infrastructures to achieve economy of scale. },
keywords = {Smart structures, Base isolation, Earthquake early warning, Internet of things},
language = {English},
publisher = {Elsevier Ltd.},
pages = {299-307}
}

In earthquake-prone countries such as Japan, effects of earthquakes are one of the major design objectives in buildings and infrastructures. Recent advances in earthquake engineering have improved the safety and reliability of buildings and infrastructures. Better understanding of geomorphology of earthquakes also enables us to better predict and estimate propagation of such natural hazard. For example, the Earthquake Early Warning (EEW) system in Japan provides advanced warnings using the different arrival times of P and S waves. On the other hand, techniques and methods in passive, semi-active and active vibration control have flourished. Base-isolation is a proven technique which enhances earthquake resilience of buildings and bridges. In general, this technique involves decoupling a superstructure from its foundation and lengthens its natural period of vibration. This technique is mature and commercialization has taken place worldwide. However, wind-resistance of base-isolated structures is generally a concern as the lateral stiffness of a base-isolated structure is low and serviceability wind effects may induce unacceptable lateral movement and/or vibration of the structure. This paper presents a new concept which the base-isolation system is activated by EEW system through a mechatronic system. In other times the structure is not base-isolated and provides strong lateral resistance against wind loads. As a backup design, the proposed system also equips with its own network of accelerometers which can trigger base isolation system independent from EEW system. The smart mechatronic base isolation system is fully automated, and resets itself after each ground motion. The paper describes the conceptual framework of proposed system and presents laboratory-scaled proof-of-concept experiments. Four historical earthquake time histories were used as ground excitations. Structural responses are compared between the two triggering mechanisms and results are discussed. Finally, the concept of Internet of Things (IoT) which make use of EEW is discussed, allowing connectivity between a single control unit and a network of infrastructures to achieve economy of scale.

@article{jeon_2019,
title = {A Stealthy Sensor Attack for Uncertain Cyber-Physical Systems},
author = {Jeon, H.; Eu, Y.},
journal = {Internet of Things Journal},
year = {2019},
institution = {DGIST, South Korea},
abstract = { In this paper, we present a sensor attack on Cyber-Physical Systems (CPS), which can be constructed with limited knowledge of the target system and can remain stealthy until the attack succeeds. The target CPS consists of a physical plant with unstable linear dynamics and a feedback controller. Specifically, the attack mechanism is to impede the stabilizing function of the feedback controller by injecting false data to the sensors where the false data are created using the unstable dynamics of the plant. When the only nominal model for the target dynamics is known, the stealthiness is maintained by deploying a mechanism similar to a disturbance observer which can be designed to absorb the effect of the mismatch between the nominal and actual dynamics until the attack succeeds. The success of the attack is defined by the norm of the system state exceeding a threshold. Sensor attacks that exploit unstable plant dynamics had been conceived previously. Generation of such attacks require precise knowledge of the target system for stealthiness, i.e., the attack must cancel at the sensor exactly the effect of instability in order to avoid detection. When not exact, the mismatch grows exponentially leading to the detection of abnormality. The attack presented in this work absorbs the mismatch using the disturbance observer mechanism, where the degree of absorption is selected such that the detection is delayed until the attack succeeds. Thus, the proposed attack, compared to the conventional ones, poses a greater level of threat to CPS. In this work, generation of the attack is presented, and the effect is analyzed. The consequence of the attack is illustrated and emphasized by simulations on quadrotors and inverted pendulums, respectively. },
issn = {2327-4662 },
keywords = {Cyber-physical systems, stealthy sensor attack, Model uncertainty},
language = {English},
publisher = {IEEE}
}

In this paper, we present a sensor attack on Cyber-Physical Systems (CPS), which can be constructed with limited knowledge of the target system and can remain stealthy until the attack succeeds. The target CPS consists of a physical plant with unstable linear dynamics and a feedback controller. Specifically, the attack mechanism is to impede the stabilizing function of the feedback controller by injecting false data to the sensors where the false data are created using the unstable dynamics of the plant. When the only nominal model for the target dynamics is known, the stealthiness is maintained by deploying a mechanism similar to a disturbance observer which can be designed to absorb the effect of the mismatch between the nominal and actual dynamics until the attack succeeds. The success of the attack is defined by the norm of the system state exceeding a threshold. Sensor attacks that exploit unstable plant dynamics had been conceived previously. Generation of such attacks require precise knowledge of the target system for stealthiness, i.e., the attack must cancel at the sensor exactly the effect of instability in order to avoid detection. When not exact, the mismatch grows exponentially leading to the detection of abnormality. The attack presented in this work absorbs the mismatch using the disturbance observer mechanism, where the degree of absorption is selected such that the detection is delayed until the attack succeeds. Thus, the proposed attack, compared to the conventional ones, poses a greater level of threat to CPS. In this work, generation of the attack is presented, and the effect is analyzed. The consequence of the attack is illustrated and emphasized by simulations on quadrotors and inverted pendulums, respectively.

@article{cajo_2019,
title = {A Survey on Fractional Order Control Techniques for Unmanned Aerial and Ground Vehicles},
author = {Cajo, R.; Mac, T.T.; Plaza, D.; Copot, C.; De Keyser, R.; Ionescu, C.},
journal = {IEEE Access},
year = {2019},
volume = {7},
institution = {Ghent University, Belgium; Hanoi University of Science and Technology, Vietnam; Escuela Superior Politécnica del Litoral, Ecuador; University of Antwerp, Belgium},
abstract = {In recent years, numerous applications of science and engineering for modeling and control of unmanned aerial vehicles (UAVs) and unmanned ground vehicles (UGVs) systems based on fractional calculus have been realized. The extra fractional order derivative terms allow to optimizing the performance of the systems. The review presented in this paper focuses on the control problems of the UAVs and UGVs that have been addressed by the fractional order techniques over the last decade. },
issn = {2169-3536},
keywords = {Fractional calculus, fractional order control techniques, unmanned aerial vehicles (UAVs), unmanned ground vehicles (UGVs)},
language = {English},
publisher = {IEEE},
pages = { 66864 - 66878}
}

In recent years, numerous applications of science and engineering for modeling and control of unmanned aerial vehicles (UAVs) and unmanned ground vehicles (UGVs) systems based on fractional calculus have been realized. The extra fractional order derivative terms allow to optimizing the performance of the systems. The review presented in this paper focuses on the control problems of the UAVs and UGVs that have been addressed by the fractional order techniques over the last decade.

@conference{al-younes_2019,
title = {Actuator Fault-Diagnosis and Fault-Tolerant-Control using intelligent-Output-Estimator Applied on Quadrotor UAV},
author = {Al Younes, Y.; Noura, H.; Rabhi, A.; El Hajjaji, A.},
booktitle = {2019 International Conference on Unmanned Aircraft Systems (ICUAS)},
year = {2019},
institution = {Higher Colleges of Technology, UAE; Islamic University of Lebanon, Lebanon; University of Picardie, France},
abstract = {Actuator fault is a prominent system’s issue that attracts the researchers’ attentions. One type of actuator fault is a constant Loss-of-Effectiveness (LoE). In this paper, two systematic algorithms are presented. The first algorithm is designed to detect and diagnosis the actuator fault. This Fault-Detection-and-Diagnosis (FDD) approach relies on an estimator design that is called intelligent Output-Estimator (iOE). The proposed iOE is intended to improve the estimation of the actuator fault based on the Model-Free technique. The second algorithm works online after detecting, isolating and estimating the actuator fault. This Active-Fault-Tolerant-Control (AFTC) algorithm will use the estimated actuator value in a reconfigured control design to compensate for the fault. Real-time flight tests are applied on the Qball-X4 quadrotor. Different LoE actuator-fault scenarios are presented in this paper to validate the proposed algorithms. },
language = {English},
publisher = {IEEE},
pages = {405-412}
}

Actuator fault is a prominent system’s issue that attracts the researchers’ attentions. One type of actuator fault is a constant Loss-of-Effectiveness (LoE). In this paper, two systematic algorithms are presented. The first algorithm is designed to detect and diagnosis the actuator fault. This Fault-Detection-and-Diagnosis (FDD) approach relies on an estimator design that is called intelligent Output-Estimator (iOE). The proposed iOE is intended to improve the estimation of the actuator fault based on the Model-Free technique. The second algorithm works online after detecting, isolating and estimating the actuator fault. This Active-Fault-Tolerant-Control (AFTC) algorithm will use the estimated actuator value in a reconfigured control design to compensate for the fault. Real-time flight tests are applied on the Qball-X4 quadrotor. Different LoE actuator-fault scenarios are presented in this paper to validate the proposed algorithms.

@article{ouyang_2019,
title = {Adaptive control based on neural networks for an uncertain 2-DOF helicopter system with input deadzone and output constraints},
author = {Ouyang, Y.; Dong, L.; Xue, L.; Sun, C.},
journal = {IEEE/CAA Journal of Automatica Sinica},
year = {2019},
month = {05},
volume = {6},
number = {3},
institution = {Southeast University, Nanjing, China},
abstract = {In this paper, a study of control for an uncertain 2-degree of freedom ( DOF ) helicopter system is given. The 2-DOF helicopter is subject to input deadzone and output constraints. In order to cope with system uncertainties and input deadzone, the neural network technique is introduced because of its capability in approximation. In order to update the weights of the neural network, an adaptive control method is utilized to improve the system adaptability. Furthermore, the integral barrier Lyapunov function ( IBLF ) is adopt in control design to guarantee the condition of output constraints and boundedness of the corresponding tracking errors. The Lyapunov direct method is applied in the control design to analyze system stability and convergence. Finally, numerical simulations are conducted to prove the feasibility and effectiveness of the proposed control based on the model of Quanser ʼ s 2-DOF helicopter. },
issn = {2329-9266 },
keywords = {2-degree of freedom (DOF) helicopter, adaptive control, input deadzone, integral barrier Lyapunov function, neural networks, output constraints},
language = {English},
publisher = {IEEE},
pages = {807-815}
}

In this paper, a study of control for an uncertain 2-degree of freedom ( DOF ) helicopter system is given. The 2-DOF helicopter is subject to input deadzone and output constraints. In order to cope with system uncertainties and input deadzone, the neural network technique is introduced because of its capability in approximation. In order to update the weights of the neural network, an adaptive control method is utilized to improve the system adaptability. Furthermore, the integral barrier Lyapunov function ( IBLF ) is adopt in control design to guarantee the condition of output constraints and boundedness of the corresponding tracking errors. The Lyapunov direct method is applied in the control design to analyze system stability and convergence. Finally, numerical simulations are conducted to prove the feasibility and effectiveness of the proposed control based on the model of Quanser ʼ s 2-DOF helicopter.

@article{perez-alcocer_2019,
title = {Adaptive Control for Quadrotor Trajectory Tracking With Accurate Parametrization},
author = {Pérez-Alcocer, R.; Moreno-Valenzuela, J.},
journal = {IEEE Access},
year = {2019},
volume = {7},
institution = {Instituto Politécnico Nacional–CITEDI, Mexico},
abstract = {In this paper, a novel adaptive controller for quadrotor position and orientation trajectory tracking is introduced. By taking into account the coupling between the position and the orientation dynamics, an adaptive scheme based on an accurate parameterization of the model-based feedforward compensation is presented. The adaptation update laws for the adaptation parameters are designed on Lyapunov’s theory so that the stability of the state space origin of the error dynamics is guaranteed. Barbalat’s lemma ensures convergence of the tracking errors and bounding of the adaptation parameters. The extensive real-time experimental results show the practical viability of the proposed scheme. More specifically, the performance of the proposed controller is compared with an adaptive controller taken from the literature and the non-adaptive version of the proposed controller. Better results are obtained with the novel adaptive approach. },
issn = {2169-3536 },
keywords = {Adaptive control, Lyapunov-theory, quadrotor, accurate parameterization},
language = {English},
publisher = {IEEE}
}

In this paper, a novel adaptive controller for quadrotor position and orientation trajectory tracking is introduced. By taking into account the coupling between the position and the orientation dynamics, an adaptive scheme based on an accurate parameterization of the model-based feedforward compensation is presented. The adaptation update laws for the adaptation parameters are designed on Lyapunov’s theory so that the stability of the state space origin of the error dynamics is guaranteed. Barbalat’s lemma ensures convergence of the tracking errors and bounding of the adaptation parameters. The extensive real-time experimental results show the practical viability of the proposed scheme. More specifically, the performance of the proposed controller is compared with an adaptive controller taken from the literature and the non-adaptive version of the proposed controller. Better results are obtained with the novel adaptive approach.

@article{chairez_2019,
title = {Adaptive control schemes applied to a control moment gyroscope of 2 degrees of freedom},
author = {Montoya–Cháirez, J.; Santibáñez, V.; Moreno–Valenzuela, J.},
journal = {Mechatronics},
year = {2019},
month = {02},
volume = {57},
institution = {Instituto Politécnico Nacional–CITEDI, Mexico; Instituto Tecnológico de La Laguna, Mexico},
abstract = {Control of underactuated mechanical systems has been an important trend in mechatronics and nonlinear systems. Typical examples are the Furuta pendulum and inertia wheel pendulum. On the other hand, gyroscopes are important in aerial and space systems. In this paper, a two-degree of freedom underactuated control moment gyroscope (CMG) is studied. This system is highly coupled of one joint to the another and is difficult to control, which make it an important benchmark system. The problem addressed in this paper is to achieve robust motion control of the underactuated CMG. Firstly, a trajectory tracking controller is developed by using the feedback linearization technique. Secondly, two new adaptive algorithms are introduced, which correspond to an adaptive neural network algorithm and an adaptive model regressor scheme. A real–time experimental comparison is carried out among a linear PD control law, a cascade PID-PID controller and the introduced schemes. The real-time experimental study validates the introduced theory, where the performance of the controllers is evaluated with and without a periodic disturbance at the input. },
keywords = {Control moment gyroscope, Underactuated systems, Trajectory tracking control, Adaptive control, Real–time experiments},
language = {English},
publisher = {Elsevier Ltd.},
pages = {73-85}
}

Control of underactuated mechanical systems has been an important trend in mechatronics and nonlinear systems. Typical examples are the Furuta pendulum and inertia wheel pendulum. On the other hand, gyroscopes are important in aerial and space systems. In this paper, a two-degree of freedom underactuated control moment gyroscope (CMG) is studied. This system is highly coupled of one joint to the another and is difficult to control, which make it an important benchmark system. The problem addressed in this paper is to achieve robust motion control of the underactuated CMG. Firstly, a trajectory tracking controller is developed by using the feedback linearization technique. Secondly, two new adaptive algorithms are introduced, which correspond to an adaptive neural network algorithm and an adaptive model regressor scheme. A real–time experimental comparison is carried out among a linear PD control law, a cascade PID-PID controller and the introduced schemes. The real-time experimental study validates the introduced theory, where the performance of the controllers is evaluated with and without a periodic disturbance at the input.

@article{niu_2018,
title = {Adaptive vibration suppression of time-varying structures with enhanced FxLMS algorithm},
author = {Niu, W.; Zou, C.; Li, B.; Wanga, W.},
journal = {Mechanical Systems and Signal Processing},
year = {2019},
month = {03},
volume = {118},
institution = {Northwestern Polytechnical University, China; Ohio State University, USA},
abstract = {Filtered-x least mean square (FxLMS) control algorithm has been widely used for adaptive noise and vibration control. Yet, classical FxLMS controller is not applicable for time-varying system since the secondary path identified offline cannot reflect the system characteristics in real-time. In order to overcome this challenge, here online modelling of secondary path is realized by existing signals, i.e. no noise injection. In addition, FxLMS is further enhanced with variable step size that is adaptively adjusted via bang-bang controller. The adaptation of step size is aimed to achieve the balance between control efficiency and system stability. To verify the feasibility of proposed control algorithm, numerical and experimental efforts are undertaken for the buffeting suppression of vertical tail which is a typical time-varying system. Both results demonstrate that the proposed method is able to reduce the vibration response effectively for varied structures under harmonic and random excitations, while the classical FxLMS cannot. This performance improvement indicates that the online modeling of secondary path captures the system characteristics accurately and timely. Moreover, compared with the FxLMS controller with fixed step size, the control efficiency of the proposed method is also strengthened. These multiple enhancements of the performance of FxLMS controller reveal that online modeling and variable step size are favorable for adaptive vibration control of time-varying structures. },
keywords = {Filtered-x least mean square, Bang-bang control, Variable step size, Online identification, Time-varying structures},
language = {English},
publisher = {Elsevier Ltd.}
}

Filtered-x least mean square (FxLMS) control algorithm has been widely used for adaptive noise and vibration control. Yet, classical FxLMS controller is not applicable for time-varying system since the secondary path identified offline cannot reflect the system characteristics in real-time. In order to overcome this challenge, here online modelling of secondary path is realized by existing signals, i.e. no noise injection. In addition, FxLMS is further enhanced with variable step size that is adaptively adjusted via bang-bang controller. The adaptation of step size is aimed to achieve the balance between control efficiency and system stability. To verify the feasibility of proposed control algorithm, numerical and experimental efforts are undertaken for the buffeting suppression of vertical tail which is a typical time-varying system. Both results demonstrate that the proposed method is able to reduce the vibration response effectively for varied structures under harmonic and random excitations, while the classical FxLMS cannot. This performance improvement indicates that the online modeling of secondary path captures the system characteristics accurately and timely. Moreover, compared with the FxLMS controller with fixed step size, the control efficiency of the proposed method is also strengthened. These multiple enhancements of the performance of FxLMS controller reveal that online modeling and variable step size are favorable for adaptive vibration control of time-varying structures.

@inproceedings{kasimzade_2019,
title = {Analytical and Experimental Modal Analysis of a Model Cold Formed Steel (CFS) Structures Using Microtremor Excitation},
author = {Kasimzade A.A.; Tuhta S.; Atmaca G.; Ozdemir S.},
booktitle = {Seismic Isolation, Structural Health Monitoring, and Performance Based Seismic Design in Earthquake Engineering},
year = {2019},
institution = {Ondokuz Mayis University, Turkey},
abstract = {In this study was investigated the possibility of using the recorded micro-tremor data on ground level as ambient vibration input excitation data for investigation and application Operational Modal Analysis (OMA) on the bench-scale earthquake simulator (The Quanser Shake Table) for model cold formed steel (cfs) structures. As known OMA methods (such as EFDD, SSI and so on) are supposed to deal with the ambient responses. For this purpose, analytical and experimental modal analysis of a model (cfs) structure for dynamic characteristics was evaluated. 3D Finite element model of the building was evaluated for the model (cfs) structure based on the design drawing. Ambient excitation was provided by shake table from the recorded micro tremor ambient vibration data on ground level. Enhanced Frequency Domain Decomposition is used for the output-only modal identification. From this study, best correlation is found between mode shapes. Natural frequencies and analytical frequencies in average (only) 2.99% are differences. },
keywords = {Experimental modal analysis, Modal parameter, EFDD, Shake table },
language = {English},
publisher = {Springer, Cham},
isbn = {978-3-319-93156-2},
pages = {217-231}
}

In this study was investigated the possibility of using the recorded micro-tremor data on ground level as ambient vibration input excitation data for investigation and application Operational Modal Analysis (OMA) on the bench-scale earthquake simulator (The Quanser Shake Table) for model cold formed steel (cfs) structures. As known OMA methods (such as EFDD, SSI and so on) are supposed to deal with the ambient responses. For this purpose, analytical and experimental modal analysis of a model (cfs) structure for dynamic characteristics was evaluated. 3D Finite element model of the building was evaluated for the model (cfs) structure based on the design drawing. Ambient excitation was provided by shake table from the recorded micro tremor ambient vibration data on ground level. Enhanced Frequency Domain Decomposition is used for the output-only modal identification. From this study, best correlation is found between mode shapes. Natural frequencies and analytical frequencies in average (only) 2.99% are differences.

@conference{yildrim_2019,
title = {Application of a Distributed Adaptive Control Approach to a Heterogeneous Multiagent Mechanical Platform},
author = {Yildirim, E.; Sarsilmaz, S.B.; Yucelen, T.},
booktitle = {AIAA Scitech 2019 Forum},
year = {2019},
institution = {University of South Florida, FL, USA},
abstract = {A distributed adaptive control architecture is recently developed for a class of heterogeneous uncertain multiagent systems [1]. This architecture has the capability to provide uniform ultimate boundedness for the output tracking error between each heterogeneous uncertain agent and the leader with unknown dynamics. As a special case, in addition, it allows the output of agents to asymptotically converge to the output of the leader, which converges to a constant, in the presence of matched disturbances and time-invariant system uncertainties over fixed and directed communication graph topologies. The main contribution of this paper is to provide an experimental study on a heterogeneous multiagent mechanical platform composed of two cart-inverted pendulums and a cart to demonstrate the performance of this architecture in practice. },
language = {English},
publisher = {AIAA}
}

A distributed adaptive control architecture is recently developed for a class of heterogeneous uncertain multiagent systems [1]. This architecture has the capability to provide uniform ultimate boundedness for the output tracking error between each heterogeneous uncertain agent and the leader with unknown dynamics. As a special case, in addition, it allows the output of agents to asymptotically converge to the output of the leader, which converges to a constant, in the presence of matched disturbances and time-invariant system uncertainties over fixed and directed communication graph topologies. The main contribution of this paper is to provide an experimental study on a heterogeneous multiagent mechanical platform composed of two cart-inverted pendulums and a cart to demonstrate the performance of this architecture in practice.

@article{torabi_2019,
title = {Application of a Redundant Haptic Interface in Enhancing Soft-Tissue Stiffness Discrimination},
author = {Torabi, A.; Khadem, M.; Zareinia, K.; Sutherland, G.R.; Tavakoli, M.},
journal = {IEEE Robotics and Automation Letters},
year = {2019},
month = {04},
volume = {4},
number = {2},
institution = {University of Alberta, Canada; University of Edinburgh, U.K.; Ryerson University, Canada; University of Calgary, Canada},
abstract = {Haptic-enabled teleoperated surgical systems have the potential to enhance the accuracy and performance of surgical interventions. The user interface of such a system can provide haptic feedback to the surgeon to more intuitively perform surgical tasks. In this letter, we study the added benefits of redundant manipulators as haptic interfaces for teleoperated surgical systems. First, we introduce the intrinsic benefits of employing a redundant haptic interface, namely, reduced apparent inertia and increased manipulability (one result of which is reduced friction forces). Next, we demonstrate that the haptic interface redundancy can further reduce its apparent inertia and friction via appropriately manipulating the extra degrees of freedom of the interface. This will consequently enhance the haptic feedback resolution (sensitivity) for the user. Finally, a psychophysical experiment is performed to validate the improved force perception for the user in a virtual soft-tissue palpation task. We conduct a set of perceptual experiments to evaluate how a redundant and non-redundant user interface affects the perception of the virtual stiffness. Experimental results demonstrate that the redundancy in the haptic user interface helps to enhance tissue stiffness discrimination ability of the user by reducing the distortions caused by the kinematics and dynamics of the user interface. },
issn = {2377-3766 },
keywords = {Haptics and haptic interfaces, telerobotics and teleoperation, medical robots and systems},
language = {English},
publisher = {IEEE},
pages = {1037 - 1044}
}

Haptic-enabled teleoperated surgical systems have the potential to enhance the accuracy and performance of surgical interventions. The user interface of such a system can provide haptic feedback to the surgeon to more intuitively perform surgical tasks. In this letter, we study the added benefits of redundant manipulators as haptic interfaces for teleoperated surgical systems. First, we introduce the intrinsic benefits of employing a redundant haptic interface, namely, reduced apparent inertia and increased manipulability (one result of which is reduced friction forces). Next, we demonstrate that the haptic interface redundancy can further reduce its apparent inertia and friction via appropriately manipulating the extra degrees of freedom of the interface. This will consequently enhance the haptic feedback resolution (sensitivity) for the user. Finally, a psychophysical experiment is performed to validate the improved force perception for the user in a virtual soft-tissue palpation task. We conduct a set of perceptual experiments to evaluate how a redundant and non-redundant user interface affects the perception of the virtual stiffness. Experimental results demonstrate that the redundancy in the haptic user interface helps to enhance tissue stiffness discrimination ability of the user by reducing the distortions caused by the kinematics and dynamics of the user interface.

@article{maraoui_2019,
title = {ARX model decomposed on Meixner-Like orthonormal bases},
author = {Maraoui, s.; Bouzrara, K.},
journal = {ISA Transactions},
year = {2019},
institution = {University of Monastir, Tunisia},
abstract = {The present study provides a new modeling of linear slowly starting systems. More precisely, this new approach extends the technique of filtering only the input using Meixner-Like (M-L) filters to filter both the output and input of the system outlined by an ARX model. Therefore, the idea is to develop the input and output parameters of ARX modeling over 2 M-L bases. So as to ensure an optimal representation, the two M-L poles are optimized using Newton–Raphson (N-R) and Genetic Algorithms (GA) methods. A new method is proposed for Model Predictive Control (MPC) using the obtained optimal model that is called ARX Meixner-Like (ARXM-L). A numerical example of system having delay and three examples of experimental research: A supersonic jet engine inlet, a Process Trainer PT326 and a Quanser aero experiment with one degree of freedom attitude control are made. },
keywords = {ARX model, Meixner-like basis, Poles optimization, Newton–Raphson method, Genetic algorithms, MPC control},
language = {English},
publisher = {Elsevier Ltd.}
}

The present study provides a new modeling of linear slowly starting systems. More precisely, this new approach extends the technique of filtering only the input using Meixner-Like (M-L) filters to filter both the output and input of the system outlined by an ARX model. Therefore, the idea is to develop the input and output parameters of ARX modeling over 2 M-L bases. So as to ensure an optimal representation, the two M-L poles are optimized using Newton–Raphson (N-R) and Genetic Algorithms (GA) methods. A new method is proposed for Model Predictive Control (MPC) using the obtained optimal model that is called ARX Meixner-Like (ARXM-L). A numerical example of system having delay and three examples of experimental research: A supersonic jet engine inlet, a Process Trainer PT326 and a Quanser aero experiment with one degree of freedom attitude control are made.

@article{yang_2019,
title = {Attitude Synchronization for Multiple 3-DOF Helicopters with Actuator Faults},
author = {Yang, H.; Jiang, B.; Liu, H.H.T.; Yang, H.; Zhang, Q.},
journal = {IEEE/ASME Transactions on Mechatronics},
year = {2019},
institution = {Nanjing University of Aeronautics and Astronautics, China; Institute for Aerospace Studies, University of Toronto, Canada},
abstract = {The attitude synchronization for multiple three-degree-of-freedom (3-DOF) helicopters in the presence of system uncertainties and time-varying actuator faults is investigated. A fault tolerant cooperative control algorithm based on robust adaptive control is proposed to synchronize attitudes of multiple helicopter systems in the case where some of the helicopters are subjected to both partial losses of control effectiveness and additive actuator faults. The proposed design is a distributed control method which allows each vehicle to track external reference signals merely in light of its neighborhood information. With the proposed design, time-varying actuator faults are tolerated without sacrificing the attitude synchronization performance. The effectiveness of the proposed control method is verified via a comparative experimental study. },
issn = {1083-4435},
keywords = {Fault tolerant control, cooperative control, three degree-of-freedom helicopter, adaptive control, robust control},
language = {English},
publisher = {IEEE}
}

The attitude synchronization for multiple three-degree-of-freedom (3-DOF) helicopters in the presence of system uncertainties and time-varying actuator faults is investigated. A fault tolerant cooperative control algorithm based on robust adaptive control is proposed to synchronize attitudes of multiple helicopter systems in the case where some of the helicopters are subjected to both partial losses of control effectiveness and additive actuator faults. The proposed design is a distributed control method which allows each vehicle to track external reference signals merely in light of its neighborhood information. With the proposed design, time-varying actuator faults are tolerated without sacrificing the attitude synchronization performance. The effectiveness of the proposed control method is verified via a comparative experimental study.

@conference{skosarev_2019,
title = {Case Study on Energy-Aware Position Control for Flexible Link Mechatronic Systems},
author = {Skosarev, E.; Kolyubin, S.; },
booktitle = {2019 IEEE International Conference on Mechatronics (ICM)},
year = {2019},
institution = {ITMO University, Russia Innopolis University, Russia},
abstract = {The paper studies how the concept of embedded energy-aware actuators (E2A2) can be applied for position control of flexible link robots, which are widely used for manipulation tasks. Quanser rotary flexible link mechatronic system is used as a testbed for research. At the first stage, a dynamic model of a system was obtained based on the Euler-Lagrange equations and the method of assumed modes. The resulting model has finite dimension and can be easily adopted for simulation in order to study the dynamic characteristics of the system and further for trajectories planning and motion control. Next, the algorithm for combined feedforward and PD feedback control for rest-to-rest motion in a horizontal plane is presented. After studying how E2A2 switching policy affects the deformation of the link we suggest a modified scheme for smoother torque profiles, which led to reduced residual flexible link oscillations caused by an instant jump in control. Simulation and experimental results demonstrate system behaviour for different trajectories. },
keywords = {manipulators, robots with flexible links, modelling, dynamics, control, energy},
language = {English},
publisher = {IEEE},
isbn = {978-1-5386-6960-0 }
}

The paper studies how the concept of embedded energy-aware actuators (E2A2) can be applied for position control of flexible link robots, which are widely used for manipulation tasks. Quanser rotary flexible link mechatronic system is used as a testbed for research. At the first stage, a dynamic model of a system was obtained based on the Euler-Lagrange equations and the method of assumed modes. The resulting model has finite dimension and can be easily adopted for simulation in order to study the dynamic characteristics of the system and further for trajectories planning and motion control. Next, the algorithm for combined feedforward and PD feedback control for rest-to-rest motion in a horizontal plane is presented. After studying how E2A2 switching policy affects the deformation of the link we suggest a modified scheme for smoother torque profiles, which led to reduced residual flexible link oscillations caused by an instant jump in control. Simulation and experimental results demonstrate system behaviour for different trajectories.

@conference{muhammad_2019,
title = {CCD Camera-Based Ball Balancer System with Fuzzy PD Control in Varying Light Conditions},
author = {Muhammad, T.; Guo,Y.; Wu, Y.; Yao, W.; Zeeshan, A.},
booktitle = {2019 IEEE 16th International Conference on Networking, Sensing and Control (ICNSC)},
year = {2019},
institution = {Nanjing University of Science and Technology, China},
abstract = {The Ball Balancer System (BBS) is a 2-DOF system with visual feedback. BBS has broad applications in the field of automotive industry, defense and communication antenna’s automation. The accurate trajectory tracking in BBS has always been challenging for researchers. The proposed method focuses on designing the robust Fuzzy-tuned PD (FPD) controller having better error tracking and least oscillation of the ball in varying lighting conditions. The PD parameters, i.e., K p and K d are calculated by using the Fuzzy rules. Furthermore, the Blob analysis algorithm is proposed which can detect the ball even in changing lighting conditions. The proposed method is compared with widely used techniques, i.e., color-based segmentation and PD controller. The rectangular trajectory is achieved using Blob analysis embedded with FPD, whose results are compared with the PD controller combined with color based segmentation technique. The proposed method gave promising results. },
keywords = {Proportional derivative (PD) controller, fuzzy PD, color-based image segmentation, Blob analysis},
language = {English},
publisher = {IEEE},
isbn = {978-1-7281-0085-2 }
}

The Ball Balancer System (BBS) is a 2-DOF system with visual feedback. BBS has broad applications in the field of automotive industry, defense and communication antenna’s automation. The accurate trajectory tracking in BBS has always been challenging for researchers. The proposed method focuses on designing the robust Fuzzy-tuned PD (FPD) controller having better error tracking and least oscillation of the ball in varying lighting conditions. The PD parameters, i.e., K p and K d are calculated by using the Fuzzy rules. Furthermore, the Blob analysis algorithm is proposed which can detect the ball even in changing lighting conditions. The proposed method is compared with widely used techniques, i.e., color-based segmentation and PD controller. The rectangular trajectory is achieved using Blob analysis embedded with FPD, whose results are compared with the PD controller combined with color based segmentation technique. The proposed method gave promising results.

@conference{thompson_2019,
title = {Characterizing Architectures of Soft Pneumatic Actuators for a Cable-Driven Shoulder Exoskeleton},
author = {Thompson, N.; Sinha, A.; Krishnan, G.},
booktitle = {2019 International Conference on Robotics and Automation (ICRA)},
year = {2019},
institution = {University of Illinois at Urbana-Champaign, USA},
abstract = {Low weight and innate compliance make soft pneumatic actuators an attractive method for actuating wearable robots. Performance of soft pneumatic actuators can be tailored to an application by combining them in novel architectures. We modeled and constructed nested linear and pennate architectures using fiber-reinforced elastomeric enclosures (FREEs) with identical manufacturing parameters and total effective lengths to compare their suitability for a cable-driven exoskeleton for augmenting shoulder flexion. We determined actuator performance requirements using a static model for the transmission of actuator forces to the upper arm via Bowden cables. We experimentally characterized the architectures by measuring their force-displacement curves at a range of pressures, yielding greater force and displacement from the nested architecture in the domain required by our exoskeleton. Results also indicated a force threshold above which the pennate structure produced greater force at any given displacement. We validated the nested linear architecture using a prototype exoskeleton installed on a passive mannequin. Measured joint angles at varying pressures were close to predicted values, adjusted for measured losses due to cable anchor movement. },
language = {English},
publisher = {IEEE}
}

Low weight and innate compliance make soft pneumatic actuators an attractive method for actuating wearable robots. Performance of soft pneumatic actuators can be tailored to an application by combining them in novel architectures. We modeled and constructed nested linear and pennate architectures using fiber-reinforced elastomeric enclosures (FREEs) with identical manufacturing parameters and total effective lengths to compare their suitability for a
cable-driven exoskeleton for augmenting shoulder flexion. We determined actuator performance requirements using a static model for the transmission of actuator forces to the upper arm via Bowden cables. We experimentally characterized the architectures by measuring their force-displacement curves at
a range of pressures, yielding greater force and displacement from the nested architecture in the domain required by our exoskeleton. Results also indicated a force threshold above which the pennate structure produced greater force at any given displacement. We validated the nested linear architecture using a prototype exoskeleton installed on a passive mannequin. Measured joint angles at varying pressures were close to predicted values, adjusted for measured losses due to cable anchor movement.

@article{fu_2019,
title = {Comparative studies of vibration control effects between structures with particle dampers and tuned liquid dampers using substructure shake table testing methods},
author = {Fu, B.; Jiang, H.; Wu, T.},
journal = {Soil Dynamics and Earthquake Engineering},
year = {2019},
month = {06},
volume = {121},
institution = {Chang’an University, China; Tongji University, China},
abstract = {This paper compares the vibration control performance of particle dampers (PDs) and tuned liquid dampers (TLDs) by using the up-to-date substructure shake table testing (SSTT) method. In implementing the SSTT, three representative model-based integration algorithms, whose algorithmic parameters are functions of the complete model of the structure system to enable unconditional stability to be achieved within the framework of an explicit formulation, are adopted. The experimental procedures of the SSTT methods using the three integration algorithms are presented. The SSTT system of the single-degree-of-freedom (SDOF) structures with PDs/TLDs is constructed and verified by comparing the experimental results of the SSTTs and the corresponding complete structure shake table tests. The vibration reduction effects of PDs and TLDs with the same mass ratio are investigated and compared by conducting a series of SSTTs of the SDOF systems with such devices under the excitation of ground motion. The influences of mass ratio, damping ratio and structural frequency on control efficiency of PDs and TLDs are studied. The results from the parametric analyses demonstrate that all the aforementioned factors have significant impacts on the vibration control performance of both dampers. Most experimental results indicate that the PDs have better vibration control performance than the counterpart TLDs. },
keywords = {Substructure shake table testing, Particle damper, Tuned liquid damper, Vibration control, Integration algorithm},
language = {English},
publisher = {Elsevier B.V.},
pages = {421-435}
}

This paper compares the vibration control performance of particle dampers (PDs) and tuned liquid dampers (TLDs) by using the up-to-date substructure shake table testing (SSTT) method. In implementing the SSTT, three representative model-based integration algorithms, whose algorithmic parameters are functions of the complete model of the structure system to enable unconditional stability to be achieved within the framework of an explicit formulation, are adopted. The experimental procedures of the SSTT methods using the three integration algorithms are presented. The SSTT system of the single-degree-of-freedom (SDOF) structures with PDs/TLDs is constructed and verified by comparing the experimental results of the SSTTs and the corresponding complete structure shake table tests. The vibration reduction effects of PDs and TLDs with the same mass ratio are investigated and compared by conducting a series of SSTTs of the SDOF systems with such devices under the excitation of ground motion. The influences of mass ratio, damping ratio and structural frequency on control efficiency of PDs and TLDs are studied. The results from the parametric analyses demonstrate that all the aforementioned factors have significant impacts on the vibration control performance of both dampers. Most experimental results indicate that the PDs have better vibration control performance than the counterpart TLDs.

@conference{pyrhonen_2019,
title = {Composite Nonlinear Feedback Control of a Jib Trolley of a Tower Crane},
author = {Pyrhonen, V.-P.; Vilkko, M.K.},
booktitle = {2019 18th European Control Conference (ECC)},
year = {2019},
institution = {Tampere University, Finland},
abstract = {Cranes are required to lift and carry loads swiftly to desired positions without causing excessive swaying motion of the load. These are conflicting requirements, which make feedback control of crane systems challenging. Furthermore, variations in rope length and load mass complicate controller design, since they significantly influence swaying dynamics. This paper considers automatic control of Quanser 3DOF tower crane system using composite nonlinear feedback (CNF) methodology. To be more specific, a CNF controller is designed for the jib trolley position of the crane using partial state measurements. The performance of the CNF controller is compared with Quanser’s built-in linear quadratic regulator (LQR) controller both in simulation and experimental setups. The results show that the CNF controller provides better load handling capability in terms of fast positioning of the jib trolley and damping of load swaying. },
language = {English},
publisher = {EUCA}
}

Cranes are required to lift and carry loads swiftly to desired positions without causing excessive swaying motion of the load. These are conflicting requirements, which make feedback control of crane systems challenging. Furthermore, variations in rope length and load mass complicate controller
design, since they significantly influence swaying dynamics. This paper considers automatic control of Quanser 3DOF tower crane system using composite nonlinear feedback (CNF) methodology. To be more specific, a CNF controller is designed for the jib trolley position of the crane using partial state
measurements. The performance of the CNF controller is compared with Quanser’s built-in linear quadratic regulator (LQR) controller both in simulation and experimental setups. The results show that the CNF controller provides better load handling capability in terms of fast positioning of the jib trolley and damping of load swaying.

@article{abbasi_2019,
title = {Controlling of Rotary Inverted Pendulum with Self-Tune Fuzzy PID},
author = {Abbasi, A.A.; Nighat, A.; Shaikh, M.F.; Bhutto, S.; Ansari, A.B.},
journal = {Engineering Science and Technology International Research Journal},
year = {2019},
month = {03},
volume = {3},
number = {1},
institution = {Mehran UET, Pakistan; ISRA University, Pakistan},
abstract = {Inverted pendulum is a widely used mechanism in designing of robotic arm. The aim of this research is to model a self-tuned hybrid fuzzy logic (P+D & fuzzy) controller for inverted-pendulum; real time parameters are used in NI Lab-View software, for its proper modeling and controlling. This self-tuned PD works on error and is sent to computer-based model to generate suitable output for pendulum. The microcontroller-based interface gets input from rotational inverted pendulum; as per difference in error movement is updated via feedback signal of rotational angle measured by optical encoder until the stable position is achieved. The parameters of PD are set by self-tuning algorithm. Thus, the comparative analysis with previous work concludes that the research is very helpful for implementing the concept in self-stabilizing robots. },
issn = {2521-5027},
keywords = {Inverted pendulum, PD control, Self-tuned fuzzy controller, Lab-View, Stability},
language = {English}
}

Inverted pendulum is a widely used mechanism in designing of robotic arm. The aim of this research is to model a self-tuned hybrid fuzzy logic (P+D & fuzzy) controller for inverted-pendulum; real time parameters are used in NI Lab-View software, for its proper modeling and controlling. This self-tuned PD works on error and is sent to computer-based model to generate suitable output for pendulum. The microcontroller-based interface gets input from rotational inverted pendulum; as per difference in error movement is updated via feedback signal of rotational angle measured by optical encoder until the stable position is achieved. The parameters of PD are set by self-tuning algorithm. Thus, the comparative analysis with previous work concludes that the research is very helpful for implementing the concept in self-stabilizing robots.

@article{narayanamoorthi_2019,
title = {Cross Interference Minimization and Simultaneous Wireless Power Transfer to Multiple Frequency Loads Using Frequency Bifurcation Approach},
author = {Narayanamoorthi R.; Vimala Juliet A.; Bharatiraja, C.},
journal = {IEEE Transactions on Power Electronics},
year = {2019},
institution = {SRM Institute of Science and Technology, India},
abstract = {Simultaneous power distribution to multiple loads using a single source in the wireless power transfer (WPT) system is a challenging issue due to cross-coupling between the load coils, which reduces the power transfer efficiency. In a resonant WPT system, when two or more coils operated under over coupled (OC) condition, the original operating resonant frequency gets bifurcated, and thereby reduction in the power transfer efficiency. Different techniques are investigated in the literature to mitigate the frequency bifurcation phenomena in the resonant WPT system. However, the utilization of frequency bifurcation approach for the simultaneous power transfer to multiple loads is not addressed. This paper proposes a simultaneous power transfer approach using frequency bifurcation for the multiple load system designed with different operating frequency. Mathematical, simulation and experimental studies performed for dual, triple, and four coil WPT systems with multiple loads. In addition, an automatic power flow control method is implemented to estimate the load current from the source, which helps to select a new set of load coils to be charged. The experimental results confirm the proposed power transfer, helps to attain higher power transfer efficiency of 39.34%, 49.31%, 68.22% and cross interference of -31.2 dBV, -36.2 dBV, -41.2 dBV for dual, triple, and four coil WPT system respectively. },
keywords = {Wireless Power, Selective Wireless Power Transfer, Multiple receivers, Simultaneous power transfer, Frequency Bifurcation},
language = {English},
publisher = {IEEE}
}

Simultaneous power distribution to multiple loads using a single source in the wireless power transfer (WPT) system is a challenging issue due to cross-coupling between the load coils, which reduces the power transfer efficiency. In a resonant WPT system, when two or more coils operated under over coupled (OC) condition, the original operating resonant frequency gets bifurcated, and thereby reduction in the power transfer efficiency. Different techniques are investigated in the literature to mitigate the frequency bifurcation phenomena in the resonant WPT system. However, the utilization of frequency bifurcation approach for the simultaneous power transfer to multiple loads is not addressed. This paper proposes a simultaneous power transfer approach using frequency bifurcation for the multiple load system designed with different operating frequency. Mathematical, simulation and experimental studies performed for dual, triple, and four coil WPT systems with multiple loads. In addition, an automatic power flow control method is implemented to estimate the load current from the source, which helps to select a new set of load coils to be charged. The experimental results confirm the proposed power transfer, helps to attain higher power transfer efficiency of 39.34%, 49.31%, 68.22% and cross interference of -31.2 dBV, -36.2 dBV, -41.2 dBV for dual, triple, and four coil WPT system respectively.

@article{huang2_2019,
title = {Data-Driven Backstepping Control of Underactuated Mechanical Systems},
booktitle = {Huang, J.; Zhang, T.; Sun, J.-Q.},
journal = {Journal of Dynamic Systems, Measurement and Control},
year = {2019},
institution = {Beijing University of Chemical Technology, China; University of California, Merced, CA, USA},
abstract = {This paper studies control problems of underactuated mechanical systems with model uncertainties. The control is designed with the method of backstepping. The first-order low-pass filters are used to estimate the unknown quantities and to avoid the ``explosion of terms''. A novel method is also proposed to implement the control without the knowledge of the control coefficient, which makes the whole process of backstepping control data-driven. The stability of the proposed control in the Lyapunov sense is studied. It is numerically and experimentally validated, and compared with the well-known model-based LQR control. The data-driven backstepping control is found to provide comparable performances to that of the LQR control with the advantage of being model-free and robust. },
keywords = {Backstepping; Underactuated mechanical systems; Tracking control; Datadriven; Flexible link},
language = {English},
publisher = {ASME}
}

This paper studies control problems of underactuated mechanical systems with model uncertainties. The control is designed with the method of backstepping. The first-order low-pass filters are used to estimate the unknown quantities and to avoid the ``explosion of terms''. A novel method is also proposed to implement the control without the knowledge of the control coefficient, which makes the whole process of backstepping control data-driven. The stability of the proposed control in the Lyapunov sense is studied. It is numerically and experimentally validated, and compared with the well-known model-based LQR control. The data-driven backstepping control is found to provide comparable performances to that of the LQR control with the advantage of being model-free and robust.

@article{dong_20198,
title = {Decentralized robust zero-sum neuro-optimal control for modular robot manipulators in contact with uncertain environments: theory and experimental verification},
author = {Dong, B.; An, T.; Zhou, F.; Liu; K.; Li, Y.},
journal = {Nonlinear Dynamics},
year = {2019},
institution = {Changchun University of Technology, China},
abstract = {This paper presents a decentralized robust zero-sum optimal control approach for modular robot manipulators (MRMs) in contact with uncertain environments based on the adaptive dynamic programming (ADP) algorithm. The dynamic model of MRMs is formulated via joint torque feedback technique that is deployed for each joint module to design the model compensation controller. An uncertainty decomposition-based robust control is developed to compensate the model uncertainties, and then, the robust optimal control problem of the MRM system is transformed into a two-player zero-sum optimal control one. According to the ADP algorithm, the Hamilton–Jacobi–Isaacs equation can be solved by establishing action and critic neural networks, thus making the derivation of the approximate optimal control policy feasible. Based on the Lyapunov theory, the closed-loop robotic system is proved to be asymptotic stable under the developed decentralized control method. Finally, experiments are conducted to verify the effectiveness and advantages of the proposed method. },
issn = {0924-090X},
keywords = {Modular robot manipulators, Adaptive dynamic programming, Decentralized control, Optimal control, Zero-sum game },
language = {English},
publisher = {Springer Netherlands}
}

This paper presents a decentralized robust zero-sum optimal control approach for modular robot manipulators (MRMs) in contact with uncertain environments based on the adaptive dynamic programming (ADP) algorithm. The dynamic model of MRMs is formulated via joint torque feedback technique that is deployed for each joint module to design the model compensation controller. An uncertainty decomposition-based robust control is developed to compensate the model uncertainties, and then, the robust optimal control problem of the MRM system is transformed into a two-player zero-sum optimal control one. According to the ADP algorithm, the Hamilton–Jacobi–Isaacs equation can be solved by establishing action and critic neural networks, thus making the derivation of the approximate optimal control policy feasible. Based on the Lyapunov theory, the closed-loop robotic system is proved to be asymptotic stable under the developed decentralized control method. Finally, experiments are conducted to verify the effectiveness and advantages of the proposed method.

@article{li2_2019,
title = {Decentralized Trajectory Tracking Control for Modular and Reconfigurable Robots With Torque Sensor: Adaptive Terminal Sliding Control-Based Approach},
author = {Li, Y.; Lu, Z.; Zhou, F.; Dong, B.; Liu, K.; Li, Y. },
journal = {Journal of Dynamic Systems, Measurement, and Control},
year = {2019},
volume = {141},
number = {6},
institution = {Changchun University of Technology, China},
abstract = {The main technical challenge in decentralized control of modular and reconfigurable robots (MRRs) with torque sensor is related to the treatment of interconnection term and friction term. This paper proposed a modified adaptive sliding mode decentralized control strategy for trajectory tracking control of the MRRs. The radial basis function (RBF) neural network is used as an effective learning method to approximate the interconnection term and friction term, eliminating the effect of model uncertainty and reducing the controller gain. In addition, in order to provide faster convergence and higher precision control, the terminal sliding mode algorithm is introduced to the controller design. Based on the Lyapunov method, the stability of the MRRs is proved. Finally, experiments are performed to confirm the effectiveness of the method. },
keywords = {Friction, Sensors, Control equipment, Robots, Trajectories (Physics), Design, Artificial neural networks, Errors, Torque, Tracking control},
language = {English},
publisher = {ASME}
}

The main technical challenge in decentralized control of modular and reconfigurable robots (MRRs) with torque sensor is related to the treatment of interconnection term and friction term. This paper proposed a modified adaptive sliding mode decentralized control strategy for trajectory tracking control of the MRRs. The radial basis function (RBF) neural network is used as an effective learning method to approximate the interconnection term and friction term, eliminating the effect of model uncertainty and reducing the controller gain. In addition, in order to provide faster convergence and higher precision control, the terminal sliding mode algorithm is introduced to the controller design. Based on the Lyapunov method, the stability of the MRRs is proved. Finally, experiments are performed to confirm the effectiveness of the method.

@article{konoiko_2019,
title = {Deep learning framework for controlling an active suspension system},
author = {Konoiko, A.; Kadhem, A.; Saiful, I.; Ghorbanian, N.; Zweiri, Y.; Sahinkaya, M.N.},
journal = {Journal of Vibration and Control},
year = {2019},
institution = {Kingston University London, UK},
abstract = {In this paper, a feed-forward deep neural network (DNN) and automated search method for optimum network structure are developed to control an active suspension system (ASS). The network was trained through supervised learning using the backpropagation algorithm. The training data were generated from an optimal proportional–integral–derivative controller tuned based on a full state feedback optimal controller. The trained network was implemented in an ASS test rig for a quarter-car model and was initially tested in simulation under parameter uncertainties. Experimental results showed that the developed DNN controller outperforms the optimal controller under uncertainties in terms of reducing the sprung mass acceleration and actuator energy consumption, with a 4% and 14% reduction, respectively. },
keywords = {Active suspension system, control systems, control design, deep learning, deep neural networks, machine learning, backpropagation, optimal control, optimal proportional-integral-derivative controller},
language = {English},
publisher = {SAGE}
}

In this paper, a feed-forward deep neural network (DNN) and automated search method for optimum network structure are developed to control an active suspension system (ASS). The network was trained through supervised learning using the backpropagation algorithm. The training data were generated from an optimal proportional–integral–derivative controller tuned based on a full state feedback optimal controller. The trained network was implemented in an ASS test rig for a quarter-car model and was initially tested in simulation under parameter uncertainties. Experimental results showed that the developed DNN controller outperforms the optimal controller under uncertainties in terms of reducing the sprung mass acceleration and actuator energy consumption, with a 4% and 14% reduction, respectively.

@conference{kim_2019,
title = {Deep Q-Network Based Rotary Inverted Pendulum System and Its Monitoring on the EdgeX Platform},
author = {Kim, J.-B.; Lim, H.-K.; Kwon, D.-H.; Kim, M.-S.; Hong, Y.-G.; Han, Y.-H. },
booktitle = {2019 International Conference on Artificial Intelligence in Information and Communication (ICAIIC)},
year = {2019},
institution = {Korea University of Technology and Education, Korea; Electronics and Telecommunications Research Institute, Korea},
abstract = {A rotary inverted pendulum is an unstable and highly nonlinear device and is used as a common model for engineering applications in linear and nonlinear control. In this study, we created a cyber physical system (CPS) to demonstrate that a deep reinforcement learning agent using a rotary inverted pendulum can successfully control a remotely located physical device. The device we created is composed of a cyber environment and physical environment using the Message Queuing Telemetry Transport (MQTT) protocol with an Ethernet connection to connect the cyber environment and the physical environment. The reinforcement learning agent controls the physical device, which is located remotely from the controller and a classical proportional integral derivative (PID) controller is utilized to implement imitation and reinforcement learning and facilitate the learning process. In addition, the control and monitoring system is built on the open source EdgeX platform, so that learning tasks performed near the source of data generation and real-time data emitted from the physical device can be observed while reinforcement learning is performed. From our CPS experimental system, we verify that a deep reinforcement learning agent can control a remotely located real-world device successfully. },
keywords = {EdgeX, Deep Q-Network (DQN), Deep Reinforcement Learning, Rotary Inverted Pendulum},
language = {English},
publisher = {IEEE},
isbn = {978-1-5386-7823-7 }
}

A rotary inverted pendulum is an unstable and highly nonlinear device and is used as a common model for engineering applications in linear and nonlinear control. In this study, we created a cyber physical system (CPS) to demonstrate that a deep reinforcement learning agent using a rotary inverted pendulum can successfully control a remotely located physical device. The device we created is composed of a cyber environment and physical environment using the Message Queuing Telemetry Transport (MQTT) protocol with an Ethernet connection to connect the cyber environment and the physical environment. The reinforcement learning agent controls the physical device, which is located remotely from the controller and a classical proportional integral derivative (PID) controller is utilized to implement imitation and reinforcement learning and facilitate the learning process. In addition, the control and monitoring system is built on the open source EdgeX platform, so that learning tasks performed near the source of data generation and real-time data emitted from the physical device can be observed while reinforcement learning is performed. From our CPS experimental system, we verify that a deep reinforcement learning agent can control a remotely located real-world device successfully.

@article{murali_2019,
title = {Design and evaluation of a distally actuated powered finger prosthesis with self-contained transmission for individuals with partial hand loss},
author = {Murali, B.; Huddle, S.; Weir, R.F.},
journal = {Advances in Mechanical Engineering},
year = {2019},
volume = {11},
number = {4},
institution = {Rice University, USA; University of Colorado at Denver, USA},
abstract = {Partial hand loss accounts for the overwhelming majority of upper limb deficiencies. Despite this, individuals with partial hand loss have a limited number of prosthetic options at their disposal. Existing externally powered devices typically house both motor and gear transmission in the proximal phalanx, which provides function at the expense of anthropomorphism. We present a novel design for an externally powered finger prosthesis with a custom gear transmission that is capable of higher intermittent torques compared to commercial gearheads of equivalent volume. We manufacture a fully functional transmission using a high-strength maraging steel alloy and direct laser metal sintering. The transmission consists of multiple planetary and spur gear stages arranged in a stackable (or laminar) configuration and accommodates joint movement at the proximal interphalangeal joint. The powered finger is equivalent in size to a 50th percentile female index finger and is capable of generating pinch forces comparable to those of commercial powered fingers at flexion speeds that exceed those of existing devices. While there are several practical and functional improvements for future iterations, our design represents a viable option for a powered finger capable of accommodating a wide range of individuals with partial hand loss. },
keywords = {Powered finger, partial hand loss, amputation, prosthesis, transmissions, prosthetic hand, assistive device},
language = {English},
publisher = {SAGE}
}

Partial hand loss accounts for the overwhelming majority of upper limb deficiencies. Despite this, individuals with partial hand loss have a limited number of prosthetic options at their disposal. Existing externally powered devices typically house both motor and gear transmission in the proximal phalanx, which provides function at the expense of anthropomorphism. We present a novel design for an externally powered finger prosthesis with a custom gear transmission that is capable of higher intermittent torques compared to commercial gearheads of equivalent volume. We manufacture a fully functional transmission using a high-strength maraging steel alloy and direct laser metal sintering. The transmission consists of multiple planetary and spur gear stages arranged in a stackable (or laminar) configuration and accommodates joint movement at the proximal interphalangeal joint. The powered finger is equivalent in size to a 50th percentile female index finger and is capable of generating pinch forces comparable to those of commercial powered fingers at flexion speeds that exceed those of existing devices. While there are several practical and functional improvements for future iterations, our design represents a viable option for a powered finger capable of accommodating a wide range of individuals with partial hand loss.

@conference{mehrabi_2019,
title = {Design and Implementation of a Two-DOF Robotic System with an Adjustable Force Limiting Mechanism for Ankle Rehabilitation},
author = {Mehrabi, V.; Atashzar, S.F.; Talebi, H.A.; Patel, R.V.},
booktitle = {2019 International Conference on Robotics and Automation (ICRA)},
year = {2019},
institution = {Western University, Canada; Imperial College London, U.K.},
abstract = {This paper presents a novel light-weight backdrivable inherently-safe robotic mechanism for delivering ankle rehabilitation therapies. The robot is designed to be used as the ankle module of a multi-purpose lower-limb rehabilitation robot. A novel friction-based safety feature has been introduced that enables mechanical adjustment of the maximum amount of allowable transfer forces and torques to the patient’s limb. The design procedure, mathematical modeling and experimental validations are provided to demonstrate the performance of the proposed system. },
language = {English},
publisher = {IEEE}
}

This paper presents a novel light-weight backdrivable inherently-safe robotic mechanism for delivering ankle rehabilitation therapies. The robot is designed to be used as the ankle module of a multi-purpose lower-limb rehabilitation robot. A novel friction-based safety feature has been introduced that enables mechanical adjustment of the maximum amount of allowable transfer forces and torques to the patient’s limb. The design procedure, mathematical modeling and experimental validations are provided to demonstrate the performance of the proposed system.

@conference{ansari_20019,
title = {Design and Implementation of Robust Generalized Dynamic Inversion Control for Stabilizing Rotary Inverted Pendulum},
author = {Ansari, U.; Mehedi, I.M.; Bajodah, A.H.; Al-Saggaf, U.M.},
booktitle = {2019 18th European Control Conference (ECC)},
year = {2019},
institution = {King Abdulaziz University, Saudi Arabia},
abstract = {This paper will illustrate the application of constraint based Robust Generalized Dynamic Inversion (RGDI) control for balancing the Rotary Inverted Pendulum system. The proposed control law is established by hybridizing the equivalent control (conventional GDI) and the robust control. The equivalent control is constructed by formulating the dynamical constraints, based on the attitude deviation functions of the rotary arm and the vertical pendulum. The constraint dynamics are then inverted using dynamically scaled Moore-Penrose Generalized Inverse to solve for the equivalent control. For the robust term, sliding mode control is utilized, that will provide robustness against parametric uncertainties, system nonlinearities, such that semi-global practically stable angular position tracking is guaranteed. The controller’s capability is verified through computer simulation and experimental studies on the Quanser’s SRV02 Rotary Inverted Pendulum system. },
language = {English},
publisher = {EUCA}
}

This paper will illustrate the application of constraint based Robust Generalized Dynamic Inversion (RGDI) control for balancing the Rotary Inverted Pendulum system. The proposed control law is established by hybridizing the equivalent control (conventional GDI) and the robust control. The equivalent control is constructed by formulating the dynamical constraints, based on the attitude deviation functions of the rotary arm and the vertical pendulum. The constraint dynamics are then inverted using dynamically scaled Moore-Penrose Generalized Inverse to solve for the equivalent control. For the robust term, sliding mode control is utilized, that will provide robustness against parametric uncertainties, system nonlinearities, such that semi-global practically stable angular position tracking is guaranteed. The controller’s capability is verified through computer simulation and experimental studies on the Quanser’s SRV02 Rotary Inverted Pendulum system.

@article{tang_2019,
title = {Design and Kinematic Control of the Cable-Driven Hyper-Redundant Manipulator for Potential Underwater Applications},
author = {Tang, J.; Zhang, Y.; Huang, F.; Li, J.; Chen, Z.; Song, W.; Zhu, S.; Gu, J.},
journal = {Journal of Applied Sciences},
year = {2019},
volume = {9},
number = {6},
institution = {Zhejiang University, China; Dalhousie University, NS, Canada},
abstract = {Underwater manipulators are important robotic tools in the exploration of the ocean environment. Up to now, most existing underwater manipulators are rigid and with fixed 5 or 7 degrees of freedom (DOF), which may not be very suitable for some complicated underwater scenarios (e.g., pipe networks, narrow deep cavities, etc.). The biomimetic concept of muscles and tendons is also considered as continuum manipulators, but load capacity and operation accuracy are their essential drawbacks and thus limit their practical applications. Recently, the cable-driven technique has been developed for manipulators, which can include numerous joints and hyper-redundant DOF to execute tasks with dexterity and adaptability and thus they have strong potential for these complex underwater applications. In this paper, the design of a novel cable-driven hyper-redundant manipulator (CDHRM) is introduced, which is driven by multiple cables passing through the tubular structure from the base to the end-effector, and the joint numbers can be extended and decided by the specific underwater task requirements. The kinematic analysis of the proposed CDHRM is given which includes two parts: the cable-joint kinematics and the joint-end kinematics. The geometric relationship between the cable length and the joint angles are derived via the established geometric model for the cable-joint kinematics, and the projection relationship between the joint angles and end-effector’s pose is established via the spatial coordinate transformation matrix for the joint-end kinematics. Thus, the complex mapping relationships among the cables, joints and end-effectors are clearly achieved. To implement precise control, the kinematic control scheme is developed for the CDHRM with series-parallel connections and hyper-redundancy to achieve good tracking performance. The experiment on a real CDHRM system with five joints is carried out and the results verify the accuracy of kinematics solution, and the effectiveness of the proposed control design. Particularly, three experiments are tested in the underwater environment, which verifies its good tracking performance, load carrying and grasping capacity. },
issn = {2076-3417},
keywords = {hyper redundancy; cable-driven manipulator; mechanical design; kinematics},
language = {English},
publisher = {MDPI},
pages = {1142-1161}
}

Underwater manipulators are important robotic tools in the exploration of the ocean environment. Up to now, most existing underwater manipulators are rigid and with fixed 5 or 7 degrees of freedom (DOF), which may not be very suitable for some complicated underwater scenarios (e.g., pipe networks, narrow deep cavities, etc.). The biomimetic concept of muscles and tendons is also considered as continuum manipulators, but load capacity and operation accuracy are their essential drawbacks and thus limit their practical applications. Recently, the cable-driven technique has been developed for manipulators, which can include numerous joints and hyper-redundant DOF to execute tasks with dexterity and adaptability and thus they have strong potential for these complex underwater applications. In this paper, the design of a novel cable-driven hyper-redundant manipulator (CDHRM) is introduced, which is driven by multiple cables passing through the tubular structure from the base to the end-effector, and the joint numbers can be extended and decided by the specific underwater task requirements. The kinematic analysis of the proposed CDHRM is given which includes two parts: the cable-joint kinematics and the joint-end kinematics. The geometric relationship between the cable length and the joint angles are derived via the established geometric model for the cable-joint kinematics, and the projection relationship between the joint angles and end-effector’s pose is established via the spatial coordinate transformation matrix for the joint-end kinematics. Thus, the complex mapping relationships among the cables, joints and end-effectors are clearly achieved. To implement precise control, the kinematic control scheme is developed for the CDHRM with series-parallel connections and hyper-redundancy to achieve good tracking performance. The experiment on a real CDHRM system with five joints is carried out and the results verify the accuracy of kinematics solution, and the effectiveness of the proposed control design. Particularly, three experiments are tested in the underwater environment, which verifies its good tracking performance, load carrying and grasping capacity.

@article{kutuk_2019,
title = {Design of a robot-assisted exoskeleton for passive wrist and forearm rehabilitation},
author = {Kütük, M.E.; Dülger, L.C.; Daş, M.T.},
journal = {Journal of Mechanical Sciences},
year = {2019},
volume = {10},
number = {1},
institution = {Gaziantep University, Turkey; Izmir University of Economics, Turkey; University of Waterloo, Canada},
abstract = {This paper presents a new exoskeleton design for wrist and forearm rehabilitation. The contribution of this study is to offer a methodology which shows how to adapt a serial manipulator that reduces the number of actuators used on exoskeleton design for the rehabilitation. The system offered is a combination of end-effector- and exoskeleton-based devices. The passive exoskeleton is attached to the end effector of the manipulator, which provides motion for the purpose of rehabilitation process. The Denso VP 6-Axis Articulated Robot is used to control motion of the exoskeleton during the rehabilitation process. The exoskeleton is designed to be used for both wrist and forearm motions. The desired moving capabilities of the exoskeleton are flexion–extension (FE) and adduction–abduction (AA) motions for the wrist and pronation–supination (PS) motion for the forearm. The anatomical structure of a human limb is taken as a constraint during the design. The joints on the exoskeleton can be locked or unlocked manually in order to restrict or enable the movements. The parts of the exoskeleton include mechanical stoppers to prevent the excessive motion. One passive degree of freedom (DOF) is added in order to prevent misalignment problems between the axes of FE and AA motions. Kinematic feedback of the experiments is performed by using a wireless motion tracker assembled on the exoskeleton. The results proved that motion transmission from robot to exoskeleton is satisfactorily achieved. Instead of different exoskeletons in which each axis is driven and controlled separately, one serial robot with adaptable passive exoskeletons is adequate to facilitate rehabilitation exercises. },
language = {English},
publisher = {Copernicus Publications}
}

This paper presents a new exoskeleton design for wrist and forearm rehabilitation. The contribution of this study is to offer a methodology which shows how to adapt a serial manipulator that reduces the number of actuators used on exoskeleton design for the rehabilitation. The system offered is a combination of end-effector- and exoskeleton-based devices. The passive exoskeleton is attached to the end effector of the manipulator, which provides motion for the purpose of rehabilitation process. The Denso VP 6-Axis Articulated Robot is used to control motion of the exoskeleton during the rehabilitation process. The exoskeleton is designed to be used for both wrist and forearm motions. The desired moving capabilities of the exoskeleton are flexion–extension (FE) and adduction–abduction (AA) motions for the wrist and pronation–supination (PS) motion for the forearm. The anatomical structure of a human limb is taken as a constraint during the design. The joints on the exoskeleton can be locked or unlocked manually in order to restrict or enable the movements. The parts of the exoskeleton include mechanical stoppers to prevent the excessive motion. One passive degree of freedom (DOF) is added in order to prevent misalignment problems between the axes of FE and AA motions. Kinematic feedback of the experiments is performed by using a wireless motion tracker assembled on the exoskeleton. The results proved that motion transmission from robot to exoskeleton is satisfactorily achieved. Instead of different exoskeletons in which each axis is driven and controlled separately, one serial robot with adaptable passive exoskeletons is adequate to facilitate rehabilitation exercises.

@article{kajiwara_2019,
title = {Design of dielectric elastomer actuators for vibration control at high frequencies},
author = {Kajiwara, I.; Kitabatake, S.; Hosoya, N.; Maeda, S.},
journal = {International Journal of Mechanical Sciences},
year = {2019},
month = {07},
volume = {157},
institution = {Hokkaido University, Japan; Shibaura Institute of Technology, Japan},
abstract = {This study evaluates the basic characteristics of smart structures composed of dielectric elastomer actuators (DEAs) to suppress vibrations. A DEA, which is a lightweight, flexible polymer that can induce high deformations, should realize next-generation actuators. Additionally, DEA can achieve vibration control of structures with complex shapes or curved surfaces. Herein the performance and efficacy of DEAs are evaluated as an actuator for vibration control at high frequencies. First, the appropriate DEA structure is considered. Second, the control system for the smart structure using the DEA is modeled and designed as an actuator. Third, a method to determine DEA's optimum arrangement and shape is discussed by focusing on the structure's strain energy. Finally, a control simulation and a control experiment validate the vibration suppression effects and the efficacy of the DEA. },
keywords = {Dielectric elastomer actuator, Smart structure, Vibration control, Modal analysis, Modal strain energy},
language = {English},
publisher = {Elsevier B.V.},
pages = {849-857}
}

This study evaluates the basic characteristics of smart structures composed of dielectric elastomer actuators (DEAs) to suppress vibrations. A DEA, which is a lightweight, flexible polymer that can induce high deformations, should realize next-generation actuators. Additionally, DEA can achieve vibration control of structures with complex shapes or curved surfaces. Herein the performance and efficacy of DEAs are evaluated as an actuator for vibration control at high frequencies. First, the appropriate DEA structure is considered. Second, the control system for the smart structure using the DEA is modeled and designed as an actuator. Third, a method to determine DEA's optimum arrangement and shape is discussed by focusing on the structure's strain energy. Finally, a control simulation and a control experiment validate the vibration suppression effects and the efficacy of the DEA.

@article{ansari_2019,
title = {Development and experimental investigation of a Quadrotor’s robust generalized dynamic inversion control system},
author = {Ansari, U., Bajodah, A.H.; Kada, B.},
journal = {Nonlinear Dynamics},
year = {2019},
institution = {King Abdulaziz University, Saudi Arabia},
abstract = {The development of a two-loops Quadrotor’s robust generalized dynamic inversion (RGDI)-based control system is presented. The outer (position) loop utilizes PD position control of the Quadrotor’s center of gravity (CG) in the three-dimensional inertial space, and it provides reference pitch and roll tilting angles commands to the inner loop, in addition to the thrust command that is required to track desired altitude trajectories. The inner (attitude) loop applies RGDI control of a prescribed asymptotically stable dynamics of tilting and attitude errors from reference-tilting and desired-attitude trajectories, and it provides the three required control torque values such that desired CG positions in instantaneous horizontal inertial planes and desired-attitude trajectories of the Quadrotor are tracked. The proposed closed loop system is shown to guarantee finite-time semi-global practically stable trajectory tracking. Numerical simulations of the proposed closed loop control system are performed on a six degrees of freedom Quadrotor’s mathematical model for nominal conditions and under parametric uncertainties and exogenous disturbances. Apart from numerical simulations, experimental tests are conducted on a three degrees of freedom Quadrotor test bench to assess performance of the RGDI control loop. Experimental results demonstrate improved tracking performance in comparison with classical Linear-Quadratic optimal control and conventional sliding mode control. },
issn = {0924-090X},
keywords = {Robust generalized dynamic inversion, Sliding mode control, Quadrotor control, Hover experimental test bench, Null control vector, Trajectory tracking, Finite-time stability, Semiglobal practical stability},
language = {English},
publisher = {Springer Nature}
}

The development of a two-loops Quadrotor’s robust generalized dynamic inversion (RGDI)-based control system is presented. The outer (position) loop utilizes PD position control of the Quadrotor’s center of gravity (CG) in the three-dimensional inertial space, and it provides reference pitch and roll tilting angles commands to the inner loop, in addition to the thrust command that is required to track desired altitude trajectories. The inner (attitude) loop applies RGDI control of a prescribed asymptotically stable dynamics of tilting and attitude errors from reference-tilting and desired-attitude trajectories, and it provides the three required control torque values such that desired CG positions in instantaneous horizontal inertial planes and desired-attitude trajectories of the Quadrotor are tracked. The proposed closed loop system is shown to guarantee finite-time semi-global practically stable trajectory tracking. Numerical simulations of the proposed closed loop control system are performed on a six degrees of freedom Quadrotor’s mathematical model for nominal conditions and under parametric uncertainties and exogenous disturbances. Apart from numerical simulations, experimental tests are conducted on a three degrees of freedom Quadrotor test bench to assess performance of the RGDI control loop. Experimental results demonstrate improved tracking performance in comparison with classical Linear-Quadratic optimal control and conventional sliding mode control.

@conference{gruenwald_2019,
title = {Direct Uncertainty Minimization in Model Reference Adaptive Control: Experimental Results},
author = {Gruenwald, B.C.; Yucelen, T.; Muse, J.A. },
booktitle = {AIAA Scitech 2019 Forum},
year = {2019},
institution = {University of South Florida; USA; Air Force Research Laboratory; USA},
abstract = {This paper presents an application of a recently developed direct uncertainty minimization approach for model reference adaptive control on a dual-rotor helicopter testbed. Specifically, the direct minimization approach uses a gradient minimization procedure to construct modification terms that are included in the adaptive control law and the update laws to improve the closed-loop system performance. These modification terms are activated when the system error between the uncertain dynamical system and a given reference model capturing the desired closed-loop dynamical system behavior is nonzero and then vanish as the system reaches steady-state. The experimental results in this paper demonstrate the capability of the direct minimization approach to improve the closed-loop system performance and enforce performance bounds. },
language = {English}
}

This paper presents an application of a recently developed direct uncertainty minimization approach for model reference adaptive control on a dual-rotor helicopter testbed. Specifically, the direct minimization approach uses a gradient minimization procedure to construct modification terms that are included in the adaptive control law and the update laws to improve the closed-loop system performance. These modification terms are activated when the system error between the uncertain dynamical system and a given reference model capturing the desired closed-loop dynamical system behavior is nonzero and then vanish as the system reaches steady-state. The experimental results in this paper demonstrate the capability of the direct minimization approach to improve the closed-loop system performance and enforce performance bounds.

@article{wu_2019,
title = {Discrete-Time Modified UDE-Based Current Control for LCL-Type Grid-Tied Inverters},
author = {Wu, Y.; Ye, Y.; Zhao, Q.; Cao, Y.; Xiong, Y.},
journal = {IEEE Transactions on Industrial Electronics},
year = {2019},
institution = {Zhongyuan University of Technology, China; Nanjing University of Aeronautics and Astronautics, China},
abstract = { In LCL-type grid tied inverters, the lumped disturbance, including parameter uncertainties, unmodeled dynamics, grid harmonics, will deteriorate the current tracking performance and lead to high total harmonic distortion (THD). The uncertainty and disturbance estimator (UDE) scheme provides an effective way to attenuate the lumped disturbance. However, UDE for the current control in LCL-type grid-tied inverters is far from perfection. In this paper, a discrete-time modified UDE (MUDE) scheme is proposed to improve the current tracking performance and robustness. In MUDE, a reduced-order model of the LCL filter combining with an active damping scheme is proposed. The stability performance is discussed in detail, and a rigorous stability condition is proposed in the first time. Moreover, the analysis of the controller sampling frequency and grid impedance, and their influences on the system stability is presented. A design case based on the stability condition is also given. Comparative experiments are conducted to verify the effectiveness of the proposed scheme. },
issn = {0278-0046 },
keywords = {Grid-tied inverter, LCL filter, uncertainty and disturbance estimator (UDE), stability analysis, total harmonic distortion (THD)},
language = {English},
publisher = {IEEE}
}

In LCL-type grid tied inverters, the lumped disturbance, including parameter uncertainties, unmodeled dynamics, grid harmonics, will deteriorate the current tracking performance and lead to high total harmonic distortion (THD). The uncertainty and disturbance estimator (UDE) scheme provides an effective way to attenuate the lumped disturbance. However, UDE for the current control in LCL-type grid-tied inverters is far from perfection. In this paper, a discrete-time modified UDE (MUDE) scheme is proposed to improve the current tracking performance and robustness. In MUDE, a reduced-order model of the LCL filter combining with an active damping scheme is proposed. The stability performance is discussed in detail, and a rigorous stability condition is proposed in the first time. Moreover, the analysis of the controller sampling frequency and grid impedance, and their influences on the system stability is presented. A design case based on the stability condition is also given. Comparative experiments are conducted to verify the effectiveness of the proposed scheme.

@article{mehta_2019,
title = {Discrete-time Sliding Mode Protocols for Leader-following consensus of Discrete Multi-Agent System with Switching Graph Topology},
author = {Mehta, A.; Patel, K.},
journal = {European Journal of Control},
year = {2019},
institution = {Institute of Infrastructure Technology Research and Management, India},
abstract = {In this paper, discrete-time sliding mode protocols for consensus of a leader following discrete multi-agent system having switching topologies are proposed. The discrete multi-agent system is described with a fixed, undirected switching graph topology as a global system having one leader and other as follower agents. Sliding surface for global consensus of agents for switching graph topology is defined and discrete-time sliding mode protocols using enhanced Gao’s and Power rate reaching laws are derived. Under the influence of switching topology, the graph topology switches in a different no. of step intervals and ensure that consensus protocols asymptotically synchronize follower agents with leader agent. The condition for global stability in both cases is also derived using the Lyapunov function. Further, the algorithms are implemented on the multi-agent system comprise of multiple 2-DOF (Degree of Freedom) helicopter systems where the pitch angle and its velocity yaw angle and its velocity are synchronized with the leader. It is inferred from simulation results that the consensus using Power rate reaching law give better performance compared with consensus using Gao’s reaching law. Finally, the robustness property of both the algorithms is checked by applying the matched disturbances in follower agents. },
keywords = {Discrete- time sliding mode control (DSMC), Discrete multi-agent system (DMAS), 2-DOF helicopter system},
language = {English},
publisher = {Elsevier Ltd.}
}

In this paper, discrete-time sliding mode protocols for consensus of a leader following discrete multi-agent system having switching topologies are proposed. The discrete multi-agent system is described with a fixed, undirected switching graph topology as a global system having one leader and other as follower agents. Sliding surface for global consensus of agents for switching graph topology is defined and discrete-time sliding mode protocols using enhanced Gao’s and Power rate reaching laws are derived. Under the influence of switching topology, the graph topology switches in a different no. of step intervals and ensure that consensus protocols asymptotically synchronize follower agents with leader agent. The condition for global stability in both cases is also derived using the Lyapunov function. Further, the algorithms are implemented on the multi-agent system comprise of multiple 2-DOF (Degree of Freedom) helicopter systems where the pitch angle and its velocity yaw angle and its velocity are synchronized with the leader. It is inferred from simulation results that the consensus using Power rate reaching law give better performance compared with consensus using Gao’s reaching law. Finally, the robustness property of both the algorithms is checked by applying the matched disturbances in follower agents.

@article{li_2019,
title = {Distal-end force prediction of tendon-sheath mechanisms for flexible endoscopic surgical robots using deep learning},
author = {Li, X.; Cao, L.; Huat Tiong, A.M.; Phan, P.T.; Phee, S.J.},
journal = {Mechanism and Machine Theory},
year = {2019},
month = {04},
volume = {134},
institution = {Nanyang Technological University, Singapore},
abstract = {Accurate haptic feedback is highly challenging for flexible endoscopic surgical robots due to space limitation for sensors on small end-effectors and critical force hysteresis of their tendon-sheath mechanisms (TSMs). This paper proposes a deep learning approach to predicting the distal force of TSMs when manipulating a biological tissue based on only proximal-end measurements. Both Multilayer Perceptron (MLP) and Recurrent Neural Network (RNN) were investigated to study their capabilities of making sequential distal force predictions. The results were compared with those of the conventional modelling approach. It was observed that, when sufficient data was provided for training, RNN achieved the most accurate prediction (RMSE = 0.0219 N) in experiments with constant system velocity. The effects of insufficient training data, varying system velocity and irregular motion trajectories on the performance of RNN were further studied. Notably, RNN could precisely identify the current system phase in the force hysteresis profile and can be applied to TSMs with realistic non-periodic movement such as manual manipulation trajectory (RSME = 0.2287 N). The proposed approach can be applied to any TSM-driven robotic systems for accurate haptic feedback without requiring sensors at the distal ends of the robots. },
keywords = {Haptic feedback, Surgical robot, Tendon sheath mechanisms, Deep learning, Hysteresis},
language = {English},
publisher = {Elsevier Ltd.},
pages = {323-337}
}

Accurate haptic feedback is highly challenging for flexible endoscopic surgical robots due to space limitation for sensors on small end-effectors and critical force hysteresis of their tendon-sheath mechanisms (TSMs). This paper proposes a deep learning approach to predicting the distal force of TSMs when manipulating a biological tissue based on only proximal-end measurements. Both Multilayer Perceptron (MLP) and Recurrent Neural Network (RNN) were investigated to study their capabilities of making sequential distal force predictions. The results were compared with those of the conventional modelling approach. It was observed that, when sufficient data was provided for training, RNN achieved the most accurate prediction (RMSE = 0.0219 N) in experiments with constant system velocity. The effects of insufficient training data, varying system velocity and irregular motion trajectories on the performance of RNN were further studied. Notably, RNN could precisely identify the current system phase in the force hysteresis profile and can be applied to TSMs with realistic non-periodic movement such as manual manipulation trajectory (RSME = 0.2287 N). The proposed approach can be applied to any TSM-driven robotic systems for accurate haptic feedback without requiring sensors at the distal ends of the robots.

@article{chen_2019,
title = {Distributed fixed-time control under directed graph using input shaping},
author = {Chen, T.; Shan, J.},
journal = {Journal of the Franklin Institute},
year = {2019},
institution = {York University, Canada},
abstract = {This paper presents novel fixed-time controllers for the distributed tracking of multi-agent systems with double-integrator dynamics based on the input shaping technique under directed graphs. It is assumed that there is no cycle in the directed graph with a globally reachable leader. Distributed fixed-time controllers are designed for cases with various initial conditions by placing input shapers in all communication edges in the graph. Numerical simulations and experimental studies are conducted to verify the effectiveness of the proposed controllers. },
keywords = {Distributed control, Fixed-time control, Input shaping, Multi-agent systems, Directed graphs},
language = {English},
publisher = {Elsevier B.V.}
}

This paper presents novel fixed-time controllers for the distributed tracking of multi-agent systems with double-integrator dynamics based on the input shaping technique under directed graphs. It is assumed that there is no cycle in the directed graph with a globally reachable leader. Distributed fixed-time controllers are designed for cases with various initial conditions by placing input shapers in all communication edges in the graph. Numerical simulations and experimental studies are conducted to verify the effectiveness of the proposed controllers.

@article{tuhta_2019,
title = {Dynamic Analysis of Model Steel Structures Retrofitted with GFRP Composites under Microtremor Vibration},
author = {Tuhta, S.; Gunday, F.; Aydin, H.},
journal = {International Journal of Trend in Scientific Research and Development},
year = {2019},
volume = {3},
number = {2},
institution = {Ondokuz Mayis University, Turkey},
abstract = {There are many varieties of the structural and architectural structures strengthened with different FRP composites are gaining popularity, and there is a growing need to understand and compare the behavior of these structures before-after GFRP composite strengthening. In this study, model steel structure was tested on the bench-scale earthquake simulator (The Quanser Shake Table) using ambient vibration, to determine the dynamic response. After this, slabs of the model steel structure was strengthened with GFRP composite, and tested on the bench-scale earthquake simulator (The Quanser Shake Table) using ambient vibration, to determine the dynamic behavior. Finally, dynamic responses of model steel structure before and after GFRP composite strengthening, such as displacements and maximum-minimum acceleration, were compared. At the end of the study, it is seen that displacements had decreased along the height of the model steel structure. Also, it is seen from the earthquake analyses that GFRP strengthening is very effective on the dynamic responses of the model steel structure. },
issn = {2456 - 6470},
keywords = {Dynamic Analysis; GFRP; Microtremor Vibration; Shake Table},
language = {English}
}

There are many varieties of the structural and architectural structures strengthened with different FRP composites are gaining popularity, and there is a growing need to understand and compare the behavior of these structures before-after GFRP composite strengthening. In this study, model steel structure was tested on the bench-scale earthquake simulator (The Quanser Shake Table) using ambient vibration, to determine the dynamic response. After this, slabs of the model steel structure was strengthened with GFRP composite, and tested on the bench-scale earthquake simulator (The Quanser Shake Table) using ambient vibration, to determine the dynamic behavior. Finally, dynamic responses of model steel structure before and after GFRP composite strengthening, such as displacements and maximum-minimum acceleration, were compared. At the end of the study, it is seen that displacements had decreased along the height of the model steel structure. Also, it is seen from the earthquake analyses that GFRP strengthening is very effective on the dynamic responses of the model steel structure.

@article{lee_2019,
title = {Enhancement of Energy-Based Swing-Up Controller via Entropy Search},
author = {Lee, C.S.; Chang, D.E.},
year = {2019},
institution = {KAIST, Korea},
abstract = {An energy based approach for stabilizing a mechanical system has offered a simple yet powerful control scheme. However, since it does not impose such strong constraints on parameter space of the controller, finding appropriate parameter values for an optimal controller is known to be hard. This paper intends to generate an optimal energy-based controller for swinging up a rotary inverted pendulum, also known as the Furuta pendulum, by applying the Bayesian optimization called Entropy Search. Simulations and experiments show that the optimal controller has an improved performance compared to a nominal controller for various initial conditions. },
language = {English}
}

An energy based approach for stabilizing a mechanical system has offered a simple yet powerful control scheme. However, since it does not impose such strong constraints on parameter space of the controller, finding appropriate parameter values for an optimal controller is known to be hard. This paper intends to generate an optimal energy-based controller for swinging up a rotary inverted pendulum, also known as the Furuta pendulum, by applying the Bayesian optimization called Entropy Search. Simulations and experiments show that the optimal controller has an improved performance compared to a nominal controller for various initial conditions.

@conference{alavi,
title = {Enhancing a Control Systems Design Course by Using Experiential Learning Model},
author = {Alavi, Z.; Meehan, K.},
booktitle = {2019 ASEE Annual Conference & Exposition},
year = {2019},
institution = {California State University, Chico},
abstract = { In this paper, authors present the outcomes of implementing an experiential learning model to explore innovative teaching pedagogy in CSU Chico EECE 482 Control Systems Design course. To reach this goal, multiple projects and demonstrations are designed to engage students of senior level Control Systems Design course in actual engineering problems to develop their practical engineering skills and to enhance students’ connection with junior level courses such as microcontroller programming. By utilizing the available resources within the College of Engineering at CSU Chico, multiple projects were developed for the Control Systems Design course. These projects benefited from existing laboratory spaces and equipment, which included a wind tunnel and a solar photovoltaic array at the Energy Systems Lab and a water flume at the Fluid and Mechanics Lab. The control systems were implemented using either the TM4C123GH6PM, the Tiva™ C Series microprocessor, which students use in the two required embedded systems courses in the curriculum, or an Arduino microcontroller. Prior to the assignment of the projects, the properties of several control algorithms were discussed during the course lectures. Hands-on demonstrations of the algorithms were performed using a Quanser QUBE Servo 2 inverted pendulum. To continue this learning, students were asked to form small teams and to select a project from a list provided by the course instructor. Examples of three projects will be described in this paper. In the first project, a controller was designed to optimize the performance of the wind turbine by maximizing the power delivered to the wind turbine load. The second project was an optimization of performance of a motorized solar photovoltaic panel where students designed a sun tracker, a proportional-integral-derivative (PID) controller to maximize the power generated by the solar panel by adjusting the angle of the panel with respect to the solar irradiance. The third project was a control system to fix the lateral position of a boat in the water flume while it was navigating along the flume to prevent contacts with the walls. Finally, a discussion on how the set of demonstrations and the design projects boosted students’ interest in the Control Systems Design course. An assessment has been conducted to evaluate the impact of the demonstrations, labs and project on the student learning outcomes and the depth of their understanding of key concepts in comparison to that obtained in the previous semesters. The assessment results show that the inclusion of the demonstrations, labs and design projects in the course resulted in increased mastery of control theory concepts through the visualization and hands-on experience and that students were better able to relate theory to practice. },
language = {English},
publisher = {ASEE}
}

In this paper, authors present the outcomes of implementing an experiential learning model to explore innovative teaching pedagogy in CSU Chico EECE 482 Control Systems Design course. To reach this goal, multiple projects and demonstrations are designed to engage students of senior level Control Systems Design course in actual engineering problems to develop their practical engineering skills and to enhance students’ connection with junior level courses such as microcontroller programming. By utilizing the available resources within the College of Engineering at CSU Chico, multiple projects were developed for the Control Systems Design course. These projects benefited from existing laboratory spaces and equipment, which included a wind tunnel and a solar photovoltaic array at the Energy Systems Lab and a water flume at the Fluid and Mechanics Lab. The control systems were implemented using either the TM4C123GH6PM, the Tiva™ C Series microprocessor, which students use in the two required embedded systems courses in the curriculum, or an Arduino microcontroller.

Prior to the assignment of the projects, the properties of several control algorithms were discussed during the course lectures. Hands-on demonstrations of the algorithms were performed using a Quanser QUBE Servo 2 inverted pendulum. To continue this learning, students were asked to form small teams and to select a project from a list provided by the course instructor. Examples of three projects will be described in this paper. In the first project, a controller was designed to optimize the performance of the wind turbine by maximizing the power delivered to the wind turbine load. The second project was an optimization of performance of a motorized solar photovoltaic panel where students designed a sun tracker, a proportional-integral-derivative (PID) controller to maximize the power generated by the solar panel by adjusting the angle of the panel with respect to the solar irradiance. The third project was a control system to fix the lateral position of a boat in the water flume while it was navigating along the flume to prevent contacts with the walls. Finally, a discussion on how the set of demonstrations and the design projects boosted students’ interest in the Control Systems Design course. An assessment has been conducted to evaluate the impact of the demonstrations, labs and project on the student learning outcomes and the depth of their understanding of key concepts in comparison to that obtained in the previous semesters. The assessment results show that the inclusion of the demonstrations, labs and design projects in the course resulted in increased mastery of control theory concepts through the visualization and hands-on experience and that students were better able to relate theory to practice.

@article{schleer_2019,
title = {Evaluation of Different Modes of Haptic Guidance for Robotic Surgery},
author = {Schleer, P.; Drobinsky, S.; Radermacher, K.},
journal = {IFAC-PapersOnLine},
year = {2019},
volume = {51},
number = {34},
institution = {RWTH Aachen University, Germany},
abstract = {The evolution of surgery has resulted in a plethora of systems varying in their application field, size, as well as degree of autonomy. Especially systems which combine principles of so-called synergistic robotic systems and master-slave-telemanipulators are interesting concerning cooperative aspects of surgeon and robotic system. While the former provide haptic guidance information (“virtual fixtures”), the latter provide haptic feedback from position or force sensor information of the slave device. During the design of these combined systems particular attention has to be paid during the allocation of information to the haptic information channel as superimposing of haptic guidance information and haptic sensor feedback can lead to concealment of essential feedback information. This paper reports on an experimental usability evaluation of different haptic guidance modes varying in their degree of autonomy as well as degree of freedom (DOF) with respect to three surgical scenarios, namely reaching a predefined position and orientation, tracking a predefined 3D trajectory, and applying a defined force (such as during e.g. a 3D-bone milling task). The goal was to evaluate whether some DOF of haptic guidance information can be left free for force sensor information feedback. General findings indicate that haptic guidance does not have to be augmented on three DOF to improve usability. Therefore, a combination of haptic sensor information feedback and haptic guidance information divided between individual DOF seems to be a potential solution. },
keywords = {Robotics, Telerobotics, Telemanipulation, Robotic manipulators, Robotic surgery, Robot navigation, Trajectories, Shared Control, Guidance systems, Haptics},
language = {English},
publisher = {Elsevier Ltd.}
}

The evolution of surgery has resulted in a plethora of systems varying in their application field, size, as well as degree of autonomy. Especially systems which combine principles of so-called synergistic robotic systems and master-slave-telemanipulators are interesting concerning cooperative aspects of surgeon and robotic system. While the former provide haptic guidance information (“virtual fixtures”), the latter provide haptic feedback from position or force sensor information of the slave device. During the design of these combined systems particular attention has to be paid during the allocation of information to the haptic information channel as superimposing of haptic guidance information and haptic sensor feedback can lead to concealment of essential feedback information. This paper reports on an experimental usability evaluation of different haptic guidance modes varying in their degree of autonomy as well as degree of freedom (DOF) with respect to three surgical scenarios, namely reaching a predefined position and orientation, tracking a predefined 3D trajectory, and applying a defined force (such as during e.g. a 3D-bone milling task). The goal was to evaluate whether some DOF of haptic guidance information can be left free for force sensor information feedback. General findings indicate that haptic guidance does not have to be augmented on three DOF to improve usability. Therefore, a combination of haptic sensor information feedback and haptic guidance information divided between individual DOF seems to be a potential solution.

@article{muniraj_2019,
title = {Evaluation of various benchmark processes with appropriate controller design in LabVIEW platform},
author = {Muniraj, R.; Sivapalanirajan, M.; Jarinb, T.; Boselin Prabhu, S.R.},
journal = {Journal of Instrumentation},
year = {2019},
month = {05},
volume = {14},
institution = {National Engineering College, India; Jyothi Engineering College, India; Surya Engineering College, India},
abstract = {Engineering education needs simulation studies and it is the best way of understanding engineering concepts with minimal cost and energy. The main focus of this present work is to provide a workspace especially in LabVIEW for analyzing the performance of the system and to operate them in stable and controlled regions. LabVIEW is a simulation platform which facilitates the simulation of various systems and their response with various controllers programmed using functional blocks that are easy to understand. In this work, the benchmark test systems like DC series motor as first order system, general second order system and a Real time rotary Inverted Pendulum (RIP) model which has been reduced with high order system reduction technique are considered. The test systems are controlled with PID controller tuned by various tuning methods. The PID controller is tuned with conventional methods like Ziegler-Nichols (ZN), Internal Model Control (IMC), and Direct Synthesis (DS) and the responses of the systems are analysed in LabVIEW platform. The common platform has been developed and tested for supporting the performance and analysis of the system with adjustable PID controller parameters like proportional gain Kp, integral time constant Ti, and derivative time constant Td. The performance specifications are phase margin, gain margin, bandwidth, settling time, rise time and integral errors. This LabVIEW platform facilitates the learners to analyze the system effectively with various controllers and their performance parameters are compared easily. },
keywords = {Control systems; Overall mechanics design (support structures and materials, vibration analysis etc); Voltage distributions},
language = {English},
publisher = {IOP Publishing}
}

Engineering education needs simulation studies and it is the best way of understanding engineering concepts with minimal cost and energy. The main focus of this present work is to provide a workspace especially in LabVIEW for analyzing the performance of the system and to operate them in stable and controlled regions. LabVIEW is a simulation platform which facilitates the simulation of various systems and their response with various controllers programmed using functional blocks that are easy to understand. In this work, the benchmark test systems like DC series motor as first order system, general second order system and a Real time rotary Inverted Pendulum (RIP) model which has been reduced with high order system reduction technique are considered. The test systems are controlled with PID controller tuned by various tuning methods. The PID controller is tuned with conventional methods like Ziegler-Nichols (ZN), Internal Model Control (IMC), and Direct Synthesis (DS) and the responses of the systems are analysed in LabVIEW platform. The common platform has been developed and tested for supporting the performance and analysis of the system with adjustable PID controller parameters like proportional gain Kp, integral time constant Ti, and derivative time constant Td. The performance specifications are phase margin, gain margin, bandwidth, settling time, rise time and integral errors. This LabVIEW platform facilitates the learners to analyze the system effectively with various controllers and their performance parameters are compared easily.