@article{tran_2109,
title = {Digital Implementation of Homomorphically Encrypted Feedback Control for Cyber-Physical Systems},
author = {Tran, J.; Farokhi, F.; Cantoni, M.; Shames, I.},
year = {2109},
institution = {University of Melbourne, Australia},
abstract = {This paper is about an encryption based approach to the secure implementation of feedback controllers for cyberphysical systems. Specifically, Paillier’s homomorphic encryption is used in a custom digital implementation of a class of linear dynamic controllers, including static gain as a special case. The implementation is amenable to Field Programmable Gate Array (FPGA) realization. Experimental results, including timing analysis and resource usage characteristics for different encryption key lengths, are presented for the realization of a controller for an inverted pendulum; as this is an unstable plant, the control is necessarily fast. },
language = {English}
}

This paper is about an encryption based approach to the secure implementation of feedback controllers for cyberphysical systems. Specifically, Paillier’s homomorphic encryption is used in a custom digital implementation of a class of linear dynamic controllers, including static gain as a special case. The implementation is amenable to Field Programmable Gate Array (FPGA) realization. Experimental results, including timing analysis and resource usage characteristics for different encryption key lengths, are presented for the realization of a controller for an inverted pendulum; as this is an unstable plant, the control is necessarily fast.

@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{kamal_2020,
title = {A New Class of Uniform Continuous Higher Order Sliding Mode Controllers},
author = {Kamal, S.; Ramesh Kumar, P.; Chalanga, A.; Kumar Goyal, J.; Bandyopadhyay, B.; Fridman, L.},
journal = {Journal of Dynamic Systems, Measurement, and Control},
year = {2020},
month = {01},
volume = {142},
number = {1},
institution = {Indian Institute of Technology (BHU) Varanasi, India; Government Engineering College Thrissur, India; University College London, UK; IIT Bombay, India; Universidad Nacional Aut ´onoma de M´exico (UNAM), Mexico },
abstract = {This paper proposes a new class of uniform continuous higher-order sliding mode algorithm (UCHOSMA) for the arbitrary relative degree systems. The proposed methodology is a combination of two controllers where one of the components is a uniform super-twisting control which acts as the disturbance compensator and the second part gives the uniform finite time convergence for the disturbance free system. This algorithm provides uniform finite time convergence of the output and its higher derivatives using an absolutely continuous control signal and thus alleviating the chattering phenomenon. The attractive feature of the proposed controller is that irrespective of the different initial conditions, the control is able to bring the states of the system to the equilibrium point uniformly in finite time. The effectiveness of the proposed controller has been demonstrated with both simulation and experimental results. },
language = {English},
publisher = {ASME}
}

This paper proposes a new class of uniform continuous higher-order sliding mode algorithm (UCHOSMA) for the arbitrary relative degree systems. The proposed methodology is a combination of two controllers where one of the components is a uniform super-twisting control which acts as the disturbance compensator and the second part gives the uniform finite time convergence for the disturbance free system. This algorithm provides uniform finite time convergence of the output and its higher derivatives using an absolutely continuous control signal and thus alleviating the chattering phenomenon. The attractive feature of the proposed controller is that irrespective of the different initial conditions, the control is able to bring the states of the system to the equilibrium point uniformly in finite time. The effectiveness of the proposed controller has been demonstrated with both simulation and experimental results.

@article{guo_2020,
title = {Composite learning control of robotic systems: A least squares modulated approach},
author = {Guo, K.; Pan, Y.; Zheng, D.; Yu, H.},
journal = {Automatica},
year = {2020},
month = {01},
volume = {111},
institution = {Shandong University, China; Sun Yat-sen University, China; National University of Singapore, Singapore},
abstract = {Most current studies of adaptive robot control concentrate on parameter convergence in the steady state, while parameter convergence rates are rarely investigated. This paper proposes a least-squares modulated composite learning robot control based on Moore–Penrose pseudoinverse to improve the performance of parameter convergence. In the composite learning, a prediction error is constructed based on online historical data and regressor extension, and both the prediction and tracking errors are applied to update parameter estimates such that accurate and smooth parameter estimation is obtained under a weak excitation condition termed interval excitation (IE). The distinctive features of the proposed method include: (1) Asymptotic stability of the closed-loop system is proven without the IE condition; (2) exponential stability is proven and balanced and easily tunable rates of parameter convergence are achieved under the IE condition, where the rates are independent of unpredictable excitation levels in different regressor channels. These two features are generally not achievable with the existing adaptive robot control methods. Experimental results on an industrial manipulator have demonstrated the effectiveness and superiority of the proposed approach. },
keywords = {Adaptive control, Composite learning, Least squares, Moore–Penrose pseudoinverse, Robot manipulators},
language = {English},
publisher = {Elsevier Ltd.}
}

Most current studies of adaptive robot control concentrate on parameter convergence in the steady state, while parameter convergence rates are rarely investigated. This paper proposes a least-squares modulated composite learning robot control based on Moore–Penrose pseudoinverse to improve the performance of parameter convergence. In the composite learning, a prediction error is constructed based on online historical data and regressor extension, and both the prediction and tracking errors are applied to update parameter estimates such that accurate and smooth parameter estimation is obtained under a weak excitation condition termed interval excitation (IE). The distinctive features of the proposed method include: (1) Asymptotic stability of the closed-loop system is proven without the IE condition; (2) exponential stability is proven and balanced and easily tunable rates of parameter convergence are achieved under the IE condition, where the rates are independent of unpredictable excitation levels in different regressor channels. These two features are generally not achievable with the existing adaptive robot control methods. Experimental results on an industrial manipulator have demonstrated the effectiveness and superiority of the proposed approach.

@inbook{taskin_2020,
title = {Robust and Intelligent Control Techniques for Twin Rotor System},
author = {Taskin, Y.; Hacioglu, Y.},
booktitle = {Handbook of Research on Advanced Mechatronic Systems and Intelligent Robotics},
year = {2020},
institution = {Istanbul University, Turkey},
abstract = {During recent decades, popularity of unmanned aerial vehicles has increased throughout academics, engineers, as well as students because of their wide range of application areas such as inspection, communication, and transportation. The twin rotor system represents the nonlinear and coupled dynamics of a helicopter to a certain extent. Therefore, it provides a good test bed for engineering students’ education on dynamics of aerial vehicles and control of mechatronic systems. In this study, sliding mode and fuzzy logic controllers are designed to control hovering motion of this highly nonlinear system. A robust sliding mode controller is preferred since it is insensitive to external disturbances, and intelligent fuzzy logic control is preferred since it is applicable to nonlinear systems where exact model of the system is not needed. Designed controllers, which are robust and intelligent, are then applied to the twin rotor system in real time. Then, experimental results are presented and discussed in terms of control performances of the designed controllers in detail. },
language = {English},
pages = {401-420}
}

During recent decades, popularity of unmanned aerial vehicles has increased throughout academics,
engineers, as well as students because of their wide range of application areas such as inspection, communication,
and transportation. The twin rotor system represents the nonlinear and coupled dynamics of
a helicopter to a certain extent. Therefore, it provides a good test bed for engineering students’ education
on dynamics of aerial vehicles and control of mechatronic systems. In this study, sliding mode and fuzzy
logic controllers are designed to control hovering motion of this highly nonlinear system. A robust sliding
mode controller is preferred since it is insensitive to external disturbances, and intelligent fuzzy logic
control is preferred since it is applicable to nonlinear systems where exact model of the system is not
needed. Designed controllers, which are robust and intelligent, are then applied to the twin rotor system
in real time. Then, experimental results are presented and discussed in terms of control performances
of the designed controllers in detail.

@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{zakerimanesh2_2019,
title = {A cooperative paradigm for task-space control of multilateral nonlinear teleoperation with bounded inputs and time-varying delays},
author = {Zakerimanesh, A.; Hashemzadeh, F.; Torabi, A.; Tavakoli, M.},
journal = {Mechatronics},
year = {2019},
month = {10},
volume = {62},
institution = {University of Tabriz, Iran; University of Alberta, Canada},
abstract = {In this article, a novel multilateral teleoperation structure is presented for cooperative control of a redundant remote robot in the task-space. In the structure, each local robot is assigned a real number between zero and one, as its dominance factor. The sum of all the assigned factors is equal to one, and a greater dominance factor implies that its corresponding operator will have more power in controlling the remote robot. The time-varying delays in the communication channels, the actuators saturation, and the nonlinear dynamics are incorporated into the controller development. Using Barbalat’s lemma and a Lyapunov-Krasovskii functional, the asymptotic stability analysis of the closed-loop dynamics are shown, and the performance claims are delivered. Simulation and experimental results are provided to verify the theoretical findings. },
keywords = {Cooperative control, Multilateral teleoperation, Saturation control, Task-space synchronization, Time-varying delay},
language = {English},
publisher = {Elsevier Ltd.}
}

In this article, a novel multilateral teleoperation structure is presented for cooperative control of a redundant remote robot in the task-space. In the structure, each local robot is assigned a real number between zero and one, as its dominance factor. The sum of all the assigned factors is equal to one, and a greater dominance factor implies that its corresponding operator will have more power in controlling the remote robot. The time-varying delays in the communication channels, the actuators saturation, and the nonlinear dynamics are incorporated into the controller development. Using Barbalat’s lemma and a Lyapunov-Krasovskii functional, the asymptotic stability analysis of the closed-loop dynamics are shown, and the performance claims are delivered. Simulation and experimental results are provided to verify the theoretical findings.

@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.

@article{alli_2019,
title = {A LabVIEW-based online DC servomechanism control experiments incorporating PID controller for students’ laboratory},
author = {Alli, K.S.},
journal = {The International Journal of Electrical Engineering & Education},
year = {2019},
institution = {The University of the West Indies, Jamaica},
abstract = {This research designed a DC motor control system experiments and developed a platform for on-line implementation of these experiments. This was with a view to contributing to the number of online laboratory experiments while providing a common platform for other on-line users. In this research, three experiments were designed using LabVIEW software. The developed platform is implemented online using the Massachusetts Institute of Technology interactive laboratory architecture. The control system performance was then evaluated by administering questionnaires to users with the aim of eliciting information on the ease of use of the operating system. The successful control of the DC motor and integration of the experiment engines into the iLab Interactive architecture were achieved. In conclusion, the online DC motor control laboratory was deployed and provided ready access to a DC motor control over the Internet with beginner and intermediate-level experiments in the field of control system and engineering. },
keywords = {LabVIEW, i-Lab, PID controller},
language = {English},
publisher = {SAGE}
}

This research designed a DC motor control system experiments and developed a platform for on-line implementation of these experiments. This was with a view to contributing to the number of online laboratory experiments while providing a common platform for other on-line users. In this research, three experiments were designed using LabVIEW software. The developed platform is implemented online using the Massachusetts Institute of Technology interactive laboratory architecture. The control system performance was then evaluated by administering questionnaires to users with the aim of eliciting information on the ease of use of the operating system. The successful control of the DC motor and integration of the experiment engines into the iLab Interactive architecture were achieved. In conclusion, the online DC motor control laboratory was deployed and provided ready access to a DC motor control over the Internet with beginner and intermediate-level experiments in the field of control system and engineering.

@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{cheng_2019,
title = {A multilateral impedance-controlled system for haptics-enabled surgical training and cooperation in beating-heart surgery},
author = {Cheng, L.; Tavakoli, M.},
journal = {International Journal of Intelligent Robotics and Applications},
year = {2019},
institution = {University of Alberta, Canada},
abstract = {In this paper, an impedance-controlled multi-master/single-slave telerobotic system is developed for haptics-enabled surgical training and cooperation in beating-heart surgery. This system not only can enable automatically motion compensation for the beating heart’s motion as well as non-oscillatory force feedback to the human operators but can also enable training and cooperation for multiple users. A multi-user shared control architecture is developed, and a multilateral impedance-controlled strategy is employed for this architecture. The desired objectives of the proposed system are (a) providing position guidance to the trainees during training procedure, (b) providing force feedback to all human operators (trainer and trainees) regardless of their levels of authority over the slave robot, (c) motion compensation for the heart’s motion, and (d) reflecting only the non-oscillatory force portion of the slave-heart tissue interaction force to all human operators. To this end, virtual fixtures and a dominance factor are introduced, and a reference impedance model with adjusted parameters is designed for each master or slave robot. The proposed impedance-based control methodology is evaluated experimentally. The experimental results demonstrated that the proposed method could be used for surgical training and cooperation in beating-heart surgery by providing appropriate position guidance and environmental force feedback to the human operators. },
issn = {2366-5971},
keywords = {Motion compensation, Haptic feedback, Impedance model, Teleoperation system, Medical robots },
language = {English},
publisher = {Springer, Singapore}
}

In this paper, an impedance-controlled multi-master/single-slave telerobotic system is developed for haptics-enabled surgical training and cooperation in beating-heart surgery. This system not only can enable automatically motion compensation for the beating heart’s motion as well as non-oscillatory force feedback to the human operators but can also enable training and cooperation for multiple users. A multi-user shared control architecture is developed, and a multilateral impedance-controlled strategy is employed for this architecture. The desired objectives of the proposed system are (a) providing position guidance to the trainees during training procedure, (b) providing force feedback to all human operators (trainer and trainees) regardless of their levels of authority over the slave robot, (c) motion compensation for the heart’s motion, and (d) reflecting only the non-oscillatory force portion of the slave-heart tissue interaction force to all human operators. To this end, virtual fixtures and a dominance factor are introduced, and a reference impedance model with adjusted parameters is designed for each master or slave robot. The proposed impedance-based control methodology is evaluated experimentally. The experimental results demonstrated that the proposed method could be used for surgical training and cooperation in beating-heart surgery by providing appropriate position guidance and environmental force feedback to the human operators.

@article{sajjadi_2019,
title = {A Nonlinear Adaptive Model-Predictive Approach for Visual Servoing of Unmanned Aerial Vehicles},
author = {Sajjadi, S.; Mehrandezh, M.; Janabi-Sharifi, F.},
booktitle = {Progress in Optomechatronic Technologies},
year = {2019},
institution = {University of Regina, Canada; Ryerson University, Canada},
abstract = {Aerial vehicles, due to the nature of their operations, are subject to many uncertainties. In particular, their positioning control problem is aggravated in GPS-denied environments. As a result, vision-based control (or visual servoing) solutions are sought to address their navigation control issue. In this work, visual servoing is formulated as a nonlinear optimization problem in the image plane. The proposed approach is based on a class of nonlinear model-predictive control that takes constraints into consideration. A 2-DOF model helicopter is considered for initial formulations and verification of the approach. The considered model helicopter has a coupled nonlinear pitch/yaw dynamics. It is also capable of a pitch over (i.e., hover at a non-zero pitch angle) around its pivotal axis of rotation due to the offset between the center of mass (CoM) of its fuselage and the rotation axis. This further makes the linearized model (calculated around any pitch angle). A linear parameter varying (LPV) system for an adaptive control is formulated under a model-predictive visual servoing framework. In this paper, a design guideline is provided under a model-predictive visual servoing paradigm that considers field of view (FOV) constraints, the constraint on the pitch angle, and also the maximum voltages that can be applied to independently controlled pitch/yaw motors. The control space is parameterized via Laguerre basis network functions that make the optimization scheme computationally less expensive, thus suitable for real-time applications. },
language = {English},
series = {Springer Proceedings in Physics},
publisher = {Springer, Singapore},
isbn = {978-981-32-9631-2},
pages = {153-164}
}

Aerial vehicles, due to the nature of their operations, are subject to many uncertainties. In particular, their positioning control problem is aggravated in GPS-denied environments. As a result, vision-based control (or visual servoing) solutions are sought to address their navigation control issue. In this work, visual servoing is formulated as a nonlinear optimization problem in the image plane. The proposed approach is based on a class of nonlinear model-predictive control that takes constraints into consideration. A 2-DOF model helicopter is considered for initial formulations and verification of the approach. The considered model helicopter has a coupled nonlinear pitch/yaw dynamics. It is also capable of a pitch over (i.e., hover at a non-zero pitch angle) around its pivotal axis of rotation due to the offset between the center of mass (CoM) of its fuselage and the rotation axis. This further makes the linearized model (calculated around any pitch angle). A linear parameter varying (LPV) system for an adaptive control is formulated under a model-predictive visual servoing framework. In this paper, a design guideline is provided under a model-predictive visual servoing paradigm that considers field of view (FOV) constraints, the constraint on the pitch angle, and also the maximum voltages that can be applied to independently controlled pitch/yaw motors. The control space is parameterized via Laguerre basis network functions that make the optimization scheme computationally less expensive, thus suitable for real-time applications.

@article{butt_2019,
title = {A Nonlinear Integral Sliding Surface to Improve the Transient Response of a Force-Controlled Pneumatic Actuator With Long Transmission Lines},
author = {Butt, K.; Sepehri, N.},
journal = {Journal of Dynamic Systems, Measurement, and Control},
year = {2019},
month = {12},
volume = {141},
number = {12},
institution = {University of Manitoba, Canada},
abstract = {A force-controlled pneumatic actuator with long connecting tubes is a well-accepted solution to develop magnetic resonance imaging (MRI)-compatible force control applications. Such an actuator represents an uncertain, second-order, nonlinear system with input delay. The integral sliding mode control, because of guaranteed robustness against matched uncertainties throughout the system response, provides a favorable option to design a robust controller for the actuator. However, if the controller is based on a linear integral sliding surface (LISS), the response of the actuator overshoots, especially when there are large initial errors. Minimizing overshoot results in a smaller controller bandwidth and a slower system response. This paper presents a novel nonlinear integral sliding surface (NLISS) for a sliding mode controller to improve the transient response of the actuator. The proposed surface is a LISS augmented by a nonlinear function of tracking error and does not have a reaching phase when there are initial errors and even multiple steps in the desired trajectory. The surface enables the integral sliding mode controller to offer variable damping, which changes from low to high as the transient error approaches small values and vice versa. Simulation studies and experimental results show that the controller based on the proposed sliding surface successfully eliminates the overshoot without compromising the controller bandwidth, rise, and settling times. For performance evaluation, the controller parameters are tuned using the globalized and bounded Nelder–Mead (GBNM) algorithm with deterministic restarts. The study also establishes the asymptotic stability of the controller based on the proposed sliding surface using Lyapunov's stability criterion. },
keywords = {force control, pneumatic actuator, input delay, integral sliding mode control, nonlinear integral sliding surface},
language = {English},
publisher = {ASME}
}

A force-controlled pneumatic actuator with long connecting tubes is a well-accepted solution to develop magnetic resonance imaging (MRI)-compatible force control applications. Such an actuator represents an uncertain, second-order, nonlinear system with input delay. The integral sliding mode control, because of guaranteed robustness against matched uncertainties throughout the system response, provides a favorable option to design a robust controller for the actuator. However, if the controller is based on a linear integral sliding surface (LISS), the response of the actuator overshoots, especially when there are large initial errors. Minimizing overshoot results in a smaller controller bandwidth and a slower system response. This paper presents a novel nonlinear integral sliding surface (NLISS) for a sliding mode controller to improve the transient response of the actuator. The proposed surface is a LISS augmented by a nonlinear function of tracking error and does not have a reaching phase when there are initial errors and even multiple steps in the desired trajectory. The surface enables the integral sliding mode controller to offer variable damping, which changes from low to high as the transient error approaches small values and vice versa. Simulation studies and experimental results show that the controller based on the proposed sliding surface successfully eliminates the overshoot without compromising the controller bandwidth, rise, and settling times. For performance evaluation, the controller parameters are tuned using the globalized and bounded Nelder–Mead (GBNM) algorithm with deterministic restarts. The study also establishes the asymptotic stability of the controller based on the proposed sliding surface using Lyapunov's stability criterion.

@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.

@conference{erwin_2019,
title = {A Robotic Platform for 3D Forelimb Rehabilitation with Rats},
author = {Erwin, A.; Gallegos, C.; Cao, Q.; O’Malley, M.K. },
booktitle = {2019 IEEE 16th International Conference on Rehabilitation Robotics (ICORR)},
year = {2019},
institution = {Universities Space Research Association, USA; The University of Texas Health Science Center, USA; Rice University, USA},
abstract = { In an attempt to promote greater functional recovery after spinal cord injury, researchers have begun exploring combinatorial treatments, such as robotic rehabilitation combined with stem cell transplantation. Since these treatment methods are in their nascent stages, rodent models have been proposed for initial investigations. Robots have been built for locomotion rehabilitation and planar forelimb reach and grasp assessment with rodents; however, a robotic platform suitable for three-dimensional movement rehabilitation of the rodent forelimb has not yet been developed. In this paper, a novel three degree of freedom robotic manipulator for automated forelimb rehabilitation combined with stem cell transplantation after cervical spinal cord injury with rats is proposed. The robot interfaces with a rat in an end-effector manner, measuring and interacting with the forelimb in the 3D Cartesian space. In this work, we trained two rats through behavioral shaping to actively interact with the device during two robot control modes. This work provides preliminary investigations into the feasibility of 3D forelimb rehabilitation with rats, which could be translated as a paradigm for combinatorial treatments after spinal cord injury in a controlled manner. },
issn = {1945-7898},
keywords = {Rats, Training, Wrist, Three-dimensional displays, End effectors, Robot kinematics},
language = {English},
publisher = {IEEE},
isbn = {978-1-7281-2756-9 }
}

In an attempt to promote greater functional recovery after spinal cord injury, researchers have begun exploring combinatorial treatments, such as robotic rehabilitation combined with stem cell transplantation. Since these treatment methods are in their nascent stages, rodent models have been proposed for initial investigations. Robots have been built for locomotion rehabilitation and planar forelimb reach and grasp assessment with rodents; however, a robotic platform suitable for three-dimensional movement rehabilitation of the rodent forelimb has not yet been developed. In this paper, a novel three degree of freedom robotic manipulator for automated forelimb rehabilitation combined with stem cell transplantation after cervical spinal cord injury with rats is proposed. The robot interfaces with a rat in an end-effector manner, measuring and interacting with the forelimb in the 3D Cartesian space. In this work, we trained two rats through behavioral shaping to actively interact with the device during two robot control modes. This work provides preliminary investigations into the feasibility of 3D forelimb rehabilitation with rats, which could be translated as a paradigm for combinatorial treatments after spinal cord injury in a controlled manner.

@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.

@conference{kutuk_2019,
title = {A Simulation Tool for Kinematics Analysis of a Serial Robot},
author = {Kutuk, M.E.; Dulger, L.C.; Das, M.T.},
booktitle = {DSMIE 2019: Advances in Design, Simulation and Manufacturing },
year = {2019},
institution = {Gaziantep University, Turkey; Izmir University of Economics, Turkey; Kirrikale University, Turkey},
abstract = {Robot programming is a very significant task in the field of robotics. Off-line programming (OLP) is a method performed before robot manipulation. It is the manual editing of the robot code using computer software to simulate the real robotic scenarios. Task sequence planning, short-term production, flexibility during operation and expecting real behaviour of the robots are some of the reasons that make the users prefer OLP. Operations can be visualized in many processes such as welding, cutting, even medical applications. In this study, off-line models are offered including the forward and inverse kinematics of a six Degree-Of-Freedom (DOF) serial robot manipulator (Denso VP-6242G). Robotic Toolbox combined with GUI Development Environment in Matlab® is used for the forward kinematics solution. A Matlab® Simulink model with Simmechanics blocks is used in the inverse kinematic analysis. Visualization is enriched by 3D Solidworks® models of the robot parts. Basic motion examples that can be used in many areas are presented. },
keywords = {Off-line programming (OLP), Denso VP-6242G, Forward and inverse kinematics, Robotic toolbox },
language = {English},
publisher = {Springe, Cham},
isbn = {978-3-030-22364-9}
}

Robot programming is a very significant task in the field of robotics. Off-line programming (OLP) is a method performed before robot manipulation. It is the manual editing of the robot code using computer software to simulate the real robotic scenarios. Task sequence planning, short-term production, flexibility during operation and expecting real behaviour of the robots are some of the reasons that make the users prefer OLP. Operations can be visualized in many processes such as welding, cutting, even medical applications. In this study, off-line models are offered including the forward and inverse kinematics of a six Degree-Of-Freedom (DOF) serial robot manipulator (Denso VP-6242G). Robotic Toolbox combined with GUI Development Environment in Matlab® is used for the forward kinematics solution. A Matlab® Simulink model with Simmechanics blocks is used in the inverse kinematic analysis. Visualization is enriched by 3D Solidworks® models of the robot parts. Basic motion examples that can be used in many areas are presented.

@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.

@article{rodriguez-cortes_2019,
title = {A swinging up controller for the Furuta pendulum based on the Total Energy Control System approach},
author = {Rodriguez-Cortes, H.},
journal = {Kybernetika},
year = {2019},
volume = {55},
number = {2},
institution = {CINVESTAV-IPN, Mexico},
abstract = {This paper considers the problem of swinging up the Furuta pendulum and proposes a new smooth nonlinear swing up controller based on the concept of energy. This new controller results from the Total Energy Control System (TECS) approach in conjunction with a linearizing feedback controller. The new controller commands to the desired reference the total energy rate of the Furuta pendulum; thus, the Furuta pendulum oscillates and reaches a neighborhood of its unstable configuration while the rotation of its base remains bounded. Once the Furuta pendulum configuration is in the neighborhood of its unstable equilibrium point, a linear controller stabilizes the unstable configuration of the Furuta pendulum. Real-time experiments are included to support the theoretical developments. },
keywords = {total energy control system, Furuta pendulum, swinging up control, real-time experiments},
language = {English},
publisher = {Institute of Information Theory and Automation AS CR},
pages = {402-421}
}

This paper considers the problem of swinging up the Furuta pendulum and proposes a new smooth nonlinear swing up controller based on the concept of energy. This new controller results from the Total Energy Control System (TECS) approach in conjunction with a linearizing feedback controller. The new controller commands to the desired reference the total energy rate of the Furuta pendulum; thus, the Furuta pendulum oscillates and reaches a neighborhood of its unstable configuration while the rotation of its base remains bounded. Once the Furuta pendulum configuration is in the neighborhood of its unstable equilibrium point, a linear controller
stabilizes the unstable configuration of the Furuta pendulum. Real-time experiments are included to support the theoretical developments.

@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. },
issn = {2373-6720},
language = {English},
publisher = {IEEE},
isbn = {978-1-7281-0334-1},
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{boby_2019,
title = {Adaptive control of nonlinear system based on QFT application to 3-DOF flight control system},
author = {Boby, R.I.; Abdullah, K.; Jusoh, A.Z.; Parveen, N.; Mahmud, M.},
journal = {Telekomnika},
year = {2019},
month = {10},
volume = {17},
number = {5},
institution = {International Islamic University Malaysia},
abstract = {Research on unmanned aerial vehicle (UAV) became popular because of remote flight access and cost-effective solution. 3-degree of freedom (3-DOF) unmanned helicopters is one of the popular research UAV, because of its high load carrying capacity with a smaller number of motor and requirement of forethought motor control dynamics. Various control algorithms are investigated and designed for the motion control of the 3DOF helicopter. Three-degree-of-freedom helicopter model configuration presents the same advantages of 3-DOF helicopters along with increased payload capacity, increase stability in hover, manoeuvrability and reduced mechanical complexity. Numerous research institutes have chosen the three-degree-of-freedom as an ideal platform to develop intelligent controllers. In this research paper, we discussed about a hybrid controller that combined with Adaptive and Quantitative Feedback theory (QFT) controller for the 3-DOF helicopter model. Though research on Adaptive and QFT controller are not a new subject, the first successful single Adaptive aircraft flight control systems have been designed for the U.S. Air Force in Wright Laboratories unmanned research vehicle, Lambda [1]. Previously researcher focused on structured uncertainties associated with controller for the flight conditions theoretically. The development of simulation based design on flight control system response, opened a new dimension for researcher to design physical flight controller for plant parameter uncertainties. At the beginning, our research was to investigates the possibility of developing the QFT combined with Adaptive controller to control a single pitch angle that meets flying quality conditions of automatic flight control. Finally, we successfully designed the hybrid controller that is QFT based adaptive controller for all the three angles. },
issn = {1693-6930},
keywords = {3-degree of freedom (3-DOF), adaptive controller, hybride controller, quantitative feedback theory (QFT), UAV},
language = {English}
}

Research on unmanned aerial vehicle (UAV) became popular because of remote flight access and cost-effective solution. 3-degree of freedom (3-DOF) unmanned helicopters is one of the popular research UAV, because of its high load carrying capacity with a smaller number of motor and requirement of forethought motor control dynamics. Various control algorithms are investigated and designed for the motion control of the 3DOF helicopter. Three-degree-of-freedom helicopter model configuration presents the same advantages of 3-DOF helicopters along with increased payload capacity, increase stability in hover, manoeuvrability and reduced mechanical complexity. Numerous research institutes have chosen the three-degree-of-freedom as an ideal platform to develop intelligent controllers. In this research paper, we discussed about a hybrid controller that combined with Adaptive and Quantitative Feedback theory (QFT) controller for the 3-DOF helicopter model. Though research on Adaptive and QFT controller are not a new subject, the first successful single Adaptive aircraft flight control systems have been designed for the U.S. Air Force in Wright Laboratories unmanned research vehicle, Lambda [1]. Previously researcher focused on structured uncertainties associated with controller for the flight conditions theoretically. The development of simulation based design on flight control system response, opened a new dimension for researcher to design physical flight controller for plant parameter uncertainties. At the beginning, our research was to investigates the possibility of developing the QFT combined with Adaptive controller to control a single pitch angle that meets flying quality conditions of automatic flight control. Finally, we successfully designed the hybrid controller that is QFT based adaptive controller for all the three angles.

@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_2019,
title = {Adaptive phase compensator for vibration suppression of structures with parameter perturbation},
author = {Niu, W.; Li, B.},
journal = {Aerospace Science and Technology},
year = {2019},
institution = {Northwestern Polytechnical University, China},
abstract = {The constant all-pass filter has been widely used for phase compensation of control systems. However, it is not applicable to compensating phase deviation caused by additional filters to enhance the signal quality in vibration control systems with parameter perturbation. To overcome this challenge, an adaptive phase compensator (APC) is developed by transforming the constant parameters of an all-pass filter into frequency-dependent parameters. In addition, the sources of phase deviations in the control system are analyzed to design the APC, including the additional filters, non-collocated actuator/sensor configuration, and hardware hysteresis. The phase deviations are determined through simulation and experiment. Polynomial fitting is implemented to obtain the APC parameters. To verify the feasibility of the proposed APC, numerical and experimental efforts are undertaken for buffeting suppression of the vertical tail, which is a typical structure with parameter perturbation. Both results demonstrate that the stability and robustness of control system adopting APC are strengthened compared to that of the control system using a constant phase compensator. Moreover, a control system that adopts APC can also effectively reduce the vibration response for structures with parameter perturbation under harmonic and random excitations. This performance improvement indicates that the proposed APC provides more effective compensation performance for the phase deviation of control systems with time-varying perturbations. },
keywords = {Adaptive phase compensator, Phase compensation for additional filter, Estimation of phase deviation, Structure with parameter perturbation, Vibration control of vertical tail},
language = {English},
publisher = {Elsevier Masson SAS}
}

The constant all-pass filter has been widely used for phase compensation of control systems. However, it is not applicable to compensating phase deviation caused by additional filters to enhance the signal quality in vibration control systems with parameter perturbation. To overcome this challenge, an adaptive phase compensator (APC) is developed by transforming the constant parameters of an all-pass filter into frequency-dependent parameters. In addition, the sources of phase deviations in the control system are analyzed to design the APC, including the additional filters, non-collocated actuator/sensor configuration, and hardware hysteresis. The phase deviations are determined through simulation and experiment. Polynomial fitting is implemented to obtain the APC parameters. To verify the feasibility of the proposed APC, numerical and experimental efforts are undertaken for buffeting suppression of the vertical tail, which is a typical structure with parameter perturbation. Both results demonstrate that the stability and robustness of control system adopting APC are strengthened compared to that of the control system using a constant phase compensator. Moreover, a control system that adopts APC can also effectively reduce the vibration response for structures with parameter perturbation under harmonic and random excitations. This performance improvement indicates that the proposed APC provides more effective compensation performance for the phase deviation of control systems with time-varying perturbations.

@article{zaare_2019,
title = {Adaptive sliding mode control of n flexible-joint robot manipulators in the presence of structured and unstructured uncertainties},
author = {Zaare, S.; Soltanpour, M.R.; Moattari, M.},
journal = {Multibody System Dynamics},
year = {2019},
institution = {Islamic Azad University, Iran; Shahid Sattari Aeronautical University of Science and Technology, Iran},
abstract = {This study investigates a voltage-based adaptive sliding mode control (VB-ASMC) to tracking the position of an n rigid-link flexible-joint (RLFJ) robot manipulator under the presence of uncertainties and external disturbances. First, the dynamic equations of the n-RLFJ robot manipulator have been divided into n subsystems, and for each of them a voltage-based sliding mode control (VB-SMC) is designed simultaneously. The mathematical proof shows that the closed-loop system under VB-SMC has global asymptotic stability. Second, due to the use of the sign function in the VB-SMC structure, the occurrence of chattering is inevitable. Therefore, to overcome this problem, an adaptive estimator is designed to estimate the boundary of uncertainties. Since the adaptive estimator part in the VB-ASMC has only one law, the proposed control has a very low computational volume. The Lyapunov stability theorem shows that the controlled closed-loop system under the VB-ASMC has global asymptotic stability. Finally, extensive simulations on the single and 2-RLFJ robot manipulator and practical implementation on the single-RLFJ robot manipulator are presented to demonstrate the effectiveness and improved performance of the proposed control scheme. },
issn = {1384-5640},
keywords = {Robot manipulator, Joint flexibility, Uncertainty, Chattering, Adaptive estimator, Adaptive sliding mode control },
language = {English},
publisher = {Springer Netherlands}
}

This study investigates a voltage-based adaptive sliding mode control (VB-ASMC) to tracking the position of an n rigid-link flexible-joint (RLFJ) robot manipulator under the presence of uncertainties and external disturbances. First, the dynamic equations of the n-RLFJ robot manipulator have been divided into n subsystems, and for each of them a voltage-based sliding mode control (VB-SMC) is designed simultaneously. The mathematical proof shows that the closed-loop system under VB-SMC has global asymptotic stability. Second, due to the use of the sign function in the VB-SMC structure, the occurrence of chattering is inevitable. Therefore, to overcome this problem, an adaptive estimator is designed to estimate the boundary of uncertainties. Since the adaptive estimator part in the VB-ASMC has only one law, the proposed control has a very low computational volume. The Lyapunov stability theorem shows that the controlled closed-loop system under the VB-ASMC has global asymptotic stability. Finally, extensive simulations on the single and 2-RLFJ robot manipulator and practical implementation on the single-RLFJ robot manipulator are presented to demonstrate the effectiveness and improved performance of the proposed control scheme.

@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.

@article{sun_2019,
title = {An artificial muscle driven by decomposition of gas solution},
author = {Sun, E.; Wang, T.},
journal = {Smart Materials and Structures},
year = {2019},
institution = { Zhejiang University, China},
abstract = {This note develops an artificial muscle driven by the decomposition of gas solution. It mainly consists of a silicone tube, a resistive wire, a braided mesh shell, and an amount gas solution which can be decomposed reversibly by temperature variation. It can be operated directly by supplying the resistive wire with controllable electrical power, which is different from traditional fluidic artificial muscles requiring external pressure generating devices. To verify the effectiveness of the artificial muscle, prototypes are fabricated and the process is presented in detail. Ammonia solution is employed in the prototypes due to its high solubility and low decomposition temperature. Experiments under both of isometric and isotonic contractions are implemented and the results show that the prototypes can achieve good mechanical performance. },
keywords = {Artificial muscle, fluid power, gas solution, decomposition, isometric and isotonic contractions},
language = {English},
publisher = {IOP Publishing}
}

This note develops an artificial muscle driven by the decomposition of gas solution. It mainly consists of a silicone tube, a resistive wire, a braided mesh shell, and an amount gas solution which can be decomposed reversibly by temperature variation. It can be operated directly by supplying the resistive wire with controllable electrical power, which is different from traditional fluidic artificial muscles requiring external pressure generating devices. To verify the effectiveness of the artificial muscle, prototypes are fabricated and the process is presented in detail. Ammonia solution is employed in the prototypes due to its high solubility and low decomposition temperature. Experiments under both of isometric and isotonic contractions are implemented and the results show that the prototypes can achieve good mechanical performance.

@conference{kutuk2_2019,
title = {An Exoskeleton Design Robotic Assisted Rehabilitation: Wrist & Forearm},
author = {Kutuk, M.E.; Das, M.T.; Dulger, L.C.},
booktitle = {2019 IFToMM World Congress on Mechanism and Machine Science},
year = {2019},
institution = {Gaziantep University, Turkey; Izmir University of Economics, Turkey; Kirrikale University, Turkey},
abstract = {Robotic systems are being used in physiotherapy for medical purposes. Providing physical training (therapy) is one of the main applications of fields of rehabilitation robotics. Upper-extremity rehabilitation involves shoulder, elbow, wrist and fingers’ actions that stimulate patients’ independence and quality of life. An exoskeleton for human wrist and forearm rehabilitation is designed and manufactured. It has three degrees of freedom which must be fitted to real human wrist and forearm. Anatomical motion range of human limbs is taken into account during design. A six DOF Denso robot is adapted. An exoskeleton driven by a serial robot has not been come across in the literature. It is feasible to apply torques to specific joints of the wrist by this way. Studies are still continuing in the subject. },
keywords = {Robotic Rehabilitation, Wrist&Forearm, Exoskeleton },
language = {English},
publisher = {Springe, Cham},
isbn = {978-3-030-20130-2}
}

Robotic systems are being used in physiotherapy for medical purposes. Providing physical training (therapy) is one of the main applications of fields of rehabilitation robotics. Upper-extremity rehabilitation involves shoulder, elbow, wrist and fingers’ actions that stimulate patients’ independence and quality of life. An exoskeleton for human wrist and forearm rehabilitation is designed and manufactured. It has three degrees of freedom which must be fitted to real human wrist and forearm. Anatomical motion range of human limbs is taken into account during design. A six DOF Denso robot is adapted. An exoskeleton driven by a serial robot has not been come across in the literature. It is feasible to apply torques to specific joints of the wrist by this way. Studies are still continuing in the subject.

@article{copur_2019,
title = {An update algorithm design using moving Region of Attraction for SDRE based control law},
author = {Copur, E.H.; Arican, A.C.; Ozcan, S.; Salamci, M.U.},
journal = {Journal of the Franklin Institute},
year = {2019},
institution = {Necmettin Erbakan University, Turkey; Gazi University, Turkey; Turkish Aerospace, Turkey},
abstract = {tate Dependent Riccati Equation (SDRE) methods have the considerable advantages over other nonlinear control methods. However, stability issues can be arisen in SDRE based control system due to the lack of the global asymptotic stability property. Therefore, the previous studies have usually shown that local asymptotic stability can be ensured by estimating a Region of Attraction (ROA) around the equilibrium point. These estimated regions for stability may become narrow or the condition to keep the states in this region may be very conservative. To resolve these issues, this paper proposes a novel SDRE method employing an update algorithm to re-estimate the ROA when the states tend to move out of the stable region. The tendency is checked using a condition which is developed based on a new theorem. The theorem proves that it is possible to redesign the previous ROA with respect to the current states lying close to its boundary for ensuring the “non-local” stability along the trajectory without the need of solving SDRE at each time instant, unlike the standard SDRE approach. Therefore, the new theorem is now able to enhance the stability of the SDRE based closed-loop control system. The feasibility of the proposed SDRE control method is tested in both simulations and experiments. A validated 3-DOF laboratory helicopter is used for experiments and the control objective for the helicopter is to realise a preplanned movement in both elevation and travel axes. The results reveal that the proposed SDRE approach enables the controlled plant to track the desired trajectory as satisfactorily as the standard SDRE approach, while only solving SDRE when needed. The proposed SDRE method reduces the computational load for practical implementation of the control algorithm whilst ensuring the stability over the operational region. },
language = {English},
publisher = {Elsevier B.V.}
}

tate Dependent Riccati Equation (SDRE) methods have the considerable advantages over other nonlinear control methods. However, stability issues can be arisen in SDRE based control system due to the lack of the global asymptotic stability property. Therefore, the previous studies have usually shown that local asymptotic stability can be ensured by estimating a Region of Attraction (ROA) around the equilibrium point. These estimated regions for stability may become narrow or the condition to keep the states in this region may be very conservative. To resolve these issues, this paper proposes a novel SDRE method employing an update algorithm to re-estimate the ROA when the states tend to move out of the stable region. The tendency is checked using a condition which is developed based on a new theorem. The theorem proves that it is possible to redesign the previous ROA with respect to the current states lying close to its boundary for ensuring the “non-local” stability along the trajectory without the need of solving SDRE at each time instant, unlike the standard SDRE approach. Therefore, the new theorem is now able to enhance the stability of the SDRE based closed-loop control system. The feasibility of the proposed SDRE control method is tested in both simulations and experiments. A validated 3-DOF laboratory helicopter is used for experiments and the control objective for the helicopter is to realise a preplanned movement in both elevation and travel axes. The results reveal that the proposed SDRE approach enables the controlled plant to track the desired trajectory as satisfactorily as the standard SDRE approach, while only solving SDRE when needed. The proposed SDRE method reduces the computational load for practical implementation of the control algorithm whilst ensuring the stability over the operational region.

@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{zhang-q_2019,
title = {Ankle Dorsiflexion Strength Monitoring by Combining Sonomyography and Electromyography},
author = {Zhang, Q.; Sheng, Z.; Moore-Clingenpeel, F.; Kim, K.; Sharma, N.},
booktitle = {2019 IEEE 16th International Conference on Rehabilitation Robotics (ICORR)},
year = {2019},
institution = {University of Pittsburgh, USA},
abstract = {Ankle dorsiflexion produced by Tibialis Anterior (TA) muscle contraction plays a significant role during human walking and standing balance. The weakened function or dysfunction of the TA muscle often impedes activities of daily living (ADL). Powered ankle exoskeleton is a prevalent technique to treat this pathology, and its intelligent and effective behaviors depend on human intention detection. A TA muscle contraction strength monitor is proposed to evaluate the weakness of the ankle dorsiflexion. The new method combines surface electromyography (sEMG) signals and sonomyography signals to estimate ankle torque during a voluntary isometric ankle dorsiflexion. Changes in the pennation angle (PA) are derived from the sonomyography signals. The results demonstrate strong correlations among the sonomyography-derived PA, the sEMG signal, and the measured TA muscle contraction force. Especially, the TA muscle strength monitor approximates the TA muscle strength measurement via a weighted summation of the sEMG signal and the PA signal. The new method shows an improved linear correlation with the muscle strength, compared to the correlations between the muscle strength and sole sEMG signal or sole PA signal, where the R-squared values are improved by 4.21 % and 1.99 %, respectively. },
issn = {1945-7898 },
keywords = {Muscles, Monitoring, Electromyography, Legged locomotion, Force, Correlation, Probes},
language = {English},
publisher = {IEEE},
isbn = {978-1-7281-2756-9 }
}

Ankle dorsiflexion produced by Tibialis Anterior (TA) muscle contraction plays a significant role during human walking and standing balance. The weakened function or dysfunction of the TA muscle often impedes activities of daily living (ADL). Powered ankle exoskeleton is a prevalent technique to treat this pathology, and its intelligent and effective behaviors depend on human intention detection. A TA muscle contraction strength monitor is proposed to evaluate the weakness of the ankle dorsiflexion. The new method combines surface electromyography (sEMG) signals and sonomyography signals to estimate ankle torque during a voluntary isometric ankle dorsiflexion. Changes in the pennation angle (PA) are derived from the sonomyography signals. The results demonstrate strong correlations among the sonomyography-derived PA, the sEMG signal, and the measured TA muscle contraction force. Especially, the TA muscle strength monitor approximates the TA muscle strength measurement via a weighted summation of the sEMG signal and the PA signal. The new method shows an improved linear correlation with the muscle strength, compared to the correlations between the muscle strength and sole sEMG signal or sole PA signal, where the R-squared values are improved by 4.21 % and 1.99 %, respectively.

@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{muratore_2019,
title = {Assessing Transferability from Simulation to Reality for Reinforcement Learning},
author = {Muratore, F.; Gienger, M.; Peters, J.},
year = {2019},
institution = {Technische Universitat Darmstadt, Germany; Honda Research Institute Europe, Germany; Max Planck Institute for Intelligent Systems, Germany},
abstract = {Learning robot control policies from physics simulations is of great interest to the robotics community as it may render the learning process faster, cheaper, and safer by alleviating the need for expensive real-world experiments. However, the direct transfer of learned behavior from simulation to reality is a major challenge. Optimizing a policy on a slightly faulty simulator can easily lead to the maximization of the 'Simulation Optimization Bias' (SOB). In this case, the optimizer exploits modeling errors of the simulator such that the resulting behavior can potentially damage the robot. We tackle this challenge by applying domain randomization, i.e., randomizing the parameters of the physics simulations during learning. We propose an algorithm called Simulation-based Policy Optimization with Transferability Assessment (SPOTA) which uses an estimator of the SOB to formulate a stopping criterion for training. The introduced estimator quantifies the over-fitting to the set of domains experienced while training. Our experimental results in two different environments show that the new simulation-based policy search algorithm is able to learn a control policy exclusively from a randomized simulator, which can be applied directly to real system without any additional training on the latter. },
keywords = {Reinforcement Learning, Domain Randomization, Sim-to-Real Transfer},
language = {English}
}

Learning robot control policies from physics simulations is of great interest to the robotics community as it may render the learning process faster, cheaper, and safer by alleviating the need for expensive real-world experiments. However, the direct transfer of learned behavior from simulation to reality is a major challenge. Optimizing a policy on a slightly faulty simulator can easily lead to the maximization of the 'Simulation Optimization Bias' (SOB). In this case, the optimizer exploits modeling errors of the simulator such that the resulting behavior can potentially damage the robot. We tackle this challenge by applying domain randomization, i.e., randomizing the parameters of the physics simulations during learning. We propose an algorithm called Simulation-based Policy Optimization with Transferability Assessment (SPOTA) which uses an estimator of the SOB to formulate a stopping criterion for training. The introduced estimator quantifies the over-fitting to the set of domains experienced while training. Our experimental results in two different environments show that the new simulation-based policy search algorithm is able to learn a control policy exclusively from a randomized simulator, which can be applied directly to real system without any additional training on the latter.

@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.

@article{polzounov_2019,
title = {Blue River Controls: A toolkit for Reinforcement Learning Control Systems on Hardware},
author = {Polzounov, K.; Redden, L.; Sundar, R.},
year = {2019},
institution = {University of Calgary, Canada; Blue RiverTechnology, USA},
abstract = {Much of the recent success of Reinforcement learning (RL) has been made possible with training and testing tools like OpenAI Gym and Deepmind Control Suite [1, 2]. Unfortunately, tools for quickly testing and transferring high-frequency RL algorithms from simulation to real hardware environment remain mostly absent. We present Blue River Controls, a tool that allows to train and test reinforcement learning algorithms on real-world hardware. It features a simple interface based on OpenAI Gym, that works directly on both simulation and hardware. We use Quanser’s Qube Servo2-USB platform, an underactuated rotary pendulum as an initial testing device. We also provide tools to simplify training RL algorithms on other hardware. Several baselines, from both classical controllers and pretrained RL agents are included to compare performance across tasks. Blue River Controls is available at this https URL: github.com/BlueRiverTech/quanser-openai-driver },
language = {English}
}

Much of the recent success of Reinforcement learning (RL) has been made possible with training and testing tools like OpenAI Gym and Deepmind Control Suite [1, 2]. Unfortunately, tools for quickly testing and transferring high-frequency RL algorithms from simulation to real hardware environment remain mostly absent. We present Blue River Controls, a tool that allows to train and test reinforcement learning algorithms on real-world hardware. It features a simple interface based on OpenAI Gym, that works directly on both simulation and hardware. We use Quanser’s Qube Servo2-USB platform, an underactuated rotary pendulum as an initial testing device. We also provide tools to simplify training RL algorithms on other hardware. Several baselines, from both classical controllers and pretrained RL agents are included to compare performance across tasks. Blue River Controls is available at this https URL: github.com/BlueRiverTech/quanser-openai-driver

@article{rhudy_2019,
title = {Breaking away from the traditional lab report: A technical email as a writing assignment in an engineering laboratory course},
author = {Rhudy, M.},
journal = {The Prompt Journal},
year = {2019},
volume = {3},
number = {2},
institution = {Pennsylvania State University, USA},
abstract = {Engineering laboratory courses often contain laboratory reports as writing assignments to be used as an assessment and grading tool for the course. While laboratory report writing is a useful skill, this article discusses an assignment which was used as an alternative to a traditional laboratory report within a dynamic systems laboratory course. This writing assignment is framed within the context of a hypothetical scenario involving a supervisor requesting a laboratory experiment to compare the effectiveness of two different designs for controlling the speed of a gearbox unit. Performance goals are specified by the ``customer'' so that students have a reference with which to frame their responses. Despite the shortened length of the writing assignment, students are forced to apply critical thinking and use evidence from their experiments to answer the posed question with a clear conclusion. },
language = {English}
}

Engineering laboratory courses often contain laboratory reports as writing assignments to be used as an assessment and grading tool for the course. While laboratory report writing is a useful skill, this article discusses an assignment which was used as an alternative to a traditional laboratory report within a dynamic systems laboratory course. This writing assignment is framed within the context of a hypothetical scenario involving a supervisor requesting a laboratory experiment to compare the effectiveness of two different designs for controlling the speed of a gearbox unit. Performance goals are specified by the ``customer'' so that students have a reference with which to frame their responses. Despite the shortened length of the writing assignment, students are forced to apply critical thinking and use evidence from their experiments to answer the posed question with a clear conclusion.

Functional electrical stimulation (FES) has proven to be an effective method for improving health and regaining muscle function for people with limited or reduced motor skills. Closed-loop control of motorized FES-cycling can facilitate recovery. Many people with movement disorders (e.g., stroke) have asymmetries in their motor control, motivating the need for a closed-loop control system that can be implemented on a split-crank cycle. In this paper, nonlinear sliding mode controllers are designed for the FES and electric motor on each side of a split-crank cycle to maintain a desired cadence and a crank angle offset of 180 degrees, simulating standard pedaling conditions. A Lyapunov-like function is used to prove stability and tracking of the desired cadence and position for the combined cycle-rider system. One experimental trial on an able-bodied individual demonstrated the feasibility and stability of the closed-loop controller, which resulted in an average cadence error of 2:62 ± 3:54 RPM for the dominant leg and an average position and cadence error of 39:84 ± 10:77 degrees and -0:04 ± 8:79 RPM for the non-dominant leg.

@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{obuz_2019,
title = {Closed-Loop Neuromuscular Electrical Stimulation Method Provides Robustness to Unknown Time-Varying Input Delay in Muscle Dynamics},
author = {Obuz, S.; Duenas, V.H.; Downey, R.J.; Klotz, J.R.; Dixon, W.E.},
journal = {IEEE Transactions on Control Systems Technology},
year = {2019},
institution = {Eskisehir Osmangazi University, Turkey; University of Florida, USA; Medical University of South Carolina, USA; Department of Defense, USA},
abstract = {Neuromuscular electrical stimulation (NMES) is commonly used to rehabilitate people with motor impairment (e.g., following stroke or spinal cord injury). Closed-loop NMES holds the promise to facilitate coordinated limb motion, but technical challenges remain. In particular, there is a potentially destabilizing delay between the application of the electrical stimulation and the ensuing muscle contraction, which changes as muscle fatigues. In this brief, a closed-loop NMES method is developed to yield lower limb tracking, despite an unknown time-varying input delay, uncertain nonlinear limb dynamics, and additive bounded disturbances. A novel filtered error signal is designed using the past states in a finite integral over a constant estimated delay interval. The control development is based on an approach that uses Lyapunov-Krasovskii functionals in a Lyapunov-based stability analysis to prove ultimately bounded tracking. Experimental results in healthy individuals and participants with neurological conditions are provided to demonstrate the performance of the developed controller. },
issn = {1063-6536},
keywords = {Delay systems, Lyapunov methods, neuromuscular electrical stimulation (NMES), nonlinear control systems, robust control, uncertain systems, unknown time-varying input delay},
language = {English},
publisher = {IEEE}
}

Neuromuscular electrical stimulation (NMES) is commonly used to rehabilitate people with motor impairment (e.g., following stroke or spinal cord injury). Closed-loop NMES holds the promise to facilitate coordinated limb motion, but technical challenges remain. In particular, there is a potentially destabilizing delay between the application of the electrical stimulation and the ensuing muscle contraction, which changes as muscle fatigues. In this brief, a closed-loop NMES method is developed to yield lower limb tracking, despite an unknown time-varying input delay, uncertain nonlinear limb dynamics, and additive bounded disturbances. A novel filtered error signal is designed using the past states in a finite integral over a constant estimated delay interval. The control development is based on an approach that uses Lyapunov-Krasovskii functionals in a Lyapunov-based stability analysis to prove ultimately bounded tracking. Experimental results in healthy individuals and participants with neurological conditions are provided to demonstrate the performance of the developed controller.

@article{falcon_2019,
title = {Comparative analysis of continuous sliding-modes control strategies for quad-rotor robust tracking},
author = {Falcon, R.; Rios, H.; Dzul, A.},
journal = {Control Engineering Practice},
year = {2019},
month = {09},
volume = {90},
institution = {Tecnológico Nacional de México, Mexico},
abstract = {This paper presents a comparative analysis involving four Continuous Sliding-Modes Control (Continuous-SMC) algorithms and a robustified PID control for a Quad-Rotor that can be used to deal with the tracking problem under the influence of external disturbances and uncertainties only by means of the measurable positions and angles. Such an approach is composed of a Finite-Time Sliding-Mode Observer (FT-SMO), which estimates the full state and identifies some type of disturbances, and a robust control strategy for underactuated systems. Several real-time experimental tests are carried out on the Quad-Rotor QBall2 platform by Quanser\protect \protect \relax \special {t4ht=©} under the influence of wind gusts and load disturbances. A quantitative comparison analysis is performed for all of the proposed controllers in order to illustrate their robustness properties. },
keywords = {Robust output-based control, Quad-rotor, Continuous sliding-mode control},
language = {English},
publisher = {Elsevier Ltd.},
pages = {241-256}
}

This paper presents a comparative analysis involving four Continuous Sliding-Modes Control (Continuous-SMC) algorithms and a robustified PID control for a Quad-Rotor that can be used to deal with the tracking problem under the influence of external disturbances and uncertainties only by means of the measurable positions and angles. Such an approach is composed of a Finite-Time Sliding-Mode Observer (FT-SMO), which estimates the full state and identifies some type of disturbances, and a robust control strategy for underactuated systems. Several real-time experimental tests are carried out on the Quad-Rotor QBall2 platform by Quanser\protect \protect \relax \special {t4ht=©} under the influence of wind gusts and load disturbances. A quantitative comparison analysis is performed for all of the proposed controllers in order to illustrate their robustness properties.

@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.