@article{furtado2_2018,
title = {3-D UAV Path Planning in a Cluttered Environment using PSO},
author = {Furtado, J.S.; Liu, H.H.T.},
year = {2018},
institution = {University of Toronto Institute for Aerospace Studies, Canada},
abstract = {The use of Unmanned Aerial Vehicles (UAVs) in a wide variety of civilian and military applications such as surveillance, inspection, and precision agriculture has become increasingly popular over the last few years. The performance of the mission is based on the time taken to complete the mission. Path planning is therefore a key component in most UAV applications. The main objective of this work is to plan efficient three-dimensional (3-D) paths for a UAV to get from its start location to its goal location avoiding any collision with obstacles in the environment. Based on literature review, Swarm Intelligence (SI) based algorithm, Particle Swarm Optimisation (PSO) is utilised to generate collision free trajectories for a UAV in a cluttered environment. SI is an innovative distributed and intelligent paradigm used for solving optimization problems. It is inherently robust, scalable and stochastic, inspired by the collective behaviour seen in biological systems. The objective function being optimised is the length of the path to be own by the UAV subject to collision constraints. The algorithm generates discrete waypoints using which a smooth flyable path is generated by spline interpolation. Simulation as well as experimental results are shown to demonstrate the results of this work after testing in different scenarios. },
language = {English}
}

The use of Unmanned Aerial Vehicles (UAVs) in a wide variety of civilian and military applications such as surveillance, inspection, and precision agriculture has become increasingly popular over the last few years. The performance of the mission is based on the time taken to complete the mission. Path planning is therefore a key component in most UAV applications. The main objective of this work is to plan efficient three-dimensional (3-D) paths for a UAV to get from its start location to its goal location avoiding any collision with obstacles in the environment. Based on literature review, Swarm Intelligence (SI) based algorithm, Particle Swarm Optimisation (PSO) is utilised to generate collision free trajectories for a UAV in a cluttered environment. SI is an innovative distributed and intelligent paradigm used for solving optimization problems. It is inherently robust, scalable and stochastic, inspired by the collective behaviour seen in biological systems. The objective function being optimised is the length of the path to be own by the UAV subject to collision constraints. The algorithm generates discrete waypoints using which a smooth flyable path is generated by spline interpolation. Simulation as well as experimental results are shown to demonstrate the results of this work after testing in different scenarios.

@article{kammer_2018,
title = {A Data-Driven Fixed-Structure Control Design Method with Application to a 2-DOF Gyroscope},
author = {Kammer, C.; Karimi, A.},
year = {2018},
institution = {Laboratoire d’Automatique, Ecole Polytechnique Federale de Lausanne, Switzerland},
abstract = {This paper presents the practical aspects and application of a novel data-driven, fixed-structure, robust control design method. Only the frequency response data of the system is needed for the design, and no parametric model is required. The method can be used to design fully parametrized continuous- or discrete-time matrix transfer function controllers. The control performance is specified as constraints on the H-infinity or H2 norm of weighted sensitivity functions, and a convex formulation of the robust design problem is proposed. An application of the presented method is explored on an experimental setup, where a multivariable controller for a gyroscope is designed based only on the measured frequency response of the system. },
language = {English}
}

This paper presents the practical aspects and application of a novel data-driven, fixed-structure, robust control design method. Only the frequency response data of the system is needed for the design, and no parametric model is required. The method can be used to design fully parametrized continuous- or discrete-time matrix transfer function controllers. The control performance is specified as constraints on the H-infinity or H2 norm of weighted sensitivity functions, and a convex formulation of the robust design problem is proposed. An application of the presented method is explored on an experimental setup, where a multivariable controller for a gyroscope is designed based only on the measured frequency response of the system.

@article{zhou_2018,
title = {A Multi-Time-Scale Finite Time Controller for the Quadrotor UAVs with Uncertainties},
author = {Zhou, Z.; Wang, H.; Hu, Z.; Wang, Y.; Wang, H.},
journal = {Journal of Intelligent & Robotic Systems},
year = {2018},
institution = {Yanshan University, China},
abstract = {A control method with a multi-time-scale structure is proposed to perform finite time motion control of the quadrotor unmanned aerial vehicles (UAVs) with uncertainties. In order to facilitate the controller-design, finite time extended state observer (ESO) in the first and second time scales is applied to estimate the system uncertainties; the attitude controllers and the height controller are designed for finite time stabilization of the equilibriums in the third time scale; and finally, the output feedback technique is utilized to design the horizontal auxiliary controllers, meanwhile the reference angles are settled for the attitude dynamics in the fourth and slowest time scale. It allows us to analyze the system dynamics in each time scale independently, and conclusions on finite time stabilization are achieved gradually with a large region of attraction. Simulation and experimental results on the Qball2 platform are given to verify the efficacy of the strategy and establish the feasibility of implementation. },
issn = {0921-0296},
keywords = {Finite time control, Extended state observer, Multi-time-scale, System uncertainties, Quadrotor UAVs},
language = {English},
publisher = {Springer Netherlands}
}

A control method with a multi-time-scale structure is proposed to perform finite time motion control of the quadrotor unmanned aerial vehicles (UAVs) with uncertainties. In order to facilitate the controller-design, finite time extended state observer (ESO) in the first and second time scales is applied to estimate the system uncertainties; the attitude controllers and the height controller are designed for finite time stabilization of the equilibriums in the third time scale; and finally, the output feedback technique is utilized to design the horizontal auxiliary controllers, meanwhile the reference angles are settled for the attitude dynamics in the fourth and slowest time scale. It allows us to analyze the system dynamics in each time scale independently, and conclusions on finite time stabilization are achieved gradually with a large region of attraction. Simulation and experimental results on the Qball2 platform are given to verify the efficacy of the strategy and establish the feasibility of implementation.

@article{sadala_2018,
title = {A new continuous sliding mode control approach with actuator saturation for control of 2-DOF helicopter system},
author = {Sadala, S.P.; Patre, B.M.},
journal = {ISA Transactions},
year = {2018},
institution = {Shri Guru Gobind Singhji Institute of Engineering and Technology, India},
abstract = {The 2-degree of freedom (DOF) helicopter system is a typical higher-order, multi-variable, nonlinear and strong coupled control system. The helicopter dynamics also includes parametric uncertainties and is subject to unknown external disturbances. Such complicated system requires designing a sophisticated control algorithm that can handle these difficulties. This paper presents a new robust control algorithm which is a combination of two continuous control techniques, composite nonlinear feedback (CNF) and super-twisting control (STC) methods. In the existing integral sliding mode (ISM) based CNF control law, the discontinuous term exhibits chattering which is not desirable for many practical applications. As the continuity of well known STC reduces chattering in the system, the proposed strategy is beneficial over the current ISM based CNF control law which has a discontinuous term. Two controllers with integral sliding surface are designed to control the position of the pitch and the yaw angles of the 2- DOF helicopter. The adequacy of this specific combination has been exhibited through general analysis, simulation and experimental results of 2-DOF helicopter setup. The acquired results demonstrate the good execution of the proposed controller regarding stabilization, following reference input without overshoot against actuator saturation and robustness concerning to the limited matched disturbances. },
keywords = {Composite nonlinear feedback (CNF) Actuator saturation 2-DOF helicopter Siding mode control (SMC) Integral sliding mode control (ISMC) Super-twisting control (STC)},
language = {English},
publisher = {Elsevier B.V.}
}

The 2-degree of freedom (DOF) helicopter system is a typical higher-order, multi-variable, nonlinear and strong coupled control system. The helicopter dynamics also includes parametric uncertainties and is subject to unknown external disturbances. Such complicated system requires designing a sophisticated control algorithm that can handle these difficulties. This paper presents a new robust control algorithm which is a combination of two continuous control techniques, composite nonlinear feedback (CNF) and super-twisting control (STC) methods. In the existing integral sliding mode (ISM) based CNF control law, the discontinuous term exhibits chattering which is not desirable for many practical applications. As the continuity of well known STC reduces chattering in the system, the proposed strategy is beneficial over the current ISM based CNF control law which has a discontinuous term. Two controllers with integral sliding surface are designed to control the position of the pitch and the yaw angles of the 2- DOF helicopter. The adequacy of this specific combination has been exhibited through general analysis, simulation and experimental results of 2-DOF helicopter setup. The acquired results demonstrate the good execution of the proposed controller regarding stabilization, following reference input without overshoot against actuator saturation and robustness concerning to the limited matched disturbances.

@conference{xie_2018,
title = {A position estimation and control system for the quadrotor in GPS-deny situation based on FAST detection and optical flow},
author = {Xie, N.; Li, X.; Yu, Y.},
booktitle = {2018 33rd Youth Academic Annual Conference of Chinese Association of Automation (YAC)},
year = {2018},
institution = {University of Science and Technology Beijing, China},
abstract = {Position estimation based on vision system is essential for a UAV in the GPS-deny situation to realize the position control. However, in the practice, the hardware and software are not ideal for the UAV to carry when flying. Thus, this study is aiming at the problem of position estimation and control for a quadrotor UAV based on vision. Firstly, a position estimation algorithm based on vision is proposed, in which optical flow is used combining with FAST corner detection to ensure the real-time performance of the estimation in condition with limited loader. Meanwhile, a robust controller with nonlinear compensating input has been designed in this paper to deal with the position control for the quadrotor. A simulation is presented in this paper to verify the performance of the controller. Moreover, an experiment is also utilized in this paper to show that the method is practical and with high performance. },
keywords = {quadrotor UAV, optical flow, FAST detection, sliding model control, position estimation and control},
language = {English},
publisher = {IEEE},
isbn = {978-1-5386-7256-3 }
}

Position estimation based on vision system is essential for a UAV in the GPS-deny situation to realize the position control. However, in the practice, the hardware and software are not ideal for the UAV to carry when flying. Thus, this study is aiming at the problem of position estimation and control for a quadrotor UAV based on vision. Firstly, a position estimation algorithm based on vision is proposed, in which optical flow is used combining with FAST corner detection to ensure the real-time performance of the estimation in condition with limited loader. Meanwhile, a robust controller with nonlinear compensating input has been designed in this paper to deal with the position control for the quadrotor. A simulation is presented in this paper to verify the performance of the controller. Moreover, an experiment is also utilized in this paper to show that the method is practical and with high performance.

Interconnection and damping assignment passivity based control (IDA-PBC) is a method that has been developed to (asymptotically) stabilize nonlinear systems formulated in port-controlled Hamiltonian (PCH) structure. This method has gained increasing popularity and has been successfully applied to a wide range of dynamical systems. However, little is known about the robustness of this method in response to the effects of uncertainty which could result from disturbances, noises, and modeling errors. This paper explores the possibility of extending some energy shaping methods, taking into account the robustness aspects, with the aim of maintaining (asymptotic) stability of the system in the presence of perturbations which inevitably exist in any realistic applications. We propose constructive results on robust IDA-PBC controllers for underactuated mechanical systems that are quite commonly found in practice and have the most challenging control problems within this context. The proposed results extend some existing methods and provide a new framework that allows the implementation of integral and input-to-state stability controllers to underactuated mechanical system.

@article{jurado_2018,
title = {A wavelet neural control scheme for a quadrotor unmanned aerial vehicle},
author = {Jurado, F.; Lopez, S.},
journal = {Philosophical Transactions of the Royal Society of Mathematical, Physical and Engineering Sciences},
year = {2018},
volume = {376},
number = {2126},
institution = {Tecnológico Nacional de México, Mexico; Instituto Tecnológico de La Laguna, Mexico},
abstract = {Wavelets are designed to have compact support in both time and frequency, giving them the ability to represent a signal in the two-dimensional time–frequency plane. The Gaussian, the Mexican hat and the Morlet wavelets are crude wavelets that can be used only in continuous decomposition. The Morlet wavelet is complex-valued and suitable for feature extraction using the continuous wavelet transform. Continuous wavelets are favoured when high temporal and spectral resolution is required at all scales. In this paper, considering the properties from the Morlet wavelet and based on the structure of a recurrent high-order neural network model, a novel wavelet neural network structure, here called a recurrent Morlet wavelet neural network, is proposed in order to achieve a better identification of the behaviour of dynamic systems. The effectiveness of our proposal is explored through the design of a decentralized neural backstepping control scheme for a quadrotor unmanned aerial vehicle. The performance of the overall neural identification and control scheme is verified via simulation and real-time results. This article is part of the theme issue ‘Redundancy rules: the continuous wavelet transform comes of age’. },
keywords = {backstepping control, Morlet wavelet, quadrotor, recurrent wavelet neural network},
language = {English},
publisher = {The Royal Society Publishing}
}

Wavelets are designed to have compact support in both time and frequency, giving them the ability to represent a signal in the two-dimensional time–frequency plane. The Gaussian, the Mexican hat and the Morlet wavelets are crude wavelets that can be used only in continuous decomposition. The Morlet wavelet is complex-valued and suitable for feature extraction using the continuous wavelet transform. Continuous wavelets are favoured when high temporal and spectral resolution is required at all scales. In this paper, considering the properties from the Morlet wavelet and based on the structure of a recurrent high-order neural network model, a novel wavelet neural network structure, here called a recurrent Morlet wavelet neural network, is proposed in order to achieve a better identification of the behaviour of dynamic systems. The effectiveness of our proposal is explored through the design of a decentralized neural backstepping control scheme for a quadrotor unmanned aerial vehicle. The performance of the overall neural identification and control scheme is verified via simulation and real-time results.

This article is part of the theme issue ‘Redundancy rules: the continuous wavelet transform comes of age’.

@article{bolat_2018,
title = {Active Control of a Small-Scale Wind Turbine Blade Containing Magnetorheological Fluid},
author = {Bolat, F.C.; Sivrioglu, S.},
journal = {Micromachines},
year = {2018},
volume = {9},
number = {2},
institution = {Bayburt University, Turkey; Gebze Technical University, Turkey},
abstract = {This research study proposes a new active control structure to suppress vibrations of a small-scale wind turbine blade filled with magnetorheological (MR) fluid and actuated by an electromagnet. The aluminum blade structure is manufactured using the SH3055 (Bergey Windpower Co. Inc., Norman, OK, USA) code numbered airfoil which is designed for use on small wind turbines. A dynamic interaction model between the MR fluid and the electromagnetic actuator is constructed to obtain a force relation. A detailed characterization study is presented for the proposed actuator to understand the nonlinear behavior of the electromagnetic force. A norm based multi-objective H2/H∞ controller is designed using the model of the elastic blade element. The H2/H∞ controller is experimentally implemented under the impact and steady state aerodynamic load conditions. The results of experiments show that the MR fluid- electromagnetic actuator is effective for suppressing vibrations of the blade structure. },
keywords = {active vibration control; elastic blade; magnetorheological fluid; robust control},
language = {English}
}

This research study proposes a new active control structure to suppress vibrations of a small-scale wind turbine blade filled with magnetorheological (MR) fluid and actuated by an electromagnet. The aluminum blade structure is manufactured using the SH3055 (Bergey Windpower Co. Inc., Norman, OK, USA) code numbered airfoil which is designed for use on small wind turbines. A dynamic interaction model between the MR fluid and the electromagnetic actuator is constructed to obtain a force relation. A detailed characterization study is presented for the proposed actuator to understand the nonlinear behavior of the electromagnetic force. A norm based multi-objective H2/H∞ controller is designed using the model of the elastic blade element. The H2/H∞ controller is experimentally implemented under the impact and steady state aerodynamic load conditions. The results of experiments show that the MR fluid- electromagnetic actuator is effective for suppressing vibrations of the blade structure.

@article{das_2018,
title = {Adaptive Predator-Prey Optimization for Tuning of Infinite Horizon LQR applied to Vehicle Suspension System},
author = {Das, R.R.; Elumalai, V.K.; Subramanian, R.G.; Venkata, K.; Kumar, A.},
journal = {Applied Soft Computing},
year = {2018},
institution = {Eindhoven University of Technology, The Netherlands; VIT University, India; Larson and Toubro Limited, India},
abstract = {This paper puts forward an adaptive predator-prey optimization algorithm to solve the weight selection problem of linear quadratic control applied for vibration control of vehicle suspension system. The proposed technique addresses the two key issues of PSO, namely (a) the premature convergence of the particles, and (b) the imbalance between exploration and exploitation of the particles in finding the global optimum. The main principle behind this optimization algorithm is that the inertia weight is adaptively updated based on the success rate of the particles to increase the convergence, and the predator-prey strategy is reinforced to avoid the particles getting trapped in a local minimum thereby, guaranteeing convergence of the particles towards the global optimal solution. The convergence of the particles towards the global minimum is guaranteed on the basis of a passivity argument. Moreover, the strength of this new adaptive optimization technique to tune the gains of linear quadratic regulator is validated experimentally on a laboratory scale active vehicle suspension system for improved ride comfort and passenger safety. },
keywords = {LQR, Active Vehicle Suspension System, PSO, AIWF, Predator-Prey strategy},
language = {English},
publisher = {Elsevier B.V.}
}

This paper puts forward an adaptive predator-prey optimization algorithm to solve the weight selection problem of linear quadratic control applied for vibration control of vehicle suspension system. The proposed technique addresses the two key issues of PSO, namely (a) the premature convergence of the particles, and (b) the imbalance between exploration and exploitation of the particles in finding the global optimum. The main principle behind this optimization algorithm is that the inertia weight is adaptively updated based on the success rate of the particles to increase the convergence, and the predator-prey strategy is reinforced to avoid the particles getting trapped in a local minimum thereby, guaranteeing convergence of the particles towards the global optimal solution. The convergence of the particles towards the global minimum is guaranteed on the basis of a passivity argument. Moreover, the strength of this new adaptive optimization technique to tune the gains of linear quadratic regulator is validated experimentally on a laboratory scale active vehicle suspension system for improved ride comfort and passenger safety.

@article{riviere_2018,
title = {Agile Robotic Fliers: A Morphing-Based Approach},
author = {Riviere, V.; Manecy, A.; Viollet, S.},
journal = {Soft Robotics},
year = {2018},
institution = {Aix Marseille University, France; ONERA Midi-Pyrenees Toulouse Center, France},
abstract = {The aerial robot presented here for the first time was based on a quadrotor structure, which is capable of unique morphing performances based on an actuated elastic mechanism. Like birds, which are able to negotiate narrow apertures despite their relatively large wingspan, our Quad-Morphing robot was able to pass through a narrow gap at a high forward speed of 2.5 m.s−1 by swiftly folding up the structure supporting its propellers. A control strategy was developed to deal with the loss of controllability on the roll axis resulting from the folding process, while keeping the robot stable until it has crossed the gap. In addition, a complete recovery procedure was also implemented to stabilize the robot after the unfolding process. A new metric was also used to quantify the gain in terms of the gap-crossing ability in comparison with that observed with classical quadrotors with rigid bodies. The performances of these morphing robots are presented, and experiments performed with a real flying robot passing through a small aperture by reducing its wingspan by 48% are described and discussed. },
keywords = {morphing robot, quadrotors, obstacle avoidance, bioinspired, aerial robot, elastic folding mechanism},
language = {English},
publisher = {Mary Ann Liebert, Inc.}
}

The aerial robot presented here for the first time was based on a quadrotor structure, which is capable of unique morphing performances based on an actuated elastic mechanism. Like birds, which are able to negotiate narrow apertures despite their relatively large wingspan, our Quad-Morphing robot was able to pass through a narrow gap at a high forward speed of 2.5 m.s−1 by swiftly folding up the structure supporting its propellers. A control strategy was developed to deal with the loss of controllability on the roll axis resulting from the folding process, while keeping the robot stable until it has crossed the gap. In addition, a complete recovery procedure was also implemented to stabilize the robot after the unfolding process. A new metric was also used to quantify the gain in terms of the gap-crossing ability in comparison with that observed with classical quadrotors with rigid bodies. The performances of these morphing robots are presented, and experiments performed with a real flying robot passing through a small aperture by reducing its wingspan by 48% are described and discussed.

@article{hernandez-perez_2018,
title = {An improvement on the PI controller for a class of high-order unstable delayed systems: Application to a thermal process},
author = {Hernandez-Perez, M.A.; del Muro-Cuellar, B.; Velasco-Villa, M.; Novella-Rodriguez, D.F.; Garrido-Moctezuma, R.A.; Garcia-Ramirez, P.J.},
journal = {Control Engineering and Applied Informatics},
year = {2018},
volume = {20},
number = {1},
institution = {Universidad Veracruzana, Mexico; Instituto Politécnico Nacional, Mexico; CINVESTAV-IPN, Mexico},
abstract = {This work addresses the stabilization and control problem of a class of input-output delayed unstable linear systems, i.e. n -order systems with one unstable pole and possibly one minimum phase zero. The problem is solved employing a modified version of the traditional PI, called the PIf controller, which incorporates a low-pass first order filter. This new scheme allows improving the existing results using the PI controller for high-order systems with time delay. The proposed control strategy is experimentally assessed through the temperature control of an unstable heat flow process. },
keywords = {Linear Systems, time–delay, modified PI control, unstable process, thermal process},
language = {English}
}

This work addresses the stabilization and control problem of a class of input-output delayed unstable linear systems, i.e. n -order systems with one unstable pole and possibly one minimum phase zero. The problem is solved employing a modified version of the traditional PI, called the PIf controller, which incorporates a low-pass first order filter. This new scheme allows improving the existing results using the PI controller for high-order systems with time delay. The proposed control strategy is experimentally assessed through the temperature control of an unstable heat flow process.

Plant-wide control implies advanced supervisory algorithms to maintain desired performance in the involved coupled sub-systems. The dynamical interactions among these sub-systems can vary with the operating point, material properties and disturbances present in the process. Recirculating loops introduce additional phenomena in the dynamic response, further challenging the control tasks. Complex process dynamics may be linear parameter varying (LPV) and may be difficult, if not impossible, to identify properly. In this context, maintaining global performance is a challenge one must undertake with limited information at hand. This paper investigates the trade-off between the complexity of the implementation and achieved performance, using supervisory predictive control with limited information shared, applied on a test-bench representative for process control industry. The robustness of the proposed algorithms is tested against a nominal scenario in which the prediction model is fully identified, with complete information exchange. Experimental tests are performed on a test-bench process characterized by strong interactions, and the results illustrate the usefulness of this work.

@article{chang_2018,
title = {Analytical and experimental investigations of Modified Tuned Liquid Dampers (MTLDs)},
author = {Chang, Y.; Noormohamed, A.; Mercan, O.},
journal = {Journal of Sound and Vibration},
year = {2018},
volume = {428},
institution = {University of Toronto, Canada},
abstract = {Modified Tuned Liquid Dampers (MTLDs) are a variation of a traditional Tuned Liquid Damper (TLD) which utilize a rotational spring system at the base, and therefore experience combined horizontal and rotational motions as the structure sways. To date, there have been very few studies conducted on MTLDs with experimental validation. In this research study, an MTLD-structure system is investigated using Lu's analytical model. Using Real-Time Hybrid Simulation (RTHS), a state-of-the-art testing method, the capabilities of the analytical model are experimentally verified. Important MTLD parameters such as the dimensionless rotational stiffness parameter, frequency ratio, and damping ratio are studied in detail. RTHS is used to study the effectiveness of the MTLD in mitigating structural response under sinusoidal inputs, as well as a range of ground motion records. It is shown both analytically and experimentally that when properly designed, the MTLD can exhibit more efficiency than a traditional TLD in mitigating vibrations. },
keywords = {Earthquake response, Energy dissipation, Modified Tuned Liquid Damper, Passive control, Real time hybrid simulation, Vibration control},
language = {English},
publisher = {Elsevier B.V.},
pages = {179-194}
}

Modified Tuned Liquid Dampers (MTLDs) are a variation of a traditional Tuned Liquid Damper (TLD) which utilize a rotational spring system at the base, and therefore experience combined horizontal and rotational motions as the structure sways. To date, there have been very few studies conducted on MTLDs with experimental validation. In this research study, an MTLD-structure system is investigated using Lu's analytical model. Using Real-Time Hybrid Simulation (RTHS), a state-of-the-art testing method, the capabilities of the analytical model are experimentally verified. Important MTLD parameters such as the dimensionless rotational stiffness parameter, frequency ratio, and damping ratio are studied in detail. RTHS is used to study the effectiveness of the MTLD in mitigating structural response under sinusoidal inputs, as well as a range of ground motion records. It is shown both analytically and experimentally that when properly designed, the MTLD can exhibit more efficiency than a traditional TLD in mitigating vibrations.

@article{dede_2018,
title = {Analytical Dynamic Analysis of a Kinesthetic Haptic Device},
author = {Dede, M.I.C.; Maaroof, O.W.; Ceccarelli, M.},
journal = {Journal of Science and Engineering},
year = {2018},
month = {05},
volume = {20},
number = {59},
institution = {Izmit Institute of Technology, Turkey; University of Cassino, Italy},
abstract = {A hybrid-structured kinesthetic haptic device based on an R-CUBE mechanism and a serial spherical wrist mechanism is considered in this article. This device is designed to simulate point-type contacts on the user. Hence, only three-dimensional forces are simulated to the user through the R-CUBE mechanism. This paper presents the quasi-static force analysis, gravity compensation calculations and dynamic analysis of the R-CUBE mechanism to serve for better understanding the capabilities of the mechanism and to be used in haptics controller development in the future studies. Making use of the derived dynamic equations, torque requirements from the actuators are examined for use in the haptic application scenarios. },
keywords = {haptics, parallel mechanisms, dynamics},
language = {English},
pages = {492-508}
}

A hybrid-structured kinesthetic haptic device based on an R-CUBE mechanism and a serial spherical wrist mechanism is considered in this article. This device is designed to simulate point-type contacts on the user. Hence, only three-dimensional forces are simulated to the user through the R-CUBE mechanism. This paper presents the quasi-static force analysis, gravity compensation calculations and dynamic analysis of the R-CUBE mechanism to serve for better understanding the capabilities of the mechanism and to be used in haptics controller development in the future studies. Making use of the derived dynamic equations, torque requirements from the actuators are examined for use in the haptic application scenarios.

@article{alemaryeen_2018,
title = {Antenna Effects on Respiratory Rate Measurement using a UWB Radar System},
author = {Alemaryeen, A.; Noghanian, S.; Fazel-Rezai, R.},
journal = {IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology},
year = {2018},
institution = {Electrical Engineering, University of North Dakota, USA},
abstract = {State-of-the-art advances in the field of radar technology have made it possible to design non-invasive sensing devices of vital signs. This paper presents the effects of antenna characteristics on Ultra Wide Band (UWB) radar-based respiratory rate measurement system for tele-health-monitoring applications. The performance of three types of antenna for a UWB radar respiratory rate measurement system was studied in this work. In this context, the proposed system was comprehensively evaluated using two experimental sets. First, a mechanical setup was used to provide a series of controlled frequency and distance motions for measurement test. The error analysis for various parameters associated with pulmonary activities such as breathing frequency and chest displacement was performed. Results indicated that the proposed sensing system used effectively as a respiratory rate measurement is less affected and shows less error when an antenna with directive radiation pattern, low cross-polarization and stable phase center was used. Due to its good radiation characteristics and small form-factor this antenna was selected to study the respiratory rates of ten test subjects. The results were compared with a standard respiratory-rate measurement using respiration belt transducer. The measurement results using the proposed and the standard systems showed excellent agreement. The mean error value of the respiratory rate measurements was 0.03 Hz with a statistical standard deviation of 0.03 Hz. },
issn = {2469-7249},
keywords = {Antennas, respiratory rate detection, remote sensing, ultra-wide band (UWB) radar},
language = {English},
publisher = {IEEE}
}

State-of-the-art advances in the field of radar technology have made it possible to design non-invasive sensing devices of vital signs. This paper presents the effects of antenna characteristics on Ultra Wide Band (UWB) radar-based respiratory rate measurement system for tele-health-monitoring applications. The performance of three types of antenna for a UWB radar respiratory rate measurement system was studied in this work. In this context, the proposed system was comprehensively evaluated using two experimental sets. First, a mechanical setup was used to provide a series of controlled frequency and distance motions for measurement test. The error analysis for various parameters associated with pulmonary activities such as breathing frequency and chest displacement was performed. Results indicated that the proposed sensing system used effectively as a respiratory rate measurement is less affected and shows less error when an antenna with directive radiation pattern, low cross-polarization and stable phase center was used. Due to its good radiation characteristics and small form-factor this antenna was selected to study the respiratory rates of ten test subjects. The results were compared with a standard respiratory-rate measurement using respiration belt transducer. The measurement results using the proposed and the standard systems showed excellent agreement. The mean error value of the respiratory rate measurements was 0.03 Hz with a statistical standard deviation of 0.03 Hz.

@conference{kogan_2018,
title = {Architecture for testing learning-based autonomous vehicle control design},
author = {Kogan, M.; Jardine, P.T.; Givigi, S.N.},
booktitle = {2018 Annual IEEE International Systems Conference (SysCon)},
year = {2018},
institution = {Royal Military College of Canada, Canada},
abstract = {This paper presents the architecture for the testing of autonomous vehicle controllers designed using machine learning. A localization system feeds measurement data into a ground station. The ground station processes this data and provides the position of the vehicle to the controller, which has been tuned offline via machine learning. Control inputs are then generated and provided to the vehicle in order to accomplish the desired mission. The performance of the learned controller is compared to a nominal case. During the offline tuning process, a vehicle model is used to simulate the actual vehicle. Once tuning is complete, the parameters are used to control a real vehicle in order to accomplish the desired mission. The proposed architecture was tested by tuning a model predictive controller to guide a differential drive robot to a series of waypoints using a Reinforced Learning technique known as Learning Automata. The controller was then tested online with a similar but different problem on a real differential drive robot. The results showed that after tuning, the vehicle performed significantly better. This demonstrated that offline learning techniques can be used to optimally select controller parameters. },
issn = {2472-9647},
keywords = {Computer architecture, Testing, Machine learning, Tuning, Mathematical model, Robot kinematics},
language = {English},
publisher = {IEEE},
isbn = {978-1-5386-3665-7}
}

This paper presents the architecture for the testing of autonomous vehicle controllers designed using machine learning. A localization system feeds measurement data into a ground station. The ground station processes this data and provides the position of the vehicle to the controller, which has been tuned offline via machine learning. Control inputs are then generated and provided to the vehicle in order to accomplish the desired mission. The performance of the learned controller is compared to a nominal case. During the offline tuning process, a vehicle model is used to simulate the actual vehicle. Once tuning is complete, the parameters are used to control a real vehicle in order to accomplish the desired mission. The proposed architecture was tested by tuning a model predictive controller to guide a differential drive robot to a series of waypoints using a Reinforced Learning technique known as Learning Automata. The controller was then tested online with a similar but different problem on a real differential drive robot. The results showed that after tuning, the vehicle performed significantly better. This demonstrated that offline learning techniques can be used to optimally select controller parameters.

@inbook{shakev_2018,
title = {Autonomous Flight Control and Precise Gestural Positioning of a Small Quadrotor},
author = {Shakev N.G., Ahmed S.A., Topalov A.V., Popov V.L., Shiev K.B.},
booktitle = { Learning Systems: From Theory to Practice},
year = {2018},
volume = {756},
institution = {Control Systems Department, TU–Sofia, Bulgaria},
abstract = {Precise gestural positioning interface of a small quadrotor, presented here, is an advance continuation (ending stage) of intelligent autonomous flight control strategy. It is based on gestures and visual computing techniques and ensures intuitive way of prepositioning (fine movements in flight’s end point proximity) in absence of GPS signal or when human interaction is crucial. Therefore, a human operator could control the implementation of various maneuvers during the flight of the rotorcraft via specific gestures and body postures. A Parrot AR. Drone quadrotor and a Microsoft Kinect sensor have been used to implement and evaluate the proposed autonomous and semi-autonomous flight control. },
language = {English},
series = {Studies in Computational Intelligence},
publisher = {Springer, Cham},
isbn = {978-3-319-75180-1},
pages = {179-197}
}

Precise gestural positioning interface of a small quadrotor, presented here, is an advance continuation (ending stage) of intelligent autonomous flight control strategy. It is based on gestures and visual computing techniques and ensures intuitive way of prepositioning (fine movements in flight’s end point proximity) in absence of GPS signal or when human interaction is crucial. Therefore, a human operator could control the implementation of various maneuvers during the flight of the rotorcraft via specific gestures and body postures. A Parrot AR. Drone quadrotor and a Microsoft Kinect sensor have been used to implement and evaluate the proposed autonomous and semi-autonomous flight control.

@article{brentari_2018,
title = {Benchmark model of Quanser’s 3 DOF Helicopter},
author = {Brentari, M.; Bosetti, P.; Queinnec, I.; Zaccarian, L.},
year = {2018},
institution = {University of Trento, Italy; Universite de Toulouse, CNRS, France},
abstract = {This paper proposes a software benchmark tool for the Quanser “3 DOF Helicopter” in the Mathworks Simscape environment, based on a multi-body model of the experimental setup. The proposed benchmark tool takes into account a number of implementation features of the experimental setup and aims at providing a tool for simulative validation and performance analysis of control strategies. Along with this software-in-the-loop tool, a novel reduced complexity non-linear model for theQuanser “3 DOF Helicopter” is derived from the Lagrangian description of the full multi-body model, with the scope of being used in the control synthesis phase. The identification of the models parameters is carried out following a “gray-box” type of paradigm in order to match the models with the experimental setup. A feedback linearizing control law is as well proposed, based on the reduced complexity model. Closed-loop experimental results both show the accuracy of the simulated response compared to the experimental response, and the effectiveness of the proposed control strategy in a set-point regulation task. },
language = {English}
}

This paper proposes a software benchmark tool for the Quanser “3 DOF Helicopter” in the Mathworks Simscape
environment, based on a multi-body model of the experimental setup. The proposed benchmark tool takes into account a number of implementation features of the experimental setup and aims at providing a tool for simulative validation and performance analysis of control strategies. Along with this software-in-the-loop tool, a novel reduced complexity non-linear model for theQuanser
“3 DOF Helicopter” is derived from the Lagrangian
description of the full multi-body model, with the scope of being used in the control synthesis phase. The identification of the models parameters is carried out following a “gray-box” type of paradigm in order to match the models with the experimental setup. A feedback linearizing control law is as well proposed, based on the reduced complexity model. Closed-loop experimental results both show the accuracy of the simulated response compared to the experimental response, and the effectiveness of the proposed control strategy in a set-point regulation task.

@article{nandi_2018,
title = {Chance Constraint based Design of Open-Loop Controllers for Linear Uncertain Systems},
author = {Nandi, S.; Singh, T.},
journal = { IEEE/ASME Transactions on Mechatronics},
year = {2018},
institution = {University at Buffalo, USA},
abstract = {This paper considers the problem of state-to-state transition with state and control constraints, for a linear system with time invariant model parameter uncertainties. Polynomial chaos is used to transform the stochastic model to a deterministic surrogate model. This surrogate model is used to pose a chance constrained optimal control problem where the state constraints and the residual energy cost are represented in terms of the mean and variance of the stochastic states. The resulting convex optimization is illustrated on the problem of rest-to-rest maneuver of the benchmark floating oscillator and on an experimental two-tank setup. },
issn = {1083-4435 },
keywords = {Uncertain System, Vibration Control, Chance Constraint, Polynomial Chaos, Stochastic Optimal Control},
language = {English},
publisher = {IEEE}
}

This paper considers the problem of state-to-state transition with state and control constraints, for a linear system with time invariant model parameter uncertainties. Polynomial chaos is used to transform the stochastic model to a deterministic surrogate model. This surrogate model is used to pose a chance constrained optimal control problem where the state constraints and the residual energy cost are represented in terms of the mean and variance of the stochastic states. The resulting convex optimization is illustrated on the problem of rest-to-rest maneuver of the benchmark floating oscillator and on an experimental two-tank setup.

@conference{furtado_2018,
title = {Comparative Analysis of OptiTrack Motion Capture Systems},
author = {Furtado, J.S.; Liu, H.H.T.; Lai, G.; Lacheray, H.; Desouza-Coelho, J.},
booktitle = {CSME International Congress 2018},
year = {2018},
institution = {University of Toronto Institute for Aerospace Studies, Canada; Quanser, Canada},
abstract = {A comparative analysis of four different OptiTrack motion capture systems is provided in this paper. Tracking accuracy, workspace volume, marker size and camera range are the main criteria used for comparison. The tracking accuracy is tested using Quanser’s linear motion platform by comparing the measured position of the cart with the position obtained using the encoder. The workspace volume limits are obtained by flying a LiteHawk Neon drone in the circles of increasing radii at different heights until tracking fails. The relationship between marker size and camera range is obtained through theoretical calculations. The experimental as well as theoretical results are presented, illustrating the performance of these four systems. These will serve as a baseline to select the right motion capture system for any particular application. },
keywords = {Motion capture; OptiTrack; Optical-Passive},
language = {English},
publisher = {CSME}
}

A comparative analysis of four different OptiTrack motion capture systems is provided in this paper. Tracking accuracy, workspace volume, marker size and camera range are the main criteria used for comparison. The tracking accuracy is tested using Quanser’s linear motion platform by comparing the measured position of the cart with the position obtained using the encoder. The workspace volume limits are obtained by flying a LiteHawk Neon drone in the circles of increasing radii at different heights until tracking fails. The relationship between marker size and camera range is obtained through theoretical calculations. The experimental as well as theoretical results are presented, illustrating the performance of these four systems. These will serve as a baseline to select the right motion capture system for any particular application.

@article{keshavarz_2018,
title = {Comparing simulator sickness in younger and older adults during simulated driving under different multisensory conditions},
author = {Keshavarz, B.; Ramkhalawansingh, R.; Haycock, B.; Shahab, S.; Campos, J.L.},
journal = {Transportation Research Part F: Traffic Psychology and Behaviour},
year = {2018},
month = {04},
volume = {54},
institution = {University Health Network, Toronto Rehabilitation Institute, Canada; Ryerson University, Canada; University of Toronto, Canada; Centre for Addiction and Mental Health, Research Imaging Centre, Canada},
abstract = {Driving simulators are valuable tools for traffic safety research as they allow for systematic reproductions of challenging situations that cannot be easily tested during real-world driving. Unfortunately, simulator sickness (i.e., nausea, dizziness, etc.) is common in many driving simulators and may limit their utility. The experience of simulator sickness is thought to be related to the sensory feedback provided to the user and is also thought to be greater in older compared to younger users. Therefore, the present study investigated whether adding auditory and/or motion cues to visual inputs in a driving simulator affected simulator sickness in younger and older adults. Fifty-eight healthy younger adults (age 18–39) and 63 healthy older adults (age 65+) performed a series of simulated drives under one of four sensory conditions: (1) visual cues alone, (2) combined visual + auditory cues (engine, tire, wind sounds), (3) combined visual + motion cues (via hydraulic hexapod motion platform), or (4) a combination of all three sensory cues (visual, auditory, motion). Simulator sickness was continuously recorded while driving and up to 15 min after driving session termination. Results indicated that older adults experienced more simulator sickness than younger adults overall and that females were more likely to drop out and drove for less time compared to males. No differences between sensory conditions were observed. However, older adults needed significantly longer time to fully recover from the driving session than younger adults, particularly in the visual-only condition. Participants reported that driving in the simulator was least realistic in the visual-only condition compared to the other conditions. Our results indicate that adding auditory and/or motion cues to the visual stimulus does not guarantee a reduction of simulator sickness per se, but might accelerate the recovery process, particularly in older adults. },
keywords = {Motion sickness Driving Aging Multimodal cue combination Vection},
language = {English},
publisher = {Elsevier B.V.},
pages = {47-62}
}

Driving simulators are valuable tools for traffic safety research as they allow for systematic reproductions of challenging situations that cannot be easily tested during real-world driving. Unfortunately, simulator sickness (i.e., nausea, dizziness, etc.) is common in many driving simulators and may limit their utility. The experience of simulator sickness is thought to be related to the sensory feedback provided to the user and is also thought to be greater in older compared to younger users. Therefore, the present study investigated whether adding auditory and/or motion cues to visual inputs in a driving simulator affected simulator sickness in younger and older adults. Fifty-eight healthy younger adults (age 18–39) and 63 healthy older adults (age 65+) performed a series of simulated drives under one of four sensory conditions: (1) visual cues alone, (2) combined visual + auditory cues (engine, tire, wind sounds), (3) combined visual + motion cues (via hydraulic hexapod motion platform), or (4) a combination of all three sensory cues (visual, auditory, motion). Simulator sickness was continuously recorded while driving and up to 15 min after driving session termination. Results indicated that older adults experienced more simulator sickness than younger adults overall and that females were more likely to drop out and drove for less time compared to males. No differences between sensory conditions were observed. However, older adults needed significantly longer time to fully recover from the driving session than younger adults, particularly in the visual-only condition. Participants reported that driving in the simulator was least realistic in the visual-only condition compared to the other conditions. Our results indicate that adding auditory and/or motion cues to the visual stimulus does not guarantee a reduction of simulator sickness per se, but might accelerate the recovery process, particularly in older adults.

@article{saadatzi_2018,
title = {Comparison of Human-Robot Interaction Torque Estimation Methods in a Wrist Rehabilitation Exoskeleton},
author = {Saadatzi, M.; Long, D.C.; Celik, O.},
journal = {Journal of Intelligent & Robotic Systems},
year = {2018},
institution = {Colorado School of Mines, USA},
abstract = {In this paper, experimental implementation and comparative accuracy evaluation of five methods for estimation of human-robot interaction torques are presented. These methods vary from the simplest case of using solely commanded motor torques, to partial consideration of the robot dynamics, to advanced methods considering full robot dynamics such as inverse dynamics (ID) and nonlinear disturbance observer (NDO) based algorithms. Dynamic and friction models of the exoskeleton were developed and their parameters were identified using an evolutionary optimization algorithm to ensure high parameter accuracy. When used with accurate model parameters, ID method led to 20 to 22% average error, while NDO method generated 12 to 18% average error, as evaluated in experiments with a force sensor. These values compare to average error values of up to 132% for using motor torques only, and between 25 to 69% when partial dynamics were used. A sensitivity analysis of the ID and NDO methods to inaccuracies in model parameter estimations revealed considerable sensitivity of these advanced methods to model parameter variations. A summary is provided for the typical estimation accuracy levels that can be expected of these methods and discuss the limitations and considerations that should be taken into account for their use. },
issn = {0921-0296},
keywords = {Nonlinear disturbance observer, Force estimation, System identification, Sensitivity analysis, Friction modeling, Exoskeletons},
language = {English},
publisher = {Springer Netherlands}
}

In this paper, experimental implementation and comparative accuracy evaluation of five methods for estimation of human-robot interaction torques are presented. These methods vary from the simplest case of using solely commanded motor torques, to partial consideration of the robot dynamics, to advanced methods considering full robot dynamics such as inverse dynamics (ID) and nonlinear disturbance observer (NDO) based algorithms. Dynamic and friction models of the exoskeleton were developed and their parameters were identified using an evolutionary optimization algorithm to ensure high parameter accuracy. When used with accurate model parameters, ID method led to 20 to 22% average error, while NDO method generated 12 to 18% average error, as evaluated in experiments with a force sensor. These values compare to average error values of up to 132% for using motor torques only, and between 25 to 69% when partial dynamics were used. A sensitivity analysis of the ID and NDO methods to inaccuracies in model parameter estimations revealed considerable sensitivity of these advanced methods to model parameter variations. A summary is provided for the typical estimation accuracy levels that can be expected of these methods and discuss the limitations and considerations that should be taken into account for their use.

@article{rios_2018,
title = {Continuous Sliding-Modes Control Strategies for Quad-Rotor Robust Tracking: Real-Time Application},
author = {Rios, H.; Falcon, R.; Gonzalez, O.A.; Dzul, A.E.},
journal = {IEEE Transactions on Industrial Electronics},
year = {2018},
institution = {Instituto Tecnologico de La Laguna, Mexico},
abstract = {The design of robust tracking control for Quad-Rotors is an important and challenging problem nowadays. In this paper a robust tracking output-control strategy is proposed for a Quad-Rotor under the influence of external disturbances and uncertainties. Such a strategy is composed of a Finite-Time Sliding-Mode Observer (FTSMO) which estimates the full state from the measurable output and identifies some type of disturbances; and also of a combination between PID controllers and Continuous Sliding-Modes Controllers (Continuous-SMCs), that robustly track a desired time-varying trajectory with exponential convergence and despite the influence of external disturbances and uncertainties. The closed-loop stability is provided based on Input-to-State Stability (ISS) and Finite- Time ISS (FT-ISS) properties. Finally, experimental results in real-time show the performance of the proposed control strategy. },
issn = {0278-0046 },
keywords = {Robust Output-Control, Quad-Rotor, Continuous Sliding-Mode Control },
language = {English},
publisher = {IEEE}
}

The design of robust tracking control for Quad-Rotors is an important and challenging problem nowadays. In this paper a robust tracking output-control strategy is proposed for a Quad-Rotor under the influence of external disturbances and uncertainties. Such a strategy is composed of a Finite-Time Sliding-Mode Observer (FTSMO) which estimates the full state from the measurable output and identifies some type of disturbances; and also of a combination between PID controllers and Continuous Sliding-Modes Controllers (Continuous-SMCs), that robustly track a desired time-varying trajectory with exponential convergence and despite the influence of external disturbances and uncertainties. The closed-loop stability is provided based on Input-to-State Stability (ISS) and Finite- Time ISS (FT-ISS) properties. Finally, experimental results in real-time show the performance of the proposed control strategy.

@article{medina-dorantes_2018,
title = {Controller with time-delay to stabilize first-order processes with dead-time},
author = {Medina-Dorantes, F.; Villafuerte-Segura, R.; Aguirre-Hernandez, B.},
journal = {Journal of Control Engineering and Applied Informatics},
year = {2018},
volume = {20},
number = {2},
institution = {Universidad Autónoma Metropolitana-Iztapalapa, Mexico; Universidad Autónoma del Estado de Hidalgo, Mexico},
abstract = {This paper focuses on the stability analysis of analytic functions with two transcendental terms in order to obtain parameters that guarantee an exponential decay rate σ in the response of the linear time-invariant system associated with the analytic function. As a consequence of this stability analysis, analytic expressions to tune all of the gains of a controller with time-delay action called Proportional Integral Retarded (PIR) control law that σ -stabilizes a first-order process with dead-time are obtained. To illustrate the effectiveness of the theoretical results proposed, an application on a Quanser thermal platform is given. Furthermore, a comparison with a classical PID control law is made. },
keywords = {D-composition method, first-order system, time delay systems, stability analysis, stabilizing feedback},
language = {English},
pages = {42-50}
}

This paper focuses on the stability analysis of analytic functions with two transcendental terms in order to obtain parameters that guarantee an exponential decay rate σ in the response of the linear time-invariant system associated with the analytic function. As a consequence of this stability analysis, analytic expressions to tune all of the gains of a controller with time-delay action called Proportional Integral Retarded (PIR) control law that σ -stabilizes a first-order process with dead-time are obtained. To illustrate the effectiveness of the theoretical results proposed, an application on a Quanser thermal platform is given. Furthermore, a comparison with a classical PID control law is made.

@article{liang_2018,
title = {Design a software real-time operation platform for wave piercing catamarans motion control using linear quadratic regulator based genetic algorithm},
author = {Liang, L.; Yuan, J.; Zhang, S.; Zhao, P.},
journal = {Plos One},
year = {2018},
volume = {13},
number = {4},
institution = {Harbin Engineering University, China},
abstract = {This work presents optimal linear quadratic regulator (LQR) based on genetic algorithm (GA) to solve the two degrees of freedom (2 DoF) motion control problem in head seas for wave piercing catamarans (WPC). The proposed LQR based GA control strategy is to select optimal weighting matrices (Q and R). The seakeeping performance of WPC based on proposed algorithm is challenged because of multi-input multi-output (MIMO) system of uncertain coefficient problems. Besides the kinematical constraint problems of WPC, the external conditions must be considered, like the sea disturbance and the actuators (a T-foil and two flaps) control. Moreover, this paper describes the MATLAB and LabVIEW software plats to simulate the reduction effects of WPC. Finally, the real-time (RT) NI CompactRIO embedded controller is selected to test the effectiveness of the actuators based on proposed techniques. In conclusion, simulation and experimental results prove the correctness of the proposed algorithm. The percentage of heave and pitch reductions are more than 18% in different high speeds and bad sea conditions. And the results also verify the feasibility of NI CompactRIO embedded controller. },
language = {English}
}

This work presents optimal linear quadratic regulator (LQR) based on genetic algorithm (GA) to solve the two degrees of freedom (2 DoF) motion control problem in head seas for wave piercing catamarans (WPC). The proposed LQR based GA control strategy is to select optimal weighting matrices (Q and R). The seakeeping performance of WPC based on proposed algorithm is challenged because of multi-input multi-output (MIMO) system of uncertain coefficient problems. Besides the kinematical constraint problems of WPC, the external conditions must be considered, like the sea disturbance and the actuators (a T-foil and two flaps) control. Moreover, this paper describes the MATLAB and LabVIEW software plats to simulate the reduction effects of WPC. Finally, the real-time (RT) NI CompactRIO embedded controller is selected to test the effectiveness of the actuators based on proposed techniques. In conclusion, simulation and experimental results prove the correctness of the proposed algorithm. The percentage of heave and pitch reductions are more than 18% in different high speeds and bad sea conditions. And the results also verify the feasibility of NI CompactRIO embedded controller.

@conference{chiaradia_2018,
title = {Design and Embedded Control of a Soft Elbow Exosuit},
author = {Chiaradia, D.; Xiloyannis, M.; Antuvan, C.W.; Frisoli, A.; Masia, L.},
booktitle = {IEEE International Conference on Soft Robotics},
year = {2018},
institution = {Scuola Superiore Sant’Anna, Italy; Nanyang Technological University, Singapore},
abstract = {The use of soft materials to transmit power to the human body has numerous advantages, amongst which safety and kinematic transparency stand out. In previous work we showed that a tethered fabric-based exosuit for the elbow joint, driven by an electric motor through a Bowden cable transmission, reduces the muscular effort associated with flexion movements by working in parallel with its wearer's muscles. We herein propose a refined design of the suit and present an untethered control architecture for gravity compensation and motion-intention detection. The architecture comprises four interconnected modules for power management, low-level motor control and high-level signal processing and data streaming. The controller uses a silicone stretch sensor and a miniature load cell, integrated in the fabric frame, to estimate and minimise the torque that its user needs to exert to perform a movement. We show that the device relieves its wearer from an average of 77% of the total moment required to sustain and move a light weight, with a consequent average reduction in muscular effort of 64.5%. },
language = {English}
}

The use of soft materials to transmit power to the human body has numerous advantages, amongst which safety and kinematic transparency stand out. In previous work we showed that a tethered fabric-based exosuit for the elbow joint, driven by an electric motor through a Bowden cable transmission, reduces the muscular effort associated with flexion movements by working in parallel with its wearer's muscles. We herein propose a refined design of the suit and present an untethered control architecture for gravity compensation and motion-intention detection. The architecture comprises four interconnected modules for power management, low-level motor control and high-level signal processing and data streaming. The controller uses a silicone stretch sensor and a miniature load cell, integrated in the fabric frame, to estimate and minimise the torque that its user needs to exert to perform a movement. We show that the device relieves its wearer from an average of 77% of the total moment required to sustain and move a light weight, with a consequent average reduction in muscular effort of 64.5%.

@conference{wang_2018,
title = {Design and implementation of fractional PID controller for rotary inverted pendulum},
author = {Wang, C.; Liu, X.; Shi, H.; Xin, R.; Xu, X.},
booktitle = {2018 Chinese Control And Decision Conference (CCDC)},
year = {2018},
institution = {Changchun University of Science and Technology, China},
abstract = {As for the stability control problem for rotary inverted pendulum, the two closed-loop fractional order PID control scheme is used to control the pendulum. First, the mathematical model of rotary inverted pendulum is established according to the Euler-Lagrange equation. Then, a fractional order PID controller is designed based on the Bode ideal transfer function. Finally, the fractional order PID (FOPID) controller, fractional PD (FOPD) controller and integer order PD (IOPD) controller are applied to the rotary inverted pendulum system which based on the Quanser company loop simulation experiment platform. The results show that the FOPID controller is better than the FOPD and IOPD controller in stabilizing the system and the angle of the pendulum is closest to the stable equilibrium point. },
issn = {1948-9447 },
keywords = {rotary inverted pendulum; fractional PID controller; Bode ideal transfer function; stable control},
language = {English},
publisher = {IEEE}
}

As for the stability control problem for rotary inverted pendulum, the two closed-loop fractional order PID control scheme is used to control the pendulum. First, the mathematical model of rotary inverted pendulum is established according to the Euler-Lagrange equation. Then, a fractional order PID controller is designed based on the Bode ideal transfer function. Finally, the fractional order PID (FOPID) controller, fractional PD (FOPD) controller and integer order PD (IOPD) controller are applied to the rotary inverted pendulum system which based on the Quanser company loop simulation experiment platform. The results show that the FOPID controller is better than the FOPD and IOPD controller in stabilizing the system and the angle of the pendulum is closest to the stable equilibrium point.

@conference{sun_2018,
title = {Design of fractional order proportional differentiation controller for second order position servo system},
author = {Sun, J.;Wang, C.; Xin, R.},
booktitle = {2018 Chinese Control And Decision Conference (CCDC)},
year = {2018},
institution = {Changchun University of Science and Technology, China},
abstract = {This paper considers a tuning method of factional order proportional derivative (FOPD) controller based on vector model for the second order position servo system. This method is designed to improve the closed-loop system's dynamic performance and robustness. Simulations in MATLAB/Simulink and tests on Quanser semi-physical experiment platform are performed after the design of controller for position servo system. The simulation and experimental results reveal that the designed factional order proportional derivative (FOPD) controller works more effectively than integer order proportional integral derivative (IOPID) controller, with the improved performance of faster response speed and stronger anti-jamming capability. },
issn = {1948-9447},
keywords = {Fractional order proportional differentiation controller, Vector model, Position servo system, Quanser experiment device, Robustness},
language = {English},
publisher = {IEEE}
}

This paper considers a tuning method of factional order proportional derivative (FOPD) controller based on vector model for the second order position servo system. This method is designed to improve the closed-loop system's dynamic performance and robustness. Simulations in MATLAB/Simulink and tests on Quanser semi-physical experiment platform are performed after the design of controller for position servo system. The simulation and experimental results reveal that the designed factional order proportional derivative (FOPD) controller works more effectively than integer order proportional integral derivative (IOPID) controller, with the improved performance of faster response speed and stronger anti-jamming capability.

@inbook{max_2018,
title = {Development of Robust H-Infinity Steering Control System for Autonomous Vehicles},
author = {Max, G.; Vass, S.; Kiss, B.},
booktitle = {Vehicle and Automotive Engineering 2. VAE 2018},
year = {2018},
institution = {Budapest University of Technology and Economics, Hungary},
abstract = {Undoubtedly one of the most significant security systems for today’s autonomous ground vehicles is their steering system. A commonly used approach for control purposes in the automotive industry is the steering-by-wire concept. Despite its simplicity, this method is rather new and several concerns may arise regarding external loads arising from the tire-ground contact patch. This paper discusses the robust controller design of an electric steering-by-wire system taking into account multiple sources of uncertainty. In order to achieve robust performance, an H∞ controller was selected for the task. This allows excellent disturbance rejection while requiring low computational needs. The design is verified using simulations and the final verification phase includes testing on the RECAR autonomous vehicle by utilizing rapid prototyping and hardware-in-the-loop tools. },
keywords = {H-infinity controller, steer-by-wire, autonomous vehicle},
language = {English},
series = {Lecture Notes in Mechanical Engineering},
publisher = {Springer, Cham},
isbn = {978-3-319-75676-9},
pages = {393-402}
}

Undoubtedly one of the most significant security systems for today’s autonomous ground vehicles is their steering system. A commonly used approach for control purposes in the automotive industry is the steering-by-wire concept. Despite its simplicity, this method is rather new and several concerns may arise regarding external loads arising from the tire-ground contact patch. This paper discusses the robust controller design of an electric steering-by-wire system taking into account multiple sources of uncertainty. In order to achieve robust performance, an H∞ controller was selected for the task. This allows excellent disturbance rejection while requiring low computational needs. The design is verified using simulations and the final verification phase includes testing on the RECAR autonomous vehicle by utilizing rapid prototyping and hardware-in-the-loop tools.

In terms of vibrations along bidirectional earthquake forces, several problems are faced when modelling and controlling the structure of a building, such as lateral-torsional vibration, uncertainties surrounding the rigidity and the difficulty of estimating damping forces.

In this paper, we use a fuzzy logic model to identify and compensate the uncertainty which does not require an exact model of the building structure. To attenuate bidirectional vibration, a novel discrete-time sliding mode control is proposed. This sliding mode control has time-varying gain and is combined with fuzzy sliding mode control in order to reduce the chattering of the sliding mode control. We prove that the closed-loop system is uniformly stable using Lyapunov stability analysis. We compare our fuzzy sliding mode control with the traditional controllers: proportional–integral–derivative and sliding mode control. Experimental results show significant vibration attenuation with our fuzzy sliding mode control and horizontal-torsional actuators. The proposed control system is the most efficient at mitigating bidirectional and torsional vibrations.

@article{chen2_2018,
title = {Distributed adaptive control for multiple under-actuated Lagrangian systems under fixed or switching topology},
author = {Chen, T.; Shan, J.; Ramkumar, G.},
journal = {Nonlinear Dynamics},
year = {2018},
institution = {York University, ON, Canada},
abstract = {This paper presents distributed adaptive tracking control algorithms under fixed or switching communication graph for a team of agents, each of which is a special class of under-actuated Lagrangian system with uncertain parameters. The reference velocities of the unactuated and actuated variables are defined by an auxiliary system and the summation of the synchronization error and its integral, respectively. Based on such reference velocities and the linear-in-parameter property, distributed adaptive tracking controllers are designed for fixed graph with globally reachable leader, switching graph with globally reachable leader in each dwell time and switching graph with jointly globally reachable leader. Theoretical analyses are presented to demonstrate the convergence conditions of the proposed controllers. Finally, numerical simulations and experimental studies are performed to verify the effectiveness of the distributed adaptive tracking controllers. },
issn = {0924-090X},
keywords = {Distributed adaptive control, Consensus, Under-actuated Lagrangian systems, Switching topology },
language = {English},
publisher = {Springer Netherlands}
}

This paper presents distributed adaptive tracking control algorithms under fixed or switching communication graph for a team of agents, each of which is a special class of under-actuated Lagrangian system with uncertain parameters. The reference velocities of the unactuated and actuated variables are defined by an auxiliary system and the summation of the synchronization error and its integral, respectively. Based on such reference velocities and the linear-in-parameter property, distributed adaptive tracking controllers are designed for fixed graph with globally reachable leader, switching graph with globally reachable leader in each dwell time and switching graph with jointly globally reachable leader. Theoretical analyses are presented to demonstrate the convergence conditions of the proposed controllers. Finally, numerical simulations and experimental studies are performed to verify the effectiveness of the distributed adaptive tracking controllers.

@article{mu_2018,
title = {Distributed LQR Consensus Control for Heterogeneous Multi-Agent Systems: Theory and Experiments},
author = {Mu, B.; Shi, Y.},
journal = {IEEE/ASME Transactions on Mechatronics},
year = {2018},
institution = {University of Victoria, British Columbia Canada },
abstract = {Controlling heterogeneous multi-agent systems (MASs) to cooperatively accomplish tasks is currently an emerging topic in the application-oriented research of robotics. This paper investigates the consensus problem of an MAS consisting of quadrotors and two-wheeled mobile robots (2WMRs). Directed and switching interaction topologies over the network are considered. We propose a distributed linear quadratic regulation (LQR) consensus protocol for the quadrotors and design an LQR-based Rotate&Run Consensus Scheme for the 2WMRs to update the states. We use the algebraic graph theory and stochastic matrix analysis to conduct the convergence analysis of consensus. The underactuation characteristic of the 2WMR dynamics is considered in the controller design. The effectiveness of the control methods is verified by experiments. },
issn = {1941-014X },
keywords = {Consensus, multi-agent systems, two-wheeled mobile robot, quadrotor, distributed LQR},
language = {English},
publisher = {IEEE}
}

Controlling heterogeneous multi-agent systems (MASs) to cooperatively accomplish tasks is currently an emerging topic in the application-oriented research of robotics. This paper investigates the consensus problem of an MAS consisting of quadrotors and two-wheeled mobile robots (2WMRs). Directed and switching interaction topologies over the network are considered. We propose a distributed linear quadratic regulation (LQR) consensus protocol for the quadrotors and design an LQR-based Rotate&Run Consensus Scheme for the 2WMRs to update the states. We use the algebraic graph theory and stochastic matrix analysis to conduct the convergence analysis of consensus. The underactuation characteristic of the 2WMR dynamics is considered in the controller design. The effectiveness of the control methods is verified by experiments.

@article{chen_2018,
title = {Effects of different coherency models on utility tunnel through shaking table test},
author = {Chen, Z.; Liang, S.; He, C.},
journal = {Journal of Earthquake Engineering },
year = {2018},
institution = {Tongji University, China; Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, China},
abstract = {Since defining ground motions is crucial for reliable analysis of structural responses, it is vital to select coherency model when conducting seismic analyses of extended structures under non-uniform excitation. In the present paper, a series of shaking table tests are conducted to study the effect of coherency models on seismic performances of a utility tunnel. The test results show that there are significant differences in seismic performances of the utility tunnel for using different coherency models. Structural strain and acceleration responses are relative to the decaying of coherency models at low frequency and high frequency, respectively. },
keywords = {Non-Uniform Excitation; Coherency Models; Utility Tunnel; Shaking Table Test; Spatially Varying Ground Motion},
language = {English}
}

Since defining ground motions is crucial for reliable analysis of structural responses, it is vital to select coherency model when conducting seismic analyses of extended structures under non-uniform excitation. In the present paper, a series of shaking table tests are conducted to study the effect of coherency models on seismic performances of a utility tunnel. The test results show that there are significant differences in seismic performances of the utility tunnel for using different coherency models. Structural strain and acceleration responses are relative to the decaying of coherency models at low frequency and high frequency, respectively.

@article{calhoun_2018,
title = {Enhancing the teaching of seismic isolation using additive manufacturing},
author = {Calhoun, S.J.; Harvey Jr., P.S.},
journal = {Engineering Structures},
year = {2018},
month = {07},
volume = {167},
institution = {University of Oklahoma, USA},
abstract = {This paper provides a complementary study to two previous papers by Virgin (2017a,b). In those papers, 3D printing was used to provide hands-on experience for students studying structural analysis and structural dynamics, respectively. In this paper, the application of 3D printing is extended to investigate advanced seismic design strategies, namely seismic isolation. This paper describes the use of 3D printing to fabricate pendulum-type isolation bearings under parametric variation. Both sliding and rolling mechanisms are modeled, designed, fabricated and tested, and the influence of bearing geometry (radius) and damping (friction versus rolling resistance) on dynamic characteristics and isolation performance is explored. },
keywords = {Seismic isolation, Rolling Sliding Pendulum, Additive manufacturing, 3D printing},
language = {English},
publisher = {Elsevier Ltd.},
pages = {494-503}
}

This paper provides a complementary study to two previous papers by Virgin (2017a,b). In those papers, 3D printing was used to provide hands-on experience for students studying structural analysis and structural dynamics, respectively. In this paper, the application of 3D printing is extended to investigate advanced seismic design strategies, namely seismic isolation. This paper describes the use of 3D printing to fabricate pendulum-type isolation bearings under parametric variation. Both sliding and rolling mechanisms are modeled, designed, fabricated and tested, and the influence of bearing geometry (radius) and damping (friction versus rolling resistance) on dynamic characteristics and isolation performance is explored.

@article{ahmed_2018,
title = {Environmental monitoring using a robotized wireless sensor network},
author = {Ahmed, S.A.; Popov, V.L.; Topalov, A.V.; Shakev, N.G.},
journal = {AI & Society},
year = {2018},
institution = {Technical University of Sofia, branch Plovdiv, Bulgaria},
abstract = {Big cities and growing industrial areas bring high risk of different kinds of pollutions which would implicate to the quality of life of the society. Discovering and monitoring of polluted areas using autonomous mobile robots is nowadays a frequently considered solution concerning both environmental and human safety problems. Being part of a distributed control system, such robots can help to improve the efficiency of the existing conventional pollution prevention systems. On the other hand, during the last decade, wireless sensor networks (WSN) have provoked the interest of specialists from different areas by imposing a large number of theoretical and practical challenges related to their implementation. This paper attempts to deal with both issues by presenting a possible way for building robotized WSNs that can be suitable for solving different environmental monitoring tasks. The goal is to transform the WSN into an adaptive sensor system with intelligent behavior that can be used to discover and track spots or areas where given monitored environmental parameters violate defined thresholds. The inclusion of robotized agents into the WSN structure can provide additional flexibility with respect to the installation of the network sensors and allow reliable information gathering and transfer. The proposed algorithmic methods have been tested on a pre-built laboratory prototype of a robotized WSN. The robotized agents (mobile network nodes) have been built using iRobot Create mobile platforms that are additionally equipped with a single-chip computers Gumstix Verdex pro TM XL6P with various expansion modules. },
issn = {0951-5666},
keywords = {Mobile robots, Wireless sensor networks, Intelligent control, Collective robotics, Intelligent sensors, Multiagent systems},
language = {English},
publisher = {Springer, London}
}

Big cities and growing industrial areas bring high risk of different kinds of pollutions which would implicate to the quality of life of the society. Discovering and monitoring of polluted areas using autonomous mobile robots is nowadays a frequently considered solution concerning both environmental and human safety problems. Being part of a distributed control system, such robots can help to improve the efficiency of the existing conventional pollution prevention systems. On the other hand, during the last decade, wireless sensor networks (WSN) have provoked the interest of specialists from different areas by imposing a large number of theoretical and practical challenges related to their implementation. This paper attempts to deal with both issues by presenting a possible way for building robotized WSNs that can be suitable for solving different environmental monitoring tasks. The goal is to transform the WSN into an adaptive sensor system with intelligent behavior that can be used to discover and track spots or areas where given monitored environmental parameters violate defined thresholds. The inclusion of robotized agents into the WSN structure can provide additional flexibility with respect to the installation of the network sensors and allow reliable information gathering and transfer. The proposed algorithmic methods have been tested on a pre-built laboratory prototype of a robotized WSN. The robotized agents (mobile network nodes) have been built using iRobot Create mobile platforms that are additionally equipped with a single-chip computers Gumstix Verdex pro TM XL6P with various expansion modules.

@conference{jiang_2018,
title = {Evaluation of the Effectiveness of Using Mobile Learning in Engineering Dynamics and Vibrations Courses},
author = {Jiang, Z.; Maxwell, A.W.; Merchant, Z.H.; Harvey Jr., P.S.; Tsuchiya, N.; Chen, C.},
booktitle = {2018 ASEE Annual Conference & Exposition},
year = {2018},
institution = {San Francisco State University, USA; University of Oklahoma, USA; California State Polytechnic University, Pomona, USA},
abstract = { Learning style changes from generation to generation. With the advancement of technologies, the current and incoming tech-savvy learners grow up with the digital world. Such technology advancement makes learning more accessible. As one of the examples, mobile learning has become a commonly accepted and embraced concept among the younger generations. Effective learning occurs when the teaching styles align well with the learning styles. To better serve the need of the next-generation learners in a more accessible way, a standalone mobile learning module was recently developed for dynamics and vibration courses at San Francisco State University (SFSU). The developed mobile learning module consisted of three interconnected components, namely Analysis, Simulation and Experiment, representing the three important elements in a good engineering learning environment - theory, practical example and physical experimentation. In addition to deliver the theoretical knowledge and animated simulations in the interactive Apps, the module features a mobile remote shake table laboratory which provides students the opportunity to remotely participate and conduct physical shake table experiments in real-time through smart mobile devices (e.g. smartphones and tablets). The results from a pilot implementation at SFSU were very encouraging. To further evaluate its effectiveness in a larger scale, the mobile learning module is implemented in three dynamics and vibration classes in three different universities. The classes are carefully selected to evaluate the adaptability and expandability of the module and its effectiveness in advancing the learning of students from various backgrounds and knowledge levels (junior, senior, undergraduate, small size, and large size class). Three measures namely Smart Tablet Readiness Measure, Engineering Concepts Achievement Test, and Engineering Concepts Self-Efficacy Test, are developed to perform the evaluation. Results clearly demonstrated the student readiness of using mobile device as a tool for learning activities, and that the mobile learning module can improve students’ knowledge competence and has great potential in increase students’ self-efficacy. },
language = {English},
publisher = {ASEE}
}

Learning style changes from generation to generation. With the advancement of technologies, the current and incoming tech-savvy learners grow up with the digital world. Such technology advancement makes learning more accessible. As one of the examples, mobile learning has become a commonly accepted and embraced concept among the younger generations.

Effective learning occurs when the teaching styles align well with the learning styles. To better serve the need of the next-generation learners in a more accessible way, a standalone mobile learning module was recently developed for dynamics and vibration courses at San Francisco State University (SFSU). The developed mobile learning module consisted of three interconnected components, namely Analysis, Simulation and Experiment, representing the three important elements in a good engineering learning environment - theory, practical example and physical experimentation. In addition to deliver the theoretical knowledge and animated simulations in the interactive Apps, the module features a mobile remote shake table laboratory which provides students the opportunity to remotely participate and conduct physical shake table experiments in real-time through smart mobile devices (e.g. smartphones and tablets).

The results from a pilot implementation at SFSU were very encouraging. To further evaluate its effectiveness in a larger scale, the mobile learning module is implemented in three dynamics and vibration classes in three different universities. The classes are carefully selected to evaluate the adaptability and expandability of the module and its effectiveness in advancing the learning of students from various backgrounds and knowledge levels (junior, senior, undergraduate, small size, and large size class). Three measures namely Smart Tablet Readiness Measure, Engineering Concepts Achievement Test, and Engineering Concepts Self-Efficacy Test, are developed to perform the evaluation. Results clearly demonstrated the student readiness of using mobile device as a tool for learning activities, and that the mobile learning module can improve students’ knowledge competence and has great potential in increase students’ self-efficacy.

@inproceedings{solowjow_2018,
title = {Event-triggered Learning for Resource-efficient Networked Control},
author = {Solowjow, F.; Baumann, D.; Garcke, J.; Trimpe, S.},
journal = {2018 American Control Conference},
year = {2018},
institution = {Max Planck Institute for Intelligent Systems, Germany; University of Bonn, Germany, Fraunhofer SCAI, Germany},
abstract = {Common event-triggered state estimation (ETSE) algorithms save communication in networked control systems by predicting agents' behavior, and transmitting updates only when the predictions deviate significantly. The effectiveness in reducing communication thus heavily depends on the quality of the dynamics models used to predict the agents' states or measurements. Event-triggered learning is proposed herein as a novel concept to further reduce communication: whenever poor communication performance is detected, an identification experiment is triggered and an improved prediction model learned from data. Effective learning triggers are obtained by comparing the actual communication rate with the one that is expected based on the current model. By analyzing statistical properties of the inter-communication times and leveraging powerful convergence results, the proposed trigger is proven to limit learning experiments to the necessary instants. Numerical and physical experiments demonstrate that event-triggered learning improves robustness toward changing environments and yields lower communication rates than common ETSE. }
}

Common event-triggered state estimation (ETSE) algorithms save communication in networked control systems by predicting agents' behavior, and transmitting updates only when the predictions deviate significantly. The effectiveness in reducing communication thus heavily depends on the quality of the dynamics models used to predict the agents' states or measurements. Event-triggered learning is proposed herein as a novel concept to further reduce communication: whenever poor communication performance is detected, an identification experiment is triggered and an improved prediction model learned from data. Effective learning triggers are obtained by comparing the actual communication rate with the one that is expected based on the current model. By analyzing statistical properties of the inter-communication times and leveraging powerful convergence results, the proposed trigger is proven to limit learning experiments to the necessary instants. Numerical and physical experiments demonstrate that event-triggered learning improves robustness toward changing environments and yields lower communication rates than common ETSE.

@article{dobrilla_2018,
title = {Experimental Analysis of Stracture Response to Non-uniform Support Excitation},
author = {Dobrilla, S.; Ceh, N.; Tuhtan, M.; Jelenic, G.},
year = {2018},
institution = {University of Rijeka, Croatia},
abstract = {Experimental testing of the dynamic response of a simply supported beam model with discrete masses has been carried out. The range of excitation amplitudes for which the response is linear have been determined. The experimentally obtained displacements are presented for the case of harmonic uniform and non-uniform excitation, as well as for the simulation of the Northridge earthquake, which could be used as experimental benchmarks for multiple support excitation. },
keywords = {dynamic analysis, non-uniform earthquake excitation, shake tables, optical displacement measurement, beam structures},
language = {English}
}

Experimental testing of the dynamic response of a simply supported beam model with discrete masses has been carried out. The range of excitation amplitudes for which the response is linear have been determined. The experimentally obtained displacements are presented for the case of harmonic uniform and non-uniform excitation, as well as for the simulation of the Northridge earthquake, which could be used as experimental benchmarks for multiple support excitation.

@article{prado_2018,
title = {Experimental evaluation of HJB optimal controllers for the attitude dynamics of a multirotor aerial vehicle},
author = {Acampora Prado I.A. , de Freitas Virgílio Pereira M., Ferreira de Castro M., dos Santos D.A., Balthazar J.M.},
journal = {ISA Transactions},
year = {2018},
institution = {Instituto Tecnologico de Aeronautica, Brazil},
abstract = {The present paper is concerned with the design and experimental evaluation of optimal control laws for the nonlinear attitude dynamics of a multirotor aerial vehicle. Three design methods based on Hamilton-Jacobi-Bellman equation are taken into account. The first one is a linear control with guarantee of stability for nonlinear systems. The second and third are a nonlinear suboptimal control techniques. These techniques are based on an optimal control design approach that takes into account the nonlinearities present in the vehicle dynamics. The stability Proof of the closed-loop system is presented. The performance of the control system designed is evaluated via simulations and also via an experimental scheme using the Quanser 3-DOF Hover. The experiments show the effectiveness of the linear control method over the nonlinear strategy. },
keywords = {Multirotor Aerial Vehicles; Hamilton-Jacobi-Bellman equation; Optimal control; Attitude control},
language = {English},
publisher = {Elsevier Ltd.}
}

The present paper is concerned with the design and experimental evaluation of optimal control laws for the nonlinear attitude dynamics of a multirotor aerial vehicle. Three design methods based on Hamilton-Jacobi-Bellman equation are taken into account. The first one is a linear control with guarantee of stability for nonlinear systems. The second and third are a nonlinear suboptimal control techniques. These techniques are based on an optimal control design approach that takes into account the nonlinearities present in the vehicle dynamics. The stability Proof of the closed-loop system is presented. The performance of the control system designed is evaluated via simulations and also via an experimental scheme using the Quanser 3-DOF Hover. The experiments show the effectiveness of the linear control method over the nonlinear strategy.

@article{mager_2018,
title = {Feedback Control Goes Wireless: Guaranteed Stability over Low-power Multi-hop Networks},
author = {Mager, F.; Baumann, D.; Jacob, R.; Thiele, L.; Trimpe, S.; Zimmerling, M.},
year = {2018},
institution = {TU Dresden, Germany; ETHZ, Switzerland; Max Planck Institute for Intelligent Systems, Germany},
abstract = {Closing feedback loops fast and over long distances is key to emerging applications; for example, robot motion control and swarm coordination require update intervals below 100 ms. Low-power wireless is preferred for its flexibility, low cost, and small form factor, especially if the devices support multi-hop communication. Thus far, however, closed-loop control over multi-hop low-power wireless has only been demonstrated for update intervals on the order of multiple seconds. This paper presents a wireless embedded system that tames imperfections impairing control performance such as jitter or packet loss, and a control design that exploits the essential properties of this system to provably guarantee closed-loop stability for linear dynamic systems. Using experiments on a testbed with multiple cart-pole systems, we are the first to demonstrate the feasibility and to assess the performance of closed-loop control and coordination over multi-hop low-power wireless for update intervals from 20 ms to 50 ms. }
}

Closing feedback loops fast and over long distances is key to emerging applications; for example, robot motion control and swarm coordination require update intervals below 100 ms. Low-power wireless is preferred for its flexibility, low cost, and small form factor, especially if the devices support multi-hop communication. Thus far, however, closed-loop control over multi-hop low-power wireless has only been demonstrated for update intervals on the order of multiple seconds. This paper presents a wireless embedded system that tames imperfections impairing control performance such as jitter or packet loss, and a control design that exploits the essential properties of this system to provably guarantee closed-loop stability for linear dynamic systems. Using experiments on a testbed with multiple cart-pole systems, we are the first to demonstrate the feasibility and to assess the performance of closed-loop control and coordination over multi-hop low-power wireless for update intervals from 20 ms to 50 ms.

@article{razavian_2018,
title = {Feedback Control of Functional Electrical Stimulation for 2D Arm Reaching Movements},
author = {Razavian, R.S.; Ghannadi, B.; mehrabi, N.; Charlet, M.; McPhee, J.},
journal = {IEEE Transactions on Neural Systems and Rehabilitation Engineering},
year = {2018},
institution = {University of Waterloo, Canada; University of Washington, USA},
abstract = {Functional electrical stimulation (FES) can be used as a neuroprosthesis in which muscles are stimulated by electrical pulses to compensate for the loss of voluntary movement control. Modulating the stimulation intensities to reliably generate movements is a challenging control problem. This paper introduces a feedback controller for a multi-muscle FES system to control hand movements in a two-dimensional (table-top) task space. This feedback controller is based on a recent human motor control model, which uses muscle synergies to simplify its calculations and improve the performance. This synergy-based controller employs direct relations between the muscle synergies and the produced hand force, thereby allowing for the real-time calculation of six muscle stimulation levels required to reach an arbitrary target. The experimental results show that this control scheme can perform arbitrary point-to-point reaching tasks in the two-dimensional task space in real-time, with an average of ~2 cm final hand position error from the specified targets. The success of this prototype demonstrates the potential of the proposed method for the feedback control of functional tasks with FES. },
keywords = {Functional electrical stimulation (FES), muscle synergies, feedback control, task space control, biomechanics},
language = {English},
publisher = {IEEE}
}

Functional electrical stimulation (FES) can be used as a neuroprosthesis in which muscles are stimulated by electrical pulses to compensate for the loss of voluntary movement control. Modulating the stimulation intensities to reliably generate movements is a challenging control problem. This paper introduces
a feedback controller for a multi-muscle FES system to control hand movements in a two-dimensional (table-top) task space. This feedback controller is based on a recent human motor control model, which uses muscle synergies to simplify its calculations and improve the performance. This synergy-based controller employs direct relations between the muscle synergies and the produced hand force, thereby allowing for the real-time calculation of six muscle stimulation levels required to reach an arbitrary target. The experimental results show that this control scheme can perform arbitrary point-to-point reaching tasks in the two-dimensional task space in real-time, with an average of ~2 cm final hand position error from the specified targets. The success of this prototype demonstrates the potential of the proposed method for the feedback control of functional tasks with FES.

@article{ce_2018,
title = {Finite-Time Switched Second-Order Sliding-Mode Control of Nonholonomic Wheeled Mobile Robot Systems},
author = {Ce, H.; Hongbin, W.; Xiaoyan, C.; Zhen, Z.; Shungang, G.; Zhongquan, H.},
journal = {Complexity},
year = {2018},
volume = {2018},
institution = {Yanshan University, China},
abstract = {A continuous finite-time robust control method for the trajectory tracking control of a nonholonomic wheeled mobile robot (NWMR) is presented in this paper. The proposed approach is composed of conventional sliding-mode control (SMC) in the internal loop and modified switched second-order sliding-mode (S-SOSM) control in the external loop. Sliding-mode controller is equivalently represented as stabilization of the nominal system without uncertainties. An S-SOSM control algorithm is employed to counteract the impact of state-dependent unmodeled dynamics and time-varying external disturbances, and the unexpected chattering has been attenuated significantly. Particularly, state-space partitioning is constructed to obtain the bounds of uncertainty terms and accomplish different control objectives under different requirements. Simulation and experiment results are used to demonstrate the effectiveness and applicability of the proposed approach. },
language = {English},
publisher = {Hindawi Publishing Corp.}
}

A continuous finite-time robust control method for the trajectory tracking control of a nonholonomic wheeled mobile robot (NWMR) is presented in this paper. The proposed approach is composed of conventional sliding-mode control (SMC) in the internal loop and modified switched second-order sliding-mode (S-SOSM) control in the external loop. Sliding-mode controller is equivalently represented as stabilization of the nominal system without uncertainties. An S-SOSM control algorithm is employed to counteract the impact of state-dependent unmodeled dynamics and time-varying external disturbances, and the unexpected chattering has been attenuated significantly. Particularly, state-space partitioning is constructed to obtain the bounds of uncertainty terms and accomplish different control objectives under different requirements. Simulation and experiment results are used to demonstrate the effectiveness and applicability of the proposed approach.

@article{yuan_2018,
title = {Force Reflecting Control for Bilateral Teleoperation System under Time-Varying Delays},
author = {Yuan Y., Wang Y., Guo L.},
journal = { IEEE Transactions on Industrial Informatics},
year = {2018},
institution = {Northwestern Polytechnical University, China; Beihang University, China},
abstract = {In this paper, the force reflection control problem is addressed for a bilateral teleoperation system with time-varying delays. A dynamic gain force observer is proposed to obtain the force information for the force reflection control scheme. In virtue of the adaptive law, the internal uncertainties can be estimated based on the prescribed performance functions. The corrective wave variable method is utilized such that the bilateral teleoperation system could achieve a satisfactory control performance. A number of practical experiments are implemented on the bilateral teleoperation system to demonstrate the validation of the proposed methodology. },
issn = {1551-3203},
keywords = {Bilateral teleoperation system, force reflecting control, force observer, adaptive law},
language = {English},
publisher = {IEEE}
}

In this paper, the force reflection control problem is addressed for a bilateral teleoperation system with time-varying delays. A dynamic gain force observer is proposed to obtain the force information for the force reflection control scheme. In virtue of the adaptive law, the internal uncertainties can be estimated based on the prescribed performance functions. The corrective wave variable method is utilized such that the bilateral teleoperation system could achieve a satisfactory control performance. A number of practical experiments are implemented on the bilateral teleoperation system to demonstrate the validation of the proposed methodology.

@article{sun_2018,
title = {Fuzzy Neural Network Control of a Flexible Robotic Manipulator Using Assumed Mode Method},
author = {Sun, C.; Gao, H.; He, W.; Yu, Y.},
journal = {IEEE Transactions on Neural Networks and Learning Systems},
year = {2018},
institution = {Southeast University, China; University of Science and Technology Beijing, China; },
abstract = {In this paper, in order to analyze the single-link flexible structure, the assumed mode method is employed to develop the dynamic model. Based on the discrete dynamic model, fuzzy neural network (NN) control is investigated to track the desired trajectory accurately and to suppress the flexible vibration maximally. To ensure the stability rigorously as the goal, the system is proved to be uniform ultimate boundedness by Lyapunov's stability method. Eventually, simulations verify that the proposed control strategy is effective, and the control performance is compared with the proportion derivative control. The experiments are implemented on the Quanser platform to further demonstrate the feasibility of the proposed fuzzy NN control. },
issn = {2162-2388 },
keywords = {Adaptive control, assumed mode method (AMM), dynamic modeling, flexible robotic manipulator, neural networks (NNs), vibration control},
language = {English},
publisher = {IEEE}
}

In this paper, in order to analyze the single-link flexible structure, the assumed mode method is employed to develop the dynamic model. Based on the discrete dynamic model, fuzzy neural network (NN) control is investigated to track the desired trajectory accurately and to suppress the flexible vibration maximally. To ensure the stability rigorously as the goal, the system is proved to be uniform ultimate boundedness by Lyapunov's stability method. Eventually, simulations verify that the proposed control strategy is effective, and the control performance is compared with the proportion derivative control. The experiments are implemented on the Quanser platform to further demonstrate the feasibility of the proposed fuzzy NN control.

@article{kumar_2018,
title = {H∞ tracking control for an inverted pendulum},
author = {Kumar, M.A.; Kanthalakshmi, S.},
journal = {Journal of Vibration and Control},
year = {2018},
institution = {PSG College of Technology, Coimbatore, India},
abstract = {The objective of this paper is to design an H∞ controller for an inverted pendulum system, synthesized using the H-infinity loop shaping technique. In the H∞ loop shaping technique, a linear plant model is augmented with certain weight functions, such as the sensitivity weight function and complementary sensitivity weight function, so that the closed loop transfer function of the plant will have the desired performance. In this work, the H-infinity controller is synthesized and the analysis on robustness and performance of the system is done by taking the singular value response and robustness indicator plots. },
keywords = {Uncertainty, perturbation model, loop shaping, H∞ norm, H∞ control, inverted pendulum, weighted sensitivity, linear fractional transformation},
language = {English},
publisher = {SAGE}
}

The objective of this paper is to design an H∞ controller for an inverted pendulum system, synthesized using the H-infinity loop shaping technique. In the H∞ loop shaping technique, a linear plant model is augmented with certain weight functions, such as the sensitivity weight function and complementary sensitivity weight function, so that the closed loop transfer function of the plant will have the desired performance. In this work, the H-infinity controller is synthesized and the analysis on robustness and performance of the system is done by taking the singular value response and robustness indicator plots.

@article{ahn_2018,
title = {Hankel-Norm Approach to Robust FIR Estimation of Dynamic Systems Under External Disturbances},
author = {Ahn, C.K.;Shmaliy, Y.; Zhao, S.},
journal = {IEEE/ASME Transactions on Mechatronics},
year = {2018},
institution = {Korea University, Korea; Universidad de Guanajuato, Mexico; Jiangnan University, China},
abstract = {We propose and develop a new Hankel-norm approach to the robust receding horizon (RH) finite impulse response (FIR) filter design in discrete-time state space under intensive external disturbances. A new condition is developed for the RH Hankel-norm FIR filter (HNFF) design based on the linear matrix inequality and an equality constraint. The proposed RH HNFF ensures unwanted memory reduction and reduces the effect of memory on errors caused by past disturbances. Another condition is also examined to avoid using the equality constraint. The approach is tested and compared with existing filters based on a numerical example to verify its high robustness against unpredictable model changes for an F-404 turbofan engine system model. An experimental study on the one-degree-of-freedom (1-DOF) torsion system is also provided to demonstrate its validity. },
keywords = {Hankel norm, receding horizon, finite impulse response, filtering, robustness, deadbeat prope},
language = {English},
publisher = {IEEE}
}

We propose and develop a new Hankel-norm approach to the robust receding horizon (RH) finite impulse response (FIR) filter design in discrete-time state space under intensive external disturbances. A new condition is developed for the RH Hankel-norm FIR filter (HNFF) design based on the linear matrix inequality and an equality constraint. The proposed RH HNFF ensures unwanted memory reduction and reduces the effect of memory on errors caused by past disturbances. Another condition is also examined to avoid using the equality constraint. The approach is tested and compared with existing filters based on a numerical example to verify its high robustness against unpredictable model changes for an F-404 turbofan engine system model. An experimental study on the one-degree-of-freedom (1-DOF) torsion system is also provided to demonstrate its validity.

@conference{zhang_2018,
title = {Hardware in the Loop Experimental Study of 3-DOF Helicopter},
author = {Zhang, J.; Zheng, T.; Cui, W.; Liu, M.},
booktitle = {2018 Chinese Control And Decision Conference (CCDC)},
year = {2018},
institution = {Zhejiang University of Technology, China; },
abstract = {A helicopter flight control system is a typical multi-input, multi-output system with strong channel-coupling and nonlinear characteristics. In order to cope with the problems encountered in current controller design, three control methods including H2 control, Hinf control and mix H2/Hinf control for regulation and tracking problem of a 3-Degree-of-Freedom (3-DOF) helicopter are presented. By analyzing the helicopter system, a state-space representation of the system is established according to the characteristics of each degree-of-freedom motion. Then we designed the H2 controller, Hinf controller and mix H2/Hinf controller, and implemented these controllers by using MATLAB LMI toolbox. All these three control methods are discussed and compared with each other. Numerical study of the three controllers for tracking of a 3-DOF helicopter are conducted, and a hardware-in-the-loop experimental study of the three controllers of the 3-DOF helicopter is made for regulation and tracking problem. To analyze the robust performances of helicopter control system, an Active Mass Disturbance System interference is considered. Numerical simulation and HIL experimental studies show that H2 control is valid and has a satisfactory performance for a 3-DOF helicopter and the Hinf control could increase the robustness of the 3 DOF helicopter system while the mix H2/Hinf control has the both advantages of the H2 and H^ controller. },
issn = {1948-9447 },
keywords = {robust control, 3-DOF helicopter, hardware in the loop, mixed H2/Hinf, tracking, experiment},
language = {English},
publisher = {IEEE},
isbn = {978-1-5386-1245-3 }
}

A helicopter flight control system is a typical multi-input, multi-output system with strong channel-coupling and nonlinear characteristics. In order to cope with the problems encountered in current controller design, three control methods including H2 control, Hinf control and mix H2/Hinf control for regulation and tracking problem of a 3-Degree-of-Freedom (3-DOF) helicopter are presented. By analyzing the helicopter system, a state-space representation of the system is established according to the characteristics of each degree-of-freedom motion. Then we designed the H2 controller, Hinf controller and mix H2/Hinf controller, and implemented these controllers by using MATLAB LMI toolbox. All these three control methods are discussed and compared with each other. Numerical study of the three controllers for tracking of a 3-DOF helicopter are conducted, and a hardware-in-the-loop experimental study of the three controllers of the 3-DOF helicopter is made for regulation and tracking problem. To analyze the robust performances of helicopter control system, an Active Mass Disturbance System interference is considered. Numerical simulation and HIL experimental studies show that H2 control is valid and has a satisfactory performance for a 3-DOF helicopter and the Hinf control could increase the robustness of the 3 DOF helicopter system while the mix H2/Hinf control has the both advantages of the H2 and H^ controller.

@article{yang_2018,
title = {Hybrid Analog/Digital Control of Bilateral Teleoperation Systems},
author = {Yang, T.; Hu, J.; Geng, W.; Wang, D.; Fu, Y.; Tavakoli, M. },
journal = {Journal of Dynamic Systems, Measurement, and Control},
year = {2018},
month = {07},
volume = {140},
number = {12},
institution = {Harbin Institute of Technology, China; Xuzhou Medical University, China; University of Alberta, Canada},
abstract = {Hybrid analog/digital control of bilateral teleoperation systems can lead to superior performance (transparency) while maintaining stability compared to pure analog or digital control methods. Such hybrid control is preferable over pure analog control, which is inflexible and not ideal for realizing complex teleoperation control algorithms, and pure digital control, which restricts teleoperation performance due to a well-known stability-imposed upper bound on the product of the digital controller's proportional gain and the sampling period. In this paper, a hybrid controller combining a Field programmable analog array (FPAA) based analog controller and a personal computer-based digital controller is compared in terms of performance and stability to its analog and digital counterparts. A stability analysis indicates that the addition of analog derivative term widens the range of teleoperation controls gains that satisfy the stability conditions, paving the way for improving the teleoperation performance. We also show how the hybrid controller leads to better teleoperation performance. To this end, we study the human's performance of a switch flipping task and a stiffness discrimination task in the teleoperation mode. In both tasks, the hybrid analog/digital controller allows the human operators to achieve the highest task success rates. },
keywords = {Bilateral teleoperation; analog control; digital control; stability; transparency; task performance},
language = {English},
publisher = {ASME}
}

Hybrid analog/digital control of bilateral teleoperation systems can lead to superior performance (transparency) while maintaining stability compared to pure analog or digital control methods. Such hybrid control is preferable over pure analog control, which is inflexible and not ideal for realizing complex teleoperation control algorithms, and pure digital control, which restricts teleoperation performance due to a well-known stability-imposed upper bound on the product of the digital controller's proportional gain and the sampling period. In this paper, a hybrid controller combining a Field programmable analog array (FPAA) based analog controller and a personal computer-based digital controller is compared in terms of performance and stability to its analog and digital counterparts. A stability analysis indicates that the addition of analog derivative term widens the range of teleoperation controls gains that satisfy the stability conditions, paving the way for improving the teleoperation performance. We also show how the hybrid controller leads to better teleoperation performance. To this end, we study the human's performance of a switch flipping task and a stiffness discrimination task in the teleoperation mode. In both tasks, the hybrid analog/digital controller allows the human operators to achieve the highest task success rates.

@article{forbrigger_2018,
title = {Improving Haptic Transparency for Uncertain Virtual Environments using Adaptive Control and Gain-Scheduled Prediction},
author = {Forbrigger, S.T. ; Pan, Y.-J.},
journal = {IEEE Transactions on Haptics},
year = {2018},
institution = {Dalhousie University, NS, Canada},
abstract = {The realism or transparency of haptic interfaces is becoming more critical as they are applied to training in fields like minimally invasive surgery (MIS). Surgical training simulators must provide a transparent virtual environment (VE) at a high update rate. Complex, deformable, cuttable tissue models have nonlinear dynamics and are computationally expensive, making it difficult to provide sufficient update rates. The objective of this work is to improve the transparency for this type of VE by formulating the unknown nonlinear dynamics as a quasi-linear parameter varying (LPV) system and designing a predictor to provide an output at a much higher update rate. An adaptive controller based on gain-scheduled prediction is considered for a nonlinear haptic device and a nonlinear, delayed and sampled VE. The predictor uses feedback from the more accurate but slow-updating VE to update a simplified dynamic model. The predictor is designed based on numerical solutions to a linear matrix inequality derived using Lyapunov-based methods. Experimental results demonstrate the effectiveness of the gain-scheduled predictor approach and compare it to previous work using a constant-gain predictor. The gain-scheduled predictor results in significant performance improvements compared to a haptic system without prediction, but less significant improvement compared to the constant-gain approach. },
issn = {1939-1412 },
keywords = {Haptics, adaptive control, linear parameter-varying systems, prediction methods, transparency, virtual environments},
language = {English},
publisher = {IEEE}
}

The realism or transparency of haptic interfaces is becoming more critical as they are applied to training in fields like minimally invasive surgery (MIS). Surgical training simulators must provide a transparent virtual environment (VE) at a high update rate. Complex, deformable, cuttable tissue models have nonlinear dynamics and are computationally expensive, making it difficult to provide sufficient update rates. The objective of this work is to improve the transparency for this type of VE by formulating the unknown nonlinear dynamics as a quasi-linear parameter varying (LPV) system and designing a predictor to provide an output at a much higher update rate. An adaptive controller based on gain-scheduled prediction is considered for a nonlinear haptic device and a nonlinear, delayed and sampled VE. The predictor uses feedback from the more accurate but slow-updating VE to update a simplified dynamic model. The predictor is designed based on numerical solutions to a linear matrix inequality derived using Lyapunov-based methods. Experimental results demonstrate the effectiveness of the gain-scheduled predictor approach and compare it to previous work using a constant-gain predictor. The gain-scheduled predictor results in significant performance improvements compared to a haptic system without prediction, but less significant improvement compared to the constant-gain approach.

@article{gonzalez_2018,
title = {Influence of Elbow Flexion and Stimulation Site on Neuromuscular Electrical Stimulation of the Biceps Brachii},
author = {Gonzalez, E.J.; Downey, R.J.; Rouse, C.A.; Dixon, W.E.},
journal = {IEEE Transactions on Neural Systems and Rehabilitation Engineering},
year = {2018},
institution = {University of Florida, USA; Stanford University, USA; Medical University of South Carolina, USA},
abstract = {Functional electrical stimulation (FES) can help individuals with physical disabilities by assisting limb movement; however, the change in muscle geometry associated with limb movement may affect the response to stimulation. The aim of this study was to quantify the effects of elbow flexion and stimulation site on muscle torque production. Contraction torque about the elbow was measured in 12 healthy individuals using a custom elbow flexion testbed and a transcutaneous electrode array. Stimulation was delivered to 6 distinct sites along the biceps brachii over 11 elbow flexion angles. Flexion angle was found to significantly influence the optimal (i.e., torque-maximizing) stimulation site (χ2(10, N=24) = 135.75, p = 3.12×10-24), with post hoc analysis indicating a proximal shift in optimal stimulation site with increased flexion. Similarly, the biceps stimulation site was found to significantly influence the flexion angle at which peak torque occurred (χ2(5, N=24) = 101.82, p = 2.18×10-20), with post hoc analysis indicating an increase in peak-torque flexion angle as stimulation site is moved proximally up the biceps. Since maximizing muscle force per unit stimulation is a common goal in rehabilitative FES, future efforts could examine methods which compensate for the shift in optimal stimulation site during FESinduced limb movement. },
issn = {1534-4320},
keywords = {Elbow Flexion, Electrode Array, Functional Electrical Stimulation (FES), Neuromuscular Electrical Stimulation (NMES)},
publisher = {IEEE}
}

Functional electrical stimulation (FES) can help individuals with physical disabilities by assisting limb movement; however, the change in muscle geometry associated with limb movement may affect the response to stimulation. The aim of this study was to quantify the effects of elbow flexion and stimulation site on muscle torque production. Contraction torque about the elbow was measured in 12 healthy individuals using a custom elbow flexion testbed and a transcutaneous electrode array. Stimulation was delivered to 6 distinct sites along the biceps brachii over 11 elbow flexion angles. Flexion angle was found to significantly influence the optimal (i.e., torque-maximizing) stimulation site (χ2(10, N=24) = 135.75, p = 3.12×10-24), with post hoc analysis indicating a proximal shift in optimal stimulation site with increased flexion. Similarly, the biceps stimulation site was found to significantly influence the flexion angle at which peak torque occurred (χ2(5, N=24) = 101.82, p = 2.18×10-20), with post hoc analysis indicating an increase in peak-torque flexion angle as stimulation site is moved proximally up the biceps. Since maximizing muscle force per unit stimulation is a common goal in rehabilitative FES, future efforts could examine methods which compensate for the shift in optimal stimulation site during FESinduced limb movement.