@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{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.

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{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{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.

@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.

@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{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%.

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{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.

@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{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{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{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.

@article{ozdagli_2018,
title = {Low-cost, efficient wireless intelligent sensors (LEWIS) measuring real-time reference-free dynamic displacements},
author = {Ozdagli, A.I.; Liu, B.; Moreu, F.},
journal = {Mechanical Systems and Signal Processing},
year = {2018},
month = {07},
volume = {107},
institution = {University of New Mexico, USA; Institute of Disaster Prevention, Beijing, China},
abstract = {According to railroad managers, displacement of railroad bridges under service loads is an important parameter in the condition assessment and performance evaluation. However, measuring bridge responses in the field is often costly and labor-intensive. This paper proposes a low-cost, efficient wireless intelligent sensor (LEWIS) platform that can compute in real-time the dynamic transverse displacements of railroad bridges under service loads. This sensing platform drives on an open-source Arduino ecosystem and combines low-cost microcontrollers with affordable accelerometers and wireless transmission modules. The proposed LEWIS system is designed to reconstruct dynamic displacements from acceleration measurements onboard, eliminating the need for offline post-processing, and to transmit the data in real-time to a base station where the inspector at the bridge can see the displacements while the train is crossing, or to a remote office if so desired by internet. Researchers validated the effectiveness of the new LEWIS by conducting a series of laboratory experiments. A shake table setup simulated transverse bridge displacements measured on the field and excited the proposed platform, a commercially available wired expensive accelerometer, and reference LVDT displacement sensor. The responses obtained from the wireless system were compared to the displacements reconstructed from commercial accelerometer readings and the reference LVDT. The results of the laboratory experiments demonstrate that the proposed system is capable of reconstructing transverse displacements of railroad bridges under revenue service traffic accurately and transmitting the data in real-time wirelessly. In conclusion, the platform presented in this paper can be used in the performance assessment of railroad bridge network cost-effectively and accurately. Future work includes collecting real-time reference-free displacements of one railroad bridge in Colorado under train crossings to further prove LEWIS’ suitability for engineering applications. },
keywords = {Real-time monitoring, Low-cost sensing, Wireless sensing, Acceleration, Displacement, Intelligent sensor, Railroad bridges},
language = {English},
publisher = {Elsevier B.V.},
pages = {343-356}
}

According to railroad managers, displacement of railroad bridges under service loads is an important parameter in the condition assessment and performance evaluation. However, measuring bridge responses in the field is often costly and labor-intensive. This paper proposes a low-cost, efficient wireless intelligent sensor (LEWIS) platform that can compute in real-time the dynamic transverse displacements of railroad bridges under service loads. This sensing platform drives on an open-source Arduino ecosystem and combines low-cost microcontrollers with affordable accelerometers and wireless transmission modules. The proposed LEWIS system is designed to reconstruct dynamic displacements from acceleration measurements onboard, eliminating the need for offline post-processing, and to transmit the data in real-time to a base station where the inspector at the bridge can see the displacements while the train is crossing, or to a remote office if so desired by internet. Researchers validated the effectiveness of the new LEWIS by conducting a series of laboratory experiments. A shake table setup simulated transverse bridge displacements measured on the field and excited the proposed platform, a commercially available wired expensive accelerometer, and reference LVDT displacement sensor. The responses obtained from the wireless system were compared to the displacements reconstructed from commercial accelerometer readings and the reference LVDT. The results of the laboratory experiments demonstrate that the proposed system is capable of reconstructing transverse displacements of railroad bridges under revenue service traffic accurately and transmitting the data in real-time wirelessly. In conclusion, the platform presented in this paper can be used in the performance assessment of railroad bridge network cost-effectively and accurately. Future work includes collecting real-time reference-free displacements of one railroad bridge in Colorado under train crossings to further prove LEWIS’ suitability for engineering applications.

@article{ozdagli3_2018,
title = {Low-cost, efficient wireless intelligent sensors (LEWIS) measuring real-time reference-free dynamic displacements},
author = {Ozdagli, A.I.; Liu, B.; Moreu, F.},
journal = {Mechanical Systems and Signal Processing},
year = {2018},
month = {07},
volume = {107},
institution = {Institute of Disaster Prevention, Sanhe, China; University of New Mexico, Albuquerque, NM, USA},
abstract = {According to railroad managers, displacement of railroad bridges under service loads is an important parameter in the condition assessment and performance evaluation. However, measuring bridge responses in the field is often costly and labor-intensive. This paper proposes a low-cost, efficient wireless intelligent sensor (LEWIS) platform that can compute in real-time the dynamic transverse displacements of railroad bridges under service loads. This sensing platform drives on an open-source Arduino ecosystem and combines low-cost microcontrollers with affordable accelerometers and wireless transmission modules. The proposed LEWIS system is designed to reconstruct dynamic displacements from acceleration measurements onboard, eliminating the need for offline post-processing, and to transmit the data in real-time to a base station where the inspector at the bridge can see the displacements while the train is crossing, or to a remote office if so desired by internet. Researchers validated the effectiveness of the new LEWIS by conducting a series of laboratory experiments. A shake table setup simulated transverse bridge displacements measured on the field and excited the proposed platform, a commercially available wired expensive accelerometer, and reference LVDT displacement sensor. The responses obtained from the wireless system were compared to the displacements reconstructed from commercial accelerometer readings and the reference LVDT. The results of the laboratory experiments demonstrate that the proposed system is capable of reconstructing transverse displacements of railroad bridges under revenue service traffic accurately and transmitting the data in real-time wirelessly. In conclusion, the platform presented in this paper can be used in the performance assessment of railroad bridge network cost-effectively and accurately. Future work includes collecting real-time reference-free displacements of one railroad bridge in Colorado under train crossings to further prove LEWIS’ suitability for engineering applications. },
keywords = {Real-time monitoring Low-cost sensing Wireless sensing Acceleration Displacement Intelligent sensor Railroad bridges},
language = {English},
publisher = {Elsevier Ltd.},
pages = {343-356}
}

According to railroad managers, displacement of railroad bridges under service loads is an important parameter in the condition assessment and performance evaluation. However, measuring bridge responses in the field is often costly and labor-intensive. This paper proposes a low-cost, efficient wireless intelligent sensor (LEWIS) platform that can compute in real-time the dynamic transverse displacements of railroad bridges under service loads. This sensing platform drives on an open-source Arduino ecosystem and combines low-cost microcontrollers with affordable accelerometers and wireless transmission modules. The proposed LEWIS system is designed to reconstruct dynamic displacements from acceleration measurements onboard, eliminating the need for offline post-processing, and to transmit the data in real-time to a base station where the inspector at the bridge can see the displacements while the train is crossing, or to a remote office if so desired by internet. Researchers validated the effectiveness of the new LEWIS by conducting a series of laboratory experiments. A shake table setup simulated transverse bridge displacements measured on the field and excited the proposed platform, a commercially available wired expensive accelerometer, and reference LVDT displacement sensor. The responses obtained from the wireless system were compared to the displacements reconstructed from commercial accelerometer readings and the reference LVDT. The results of the laboratory experiments demonstrate that the proposed system is capable of reconstructing transverse displacements of railroad bridges under revenue service traffic accurately and transmitting the data in real-time wirelessly. In conclusion, the platform presented in this paper can be used in the performance assessment of railroad bridge network cost-effectively and accurately. Future work includes collecting real-time reference-free displacements of one railroad bridge in Colorado under train crossings to further prove LEWIS’ suitability for engineering applications.

@article{arnal_2018,
title = {Magneto-optical nanoparticles for cyclic magnetomotive photoacoustic imaging},
author = {Arnal, B.; Yoon, S.J.; Li, J.; Gao, X.; O'Donnell, M.},
journal = {Physica C: Superconductivity and its Applications},
year = {2018},
month = {05},
volume = {548},
institution = {Department of Bioengineering, University of Washington, USA},
abstract = {Photoacoustic imaging is a highly promising tool to visualize molecular events with deep tissue penetration. Like most other modalities, however, image contrast under in vivo conditions is far from optimal due to background signals from tissue. Using iron oxide-gold core-shell nanoparticles, we previously demonstrated that magnetomotive photoacoustic (mmPA) imaging can dramatically reduce the influence of background signals and produce high-contrast molecular images. Here we report two significant advances toward clinical translation of this technology. First, we introduce a new class of compact, uniform, magneto-optically coupled core-shell nanoparticle, prepared through localized copolymerization of polypyrrole (PPy) on an iron oxide nanoparticle surface. The resulting iron oxide-PPy nanoparticles solve the photo-instability and small-scale synthesis problems previously encountered by the gold coating approach, and extend the large optical absorption coefficient of the particles beyond 1000 nm in wavelength. In parallel, we have developed a new generation of mmPA imaging featuring cyclic magnetic motion and ultrasound speckle tracking, with an image capture frame rate several hundred times faster than the photoacoustic speckle tracking method demonstrated previously. These advances enable robust artifact elimination caused by physiologic motion and first application of the mmPA technology in vivo for sensitive tumor imaging. },
keywords = {Magnetic nanoparticles (MNPs) Core-shell nanoparticles Polypyrrole},
language = {English},
publisher = {Elsevier B.V.},
pages = {90-92}
}

Photoacoustic imaging is a highly promising tool to visualize molecular events with deep tissue penetration. Like most other modalities, however, image contrast under in vivo conditions is far from optimal due to background signals from tissue. Using iron oxide-gold core-shell nanoparticles, we previously demonstrated that magnetomotive photoacoustic (mmPA) imaging can dramatically reduce the influence of background signals and produce high-contrast molecular images. Here we report two significant advances toward clinical translation of this technology. First, we introduce a new class of compact, uniform, magneto-optically coupled core-shell nanoparticle, prepared through localized copolymerization of polypyrrole (PPy) on an iron oxide nanoparticle surface. The resulting iron oxide-PPy nanoparticles solve the photo-instability and small-scale synthesis problems previously encountered by the gold coating approach, and extend the large optical absorption coefficient of the particles beyond 1000 nm in wavelength. In parallel, we have developed a new generation of mmPA imaging featuring cyclic magnetic motion and ultrasound speckle tracking, with an image capture frame rate several hundred times faster than the photoacoustic speckle tracking method demonstrated previously. These advances enable robust artifact elimination caused by physiologic motion and first application of the mmPA technology in vivo for sensitive tumor imaging.

@conference{torabi_2018,
title = {Manipulability of teleoperated surgical robots with application in design of master/slave manipulators},
author = {Torabi A., Khadem M., Zareinia K., Sutherland G.R., Tavakoli M.},
booktitle = {2018 International Symposium on Medical Robotics (ISMR)},
year = {2018},
institution = {University of Alberta, Canada; University of Calgary, Canada},
abstract = {Teleoperated surgical robots can significantly improve the performance of minimally invasive surgeries. The performance of a master-slave robotic system depends significantly on the capability of its master device to appropriately interface the user with the slave robot. However, master robots currently used in the clinic present several drawbacks such as the mismatch between the slave and master workspaces and the inability to intuitively transfer the slave robot's dexterity and joint limits to the user. In this paper, the "teleoperation manipulability index (TMI)" is introduced as a quantifiable measure of the combined master-slave system manipulability. We also demonstrate the application of the TMI in the design of master-slave robotic systems. By employing the proposed manipulability index, we are able to modify the design of a commercially available master robot that 1) enhances surgeon's control over force/velocity of a surgical robot, 2) minimizes the master robot's footprint, 3) optimizes the surgeons' control effort, and 4) avoids singularities and joint limits of the master and slave robots. A simulation study is performed to validate the performance of the modified master-slave robotic system. },
keywords = {Indexes, Ellipsoids, Jacobian matrices, Surgery, Master-slave, Medical robotics},
language = {English},
publisher = {IEEE},
isbn = {978-1-5386-2513-2 }
}

Teleoperated surgical robots can significantly improve the performance of minimally invasive surgeries. The performance of a master-slave robotic system depends significantly on the capability of its master device to appropriately interface the user with the slave robot. However, master robots currently used in the clinic present several drawbacks such as the mismatch between the slave and master workspaces and the inability to intuitively transfer the slave robot's dexterity and joint limits to the user. In this paper, the "teleoperation manipulability index (TMI)" is introduced as a quantifiable measure of the combined master-slave system manipulability. We also demonstrate the application of the TMI in the design of master-slave robotic systems. By employing the proposed manipulability index, we are able to modify the design of a commercially available master robot that 1) enhances surgeon's control over force/velocity of a surgical robot, 2) minimizes the master robot's footprint, 3) optimizes the surgeons' control effort, and 4) avoids singularities and joint limits of the master and slave robots. A simulation study is performed to validate the performance of the modified master-slave robotic system.

@article{ozdagli2_2018,
title = {Measuring Total Transverse Reference-Free Displacements for Condition Assessment of Timber Railroad Bridges: Experimental Validation},
author = {Ozdagli, A.I.; Liu, B., P.E.; Moreu, F.},
journal = { Journal of Structural Engineering },
year = {2018},
month = {06},
volume = {144},
number = {6},
institution = {Institute of Disaster Prevention, Sanhe, China; University of New Mexico, Albuquerque, NM, USA},
abstract = {Today, the railroad industry carries 40% of the United States’ total freight ton-miles over 100,000 bridges spanning over 225,000 km (140,000 mi) of rail tracks and the demand for railroads will increase by 88% by 2035. Railroads maintain their infrastructure to meet this demand and ensure the ability of the bridges to safely carry trains. However, railroad funds are limited and the allocation of resources for operations of maintenance, repair, and replacement (MRR) must be conducted cost effectively. Railroad managers are interested in new and innovative methods to efficiently quantify the structural performance of their bridges. Total transverse bridge displacements provide objective data about structural integrity, informing the prioritization of MRR operations. Measuring bridge displacement with traditional sensors such as a linear variable differential transformer (LVDT) is often difficult because of the need for a fixed reference frame. Likewise, modern reference-free and noncontact response measurement approaches require methods that are expensive, technologically complex, or computationally prohibitive for bridge managers. This paper investigates the feasibility of a novel approach for measuring total reference-free transverse displacements of railroad bridges by aggregating data obtained from multiple sensors, where train derailment because of excessive transverse movement is the main concern. The method implements a finite impulse response (FIR) filter to compute drift-free dynamic displacement by using acceleration measurements. Similarly, a moving average (MA) filter extracts the low-frequency content from inclination captured with two accelerometers. The low-frequency inclination is then converted to pseudostatic displacement using Euler–Bernoulli beam equations. These pseudostatic responses are combined with dynamic displacements derived from accelerometer data, allowing estimatation of the total reference-free transverse displacement in the field. To verify the performance of the proposed method, a cantilever column representing a timber bridge pile was tested in the laboratory using a shake table and excited with a number of displacement measurements taken in the field from a timber railroad bridge. The results were compared to reference displacements captured with an LVDT, demonstrating that total reference-free transverse displacements can be accurately measured. As a conclusion, the proposed approach can be used as a viable tool supporting data-based informed decisions and has the potential to maximize the efficiency of railroad bridge network management systems. },
keywords = {Timber railroad bridges; Displacement; Inclination; Acceleration; Bridge management},
language = {English},
publisher = {ASCE}
}

Today, the railroad industry carries 40% of the United States’ total freight ton-miles over 100,000 bridges spanning over 225,000 km (140,000 mi) of rail tracks and the demand for railroads will increase by 88% by 2035. Railroads maintain their infrastructure to meet this demand and ensure the ability of the bridges to safely carry trains. However, railroad funds are limited and the allocation of resources for operations of maintenance, repair, and replacement (MRR) must be conducted cost effectively. Railroad managers are interested in new and innovative methods to efficiently quantify the structural performance of their bridges. Total transverse bridge displacements provide objective data about structural integrity, informing the prioritization of MRR operations. Measuring bridge displacement with traditional sensors such as a linear variable differential transformer (LVDT) is often difficult because of the need for a fixed reference frame. Likewise, modern reference-free and noncontact response measurement approaches require methods that are expensive, technologically complex, or computationally prohibitive for bridge managers. This paper investigates the feasibility of a novel approach for measuring total reference-free transverse displacements of railroad bridges by aggregating data obtained from multiple sensors, where train derailment because of excessive transverse movement is the main concern. The method implements a finite impulse response (FIR) filter to compute drift-free dynamic displacement by using acceleration measurements. Similarly, a moving average (MA) filter extracts the low-frequency content from inclination captured with two accelerometers. The low-frequency inclination is then converted to pseudostatic displacement using Euler–Bernoulli beam equations. These pseudostatic responses are combined with dynamic displacements derived from accelerometer data, allowing estimatation of the total reference-free transverse displacement in the field. To verify the performance of the proposed method, a cantilever column representing a timber bridge pile was tested in the laboratory using a shake table and excited with a number of displacement measurements taken in the field from a timber railroad bridge. The results were compared to reference displacements captured with an LVDT, demonstrating that total reference-free transverse displacements can be accurately measured. As a conclusion, the proposed approach can be used as a viable tool supporting data-based informed decisions and has the potential to maximize the efficiency of railroad bridge network management systems.

@article{okyay_2018,
title = {Mechatronic design, actuator optimization, and control of a long stroke linear nano-positioner},
author = {Okyay, A.; Erkorkmaz, K.; Khamesee, M.B.},
journal = {Precision Engineering},
year = {2018},
institution = {University of Waterloo, Canada},
abstract = {In this paper, mechatronic design, actuator optimization and controls of a long-stroke (20 mm) linear nano-positioner are presented. The mechatronic design is described in terms of the stage’s most prominent features regarding mechanical design, assembly, actuator configuration, and power supply. A novel air-bearing/bushing arrangement has been used in which the commonly employed double shaft arrangement is replaced with a single shaft supported by an air bearing from the bottom to constrain the roll motion. The assembly is greatly simplified by exploiting the self-aligning property of the air-bushings which are held in the housings by O-rings. Also, the footprint of the stage is reduced. Voice coil actuators (VCA) in moving magnet mode have been used in complementary double configuration for uniformity of force response. The performance objectives of previously optimized VCA’s as standalone actuators are re-evaluated in this configuration. It is observed that while the performance objectives decrease a bit, the desirability of the design point is still retained. Controller design has been made for the current control and position control loops. Heydemann’s method for the compensation of encoder quadrature detection errors is implemented. The positioning resolution of the stage as measured from the sensor output is experimentally determined to be +/−5 nm. Dynamic Error Budgeting (DEB) method has been used to analyze the contributing factors to the positioning error, and sensor broadband noise is determined to be the major contributor. The actual positioning accuracy of the stage is estimated by DEB to be 0.682 nm root-mean-square (RMS). The trajectory following accuracy is determined to be +/−15 nm. It is expected that trajectory following accuracy can substantially improve if more advanced compensation methods for encoder quadrature errors are implemented. },
keywords = {Voice coil actuator, Topology optimization, Dynamic Error Budgeting, Air bearing, Nano-positioning, Optical encoder, Encoder quadrature detection errors, Eddy currents},
language = {English},
publisher = {Elsevier B.V.}
}

In this paper, mechatronic design, actuator optimization and controls of a long-stroke (20 mm) linear nano-positioner are presented. The mechatronic design is described in terms of the stage’s most prominent features regarding mechanical design, assembly, actuator configuration, and power supply. A novel air-bearing/bushing arrangement has been used in which the commonly employed double shaft arrangement is replaced with a single shaft supported by an air bearing from the bottom to constrain the roll motion. The assembly is greatly simplified by exploiting the self-aligning property of the air-bushings which are held in the housings by O-rings. Also, the footprint of the stage is reduced. Voice coil actuators (VCA) in moving magnet mode have been used in complementary double configuration for uniformity of force response. The performance objectives of previously optimized VCA’s as standalone actuators are re-evaluated in this configuration. It is observed that while the performance objectives decrease a bit, the desirability of the design point is still retained. Controller design has been made for the current control and position control loops. Heydemann’s method for the compensation of encoder quadrature detection errors is implemented. The positioning resolution of the stage as measured from the sensor output is experimentally determined to be +/−5 nm. Dynamic Error Budgeting (DEB) method has been used to analyze the contributing factors to the positioning error, and sensor broadband noise is determined to be the major contributor. The actual positioning accuracy of the stage is estimated by DEB to be 0.682 nm root-mean-square (RMS). The trajectory following accuracy is determined to be +/−15 nm. It is expected that trajectory following accuracy can substantially improve if more advanced compensation methods for encoder quadrature errors are implemented.

@article{meller_2018,
title = {Model-based feedforward and cascade control of hydraulic McKibben muscles},
author = {Meller, M.; Kogan, B.; Bryant, M.; Garcia, E.},
journal = {Sensors and Actuators A: Physical},
year = {2018},
institution = {Cornell University, USA; North Carolina State University, USA},
abstract = {McKibben artificial muscle actuators are predominantly pneumatically powered. Recently, hydraulic operation has gained interest due to its higher rigidity and efficiency. While there has been extensive control system development for pneumatic artificial muscles, little has been conducted hydraulically. This paper investigates three different controllers developed for a loaded robotic arm actuated with oil-hydraulic McKibben muscles. The goal was to achieve good angular position tracking over a range of frequencies up to 1 Hz. The first scheme, serving as the baseline, is a proportional-integral controller. The second architecture adds a nonlinear model-based feedforward term to the baseline controller; the feedforward includes the expected flowrate demands based on the actuator kinematics as well as the valve flow gain. The last scheme adds an inner pressure feedback loop to the second architecture. All controllers were evaluated with frequency and step response experiments. The results show that a simple proportional-integral controller has significant phase lag and attenuation at the higher frequencies tested; including the feedforward term almost completely eliminates these. The cascaded loop improves rise and settling times. },
keywords = { McKibben muscle; Fluidic artificial muscle; hydraulic artificial muscle; fluid power control; hydraulic control; robotics},
language = {English},
publisher = {Elsevier B.V.}
}

McKibben artificial muscle actuators are predominantly pneumatically powered. Recently, hydraulic operation has gained interest due to its higher rigidity and efficiency. While there has been extensive control system development for pneumatic artificial muscles, little has been conducted hydraulically. This paper investigates three different controllers developed for a loaded robotic arm actuated with oil-hydraulic McKibben muscles. The goal was to achieve good angular position tracking over a range of frequencies up to 1 Hz. The first scheme, serving as the baseline, is a proportional-integral controller. The second architecture adds a nonlinear model-based feedforward term to the baseline controller; the feedforward includes the expected flowrate demands based on the actuator kinematics as well as the valve flow gain. The last scheme adds an inner pressure feedback loop to the second architecture. All controllers were evaluated with frequency and step response experiments. The results show that a simple proportional-integral controller has significant phase lag and attenuation at the higher frequencies tested; including the feedforward term almost completely eliminates these. The cascaded loop improves rise and settling times.

@conference{pecly_2018,
title = {Model-reference model-mediated control for time-delayed teleoperation systems},
author = {Pecly, L.S.D.; Souza, M.L.O.; Hashtrudi-Zaad, K.},
booktitle = {2018 IEEE Haptics Symposium (HAPTICS)},
year = {2018},
institution = {National Institute for Space Research-INPE, Brazil; Queen's University, Canada},
abstract = {Time delays in bilateral teleoperation systems can degrade the transparency and result in instability. For large delays, model predictive control or impedance reflective methods in which the operator interacts with the slave and environment model, can help overcome this issue. An important key to the success of these systems is to have the local virtual slave model synchronized with the slave. This is especially important when the slave gets into contact with hard environments, resulting in rapid contact force build up and slave chattering. In this paper, we propose a model-reference model-mediated teleoperation control architecture that provides enhanced synchronization between the slave and virtual slave models and keeps both the master and slave responsive. The proposed architecture is evaluated against through simulations and experiments carried out on a 1-DOF master-slave testbed. },
issn = {2324-7355},
keywords = {Impedance, Force, Iron, Delay effects, Virtual environments, Robot sensing systems, Delays},
language = {English},
publisher = {IEEE}
}

Time delays in bilateral teleoperation systems can degrade the transparency and result in instability. For large delays, model predictive control or impedance reflective methods in which the operator interacts with the slave and environment model, can help overcome this issue. An important key to the success of these systems is to have the local virtual slave model synchronized with the slave. This is especially important when the slave gets into contact with hard environments, resulting in rapid contact force build up and slave chattering. In this paper, we propose a model-reference model-mediated teleoperation control architecture that provides enhanced synchronization between the slave and virtual slave models and keeps both the master and slave responsive. The proposed architecture is evaluated against through simulations and experiments carried out on a 1-DOF master-slave testbed.

@conference{savoie_2018,
title = {Modelling and Compensation of Hysteresis in Polarization of Piezoelectric Actuators},
author = {Savoie, M.; Shan J.},
booktitle = {2018 AIAA/AHS Adaptive Structures Conference},
year = {2018},
institution = {York University, ON, Canada},
abstract = {This paper presents a domain wall modelling approach to linearise the polarization of a unipolar piezoelectric actuator. Polarization is measured through its impedance which is determined with a low amplitude overlaid sinusoidal signal. Linearisation is achieved through the inversion of the physical model and the physical significance of the parameters are retained. The controlled output showed a maximum error of 5% which could be reduced further by modifying the proposed model to account for minor hysteresis loops. },
language = {English},
publisher = {AIAA}
}

This paper presents a domain wall modelling approach to linearise the polarization of a unipolar piezoelectric actuator. Polarization is measured through its impedance which is determined with a low amplitude overlaid sinusoidal signal. Linearisation is achieved through the inversion of the physical model and the physical significance of the parameters are retained. The controlled output showed a maximum error of 5% which could be reduced further by modifying the proposed model to account for minor hysteresis loops.

@article{duenas_2018,
title = {Motorized and Functional Electrical Stimulation Induced Cycling via Switched Repetitive Learning Control},
author = {Duenas, V.H.; Cousin, C.A.; Parikh, A.; Freeborn, P.; Fox, E.J.; Dixon, W.E.},
journal = {IEEE Transactions on Control Systems Technology},
year = {2018},
institution = {University of Florida, USA; Brooks Rehabilitation Motion Analysis Center, USA},
abstract = {Cycling induced by functional electrical stimulation (FES) coupled with motorized assistance is a promising rehabilitative strategy. A switching controller that activates lower limb muscles alongside an electric motor based on the crank angle is developed to facilitate cycling. Due to the periodic nature of cadence tracking in cycling, a repetitive learning controller (RLC) is developed to track a desired cadence trajectory with a known period. The RLC is developed for an uncertain, nonlinear cycle-rider system with autonomous state-dependent switching. Electrical stimulation switches across multiple lower limb muscle groups based on the torque effectiveness throughout the crank cycle. The electric motor provides assistance when the muscle groups yield low torque production. A Lyapunov-based stability analysis that invokes a recently developed LaSalle-Yoshizawa corollary for nonsmooth systems is used to guarantee asymptotic tracking. The developed controller was tested during FES-cycling experiments in five able-bodied individuals and three participants with neurological conditions. The added value of the RLC in cadence tracking is illustrated by comparing the results of two trials with and without the learning feedforward term. The results indicate that the RLC yields a lower mean root-mean-squared cadence tracking error. },
issn = {1063-6536},
keywords = {Functional electrical stimulation (FES), FES-cycling, repetitive learning control (RLC), switching control},
language = {English},
publisher = {IEEE}
}

Cycling induced by functional electrical stimulation (FES) coupled with motorized assistance is a promising rehabilitative strategy. A switching controller that activates lower limb muscles alongside an electric motor based on the crank angle is developed to facilitate cycling. Due to the periodic nature of cadence tracking in cycling, a repetitive learning controller (RLC) is developed to track a desired cadence trajectory with a known period. The RLC is developed for an uncertain, nonlinear cycle-rider system with autonomous state-dependent switching. Electrical stimulation switches across multiple lower limb muscle groups based on the torque effectiveness throughout the crank cycle. The electric motor provides assistance when the muscle groups yield low torque production. A Lyapunov-based stability analysis that invokes a recently developed LaSalle-Yoshizawa corollary for nonsmooth systems is used to guarantee asymptotic tracking. The developed controller was tested during FES-cycling experiments in five able-bodied individuals and three participants with neurological conditions. The added value of the RLC in cadence tracking is illustrated by comparing the results of two trials with and without the learning feedforward term. The results indicate that the RLC yields a lower mean root-mean-squared cadence tracking error.

@article{gao_2018,
title = {Neural Network Control of a Two-Link Flexible Robotic Manipulator Using Assumed Mode Method},
author = {Gao, H.; He, W.; Zhou, C.;Sun, C.},
journal = {IEEE Transactions on Industrial Informatics},
year = {2018},
institution = {University of Science and Technology Beijing, China; Southeast University, China},
abstract = {In this paper, the n-dimensional discretized model of the two-link flexible manipulator is developed by the assumed mode method (AMM). Subsequently, based on the discretized dynamic model, both full state feedback control and output feedback control are investigated to achieve the trajectory tracking and vibration suppression. In order to guarantee the stability strictly, uniform ultimate boundedness (UUB) of the closed-loop system is realized by the Lyapunov's stability. Furthermore, through appropriately choosing control parameters, the states of the system will converge to zero with a small neighborhood. Eventually, extensive simulations and experiments on the Quanser platform for a two-link robotic manipulator are carried out to demonstrate the feasibility of the proposed neural network (NN) controller. },
issn = {1551-3203},
keywords = {Neural Networks, Vibration Control, Assumed Mode Method, Dynamic Modeling, Flexible Robotic Manipulator, Two-Link, Flexible Structure},
language = {English},
publisher = {IEEE}
}

In this paper, the n-dimensional discretized model of the two-link flexible manipulator is developed by the assumed mode method (AMM). Subsequently, based on the discretized dynamic model, both full state feedback control and output feedback control are investigated to achieve the trajectory tracking and vibration suppression. In order to guarantee the stability strictly, uniform ultimate boundedness (UUB) of the closed-loop system is realized by the Lyapunov's stability. Furthermore, through appropriately choosing control parameters, the states of the system will converge to zero with a small neighborhood. Eventually, extensive simulations and experiments on the Quanser platform for a two-link robotic manipulator are carried out to demonstrate the feasibility of the proposed neural network (NN) controller.

@article{schindeler_2018,
title = {Online Identification of Environment Hunt–Crossley Models Using Polynomial Linearization},
author = {Schindeler, R.; Hashtrudi-Zaad, K.},
journal = { IEEE Transactions on Robotics},
year = {2018},
volume = {34},
number = {2},
institution = {Queen's University, Kingston, ON, Canada},
abstract = {Online environment dynamic estimates are often used for the control of robots, telerobots, and haptic systems. The nonlinear Hunt–Crossley (HC) model, which is physically consistent with the behavior of soft objects with limited deformation at a single point of contact, is being increasingly used in robotic control systems. The HC model can be identified online using a single-stage log linearization technique; however, the accuracy and applicability of the existing method is limited. We propose a two-stage polynomial identification method, which uses a quadratic approximation in the first stage to generate a linearly parameterized model of the HC dynamics (Quad-Poly). The coefficients of the Quad-Poly model are then used in the second stage to extract the HC parameters using a lookup table and recursive least squares parameter estimation. The proposed method is experimentally assessed against a previous natural logarithm linearization method, and further tested for time-varying environment dynamics and human-generated trajectories and for robustness against uncertainties in the measured data and system parameters. },
issn = {1552-3098},
keywords = {Hunt–Crossley (HC), Kelvin Voight (KV), online model identification, parameter estimation, polynomial linearization},
language = {English},
publisher = {IEEE},
pages = {447-458}
}

Online environment dynamic estimates are often used for the control of robots, telerobots, and haptic systems. The nonlinear Hunt–Crossley (HC) model, which is physically consistent with the behavior of soft objects with limited deformation at a single point of contact, is being increasingly used in robotic control systems. The HC model can be identified online using a single-stage log linearization technique; however, the accuracy and applicability of the existing method is limited. We propose a two-stage polynomial identification method, which uses a quadratic approximation in the first stage to generate a linearly parameterized model of the HC dynamics (Quad-Poly). The coefficients of the Quad-Poly model are then used in the second stage to extract the HC parameters using a lookup table and recursive least squares parameter estimation. The proposed method is experimentally assessed against a previous natural logarithm linearization method, and further tested for time-varying environment dynamics and human-generated trajectories and for robustness against uncertainties in the measured data and system parameters.

@article{sen_2018,
title = {Optimisation of a PID controller for a two-floor structure under earthquake excitation based on the bees algorithm},
author = {Sen, M.A.; Tinkir, M.; Kalyoncu, M.},
journal = {Journal of Low Noise, Vibration and Active Control},
year = {2018},
institution = {Selçuk University, Turkey; Necmettin Erbakan University, Turkey},
abstract = {The control of vibration and displacement in structures under seismic excitation is very challenging, and designing a structural control system against disturbances has drawn great attention. This paper concentrates on implementing the bees algorithm to tune gains of traditional PID controller for active vibration control of a building-like structure with two floors under Northridge Earthquake excitation. Bees algorithm is a diverse method to ensure an efficient solution for optimisation of a controller according to customary trial-error design methods. The main aim of this study is optimisation of KP, KI and KD gains with bees algorithm in order to obtain a more effective PID controller to suppress vibrations of the floors during the earthquake excitation. After definition of the system and bees algorithm, PID controller offline tuned with bees algorithm using mathematical model of system. Moreover, the aim is to compare the performances of the BA with an existing optimisation method, genetic algorithm (GA), implemented on the system. The paper presents the experimental results that were obtained from the structure system to show the efficiency of the tuned PID controller. As a result, the performance and effectiveness of the tuned PID controller are investigated and verified experimentally. The displacements and accelerations of the floors and the cart are decreased considerably. The experimental responses of the system are given in graphical form. },
issn = {1461-3484},
keywords = {Bees algorithm, two-floor structure, PID controller, active mass damping, Northridge earthquake},
language = {English},
publisher = {SAGE}
}

The control of vibration and displacement in structures under seismic excitation is very challenging, and designing a structural control system against disturbances has drawn great attention. This paper concentrates on implementing the bees algorithm to tune gains of traditional PID controller for active vibration control of a building-like structure with two floors under Northridge Earthquake excitation. Bees algorithm is a diverse method to ensure an efficient solution for optimisation of a controller according to customary trial-error design methods. The main aim of this study is optimisation of KP, KI and KD gains with bees algorithm in order to obtain a more effective PID controller to suppress vibrations of the floors during the earthquake excitation. After definition of the system and bees algorithm, PID controller offline tuned with bees algorithm using mathematical model of system. Moreover, the aim is to compare the performances of the BA with an existing optimisation method, genetic algorithm (GA), implemented on the system. The paper presents the experimental results that were obtained from the structure system to show the efficiency of the tuned PID controller. As a result, the performance and effectiveness of the tuned PID controller are investigated and verified experimentally. The displacements and accelerations of the floors and the cart are decreased considerably. The experimental responses of the system are given in graphical form.

@article{he_2018,
title = {PDE Model-Based Boundary Control Design for a Flexible Robotic Manipulator With Input Backlash},
author = {He, W.; He, X.; Zou, M.; Li, H.},
journal = {IEEE Transactions on Control Systems Technology},
year = {2018},
institution = {University of Science and Technology Beijing, China; University of Electronic Science and Technology of China, China; Bohai University, China},
abstract = {This brief considers the control design problem for a flexible robotic manipulator. Our control strategies are to: 1) move the manipulator to the certain desired angle; 2) suppress the vibration at the neighborhood of the desired angle; and 3) handle the backlash nonlinearity existing in the practical system. Based on the infinite-dimensional dynamic model, a boundary controller with input backlash is designed to achieve the control aims. An output feedback method is adopted to represent a controller to handle the feedback signals that are not able to be measured directly. The effectiveness of the designed controllers and the stability of the system are demonstrated by theoretical analysis, numerical simulations, and physical experiments. },
issn = {1558-0865 },
keywords = {Distributed parameter system, flexible robotic manipulator, input backlash, output feedback, vibration control},
language = {English},
publisher = {IEEE}
}

This brief considers the control design problem for a flexible robotic manipulator. Our control strategies are to: 1) move the manipulator to the certain desired angle; 2) suppress the vibration at the neighborhood of the desired angle; and 3) handle the backlash nonlinearity existing in the practical system. Based on the infinite-dimensional dynamic model, a boundary controller with input backlash is designed to achieve the control aims. An output feedback method is adopted to represent a controller to handle the feedback signals that are not able to be measured directly. The effectiveness of the designed controllers and the stability of the system are demonstrated by theoretical analysis, numerical simulations, and physical experiments.

@article{li_2018,
title = {Relative posture-based kinematic calibration of a 6-RSS parallel robot by optical coordinate measurement machine},
author = {Li, P.; Zeng2, R.; Xie, W.; Zhang, X.},
journal = { International Journal of Advanced Robotic Systems},
year = {2018},
volume = {15},
number = {2},
institution = {Concordia University, Canada; Beihang University, China},
abstract = {In this article, a relative posture-based algorithm is proposed to solve the kinematic calibration problem of a 6-RSS parallel robot using the optical coordinate measurement machine system. In the research, the relative posture of robot is estimated using the detected pose with respect to the sensor frame through several reflectors which are fixed on the robot end-effector. Based on the relative posture, a calibration algorithm is proposed to determine the optimal error parameters of the robot kinematic model and external parameters introduced by the optical sensor. This method considers both the position and orientation variations and does not need the accurate location information of the detection sensor. The simulation results validate the superiority of the algorithm by comparing with the classic implicit calibration method. And the experimental results demonstrate that the proposal relative posture-based algorithm using optical coordinate measurement machine is an implementable and effective method for the parallel robot calibration. },
keywords = {Parallel robot, calibration, optical sensor, kinematic analysis},
language = {English},
publisher = {SAGE}
}

In this article, a relative posture-based algorithm is proposed to solve the kinematic calibration problem of a 6-RSS parallel robot using the optical coordinate measurement machine system. In the research, the relative posture of robot is estimated using the detected pose with respect to the sensor frame through several reflectors which are fixed on the robot end-effector. Based on the relative posture, a calibration algorithm is proposed to determine the optimal error parameters of the robot kinematic model and external parameters introduced by the optical sensor. This method considers both the position and orientation variations and does not need the accurate location information of the detection sensor. The simulation results validate the superiority of the algorithm by comparing with the classic implicit calibration method. And the experimental results demonstrate that the proposal relative posture-based algorithm using optical coordinate measurement machine is an implementable and effective method for the parallel robot calibration.

@article{prakash_2018,
title = {Robust and novel two degree of freedom fractional controller based on two-loop topology for inverted pendulum},
author = {Dwivedi, P.; Pandey, S.; Junghare, A.S.},
journal = {ISA Transactions},
year = {2018},
institution = {National Institute of Technology, Uttarakhand, India; Visvesvaraya National Institute of Technology, Nagpur, India},
abstract = {A rotary single inverted pendulum (RSIP) typically represents a space booster rocket, Segway and similar systems with unstable equilibrium. This paper proposes a novel two degree of freedom (2-DOF) fractional control strategy based on 2-loop topology for RSIP system which can be extended to control the systems with unstable equilibrium. It comprises feedback and feed-forward paths. Primary controller relates the perturbation attenuation while the secondary controller is accountable for set point tracking. To tune the parameters of proposed fractional controller a simple graphical tuning method based on frequency response is used. The study will serve the outstanding experimental results for both, stabilization and trajectory tracking tasks. The study will also serve to present a comparison of the performance of the proposed controller with the 1-DOF FOPID controller and sliding mode controller (SMC) for the RSIP system. Further to confirm the usability of the proposed controller and to avoid the random perturbations sensitivity, robustness, and stability analysis through fractional root-locus and Bode-plot is investigated. },
keywords = {FOPID controller, 2-DOF PID controller, Inverted pendulum, Sliding mode controller, Iso-damping, Fractional root-locus},
language = {English},
publisher = {Elsevier Ltd.}
}

A rotary single inverted pendulum (RSIP) typically represents a space booster rocket, Segway and similar systems with unstable equilibrium. This paper proposes a novel two degree of freedom (2-DOF) fractional control strategy based on 2-loop topology for RSIP system which can be extended to control the systems with unstable equilibrium. It comprises feedback and feed-forward paths. Primary controller relates the perturbation attenuation while the secondary controller is accountable for set point tracking. To tune the parameters of proposed fractional controller a simple graphical tuning method based on frequency response is used. The study will serve the outstanding experimental results for both, stabilization and trajectory tracking tasks. The study will also serve to present a comparison of the performance of the proposed controller with the 1-DOF FOPID controller and sliding mode controller (SMC) for the RSIP system. Further to confirm the usability of the proposed controller and to avoid the random perturbations sensitivity, robustness, and stability analysis through fractional root-locus and Bode-plot is investigated.

@article{cheng_2018,
title = {Switched-Impedance Control of Surgical Robots in Teleoperated Beating-Heart Surgery},
author = {Cheng, L.; Tavakoli, M.},
journal = {Journal of Medical Robotics Research},
year = {2018},
institution = {University of Alberta, Canada},
abstract = {A novel switched-impedance control method is proposed and implemented for telerobotic beating-heart surgery. Differing from cardiopulmonary-bypass-based arrested-heart surgery, beating-heart surgery creates challenges for the human operator (surgeon) due to the heart's fast motions and, in the case of a teleoperated surgical robot, the oscillatory haptic feedback to the operator. This paper designs two switched reference impedance models for the master and slave robots to achieve both motion compensation and non-oscillatory force feedback during slave-heart interaction. By changing the parameters of the impedance models, different performances for both robots are obtained: (a) when the slave robot does not make contact with the beating heart, the slave robot closely follows the motion of the master robot as in a regular teleoperation system, (b) when contact occurs, the slave robot automatically compensates for the fast motions of the beating heart while the human operator perceives the non-oscillatory component of the slave-heart interaction forces, creating the feeling of making contact with an idle heart for the human operator. The proposed method is validated through simulations and experiments. },
keywords = {Beating-heart surgery; teleoperation; motion compensation; non-oscillatory haptic feedback},
language = {English},
publisher = {World Scientific Publishing Company}
}

A novel switched-impedance control method is proposed and implemented for telerobotic beating-heart surgery. Differing from cardiopulmonary-bypass-based arrested-heart surgery, beating-heart surgery creates challenges for the human operator (surgeon) due to the heart's fast motions and, in the case of a teleoperated surgical robot, the oscillatory haptic feedback to the operator. This paper designs two switched reference impedance models for the master and slave robots to achieve both motion compensation and non-oscillatory force feedback during slave-heart interaction. By changing the parameters of the impedance models, different performances for both robots are obtained: (a) when the
slave robot does not make contact with the beating heart, the slave robot closely follows the motion of the master robot as in a regular teleoperation system, (b) when contact occurs, the slave robot automatically compensates for the fast motions of the beating heart while the human operator perceives the non-oscillatory component of the slave-heart interaction forces, creating the feeling of making contact with an idle heart for the human operator. The proposed method is validated through simulations and experiments.

@conference{saleem_2018,
title = {Synergistic speed control strategy for PMDC motor},
author = {Saleem, O.; Omer, U.},
booktitle = {2017 International Multi-topic Conference (INMIC)},
year = {2018},
institution = {National University of Computer and Emerging Sciences, Pakistan},
abstract = {This paper presents the synthesis of a linear-quadratic-regulator (LQR) augmented with a nonlinear-integral controller to optimize the speed regulation of a permanent magnet DC (PMDC) motor. The LQR utilizes the full state-feedback and minimizes the quadratic performance index to deliver optimal speed control decisions. However, the LQR lacks the ability to eliminate the steady-state error and damp the oscillations occurring during transients. For this purpose, the LQR is combined with an integral controller. In order to synergize the controller combination, the integral gain is dynamically varied via smooth hyperbolic secant function of error-dynamics in motor speed; such that, the contribution rendered by the integral-action increases as the response converges towards the reference speed and vice-versa. The results of real-time experiments are presented and analyzed to validate the effectiveness of the proposed controller. },
keywords = {PMDC motor, LQR, integral controller, hyperbolic secant function},
language = {English},
publisher = {IEEE}
}

This paper presents the synthesis of a linear-quadratic-regulator (LQR) augmented with a nonlinear-integral controller to optimize the speed regulation of a permanent magnet DC (PMDC) motor. The LQR utilizes the full state-feedback and minimizes the quadratic performance index to deliver optimal speed control decisions. However, the LQR lacks the ability to eliminate the steady-state error and damp the oscillations occurring during transients. For this purpose, the LQR is combined with an integral controller. In order to synergize the controller combination, the integral gain is dynamically varied via smooth hyperbolic secant function of error-dynamics in motor speed; such that, the contribution rendered by the integral-action increases as the response converges towards the reference speed and vice-versa. The results of real-time experiments are presented and analyzed to validate the effectiveness of the proposed controller.

@conference{cleveland_2018,
title = {The effect of discretization techniques on uncoupled stability of haptic simulation systems},
author = {Cleveland, D.; Hashtrudi-Zaad, K.},
booktitle = {2018 IEEE Haptics Symposium (HAPTICS)},
year = {2018},
institution = {Queen's University, Canada},
abstract = {Haptic simulation systems allow human users to kinesthetically interact with virtual environment models through a robotic mechanism known as a haptic interface. The range of environment dynamics that can be stably rendered in a haptic simulation system is determined by a number of factors, including the method by which the virtual environment is implemented in discrete-time domain. Uncoupled stability, the stability of the system when it is not interfaced to any user, is regarded as one of the most stringent stability conditions for impedance-type interfaces. In this work, we analytically and experimentally investigate the system uncoupled stability conditions for various discrete implementation of damper-spring environments when position or velocity is sampled. The results point at different ranges of environment dynamics suitable for various applications. },
issn = {2324-7355},
keywords = {Haptic interfaces, Stability criteria, Damping, Manipulator dynamics, Numerical stability, Virtual environments},
language = {English},
publisher = {IEEE},
isbn = {978-1-5386-5425-5 }
}

Haptic simulation systems allow human users to kinesthetically interact with virtual environment models through a robotic mechanism known as a haptic interface. The range of environment dynamics that can be stably rendered in a haptic simulation system is determined by a number of factors, including the method by which the virtual environment is implemented in discrete-time domain. Uncoupled stability, the stability of the system when it is not interfaced to any user, is regarded as one of the most stringent stability conditions for impedance-type interfaces. In this work, we analytically and experimentally investigate the system uncoupled stability conditions for various discrete implementation of damper-spring environments when position or velocity is sampled. The results point at different ranges of environment dynamics suitable for various applications.

@conference{coronado_2017,
title = {A Comparison of Fuzzy Schemes for Trajectory Tracking on the Furuta Pendulum},
author = {Coronado, A.; Penaloza-Mejia, O.; Estrada-Manzo, V.; Bernal, M.},
booktitle = {National Congress on Automatic Control 2017},
year = {2017},
month = {10},
institution = {Sonora Institute of Technology, Mexico},
abstract = {This paper presents real-time implementation of trajectory tracking on a Furuta pendulum via two fuzzy output regulation schemes: the first one uses convex representations; the second one employs dynamic mappings. Additionally, the stabilizing part of the control law is computed by means of linear matrix inequalities, so speed convergence and input constraints can be directly considered. Simulation and real-time results are given to show the effectiveness of the approaches },
keywords = {Trajectory tracking; output regulation; fuzzy mappings; dynamic mapping; fuzzy modeling; Furuta pendulum},
language = {English},
pages = {499-503}
}

This paper presents real-time implementation of trajectory tracking on a Furuta pendulum via two fuzzy output regulation schemes: the first one uses convex representations; the second one employs dynamic mappings. Additionally, the stabilizing part of the control law is computed by means of linear matrix inequalities, so speed convergence and input constraints can be directly considered. Simulation and real-time results are given to show the effectiveness of the approaches

@conference{fauser_2017,
title = {A comparison of inertial-based navigation algorithms for a low-cost indoor mobile robot},
author = {Fauser, T.; Bruder, S.; El-Osery, A.},
booktitle = {2017 12th International Conference on Computer Science and Education (ICCSE)},
year = {2017},
institution = {Embry-Riddle Aeronautical University, AZ, USA; New Mexico Tech, NM, USA},
abstract = {Reliable navigation of a low-cost mobile robot in an indoor environment can prove to be challenging as position fixing sensors, such as a GNSS receiver, are typically unavailable. Subscribing to the premise of a baseline of odometry and inertial sensors, this paper compares three navigation strategies, namely, a full 6-DOF inertial measurement unit (IMU) with kinematic constraints, a partial IMU with gyro pseudo-measurements, and an IMU with a depth camera. In the third configuration, by embracing the reality that vertical and horizontal planes dominate the indoor environment, an infrared depth camera is employed to determine surface normals and thereby provide attitude aiding. The paper presents a theoretical basis of the aided inertial navigational problems, MATLAB/Simulink-based simulation results, and finally the performance realized from the implementation of the algorithms on a QUANSER QBot 2 mobile robot employing a VectorNav VN-200 IMU and Kinect IR depth camera. },
issn = {2473-9464 },
keywords = {Localization, inertial navigation, inertial measurement unit, odometry, mobile robot, depth camera, aided inertial navigation},
language = {English},
publisher = {IEEE},
isbn = {978-1-5090-2509-1}
}

Reliable navigation of a low-cost mobile robot in an indoor environment can prove to be challenging as position fixing sensors, such as a GNSS receiver, are typically unavailable. Subscribing to the premise of a baseline of odometry and inertial sensors, this paper compares three navigation strategies, namely, a full 6-DOF inertial measurement unit (IMU) with kinematic constraints, a partial IMU with gyro pseudo-measurements, and an IMU with a depth camera. In the third configuration, by embracing the reality that vertical and horizontal planes dominate the indoor environment, an infrared depth camera is employed to determine surface normals and thereby provide attitude aiding. The paper presents a theoretical basis of the aided inertial navigational problems, MATLAB/Simulink-based simulation results, and finally the performance realized from the implementation of the algorithms on a QUANSER QBot 2 mobile robot employing a VectorNav VN-200 IMU and Kinect IR depth camera.