@article{dwivedi2_2017,
title = {Stabilization of Unstable Equilibrium Point of Rotary Inverted Pendulum using Fractional Controller},
author = {Dwivedi, P.; Pandey, S.; Junghare, A.S.},
journal = {Journal of Franklin Institute},
year = {2107},
institution = {National Institute of Technology, Uttarakhand, India},
abstract = {Many studies have been conducted by researchers globally in the recent past on the control schemes to enhance the performance of Rotary Single Inverted Pendulum (RSIP). The present paper seeks to investigate into a method to stabilize a pendulum link in upright position with a focus to minimize the deviation in rotational arm. Based on the fractional calculus, the proposed control scheme consists of two loop fractional controller in order to intensify the potentiality of RSIP. To tune the parameters of proposed fractional controller a simple graphical tuning method based on frequency response is used. The same parameters will also tuned using dynamic particle swarm optimization (dPSO). The study will also serve to present a comparison of the performance of the proposed controller with the dynamic particle swarm optimization (dPSO) based fractional controller. Back calculation anti-windup technique will also be incorporated to compensate the saturation non-linearity. Further to confirm the usability of the proposed controller and to avoid the random perturbations sensitivity and robustness is investigated. },
keywords = {Fractional Controller, PID Controller, Nyquist Criteria, Sensitivity, Antiwindup},
language = {English},
publisher = {Elsevier Ltd.}
}

Many studies have been conducted by researchers globally in the recent past on the control schemes to enhance the performance of Rotary Single Inverted Pendulum (RSIP). The present paper seeks to investigate into a method to stabilize a pendulum link in upright position with a focus to minimize the deviation in rotational arm. Based on the fractional calculus, the proposed control scheme consists of two loop fractional controller in order to intensify the potentiality of RSIP. To tune the parameters of proposed fractional controller a simple graphical tuning method based on frequency response is used. The same parameters will also tuned using dynamic particle swarm optimization (dPSO). The study will also serve to present a comparison of the performance of the proposed controller with the dynamic particle swarm optimization (dPSO) based fractional controller. Back calculation anti-windup technique will also be incorporated to compensate the saturation non-linearity. Further to confirm the usability of the proposed controller and to avoid the random perturbations sensitivity and robustness is investigated.

@article{du_2017,
title = {A Control Performance Index for Multicopters Under Off-nominal Conditions},
author = {Du, G.-X.; Quan, Q.; Xi, Z.; Liu, Y.; Cai, K.-Y.},
year = {2017},
institution = {School of Automation Science and Electrical Engineering, Beihang University, China},
abstract = {In order to prevent loss of control (LOC) accidents, the real-time control performance monitoring (CPM) problem is studied for multicopters. Different from the existing literature, this paper does not try to monitor the performance of the controllers directly. Conversely, the unknown disturbances of the multicopter under off-nominal conditions are modeled and assessed. The monitoring results will tell the user whether a multicopter will be LOC or not. Firstly, a new degree of controllability (DoC) will be proposed for multicopters subject to control constrains and off-nominal conditions. Then a control performance index (CPI) will be defined based on the new DoC to reflect the control performance of the multicopters. Besides, the proposed CPI is applied to a new switching control framework to guide the control decision of multicopter under off-nominal conditions. Finally, simulation and experimental results will show the effectiveness of the CPI and the switching control framework proposed in this paper. },
keywords = {Multicopters, loss of control, control performance monitoring, degree of controllability},
language = {English}
}

In order to prevent loss of control (LOC) accidents, the real-time control performance monitoring (CPM) problem is studied for multicopters. Different from the existing literature, this paper does not try to monitor the performance of the controllers directly. Conversely, the unknown disturbances of the multicopter under off-nominal conditions are modeled and assessed. The monitoring results will tell the user whether a multicopter will be LOC or not. Firstly, a new degree of controllability (DoC) will be proposed for multicopters subject to control constrains and off-nominal conditions. Then a control performance index (CPI) will be defined based on the new DoC to reflect the control performance of the multicopters. Besides, the proposed CPI is applied to a new switching control framework to guide the control decision of multicopter under off-nominal conditions. Finally, simulation and experimental results will show the effectiveness of the CPI and the switching control framework proposed in this paper.

@article{sanz_2017,
title = {A generalized smith predictor for unstable time-delay SISO systems},
author = {Sanz, R.; Garcia, P.; Albertos, P.},
journal = {ISA Transactions},
year = {2017},
institution = {Universitat Politecnica de Valencia, Spain},
abstract = {In this work, a generalization of the Smith Predictor (SP) is proposed to control linear time-invariant (LTI) time-delay single-input single-output (SISO) systems. Similarly to the SP, the combination of any stabilizing output-feedback controller for the delay-free system with the proposed predictor leads to a stabilizing controller for the delayed system. Furthermore, the tracking performance and the steady-state disturbance rejection capabilities of the equivalent delay-free loop are preserved. In order to place this contribution in context, some modifications of the SP are revisited and recast under the same structure. The features of the proposed scheme are illustrated through simulations, showing a comparison with respect to the corresponding delay-free loop, which is here considered to be the ideal scenario. In order to emphasize the feasibility of this approach, a successful experimental implementation in a laboratory platform is also reported. },
keywords = {Smith Predictor, Time delay, External disturbances, Single-input single-output system},
language = {English},
publisher = {Elsevier Ltd.}
}

In this work, a generalization of the Smith Predictor (SP) is proposed to control linear time-invariant (LTI) time-delay single-input single-output (SISO) systems. Similarly to the SP, the combination of any stabilizing output-feedback controller for the delay-free system with the proposed predictor leads to a stabilizing controller for the delayed system. Furthermore, the tracking performance and the steady-state disturbance rejection capabilities of the equivalent delay-free loop are preserved. In order to place this contribution in context, some modifications of the SP are revisited and recast under the same structure. The features of the proposed scheme are illustrated through simulations, showing a comparison with respect to the corresponding delay-free loop, which is here considered to be the ideal scenario. In order to emphasize the feasibility of this approach, a successful experimental implementation in a laboratory platform is also reported.

@article{atashzar_2017_2,
title = {A grasp-based passivity signature for haptics-enabled human-robot interaction: Application to design of a new safety mechanism for robotic rehabilitation},
author = {Atashzar, S.F.; Shahbazi, M.; Tavakoli, M.; Patel, R.V.},
journal = {International Journal of Robotics Research},
year = {2017},
institution = {University of Western Ontario, Canada; University of Alberta, Canada},
abstract = {In this paper, the biomechanical capability of the human upper limb in absorbing physical interaction energy during human-robot interaction is analyzed. The outcome is a graphical map that can quantitatively correlate the extent of the grasp pressure and the geometry of interaction to the extent of hand passivity. For this purpose, a user study has been conducted for 11 healthy human subjects to characterize the energy absorption capability in their arm and wrist. The above correlation is statistically validated. The identified user-specific grasp-based passivity signature map can be used as a graphical tool to assess the biomechanical capabilities of the upper limb in absorbing interaction energy. In this paper, the proposed grasp-based passivity signature map is utilized in the design of a new stabilizer for haptic systems, that takes into account the variation in energy absorption during haptic task execution. The goal is to optimize the haptic system fidelity while guaranteeing human-robot interaction stability despite the potential existence of delays and a non-passive environment. The controller is termed grasp-based passivity signature map stabilizer. If the user provides minimum to no energy absorption during the interaction, the controller makes the force reflection gate tight to guarantee stability. However, when the user demonstrates high capability in absorbing interaction energy, the controller allows the forces to be reflected. The grasp-based passivity signature map stabilizer is an alternative for both conventional stabilizers of haptic/telerobotic systems and fixed conservative force limits in rehabilitation systems where patient-robot interaction safety is a crucial requirement. This provides the practical motivation for this work. Experimental results are presented. },
keywords = {Human-robot interaction, excess of passivity, haptics, non-passive environments, physical energy dissipation, safety and stability, rehabilitation robotics, telerobotic and haptic systems},
language = {English},
publisher = {SAGE}
}

In this paper, the biomechanical capability of the human upper limb in absorbing physical interaction energy during human-robot interaction is analyzed. The outcome is a graphical map that can quantitatively correlate the extent of the grasp pressure and the geometry of interaction to the extent of hand passivity. For this purpose, a user study has been conducted for 11 healthy human subjects to characterize the energy absorption capability in their arm and wrist. The above correlation is statistically validated. The identified user-specific grasp-based passivity signature map can be used as a graphical tool to assess the biomechanical capabilities of the upper limb in absorbing interaction energy. In this paper, the proposed grasp-based passivity signature map is utilized in the design of a new stabilizer for haptic systems, that takes into account the variation in energy absorption during haptic task execution. The goal is to optimize the haptic system fidelity while guaranteeing human-robot interaction stability despite the potential existence of delays and a non-passive environment. The controller is termed grasp-based passivity signature map stabilizer. If the user provides minimum to no energy absorption during the interaction, the controller makes the force reflection gate tight to guarantee stability. However, when the user demonstrates high capability in absorbing interaction energy, the controller allows the forces to be reflected. The grasp-based passivity signature map stabilizer is an alternative for both conventional stabilizers of haptic/telerobotic systems and fixed conservative force limits in rehabilitation systems where patient-robot interaction safety is a crucial requirement. This provides the practical motivation for this work. Experimental results are presented.

@article{paul_2017,
title = {A method for bidirectional active control of structures},
author = {Paul, S.; Yu, W.},
journal = {Journal of Vibration and Control},
year = {2017},
institution = {Departamento de Control Automatico, CINVESTAV-IPN (National Polytechnic Institute), Mexico City, Mexico},
abstract = {Proportional-derivative (PD) and proportional-integral-derivative (PID) controllers are popular control algorithms in industrial applications, especially in structural vibration control. In this paper, the designs of two dampers, namely the horizontal actuator and torsional actuator, are combined for the lateral and torsional vibrations of the structure. The standard PD and PID controllers are utilized for active vibration control. The sufficient conditions for asymptotic stability of these controllers are validated by utilizing the Lyapunov stability theorem. An active vibration control system with two floors equipped with a horizontal actuator and a torsional actuator is installed to carry out the experimental analysis. The experimental results show that bidirectional active control has been achieved. },
keywords = {PID control, bidirectional control, active vibration control, stability, building structure},
language = {English},
publisher = {SAGE}
}

Proportional-derivative (PD) and proportional-integral-derivative (PID) controllers are popular control algorithms in industrial applications, especially in structural vibration control. In this paper, the designs of two dampers, namely the horizontal actuator and torsional actuator, are combined for the lateral and torsional vibrations of the structure. The standard PD and PID controllers are utilized for active vibration control. The sufficient conditions for asymptotic stability of these controllers are validated by utilizing the Lyapunov stability theorem. An active vibration control system with two floors equipped with a horizontal actuator and a torsional actuator is installed to carry out the experimental analysis. The experimental results show that bidirectional active control has been achieved.

@article{alibeji3_2017,
title = {A Modified Dynamic Surface Controller for Delayed Neuromuscular Electrical Stimulation},
author = {Alibeji, N.; Kirsch, N.; Dicianno, B.; Sharma, N.},
journal = {IEEE/ASME Transactions on Mechatronics},
year = {2017},
institution = {Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA,USA},
abstract = {A widely accepted model of muscle force generation during neuromuscular electrical stimulation (NMES) is a second-order nonlinear musculoskeletal dynamics cascaded to a delayed first-order muscle activation dynamics. However, most nonlinear NMES control methods have either neglected the muscle activation dynamics or used ad hoc strategies to tackle the muscle activation dynamics, which may not guarantee control stability. We hypothesized that a nonlinear control design that includes muscle activation dynamics can improve the control performance. In this paper, a dynamic surface control (DSC) approach was used to design a PID-based NMES controller that compensates for EMD in the activation dynamics. Because the muscle activation is unmeasurable, a model based estimator was used to estimate the muscle activation in realtime. The Lyapunov stability analysis confirmed that the newly developed controller achieves uniformly ultimately bounded (SGUUB) tracking for the musculoskeletal system. Experiments were performed on two able-bodied subjects and one spinal cord injury subject using a modified leg extension machine. These experiments illustrate the performance of the new controller and compare it to a previous PID-DC controller that did not consider muscle activation dynamics in the control design. These experiments support our hypothesis that a control design that includes muscle activation improves the NMES control performance. },
issn = {1083-4435},
keywords = {Muscles, Dynamics, Delays, Control design, Stability analysis, Knee},
language = {English},
publisher = {IEEE}
}

A widely accepted model of muscle force generation during neuromuscular electrical stimulation (NMES) is a second-order nonlinear musculoskeletal dynamics cascaded to a delayed first-order muscle activation dynamics. However, most nonlinear NMES control methods have either neglected the muscle activation dynamics or used ad hoc strategies to tackle the muscle activation dynamics, which may not guarantee control stability. We hypothesized that a nonlinear control design that includes muscle activation dynamics can improve the control performance. In this paper, a dynamic surface control (DSC) approach was used to design a PID-based NMES controller that compensates for EMD in the activation dynamics. Because the muscle activation is unmeasurable, a model based estimator was used to estimate the muscle activation in realtime. The Lyapunov stability analysis confirmed that the newly developed controller achieves uniformly ultimately bounded (SGUUB) tracking for the musculoskeletal system. Experiments were performed on two able-bodied subjects and one spinal cord injury subject using a modified leg extension machine. These experiments illustrate the performance of the new controller and compare it to a previous PID-DC controller that did not consider muscle activation dynamics in the control design. These experiments support our hypothesis that a control design that includes muscle activation improves the NMES control performance.

@article{elumalai_2017,
title = {A new algebraic LQR weight selection algorithm for tracking control of 2 DoF torsion system},
author = {Elumalai V.K.; Subramanian, R.G.},
journal = {Archives of Electrical Engineering},
year = {2017},
volume = {66},
number = {1},
institution = {VIT University, India; Eindhoven University of Technology, The Netherlands},
abstract = {This paper proposes a novel linear quadratic regulator (LQR) weight selection algorithm by synthesizing the algebraic Riccati equation (ARE) with the Lagrange multiplier method for command following applications of a 2 degree of freedom (DoF) torsion system. The optimal performance of LQR greatly depends on the elements of weighting matrices Q and R. However, normally these weighting matrices are chosen by a trial and error approach which is not only time consuming but cumbersome. Hence, to address this issue, blending the design criteria in time domain with the ARE, we put forward an algebraic weight selection algorithm, which makes the LQR design both simple and modular. Moreover, to estimate the velocity of a servo angle, a high gain observer (HGO) is designed and integrated with the LQR control scheme. The efficacy of the proposed control scheme is tested on a benchmark 2 DoF torsion system for a trajectory tracking application. Both the steady state and dynamic characteristics of the proposed controller are assessed. The experimental results accentuate that the proposed HGO based LQR scheme can guarantee the system to attain the design requirements with minimal vibrations and tracking errors. },
keywords = {ARE, high gain observer, LQR, Q and R matrices, 2 DoF torsion system, trajectory tacking},
language = {English}
}

This paper proposes a novel linear quadratic regulator (LQR) weight selection algorithm by synthesizing the algebraic Riccati equation (ARE) with the Lagrange multiplier method for command following applications of a 2 degree of freedom (DoF) torsion system. The optimal performance of LQR greatly depends on the elements of weighting matrices Q and R. However, normally these weighting matrices are chosen by a trial and error approach which is not only time consuming but cumbersome. Hence, to address this issue, blending the design criteria in time domain with the ARE, we put forward an algebraic weight selection algorithm, which makes the LQR design both simple and modular. Moreover, to estimate the velocity of a servo angle, a high gain observer (HGO) is designed and integrated with the LQR control scheme. The efficacy of the proposed control scheme is tested on a benchmark 2 DoF torsion system for a trajectory tracking application. Both the steady state and dynamic characteristics of the proposed controller are assessed. The experimental results accentuate that the proposed HGO based LQR scheme can guarantee the system to attain the design requirements with minimal vibrations and tracking errors.

@conference{bucak_2017,
title = {A new design concept of magnetically levitated 4 pole hybrid mover driven by linear motor},
author = {Bucak, M.; Bozkurt, A.F.; Erkan, K.; Uvet, H.},
booktitle = {2017 IEEE International Conference on Robotics and Automation (ICRA)},
year = {2017},
institution = {Yıldız Technical University, Istanbul, Turkey},
abstract = {This paper reports a new design topology of 4 pole hybrid electromagnetic levitation system in conjunction with linear synchronous motor. The mover, 4 pole hybrid electromagnet, is levitated underneath of the linear motor with zero power control algorithm. Propulsion and one-dimensional planar motion of the hybrid electromagnet is provided by the vector controlled linear motor. The new design of 4 pole hybrid electromagnet has several improvements over older systems, such as weight reduction and less material usage. Diagonal drive integration of mover and linear motor is proposed and experimental results are presented. },
keywords = {Permanent magnet motors, Induction motors, Synchronous motors, Coils, Magnetic levitation, Magnetic cores},
language = {English},
publisher = {IEEE}
}

This paper reports a new design topology of 4 pole hybrid electromagnetic levitation system in conjunction with linear synchronous motor. The mover, 4 pole hybrid electromagnet, is levitated underneath of the linear motor with zero power control algorithm. Propulsion and one-dimensional planar motion of the hybrid electromagnet is provided by the vector controlled linear motor. The new design of 4 pole hybrid electromagnet has several improvements over older systems, such as weight reduction and less material usage. Diagonal drive integration of mover and linear motor is proposed and experimental results are presented.

@inproceedings{zhang2_2017,
title = {A Novel Sliding Mode Control Algorithm for a Servo Gantry with Guaranteed Transient Performance},
author = {Zhang, Y.; Yan, P.},
booktitle = {Proceedings of the 36th Chinese Control Conference},
year = {2017},
institution = {Beihang University, China; Shandong University, Jinan, China},
abstract = {This paper investigates the tracking control problems of a voice coil motor (VCM) actuated servo gantry system. A novel sliding mode disturbance observer based control algorithm is proposed to accommodate both model uncertainties and various disturbances. In the proposed control architecture, the sliding mode observer is introduced to estimate the total disturbances such that the observer error can converge to zero in a finite time, and the fast terminal sliding mode (TSM) control technique is adopted to solve the tracking problem such that the tracking error can converge to zero in a finite time. Particularly, the singularity problem in the conventional TSM systems is avoided by switching the sliding mode function between two different terminal sliding structures. The finite-time stability of the whole closed-loop system is also proved. Finally, numerical simulations and real time experiments demonstrate excellent tracking performance of the proposed criteria. },
issn = {1934-1768 },
keywords = {Finite Time Control, Sliding Mode Control, Voice Coil Motor, Motion Control},
language = {English},
publisher = {IEEE},
isbn = {978-1-5386-2918-5 }
}

This paper investigates the tracking control problems of a voice coil motor (VCM) actuated servo gantry system. A novel sliding mode disturbance observer based control algorithm is proposed to accommodate both model uncertainties and various disturbances. In the proposed control architecture, the sliding mode observer is introduced to estimate the total disturbances such that the observer error can converge to zero in a finite time, and the fast terminal sliding mode (TSM) control technique is adopted to solve the tracking problem such that the tracking error can converge to zero in a finite time. Particularly, the singularity problem in the conventional TSM systems is avoided by switching the sliding mode function between two different terminal sliding structures. The finite-time stability of the whole closed-loop system is also proved. Finally, numerical simulations and real time experiments demonstrate excellent tracking performance of the proposed criteria.

@article{alibeji2_2017,
title = {A PID-Type Robust Input Delay Compensation Method for Uncertain Euler-Lagrange Systems},
author = {Alibeji, N.; Sharma, N.},
journal = {IEEE Transactions on Control Systems Technology},
year = {2017},
institution = {Department of Mechanical Engineering and Materials Science, University of Pittsburgh, USA},
abstract = {Robust delay compensation techniques for uncertain nonlinear systems with unknown input delays are, in general, lacking. The result in this brief extends a modified proportional-integral derivative (PID)-type controller that contains a distributed delay term to Euler-Lagrange systems with an unknown constant input delay. Additive disturbances and uncertainties in the nonlinear system were considered in the control development and stability analysis. The stability analysis also hinges upon Lyapunov-Krasovskii functionals that were designed to prove semiglobal uniformly ultimately bounded tracking. Experiments on a 3-degree of freedom robot were performed to depict the performance of the new controller. },
issn = {1063-6536},
keywords = {Delay compensation, Euler-Lagrange systems, robust control, unknown input delay},
language = {English},
publisher = {IEEE}
}

Robust delay compensation techniques for uncertain nonlinear systems with unknown input delays are, in general, lacking. The result in this brief extends a modified proportional-integral derivative (PID)-type controller that contains a distributed delay term to Euler-Lagrange systems with an unknown constant input delay. Additive disturbances and uncertainties in the nonlinear system were considered in the control development and stability analysis. The stability analysis also hinges upon Lyapunov-Krasovskii functionals that were designed to prove semiglobal uniformly ultimately bounded tracking. Experiments on a 3-degree of freedom robot were performed to depict the performance of the new controller.

@article{zhao_2017,
title = {A PIMR-type Repetitive Control for a Grid-tied Inverter: Structure, Analysis, and Design},
author = {Zhao, Q.; Ye, Y.},
journal = {IEEE Transactions on Power Electronics},
year = {2017},
institution = {Nanjing University of Aeronautics and Astronautics, China},
abstract = {This paper proposes a proportional integral (inertial) multi-resonant (PIMR) type repetitive control (PIMRtype RC) scheme for a grid-tied inverter. The proposed control scheme is composed of a repetitive controller in parallel with a proportional gain for the purpose of replacing lots of parameters of the conventional proportional multi-resonant controller, and therefore, only a few parameters need to be designed. The proportional gain not only improves the dynamic response, but also enables RC to accommodate a larger RC gain, and hence a faster convergence rate. Theoretical analysis and stability analysis of PIMR-type RC are given, and then a practical step-by-step design tutorial is also provided. The experimental results validate the feasibility and outstanding performance of the proposed control scheme. },
issn = {0885-8993},
keywords = {Proportional integral multi-resonant control, grid-tied inverter, repetitive control, convergence rate},
language = {English},
publisher = {IEEE}
}

This paper proposes a proportional integral (inertial) multi-resonant (PIMR) type repetitive control (PIMRtype RC) scheme for a grid-tied inverter. The proposed control scheme is composed of a repetitive controller in parallel with a proportional gain for the purpose of replacing lots of parameters of the conventional proportional multi-resonant controller, and therefore, only a few parameters need to be designed. The proportional gain not only improves the dynamic response, but also enables RC to accommodate a larger RC gain, and hence a faster convergence rate. Theoretical analysis and stability analysis of PIMR-type RC are given, and then a practical step-by-step design tutorial is also provided. The experimental results validate the feasibility and outstanding performance of the proposed control scheme.

@article{atashzar_2017,
title = {A Small-Gain Approach for Non-Passive Bilateral Telerobotic Rehabilitation: Stability Analysis and Controller Synthesis},
author = {Atashzar, S.F.; Polushin, I.G.; Patel, R.V.},
journal = {IEEE Transactions on Robotics},
year = {2017},
volume = {33},
number = {1},
institution = {Department of Electrical and Computer Engineering, Western University, London, ON, Canada},
abstract = {In this paper, the design of a novel bilateral telerobotic architecture for rehabilitation purposes is proposed and the related feasibility, stability, and control challenges are studied. The objective is to incorporate the supervision of a local/remote human physiotherapist into haptics-enabled rehabilitation systems and allow the therapist to provide nonpassive nonlinear assistive/resistive forces in response to the patient's movements. This can address a challenge of conventional software-based rehabilitation systems, i.e., limited capability in adjusting the therapy. To guarantee human–robot interaction safety, a new design framework and a stabilizing controller are developed based on the small-gain approach. System stability and transparency are analyzed in the presence of the nonpassive, nonlinear, and nonautonomous behavior of the terminals (the therapist and the patient) and time-varying delays for the case of remote and cloud-based therapy. Several practical considerations have been taken into account to match the clinical needs and minimize the implementation cost. Simulation studies, practical implementation, and experimental evaluations are presented. },
issn = {1552-3098},
keywords = {Haptics, physical human–robot interaction, rehabilitation robotics, stability, telerobotics},
language = {English},
publisher = {IEEE},
pages = {49-66}
}

In this paper, the design of a novel bilateral telerobotic architecture for rehabilitation purposes is proposed and the related feasibility, stability, and control challenges are studied. The objective is to incorporate the supervision of a local/remote human physiotherapist into haptics-enabled rehabilitation systems and allow the therapist to provide nonpassive nonlinear assistive/resistive forces in response to the patient's movements. This can address a challenge of conventional software-based rehabilitation systems, i.e., limited capability in adjusting the therapy. To guarantee human–robot interaction safety, a new design framework and a stabilizing controller are developed based on the small-gain approach. System stability and transparency are analyzed in the presence of the nonpassive, nonlinear, and nonautonomous behavior of the terminals (the therapist and the patient) and time-varying delays for the case of remote and cloud-based therapy. Several practical considerations have been taken into account to match the clinical needs and minimize the implementation cost. Simulation studies, practical implementation, and experimental evaluations are presented.

@article{abdi_2017,
title = {Achieving System-level Fault-tolerance with Controlled Resets},
author = {Abdi, F.; Mancuso, R.; Tabish, R.; Caccamo, M.},
year = {2017},
institution = {Department of Computer Science University of Illinois at Urbana-Champaign, USA},
abstract = {Embedded systems in safety-critical environments are continuously required to deliver more performance and functionality, leading to increased complexity and connectivity. Despite the fast growing complexity, guaranteeing safety is of the utmost importance. Nonetheless, platform-wide software verification is often expensive. Therefore, design methods that enable utilization of components such as real-time operating systems (RTOS), without requiring their correctness to guarantee safety, is necessary. In this paper, we propose a design approach to deploy safe-by-design embedded systems. To attain this goal, we rely on a small core of verified software to detect faults in applications and RTOS and recover from them while ensuring that timing constraints of safety-critical tasks are always satisfied. Faults are detected by monitoring the state of the physical plant and application timing. Fault-recovery is achieved via full platform restart and software reload, enabled by the short restart time of embedded systems. Schedulability analysis is used to ensure that the timing constraints of critical plant control tasks are always satisfied in spite of faults and consequent restarts. We derive schedulability results for four restart tolerant task models. We use a simulator to evaluate and compare the performance of the considered scheduling models. Finally, we implement a controller for a 3 degree of freedom (3DOF) helicopter using one of such models on real hardware and demonstrate that the system remains safe despite faults in the RTOS and applications. },
language = {English},
publisher = {University of Illinois at Urbana-Champaign}
}

Embedded systems in safety-critical environments are continuously required to deliver more performance and functionality, leading to increased complexity and connectivity. Despite the fast growing complexity, guaranteeing safety is of the utmost importance. Nonetheless, platform-wide software verification is often expensive. Therefore, design methods that enable utilization of components such as real-time operating systems (RTOS), without requiring their correctness to guarantee safety, is necessary. In this paper, we propose a design approach to deploy safe-by-design embedded systems. To attain this goal, we rely on a small core of verified software to detect faults in applications and RTOS and recover from them while ensuring that timing constraints of safety-critical tasks are always satisfied. Faults are detected by monitoring the state of the physical plant and application timing. Fault-recovery is achieved via full platform restart and software reload, enabled by the short restart time of embedded systems. Schedulability analysis is used to ensure that the timing constraints of critical plant control tasks are always satisfied in spite of faults and consequent restarts. We derive schedulability results for four restart tolerant task models. We use a simulator to evaluate and compare the performance of the considered scheduling models. Finally, we implement a controller for a 3 degree of freedom (3DOF) helicopter using one of such models on real hardware and demonstrate that the system remains safe despite faults in the RTOS and applications.

@article{abdi3_2017,
title = {Achieving System-level Fault-tolerance with Controlled Resets},
author = {Abdi, F.; Mancuso, R.; Tabish, R.; Caccamo, M.},
year = {2017},
institution = {Department of Computer Science University of Illinois at Urbana-Champaign, USA},
abstract = {Embedded systems in safety-critical environments are continuously required to deliver more performance and functionality, leading to increased complexity and connectivity. Despite the fast growing complexity, guaranteeing safety is of the utmost importance. Nonetheless, platform-wide software verification is often expensive. Therefore, design methods that enable utilization of components such as real-time operating systems (RTOS), without requiring their correctness to guarantee safety, is necessary. In this paper, we propose a design approach to deploy safe-by-design embedded systems. To attain this goal, we rely on a small core of verified software to detect faults in applications and RTOS and recover from them while ensuring that timing constraints of safety-critical tasks are always satisfied. Faults are detected by monitoring the state of the physical plant and application timing. Fault-recovery is achieved via full platform restart and software reload, enabled by the short restart time of embedded systems. Schedulability analysis is used to ensure that the timing constraints of critical plant control tasks are always satisfied in spite of faults and consequent restarts. We derive schedulability results for four restart-tolerant task models. We use a simulator to evaluate and compare the performance of the considered scheduling models. Finally, we implement a controller for a 3 degree of freedom (3DOF) helicopter using one of such models on real hardware and demonstrate that the system remains safe despite faults in the RTOS and applications. },
language = {English},
pages = {1-15}
}

Embedded systems in safety-critical environments are continuously required to deliver more performance and functionality, leading to increased complexity and connectivity. Despite the fast growing complexity, guaranteeing safety is of the utmost importance. Nonetheless, platform-wide software verification is often expensive. Therefore, design methods that enable utilization of components such as real-time operating systems (RTOS), without requiring their correctness to guarantee safety, is necessary. In this paper, we propose a design approach to deploy safe-by-design embedded systems. To attain this goal, we rely on a small core of verified software to detect faults in applications and RTOS and recover from them while ensuring that timing constraints of safety-critical tasks are always satisfied. Faults are detected by monitoring the state of the physical plant and application timing. Fault-recovery is achieved via full platform restart and software reload, enabled by the short restart time of embedded systems. Schedulability analysis is used to ensure that the timing constraints of critical plant control tasks are always satisfied in spite of faults and consequent restarts. We derive schedulability results for four restart-tolerant task models. We use a simulator to evaluate and compare the performance of the considered scheduling models. Finally, we implement a controller for a 3 degree of freedom (3DOF) helicopter using one of such models on real hardware and demonstrate that the system remains safe despite faults in the RTOS and applications.

@article{zeglache_2017,
title = {Active fault tolerant control based on interval type-2 fuzzy sliding mode controller and non linear adaptive observer for 3-DOF laboratory helicopter},
author = {Zeglache, S.; Benslimane, R.; Bouguerra, A.},
journal = {ISA Transactions},
year = {2017},
institution = {University of Msila, Algeria},
abstract = {In this paper, a robust controller for a three degree of freedom (3 DOF) helicopter control is proposed in presence of actuator and sensor faults. For this purpose, Interval type-2 fuzzy logic control approach (IT2FLC) and sliding mode control (SMC) technique are used to design a controller, named active fault tolerant interval type-2 Fuzzy Sliding mode controller (AFTIT2FSMC) based on non-linear adaptive observer to estimate and detect the system faults for each subsystem of the 3-DOF helicopter. The proposed control scheme allows avoiding difficult modeling, attenuating the chattering effect of the SMC, reducing the rules number of the fuzzy controller. Exponential stability of the closed loop is guaranteed by using the Lyapunov method. The simulation results show that the AFTIT2FSMC can greatly alleviate the chattering effect, providing good tracking performance, even in presence of actuator and sensor faults. },
keywords = {Type-2 fuzzy logic; Sliding mode controller; Fault tolerant control; 3-DOF helicopter; Non linear observer; Stability},
language = {English},
publisher = {Elsevier B.V.}
}

In this paper, a robust controller for a three degree of freedom (3 DOF) helicopter control is proposed in presence of actuator and sensor faults. For this purpose, Interval type-2 fuzzy logic control approach (IT2FLC) and sliding mode control (SMC) technique are used to design a controller, named active fault tolerant interval type-2 Fuzzy Sliding mode controller (AFTIT2FSMC) based on non-linear adaptive observer to estimate and detect the system faults for each subsystem of the 3-DOF helicopter. The proposed control scheme allows avoiding difficult modeling, attenuating the chattering effect of the SMC, reducing the rules number of the fuzzy controller. Exponential stability of the closed loop is guaranteed by using the Lyapunov method. The simulation results show that the AFTIT2FSMC can greatly alleviate the chattering effect, providing good tracking performance, even in presence of actuator and sensor faults.

@article{dinh2_2017,
title = {Adaptive backlash compensation in upper limb soft wearable exoskeletons},
author = {Dinh, B.K.; Xiloyannis, M.; Capello, L.;Antuvan, C.W.; Yen, S.-C.; Masia, L.},
journal = {Robotics and Autonomous Systems},
year = {2017},
volume = {92},
institution = {Nanyang Technological University, Singapore; Harvard University, MA, USA; National University of Singapore, Singapore},
abstract = {A new frontier of assistive devices aims at designing exoskeletons based on fabric and flexible materials for applications where kinematic transparency is the primary requirement. Bowden-cable transmission is the widely employed solution in most of the aforementioned applications due to advantages in durability, lightweight, safety, and flexibility. The major advantages of soft assistive devices driven by bowden-cable transmissions can be identified in the superior ergonomics and wearability, allowing users to freely move and allocating the actuation stages far from the end-effector. However, control accuracy in bowden-cable transmission presents some intrinsic limitation due to nonlinearities such as static and dynamic friction, occurring between the cables and the bowden sheaths, and backlash hysteresis. Friction and backlash effects are known to be related to the curvature of the flexible sheath, which is not directly measurable and can vary during human motion. In this paper we describe our new wearable exosuit for upper limb assistance and in particular we introduce a mathematical model for backlash hysteresis compensation. The implementation of a nonlinear adaptive controller is described in detail and experimentally tested on the proposed design as a backlash compensation strategy: results report that the adaptive controller improves the accuracy in position tracking (i.e. RMSERMSE in trajectory tracking app. 1 degree) by compensating for time-varying backlash and continuously updating the model parameters. The backlash hysteresis model and the proposed control scheme are validated first on a custom-designed test bench and then applied to control the soft exoskeleton worn by a subject affected by bilateral brachial plexus injury. },
keywords = {Bowden cable transmission; Wearable devices; Soft exoskeletons; Adaptive control; Nonlinear friction; Backlash hysteresis},
language = {English},
publisher = {Elsevier Ltd.},
pages = {173-186}
}

A new frontier of assistive devices aims at designing exoskeletons based on fabric and flexible materials for applications where kinematic transparency is the primary requirement. Bowden-cable transmission is the widely employed solution in most of the aforementioned applications due to advantages in durability, lightweight, safety, and flexibility. The major advantages of soft assistive devices driven by bowden-cable transmissions can be identified in the superior ergonomics and wearability, allowing users to freely move and allocating the actuation stages far from the end-effector. However, control accuracy in bowden-cable transmission presents some intrinsic limitation due to nonlinearities such as static and dynamic friction, occurring between the cables and the bowden sheaths, and backlash hysteresis. Friction and backlash effects are known to be related to the curvature of the flexible sheath, which is not directly measurable and can vary during human motion. In this paper we describe our new wearable exosuit for upper limb assistance and in particular we introduce a mathematical model for backlash hysteresis compensation. The implementation of a nonlinear adaptive controller is described in detail and experimentally tested on the proposed design as a backlash compensation strategy: results report that the adaptive controller improves the accuracy in position tracking (i.e. RMSERMSE in trajectory tracking app. 1 degree) by compensating for time-varying backlash and continuously updating the model parameters. The backlash hysteresis model and the proposed control scheme are validated first on a custom-designed test bench and then applied to control the soft exoskeleton worn by a subject affected by bilateral brachial plexus injury.

@conference{srivastava_2017,
title = {Adaptive neural Preisach model and model predictive control of Shape Memory Alloy actuators},
author = {Srivastava, A.; Ward, C.; Pate, R.V.},
booktitle = {2017 IEEE International Conference on Advanced Intelligent Mechatronics (AIM)},
year = {2017},
month = {7},
institution = {Canadian Surgical Technologies and Advanced Robotics (CSTAR), London, Ontario, Canada},
abstract = {Shape memory alloy (SMA) actuators are potential alternatives to conventional actuators in many surgical, aeronautic and biorobotic applications. However, their highly nonlinear hysteretic behavior between temperature and strain makes them difficult to use in real-time applications. The Preisach model is a well-known phenomenological method to accurately model the hysteresis of many physical system. In this paper, the numerical Preisach model is modified such that it can adapt to changes in the operating conditions, and can easily be used in real-time for controlling the strain in the SMA actuators. For this purpose, both the first-order descending and ascending curves are used and each of these curves is approximated by an artificial neural network (ANN). Weights of the ANNs are then updated online using the extended Kalman filter algorithm. To control the strain in the SMA actuator, a model predictive controller is implemented that uses the temperature dynamics and the adaptive modified Preisach model to calculate the optimal control signal using the Levenberg-Marquardt algorithm. Performance of the proposed model and the control scheme are validated using an experimental setup. },
issn = {2159-6255},
keywords = {Adaptation models, Actuators, Strain, Predictive models, Numerical models, Real-time systems, Hysteresis},
language = {English},
publisher = {IEEE}
}

Shape memory alloy (SMA) actuators are potential alternatives to conventional actuators in many surgical, aeronautic and biorobotic applications. However, their highly nonlinear hysteretic behavior between temperature and strain makes them difficult to use in real-time applications. The Preisach model is a well-known phenomenological method to accurately model the hysteresis of many physical system. In this paper, the numerical Preisach model is modified such that it can adapt to changes in the operating conditions, and can easily be used in real-time for controlling the strain in the SMA actuators. For this purpose, both the first-order descending and ascending curves are used and each of these curves is approximated by an artificial neural network (ANN). Weights of the ANNs are then updated online using the extended Kalman filter algorithm. To control the strain in the SMA actuator, a model predictive controller is implemented that uses the temperature dynamics and the adaptive modified Preisach model to calculate the optimal control signal using the Levenberg-Marquardt algorithm. Performance of the proposed model and the control scheme are validated using an experimental setup.

@inproceedings{wang3_2017,
title = {Adaptive Robust Control of Quadrotor Helicopter towards Payload Transportation Applications},
author = {Wang, B.; Mu, L.; Zhang, Y.},
booktitle = {Proceedings of the 36th Chinese Control Conference},
year = {2017},
institution = {Concordia University, Quebec, Canada; Northwestern Polytechnical University, Xi'an, China},
abstract = {Sliding mode control is known as a robust control approach to maintain system performance and keep it insensitive to disturbances. This paper proposes an integral sliding mode based adaptive robust control for a quadrotor helicopter with parametric uncertainties and disturbances. With the help of the synthesized on-line adaptive scheme, the uncertain parameters can be accurately estimated without the knowledge of the uncertainty bounds. In this case, there is no need to increase the discontinuous control gain, which may stimulate control chattering effect, to maintain the robustness of the controller. The effectiveness of the proposed control strategy is validated through a simulation of the payload transportation application. Compared to the commonly used linear quadratic regulator (LQR) approach, the proposed adaptive robust control strategy can maintain the tracking performance during the whole flight phase. },
issn = {1934-1768},
keywords = {Adaptive robust control, integral sliding mode, quadrotor helicopter, payload transportation},
language = {English},
publisher = {IEEE},
isbn = {978-1-5386-2918-5}
}

Sliding mode control is known as a robust control approach to maintain system performance and keep it insensitive to disturbances. This paper proposes an integral sliding mode based adaptive robust control for a quadrotor helicopter with parametric uncertainties and disturbances. With the help of the synthesized on-line adaptive scheme, the uncertain parameters can be accurately estimated without the knowledge of the uncertainty bounds. In this case, there is no need to increase the discontinuous control gain, which may stimulate control chattering effect, to maintain the robustness of the controller. The effectiveness of the proposed control strategy is validated through a simulation of the payload transportation application. Compared to the commonly used linear quadratic regulator (LQR) approach, the proposed adaptive robust control strategy can maintain the tracking performance during the whole flight phase.

@conference{wang_2017,
title = {Adaptive robust tracking control of quadrotor helicopter with parametric uncertainty and external disturbance},
author = {Wang, B.; Mu, L.; Zhang, Y.},
booktitle = {2017 International Conference on Unmanned Aircraft Systems (ICUAS)},
year = {2017},
institution = {Concordia University, Montreal, Quebec, Canada},
abstract = {This paper proposes an adaptive robust tracking control strategy for a quadrotor helicopter with parametric uncertainties and external disturbances based on sliding mode control. The inner loop of the control strategy is concerned about the attitude and altitude control of the quadrotor helicopter, while the outer loop is employed to track the desired horizontal positions. By assuming knowledge of the bounds on external disturbances, an integral sliding mode control is designed to maintain system performance and keep it insensitive to disturbances. For parametric uncertainties (e.g., total mass and moments of inertia) of the quadrotor helicopter, an on-line adaptive scheme is proposed and incorporated into the nominal sliding mode control to deal with it. With this adaptive scheme, there is no need to know the parametric uncertainty bounds. A guaranteed transient and steady-state tracking performance can be obtained with the adaptive robust sliding mode controller. The effectiveness of the proposed control strategy is validated through a simulation on a quadrotor helicopter subject to parametric uncertainties and external disturbances. },
keywords = {Helicopters, Uncertainty, Rotors, Payloads, Sliding mode control, Torque, Robustness},
language = {English},
publisher = {IEEE},
isbn = {978-1-5090-4496-2}
}

This paper proposes an adaptive robust tracking control strategy for a quadrotor helicopter with parametric uncertainties and external disturbances based on sliding mode control. The inner loop of the control strategy is concerned about the attitude and altitude control of the quadrotor helicopter, while the outer loop is employed to track the desired horizontal positions. By assuming knowledge of the bounds on external disturbances, an integral sliding mode control is designed to maintain system performance and keep it insensitive to disturbances. For parametric uncertainties (e.g., total mass and moments of inertia) of the quadrotor helicopter, an on-line adaptive scheme is proposed and incorporated into the nominal sliding mode control to deal with it. With this adaptive scheme, there is no need to know the parametric uncertainty bounds. A guaranteed transient and steady-state tracking performance can be obtained with the adaptive robust sliding mode controller. The effectiveness of the proposed control strategy is validated through a simulation on a quadrotor helicopter subject to parametric uncertainties and external disturbances.

@conference{jardine_2017,
title = {Adaptive State-Space Model Approximation for Quadcopter using Fast Orthogonal Search},
author = {Jardine, P.T.; Givigi, S.N.; Yousefi, S.; Korenberg, M.J.},
booktitle = {2017 IEEE 30th Canadian Conference on Electrical and Computer Engineering (CCECE)},
year = {2017},
institution = {Royal Military College of Canada, ON, Canada; Queen's University, ON, Canada},
abstract = {This paper presents a novel application of Fast Orthogonal Search (FOS) to select the basis and coefficients for a linear, state-space model representing the dynamics of a quadcopter. This is developed in the context of Model Predictive Control (MPC) by evaluating the performance of the approximate model over finite prediction horizons in different flight regimes. A time-varying model is implemented using sliding window (SW-FOS) and recursive (R-FOS) techniques. FOS was selected because it provides a numerically efficient technique for selecting which basis terms are important in the model while simultaneously solving for their coefficients. Based on experimental data from an actual quadcopter, SWFOS provided mean squared error performance similar to Least Squares (LS) while requiring on average 5 fewer states in the state-space model. R-FOS produced more accurate results with significantly reduced computation times. Both SW-FOS and R-FOS provided linear, time-varying models that adapted to various flight regimes. },
keywords = {Computational modeling, State-space methods, Nonlinear dynamical systems, Computers, Numerical models, Adaptation models},
language = {English},
publisher = {IEEE},
isbn = {978-1-5090-5539-5},
pages = {465-470}
}

This paper presents a novel application of Fast Orthogonal Search (FOS) to select the basis and coefficients for a linear, state-space model representing the dynamics of a quadcopter. This is developed in the context of Model Predictive Control (MPC) by evaluating the performance of the approximate model over finite prediction horizons in different flight regimes. A time-varying model is implemented using sliding window (SW-FOS) and recursive (R-FOS) techniques. FOS was selected because it provides a numerically efficient technique for selecting which basis terms are important in the model while simultaneously solving for their coefficients. Based on experimental data from an actual quadcopter, SWFOS provided mean squared error performance similar to Least Squares (LS) while requiring on average 5 fewer states in the state-space model. R-FOS produced more accurate results with significantly reduced computation times. Both SW-FOS and R-FOS provided linear, time-varying models that adapted to various flight regimes.

@article{kara-mohamed_2017,
title = {Advanced trajectory tracking for UAVs using combined feedforward/feedback control design},
author = {Kara-Mohamed, K.},
journal = {Robotics and Autonomous Systems},
year = {2017},
volume = {96},
institution = {School of Engineering and The Built Environment, Birmingham City University, UK},
abstract = {Trajectory tracking is a major challenge for UAVs. The more complex the trajectory is, the more accurate tracking is required with minimum divergence from the trajectory. Apart from active trajectory tracking mechanisms, current solutions to accurate trajectory tracking in narrow areas require low speed motions. This paper presents a systematic design methodology using centralised feedforward/feedback control architecture for advanced trajectory tracking without compromising the speed of the vehicle. Using the H-infinity norm as a measure for the design criteria, the proposed method proves fast tracking with no overshooting and less actuators energy compared with single degree-of-freedom feedback control method. The results are verified using simulations for two systems: a tri-rotor VTOL UAV (fully actuated system), and a quadrotor trainer (over-actuated system). },
issn = {0921-8890},
language = {English},
publisher = {Elsevier B.V.},
pages = {143-156}
}

Trajectory tracking is a major challenge for UAVs. The more complex the trajectory is, the more accurate tracking is required with minimum divergence from the trajectory. Apart from active trajectory tracking mechanisms, current solutions to accurate trajectory tracking in narrow areas require low speed motions. This paper presents a systematic design methodology using centralised feedforward/feedback control architecture for advanced trajectory tracking without compromising the speed of the vehicle. Using the H-infinity norm as a measure for the design criteria, the proposed method proves fast tracking with no overshooting and less actuators energy compared with single degree-of-freedom feedback control method. The results are verified using simulations for two systems: a tri-rotor VTOL UAV (fully actuated system), and a quadrotor trainer (over-actuated system).

@article{liang_2017,
title = {An Adaptive Control System for Variable Mass Quad-Rotor UAV Involved in Rescue Missions},
author = {Liang, X.; Chen, G.; Wang, J.; Bi, Z.; Sun, P.},
journal = {International Journal of Simulation Systems, Science & Technology},
year = {2017},
volume = {17},
number = {29},
institution = {School of Automation , Shenyang Aerospace University, China},
abstract = {Because the mass of quad-rotor helicopter Unmanned Aerial Vehicles (UAV) changes after delivering relief supplies, an adaptive control strategy based on model reference adaptation is proposed. First a quad-rotor model is established based on the Quanser 3-DOF hover platform. Then a control strategy is developed consisting of two layers: a baseline controller using a Linear Quadratic Regulator (LQR) and Model Reference Adaptive Controller (MRAC) to eliminate the impact of load change. In simulation, the results illustrate that the strategy can improve the effectiveness of the control system when the mass and the moment of inertia change in applications such as rescue missions. },
keywords = {quad-rotor; rescue mission; variable mass; linear quadratic regulator; model reference adaptive control},
language = {English}
}

Because the mass of quad-rotor helicopter Unmanned Aerial Vehicles (UAV) changes after delivering relief supplies, an adaptive control strategy based on model reference adaptation is proposed. First a quad-rotor model is established based on the Quanser 3-DOF hover platform. Then a control strategy is developed consisting of two layers: a baseline controller using a Linear Quadratic Regulator (LQR) and Model Reference Adaptive Controller (MRAC) to eliminate the impact of load change. In simulation, the results illustrate that the strategy can improve the effectiveness of the control system when the mass and the moment of inertia change in applications such as rescue missions.

@conference{jabbari-asl_2017,
title = {An Assist-as-Needed Control Scheme for Robot-Assisted Rehabilitation},
author = {Jabbari Asl, H.; Narikiyo, T.; Kawanishi, M.},
booktitle = {2017 American Control Conference},
year = {2017},
month = {5},
institution = {Department of Advanced Science and Technology, Toyota Technological Institute, Japan},
abstract = {This paper addresses the assist-as-needed (AAN) control problem for robotic orthoses. The objective is to design a stable AAN controller with an adjustable assistance level. The controller aims to follow a desired trajectory while allowing an adjustable tracking error with low control effort to provide a freedom zone for the user. By ensuring the stability of the system and providing the freedom zone, the controller combines the advantages of both model-based and non-modelbased AAN controllers existing in the literature. Furthermore, the controller provides a priori bounded control command, and includes an adaptive neural network term to compensate for the uncertainties of dynamic model of the system, mainly when a precise tracking is of interest. The stability of the closed-loop system is well analysed based on the Lyapunov method. The effectiveness of the proposed control scheme is validated through experiments using a lower extremity robotic exoskeleton. },
keywords = {Assist-as-needed control, rehabilitation, robotic orthosis, adaptive neural network, exoskeleton},
language = {English},
pages = {198-203}
}

This paper addresses the assist-as-needed (AAN) control problem for robotic orthoses. The objective is to design a stable AAN controller with an adjustable assistance level. The controller aims to follow a desired trajectory while allowing an adjustable tracking error with low control effort to provide a freedom zone for the user. By ensuring the stability of the system and providing the freedom zone, the controller combines the advantages of both model-based and non-modelbased AAN controllers existing in the literature. Furthermore, the controller provides a priori bounded control command, and includes an adaptive neural network term to compensate for the uncertainties of dynamic model of the system, mainly when a precise tracking is of interest. The stability of the closed-loop system is well analysed based on the Lyapunov method. The effectiveness of the proposed control scheme is validated through experiments using a lower extremity robotic exoskeleton.

@article{vakanski_2017,
title = {An image-based trajectory planning approach for robust robot programming by demonstration},
author = {Vakanski, A.; Janabi-Sharifi, F.; Mantegh, I.},
journal = {Robotics and Autonomous Systems},
year = {2017},
institution = {University of Idaho, USA; Ryerson University, Canada; National Research Council Canada - Institute for Aerospace Research, Canada},
abstract = {The article proposes a new robot programming-by-demonstration framework, which integrates a visual servoing tracking control to robustly follow a trajectory generated from observed demonstrations. The constraints originating from the use of a visual servoing controller are incorporated into the trajectory learning phase, to guarantee feasibility of the generated plan for task execution. The observational learning is solved as a constrained optimization problem, with an objective to generalize from a set of trajectories of salient features in the image space of a vision camera. The proposed approach is evaluated experimentally for learning trajectories acquired from kinesthetic demonstrations. },
keywords = {Cognitive robotics; Visual servoing; Programming by demonstration},
language = {English},
publisher = {Elsevier B.V.}
}

The article proposes a new robot programming-by-demonstration framework, which integrates a visual servoing tracking control to robustly follow a trajectory generated from observed demonstrations. The constraints originating from the use of a visual servoing controller are incorporated into the trajectory learning phase, to guarantee feasibility of the generated plan for task execution. The observational learning is solved as a constrained optimization problem, with an objective to generalize from a set of trajectories of salient features in the image space of a vision camera. The proposed approach is evaluated experimentally for learning trajectories acquired from kinesthetic demonstrations.

@article{zhou_2017,
title = {An Inversion-Based Learning Approach for Improving Impromptu Trajectory Tracking of Robots with Non-Minimum Phase Dynamics},
author = {Zhou. S.; Helwa, M.K.; Schoellig, A.P.},
year = {2017},
institution = {Dynamic Systems Lab, Institute for Aerospace Studies, University of Toronto, Canada},
abstract = {This paper presents a learning-based approach for impromptu trajectory tracking of non-minimum phase systems — systems with unstable inverse dynamics. In the control systems literature, inversion-based feedforward approaches are commonly used for improving the trajectory tracking performance; however, these approaches are not directly applicable to non-minimum phase systems due to the inherent instability. In order to resolve the instability issue, they assume that models of the systems are known and have dealt with the non-minimum phase systems by pre-actuation or inverse approximation techniques. In this work, we extend our deep- neural-network-enhanced impromptu trajectory tracking approach to the challenging case of non-minimum phase systems. Through theoretical discussions, simulations, and experiments, we show the stability and effectiveness of our proposed learning approach. In fact, for a known system, our approach performs equally well or better as a typical model-based approach but does not require a prior model of the system. Interestingly, our approach also shows that including more information in training (as is commonly assumed to be useful) does not lead to better performance but may trigger instability issues and impede the effectiveness of the overall approach. }
}

This paper presents a learning-based approach for impromptu trajectory tracking of non-minimum phase systems — systems with unstable inverse dynamics. In the control systems literature, inversion-based feedforward approaches are commonly used for improving the trajectory tracking performance; however, these approaches are not directly applicable to non-minimum phase systems due to the inherent instability. In order to resolve the instability issue, they assume that models of the systems are known and have dealt with the non-minimum phase systems by pre-actuation or inverse approximation techniques. In this work, we extend our deep-
neural-network-enhanced impromptu trajectory tracking approach to the challenging case of non-minimum phase systems. Through theoretical discussions, simulations, and experiments, we show the stability and effectiveness of our proposed learning approach. In fact, for a known system, our approach performs equally well or better as a typical model-based approach but does not require a prior model of the system. Interestingly, our approach also shows that including more information in training (as is commonly assumed to be useful) does not lead to better performance but may trigger instability issues and impede the effectiveness of the overall approach.

@article{abdi_2017,
title = {Application and System-Level Software Fault Tolerance Through Full System Restarts},
author = {Abdi, F; Tabish, R.; Rungger, M.; Zamani, M.; Caccamo, M.},
year = {2017},
institution = {University of Illinois at Urbana-Champaign, USA; echnical University of Munich, Germany},
abstract = {Due to the growing performance requirements, embed- ded systems are increasingly more complex. Meanwhile, they are also expected to be reliable. Guaranteeing re- liability on complex systems is very challenging. Con- sequently, there is a substantial need for designs that enable the use of unveri ed components such as real- time operating system (RTOS) without requiring their correctness to guarantee safety. In this work, we propose a novel approach to design a controller that enables the system to restart and remain safe during and after the restart. Complementing this controller with a switching logic allows the system to use complex, unveri ed controller to drive the system as long as it does not jeopardize safety. Such a design also tolerates faults that occur in the underlying software layers such as RTOS and middleware and recovers from them through system-level restarts that reinitialize the software (middleware, RTOS, and applications) from a read-only storage. Our approach is implementable using one commercial off-the-shelf (COTS) processing unit. To demonstrate the efficacy of our solution, we fully implement a controller for a 3 degree of freedom (3DOF) helicopter. We test the system by injecting various types of faults into the applications and RTOS and verify that the system remains safe. },
language = {English}
}

Due to the growing performance requirements, embed- ded systems are increasingly more complex. Meanwhile, they are also expected to be reliable. Guaranteeing re- liability on complex systems is very challenging. Con- sequently, there is a substantial need for designs that enable the use of unveri ed components such as real- time operating system (RTOS) without requiring their correctness to guarantee safety. In this work, we propose a novel approach to design a controller that enables the system to restart and remain safe during and after the restart. Complementing this controller with a switching logic allows the system to use complex, unveri ed controller to drive the system as long as it does not jeopardize safety. Such a design also tolerates faults that occur in the underlying software layers such as RTOS and middleware and recovers from them through system-level restarts that reinitialize the software (middleware, RTOS, and applications) from a read-only storage. Our approach is implementable using one commercial off-the-shelf (COTS) processing unit. To demonstrate the efficacy of our solution, we fully implement a controller for a 3 degree of freedom (3DOF) helicopter. We test the system by injecting various types of faults into the applications and RTOS and verify that the system remains safe.

Active exoskeleton controllers are designed to control the interaction force. Compliant exoskeletons need to be controlled in both position and force due to the coupling with a human in all rehabilitation conditions, which give rise to human-exoskeleton interaction dynamics, high nonlinear uncertain exoskeleton dynamics, noisy sensors and other parametric uncertainties, such as environmental contacts. These factors do not allow to account on a precise dynamical model, thus model-based controllers are difficult to implement. This paper presents an auto-tuning force/position controller based on fuzzy inference system to control a previously designed five degrees of freedom upper limb exoskeleton. The exoskeleton control system aims to achieve the best control performances together with stability and safety guarantees.

@article{wang_x_2017,
title = {Autonomous Switched Control of Load Shifting Robot Manipulators},
author = {Wang, X.; Zhao, J.},
journal = {IEEE Transactions on Industrial Electronics},
year = {2017},
institution = {Hebei University, China},
abstract = {An autonomous switched controller is pro- posed for a robot manipulator to ensure asymptotical tracking performance in the presence of shifting loads. Since the manipulator parameter jumps along with the load shift, the manipulator is modeled as a switched system whose switching signal depicts the load change. When the load change is not detectable, the switching signal of the switched system is unavailable. In this case, another “autonomous” switching law is designed for the given sub- controllers using a switched reset supervisory variable. Asymptotic tracking is ensured for slow load shifting. The effectiveness of the proposed method is verified by both simulations of a 2-DOF robot manipulator and experiments of a closed-chain five-bar robot. },
issn = {0278-0046},
keywords = {Manipulators, Load modeling, Uncertainty, Autonomous switching, Average dwell time, Shifting load},
language = {English},
publisher = {IEEE}
}

An autonomous switched controller is pro- posed for a robot manipulator to ensure asymptotical tracking performance in the presence of shifting loads. Since the manipulator parameter jumps along with the load shift, the manipulator is modeled as a switched system whose switching signal depicts the load change. When the load change is not detectable, the switching signal of the switched system is unavailable. In this case, another “autonomous” switching law is designed for the given sub- controllers using a switched reset supervisory variable. Asymptotic tracking is ensured for slow load shifting. The effectiveness of the proposed method is verified by both simulations of a 2-DOF robot manipulator and experiments of a closed-chain five-bar robot.

@conference{paul_2017,
title = {Bidirectional Fuzzy PD Control for Active Vibration Control of Building Structure},
author = {Paul, S.; Yu, W.},
booktitle = {2017 IEEE International Conference on Industrial Technology (ICIT)},
year = {2017},
institution = {CINVESTAV-IPN, National Polytechnic Institute, Mexico City, Mexico},
abstract = {Proportional-derivative (PD) is a popular algorithm in the field of building structure vibration control, but there are infrequent broadcasted theory results of PD controller in connection to structural vibration control applications. In order to maintain minimum regulation error, a PD control requires sufficiently high proportional and derivative gains. The effect of these diminishes the transient performances of the vibration control. In this paper, a straight forward combination of PD control with fuzzy compensation is laid down. We state comprehensive sufficient conditions for choosing the PD gains. The stability theories are verified through numerical simulations and a two-story building prototype. The extracted results validates our theory analysis. },
language = {English},
publisher = {IEEE},
isbn = {978-1-5090-5321-6 }
}

Proportional-derivative (PD) is a popular algorithm in the field of building structure vibration control, but there are infrequent broadcasted theory results of PD controller in connection to structural vibration control applications. In order to maintain minimum regulation error, a PD control requires sufficiently high proportional and derivative gains. The effect of these diminishes the transient performances of the vibration control. In this paper, a straight forward combination of PD control with fuzzy compensation is laid down. We state comprehensive sufficient conditions for choosing the PD gains. The stability theories are verified through numerical simulations and a two-story building prototype. The extracted results validates our theory analysis.

@article{alibeji_2017,
title = {Bilateral control of functional electrical stimulation and robotics-based telerehabilitation},
author = {Alibeji, N.; Dicianno, B.E.; Sharma, N.},
journal = {International Journal of Intelligent Robotics and Applications},
year = {2017},
institution = {University of Pittsburgh, USA},
abstract = {Currently, a telerehabilitation system includes a therapist and a patient where the therapist interacts with the patient, typically via a verbal and visual communication, for assessment and supervision of rehabilitation interventions. This mechanism often fails to provide physical assistance, which is a modus operandi during physical therapy or occupational therapy. Incorporating an actuation modality such as functional electrical stimulation (FES) or a robot at the patientÍs end that can be controlled by a therapist remotely to provide therapy or to assess and measure rehabilitation outcomes can significantly transform current telerehabilitation technology. In this paper, a position-synchronization controller is derived for FES-based telerehabilitation to provide physical assistance that can be controlled remotely. The newly derived controller synchronizes an FES-driven human limb with a remote physical therapistÍs robotic manipulator despite constant bilateral communication delays. The control design overcomes a major stability analysis challenge: the unknown and unstructured nonlinearities in the FES-driven musculoskeletal dynamics. To address this challenge, the nonlinear muscle model was estimated through two neural network functions that approximated unstructured nonlinearities and an adaptive control law for structured nonlinearities with online update laws. A Lyapunov-based stability analysis was used to prove the globally uniformly ultimately bounded tracking performance. The performance of the state synchronization controller was validated through experiments on an able-bodied subject. Specifically, we demonstrated bilateral control of FES-elicited leg extension and a human-operated robotic manipulator. The controller was shown to effectively synchronize the system despite unknown and different delays in the forward and backward channels. },
issn = {2366-5971},
language = {English},
publisher = {Springer Singapore}
}

Currently, a telerehabilitation system includes a therapist and a patient where the therapist interacts with the patient, typically via a verbal and visual communication, for assessment and supervision of rehabilitation interventions. This mechanism often fails to provide physical assistance, which is a modus operandi during physical therapy or occupational therapy. Incorporating an actuation modality such as functional electrical stimulation (FES) or a robot at the patientÍs end that can be controlled by a therapist remotely to provide therapy or to assess and measure rehabilitation outcomes can significantly transform current telerehabilitation technology. In this paper, a position-synchronization controller is derived for FES-based telerehabilitation to provide physical assistance that can be controlled remotely. The newly derived controller synchronizes an FES-driven human limb with a remote physical therapistÍs robotic manipulator despite constant bilateral communication delays. The control design overcomes a major stability analysis challenge: the unknown and unstructured nonlinearities in the FES-driven musculoskeletal dynamics. To address this challenge, the nonlinear muscle model was estimated through two neural network functions that approximated unstructured nonlinearities and an adaptive control law for structured nonlinearities with online update laws. A Lyapunov-based stability analysis was used to prove the globally uniformly ultimately bounded tracking performance. The performance of the state synchronization controller was validated through experiments on an able-bodied subject. Specifically, we demonstrated bilateral control of FES-elicited leg extension and a human-operated robotic manipulator. The controller was shown to effectively synchronize the system despite unknown and different delays in the forward and backward channels.

@conference{mcdonald_2017,
title = {Characterization of surface electromyography patterns of healthy and incomplete spinal cord injury subjects interacting with an upper-extremity exoskeleton},
author = {McDonald, C.G.; Dennis, T.A.; O'Malley, M.K.},
booktitle = {2017 International Conference on Rehabilitation Robotics (ICORR)},
year = {2017},
institution = {Mechatronics and Haptic Interfaces Lab, Rice University, Houston, TX, USA},
abstract = {Rehabilitation exoskeletons may make use of myoelectric control to restore in patients with significant motor impairment following a spinal cord injury (SCI) a sense of volitional control over their limb — a crucial component for recovery of movement. Little investigation has been done into the feasibility of using surface electromyography (sEMG) as an exoskeleton control interface for SCI patients, whose impairment manifests in a highly variable way across the patient population. We have demonstrated that by using only a small subset of features extracted from eight bipolar electrodes recording on the upper arm and forearm muscles, we can achieve high predictive accuracy for the intended direction of motion. Five healthy subjects and two SCI subjects performed voluntary isometric contractions while wearing an exoskeleton for the wrist and elbow joints, generating six distinct single and multi-DoF motions in a total of sixteen possible directions. Using linear discriminant analysis, classification performance was then evaluated using randomly selected holdout test data from the same recording session. Commonalities across subjects, both healthy and SCI, were analyzed at the levels of selected features and the values of commonly selected features. Future work will be to investigate group-specific classification of SCI subjects' intended movements for use in the real-time control of a rehabilitation exoskeleton. },
issn = {1945-7901 },
keywords = { Electromyography, Wrist, Elbow, Exoskeletons, Muscles, Feature extraction, Electrodes },
language = {English},
publisher = {IEEE}
}

Rehabilitation exoskeletons may make use of myoelectric control to restore in patients with significant motor impairment following a spinal cord injury (SCI) a sense of volitional control over their limb — a crucial component for recovery of movement. Little investigation has been done into the feasibility of using surface electromyography (sEMG) as an exoskeleton control interface for SCI patients, whose impairment manifests in a highly variable way across the patient population. We have demonstrated that by using only a small subset of features extracted from eight bipolar electrodes recording on the upper arm and forearm muscles, we can achieve high predictive accuracy for the intended direction of motion. Five healthy subjects and two SCI subjects performed voluntary isometric contractions while wearing an exoskeleton for the wrist and elbow joints, generating six distinct single and multi-DoF motions in a total of sixteen possible directions. Using linear discriminant analysis, classification performance was then evaluated using randomly selected holdout test data from the same recording session. Commonalities across subjects, both healthy and SCI, were analyzed at the levels of selected features and the values of commonly selected features. Future work will be to investigate group-specific classification of SCI subjects' intended movements for use in the real-time control of a rehabilitation exoskeleton.

@article{atashzar__2016,
title = {Characterization of Upper-limb Pathological Tremors: Application to Design of an Augmented Haptic Rehabilitation System},
author = {Atashzar, S.F.; Shahbazi, M.; Samotus, O.; Tavakoli, M.; Jog, M.S.; Patel, R.V.},
journal = {IEEE Journal of Selected Topics in Signal Processing},
year = {2017},
volume = {10},
number = {5},
abstract = {In this paper, an adaptive filtering technique is proposed to estimate and characterize pathological tremors caused by Parkinson's Disease (PD) and Essential Tremor (ET). The technique is based on the formulation of band-limited multiple Fourier Linear Combiners (BMFLC) and is called Enhanced-BMFLC (E-BMFLC). The effectiveness of the designed filter is statistically evaluated through a clinical study involving 14 PD and 13 ET patients. The hand tremors of the participants are studied in three Degrees Of Freedom (DOF). Using statistical analysis, it is shown that the new design of the filter significantly enhances the accuracy in comparison with the performance of conventional BMFLC filtering. In addition, E-BMFLC significantly reduces the sensitivity to parameter tuning and intrapatient variabilities. The observed improvements are achieved by modulating the memory of the proposed filter, and by enriching the utilized harmonic model. The proposed filter is then used to develop a safe haptics-enabled robotic rehabilitation architecture, designed for patients having hand tremors. The architecture is entitled Augmented Haptic Rehabilitation (AHR), which enables adaptive management of the involuntary components of the hand motion while delivering assist-as-needed haptic therapy (for the voluntary component) and avoiding unsafe amplification of hand tremors. Experimental evaluations are provided to evaluate the efficacy of the proposed AHR system. },
issn = {1932-4553},
keywords = {Adaptive filters, pathological hand tremors, assist-as-needed robotic rehabilitation},
language = {English},
publisher = {IEEE},
pages = {883-903}
}

In this paper, an adaptive filtering technique is proposed to estimate and characterize pathological tremors caused by Parkinson's Disease (PD) and Essential Tremor (ET). The technique is based on the formulation of band-limited multiple Fourier Linear Combiners (BMFLC) and is called Enhanced-BMFLC (E-BMFLC). The effectiveness of the designed filter is statistically evaluated through a clinical study involving 14 PD and 13 ET patients. The hand tremors of the participants are studied in three Degrees Of Freedom (DOF). Using statistical analysis, it is shown that the new design of the filter significantly enhances the accuracy in comparison with the performance of conventional BMFLC filtering. In addition, E-BMFLC significantly reduces the sensitivity to parameter tuning and intrapatient variabilities. The observed improvements are achieved by modulating the memory of the proposed filter, and by enriching the utilized harmonic model. The proposed filter is then used to develop a safe haptics-enabled robotic rehabilitation architecture, designed for patients having hand tremors. The architecture is entitled Augmented Haptic Rehabilitation (AHR), which enables adaptive management of the involuntary components of the hand motion while delivering assist-as-needed haptic therapy (for the voluntary component) and avoiding unsafe amplification of hand tremors. Experimental evaluations are provided to evaluate the efficacy of the proposed AHR system.

@article{matteo_2017,
title = {Combining TMD and TLCD: analytical and experimental studies},
author = {Di Matteo, A.; Pirotta, A.; Tumminelli, S.},
journal = {Journal of Wind Engineering and Industrial Aerodynamics},
year = {2017},
month = {8},
volume = {167},
institution = {Universita degli Studi di Palermo, Italy; University of Liverpool, United Kingdom},
abstract = {In these years several research efforts have been focused on developing efficient and reliable control devices for mitigating the structural response of tall and lightly damped buildings in case of strong dynamic excitations, such as wind and earthquake ones. In this context, Tuned Mass Dampers (TMDs) represent probably the most common control device due to their high control performances. On the other hand, Tuned Liquid Column Dampers (TLCDs) are increasingly becoming more popular because of some of their attractive features, cost-effectiveness among the others, even though they yield slightly less control performance compared to the classical TMDs. Aiming at combining the beneficial effects of the TMD and the attractive characteristics of the TLCD, in this paper a novel control device is introduced which is realized joining this two systems. The pertinent equations of motion are derived, and the analytical study is developed to analyze the control performance of this device. Finally, theoretical results are validated via vast experimental campaign undertaken in the Laboratory of Experimental Dynamics of the University of Palermo, Italy. },
keywords = {Tuned liquid column damper; Tuned mass damper; Combined tuned damper; Experimental investigation},
language = {English},
publisher = {Elsevier B.V.},
pages = {101-113}
}

In these years several research efforts have been focused on developing efficient and reliable control devices for mitigating the structural response of tall and lightly damped buildings in case of strong dynamic excitations, such as wind and earthquake ones. In this context, Tuned Mass Dampers (TMDs) represent probably the most common control device due to their high control performances. On the other hand, Tuned Liquid Column Dampers (TLCDs) are increasingly becoming more popular because of some of their attractive features, cost-effectiveness among the others, even though they yield slightly less control performance compared to the classical TMDs. Aiming at combining the beneficial effects of the TMD and the attractive characteristics of the TLCD, in this paper a novel control device is introduced which is realized joining this two systems. The pertinent equations of motion are derived, and the analytical study is developed to analyze the control performance of this device. Finally, theoretical results are validated via vast experimental campaign undertaken in the Laboratory of Experimental Dynamics of the University of Palermo, Italy.

@conference{liang2_2017,
title = {Compensation research on the friction characteristic of the DDVC Flange-type Rotary Vane Steering Gear},
author = {Liang, L.H.; Wang, L.Y.; Wang, J.F.},
booktitle = {2017 36th Chinese Control Conference (CCC)},
year = {2017},
institution = {Harbin Engineering University, China},
abstract = {Direct Drive Volume Control (DDVC) flange-type rotary vane steering gear is a greatly promising component to be applied in the controlling course and posture of vessel due to the superior advantages of compact structure, powerful vibration absorption, simple control and etc. However, the nonlinear friction is a main limit for DDVC flange-type rotary vane steering gear to meat the accuracy requirement of vessel. In this paper, we proposed a high gain PID methods to suppress the non-linear friction so as to control the rudder effectively and precisely. According to the principle of the DDVC flange-type rotary vane steering gear, we established the mathematical model, transfer function of the steering gear system and the mathematical model about the impact of nonlinear friction on rudder system. To suppress the nonlinear friction, a compensation method independent of friction model by high gain PID control strategy was proposed, studied theoretically and experimentally. Measured results by prototype testing reveal that both the two methods can compensate the nonlinear friction, while the performance increased up to 40 percent than no compensation state. The outcome of this research will contribute to the rapidity and stability of DDVC flange-type rotary vane steering gear system. },
issn = {1934-1768},
keywords = {DDVC, Flange-type Rotary Vane Steering Gear, Friction, Compensation},
language = {English},
publisher = {IEEE},
isbn = {978-1-5386-2918-5}
}

Direct Drive Volume Control (DDVC) flange-type rotary vane steering gear is a greatly promising component to be applied in the controlling course and posture of vessel due to the superior advantages of compact structure, powerful vibration absorption, simple control and etc. However, the nonlinear friction is a main limit for DDVC flange-type rotary vane steering gear to meat the accuracy requirement of vessel. In this paper, we proposed a high gain PID methods to suppress the non-linear friction so as to control the rudder effectively and precisely. According to the principle of the DDVC flange-type rotary vane steering gear, we established the mathematical model, transfer function of the steering gear system and the mathematical model about the impact of nonlinear friction on rudder system. To suppress the nonlinear friction, a compensation method independent of friction model by high gain PID control strategy was proposed, studied theoretically and experimentally. Measured results by prototype testing reveal that both the two methods can compensate the nonlinear friction, while the performance increased up to 40 percent than no compensation state. The outcome of this research will contribute to the rapidity and stability of DDVC flange-type rotary vane steering gear system.

@article{wang_2017,
title = {Consensus Control for a Multi-agent System with Integral-type Event-triggering Condition and Asynchronous Periodic Detection},
author = {Wang, A.; Mu, B.; Shi, Y.},
journal = {IEEE Transactions on Industrial Electronics},
year = {2017},
institution = {Harbin Institute of Technology, China},
abstract = {In this paper, we use an event-triggered control method to study the consensus problem for an asynchronous distributed multi-agent system. An integral-type event-triggering condition is proposed. Each agent periodically checks its triggering condition by its own clock. When the triggering condition for an agent is satisfied, then control inputs of this agent and its neighbors are updated. Based on local information, we present the consensus protocol, and using Lyapunov methods, we show that all agents asymptotically reach an agreement on states. Finally, experiments are presented to demonstrate the effectiveness of our proposed protocol. },
issn = {0278-0046},
keywords = {Multi-agent systems; asynchronous consensus control; integral-type event-triggering condition; two-wheeled mobile robot},
language = {English},
publisher = {IEEE}
}

In this paper, we use an event-triggered control method to study the consensus problem for an asynchronous distributed multi-agent system. An integral-type event-triggering condition is proposed. Each agent periodically checks its triggering condition by its own clock. When the triggering condition for an agent is satisfied, then control inputs of this agent and its neighbors are updated. Based on local information, we present the consensus protocol, and using Lyapunov methods, we show that all agents asymptotically reach an agreement on states. Finally, experiments are presented to demonstrate the effectiveness of our proposed protocol.

@conference{pandey_2017,
title = {Controller design for a 3-DOF helicopter using multiple models with second level adaptation},
author = {Pandey, V.K.; Kar, I.; Mahanta, C.},
booktitle = {2017 Indian Control Conference (ICC)},
year = {2017},
institution = {Indian Institute of Technology, Guwahati, India},
abstract = {In this article, an adaptive model following control of a nonlinear multi-input multi-output (MIMO) coupled system with unknown parameters is considered. The decoupling matrix of the system is assumed to be singular, so that the system can not be decoupled by static state feedback. A dynamic state feedback with nonlinear structure algorithm is applied to design the controller. An observer is used to estimate the unknown parameters of the system. A multiple model with second level adaptation is introduced for the nonlinear MIMO coupled system. A 3-DOF (degree-of-freedom) helicopter model is simulated to validate the theoretical establishments. The advantage of using second level adaptation is established by conducting simulation studies. },
keywords = {Adaptation models, Helicopters, Mathematical model, MIMO, Estimation, State feedback, Rotors},
language = {English},
publisher = {IEEE},
isbn = {978-1-5090-1796-6}
}

In this article, an adaptive model following control of a nonlinear multi-input multi-output (MIMO) coupled system with unknown parameters is considered. The decoupling matrix of the system is assumed to be singular, so that the system can not be decoupled by static state feedback. A dynamic state feedback with nonlinear structure algorithm is applied to design the controller. An observer is used to estimate the unknown parameters of the system. A multiple model with second level adaptation is introduced for the nonlinear MIMO coupled system. A 3-DOF (degree-of-freedom) helicopter model is simulated to validate the theoretical establishments. The advantage of using second level adaptation is established by conducting simulation studies.

@article{kocagil_2017,
title = {Controller Designs for Nonlinear Systems with Application to 3 DOF Helicopter Model},
author = {Kocagil, B.M.; Ancan, A.C.; Guzey, U.M.; Ozcan, S.; Salamci, M.U.},
journal = {Gazi University Journal of Science, Part A: Engineering and Innovation},
year = {2017},
volume = {4},
number = {3},
institution = {Gazi University, Turkey},
abstract = {The paper introduces different control design methods for nonlinear systems with their application to the nonlinear mathematical model of a 3 DOF helicopter. Recent studies on the control design approaches, such as State Dependent Riccati Equation based optimal controller, Model Reference Adaptive Control and Sliding Mode Control, are reviewed and design methodologies are given. Then the mathematical model of a 3 DOF helicopter dynamics is derived and simplified with the software called CIFER. By using the simplified mathematical model of the 3 DOF helicopter, the control algorithms are applied to the model in order to explore the performances of the controllers. The results are given in the simulation environment. The paper is presented in a tutorial manner in order to explain the applications of the proposed nonlinear control methodologies. },
keywords = {Nonlinear Systems, Controller Design, State Dependent Riccati Equations, Sliding Mode Control, Model Reference Adaptive Control },
language = {English},
publisher = {DergiPark Akademik},
pages = {47-66}
}

The paper introduces different control design methods for nonlinear systems with their application to the nonlinear mathematical model of a 3 DOF helicopter. Recent studies on the control design approaches, such as State Dependent Riccati Equation based optimal controller, Model Reference Adaptive Control and Sliding Mode Control, are reviewed and design methodologies are given. Then the mathematical model of a 3 DOF helicopter dynamics is derived and simplified with the software called CIFER. By using the simplified mathematical model of the 3 DOF helicopter, the control algorithms are applied to the model in order to explore the performances of the controllers. The results are given in the simulation environment. The paper is presented in a tutorial manner in order to explain the applications of the proposed nonlinear control methodologies.

@article{ye_2017,
title = {Cyclic Repetitive Control of CVCF PWM DC-AC Converters},
author = {Ye, Y.; Wu, Y.; Xu, Y.; Zhang, B.},
journal = {IEEE Transactions on Industrial Electronics},
year = {2017},
institution = {Nanjing University of Aeronautics and Astronautics, China; University of South Carolina, SC, USA},
abstract = {In this paper, a cyclic repetitive control (CYRC) scheme is developed and applied to a constant-voltage constant-frequency (CVCF) pulse-width modulation (PWM) converter to achieve high tracking accuracy with less consumption of memory space. In this scheme, a novel cyclic sampling strategy is adopted by a down-sampled repetitive controller. The cyclic sampling strategy, which shifts the sampling points every cycle, can provide fractional order phase lead compensation and enlarge the stability margin. And the gain of the CYRC controller can be increased to decrease the tracking error. With much less memory space consumption, the steady-state tracking performance of CYRC is comparable to that of conventional repetitive control (CRC), and is much better than down-sampled repetitive control (DSRC). The stability criterion, as well as the realization of the CYRC scheme are discussed in detail. Comparison experiments with different controllers are performed in different load situations, and the results demonstrate the effectiveness of the CYRC scheme. },
issn = {0278-0046},
keywords = {Repetitive control, CVCF PWM converter, cyclic sampling, fractional order phase lead compensation},
language = {English},
publisher = {IEEE}
}

In this paper, a cyclic repetitive control (CYRC) scheme is developed and applied to a constant-voltage constant-frequency (CVCF) pulse-width modulation (PWM) converter to achieve high tracking accuracy with less consumption of memory space. In this scheme, a novel cyclic sampling strategy is adopted by a down-sampled repetitive controller. The cyclic sampling strategy, which shifts the sampling points every cycle, can provide fractional order phase lead compensation and enlarge the stability margin. And the gain of the CYRC controller can be increased to decrease the tracking error. With much less memory space consumption, the steady-state tracking performance of CYRC is comparable to that of conventional repetitive control (CRC), and is much better than down-sampled repetitive control (DSRC). The stability criterion, as well as the realization of the CYRC scheme are discussed in detail. Comparison experiments with different controllers are performed in different load situations, and the results demonstrate the effectiveness of the CYRC scheme.

@article{pezent_2017,
title = {Design and Characterization of the OpenWrist: A Robotic Wrist Exoskeleton for Coordinated Hand-Wrist Rehabilitation},
author = {Pezent, E.; Rose, C.G.; Deshpande, A.D.; O'Malley, M.K.},
booktitle = {15th International Conference on rehabilitation Robotics},
year = {2017},
institution = {Mechatronics and Haptic Interface Laboratory, Rice University, TX, USA; ReNeu Robotics Lab, University of Texas, Austin, TX, USA},
abstract = {Robotic devices have been clinically verified for use in long duration and high intensity rehabilitation needed for motor recovery after neurological injury. Targeted and coordinated hand and wrist therapy, often overlooked in rehabilitation robotics, is required to regain the ability to perform activities of daily living. To this end, a new coupled hand-wrist exoskeleton has been designed. This paper details the design of the wrist module and several human-related considerations made to maximize its potential as a coordinated hand-wrist device. The serial wrist mechanism has been engineered to facilitate donning and doffing for impaired subjects and to insure compatibility with the hand module in virtual and assisted grasping tasks. Several other practical requirements have also been addressed, including device ergonomics, clinician-friendliness, and ambidextrous reconfigurability. The wrist module’s capabilities as a rehabilitation device are quantified experimentally in terms of functional workspace and dynamic properties. Specifically, the device possesses favorable performance in terms of range of motion, torque output, friction, and closed-loop position bandwidth when compared with existing devices. The presented wrist module’s performance and operational considerations support its use in a wide range of future clinical investigations. }
}

Robotic devices have been clinically verified for use in long duration and high intensity rehabilitation needed for motor recovery after neurological injury. Targeted and coordinated hand and wrist therapy, often overlooked in rehabilitation robotics, is required to regain the ability to perform activities of daily living. To this end, a new coupled hand-wrist exoskeleton has been designed. This paper details the design of the wrist
module and several human-related considerations made to maximize its potential as a coordinated hand-wrist device. The serial wrist mechanism has been engineered to facilitate donning and doffing for impaired subjects and to insure compatibility with the hand module in virtual and assisted grasping tasks. Several other practical requirements have also been addressed, including device ergonomics, clinician-friendliness, and ambidextrous reconfigurability. The wrist module’s capabilities as a rehabilitation device are quantified experimentally in terms of functional workspace and dynamic properties. Specifically, the device possesses favorable performance in terms of range of motion, torque output, friction, and closed-loop position bandwidth when compared with existing devices. The presented wrist module’s performance and operational considerations support its use in a wide range of future clinical investigations.

@article{trejos_2017,
title = {Design and Evaluation of a Sterilizable Force Sensing Instrument for Minimally Invasive Surgery},
author = {Trejos, A.L.; Escoto, A.; Naish, M.; Patel, R.},
journal = {IEEE Sensors Journal},
year = {2017},
institution = {Department of Electrical and Computer Engineering, Western University, Canada},
abstract = {Although the inability to feel tool–tissue interaction forces during minimally invasive surgery (MIS) has been recognized as a significant difficulty encountered by surgeons during these procedures, existing sensorized technologies have not yet been approved for use in humans. The challenges of properly cleaning and sterilizing these instruments prevents them from being operating-room ready. The focus of this work was to develop a sterilizable instrument that uses strain gauges, the most common force-sensing method, to measure the tool–tissue interaction forces in three degrees of freedom (DOF) during MIS. A series of experiments were conducted to identify cables and connectors, as well as strain gauge adhesives and coatings to allow the instruments to successfully withstand autoclave sterilization. This resulted in the construction of a final prototype capable of measuring forces in 3 DOF, which was able to withstand 6 sterilization cycles with good sensing performance (0.15–1.70 N accuracy, 0.02–1.20 N repeatability and 0.11–1.05 N hysteresis depending on the measurement direction). This work demonstrates that autoclave sterilization is possible for a strain-gauge instrumented device and can lead to more advances in the development of sensorized instruments for surgery and therapy. },
issn = {1558-1748},
keywords = {Minimally invasive surgery, force sensing, sensorized instrument, sterilizable instrument, autoclave sterilization, strain-gauge sensing},
language = {English}
}

Although the inability to feel tool–tissue interaction forces during minimally invasive surgery (MIS) has been recognized as a significant difficulty encountered by surgeons during these procedures, existing sensorized technologies have not yet been approved for use in humans. The challenges of properly cleaning and sterilizing these instruments prevents them from being operating-room ready. The focus of this work was to develop a sterilizable instrument that uses strain gauges, the most common force-sensing method, to measure the tool–tissue interaction forces in three degrees of freedom (DOF) during MIS. A series of experiments were conducted to identify cables and connectors, as well as strain gauge adhesives and coatings to allow the instruments to successfully withstand autoclave sterilization. This resulted in the construction of a final prototype capable of measuring forces in 3 DOF, which was able to withstand 6 sterilization cycles with good sensing performance (0.15–1.70 N accuracy, 0.02–1.20 N repeatability and 0.11–1.05 N hysteresis depending on the measurement direction). This work demonstrates that autoclave sterilization is possible for a strain-gauge instrumented device and can lead to more advances in the development of sensorized instruments for surgery and therapy.

@article{fu_2017,
title = {Design and performance analysis of position-based impedance control for an electrohydrostatic actuation system},
author = {Fu, Y.; Han, X.; Sepehri, N.; Zhou, G.; Fu, J.; Yu, L.; Yang, R.},
journal = {Chinese Journal of Aeronautics},
year = {2017},
institution = {Beihang University, China; University of Manitoba, Canada; China Academy of Launch Vehicle Technology, China},
abstract = {Electrohydrostatic actuator (EHA) is a type of power-by-wire actuator that is widely implemented in the aerospace industry for flight control, landing gears, thrust reversers, thrust vector control, and space robots. This paper presents the development and evaluation of position-based impedance control (PBIC) for an EHA. Impedance control provides the actuator with compliance and facilitates the interaction with the environment. Most impedance control applications utilize electrical or valve-controlled hydraulic actuators, whereas this work realizes impedance control via a compact and efficient EHA. The structures of the EHA and PBIC are firstly introduced. A mathematical model of the actuation system is established, and values of its coefficients are identified by particle swarm optimization. This model facilitates the development of a position controller and the selection of target impedance parameters. A nonlinear proportional-integral position controller is developed for the EHA to achieve the accurate positioning requirement of PBIC. The controller compensates for the adverse effect of stiction, and a position accuracy of 0.08 mm is attained. Various experimental results are presented to verify the applicability of PBIC to the EHA. The compliance of the actuator is demonstrated in an impact test. },
keywords = {Actuation system, Aerospace, Electrohydrostatic actuator, Force control, Nonlinear dynamics, Particle swarm optimization, Position control},
language = {English},
publisher = {Elsevier Ltd.}
}

Electrohydrostatic actuator (EHA) is a type of power-by-wire actuator that is widely implemented in the aerospace industry for flight control, landing gears, thrust reversers, thrust vector control, and space robots. This paper presents the development and evaluation of position-based impedance control (PBIC) for an EHA. Impedance control provides the actuator with compliance and facilitates the interaction with the environment. Most impedance control applications utilize electrical or valve-controlled hydraulic actuators, whereas this work realizes impedance control via a compact and efficient EHA. The structures of the EHA and PBIC are firstly introduced. A mathematical model of the actuation system is established, and values of its coefficients are identified by particle swarm optimization. This model facilitates the development of a position controller and the selection of target impedance parameters. A nonlinear proportional-integral position controller is developed for the EHA to achieve the accurate positioning requirement of PBIC. The controller compensates for the adverse effect of stiction, and a position accuracy of 0.08 mm is attained. Various experimental results are presented to verify the applicability of PBIC to the EHA. The compliance of the actuator is demonstrated in an impact test.

@article{cho_2017,
title = {Design of an Optical Soft Sensor for Measuring Fingertip Force and Contact Recognition},
author = {Cho, Haedo; Lee, Hyosang; Kim, Yeongjin; Kim, Jung},
journal = {International Journal of Control, Automation and Systems},
year = {2017},
institution = {Department of Mechanical EngineeringKorea Advanced Institute of Science and TechnologyDaejeonKorea},
abstract = {Among the various ways to estimate user intention in hand exoskeletons, a contact force measurement is definitely the most straightforward and intuitive method. A force sensor, located at the center of a fingertip usually, hinders the tactile sensation of the user by blocking the contact between an object and the fingertip. To overcome this problem, a soft force sensor with horse shoe shape is utilized to measure the contact force and provide the tactile sensation to the user. This work presents the mechanical design, implementation and evaluation of a soft fingertip force sensor. To maximize tactile sensation of the user, we adopted a horse shoe shape structure to leave the finger pad exposed. An optical sensing mechanism was selected for its relatively fast response compared to other soft sensors. The whole sensor system has a soft exterior providing flexibility and a user-friendly interface. To evaluate the sensorÍs performance, we carried out sensor optimization process and calibration experiment with a customized test bed. Then, we investigated both static and dynamic response and observed the mechanical behavior and light intensity changes caused by the cross sectional shape and base/agent ratio of PDMS. Lastly, we applied the proposed sensor to the glove type fingertip force monitoring system. The sensor estimates the index finger tip force with high accuracy (R^2 = 0:96) within 5N range. },
issn = {1598-6446},
keywords = {Flexible sensor, force sensor, hand exoskeleton, open finger pad structure, optical sensor},
language = {English},
publisher = {Springer-Verlag Berlin Heidelberg}
}

Among the various ways to estimate user intention in hand exoskeletons, a contact force measurement is definitely the most straightforward and intuitive method. A force sensor, located at the center of a fingertip usually, hinders the tactile sensation of the user by blocking the contact between an object and the fingertip. To overcome this problem, a soft force sensor with horse shoe shape is utilized to measure the contact force and provide the tactile sensation to the user. This work presents the mechanical design, implementation and evaluation of a soft fingertip force sensor. To maximize tactile sensation of the user, we adopted a horse shoe shape structure to leave the finger pad exposed. An optical sensing mechanism was selected for its relatively fast response compared to other soft sensors. The whole sensor system has a soft exterior providing flexibility and a user-friendly interface. To evaluate the sensorÍs performance, we carried out sensor optimization process and calibration experiment with a customized test bed. Then, we investigated both static and dynamic response and observed the mechanical behavior and light intensity changes caused by the cross sectional shape and base/agent ratio of PDMS. Lastly, we applied the proposed sensor to the glove type fingertip force monitoring system. The sensor estimates the index finger tip force with high accuracy (R^2 = 0:96) within 5N range.

In order to solve the trajectory tracking of a quadrotor called QBall2 which is produced by Quanser Company of Canada, an integral backstepping controller is designed. A nonlinear mathematical model of QBall2 in the presence of external disturbances is obtained and a MATLAB/Simulink simulation system is built to validate the nonlinear trajectory tracking controller and compare the difference of PID and integral backstepping. The simulation results illustrate the good tracking performances of the designed nonlinear trajectory tracking controller.

@article{roozegar_2017,
title = {Design, modelling and estimation of a novel modular multi-speed transmission system for electric vehicles},
author = {Roozegar, M.; Setiawan, Y.D.; Angeles, J.},
journal = {Mechatronics},
year = {2017},
month = {08},
volume = {45},
institution = {McGill University, Montreal, Canada},
abstract = {The efficiency of electric vehicles (EVs) should be improved to make them viable, especially in light of the current low energy-storage capacity of electric batteries. Research demonstrates that applying a multi-speed transmission (MST) in an EV can reduce the energy consumption of the vehicle through gear-shifting. However, for effective gear-shifting control in MSTs, first of all, the model of the transmission is required. Moreover, reliable methods should be employed for estimation of the unmeasurable loads and states of the system, under model-based control. This study establishes the mathematical model and estimation algorithms for a novel MST designed for EVs. The main advantages of the designed MST are simplicity and modularity. After devising the dynamics of our proposed transmission, the Kalman filter, the Luenberger obsever and neural networks (NNs) are used to estimate the states, the unknown arbitrary disturbance and the unknown clutch torque applied to the system. Simulation results demonstrate that the proposed approach is suitable for estimation purposes. Experiments were conducted using an in-house prototyped transmission testbed, to validate the simulation results and assess the estimation algorithms. },
keywords = {Multi-speed transmission design Estimation algorithm Kalman filter Neural networks Mathematical modelling Electric vehicle},
language = {English},
publisher = {Elsevier Ltd.},
pages = {119-129}
}

The efficiency of electric vehicles (EVs) should be improved to make them viable, especially in light of the current low energy-storage capacity of electric batteries. Research demonstrates that applying a multi-speed transmission (MST) in an EV can reduce the energy consumption of the vehicle through gear-shifting. However, for effective gear-shifting control in MSTs, first of all, the model of the transmission is required. Moreover, reliable methods should be employed for estimation of the unmeasurable loads and states of the system, under model-based control. This study establishes the mathematical model and estimation algorithms for a novel MST designed for EVs. The main advantages of the designed MST are simplicity and modularity. After devising the dynamics of our proposed transmission, the Kalman filter, the Luenberger obsever and neural networks (NNs) are used to estimate the states, the unknown arbitrary disturbance and the unknown clutch torque applied to the system. Simulation results demonstrate that the proposed approach is suitable for estimation purposes. Experiments were conducted using an in-house prototyped transmission testbed, to validate the simulation results and assess the estimation algorithms.

@article{sayyaf_2017,
title = {Desirably Adjusting Gain Margin, Phase Margin, and Corresponding Crossover Frequencies Based on Frequency Data},
author = {Sayyaf, N.; Tavazoei, M.S.},
journal = {IEEE Transactions on Industrial Informatics},
year = {2017},
institution = {Electrical Engineering Department, Sharif University of Technology, Tehran, Iran},
abstract = {This paper presents an analytical method to tune a fixed-structure fractional order compensator for satisfying desired phase and gain margins with adjustable crossover frequencies. The proposed method is based on the measured frequency data of the plant. Since no analytical model for the plant is needed in the compensator tuning procedure, the resulted compensator does not depend on the order and complexity of the plant. Also, sufficient conditions for the existence of a compensator with no zero and pole in the right half-plane for satisfying the aforementioned objectives are analytically derived. Furthermore, different hardware-in-the-loop experimental results are presented to show the efficiency of the proposed tuning method. },
issn = {1551-3203},
keywords = {Control systems, Tuning, Poles and zeros, Lead, Analytical models, Crossover frequency, Frequency domain design, Fractional order controller, Phase margin, Gain margin},
language = {English},
publisher = {IEEE}
}

This paper presents an analytical method to tune a fixed-structure fractional order compensator for satisfying desired phase and gain margins with adjustable crossover frequencies. The proposed method is based on the measured frequency data of the plant. Since no analytical model for the plant is needed in the compensator tuning procedure, the resulted compensator does not depend on the order and complexity of the plant. Also, sufficient conditions for the existence of a compensator with no zero and pole in the right half-plane for satisfying the aforementioned objectives are analytically derived. Furthermore, different hardware-in-the-loop experimental results are presented to show the efficiency of the proposed tuning method.

@conference{albeanu_2107,
title = {Developing IoT Enabled Applications for Augmented Engineering Education},
author = {Popentiu-Vladicescu, F.; Albeanu, G.; Madsen, H.; Hadj, B.; Grosu, R.-R.},
booktitle = {13th International Scientific Conference eLearning and Software Education},
year = {2017},
volume = {3},
institution = {Academy of Romanian Scientists, Romania; “Spiru Haret” University, Romania; Technical University of Denmark, Denmark; Politehnica University, Bucharest, Romania; Sultan Qaboos University, Oman},
abstract = {Engineering education through real life projects asks for augmenting the already established curriculum with items of the new IoT world, and the science of developing IoT enabled applications, addressing sets of different technologies working together. The FOG world consists of devices, sensors, data and the cloud. Unlike a desktop/laptop computer or tablet, IoT devices can access specific hardware like lights, sensors and motors. Therefore, a large plethora of real life projects can be implemented during practical lessons. Based on FOG approach of the new IoT based world, this paper describes architectures and methodologies to be applied both for massive and critical IoT enabled applications. The adequacy of programming languages, application programming interfaces' availability and new frameworks for IoT enabled applications for various boards including Raspberry PI, Dragon board, Intel Joule, and Minnow are considered. As results of this project, a syllabus and an e-book for the course "Developing IoT enabled applications" are obtained. Theoretical and practical case studies can be used in a blended learning approach to teach such a new subject. By taking this course or/and studying the e-book, the students will gain knowledge on developing IoT smart applications using eclipse IoT technology. },
keywords = {IoT enabled applications, software development, engineering education},
language = {English},
publisher = {"Carol I" National Defence University},
pages = {328-335}
}

Engineering education through real life projects asks for augmenting the already established curriculum with items of the new IoT world, and the science of developing IoT enabled applications, addressing sets of different technologies working together. The FOG world consists of devices, sensors, data and the cloud. Unlike a desktop/laptop computer or tablet, IoT devices can access specific hardware like lights, sensors and motors. Therefore, a large plethora of real life projects can be implemented during practical lessons. Based on FOG approach of the new IoT based world, this paper describes architectures and methodologies to be applied both for massive and critical IoT enabled applications. The adequacy of programming languages, application programming interfaces' availability and new frameworks for IoT enabled applications for various boards including Raspberry PI, Dragon board, Intel Joule, and Minnow are considered. As results of this project, a syllabus and an e-book for the course "Developing IoT enabled applications" are obtained. Theoretical and practical case studies can be used in a blended learning approach to teach such a new subject. By taking this course or/and studying the e-book, the students will gain knowledge on developing IoT smart applications using eclipse IoT technology.

@article{ozdagli_2017,
title = {Development and Verification of Distributed Real-Time Hybrid Simulation Methods},
author = {Li, X.; Ozdagli, A.I.; Dyke, S.; Lu, X.},
journal = {Journal of Computing in Civil Engineering},
year = {2017},
institution = {Tongji University, China; Purdue University, IN, USA},
abstract = {Hybrid simulation combines numerical simulation and physical testing, and is thus considered to be an efficient alternative to traditional testing methodologies in the evaluation of global performance of large or complex structures. Real-time hybrid simulation (RTHS) is performed when it is important to fully capture rate-dependent behaviors in the physical substructure. Although the demand to test more complex systems grows, not every laboratory has the right combination of computational and equipment resources available to perform large-scale experiments. Distributed real-time hybrid simulation (dRTHS) facilitates testing that is to be conducted at multiple geographically distributed laboratories while utilizing the Internet to couple the substructures. One major challenge in dRTHS is to accommodate the unpredictable communication time delays between the various distributed sites that occur as a result of Internet congestion. Herein, a dRTHS framework is proposed where a modified Smith predictor is adopted to accommodate such communication delays. To examine and demonstrate the sensitivity of the proposed framework to communication delays and to modeling errors, parametric analytical case studies are presented. Additionally, the effectiveness of this dRTHS framework is verified through successful execution of multisite experiments. The results demonstrate that this framework provides a new option for researchers to evaluate the global response of structural systems in a distributed real-time environment. },
keywords = {Distributed real-time hybrid simulation; Smith predictor; Magnetorheological damper},
language = {English},
publisher = {ASCE}
}

Hybrid simulation combines numerical simulation and physical testing, and is thus considered to be an efficient alternative to traditional testing methodologies in the evaluation of global performance of large or complex structures. Real-time hybrid simulation (RTHS) is performed when it is important to fully capture rate-dependent behaviors in the physical substructure. Although the demand to test more complex systems grows, not every laboratory has the right combination of computational and equipment resources available to perform large-scale experiments. Distributed real-time hybrid simulation (dRTHS) facilitates testing that is to be conducted at multiple geographically distributed laboratories while utilizing the Internet to couple the substructures. One major challenge in dRTHS is to accommodate the unpredictable communication time delays between the various distributed sites that occur as a result of Internet congestion. Herein, a dRTHS framework is proposed where a modified Smith predictor is adopted to accommodate such communication delays. To examine and demonstrate the sensitivity of the proposed framework to communication delays and to modeling errors, parametric analytical case studies are presented. Additionally, the effectiveness of this dRTHS framework is verified through successful execution of multisite experiments. The results demonstrate that this framework provides a new option for researchers to evaluate the global response of structural systems in a distributed real-time environment.

@article{bayar2_2017,
title = {Development of a Voronoi diagram based tree trunk detection system for mobile robots used in agricultural applications},
author = {Bayar, G.},
journal = {Industrial Robot: An International Journal},
year = {2017},
volume = {44},
number = {4},
institution = {Bulent Ecevit Universitesi, Zonguldak, Turkey},
abstract = {Purpose: In this study, the purpose is to develop a methodology for detecting tree trunks for autonomous agricultural applications performed using mobile robots. Design/methodology/approach: The system is constructed by following the principles of Voronoi diagram method which is one of the machine learning algorithms used by the robotics, mechatronics, and automation researchers. Findings: In order to analyze the accuracy and performance, and make verification and evaluation, both simulation and experimental studies are conducted. The results indicate that the tree trunk detection system developed using Voronoi diagram method can be able to detect tree trunks with high precision. Originality/value: A novel solution technique to detect tree trunks is proposed. The adaptation of Voronoi diagram method in an agricultural (orchard) task is presented. },
issn = {0143-991X},
keywords = {Voronoi diagram, tree trunk detection, agricultural application, mobile robot},
language = {English},
publisher = {Emerald Publishing Ltd.}
}

Purpose: In this study, the purpose is to develop a methodology for detecting tree trunks for autonomous agricultural applications performed using mobile robots. Design/methodology/approach: The system is constructed by following the principles of Voronoi diagram method which is one of the machine learning algorithms used by the robotics, mechatronics, and automation researchers. Findings: In order to analyze the accuracy and performance, and make verification and evaluation, both simulation and experimental studies are conducted. The results indicate that the tree trunk detection system developed using Voronoi diagram method can be able to detect tree trunks with high precision. Originality/value: A novel solution technique to detect tree trunks is proposed. The adaptation of Voronoi diagram method in an agricultural (orchard) task is presented.

@article{jafari_2017,
title = {Development of an Assistive Robotic System with Virtual Assistance to Enhance Play for Children with Disabilities: A Preliminary Study},
author = {Jafari, N.; Adams, K.D.; Tavakoli, M.; Wiebe, S.},
journal = {Journal of Medical and Biological Engineering},
year = {2017},
institution = {University of Alberta, Edmonton, Canada; Glenrose Rehabilitation Hospital, Edmonton, Canada},
abstract = {Children with disabilities typically have fewer opportunities for manipulation and play, due to their physical limitations, resulting in delayed cognitive and perceptual development. A switched-controlled device can remotely do tasks for a child or a human helper can mediate the child’s interaction with the environment during play. However, these approaches disconnect children from the environment and limit their opportunities for interactive play with objects. This paper presents a novel application of a robotic system with virtual assistance, implemented by virtual fixtures, to enhance interactive object play for children in a set of coloring tasks. The assistance conditions included zero assistance (No-walls), medium level assistance (Soft-walls) and high level assistance (Rigid-walls), which corresponded to the magnitude of the virtual fixture forces. The system was tested with fifteen able-bodied adults and results validated the effectiveness of the system in improving the user’s performance. The Soft- and Rigid-walls conditions significantly outperformed the No-walls condition and led to relatively the same performance improvements in terms of: (a) a statistically significant reduction in the ratio of the colored area outside to the colored area inside the region of interest (with large effect sizes, Cohen’s d > .8), (b) and a substantial reduction in the travelled distance outside the borders (with large effect sizes). The developed platform will next be tested with typically developing children and then children with disabilities. Future development will include adding artificial intelligence to adaptively tune the level of assistance according to the user’s level of performance (i.e. providing more assistance only when the user is committing more errors). },
issn = {1609-0985},
keywords = {Haptic, Haptic interaction, Haptic interface, Virtual assistance, Task performance, Object manipulation, Children with disabilities },
language = {English},
publisher = {Springer Berlin Heidelberg}
}

Children with disabilities typically have fewer opportunities for manipulation and play, due to their physical limitations, resulting in delayed cognitive and perceptual development. A switched-controlled device can remotely do tasks for a child or a human helper can mediate the child’s interaction with the environment during play. However, these approaches disconnect children from the environment and limit their opportunities for interactive play with objects. This paper presents a novel application of a robotic system with virtual assistance, implemented by virtual fixtures, to enhance interactive object play for children in a set of coloring tasks. The assistance conditions included zero assistance (No-walls), medium level assistance (Soft-walls) and high level assistance (Rigid-walls), which corresponded to the magnitude of the virtual fixture forces. The system was tested with fifteen able-bodied adults and results validated the effectiveness of the system in improving the user’s performance. The Soft- and Rigid-walls conditions significantly outperformed the No-walls condition and led to relatively the same performance improvements in terms of: (a) a statistically significant reduction in the ratio of the colored area outside to the colored area inside the region of interest (with large effect sizes, Cohen’s d > .8), (b) and a substantial reduction in the travelled distance outside the borders (with large effect sizes). The developed platform will next be tested with typically developing children and then children with disabilities. Future development will include adding artificial intelligence to adaptively tune the level of assistance according to the user’s level of performance (i.e. providing more assistance only when the user is committing more errors).

@article{doll_2017,
title = {Dynamic Optimization of Stimulation Frequency to Reduce Isometric Muscle Fatigue Using a Modified Hill-Huxley Model},
author = {Doll, B.D.; Kirsch, N.A.; Bao, X.; Dicianno, B.E.; Sharma, N.},
journal = {Muscle & Nerve},
year = {2017},
institution = {University of Pittsburgh, Pittsburgh, PA, USA; Bechtel Marine Propulsion Corporation, Pittsburgh, PA, USA; Iam Robotics, Pittsburgh, PA. USA},
abstract = {Introduction: Optimal frequency modulation during functional electrical stimulation (FES) may minimize or delay the onset of FES-induced muscle fatigue. Methods: An offline dynamic optimization method, constrained to a modified Hill-Huxley model, was used to determine the minimum number of pulses that would maintain a constant desired isometric contraction force. Results: Six able-bodied subjects were recruited for the experiments, and their quadriceps muscles were stimulated while they sat on a leg extension machine. The force-time integrals and peak forces after the pulse train was delivered were found to be statistically significantly greater than the force-time integrals and peak forces obtained after a constant frequency train was delivered. Discussion: Experimental results indicated that the optimized pulse trains induced lower levels of muscle fatigue compared to constant frequency pulse trains. This could have a potential advantage over current FES methods that often choose a constant frequency stimulation train. This article is protected by copyright. All rights reserved. },
keywords = {Neuromuscular Electrical Stimulation (NMES), Muscle Force Prediction, Muscle Fatigue, Hill-Huxley Model, Dynamic Optimization, Functional Electrical Stimulation (FES)},
language = {English},
publisher = {Wiley Periodicals, Inc.}
}

Introduction: Optimal frequency modulation during functional electrical stimulation (FES) may minimize or delay the onset of FES-induced muscle fatigue.
Methods: An offline dynamic optimization method, constrained to a modified Hill-Huxley model, was used to determine the minimum number of pulses that would maintain a constant desired isometric contraction force.
Results: Six able-bodied subjects were recruited for the experiments, and their quadriceps muscles were stimulated while they sat on a leg extension machine. The force-time integrals and peak forces after the pulse train was delivered were found to be statistically significantly greater than the force-time integrals and peak forces obtained after a constant frequency train was delivered.
Discussion: Experimental results indicated that the optimized pulse trains induced lower levels of muscle fatigue compared to constant frequency pulse trains. This could have a potential advantage over current FES methods that often choose a constant frequency stimulation train. This article is protected by copyright. All rights reserved.