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Zhang D.,Shanghai JiaoTong University | Poignet P.,Montpellier Laboratory of Computer Science | Widjaja F.,Nanyang Technological University | Tech Ang W.,Nanyang Technological University
Control Engineering Practice | Year: 2011

This paper explores the possibility to adopt neural oscillators for pathological tremor attenuation. The objective is to suppress the tremor of a single joint of upper limb via functional electrical stimulation (FES). A biologically inspired neural oscillator is developed, which generates the anti-tremor rhythmic stimulation patterns to stimulate a pair of antagonist muscles. Surface electromyographic (EMG) signal is used to entrain the neural oscillator reciprocally and shape the stimulation pattern adaptively. The neural oscillator serves as an adaptive feedforward controller, which is combined with a feedback regulator. Simulation study is performed on musculoskeletal models of wrist joint and elbow joint separately, and some promising results are presented. © 2010 Elsevier Ltd.

Natal G.S.,Universal Robots | Chemori A.,Montpellier Laboratory of Computer Science | Pierrot F.,Montpellier Laboratory of Computer Science
IEEE Transactions on Control Systems Technology | Year: 2015

In this paper, three control schemes are proposed and experimentally compared on the R4 redundantly actuated parallel manipulator for applications with very high accelerations. First, a proportional-integral-differential (PID) in operational space is proposed to adequately take into consideration the actuation redundancy. Because of its lack of performance, a dual-space feedforward control scheme based on the dynamic model of R4 is proposed. The improvements obtained with this controller allowed the implementation of an experiment, which consisted in the tracking of a trajectory with a maximum acceleration of more than 100G. However, such a controller may have loss of performance in case of any operational change (such as different payloads). Therefore, a dual-space adaptive control scheme is proposed. The stability analysis of the R4 parallel robot when controlled by the proposed dual-space adaptive controller is provided. The objective of this paper is to show that the proposed dual-space adaptive controller not only maintains its good performance independently of the operational conditions but also has a better performance than both the PID and the dual-space feedforward controllers, even when the latter is best configured for the given case (which confirms its applicability in an industrial environment). © 2014 IEEE.

Widjaja F.,Nanyang Technological University | Shee C.Y.,Nanyang Technological University | Ang W.T.,Nanyang Technological University | Au W.L.,National Neuroscience Institute | Poignet P.,Montpellier Laboratory of Computer Science
Journal of Mechanics in Medicine and Biology | Year: 2011

Tremor is the most common movement disorder and it is affecting more and more people as the world is aging. The cost involved is big considering the financial and social impact. This paper explores an assistive technology solution for upper limb pathological tremor compensation. Using both surface electromyography (SEMG) and accelerometer (ACC), a real-time pathological tremor compensation with functional electrical stimulation (FES) is proposed. One advantage of using SEMG is the electromechanical delay (SEMG data precedes the ACC data by 20100 ms). Hence by detecting the tremor in advance, there is enough time window to do the necessary computation and to actuate the antagonist muscle by FES. This is also possible because the time taken for FES to actuate the muscle is significantly less than that of the neural signal, as detected by SEMG. For estimation of tremor parameters and separation between voluntary motion and tremor, an algorithm based on extended Kalman filter (EKF) is proposed. Experimental result from one essential tremor patient has shown 57% reduction in tremor power as measured by the ACC.© 2011 World Scientific Publishing Company.

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