The FES-assisted control for a lower limb rehabilitation robot: simulation and experiment

Abstract

To design a control strategy for iLeg, an exoskeleton robot developed for lower limb rehabilitation aiming at investigating the feasibility of integrating functional electrical stimulation (FES) with robot-based rehabilitation training, an FES-assisted training strategy combined with impedance control, has been proposed in this paper. Through impedance control, an active compliance of the robot is established, and the patient's voluntary effort to accomplish the training task is inspired. During the training process, the patient's related muscles are applied with FES which provides an extra assistance to the patient. The intensity of the FES is properly chosen in order to induce a desired active torque which is proportional to the voluntary effort extracted from the electromyography signals of the related muscles using back propagation neural networks. This kind of enhancement serves as a positive feedback which reminds the patient of the correct attempt to fulfill the desired motion. FES control is conducted by a combination of neural network-based feedforward controller and a PD feedback controller. Simulation conducted using Matlab and the experiment with a spinal cord injury subject and a healthy subject have shown satisfactory results which verify the feasibility of this control strategy.

An RBF-based neuro-adaptive control scheme to drive a lower limb rehabilitation robot

“…In order to implement the performance that the robot can adaptively compensate to the patient's different voluntary efforts, a robust adaptive control law will be designed for the actual output torque. The dynamics model structure of human-robot hybrid system can be described as [19] …”

A Preliminary Evaluation of Linear Control Schemes for FES-Assisted Movements

“…The coordination of the human body is accomplished by the central nervous system using signals which are in an electrical form originating from ionic currents. This makes the application of electrical signals useful for quite a number medical therapies such as pain suppression, wound healing, muscle conditioning and revival of functions such as for sight, hearing, heart contractions, bladder functions and movement revival by using stimulating the appropriate nerve cells/muscles involved (Chen, Hu, Peng, & Hou, 2014;Durfee, 2006;Ferrari de Castro & Cliquet, 2000;Jezernik, Inderbitzin, Keller, & Reiner, 2002).…”

“…In electrical stimulation usually electrical signals of certain characteristics are used (usually of low amplitudes) to help to revert or reduce abnormalities in utterances or responses of the human body parts due to the nervous system failure as a result of diseases, trauma or complications (such as spinal cord injury, head injury, stroke and other disorders) which are usually controlled by the central nervous system (CNS) (Arantes et al, 2007;Braz, Russold, & Davis, 2009;Chen et al, 2014;Durfee, 2006;Ethier, Oby, Bauman, & Miller, 2012;Jezernik et al, 2002;Kern et al, 2010;Lee et al, 2013;Papachristos, 2014;Tan et al, 2014). The function reversal/revival of the affected body part is achieved by systematically applying the desirable electrical signals its muscles/nerves.…”

Cooperative Control for A Hybrid Rehabilitation System Combining Functional Electrical Stimulation and Robotic Exoskeleton

“…Compared with orthoses, powered exoskeletons using mechanical actuators can compensate insufficient torque generated by FES. Recently, some achievements in hybrid FES-exoskeleton systems have been made, such as WalkTrainer (Stauffer et al, 2009 ), Vanderbilt Exoskeleton (Ha et al, 2012 ), Kinesis (del Ama et al, 2014 ), iLeg (Chen et al, 2014 ) and so on. In WalkTrainer system, Stauffer et al ( 2009 ) developed closed-loop control of FES that modulated muscle stimulation to minimize the interaction force between the wearer and the exoskeleton, or modulated the desired torques as a function of the gait cycle.…”