Improving energy consumption in Exoped® Lower-limb Exoskeleton by means of Functional Electrical Stimulation

Abstract

Walking and standing are the two fundamental problems in patients with spinal cord injury. Gait disorders in neurologically disabled people can be treated by various techniques available today. Exoskeleton robots and functional electrical stimulation (FES) are the two important solutions in this field. However, each of them has its own drawback. The patient using an exoskeleton doesn't participate in walking, in addition, battery consumption is a limiting problem. On the other hand, the muscles fatigue and complexity of joints control should be noticed in functional electrical stimulation. In this paper, in order to solve these problems, combining exoskeleton and FES system is considered. The Exoped® exoskeleton robot which consists of four motors in knee and hip joints is used for implementation of proposed method. For FES quadriceps and hamstring muscles are assumed actuate the knee joint during swing phase. The muscle stimulation is adjusted in a way that the interaction torque between the robot joint and the patient is minimized, i.e., the FES torque assists the robot. In order to show that the approach is efficient, it is implemented on Exoped® by healthy person. Experimental data and simulation results indicate that the proposed method reduces the torque and power output required for knee motors of the exoskeleton compared to walking without FES.