Weighted Point-to-Point Repetitive Control for Drop-Foot Assistance

Abstract

Drop-foot is a neurological condition caused by nerve damage or as a result of a brain/spinal injury. The condition leads to a abnormal, slow, tiring gait with an increased probability of falls. Functional electrical stimulation (FES) has had considerable success in treating drop-foot, but commercial approaches lack closed loop control which degrades there performance. Currently closed loop controllers available in the research domain require significant sensory data or have limited accuracy, making them unsuitable for implementation. This paper is the first application of repetitive control (RC) to this problem. To overcome data requirements whilst maintaining accuracy of key gait events, a comprehensive point to point framework is derived. Further to this, a weighted modification is proposed allowing prioritisation of points. Simulation results for the ‘weighted point-to-point’ and ‘point-to-point’ RC frameworks for FES-assisted drop-foot confirm their improved convergence and robust performance properties.