Point-to-point repetitive control with application to drop-foot

Page, A. P., Freeman, C. T. and Chu, B. (2018) Point-to-point repetitive control with application to drop-foot. In 2018 European Control Conference, ECC 2018. IEEE. pp. 2399-2404 . (doi:10.23919/ECC.2018.8550097).

Record type: Conference or Workshop Item (Paper)

Abstract

Drop-foot is characterised by ankle dorsiflexion weakness, caused by either nerve damage or a result of a brain or spinal injury. It results in abnormal gait, producing slow, tiring and often unsafe ambulation. Established treatment is via passive orthoses, but these have high rejection rates caused by discomfort, loss of muscle control and ankle instability. Functional electrical stimulation (FES) has had considerable success, but current commercial control approaches are open loop or triggered, and the few exisiting feedback approaches require extensive sensor data, lack accuracy, or are highly dependent on an identified model. This paper is the first application of repetitive control (RC) to this problem, providing improved gait performance by learning from errors over previous gait cycles. To address the drawbacks of previous approaches, a comprehensive extension to a general class of RC law is developed which enables it to track only isolated time points. Simulation results of the resulting 'point-to-point' RC framework on FES-assisted drop-foot confirm its improved convergence and robust performance properties.

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