Shared control for switched motorized FES-cycling on a split-crank cycle accounting for muscle control input saturation

• DOI: 10.1016/j.automatica.2020.109294
• Publication Date: 2020-11-02T05:12:47Z
• Authors: Courtney A. Rouse; Christian A. Cousin; Brendon C. Allen; Warren E. Dixon
• Keywords: 0209 industrial biotechnology; 02 engineering and technology; 16. Peace & justice

Abstract Closed-loop functional electrical stimulation (FES) control methods are developed to enable motorized assistive split-crank (i.e., a cycle without mechanical coupling between the lower limbs) cycling for rehabilitation efforts for people with lower limb movement disorders. The non-dominant side tracks a desired range of cadence and the dominant side tracks a range of position offsets centered around the position of the non-dominant side. A multi-level switched system with switched control objectives is applied to both sides of the cycle-rider system. Assistive, uncontrolled, and resistive modes for the dominant and non-dominant subsystems are based on position and cadence, respectively. Global exponential tracking to upper and lower bounds of an uncontrolled desired region is proven for each side via Lyapunov-based analysis using switched system methods. Experiments on both able-bodied participants and participants with neuromuscular conditions show the performance of the switched control system for split-crank FES-cycling. From volitional to controlled pedaling in able-bodied participants, average RMS cadence error of the non-dominant, RMS position error of the dominant, and cadence differential between the two legs improved by 76.2%, 65.3%, and 58.0%, respectively. On average, experiments on participants with neuromuscular conditions resulted in RMS errors that were 45.8%, 92.6%, and 52.0% higher than controlled trials on able-bodied participants, but 65.3%, 33.3%, and 36.3% lower than volitional-only trials of able-bodied participants.