FES and Motor Assisted Cycling to Track Power and Cadence to Desired Voluntary Bounds

Cycling is a common rehabilitation exercise for people recovering from neurological impairments. Both functional electrical stimulation (FES) and a motor can assist a person in pedaling a cycle, and by switching amongst multiple muscle groups and a motor, a human-cycle system can track a desired power and cadence. However, with motivation to maximize physiological effects, the person should contribute volitionally as much as possible and be assisted only when necessary, which can be done by limiting cadence assistance to outside a desired region. Torque tracking to a single value is desired so that the muscle is being sufficiently exercised. In this paper, a human contributing torque through FES and volition works alongside an electric motor to instantaneously track cadence to a desired region and discretely track torque to a known bound for all time. Lyapunov methods are used to prove the stability of the switched system.