Split-Crank Functional Electrical Stimulation Cycling: An Adapting Admitting Rehabilitation Robot

Motorized functional electrical stimulation (FES) cycling is a promising rehabilitation strategy for individuals with movement disorders, particularly when the pedals of the FES cycle are decoupled to measure and address asymmetries. In this article, a rehabilitation robot, i.e., a split-crank FES cycle, is developed which utilizes a combined admittance-cadence controller to address rider asymmetries through adaptation, ensure rider safety, and electrically stimulate the rider’s leg muscles to pedal the cycle at the desired cadence. The theoretical development of the controllers is based on a combined Lyapunov-passivity switched systems stability analysis. Experiments were conducted on one able-bodied participant and three participants with various movement disorders, resulting in an average admittance tracking error of −0.13 ± 1.77 RPM with adaptation and −0.03 ± 4.05 RPM without adaptation. The split-crank FES cycle successfully admits to the rider, preserves rider safety, and offers a promising robotic rehabilitation strategy for individuals affected by movement disorders.