Control Barrier Functions for Safe Teleoperation of a Functional Electric Stimulation Enabled Rehabilitation System

There is a growing need for telerehabilitation. For people with neuromuscular disorders, Functional Electrical Stimulation (FES) cycling is a commonly used rehabilitation technique. Studies have shown that by coordinating movement between the lower and upper limbs can lead to faster restoration of walking in many cases. The author’s previous development of a strongly coupled bilateral telerobotic system met two separate goals: enabling a therapist to direct rehabilitative efforts remotely, and extend the benefit of in-home FES rehabilitation sessions by coordinating limb movement. However, the previously developed system did not restrict the trajectories of the leader-cycle system, thus increasing the possibility that the system might operate outside of beneficial rehabilitative cadence ranges. In this work, a control barrier function (CBF) is designed to ensure safety of the leader-cycle system (i.e., constrain the cadence within a desired operating range). Once safety of the leader is guaranteed, Lyapunov-based analysis is used to show that the follower-cycle FES/motor actuated system produces global exponential tracking of the leader-cycle position and cadence.