Assist-as-Needed Impedance and Admittance Switching Control for an Upper-Limb Compliant Rehabilitation Orthosis

Individuals affected by stroke often experience spasticity, which limits movement and impact activities of daily living. Physical therapy is essential for improving voluntary movement; however, therapists often face time constraints that limit their ability to provide optimal care for patients with spasticity. To address this issue, an assist-as-needed admittance and impedance-switching controller has been developed for an upper-limb compliant rehabilitation orthosis currently in development. This controller allows patients with spasticity to perform exercises independently while complementing therapist-provided care, enabling both autonomy and assistance during rehabilitation. This paper presents the controller and simulation results, demonstrating the ability to accurately track the patient's voluntary movements and follow a therapist-prescribed trajectory, even in case of impaired motor function or spasticity-related challenges like increased muscle tone.