Design, Modeling, and Control of a Variable Stiffness Device for Wrist Rehabilitation

At a point in the future there may be few physical therapists for the number of patients who need treatment. To address the problem, we have created a device that can rehabilitate the wrist movements like flexion/extension and abduction/adduction, in addition to being able to fit either the left or right wrist. This paper presents the design and development of a single degree of freedom (DOF) rehabilitation device driven by a pneumatic Variable Stiffness Actuator (pVSA). This mechanism is intended to rehabilitate and aid with wrist movements. The proposed device is designed to be stationary, placing the patient's forearm on the device, where he/she grabs a handle.The dynamic model of the apparatus is presented along with a suitable control law. For this, a kinematic analysis of the mechanism and dynamic modeling of the pneumatic cylinder were developed. The pneumatic system allows the control of both the output force and stiffness of the system by pressure control.