Stiffness control of a pneumatic rehabilitation robot for exercise therapy with multiple stages

In exercise therapy, the training program will differ depending on the degree of disability. In order to gradually transition from passive exercise to exercises with more voluntary movements, it is important to reduce the assistance provided by the therapist in stages. Since stiffness control is the key factor of assistance adjustment in robotic movement rehabilitation, this paper focuses on stiffness control as a tool to adjust the assistance in stages. It is necessary to set a proper stiffness ellipse to perform assistance with directivity, especially in the case of active-assistive exercise. The performance of the proposed stiffness control for exercise therapy is validated through experimental results.