Control of a hip rehabilitation robot using a virtual prototype

A hip fracture causes musculoskeletal problems which affect the patient to carry out activities of daily living (ADLs) such as standing and walking. Rehabilitation therapies are procedures to restore the movement of a joint or a muscle due to illness or injury. The goal of rehabilitation therapeutic exercises is to perform specific movements that cause muscle activation to the patient, in order to recover and minimize the damage after a prolonged immobilization. In this paper, a hip rehabilitation robot using a virtual prototype is presented which provides flexion/extension movements with a Generalized Proportional Integral (GPI) controller that performs soft movements. A GPI controller is proposed for the efficient rejection of an unknown perturbation input due the weight of the leg and unexpected reflexes of the muscles during the therapy. Simulation results using a GPI controller in a robust perturbation rejection scheme for a trajectory tracking task are presented. In order to assess the performance and outstanding disturbance rejection capabilities of the proposed robust GPI controller, a comparison with a PD and PID controller is also presented.