Hybrid force-position control yields cooperative behaviour of the rehabilitation robot LOKOMAT

Abstract

The rehabilitation robot LOKOMAT has been developed at the Spinal Cord Injury Center of the University Hospital Balgrist, Zurich. It allows automated treadmill training for patients with mobility impairment of the lower limbs. Former position control strategies did not allow voluntary active movements of the patient. This paper presents a new cooperative control architecture for the LOKOMAT that enforces active force contribution of the patient. Based on a dynamic model of the human gait, the patient is supported by an arbitrary percentage of the force required to walk. Online gait event detectors have been developed and implemented since the controller mode changes depending on the gait phase. The new control strategy is highly patient-driven and enables the patient to accomplish free walking movements. Thus, it is expected, that the motivation of the patient can be maximized and the rehabilitation progress accelerated.