Torque-dependent compliance control in the joint space of an operational robotic machine for motor therapy

This paper is focused on the design of interaction control of robotic machines for rehabilitation motor therapy of the upper limb. The control approach tries to address requirements deriving from the application scenario and adopts a bio-inspired approach for regulating robot behavior in the interaction with the patient. The coactivation-based compliance control law in the joint space [Zollo, L, et al., 2003] is resumed and a new control law for regulating robot compliance in the free space is proposed, that is borrowed from studies on the biological mechanisms of regulation of the elastic properties of a healthy human arm. Moreover, a direct force control loop is added, in order to tune the level of force in the interaction with the patient. The control law is tested on a purposively developed simulation tool, which models the dynamics of the MIT-MANUS robot interacting with a human subject. The capability of the control system of counterbalancing incorrect movements depending on the level of pathology is finally validated.