Controlling shoulder impedance in a rehabilitation arm exoskeleton

A control methodology is developed for modulating shoulder impedance in an arm exoskeleton during physical therapy. Setting the remote center of compliance at the shoulder will allow the exoskeleton to enact resistance training protocols that strengthen the rotator cuff and other joint musculature supporting the shoulder complex. The rotational kinematics for the shoulder are first derived, and then the torques applied at the shoulder are estimated using force sensors placed at the hand and elbow interfaces. Impedance and admittance control schemes are both developed for realizing isolateral strengthening exercises, and some preliminary experimental results are presented for implementation on an arm exoskeleton currently under development.