Control concepts for an industrial robot used as kinesthetic knee joint simulator

A novel 6 DOF robotic haptic device for orthopedic training is presented for display of the motion dynamics of a virtual human knee joint. For achieving the high impedances required by this application an industrial robot has been selected as an actuator and extended with a PC-based high performance controller hardware and redundant safety features. Two possible control architectures - a force-command and motion-command control - are presented and both implemented in a 1 DOF application. Based on a new method for evaluation and comparison of controller performance in terms of impedance error the experimental results reveal that motion-command control provides better accuracy for display of the high impedances specific to the human knee application.