Abstract: A three degrees of freedom (DOFs) wrist rehabilitation robot and the assistive control system with the force feedback function are designed. The assistive force provided by motors is determined according to the force/torque detected from the patient. The system ensures the patient can keep the same force/torque in assistive training. Compared with the electro-encephalogram (EEG) or surface electromyography (sEMG), the force feedback possesses many advantages such as high operability, accuracy, stability and low cost. Three closed loops with current, velocity and current system are applied in the control system. Proportional-integral (PI) regulator is applied in both current and velocity loops, and sliding variant structure regulator is adopted in the position loop, which effectively improves the accuracy and robustness of the system. System simulation has proved the validity of this control system.

Key words: rehabilitation robot, wrist, assistive rehabilitation training, force feedback