Admittance Control Strategy with Output Joint Space Constraints for a Lower Limb Rehabilitation Robot

An increasing attention has been paid to the robot compliance and patient's safety during-aided rehabilitation training. In this paper, an admittance control strategy with output joint space constraints is proposed for a lower limb rehabilitation robot (LLRR) to ensure robot compliance and patients' safety during robot-aided rehabilitation training. A model-based controller with a disturbance observer is adopted in the inner-loop to guarantee the patients' safety. Then, an admittance controller is used in the outer-loop, which can ensure the LLRR comply with the patients' intention. Finally, simulation experiments are carried out, and the results show that the admittance control strategy with output joint space constraints has a significant advantage for the robot compliance and patient's safety when regarding the disturbances and system uncertainties.