Kinematics Modeling and Gait Trajectory Tracking for Lower Limb Exoskeleton Robot based on PD Control with Gravity Compensation

Recently, the lower limb exoskeleton robot, which is a kind of wearable equipment, has been widely developed to help disabled people. To reduce the gait trajectory tracking errors of the lower limb exoskeleton robot during walking, a method of gravity compensation based on PD control was proposed in this paper. Firstly, the accurate kinematics model of two-link structure was established according to the Newton-Euler equations. Secondly, all parameters of the actual human-machine integrated robot system were identified and calculated by kinematics analysis. And then stability of the system with proposed controller was proved by Lyapunov stability theorem. At last, a simulation was presented based on MATLAB/Simulink platform. The simulation results show that the dynamics model is right and reliable, the gait trajectory tracking performance is excellent, and the controller can reduce the error of gait trajectory tracking to zero. The experiment demonstrated that the design of mechanical structure and control system was reasonable.