Research On Gait Trajectory Tracking Control Strategy Of Lower Limb Exoskeleton Rehabilitation Robot

The lower limb exoskeleton rehabilitation robot can help patient with rehabilitation exercise,and has the advantages of reliable effect and high efficiency.The research of lower limb exoskeleton rehabilitation robot has promoted the development of rehabilitation medicine.Patients are divided into different stages including passive training and active training according to their physical condition.So it is necessary to develop different control strategies to fit the different control targets.In this paper,a kind of vertical lower limb exoskeleton rehabilitation robot is researched to study the gait trajectory tracking control strategy in different stages.The main is as follows.Firstly,the kinematics model of human-robot system is established.And then two kind of dynamic model of human-robot system are established according to the rehabilitation stages.Especially during the active stage,the human body and the robot are modeled separately because of the active torque generated by patient.Secondly,the problem of gait trajectory tracking is the most important problem during passive stage.Considering the nonlinearity and uncertainty of the system,a PD feedback control method based on calculated torque and a nonlinear PD feedback control based on robust adaptive method are adopted.The former controller has the ability to decouple the nonlinear of the system,but the gait reference trajectory would just be tracked with bias using it because of the existence of uncertainty.The latter controller has the ability to estimate the upper bound of uncertainty,which leads to the great effect of reference trajectory tracking.The simulation results also prove the effectiveness and robustness of the latter controller.Finally,the effect of the active torque which is generated by patient during active stage on the system’s gait trajectory is studied.The impedance controller can adjust the desired trajectory to a command trajectory which achieves compliance control between human and robot during active stage.The simulation results can prove the effectiveness of compliance training coursed by impedance control.