Research On Active And Passive Control Strategy Of Lower Extremity Exoskeleton In Rehabilitation

The rehabilitation lower limb exoskeleton robot is a medical device designed to assist patients with lower limb motor function impairment in rehabilitation training.In recent years,due to the increasing number of patients with lower limb hemiplegia,the combination of robotics and rehabilitation medical engineering is a hot research topic at home and abroad,and wearable exoskeleton robots are a typical product of this combination.Using a rehabilitation lower limb exoskeleton robot to provide efficient and intelligent rehabilitation training for patients with lower limb hemiplegia effectively makes up for the shortcomings of traditional rehabilitation and the low efficiency of rehabilitation.Therefore,during the rehabilitation stage,limbs and exoskeletons should have good follow-up,and repetitive exercise should be used to prevent muscle atrophy.Moreover,it is also necessary to consider the patient’s active motor intentions and allow the patient to actively participate in the rehabilitation training process to achieve the goal of helping patients with lower limb hemiplegia recover.Therefore,the following research work has been carried out in this article:(1)Research on kinematics and dynamics of rehabilitation lower limb exoskeleton robot.The kinematics model of the exoskeleton robot is established by D-H method,and the relationship between the position of the end effector and the joint angles is solved;The Lagrange method was used to solve the driving torque of each joint of the rehabilitation robot during movement,providing a theoretical basis for active and passive control in the following text.(2)Research on gait planning of rehabilitation lower limb exoskeleton robots under passive control stage.Using the three-point programming method,the displacement and angle equations of the hip and knee joints of the rehabilitation robot’s swinging leg were listed,and reasonable gait parameters were selected.Solved the walking angle,displacement curve,and motion speed of the hip and knee joints.Secondly,based on the dynamic trajectory equation,the ZMP trajectory curve for stable walking of the rehabilitation robot was solved,and the hip joint parameters were optimized using the artificial bee colony algorithm to make the designed gait curve more in line with the actual human walking pattern.(3)Research on trajectory tracking control methods for rehabilitation lower limb exoskeleton robots.The feedback linearization theory is used to transform the lower limb exoskeleton robot,a nonlinear system,into a linear controllable system.The unmodeled dynamic term is compensated by the sliding mode term,the whole process robustness of the control system is guaranteed by the integral sliding mode surface,and the chattering phenomenon is greatly weakened by using the saturation function instead of the symbolic function.The feedback linearized integral Sliding mode control has better robustness and faster response time by using fuzzy system to approximate the sliding mode term of the control law.Finally,by analyzing the unit step response under external disturbance,it is proved that feedback linearized integral Sliding mode control has better robustness than single feedback control,Sliding mode control and PD control.(4)Research on active control methods for rehabilitation lower limb exoskeleton robots.Firstly,the patient’s thighs and the exoskeleton robot’s thighs were considered as a "mass spring damping" system,and a position impedance controller was further designed to explore the influence of target impedance parameters on the control system.The impedance parameters were optimized using particle swarm optimization algorithm to ensure that the control system still has good force tracking performance in the presence of modeling errors and external interference.Using the reference model adaptive method to design PID feedback terms,the problem of poor robustness in position impedance control is solved by indirectly adjusting the system’s impedance.This enables impedance control to adjust impedance parameters in a timely manner when facing changes in the external environment,improving the system’s adaptive ability.