Research On Key Control Technology For Gait Trajectory Tracking Of Lower Limb Exoskeleton Robot

Lower extremity exoskeleton robot is equipment used to enhance the human lower extremity movement ability.This topic focuses on the application of lower extremity exoskeletons in the field of rehabilitation medicine.It will conduct research from six aspects: the mechanical structure,dynamic model,hardware control system,control strategy,Simulink simulation,and single joint control experiment of lower extremity exoskeletons.The structure of the exoskeleton and the embedded system are the hardware basis for the research of completing the subsequent control algorithm.In the design of the mechanical structure,the anatomical surface of the human body and the gait phase of the lower extremities were analyzed,the driving method of the exoskeleton was selected,and the mechanical structure of the exoskeleton of the lower extremities was determined using a four-degree-of-freedom link mechanism at the hip joint of each leg The sagittal plane degrees of freedom of the knee joint are set to be actively driven,and the experimental prototype is assembled according to the Solid Works design drawing.Then plan the control system,select the sensors,determine the control board and electric cylinder on the hardware,and then build the embedded control system.By collecting the patient's joint motion data,the fuzzy sliding mode control controller is used to correct the system errors in real time,so that the exoskeleton robot can accurately follow the set gait trajectory,and the patient's lower limbs can undergo repeated movements to promote blood circulation.Enhance the patient's muscle activity and encourage them to gradually achieve the purpose of normal gait movement.In the dynamic modeling of the lower extremity exoskeleton,one leg of the lower extremity exoskeleton is mapped to a two-degree-of-freedom link mechanism,and the mechanism is dynamically modeled using the Lagrangian method,and the relationship between the exoskeleton rotation angle and the displacement of the electric cylinder is analyzed,and the collected gait angle is converted into the displacement of the electric cylinder.Aiming at this model,a fuzzy PID control algorithm and a sliding mode control algorithm with fuzzy switching gain adjustment based on reaching law are proposed,and Lyapunov stability analysis is performed on the control law to verify the stability of the control strategy.In addition,by blurring the switching gain,the influence of uncertain terms is offset,so that after the system reaches the sliding mode surface,it can be kept on the sliding mode surface.Simulink control block diagrams are constructed for fuzzy PID controller and fuzzy sliding mode controller respectively.The simulation compares the tracking effect of fuzzy PID algorithm and fuzzy sliding mode control algorithm on the input curve without disturbance and disturbance.In the case of both,both controllers can follow the target curve well,and at the same time,under the effect of strong disturbances,the fuzzy sliding mode control algorithm has a small overshoot and strong stability compared with the traditional fuzzy PID algorithm.Finally,through the human gait curve tracking experiment of the hip joint,it is found that the fuzzy PID controller has a large error in the initial position,and overshoot occurs at the peak and trough,and the fuzzy sliding mode controller can accurately follow the target curve,in addition,further conducted experiments on the hip and knee joints with normal human gait data.The experimental results verified the effectiveness and superiority of the fuzzy sliding mode control algorithm,and realized the effective tracking of the human gait curve by the lower exoskeleton.