Research On Human-robot Cooperative Control Technology Of Lower Extremity Exoskeleton

The wearable lower extremity exoskeleton robot is a typical human-robot coupling system,which requires the coordination of the exoskeleton and the human body movement state,thereby assisting the human body movement and improving the human body’s sports function.This paper studies the trajectory following control technology of the lower limb exoskeleton driven by compound Bowden-cables transmission;designing a human-robot cooperative control system to control the exoskeleton to assist the human body and improve the human body’s sports function.First,this paper analyzes the characteristics of the compound Bowden-cables transmission and establishes the model of the Bowden-cables transmission.Analyzing the structure of the exoskeleton of the lower extremity,establishes the dynamic model of the lower extremity exoskeleton according to the Lagrange equation.Then,according to the interaction force between the human and the exoskeleton,the dynamic model of human-robot coupling is established.Combined with the friction model,the static and dynamic experiments of friction parameter design in the human-robot coupled model are identified offline.Second,this paper designs the hardware and software of the exoskeleton control system.By analyzing the design requirements of the exoskeleton control system,the industrial computer is selected as the main control device,and the sensor system of the exoskeleton system is designed for real-time measurement of exoskeleton movement information.The host computer software is designed to monitor and regulating exoskeleton,which has laid the foundation for the subsequent algorithm.Subsequently,this paper designed a trajectory following control algorithm for the handicapped’s lower extremity movement disorder.Since the compound Bowden-cablesdriven exoskeleton system is a typical nonlinear system,a fuzzy PD control algorithm is designed to control the movement of the exoskeleton system,which improves the tracking hysteresis of the control system.In order to improve the trajectory control effect,a sliding mode controller is designed based on the human-robot coupled dynamic model,and obtains a small base following error and a faster response following effect,but the system has small jitter.Therefore,based on the optimization of the sliding mode controller,a sliding mode controller based on fuzzy gain is proposed,which further reduces the trajectory following error value.By analyzing and comparing the experimental results of the three controllers,it is concluded that the control effect of the sliding mode controller based on fuzzy gain is optimal.When controlling the lower extremity exoskeleton to assist the human body,it needs to constantly adjust the human-robot interaction state.In order to better realize the human-robot cooperative motion control,this paper uses the orthogonal encoders and the human-robot interaction force sensor to identify the human body’s movement intention through the RBF neural network.By analyzing the gait phase of the human body,an impedance control strategy is designed,and the output of the controller is adjusted by setting a target penalty function to realize human-robot cooperative control.Finally,this paper designs a human-robot cooperation evaluation system for the performance of exoskeleton,which mainly evaluates from three aspects: load reduction,boosting effect and wearing flexibility,and designs corresponding performance evaluation indexes.Comparative experiments on the design of a human-robot cooperation control system,and through data analysis of the sensor detection module,it is proved that the exoskeleton robot has a certain boosting effect on the human body and can improve the human’s sports function.