Control System Research Of Hydraulic Driven Lower Limb Exoskeleton In Swing Phase

In recent years,prototypes of lower limb exoskeleton robot have been developed tremendously and were mainly designed for assistance and medical rehabilitation.As a typical human-machine interactive robot,lower limb exoskeleton is a cross-disciplinary integration including mechanics,electronics,computer science,cybernetics,bionics and other high-tech fields.As hydraulic driven lower limb exoskeleton is also an application of nonlinear system,how to achieve friendly human-machine interaction,which means the exoskeleton can provide maximum force assistance without affecting the flexibility of the wearer,is a systematic research subject.In chapter ?,the background and significance of lower limb exoskeleton robot are introduced based on a large number of state-of-the-art domestic and foreign literature.In chapter ?,the parameters of the system are optimized by CAD(Computer Aided Design)and numerical calculation method and other tools.Then,a three-dimensional model of hydraulic driven lower limb exoskeleton is developed using SolidWorks.Based on the model,hydraulic system and electrical control system are designed to complete the construction of the final lower limb exoskeleton platform.Kinematic model and dynamic model of the hydraulic driven lower limb exoskeleton are built in chapter ?.In the lower controller of the model,three methods are proposed by building nonlinear model of hydraulic cylinder so as to overcome the problems caused by the traditional DLS method when solving the singular problem of the inverse Jacobian matrix in wearable robots.Finally,these methods are verified by MATLAB simulation.In chapter ?a novel method is first introduced by this paper where the process of inferring wearer's motion intention is divided into two subsystems.The first subsystem captures the real-time phase of the leg of the lower limb exoskeleton.This function relies on the multi-sensor system in the shoes.In the second subsystem,the physical information of the body is obtained by installing multi-axis force sensors installed between wearer and exoskeleton and introducing an admittance model as a motion intention inferring method to form a connection between the wearer and the human-machine interaction force.Finally,an architectural diagram of the overall human-machine interaction system is established to clarify the different effects of the upper and lower controller.In chapter ?,in order to solve the nonlinearity and unknown disturbance of the hydraulic driven lower limb exoskeleton,sliding mode control is introduced.Moreover,integral sliding surface is introduced to decrease the steady-state tracking error.However,the integral wind-up effect may emerge because of the initial tracking error.To solve this problem,two methods are proposed in the paper.Reaching law is also introduced to improve the effect of the reaching process.The effect of the controller is verified by MATLAB simulation.To decrease the chattering problem and improve the smoothness,fuzzy logic controller is adopted to approach the disturbance torque.Comparative experiments are given to demonstrate the effectiveness and robustness of the proposed approaches.In chapter ??considering the difficulty to get the precise dynamic model of the nonlinear robot system,the model-based controller is restricted in hydraulic driven lower limb exoskeleton.Therefore,an improved single input direct adaptive fuzzy sliding mode controller is proposed in this paper,which combines the general approximate characteristic of fuzzy system and strong robustness of adaptive system.Comparative experiments are given to demonstrate the effectiveness and robustness of the proposed approach.In chapter ?,the major work of the study is summarized,and the conclusions and innovations of the study are elaborated.