Dynamics Model-based Auto Disturbance Rejection Control For Exoskeleton

The lower limb exoskeleton is a wearable intelligent walking aid.It can provide assistance for the elderly with dyskinesia in the lower limbs during standing and walking,improve the quality of life for the elderly effectively,and then alleviate the pressure of social and family pensions.Therefore,the analysis and research of the lower limb exoskeleton has important theoretical significance and application value.The paper mainly studies the movement of human body under five kinds of road conditions?the dynamics modeling of human-exoskeleton coupling and the control strategy of lower limb exoskeleton.The main contents are as follows:Firstly,the VICON MX three-dimensional gait information acquisition platform is used to collect the hip?knee and ankle joint angles of the normal human in five kinds of road conditions: flat,up/down stairs and up/down slope.According to the collected angle information,the human walking mode and walking torque under different road conditions are analyzed,which lays a foundation for the subsequent exoskeleton control.Secondly,the D-H coordinate system is established for the human and the exoskeleton respectively.The base coordinate of the right toe is selected,and local coordinates are established at other joints.Based on the D-H coordinate system,the dynamics model of human-machine is established according to the Newton-Eulerian equation.The interaction between human and exoskeleton is simplified to the elastic force added to the dynamics equation,which constitutes the dynamics model of human-exoskeleton coupling.A virtual model of the human body wearing exoskeleton is established in Adams,and the joint torque calculated by the dynamics equation is added to verify the correctness of the established dynamics model.Finally,based on the control idea of self-disturbance,the control framework of the lower limb exoskeleton is established.The extended state observer module is used to estimate the exoskeleton state variables and external and internal disturbances of the lower extremities.The total disturbance is compensated by the controller.In order to improve its response speed and robustness,sliding mode control is added to complete the auto disturbance rejection-based sliding mode control of the lower limb exoskeleton.Then the simulation model is built on the Simulink simulation platform,and the control method is simulated and verified.The simulation results show that the sliding mode control based on Auto disturbance rejection has good control effect and strong anti-disturbance ability for lower limb exoskeleton.