Lower Limb Exoskeleton Based On Series Elastic Actuator Research On Hip Joint Design And Control Method

With the development of modern society,the introduction of wearable exoskeletal devices has provided people with better experience and security in their work and life.At this stage,weight-bearing exoskeletons that help the human body to lift weights or rehabilitation exoskeletons that help the human body to recover have obtained more research results,but the research on assisted lower limb exoskeletons is still insufficient.Assist-type robots assist the wearer by simulating human leg movements and function in rugged environments,such as disaster sites and jungle mountains.Most of the domestic and foreign researches use rigid drive,which has the problems of insufficient flexibility and poor safety.Therefore,in this paper,we design a hip exoskeleton based on a flexible tandem elastic actuator,and based on this,we model the system,design the control algorithm and validate it.The main research contents and results of this paper are as follows.(1)Design of hip joint structure based on tandem elastic actuator.Firstly,by analyzing the human walking state,the range of motion and structure of the hip joint are analyzed,and the size and driving scheme of the tandem elastic actuator are determined.Secondly,the connection structure was optimized,and the joint size design and drive system selection were completed.Finally,the three-dimensional model of the tandem elastic actuator was constructed.(2)Sliding mode control of hip joint based on finite time dilation state observer.The object of the assisted exoskeleton is a healthy population,on the one hand,there is no deficiency in human locomotion,and it can complete some movements autonomously,so there is a problem of matching human-computer movements,and secondly,the gait activities are more complex and diverse.This will increase the uncertainty in the control.Therefore,in order to ensure the tracking control effect,this paper adopts the robust sliding mode control method.First,the lower limb exoskeleton with rigid joints is controlled,the control system is designed and the hip exoskeleton control system design is completed accordingly.Then,the dynamics model is determined according to the designed tandem elastic actuator,the flexible joint is added to the lower limb exoskeleton,and the sliding mode control algorithm is used to target the trajectory tracking control,and the disturbance is estimated using the expanded state observer as a negative feedback to compensate the internal uncertainty of the system,and the internal uncertainty and external disturbance of the system are regarded as the expanded state to enhance the stability.(3)Joint simulation validation based on ADAMS and MATLAB.Firstly,the joint simulation of the rigid lower limb exoskeleton sliding mode control algorithm is carried out,based on which the joint simulation of the flexible lower limb exoskeleton sliding mode control algorithm is carried out in conjunction with the SEA control in Chapter 4.The results show that the sliding mode control algorithm designed in this paper using a finite-time dilated state observer can better track the human gait trajectory compared with no observer.