Research On Soft Exoskeleton Robot For Ankle Rehabilitation Training

In recent years,the number of patients with impaired ankle function caused by stroke hemiplegia is very large and increasing every year.Therefore,it is extremely urgent to study the wearable exoskeleton robot assisted human ankle movement.Traditional wearable exoskeleton robots are mostly composed of rigid structures connected with human body.Due to the inherent characteristics of human joints,there are some problems between exoskeleton robots and wearers,such as difficult alignment of human-machine joints,large mass of end effectors,inconsistent gait and so on.In order to assist the movement of patients with impaired ankle function more efficiently,this subject is committed to the research of a lightweight and easy to wear soft exoskeleton robot system.The soft exoskeleton robot is a complex human-computer interaction system,involving many disciplines such as mechanics,bionics,human sports biology and so on.Firstly,this paper designs a human gait recognition system to divide the gait phase,and then accurately recognize the human gait and posture.The soft light drive transmits the power to the heel and forefoot of the human body by shrinking the distance between Bowden lines to assist the movement of the human ankle.Finally,the control method of soft exoskeleton robot is studied,and the displacement of inner core of Bowden line is adjusted to realize the tracking control of position trajectory and torque trajectory.The main research contents of this paper are as follows:(1)Design of gait acquisition system:Firstly,the movement mode and mechanism of ankle joint are analyzed.Through the analysis of human gait phase,a portable human gait data acquisition system is designed,mainly including the design of plantar force module based on plantar pressure sensor and the design of posture motion information acquisition module based on IMU.Through the human walking experiment,the feasibility of the designed gait data acquisition system is proved,and then the gait detection and recognition method is designed,which can accurately identify the human gait.(2)Structural design of ankle flexible exoskeleton:According to the structural design requirements of soft exoskeleton robot and the motion mode of ankle joint,the man-machine connection transmission mode is constructed.On this basis,the motion model of exoskeleton robot is established,and the correctness of the model is verified by solution analysis,which provides a theoretical basis for structural design.Considering the requirements of comfort and lightweight of soft exoskeleton robot,a soft wearable device close to the contour of human body is designed.At the same time,considering the requirements of small volume and light weight of the driving unit,a small and highly integrated rope driven modular joint is designed.Based on the design of the above soft exoskeleton,the overall structure design of the robot is finally completed.(3)Research on driving and control methods of soft exoskeleton:Firstly,the requirements of the control system are analyzed,and then the FOC driving principle of the rope driven modular joint and the control methods of position,speed and torque are studied.Aiming at the research on the control method of soft exoskeleton robot.firstly,the generation curve of upper assistance trajectory is planned,The displacement of the inner core of Bowden line is controlled by the control method of pre admittance combined with position PID to track the desired torque trajectory in real time,so as to realize the auxiliary movement of the robot.(4)Experimental study on soft exoskeleton robot:The hardware and software of the soft exoskeleton robot are designed.Firstly,the performance test of modular joint is carried out.Under no-load condition,the sinusoidal trajectory tracking error is only about 0.015 rad,and under load,the error is about 0.02 rad.Then,the wearable walking experiment of the soft exoskeleton robot is carried out.By adjusting the displacement of the inner core of the Bowden line,the wearer’s ankle motion is assisted,the power assisted trajectory tracking is carried out in the support phase,and the ankle angle trajectory tracking is carried out in the swing phase.The experiment verifies that the soft exoskeleton structure and control method designed in this paper are effective.