Design Of A Cable-driven Ankle Rehabilitation Robot With Flexible Equivalent Axis

The proportion of elderly people in China’s social population is increasing,and the number of patients with impaired ankle motor function due to stroke,sports sprains,and traffic accidents is rapidly increasing.Using ankle rehabilitation robots to replace traditional doctors for rehabilitation treatment is the future development trend.However,the current research on ankle rehabilitation robots mostly uses rigid structures to achieve motion function goals,with little consideration given to the adaptation of mechanism motion to human ankle motion characteristics,as well as the human-machine coupling effect in the rehabilitation process.Aiming at the problem of mismatch between machine and human ankle joints during the movement of traditional ankle joint rehabilitation robots and poor human-machine coupling performance,which can easily lead to additional joint loads,this paper proposes a design scheme of a rope driven ankle joint rehabilitation robot with a flexible equivalent axis.The specific work content of the paper is as follows:Firstly,starting from the physiological structure and motion characteristics of the ankle joint,the functions of the bones,muscles,and ligaments of the ankle joint,as well as the changes in axial motion during dorsoplantar flexion and varus movements,are studied.Based on this,a flexible equivalent axis rope driven ankle rehabilitation robot human design configuration with composite motion is proposed,and an equivalent simplified model of the ankle joint is established based on the axial characteristics of the ankle joint to solve the motion space of the ankle joint.Secondly,based on the proposed robot configuration,a three-dimensional structure of the ankle rehabilitation robot is designed,and the kinematics and dynamics of the robot are analyzed.The workspace of the robot is solved.By comparing the motion space of the ankle and the workspace of the robot,the completeness of the robot’s motion function is verified.Thirdly,a human-machine coupling dynamics model and simulation model were established to solve the variation law of human-machine coupling joint torque during the motion of the human-machine coupling system.The ankle joint motion curve of healthy individuals was compared with the human-machine coupling motion curve.The results show that the torque value of the human-machine coupling joint is small and changes smoothly,and the burden on the joints during the robot movement is relatively small.The movement trend and range of the robot are similar to those of the ankle joint,verifying that the robot has good human-machine coupling characteristics during the movement process.Finally,a prototype of the ankle rehabilitation robot was built and motion function experiments were conducted under both no-load and human-machine coupling states.During the experiment,the motion angle of the system was collected through attitude angle sensors,and the actual motion angle of the ankle joint was compared to verify that the motion performance of the rehabilitation robot can meet the requirements for the use of the rehabilitation ankle joint.