| Rehabilitation robot is a kind of medical robot,which can assist human body to complete the movement function of limbs and joints,so as to realize human rehabilitation treatment,assist walking,and evaluate the movement ability of patients.At present,most of the rehabilitation mechanisms for human joints reported in the literature are for the rehabilitation of a single human joint.This paper designs a PPPS-CRR multi-functional rehabilitation mechanism,which can carry out rehabilitation training for ankle joint and wrist joint of human body with different rotation centers through adjustment,and carries out kinematic analysis and rehabilitation effect evaluation for this mechanism.Firstly,based on the physiological structure and movement mechanism of ankle and wrist joints,as well as the main muscles involved in the movement,the rotation center of the ankle joint is located in the ankle fossa above the heel,while the rotation center of the wrist joint is located at the end of the forearm.In order to better realize the rehabilitation movement of ankle and wrist joints,it is necessary to make the rotation center of each joint coincide with the rotation center of the mechanism.A PPPS-CRR traction ankle and wrist rehabilitation mechanism is proposed.The mechanism is designed with an adjusting device,which can adjust the rotation center of the mechanism.Based on screw theory,the mechanism has four degrees of freedom,i.e.3 rotations and 1 translation.It can realize the dorsiflexion / palmar flexion,ulnar deviation(adduction)/ radial deviation(abduction)of wrist joint,and internal / external rotation of the forearm;it can also realize dorsiflexion /plantar flexion,adduction / abduction,inversion / eversion of ankle joint,as well as the stretching movement of ankle joint along the lower leg.Secondly,the kinematic analysis of the PPPS-CRR rehabilitation mechanism is carried out.The forward and inverse solution of the mechanism’s position is solved using geometric method.Because of the dorsiflexion / plantar flexion,adduction / abduction of ankle joint,and dorsiflexion / palmar flexion,ulnar deviation / radial deviation of wrist joint are all controlled by two mutually unaffected drivers on the PPPS limb,given the different driving velocities and accelerations of the drivers,the mechanism can realize a single movement or a compound movement.Through Motion analysis,the workspace of the mechanism is obtained.The first-order and second-order motion influence coefficient matrices are obtained by deriving the inverse position solution.Then the statics analysis and finite element analysis of the mechanism are carried out.The variations of the stress and strain of the mechanism under static load are analyzed.Then,comprehensively using Adams and Solid Works software,the PPPS-CRR rehabilitation mechanism is modeled and the kinematics is analyzed.The stability of the mechanism in the process of movement is analyzed using STEP function.The inverse kinematics of the mechanism is analyzed.Given the joint motion angle,the variation of the displacement of the driven output is obtained,so as to optimize the dimension of the mechanism.Finally,using AnyBody biomechanics modeling software and its programming language,the man-machine system is integrated,and the AnyBody human body model is connected with the PPPS-CRR rehabilitation mechanism.During the inverse kinematics simulation of the ankle joint and wrist joint,through setting the initial posture,initial angle,and driving velocity of the joints,the variations of the force on the main muscles,muscle expansion amount and muscle activity when theankle and wrist joints do rehabilitation exercises,so as to obtain the evaluation value of the PPPS-CRR rehabilitation mechanism on human body rehabilitation effect. |
