Design And Performance Analysis Of Hybrid Elbow Wrist Joint Rehabilitation Mechanism

Elbow joint and wrist joint are the most common joints in daily life and work.They are also the most vulnerable joints.Reasonable and effective rehabilitation training is very necessary to recover after injury.In this paper,combining the physiological structure,movement characteristics and medical rehabilitation theory of the elbow and wrist joints,a hybrid elbow wrist joint rehabilitation mechanism is proposed,and the kinematic performance of the mechanism is studied,and the evaluation method of the rehabilitation effect is discussed.Firstly,based on the anatomical theory of human elbow and wrist joints,clinical medicine and medical rehabilitation theory,the structure and motion mechanism of human elbow wrist joint are analyzed,and the configuration of elbow and wrist joints rehabilitation mechanism are determined.According to the requirements of rehabilitation training after elbow wrist injury,a type of(2-RPU-RPS)&RR hybrid elbow wrist rehabilitation mechanism based on2-RPU-RPS parallel mechanism is proposed.The mechanism has five degrees of freedom,which can realize palmar flexion/ dorsiflexion,adduction/abduction,internal rotation/external rotation of the wrist joint,and the flexion and extension of the elbow joint in a single way.It can also combine various forms of motion to carry out compound motion.Secondly,the movement screw matrix of 2-RPU-RPS parallel mechanism is established by using screw theory,and the modified Kutzbach-Grübler formula is used to verify the obtained degrees of freedom.Based on the structural characteristics of the mechanism,the constraint equation is established,and the inverse position solution of the parallel mechanism is obtained using closed-loop vector method.The particle swarm optimization(PSO)algorithm is used to construct the optimal solution equation,and the corresponding positive solution example is obtained,and the best fitness curve of the positive solution of the mechanism position is obtained in Matlab.The reachable workspace of the mechanism is obtained by using three-dimensional dynamic method and numerical search method.The results show that the workspace of the mechanism is continuous and there is no cavity in the range of parameters,and the kinematic performance of the mechanism is good.Thirdly,based on the inverse position equation,the first-order motion influence coefficient matrix of 2-RPU-RPS parallel mechanism is obtained,the second-order influence coefficient matrix of the mechanism is obtained by deriving the velocity mapping equation,the force Jacobian matrix of the mechanism is obtained through the first-order influence coefficient matrix,the obtained results show that the velocity mapping and force mapping between the drive input of the parallel mechanism and the moving platform have a dual relationship.The dynamic model of the parallel mechanism is established.The dynamic equation obtained can be used to calculate the input torque when the motion is known,or the motion of the system when the input torque is given.Then,use the Solid Works software to model the virtual prototype of the(2-RPU-RPS)&RR hybrid rehabilitation mechanism,and import it into the Adams software for kinematics simulation analysis.By setting different Step functions,the forward and inverse kinematics of the 2-RPU-RPS parallel mechanism are analyzed,and the correctness of the position solution is verified.Then,the variation laws of motion,angular velocity and angular acceleration with time of the output end of the hybrid rehabilitation mechanism during rehabilitation training are measured.The results show that can meet the rehabilitation needs of human elbow and wrist jointsFinally,the inverse dynamic model of human upper limb is constructed by Any Body software,and the human-machine interaction system of rehabilitation mechanism and human model is established on this basis.By setting the corresponding Anyscript statement,the inverse dynamics analysis of the system model is carried out,it is concluded that the maximum activity of muscle group is less than 1 under the different rehabilitation training modes,which does not exceed the maximum strength that the muscle can bear.The main muscles involved in various motion are selected and the changes of muscle length and force are studied in depth.The results show that the relevant muscles of the patient have been effectively exercised during the rehabilitation training process.It is proved that this rehabilitation mechanism can be well applied to the rehabilitation training of elbow and wrist joints,which provides a theoretical basis for making a more reasonable rehabilitation effect evaluation strategy.