Design And Kinematics Performance Analysis Of A Rehabilitation Mechanism For Cervical Vertebra Traction

This paper proposes a cervical vertebra traction rehabilitation mechanism based on 2-UPR+RPS parallel mechanism to achieve angle traction.The mechanism can not only complete traditional upright traction,but also achieve variable angle traction according to the special requirements of the patients.The mechanism has the advantages of high precision and compact structure,and effectively solves the defect that the traditional cervical vertebra traction equipment can only traction in the upright position and cannot effectively correct the physiological curvature.The paper mainly analyzes and optimizes the performance of the parallel mechanism of cervical traction rehabilitation in the following aspects.1.A cervical traction rehabilitation mechanism is designed.According to the structure,physiological and kinematic characteristics of the human cervical vertebra,and the degree of freedom required for traction,a cervical traction rehabilitation mechanism based on parallel mechanism is designed.The rotation movement in this mechanism adopts 2-UPR+RPS parallel mechanism.It is proved that the mechanism has three degrees of freedom using screw theory and G-K formula,which can achieve the traction action of upright position,forward flexion and extension,and lateral flexion,so as to achieve angular traction and achieve good rehabilitation effect.2.The position of 2-UPR+RPS parallel mechanism is analyzed.Based on closed-loop vector method,a mathematical model of the inverse position solution of the parallel mechanism is established.An example of the corresponding inverse position calculation is calculated using MATLAB.Based on particle swarm algorithm,the forward solution of the parallel mechanism is solved.A flowing particle swarm optimization algorithm is presented.Through the comparison of the positive and inverse solution,the correctness of the solution is verified3.The kinematics performance of the 2-UPR+RPS mechanism is analyzed.The variations of the velocity and acceleration of the parallel mechanism are obtained using derivation method.The Jacobian matrix is derived.An example is given to calculate the curve of the velocity and acceleration.A virtual prototype model is established.and give a certain trajectory for kinematics simulation.The simulation results show that the movement process of the cervical rehabilitation mechanism is smooth and the cervical traction process is safe.4.The reachable workspace of the 2-UPR+RPS mechanism is solved.The single singularity and constraints affecting the workspace of the 2-UPR+RPS parallel mechanism are analyzed.The point set diagram of the reachable workspace of the parallel mechanism is obtained using numerical search method,which is compared with the reachable workspace simulated by boundary search method.Taking the maximum rotation angle of the parallel mechanism as the optimization objective,the size of the parallel mechanism is optimized using flow particle swarm algorithm.5.The dexterity of the optimized 2-UPR+RPS parallel mechanism is analyzed.The performance atlas and its changing trend of the dexterity with the change of ?,? and z,using the dexterity evaluation index of Jacobian matrix.The results show that the optimized mechanism has excellent motion performance and the rotation range is obviously increased.It can satisfy the requirements of angular traction to the greatest extent.The cervical traction rehabilitation mechanism based on 2-UPR+RPS parallel mechanism will have a wide range of practical value.