Analysis And Optimization Design Of (PRS+PUR+PUS)+(UPR+RCR) Hybrid Mechanism

Hybrid mechanism,which combines the advantages of series mechanism and parallel mechanism,has the characteristics of good rigidity,large working space and attitude Angle,etc.,and is widely used in industrial production.In this paper,a new five-degree-of-freedom hybrid mechanism is proposed,the kinematic model of the hybrid mechanism is established,and the performance of the hybrid mechanism is optimized.The main research contents are as follows:In this paper,a hybrid mechanism(PRS+PUR+PUS)+(UPR+RCR)is proposed,and the properties of degrees of freedom of the mechanism under general orientation are analyzed.Secondly,the kinematic model of the hybrid mechanism was constructed.Starting with the constraint equations of single-layer PRS+PUR+PUS and UPR+RCR mechanisms,the positive and negative solutions of the sub-parallel mechanism were calculated respectively.Based on Sylvester junction elimination method,the analytical solution of the inverse position solution of the hybrid mechanism is solved,and the positive position solution of the hybrid mechanism is solved by superposition method.Then the velocity models of the sub-mechanism and the whole machine are constructed according to the closed-loop vector equation method.Finally,Soild Works software was used to draw the 3D sketch and assembly model of the hybrid mechanism,and the kinematic model of the hybrid mechanism was verified.Then,according to the coupling equation of the end pose of(PRS+PUR+PUS)+(UPR+RCR)mechanism and the homotopy algorithm,the numerical solution model of the inverse solution of the position of the hybrid mechanism was established.Based on this,the reachable workspace of the hybrid mechanism was solved.Meanwhile,the maximum tangent circle in the reachable workspace was set as the task workspace and solved.The space utilization index was established according to the volume ratio occupied by the task workspace and the reachable workspace of the hybrid mechanism.Based on LTI index of parallel mechanism,GTI index of hybrid mechanism was established.The stiffness model of hybrid mechanism was established,and the maximum linear deformation of unit load/moment was defined as the stiffness index of hybrid mechanism.Finally,NSGA-Ⅱ algorithm was used to optimize the size of the hybrid mechanism.Secondly,based on the closed-loop velocity equation,the angular velocity,angular acceleration and linear acceleration models of each branch of the hybrid mechanism were solved.Based on the principle of virtual work,the rigid body dynamics model(PRS+PUR+PUS)+(UPR+RCR)was solved by using the mapping relationship between velocity and acceleration of sub-parallel mechanisms and hybrid mechanisms.Finally,a prototype of the hybrid mechanism(PRS+PUR+PUS)+(UPR+RCR)was built,the mechanical components were introduced,and the components of the control cabinet were briefly described.At the same time,pose and stiffness experiments were carried out on the sub-mechanism and hybrid mechanism prototype,which verified that the hybrid mechanism had good pose and stiffness performance.