Dynamic Modeling And Analysis Of 2UPR-RPU Parallel Manipulator

With the application of parallel manipulator in industry robots,PM shows more and more advantages.But research of parallel mechanism has some defects,now the research of parallel mechanism is mainly concentrated in the aspect of kinematics.Kinematics research is far from enough only in the real-time control.It needs to consider effect of external forces when the mechanism working,so it’s very important to study the dynamic about the mechanism.In this dissertation,the 2UPR-RPU parallel mechanism is taken as the research object,the kinematics,dynamics and dynamic performance of the mechanism are analyzed.The main research contents include:The degree of freedom and kinematics of 2UPR-RPU parallel mechanism are analyzed.The DOF of the 2UPR-RPU parallel mechanism in initial configuration and general configuration is analyzed.The results show that the mechanism has three degrees of freedom with two rotations and one translation.The kinematics analysis of the mechanism is presented,and the inverse positional solution of the mechanism is obtained by the closed-loop vector method.The mapping relationship between the moving platform velocity and generalized velocity is obtained.Lagrange method is used to establish the dynamics model of 2UPR-RPU parallel mechanism.The velocity of the links and the moving platform is analyzed by the rigid body elementary kinematics.The total energy of the mechanism is obtained by the method of energy superposition.The Lagrange function is established.The inverse dynamic equation of the mechanism is obtained by Lagrange method and verified by ADAMS.The dynamic modeling of 2UPR-RPU parallel mechanism is carried out by screw theory.The branch coordinate system is established,and the transformation matrix of the branch is obtained.The velocity and acceleration of the branch and the moving platform are analyzed by using the screw theory.Inverse dynamics model is established by principle of virtual work,verified by ADAMS.Two methods are compared and analyzed.The modeling process of Lagrange method is simple,but a lot of differential calculation is applied,and the operation complexity is high.The modeling process of screw theory is easy to understand and does not involve differential operation.The dynamics equation is concise.Comprehensive consideration,the screw theory method is more suitable for parallel mechanism dynamics modeling.Dynamic performance of the mechanism in rotation and translation is analyzed based on the index of dynamic manipulability ellipsoid.The performance diagram of the inertial ellipsoid of the mechanism is drawn and analyzed.The performance of the mechanism in the working space is obtained,which provided theoretical basis for dynamic control of the mechanism in the future.The research work in this dissertation provides strong support for dynamic control of 2UPR-RPU parallel mechanism,and is instructive to the practical application and development of 2UPR-RPU parallel machine tool.