Error Compensation And Kinematic Calibration Of A Novel Four-degree-of-freedom Parallel Mechanism

The parallel mechanism has always occupied a place in the manufacturing industry because of its high stiffness and strong bearing capacity.However,the precision problem still restricts the development of parallel mechanism.Facing different tasks,the end precision requirements of parallel mechanism are also slightly different.In addition,there is little information about the error research of parallel mechanism with fewer degrees of freedom.In this thesis,the four-degree-of-freedom2UPS+(RPR+R)PU parallel mechanism is taken as the research object.Its characteristics are that it has certain application prospects in clamping handling objects.Therefore,the error modeling and error compensation are carried out for the parallel mechanism,so as to improve the end accuracy of the parallel mechanism,so that the parallel mechanism can be more accurate in the griping handling process.The main research results are as follows:Firstly,based on the 2UPS+(RPR+R)PU parallel mechanism,the structure of the parallel mechanism is introduced in detail,and the inverse solution model of the parallel mechanism is established by geometric method.The forward kinematics model of the parallel mechanism is derived by numerical method,and the solving speed is improved by simplifying the Newton iteration method.The kinematic space of parallel mechanism is analyzed by using Monte Carlo method based on MATLAB platform.Secondly,the source of the error of 2UPS+(RPR+R)PU parallel mechanism is analyzed,and the vector chain error model of the parallel mechanism is constructed by using the vector method.Based on the finite element analysis method,the error analysis of the parallel mechanism was carried out,and the Ansys simulation model was built to reveal the mechanism of deformation error.Based on the interval analysis theory,the sensitivity analysis index function was constructed,and the influence law of the geometric error source of the parallel mechanism on the pose error of the end of the moving platform was obtained,which provided theoretical support for the selection of prototype parts of the parallel mechanism in the future.Finally,the objective function of genetic algorithm is designed based on genetic algorithm,and the nonlinear vector chain error model is transformed into an optimization problem,and then into a minimum problem.The error identification of the genetic algorithm is completed and the kinematics calibration of the parallel mechanism is realized.The simulation calibration experiment was designed with the help of MATLAB platform,and through the analysis of the simulation results,it is verified that the method can complete the error compensation of the parallel mechanism,and effectively improve the precision of the parallel mechanism.