| The motion accuracy is one of the most important performance index of parallelrobot, which directly influences the working performance of parallel robot andrestricts the further development of parallel robot. In order to improve the motionaccuracy of parallel robot, it is essential in both theory aspect and practical aspect tostudy the compensation method for motion error. In this paper, based on thecomprehensive analysis on the research status of the influence factors andcompensation method for the motion accuracy, the mechanism error and the flexibleerror are taken into consideration and the corresponding compensation model isestablished respectively. Then a comprehensive compensation method for motion erroris proposed which can be implemented in trajectory planning process to improve themotion precision. The detail works are as follows:Firstly, the mechanism error model of parallel robot is established based on theclosed loop vector method, and variation rules of the mechanism error are obtained bythe simulation analysis. The flexible error model of parallel robot is established basedon the finite element theory and Lagrange equation, and the entropy model of flexibleerror is established to quantitatively describe comprehensive energy of flexible error.Then the simulation analysis of the flexible error is conducted to obtain the variationrules of the flexible error.Secondly, the compensation method for mechanism error and flexible errorimplemented in the trajectory planning process of parallel robot are researchedrespectively: Based on the mechanism error model of parallel robot, a mechanismerror compensation method based on the improved particle swarm optimizationalgorithm is proposed to correct the desired trajectory in joint space of drive rod.Meanwhile, according to the flexible error model of parallel robot, a trajectoryoptimization method for drive rod based on the flexible error entropy and groupsearching algorithm is designed to compensate the flexible error of parallel robot. Atlast, the simulation analysis is conducted respectively to verify the compensation methods for mechanism error and flexible error of parallel robot.Furthermore, a comprehensive error compensation model implemented intrajectory planning process of parallel robot is established based on the compensationmethod for mechanism error and flexible error. The coupling error of the mechanismerror and the flexible error produced in the comprehensive compensation model isanalysed and a compensation strategy for the coupling error is presented. The validityof the comprehensive compensation method for the motion error is demonstrated bysimulation analysis.Finally, the experimental work is carried out based on the parallel kinematicsmachine. The modeling of mechanism error and the flexible error are realized basedon the analysis of the parallel kinematics machine. Based on the proposedcompensation method, a comprehensive compensation model for motion error of theparallel kinematics machine is established. And the feasibility and effectiveness of themethod is validated by the simulating experiment conducted on the parallel kinematicsmachine. |
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