Kinematic Analysis and Multi-objective Optimization of Novel 2URU-2RSS Parallel Robot Mechanism
A semi symmetric 2URU-2RSS parallel robot mechanism was proposed,consisting of 4 branch chains,with a compact structure and good rotational performance.According to the theory of directional feature sets,the motion and degree of freedom properties of the mechanism were studied.Based on the rod length constraint,a kinematic equation was established,and the forward and inverse po-sition solutions were obtained.Two sets of numerical examples were used to analyze and verify the correctness of the motion equation so-lution.At the same time,by planning the spiral motion of the space,the change of the driving pairφi was studied,so as to verify the mo-tion performance of the mechanism.The Jacobian matrix was used to determine the forward singular configuration and the reverse singu-lar configuration,and the spatial distribution patterns of the maximum and minimum rotation angles of the moving platform in the theo-retical workspace and the reachable workspace of the mechanism were analyzed respectively.The influence trend of different structural parameters on the performance was studied.Finally,the utilization rate of the full cycle rotation capacity in the task workspace was pro-posed as an evaluation indicator to reflect the actual rotation capacity,and the task workspace utilization rateηand the full cycle rotation capacity utilization rate μwere established as optimization objectives.NSGA-II algorithm was selected to obtain the Pareto optimal scale parameter solution,and numerical analysis was conducted to verify the effectiveness of the target model.The results show that the index of the whole cycle turning ability in the task workspace can be up to 99%,and the utilization rate of the task workspace can be up to 40%.The overall performance of the mechanism is greatly improved.
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