Time-optimal Trajectory Planning of 6-RUS Parallel Robots Based on Grid Search Algorithm

Aiming at the problems of uneven reproducing trajectory and low trajectory planning efficiency of 6-RUS parallel painting robots, a trajectory planning method of optimal time of 6-RUS parallel painting robots was proposed based on optimizing the position of Bezier curve nodes. Firstly, the preprocessed trajectory was discretized to grid points, the node parameters were updated and the arc length of Bezier curve was optimized, and the path of small line segment was further fitted to obtain the optimal geometric path. Then, the optimal velocity corresponding to different coarse grid points and the solution time were calculated, and the appropriate coarse grid points were selected. The paths between grid points were further densified by small steps, and the forward and backward maximum velocity were iteratively solved. The maximum feasible velocity curve of the path was searched to obtain the optimal running time of the 6-RUS parallel robots. Finally, the experiments were carried out on a self-developed 6-RUS parallel robot platform. The results show that under the same teaching trajectory, the path length of the improved Bessel curve algorithm herein is as 8.12 m, which is better than that of traditional Bezier curve and G2CBS(G2 continuous cubic Bezier spiral) algorithm. Meanwhile, the improved time-optimal path parameterization algorithm herein was used for the optimized teaching path. The solution time of the optimal velocity curve of the algorithm herein is as 416.4 ms, which is 244.7 ms less than that of TOPP-RA algorithm. Moreover, the time-optimal trajectory planning time of the algorithm herein is also better than that of TOPP-RA algorithm. The method improves the solving speed of the optimal velocity, shortens the track reproduction time of 6-RUS parallel robots, and improves the working efficiency. © 2023 China Mechanical Engineering Magazine Office. All rights reserved.