Study On Spraying Path Planning For Complex Free-form Surface

Spraying robots have been widely used in the surface spraying operation of automobile,ships,furniture and other products.A reasonable spraying path can improve spraying quality and efficiency,reduce paint waste and energy consumption.Complex free-form surfaces are more difficult to plan than elementary analytic surfaces because of their irregular geometry,arbitrary surface curvature and complex topological features.This thesis focuses on the key technology of spraying path planning for complex free-form surfaces.The main research includes the following three aspects:(1)A spraying path planning algorithm based on direction’s priority level is proposed to address the holes on the workpiece surface.First,the workpiece surface is represented as a twodimensional raster map.The size of cell and the movement speed of gun are determined according to the paint film thickness distribution model of the gun.Then,taking account of the shortest path of the gun movement and the least turn as the goal,the priority order of the eight directions of a certain grid cell is set to determine the position of the gun at each moment.The full coverage of the workpiece surface spraying could be completed step by step.This algorithm is easy to implement.It could greatly reduce the complexity of path planning.(2)A cooperative spraying path planning algorithm for dual robotic arms based on vertex reward is proposed by considering the characteristics of complex and diverse workpiece surfaces in industrial production,and the limitations of single robotic arm work.First,the STL model rasterization algorithm is proposed to build a 2.5D raster map representation of the complex workpiece spraying model based on the STL model.Second,the reward function is designed considering the robotic arms anti-collision,the uniform distribution of spraying path length,the number of turns and intersections.Selecting the raster cell with the best reward function in the neighborhood of the cell where the gun is located at the current moment as the location of the gun for the next moment until all the cells to be sprayed are covered.Next,the weights of the reward function are optimized with the total path length and the difference between the path lengths of the two robotic arms as the objective function.Finally,the feasibility and practicality of the algorithm are verified based on the STL model of the bus rear perimeter.(3)A multi-color spraying path planning based on hybrid heuristic algorithm is proposed to address the existing spraying path planning algorithms cannot meet the demand of personalized pattern spraying.First,the multi-color spraying path planning for single-nozzle gun is described as Cluster Travelling Salesman Problem(CTSP).A hybrid heuristic algorithm combining Greedy Randomized Adaptive Search Procedures(GRASP)and Variable Neighborhood Search(VNS)is designed to solve CTSP.Next,the multi-color spraying path planning of the dual-nozzle gun is defined as the set-Cluster Travelling Salesman Problem(setCTSP).Considering the effect of different color combinations of the dual-nozzle gun on the spraying path length,and a hybrid heuristic algorithm incorporating the probability of color combinations is proposed to obtain the minimum path of the gun movement.Finally,extensive experiments with different sizes of patterns are performed to verify the feasibility of the hybrid heuristic algorithm.