An Algorithm for Painting Large Objects Based on a Nine-Axis UR5 Robotic Manipulator

Featured Application The proposed algorithm for painting large objects based on a nine-axis UR5 robotic manipulator can be applicable in many automobile repair shops where paint jobs can be performed. With the help of a nine-axis UR5 robotic manipulator with the proposed algorithm, vehicles can be automatically painted with the least amount of human manual labor. Simultaneously, the quality and efficiency of the paint jobs can be drastically improved, since the UR5 robot maintains its consistency, accuracy, and proficiency while conducting paint jobs. An algorithm for automatically planning trajectories designed for painting large objects is proposed in this paper to eliminate the difficulty of painting large objects and ensure their surface quality. The algorithm was divided into three phases, comprising the target point acquisition phase, the trajectory planning phase, and the UR5 robot inverse solution acquisition phase. In the target point acquisition phase, the standard triangle language (STL) file, algorithm of principal component analyses (PCA), and k-dimensional tree (k-d tree) were employed to obtain the point cloud model of the car roof to be painted. Simultaneously, the point cloud data were compressed as per the requirements of the painting process. In the trajectory planning phase, combined with the maximum operating space of the UR5 robot, the painting trajectory of the target points was converted into multiple traveling salesman problem (TSP) models, and each TSP model was created with a genetic algorithm (GA). In the last phase, in conformity with the singularities of the UR5 robot's motion space, the painting trajectory was divided into a recommended area trajectory and a non-recommended area trajectory and created by the analytical method and sequential quadratic programming (SQP). Finally, the proposed algorithm for painting large objects was deployed in a simulation experiment. Simulation results showed that the accuracy of the algorithm could meet the requirements of painting technology, and it has promising engineering practicability.