A whole-path posture optimization method of robotic grinding based on multi-performance evaluation indices

Abstract

Industrial robots are promising and competitive alternatives for performing machining operations due to their advantages of good mobility, high flexibility and low cost. However, the application of industrial robots in the field of high-precision machining such as grinding is hugely limited by the characteristic of weak stiffness. Aiming at this problem, a whole-path posture optimization method of robotic grinding based on multi-performance evaluation indices is proposed in this paper. Firstly, a kinematic performance evaluation index is utilized to directly refine the regions of the robot workspace. Secondly, a stiffness performance evaluation index comprehensively considering the characteristics of grinding process is put forward. Simultaneously, a space conversion method is proposed to convert the stiffness index from the robot end to the tool end, and then a task-oriented flexibility ellipsoid on the tool-workpiece contact point is established. Furtherly, on these bases, aiming for the motion smoothness and the overall maximum stiffness of the robot in the whole grinding path, and taking the performance of the robot body as the constraint synergistically, an optimization model is established to optimize the posture of the robot. Finally, three groups of comparative grinding experiments are carried out on a KUKA kr210–2 robotic grinding platform. The results demonstrate that by using the posture optimization algorithm proposed in this paper, a better comprehensive performance including stiffness and motion smoothness in the whole grinding path can be achieved, and the workpiece after grinding has a higher removal depth and a better consistency, whose roughness has also been enhanced. These phenomenons indicate that the proposed method can significantly improve the accuracy and stability of grinding, thereby the effectiveness of this method is verified.