Research on machining error prediction and compensation technology for a stone-carving robotic manipulator

Stone-carving robotic manipulators (SCRMs) have a broad range of applications due to their high efficiency, diverse processing capabilities, and strong flexibility. However, due to its weak rigidity, the milling accuracy of an SCRM is lower than that of a computer numerical control (CNC) machine for working stone into special shapes, making it difficult to meet the requirements of stone milling processing. To improve the milling accuracy of SCRMs, multi-iteration error compensation technology considering the coupling relationship between compensation and deformation is proposed in this paper. First, a global stiffness model of an SCRM in which the robot arm bars are regarded as flexible links is established, and the relationship between the milling force and milling depth is fitted based on a milling force prediction model. Then, the machining error and milling depth when processing a marble workpiece are predicted. Finally, a multi-iteration method is applied for calculation using an interval correction strategy to construct a discrete control system for error compensation in the SCRM. The feasibility and effectiveness of the proposed compensation technology are verified by an experiment using the KUKA-240-2900 SCRM system.