Precise contact tracking on complex geometries using polishing machine tools via smooth trajectories within online constant force control

Effective motion control techniques are necessary to achieve high precision in contact applications, especially for complex geometries in the manufacturing sector. This paper presents a novel method for smooth trajectory planning under constant admittance force control for the polishing process. The proposed method aims to improve polishing accuracy while minimizing processing time and effort. It combines mixed-degree B-spline trajectories with an Online Admittance Controller to produce a novel force–position controller, named the BOAC algorithm. The B-spline trajectory directs the online admittance controller to regulate both contact force and trajectory accuracy. Simulation studies on three complex geometries a vase, a star, and an iPad demonstrate the robustness of the BOAC controller in tracking the actual trajectory and maintaining the applied contact force. For experimental validation, the BOAC method was compared with a conventional admittance controller (CAC) during real-time polishing of complex iPad edges using a 6-axis polishing machine. The results show that BOAC consistently achieves precise trajectories while maintaining accurate contact forces, leading to a significant reduction in force errors compared to CAC. This method enhances automation in processes such as grinding and polishing by enabling precise control of contact force and ensuring smooth motion.