Motion Planning and Cross-Coupled Control for Contouring Error Reduction in CNC Machining

Contouring error significantly degrades the CNC machining quality. This project proposes to develop a new methodology to minimize the contouring error in CNC machining by using (1) improved motion planning with a novel velocity profile, and (2) a cross-coupled control for position synchronization of multi-axis motions. In traditional motion planning, the s- or T- curve velocity profile is generally utilized in successive movements, where the machining tool accelerates to the maximum velocity and decelerates to zero in each linear segment, which generates fluctuations and wastes the machining time. A new motion planning methodology with a novel s-curve velocity profile will be proposed in this project, by which the velocity decelerates from the maximum velocity to a non-zero constant velocity at the connection to the next segment, so that both efficiency and accuracy can be improved. In the follow-on control design, a cross-coupled synchronization strategy will be proposed for coordination of multi-axis motions. The contouring errors will be represented by the position synchronization errors, which are defined as differential position errors between each axis and the adjacent ones. Then, a decentralized tracking controller will be developed to asymptotically stabilize both position and synchronization errors to zero.