A Novel Evaluation Method on the Precision of Linear Motor Feed System in High-Speed Machine Tools

The linear motor feed system can realize high-precision motion with high-speed and high-acceleration, which has a broad application in high-speed machine tools. In its unique zero transmission structure, the motor is connected directly with the mechanical system. The thrust harmonics and other disturbances act on the motor mover directly, which makes the tracking fluctuation more prominent. The traditional accuracy and repeatability of positioning cannot reflect the precision of the linear motor feed system in the process of high-speed movement. In this paper, a novel precision evaluation method which takes the dynamic precision as the index is proposed for the linear motor feed system in high-speed machine tools. The performance and precision of linear motor feed system are evaluated by the transient error, steady-state follow error and tracking fluctuation, respectively. Then the servo control model is established oriented to dynamic precision. The influences of NC instructions, servo system and mechanical system on the dynamic precision are discussed. It can be obtained that this new evaluation method on the precision can evaluate systematically the performance of the linear motor feed system in high-speed machine tools. Meanwhile it can reveal efficiently main factors which lead to the decline of dynamic precision and propose effective improvement methods.