A Practical Precision Control Method Base on Linear Extended State Observer and Friction Feedforward of Permanent Magnet Linear Synchronous Motor

In this paper, a detailed model of motion stage driven by iron-less permanent magnet linear synchronous motor (PMLSM) and supported by rolling guides are presented. This stage is a prototype of the feeding system for a precise turning machine tool. In this model, there are two categories disturbances including slow-varying ones mainly produced by the thrust ripple of PMLSM and abrupt-changing ones caused by nonlinear friction of rolling guide. To overcome these disturbances, a simple, effective and practical servo control method based on the general-purpose two-degree-of-freedom PID (2DoF-PID) type controller integrated with the linear extended state observer (LESO) and the friction feedforward (FFF) controller is presented. In this control framework, the linear ESO is designed to estimate and compensate for the slow-varying disturbance and the FFF controller is adopted to eliminate the abrupt-changing nonlinear friction effects. Finally, comparative simulations indicate that the 2DoF-PID-LESO-FFF is effective and achieves better performance compared with traditional controllers, and experiment results demonstrate that the tracking error of the proposed method can be kept in the bounds of 1.5 μm under different conditions.