Dual-Position-Controller Design for the Linear-Motor-Driven Motion System*

This work develops a dual-controller composed of a macroscopic controller (MAC) and a microscopic controller (MIC) for improving motion precision of a linear-motor-driven motion system. Based on the macroscopic model in which Coulomb friction model is considered, the MAC is designed. In the presliding region however, the MIC design is based on the lineralized microscopic model. Furthermore, a switching algorithm is developed for bumpless transfer in shifting control action between two controllers. Thus, when the table of motion stage moves to the desired position, the control action can be smoothly switched from the MAC to the MIC. The whole system with the proposed dual-controller has the advantage that it serves as a long stroke (coarse stage) and a short stroke (fine stage) to achieve high precision motion control. The experimental results reveal that it totally takes 2.59 seconds to reach the 1000μm target position with the accuracy of one BLU (basic length unit; sensor resolution), 20nm; the result has over 29% improvement when compared with the result using single MAC. In addition, good nanometer-scale tracking performance with the accuracy of one BLU, 20nm, can be obtained by using the MIC.