Integrating Time-Optimal Motion Profiles With Position Control For A High-Speed Permanent Magnet Linear Synchronous Motor Planar Motion Stage

This note addresses the high-speed, high-precision point-to-point motion control of an air-bearing planar stage. The custom-designed stage uses four air-bearings to levitate the stage for the high-speed frictionless operation. Because of the floating nature, the controller for the system needs to overcome the nonlinear free-moving dynamics of the stage and achieve the required performance. To fulfill this purpose, we propose a unique integrated control structure that allows both velocity and reference position inputs. With the proposed structure and the weighting design, it is possible to use the H-infinity chain scattering description (H-infinity-CSD) synthesis for the control parameters. The single structure is used for both the point-to-point movement and the high precision positioning. The reference velocity input enables the long-stroke time-optimal velocity profile injection. The controller converges to the popular PDF control when the stage comes close to the target position. The H-infinity specifications enable a robust performance against the load uncertainty. The control undergoes no switching and is thus free from the undesirable chattering. The experimental results show that the proposed control achieves an ultrahigh precision control of 20 nm within 200 ms for a 9-kg stage with 20-mm x, y motion ranges.