Controller parameter optimization for passive magnetic levitation tray using Taguchi method

In a magnetic levitation tray system, when the magnets are installed on the fixed frame, the moving platform does not require any circuits and, thus, can be completed powerless (passive), which is a great benefit in vacuum environment. However, because the reaction plate is moving, the locations and magnitudes of the reaction forces are not continuous around the edge of the moving platform. Therefore, the relative longitudinal positions of magnets to the moving platform are a noise (uncontrollable) factor for the controller. The control gains should be robust against the noise factor to get the reliable performance. Taguchi method was used to determine optimal control parameters under the noise factor. The optimized parameters reduced the position variation of the levitated tray by 40% in Root Mean Square (RMS).