Robust Control of Magnetic Levitation Systems by Means of H^∞Control/μ-Synthesis

This study is concerned with an application of H^∞control and μ synthesis to magnetic levitation systems which have special flexible structures and the solution of the spillover problem. At first, we show the typical spillover phenomenon caused by the interaction between the control system and the flexible structure system using PID control. Next, applying mixed-sensitivity H^∞control to the magnetic levitation system, we design the control system for it without spillover and describe in detail how to design an controller. Finally, we analyze the structured singular value and design the μ controller using D-K iteration. In this paper, we assume the magnetic levitation system as an uncoupled system between the X and Y directions for simplicity, which is the third-order system with the exception of the guideway. As a result, it has been clarified that the H^∞controller and μ-controller have the characteristics of two kinds of filters, a low-pass filter and a notch filter. It is found that the μ controller is superior to the H^∞controller in terms of robust stability and robust performance. From experiments, we obtained good data on the magnetic levitation without spillover.