Analysis of Multiple Equilibrium Points and Research on the Stability of Fixed-current Control in Maglev System

The problem of multiple equilibrium points caused by fixed-current levitation control was researched in this paper. Mathematic model of hybrid maglev system with permanent added into suspension magnet was established at first. The contacted force and electromagnetic force between magnet and guide way were expressed separately. Then fixed-current controller based on proportional-integral-differential feedback was introduced. Equilibrium point and its existing conditions were analyzed, and the results showed that there were three equilibrium points when fixed-current controller was used. Then stability of each equilibrium point was studied as follows. The proper area of parameters in controller was calculated, in which desired stable equilibrium point would be stable indeed. The behavior near the equilibrium point which was not stable was also studied, in order to guide how to design a appropriate controller in the future.