Initial condition adapting robust control for a high-speed moving iron type lift actuator

We deal with a robust control method for a high-speed moving iron type lift actuator. This actuator is driven by magnetic force generated between an electric magnet and an armature sprung by a spring that enables high-speed piston motion of the armature. Our aim of control is to moderate motion speed of the armature when it touches the magnet to reduce mechanical shock or noise adjusting electric magnet current. Problems come from magnetic force properties: hard nonlinearity and instability, and the fact that the spring can exert only a pulling force and therefore push-pull forces are available to adjust armature speed in only the vicinity of the stroke end. To overcome them robustly we developed a kind of adaptive control scheme, which changes control effort depending on an initial condition at which control effort begins to be effective.