Force control for magnetic levitation system using flux density measurement

This paper demonstrates theoretically and experimentally the idea of magnetic force control in magnetic levitation systems using flux density measurements. A Hall-effect sensor is used to sense the flux density in the airgap. The magnetic force is obtained by its proportional relation to the flux density. A simple magnetic levitation system which consists of a U-shaped electromagnet and a manipulator is used. First, the system dynamics are described in state space form using airgap displacement, velocity of the magnetically levitated manipulator, and the flux density as state variables. Second, the magnetic levitation system is stabilized using digital state feedback control. The magnetic force is then regulated using a digital H_∞ controller to achieve robust stability, disturbance/noise rejection and asymptotic tracking. Simulation and experimental results in terms of speed and accuracy are presented