Stabilizing control of a 1-DOF electromagnetic levitation of pivoted-free rigid ferromagnetic beam

The paper presents design, fabrication and feedback control of a 1-Degree-of-Freedom (1-DOF) attractive type electromagnetic levitation of a pivoted-free ferromagnetic rigid beam (PFB). Previous work primarily utilizes single electromagnet as opposed to the one presented here. The difficult problem of stabilizing an open loop unstable PFB between the two electromagnets (EM) that are mounted above and below PFB with equal air gap is considered. A current controller circuit is developed to precisely regulate the switching of control current to the EM. The EM exhibit a nonlinear force-current-displacement behaviour, hence to design a linear controller, the total range for displacement of PFB at the levitated end is restricted to a small gap around the equilibrium position. The force-current-air-gap relationship is linearized and a stabilizing classical Proportional Integral Derivative (PID) controller is designed and implemented in real-time on a 1-DOF PFB test rig. The closed loop responses for command tracking and disturbance rejection from simulated and experimental studies are also presented.