Stabilization and control of three pole active magnetic bearing: A sliding mode control approach on extended system dynamics

A magnetic bearing is a bearing which supports the load using magnetic levitation, which could provide a contact-less, low frictional losses, lubrication free, high speed operations compared to the conventional bearings. The contact forces are generated by actively controlling the dynamics of an electromagnet. An Active Magnetic Bearing (AMB) system is inherently nonlinear on account of the nonlinearities of its electromagnetic field, which considerably make difficulties in designing efficient and effective system controllers. More over the cost of the AMB is obstructing the industry from implementing an AMB. The possible solution is to reduce the number of magnetic poles, and hence the three pole AMB system is devised. But it has the major disadvantage of magnetic flux coupling, an added nonlinearity. This paper studies the feasibility of an extended systems and sliding mode control scheme to design a robust controller to control the nonlinear three pole Active Magnetic Bearing (AMB). The simulation analysis is done to quantify the robustness of the proposed controller.