Stabilization of three pole Active Magnetic Bearing by sliding mode control techniques

An AMB is a mechatronic device, which could ensure contact-less, low frictional losses, lubrication free, high speed applicationscompared to conventional bearings. These bearing systems work on the principle of magnetic levitation. Hence the transmission losses in the electrical drives systems and the use of lubricants, which are mostly pollutants, are reduced considerably. Thus AMBs are classified under the efficient and pollution free bearing systems available. The limited use of AMBs in industry is due to the expensive cost. The possible way to cost down the AMB is to reduce the number of magnetic poles. The three pole AMB has the major disadvantage of strong nonlinearity due to the magnetic flux coupling. This paper presents an extended sliding mode control approach to control nonlinear three pole Active Magnetic Bearing (AMB), along with nonlinear rotor dynamics, subjected to parametric variations and external disturbances. A comparison of performances of the AMB with extended controller and that of the AMB with conventional sliding mode controller is done, by simulation analysis, to quantify the robustness of the proposed controller.