Active magnetic bearing control: Comparison of LTI vs. LPV approaches.

An active magnetic bearing (AMB) system for the rotor of a rotating machine is considered as a test-bench to compare different control techniques. The plant can be modeled as a Linear Parameter Varying (LPV) system. The objec tive of this work is to compare time invariant vs. time varying and nominal vs. robust designs on this particular application. First, the nominal mode l has been simplified to a diagonal one and a controller has been designed via pole-placement. Next, using the complete model, a MIMO time invariant m u-synthesis controller has been designed. Finally a time varying LPV contro ller has been synthesized for the uncertain plant. Due to the recent develo pment of the latter techniques (Packard, 1993; Becker and Packard, 1994) we have included a brief introduction to LPV controllers. Other designs which use different procedures (loop-shaping, H-infinity optimal control) have b een referenced. Simulation results are compared in terms of disturbance rej ection and robustness. These results are also compared to previous works in this area.