Experimental results with stable and unstable LPV controllers for active magnetic bearing systems

Active magnetic bearing spindles are subject to synchronous vibrations due to mass-imbalances. These sinusoidal disturbances depend on the rotational speed. In order to attenuate these disturbances, an LTI plant-LPV weighting function is used to synthesize LPV controllers. We design and implement an LPV controller using a model for the rigid body dynamics. For an AMB-spindle model that contains flexible modes, the synthesized LPV controller is found to be unstable. We implement this controller by using a Youla parametrization which depends on the rotational speed measurement.