Active magnetic bearings for the identification and fault diagnosis in turbomachinery

Active magnetic bearings, a typical mechatronic product, have been successfully applied in industrial turbomachinery. Their main advantages are the contactless working principle,the frictionless suspension, and that they represent an active system. Therefore, the active magnetic bearings are well suited to operate contactless as actuator and sensor elements in rotating machinery. The aim of the presented projects of the Special Research Program (SFB 241) supported by the German Research Council (DFG) is to use active magnetic bearings as an identification and diagnosis tool for turbomachines. The identification and diagnosis procedures are. based on frequency response functions. For this type of diagnosis using transfer functions, an accurate force measurement is crucial. The paper compares force measurement results and achievable accuracies of a radial magnetic bearing using different measurement techniques over a large operating range. Furthermore, a state-space model of the entire mechatronic system is developed to facilitate the diagnosis procedure. (C) 2002 Published by Elsevier Science Ltd.