MODELING OF RIGID AND ELASTIC STRUCTURES IN ACTIVE MAGNETIC BEARINGS

Active magnetic bearings (AMB) are very often presented as a progressive alternative of bearing for High Speed Cutting (HSC) applications. However, AMBs have also several significant disadvantages. One of the most crucial is very high complexity, which results in relatively high probability of failures. Properties of the AMBs are completely dependent on the quality of the control system. To improve properties of the overall system a multi level control system for HSC spindle with AMBs was proposed. The top level of such system (supervision level) performs several tasks, which allow us to eliminate negative properties of AMBs. This paper deals with modeling both rigid and elastic structures in active magnetic bearings as a part of the supervision system. Simple lumped mass, rigid beam, rigid rotor, elastic beam and elastic rotor models are presented. Simulation models in MATLAB were developed to be a part of above mentioned supervision system. Models were partly experimentally verified on two test rigs: (1) rigid rotor with one axial and two radial active magnetic bearings, and (2) elastic beam supported on one side by rolling element bearing and by the active magnetic bearing (opposed electromagnets).