Identification of active magnetic bearing system with a flexible rotor

• Transfer function matrix model is identified based on frequency–response data.
• Theoretical model is used to construct the proposal with three sequential steps.
• The delay that is very common yet important in large-size EMB systems is considered.
• No force sensors are required.

Active magnetic bearings (AMBs) are widely applied in high-speed rotating machinery, especially in special environments. In designing and adjusting an AMB system, the mathematical model of the system plays an important role. Identification is a useful method to obtain the models of AMB systems. This paper concentrates on identification method for an AMB system with a flexible rotor. Based on the theoretical system model and the measured frequency–response model, the proposed method estimates the unknown parameters and establishes the transfer function matrix model of the AMB system. According to the theoretical model, this paper decomposes the identification procedure into a few steps and the model is sequentially reduced by these steps. In this procedure, the submodels are identified separately and finally combined together. The proposed method is validated by experiments on three AMB systems.