High performance H∞ control of non-minimum phase Active Magnetic Bearing system

A high performance H_∞ controller designed to control an Active Magnetic Bearing (AMB) system is considered in this paper. A digital signal processor (DSP) is used to implement the designed controller in real-time. The designed H_∞ controller is compared with a conventional lead-lag type compensator and the on-board analogue controller of the AMB under various conditions and disturbances acting on the system. Designing the controller based on classical methods could become tedious, especially for systems with high order model. By contrast, H_∞ controller design requires only two properly designed weighting functions regardless of the model order. These weighting functions are selected to reflect the trade-off between the system´s performance and robustness. In this paper we show that appropriate selection of these weighting functions is the key to a practically useful controller in terms of co-norm optimization. The experimental results have verified the enhanced performance and robustness of the system under H_∞ control in the presence of disturbances.