화학공학소재연구정보센터
Automatica, Vol.39, No.2, 299-307, 2003
Frequency domain control-relevant identification of MIMO AMB rigid rotor
This paper describes an application of frequency domain control-relevant identification and controller design based on an LQ criterion, which has moderately enhanced the performance of a MIMO active magnetic bearing (AMB) rigid rotor system. Unlike existing schemes using LQG criteria, the controller gain has not been tuned using frequency weighting calculated by the differences between measured and predicted input-output signals during iteration. Instead, the performance enhancement provided by frequency domain control-relevant identification of an open-loop plant is emphasized. The non-parametric frequency response functions of a MIMO open-loop plant including all additional dynamics such as sensor, amplifier, and discretization are estimated from measured input and output signals of the closed-loop plant. An approximate MIMO model of the matrix fractional description form is obtained with control-relevant weightings and the LQG/LTR controller is designed iteratively based on the identified model. The performance enhancements through the frequency domain control-relevant identification of an open-loop plant may not be as dramatic as those obtained with the existing schemes, since we limit the order of the controller by eliminating the frequency weighting in the controller design stage. However, the performance of a MIMO AMB rigid rotor system has been moderately enhanced with the resulting limited-order controller.