Frequency weighted closed-loop order reduction in the control design configuration

This paper focuses on order reduction within a general control design configuration. The plant dynamics and the controller dynamics are written as a feedback loop in a frequency weighted interconnection. A straightforward extension of frequency weighted balanced reduction is explained that can be applied to the plant model and/or controller model in the control design configuration. A software tool is developed that helps the control engineer to find an acceptable trade-off between closed-loop performance and controller order, even for an extremely high-order plant. The user-interface of the tool supports the central engineer in evaluating the performance in the frequency domain, and provides additional frequency weights to be constructed 'on screen' in the form of piecewise quadratic functions. These functions define power spectra of the exogeneous signals of the control design configuration and are incorporated in the closed-loop balanced reduction algorithm in a very direct way. The ease of entering and adjusting frequency weighting functions facilitates the search for low-order controllers with minimal performance degradation.<<ETX>>