LQR-BASED LEAST-SQUARES OUTPUT-FEEDBACK CONTROL OF ROTOR VIBRATIONS USING THE COMPLEX-MODE AND BALANCED REALIZATION METHODS

The complex mode and balanced realization methods are used separately to obtain reduced-order models for general linear asymmetric rotor sys tems. The methods are outlined and then applied to a typical rotor sys tem represented by a 52 degree-of-freedom finite element model. The ac curacy of the two methods is compared for this model and the complex m odel method is found to be more accurate than the balanced realization method for the desired frequency bandwidth and for models of the same reduced order. However, with some limitations, it is also shown that the balanced realization method can be applied to the reduced-order co mplex mode model to obtain further order reduction without loss of mod el accuracy. A ''Linear-Quadratic-Regulator-based least-squares output feedback control'' procedure is developed for the vibration control o f rotor systems. This output feedback procedure eliminates the require ment of an observer for the use of an LQ regulator, and provides the a dvantage that the rotor vibration can be effectively controlled by mon itoring only one single location along the rotor shaft while maintaini ng an acceptable performance. The procedures presented are quite gener al and may be applied to a large class of vibration problems including rotordynamics.