Quantitative Feedback Design of Uncertain Multivariable Control Systems

• Main Authors: Cheng, Ching-Cheng, 鄭錦政
• Other Authors: Wang Te-Shing
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/09611172613573227453

博士 === 國立交通大學 === 電子工程學系 === 85 === In this thesis, several quantitative feedback design schemes are provided for designing the linear time-invariant multivariable feedback control system with large plant uncertainty. Each element of the plant transfer function matrix is described with a bounded parameter range. The objective is to find proper robust compensators, embedded in a two-degree-of-freedom structure, such that not only is the channel interaction suppressed to an acceptable level, but the system frequency response should lie within the prescribed main channel performance boundaries. Under the proposed design framework, the synthesis of an n x n MIMO control system is replaced by n single-input single-output(SISO) design problems, so that the SISO-QFT method can be directly invoked for designing. Based on Schauder''s fixed-point theorem, two sufficient conditions have been derived for assuring the achievement of the noninteracting performance, or alternatively, the off-diagonal performance. Two new interaction indexes, the relative error and the absolute error, are derived to serve as a practical measure for assessing the achieved noninteraction of the system. The use of these indexes as noninteraction measure is shown to be very simple even for the system of large dimension. On the other hand, the division of the given main channel performance tolerance is either re-allocated in a systematical basis or omitted completely by using the concept of the relative error and the absolute error, which forms a foundation for achieving the prescribed main channel performance. Remarkably, the proposed approach is with the capability to trade off the performance bound between the loops, so that the cost of feedback in each loop can be compromised. Finally, we give a practical decoupling mechanism, using a full-order compensator, to reduce the inherent overdesign limited by using a diagonal compensator.