Static Normalizing Pre-compensator: the First step in the Design of Robust Multivariable Controllers using the Characteristic

Locus Method

Professor Joao Carlos Basilio

Federal University of Rio de Janeiro

Department of Electrical Engineering

Abstract. In this talk, the Characteristic Locus Method (CLM) is revisited. Although it is an effective tool for the design of multivariable control systems, since it generalizes the frequency response tools used in the design of scalar control systems to multivariable systems, it may lead to unreliable controllers for plants whose frequency responses are far from normal at a certain frequency band. This is due to the fact that the CLM is based on the frequency response of the eigenfunctions (the characteristic loci) of the plant transfer matrix; and eigenvalues are known to be very sensitive to parameter perturbations in matrices that are far from normal. When this is the case, it is necessary to design a normalizing precompensator, before actually design a controller to address control objectives such as stability (robustness included), tracking of a reference signal, and disturbance rejection. Recent studies have shown that it is necessary to design only a static pre-compensator that makes the pre-compensated plant as closely as possible to a normal matrix at the vicinity of the crossover frequency; therefore avoiding the need for normalization in the whole frequency range, as usually done.

Friday, January 19. 2007

3:30 – 4:30 p.m.

Rm. 1500 EECS