ORDER REDUCTION AND ITS APPLICATIONS IN THE DESIGN OF CONTROLLERS

Abstract

Reduced order modelling of linear time invariant systems had been a topic of interest to a large number of research workers all over the world. It is interesting to rate that different methodologies developed for order reduction can be put broadly under two groups, like, time and frequency domain, being obviously the two accepted methods of system modelling. The reasons behind interest in reduced order modelling are many, but can be precisely put as (1) to have less computation time for analysis and design of system and (ii) to have economy in hardware requirements for on line simulation of a system. The work Included In this dissertation deals, with model reduction techniques (cauer forms) in frequency domain i.e. based on a transfer function description of the original system. Simple method is used for step response. A design procedure for system compensators (PID type) is proposed using low order models. The desired closed loop system performance is decided using a second order model including both the plant and the compensator. The original system is reduced to second order using its closed loop unit feedback transfer function. Resulting transfer function including the compensator is of third order having unknown terms as the elements of the compensator which are determined by matching initial few time moments of the second order model transfer function. The computer programs in "c" for model reduction, step response and compensator design, have been developed and implemented successfully on a PC.