ORDER REDUCTION OF A DISCRETE SYSTEM USING STEP RESPONSE MATCHING

Abstract

Order reduction of linear time invariant systems had been a topic of research all over the world. The reason behind interest in order reduction are many, but can be precisely put as (i) 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. Based on the domain in which large scale system model is represented the order reduction methods are grouped into two initial categories: time domain and frequency domain. The attempt is to develop three methods of order reduction of a discrete system in frequency domain. The transfer function model is in Z-domain. The object is to match, the unit step response of original system and reduced order system There are some common philosophies among methods using step response matching and these can be put as: (i) Retention of dominant poles of the original system in the reduced order system. (ii) Exact forced matching of the steady state parts of the unit step responses of the original and reduced order systems. (iii)Minimization of the error between the transient parts of the unit step response of the original and reduced order systems