Abstract: The authors present an algorithm for order reduction of linear dynamic SISO discrete systems using the combined advantages of the improved generalised Least squares method and error minimization by Differential Evolution technique (DE). The denominator of the reduced order model is obtained by improved generalise least squares method and the numerator coefficients are determined by minimizing the integral square error between the transient responses of original and reduced order models using DE technique, pertaining to unit step input. The reduction procedure is simple, efficient and computer oriented. The algorithm is illustrated with the help of two numerical examples to highlight the advantages of the approach and the results are compared with the other existing techniques.

Keywords: Improved Least Squares, Integral square error, Order Reduction, Differential algorithm.