Linear time-invariant system reduction using a mixed methods approach

In this study, we propose a new method for obtaining a reduced order model of high order linear time-invariant single input-single output (SISO) and multiple input-multiple output (MIMO) systems, which is based on the stability equation method and factor division algorithm. For a given higher order linear time-invariant system, the coefficients of the numerator polynomial are estimated by the factor division algorithm while the coefficients of the denominator polynomial are calculated by the stability equation method. The distinctive feature of the proposed method is that the reduced model will always be stable if the original system is stable. Numerical examples are provided that demonstrate the superior performance of the proposed method compared with other well-known published methods.