Modeling of physical systems usually results in system of higher order generally greater than two. Design of controllers for such physical system becomes tedious when system order is high. So, it is desirable to approximate these models by reduced order models. In this paper a reduced order model is obtain by Modified Cauer Form and factor division algorithm. The controller is designed for the reduced order model and is connected in cascade with the original system to obtain the desired specifications. The proposed method assures the stability of the system under the reduced order model case. The proposed method is illustrated by a numerical example.

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Keywords: Modified Cauer Form, Order Reduction, Factor Division, Transfer function, PID Controller.