Order reduction of interval systems using direct truncation and stability equation method

In the present work, a new mixed technique is proposed for the approximation of complex high order continuous interval systems. The stability equation method is employed to determine the coefficients of the denominator of the reduced order model while the numerator parameters are evaluated by the direct truncation method. The remarkable attribute of the proposed scheme is that, the resulting approximants are always stable if the original high order system is stable. In order to establish the supremacy of the proposed technique over existing techniques of order reduction, comparative analysis with the help of numerical examples is included through performance indices and step responses.