Two classes of useful order reduction approaches in engineering practice

In terms of the basic principles of step response modeling and moment modeling, two classes of useful order reduction approaches, graphical order reduction approach and moment order reduction approach, are proposed in this paper. The procedures for parameter determination of the low-order approximating models are illustrated in detail. Graphical order reduction approach can be traced back to one of the classical modeling methods, by which the parameters of a low-order model can be specified by plotting and calculating. Moment order reduction approach is an impulse response based method, by which the low-order model parameters can be specified from the first two or three moments of the impulse response. Detailed comparisons are done by a large number of simulations to verify the approximating abilities of the low-order models yielded by the methods proposed in this paper.