A NEW INTERPRETATION OF ORDER-CHANGES IN TERMS OF MODE-SHIFTS IN A DESCRIPTOR SYSTEM

摘要

A descriptor form that is convenient to investigate the effects of order-changes caused in a certain manner is proposed. Using this form, such effects are given new interpretations in terms of associated shifts of modes among the exponential, the static, and the impulsive modes of a descriptor system. It is shown that when the order is reduced, a dynamic mode changes to a static/impulsive mode that is disconnected to the output and is impulse-unobservable. Such a static/impulsive mode can be interpreted as a reminiscence of a dynamic mode that disappeared from but remained within the system expression after the order reduction. While this interpretation is obtained under a particular rule of order-changes, the basic insights obtained should be useful in analysing and designing control systems that can involve, directly or indirectly, order changes.