Model-following system with assignable error dynamics and its application to aircraft

A main objective of this paper is to propose a practical tool for designing a model-following system. Successive differentiations of output errors between a linear time-invariant system (a plant) and a model yield controllable output error dynamics in a block-decoupled companion form. Such a particular form of the error dynamics makes it easy to determine a model-following control law such that the output error dynamics have arbitrarily assigned stability characteristics. Assigning asymptotic stability to the output error dynamics alone does not guarantee system stability. The transmission zeros which are inherent to the input-output relations must be in the left-hand half-plane for internal system stability. The approach has been applied to a variable stability and response aircraft under development. An example of the longitudinal model-following system on this aircraft is shown to demonstrate the proposed method.