OPTIMAL DISCRETE-TIME STATIC OUTPUT-FEEDBACK DESIGN - A W-DOMAIN APPROACH

Presented in this paper is an alternative design methodology for optimal discrete-time control-law synthesis (i..e, what we call a W-design method). The proposed method solves an optimal static output-feedback design for sampled-data systems with a given known sampling time. The overall scheme involves the formulation of an exact optimal control problem for discrete-time systems using a state-space transformation and an equivalent quadratic cost function in the w domain. A one-to-one relationship between a set of stabilizing feedback gains in the w domain and those in the traditional z domain has been established. The optimal output-feedback gain obtained from the minimization of the equivalent cost functional expressed in the w domain will yield the same optimum solution as the one obtained traditionally in the z domain. An attractive feature of this procedure is that design solutions can be obtained using only continuous-time-domain techniques. The procedure is demonstrated with the synthesis of a longitudinal-axis stability augmentation system for a commercial transport.