Abstract
This paper presents a redesign method of discrete-time adaptive control system for continuous-time systems. Using appropriate approximate discrete-time models of the continuous-time system, called limiting-zero model and modified delta-model, we avoid the problem of the unstable zeros which arise in the case of rapid sampling of the continuous-time system having the relative degree greater than one. In this paper, first, we discuss the motivation and principle of the limiting-zero model of the continuous-time system. Next, it is shown that, in modeling error at high frequency range, the limiting-zero model is superior to delta-model. Moreover, the modified delta-model is introduced by regarding the phase-shift characteristics of the limiting-zero polynomials. Finally, in order to confirm the effectivenese of the adaptive control system using the proposed models, computer simulations are carried out for a continuoustime system having the relative degree equal to 3. It is shown that the proposed models can be successfully applied.
