Robust stability of state-predictive and Smith control systems for plants with a pure delay

Abstract

Robust stability of the state-predictive and the Smith control systems for plants with a pure delay is studied. First, the Nyquist-type stability condition is derived for robust stability. Then, the condition is transformed and a robust stability criterion is given in terms of the Nyquist plots of the complementary sensitivity function and the error function. Based on this criterion, we present a method to obtain graphically stability margins in the delay-time and the gain. © 1998 John Wiley & Sons, Ltd.