Stability theory for linear time-invariant plants with periodic digital controllers

The control of a linear time-invariant plant by a digital controller composed of a sampler, a periodic discrete-time component, and a zero-order hold is considered. The stability of such a configuration is analyzed. It is shown how closed-loop zeros can be placed using such a scheme. As a consequence, it is proved that the gain margin can be arbitrarily assigned by suitable choice of sampling time and digital controller. The design procedure is constructive, using state-space methods.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>