Applying the RMMAC methodology to an unstable plant

In this paper we revisit previous work on Robust Multiple Models Adaptive Control (RMMAC) of uncertain plants [1]. RMMAC was originally developed to control open-loop stable plants. We formulate and study the problem of robust adaptive control of open-loop unstable plants with structured and unstructured uncertainty in the presence of external disturbances and measurement noises, an issue that poses considerable theoretical and practical challenges. In particular, we show, with the help of an example, how a slight modification of the technique introduced in previous work on the RMMAC for stable plants yields a methodology that has the potential to deal with unstable plants. A design example and several nontrivial computer simulations are presented and discussed.