A simple (intelligent?) adaptive controller

A short tutorial on simple adaptive controllers, based on the stabilizability properties of the plants, is presented. Modern control systems, such as nonlinear, adaptive, or intelligent systems, use nonstationary controllers. They try to adapt their controllers to the specific conditions imposed by plant uncertainties or changing external environments so that the performance and stability of the control system are maintained. Nonstationary controllers, however, raise new problems related to eventual instability, even under the same conditions that would guarantee stability with fixed controllers. It has been shown that stabilizability properties can be used to implement simple and robust nonlinear adaptive controllers, and that the conditions usually required for stability of adaptive controllers may be overly restrictive