Adaptive control based on special compensation methods for ill-modelled time-varying plants

An adaptive controller based on some compensation methods that preserves stability for fast time-varying plants in the presence of bounded output disturbances and unmodelled dynamics is presented. The unknown plant parameters are estimated by a normalized algorithm with dead zone. The design is completed with a modified control law which adds an internal impulse to the system whenever the controllability of the estimated model is lost. This strategy confers a self-excitation capability to the system, so that it makes unnecessary the presence of external persistently exciting signals. As a result, the estimated models are sufficiently controllable by the underlying control law based on the special compensation methods and global stability is ensured. The performance of the given scheme is evaluated by simulations.