Design of adaptive control systems for unstable plants in the presence of input saturation

It is important to consider input saturation in adaptive control systems to prevent the deterioration of control performance caused by excessive adaptation. This paper deals with a model reference adaptive control problem for a first order time-invariant continuous-time unstable plant in the presence of input saturation. We propose an algorithm considering error feedback and easing reference signal conditions. Moreover the adaptation law is switched according to the input conditions to inhibit excessive adaptation caused by the input saturation. Further, we give a necessary condition for locally asymptotic stability. By this algorithm, design flexibility of the system becomes higher than conventional algorithms. These results are confirmed by simulation studies.