Robust adaptive control in the presence of bounded disturbances

The model reference adaptive control of a linear plant subjected to bounded disturbances is considered. By analyzing a set of nonlinear differential equations, it is shown that the global behavior of the adaptive system depends upon the persistent excitation of the reference input as well as the amplitude of the external disturbances. The principal contribution of the paper is the derivation of sufficient conditions on the persistent excitation of the reference input, given the maximum amplitude of disturbance, for the signals in the adaptive system to be globally bounded.