SIMPLE ROBUST ADAPTIVE-CONTROL FOR A CLASS OF NONLINEAR-SYSTEMS - AN ADAPTIVE SIGNAL SYNTHESIS APPROACH

A simple robust adaptive control is presented for a class of non-linea r systems with parameter uncertainty and under bounded disturbances. I n the proposed scheme, assuming that a nominal control law, designed w ith the knowledge of the plant parameters ensures the uniform asymptot ic stability of the closed loop system in the absence of the parameter uncertainty and free of disturbances, an adaptive compensation signal is synthesized to guarantee the uniform ultimate stability (Corless, M., and G. Leitmann, IEEE Trans. Automatic Control, AC-26, 1139-1144 ( 1981)) in the presence of the uncertainty and disturbances. Unlike in traditional parameter adaptive control, in this adaptive signal synthe sis approach only the upper bounds on the parameter uncertainty and di sturbances are updated. This gives a simple control law for its implem entation, since the difficulty of tuning numerous adaptation gains is avoided, and robustness with respect to disturbances, since the parame ter drift due to disturbances is overcome. A simulation example is inc luded to illustrate the main features of this approach.