On Generalization of Integral Control to a Class of Nonlinear Uncertain Systems

The paper is concerned with some new view on the problem of integral control in the context of nonlinear uncertain systems. There is demonstrated that a standard integral action, applied to linear control system with so-called load disturbances, can be generalized to comprise a class of linearly parametrized nonlinear SISO systems with functional uncertainty. In the last case the integral action turned out to be in fact an adaptation law of unknown parameters. It has been found that the obtained proportional-integral controller's variable gains are in fact the basis functions of the system unknown nonlinearity approximator.