An estimation based robust adaptive control of nonlinear systems with a general set of uncertainty

A novel estimation-technique-based robust adaptive control scheme is presented for a class of uncertain nonlinear systems with a general set of uncertainties. Firstly, we introduce an extended semi-strict feedback form which generalizes the systems studied in recent years. Secondly, a novel estimation technique is proposed to estimate the states of unmodeled dynamics under very mild conditions. With the introduction of powerful functions, the estimation error can be tuned to a desired small region around the origin via the estimator parameters. Thirdly, with a γ-function, a modification of adaptive backstepping for dynamic uncertainties is presented in order to drive the output to an arbitrarily small region around the origin by an appropriate choice of the design parameters. With our proposed scheme, we can remove or relax the assumptions of existing results