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

In this paper, a novel estimation technique based robust adaptive control scheme is presented for a class of uncertain nonlinear systems with a general set of uncertainty. Firstly, we introduce a more 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, estimation error can be tuned to a desired small region around the origin via the estimator parameters. Thirdly, with γ function, a modification of adaptive backstepping for dynamic uncertainties is presented to drive the output to an arbitrarily small region around the origin by appropriate choice of the design parameters. With our proposed schemes, we can remove or relax the assumptions of the existing results.