Non-recursive robust/adaptive integrated control design framework for nonlinear systems with mismatched disturbances

For a class of nonlinear systems with mismatched disturbances, it is a common design approach to develop robust/adaptive control laws based on recursive schemes, such as backstepping method and its derivatives. However, recursive control laws are usually composed of multiple virtual controllers with multiple partial differential terms, which are complex in form and difficult to select control parameters, they are prone to “complexity explosion”. Therefore, it is hard to be applied to practical engineering. Additionally, due to the handling variations between nonlinear terms with uncertainties via recursive designs, it is in trouble to achieve an intrinsic blend of robust/adaptive control. In this paper, a novel non-recursive control manner is proposed to integrate robust/adaptive control design framework to achieve an offset-free tracking result for the systems with mismatched disturbances. With a one-step coordinate transformation, the system can flexibly switch to the appropriate bandwidth property according to the practical operating conditions in the framework of an equivalent stabilizable system, providing engineers with two alternative control laws at the same time. Compared with existing algorithms, the proposed control strategy has the following features: the controller form is simple to be implemented, easy to adjust parameters, and has a wide range of applications. Case studies and simulations illustrate the simplicity and effectiveness of the proposed approach. Meanwhile, the selection principles of the integrated controller operating modes are provided. © 2022 South China University of Technology. All rights reserved.