Control of non-affine nonlinear systems: A survey

As a more general description of affine nonlinear systems, the practical applications corresponding to non-affine nonlinear systems are more comprehensive and closer to reality. Therefore, it is essential to study the control problems of non-affine nonlinear systems. However, the closed-loop system’s control signal appears as a nonlinear function due to the non-affine properties of nonlinear systems, which can lead to issues including singularity, zero-crossing, and uncertain control direction. From this point, solving control problems of non-affine nonlinear systems is a considerable challenge. This paper first introduces the relevant background knowledge of affine, strict feedback, and high-order systems, and then summarizes three solutions through literature research: function transformation method, reference model method, and data-driven method. Finally, based on existing research findings, the challenges and development trends faced in the field of non-affine nonlinear system research are proposed. © 2024 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.