Research On Auto-coupling PID Control Method For Strict Feedback Nonlinear Unknown System

With the development of modern science and technology,the study of strict feedback nonlinear unknown system control problems has attracted more and more attention from scholars at home and abroad.Various existing control methods have proposed corresponding solutions to the control problems of strict feedback nonlinear systems,and have achieved certain control effects.However,there are limitations such as poor control accuracy and complicated controller structure.Aiming at the control problem of strict feedback nonlinear unknown system,based on the auto-coupling PID control method,an auto-coupling PID control method of strict feedback nonlinear uncertain system is studied.The control method draws on the main idea of PID "eliminating errors based on errors" and the definition of "sum disturbance" of auto disturbance rejection control.The unknown dynamics and external bounded disturbances are defined as a sum disturbance,so that the strict feedback nonlinear system is mapped to a linear uncertain system of integral series type,and then a controlled error system under the anti-phase excitation of the sum disturbance is constructed.Taking the links with three different attributes of proportionality,integral and differentiation as an inseparable and organically unified whole,an auto-coupled PID control method with speed factor as the core coupling factor is designed.Theoretical analysis of the global stability and robustness of the closed-loop control system against total disturbances.This method solves the problem of traditional PID parameter setting,and avoids the problem of high-frequency chattering in sliding mode control and the problem of large calculation amount of auto disturbance rejection control.The paper has the following characteristics and innovations:1)Using the transition time of the controlled object from the dynamic state to the steady state to set the minimum speed factor,so that the ACPID controller model and parameter setting rules are only related to the speed factor and not to the controlled system model.And there is only one parameter of the speed factor to be tuned,which avoids the chattering and overshooting phenomenon existing in the traditional PID control,and simplifies the controller structure while solving the problem of PID gain setting.2)In order to improve the dynamic performance of the control system,an adaptive speed factor model is designed on the basis of the speed factor,which avoids the overshoot and oscillation phenomenon of the control system due to integral saturation during the dynamic process,and improves the anti-disturbance ability and control accuracy.In order to verify the effectiveness of the paper's research method,the paper applies the auto-coupled PID control method to three different strict feedback nonlinear unknown systems,and conducts MATLAB simulation experiments.It is validated that the control method of the paper not only has fast response speed,high control accuracy,simple controller structure,but also has good anti-disturbance robustness.It provides some theoretical references for the control problem of strict feedback uncertain nonlinear systems and the simplification of the controller structure.It has important application value in the field of strict feedback nonlinear unknown systems.