Research On Anti-jamming Problems Of A Class Of Nonlinear Systems

The existing control theories and methods of nonlinear systems have their own limita-tions.What’s worse is tha,because of the unique nature of underactuated systems,the control theory and method of nonlinear systems can not be directly applied to underactuated systems.However,with the continuous development of underactuated systems,it is of great theoretical significance and practical value to study the anti-disturbance stability of underactuated sys-tems.Firstly,the extended disturbance observer is designed for general uncertain nonlinear systems.Then,taking the quadrotor aircraft as an example of underactuated system,a sliding mode controller based on extended state observer is designed to realize the global asymptotic stability of the quadrotor system.The main contents of this paper are as follows.1.Design of Extended Disturbance Observer for Mismatched Nonlinear Systems.Considering the general nonlinear systems with mismatched disturbances,this paper im-proves the existing extended disturbance observers to estimate the mismatched disturbances accurately.Based on the extended observer,a new integral sliding mode controller is designed to realize the asymptotic stability of the nonlinear system.The most important part,in this paper,the control strategy obtained from the second-order nonlinear system is extended to the norder mismatched nonlinear system,and its correctness is proved.In the simulation ex-periment,the effectiveness and superiority of the proposed control strategy can be verified by comparing the results with the traditional control method.2.Establishment of dynamic model of quadrotor aircraftThe structure and flight principle of the quadrotor aircraft are analyzed,and the coordi-nate system for describing the basic motion of the quadrotor aircraft is established.Based on Newton-Euler equation,the position model and attitude model of quadrotor aircraft are derived respectively.3.Stability study of quadrotor aircraft based on ESOA sliding mode control method based on extended state observer is studied for a quadro-tor aircraft system with unknown disturbances.The quadrotor aircraft system is considered to be composed of position subsystem and attitude subsystem.Firstly,the position subsystem is globally asymptotically stable by using the traditional sliding mode control method.Then an extended state observer is proposed to estimate the unknown disturbances in the attitude subsystem,and an appropriate sliding mode controller is designed based on the observer to make the attitude subsystem globally asymptotically stable.Finally,the effectiveness and robustness of the proposed control method are verified by simulation experiments.