Active Disturbance Rejection For Time-delay System

In process control,fluid control,networked control and other systems,time-delay and unknown dynamic interference are common.The control problem has been a hot topic in the control field.Unknown disturbance is often the main factor that restricts the system performance.These uncertain factors often seriously affect the response speed and control accuracy of the system.Therefore,it is of great significance and value to study the phenomena with unknown disturbance and time delay in the system.As a new type of controller,active disturbance rejection controller(ADRC)has stability and robustness.The extended state observer is introduced to realize real-time observation and compensate the disturbance,and the system has disturbance rejection capability.Because it has the advantages of PID,at the same time,it does not rely on the precise mathematical model.Therefore,it is of great significance to explore how the ADRC can overcome the adverse reactions caused by time delay or delay change on the premise of reflecting its anti-disturbance characteristics in the time-delay system.The specific research contents and work are as follows:(1)The research progress and development process of ADRC are introduced.Compared with PID,ADRC has more obvious advantages in anti-interference and robust performance.However,considering the problem that ADRC needs to adjust more parameters,a new adjustment strategy is proposed for the parameter setting of observer and controller.Under the assumption of adjustment time,only one control parameter needs to be adjusted to set the controller parameters.The mathematical characteristics of the available mathematical models for ADRC are analyzed,which are not limited to the matching uncertain system,further increasing the available range of the algorithm.(2)In order to pursue higher control accuracy and observation ability,the improved switching observer is designed to make up for the advantages of linear observer and nonlinear observer.In this thesis,a scheme of observing system state by linear/nonlinear observer is proposed.After the stability of the observer is proved by time domain analysis method,the controller is designed by using the inverse step strategy combined with the idea of active disturbance rejection.The performance of the improved observer is further verified by numerical simulation.(3)An improved error feedback control scheme based on the extended state observer is designed,which further simplifies the control scheme and facilitates the optimization without sacrificing the control performance.Through dynamic simulation of given temperature signals of different types,the results show that the algorithm can track temperature signals accurately and quickly.At the same time,compared with the traditional ADRC scheme and PID controller,it is concluded that the error-based algorithm system has faster response speed,smaller overshoot and better stability.In addition,the test results of tracking dynamic signals show that the control method can achieve better control effect and has stronger response performance when the controlled system has set value and uncertain external disturbance.