Tuning Of Reduced-order Active Disturbance Rejection Controllers

With the continuous development of social economy and the continuous advancement of industrialization,the traditional PID controller is limited due to its structure and faces more and more challenges in industrial process control.Active disturbance rejection control(ADRC),as a new control technique based on modern control theory,inherits the traditional PID controller's core idea,i.e.,error elimination based on error estimation.ADRC does not depend on the accurate mathematical model of plants.It treats all the model uncertainties and external disturbances as a generalized disturbance,and use the extended state observer(ESO)and the feedback controller to estimate and compensate it in real time,thus the ADRC has a good load disturbance rejection performance,fast set-point tracking performance,and strong robustness.As the linear version of ADRC,the linear active disturbance rejection control(LADRC)has a relatively simple structure and its parameters can be tuned with the bandwidths of observer and controller.So it is convenient for engineering application and it is widely adopted in practice.In addition,as some of the output information of the plant can be directly obtained in the actual processes,it is not necessary for the ESO to estimate them and only other output information is needed to observe,thus reduced-order extended state observer(RESO)is more practical in structure.Compared with the normal linear ADRC,the structure of the reduced-order linear active disturbance rejection control(RLADRC)is simpler and the phase is more advanced.Due to the lack of research on the parameters tuning of the reduced order linear ADRC,this paper proposes a parameter tuning method for second order reduced order linear ADRC.First,the structure and characteristics of reduced order linear ADRC are studied and analyzed.Then,for the first-order process with dead-time plants,a parameter tuning method for second-order reduced order linear ADRC is obtained by solving an optimization problem.Finally,a series of simulation experiments are carried out on the first-order process with dead-time models,benchmark models and hydro turbine load frequency control system to verify the effectiveness and practicability of the proposed method.