Research On Linear Active Disturbance Rejection Control For Time-Delay Processes With Step Disturbance

The development and change of the times have brought new challenges to the process industry,which requires the process industry to achieve fine production,reduce costs and increase output,and thus puts forward higher requirements for the control of various industrial devices.The control problem generally has two main problems: servo problems and machine tuning problems.The former corresponds to fast tracking of the reference set value,and the latter corresponds to good disturbance rejection.The characteristics of infrequent changes in the set value of the industry processes and frequent disturbances determine that the suppression of interference will be the main goal of process control.On the other hand,as a relatively new anti-interference technology,active disturbance rejection technology is being studied by many scholars and has been applied to many fields.This paper will take time-delay processes as the object and the antidisturbance rejection as the goal to explore the control problem of the timedelay processes using active disturbance rejection technology in the presence of step disturbances.The main contents and results of this study include:1.Parameter domain search of reduced-order linear active disturbance rejection controller for time-delay processes.The existence of time delay makes theoretical analysis of the active disturbance rejection controller difficult,and it also limits the performance of the controller.Aiming at the time-delay process,this paper first proposes a reduced-order active disturbance rejection controller structure for time-delay processes in the frequency domain.When tuning the parameters of the controller,it is necessary to know a rough parameter domain to ensure the stability of the system.Due to the unique structure and the special form of linear active disturbance rejection controller,it is difficult to analytically obtaine the parameter domain.Therefore,this paper proposes a graphical method using D-decomposition.The parameters of the active disturbance rejection controller are mapped into a parameter space by the graphical method,and the parameter domain satisfying the stability condition and the specific robustness condition is obtained.Simulation results show that the reduced order active disturbance rejection controller has better anti-interference performance without changing the parameters,and the found parameter domain can provide the conditions for the optimization of the subsequent controllers.2.An adaptive active disturbance rejection controller based on multiinnovation online closed-loop identification.Another way to deal with the time-delay problem of time-delay systems is to use predictors to remove the effect of time-delay from the structure.The most used predictor is the Smith predictor.Smith predictor has an excellent effect in dealing with time lag when the model is accurate,but it is also sensitive to model uncertainty.Once a model mismatch occurs,it may affect the system's antiinterference performance.To solve this problem,this paper proposes an online closed-loop multi-information identification method for secondorder processes with time delay.The method has relatively loose requirements on the number of sampling points and sampling time,and it can identify the system model in a shorter time when the characteristics of the object change.Through the simulation,it can be seen that the proposed effective auxiliary controller parameter adjustment.3.Active disturbance rejection controller parameters optimization method based on differential variable step size Ant-Lion algorithm.An important part of controller design is parameter setting,which can be summarized as a nonlinear optimization problem with constraints.It is often difficult and complicated to solve the problem directly.This paper proposes an improved Ant-Lion algorithm.Firstly,differential evolution is introduced to increase the diversity of the population and improve the global search ability of the algorithm.Then the step size scaling strategy is adopted to ensure that the algorithm can get higher accuracy in local search.The improved Ant-lion algorithm is used to optimize the parameters of active disturbance rejection controller.Simulation results show that the improved algorithm can search better parameters.4.Generalized active disturbance rejection control for uncertain multivariable processes with time delay based on effective open loop transfer function.Multivariable uncertainty systems exist widely in process industry.The paper puts forward a set of generalized uncertain time-delay process(active disturbance rejection controller)design process.Firstly,the multi-loop control problem is decomposed into a single-loop control problem by using an efficient open-loop transfer function.Then,the improved Ant-lion algorithm proposed above is used to reduce the order of the model.Finally,the ability of disturbance rejection,the stability condition of uncertain time-delay system and the robustness requirement cause by the unmodeled dynamics and model order reduction are considerd synthesizely.The simulation results show that the proposed method can design the controller with better effect.