Event-triggered Controller Design Of Nonlinear Networked Cascade Control Systems

Cascade system is a common control system in industrial production,and its cascade structure can speed up the response and improve the anti-disturbance capability.However,the traditional point-to-point structure can no longer meet the needs of modern industrial production,so Networked Cascade Control Systems(NCCSs)are gradually entering people’s vision.The networked control system has the unique advantages of high control accuracy and easy detection and maintenance,it has a wide range of application prospects.However,there are inevitably factors affecting the stability of NCCSs,such as Limited communication bandwidth,induced delay in data transmission,disturbance.Therefore,the stability control of NCCSs is a very difficult task.Especially,the controlled objects in industrial production often produce nonlinear variations,which further enhances the difficulty of controller design.In this thesis,to address the above problems in networked cascade control systems,we combine Lurie nonlinear systems and event-triggered mechanisms to establish mathematical models of two types of nonlinear NCCSs from both continuous and discrete perspectives,and give sufficient conditions for system stability with responsive event-triggered parameters,and further collaboratively design the event trigger and primary and secondary controllers of the system.Then,considering the disturbance phenomenon in the system,the suppression of the system disturbance is achieved by co-designing the primary and secondary controllers and event-triggered scheme.Finally,the practicality and effectiveness are verified by two different sets of boiler system simulation examples,which provide a feasible basis for production applications.The details of the study are summarized as follows.1.Considering that nonlinear factors are inevitable in actual industrial production,Lurie nonlinear system is introduced into nonlinear NCCSs and applied to its sub-controlled objects.On the other hand,between the unique advantages of event-triggered control for saving network resources,a new mathematical model is established by combining event-triggered control and nonlinear system simultaneously into NCCSs for the first time,and the adequacy proof of system stability is completed from both perturbed and unperturbed aspects,while the event-triggered condition is obtained.Finally,based on the obtained conditions,Finally,the corresponding event trigger and primary and secondary controllers are further co-designed,and the feasibility of the design scheme is verified by a marine boiler simulation example.2.The discrete event-triggered condition can avoid Zeno phenomenon,plus the discrete system is convenient for data calculation and transmission,which can further improve the stability speed of the system,so a new mathematical model of the discrete system is established by combining the Lurie system with another event-triggered scheme.Considering the two cases of system without disturbance and with disturbance,the primary and secondary controllers and event-triggered scheme in the discrete state are co-designed respectively.Finally,the effectiveness of this method for disturbance suppression is verified by a simulation example of a main steam temperature control system.