Design Of Sliding Mode Controller For Networked Cascade Control System

Cascade system(CCS)is a widely used control system in practice,which has a dual closed-loop structure to accelerate system response speed and improve disturbance resistance.Along with practical needs,it is combined with Networked Control System(NCS)to form Networked Cascade Control Systems(NCCSs).It not only has the flexibility and scalability of NCS but also has the advantages of CCS.This makes NCCSs more suitable for practical production and application.In recent years,there has been a lot of research on the nonlinear problems of NCSs,but compared to NCCSs,there are relatively few nonlinear studies.There are many factors that affect stability in NCCSs,such as network-induced delay,nonlinear factors in the system,and so on.Therefore,it is very difficult but meaningful to realize the stability control of NCCSs.In this thesis,considering different NCCSs.First of all,in nonlinear discrete NCCSs,the problem of the cooperative design of state feedback primary and secondary controllers is considered.Then,combined with nonlinear systems and sliding mode control(SMC),mathematical models of continuous and discrete nonlinear NCCSs are established.Based on the combined system of sliding mode control and NCCSs,sufficient conditions for the stability of different types of systems are given,and the state feedback primary controller and sliding mode secondary controller of the system are further designed cooperatively.At the same time,the system is optimized using the sliding mode reaching law of the system.Finally,through a simulation example,its practicality and effectiveness are verified,providing a feasible basis for production applications.The specific research content is summarized as follows:1.Considering that nonlinear factors are unavoidable in actual industrial production,nonlinear systems are introduced into nonlinear NCCSs and applied to their inner objects.Based on the model and Lyapunov functional method,the primary controller and the secondary controller of the system are designed using the linear matrix inequality technique.In addition,the effectiveness of the proposed design method is verified through a model of a thermal power plant with this structure.2.According to the actual industrial demand,sliding mode control is introduced into NCCSs,and the mathematical model of the system is established.Based on this model and the Lyapunov functional method,the state feedback primary controller and the sliding mode secondary controller for this system are co-designed by using the linear matrix inequality technique.Finally,an example of a thermal power plant is given to illustrate the effectiveness of the proposed co-design method.The main advantages are that the SMC is introduced into the cascade control system and the design method of sliding mode controller for this system is proposed for the first time.On the premise of ensuring the stability of the system,it can be driven to the sliding mode surface in a limited time,and remain on the sliding mode surface in all subsequent times.Finally,the effectiveness of the proposed design method for the primary and secondary controllers is verified through simulation.3.Generally,sliding mode controllers will have a chattering phenomenon,so integral SMC is considered to eliminate chattering for the secondary controller of continuous NCCSs.The modeling and controller design of a class of continuous NCCSs based on integral SMC is studied.Based on the model and Lyapunov functional method,the state feedback primary controller and the integral sliding mode secondary controller of the system is designed using the linear matrix inequality technique.In addition,a thermal power plant model is given to verify the effectiveness of the proposed design method.