Controller Design For Discrete Cascade Control Systems

Cascade control systems(CCSs)have been widely used in actual industrial production systems.Currently,most of the research in CCSs focuses on the co-design of two proportional(P)controllers,but this is difficult to content the requirements of actual industrial process control.In response to actual needs and in order to improve the control effect in CCS,the proportional integral(PI)controller is introduced into CCSs and design the parameters of the controllers.With the development of modern industry,the traditional industrial point-to-point connection method cannot content modern industrial control well,introducing network to achieve communication between control components on the basis of CCS,forming networked cascade control systems(NCCSs),At the same time,due to the existence of network communication delay,it is very difficult to stability analyze and control of NCCSs.pointing at the above-mentioned problems in CCS and NCCSs,this article establishes different mathematical models based on the above problems,Then,a suitable Lyapunov function is constructed,and sufficient conditions for stabilizing the system are given.Further consideration is given to the design method of the controller parameters of the system.Finally,a temperature control simulation example with a cascade structure is used to verify the effectiveness of the method,and it supplies a feasible basis for the practice modern industrial production.The concrete research contents of this thesis are as below:1.State delay is common in networked cascade control systems.Event-triggered control has a good superiority in economizing network bandwidth resources.In this thesis,the eventtriggered control of discrete NCCSs with state delay is studied for the first time.Firstly,on the basis of modeling,by constructing an appropriate Lyapunov function and using linear matrix inequality(LMI)technology,the sufficient conditions for the stability of the system are given,and further,the co-design method for the main and secondary controller parameters,and four event-triggered parameters is presented.Finally,a simulation example of a main steam temperature control system with a cascade structure is provided to demonstrate the effectiveness of this method.2.According to the actual needs of industry,this article introduces PI controller into the CCSs for the first time and researches the question of controller devise,in which the main controller uses PI controller and the secondary controller uses P controller.On this basis,the mathematical model of this system is set up.After that construct a new Lyapunov function,provide sufficient conditions for system stability using LMI technology,and then co-design the parameters of the primary and secondary controllers.Finally,a simulation example of a main steam temperature control system with a cascade structure is provided to demonstrate the effectiveness of this method.3.The general position PI controller maybe cause the integral saturate,but incremental PI controller can avoid integral saturation.This thesis first considers the controller design of a class of discrete CCS whose main controller is an incremental PI controller.First,a mathematical model of cascade control system is established based on the above-mentioned conditions.After that a new Lyapunov function is established,and sufficient conditions for system stability are given by LMI technology.Next,the controller design part is given.Finally,a simulation example of a main steam temperature with cascade structure is given to illustrate the feasibility of this method.