Study On Control Problems Of Networked Cascade Systems

When discrete nodes of close-loop control system exchanging their data using com-munication channel for the connecting medium, then the system is called Networked Control Systems(NCS). Networked Cascade Control System (NCCS) is fully integrated of complex process control and networked control system. Compared to traditional line connection system, it can effectively reduce design complexity, sharing of information resources between internodes, making intelligent decisions by effectively using inte-gration of global information and arrangement of system components in larger space, etc.This paper takes the networked cascade control system as the research object, prob-lems of designing the robust H-infinite feedback controller for the system under the short random delay, network predictive control for control systems under Markov delay and packet loss, networked predictive control for the system with external disturbance in the inner loop have been studied. The concrete research content described as follows:First, we give out a brief introduction of basic knowledge of cascade control sys-tem and common control network, the basic problems that should be considered when networked cascade control system is analyzed. Then we introduces the practical pro-cess of industrial networked cascade control system is commonly used in four kinds of network configuration mode and the characteristics of each mode in detail At the same time, the principle of network predictive control strategy is given and expounded to the unknown inputs (or disturbance) observer to estimate the PI observer design method.Secondly, the method of robust H-infinite controller design for networked cas-cade system based on Fieldbus has been proposed. Based on field bus system induced the random characteristic of short time delay, after discretization by discretization aug-mented state model for the system. Then define the augmented state system, the Lya-punov function by using linear matrix inequality and Schur lemma and other knowledge, gives systems under output feedback robust H-infinite asymptotic stability condition and the corresponding main or deputy feedback matrix method to calculate the control law. Simulation experiments based on the main steam temperature control system based on fieldbus modeling and analysis to verify the effectiveness of the control law design methods.Then, network predictive control strategy for networked cascade system under ran-dom time delay has been proposed. At first, the corresponding augmented state equation of networked cascade control system is given and the augmented system state estima-tor was designed to predict control is given input sequence and compensator selection control input. Then, using the theory of switched systems knowledge NCCS network forecasting stochastic stability condition is given.In addition, network predictive control for the networked cascade system with dis-turbances is also been studied. First, we establish PI-observer of NCCS with distur-bances, the observer was used to estimate the disturbance and the state, the condition of PI observer for the NCCS can be design is given later. Combining related theory of switched systems, we give out the random output bounded stability condition of network predictive control for NCCS with disturbances.Finally, the main research contents are briefly summarized, combined with the latest research achievements and the problems in our current study, the future research direction were given out.