Control Design Method Research Of Multivariable System With Multiple Time Delays

Up to now, the research and development of multi-variable system has been the hot spot and difficulty in research field. The method solving the difficulty lies in the solving the relationship between multiple circuits and evaluating the performance of control system. The main feature of chemical object is multi-variable feature. In the past decades, the control objects of multivariable system control mainly are focused on the coupling problem research, including evaluating the effect of coupling and the way to reduce the effects of coupling. As for decentralized control, the loop pairing according to the loop coupling effect is the major concerns, and then the decentralized controller could be designed for the loop pairing. As for decoupling control, the main research direction mainly lies in the design of decoupler and eliminating coupling. At present, the dominant control scheme on the market is still PID control or single-circuit feedback control in the classics of Sweden scholars published in 1995 and 2006. And above 95% single-circuit control system uses PID control strategy. The IMC-PID control is combined with the internal model control and PID, containing the both advantages of them. Besides, it is to convert between negative feedback control structure and internal model control structure, which provides a new control strategy for multivariable system.On the premise of understanding traditional PID control, the paper conducts research on centralized controller and decentralized controller design methods, in order to present effective and practical control methods in multivariable system control. At the beginning, this article has carried on a progress research of the multivariable systems control, and then a loop pairing method is proposed. Then, under the relevant elaborate theories, the centralized decoupling control method and decentralized controller are proposed combined with the equivalent transfer function concepts in this paper. On the basis of RGA combining with RNGA and direct synthesis and decoupling control, the decentralized controller for two input and two output systems designed in this paper, and the time delay compensated structure controller is used in multivariable system. At the same time, ETF method is promoted to multivariable system with non-minimum phase and non-square system, resulting in a centralized controller. As for the multi-variable system with severe coupling and especially in some classical chemical process model, considering the stability margins of system, the decentralized controller with PI and PID forms is proposed. Finally, we have drawn a conclusion of the subject research of this paper, and the research work plan in the future was prospected at the end of article.Based on the knowledge in frequency domains, this paper have considered several design methods of multivariable control system, and to a certain extent, the theory of multivariable system has been developed.