Improved Dual-Control Strategy And It’s Application In Industry

There is a situation in the industry that one controlled variable is controlled by two or more manipulated variables. In this situation, we usually take these variables as a single loop separately: to fix one of the variables and then control the other one or to parallel the two variables. But the selection of the manipulated variable should not only take the economy and the reasonable of the technology into consideration but also consider the fastness of the control performance. Both of these two situations often exist in a process. In the moisture control system of the tobacco drying cylinder, the conventional method is to adjust the temperature of the cylinder with the moisture discharge fixed or adjust the moisture discharge with the temperature of the cylinder fixed. This method cannot combine the advantages of the both control mode organically. This paper introduces the advantages of the Dual-Control and makes the PPI algorithm applied to the Dual-Control system. At the same time, this strategy has been operated on the moisture control system in tobacco drying cylinder successfully. The paper will be divided into the following several sections according to this structure:(1) First, the advantages of the traditional Dual-Control system are analyzed theoretically; then, comparison is made among the fast-response, slow-response and the Dual-Control system. At the same time, the paper introduces an improved Dual-Control system according to the complicate disturbance in the industrial process. At last, the paper will illustrate the effect of the improved Dual-Control through the industrial process control case.(2) Because of the deficiency of the traditional algorithm based on the Dual-Control, a predictive PI algorithm is introduced which is aimed at the industrial processes with large time delay. At First, this part will write about the advantages and the principle of the PPI algorithm. Then will declare the PID algorithm with the different tuning methods. At last, the Dual-Control system with the PID algorithm with different tuning methods and the PPI algorithm are simulated in Matlab. Simultaneously, the comparison of the result of the simulation is done to analyze the superiority of the PPI algorithm.(3) To industrialize the theory of the Dual-Control system, a real-time simulation is built through the OPC connection between Simulink and the Opto22PAC with the PAC Project software suite. This simulation system will imitate the practical industrial process, and will use the Dual-Control system based on the PPI algorithm. At last, the output of the system is used to prove the superiority of this control strategy. (4) Tobacco drying cylinder is an important part of the tobacco drying process. It’s moisture control target is also very strict. Traditionally, the moisture of tobacco drying cylinder is controlled by single loop control strategy, such as PID algorithm. This method may result in big moisture fluctuation and low precision. The application in the tobacco drying cylinder in a cigarette factory with the improved Dual-Control strategy is introduced which has achieved the excellent control effect.