The Application of Multiple Control Strategy to Tobacco Re-drying Process

In the tobacco re-drying process, there is a problem in which the control of the outlet moisture content has poor accuracy and the regulating valve does not regulate effectively due to being saturated. We design a triplex control strategy that can control multiple variables. Because the regulation of the high pressure water pump in the resurgence section has a direct and rapid effect on the outlet moisture, we employ the predictive proportional-integral (PI) control algorithm to the control object of the main controller. Because the regulation of the mixed water slowly changes the humidity in the resurgence section, we employ the PI control algorithm to the first subsidiary controller of the main controller. In order to prevent openness in the high pressure pump and the saturation of the mixed-water regulating valve, we chose a set value of the moisture content in the cooling section as the second subsidiary controlled object to indirectly influence the outlet moisture content. The actual operation results show that the proposed control algorithm can precisely control the outlet moisture content and promptly coordinate the degree of openness of the regulating valve. This strategy provides a new control method for industrial production, improves the automation level of the production line, and will prove to be greatly beneficial in industrial applications.