Application of Cascade PID System in Moisture Content Control of Casing Process

The opened-loop single PID control mode used in the moisture content control system for casing process in primary processing line of DIET system in Hangzhou Cigarette Factory has the shortcomings of low control accuracy and not timely operator intervention, therefore, a new control system based on cascade PID control model was designed, wherein the output moisture content of ordering cylinder delayed for 3 minutes was adopted as the input moisture content of casing cylinder for casing cylinder control. The output moisture content of casing cylinder was used for PID cascade loop control and the internal water flow in casing cylinder as major loop of PID control. The results of practical application showed that cascade PID system realized the automatic feedback regulation function according to the fluctuation of output and input moisture contents and decreased the fluctuation range of moisture content; by its double feedback control mode the system enhanced the ability of prejudgment and real-time control, basically eliminated the time lag in moisture content control. The monthly acceptable rate of moisture content increased from 83% to 92%.