基于分层递阶的片烟干燥智能控制系统

摘要

To overcome the shortcomings of traditional control means in tobacco strip dryer, a system based on multilevel hierarchical control was developed, which was composed of three levels: base temperature optimizing module (organization level), moisture content controlling module (coordination level), and hot air temperature single loop PID control (execution level). The steam valve was regulated by comparing the actual temperature with the set value at each drying section to control hot air temperature, and moisture content was stabilized by moisture content control module and PID control. Under head and tail tobacco drying mode, a database relating steam valve opening to different tobacco grades was established to be extracted and executed by PLC. Under normal drying mode, a database relating hot air temperature value in each section to different tobacco grades was established to be extracted and executed by PLC. The results showed that: 1) The system could automatically identify the state of strips during drying, and adjust the hot air temperature in each section separately and accurately control moisture content in dried strips. 2) Comparing with traditional control system, its new control system reduced the deviation of hot air temperature at head and tail tobacco drying mode from 5 ℃-15 ℃ to 1 ℃, decreased the amount of head and tail tobacco with unqualified moisture content from 2 000-3 000 kg to less than 300 kg, increased the proportion of properly dried strips from less than 90% to more than 95%, and the standard deviations of moisture content in strips in cooling section and in finished strips were controlled under 0.5% and 0.25%, respectively. The processing quality of strips was promoted effectively.%为弥补传统片烟干燥控制模式的不足，建立了一种基于分层递阶的片烟干燥智能控制系统。该系统由温度基准寻优模块（组织级）、含水率稳定控制模块（协调级）、热风温度单回路PID控制（执行级）3个层次构成。通过采集各干燥区温度值与设定值进行比较，控制蒸汽阀门的开度，实现热风温度的稳定控制。利用含水率和PID控制模块，实现含水率的稳定控制。在料头料尾模式下，建立不同烟叶类别蒸汽阀门开度值数据库，调取相应阀门开度值并通过PLC进行控制。在正常生产模式下，建立不同烟叶类别各区热风温度值数据库，调取相应温度值并通过PLC进行控制。结果表明：①根据工况改变，系统能够自动识别片烟干燥过程中的物料状态，对各干燥区热风温度分区调整，实现片烟干燥含水率的精准控制。②与传统控制模式相比，采用智能控制系统处理的料头料尾干燥热风温度偏差由5℃～15℃减小到1℃，含水率不合格的料头料尾量由2000～3000 kg减少到300 kg以内；片烟烤透率由低于90%提高到95%以上，冷房片烟和成品片烟的含水率标准偏差分别在0.5%和0.25%以内，有效提高了片烟加工质量的控制水平。