Application Of Expert Control Used In The Pulp Consistency

The Pulp consistency is one of the most important physical measurements.The consistency, especially the consistency before the headbox, determined thepaper quality. So important the pulp consistency is, the acquirement ofconsistency control system is more strict then the other system in the DCS.PID algorithm is used widely in the consistency control system, and the PIDalgorithm has some advanced feature, such as the simple construct, the easyrealization, and the good adaptive. However, it produced some disadvantage byused in the consistency control. Slow responsibility, bad anti-disturbance andsteady is the major thing. Contract with the other circle in the pulp-makingprocess, when the set-point is changed, the adjust time of consistency is thelongest one. At the same time, the change of pulp-motor's speed and shake ofpulp's consistency may move the consistency out of the set-point. All of thetroubles pull down improvement of the consistency control, and limited theadvance of paper quality.This paper combined with the pulp-making process, analysis theconsistency control process. After the analysis, it is found that the disadvantageof the consistency control is made by the isolation of many of the consistencycontrol circle.Based on this understanding, this article raised a new guiding ideology forthe consistency control, what combined many of consistency circles in the sameline as a whole, and distributed the role in the large systems in accordance withthe control precision.This paper analysis the interrelationship in the three consistency circuits inthe Xin layer pulp. In accordance with the results of analysis, the article putforwards the relationship model, and done some certification about it.Handling the large system that is composed of many consistency circuits,the main basis in the control algorithm selection is how to avoid the lack ofdetailed accurate mathematical model of system. For this reason, this paperraised a new idea to pulp consistency control based on the expert control.The application of expert control, is taken into account the PID algorithms,and coordinated the relation between the circuits. In combination with the PID,the expert controller focused on a number of contingencies. Although the PIDcontrol parameters are involved, but the fundamental purpose is to get the controlcircuits away the bad effects on control quality.Expert controller in the single circuit is based on the experience, which issummarized from the effective measures when the accidents happened, andrecorded in the form of expert rule. The control rules in the multi-circuits arebased on the relationship between the circuits in the large system, and themeasures to deal with the fluctuations in some consistency circuit.Expert controller simulate in the Matlab with the other part model in controlcircuit. The result curve of simulation proved that the expert PID has moreadvantage than the traditional PID in increasing response speed, enhancing theanti-interference capabilities and so on.The new control program was realized in the Siemens PLC platform, andtaken into operation in a paper-making line in Fuyang. As same as the simulationresults, the fact runtime trend curve proved that the new algorithm is practical;the effect in improving the control performance is obvious. So the application ofexpert control in the pulp consistency has an extensive space to popularize.