The Research Of Application Of Fuzzy Control In Pulp And Paper Making

Pulp and paper making is a complex process, with the characteristics of uncertainty,Nonlinear, time-varying, large time-delay. Conventional PID is difficult to meet the qualityrequirements. The traditional DCS control system with complex structure, poor generality isdifficult to be maintained. And it need to be improved in the pulp and paper making processcontrol. With the development of control Theory, computer and network technology, advanceprocess control and intelligent device are discussed to be used in pulp and paper making.Fuzzy control is an advanced control, which does not depend on the mathematical modelof controlled object, has been widely used in all walks of life, and has a more favorable effectsthan traditional control system. Therefore it is of great significance to discuss the application offuzzy control in pulp and paper making.Temperature control system in paper bleaching based on two level Smith predictors, blackliquid concentration control based on fuzzy cascade control, caustic temperature control basedon fuzzy forward feed-back control for bleaching section, black liquor evaporation section andcaustic process were designed. Combined with Smith predictors, cascade control andfeed-forward, fuzzy controller and the corresponding ruler was designed. Matlab simulationshows that fuzzy control has a better performance in self-adaptability, dynamic and staticcharacteristic, anti-interference and Robustness.On the basis of these simulation, fuzzy PID algorithm was applied to the level controlbased on fieldbus system. The fuzzy control algorithm designed with the Siemens S7-300PLCand the configuration software STEP7was applied to the level control of single tank. PLCcontroller communicate with intelligent sensors and valve positioner through profibus fieldbus.The scheme can solve the problem of structure complexity, difficult to be maintained and poorgenerality of DCS system. The control algorithm was achieved by the method of checkingtables in STEP7. By off-line calculation parameters, an on-line PID parameters look-upprocedure was established. The algorithm reduces the CPU load effectively.In addition, the monitoring interface was designed in the software WINCC to monitorcontrol process. Experimental results show that the fuzzy control with good dynamic and staticcharacteristics, self-adaptability and robust can provide a better solution for pulp and papermaking process.