The Level Control Scheme’s Design And Implementation Based On Self-tuning PID About Pva Polymerization Kettle

Polyvinyl alcohol(PVA) product is a polyvinyl alcohol production device, its main purpose is vinylon fiber processing agent, emulsifying agent, modifier, acetal, etc., in recent years the request of high degree of polymerization PVA fiber increased rapidly, and prospects are very broad. In the polymerization process the reacting time is an important factor,the time is controlled by controlling the reactor level.Before modification the level is controlled by conventional PID control, after high degree of polymerization PVA is put into production, the liquid level control precision is reduced, and the system is not stable, then try to find a method of PID parameters self-tuning.The article summarizes how to improve performance of the liquid level control system of the polymerization kettle. Research present situation at home and abroad, establish that the polymerization production process is the non-linear, time delay and uncertainty, it is difficult to establish accurate mathematical model. So design and improve the scheme of the level control system. Use the self-tuning PID control to modify the liquid level control scheme. The method is based on the step response curve of the pattern recognition, the research found that it has the function of not only the conventional PID control, but also the online self-tuning function to the complex object controller parameters. According to the polymerize process,choice the corresponding level transmitter and the regulating valve, lap the hardware circuits, Configurate circuit in application of the configuration software of CS3000 system of Yokogawa company. During the configuration process,analysis and determine the self-tuning PID control block’s function parameters. After programming, download, debug and tune it on the EWS or ICS.At the end, test the circuit,put the self-tuning PID control system into operation, on the ICS observed the process and curves. According to the self-tuning PID requirements, get the optimum parameters of the P, I, D. When the liquid level come to the given value, switch to the conventional PID control function to control the polymerize reaction time correctly.