Research On Control Strategy And Fluctuation Of Liquid Level Control System

Process of the development of automatic control technology makes the continuous process industry has been a rapid development,the production unit scale is more and more big,high yield,stable product quality,good security,among them,not only benefit from including testing instrument,DCS control system,regulating valve,the instrument control system of progress,including the development of control theory and technology.Liquid level control system in the field of petroleum chemical industry,thermal power,nuclear power and other large industrial production process is very common,such as nuclear power plant steam generator level three impulse control,safe,stable and efficient production for nuclear power plants is of great significance,the liquid level constant value control and process control are required to have high dynamic and static performance,long wave divergence and even lead to accident parking is not allowed.Based on a small experiment device,liquid level control system based on the process system,including piping,pump,valve,tank and fluid mechanics mechanism modeling and experimental identification,and independent design of control algorithm,liquid level control system experimental device was to obtain a complete mathematical model,through the open loop and closed loop experiment,verify the accuracy of the mechanism of the liquid level control system model.After the simulation model accuracy of the liquid level control system is verified,a series of studies are carried out on the feedforward control strategy of the liquid level control system.First to feedforward control is briefly analyzed,and static feedforward compensator was proposed and designed for dynamic feed-forward compensator,and simulated in the simulation model and experimental platform of the comparison of the two kinds of feedforward compensator,the results show that two kinds of feedforward compensation has obvious inhibiting effect on liquid level fluctuation,and the dynamic feedforward compensation is better than that of static feedforward compensation,has important practical significance.Secondly,a new feedforward cascade control strategy is proposed,which is compared with the traditional feedforward cascade control strategy on the simulation model and experimental platform.The results show that the control effect of the new feedforward cascade control strategy is better than that of the traditional feedforward cascade control strategy.Finally,the paper studies the two kinds of problems found in many practical applications.Firstly,the paper studies the mechanism of viscosity phenomenon caused by the change of friction force in the filling of the regulating valve,thus causing the transmission mechanism of the fluctuation of liquid level control.The conclusion is verified by simulation and experimental studies.Secondly,the paper studies the noise phenomenon of detection signals caused by the unstable pressure taking of the transmitter(pressure,liquid level)due to impurities and other factors,and thus causes the transmission mechanism of liquid level control fluctuation.Simulation and experimental studies have also verified this conclusion.