Research On Control Strategy Of Intelligent Positioner In Valve-flow Pipeline System

With the strategy,the‘Made In China 2025',being proposed,the extensive attention has been paid to the vast market of China manufacturing industry.However,in the intelligent positioner consumer market,a considerable market share is still occupied by foreign products.It is of great significance to develop domestic intelligent valve positioners owning the actuators with digitization,online diagnosis and intelligence to seize this market.Taking regulating valve as research object in this thesis,the linear and non-linear mathematical models of the regulating valve fluid-conveying pipeline system were established.By studying the characteristics of the system,the fuzzy adaptive PID controller with Smith's prediction suiting its characteristics was designed.And the simulations to the both linear and non-linear regulating valve delivery piping systems were conducted respectively.The linear and nonlinear mathematical models of a regulating valve system were established.By analyzing the mathematical model of the regulating valve system,the movement law of the pneumatic diaphragm regulating valve control system was studied.According to its motion characteristics,the valve core-stem system was simplified into a spring-mass-damping system,and a mechanical balance equation of the actuators was established as well.Linearizing this system,and an open-loop delivery function of the regulating valve positioner system was obtained.For the regulating valve-conveying pipeline system,a hybrid model of the multi-body system delivery matrix method and the dynamics method was made and solved.The valve plug-stem system was modeled by a dynamics method and used as a main system.Considering full coupling for the both ends of the pipe and valve,a model was established by the multi-body system delivery matrix and was seen as a branch system.According to the model established above,based on the characteristics of nonlinearity,time-varying and large hysteresis of the system,a fuzzy self-adaptive PID controller based on Smith prediction is designed;under the Matlab/Simulink platform,the traditional PID controller is simulated and compared.Fuzzy adaptive PID controller and Smith's fuzzy self-adaptive PID controller;Research shows that Smith's fuzzy self-adaptive PID is obviously better than the other two controllers,the overshoot is small,and the adjustment time is 0.18 seconds.When the regulating valve system is disturbed by the pressure given by the pipeline,the displacement of the valve of the regulating valve synchronously occurs due to the disturbance of the pipeline,but under the action of the positioner,the disturbance is quickly smoothed and reaches the target opening.Under the Matlab/Simulink platform,a non-linear model of the regulating valve was established using modular modeling.Under the constant pressure difference,different target opening simulations are carried out to obtain the simulation results of valve core displacement,velocity,fluid force and control force under different working conditions.Under the control of the controller,the 0.28 second adjustment time can achieve the target.The opening degree verifies that the control algorithm also has a better control effect on the nonlinear control valve control system.The simulation of the system found that when the pipeline input sinusoidal pressure fluctuations,the pipeline system also showed a sinusoidal disturbance to the regulating valve system,but under the influence of Smith's fuzzy adaptive PID controller,the vibration was compensated,indicating that the controller for complex nonlinear fluid-solid coupling systems,it also has good adaptability.