Research And Implementation Of Intelligent PID Based On PLC

PLC is the main controller in the automation field,with the development of industry,the control object is more and more complex,conventional PID control often makes the poor performance of the control system due to poor parameter tuning;The intelligent PID controller,which is composed of intelligent control and conventional PID control,shows strong advantages;At the same time,the intelligent PID control algorithm embedded in PLC has become a hot research topic.The main work of this paper is as follows:(1)This paper analyzes the structure and process flow of the three tank water level control system,the hardware and software system of CompactLogix series PLC;Based on the structure and characteristics of cascade PID control,liquid level cascade PID control is designed and realized on CompactLogix.(2)This paper studies the composition of fuzzy control system and the design principle of fuzzy controller;Based on the conventional PID control algorithm,fuzzy adaptive PID controller is designed;With the help of graphical interface(GUI)tool provided by fuzzy logic toolbox in MATLAB,offline control table is created,then stored the table in the PLC tag;And then through the RSLogix5000 programming software realizes the fuzzy conversion of input,according to the obtained fuzzy quantity,it can carry out the on-line look-up table operation,and finally realize the adaptive adjustment PID parameters;Then,the fuzzy adaptive PID algorithm is improved,which makes the weighting coefficient of the error and error both change adjustable to meet the control requirements of different control processes.(3)This paper studies the structure and principle of neural network control system,using RBF neural network to identify the information of controlled object online;according to the running state of the system and identification information provided by the RBF neural network,the BP neural network through the adjustment of its own weight coefficient,to achieve the PID parameters online adaptation;Aiming at the problem of slow convergence speed of BP network,an algorithm was improved by introducing the momentum;According to the characteristics of the RSLogix5000 programming software,design and implementation of neural network adaptive PID control algorithm in CompactLogix series PLC.(4)Finally,using Factory Talk View monitoring software design the monitoring interface,it can display the current operating status and historical data,and also can provide interface for control.Then,using three tank liquid level monitoring interface to tests the experimental device,the results show that the intelligent PID control has better robustness and adaptability than the conventional PID control.