Research On PID Control Algorithms For Large Time Delay Processes Based On Particle Swarm Optimization

Large time delay commonly exists industrial process.Time delay processes control has always been a typical problem in control field and has been widely concerned.However,the traditional view that the PID controller is not suitable for the large time delay process control.But we have shown that the key of whether PID controller can be used in large time delay process control is how to set the controller parameters.And the intelligent algorithm is applied to tune PID controller parameters,which is an effective control system design method.As an efficient and simple parallel search algorithm,particle swarm optimization algorithm(PSO)has been widely used in PID parameters tuning.However,the standard PSO algorithm has such problems as premature,easy to fall into local optimal and slow convergence speed in tuning PID parameters for large time delay processes.Its tuning results of such controller always could not get good control effect.For the above reasons,this thesis is supported by the project of Shaanxi key science and technology innovation team(2014KCT-15).Focus on the problem of PID parameter tuning in large time delay process based on PSO algorithm.The improved PSO algorithm is studied,and it is applied to the paper basis weight control system of fourdrinier machine.The main contributions are as follow:?.Tuning PID Controller Parameters Based on Information Entropy PSO Algorithm with H? Theory for Large Time Delay ProcessesAiming at the problem that during tuning PID parameters for large time delay processes,PSO algorithm with large search space will have poor search ability,even can't converge,a modified particle swarm optimization based on H ? theory with the objective initialization of particle swarm(HOI-PSO)is proposed.MATLAB simulation experiments show that: HOI-PSO algorithm enhances the convergence speed and has the similar or even better global search capability as the scope of large range search;for large time delay process control,the control performance of the closed loop system is greatly improved.?.Application of the Hybrid PSO Based on Conjugate Gradient to PID Parameter Optimization for Large Time Delay ProcessFor the problem that PSO is easy to be premature convergence,a hybrid PSO(CGM-PSO)algorithm based on conjugate gradient method(CGM)and convergence judgement mechanism is proposed.In this way,it can not only enhance the local search ability,but also help accelerate the convergence speed.In this chapter,CGM-PSO algorithm is applied to optimize PID controller parameters for large time delay process,MATLAB simulation experiments show that: the CGM-PSO algorithm proposed in this paper can effectively solve PSO precocious problem,and the control performance of the closed loop system can be improved well.?.PSO Algorithm-based Parameters Tuning with Two-degree-of-freedom IMC-PID Control Method for Large Time Delay ProcessesWith the aid of the dual controller design technique and PSO algorithm,a two-degree-of-freedom(TDF)internal model control(IMC)PID method based on PSO algorithm is proposed.According to the typical large time delay process,regarding ITAE as the objective function,using PSO algorithm to optimize and tune IMC filter time constants.MATLAB simulation results show that TDF-IMC-PID control method based on PSO algorithm has the advantages of simple algorithm,fast searching speed and high efficiency,which can improve the tracking performance and robustness of TDF-IMC.?.Design and Implementation of Research Results in Paper Basis Weight Control System of Fourdriner MachineSet up Mathematical model of basis weight control loop by using step response modeling method.And apply the previous part to basis weight control loop.Without affecting the normal operation of the existing quality control system(QCS),an implementation of paper basis weight control system based on OPC technology was given by using Siemens S7-300 PLC controller hardware,and Win CC&Step7 software development platform.And then the proposed PID control algorithm for large time delay process to be applied to production practice.This thesis analyzes the performance of standard PSO algorithm and its problems in tuning PID parameters for large time delay processes.Based on the above research,three improved methods of PSO are proposed.With the help of OPC technology and industrial Ethernet communication technology,the concrete project realization scheme of PID control algorithm for paper quantitative control loop is given.The scheme is successfully applied to the existing QCS system in Zhejiang paper factory.Engineering application results showed that the PID control algorithm proposed in this paper is effective in large time delay process control.