Research And Application Of PID Control Methods In Multivariable System

The primary question of this paper is how to tune reasonable and optimization PID parameters for model error, the system with big delay time and the multivariable system with coupling, because these instances often appear in industrial processes. Comparing the traditional methods of PID parameters tuning, the tuning methods that is referred to in this paper have better control effect and adaptability for complex industrial processes.This paper firstly introduces the summary about the basic principle and characteristic of PID controller. Secondly, the paper explains the sort and traditional method of PID parameters tuning. Third, the paper analyses multivariable systems. Then the paper brings forward the advanced PID parameters tuning methods that combine APC with PID control. Then the paper researches four multivariable PID control methods. This paper conducts the simulation research for the single variable and the multivariable systems, includes following several aspects specifically.First is IMC-PID parameters tuning method that combines the idea of IMC with PID control. Two kinds of models are got by system identification. They are continuous model and discrete models. So the paper explains continuous IMC-PID tuning method and discrete IMC-PID tuning method according to the result of system identification. The conclusion is different case should adopt different IMC-PID tuning method after comparing the two kinds of IMC-PID tuning methods.Second is Predictive-PID parameters tuning method that combines the idea of GPC with PID control. Comparing with the traditional PID parameters tuning methods (for example, the Z-N tuning method), Predictive-PID tuning method not only has better dynamic response characteristic, but also has satisfying control effect for the instances which have difficulties in controlling for traditional tuning methods, for example, model error and big delay time. Because traditional Predictive-PID tuning method has some disadvantages, this paper brings forward amelioration Predictive-PID parameters tuning method which obtains satisfying control result.Third, this paper researches four multivariable PID control methods, including decoupling PID control, control of multivariable systems with the advanced PID parameters tuning methods, multivariable PID control through tuning emendation genes and multivariable IMC-PID control. Then these methods are compared by control effect and feasibility. Finally in this paper gives the design method of DCS optimization software and makes the PID parameters tuning methods using in engineering applications. Then this paper shows application cases of DCS optimization software in natural gas purge equipment.