1、 Content abstract

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2、 Content description

pick   want ： This design simulates a given flow control system , It has been confirmed that the system is a simple control system , And control strategy selection PI control . The critical proportional degree method is adopted respectively （ Stable boundary method ）、 Attenuation curve method 、 The empirical method is used to set the parameters of this system . Its performance indicators are measured according to Engineering Standards . The system assumes that the transfer function of the generalized object is unknown , The transfer function of the actual generalized object is known .

key word ： Flow control system ;PI control ; Critical proportionality method ; Setting ; Simulation

Access to information , And combine what you have learned , We use the critical proportionality method 、 Attenuation curve method 、 The empirical method is used to set the parameters of the system .

2.1.1 Critical proportionality method

The stable boundary method is also called the critical proportionality method , It is the most widely used regulator parameter setting method at present . If the production process allows , Let the regulator work in proportion . Gradually change the proportion of the regulator from large to small , Until the system produces constant amplitude oscillation ; Record the proportionality and equal amplitude oscillation period at this time , Then through empirical formula , Calculate the setting parameters of the regulator .

The stable boundary method is suitable for general flow 、 pressure 、 Liquid level and temperature control system , But it is not applicable to the process with particularly small proportion .

2.1.2 Attenuation curve method

The attenuation curve method regards the system as a closed automatic regulation system under the action of pure proportion , If the proportional band of the regulator is gradually reduced , When there is a 4：1 When the attenuation process of , determine 4：1 Attenuation scale band and 4：1 Attenuation operation cycle , Then calculate the specific parameters according to the empirical formula . advantage ： The measurement distance can be far 、 Remote measurement is very accurate .

The attenuation curve method is carried out when the regulator is put into operation , There is no need for the system to operate on a stable boundary , To compare safety , And easy to control , It can be applied to all kinds of control systems .

2.1.3 Experience method

Empirical method is essentially an empirical trial and error method , It does not require experiments and calculations , It is based on operating experience and prior knowledge , First determine a set of adjustment parameters , Then artificially add step disturbance , Observe the response curve of the controlled parameters , And according to the influence of the parameters of the regulator on the regulation process , Change the corresponding setting parameter value one by one , Generally according to the first proportion , Re integration time 、 The order of differential time is set one by one , Until you get satisfactory control quality .

The advantage of empirical method is that there is no need for special experiments 、 Little impact on the production process ; The disadvantage is that there is no corresponding calculation formula for reference , The choice of initial value depends entirely on experience , There is a certain blindness .

3、 Simulation analysis

4、 Reference paper

[1] Yang Yanxi ． Process control and automation instrumentation ． Beijing ： Mechanical industry press ．2017

[2] Li Yida ． Control system design and simulation ． Beijing ： Mechanical industry press ．2014

[3] Wang Yi ． Process equipment control technology and Application （2 edition ）, Beijing ： Chemical Industry Press .2012

[4] Wang Shuqing ． Process control engineering （ The first 2 edition ）． Chemical Industry Press ．2011

[5] PID Two control tutorials （《PID Algorithm analysis 》、《 From entry to mastery — Read and PID》. I & C Engineering Network

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