VII Международная студенческая научная конференция Студенческий научный форум - 2015

The key aim of this paper is to count the coefficients of Proportional-integral-derivative (PID) controller.

It is known that the PID controller is the most common type of regulators.

PID controller is a device in a control loop with feedback. It is used in automatic control systems for generating a control signal. The PID controller is used in order to obtain the necessary accuracy and quality of the transient. PID controller generates a control signal that consists of three parts. One of them is proportional to the difference between the input signal and the feedback signal (error signal), the second one is the integral of the error signal, and the third one is the derivative of the error signal.

I analyzed multiple data sources for finding a method for calculation of coefficients of PID controller. So, as a result, I chose engineering methods of Ziegler-Nikolsa, because this method does not require complex mathematical calculations. It is easy for using.

The essence of the method is as follows:

a) Recording potentiometer is connected to the output of the regulator or the object. Integral and differential action of regulator are excluded.

b) After this the coefficient of proportionality of regulator K is gradually increased, until stable oscillations with a period Tp are set at a certain value of the coefficient Kp in the system.

c) Further, the controller parameters are calculated and set. Controller parameters are based on the following ratios (fig.1):

PID controller K = 0.6 Kp, Ti = Tp / 2, Td = Tp / 8.

Fig.1 The model PID controller with coefficients K, Ti, Td.

Transition process of PID object is shown on figure 2.

Fig.2 The graph of transition process

Thus, assessment of the quality of the transition process is the following:

• Time of transition process is equal 6s.

• Overshoot is equal 0%.

• Absence of a static error is equal 0%.

So, the popularity of this method is lack of complex mathematical calculations, quick setting of the controller and system settings to time of transition process, the absence of a static error and overshoot.

To sum it up, I can say that PID controller meets all the requirements. This issue may be interesting for specialists in automation and control sphere.

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