SU1211687A1 - Differentiator - Google Patents

Description

one

The invention relates to the technical means of correcting automatic control systems and can be widely used in automatic control systems of steam generators.

The purpose of the invention is to increase the accuracy of the device,

Figure 1 shows the circuit diagram of the driveable device; figure 2 is the logarithmic frequency characteristics of the proposed device. .

The device contains the second operational amplifier 1, the fifth resistor 2, the capacitor 3, the fourth resistor 4, the first operational amplifier 5, the third, the second and the first resistors 6-8.

In FIG. 2, the following symbols are accepted: U, U2 input and output signals of the device; L (iJj, V (tJ) - amplitude and phase characteristics of the device; Lf, tiJ) amplitude and phase characteristics of the prototype.

Thus, the differentiation device contains a second operating amplifier covered by a deep negative feedback through resistor 2, amplifier 1, to the input of which is connected a circuit consisting of a series-connected capacitor 3 and resistor 4, a; also the first deeply negative feedback operational amplifier 5, in which this connection is implemented through a resistor 6. The output of the second operational amplifier, which is the output of the device, is connected via a resistor 7 to the input of the first operational amplifier 5, to which a resistor is also connected 8, which provides input to the device as a whole, and the output of the first operational amplifier 5 is connected to the input of the second operational amplifier 1 through a circuit consisting of a series-connected capacitor 3 and a resistor 4.

Differentiation device operates as follows.

The input signal + U / is supplied to a resistor 8, which is connected to the input of the first operational amplifier 5, covered by a deep negative feedback.

7

through the resistor 6. The output signal of the device Ut is fed to the input of the first amplifier formed by the operational amplifier 5 and resistors 6 and 7 and operating in the inverter mode, since the resistance 7 at its input is equal to the resistance of the deep negative feedback 6, which covers the first

operational amplifier 5.

The signal (and ,, + Ui) from the output of the amplifier formed by the first operational amplifier 5 and the resistors 6 and 7 is fed to the input of the second

The opto-amplifier 1 is connected through a circuit consisting of series-connected capacitors 3 and a resistor 4. In the second amplifier, formed by the operational amplifier 1, resistors 2 and 4, and capacitor 3, an operation is performed that can be described by

- .rj. .1- Wed

-1- R.

- (and, + uj

Rt CP

(Ui - iG), 1+ RiCp

where we get the formula UaK

- - - - - - - 31 m - 1.-.

(one)

Ui + Uz 1 + Tr where R, and .R-2 - even resistance

the correct and nth resistors 4 and 2; C - capacitor capacitance 3.

Then from the expression (1) can be obtained dependence

(1 + Tp) Uj Cr (and, + i) or after grouping like members,

(1 - Tr - Kr) u KpU ,. (2)

The expression (2) makes it possible to write the transfer function of the proposed differentiating device in the form

W (P) --- - --- P (1)

 and, LU (T-k) p.

those. show that during the operation the process of differentiation of the input signal U really goes. However, unlike the proto-. the type whose transfer function

s (p) .K.R ..

 1 + Tr (4)

here, according to the expression (3), it is theoretically possible to achieve complete compensation of the inertia of the differentiating device, estimated by the constant time T, if we take

T to where

W (P) Cr, (5)

those. the dependency is of the form Uj - KpUi

dU

Ui K

dt

(6)

which characterizes the optimal differentiation of the input signal U |. From a practical point of view, equality can be achieved only with a certain accuracy. Therefore, the expression (3) we write as follows:

.Kuz .Kf ... (7)

W {p)

Ui 1 + 1 $

where the new time constant can be made arbitrarily less than the prototype one, i.e.

"

(eight)

This is presented as the effect of compensating the inertia of the differentiator.

For the base object, the device is taken by source (1). This device10

15

116874

the property has a transfer function

V (j (p) cr,

those. the output signal is strictly proportional to the arbitrary from the input at each time point (see 5 and 6), which means the achievement of the optimal differentiation process. However, such a basic device, having an infinite bandwidth, has low intrinsic noise immunity, is prone to self-excitation, which is often brought into the automatic control system.

The efficiency of the proposed differentiating device can be shown by the lag-frequency frequency characteristics of the amplitude L- (u)) and phase Af (ij) shown in FIG. 2. Here, for comparison, the same characteristics are given for prototype LhW) and y (J). For example, a typical prototype is one in which K T is 0.1 C. Then, for the proposed differentiating device

The mating frequency (T-K) can easily be shifted to the high-frequency region, provided T ,10 0.102 s, K 0.101 s. Such parameters of the device provide 1 hour of differentiation in the frequency range of 4 decades, which is a hundred times higher than that of the prototype.

20

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(g- ";

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Claims (1)

A DIFFERENTIATING DEVICE containing the first and second resistors connected by the first terminals to the first terminal of the third resistor 'and to the input of the first operational amplifier j connected by the output to the second terminal of the third resistor and to the first capacitor plate connected by the second plate through the fourth resistor to the first terminal of the fifth resistor and to the input of the second operational amplifier connected by the output to the second output of the fifth resistor, characterized in that, in order to expand the frequency range of the device, not output of the second operational amplifier is connected to a second terminal of the second resistor. 12) 1687