SU1246051A1 - Pneumatic proportional-integral regulator - Google Patents

Abstract

The invention relates to pneumatic control systems. A disadvantage of known pneumatic controllers is the low dynamic accuracy due to the output of the set limit levels (controller saturation) by the output signal. The proposed regulator, built on a comparison element, switching valves, diodes, throttles, including a proportional link, allows the output signal of the regulator to be limited to predetermined levels and to protect it from saturation. In addition, the circuit allows for a shock-free transition from remote control to automatic. 1 il. s (l n5 4

Description

The invention relates to instrumentation, namely, to pneumatic proportional-integral regulators with output limitations with saturation protection and unaccented switching from manual (remote) control mode to automatic, even if the controlled parameter does not equal its specified value.

The aim of the invention is to increase the dynamic accuracy of the controller.

The drawing shows a schematic diagram of the controller.

The controller contains a proportional link 1, a capacitance 2, a variable choke 3, a multi-membrane comparison element 4, the first, second and third switching valves 5-7, the first, the second and third constant chokes 8-10, two oppositely connected and parallel-installed diode 11 and 12 with shifts and reference pressure adjuster 13 Poiv.

The inputs of the proportional link 1 are connected to the input channels of the PZ setting and the parameter P, its output is РВЬ ,, through the switching valve 5 connected to the output canal P (actuator) of the regulator and one input of the third switching valve 7, the other input of which is connected to the setpoint adjuster 13 pressure P. Another input of the first switching valve 5 can be connected to the channel Rd., remote control. The output of the PQ-comparison membrane element 4 through the second switching valve 6, the second constant choke 9 and the diodes 11 and 12 are connected to the capacitance 2, a single input proportional to the link 1, through the first constant choke 8 of the comparison, through the third constant choke 10 - with a different output of the second switching valve 6. Proportional link 1, podklk Chen also to the first negative chamber of the comparison element 4, and through variable choke 3 - to capacity 2. Another positive input: comparison element 4 -float li ne to the output of the third switching valve 7. The control chamber of the switching valve connected to the channel command signal com.

The regulator works as follows.

2460512

Preliminarily, the reference pressure P is set by the s-ad unit 13, and on the diodes 11 and 12,

fatal shifts d, il), equal to d „Р„ „

ROI. where P "and and the upper value

th, 0

d

s

d - r

Re

(

AND

- bottom

specified range

the zone of change of the output signal P of the proportional link 1. The value of the reference pressure P is selected within the specified range of change P ".

Bwa

If Р „, (Р„ + yi ii, then the shifts on the diodes will be the same: (Re Pu) / 2.

In the automatic control mode, the command signal is zero (O kPa), so that the output channel P (the actuator) is connected to the output P, the proportional link through the first switching valve 5, the output signal PO of the setpoint 13 through the third

the valve 7 is connected to the positive chamber of the reference element 4, the output (PO) of which through the second valve 6 and the choke 9 enters the inputs of diodes 11 and 12. Both diodes II and 12 are closed when the condition is met

Р Р

last weekend

R

In other words, while lRV is changing, intraHbiX

For a given range, the controller operates in a linear mode and implements the standard proportional-integral control law.

If the output signal P, the change becomes larger than the upper limit level P, the pressure P at the output of the reference element 4 decreases and the diode 12 goes into a conducting state (opens). Indeed, the diode 12 opens if in static mode the pressure P , in the tank 2 becomes larger than the sum DABLEINY P at the output of the comparison element 4 and the force 4 g of the diode spring,

+ l

at

where Р „Р,

R..

com mode),

would,

(one)

(in static U, Pn - P,

Then the expression (1)

he

will rewrite

R., R.

+ P

dn

- R,

OR P P - P, +

or o - P + P,

ftblx

I.

those.

 R"

- ROI

Thus, the condition (1) is equivalent to the condition Р Р, when fulfilled

3

The diode 12 opens in this way. Due to this, the pressure in the tank 2 begins to decrease and, accordingly, the output signal P ,,,. before

Dpi J (

restoring equality "., P".

Pl l p

Similarly, when reducing the output signal P "below the boundary

Bgh

the value of P is the pressure P, at the output of the reference element 4 is increased, and the nozzle of diode II opens. As a result, the pressure in the tank 2 and the signal P,

G1 (L

at the output of the proportional link 1 is increased until the condition,. R .

tjbtX and

in contrast to the known regulators, the process of limiting the output. the signal is not accompanied by auto-oscillations, since the comparison element 4 implements the operation of continuous summation. In addition, to improve the dynamics of the output signal limiting process, the first 8 and second 9 constant chokes (fo, 18 and 0.32 mm) are installed.

In the remote control mode, a command signal P equal to one (140 kPa) is given, as a result of which valves 5-7 are switched. The actuator is controlled from the remote control channel P. The channel pressure P through the switching valve 7 enters the positive chamber of the comparison element 4, the output of which through the switching valve 6 and the third constant choke 10 (FO, 5 mm) is now connected to the tank 2, Thus, on the basis of elements 2.4, 6, 8, and 10, the integral link is dialed, as an adjustable variable to which the output signal Pgtix of proportional link 1 is supplied, and as a reference is the pressure of the remote control channel Rud.

An integral element dialed on elements 2,4,6,8 and 10 changes the pressure P in the tank 2 until the condition P P is fulfilled. Meaning pressure

output P ,, v monitors the pressure in the output

ftP X

channel P regulator. Thus, the transition to the automatic control mode is carried out without a pressure jump in the output channel P pe46051

tuller, even with the inequality of the regulated value, P, its given value P,.

Claims (1)

5 claims A pneumatic proportional-integral regulator containing a proportional link, a capacitance and to variable throttle isodrome time adjustment, a multi-membrane comparison element with the first constant throttle at the entrance to its first positive chamber and three switching J5 valves, the control chambers of which are connected to the channel of the command signal, the inputs of the proportional link are connected to the input channels of the reference and the parameter, and its output through 2Q, the first switching valve is connected to the output channel, through a variable choke to the tank and the single input of the proportional link, the output of which is also connected to the first minus chamber of the multi-membrane comparison element, the output of which is connected to its other mini-chamber and the input of the second switching valve; The other input of the first switching valve is connected to the remote control channel, which also requires that, in order to increase the dynamic accuracy of the regulator, it additionally has a reference sensor first pressure, the second and the third constant throttles and two counter-connected and parallel-installed pneumatic diodes with shifts, the outputs of which are connected to the tank and the first constant choke, and the inputs of the diodes through the second constant choke connected to the first output of the second switching valve, the other output of which through the third constant The throttle is also connected to the tank, and the reference pressure adjuster is connected to another input of the third switching valve.