1961-02-08

Abstract of GB860757 860,757. Fluid-pressure servomotor-control systems. GERATE-UND REGLER-WERKE TELTOW VEB. Feb. 11, 1957, No. 4577/57. Class 135. An automatic process controller includes a member responsive to an input signal corresponding to the value of a controlled condition, a member rotatable in one or other direction by said input signal responsive member, and means operable by said rotatable member to generate an output signal, the rotatable member only being rotated to vary the output signal when the deviation of the input signal from a desired value is increasing but remaining stationary to cause the output signal to remain constant when the deviation of the input signal is decreasing. The input signal is fed to a bellows 2 which actuates a driving member 4 located between the left-hand ends of two pivoted levers 15, the other ends of which lie between two adjustable stops 13, 14. If the bellows 2 expands or contracts to move the driving member 4 from the set position one or other of the pawls 5, 6 is actuated to rotate the ratchet-wheel 7. When the driving member 4 is moving back to the set position the brake 8 holds the ratchet-wheel 7 stationary. The ratchet 7 controls a lever 10 which actuates a bleed valve 11 connected by a line 17 to a source of fluid pressure. The back pressure of the bleed valve 11 constitutes the output signal on the line 18 and is fed back to the bellows 12. The system may be used in association with a conventional single or compound action controller. In a modification, Fig. 2 (not shown), additional line connections and cocks are provided to allow the input signal to pass directly to the output line if desired.

0

1961-02-08

G05B6/05 ; G05B11/50 ; G05B6/00 ; G05B11/00

G05B6/05 ; G05B11/50

GB19570004577 19570211

GB19570004577 19570211

FR1168490 (A)

1	Improvements in or relating to automatic process controllers
	Inventor:	Applicant: TELTOV GERAETE REGLER
	EC:G05B6/05; G05B11/50	IPC: G05B6/05; G05B11/50;G05B6/00(+1)
	Publication info: FR1168490 A - 1958-12-09
2	Improvements in or relating to automatic process controllers
	Inventor: FERNER VALENTIN	Applicant: TELTOV GERAETE REGLER
	EC:G05B6/05; G05B11/50	IPC: G05B6/05; G05B11/50;G05B6/00(+1)
	Publication info: GB860757 A - 1961-02-08

WHAT WE CLAIM IS: 120

1 An automatic process controller comprising a member responsive to an input signal corresponding to the value of a controlled condition, a member rotatable in one or other direction by said input signal responsive mem 125 ber, and means operable by said rotatable member to generate an output signal, the rotatable member only being rotated to vary the output signal when the deviation of the input signal from a desired value is increas 150 860,757 ing but remaining stationary to cause the output signal to remain constant when the deviation of the input signal from a desired value is decreasing.

2 An automatic process controller as claimed in Claim 1, wherein the said input signal responsive member comprises a bellows, and the rotatable member comprises a toothed wheel rotatable by one or other of a pair of pawls actuated respectively by expansion and contraction of the bellows.

3 An automatic controller as claimed in Claim 1, wherein said output signal generating means comprises a bellows connected in a fluid line leading to a plant-regulating member, said fluid line including a throttle the setting of which is varied in one or other direction from a position corresponding to the controlled condition thereby to vary the signal transmitted to said regulating member.

4 An automatic controller substantially as hereinbefore described with reference to the accompanying drawings.

For the Applicants:

MATTHEWS, HADDAN & CO, Chartered Patent Agents, 31/32, Bedford Street, Strand, London, W C 2.

Leamington Spa: Printed for Her Majesty's Stationery Office, by the Courier Press -1961 Published at The Patent Office, 25, Southampton Buildings, London, W C 2, from which copies may be obtained

PATENT SPECIFICATON

DRAWINGS ATTACHED Inventor: VALENTIN FERNER 8 G@,757

Date of Appikation and filing Complete Specification Feb 11, 1957.

No 4577/57.

Complete Specification Published Feb 8, 1961.

Index at acceptance: -Class 135, P( 1 X: 7:9 A 6:16 E 3).

International C 2 assification: -G 05 b.

COMPLETE SPECIFICATION

Improvements in or relating to Automatic Process Controllers We, VEB GERATE-UND REGLER-WERKE TELTOW, an East,German National Corporation, of 74-76, Oderstrasse, Teltow bei Berlin, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: -

This invention relates to automatic process control systems.

In conventional proportional action controllers the output signal from the controller is proportional to the deviation of the controlled condition from the desired value The output signal determines the action of a regulating member, by the adjustment of which a disturbance in the plant, known as a deviation of the controlled condition, is eliminated and the controlled condition is restored to the desired value Such controllers have the disadvantage that they cannot completely eliminate the influence of a permanent disturbance.

so that a sustained offset, the magnitude of which is dependent both upon the proportional band and the magnitude of the disturbance must be accepted If it is desired to eliminate the offset which is set up when a proportional action controller is employed, it is usual to provide an integral action in addi-30 tion to the proportional action of the controller The controller then becomes a compound proportional and integral action controller The integral action part of such a controller, however, can only slowly eliminate an offset which is set up by the action of the proportional action part Moreover, the addition of the integral action involves further outlay for equipment Another particular disadvantage resides in the fact that the compound proportional and integral action controller has two control factors, and incorrect adjustment of either factor results in instability of the regulation.

Frequent endeavours have been made to lPrice 3 s 6 d 1 improve the action of the proportional action 45 controller or of the compound proportional and integral action controller by incorporating derivative action This derivative action additionally causes the output 'signal to vary directly with the rate of change of the devia 50 tion from the desired value A two-term (proportional and derivative action) controller or a three-term controller is then obtained The provision of derivative action has, in addition to the increased outlay for equipment, the 55 disadvantage that a derivative control factor is added to the existing control factor or factors Since all control factors influence the stable behaviour of a control circuit, the optimum adjustment of a controller becomes 60 more difficult as the number of such factors is increased The simplest, most reliably operating and most readily handled controllers are therefore those having only one control factor, and there has been no lack of attempts to 65 develop compound action controllers in which the several control factors can be varied with the aid of a single control member However, such compound action controllers can be successfully employed only in the control of very 70 particular plants, and compound controllers having a single control member are not generally applicable.

There is nevertheless a great demand for a controller, having only one control factor, 75 which is at least equivalent, if not superior, in its control properties to the usual compound proportional and integral action or the three-term controllers and which can readily be adapted to any plant To this end, accord 80 ing to the invention, there is provided an automatic process controller comprising a member responsive to an input:signal corresponding to the value of a controlled condition, a member rotatable in one or other direc 85 tion by said input signal responsive member, and means operable by said rotatable member to generate an output 'signal, the rotatable 860,757 member only being rotated to vary the output signal when the deviation of the input signal from a desired value is increasing but remaining stationary to cause the output signal to remain constant when the deviation of the input signal from a desired value is decreasing.

The arrangement according to the invention which may thus be considered as a partially proportional action device, may thus be employed as an attachment to any proportional action controller, it being possible for such controller to be adjusted by variation of the proportional band of the partially proportional action device In cases where a derivative action or an integral action, or a combination thereof has hitherto been provided, the device according to the invention can ibe added to the proportional action part in order to obtain equivalent or improved results In addition to a proportional action, part, further members having different behaviour can be connected at the input or the output side of the partially proportional action device Thus, in particular cases, it is possible to improve the results obtained by connecting a derivative or differential action part to the input side of the partially proportional action device as well as a proportional action part.

The invention will be more fully described with reference to a preferred construction of a pneumatic mechanical control device as illustrated in the accompanying drawings, in which:Figure 1 illustrates diagrammatically the construction of a partially proportional action device according to the invention; Figure 2 illustrates a modification of Figure 1 which additionally provides for changingover to purely proportional action control; and Figure 3 is a graph representing a sinusoidal input signal and the associated output signal of the partially proportional action device.

Referring to the drawings and first to Figure 1, the input signal Xe entering the line, which signal is here the pressure of a fluid bearing a linear relation to the controlled condition X, actuates a rod 3 and a driver 4 connected thereto, in dependence on said pressure, through a spring-loaded bellows 2 According to the direction in which the member 4 moves, one of two pawls 5, 6 is driven so as to engage in a finely toothed wheel 7 and rotate it in one or the other direction In the position shown in Figure 1 the driver 4 is in the midway position corresponding to the desired value and the pawls 5, 6 are out of engagement with wheel 7 If the pressure rises above the desired value, or drops below it, the movement of the rod 3 causes one or other of the two pawis 5, 6 to turn the wheel 7 in the anti-clockwise or the clockwise direction respectively, while on adjustment of the input signal X towards the desired value, the paw Is remain out of engagement until this has been reached and that one which was engaged is returned to its initial position under the action of a spring 15, while the wheel 7 is fixed in the position it is in at that moment, by means of a brake 8 The wheel 7 is thus 70 only set in motion if the input signal Xc shifts away from the desired value and it remains stationary when said signal approaches the desired value, The motion of the wheel 7 is imparted through a member 9 75 to a lever 10 which, by means of another spring-loaded bellows 12 and a regulating valve 16, controls a throttle 11 in such manner that the pressure of a fluid in the bellows 12 supplied through a conduit 17 conforms o 80 to the deviation of the input signal X from the desired value, so that the output signal -X, which appears in a conduit 18 can be used for the adjustment of a regulating member such as a conventional pneumatic adjust 85 ing motor (diaphragm motor) As a result of the movement of the lever 10, the setting of the throttle 11 is varied, whereby the pressure in the bellows 12 is also correspondingly varied until equilibrium is established 90 between said pressure and the force of the spring acting against said bellows 12 The variations in the output signal X, are thus proportional to the changes in the movement of the lever 10 By the adjustment of stops 95 13, 14 it is possible to vary the control point by adjusting both said stops in the same direction and also the amplitude of the output signal by adjusting said stops in opposite directions 100 Figure 2 shows the same arrangement as in Figure 1 but with the addition of a conduit 19 connecting the two bellows, and three cocks 20, 21, 22 If the cocks 20 and 21 are closed and the cock 22 is opened, the device of this 105 invention is disconnected and the input signal Xc is transmitted direct through conduit 19 to the output conduit 18 Figure 3 shows graphically the effect of the partially proportional action when the input 110 signal Xo moves away from the desired value X, and when it moves towards the desired value, i e when the controlled condition X produces an input signal represented as a sine wave passing through the desired value Xk 115 The partially proportional action gives an output signal Xa which, if no further member is connected thereto, is identical with the adjustment to be made by the regulating unit.