Scholars' Mine Scholars' Mine

Masters Theses Student Theses and Dissertations

1968

A fluidic liquid level control system A fluidic liquid level control system

Vinod Kumar Verma

Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses

Part of the Mechanical Engineering Commons

Department: Department:

Recommended Citation Recommended Citation Verma, Vinod Kumar, "A fluidic liquid level control system" (1968). Masters Theses. 5183. https://scholarsmine.mst.edu/masters_theses/5183

This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact scholarsmine@mst.edu.

A D~UIDIC LIQuiD L[VEL CO.:\TROL SYSTEM

BY

VINOD KUNAR VERMA /

A

~liES IS

subnitted to the faculty of

TH~ UNIVERSITY OF MISSOURI - ROLlA

in pA.rtial falfillment :::>f the rcquire;~c~:1ts for the

Degree of

E\STER 0F SCII:NCE I:J :·iECl-;AY[CAL !:::\GI:;n.::RI~G

Rolla., >fissouri

1968

ABSTRACT

The prine objective of this investigation vJas to design and

construct a \vorking "fluidic liquid level control system", and to

make a functional study of the characteristics of the devices em­

ployed therein.

ii

A 'Jerking model of a "fluidic liquid level control system" is

develop~d and experimental data is collected to describe the functional

characteristics of the fluidic circuits employed. The system con­

tains a pressure sensitive, variable frequency oscillator; appropriate

demodulation stages to convert the variable frequency alternating

signal into <i varying non-alternating signal; and on-off control

elem8nts in the final stages.

ACKNOHLEDGEl'fENTS

The author is grateful to Dr. Richard T. Johnson for the

suggestion of the topic of this thesis and for his encouragement,

direction, and assistance throughout the course of this thesis.

The author is also thankful to Mrs. Johnnye Allen for her

-.;.;ronderful cooperation in typing this thesis.

iii

TABLE OF CONTENTS

LIST OF FIGURES

1. I~TRODUCTION

1.1 Background

1. 2 Objective

2. REVIEH OF LITE:RATURE

3. DESCRIPTION OF SPECIFIC FLUID DEVICES

3.1 Proportional Fluid Amplifier

3.2 Flip-Flop

3.3 NOR Gate

3.4 Rectifier

3.5 FLICR Valve

4. TH~ FLUIDIC LIQUID Lf:<:VEL CONTROL SYSTEM

4.1 Description of Control System Elements

4.1.1 Operational System

4.1.2 Oscillator-Sensor

4.1.3 Signal Modifier

/+ .1. 4 Signal Amplifier and Isolation

~.1.5 Rectifier and Filter

4.1.6 crn~rarator

4.1.7 Actuator

4.2 Description of Control System Operation

4.3 Functional Block Diagram

4.4 Typical Operational Characteristics

4.4.1 Oscillator

Page

vi

1

1

5

6

8

8

12

15

18

20

23

23

23

23

26

26

27

27

28

28

29

33

33

iv

Page

4.4.2 Signal Modifier 38

4.4.3 Signal Amplifier and Isolation 38

4.q.4 Rectifier and Filter 38

4.4.5 Comparator 48

4.4.6 FLICR Valve 48

5. GENER.<\L CONCLUSIONS A...\1) SUGGESTIONS FOR FURTHER HORK 49

BIBLIOGRAPHY

VITA

50

51

v

Figure Number

LIST OF FIGURES

1.1 DEFLECTION OF ONE STREAM BY ANOTHER

1.2 PROPORTIONAL FLUID AMPLIFIER

3.1 BASIC CONFIGURATION OF BEAM DEFLECTION TYPE OF

PROPORTIONAL FLUID AMPLIFIER

Page

3

3

9

3. 2 CIRCUIT SCHEMATIC OF PROPORTIONAL FLUID A_."1-.fPLIFIER 9

3.3 PROPORTIONAL ,~1PLIFIER CHARACTERISTICS 11

3.4 FLIP-FLOP DESIGN 13

3. 5 FLIP-FLOP CHARACTERISTICS 14

3. 6 CIRCUIT SCHEl"lATIC OF FLIP-FLOP 14

3.7 NOR GATE DESIGN 16

3.8 NOR GATE Ca\RACTERISTICS 17

3.9 FLUIDIC RECTIFIER REPRESENTATION 19

3.10 RECTIFIER INPUT OUTPUT CHARACTERISTICS 19

3.11 FLICR VALVE 21

4.1 CIRCUIT SCHEHATIC FLUIDIC LIQUID LEVEL CONTROLLER 24

4.2 COHPLETE CONTROL SYSTEM AND INSTRUHENTATION 25

4.3 MAJOR FLUIDIC ELEMENTS OF CONTROL SYST81 25

4. 4 FUNCTIONAL BLOCK DIAGRAM 30

4. 5 FOR HARD LOOP BLOCK DIAGRAM 30

4.6 DETECTION AND SIGNAL MODIFICATION BLOCK DIAGRAM 32

4.7 CIRCUIT SCHEHATIC-FLUIDIC LIQUID LEVEL CONTROL 34

SYSTEM

4.8 OUTPUT WAVE SHAPE OF OSCILLATOR 35

vi

Figure Number

~~. 9 P-P OUTPUT PRESSURE OF OSCILLATOR AS A FUNCTION OF LIQUID LEVEL

vii

Page

36

4. 10 FREQUENCY OF OSCILLATOR AS A FUNCTION OF LIQUID LEVEL 3 7

4. 11 OUTPUT HAVE SPAPE OF SIGNAL HODIFIER 39

4. 12 P-P OUTPUT PRESSURE OF SIGNAL NODIFIER AS A FUNCTION OF 40 LIQUID LEVEL

l1-. 13 OUTPUT WAVE SHAPE OF SIGNAL ANPLIFIER AND ISOLATION STAGE 41

4.14 P-P OUTPUT PRESSURE OF SIGNAL AHPLIFIER & ISOLATION STAGE 42 AS A FUNCTION OF LIQUID LEVEL

4.15 OUTPUT HAVE SHAPE AT FILTER 43

4. 16 OUTPUT PRESSURE OF FILTER & RECTIFIER AS A FUNCTION OF 44 LIQUID LEVEL

l~. 17 DIFFERENTIAL INPUT PRESSURE OF COHPARATOR AS A FFNCTION OF 45

LIQUID LEVEL

4. 18 OUTPUT PRESSU!.ZE OF CONPARATOR AS A FUNC'l'ION OF LIQUID !+6 LEVEL

4.19 TYPICAL INPUT-OUTPUT SlHTCHING CURVE OF NOR GATE 47

FLICR VALVE

1. INTRODUCTION

1.1 Background

For most of recorded history$ the bulk of the energy, \vhich man

has controlled has been that Hhich he processes \vith his body. Man

has alHays been able to think of more things to do than he has had

the energy to do, so it isn't surprising that he looked for means

of controlling energy beyond that in the food ingested.

One of the early Hays of controlling additional energy came

about through the domestication of animals. These animals expend

large amounts of energy, but they do not contribute to man's energy

st:::innard of living because the element of control is :nissing. The

direction of energy is Hhat man wants and Hhat he 1:ceds in order to

achieve many of his goals, and he has been a prolific inventor of

ffieans to do this: Hater wheels, gun powder, steam engines, gasoline

and diesel engines, jet engines, nuclear fission,and nuclear fusion

are means of bringing various sources of energy under his control.

Nmv :it is obviously desirable that the controlled energy ought

to be grcat8r than the energy expended in the controlling process,

or, to be a little more exact, the result accomplished by the con­

trolled energy should be greater than the results \vhich could be

accomplished by the controlling energy acting directly. If this

condition is met, then the process has amplification. 111ere a!:"e,

of course, many necessary and useful controls which do not have

amplification, but those with amplification have received much more

attention.

1

2

Hydraulic, pneumatic, and electrical elements are used as

amplifying devices, some giving a continuous range and some giving

only discrete levels of output pmver. He can classify them either

II 1 II d' • 1 ana og or 1g1ta systems. Up until about a half century ago,

the operation of these systems required the motion of mechanical

parts for measurement and control. Then the vacuum tube was de-

veloped and for half a century has dominated the higher speed electri-

cal measurements and control of energy 1vith minimum use of moving

parts.

The transistor has augmented the capabilities of, and in many

cases replaced the vacuum tube, and has retained two important

chm:acteris tics: no moving parts, and single medium control.

In March, 1960 the Diamond Ordnance Fuse Laboratories (now

Harry Dimno11d Laboratories), disclosed the principles of the first

fluid amplifier, \vhich launched a new technology known variously as

fluerics, fluidics, fluid amplification, etc. It has also created

an interest in internal aerodynamics, separated flows, and fluid

circuit theory. Pure fluidic elements operate using stream inter-

actions of the 1vorking fluid and have no moving parts. Figure 1.1

is a sch0natic representation of typical fluidic stream interaction.

A fluid amplifier has a power nozzle to provide a high speed

jet or power stream. The source of energy is the pump or compressor

which supplies fluid to the nozzle. In the jet, the energy takes

the form of kinetic energy of translation of the fluid. The con-

trol nozzles determine v1hcre the kinetic energy of this stream is

a. r~:~·-r----~------~ Interaction

Region

FIG. 1.1 DEFLECTION OF ONE STREAH BY ANOTHER

Left Control Port

Vents

Right Control Port

FIG. 1.2 PROPORTIONAL FLUID N1PLIFIER

Output Port

Output Port

3

Output Receivers

delivered and hence control the flo-.:.; and pressure in the output

apertures. An amplifier such as this can have a power gain of 10

to 100 depending upon \vhat other characteristics (such as pressure

gain and efficiency) are desired.

4

Fluidic devices have various advantages Hhen compared to other

Deasurement and control devices. They have no moving parts. They

offer a wide application range because they can provide both digital

and analog control signals. Hithin their response capabilities,

fluidic controls can duplicate or, in many instances, offer improved

operation over many electromechanical, pneumatic, or other hybrid

systems. They have high reliability. Their reliability is relatively

unaffected by extreines in temperatures, radiation, etc. They are

inherently free from failure associated with explosion hazards,

electrical noise, high relative humidity, and vibrations.

Examining one of the more comn1on types of fluid amplifier

(beam deflection)(fig. 1.2) we see that it is sensible to interconnect

them in "Push-Pull" since each is a "beam deflecting" device rather

than a "beam stopping" device, as is a triode vacuum tube. But

connecting fluid amplifiers is a big problem. First the basic forces

relating fluids in motion are non linear; second, the continuity

equation must hold (Hhat goes in must come out). These t\vO facts

have special significance in fluid amplification systems. iHth

moving parts, it is easy enough to shut off fluid flow. 1\Tithout

moving parts, the continuing floH must be accommod<lted and properly

discarded after its energy has been extracted. Fluid turbulence

makes the fluid amplifier a ready converter of its steady (or de)

flmv energy into fluctuating forms, resulting in the familiar noises

a~d whistles of fluid jets, a consequence of the surface forces on

the stream of fluid \Jhich conveys the signal. Hm.,.,ever, the advan­

tages of fluidic devices outweigh these characteristics and the re­

sulting difficulties. Engineers and scientists working in this new

field have developed many useful component devices, and systems.

Applications of fluid amplification currently being investigated

include: a heart pump, a respirator, and other medical devices;

logic and timing circuits; rocket thrust vectoring, missile altitude

control; automatic piloting of aircraft; hydrofoil control and jet

engine control; and some industrial inspection and control. The

large scale application of fluidics to measurement and control is

just beginning.

5

In an attempt to add to the kno;.;rledge concerning the application

of fluidic devices to co::-ttrol systems, the goal of this investiga­

tion was to design and construct a working ''fluidic liquid level

control system''. It was decided that this liquid level control

system vwuld involve the use of vari<.:ible frequency sensing elements.

The variable frequency signal produced by the sensing elements

would be demodulated and rectified to produce a non-alternating con­

trol signal. Equipment availability required that the final control

stages be of the on-off type.

6

2. REVIEH OF LITERATURE

"Fluid Amplifier State of the Art", a NASA cor.tr.:J.ctor report(l)*

has surveyed the current state-of-the-art of fluid .::1mplifiers in-

eluding both theoretical and practical aspects of devices having no

mechanically moving parts. The report is a review of the published

literature, and information obtained from various organizations in­

volved in fluid amplifier development. J. H. Kirshne::::- (2

) has thorou;~hly

discussed the theoretical background for fluid a1t1plifiers. He has

also tried to relate the mathematics used to p:1ysical models, Hh,~rc.:J.S

the Corning''Fluidikit''Manual(3

) has only discussed prnctical appli-

cations of fluidic elements for control systems.

Proportional fluidic devices have been studied and dis~u~sed

by many. B. A. Ostap(4 ) and C. A. Belsterling and K. K. Tusi(S)

have respectively presented realistic and use.:1ble information on

vortex and beam deflection type amplifiers.

Variable frequency sensing elements and associated demodulation

circuits have been examined by many authors. A temperature control

system using frequency ~adulation and phase discrimination technique

has been developed by L. R. Kelly(6). The temperature sensing device

developed was a fluidic oscillator, having a frequency output pro-

portional to square root of absolute temperature. Another variable

frequency technique for measuring the average temper.:J.ture in a gas

*~~umbers :Ln pa:centhesis refer to nu:nbered references at the end

of this thesis.

7

turbine exhaust duct is discussed by C. G. Ringwall and L. R. Kelly(?).

They have used a phase discrimination technique to dc:;10dulate the

frequency information. Variable frequency sensing clcnents are also

discussed in "Feasibility Study of a Fluid Anplifier St2am Turbine

Speed Control" by W. A. Boothe(S). This study includes an extensive

computer analysis to determine the relative merits of all-analog,

all-digital, or hybrid analog/digital operation using frequency modu-

lation techniques. Applications of similar pure fluid techniques

(9) to a speed control is also studied by J. R. Colston and E. }1. Dexter •

One of the better discussions of the application of on-off con-

trol 1 d H I (10) . 1 . elements is given by D. J. Ne son an . wata 1n t1elr

application of pure fluid logic to on-off control systems.

8

3. DESCRIPTION OF SPECIFIC FLUID DEVICES

To better acquaint the reader 1vith the pheno;;1enologici1l be11avior

of specific fluidic devices, this section has been included. Of

particular interest are those devices employed in this investigation.

3.1 Proportional Fluid Am~ifier

The basic configuration of the beam deflection proportional

fluid amplifier is shm-m in figure 3.1. A high energy fluid is sup­

plied to the pmv-er jet chamber. Hhen the fluid pGsscs out of this

chamber through the rectangular pm..rer nozzle into the intersection

region, it becomes the pmver jet, its center line Hill strike the

divider and equal amounts of flow will enter the t1..ro output channels

and exit through the appropriate output ports. Hith equal restrictors

between output ports and the next stage, the pressure developed at

the output ports will also be equal. Usually there are only tHo

outputs, sy.nmetrically placed. They may be next to e3.ch other, or

separated by a vent. There is an optimum size and position for the

output apertures. They are far enough doHnstream to take advantage

of the deflection of the non uniform-velocity jet and yet far enoueh

upstream to recover an appreciable portion of the poHer jet stagna-

tion pressure.

If a pressure difference does exist betHeen the control jets

in the intersection chamber, a force is present lvhich deflects the

power jet so more fluid exists through one output port than the

Pmver Chamber

Left Control

FIGURE 3.1

Side Chamber (vented)

Side Chamber

BASIC CONFIGURATION OF BEAH-DEFLECTION TYPE OF PROPORTIONAL FLUID #1PLIFIER

FIGURE 3.2

CIRCUIT SCHEMATIC OF PROPORTIONAL FLUID AHPLIFIER

9

other. Hith equal output restrictors, a prcs~;ure difft·U·ncc js

generated bet\veen output ports. Thus, a control flniJ ejcct 12 d ;,t

low energy into intersection regions c.:1n control th12 re1:•t ively

high energy fluid in the pmver jet.

As shmvn in figure 3.1 the side Halls arc rc:;JOvcd bcot'.,·cen the

intersection region and the output aperture. Tl1is is Jane to pre­

vent the po\.;rer stream from attaching to the ,.,ralls and rl3king the

amplifier bistable. The shape and dii;wnsion of tl1cse cuto\Jt ;lrcas

have a considerable influence on the perfornance of the <!::';) li_ f ier.

Any fluid not collected by the output or nny di.sturba:1ccs present

in the poHer jet may be reflected from the Hall back tm-;.:n-d the

pmver jet to produce an um,;anted feed back effect. To nin:i:1ize

10

these effects in open type amplifier units, holes arc d~·illod throush

the base plate and cover plate of the amplifier ass~:ilily above and

below the cutout regions. Thus, open type units are vented through

these holes to the atnosphere. These vents are so7:1c'tines c:1lled

bleeds. They serve tHO main purposes: They tend to cqnali7.e the

static pressure across the power jet and they also provide overflow

ports for fluid not captured by the output apertures.

To accomplish a similar effect in closed units, the cutouts

are connected together to equalize the pressure across the power jet.

In this case there are no bleeds. All the fluid supplied to the

power jet and control jets must pass through the output apertures.

Closed units may operate with either liquid or gas as the working

C) H

12-.t--~-

~ 9r---~r---+----~--~L_~

'0.2 •Of. ·a& •og • JO ·I~ •14-

FLOVJ SCFM

POWER JET VS FLOW

~------------------------------r-------

OUTPUT CHARACTERISTICS

DIFFERENTIAL CONTROL

PRESSURE

0 H UJ p...

;;2 ;::J UJ UJ >zJ ;?_ 1----ll--~ p::; p...

E-' ;::J p... E-' p 0 0 ·01

OUTPUT FLOH SCFH

TRA~SFER CURVE

FIGURE 3. 3

PROPORTIONAL AHPLIFIER CHARACTERISTICS

(Source: Corning Fluidikit Hanual)

11

fluid. Open type units usually, but net necessarily, use gas as

the working fluid.

In a fluid amplifier there are four variables of interest:

12

(1) input (control) pressure, (2) input (control) flow, (3) amplifier

pressure drop, and (4) amplifier load flow. Thus He can generate the

characteristics defining the relationship betHeen (a) control flow

and control pressure, (b) load flow and amplifier pressure and (c) con­

trol flow or control pressure and load floH or ar:1plifier pressure.

These are relationships which are sufficient to describe amplifier

performance. They are also very useful in matching this fluidic

device to others for operation as a system. Typical characteristic

curves are shown in fig. 3.3.

Analog fluidic devices utilize a design concept referred to as

moment exchange. In comparison, digital devices are on-off types,

and they perform as they do because of wall attach~1ent effects.

The flip-flop is a bistable digital fluidic device employing

the coanda or wall attachment effect for its operation. The basic

configuration of the flip-flop is shmm in figure 3.4.

Referring to figure 3.4, the operation of the flip-flop may

be briefly described as follows:

In the absence of any control signal from the control ports,

fluid leaving the power jet ,.,ill be directed to either one or the

Control Channel B

Vent

Channel Fz

Supply -<f -Channel

FIGURE 3. 4

FLIP FLOP DESIGN

Vent

Wall Attachment Area

S?litter

"-._ Output Channel Fl

13

14

~------------------------------~

·5-----~--4---J----r----r---+--~~

Recovery Pressure

VS

Control Pressure

Control Pressure PSIG

---------------------+---------------------

Output Pressure

vs

Output Flow

FIGURE 3.5

FLIP-FLOP CHARACTERISTICS

Flm.;r in CFH

(Source: Corning Fluidikit Manual)

FIGURE 3.6

CIRCUIT SCHEMATIC OF FLIP-FLOP

other of the output channels. Let us say it is at F2

. As long as

there are no control signals, ad · fl n pm.;rer Jet ow continues, the out-

put will remain at F2

indefinl'tely. r.n.. ff' · wuenever a su lClent signal

is applied at control port B, the power jet flow is switched to the

opposite wall causing output at port F1 • To return the output to

the original leg, a control signal must nmv be applied to control

port A. These signals must be large enough to overcome the wall

attachment effects established by the power jet.

Typical characteristics of flip-flop operation are shown in

figure 3.5.

3.3 NOR Gate

Gate fluidic devices are perhaps the most frequently used

building blocks in fluidic circuits. The NOR Gate is a monostable

device, favoring or biased to one output leg. Biased design can be

accomplished in several ways. One approach is by the design shown

in figure 3. 7.

15

This device uses the Co3.nda or 'vall attachment effect while the

propo£tional amplifier specifically avoids this phenomenon. This

de,;ice has control ports on the same side of the device. A special

auxiliary control port with no fitting iS provided on the other side.

This auxiliary port has a larger nozzle area than that of the com-

bined control input port. This size makes it more difficult to

entrain fluid through the control nozzle than through the auxiliary

nozzle causing the power jet to be pulled to the control jet side

Auxiliary ontrol

..----..-. Port

/ L_ __ OR Output Leg

Supply Port

NOR Output Leg--

FIGURE 3. 7

NOR GAT!::: DESIGN

16

Control Port

17

Flow, CFM

..__-----------------1-.--------------------

FloH, CB-1

r---------------··-----------------------~--------------·----------------------~

~Recovery Pressure vs Control Pressur( Circuit Sclwnatic .]?-- r ~-~.::~~~---~~T.~s~~-i,--+-----·----- ·------------------f

8 _ __£<~ l~~d,~-~ Lc.>P..'D ON NoR. ()

: • ·br. -~lr-- --~---1- ~-le: · )...! ~5t- -· ~ ... -~r-:- N02:. L ~ ---- ~· ~v~~ U)

~ ·~0~--+-+-~----~--il~--~--~---~ )...!

~

~-~~~~L-~-'~U-~--~~~ ·OS ·10 ·15

Control Pressure PSIG

FIGURE 3.8

NOR GATE CHARACTERISTICS

(Source: Corning Fluidikit Manual)

18

of the device. Pressure differences established are responsible for

this behavior. Also, the wall on the auxiliary port side of the

intersection area is further from the pmver nozzle than the ,,1all on

the control port side. This type of design further reinforces the

tendency of the power jet to attach to the control port, or biased

side of the intersection area. Another way to strengthen the initial

bias 'l.vould be to move the splitter tmvard the auxiliary side.

hT"l1en pressurized fluid leaves the power jet in tre absence of

any control signal from the control ports, it becomes attached to

the biased leg and NOR output is obtained. Hhenever sufficient sig­

nal from either or both control ports is present, the pm.;rer jet flow

is switched to the OR leg. Typical characteristics of the NOR Gate

are shown in figure 3.8.

3.4 Rectifier

The fluidic rectifier is an element which provides an output

signal inversely proportional to the magnitude of the differential

input signal and independent of input signal polarity. It utilizes

jet interaction operating principles. Figure 3.9 (a) is a schematic

diagran of the device. Referring to figure 3.9 (b), rectifier opera­

tion can be described as follows: Hhen the input differential signal

is zero (equal pressure at c1

and c2) the power jet impinges on the

signal output receiver and maximum recovery occurs at the output

port 0. If the power jet is deflected to either side by an input

signal the recovery pressure at the output receiver will be reduced

a. Circuit Schematic

Control Port

Vents

19

b. Sjlhnuette of rectifier

FIGURE 3.9

FLUIDIC RECTIFIER REPRESENTATION

Po~ ovTP<JT PRessv~tE

·~ LOilt>:oOfs,SvPI>L'>' PRt:S~OR€

•I

-·3 -·2 _.,

FIGURE 3.10

~ ~ c_ 0 ,vrR.oL Pll.~.SSUR:

Lo.q t> :. to.ooo

Sec;,.,v..

RECTIFIER INPUT OUTPUT CHARACTERISTICS

(Source: General Electric Co.)

by an amount proportional to the input sign:1l a:~p1itude.

output is independent of input signal poLnity, but is pr<•;~, 1 rtic•nal

to the magnitude of the input signal.

The fluidic rectifier is generally used in ci_rcuits sig-

nal rectification is needed. Typical applications -,rc frequency

to analog conversion, phase discrir;lination, and beat f rcqllcncy de­

tection. The rectifier can also be used for freq11c·ncy doubling.

Figure 3.10 shaHs the typical input-output pre"~sure rC'lations

of the fluidic rectifier.

3.5 FLICR Valve

The Fluidic Industrial Control valve (FLICR valve) .1!1'>t:ers the

need for higher pressure operation up to 100 psis. It i ., an inter-

face device \vhich uses the output from a ~:oR Gate to ~-''·'itch :1 :~cp.1rate

supply flmv of up to 100 psig. Its operation c;1n be c:·:p 1 a i ned as

follmvs:

Hhen the NOR leg of the NOR Gate delivers a sit_;ni1l to the con-

trol port of the FLICR valve, the signal goes to one side of a snall

piston in the valve. The piston noves causing tl1e grooved swiggle

in the valve to pivot around a center post. This pivoting directs

the high pressure air coming into the pilot valve to rove out the

leg on the NOR side of the valve. The high pressure air is routed

through the swiggle and, due to a planned tolerance bett:cen center

post and swiggle, the flow creates an air bearing between swiggle

and post. When a control signal is applied to the FLICR valve

From Comparator

Swiggle

21

.,.__- NOR Gate

FIGURE 3.11

FLICR Valve

NOR Gate, the pilot gate output switches to its OR leg actuating

the piston and swiggle and causing the valve to switch. Figure 3.11

is a schematic diagram of the FLICR valve.

22

23

1+ • THE FLUIDIC LIQUID LFVEL CONTROL SYSTEM ---·--

4.1 DescriQtion of Control System Elements

4.1.1 Operational System

The fluidic liquid level control system developed consists of

six stages and is shm·m schematl' cally · f · 4 1 d 1n lgure . an pictorially

in figures 4.2 and 4.3. A description of each stage follows.

4.1.2 Oscillator-Sensor

The oscillator is essentially a flip-flop element. As we know,

the change of the output from one leg to another is knmv-n as switching.

~n1enever the output legs feed back into the control ports and generate

control signals on the same side of the device they cause the device

to sHitch continuously. This repetitive process is knov;n as oscil-

l~tion and the device is known as an oscillator.

The frequency of oscillation is dependent on the time constant

of the feed back path. This feed back path is usually made up of

resistive and capacitive elements. By changing the value of this

R-C combination the oscillator frequency can be altered. The larger

the R--C product, the longer the time constant and hence the slower

the frequency of oscillation. For a bistable device such as the

flip-flop1

the R-C nen1orks in each feed back path must be essentially

identical to produce a balanced output oscillation. The basic liquid

level sensing element for the control system developed is a variable

capacitance in each feed back loop of the fluidic oscillator. These

®

0

J I •

1 2 ~~ 3

I •

Fluidic Power Source

! Fluidic Capacitance I

- Fluidic Resistance I

1. Oscillator 2. Signal ~odifier 3. Signal Amplifier Isolation 4. Rectifier 5. Con·.parator 6. Actuator FIGURE 4.1

l~ I . I

l . I •

l I

I

I 4 "''

FLICR Valve

Diaphragm Valve

H.P. Air

CIRCUIT SCHE~~TIC FLUIDIC LIQUID LEVEL C0~1ROLLER

6

t_

N .t--

\ \

FIGURE 4 . 2

COMPLETE CONTROL SYSTEM AND INSTRUMENTATION

FIGURE 4. 3

MAJOR FLUIDIC ELEMENTS OF CONTROL SYSTEM

t-.:: V1

\

\

FIGURE 4.2

COMPLETE CONTROL SYSTEM AND INSTRUMENTATION

FIGURE 4. 3

MAJOR FLUIDIC ELEMENTS OF CONTROL SYSTEM

" (,/1

variable capacitances cons1" t f 11 fl s o sma exible char;,bers fabricated

from toy balloons and rigid tubing. \\'hen submerged in the bot tom

of the liquid tank the volume of the balloon-tube chamber is depen­

dent on the liquid level above the chamber and the supply jet pres­

sure of the oscillator.

As the liquid level in the tank drops the increased differential

pressure across the flexible capacitors causes the volume to increase.

Since an increase in R-C product in the cscillator feed back path

increases the time constant, the frequency of oscillation decreases.

Thus, changes in liquid level are sensed as changed in tl1e frequency

of the oscillator sensor stage. Due to the digit<1l nature of the

flip-flop oscillator the amplitude of the output Have is essentia]ly

unchanged '.-lith these frequency changes.

4.1.3 Signal Modifi~r

The signal modifier consists of a proportional 3mplifier pre-

ceeding a low frequency R-C filter. The oscjllator provides the

control signal for this stage. The proportional amplifier acts as

· 1 l"f" and 1·t also helps to isolate the oscillator from a s1gna amp 1 1er

downstream disturbances. The R-C filter is set so that its output

signal amplitude diminishes Hith increasing signG.l frequency. On

the whole, this stage tends to smooth the output from the oscillator

and convert frequency information to amplitude information.

4.1.4 Signal Amplifier and Isolation

f a Proportional amplifier element.

This stage consists c At

1·s received from the sisnal modifier is this stage the sj_gnal which

27

amplified, particularly its flow. Th · lS stage helps to isolate the

preceding stages from the rectif1"er and · m1nimize loading effects of

the rectifier on these stages.

4.1.5 Rectifier and Filter

The rectifier and filter stage consists of a rectifier and

capacitor filter. The output of the signal amplifier and isolation

stage is directly fed into the control ports of the rectifier. As

pointed out previously, the output of the rectifier is independent

of the input signal polarity but is proportional to the magnitude

of the input signal. Actually it provides an output signal inversely

proportional to the magnitude of the differential input signal. At

this stage the alternating signal is simply rectified and filtered

to produce a non-alternating signal that is proportional to the fre-

quency of the alternating signal, produced by the oscillator.

4.1.6 Comparator

The comparator stage is a proportional amplifier. It essentially

compares the rectified and filtered signal to a reference signal.

The output of the filter is fed to one control port and the reference

signal is fed into the other control port. If the two control sig-

nals received are of equal magnitude, the output Hill be evenly

divided between the two output ports. h"'hen the t\.JO control signals

are different the differential output pressure of the proportional

amplifier varies. One output leg of this device is vented to the

d 1 Provides a signal above atmospheric

atmosphere and the secon eg

pressure.

system.

d depends on the state of the The actual signal magnitu e

28

4 .1. 7 Actuator

This unit consists f o FLICR valve connected to a normally open

centro s water flm-J into the diaphragm valve. The diaphragm valve 1

tank. Only one output of FLICR valve is connected to the diaphragm

valve, and the other output is blocked.

As explained in sec. 8.5, when high pressure a1·r comes out of

the output connected to diaphragm valve the flo1v valve is closed.

When the output of the FLICR valve 1"s switched to the blocked side,

an a spr1ng opens the valve pressure on the diaphragm 1·s released d ·

allowing fluid to flmv into the tank.

4.2 Description of Control System Operation

The performance of the control system as a whole can be

described as follows:

The oscillator oscillates at a fixed frequency at a particular

liquid level. Hhenever the liquid level changes, the frequency of

oscillation changes due to the capacitance change in the feedback

circuit of the oscillator. Thus, an alternating signal is generated

and fed to the signal modifier. This stage modifies the signal and

provides an approximate sinusoidal wave whose amplitude varies with

freqt:ency. This signal is fed to the signal amplifier and isolation

stage. At this stage the input signal is amplified, particularly

its flow. Variable resistances bet,veen the tHo stages are used to

remove any bias from the alternating signal which is fed from the

signal amplifier to the rectifier and filter stage. The latter

stage simply rectifies and filters the signal fed into it. This

non-alternating signal obtained, \vhich is proportional to the fre­

quency of the previous alternating signal is then compared v;i th a

reference signal in the comparator. Th. f · 1s re erence s1gnal is ad-

justed so that at a particular liquid level, the output stages will

operate, causing the flow valve to open. If the signal from the

compPxator, \vhich is fed to the NOR Gate of the FLICR valve, is in-

29

sufficient to cause S\vitching, the high pressure air is obtained from

the NOR leg of FLICR valve \vhich is connected directly to the uiaphragm

valve. Thus, there is pressure on the actuator and the flow valve

remains closed. As the water level falls the level of d1e rectified

signal falls. \fuen sufficient difference betHeen this signal and

the reference signal is developed, the comparator output from the

leg connected to the control port of the NOR Gate gives a signal

sufficient to switch the high pressure air to OR leg of the fLICR

valve. Switching this high pressure air releases the spring actuated

diaphragm valve allm-;ring water to flow into the tank. \·.'hen the signal

from the comparator decreases, the high pressure air- S\vi tches back

to the NOR leg, thus applying pressure to the diaphragm valve causing

it to close.

This type of control processes using either a fully open or

fully closed valve is called an "on-off" control process.

4.3 Functional Block Diagram

The fluidic liquid level control system can be represented by

hoPn in figure 4.4. Due to the the functional block diagram as s v

Coarse Reference Signal

t.:1-)

FLICR Valve and

S stem

Detection and Signal Modification

FIGURE 4.4

FUNCTIONAL BLOCK DIAGRAH

FIGURE 4.5

FORHARD LOOP BLOCK DIAGRAM

Lif1ui.d Lcv0

sc ill:ltor Supply Pres~ure

30

31

lack of sufficiently accurate valves and components required to

produce r·~peatable operation) satisfactory transfer functions for the

sys tern elements could not be measurec1. For 1 · t1lS re:1so>1, only a functional

block diagram has been developed.

The fonvard loop consists of the FLICR valve, flow valve and

tank and is represented as shown in figure 4. 5.

The FLICR valve is a non-linear element of the on-off type ~md

thus causes the final control stages to behave in an on-off fashion.

The flow valve is a diaphragm actuated spring return valve and is

normally open. \.Jhenever actuating pressure is applie>d to the dia-

phragm, the valve closes, stopping flm-1 into the tanl<. The tank is

72" inches high and 12" inches in diameter. A varir-;ble ontlct valve

allows the outflow to be changed or adjusted.

The feed back loop consists of the detection and signal modifi-

cation elements. These elements consist of the oscillator, signal

modifier, signal amplifier and isolation; and rectifier and filter

stages. Figure 4.6 is a block diagram of the feed back loop.

The oscillator-sensor senses the change of fluid level in the

tank and generates a signal '"hose frequency is a function of the

level. This frequency information is converted into amplitude in-

formation by the signal modifier stage.

isolation stage is essentially an impedance matching device required

The signal amplifier and

t f 11 · stages from overloading the previous stages.

o prevent the o mnng

Th Convert t he alternating signal of variable e rectifier and filter

Pressure due to liquid head

---~--~· \ Oscillator \ I M~~~~~~r I

Oscillator Supply Pressure

FIGURE 4.6

Signal !Amplifier &

Isolation

DETECTION & SIGNAL MODIFICATION BLOCK DIAGRA£1

Rectifier &

Filter ----··---

t To

Comparator

w N

amplitude and variable f requency into a non-alterna tl· ng signal of

vari2.ble level.

The comparator compares the reference signal with the feed back

signal. A coarse level adjustment is made with the reference signal

are rna e with the oscillator supply pres-and fine level adJ·ustments d

sure. The fine adjustment is necessary because of the non-linear

characteristics of the oscillator-sensor. d A justment of the oscil-

33

lator pressure produces the greatest frequency to liquid level sensi­

tivity for each range of liquid level control.

4.4 Typical __ QRerational Characteristics

The operational characteristics of each stage were obtained

experililentally. The results of these experimental measure:,1cnts are

described in the follm.;ing paragraphs.

4.4.1 Oscillator

The measurement of the output of the oscillator stage ' . .;ras made

at point a-a shown in schema tic diagram figure 4. 7. Using a pres-

sure transducer and an oscilloscope the differential output pressure

and frequency of oscillation were measured at different liquid levels,

and different oscillator povJer jet supply pressures. A typical 'l·:ave

shape for the oscillator output is shown in figure ~.8. Figure 4.9

shO\vS hm.,r the differential output pressure changes Hith changes of

liquid level at different oscillator supply pressure. The peak to

peak (P-P) output pressure is essentially inde~endent of li~uid level.

Figure 4.10 shows that the frequency of oscillation increases as

G >: ~ .... . .... (: f.: •-- t.r :~ ~ r ~ ~..F.. .....

t.) •. .....J u: :~

> t·-' ;:..:

~~ ·-~_.:; '. '-' :-r.:

35

- 1•0

- 1·5

10 20 30 SO So

Time in mill i-seconds

FIGURE 4.8

OUTPUT WAVE SHAPE OF OSCILLATOR

35

Time in milli-seconds

FIGURE 4.8

OUTPUT WAVE SHAPE OF OSCILLATOR

4-

H Cl)

ll.c

~ •ri

3 1-- {I

Q) $.I ::I Cl) Ul Q) $.I

ll.c .j.J

2 ::I

It 0

o. 0

p. .j.J

::l 0

ll.c I 1 ll.c

~ •

L- ( I 0

, 00

t7 0 t 1:.7 ~ r.:

g r: m 1(;1 It:"\

m ~

r.J

,.,.. . ~ rr.l -1':\ ·~ - (!)

poweR.. :JeT SVPPt..y

PR6SS~II ~

G

0

"l

-Level I n Inches

FIGURE 4 .9

P-P OUTPUT PRESSURE OF OSCILLATOR AS A FUNCTION OF LIQUID LEVEL

~ Psr 4 psr

5 PSZ

36

~

4 " H Cl)

~

~ •ri

3 ~ {I

Q) ).4 ::3 (J) (J) Q) ).4

~

~ 2

::3

I t 0

"' u_ 0

ll. ~ ::3

0

~ I 1 ~

~ •

~ ( I 0

, 00

t7 0 t: a (::1 r.:

g r. (!) lr.l lr;"\

m <:::)

,..,

,.,.. ~ rr.l -~

."""' - t9

poweR.. JET SUPPl-Y

PR6.SS!III ~

G

8

'\1

-Level I n Inches

FIGURE 4 . 9

P-P OUTPUT PRESSURE OF OSCILLATOR AS A FUNCTION OF LIQUID LEVEL

~ psr

4 psr

5 p~ z

36

~

U)

Pol u l::l

H

;:.., ()

l::l Q) !j cr Q)

~ !:<..

171r-----~------~------~----~-----.------~------

11

9

SUPPL. Y

7 PRe:ssuR.G

(!) ~ PST

[!) 4- P3I

'V 5 PSI.

5

0 ------~~------~------2------- ~------~------~------~ 40 45 50 55 60

30 35 Level In Inches

FIGlJRE 4.10

FREQUENCY OF OSCILLATOR AS A FUNCTION OF LIQUID LEVEL

37

U)

A-1 u !::l

H

:>-. (.)

!::l <l) :::3 0' <l)

l-4 ~

171r-----~------~----------- -~------.-----~-------

15~------r-------+-------~----

11

9

SUPPLY

7 PP.essuRG

0 ~ P~r

s 4- P3I

\/ 5 PSI.

5

0 ------~~-------~------2------- ~------~------~------~ 40 45 50 55" 60

30 35 Level In Inches

FIGURE 4.10

FREQUENCY OF OSCILLATOR AS A FUNCTION OF LIQUID LEVEL

37

liquid level increases. The nominal liquid level control r 3 nge is

from 37'' to 52" of \vater.

4.4.2 Signal Modifier

The me,:,surement of the output of this stage Has made at point

b-b shown in figure 4.7. A typical output wave from this stage is

shmm in figu::e 4.11. Figure 4.12 shoHs peak to peak differential

output pressu·re variation \vith changes of liquid level at different

oscillator s11pply pressures. The pm.;er jet pressure for this stage

was fired at 11.75 psi.

4.4.3 Sign.'ll Amplifier and Isolation

38

The measl:rement of the peak to peak differential output pressure

of this stage was made at point c-c shown in schematic diagr.1rn, figure

4.7. A typic:'l output wave from this stage is shmm in fig1Jr~ 4.13.

Figure 4.14 shmvs ho\_'1 the differential peak-to-peak output pressure

changes with variations of liquid level at different oscillator

supply pressures. The pmver jet supply pressure for this stage uas

fixed at 4.25 psi.

4.4.4 Rectifier and Filter

The measurement of output of the rectifier-filter stage was

made at point e, of the schematic diagram shmvn in figure 4. 7.

Figure 4.16 displays the non-alte~nating pressure as a function of

1 · 1 The liquid level and various oscil a tor pmver Jet supp y pressure.

power jet supply pressure for rectifier Has fixed at 7.75 psi.

Figure 4.15 is a typical output pressure level curve.

39

0 lO 40 60 eo /110 1/.o 140 '8o 2()()

Time in milli-seconds

FIGURE 4.11

OUTPUT WAVE SHAPE OF SIGNAL MODIFIER

0 lO 40 60 ea ltiO tl. o 140

Time in milli-seconds

FIGURE 4.11

OUTPUT WAVE SHAPE OF SIGNAL HODIFIER

39

'8o 2{)()

·~r-~~----~-----.-----.------------------

~ Psz

4 P..s 2.

5 p.sz.

SUPP'-Y

p Re-.ssu ~6

Q)

~ ~~--H--1------~-------+~~--~------.-------r-----~ (/) (/) Q) ~

Pol

4.J ~ ·3Sr---*---j-------t-~~~1-----~~----~~------~-------~ 4.J ;::)

0

Pol I

Pol

40

·r~ or---~~~------~------~------~-------!~----_1--____ _j 3o ~5 . 40 4S 5"0 5'S 61:>

Level In Inches

FIGURE 4.12

P-P OUTPUT PRESSURE OF SIGNAL HODIFIER AS A FUNCTION OF LIQUID LEVEL

-~--~~-----,----~-----s----------------~

PO'\NG R.

0

8

{]

~ Psz

4 P.s 2.

5 psz

S <JPP'-Y

P R c-.ssu ~6"

Q) ~ ·~~--~~r-----~~----~~~--~~-----.-------T------~ (I) (I) Q) ).I

~

4-) & ·3Sr---~--r-------f-~~~1-----~~----~~------~------~ 4-)

~ 0

~ I ~

40

.. ,~ 0 . 40 45 30 GD

Level In Inches

FIGURE 4. 12

P-P OUTPUT PRESSURE OF SIGNAL NODIFIER AS A FUNCTION OF LIQUID LEVEL

H Cl)

P-4

Q •r-1

<1) ~

g -·2. (J)

~ P-4 -·4

-·8 ' bo Bo too 12.0 140 1 'o tao 2 ao Time in milli- seconds

FIGURE 4.13

OUTPUT HAVE SHAPE OF SIGNAL AHPLIFIER AND ISOLATION STAGE

41

H C/) p..

s:: ..... Q) ~

~ -·2. (J) Q) ~ p.. -·4

-·8 ' 4o {.o Bo too 12.0 140 1 'o 1so 2 ao Time in milli-seconds

FIGURE 4.13

OUTPUT lvAVE SHAPE OF SIGNAL AMPLIFIER AND ISOLATION STAGE

41

<1) $-l ::l (/) C,') <1) $-l ~

~ ::l ~ ~

i ·0

s

1

;:s ·G 0

~ I ~

·s

•4

I--

,., J/

t(

"I

,. JJ

rr "7

~

fl

u

((

Pov-J EA. S&'T SuPPLy

pR.e s suR..&

~ <:) a PS l:

EJ 4 p3 I

v sP.sz

~ '<I" ~ n v

-~

\ ~ t--" \:ll!t- lr;'t ki\

~ ~ ........__ ~ ~~

~~ .

40 4'S oo Level I n Inches

FIGURE 4 .14

P- P OUTPUT PRESSURE OF SIGNAL AMPLI FIER AND ISOLATION STAGE AS A FUNCTION OF LIQUID LEVEL

,...., v

42

(0

J:: -~

(.;

60

·0 , ~I i

tr "I

.,

·s ... ~~

,., "J

'V

·s 1----/J-

•4 )~

{(

Pov-J E R. So-r S VPPLy

pa.essvR.&

~ <:::> a PS Z

EJ 4 p~ I

v sP.si.

~ '<I~ ~ n

v

-~

\ ~ 1"--

" \!} -m- ItO\ l\7\

~ ~ ........__ rs=._cv (~

~~ .

40 4'S oo Level In Inches

FIGURE 4 .14

P-P OUTPUT PRESSURE OF SIGNAL AMPLIFIER AND ISOLATION STAGE AS A FUNCTION OF LIQUID LEVEL

,-, v

42

(tl

1::::. -~

(;

1.!: o O

Q) 0 ~ ::l Ill -.1 Ill Q) ~

P-4 - 2

-3

-4

43

o · 2. •4 ·'- ·B t•O t ·2. t·4 1• '- •·& 2.· 0

Time in Seconds

FIGURE 4.15

OUTPUT WAVE SHAPE AT FILTER

Q) 0 J.j ;:I II) - J. (J} Q) J.j

Pol - 2

-3

-4 o ·2. •4 ·f. ·B t•O t ·2. •·4 l•f. •·& 2.· 0

Time in Seconds

FIGURE 4.15

OUTPUT WAVE SHAPE AT FILTER

43

H Cl) p..

~ .......

·o

lo"i 2

~ ~ 0 ;::) 'J) (/) Q) 1-1 p..

~ ;::) 1•5 0. ~

:::s 0

0 3o

\

PoW6R. JeT SUPPL'f p A.t!.SSVR.~

() 3 p..s t f) 4 P~r

VJ s p .s .-z

G (C')m m r:o.. ...... -

- r:JO tl

....... \!. _ _n (d" e - -8

t;J ~ C1. ~___:§ ~~ _..-.- - v

~ ~~ ~

~

35 45 50

Level In Inches

FIGURE 4 .16

OUTPUT PRESSURE OF FILTER & RECTIFIER AS A FUNCTION OF LIQUID LEVEL

~

55

·o

l,"'i 2

0

0 3o

\

PoW6R. JeT SUPPLy PR(!S~V~~

<:) 3 p.s t fJ 4 (.>.S'C

'iG s p.s~

('!) f':)(!) r:\ r:o.. "' -

- tl

-- ""\!, -·c GO f.!!~"

... ~e--8

9_.-- (;l ---YJ-- ~-..:&~ 'V~

~ ~ ~~

~ -

35 4S 50

Level In Inches

FIGURE 4.16

OUTPUT PRESSURE OF FILTER & RECTIFIER AS A FUNCTION OF LIQUID LEVEL

-

55

44

·1

H •S U)

P-t

s:: •n Q) )..1 ;j (/) (/) Q) )..1

P-1

.,

" \

I

(~ ( i7 p, .. Po\ ~s-R JG

suPPLY

~ ~

( ( J ,,

""

,, \\\ \~ \t\ ~~ J(

~<>\,. ':.~ ~ k . ~

(I ~ ~ ......

. ,,

. 'I as 40 4~

Level In Inches

FIGURE 4.17

DI FFERENTIAL INPUT PRESSURE OF CO}WARATOR AS A FUNCTION OF LIQUID LEVEL

45

p R.€ SS ORE

6.0

.,.

H •S U)

P-t

~ •r-i

Q) ).I ::l fJ) fJ) Q) ).I ~

.&.J ::l p.. ~ ·3

H

~

C'O •r-i .&.J ~ Q) ).I ·2. Q)

4-f 4-f •r-i A

.,

, \\

I

<D ( ., p,- Po\ ~e-R .:r e suPPLY

~ ~

( ( ' I '

t-l

\\\ ~\~ ,, \t\ ~~ J(

~<>\,. ':.~ ~ k '(.\

(I ~ ~

"""

,, .

. as 40 4~

Level In Inches

FIGURE 4.17

DIFFERENTIAl INPUT PRESSURE OF CO~~ARATOR AS A FUNCTION OF LIQUID LEVEL

45

p R.€SStHtE

.

6.0

H Cl) p...

~ ·r-i

. 7

~

s

Q) H ~4 ;:::s CJ) CJ) <I) H p...

~

;:::s ·~ p. ~ ;:::s

0

• I

0

/ t-l

(,. J)

,, Jl

(,.

'l

Sf

rr }'

tr -')

; ~r/ ,:#l

I I p~::. PO\ JER :ft:r

su;:. PLY p~e.s

~

y I "-I

~~ ~

~I '

"i '1

~ 'f) Q,. \J)

I(~ . [!) v

tl 0 ~"4

I

eli:-\ th o..::J 1

.40 45 Level In Inches

FIGURE 4.18

OUTPUT OF COHPARATOR AS A FUNCTION OF LIQUID LEVEL

46

svRE

. 7

" ;',.

l

6 fr J)

,, ,,

r,.

'

ff

rr } \ . '

tr 0

"')

; ~r/ ;;lil I I p~::. Po\ JER. :rt:r

su,:. PLY pf?e.s

~

y I ,....,

~~ ~

; I "

"'i

"' Q..

~ rJ \J)

I(~ . [!) "'~-

tl 0 ~

I

ri!:-. th ~

40 45 Level In Inches

FIGURE 4 . 18

OUTPUT OF CONPARATOR AS A FUNCTION OF LIQUID LEVEL

46

svRE

2 \

2 0 -~ ,~

,., ~

(;;

0

Joo-

I~

1'r

.

--4 ·~ ·6 ·.S 1•2- 1•5 1•8 ..2~1

Control Pressure PSI

FIGURE 4 .19

TYPICAL INPUT OUTPUT SWITCHING CURVE OF NOR GATE FLICR VALVE

47

2 \

2 0 -~ ...

'" ,., ~

"

0

--

I~

1J

.

- i ~ · 6 ·.9 1•2.. 1•5 I•B ..2 ~ 1 Control Pressure PSI

FIGURE 4 . 19

TYPICAL INPUT OUTPUT SWITCHING CURVE OF NOR GATE FLICR VALVE

47

4.4.5 Comparator

The measurement of input and output of this st;,[.l' ·,,::>s :~;!de at

point f and g as shovm in the schematic diogr.:r~ of figure 4. 7.

Figure 4.17 and figure 4.18 shm.;r typical input ;-,:1d output sir;nal

values as a function of liquid level.

4.4.6 FLICR Valve

A typical input-output S'tvitching curve of FLJCR v,:l vc is '!Ju\m

in figure 4.19.

' <J ..... ,

49

5. GENERAL CONCLUSIONS AND SUGGESTIONS FOR FURTHER HORK

The prime objective of this investigation \Jas to develop an

operational fluidic liquid level corttrol system and to make a functional

study of the fluidic elements used therein.

The result of the experimental test program indicated that

original objectives of this investigation were accomplished. A

"fluidic liquid level control system" was developed, which controlled

the liquid level. Experimental data were gathered to describe the

operational characteristics of the devices used in the system.

A fe\v suggestions for further work are:

(a) To develop a proportional power amplification stage

to replace the FLICR valve, thus alloHing some form

of proportional control.

(b) With the help of better instrumentation determine the

transfer characteristics of each stage.

(c) Employ more precise passive elements in the fluidic

circuits. Two desirable elements of this type would

be resettable micrometer stem valves and better fluid

capacitors.

BIBLIOGRAPHY

1. NASA Contractor Report, NASA CR-101, Volume 1, Neo;.: York General Electric Company, October, 1964.

2. Kirshner, J. H., "Fluid Amplifiers'; NeH York, Hc-Grm.J-Hi11, 1967, p. 145-270.

3. Corning Fluidikit Manual, Corning G1ass\wrks, l'e\v York.

4. Os tap, B. A. , "Experimental Study of a Proportional Vortex Fluid Amplifier", Fluid Amplification ~~osiu~, Harry Diamond Laboratories, Washington, D. C., Hay, 1964.

5. Bels terling, C. A. and Fusi, K. C. , "Applications Tec:hniques

50

for Proportional Pure Fluid Amplifiers", _Fluid ~~121'1 iJ~--~'J._t_I_ o_~ S·ymposium, Harry Dianond Laboratories, \\1ashington, D. C., ;.;,.<'• 1961.._

6. Kelly, L. R., I!A Fluidic Temperature Control Using F'req11ency Modulation and Phase Discrimination", Journal of Engineering PoHer, Trans. ASHE, June, 1967.

7. RingHall, C. G., and Kelly, L. R., "A Fluidic Technique for Heasu.ring the Average Temperature in a Gas Turbine Exhaust Duct", Journal of Engineering_ E_c~)\ver, Trans. ASHE, April, 1968.

S. Boothe, W. A., "Feasibility Study of a Fluid Anplifier Steam Turbine Speed Control", .fluid Amplification ~_f'l~~' Harry Diamond Laboratories, \\Jshington, D. C. , May, 1964.

9. Colston, J·. R., and Dexter, E. H., "Applications of Pure Fluid Techniques to a Speed Control", Fluid ~--=-l_ific:_~~i_on _?_::-.!_::!J~sium Harry Diamond Laboratories, \-{ashington, D. C. , Nay, 1964.

10. Nelson, D. J. and h·Ja ta, H. , "Application of Pure Fluid Logic to On-Off Control System", Fl~:!-id Amplific:ati_9n _s}·n_£osi~, Harry Diamond Laboratories, Hashington, D. C., Nay, 1964.

51

VITA

Vinod Kumar Verma was born on August 16, 1944, in Punjab, India.

He graduated from St. John's High School, Nagpur, in June 1958.

He received a B. Sc. and a Diploma in Nechanical Engineering from

the University of Indore and the Bhopal Board of Technical Education

in June 1962 and December 1965, respectively.

Immediately thereafter he was employed by Jyoti Ltd., Baroda.

He attained the position of Tool Room Engineer before leaving Jyoti

in August 1967.

He has been enrolled in the Graduate School of the University

of Missouri at Rolla since September 1967.