Note: Descriptions are shown in the official language in which they were submitted.
ANGULAR ~ATE SENSING APPARATUS AND METHODS
The present application is a division of Canadian Patent
Application No. 385,741, filed September 11, 1981.
BACKGROUND OF TE~E INVENTION
The present invention relates generally to rate sensing devices
and systems, and more particularly to a novel electrofluidic angular
rate sensing system, and associated apparatus and methods.
Various attempts have previously been made to design and build
a fluidic replacement for the mechanical rate gyroscope long used
as the prlmary attitude sensin~ element of conventional navigational
guidance syskems for ships, planes, guided missiles and the like.
The most common approach has been to employ a device known as the
fluidic angular rate sensor.
Such device basically comprises a body in which a chamber is
formedO Pressurised air is orced through a nozzle passage within
the body to form a jet which traverses the chamber. Spaced apart
~rom the exit of the nozzle passage, and positioned direc~ly in
the path o the je~ is a splitter de~igned to divide the jet into
two separate ~nd equal streams when ~he sensor body is at rest.
As the sensor experiences rotation about a control axis (of the
S ship, plane, missile or the like) perpendicular to the axis of
he nozzle passage, the splitter unequally divides the jet in a
prcportion representative of he ra~e and sense of such rotation.
This unequal jet division during ro~ation about the control axis
results from a relative offset between the split~er and jet caused
bX the Coriolis effectO
Each of the unequal stream~ flows into a different one o~ a
pair of recei~ing passage~ positioned o~ opposite sides Qf the
splitter within the ~odyO The streams cause a pressure (or flow
rate) diferential between ~he recei~ing passages which is indi-
lS cative of the rate and sense of the body's rotation about its con-
txcl axis. Such pressure or flow differential may thus at least
theoretically be used to ~enerate and transmit correctiJe input
signals to other component~ of the guidance system to t~ereby re~
turn the ship, plane, missile or the like ~o the correct at~itud~
relative to the control axi~.
Hereko~ore the 1uidic replacement o~ the rate gyroscope, and
navigational rate sensing systems utilizLng it, has ~een hindered
by a ~ariety of struc~ural and func~ional problems associated wit~
con~entional fluidic angular rate sensors~ For example~ una~oida~le
fabricational inaccuracies in such devices have praYented them from
obtaining the extreme accuracy needed to replace the gyroscopa.
Moxe specifically, despite the use o~ modern precision manufactur-
ing techniques, certain in~ernal asymmetries and misalignments
- - 2 ~
remain which result in unequal division (or "ofset") of t~le jet
at zero rotational rate of the sensor about its control axis~
This o~fse~, of course, introduces a continuing source of output
error into the operation of the sensor..
Greatly aggravating the jet offse~ problem is the environ-
mental sensitivity of conventional fluidic rate sensors. Changes
in the environmenk to which the conventional sensor is exposed
cause its jet to variably drift relative ~o the splitter, there~y
adding another source of unacceptable sensor output error.
Anothex e~ually vexing pro~lem has been that of o~taining a
useful (i.e., sufficiently powerful, accura~e and responsl~e)
output signal from the conventional ~luidic rate sensor. It is
desirable to convert the initial fluidic outputs of the sensor to
electrical signal outputs in order to conveniently integrate the
sensor with the electrical control surfaces of the guidance system
(e~g., the autopilot syst~m of an airplane). In addition to b~ing
unacceptably i~accura~e because of the a~ove-mentioned ofset and
drift problems, such initial fluidic outputs are ~uite weakO Thus,
great dif~iculties have been encountered in using them o driYe
pressure-t~-electric transducing devices to obtain electrical out-
put ~ignals. Attempts to utilize hot wire anemometer circuitry,
wherein ~nsing wire~ are placed in each of the sensor receiving
passages to mon~tor the varying flow rate differentials therèbetween,
have proven equally un~uccessul due to unacceptably high response
times involved in differentially cooling such sensing wires.
SUMMARY 0~ THE INVENTIOM
Accordingly, it is the general object of the present inven-
tion to provide an electrofluidic rate sensing system and methods,
utilizing an Lmproved fluidic angulax rate sensor, having the
S capability of replacing conventional rate sensing systems employ-
ing the mechanical rate gyroscope.
A more specific objec~ of this inven~ion is to pro~ide a fluidic
Angular rate sensor, and associated ~ethods~ adap~ed to xeplace the rate
g~roscope, the sensor having associated therewith calibration means
for subst~ntially eliminating ~he je~ ofset and drift pro~lems
which have been d~x~ered to be associa~ed with conventional fluidic
angular ra~e s~nsors.
A further object of the invention is to pro~ide an Lmproved
output system capable of converting the ~luidic outpu~s of the rate
sensox to an electrical output signal without introducing signi-
ficant output error ~ such conversion.
~hese and other objects and advantages-of the present in~en-
tion are specifically set forth in or ~ill become apparent from
the following detailed description of preerred em~odiments of the
inYention ~hen read in con~unction wit~ the accompanying drawlng~.
4~ ~
~3~
The present invention relates to an angular rate sensing
apparatus comprising a fluidic angular rate sensor having jet-
forming means for receiving fluid from a source thereof and dis-
charging a fluid jet, and ~et-receiving means spaced from said jet-
forming means for utilizing said jet to create a pair of fluidicoutput signals having a relative pressure differential indicative
of the rate and sense of rotation of said rate sensor about a con-
trol axis. In a~dition to means for supplying fluid to said jet-
forming means~ the apparatus comprises jet-control means operatively
associated with said fluid-supplying means for maintaining the
Reynolds number of said jet within a predetermined range to thereby
environmentally stabilize the operation of said rate sensor.
In addition, the invention provides angular rate sensing
apparatus comprising a fluidic angular rate sensor having jet-
forming means for receiving fluid from a source thereof and discharging a fluid jet, and jet-receiving means spaced from said jet-
forming means for utilizing said jet to create a pair of fluidic
output signals having a relati~e pressure differential indicative
of the rate and sense of rotation of said rate sensor about a con-
trol axis. Besides means for supplying fluid to said jet-forming
means, the apparatus comprises means for compensating for pressure
and temperature changes in said jet to assure that variations in
the position of said jet relative to said jet-receiving means occur
substant~ally solely due to variations in said rate and sense of
rotation of said rate sensor about said control axis.
The present invention further relates to apparatus for use in
preventing environmentally caused jet dr.ift in a device, such as a
fluidic rate sensor or the like, adapted to receive fluid and form
a fluid jet therefrom. The apparatus comprises means for sensing
- 4a ~
the temperature and pressure of the jet and means for varying the
velocity of the jet in response to the sensed pressure and tempera-
ture to thexeby maintain the Reynolds number of the jet within a
pxedetermined range.
- 4b -
,
BRIEF D~SCRIPTlON OF THE DRAWINGS
Fig. 1 is a schematic block diag.ram illustrating a navi~a-
tional guidance system employing principles of the present in~en-
tion;
Fig. 2 is a sLmplified cross-sectLonal ~iew taken through a
conven~ional 1uidic angular rate sensor;
Fig. 3 is a grap~ .illustrati~g ~he performance of t~e. electro-
fluidic rate ~ensing system portion of the guidance system depicted
~n Fig. l;
Fig~ 4 is a perspective view of an air~ight, thermally insula-
ted canistex in which the rate sensing system is housed;
Fi~. S is a schematic diagram o~ the rate sensing system;
Fig. 6 is a partially exploded persp~cti~e vie~ of a laminat~d
ra~e sensor and output body o~ ~he pre~ent invention;
Fig. 7 is a top plan view of the main rate sensor lamina
por~lon o~ the laminated body of Fig. 6;
Fig. 8 is an enlarged, longitudin~lly compressed illustration
o a generally central por~ion o~ the ra~e sensor lamina of Fig. 7,
S --
D ~
Fig. 9 is a graph illustrating the effect on sensor o~tput
pressures, at zero a~gular velocity, of certain calibration and
s~abilization steps of the present in~ention;
Fig. 10 is a reduced scale bottom view of the sensor and output
Sbody of Fig. 6;
Fig. il is a slightly enlarged fragmen~ary cross-sectional Yiew
taken through the rate sensor ~ody alony line 11-11 of Fig. 10;
Fig~ 12 i~ a ~ragmentary cross-sectional view taken through
the rate sensor body along line 12-12 of Fig. 6;
10Fig. 13 is a greatly enlarged, partially exploded and ~ragmented
view of the rata sensor body portion of Fig. 12;
Fig. 14 is a partially exploded perspective view of an alter-
nate ~m~odLment of the ra~e sensor and output body shDwn in Fig, 6
~ig~ 15 is a top plan view of an alternate embodLment of the
15 . main rate sensor lamina of Fig. 7;
Fig. 16 is a greatly enlarged cro~s-sectional view taken through
the alternate rate sensor lamina embodiment along line 16-16 of
~ig. 15;
Fig. 17 is a perspecti~e viaw o the assem~lied ra~e sensing
~ystem with its enclosing canister ~ody removed; and
~ lig. 18 is a ~ottom view ~f the rate sensing system of Fig~ 17
showing a portion o~ the removed canister body.
- 6 -
DETAILED DESCRIPTION
Introduction
Schematically illustrated in FigO 1 is a navigational con-
txol or guidance system 10 used to maintain a moving body 12 such
as a missile~ airplane, ship or ~he like in a desired rotational
attitude relative to thxee predetermined, mutually perpendicular
control axes - for example, the roll, pitch and yaw axes of an air-
pl~ne~ The body's rotational ra~s o~ at~itudinal d~via~ion ~L~
"
~2~ ~3 about the three con~rol a~es are monitored by a rate sensing
system 14 of the present invention w~ich receives input signals
16a~ 16b, 16c corresponding respectively to ~he rotational rates
--
of ~he moving body. Electrlcal output signals 18a, 18b,
18c, respectively i~dicative of the actual angular devia~ion ra~es
~ , 43~ are sent from the ra~e sensing system to a comparator
lS 20 (o~ conventional construction)~ The comparator compares the
output signals 18a, 18b, 18c to reference input signals 22a, 22~,
22c~ also sen~ ~o ~he comparator, which are indica~ive of the
desired 41~ 42~ ~3 (each such desired ro~ational ra~e usually being
zero).
Upo~ s~nsing differentials between the signal sets 18a and
22a, 18b and 22b~ 18c and 22c~ comparator 20 r01ays appropriate
control signals 24a, 2~b, 24c ~o the bodyls servo and control sur-
ace~ 26. In turn, ~he servo and control surfaces (for example,
. .the autopilot system of an airplane) causes corrective ~orces ~8a,
] 5 28bo 28c to be exerted upon the moving body 12 to return it to its
proper ro~atlonal at~itude relative to eac~ o the three con~rol
axe~.
:- - 7 -
For many years, conventional rate sensing systems have emplo~-
ed mechanical gyroscopes, physically coupled to the moving body,
as the prLma~y rate sensing elements~or each of the three control
axes~ In such conventional three~axis rate sensing systems, each
S of the three gyroscopes is basically a high speed rotating mass
which is rotationally ~otor-driven a~out a spin axis perpendicular
to the body control axis with which the gyroscope is associated.
Rotation of the gyroscope about its control axis (caused by undesir-
ed rotation o~ the moving body ahout the same contxol axis) causes
~h~ gyroscope to precess - i.e~, rotate about a third axis perpen-
dicular to its spin and control axes in a sense and at a rate
re~lecting the sense and rate of the controlled body's rotational
attitude deviation about the control axis. This precessional move-
ment of the gyroscope is mechanically transmitted to a transducing
device, such as a poten~iometer, which in turn sends a~ electrical
control siynal to the overall guidance system of w~ich the gyroscope
i5 a part.
Despite ~heir universal acceptance and use, rate sensing
systems employing mechanical rate gyroscopes have certain ~navoid-
able problems. For example, such systems are extremely sensitive
to the enY~ronment to which they are exposed. Changes in temper-
ature, pressure and humidity, for ~xample, adversely a~ect ~he
accuracy o~ the gyroscopic systemO Additionally, the moving mechan-
ical components of the system are ~uite delicate and of only mar-.
ginal relia~ility when su~jected to the high shock and vi~ration
environment of, for example, guided missile applications. Also,
because of the precision with which the gyroscopes and their asso-
ciated hardware must be fa~ricated, gyroscopic rate sensing systems
. ~ 8
have become highly expensive to manufacture and maintain. Finally,
the tLme required for a gyroscope rotor to obtain its steady~state
spee~ has been proven undesirable in some of the more sophisticated
~pplications.
Because of these and other problems, various attempts have
previously been made ~o replace the gyroscopic rate s~nsing system
with a fluidic system built axound a device ~nown as ~he fluidic
angular rate s~nscr. These attemp~s have not met with grea~ success
due to a variety of struc~ura~ and operational deficiencies hereto-
~ore ass,ocia~ed with the device itself and the rate sensing system
based thereon.
The rate sensing system 14 of the present invention uniquely
elim~nates or minLmizes all of these deficienoies and, for the
~irst time, provides a viable ~luidic replacement for both the
gyroscope and the gyroscopic rata sensing system.
Before describing the novel apparatus ~nd methods of the
present invention, however, the basic ~truc~ure and operation of
a representative conventional f~uidic angular xa~e sensor will be
brie~ly described with reference ~o Fig. 2 in which the sensor
i-~ diagrzmmatically depicted in greatly simplified ~orm ~or illustra-
tive purposes. Such conven~ional sensor, indicated generally at
30, is similar to that sho ~ in U.S. Paten~ 3,971,257 and includes
a ~ody 32 i~ which i5 formed a central intexnal chamber 34.
; Communicating with and ex~ending rearwardly ~ ., to ~he left in
Fig. 2~ xom the cham~er 34 i~ an intexnal nozzla passage 36 ha~ing
a ~low axi~ 38 and an exit end 40. The sensor body 32 is position-
ed relatiYe to a control axis 42 so t~at -the noz21e ~i~ 38 i5
~~3
perpendieular to the control axis (about which rotation is to he
sensed). During operation of kh~ sensor 30, a pressurized fluid,
such as air, is forced forwardly through the nozzle passage 36,
out the nozzle exit end 40, and forwardly across the chamber 34 in
the form of a jet 44.
At the forward end of the chamber 34, the jet 44 impinge~
upon the sharp leading edge 4 6 of a generally wedge-shaped internal
splitter portion 48 of the sensor body 32. The leading splitter
edge ~6 is generally aligned wi~h the nozzle flow axis 38 and, in
th~ absence of rotation of the sensor body a~out the co~trol axis
42, is designed to evenly divide the jet 44 into two equal streams
Sl, S2. Stream Sl is diverted by the splitter m2mher 48 into a
recei~ing passage 50 formed within the s~nsor body on one side of
the splitter member 48, and stream S2 is diverted into a secona
receiving passage 52 also formed withLn ~he sensor body and symme~ri-
cally positioned on the other side of the splitter mem~er 48.
In the absence of angular rotation of the sensor ~dy 32
about the control axis 42, the pressures within the receiving
passages sa, 52 are ~heore~ically equal.
Howev~r, when ~he sensor body 32 experiences rotation abou~
the control axis 42 ~for ~xample in the clockwise dirPckion indicated
by thQ arro~ 54) the Coriolis e~fec~ causes an upwaxd shif~ o~ the
jet 44 relative to the splitter edge 46 as indicated ~y the dashed
line ~et en~elope 44a in Fig~ 2. This relati~e shift between tha
2S ~et and the splitter edge is due to the fac~ that as eac~ particle
o ~he 3e~ fluid .ravels between t~e rotating nozzle exit 40 and
the concurren~ly rotating splitter e~ge 4~, the particle ~ill follow
- ~a -
. .
3 ~
a straight line in inertial space. During the time required for
such particle to travel from the nozzle exit to the splitter edge,
the splitter edge moves downwaxdly relative to the paxticle's con-
stant line o mo~ion~ The magnitude of the distance that the
splitter edge moves durLng ~he particle's ~ravel tLme ls dependent
upon both the rate of rotation o the sensor body and the velocity
of ~he par~icleO
The relative spli~ter edge shift caused ~y the Coriolis effect
in turn causes an unequal division of the jet 44 by the splitter
edge such that ~he s~ream Sl is larger ~han the stream 52~ Th~
result i5 that the pressure Ln receiYing passage 5~ is greater
than the pressure in receivLng passage 52.
I~ is th~s possible to measure ~he resulting pressure dif~er-
ential in the passages 50, 52 and corxelate such pressure differ-
eatial to the rotational ra~e ~ Lmposed upon th~ sensor 30. This
correlation technique was first propounded as early as 1942
(INSTRUMENTS, ~ol. 15~ 5ep~ember~ 1942, a~ page 345l and ~as 5ince
been implemented in various fluidic angular rate sensors. Alter-
nati~ely, by extending receivLng passages 50g 52 outwardly t~rough
th~ sensor body 32, so tha~ streams Sl, S2 flow through. 5UC~ eX~ena-
ed passage~, the flow rate differer.tial ~etWeQn streams sl~ S2 may
be used for such correlation as shown in U.S. Paten~ 3~205,715,
~owever, the practical ~arnessing o ~he Coriolis effec~ în
th~ accur~cy and response ranges required to ~luidically replace
the na~igational gyroscope has, until the present lnYention~
proven to be an el~sive goal despite numerous attempts ~o achie~
it 7
~ 11 -
In accord with the present invention, part of the reason for
past ~ailures to fluidically replace the gyroscope has been found
to be the adverse e~fect upon the conventional fluidic rate sensor's
performance caused by even minute manufacturing inaccuracies in
the nozzle and splitter portions thereof - inaccuracies which to
date have proven to be unavoidable despi~e the employment of
mode~n precision ~brication techniqu~s. Specifically, even an
extremely small offset between the splitter edge 4~ and the nozzle
axis 3B causes a false pressuxP differen~ial ~etween the receiving
passages 50, 52~ Aggravating this misalignment problem is that the
slightest degree o~ asymmetry at the nozzl~ exit 40 causPs the
axis of the jet 4~ to shif~ relative to the nozzle flow axis 38 .
Such asymmetry also causes a false pressure (or flow) differential
betwee~ the receiving passages 50, 52 at zero angular ~elocity o~
the sensor as well as during rotation thereofO
Movero~er, in the accuracy range re~uired for a na~igat onal
rate sensing device, devices such as ~he conventional angular rate
~ensor 30 have proven to be highly environmentally sensitive.
More specifically, changes in the enYiro~men~ to which thP jet 44
is exposed cause its axis to ~dri~t" relati~e to the nozzle flow
axis 38, thus introducing another source of inaccuracy into the
operation of the sensor 30.
Finallyt there haYe been acute problems i~ o~taining a
suficiently accura~e elec~rical output signal from conYentional
fluidic sensors. One approach ~o achieving useful electrical
output signals has been ~o use ~e receiYing passages 50, 52 as
10w passages for the s~reams Sl, S2, as prevlously described,
and to insert in eac~ of ~he flow passages a sensor wire portion
-- - 12 -
~ 5 '4~ ~
of a hot wire anemometer circuit as disclosed in U. S. Pa~e:~t
3,205,715. ~s the jet i~ def~ected by sensor rotation, the re5ult-
ing flow differential between the two streams cools one of the
sens~ng wires faster than the other one, causing a voltage drop
S across the anemome~er circuit. However, ~he high response t~me
i~volved in differentially cooling the t~o sensing wires, coupled
with the above-described sensor as~mmetry and misalignment problems,
renders such an approach unsatisfactory for most navigational
applications.
Another approach, suggested in U.S. Patent 3,971,257, has been
to use the pressur~ differential be~ween the recei~ing passages 50,
52 to directly drive analog type pressure-electric tra~sducers
(for example~ piezoelectric transducers). However, the rotation
induced pressure diferential, eve~ a~ maximum jet deflection,~is
~uite small and is well below that needed to obtain sufficient
navigational accuracy out of such transducing devices. ~dditionally,
because of the built-in inaccuracy problems of ~on~e~tional fluidic
rate sensors, att~mpts to interpose pressure amplification de~ices
between the sensor and a transducer would simply magnify the in-
2Q herent 3ensor ~rror, passing i~ t~rough ~o ~e ul~Lma~e elec~ric
control signals.
The presen~ invention successfully overc~mes all o th~ a~oya
problems and limitations, ana provides a three-axis electrofluidic
na~iga~ional angular rate sensing sys~m ~the system 14 in Fig. 1)
~5 utiliz~ng three uniquely des;gned, extremely a~curate 1uîaic
anyular rate sensors. The great accuracy and broad range of the
new sensing system ~for each of its control axes~ is depicted in
the graph o Fig. 3 in which the accuracy (curve 54) and ~and width
(curve 56) of each of its rate sensors are plotted against the
~en~or's jet length.
- 13 -
As can be seen in Fig~ 3, the rate sensing system 14 has the
capability of covering the entire navigational control spectrum
from ~mall guided.missiles to extreme accuracy inertial navigation
applications. For example, with a three centimeter jet length,
e.~ at a point only approximately midway along the accuracy
curve)g each of the rate sensors of the presen~ invention is
accurate enough to sense an angular velocity equal to that of the
earth's rotation, yet has a ~and ~idth o approxLmately 15 Hz.
The accuracy and response range illustrated in Fig. 3 can be,
at best, only approximated by mechanical gyroscopic systems, and
then only at great fabrication-and maintenance costs. Additionally,
the resulting gyroscopic system would be quite delicate and environ-
mentally sensitive, rendering it s~ructurally unsuited to many
applications. To date, the pexformance spectrum of Fig~ 3 has not
even been approximated by conven~ional fluidic rate sensors.
As described below, all of ~he operatin~ componants o~ the
rate sensing system are housed in a small, thenmally insulat~d~
airtight canistex 60 (Fig. 43, which is easily mounted on the
moving body whose ro~ational attitude is to be con~rolled. The
canister 6G of FigO 4 is of generally cylindrical shape and has a
quarter-round cross-section. However, other canister s~ape-q may ~e
used depending upon the size and configuration of the mounting
space available.
The system 14 is electri~ally dri~en ~y a pair of power leads
62, and respectively provides the three electrical output signals
18a, 18~, 18c of Fig. 1 via three pairs 64, 66, S8 o control leads.
- 14 ~
The power leads 62, and the controL lead pairs 64, 66~ ~n~ 68 are
conveniently.grouped in a single conduit 70 received by a pin-type
receptacle 72 mounted on a removable end plate 73 of the canister
60.
Rate Sensing SYstem 14
The rat~ sensing system 14, ~hown diagrammatic~lly in Fi~. 5,
is an electrofluidic system xepresenting a preferred embodLmen~ of
the present invention~ System 14, whose operating components are
a~l compactly arranged within ~he cani~ter 60 as subsequently
described, utilizes three specially designed fluidic angular rate
sensoxs 74, each of which serves as the angular rate sensing
elemen~ for one of the three mutually perpendicular control axes
of the guidance system 10. Except for Lmportant distinctions set
forth below, each of the ~hree rate sensors 74 functions in the
same general manner as the previously desGribed co~entional
~lu~dic rate sensor 30 (Fig~ 2) and has an inlet passage 76 communi-
cating with an internal nozzle passage~ and a pair of outle~
passages 78, 80~ each communicating with one o~ its two internal
stream-receiYing passages. ~ pressurized fluid, suc~ as air, is
supplied ~o ~he inlet 76 o* each sensor 74 by ~ ~aria~le Yolume
pump ~2, driven b~ a variable speed mo~or ~3, through an air supply
network 84 consistLng of oertain air passages l~ter described.
The outlets 78, 80 of each sensor 74 are connected to one of
~5 ~hree fluidic-to-elec~ric transduc~ng sys~ems ~6, each of which
func~ions in an unique manner ~o amplify the receiving passa~e
- 15 -
~ D~
pressures of its sensor and convert them to a paîr of o~ciLlatin~
electrical contxol signals. Each pair of such electrical control
signals corresponds to one of the control signal~ 18a, 18b, 18c
(Fig. 1) and is sent ~o the comparator portion 20 of the guidance
syste~Q 10 through one of the con~rol lead pairs 64, 66, 68.
As will be seen, the rate sensors 74, and the fluidic-electric
transducing or output sys~ms 8~ resa~iYedy, p~e highly ~ nomir~l
solutions to two of the major problems identiied by the present
inventio~ as ~ing ~he ~ n~eded flu~c replac~t of ~h~ oostl~ and
delicate gyroscopic rate sensing system - namely, ~he alignment and
a~ymmetry difficulties ~ssociated with conventional fluidic rate
sensors, and t~e problem of obtaining sufficiently accurate and
responsive output signals ~herefrom. The ~hird ma]or problem, that
of controlling of elLminating the enviro~mental sensitivity of con-
ventional fluidic rate sensors in navigational applications, issolved by a unique flow control system 90 which senses and util~ze~
certain parameters of system 14 itself to stabilize the operation of
the rate sensing system 14 and to assist in obtaining ex~reme
accuracy there~romO
]O Fluidic An~ular Rate Sensor 74
One of the angular rate sensors 74 of the r~te sensing sys~em
14 i~ shown in perspective in Fig. 6. Sensor 74 has an elongated
rectangular monolithic body 100 defined by a numher of thin metal
laminae, each of which has a su~stantially identical elongated
rectangular perip~.ery, which are stacked in precise alignment and
mutuaLly ~onded together or otherwise intersecur~d. Such laminae
include a main rate sen~or lamina 102 ~hich is sandwiched between
a serie~ of auxiliary laminae 104 above it, and a series of
auxiliary laminae 106 below it. The auxiliary laminae 104, 106
have various openings, channels and passages formed therein which
cooperatively function to ~ransfer air to and from the main lamina
102 for purposes ~escribed below. The rate sensor inlet passage
76 extends downwardly through the auxiliary laminae 104 adjacent
their left ends and is fluidically connected to the ma1n lamina 102
as described below. The rate sensor outlet passayes 78, 80, which
cor~municate wi~h the main lamina 102 through appropriate ~ody
passages defined by openings etc. in the auxiliary laminaP 104,
exit the sensor body 100 through the uppermost lamina 104 adjacent
the left end of the body 100.
Referring to Fig. 7; the elongated rec~angular main rate
sensor lamina 102 is slightly thicker than the auxiliary or air
transfer laminae 104, 106 and has a pair of opposite end edges 108,
110, and a pair of opposite, longitudinally extending side edges
112, 114. An alignment notch 116 is formed in the rig~t end edge
110 adjacent its junct ~ e with the ~ottom side edge 114u Not~h
116 îs used in conjunction with s~milarly positioned alignment
notche~ in the other laminae 104, 106 to afford a visual ~erification
that all o~ the laminae in the body lQ0 are properly oriented prior
to the bonding together of the laminae. To moun~ ~he sensor body
100 on a suitable support, four mounting holes 118 are formed
2S through the main lamina 102 (an~ the auxiliary laminae~ generally
adjacen~ each of their ~our corners as indicated in Figs. 6 and 7.
3f~
Additionally~ circular openings lZ0 and 122 are for~e~ through
the main lamina 102. Opening 120, which is laterally centered and
positioned closely adjacent the right end edge 110, defines a
portion of the inlet passage 76 which supplies air to the main
lamina 102 and other components of the xate sensing system 14 as
subsequently described. Opening 122 is positi oned slightly to the
right of the lower left mounting opening 118 and functions as a
portion of a transfer passage (not shown) within the sensor ~ody
100 which communicates with the inlet passage 76 to transfer air
to Yarious other components o~ the rate sensing system.
A relatively large opening i5 formed through a longitudinally
central portion o~ the main lamina 102 to define an interaction
ch~nnel 130. The interaction channel opening is configured to de-
fine adjacent its left end an opposed pair of laterally inward~y
directed and sharply pointed swirl attenuation vanes 13~ whose
inner ends are spaced slightly apart~ Also defined by the inter
action channel opening is a second opposed pair of laterally
inwardly directed swirl attenuation ~anes 134 positioned to the
right of the vanes 1~2, the vanes ~34 having rounded inner ends which
are spaced slightly ~urther apart than the i~nex ends of the ~anes
132. The vanes 132, 134 in turn defLne an opposed pair of laterall~Y
outwardly extending channels 136 at the left end o~ the înteraction
channel 130, an opposed pair of laterally outwardly extending
channels 138 positioned between the vanes 132, 134, and an opposed
pair of laterally outwardly extending channels 140 positioned
between the vane~ 134 and the right end of the interaction channel
130.
~ pair of receiving channels 14~, 144 a~e formed through the
lamina 102 near the right end 110 thereo, the receivin~ channels
hav ~ g inlet openings 146, 148 opening rearwardly ~i.e., l~ftwardly)
into the interaction channel 130, and closed outer ends 150, 152.
From their inlet op~nings 146, 148 the receiving channels 142,
144 extend forwardly and diverge laterally outwardly, defining a
generally wedgQ-shaped splitter member 154 having a sharp leading
splitter edge 156 which separa~es the channel inlets 146, 148 and
is laterally centPred relative ~o the lamina 102.
Through a left end portion of the lamina 102, three openings
158, 160, 162 are formed. Opening 158 is generally U-shaped and
is positioned directly adjacen~ the left l~mina end 108, openi~g
160 is positioned between opening 158 and the upper laterally ~xtend-
ing channel 136, and opening 162 is positioned between opening 158
and the lower laterally extending channel 136. Openin~s 158, 160,
162 define jet-forming means in the ~orm of an elongated nozzle
portion 164 of the lamina 102. Nozzle portion 164 ~xtends longi-
tudinally along a laterally central ~ortio~ of the lamina 102 and
is connected to the balance of lamina 102 by narrow support arms
166, 168 above the nozzle portion 164, and narrow support arms 170,
172 below i~.
Nozzle 164 has an inlet section 174 at its left end, and a
discharge section ~76 a~ its right end. Discharge section 176
is approxLmately khe same length as the inlet section 174, ~u~
is sligh~ly narrower. The inner ends o~ suppor~ arms 166, 170 are
positioned slightly foxwardly o~ the juncture of the inlet and
dischsxge sections 174, 176, and the inner ends o~ the support arms
158 r 17~ are positioned at the righ~ end of the discharge section
176. Each o~ the suppor~ arms ex~ laterally ou~wardly at a
sligh~ rear~ard angle from its juncture with the nozzle discharge
section 1~6.
., -- 19 --
An elongated nozzle inlet channel 178 is formed through the
nozzl~ inle~:section~ll4 and communicates with ~ much narr~wer
nozzle dischar~e.channel 180 entending lengthwise through the
nozzle discharge ~ection 176 and openingl int~ ~he interaction
channel 130 through an exit end 182 of nozzle discharge section 176.
The nozzle discharge channel 180, which has a flow axis 184 (see
Fig. 8, in which the main lamina 102 of Fig. 7 has been rotated 909
counterclockwise) that is substantially cen~ered betwePn the side
edges 112, 114 of the lamina 102, divides t~e nozzle discharg~
section 176 lengthwise in~o two horizontall~ extending narrow wall
members 176a, 176~ spaced apart on opposite sidPs of the nozzle flo
axis 184. Such opposite wall members 176a, 176~ are respectively
carried by the support arm pairs 166, 168 and 170, 172, and in turn
carry the nozzle inlet portion 174.
For the most part, the various openings, pa~sages, etc. just
described are ~ormed through ~e ma1n sensor lamina 102 ~y a con-
ventional chemical etching process to assure a h;gh degree o~
constructional accuracy~ ~owever, t~e lxmina areas within.t~e
dotted line enveiopes 188 (in w~i~h are located t~e nozzle inlet
and discharge passages 178, 180, the splitter edge 156, and the
receiving channels or passayes 142, 144~ are fonmed by the electric
dischar~e machining (EDM) process to yield an even hig~r degree o~
fabricational accuracy in ~he more cr;tical lamL~a portions. W~ile
such EDM process is well kno~n, and thus need not ~e describe~ ~n
de~ail herein~ it consists generally of us~ng a moving~ electrically
charged, very small-diameter wîre as a cutting instrumPnt to form
the desired lamina surface configurations within the en~relopes 188.
- -- 2û ~
During opera~ion of the sensor 74, air from the sup~1~ network
84 i5 ~orced into the sensor inlet passage 76 and downwardly there-
through into the nozzle receiving channel 178. Air entering the
receiving channel 178 is forced outwardly through the no2zle dis-
charge channel or passage 180 in the form of a fluid jet 190 ~Fig.
8~ which orwardly (i.e., upwardly in ~ig. 8) traverses ~he inter-
action chambex 130 and impinges upon the leading splitter edge 156.
The jet 190 passes successively between the inner ends of the
guide vane pairs 132, 7 34 which function to prevent fluid xecir-
culation back toward the nozzle exit. The outer ends of the
opposite channels 136 are ven~ed tby internal sensor body passages
no~ shown) to a plenum ~also no~ shown) In the sensor body to
equalize the pressures in the channel~ 136, thus preventing fluid
disturbance of the j~t adjacent the nozzle exit.
The jet 190 .~Fig. 8~ has a jet axis 192 and~ as pre~iously
generally described, is divided ~y the splitter member 154 Lr.to
separate stream~ Sl, S2. Streams Sl, S2 have a cross-sec~ional
area differential indicatiYe of the rate and sense of the ~otation
o ~he sensor 74 abou~ a control axis 194 perpendicular to its
2Q n~zzle axis 184~
More sp cifically, the splitter edge 156 i5 ~esigned to evenly.
di~ide the jet 190 ~i.e~, so tha~ the streams Sl~ S2 have su~-
~tantlally eq~al cross-sectional areas~ in the a~sence of such
ro~atlon o~ the sensor 7~ a~o~t its control a~is. A clockwise
rotation of the sensor (about the control axis 1~4) will, ~ecaus~
of the previously described Corioli~ effect, cause the relatiYe
~et-splitter edge movemen~ previously described and render the
cross-sectional area of the s~ream Sl larger than ~he cross-
sectional area of ~he ~tream S2.
Such unequal je~ di~ision (which constitutes one of t~.e rate
sensing system's input signals 16 shown in Fig. l) creates a
pressure differential in the receiving passages 142, 144. A
fluidic output is pxoduced from each of the recei~ing channels or
passages 142~ 144 by means of the sensor output passages 78, 80
which respec~ively communicate with the receiving passages 142,
144. These fluidic outputs may then be compared to determine the
rate and sense o the se~sor ! 5 ro~ation about the control axis 194
and ultLmately used to create one of ~he rate sensing system's out-
pu~ signals 18 ~igO 1).
Calibration of the Ra~e Sensor and Control
,, . _ . ., . _ . _
o~ its Environmental Sen~itiYi~
Even with the very precise construction me~hod used to form
the no~zle, splitter, and receiving passage portions of the main
sensor lamina 102 ~such splitter and receiYing passage portions
collecti~ely defin~ng a part of t~e je~-receiving means o~ the
~ensor), at least a sligh~ degre~ of fabricational inaccuracy remains
in those portions. ~s descri~ed previously, ~ ~ ~o~acyn~niest5
itself in two primary manners: ~l) as~mmetr~ of ~e nozzle dis-
2û charge portion 176 ~Fig~. 7 and 8~, which causes undesired mis-
alignment between the jet axis 192 and the nozzle discharge o~ ~low
axis 18~ (Fig. 8), and (~) lateral misalignment or offset ~etwe~n
the splitter edge 156 and the flow axis 184. As previously noted,
these two structural inaccuracies com~ine to produce a alse
pressure differential at the sensor ou~lets at ~ero angular velocity
of the sensor body lO0 (as well as during rotation thereof~ because
o~ the continuing unequal divisl~on of the jet 190.
- ~2 -
During development o the sensor ~4, it was discovere1 and
empirically demonstxated that the magnitude o~ this fal~e pressure
differential a~ ~he sensor ou~lets i5 functionally related to the
Reynolds number (NRe) of the ]et 190 in a manner graphically
S depic-~ed in FigO 9~ in which the outlet pressure differential (at
zero rotational rate of the sensor body) is plotted against the
Reynolds number of ~he je~ 190. In Fig~ 9, the monotonically
increasing dashed line curve A rPpresents this relationship when
the main sensor lamina 102 (i~ place within the sensor hody 100)
is in its as-fabricated state - i.e., ha~ing both the nozzle asym-
m try and the splitter edge offset inaccuracies.
The present invention provides a unique three-step calibration
method for compensating for these s~ructural inaccuracies in t~e
lamina 102, and ~or eliminating the pre~iously mentioned sîdeways
"drift" of the jet 190 caused by environmentally induced change~
in certain of its ~low parameters,
The first s~ep in such meth~d is to adjustably increase th~
press~re Ln one of the receiving passages 142, 144 to compensate for
the ~plitte~ edge offset by unequally Yenting the receiY ~ g passages.
Re~erring to Figs. 10 and 11, ~o accomplish this unequal ~en~ing, a
pair of su~stan~ially ~dentical ~ent passages 1~5, 196 (defined ~it~-
~n th~ sensor body 100 ~y the lo~er auxil~ary lamina 1061 axe
respectively extended ~rom the recel~ing passages 142, 144 out~ardly
through the ~ottom of the sen~or body. Ven~ passage 195 communi-
cates with the sensor outle~ passage 78 and t~e receiving passage
144, and ~ent passage 196 communicates with the sensor outlet
passage 80 and the recei~ing passage 142. From their junctures with
the r~ceiYing passages the ven~ passages .L95, 196 extend downwardly
: ~ ~3 -
to the auxiliary lamina 106x Lmmediately adjacent the lowermost
auxiliary lamina 106y, lef~wardly along the lamina 106x, and then
outwaxdly through vent outlet openings 195a, 196a formed ~hrough
the lowermost lamina 106y.
S During calibration o the rate sensor 74 (with air hein~
supplied through its internal nozzle~ it is determined which of t~e
outlet passages 78~ 80 has ~he hig~r pressure, thus indicating
whi~h receiving passage has the higher pressure. As an e~ample,
if the splitter edge 156 is offse~ to the right in Flg~ 8, receiv-
ing pa~sage 142 and outlet passage 80 wouid ha~e. t~e highar pressure.
The rate sensor outlet pressures are ~hen equalized by progressiYe-
ly restricting the ~en~ passage (i.e., vent passage 195~ c~mmuni-
~ating with the lower pr~ssure outlet passage 78 until the outlet
passage pressure~ are equalizedO Xn ~he above example, the ad~ust~
able restriction of the vent passage 195 is accomplished by pro-
gressively deforming a por~ion of the auxiliary 12mina lQ6y inward~y
into the vent passage lg6, as illustrated in Fig. 11, to restri~
the fluw o~ air therethroug~ and thus ele~ate the pressure in
recei~ing passage 144~
~hen this first step is accomplish~d, and th~ splitter edge
misalignment thus compensated for, t~e relationship ~tween t~
Reynolds number of the jet 190 and th~ outlet pressure differential
becomes that represented ~n Fig. 9 ~y ~h~ dashea line curve B~
Curve R iS a noNmonotonically increasing curve ~hich generally
representg a do~nward pi~oting of the orîginal curve A~ a~out its
oxigin, through the zero pressure diffexential line. Cur~e B,
w~ich is obtained by the step of compensa~ing for the split~er edge
misalignment, thus represents ~he sensor outlet pres~ure "oset"
- 24 ~
(as a function of the jet's Reynolds number) still remain~ng, and
which is caused by nozzle asymmetry.
Specifically, during development of the rate sensor 74, it
was discovered that such asymmetry occurs prLmarily at t~e opposite
S cornex surfaces 198 ~Fig~ 8~ defined at the junctures of the front
wall surfaces 182 of t~e nozzle discharge section 176 and the
oppositely facing inner wall su ff aces 200 of the wall memb~rs 176a,
176b thereof. These corner wall surfaces 198, although designed
to def~ne sharp edges at the exit end of the nozzle discharge
pas3age 180, in actuality have an unavoida~le degree of rounding
and unequal curvatuxe. Such slig~t rounding ana unequal cur~a~ure
of the corners 198 is shown in Fig. 8 in greatly enlarged and
exa~gerated form for purposes of illustration.
Because of this fa~rica~ion as~mmetry associ~ted with the--exit
corner surfaces 198, the jet l90 sepa.rates rom the nozzIe alon~
these opposite corner surfaces at ~eparation points 2Q2,. 2Q4 t~ro~
which are ~utually offset Ln a direction parallel to ~e nozzIe
10w axis 184. In Fig. a th~ jet separation poink 202 (along the
left nozzle corner surface 198~ is shown offset rearwardl~ o~ ~i.e.,
downwardly of~ the opposite separation point 204 along th~ rig~t
nozzle exit corner surface 198. This illustrati~e rPIat~Ye
sepa~ation point offset causes the je~ axis 1~2 to de~lect le~t-
wardly of ~e nozzle flow axis 184. Thls, in turn, also tend~ to
cause unequal diYision of t~e jet 190 even if the le~din~ splltt~r
~5 edge 15~ i~ precisely aligne~ with. the nozzle axis 184.
The second step of ~he sensor calibration me~hod o~ the present
in~ention comprises compensating for t~is nozzle ~xit e~ge asym-
metry and is accomplished generally ~ exerting a transYerse force
F (Fig~ 7~ on the inlet section 174 of the nozzle ~ember 164 to
- 25 -
thereby adjustably de~orm a predetermlned portion of th~ rate
sensor. Such foxce, which is generally perpendicular to the nozzle
axis 184, slightly upwardly deflects the inlet portion 174. This
upward deflection, in ~urn, causes a relative movement of the
opposite nozzle wall membe.rs L76a, 176b in a direction parallel to
the nozzle axis 184 as indicated by the arrows ~06 in Fig. 8.
More specifically, and with reference to Figs. 7 and 8, such
lateral deflection of the nozzle inlet section 174 forces the wall
member 176a to move forwardly (i.e., to the right in Fig~ 7 and
upwardly in Fig. 8;~ forwardly flexing the members 1667 168 which
support it, while simultaneously mo~ing the opposit~ nozzle wall
membex 176b rearwardly and rearwardly flexing its support membPrs
170, 172. 5uch relative adjustment o~ ~he wall mem~exs 176a, 178b
causes a corresponding relative movemen~ of the opposite corner
edge sur~aces 198 to bring the sepaxation points 202t 204 into
pr~cise alignment. This, in turn, pivo~s the errant jet axi~ 192
(Fig. 8~ rightwardly into precise alignment with the nozzle axi~
184, th~s correcting ~or the remaining jet-di~ision inaccuracy of
the sensor 74~
The selectiYe exertion of th~ trans~erse adjust~g for~e F
~Fig~ 7~, which aligns the je~ separa~ion point~ 2a~, ~04, (Fig.. 8
is ef~ected in the following ma~ner. As can best be seen in Figs.
12 and 13, several of the auxiliary laminae 104 tfor examplet t~e
successiYely adjacent laminae 104a, 104~, 104c) positioned imme-
dlately aboYe the main sensor lamina 102, and seYeral o the
auxili~ry laminae 106 ~for example, the successi~ely adjacent
lamina~ 106a, 106b, 106c~ positioned immediately ~elow it, are con-
figur~d along their left end portions in a manner ~uite s~milar to
the main lamina 102. More specifically, through each of these
auxiliary laminae an opening 210 is formed ~hich corresponds in
- 26 -
shape and location`to the U-shaped opening 158 adjacent the left
end 108 of the main lamina 102. These U-shaped openings 210 de-
fine in each o the auxiliary laminae 104a, 104b, 104c, 106a,r106b,
106c an elonga~ed portion 212 having a location and peripheral
configuration substantially identical to the nozzle inlet section
174 o~ the main lamina 1~2. ~owever, such por~ions 212 do not have
formed therein openings ~Lmilar ~o the nozzle inlet c~annel 178
of the main lamina 102. The only openings formed in such lamina
portions 212 are aligned openings 76 formed ~hrough the portisns 212
of the laminae 106a, 106b~ 106c which define an inner portion of
the s~nsor i~let passage 76 which delivers air downwardly into the
nozzle inlet passage 178 as previously described.
When the aligned sensor laminae are mu~ually ~onded ~ogeth~r
to form the monolithic sensor body, the lamina portions 212 abo~e
and below the nozzle inlet portion 174 define therewith a nozzle
adjustmen~ substruct~re 214 (FigO 12) within the sensor body. It
is upon this substructure 214 that the transverse nozzle adjusting
force F i5 exerted. To permi~ transverse movement o~ t~e ~u~-
structure 214 ~and thus ~he nozzle inlet portion 174~ ~e upp~r and
lower surfaces of the substructure 214 are coate~ with a bonding
agent inhibitor pr~o~ to the l~ina ~onding proce~. The appli-
cation of the inibltor prevents the ~onding ma~erial from adh~ring
the ~ubstructure 214 ~o he sensor laminae a~o~e and below ;t,
~hus permitting sliding movement of t~e su~struc~ure 214 relati~e
~5 to such laminae. To permit the previously described relati~e
movament bet~een tAe nozzle discharge wall portions 176a, 176b when
the su~structure 214 is la~erally deflectea~ inhi~itor is also
applied to the upper and lower surfaces of the support arms 166,
168, 170, 172 and the upper and lower suraces o the wall members
176a, 176b. Thus, when the substructure 214 is deflected laterally,
the wall members 176a, 176b slide in opposite direGtions between
their two immediately adjacent auxiliary laminae 104a and lOZa.
The actual relative adjustment of the nozzle exit edge corner
S surfaces 198 is accomplished by ~he use of a pair of adjusting
screws 218, 220 ~Fig. 12). Screws 218, 220, respectiYely~ extend
laterally inwardly ~hxough a pair of oppositely disposed threaded
openings 222, 224 (Fig. 13) formed through ~he sensor ~ody ~djacen~
its left end, and beax against ~he opposite sides of the adjustment
sub~tructure 214. To facilitate the proper location of such
openi~gs 222, 224 in the sensor body, an opposed pair o~ ali~n~ent
notches 226 are ~ormed in eac~ of the laminae 7 04a, 104~ la4c~
102, lQ~a, .106b, 106c slightly forwardly o~ t~ left end o~ t~
adjustment substructure 214. In the completed sen or hod~, th~se
alignment notche~ 226 provide an easily ~isible guide area through
which to tap the scxew openings 222, 224.
The screw3 218~ 220 provide for sLmple~ yet Yery pre~ise,
adjus~ment of the subs~ructure 21~ ~and thus the adjustment of t~
~et separation p~ints). For example, to effect an upward de~lec~ion
of the su~structure 214 in Fig. 12, the upper adju~ting scre~ 220
i5 backed of slightly and ~e upward adjus~ment of th~ ~u~-
structure 214 i made by tightening the o~er scre~ 218. W~n th~
proper amount of upward de~lection ig acc~mpli~e~ P upper screw
22~ is again tig~tened agains~ the adjus~ing substructure 214 t~
solidly lock it in its adjusted position.
Xeferxing aga~n to the graph of Fig. 9, this last~entioned
nozzle asymmetry adjusbmen~ warps an inte~media~e por~ion of th~
jet~s operation cu~ve B (w~ich resul~s from mak~ng the ~irst
.~
adjustment ~o compensate for the splitter misalignment), a3 indi-
cated by the solid line curve portion Bl, creating in curve B a
flat portion X which extends horizon~ally along the NRe lineO
Wi~hin the range of Reynolds numbers represented by ~he flattened
curve portion X, the pressure differential ~etween t~e sensor's
receiving passages 14Z, 144 (and thus between ~he sensor outlet
passages 78, 80) at zero angular rota~ion of the sensor a~out con-
trol axis 194 is substantially zero.
St~ed otherwise, on portions of the altered operatlng c~r~e
B to the right or left of its flattened portion X, varîatîon of
the jet's ~eynolds number causes t~e je~'s axis to varia~ly deflect
or "drit" relative to the nozzle flow axi~. The Rey~olds number
~which is the produc~ o ~he j~t fluid's densi~y, ~eloci~y, and
hydraulic diameter divided by its visocity2~ for a giYen jet velo-
city and cross-sectional configuxation, is mainly dependent upon
the ~et's temperature and pr~ssure. rh~s~ it is prLmarily c~anges
in ~h~se two parameters (arisi~g from c~anges in t~e en~lronment
to wh~ch the sensor is subjected~ w~ich cause t~e undesira~le jet
drift in the curve B portions outside ~he glattened ~urve portion
2~ X there ~O
The t~ird step of the cali~ration me~hod of the pre~ent
inven~ion comprises controlling the Reynolds num~er of t~e je~ such
that its actual operation point ~ is maintained along ~ 1 curYe
portion X. This is acc~mplished ~y the control system 90 ~Fi~ 5
which senses the jet's temp~ra~ureand pressure and u~ es ~es~
parame~ers, in a manne~ ~escri~e~ ~elow, ~o control the je~'~
_ 2g ~
Reynolds number and maintain it wit~in the confines of the curve
portion X along which t~ere is no apprecia~le false pressure
differen~ial present at ~he sensor ou~lets.
Referring ~o Fig. Sl the Reynolds number control system or
jet control means 90 (which, like t~e other c~mponents of the rate
sensing system 14, is housed within t~e in~ulated canister 60)
includes a pressure sensor 230 and a temperature sensor 232.
Pressure sensor 230 has a first air inlet 23g coupled to the s~pply
air passa~e system 84 by a branch passag~ 236, and a second air
inlet 238 which is open to the interlor of the canister 60. The
pressure dif~erential be~ween ~he pressure sensor inl~ts 234, 238
is indicatiYe of the jet pres~urec within the rate sensors 74
and produces from the pressure sensor 230 an electrical output
signal 240 ~hich is received ~y an electrical operational ampllfier
242.
TempPrature sensor 232 is an electrical semiconductor device
which is secured to and sense~ the temperature of one of t~e rate
sensor bodies 100 as indicated ~n ~ig. 5. Such sensor ~ody tempe~-
ature is substantially identical to that of t~ jet wit~in such
body as w~ll as the ot~er tw~ ra~e sensor jets. ~s t~e sensor
body temperature changes, the temperature sensor 23~ experiences a
su~stantially identical ~emperature c~ange, ~hus propor~onally
varying its resistance. ~n electrical signal corresponding to
such resistance change is sent to t~e operational amplifie~ 242
~5 Yia an electrical output lead 246 interconnected ~etw~en ~emper-
ature seasor 232 and the operational amplifier 242. Power i5
respec~ively supplied to the pressure s~nsor 23Q, the tempera~ure
5en50x 232, and th~ operational amplilex 242 ~y sub-~ranches ~44a,
244b, 244c of a branch alectrical lead 244 connected to th~ main
powe~ lead~ 62.
- 30 -
These pressure and temperature input signals 240, ~45, whi~h
together are indicative of the actual je~ Reynolds numbers, produce
~rom the amplifier 242 an output signal 248 whose magnitude i5
directly proportional to such actual ~eynolds numbersO Output
signal 248 is transmi~ed to an electr;c speed controller 250 which,
in turn~ controls the speed of the ~ariable speed motor R3 via an
output lead 252. ~ariations in the speed of ~he motor 83, in
turn, ~ary the ~olume of air supplied ~o the rate sensors 74 by the
pump 82 via the supply passage network 84. In this manner, the ~elo-
cit;es of the rate ~ensor ~ets are automatically ~aried to maLntain
such Reynolds number~ on the flattened curve X (~ig. 9) as previous-
ly des~ri~ed, ~h~s maintaLning the Reynolds ~umber~ w~thln a pr~
determined range.
As an example o the operation of the Reynolds number control
syst~m 90, let it be assumed ~a~ ~he amplifier Z42 has ~een ~et
to maintain each o the jets' Re~nolds number at the operating
poin~ P ~ Fig. 9, and ~hat the jets' temperatures and pressure~
~hen experience a Yariat~on which increa~es the jets' Re~nold~
number~ such that each jetPs operation point P is shifted right-
wardly in FigO 9 ~o point Pl~ ~he operational amplifier 242 senses
~h~se temperature and pressure variations ~via i~s pressure a~d
temperature signal~ 240, 246), which ha~e increased the Reynolds
number~ of the ~ets beyond their decired operating ~alues~ ana
a~omatically decreas~s t~e strength o~ its outpu~ signal 2480
Thi~ decreasa lowers the speed of t~e motor 83 and th~s de-
creases the ~lo~ ra~e o~ a~r supplied to ~ac~ o th~ ra~ ~ens~rs
74. The flow rate decrease, in turn, lowers ~he ~at Yelocity
in each of the rate sensors ~y an amount suficient to xe~uc~ i~s
Rsynol~s num~er ~o the proper ~alue P. ConYersely, variations ln
the je~ ~mperature and pressura causing ~ reduc~îon in the set
. - 31 -
point ~eynolds number ~f each jet causes an increase in tha strength
in the output signal 248 of the operational amplifier which in-
cr~ases the speed of the motor 83 and causes an increase in jet
velocity to correctively increase each of the ~ets' Reynolds
number.
.
The components of the Reynolds number control system 90
cooperatively function to environmentally stabilize the operation
o~ the calibrated ra~e sensors 74. It should be noted that the
insul~ted and airtight canister 60 aids in shielding the rate
sensing system 14 from rapid or large variations in tempexature and
pressure. Additionally, by setting the operational amplifier to
maintain eac~ of the je~s' operatiny points P on a g~nerally
central point of the flattened curve portion X~ the resulting ini~
~ial limited variations in the jets' Reynolds numbers are easily
kept within such curve portion ~o prevent false pressure differ-
entials at the sensor output.
. Fluidic-to-Electric Output System 86
The outlets 78, 80 o each of the rate ~ensors 74 are fluidi-
cally coupled to one o ~he three output systems 86 as indioated
in Fig. 5. Each of the uutpu~ systems 86 includes ~luidic and
elec~ric de~ices which are arranged in a novel mannex to convert
~he ~luidic output signals of its rate sensor ~o ~he hig~ly
a~cura~e elec~xlc output control signals 18~ For purpose~ of
illustration, the upper ou~put system 86 in Fig. 5 will be des-
cribed, the other two output systems 86 being identical thereto~
Output system 86 includes three fluidic proportion?.l ampli-
fiexs 256, 258, 260 which are coupled in a cascaded or series
arrangement to the ra~e sensor outlets 78, 80, a pair of fluidic
oscillators 262, 264, and a pair of microphone type pressure-to-
electxic transducers 266, 268. As indicated in Fig. 6, each of
the fluidic amplifiers and oscillators of the output system 86
comprises a metal main lamina having a peripheral configuration
substantially identical to those of the laminae in the rate sensor
74. The amplifier and oscillator laminae are interleaved between
a number of auxiliary laminae 270 and define therewith an output body 272.
The various laminae of the outpu~ body 272 and ~he r~te sensor
body 100 are mutually aligned and then bonded together to form a
combined rate sensor and fluidlc output body ~74.
The auxil~ary laminae 270 of the output body 272 have various
lS openings formed therein which cooperatively define internal
paosages in the output body 272 that fluidically collple the ~mpli-
fier laminae 256, 258, 260 and ~he oscilla~ox laminaP 252, 264 in
a manner schema~ically illustrated in Fig. 5. A first pair 276 of
such internal passages couple the rate sensor outlet passages 78,
80 to the co~trol ports of the first fluidic amplifier 25~. A
second pair 278 of in~ernal passayes couples the ou~le~s of ~he
first amplifier 256 ~o ~e ~ontrol ports of ~he sscond amplifier
258, and a third pair 280 of internal passages ~ouples the outlets
of t~e secc)nd amplifier 253 ~o the con~rol ports o~ the third or
~5 t~ Lnal amplifier 260. A four~ pair 282 o sucE~ internal passages
couples the outlets of tAe ~erminal amplifier 260 to the inlet ports of
fluidic oscillators 262, 264. ~ach of the control port~ of the
oscillators 262, 264 is fluidically coupled to one OI its ~3 ou~ets
by one of four in~ernal passages ~4 also defined ~y the auxiliary
-- 33 ~
12minae 270 within the outlet body 272. Finally, such auxiliary
laminae 270 also define three branch air supply passages 286, each
of which couples one of ~he inlet ports of ~he amplifiers 256, 258,
260, to the main supply air passage system 84.
S Extending upwardly through the output body 272 adjacent its
le~t end is an upward continuation o~ the sensor inlet passage 76.
Also extending upwardly through the ou*put body 272, on opposite
sides of the inlet passage 76, are two output passages 288, ~90.
Out~ut passages 288~ 290 respectively communicate with one o the
oscillator passages 284 of the oscillator 262, and with one of
~he oscillator passages 284 o~ the oscillator 264. In a manner sub
sequently described, such passages 288, 290 are respectively
connected to the inlet~ of the transducers 266, 268.
While the construction and operation of ~he conventional ampli
fier laminae 256, 258, 260, and the conventional os~illator laminae
262, 264, are well known in ~he fluidics art, a brie description
o such constructio~ and operation will now be given in order to
more clearly illustrate the unique and advantageous operation of
the output system ~6.
Referring again to FigO 5, the supply air bxanch passages 286
force fluid je~s 2g6 ~hrough interaction channels in each of the
amplifier laminae 256, 258, 2600 each jet be$ng centered betwee~
its amplifier's outlet passages which are positioned opposite th~
amplifier's inlet. Air entering t~e amplifier's control ports,
which are positioned on opposite sides o the jet between the
amplifier's i~le~ port and its outlet ports, deflects the je~ in a
: - 34
sense and to a degree indicative of the pressure differen~ial be-
twee~ the amplifier control port passages~ This deflection, in
turn~ creates an zmplified pressure dif~exential in the amplifier's
outle~ passage~.
As an example of the operation o~ the amplifiers 25Ç~ 258,
260, if the rotation-induced pressure in the rate sensor receiving
passage 142 is greater ~han the pressure in its receiving passage
144, ~he pressure in the lower control por~ supply passag~ 276 ~Fig. 5)
is -orxespondingly greater tha~ the pressure in the upper passage
276. This pressure differential causes an upward deflection o~
the ~et 296 of the ~irst amplifier 256. Such upward deflection
of the jet creates in the amplifier outle~ passages 278 an ampli-
~ied pressure differential - the pressure i~ the upper passage 278
being greater than ~he pressure in ~he lower passage 278. This
pressure differential, in turn, causes a downward deflection o~ the
jet 296 of the s~cond: amplifiex 258, and a further amplified
pressure differential in ~he outle~ passages 280 of the second ampli~
~ier 258 (the pressure in the lower passage 280 being greater ~han
the pressure in the upper passa~e 280). This pressure differential
2~ creates ~h~ third stage o amplification~ upwardly deflecting t~e
jet 296 of the terminal amplifier 260 and causing a higher pre~sure
in the upper amplifier outlet passage 282 than in t~e lvwer passage
282.
.
The oscillators 262, 2~4 ar~ similar in ~onstruction ~o t~e
amplifiers which precede the~ in the output ~ystem 86, the
os~illators each having a~ internal jet 298 flowing inwardly from
the outlet passage~ ~82 o the t~mlnal amplifier ~60. ~owever,
because the oscillators have their outle~ ports fluidically
.
: - 35 -
connected to their control ports by the passages 284 as previously
described~ ~ets 298 axe caused to rapidly oscillate. This o~cil-
lation alternately pressurizes the upper and lower passages 284 o~
each of the oscillators. The frequency of such oscillation is
directly proportional to ~he pressure in the oscillator's inlet
passage 282. For each of the oscilla~orsy such jet oscillation
creates in its upper and lower outlet passages 2g4 pressure pulses
of this same frequency. .
The result is that corresponding pressure pulses are created
~n the passages 288, 2gO which fluidically connect one o the
oscillator passages 284 o th~ oscillator 26~ to the ~xansducer 266,
and one of the oscillator passages 284 of the oscillator 264 to
the transducer 268. The pressure pulses in such passages 288,-2~0
thus have fre~uencies directly proportional to the pressures in t~
upper and lower outlet passages 282 of the terminal amplifier 260.
The dif~erent frequency pulsations in the transducer inlet
passages 288, 290 respeckively drive the transducers 266, 268 to
thereby create in the output leads 64 ~wo sinusoidal output signals
having a frequency differential extremely accurately re~lecting
the pressure differential in the rate sensor recei~ing passages 142,
144~ The frequency of the elec~rical outputs in ~e output leads
64, which toge~her constitute the output signal 18a (or 18~ or 18c
as the case may ~e) may then be automatically su~tracted~ fox
example at the autopilot computer center of an airplane~ to pre-
cisely indicate the actual angular rate of t~e controlled ~odyabout one o its con~rol axes.
- 3~ -
The unique coupling of the fluidic amplification ar.d oscil-
ation means just described allows ~he use of the very inexpensive
microphone (or "digitaln) type transduc rs 266, 26a instead of
murh more expensi~e analog type transducers. Since the transducers
266, 268 of each output system 86 are responsive to t~e frequency
o their inputs (instead of the input signal amplitude as with
analog transducers), much less power is required to operate them.
Moreover,. since the freque~cy-responsi~e transducers 266/ 268 are
substantially smaller and lighter than their analog counterparts,
2 mu~h better response is achieved with greatly reduced h~stexesis
and the like.
Because of the extreme accuracy built into the rate sensors 74
a~ pre~iously descri~ed, the output system 86 add no significant
error to the rate sensor output ~ignals 78, 80, despite the fact
~hat such signals are greatly amplified by ~he ou~put systemsO
It should be no~ed that, while three amplifiers ar~ used in
each of the indicated output sys~ems, a greater or lesser num~er
could be used if desired, depen~ing upon the size o the r~e
sensor~ and the type o transducers used. The cascaded amplifier
arrangement indicated in Fis~ 5 allo~s the use of standard, readily
availa~le fluidic propor~ional amplifiers to con~eniently achie~e
thQ rather high degree of ampli~ication necessary - a degree some-
what difficul~ to obtaLn ~ith a single commercially available
amplifier in many applications o~ the rate sensing system 14. O
~ourse, i desired, a single, ~pecially manufactuxed amplifier
ha~ing suficlen~ power could be used to replace the three a~pli-
Ei0r~ indicated ~, each o~ the output systems 86.
: - 37 ~
Since the transducer pairs 266, 268 produce electr.ical outputs
whose frequency differential is indicative of the pressure differ-
ential in the receiving passages of th~ rate sensor to which the
transducers are fluidically coupled, the sum of the frequencies
of such electrical outputs is indicatiYe of the rate sensor's jet
pressure. Thus, instead of using the pressure sensor 230, which
transmits the pressure output signal 240 to the operational ampli-
fier 2~2 of the Reynolds num~er contxol system 90, an electronic
frequency summer may be used, The frequency summer (indicated in
ph~tom at 302 in Fig. 5), which replaces the pressure sensor 230
and functions as a pressuxe sensi~g means, i5 conn~cted to one of
the transducer pairs by an electrical lead 304~ Lead 304 îs connect-
ed to a summing lead 306 interconnected ~etween one o~ the trans-
ducer pairs 266, ~68. 5ummer 302 transmi~s an electrical outpu~
signal 308 to the operational amplifier, the output signal 308
~eing indicatiYe o~ the rate sensor jet pressures.
.Alternate Embodiment of the Rate Sensor
An alternate embodLment of the rate sensor 74 is depicted in
Fig. 14 and indicate~ generally by the refe~ence numeral 314.
Like ~he rate sensor 74, the ra~e sensor 314 includes a main sensor
lam m a 316 sandwiched be~ween auxiliary laminae 318 a~ove i~ and
auxiliary laminae:320below ito The laminae 316; 318, 32~ arP of
substantially identical peripheral conisulation and are mutually
bonded together to ~orm a monolithic metal sensor ~ody 32~
The m~in sensor lamina 31S i3 illustra~ed in F~g. 15 and is
fonme~ frQm sever~l sublaminae 316a as indicated in Fig~ 16.
- 38 -
,3
Althcugh the lamina 31~ in Fig. 15 appears slightly smaller than
~he main lamina 102 in Fig. 7, it is actually much longer and wider
thçn th~ lamina 102, being particularly adapted to the inertial
navigation portion of the graph in Fig. 3 (whereas ~he lamina 102
and rate sensor 74 are well suited to applica~ions in the left
portion of the graph of Fig. 3).
Lamina 316 is generally of an elongated rectangular shape,
having a~ i~s right end a generally triangularly ~haped portion 324
ha~ing a pair o~ perpendicular, equal length side edges 326, 328,
which are angled forwaraly and inwardly to define at the~r juncture
a rounded forward corner 330 o~ the lamina 316 which is laterally
centered relative thereto.
Except ror the differences subsequently described, ~he structure
and operation of the lamina 316 is quite sLmilar to tnat of the
previously described main lamina 102 of Fig. 70 For ease in com-
pari80n, the portions of the lamLna 316 sLmilar in configuration
and operation to ~hose of lamina 102 have been gi~en identidal
re~erenc~ ~umber~. Lamina 316 has a nozzle section 164 through
which is formed an inle~ passage 178 and a nozzle discharge passage
180, 8uch ~assages defining a pair of oppositely aispose~ wall
members 176a, 176b which are carried by support arm~ 166~ 168, 170
172. The nozzle di~charge passage 180 opens forwardly into an
interactio~ cha~ber 13~ which defines opposed pair5 132, 134 of
guide vanes spac~d forwardly o the nozzle discharge passage 180.
At the right end o~ the interaction channel 130 ~s a splittex
memb~r 154 " having a leading splitter edge 156, upon opposite sides
o~ which are posi~ioned rece~Yiny passage~ 142, 144 which extend
forwardly fxom the interac~ion channel 130. Formed in the f:ront
~ 3g --
portion side edye 316 adjacent the forward corner 330 is an al~gn-
ment notch 116. Also formed through the lzmina 316 are five mount-
ing ope~ings 118 ~ and an air transfer op.ening 122.
In construc~ing the sensor l~mina 316, the i7 lustrated openings
S and sur~ace (except those wit~in the dotted line envelopes 188) are
formed ~y a chemical etching process in each of the su~laminae 316a.
The chemically e~ched sublaminae are then stacked in precise align-
ment and bonded together to form ~he main lamina 316~ ~inally,
the areas wi~hin the dotted li~e envelQpes 188 tincluding thP
nozzle inlet and discharge passages 178, 180, ~he spli~ter edge
156, and the rec~iving passages 142t 144~ are formed in the assem-
bled lamina 316 by the previously descri~ed EDM process~
For reasons described belo~, a pair of opposed symmetrical
calibration channels 33~, 336 are formed through the lamina 316.
Each of the channels 334~ 336 extends laterally inwardly through
one o the lamina side ~ges 112, 114, slightly rearwardly o~ the
support arms 166, 170, ~hen extends forwardly past the nozzle
discharge pas~age 180, and finally ~urns laterally inwardly lntO
one o~ the guide vanes 134~ These channels 334, 336 divide t~e
lamina 316 into two section~ 338~ 340 w~ich are held together only
by th~n end portions 342 of t~R orward guide vanes 134. To p~o-
~ide a greater degree of structural rigidi~y ~o the l~mina 316
prior $o the assem~ly of ~he sensor ~Oay 322, generally ~-shaped
thin support member~ 344 are formed on ~he lamina 316 to hold the
two lamIna sections 338, 340 together. Each o~ ~he suppor~ mem~ers
344 projects laterally outwardly o~ t~e lamîna 316 and interconnects
ad~acen~ por~ions o~ the lamina sec~;ons 338, 340 adjac~nt -k~
entrance point~ of ~he cali~ration c~annels 334, 336.
- - 40 -
As indicated in Fig. 14, each o~ the auxiliary lam~n~e 318,
320 has ~ormed therein sLmilarly configured and positioned cali~
bration channels 334, 336 so that the ass~mbled laminated body 322
is di~ided into rear and forward sec~ions 338, 3~0 which are
S connected by a thin body portion or ioining section 346 positioned
between the opposite ends of the aligned calibration channels 334,
336. Each of the auxiliary laminae 318, 320 has init;ally formed
thereon generally ~-shaped support members 344 slmilar to those
formed on the main lamina 316. When all of the lami~ae are bonded
together to form the sensor body 3229 all of the suppor~ m~m~ers
344 are ~n~d away or otherwise removed, leaving the ~ody portions
338, 340 supported only by ~he ~nall joining sa~io~.3~6~
The rate sensor 314 operates in su~stantially the same manner
as does the prevlously describad rate sensor 74. ~n inlet passage
76 extends downwardly through the rate sensor body 322 and into
the inlet channel 178. Supply air entering the înlet rhannel 178
i~ forced in jet form outwardly through the nozzle disc~arge
passage 180, forwardly ~raverses the in~eraction channel 130 and
impinges upon the leadlng splitter edge 15~ w~ere the jet is diYid-
ed and di~erted Lnto ~he receivLng passages 142, 144. Such recei~-
in~ passages 142, 144 respecti~ely communicate wit~ outlet passa~s
78, 80 extending upwardly through t~e sensor ~ody 322 adjacent lt~
righ~ e~d a8 indicated in Fig~ 14.
Unlike t~e rat~ sensor 74, the first sensor cali~ration s~ep
~i.e., that nf ~ompensating for spl;~t~r offset) is not accomplished
by adjusta~ly venting one of the receiving passages 142, 144~
Ra~her~ such fixst calibration step is accomplished ~y bending the
senso~ ~ody 32~ about an axi~ parallel ~o i~ contro~ axis 194 to
- - 41 -
3 ~
thereby actually move th~ leading splitter edge 156 into precise
alignment with the nozzle axis 184.
This adjustable bending of the sensor body 322 is effected
by a pair of adjusting scxews 350, 352. Screws 350, 352 extend
S laterally inwardly ~hrough threaded openings formed through the
opposite outer side surfaces of the forward sensor body portio~
340 slightly forwardly of its rearward ~ermination. The adjust-
ing screws 350, 352 ex~end inwardly through the opposite c~libra-
tion channel~ 334, 336 and bear upon opposi~e side surfaces of ~he
rear sensor body portion 338 as indicatea in phantom in Fig. 15.
Guide.. notches 354 are formed i~ t~e main lamina 316, and se~-
e~a~ of the auxiliary laminae 318, 320 a~ove and below it, to
~isually define ~he proper area through w~ich such threaded open-
ings are formed in the sensor body 322.
As an example of how these adjusting screws 3S0, 352 ~re used
to precisely align the split~er edge 156 with the nozzle axis 184,
let it be assumed that in FigO 15 the as-fabricated splitter edge
156 is offset slightly downwardly of t~ noz~le a~is 184. To
correct or this abrica~ional inaccuracy, the ad~usting scre~ 350
~Fig. 14) is backed off slightly and the opposite adjust~ng screw
352 is tight.ened against the rear ~ody por~ion 338 to ~hereby
slightly pivo~ the ~orward body port~ion 340 in a clockwise direction
as ~ndicated by the arrow 356 In Fig. 14. This clockwise piYot-
ing of tbe forward body section 340 mo~es the spli~ter edge 156
slightly upwardly as indicated ~y t~e arrow 358 in Fig. 15~ to
bring i~ into alignmen~ with the nozzle axis 184.
~ ~2 ~
When the desired upward deflection of the splitter edge 156
is obtained by tightening the adjusting screw 352, the other
adjusting screw 350 is then tightened against the rear sensor body
section 338 to positively lock the splitter edge 156 in its proper-
ly aligned position.
The second ca3ibration step, ~hat of compensating for nozzle
asymmetry, is accomplished in su~stantially the same manner as
was previously described for the rate sensor 74 - namely by the use
of the oppositely aisposed ad~ustLng screws 218, 220 which extend
in~ardly ~hrough guide notches 22~ formed through ~he l~mina 316
(and several of the a~xiliary laminae direc~ly above and below it3
and bear against a le~ end portion o the nozzle section 164.
The application of inhibitor to certain portions o~ the noz21e
section 164 , the opposi~e wall mem~ers 176a, 176~, and the support
arm~ 166, 168, 170, 172 is perfonmed in a manner identical to
~at previously described in conjunction with the aorresponding
portions o the rate sensor 74, to thereby permit ~o~ement of t~e
wall members 176a, 176b within the senso~ body 322 to efec~
precise alignment of ~he jet separa~ion points, also as preYiously
2~ described.
The Reynolds number con~rol system 90 ~Fig. 5~ is used a~
previously described to ~n~ironmentally stabilize t~e opera~îon
o~ the rate sensor 3140
The fluidic componen~s of ~he ou~put sys~em 86 tnamaly the
cascaded amplifiers 256t 258, 260 and the ~scîllators 262, 254~
a~e assembled to ~efin~ an output stack 362 comprised o maLn and
auxil~ary laminae as described for t~e output stack or ~ody 272 of
- ~ 43 -
~ 2~
Fig. 6~ In the case of the larger rate sensor body 322 (Fig. 14)',
each of $he laminae in the output stack 362 is of a standard size~
having a square configuration. The forward side edges 326, 328
(Fig. 15) of the main sensor lamina 3I6 and its auxiliary laminae
have lengths identical to the lengths of the sides of the output
body 362. As indica~ed in Fig. 14, the output stack or body 362
is posi~ioned on top of the generally triangular portion of the
forward sensor body section 3~ with a pair of adjacent side edges
o~ the output body 362 being aligned with the two forwardly facing
si~ edges o such triangular body portion.
I~ can be seen in Fig~ 14 that a rear corner portion of the
output stack 362 extends rearwardly beyond the narrow body portion
346 which holds ~he forward and rear sensor ~ody portions 340, 338
togethex. For this reason, the undersur~ace of such overlapping
corner portion of the output b~dy 362 is coa~ed with an in~ibitor
prior to the bonding of the laminae in the sensor body and output
body~ This permits the previou~ly described bending of the sensor
body by allowing such corner por~ion ~o slide over t~e upper ~ur-
face of the rear sensor. ~ody section 338.
Like their Pig. 6 coun~erparts, the auxiliary laminae in the
sensor and output bodies 322,.362 Ln Fiq. 14 f~nc~ion to define
various passages, cha~nels and openings in such bodies to supply
and ~ran~fer ~ir withi~ them. For example, the ~ransfer opening
122 in the main sensor laminae 31~ and the au~iliary laminae 318
above ik define a transer passage which communicates wit~ the
inlet passage 76 and transfers air upwardly in~o the main ampli-
fier and oscillatcr laminae in the outpu~ ~ody. Such amplifier
- ~4 -
L-D~
and oscilla~or laminae are ~luidically interconnected wit~in the
output body 362 in a manner schematically depicted in Fig. 5 and
previously described. Output passages 288, 290 extend upwardly
through the output body 362 for connection to one o~ the trans-
ducer pairs 266 3 268.
Const ~ti~n, Arrangement and Operation ~f t~e ~ate Sensinq S~stem
The assembled rate s nsing sy~tem 14 is shown in Figs. 17 and
18 a~d is mounted on the underside of ~he canis~er end pla~e 73.
For supporting various componen~s of the rate sensing system, an
elongated metal suppork member 364 is pro~idedO Support member 364
ha~ a base plate portion 366, a pair of oppositely disposed mount-
ing legs 368, 370 e~tending rearwardly (i.e~, to the left in ~ig.
17 and to the right in Fig. 18) from the base plat~ portion~ and
an elongated mounting block 37~ extending forwardly from such ~ase
plate. .Th~ support member 364 is ~ecured to the canister end
plate 73 by screws 374 extending rearwardly through each of the
mounting legs 368, 370.
The mounting block 372 has a substantially planar outer end
surface 376, a pair of subs~antially planar longitudinally extend-
ingt mutually spaced sid~ surfaces 378, 3B0, and a forward end
por~on 382 extending rearwardly a s~ort distance from the outer
end surface 376 and pro~ecting upwardly ~etween th~ side sur~aces
37~, 330. The planes of the side sur~aces 378, 380 are perpen-
dicular ~o ea~h other and to ~e ou~er end surface 376.
~ne o:~ the three com~ined rate sensor and output ~odies 27~i
~Fig. 6) is mouxl~ed on each of t}le mutually perp~ndicular mounting
-- ~ 5
block surfaces 376, 378, 380 by means of screws 384 received
through the mounting holes 118 in such bodies. The laminated
bodies 274 are positioned so that their vent openings 195a, 196a,
(Fig. 10) face outwardly, and their inlet and discharge openings
78~ 288, 290 face inwardly. Because the mounting block surfaces
376, 378, 380 are mutually perpendicular, the control axes of the
t~ree rate sensors secured thereto are likewise mutually perpen-
dicular.
~he variable volume air pump 8~ (Fig. 5) is of a circular
cylîndrical shape and is receîved in a circular bore 386 formed
through the mounting blo~ forward end portion 382. The varia~le
speed motor 83 is attached to the pump 82 and extends between the
base plate 366 and the mounting ~lock forward end portion 38~.
Each of the three transducer pairs 266, 268, (Fig. 5~ i~
mounted within one of three generally cylindrical transducer
housings 388 which are secured to t~ support m~mber 364v Two of
the transducer housings 388 are affLxed ~o the support member 364
~neath the upper pair o~ sensor and outpu~ bodies 374 (as can be
best seen in Fig. 18), and the other transducer housLng 388 is
mounted on the underside of the base plate 366.
The previously described supply aix passage network ~4 oX Fig.
5 i5 foxmed within the support member 364 ana i~terconnects t~e
discharge of the pump 82 with ~he inlets of the rate sensors and
the fluidic amplifiers as schema~ically depic~ed in Fig. 5.
Similarly, other passages are formed ~îth.~n the suppor~ member 364
to fluidi~ally interconnect the discharge passages 288, 290 from
the oscillator pairs 262, 264 to the transducer pairs 266 t 268
wi~hin the transducer housings 388.
The previously described pressure sensor ~30, operational
amplifier 242, and electronic 6peed con roller 250 of the ~eynolds
number ~on~rol system 90 are ~ounted beneath the base plate 366.
~ha temperature sensor ~32, as pre~iously described, is mounted
directly upon one of the rate sensors as indicated in Fig. li. The
~up~ly air branch pas-eage 236 (Fig. S) is also ~oxmed within the
support member 364 and ~luidically couples the pressure sensor 230
to the main supply passage network 84 formed within such support
member 364.
~fter the assembled rate sensing system 14 is ~ecured to the
canister end plate 73, the canister body is slipped over the
assembled system and secured to the end plate 73, ~hus enclosing
th~ rate sensor system 14 in the airtight, thermally insulated
interior of the canister.
The canister or container 60 i5 easily mounted in a conYenient
location on the controlled body 12 ~ig. 1) and oriented so that
the.control axes of the three rate sensors ~ithin the canister
are parallel ~o the desired control axes of ~e ~ody 12. The olltput
leads 64, 66, 68 are ~hen connected to the ~alance of the gu;dance
system 10 illustrated in Fi~. 1, and the power input leads 62
connected $o an electrical power source. Subsequent sotatlon of
the controlled body about any o~ its three control axes correspond-
ingly rotates the canister and varies the output signals 18a, 18~,
18~ to rapidly return the hody to the desired attitude.
- 47 ~
`3~;
It should be noted ~hat the rate sensing system 14 is an
entirely self-contained system which functions within the sealed
intexior of its enclosing canis~er. Even the aix supply or its
~rarious f luidic components i5 drawn from within the airtight,
thermally insulated c:anls~er. As indicated schematically in Fig.
5 by the arrows 390, the interac~ion chambers or channels of the
fluidic rate sensors, amplifiexs ~nd oscillators are vented, in
a conventional manner, to the ca~ister' s interior through open-
ing~ (not shown in the drawings) formed in ~eir bodies~ This
vented air, together with the aîr vented through the s~nsor vents
195a, 196a, is drawn into th~ inlet 392 of ~h~ pump 82 and forced
through the supply passage system 84 dlLring opera~ion of the rate
sensing system. Because o~ this closed air cycle, there is no
need to introduce outside supply air into the canister~
lS It is impoxtant to no e t~a~ the rate sensing system of the
present inYention has th~ ruggedness~ low cost, and ins~ant-on
capabilities inherent in fluidic deYices and sySt~Qs9 yet uniquely
provides the first viable fluidic replacQment for the mechanical
gyroscope and rate sensing systems ba~ed t~ereon. The only moYing
2 0 parts in the entire electro1uidic rate sensing system described
above are the air pump and i~s motor.
A wide variety of modifications may ~e made to t~3 abs:~Ye
described rate sensing systesn and met~a~, depending upon ~Eleir
particular navigational application. For example, ~y e~Lminatin~
2S one or two o~ the fluidic rate sensors (and t~eir associa~ed output
sys~ems~, a.two or one axis ra~e sensing system can ~e constructed.
Additionally, pres~urized fluids other than air may ~e used. Also,
a reverse pressure system may ~a u~ilized wherein the p~p da~elops
,
-- 4~ --
a higher pressure within the canister, and the jets are or a lower
pressure, being developed by suction at ~he pump inlet. Stated
othexwise, if desired, the various jets may be drawn through their
component's body instead of forced therethrough. As previously
men~ioned, the number of fluidic amplifiers in each of the output
systems may be varied if desired. ~lso, of course, the alternate
rate sensor embodiment of Fig. 14 ~or alterna~e rate sensors having
different exterior configurations and laminae arrang~ments) may be
employed if desired.
The foregoing detailed description is ~o be clearly understood
as given ~y way of illustra~ion and example only, the spirlt and
scope o~ this invention being limited solely by the appendea claLms.
:
- 49 -
