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Claims  |
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I claim:
1. Electromechanical apparatus comprising first and second relatively
rotatable parts, said first part including two oppositely facing parallel
surfaces and said second part including two parallel surfaces each of
which extends parallel to, and lies closely adjacent to, a respective one
of said two surfaces of the first part, at least one said surface of the
first part having secured thereto a first coil and the said two surfaces
of the second part each having secured thereto at least one further coil
and means for mounting said first and second parts for relative rotational
movement so as to cause said further coils secured to the two surfaces of
said second part to move along a predetermined path relative to said first
coil, the inductive coupling between each said further coil and said first
coil being dependent on the relative rotational position of said parts and
said coils providing more than one electrical cycle per complete
mechanical rotation of said relatively rotatable parts, an alternating
current voltage being supplied to said first coil and coupled to said
further coils, said apparatus further comprising electronic processing
means for producing an output representative of said relative rotational
position, said processing means being connected to said further coils and
comprising electronic storage means having a plurality of storage
locations which are individually addressable in response to addressing
signals, means for deriving said addressing signals including counter
means for counting said electrical cycles so as to identify the relevant
sector of the mechanical rotation of said relatively rotatable parts, the
said addressing signals being supplied to an address input of said storage
means and said storage means further acting to store correction signals
corresponding to respective measured values representative or angular
positions in the relevant sectors of said mechanical rotation, and
correction means for receiving said correction signals from said storage
means and for correcting said measured values in accordance with said
correction signals, said correction means providing a said output
representing each measured value thus corrected.
2. Electromechanical apparatus comprising first and second relatively
rotatable parts, said first part comprising a cylinder including two
oppositely facing cylindrical surfaces each of which is equispaced from,
and lies closely adjacent to, a respective one of said two cylindrical
surfaces of the first part, at least one said surface of the first part
having secured thereto a first coil and the said two surfaces of the
second part each having secured thereto at least one further coil, and
means for mounting said first and second parts for relative rotational
movement so as to cause said further coils secured to the two surfaces of
said second part to move along a predetermined path relative to said first
coil, the inductive coupling between each said further coil and said first
coil being dependent on the relative position of said parts and said coils
providing at least two electrical cycles per complete mechanical rotation
of said relatively rotatable parts, an alternating current voltage being
supplied to said first coil and said apparatus further comprising
electronic processing means for producing an output representative of said
relative position, said processing means being connected to said further
coils and comprising electronic storage means having a plurality of
storage locations which are individually addressable in response to
addressing signals, means for deriving said addressing signals including
counter means for counting said number of electrical cycles so as to
identify the relevant sector and the mechanical rotation of said
relatively rotatable parts the said addressing signals being supplied to
an address input of said storage means and said storage means storing
correction signals corresponding to respective measured values
representative of angular positions in said relevant sectors of said
mechanical rotation and correction means for receiving said correction
signals from said storage means and for correcting said measured values in
accordance with said correction signals, said correction means providing a
said output representing each measured value thus corrected.
3. Apparatus according to claim 2 wherein said first coil comprises a
primary winding comprising at least one pair of oppositely spiralled
coils.
4. Apparatus according to claim 3 wherein said at least one further coil
comprises a secondary winding and there is equiangular spacing between
each of the radially extending portions of said secondary winding.
5. Apparatus according to claim 4 wherein the shortest radially extending
portion of said secondary winding is longer than the longest radially
extending portion of said primary winding.
6. Apparatus according to claim 2 wherein said first coil comprises a
primary winding and said further coils each comprise a secondary winding,
the primary winding being laid out in a geometric pattern wherein the
magnetic coupling between the primary winding and the secondary windings
varies sinusoidually, the primary winding forming a rectangular spiral and
the lengths of the radially extending portions of the primary winding
varying in a predetermined non-constant relationship.
7. Apparatus according to claim 2 wherein said first coil comprises first
and second primary windings disposed on said opposite cylindrical facing
surfaces of said first part and angularly displaced from one another such
that a radially extending portion of the first primary winding lies in the
middle of a pair of the radially extending portions of the second primary
winding.
8. Apparatus according to claim 1 wherein said first coil comprises a
primary coil and each said further coil comprises a secondary coil, said
apparatus further comprising means for connecting said secondary coils in
series.
9. Apparatus according to claim 1 wherein said first coil comprises a first
secondary coil, said apparatus further comprising a second secondary coil
and said first and second secondary coils being respectively secured to
the oppositely facing surfaces of said first part.
10. Apparatus according to claim 2 wherein said coils comprise rectangular
spirals which are shaped to conform to said cylindrical surfaces.
11. Apparatus according to claim 1 wherein each of said surfaces is
substantially flat and the individual turns of each said coil lie
substantially within a respective single plane parallel to said surfaces.
12. Apparatus according to claim 1 wherein the individual turns of each
further coil are uniformly mutually spaced.
13. Apparatus according to claim 1 wherein said parts are mutually
positioned such that when said first coil is energized the density of
magnetic flux is substantially uniform over each surface carrying a said
further coil.
14. Apparatus according to claim 1 wherein each said coil comprises a
conductor pattern constituted by an electrically conductive layer secured
to the relevant said surface.
15. Apparatus according to claim 14 wherein each conductive layer comprises
a printed circuit.
16. Apparatus according to claim 8 wherein one of said parts comprises a
generally plate-like member said apparatus further comprising means for
mounting said parts for relative rotation about a common axis, and the
primary coil being generally annular and having a center which is
coincident with said axis.
17. Apparatus according to claim 1 wherein each of the coils has the form
of at leaast one rectangular spiral having two opposite parallel sides
parallel to said predetermined path.
18. Apparatus according to claim 17 wherein those conductors of the first
coil that form the at least one rectangular spiral and extend transversely
to said path are inclined at an acute angle relative to the corresponding
conductors of each further coil, the transverse conductors of each further
coil being substantially perpendicular to said path, and said acute angle
being such that the distance, in the direction of said path, between the
ends of each of the transverse conductors of the first coil is greater
than the conductor spacing of the transverse conductors in the other
coils.
19. Apparatus according to claim 17 wherein those conductors of the first
coil that form the at least one rectangular spiral and extend transversely
to said path are inclined at an acute angle relative to the corresponding
conductors of each further coil, the transverse conductors of said first
coil being substantially perpendicular to said path, and said acute angle
being such that the distance, in the direction of the path, between the
ends of each of the transverse conductors of each of further coil is
greater than the spacing of the transverse conductors of the first coil.
20. Apparatus according to claim 18 wherein each further coil is such that
its shortest conductor extending transversely of said path is longer than
the longest conductor extending transversely of the said path in said
first coil.
21. Apparatus according to claim 19 wherein each secondary coil is such
that its shortest conductor extending transversely of said path is longer
than the longest conductor extending transversely of said path in said
first coil.
22. Apparatus according to claim 8 wherein said first coil has a cyclically
repeated winding pattern.
23. Apparatus according to claim 22 wherein each secondary coil comprises a
plurality of coil parts, the secondary coils being substantially
identical, and each coil part being wound in the same manner as the
primary coil at least over one half cycle thereof.
24. Apparatus according to claim 22 wherein said secondary windings
comprise coil parts which are each wound in the same manner as the primary
coil over a whole cycle thereof.
25. Apparatus according to claim 23 wherein said plurality of coil parts
includes first and second coil parts and said apparatus further comprises
means for mounting said first and second coil parts for rotation relative
to one another and two secondary coils mutually offset by 90.degree. from
one another.
26. Apparatus according to claim 23 wherein said plurality of coil parts
includes first and second coil parts, and said apparatus further comprises
means for mounting said first and second coil parts for rotation relative
to one another and three said further coils mutually offset by 120.degree.
from one another.
27. Apparatus according to claim 1 wherein said storage means comprises a
non-volatile memory.
28. Apparatus according to claim 1 wherein said storage means comprises a
read-only memory. |
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Claims |
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Description |
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CROSS REFERENCE TO RELATED APPLICATIONS
This application contains subject matter in common with my currently filed,
commonly assigned copending application Ser. No. 878,375, entitled HIGH
ACCURACY MEASURING APPARATUS and now abandoned, and the latter application
is hereby incorporated by reference.
FIELD OF THE INVENTION
The present invention relates to an improved electromechanical position
indicator.
BACKGROUND OF THE INVENTION
In a known form of electro-mechanical position indicator, two parts are
movable relative to one another in a predetermined direction. One part is
provided with a primary winding so arranged that with an alternating
current supplied thereto, an alternating magnetic flux is generated
substantially normal to the direction of movement referred to, this
magnetic flux varying in a predetermined manner at least in this
direction. The other part of the position indicator is provided with at
least two sensing windings mutually offset in the aforesaid direction.
These sensing windings each sense the magnetic flux in proximity thereto.
Rotary devices of the type described in the preceeding paragraph are
particularly useful in measuring angles. One form of such a device is a
conventional resolver, which characteristically includes two sensing
windings disposed relative to one another at an angle of 90.degree.. A
further such device is a conventional synchro, which characteristically
includes three windings that are mutually displaced by 120.degree..
Resolvers and synchros are normally used for transmitting data
representing angles from a transmitting device to a receiving device and
continuous or continual angular transmission can be provided. Other forms
of resolvers and synchros can be used as angle-measuring devices,
particularly where an accuracy is desired which is greater than that
provided by resolvers and synchros which are now commercially available.
Such angle-measuring devices could be used to measure angles with the
degree of accuracy required, for example, for theodolites or gun-sights,
etc. In such applications, a device is normally used in which an
accurately prepared measuring pattern is placed on, for example, sheets of
glass or some other stable material and read off optically or
electronically. In order to eliminate the effect of parallax, for example,
a reading has been made at two or more positions. The number of positions
such readings require increases with the number of parts of the pattern
read off, thus lowering the accuracy requirements of an individual marking
of the measuring pattern.
Since angle-measuring devices of the aforementioned optical type must be
manufactured with a very high degree of accuracy, the devices are
extremely expensive. Such devices are also very fragile.
In the case of a conventional electro-mechanical resolver or synchro, the
whole of the mutually movable surfaces are used for the detection of an
angle, since the magnetic field which transfers the angular information
between stator and rotor often varies in the manner of a sine or cosine
fuction over the surface in question. The stability of such a component
can therefore be less with respect to each individual "electrical loop" of
the emitter winding since the output signal of the angle indicator
(resolver or synchro) constitutes the mean value of the position of a
large number of loops. If the individual loops could be fixed in a stable,
accurate manner, a resolver or a synchro would be an extremely accurate
angle-indicator. There is a further problem, however, with the use of a
conventional electro-mechanical resolver or synchro as an angle measuring
device. This problem results from the fact that such an electromechanical
device includes a multiplicity of lamellae which are joined together with
other elements. This makes it difficult to thermally match the elements
incorporated in the device, so that changes in temperature will affect the
output signal. The effect of temperature variations can cause measuring
variations of the order of magnitude of several minutes of arc.
SUMMARY OF THE INVENTION
According to the invention, an electro-mechanical position indicator
apparatus is provided which comprises first and second parts, the first
part having two oppositely facing parallel surfaces and the second part
having two parallel surfaces each of which extends parallel to and closely
adjacent a respective one of the surfaces of the first part. At least one
of the aforementioned surfaces of the first part has secured thereto a
primary or main coil while the aforementioned surfaces of the second part
each have secured thereto at least one secondary or further coil. The two
parts are mounted for relative movement to cause the further coils to
translate along a predetermined path relative to the primary coil, and the
inductive coupling between each said secondary coil and said primary coil
is dependent on the relative position of said parts. Before proceeding it
should be noted that the term "parallel" as used here and in the claims is
intended to encompass both flat surfaces and concentric cylindrical
surfaces and thus is apparently broader than the accepted definition of
the term as used in geometry. Stated somewhat differently, the term
parallel surfaces as used in this application is intended to cover
surfaces which are everywhere equidistant, whether flat or cylindrical.
In one embodiment of the invention, each of the surfaces referred to above
is substantially flat and the individual turns of each said coil occupy a
respective single plane parallel to said surfaces. In a further
embodiment, these surfaces are concentric cylindrical surfaces.
Preferably, the individual turns of each further coil are uniformly
mutually spaced. Further, parts are preferably mutually positioned such
that when the primary coil is energized, the magnetic flux density is the
same at each surface carrying a said further coil. Preferably, each said
coil is constituted by an electrically conductive pattern formed by a
conductive layer secured to the relevant surface. Each layer is preferably
a printed circuit.
In a further embodiment of the invention, one of said parts is generally
plate-like and the parts are mutually rotatable about an axis. In this
embodiment, the primary coil is generally annular and is centered on the
axis of rotation.
Preferably, each of the coils has the form of at least one rectangular
spiral having two opposite parallel sides which are also parallel to the
predetermined path referred to above. Further, those conductors of the (or
each) spiral of said primary coil which extend transversely of the path
are inclined at an acute angle relative to the corresponding conductors of
each secondary coil, the transverse conductors of each secondary coil, or
of said secondary coil, being substantially perpendicular to the path, and
the acute angle being such that the distance, in the direction of the
path, between the ends of each of the transverse conductors of the primary
coil, or of each secondary coil, is greater than the conductor spacing of
the transverse conductors in the other coil or coils.
Preferably, the shortest conductor of each secondary coil which extends
transversely of the predetermined path is longer than the longest
conductor in said primary coil extending transversely of the path.
The primary coil preferably has a cylically repeated winding pattern.
Further, each secondary coil advantageously comprises a plurality of
partial coils (coil parts), the secondary coils are substantially
identical, and each part coil is wound in the same manner as the secondary
coil at least over one half cycle thereof.
In a further embodiment, each part coil is wound in the same manner as the
primary coil over a whole cycle thereof.
In yet another embodiment, the first and second parts are mounted for
mutual rotation and there are provided two additional coils corresponding
to the secondary coils which are mutually offset by 90.degree.. A resolver
may be constructed in this manner.
In a further embodiment, the first and second parts are mounted for mutual
rotation and there are provided three coils, corresponding to the
secondary coils referred to above, which are mutually offset by
120.degree.. In this manner, a synchro may be constructed.
In a preferred measuring system, an electronic processing unit is connected
to the terminals of the secondary coils. The electronic processing unit
provides an output representing the relative position of the parts and
includes an electronic storage unit having a plurality of storage
locations individually addressable in response to addressing signals which
are dependent on an alternating voltage supplied to the primary coil and
which are supplied to an address input of the storage unit. The storage
unit stores correction values corresponding respectively to angular or
linear values of position in or along the predetermined path and supplies
correction signals representing these correction values. A correction unit
is connected to receive the correction signals so as to correct said
measured values in accordance with the correction values and is arranged
to provide an output representing each measured value thus corrected. The
storage means preferably comprises a non-volatile memory and
conventionally comprises a read-only memory.
Other features and advantages of the invention will be set forth in, or
apparent from, the detailed description of the preferred embodiments found
hereinbelow.
BRIEF DESCRIPTION OF THE DRAWINGS
To provide a better understanding of the invention, and to show how the
same may be carried into effect, reference will now be made, by way of
example, to the accompanying drawings, in which:
FIG. 1a illustrates a winding pattern;
FIG. 1b is a sectional view of an embodiment suitable for using the winding
pattern illustrated in FIG. 1a;
FIG. 2 illustrates a resolver having a winding pattern of the type shown in
FIG. 1a;
FIG. 3 illustrates a second embodiment of a winding pattern similar to that
of FIG. 1;
FIG. 4 is a sectional view of a further type of resolver;
FIGS. 5a, 5b, 5c and 5d illustrates windings of the embodiment illustrated
in FIG. 4;
FIG. 6 illustrates a further embodiment of a winding;
FIGS. 7 to 9 illustrate a further embodiment of apparatus of the type shown
in FIGS. 1a and 1b;
FIGS. 10 and 11 illustrate two embodiments of windings for a synchro; and
FIG. 12 illustrates an embodiment of a circuit for connection to sensing
windings so as to process a measurement signal.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings, wherein similar elements are referenced in the
respective figures by the same numerals and/or letters, and, in
particular, to FIG. 1a, a schematic diagram is provided of a first
embodiment of winding pattern for a measuring instrument. In the upper and
lower parts of FIG. 1a the same winding 1 is viewed from the same
direction. As illustrated, winding 1 has a cyclically repeated pattern
formed by rectangular spirals, extending horizontally and producing a
magnetic flux whose strength perpendicular to the plane of the winding
varies along the lingitudinal direction thereof. At the far right of the
FIG. 1a, at the top thereof, one "cycle" of the winding pattern is
indicated by a bracket and, as illustrated, comprises rectangular coils 1'
and 1" and a connecting conductor 6. Winding 1 is supplied with a
sinusoidal alternating current and will hereinafter be referred to as the
primary winding. In the upper half of FIG. 1a are illustrated two sensing
windings 2 and 3 which are movable along one side (side 1) of the primary
winding 1, and in the lower half of FIG. 1a are shown two further sensing
windings 4 and 5 which are movable along the other side (side 2) of
winding 1. For the sake of clarity, winding 1 is illustrated in dash
lines, but it will, of course, be understood that in reality the winding
consists of unbroken conductors.
FIG. 1b illustrates a section through a device having winding 1
incorporated therein. The arrow A in FIG. 1b shows the general direction
from which the windings of FIG. 1a are viewed in that figure. In FIG. 1b,
winding 1 is arranged in a secure stable manner on a rigid plate or
substrate 7' such as by forming the winding pattern with printed
conductors. Each "cycle" of winding 1 comprises two spirally-wound
sections (corresponding to 1' and 1") which are so wound that the magnetic
fields generated by the sections will be directed in respectively opposite
directions. These sections of each cycle are mutually connected by a
conductor 6 disposed on the other side of the plate 7' from the winding
pattern. On the side of the plate 7' which carries the winding 1, a
further plate 7" is arranged for stiffening and spacing purposes. It is
noted that a further embodiment of primary winding will be described
hereinafter with reference to FIGS. 5a and 5b. The primary winding
illustrated in FIGS. 5a and 5b is to be preferred over the primary
winding of FIG. 1 since it utilizes the plate 7' and plate 7" more
advantageously.
On the external sides of plates 7' and 7" are respectively arranged two
further opposing plates 8 and 9 which extend parallel to the plates 7' and
7". Sensing windings 2 and 3 are arranged on the side of plate 8 facing
plate 7' and sensing windings 4 and 5 are arranged on the side of the
plate 9 facing plate 7". Further, plate 7' is provided with the conductors
6 on the side thereof facing plate 8.
As will be seen from FIG. 1a, the sensing windings 2 to 5 each comprise two
winding portions which are oppositely wound, i.e., wound in opposite
senses, and which are wound in the form of rectangular spirals, as with
the primary winding 1. The portions of each sensing winding are arranged
with mutually opposite winding directions and are so spaced that, between
them, the sensing windings overlie and cover one complete cycle of said
primary winding 1. Each of sensing windings 2 to 5 on each side of the
primary winding (i.e., above and beneath the plane of the primary winding
1 in the showing in FIG. 1a) is so extended that each turn of each sensing
winding extends laterally beyond primary or emitter winding 1, i.e., on
either side of the longitudinal edges.
As will be understood by those skilled in the art, sensing windings 2 and 4
constitute a pair of "sine"-windings and sensing windings 3 and 5
constitute a pair of "cosine"-windings. The windings of the sine-winding
pair 2 and 4 and the windings of the cosine-winding pair 3 and 5 are
connected together in series. The sensing windings 2 and 3, and sensing
windings 4 and 5, are so mutually displaced that the magnetic flux sensed
by one pair of sensing windings (windings 2 and 4) is displaced 90.degree.
(i.e., 1/4 pole division) in relation to the magnetic flux sensed by the
other pair (windings 3 and 5) so that one winding pair approximately
indicates the sine value and the other the cosine value of the angular
position (i.e., the position within a cycle) of the respective pair of
sensing windings. Thus, for a reference position with positive angle 0,
the sine-winding (windings 2 and 4) provides a 0-signal and the
cosine-winding pair (windings 3 and 5) produces a maximum signal.
In order that the output signal from the sensing windings varies as
uniformly as possible, the turns of the primary windings are inclined so
that the individual conductors of the winding, which extend transversely
to the direction of movement, have an approximate inclination such that
their end to end displacement in the direction of movement is at least the
same distance as that between two adjacent conductors in the direction of
movement. The output signal from each of the series-coupled winding pairs
2, 4 and 3,5, respectively, is produced between the ends thereof in each
case. Winding 1 is supplied with a sinusoidal alternating current and the
voltage induced in each sensing winding is dependent upon the number of
turns in which current is induced by the magnetic field from the primary
winding 1. The voltage across the sensing winding is, of course, an
alternating current voltage. The effective value, the maximum value or
mean value can be sensed and utilized as an indication of angular
position.
Owing to the fact that windings 2 and 4 and windings 3 and 5, respectively,
are symmetrical and disposed on respective sides of the winding 1,
compensation is introduced for possible relative movement transversely of
the plane of the drawing. By making the shortest transverse conductor path
of each sensing winding longer than the extent of the longest ocnductor
path of the primary winding 1 in the transverse direction, the influence
of errors in the transverse setting between the units 7,8 and 9 is
reduced. In the embodiment of FIGS. 1 and 1b, it has been assumed that the
winding 1 is part of a stationary unit and the windings 2 to 5 are part of
a movable unit. Conveniently, all the windings are formed as printed
circuit conductors as provided for hereinabove.
When the position indicator according to the invention is to be used as an
angle-measuring device, the winding pattern illustrated in FIG. 1 can be
arranged on three cylinders in the manner shown in FIG. 2. In this
respect, the windings can either be formed so that the pattern between the
portion B and C shown in chain lines in FIG. 1a forms the whole
cylindrical winding or, depending upon the desired number of poles, the
pattern between B and C can be repeated a required number of times about
the circumferential surface of the cylinder. In FIG. 2, the winding 1 is
arranged on the outer surface of the cylinder 10 with the cross
conductors, corresponding to conductor 6 of FIGS. 1a and 1b, being
disposed on the inside of the cylinder 10. It will be understood that the
cylinder 10 may, alternately be provided with a primary winding of the
type described hereinafter with reference to FIG. 5a and FIG. 5b, with
winding parts on both the inside and the outside of the cylinder 10.
Sensing windings 2 and 3 are arranged on the outer surface of a further
cylinder 11 disposed radially inwardly of the cylinder 10 while sensing
windings 4 and 5 are arranged on the inner surface of the cylinder 12
disposed radially outwardly of the cylinder 10. As will be seen from FIG.
2, the cylinders 11 and 12 are connected together by means of a cross wall
13. With this arrangement, either the cylinder 10 can be made the rotor
and the parts 11 to 13 the stator, or vice versa.
FIG. 3 illustrates a further embodiment of wherein "sine" and "cosine"
windings are disposed on either side of a primary winding 1. As will be
apparent when making a comparison between FIG. 1 and FIG. 3, all the
sensing windings in FIG. 3 have been divided into two separate windings at
that location where the winding direction changes and have been divided
between side 1 and side 2 of primary winding 1. More specifically, the
winding 2 has been divided to form a winding A.sub.1 mounted on side 1 and
a winding A.sub.2 on side 2. The winding 3 has been divided into a winding
B.sub.1 mounted on side 1 and a winding B.sub.2 mounted on the side 2. The
winding 4 can also be divided into a winding A.sub.3, which may either be
mounted on side 1 or side 2, and a winding A.sub.4 which is mounted on the
opposite side from winding A.sub.3. Winding 5 is divided to form a winding
B.sub.3 disposed on the same side as winding A.sub.3 and a winding B.sub.4
disposed on the same side as the winding A.sub.4. Similarly to the FIG. 1
embodiment, the winding pattern between section D and E shown in chain
lines can be repeated and may be arranged in the manner shown in FIG. 2.
The embodiment of FIG. 2 may also be utilized as a resolver, preferably
employing cast copper coils which are iron-free.
When the FIG. 2 embodiment is utilized as a resolver, certain problems may
arise when assembling the device, since the parts 10 to 13 must be
accurately positioned relative to one another, particularly in the radial
direction. Moreover, this arrangement requires a relatively large amount
of space. To overcome these problems, a further embodiment has been
devised in which the windings are arranged annularly in mutually parallel
planes around circular plates having a common center. Either that part
which carries the primary winding or that part which carries the sensing
windings is made to be rotatable about the center. FIG. 4 is a sectional
view of this embodiment. In the embodiment of FIG. 4, primary windings 16
and 17 are mounted on a circular plate 15 which acts as a rotor and which
is provided with a shaft 14 with which plate 15 rotates. A further pair of
circular plates 18 and 19 are symmetrically and fixedly mounted around
plate 15 in parallel relation thereto. Plates 18 and 19 are joined
together by a common cross wall, as illustrated. The plates 18 and 19
carry sensing windings 20 and 21. It will, of course, be understood that
this embodiment can be modified in a manner such that the rotor carries
the sensing windings and the primary winding is arranged on the stator on
each side of the sensing windings.
FIGS. 5a to 5d illustrate the various windings on the stator and rotor as
seen in the direction of arrow G in FIG. 4. Similarly to the winding 1 in
FIGS. 1 and 3, primary windings 16 and 17 of this embodiment are also
obliquely disposed so that the conductors extending transversely of the
direction in which the winding arrangement extends do not run radially,
but rather run inwardly to form tangents with a circle 22 having a radius
R. This is seen best in FIG. 5b, where extensions of the conductors
towards the periphery of the circle 22 have been shown in dash lines. The
radius R is selected to give a smooth output characteristic.
As noted above, the embodiment of the primary winding shown in FIGS. 5a and
5b is generally to be preferred over the primary winding shown in FIGS. 1
and 3. As opposed to the primary winding 1 of FIGS. 1 and 3, which is
arranged solely in one plane, the winding of the embodiment of FIGS. 5a
and 5b is arranged on both sides of the rotor with lead-throughs between
the sides being provided at 23, 24, 25 and so on, as illustrated. The
windings on opposite sides A and B of the plate 15 are so wound as to
provide co-acting magnetic fields. This means that the winding directions
are different for spirals lying opposite each other on respective sides of
the associated rotor when viewed from the same direction. The winding on
side B is displaced a half conductor distance laterally to the left in
FIGS. 5a and 5b in relation to the winding on side A, so that each
conductor in the winding on side B will lie mid-way between two conductors
in the winding on side A. It should be noted that the winding 1 in FIGS. 2
and 3 can conveniently be replaced by a winding of the type corresponding
to windings 16 and 17, which winding would then be arranged on both sides
of the plate 15.
FIG. 5c illustrates a "cosine" sensing winding while FIG. 5d illustrates a
"sine" sensing winding. FIGS. 5c and 5d also illustrate a further
embodiment of the positioning of these windings relative to the pattern of
the primary winding. Windings in this embodiment are so arranged that each
winding part of each sensing winding is arranged across a half-pole
division of the primary winding and arranged on each side of the stator
for every second primary winding pole division. As will be seen from FIGS.
5c and 5d, the directions in which the windings are wound are different on
respective sides of the stator (as viewed from the same direction). As
will also be seen from FIG. 5c and FIG. 5d, the conductors of the sensing
windings extending transversely to the direction of movement are also
substantially radial. The specific embodiment shown in FIG. 5 has 8/16
poles and thus produces a succinct output signal within 1/8 revolution.
FIG. 5a illustrates, at 16', the manner in which a primary winding can be
designed so that the magnetic field sensed by a sensing winding in
different positions is more nearly proportional to the sine and cosine for
the angular position relative to the primary winding. As will be seen from
FIG. 5a, the transversely extending conductors of winding 16' are shorter
the more centrally they are located in the spiral. The conductors forming
winding 16' are also inclined differently, i.e., their extensions need not
extend towards the periphery of the circle 22. As a result of this winding
construction, there is obtained a greater inclination at zero throughput
and a smoothing at the maximum transition of the field detected by the
sensing windings. As illustrated, the innermost conductors are very short
compared with the outermost conductors.
Further in this regard, in order to reduce the effect of errors in the axis
orientation relative to the center of the stator, the extent of the
shortest conductors of the stator in the transverse direction has been
made longer than the longest conductors of the rotor so that a total
overlapping is obtained. The whole of the arrangement is such that
compenstion is obtained for temperature variations and radial play.
Furthermore, the arrangement is able to be readily reproduced. The two
stator units have been displaced through one pole division so as to
provide compensation for possible irregularities in the field generated by
the rotor winding.
Referring to FIG. 6, there is shown a further embodiment of an arrangement
of one sensing winding for a 24/12 pole resolver. In this embodiment, the
sensing winding, which is the winding illustrated, is arranged in a manner
similar to that illustrated in FIG. 3, with the difference being that the
sides between the dash-dot lines F and E in FIG. 3 have changed positions
in FIG. 6.
FIGS. 7 to 9 illustrate a further embodiment of a flat resolver in which
the sensing windings are obliquely disposed and arranged on a common
center member of cylindrical form as shown in FIG. 9. The illustrated
resolver is 8/4 pole device. The primary winding is not shown in FIGS. 7
to 9, but comprises windings arranged on both sides of the central member,
the windings cooperating with each other and each being of the type
illustrated in FIGS. 1 and 3. However, in this embodiment, the primary
winding comprises radially extending transverse conductors.
The "sine" windings are illustrated in FIG. 7 wherein A' indicates the
arrangement on one side of the center portion and A" indicates the
arrangement on the other side of the center portion.
FIG. 8 illustrates the "cosine" winding, with winding portion B' being
disposed on one side and winding portion B" on the other.
FIG. 9 is a perspective view of the center portion illustrating the "sine"
winding A',A", the "cosine" winding B', B" of FIG. 8 having been omitted
for the sake of clarity. FIG. 9 clearly shows the positioning of the
winding and the requisite leadthrough. For the sake of clarity, the center
portion in FIG. 9 has been made much thicker than in reality.
In a further embodiment, the primary winding has obliquely positioned, i.e.
non-radial transversely extending conductors. This embodiment differs from
the previous embodiments in that the conductors on each side of the center
point of each winding half have a different angle of inclination.
In yet another embodiment of the primary or emitter winding, one half-pole
division, is of the same design as that discussed in the preceeding
paragraph the other half-pole divisions of the conductor, are inclined in
the opposite direction to, i.e., are slanted relative to the corresponding
conductors of the first pole-half dimension.
FIG. 10 illustrates the manner in which the sensing windings can be
positioned in relation to a primary winding when the position indicating
device or angle-measuring device comprises a synchro. The synchro includes
three sensing windings, R.sub.1, S.sub.1, T.sub.1 which are mutually
displaced through 120.degree. on side 1 of the primary winding and sensing
windings R.sub.2, S.sub.2, T.sub.2 on side 2, the windings being arranged
in a manner analogous to the windings of FIGS. 1 and 3. Moreover, similar
to the embodiments of FIGS. 1 and 3, the winding 1 of FIG. 10 is the same
for side 1 and side 2 | | |
