Note: Descriptions are shown in the official language in which they were submitted.
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AIMING SYSTEM
BACKGROUND TO THE_INVENTION: ;
THIS INVENTION relates to an aiming system for
aiming an object device by movement of the head of a human
operator.
The object device could, for example, be a
weapon, camera, or the like.
German patent specification DE-A-2436169
discloses an aiming system for aiming an object device in the
form of a weapon, the system comprising a servo drive for
10 moving the weapon, a head mount in the form of a helmet ~;~
having a sight, detecting means for detecting the angular ~i~
position of the helmet, and control means for controlling the
servo drive, the control means operating in response to the
detecting means to aim the weapon in the direction in which
15 an operator wearing the helmet looks. The detecting means ~ ;
detects the angle of the hèlmet with respect to a fixed
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reference frame which does not move with the weapon. This
requires the angla sensing devices of the detecting means and
,
the control loop between the detecting means and the servo
drive to be extremely accurate and linear, to ensure that the
weapon is aimed accurately in the direction of the line of
~` sight of the operator for all angles.
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US paten~s 3,262,210 and 4,486,955 disclose
aiming systems having detecting means in the form of an
articulated mechanical link connected to a helmet. These
systems suffer from the same disadvantages as the one
described in German patent specification DE-A-2436169.
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SUP~RY OF THE INVENTION:
According to the present invention the detecting
means is arranged to detect angular deviation of the head
mount with respect to a movable structure on which the object
device is mounted, whereby the reference frame is angularly
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fixed with respect to the movable structure; and the servo
drive is operative in response to the detecting means to move
` the movable structure in the direction of said angular
deviation. `
- The movable structure may include a seat for the ; `~
` ~ ~ operator.
~; Where the head mount has associated therewith a
line of sight and where the detecting meàns comprises an
articulated mechanical link disconnectably connectable to the ;~
20 head mount, connection between the detecting means and the ;~
~;~ head mount may be is along a flat connecting interface ;~-
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perpendicular to the line of sight. ~ -
Where the servo drive is arranged to move the
movable structure about a slew axis and about an elevation
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axis perpendicular to the slew axis, and where the mechanical
link is connected at one end to the head mount via a ~irst
articulated joint having first and second mutually
perpendicular articulation axes and at the other end to the
movable structure via a second articulated joint having first
and second mutually perpendicular articulation axes, the
first articulation axis of the first articulated joint may be
in the same plane as the first articulation axis of the
second articulated joint, which plane is parallel to the slew
axis; and the second artlculation axis of the first
articulated joint may be in the same plane as the second
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articulation axis of the second articulated joint, which `
plane is parallel to the elevation axis.
~ The system may further comprise magnetic means
`~ ~ 15 for magnetically connecting the detecting means to the head
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mount along said connecting interface.
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~ The magnetic means may be fixed to the head mount
; ~ and have co-planar pole faces which define a flat surface
perpendicular to the line of sight; and the detecting means
may comprise at~the end thereof a rotatable connector disc of
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~- a ferro-magnetic material, having a flat face perpendicular :~
to its axis of rotation for contact with said pole faces.
The system may furter comprise disconnect sensing
means for detecting disconnection of the detecting means f~om
the head mount: and, in response thereto, to inhibit operation
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of the servo drive.
The disconnect sensing means may include a reed
switch sensitive to proximity o~ the magnetic means.
The system may further comprise an end-piece at
each and of the articulated mechanical link, and a tube of
flexible, air-impervious material extending from one said
end-piece to the other to form an enclosed space around the
link, from which enclosed space air can escape or into which
it can enter at a restricted rate. ~
The articulated link may be telescopically ~;
extendable; and the tube may be a concertina tube.
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The invention will now be described in more
` detail, by way of example, with refèrence to the accompanying
drawings.
BRIEF DESCRIPTION OF T~E DRAWINGS:
In thè drawings~
Figure I is a three dimensional view of an aiming
system in accordance with the invention, showing also its
operator;
Figure 2 is a cut-away three dimensional view of an
angle detecting device forming part of the system;
Figure 3 is a three-dimensional diagram, showing the
I various pivot axes associated with the angle detecting
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device;
Figure 4 is an axial section through the front end of
the angle detecting device;
Figure 5 is an end view in the direction of arrow V in
Figure 4; and
Figure 6 diagrammatically show~ the control loop
between the angle detecting device and the servo motors of
the system.
DETAILED DESCRIPTION
Referring first to Figure 1, reference numeral 10 ~-
generally indicates a system for aiming a weapon 12 whose
line of fire is indicated at 14. The weapon is mounted on a
movable structure 16 on which a seat 18 for supporting an
operator 20 is mounted as well. The operator wears a helmet
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~ 15 22. The helmet is fitted with a sight 24 whose line of sight ~
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is indicated at 26.
The movable structure 16 (including the weapon 12
and the seat 18) is mounted on a fixed pedestal 28, drive ;~
means in the Eorm of two servo motor drives being provided to
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- 20 change the elevation and slew angles, respectively, of the
movable structure with respect to the pedestal. One of the
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trunnions about which the movable structure 16 pivots to
change the elevation angle is indicated at 30.
At the back of the seat 18 there is a bracket 32
25 which is fixed with respect to the movable structure 16. ;~
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Between the bracket 32 and the helmet 22, there is an angle
detecting device 34, the rear end of the device 32 being
connected to the bracket 32 and the front end o~ the device
32 being connected to the rear of the helmet 22.
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Referring now to Figures 2 to 5, the angle
detecting device 34 comprises, at the front end thereof, a
connector 36 which includes a mild steel disc 38, and a ~-:
telescopically extendible link 40 which extends from the
connector 36 to the bracket 32. The link 40 is connected to
the connector 36 via a first articulated joint 42 and to the
~; bracket 32 via a second articulated joint 44. The first
articulated joint 42 permits the link 40 to pivot with
~:~ respect to the connector 36 about two mutually perpendicular
; articulation axes 46.1 and 46.2. With eacp articulation axis .
15 46.1, 46.2 there is associated a linear potentiometer 48.1 -~
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and 48.2 respectively. As will be described hereinafter, ``~ :~
these potentiometers are connected in an electrical circuit
so as to be able to provide an electrical output
: ~ corresponding to the degree of pivotal displacement of the ~ .
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20 link 40 about the respective articulation axes 46.1 and 46.2. ~:
The second articulated joint 44 permits the link 40 to pivot
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: with respect to the bracket 32 about two mutually ~ ~
:: perpendicular articulation axes 50.1 and 50.2. Here again, :
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:: with each articulation axis 50.1, 50.2 there is associated a
linear potentiometer 52.1, 52.2 respectively. These provide
electrical outputs corresponding to the degree of pivotal ~;;
displacement of the link 40 about the respective articulation ~:
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axes 52.1 and 52.2.
The line 46.3 in Figure 3 is a reference line
which is fixed with respect to the helmet 22 and parallel to
the line of sight 26 (see Figure 1). The line 50.3 in Figure
3 is a reference line which is fixed with respect to the
movable structure 16 and parallel to the line of fire 14 (see
Figure 1).
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The arrangement of the articulated joints 42 and
` 44 is such that the articulation axes 46.1 and 50.1 are
always in the same plane, this plane being parallel to the
slew axis of the movable structure 16. Furthermore, the :: :
arrangement of the articulated joints 42 and 44 is such that
the articulation axes 46.2 and 50.2 are always in the same -~
plane, this plane being parallel to the elevation axis of the : ;
15: movable structure 16. Conveniently, the articulation axes
46.2 and 50.2 are both ~ixed with respeGt to the link 40 and
parallel to one another. This considerably simplifies the
control circuitry as will be described hereinafter"with
rèference`;to`Figùre 6.
In a region of the helmet 22 near the neck of the
operator, there are secured three permanent magnets 54 with
lat and co-planar pole faces, to which the mild steel disc
38 can attach magnetically. The plane of the pole faces 1s
perpendicular to the line 46.3, and thus also perpendicular ~ .
to the line of sight 26.
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Wiring 56 leads from the potentiometers 48.1,
48.2, 52.1 and 52.2 to control circuitry which controls the
elevating and traversing drives of the movable structure 16.
This will be described in more detail with reference to
Figure 6.
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The link 40 and the articulated joints 42 and 44
are covered by a flexible cover consisting of a concertina
tube 58 of rubber or the like flexible, air-impervious sheet
material. At the connector end the concertina tube is fitted
~:~ IQ on an end-piece 60 which forms part of the connector 36, and
at the opposite end it is fitted on an end-piece 61, to form
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a relatively air-tight enclosure.
The two parts of the link 40 are telesGopically
movable with respect to one another, as indicated by the
15 arrow A in Figure 3. The connection between these parts is, ~:
~: however, such that they cannot rotate with respect to one ~
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another about the longitudinal axis of the link, but the
construction of the connector 36 is such that the disc 38 is
:~ able to rotate with respect to the articulation joint 42
abaut the axis 46.3, as indicated by arrow B in Figure 3.
: This allows complete freedom of movement of the operator's
: head, within l:he reach of the link 40.
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The construction of the connector 36 is
illustrated in more detail in Figures 4 and 5. The end-piece
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60 referred to earlier is of aluminium or other non-magnetic
material. The disc 38 has a flat annular face 62, and a
frusto-conical boss 63 which houses frictionless bearings 64
and 66. The assembly is held together by means of a circlip
68 and a fixing screw 70, the latter being covered by a
plastic cap 72. The positions of the three magnets 54 when
they engage with the disc 38 are shown in Figure 5.
Referring now to Figure 6, the potentiometers
; ~ 48.2 and 52.2 are connected in an electrically back-to-back
~; 10 configuration, and their wipers are connected to a summing
amplifier 74.1. Because of the electrically back-to-back
~ connection of the potentiometers, the output of the summing
; amplifier 74.1 corresponds to the difference in pivotal
displacement of the link 40 about the articulation axes 46.2
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and 50.2 respectively. Thus, whatever the pivotal
displacement of the link 40 about the articulation a~es 46.2
and 50.2, if the lines 46.3 and 50.3 are parallel, the output
of the summing amplifier 74.1 is zero. The output of the
summing amplifier 74.1 is fed via a further summing amplifier
20 76.1 ~o a servo power amplifier 78.1, which in turn is ~ ;
connected to drive a servo motor 80.1. The servo motor 80.1 "~
is operative to displace the movable structure 16 with ~ ~
respect to the pedestal 28 about the elevation axis. ~ -
The summing amplifiers 74.1 and 76.1, and the
25 power amplifier 18.1 form a first channel 82.1. The `~
circuikry comprises a second channel 82.2 including summing
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amplifiers 74.2 and 76.2, and a power amplifier 78.2 which is
connected to drive a servo motor 80.2. The servo motor 80.2
is operative to displace the movable structure 16 with
respect to the pedestal 28 about the slew axis. Inputs to
the second channel 82.2 derive from the potentiometers 48.1
and 52.1 (not shown in Figure 4). The arrangement here is
also such that, whatever the pivotal displacement of the link
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40 about the articulation axes 46.1 and 50.1, if the lines
46.3 and 50.3 are parallel, the output of the summing
amplifier 74.2 is zero.
The particular arrangement of the articulated
joints 42 and 44 makes it possible to use two simple
independent channels or control loops, one for the servo
motor 80.1 and one for the servo motor 80.2.
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:~~ 15Whenever the angle detecting device 34 senses any
angular deviation between the axes 46.3 and 50.3, one or both
of the servo motors 80.1, 80.2 operate to move the movable
structure 16 (and thus the line 50.3) in the direction of the ~;
angular deviation. If the operator 20 keeps his eyes fixed
on the object to which the weapon is to be aimed, this will
have the effect of reducing the deviation down to zero. In
this manner the line of fire 14 will follow the Line of sight ~:
26.
The summing amplifiers 76.1 and 76.2 each have a
second input 84.1 and 84.2 respectively. The second inputs
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are derived from a joystick control which permits the
operator to make lead angle and trajectory corrections.
Air is able to enter into or leave the enclosured
space formed by the concertina tube 58 and the end-pieces 60,
61 via a restricted opening (not shown) in, for example, the
end-piece 61. This has a damping effect on the detecting
device 34, to prevent excessively rapid movement thereof and
to avoid resonance problems.
To prevent the servo drives 80~1, 80.2 from
driving the weapon downwardly should tne connector 36 be
disconnected from the helmut 22 and allowed to drop, a reed
switch 86 is mounted in the connector 36 such that its
contacts are open or closed depending on whether thè magnets
54 are or are not attached to the mild steel disc 38. The
~- 15 reed switch 86 is connected to the control circuitry 82.1,
82.2 in such a manner that when the magnets 54 have been ~ ~-
detached from the dlsc 38, operation of the servo motors 80.1
and 80.2 is inhibited.
It will be seen that the control system does not
rely for its operation on a fixed reference frame
intermediate t:he helmet 22 and the ~eapon 12. The connection
of the angle detecting device 34 is direct between the helmet ~ ;~
and the movable structure 16 (on which the weapon is fixedly
mounted). This has the advantage that any non-linearities in -~
the control circuitry, changes in the loop gain, etc. will
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not affect the accuracy of operation. This, for example,
makes it possible to use inexpensive potentiometers instead
of expensive synchos. Also, the accuracy of the system is
not affected by inaccuracies in orthogonality of 'che slew and
elevation axes.
Because the connecting interface between the
helmet 22 and the angle detecting device 34 is perpendicular
to the line of sight 26, disconnection and reconnection of
the helmet can easily and rapidly be effected without
affecting the accuracy of operation. Any rotational or
translational misalignment when reconnecting the detecting
device 34 to the helmet 22 will not affect the accuracy of
operation, so long as the face of the disc 38 is alignèd with
the pole faces of the magnets 54. Also, disconnection of the
helmet 22 from khe detecting devlce 34 does not require the
unfastening of any fasteners. The parts can be disconnected
by simply pulling them~away from one another. This can be
important in case of an accident or other emergency
situation. `h
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