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Claims  |
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What is claimed is:
1. A device for quantitatively measuring the relative position and
orientation of receiving antennae with respect to transmitting antennae
serving to measure the relative position and orientation of two bodies in
the presence of metals utilizing direct current magnetic fields,
comprising:
(a) Transmitting means for transmitting direct current magnetic fields;
(b) Receiving means for receiving said transmitted direct current magnetic
fields;
(c) Means for supplying direct current electrical signals to said
transmitting means for creating said transmitted direct current magnetic
fields;
(d) Receiver Electronics for measuring, and converting output signals from
said receiving means into position and orientation measurements consisting
of a programmed computer, an analog to digital converter, a programmable
gain signal amplifier, a filter, a differential amplifier, a digital to
analog converter and a multiplexer switching unit for receiving signals
one at a time from the antennae of said receiving means which said
multiplexer switching unit, under the control of said programmed computer,
passes a selected one of said received signals to said differential
amplifier where the Earth's magnetic field signal, which was measured by
said receiver and read into said computer when the said transmitter was
shut off, is outputted from said computer to said digital to analog
converter where said digital to analog converter converts the digital
representation of the Earth's magnetic field signal strength to an analog
representation which goes to said differential amplifier, where the said
Earth's field signal is subtracted from said selected received signal
whereupon the output from said differential amplifier then goes to said
filter for removing noise from the said selected received signal which
then passes said filtered signal to said programmable gain signal
amplifier, which, under the control of said programmed computer, increases
said received filtered signal's level to a value appropriate to the signal
level limits of said analog to digital converter which converts the said
amplified received filtered signal to a digital representation that is
then passed to said programmed computer.
2. A device for quantitatively measuring the relative position and
orientation of receiving antennae with respect to transmitting antennae
serving to measure the relative position and orientation of two bodies in
the presence of metals utilizing direct current magnetic fields,
comprising:
(a) A transmitter for transmitting direct current magnetic fields
consisting of a core and a multiplicity of roughly orthogonal antenna axis
wire windings;
(b) Receiving means for receiving said transmitted direct current magnetic
fields;
(c) Transmitter electronics consisting of a programmed computer, a
digital-analog signal converter, a Multiplexer actuated by said programmed
computer in receiver electronics and simultaneously by said converter and
one direct current power source applied to the wire windings of each
transmitter antenna axis to generate a magnetic field actuated in turn by
said Multiplexer;
(d) Receiver Electronics for measuring, and converting output signals from
said receiving means into position and orientation measurements consisting
of said programmed computer, an analog to digital converter, a
programmable gain signal amplifier, a filter, a differential amplifier, a
digital to analog converter and a multiplexer switching unit for receiving
signals one at a time from the antennae of said receiving means which said
multiplexer switching unit under the control of said programmed computer,
passes a selected one of said received signals to said differential
amplifier where the Earth's magnetic field signal, which was measured by
said receiver and read into said computer when the said transmitter was
shut off, is outputted from said computer to said digital to analog
converter where said digital to analog converter converts the digital
representation of the Earth's magnetic field signal strength to an analog
representation which goes to said differential amplifier, where the said
Earth's field signal is subtracted from said selected received signal
whereupon the output from said differential amplifier then goes to said
filter for removing noise from the said selected received signal which
then passes said filtered signal to said programmable gain signal
amplifier, which, under the control of said programmed computer, increases
said filtered signal's level to a value appropriate to the signal level
limits of said analog to digital converter which converts the said
amplified received filtered signal to digital representation that is then
passed to said programmed computer.
3. A device for quantitatively measuring the relative position and
orientation of receiving antennae with respect to transmitting antennae
serving to measure the relative position and orientation of two bodies in
the presence of metals utilizing direct current magnetic fields,
comprising:
(a) A transmitter for transmitting direct current magnetic fields
consisting of a core and a multiplicity of roughly orthogonal antenna axis
wire windings;
(b) Receiving means for receiving said transmitted direct current magnetic
fields;
(c) Means for supplying direct current electrical signals to said
transmitting means for creating said transmitted direct current magnetic
fields;
(d) Receiver Electronics for measuring, and converting output signals from
said receiving means into position and orientation measurements consisting
of a programmed computer, an analog to digital converter, a programmable
gain signal amplifier, a filter, a differential amplifier, a digital to
analog converter and a multiplexer switching unit for receiving signals
one at a time from the antennae of said receiving means which said
multiplexer switching unit, under the control of said programmed computer,
passes a selected one of said received signals to said differential
amplifier where the Earth's magnetic field signal, which was measured by
said receiver and read into said computer when the said transmitter was
shut off, is outputted from said computer to said digital to analog
converter where said digital to analog converter converts the digital
representation of the Earth's magnetic field signal strength to an analog
representation which goes to said differential amplifier, where the said
Earth's magnetic field signal is subtracted from said selected received
signal whereupon the output from said differential amplifier then goes to
said filter for removing noise from the said selected received signal
which then passes said filtered signal to said programmable gain signal
amplifier, which, under the control of said programmed computer, increases
said received filtered signal's level to a value appropriate to the signal
level limits of said analog to digital converter which converts the said
amplified received filtered signal to a digital representation that is
then passed to said programmed computer.
4. A device for quantitatively measuring the relative position and
orientation of receiving antennae with respect to transmitting antennae
serving to measure the relative position and orientation of two bodies in
the presence of metals utilizing direct current magnetic fields,
comprising:
(a) Transmitting means for transmitting direct current magnetic fields;
(b) Receiving means for receiving said transmitted direct current magnetic
fields consisting of a multiplicity of roughly orthogonal antennae axes
that are sensitive to transmitted direct current magnetic fields;
(c) Means for supplying direct current electrical signals to said
transmitting means for creating said transmitted direct current magnetic
fields;
(d) Receiver Electronics for measuring, and converting output signals from
said receiving means into position and orientation measurements consisting
of a programmed computer, an analog to digital converter, a programmable
gain signal amplifier, a filter, a differential amplifier, a digital to
analog converter and a multiplexer switching unit for receiving signals
one at a time from the antennae of said receiving means which said
multiplexer switching unit, under the control of said programmed computer,
passes a selected one of said receiving signals to said differential
amplifier where the Earth's magnetic field signal, which was measured by
said receiver and read into said computer when the said transmitter was
shut off, is outputted from said computer to said digital to analog
converter where said digital to analog converter converts the digital
representation of the Earth's magnetic field signal strength to an analog
representation which goes to said differential amplifier, where the said
Earth's magnetic field signal is subtracted from said selected received
signal whereupon the output from said differential amplifier then goes to
said filter for removing noise from the said selected received signal
which then passes said filtered signal to said programmable gain signal
amplifier, which, under the control of said programmed computer, increases
said received filtered signal's level to a value appropriate to the signal
level limits of said analog to digital converter which converts the said
amplified received filtered signal to a digital representation that is
then passed to said programmed computer.
5. A device for quantitatively measuring the relative position and
orientation of receiving antennae with respect to transmitting antennae
serving to measure the relative position and orientation of two bodies in
the presence of metals utilizing direct current magnetic fields,
comprising:
(a) Transmitting means for transmitting direct current magnetic fields;
(b) Receiving means for receiving said transmitted direct current magnetic
fields;
(c) Transmitter electronics consisting of a programmed computer, a
digital-analog signal converter, a Multiplexer actuated by said programmed
computer in receiver electronics and simultaneously by said converter and
one direct current power source applied to the wire windings of each
transmitter antenna axis to generate a magnetic field actuated in turn by
said Multiplexer;
(d) Receiver Electronics for measuring and converting output signals from
said receiving means into position and orientation measurements consisting
of said programming computer, an analog to digital converter, a
programmable gain signal amplifier, a filter, a differential amplifier, a
digital to analog converter and a multiplexer switching unit for receiving
signals one at a time from the antennae of said receiving means which said
multiplexer switching unit, under the control of said programmed computer,
passes a selected one of said received signals to said differential
amplifier where the Earth's magnetic field signal, which was measured by
said receiver and read into said computer when the said transmitter was
shut off, is outputted from said computer to said digital to analog
converter where said digital to analog converter converts the digital
representation of the Earth's magnetic field signal strength to an analog
representation which goes to said differential amplifier, where the said
Earth's magnetic field signal is subtracted from said selected received
signal whereupon the output from said differential amplifier then goes to
said filter for removing noise from the said selected received signal
which then passes said filtered signal to said programmable gain signal
amplifier, which, under the control of said programmed computer, increases
said received filtered signal's level to a value appropriate to the signal
level limits of said analog to digital converter which converts the said
amplified received filtered signal to a digital representation that is
then passed to said programmed computer.
6. A device for quantitatively measuring the relative position and
orientation of receiving antennae with respect to transmitting antennae
serving to measure the relative position and orientation of two bodies in
the presence of metals utilizing direct current magnetic fields,
comprising:
(a) Transmitting means for transmitting direct current magnetic fields;
(b) Receiving means for receiving said transmitted direct current magnetic
fields consisting of a multiplicity of roughly orthogonal antennae axes
that are sensitive to transmitted direct current magnetic fields;
(c) Transmitter electronics consisting of a programmed computer, a
digital-analog signal converter, a Multiplexer actuated by said programmed
computer in receiver electronics and simultaneously by said converter and
one direct current power source applied to the wire windings of each
transmitter antenna axis to generate a magnetic field actuated in turn by
said Multiplexer;
(d) Receiver Electronics for measuring and converting output signals from
said receiving means into position and orientation measurements consisting
of said programmed computer, an analog to digital converter, a
programmable gain signal amplifier, a filter, a differential amplifier, a
digital to analog converter and a multiplexer switching unit for receiving
signals one at a time from the antenna of said receiving means which said
multiplexer switching unit, under the control of said programmed computer,
passes a selected one of said receiving signals to said differential
amplifier where the Earth's magnetic field signal, which was measured by
said receiver and read into said computer when the said transmitter was
shut off, is outputted from said computer to said digital to analog
converter where said digital to analog converter converts the digital
representation of the Earth's magnetic field signal strength to an analog
representation which goes to said differential amplifier, where the said
Earth's magnetic field signal is subtracted from said selected received
signal whereupon the output from said differential amplifier then goes to
said filter for removing noise from the said selected received signal
which then passes said filtered signal to said programmable gain signal
amplifier, which, under the control of said programmed computer, increases
said received filtered signal's level to a value appropriate to the signal
level limits of said analog to digital converter which converts the said
amplified received filtered signal to a digital representation that is
then passed to said programmed computer
7. A device for quantitatively measuring the relative position and
orientation of receiving antennae with respect to transmitting antennae
serving to measure the relative position and orientation of two bodies in
the presence of metals utilizing direct current magnetic fields,
comprising:
(a) A transmitter for transmitting direct current magnetic fields
consisting of a core and a multiplicity of roughly orthogonal antenna axis
wire windings;
(b) Receiving means for receiving said transmitted direct current magnetic
fields consisting of a multiplicity of roughly orthogonal antennae axes
that are sensitive to transmitted direct current magnetic fields;
(c) Means for supplying direct current electrical signals to said
transmitting means for creating said transmitted direct current magnetic
fields;
(d) Receiver Electronics for measuring, and converting output signals from
said receiving means into position and orientation measurements consisting
of a programmed computer, an analog to digital converter, a programmable
gain signal amplifier, a filter, a differential amplifier, a digital to
analog converter and a multiplexer switching unit for receiving signals
one at a time from the antennae of said receiving means which said
multiplexer switching unit, under the control of said programmed computer,
passes a selected one of said received signals to said differential
amplifier where the Earth's magnetic field signal, which was measured by
said receiver and read into said computer when the said transmitter was
shut off, is outputted from said computer to said digital to analog
converter where said digital to analog converter converts the digital
representation of the Earth's magnetic field signal strength to an analog
representation which goes to said differential amplifier, where the said
Earth's field signal is subtracted from said selected received signal
whereupon the output from said differential amplifier then goes to said
filter for removing noise from the said selected received signal which
then passes said filtered signal to said programmable gain signal
amplifier, which, under the control of said programmed computer, increases
said received filtered signal's level to a value appropriate to the signal
level limits of said analog to digital converter which converts the said
amplified received filtered signal to a digital representation that is
then passed to said programmed computer.
8. A device for quantitatively measuring the relative position and
orientation of receiving antennae with respect to transmitting antennae
serving to measure the relative position and orientation of two bodies in
the presence of metals utilizing direct current magnetic fields,
comprising:
(a) A transmitter for transmitting direct current magnetic fields
consisting of a core and multiplicity of roughly orthogonal antenna axis
wire windings;
(b) Receiving means for receiving said transmitted direct current magnetic
fields consisting of a multiplicity of roughly orthogonal antennae axes
that are sensitive to transmitted direct current magnetic fields;
(c) Transmitter electronics consisting of a programmed computer, a
digital-analog signal converter, a Multiplexer actuated by said programmed
computer in receiver electronics and simultaneously by said converter and
one direct current power source applied to the wire windings of each
transmitter antenna axis to generate a magnetic field actuated in turn by
said Multiplexer;
(d) Receiver Electronics for measuring and converting output signals from
said receiving means into position and orientation measurements consisting
of said programmed computer, an analog to digital converter, a
programmable gain signal amplifier, a filter, a differential amplifier, a
digital to analog converter and a multiplexer switching unit for receiving
signals one at a time from the antennae of said receiving means which said
multiplexer switching unit, under the control of said programmed computer,
passes a selected one of said received signals to said differential
amplifier where the Earth's magnetic field signal, which was measured by
said receiver and read into said computer when the said transmitter was
shut off, is outputted from said computer to said digital to analog
converter where said digital analog converter converts the digital
representation of the Earth's magnetic field signal strength to an analog
representation which goes to said differential amplifier, where the said
Earth's field signal is subtracted from said selected received signal
whereupon the output from said differential amplifier then goes to said
filter for removing noise from the said selected received signal which
then passes said filtered signal to said programmable gain signal
amplifier, which, under the control of said programmed computer, increases
said received filtered signal's level to a value appropriate to the signal
level limits of said analog to digital converter which converts the said
amplified received filtered signal to a digital representation that is
then passed to said programmed computer.
9. A device for quantitatively measuring the relative position and
orientation of receiving antennae with respect to transmitting antennae
serving to measure the relative position and orientation of two bodies in
the presence of metals utilizing direct current magnetic fields,
comprising:
(a) Transmitting means for transmitting direct current magnetic fields;
(b) Receiving means for receiving said transmitted direct current magnetic
fields;
(c) Means for supplying direct current electrical signals to said
transmitting means for creating said transmitted direct current magnetic
fields;
(d) Receiver electronics for controlling circuit elements of said
transmitting and receiving means, measuring received signals and
converting output signals from said receiving means into position and
orientation measurements consisting of a programmed computer, an analog to
digital converter, a programmable gain signal amplifier, a filter, a
differential amplifier, a digital to analog converter and a multiplexer
switching unit for receiving signals one at a time from the antennae of
said receiving means which said multiplexer switching unit, under the
control of said programmed computer, passes a selected one of said
received signals to said differential amplifier where the Earth's magnetic
field signal, which was measured by said receiver and read into said
computer when the said transmitter was shut off, is outputted from said
computer to said digital to analog converter where said digital to analog
converter converts the digital representation of the Earth's magnetic
field signal strength to an analog representation which goes to said
differential amplifier, where the said Earth's field signal is subtracted
from said selected received signal whereupon the output from said
differential amplifier then goes to said filter for removing noise from
the said selected received signal which then passes said filtered signal
to said programmable gain signal amplifier, which, under the control of
said programmed computer, increases said received filtered signal's level
to a value appropriate to the signal level limits of said analog to
digital converter which converts the said amplified received filtered
signal to a digital representation that is then passed to said programmed
computer.
10. A device for quantitatively measuring the relative position and
orientation of receiving antennae with respect to transmitting antennae
serving to measure the relative position and orientation of two bodies in
the presence of metals utilizing direct current magnetic fields,
comprising:
(a) A transmitter for transmitting direct current magnetic fields
consisting of a core and a multiplicity of roughly orthogonal antenna axis
wire windings;
(b) Receiving means for receiving said transmitted direct current magnetic
fields;
(c) Transmitter electronics consisting of a programmed computer, a
digital-analog signal converter, a multiplexer actuated by said programmed
computer in receiver electronics and simultaneously by said converter and
one direct current power source applied to the wire windings of each
transmitter antenna axis to generate a magnetic field actuated in turn by
said multiplexer;
(d) Receiver electronics for controlling circuit elements of said
transmitter and said receiving means, measuring received signals and
converting output signals from said receiving means into position and
orientation measurements consisting of a programmed computer, an analog to
digital converter, a programmable gain signal amplifier, a filter, a
differential amplifier, a digital to analog converter and a multiplexer
switching unit for receiving signals one at a time from the antennae of
said receiving means which said multiplexer switching unit under the
control of said programmed computer, passes a selected one of said
received signals to said differential amplifier where the Earth's magnetic
field signal, which was measured by said receiver and read into said
computer when the said transmitter was shut off, is outputted from said
computer to said digital to analog converter where said digital to analog
converter converts the digital representation of the Earth's magnetic
field signal strength to an analog representation which goes to said
differential amplifier, where the said Earth's field signal is subtracted
from said selected received signal whereupon the output from said
differential amplifier then goes to said filter for removing noise from
the said selected received signal which then passes said filtered signal
to said programmable gain signal amplifier, which, under the control of
said programmed computer, increases said received filtered signal's level
to a value appropriate to the signal level limits of said analog to
digital converter which converts the said amplified received filtered
signal to digital representation that is then passed to said programmed
computer.
11. A device for quantitatively measuring the relative position and
orientation of receiving antennae with respect to transmitting antennae
serving to measure the relative position and orientation to two bodies in
the presence of metals utilizing direct current magnetic fields,
comprising:
(a) A transmitter for transmitting direct current magnetic fields
consisting of a core of multiplicity of roughly orthogonal antenna axis
wire windings;
(b) A receiver for receiving said transmitted direct current magnetic
fields consisting of a multiplicity of roughly orthogonal antennae axes
that are sensitive to transmitted direct current magnetic fields;
(c) Transmitter electronics consisting of a programmed computer, a digital
to analog signal converter, a multiplexer actuated by said computer in
receiver electronics and simultaneously by said converter and one direct
current power source applied to the wire windings of each transmitter
antenna axis to generate a magnetic field actuated in turn by said
Multiplexer;
(d) Receiver electronics for controlling circuit elements of said
transmitter and said receiving means, measuring received signals and
converting output signals from said receiving means into position and
orientation measurements consisting of a programmed computer, an analog to
digital converter, a programmable gain signal amplifier, a filter, a
differential amplifier, a digital to analog converter and a multiplexer
switching unit for receiving signals one at a time from the antennae of
said receiving means which said multiplexer switching unit, under the
control of said programmed computer, passes a selected one of said
received signals to said differential amplifier, where the Earth's
magnetic field signal, which was measured by said receiver and read into
said computer when the said transmitter was shut off, outputted from said
computer to said digital to analog converter where said digital to analog
converter converts the digital representation of the Earth's magnetic
field signal strength to an analog representation which goes to said
differential amplifier, where the Earth's field signal is subtracted from
said selected received signal whereupon the output from said differential
amplifier then goes to said filter for removing noise from the said
selected received signal which then passes said filtered signal to said
programmable gain signal amplifier, which, under the control of said
programmed computer, increases said received filtered signal's level to a
value appropriate to the signal level limits of said analog to digital
converter which converts the said amplified received filtered signal to a
digital representation that is then passed to said programmed computer. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field Of The Invention:
This invention pertains to devices utilized for purposes of measuring the
position and orientation of receiving antennae with respect to
transmitting antennae using direct current signals.
2. Description Of the Prior Art:
The art of using transmitting and receiving components with electromagnetic
coupling for measuring position and orientation is well known especially
with respect to armament sighting systems where the receiver component
would be located in a gunner's helmet and a transmitter component would be
attached to a nearby electrically non-conductive structure. As the gunner
would sight-in a target through a sighting cross-hair affixed to his
helmet, the receiver located thereupon would pick up signals generated by
the transmitter. These signals would then be processed by a computer to
determine the position and orientation of the helmet and then to
contemporaneously point a unit of armament in the same direction as the
helmet mounted sight piece.
As taught in U.S. Pat. No. 4,054,881 issued Feb. 18th, 1977 to Raab and
U.S. Pat. No. 4,287,809 issued Sept. 8th, 1981 to Egli et al., and U.S.
Pat. No. 4,314,251 issued Feb. 2nd, 1982 to Raab and U.S. Pat. No.
4,396,885 issued Aug. 2nd, 1983 to Constant, an alternating current (AC)
signal is applied in a time division or frequency division format to a
transmitter consisting of two or three orthogonal coils which generate an
AC electromagnetic field which is measured by an AC receiver likewise
consisting of three or two orthogonal coils. These sensed signals are then
filtered and amplified in a method compatible with the transmitted format,
converted to a digital format and then read into a computer where various
mathematical methods are resorted to in order to extract position and
orientation with resort to applicable electromagnetic field equations.
All current systems such as the ones abovesaid that utilize an AC
transmitted signal work accurately only when there are no electrically
conductive materials located near either the transmitter or receiver
because any transmitted AC signal would invariably induce eddy currents in
these conductive materials which would in turn serve to generate an AC
magnetic field that would distort any transmitted field, and, of course,
any ultimate output position and orientation data. In fighter aircraft or
helicopters where it is desired to use these position and orientation
measuring systems, there are a lot of highly conductive materials in the
form of aluminum, titanium, magnesium, stainless steel, and copper used in
the construction of the cockpit structure, seat, wiring and helmet-mounted
displays. U.S. Pat. No. 4,287,809 teaches a method of compensating for the
errors resulting from any field distortion due to cockpit metal that does
not move with respect to the transmitter. The compensation method therein
suggested involves making measurements throughout the cockpit to determine
the amount of such distortion and then using this data to form a
correction that is applied to the sensed signals. In a similar manner,
U.S. Pat. No. 4,394,831 issued July 26th, 1983 to Egli et al. teaches a
method to accomplish compensation for errors due to eddy currents induced
in metal such as would be found in a display located on a pilot's helmet.
This compensation method again requires initial experimental measurements
of such distortion in order to effect necessary corrections and provides
moderate improvements in accuracy only when the amount of metal on the
helmet is concentrated in a single location and the helmet does not go
through large angular rotations or translations in the cockpit. These
types of compensation efforts that are required to make AC systems work
accurately are time consuming and expensive to perform and only work in
environments where there would not be too much conductive material near
transmitter or receiver units. In many helicopters, for example, AC
systems cannot be utilized at all because the distortions produced are
simply too large to be corrected merely by such mapping.
The instant device represents a radical departure from all of the prior art
relating to such transmitting and receiving position and orientation
devices, insomuch as it avoids, in-toto, resort to AC signals and instead
relies upon DC signals. Such reliance on DC signals obviates completely
any need for a priori calibration undertakings and greatly expands the
potential utility of devices of this type. Moreover, manufacture and
utilization of this device for purposes of accomplishing all that current
devices can accomplish is manifestly less expensive than such manufacture
and utilization of said currently used devices are or ever will be.
SUMMARY OF THE INVENTION
This device consists of a two- or three-axis transmitter driven by a pulsed
DC current coupled with a three- or two-axis receiver that is sensitive to
a transmitted DC magnetic field emanating from the abovesaid activated
transmitter. Moreover, there are receiver signal processing electronics
that control the receiver and serve to convert its output to a format
suitable for processing by a digital computer in conjunction with a method
for processing received signals so as to thereby develop position and
orientation data.
An object of this invention is to provide a system of transmitting and
receiving antennae that by themselves intrinsically and with inherent
electronic means together with a digital computer readily measure position
and orientation relative to one another without the need for expensive
calibration procedures undertaken in advance of implementation and further
without concern for what types of diamagnetic or paramagnetic metallic
materials such as may be nearby. For the first time, for instance, devices
of this nature could be used in helicopters.
Another object of this invention would be to provide a computer graphics
system with an effective three-dimensional "mouse" where presently only
two-dimensional "mouse" devices are known to exist. For instance, no
longer will a graphics processor need to use one hand to control a "mouse"
for length and width drafting on a computer screen and another hand to
turn knobs to achieve image depth on such a screen. With this device, one
hand can control all three dimensions on such a screen with respect to the
drafting of images including image rotation as well, while the other hand
would be free to perform other design tasks such as recording, drafting,
et cetera.
Still another object of this invention is to provide a distinctly less
expensive sighting device than is currently provided within the framework
of the present state of the art separate and apart from the cost savings
to be realized from abrogation of calibration requirements. Presently, the
cores of the transmitting components of these devices are made up of
Ferrite. Ferrite is rather expensive, but, in addition to this, it is also
rather fragile and difficult to shape. However, Ferrite is necessary as a
core piece in order to keep eddy current distortion acceptably low where
AC current is used. But, there are no AC signal components in the instant
device's steady state signal and hence, the same magnetic flux
concentration as can be had with Ferrite can likewise be had and used with
this device by resorting to less expensive iron or steel for a
transmitting core piece, since, with this device, there is no need to be
concerned with eddy currents at all.
A BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the disclosed invention.
FIG. 2 is a block diagram of the transmitter driver electronics, which
constitute an integral part of the disclosed invention.
FIG. 3 shows the construction of the transmitter component of the instant
invention.
FIG. 4 is a block diagram of the receiver signal processing electronics
that constitute an integral part of the disclosed invention.
FIG. 5 is a timing diagram showing the relationship between the transmitted
and receiving signals generated during any use of the disclosed invention.
FIG 6 is a diagram of computational and control task sequences as performed
by the computer component of this device.
A DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 depicts the major elements of the disclosed invention. The
electromagnetic position and orientation measuring system consists of: a
Transmitter Driver Circuit 1 for providing a controlled amount of DC
current to each of two or three axes of Transmitter 2 one at a time. The
amount of DC current provided by Driver 1 to the Transmitter axis to which
it is provided is controlled by Computer 5. Transmitter 2 is usually
attached to the cockpit structure of an aircraft or helicopter and would
be located within a few feet of distance from a pilot's head in its
military application, or in its computer graphics application, Transmitter
2 would be located on, under, or above any table where a computer graphics
user would be working. Transmitter 2 consists of two or three individual
antennae arranged concentrically which generate a multiplicity of DC
magnetic fields that are picked up by Receiver 3. Receiver 3 measures not
only the fields generated by Transmitter 2 but also the earth's magnetic
field to therby effect an ultimate measure of the position and orientation
of the object to which it is attached. In the military application, this
is usually the pilot' s helmet. In the computer graphics application,
Receiver 3 is usually hand-held. Receiver 3 consists of three or two axes
with driving and detecting circuits that are sensitive to DC magnetic
fields. The D.C. signal output from Receiver 3 goes to the Signal
Processing Electronics 4. Signal Processing Electronics 4 controls,
conditions, and converts analog receiver signals into a digital format
that can be read by Computer 5. Computer 5, by way of an algorithm, such
as the one detailed in FIG. 6 below, computes the position and orientation
of Receiver 3 with respect to Transmitter 2. Computer 5 then outputs this
information to an aircraft's armament control computer or in the computer
graphics application, to a graphic image controller.
FIG. 2 presents the details of the Transmitter Drive Electronics 1. The
purpose of the Transmitter Drive Electronics 1 is to provide DC current
pulses to each antennae of Transmitter 2, one antenna at a time. While a
given Transmitter 2 antenna is being provided with current, readings are
taken from the antennae of Receiver 3. For a Transmitter 2 composed of
three antennae (X, Y, and Z axis antennae) and a Receiver 3 also composed
of three antennae (X, Y, and Z axis antenna), there would be nine readings
of the transmitted signal. Transmitter 2 is initially shut off and
Receiver 3 measures the X, Y, and Z components of the Earth's magnetic
field. In respect of the operation of the Transmitter DC Drive
Electronics, Computer 5 sends to the Digital to Analog (D/A) Converter 7 a
digital number that represents the amplitude of the current pulses to be
sent to the selected transmitter antenna. The D/A Converter 7 converts
this digital representation of the amplitude to an analog control voltage.
This control voltage goes to the Multiplexer (MUX) 8 which connects or
switches the control voltage to one of the Current Sources 9, 10, or 11 as
directed by Computer 5 when it is desired to transmit on the X, Y or Z
transmitter axis. Current Sources, 9, 10, and 11 are identical. Their
purpose is to provide a DC current to the Transmitter 2's antennae one at
a time. The amplitude of such current so provided is proportional to the
input control voltage generated by the D/A 7. Construction details for
said DC current sources are not presented here because they are well known
to one skilled in the art.
Transmitter 2 as shown in FIG. 3 consists of a core about which X, Y and/or
Z antennae are wound. The core can be constructed of air, but is usually
constructed of magnetically permeable ferrite that concentrates the
magnetic flux at any given location around the antenna. Ferrite is an
expensive material, very fragile and difficult to shape but must be used
in the cores of systems that use an AC signal format because its eddy
current losses are very low. For Transmitter 2 herein disclosed there are
no AC signal components in its steady state signal and the core can
therefore be and has been constructed of very inexpensive iron or steel
and obtain the same flux concentration as the more expensive ferrite. The
antenna windings of Transmitter 2 consist of multiple turns of standard
magnetic wire. The size of the wire, the number of turns, and the enclosed
area of the antenna winding, are determined by methods well known to those
skilled in the art of designing antennae. Transmitter 2 generates a near
field signal strength variation of the order of 1/R.sup.3 (R equalling the
distance between Transmitter 2 and Receiver 3 at any one instant in time.
Receiver 3 consists of three or two antennae arranged approximately
orthogonal to each other with driving and detecting circuits. Each antenna
is capable of measuring a DC magnetic field. There are many technologies
available for use as a DC Receiver 3. A representative embodiment of
Receiver 3 would be the three axis toroidal fluxgate magnetometer detailed
in U.S. Pat. No. 3,800,213 issued Mar. 26, 1974 to Rorden. Other
representative embodiments would be | | |
