 |
Description  |
|
|
BACKGROUND OF THE INVENTION
The present invention relates generally to tracking or locating systems
and, more particularly, to a system for continuously establishing and
indicating the location of a movable object.
In the recent past, the loss of vehicles and other movable objects as the
result of theft has been increasing at an alarming rate. The problem is
particularly acute with respect to certain vehicles such as construction
vehicles which are very difficult to keep track of and expensive to
replace. The problem is also pronounced in connection with boats,
particularly expensive pleasure boats which can be easily stolen.
Various prior art devices and methods have been devised for preventing the
theft of vehicles and other movable objects. The prior art devices and
methods include the use of human guards and/or guard dogs, roving patrols,
sophisticated alarm systems, specialized locking devices, deadman
switches, and the like. While some of the prior art devices and methods
are effective in deterring or curtailing the theft of such vehicles and
other objects, none of the devices is completely effective. In addition,
if the prior art devices or methods fail for any reason, such as a guard
falling asleep on the job, an electrical surveillance device losing power
or otherwise becoming inoperative, etc., there is no protection afforded
to the vehicles or object. Moreover, none of these prior art devices or
methods facilitates the prompt recovery of a vehicle or other object that
has been stolen, despite the protective measures.
The present invention comprises a system for continuously establishing and
indicating the location of a movable object, such as a construction or
other vehicle, boat, etc. The present invention may be used in conjunction
with any of the above-described prior art protective devices or methods or
with any other such protection means. Alternatively, the present invention
may be employed by itself, not only to deter the theft of the vehicle or
other object, but to facilitate the prompt and efficient recovery of any
such vehicle or object which has been taken. The present invention may
also be employed for inventory control.
SUMMARY OF THE INVENTION
Briefly stated, the present invention comprises a system for continuously
establishing and indicating the location of a movable object. The system
includes a first transmitter means which is secured to the object and
which periodically transmits, at a first predetermined frequency, first
radio frequency signals representative of an identification code uniquely
associated with the object. A plurality of receiver/repeater stations
positioned within a predetermined geographic area, each includes a
plurality of spaced, first receiver means for each receiving and
demodulating the first radio frequency signals to provide an object
identification code signal. Means are associated with each of the first
receiver means for determining the strength of the received first radio
frequency signals and for generating a strength signal for each first
receiver means. Signal processor and computer means, centrally located
within the predetermined geographic area, and communicating with the first
receiver means and the strength determining means are employed for
receiving the signals representative of the object identification code and
the strength signals, for calculating the location of the object based
upon the strength signals and for storing signals representative of the
object identification code and the location of the object. A master
tracking station communicates with the signal processor and computing
means for each predetermined geographic area. The master tracking station
includes means for receiving and storing the signals representative of the
object identification code and the object location, and display means for
providing a visual indication of the object identification code and the
object location.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing Summary, as well as the following detailed description of a
preferred embodiment of the invention, will be better understood when read
in conjunction with the appended drawings. For the purpose of illustrating
the invention, there is shown in the drawings an embodiment which is
presently preferred, it being understood, however, that the invention is
not limited to the precise arrangement and instrumentalities shown.
In the drawings:
FIG. 1 is a schematic block diagram representation of a portion of a
preferred embodiment of the present invention;
FIG. 2 is a schematic block diagram of another portion of a preferred
embodiment of the present invention;
FIG. 3 is a schematic block diagram of the transmitter portion of the
embodiment shown in FIG. 1;
FIG. 4 is a schematic block diagram of a local communication sphere of the
embodiment shown in FIG. 1; and
FIG. 5 is a more detailed schematic block diagram of a receiver/repeater
configuration of FIG. 4.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring to the drawings, wherein like numerals indicate like elements
throughout, there is shown in FIGS. 1 and 2 a block diagram schematic
representation of a system, generally 10, for continuously establishing
and indicating the location of a movable object in accordance with the
present invention. In the embodiment shown in FIGS. 1 and 2, the movable
objects are illustrated as being construction vehicles 12 and 14, buses 16
and 18, and boats 20 and 22. However, it will be appreciated by those
skilled in the art that the present invention is not limited to such
vehicles and could be employed with some other type of vehicle, such as an
automobile, truck, trailer, mobile home, military vehicle, air-borne
vehicle or the like (not shown). Alternatively, the present invention
could be employed with any other type of movable (non-vehicle) object,
such as a container of the type used in containerized shipping, shipping
crates or the like (not shown). In addition, the present invention could
be employed with a smaller object, such as a work of art, briefcase
containing valuable documents, computer, or the like (not shown). In
general, it is expected that the present invention will be employed
primarily with vehicles and/or other objects which may be relatively easy
to move and/or difficult to locate or recover and which are generally
relatively high in value and, therefore, are more likely to be stolen.
However, the present invention may also be employed in conjunction with
other, less valuable vehicles and/or objects, if desired. Therefore, it
will be appreciated by those skilled in the art that the type of object
with which the present system is employed should not be considered to be a
limitation on the present invention. However, for the sake of brevity and
clarity, the following discussion concerning the preferred embodiment of
the invention will be limited to applications with respect to construction
vehicles 12 and 14.
As best shown in FIGS. 1 and 3, the system 10 is comprised of first
transmitter means, shown generally as 24, secured to the object or each
vehicle 12 and 14 for periodically transmitting, at a first predetermined
frequency, first radio frequency signals representative of an
identification code uniquely associated with each of the vehicles 12 or
14. In the presently preferred embodiment, the first transmitter means 24
is comprised of a high powered radio frequency (RF) transmitter 26,
preferably of the frequency modulation (FM) type which is electrically
connected to a suitable transmitting antenna 28 of a type well known in
the art. The transmitter 26 is relatively small in size and is generally
of a type which is well known in the art and commercially available from a
variety of manufacturers, including Motorola and General Electric Co.
An electronic control circuit 30 is provided for controlling the operation
of the transmitter 26. Forming a part of or electrically connected with
the electronic control circuit 30 is a non-volatile memory device 32 such
as a programmable read-only memory (PROM). While the present embodiment
employs a PROM, the non-volatile memory device 32 could be some other
memory device of a type well known in the art, such as a read-only memory
(ROM); erasable, programmable read-only memory (EPROM), or the like (not
shown). A power source, for example, a battery 34 is utilized to provide
power to the transmitter 26 and the electronic control circuit 30 for
operation of the transmitter means 24. Preferably, the battery 34 is of
the long-life type, such as nickel cadmium, suitable for providing power
at a desired level to both the transmitter 26 and the electronic control
circuit 30 for an extended period of time and, preferably, need not be
replaced more frequently than once per year. If desired, the battery 34
could be rechargeable.
The PROM 32 is programmed with an identification code uniquely associated
with the vehicle 12 or 14. In the presently preferred embodiment, the
unique identification code is in the form of a standard binary number or
binary coded decimal number which has been permanently "burned" into the
PROM 32. However, any other type of identification code or suitable means
for providing a unique identification code may alternatively be employed.
The electronic control circuit 30 is of a type which is generally well
known in the art and commercially available from a variety of sources,
including IBM, Texas Instruments and Tandy. In operation, the electronic
control circuit 30 receives an electrical signal representative of the
unique identification code from the PROM 32 and applies the identification
code signal to the transmitter 26. The electronic control circuit 30 also
controls the timing of the transmitter 26 utilizing an internal clock (not
shown) to provide for periodic transmission of the identification code
signal at precisely controlled intervals on an automatic continuous basis
without the need for outside initiation. The length of the periodic
transmissions and the time between transmissions may be varied, but, once
set, remain the same for all of the transmissions. In the presently
preferred embodiment, the transmitter 26 operates only once every five
minutes. Because the preferred identification code is relatively short in
time, in the presently preferred embodiment the transmitter 26 transmits
the identification code for a total of approximately 1/100 of a second
with precise five minute intervals between each transmission. By having
the transmitter 26 active for only a very short period of time with a
relatively long period of time between transmissions, the power drain on
the battery 34 is kept relatively small, thereby promoting extended
battery life.
In addition, by having such short transmissions which are spaced apart in
time, it is possible to establish and indicate the location of a
substantial number of different objects within the same local area
utilizing the same first radio frequency. Of course, each of the various
objects (not shown) has its own unique identification code.
For example, with a transmission period of 1/100th of a second every five
minutes for each transmitter means 24, and, assuming a delay of 1/100th of
a second between transmissions for
different objects, it would be possible to have up to 15,000 objects, each
with its own unique identification code, within a local area, with the
transmitters 26 for each object operating at the same first predetermined
frequency. Of course, with a greater number of objects within a local
area, a greater delay between transmissions or a shorter transmission time
could be employed. Alternatively, the transmitter 26 for some of the
objects could transmit at a different frequency than the transmission
frequency used by the transmitters 26 of others of the objects.
The first transmitter means 24 is self-contained within a relatively small
sized package (not shown) and is adapted to be conveniently secured to a
vehicle 12 or 14 in an inconspicuous location without any modification to
the vehicle. Preferably, the first transmitter means 24 includes a
metallic housing (not shown) which is adapted to engage a metallic surface
on the vehicle 12 or 14 so that the vehicle 12 or 14 serves as a ground
plane or ground. Thus, if the first transmitter means 24 is removed from
the vehicle 12 or 14, the ground connection for the first transmitter
means 24 is broken, preventing further transmissions. For reasons which
will hereinafter become apparent, such an unanticipated interruption in
the operation of the first transmitter means 24 results in the generation
of an indication signal, provoking a prompt investigation.
The system 10 further comprises a plurality of receiver/repeater stations
or configurations 40 at spaced locations within a predetermined geographic
area. In the presently preferred embodiment, each geographic area extends
for approximately ninety square miles and includes nine receiver/repeater
stations 40 and 41 arranged in a predetermined pattern so that each
receiver/repeater station 40 covers approximately ten square miles to
provide sufficient coverage over the entire predetermined geographic area,
as illustrated in FIG. 4. Each group of nine receiver/repeater stations 40
and 41 are interconnected to form a local communication sphere. In the
preferred embodiment, multiple local communication spheres are employed to
cover multiple geographic areas in a manner which will hereinafter become
apparent. However, for the sake of clarity and brevity, only a single
communication sphere for a single geographic area will be described.
FIG. 5 illustrates further details of a receiver/repeater station 40. The
receiver/repeater station 40 shown in FIG. 5 is comprised of a plurality
of spaced first receiver means for each receiving and demodulating the
first radio frequency signals to provide an objection identification code
signal. In the presently preferred embodiment, the plurality of first
receiver means is comprised of three individual small sized receivers 42,
44 and 46, each of which is tuned or preset to receive the signals (within
range) at the first predetermined frequency. In the presently preferred
embodiment, the receivers 42, 44 and 46 are passive, highly sensitive,
preferably battery powered, FM receivers of a type well known in the art
and generally commercially available from a variety of sources, for
example, Motorola, General Electric Co. or AT&T.
For reasons which will hereinafter become apparent, the receivers 42, 44
and 46 are installed at fixed locations approximately 1,000 feet apart. In
the presently preferred embodiment, each receiver 42, 44 and 46 is secured
to or otherwise supported by a utility pole (not shown) with the receivers
each being approximately ten utility poles apart. Signal processing means
42a, 44a and 46a are associated with each receiver 42, 44 and 46 for
determining the strength of each of the received first radio frequency
signals for each identification code signal received and for generating a
first radio frequency strength signal representative of the strength of
the received first radio frequency signals for each receiver 42, 44 and
46, including suitable antenna (not shown) of a type well known in the
art.
As shown in FIG. 5, each of the receivers 42, 44 and 46 is electrically
connected through its associated signal processing means 42a, 44a, 46a by
suitable lines, such as shielded coaxial transmission lines or cables 48,
50 and 52 to a repeater or second transmitter means 54. The second
transmitter means 54 is preferably physically collocated with one of the
receivers 42, 44 or 46, preferably the middle receiver 44, and, in the
presently preferred embodiment, is also secured to or otherwise supported
by a utility pole. The receivers 42, 44 and 46 are preferably relatively
positioned in a triangular-shaped configuration but could be positioned in
some other manner. The second transmitter means 54 receives the object
identification code signals and the associated strength signals from each
of the receivers 42, 44 and 46 and transmits, at a second predetermined
radio frequency second radio frequency signals representative of the
object identification code and the associated signal strengths for each of
the receivers 42, 44 and 46. In the presently preferred embodiment, the
second transmitter means 54 is an ultrahigh frequency (UHF) transmitter of
a size similar to that of the first transmitter 26.
As previously indicated, each local communications sphere within a
predetermined geographic area includes nine receiver/repeater stations,
preferably positioned in a spaced, relatively regular geometric relation,
as shown schematically in FIG. 4. The structure of each of the
receiver/repeater stations located around the perimeter of the geographic
is preferably as previously described and as shown in FIG. 5. However, the
central receiver repeater/station 41, preferably generally centrally
located within the geographic area, has a slightly different structure.
The central receiver/repeater station 41 includes three receivers which
are the same as receivers 42, 44 and 46 of each of the receiver/repeater
stations 40, as described above. Like the receivers 42, 44 and 46 of
receiver/repeater stations 40, the three receivers (not shown) of central
receiver/repeater station 41 are similarly spaced and are tuned to receive
signals at the first radio frequency. Signal processing means (not shown)
are also associated with each of the three receivers of the central
receiver/repeater station 41.
The central receiver/repeater station 41 does not contain a repeater 54.
Instead, the central receiver/repeater station 41 includes a second
receiver means, in the presently preferred embodiment, a second receiver
56 for receiving and demodulating the second radio frequency signals to
provide signals representative of the object identification code and the
strength signals from each of the eight receiver/repeater stations 40 in
the predetermined geographic area. The second receiver 56 is preferably a
highly sensitive UHF receiver tuned or preset to the second predetermined
frequency to facilitate receipt of the signals from the various second
transmitters or repeaters 54.
The output of the second receiver 56 is connected via a suitable electrical
transmission line to signal processor means or a signal processor 60 and
computer means or a computer 62 (see FIG. 1). The output signals from each
of the receivers (not shown) of the central receiver/repeater stations 41
are similarly connected to the signal processor 60 and the computer 62.
Preferably, both the signal processor 60 and the computer 62 are
collocated with the central receiver/repeater station 41. The signal
processor is of a type generally well known in the art and commercially
available from a variety of sources, such as AT&T or IBM. The signal
processor 60 receives the signals representative of the object
identification code and the associated signal strengths with respect to
each of the receivers 42, 44 and 46 associated with each of the
receiver/repeater configurations 40 and the receivers of the central
receiver/repeater station 41 within the local communications sphere. The
signal processor 60 conditions all of the received signals and applies the
signals to the input of the computer 62. In the presently preferred
embodiment, the computer 62 is a microcomputer or personal computer,
preferably with a hard disk having a capacity of twenty megabytes or more
and a random access memory (RAM) of at least one megabyte The computer 62
also includes a 2400-9600 baud modem. Such computers are commercially
available from a variety of manufacturers, including IBM. The computer 62
includes an operating system and the necessary software or programs to
perform the desired calculations and data manipulation functions
hereinafter described. The computer 62 receives the conditioned signals
representative of the object identification code and associated stre | | |
