U.S. patent application number 10/307814 was filed with the patent office on 2004-06-03 for tracing of transponder-tagged objects.
Invention is credited to Wijk, Wouter Uco van.
Application Number | 20040104817 10/307814 |
Document ID | / |
Family ID | 8181339 |
Filed Date | 2004-06-03 |
United States Patent
Application |
20040104817 |
Kind Code |
A1 |
Wijk, Wouter Uco van |
June 3, 2004 |
TRACING OF TRANSPONDER-TAGGED OBJECTS
Abstract
For tracing objects distributed transmitter stations are
provided, each transmitting an activation signal. Tags are attached
to objects. The tags receive the activation signals when in an
operating area of one of the transmitter stations. The received
activation signal causes the tag to transmit a reaction signal. A
receiver station receives the reaction signals. Data representing
positions of tags in accordance with the received reaction signals
are registered. The activation signals each also include a
transmitter station code associated to the transmitter station
transmitting that signal. The transmitter station codes transmitted
by different transmitter stations are mutually different. The
reaction signals transmitted by the tags each include the
transmitter station code included in the received activation signal
that caused the tag to transmit that reaction signal. Data
representing positions of tags are registered in accordance with
transmitter station codes received from the tags by the receiver
station.
Inventors: |
Wijk, Wouter Uco van;
(Maartensdijk, NL) |
Correspondence
Address: |
PEARNE & GORDON LLP
1801 EAST 9TH STREET
SUITE 1200
CLEVELAND
OH
44114-3108
US
|
Family ID: |
8181339 |
Appl. No.: |
10/307814 |
Filed: |
December 2, 2002 |
Current U.S.
Class: |
340/505 ;
340/8.1 |
Current CPC
Class: |
G01S 5/0018 20130101;
G01S 5/0045 20130101; G07C 9/28 20200101; G01S 13/767 20130101 |
Class at
Publication: |
340/505 ;
340/825.49 |
International
Class: |
G08B 026/00 |
Claims
What is claimed is:
1. A method for tracing objects, comprising: providing a plurality
of distributed transmitter stations, each of said transmitter
stations transmitting an activation signal; attaching a tag to each
object to be monitored, each of said tags receiving the activation
signal from one of said transmitter stations when in an operating
area of said one of said transmitter stations, the received
activation signal causing the tag to transmit a reaction signal and
the operating areas of said transmitter stations being spatially
distributed; providing at least one receiver station, said receiver
station receiving said reaction signals transmitted by said tags;
and registering data representing positions of tags in accordance
with said reaction signals received by said at least one receiver
station; wherein the activation signal transmitted by each of said
transmitter stations includes a predetermined transmitter station
code associated to that transmitter station, the transmitter
station codes transmitted by at least two of said transmitter
stations being mutually different and distinguishing activation
signals from at least one of said transmitter stations from
activation signals from at least one other one of said transmitter
stations; said reaction signals transmitted by activated ones of
said tags each including the transmitter station code included in
the received activation signal that caused the tag to transmit said
reaction signal; and the registration of data representing
positions of tags being carried out in accordance with different
transmitter station codes received from said tags by said receiver
station or each of said receiver stations.
2. A method according to claim 1, wherein, in a monitored area, the
transmitter station codes are unique codes each identifying one of
said transmitter stations.
3. A method according to claim 1, wherein the or each receiver
station has an operating area which includes the operating areas of
a plurality of the transmitter stations.
4. A method according to claim 1, further including transmitting an
activation signal receivable by any tag in a monitoring area,
registering reaction signals received in response to said
activation signal, comparing said registered reaction signals with
registered data representing tags in said monitoring area and
generating a warning signal in response to data representing tags
in said monitoring area not matched by any of said registered
reaction signals.
5. A method according to claim 1, wherein the or each receiver
station has an operating range within which the receiver station is
capable of receiving reaction signals from the tags, said operating
range being at least three times as large as the operating range of
the transmitter stations(2-6) within which the tags are activated
by the transmitter stations.
6. A method for tracing objects, comprising: providing a plurality
of distributed transmitter stations, each of said transmitter
stations transmitting an activation signal; attaching a tag to each
object to be monitored, each of said tags receiving the activation
signal from one of said transmitter stations when in an operating
area of said one of said transmitter stations, the received
activation signal causing the tag to transmit a reaction signal and
the operating areas of said transmitter stations being spatially
distributed; providing at least one receiver station, said receiver
station receiving said reaction signals transmitted by said tags;
and registering data representing positions of tags in accordance
with said reaction signals received by said at least one receiver
station; wherein the activation signal transmitted by each of said
transmitter stations includes a predetermined transmitter station
code associated to that transmitter station, the transmitter
station codes transmitted by at least two of said transmitter
stations being mutually different and distinguishing activation
signals from at least one of said transmitter stations from
activation signals from at least one other one of said transmitter
stations; said reaction signals transmitted by activated ones of
said tags each including the transmitter station code included in
the received activation signal that caused the tag to transmit said
reaction signal; the registration of data representing positions of
tags being carried out in accordance with transmitter station codes
received from said tags by said at least one receiver station; and
said receiver station receiving said reaction signals transmitted
by said tags located in said operating area of said one of said
transmitter stations being located outside said operating area of
said transmitter station.
7. A method for tracing objects, comprising: providing a plurality
of distributed transmitter stations, each of said transmitter
stations transmitting an activation signal; attaching a tag to each
object to be monitored, each of said tags receiving the activation
signal from one of said transmitter stations when in an operating
area of said one of said transmitter stations, the received
activation signal causing the tag to transmit a reaction signal and
the operating areas of said transmitter stations being spatially
distributed; providing at least one receiver station, said receiver
station receiving said reaction signals transmitted by said tags;
and registering data representing positions of tags in accordance
with said reaction signals received by said at least one receiver
station; wherein the activation signal transmitted by each of said
transmitter stations includes a predetermined transmitter station
code associated to that transmitter station, the transmitter
station codes transmitted by at least two of said transmitter
stations being mutually different and distinguishing activation
signals from at least one of said transmitter stations from
activation signals from at least one other one of said transmitter
stations; said reaction signals transmitted by activated ones of
said tags each including the transmitter station code included in
the received activation signal that caused the tag to transmit said
reaction signal; the registration of data representing positions of
tags being carried out in accordance with transmitter station codes
received from said tags by said at least one receiver station; the
operating areas of said transmitter stations being spatially
separated from each other; and at least one of said objects being
located in an enclosed area, the enclosure of said area having at
least one passage allowing entry and exit of said objects, the
operating areas of said transmitter stations each including at
least one of said passages.
8. A method according to claim 7, wherein the operating area of
each transmitter station includes at most one of said passages.
9. A method for tracing objects, comprising: providing a plurality
of distributed transmitter stations, each of said transmitter
stations transmitting an activation signal; attaching a tag to each
object to be monitored, each of said tags receiving the activation
signal from one of said transmitter stations when in an operating
area of said one of said transmitter stations, the received
activation signal causing the tag to transmit a reaction signal and
the operating areas of said transmitter stations being spatially
distributed; providing at least one personal tag carried by a
person, the or each personal tag receiving the activation signal
from one of said transmitter stations being activated to transmit a
reaction signal when in an operating area of said one of said
transmitter stations; providing at least one receiver station, said
receiver station receiving said reaction signals transmitted by
said tags; and registering data representing positions of tags in
accordance with said reaction signals received by said at least one
receiver station; wherein the activation signal transmitted by each
of said transmitter stations includes a predetermined transmitter
station code associated to that transmitter station, the
transmitter station codes transmitted by at least two of said
transmitter stations being mutually different and distinguishing
activation signals from at least one of said transmitter stations
from activation signals from at least one other one of said
transmitter stations; said reaction signals transmitted by
activated ones of said tags each including the transmitter station
code included in the received activation signal that caused the tag
to transmit said reaction signal; the registration of data
representing positions of tags being carried out in accordance with
transmitter station codes received from said tags by said at least
one receiver station; and a warning signal being generated if the
reaction signal received by said at least one receiver station
matches a predetermined warning condition; wherein, in response to
receipt within a common period of time of a reaction signal
matching a warning condition and a reaction signal including a
predetermined personal tag code and the same transmitter station
code as the transmitter station code in the reaction signal
matching the warning condition, said warning signal is not
generated or generated in modified form.
10. A method for tracing objects, comprising: providing a plurality
of distributed transmitter stations, each of said transmitter
stations transmitting an activation signal; attaching a tag to each
object to be monitored, each of said tags receiving the activation
signal from one of said transmitter stations when in an operating
area of said one of said transmitter stations, the received
activation signal causing the tag to transmit a reaction signal, at
least one protected one of said tags further including a motion
and/or tamper detector, said protected tag being adapted for
transmitting a reaction signal including a warning code in reaction
to motion and/or tampering of the tag detected by said motion
and/or tamper detector, the operating areas of said transmitter
stations being spatially distributed; providing at least one
receiver station, said receiver station receiving said reaction
signals transmitted by said tags; and registering data representing
positions of tags in accordance with said reaction signals received
by said at least one receiver station; wherein the activation
signal transmitted by each of said transmitter stations includes a
predetermined transmitter station code associated to that
transmitter station, the transmitter station codes transmitted by
at least two of said transmitter stations being mutually different
and distinguishing activation signals from at least one of said
transmitter stations from activation signals from at least one
other one of said transmitter stations; said reaction signals
transmitted by activated ones of said tags each including the
transmitter station code included in the received activation signal
that caused the tag to transmit said reaction signal; the
registration of data representing positions of tags is carried out
in accordance with transmitter station codes received from said
tags by said at least one receiver station; and a warning signal
being generated in response to a reaction signal including said
warning code.
11. A system for tracing objects, comprising: a plurality of
distributed transmitter stations for transmitting activation
signals; a plurality of tags for attachment to objects to be
monitored, each of said tags including a receiver for receiving the
activation signal from one of said transmitter stations when in the
operating area of said one of said transmitter stations and a
transmitter communicating with the receiver for activation of the
transmitter to transmit a reaction signal in response to receipt of
an activation signal by the receiver, the operating areas of said
transmitter stations being spatially distributed; at least one
receiver station for receiving said reaction signals transmitted by
said tags; and a data registration structure communicating with
said at least one receiver station for registering data
representing positions of tags in accordance with said reaction
signals received by said at least one receiver station; wherein
said transmitter stations are each adapted for including a
predetermined transmitter station code in the activation signal,
the transmitter station codes of at least two of said transmitter
stations being mutually different and mutually distinguishing
activation signals from at least one of said transmitter stations
from activation signals from at least one other one of said
transmitter stations; said tags each being adapted for receiving
transmitter station codes in the received activation signal and for
including the transmitter station code of the activation signal
that caused the reaction signal to be transmitted in the reaction
signal transmitted by that tag; and said data registration
structure being adapted for registration of data representing
different positions of activated ones of tags in accordance with
different transmitter station codes received from said tags by said
receiver station or each of said receiver stations.
12. A system according to claim 11, wherein each of said
transmitter stations in a monitored area is adapted for
transmitting a different transmitter station code identifying the
transmitter station.
13. A system for tracing objects, comprising: a plurality of
distributed transmitter stations for transmitting activation
signals; a plurality of tags for attachment to objects to be
monitored, each of said tags including a receiver for receiving the
activation signal from one of said transmitter stations when in the
operating area of said one of said transmitter stations and a
transmitter communicating with the receiver for activation of the
transmitter to transmit a reaction signal in response to receipt of
an activation signal by the receiver, the operating areas of said
transmitter stations being spatially distributed; at least one
receiver station for receiving said reaction signals transmitted by
said tags; and a data registration structure communicating with
said at least one receiver station for registering data
representing positions of tags in accordance with said reaction
signals received by said at least one receiver station; wherein
said transmitter stations are each adapted for including a
predetermined transmitter station code in the activation signal,
the transmitter station codes of at least two of said transmitter
stations being mutually different and mutually distinguishing
activation signals from at least one of said transmitter stations
from activation signals from at least one other one of said
transmitter stations; said tags each being adapted for receiving
transmitter station codes in the received activation signal and for
including the transmitter station code of the activation signal
that caused the reaction signal to be transmitted in the reaction
signal transmitted by that tag; and said data registration
structure being adapted for registration of data representing
positions of tags in accordance with transmitter station codes
received from said tags by said at least one receiver station,
further including at least one tag including a motion and/or tamper
detector and a control member communicating with the motion and/or
tamper detector and for activating the transmitter for transmitting
a reaction signal in reaction to at least motion or tampering of
the tag detected by said motion and/or tamper detector.
14. A system for tracing objects, comprising: a plurality of
distributed transmitter stations for transmitting activation
signals; a plurality of tags for attachment to objects to be
monitored, each of said tags including a receiver for receiving the
activation signal from one of said transmitter stations when in the
operating area of said one of said transmitter stations and a
transmitter communicating with the receiver for activation of the
transmitter to transmit a reaction signal in response to receipt of
an activation signal by the receiver, the operating areas of said
transmitter stations being spatially distributed; at least one
receiver station for receiving said reaction signals transmitted by
said tags; and a data registration structure communicating with
said at least one receiver station for registering data
representing positions of tags in accordance with said reaction
signals received by said at least one receiver station; wherein
said transmitter stations are each adapted for including a
predetermined transmitter station code in the activation signal,
the transmitter station codes of at least two of said transmitter
stations being mutually different and mutually distinguishing
activation signals from at least one of said transmitter stations
from activation signals from at least one other one of said
transmitter stations; said tags each being adapted for receiving
transmitter station codes in the received activation signal and for
including the transmitter station code of the activation signal
that caused the reaction signal to be transmitted in the reaction
signal transmitted by that tag; said data registration structure
being adapted for registration of data representing positions of
tags in accordance with transmitter station codes received from
said tags by said at least one receiver station; wherein said
receiver for receiving said reaction signals transmitted by said
tags located in said operating area of said one of said transmitter
stations is located outside said operating area of said transmitter
station.
15. A system according to claim 14, wherein the or each receiver
station has an operating area which includes the operating areas of
a plurality of the transmitter stations.
16. A system according to claim 14, wherein the or each receiver
station has an operating range within which the receiver station is
capable of receiving reaction signals from the tags, said operating
range being at least three times as large as the operating range of
the transmitter stations(2-6) within which the tags are activated
by the transmitter stations.
17. A system for tracing objects, comprising: a plurality of
distributed transmitter stations for transmitting activation
signals; a plurality of tags for attachment to objects to be
monitored, each of said tags including a receiver for receiving the
activation signal from one of said transmitter stations when in the
operating area of said one of said transmitter stations and a
transmitter communicating with the receiver for activation of the
transmitter to transmit a reaction signal in response to receipt of
an activation signal by the receiver, the operating areas of said
transmitter stations being spatially distributed; at least one
receiver station for receiving said reaction signals transmitted by
said tags; and a data registration structure communicating with
said at least one receiver station for registering data
representing positions of tags in accordance with said reaction
signals received by said at least one receiver station; wherein
said transmitter stations are each adapted for including a
predetermined transmitter station code in the activation signal,
the transmitter station codes of at least two of said transmitter
stations being mutually different and mutually distinguishing
activation signals from at least one of said transmitter stations
from activation signals from at least one other one of said
transmitter stations; said tags are each adapted for receiving
transmitter station codes in the received activation signal and for
including the transmitter station code of the activation signal
that caused the reaction signal to be transmitted in the reaction
signal transmitted by that tag; and said data registration
structure is adapted for registration of data representing
positions of tags in accordance with transmitter station codes
received from said tags by said at least one receiver station; the
operating areas of said transmitter stations are spatially
separated from each other; and at least one of said objects is
located in an enclosed area, the enclosure of said area having at
least one passage allowing entry and exit of said objects, the
operating areas of said transmitter stations each including at
least one of said passages.
18. A computer program for use in a system for tracing objects,
comprising instructions for causing a data registration structure
to read reaction signals inputted from a receiver station and to
register data representing positions of tags in accordance with
said inputted reaction signals; instructions for reading
transmitter station codes included in said inputted reaction
signals and instructions for registering data representing
positions of tags in accordance with transmitter station codes
included in said inputted reaction signals; instructions for
comparing inputted reaction signals with a predetermined warning
condition, instructions for generating a warning signal if the
inputted reaction signal matches the predetermined warning
condition, and instructions for causing said comparing and
generating instructions to be carried out in real-time;
instructions for registering data representing positions of
personal tags in accordance with inputted reaction signals
including the transmitter station code included in the received
activation signal that caused the reaction signal to be
transmitted; instructions for combining said data representing
positions of personal tags with data representing positions of tags
that have been received by the receiver station in a common period
of time; and instructions causing said warning signal not to be
generated or to be generated in modified form in response to data
representing a combination of a reaction signal matching a warning
condition and a reaction signal including a predetermined personal
tag code and including the same transmitter station code as the
transmitter station code included in the reaction code matching the
warning condition.
19. A system according to claim 15, wherein the or each receiver
station has an operating range within which the receiver station is
capable of receiving reaction signals from the tags, said operating
range being at least three times as large as the operating range of
the transmitter stations(2-6) within which the tags are activated
by the transmitter stations.
Description
FIELD AND BACKGROUND OF THE INVENTION
[0001] The invention relates to a method for tracing objects, to a
system for tracing objects, to a tag for a system for tracing
objects, to a transmitter station for a system for tracing objects
and to a computer program for use in a system for tracing
objects.
BACKGROUND OF THE INVENTION
[0002] A method, a system, a tag, a transmitter station and a
computer program for tracing objects are described in U.S. Pat. No.
6 057 756. According to this patent a set of receiver stations is
used which receive reaction signals from the tags. The transmitters
and receivers are coupled to a controller by a transmitter bus and
a receiver bus. The controller is typically activated by a request
for an item and causes an interrogation signal to be transmitted by
at least one of the transmitters. Various tagged objects will be
subjected to the interrogation signal, but only one object - the
one requested by the user - will respond to the interrogation
signal. The interrogation signal triggers the tag matching the
interrogation signal to send a responsive signal, which signal is
detected by the nearest one of the receiver stations and the
location of the object can then be reported.
[0003] European patent application 0 467 036 describes a system in
which the transmitter and the receiver are combined in interrogator
stations. It is described to determine the approximate location of
tags by identifying the location of the interrogator, which has
received the responsive signal from the tag.
[0004] Other examples in which the approximate location of tags is
determined in accordance with the positions of receivers are
described in international patent applications WO 98/16849,
WO/99/23623, WO 99/62039, WO 99/67737, WO 00/16564. A disadvantage
of these known methods and systems is that each of the
interrogators needs to communicate individually with the
controller.
[0005] A similar disadvantage also applies to the system described
in UK patent application 2 298 098 according to which a plurality
of slave stations receive signals from a transponder and the
position of the transponder is determined from the time delays with
which signals from the transponder are received by the slave
stations.
[0006] In European patent application 0 965 857 a system for
determining the position of a tag, with particular accuracy in the
area of an entrance is described. According to this document, an
angular difference of preferably 180.degree. between the phases of
the field of a cell in which the transponder is detected and of the
fields of neighbouring overlapping cells is provided, so that the
transponder can detect and signal to a receiver that it is in de
area of the overlap and the direction in which the transponder is
moving can be determined from the phase change occurring when
passing from one field into the overlap and from the overlap into
the other field. This allows detection of the position and
direction of motion of a transponder in the area of for instance a
gate at the exit of a building with an accuracy of a few
centimetres, which, in turn, allows early and reliable warning that
a transponder is brought outside the building. However, the
transmitters need to be able to communicate individually with the
control unit to be able to change the phase of the field generated
thereby in response to detection of a transponder in a neighbouring
field.
[0007] In UK patent application 2 353 910, an asset tracking system
is described in which a beacon transmits a signal including an ID
signal. An asset decodes the signal to determine the ID signal and
sends the beacon ID to a central server. It is further described
that this transmission may be over any communications network, for
example a LAN or a telephone network, or a wireless network
comprising a relay system through the beacons themselves. The
server computes the physical location from the beacon ID, or the
server detects a change of location of the asset determined from a
list of beacons and a list of asset locations held by the server.
Bluetooth digital radio technology is described as the preferred
implementation. A problem of this system is that a network is
required to communicate the signals from the asset to the central
server.
SUMMARY OF THE INVENTION
[0008] It is an object of the invention to facilitate tracing of
objects (which may also includes human persons or animals), in
particular by providing a solution requiring relatively little
installation effort.
[0009] According to the present invention, this object is achieved
by. providing a method for tracing objects, comprising:
[0010] providing a plurality of distributed transmitter stations,
each of said transmitter stations transmitting an activation
signal;
[0011] attaching a tag to each object to be monitored, each of said
tags receiving the activation signal from one of said transmitter
stations when in an operating area of said one of said transmitter
stations, the received activation signal causing the tag to
transmit a reaction signal and the operating areas of said
transmitter stations being spatially distributed;
[0012] providing at least one receiver station, said receiver
station receiving said reaction signals transmitted by said tags;
and
[0013] registering data representing positions of tags in
accordance with said reaction signals received by said at least one
receiver station;
[0014] wherein the activation signal transmitted by each of said
transmitter stations includes a predetermined transmitter station
code associated to that transmitter station, the transmitter
station codes transmitted by at least two of said transmitter
stations being mutually different and distinguishing activation
signals from at least one of said transmitter stations from
activation signals from at least one other one of said transmitter
stations;
[0015] said reaction signals transmitted by activated ones of said
tags each including the transmitter station code included in the
received activation signal that caused the tag to transmit said
reaction signal; and
[0016] the registration of data representing positions of tags
being carried out in accordance with different transmitter station
codes received from said tags by said receiver station or each of
said receiver stations.
[0017] The invention can also be embodied in a system specifically
adapted for use in such a method, which system, includes:
[0018] a plurality of distributed transmitter stations for
transmitting activation signals;
[0019] a plurality of tags for attachment to objects to be
monitored, each of said tags including a receiver for receiving the
activation signal from one of said transmitter stations when in the
operating area of said one of said transmitter stations and a
transmitter communicating with the receiver for activation of the
transmitter to transmit a reaction signal in response to receipt of
an activation signal by the receiver, the operating areas of said
transmitter stations being spatially distributed;
[0020] at least one receiver station for receiving said reaction
signals transmitted by said tags; and
[0021] a data registration structure communicating with said at
least one receiver station for registering data representing
positions of tags in accordance with said reaction signals received
by said at least one receiver station;
[0022] wherein said transmitter stations are each adapted for
including a predetermined transmitter station code in the
activation signal, the transmitter station codes of at least two of
said transmitter stations being mutually different and mutually
distinguishing activation signals from at least one of said
transmitter stations from activation signals from at least one
other one of said transmitter stations;
[0023] said tags each being adapted for receiving transmitter
station codes in the received activation signal and for including
the transmitter station code of the activation signal that caused
the reaction signal to be transmitted in the reaction signal
transmitted by that tag; and
[0024] said data registration structure being adapted for
registration of data representing different positions of activated
ones of tags in accordance with different transmitter station codes
received from said tags by said receiver station or each of said
receiver stations.
[0025] The invention can also be embodied in a computer program,
that may be provided in machine readable form as a signal or on a
data carrier, for controlling a particular embodiment of the method
according to the invention in which warning signals are selectively
not generated in response to authorized combinations of codes
received from the tags. According to the invention this object is
achieved with a computer program including:
[0026] instructions for causing a data registration structure to
read reaction signals inputted from a receiver station and to
register data representing positions of tags in accordance with
said inputted reaction signals;
[0027] instructions for reading transmitter station codes included
in said inputted reaction signals and instructions for registering
data representing positions of tags in accordance with transmitter
station codes included in said inputted reaction signals;
[0028] instructions for comparing inputted reaction signals with a
predetermined warning condition, instructions for generating a
warning signal if the inputted reaction signal matches the
predetermined warning condition, and instructions for causing said
comparing and generating instructions to be carried out in
real-time;
[0029] instructions for registering data representing positions of
personal tags in accordance with inputted reaction signals
including the transmitter station code included in the received
activation signal that caused the reaction signal to be
transmitted;
[0030] instructions for combining said data representing positions
of personal tags with data representing positions of tags that have
been received by the receiver station in a common period of time;
and
[0031] instructions causing said warning signal not to be generated
or to be generated in modified form in response to data
representing a combination of a reaction signal matching a warning
condition and a reaction signal including a predetermined personal
tag code and including the same transmitter station code as the
transmitter station code included in the reaction code matching the
warning condition.
[0032] Further objects, features, effects and details of the
invention are set forth in the description of exemplary embodiments
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a schematic representation in top plan view of an
example of an installed system according to the invention,
[0034] FIG. 2 is a schematic representation of an example of a tag
according to the invention,
[0035] FIG. 3 is an exemplary flow chart of the processing of a
reaction signal received from a tag; and
[0036] FIG. 4 is a partial representation of a data table of
warning conditions.
DETAILED DESCRIPTION
[0037] The invention is first described with reference to FIG. 1 in
which an installed example of a system for tracing objects as
proposed is shown. For the sake of clarity and conciseness of the
description, the described example is a quite small system although
system as proposed are very suitable for larger applications in
which objects in a far larger area are traced.
[0038] FIG. 1 shows a floor plan of a building 1 which may for
instance be an office, a centre for medical care or a school. In
this example the building consists of only one floor, but the
system can also be applied to multi-storey buildings.
[0039] The system includes a number of transmitter stations 2-6 for
transmitting activation signals. The transmitter stations 2-6 are
located at distributed positions throughout the building 1.
[0040] In the building 1 a number of objects are present of which
the location is to be monitored. These include normally stationary
objects 7-9 for instance paintings, stationary CRT displays,
projectors etc. and objects 10-13 which are moved regularly, such
as notebook computers, portable projectors, portable medical
instruments, trolleys etc. To each of these objects 7-13, a
transponder tag 14-20 is attached.
[0041] The tags are further described with reference to FIG. 2. The
tag shown in FIG. 2 is a universal tag which can be used for
monitoring normally stationary objects, but which can also be used
for monitoring normally mobile objects. As is explained below in
more detail, if it is not required that tags can be used for
monitoring both mobile and stationary items, some of the features
of this tag can be dispensed with.
[0042] The tag has a receiver 21 with an antenna 22 for receiving
the activation signal from one of the transmitter stations 2-6 when
in the operating area 23-27 of that transmitter station 2-6 and a
transmitter 28 with an antenna 29. The transmitter 28 communicates
with the receiver 21 via a data processor 30 for activation of the
transmitter 28 to transmit a reaction signal in response to receipt
of an activation signal by the receiver 21. The tag further
includes a memory 31, preferably in the form of a flash memory, for
storing settings of the tag such as its identification code, which
memory 31 communicates with the processor 30. The tag further
includes a tamper sensor 32 and a motion sensor 33 which also
communicate with the data processor 30 and an acoustic device 34
such as a buzzer or a piezo electric beeper connected to the data
processor for generating an alarm signal under control of the data
processor. Furthermore a battery 35 is provided for feeding the
circuit of the tag including the above-described units.
[0043] Depending on the object onto which the tag is to be
attached, the memory 31 can be programmed differently. If the tag
is to be attached to a stationary object, the memory can for
example be programmed such that the data processor activates the
acoustic device 34 and the transmitter 28 in response to a signal
from the motion detector 33 signalling motion of the tag. If the
tag is to be attached to an object of which the normal use involves
at least occasional movement of that object, the memory 31 can be
programmed such that the data processor 30 disregards signals from
the motion detector 33 or only to activate the receiver 21 in
response to motion from the motion detector 33. The motion detector
33 can also be left out if the tag is to be attached to regularly
moved objects only. The acoustic device 34 can also be left out if
acoustic alarm is not desired. Conversely, the receiver 21 and the
associated antenna 22 can be left out if only movement of the
object and tampering with the tag needs to be detected and
transmission of a reaction signal in response to presence in one of
the operating areas 23-27 is not required.
[0044] The operating areas 23-27 of the transmitter stations 2-6 in
which tags 14-20, when located in such an area, are activated to
transmit a reaction signal are spatially distributed.
[0045] For receiving the reaction signals transmitted by the tags
14-20, a receiver station 36 with an antenna 37 is provided. The
receiver station 36 is connected to a network via a network
interface unit 37. One of the transmitter stations 6 is also
connected to the network interface unit 37. The communication
between the network interface unit 37, the receiver 36 and the
transmitter 6 can for instance be set up in accordance with the
RS(EIA)-485 standard. According to this example, the network to
which the network interface unit is connected is a TCP/IP network.
Via this network, the network interface unit 37 communicates with a
server 38 which forms a data registration structure communicating
for registering data representing positions of tags in accordance
with the reaction signals received from the receiver station 36. A
user interface of the tracing system is formed by a client computer
system 39 also connected to the TCP/IP network and allowing access
to programs and data of the tracing system for an operator logged
in as a user having the required permissions. To such a network
typically also other client computers will be connected in which
can each provide access to programs and data of the tracing system
for an operator logged in as a user having the required
permissions, unless the programs of the tracing systems are set to
communicate only to one or more selected client computer
systems.
[0046] The transmitter stations 2-6 are each adapted for including
a predetermined transmitter station code in the activation signal.
In FIG. 1 exemplary transmitter station codes are each indicated by
a three-digit number adjacent the transmitter stations 2-6. The
transmitter station codes of the transmitter stations 2-6 are
mutually different and mutually distinguishing activation signals
from each of the transmitter stations 2-6 from activation signals
from the other transmitter stations 2-6. If it is not necessary to
distinguish between tags in the operating area of one of the
transmitter stations and tags in an operating area of another one
of the transmitter stations, it is also possible to provide that
two or more of the transmitter stations have the same transmitter
station code.
[0047] The tags 14-20 are each adapted for receiving transmitter
station codes in the received activation signal and for including
the transmitter station code of the activation signal that caused
the reaction signal to be transmitted in the reaction signal
transmitted by that tag 14-20. If for instance, as is shown in
FIGS. 1 and 2, an activation signal 39 with the code "003" is
received from the transmitter 6 and the tag identity code stored in
the memory 31 of the tag is "008", the tag 20 responds by
transmitting the reaction signal 40 including the codes "008" and
"003". This combination of codes is received by the receiver 36 and
communicated via the network interface unit 37 to the server
38.
[0048] On the central server 38 a computer program is installed
which includes instructions for causing a data registration
structure to read reaction signals inputted from the receiver
station 36 and to register data representing positions of tags
14-20 in accordance with the inputted reaction signals and
instructions for reading transmitter station codes included in the
inputted reaction signals and instructions for registering data
representing positions of tags 14-20 in accordance with transmitter
station codes included in the inputted reaction signals. Thus, in
operation, data 41 representing positions of tags 17, 18, 20 in
cells 24, 25, 27 are stored in accordance with transmitter station
codes received from the tags by the receiver station 36
[0049] By accessing these data via the client computer system 39, a
user can trace where certain tags have been detected most recently
and by maintaining a log of tag detections, movement paths of tags
can also be traced.
[0050] If it is not required to distinguish between certain
objects, for instance because the objects are identical and
interchangeable or because it is sufficient to trace certain types
of objects, it is also possible to provide that some tags contain
and transmit the same tag identity code or even that none of the
tags contains and transmits a tag identity code.
[0051] If it is not required to distinguish between some of the
transmitter stations, it is also possible to provide that some of
the transmitters are set to transmit the same transmitter station
code. This allows for instance to create elongate or other
non-circular cells in which the activation signals are generated by
a plurality of transmitter stations transmitting the same
transmitter station code.
[0052] Settings of the transmitter station codes to be transmitted
can for instance be stored in a non-volatile memory in which data
can be changed using a personal computer to which the card is
temporarily connected.
[0053] Since the transmitter station code is included in the
reaction signal transmitted by a tag and received by a receiver
which can be located outside the operating area of the transmitter
station, communication between the transmitter and the central
control unit 38 is not necessary. This facilitates installation
because the transmitter stations can be installed as stand-alone
units, which do not need to be connected to a communication
network. Furthermore, this allows monitoring changes in the
positions of objects without requiring separate communication
between the central control unit 38 and each of the transmitters
2-6. Accordingly, the signals indicating the presence of tags in
the operating areas of the transmitter stations, which signals need
to be transported with particular urgency to obtain a quick
response, do not increase the communication intensity via the
network.
[0054] In FIG. 1, the border of the operating area is indicated by
reference numeral 41. If objects need to be traced in a
substantially larger area, it is possible to provide more than one
receiver station. However, the positional information regarding the
tags is still derived from the transmitter code included in the
reaction signals transmitted by the tags when present in one of the
cells 23-27.
[0055] For stationary objects like the objects 7-9 it can be
advantageous to generate early warning signals in response to
detection of motion by the motion detector 32 of the tag 14-16
attached to that object. For instance, for costly objects which
should not be moved at all, it is important to be warned of any
movement thereof as soon as possible. This can for instance be
achieved by programming the tags in such a manner, that a reaction
signal is also transmitted in response to movement of the tag.
Instead of the transmitter station code, the code added to the tag
identity code is then preferably a code representing detection of
motion by the motion detector 33. The same principle can be applied
to detection of tampering by the tamper detector 32. The server is
then preferably programmed to cause generation of a warning signal
at the client computer system 39 in response to any reaction signal
including the motion or tamper code. It is a particular advantage
of the shown system that data relating to the detected position and
to detected occurrences such as movement and tampering can be
received and processed via the same receiver independent of the
actual position of the object in the monitored area (in this
example the building 1).
[0056] As is illustrated by FIGS. 3 and 4, generation of warning
signals is preferably controlled by comparing the reaction signal
received by the receiver station 36 (or at least one of the
receiver stations if there are more receiver stations 36) with a
predetermined warning condition. To this end, the codes included in
the signal are first read (step 42), then the read codes are
checked against not allowed combinations (step 43). An example of
some not allowed combinations is shown in the table in FIG. 4.
According to this table, any reaction signal including tag identity
code 001 or 003 causes a warning signal to be generated. The tag
identity codes 002 and 004 associated to regularly mobile objects
11, 12 do not cause generation of a warning signal unless combined
with front door transmitter station code 003. Accordingly, it is
also possible to provide for the generation of warning signals for
certain tags of which movement is allowed, but which are not
allowed to leave the room or not allowed to enter certain areas
(for instance apparatus sensitive to humidity should not be brought
into a swimming pool area). If the combination tag and transmitter
station codes is not allowed and a warning signal is generated
(step 44), it is also checked whether, in addition to a warning
signal, an alarm signal should be generated by activating acoustic
device 34 (step 45). This can for instance be determined by
comparing the received combination of tag code and transmitter
station code with another set of data. In the example shown in FIG.
1, such combinations can only include the transmitter station code
"003" of the front door transmitter station 6, because this
transmitter station 6 is the only transmitter station connected to
the central server 38 for receiving commands causing the
transmitter station to transmit a signal which activates the
acoustic device of any tag in the operating area 27 of that
transmitter 6. If the combination of received codes is found to
match the data defining the acoustic alarm condition, the central
server 38 activates the transmitter 6 to transmit an acoustic alarm
command signal and the tag in the operating area of that
transmitter 6 is caused to generate an acoustic alarm (step 46),
preferably for a minimum duration of time independent of the
subsequent location of the tag.
[0057] Independent of generation of any warning or alarm signals,
any received combination of tag and activator codes is stored in a
log (step 47) preferably in combination with time and date. This
also applies to any warnings and alarms, which have been generated
(step 48).
[0058] In order to obtain a quick response to occurrence of a
warning or alarm condition, the processing of signals received by
receiver station 36 into warning signals and alarm signals is
preferably carried out in real-time, i.e. in closely timed relation
to the receipt of the respective signals. To achieve this, a
continuously active service process interrogating the receiver
station 36 or a port connected thereto can be provided.
[0059] Control of the tags to generate acoustic or other alarm
signals by the central server via a transmitter connected thereto
is advantageous, because it allows central control over alarm
conditions which should cause tags to generate alarm signals.
However, it is also possible to program the tags to determine in
response to which conditions alarm signals should be generated by
the tag, for instance in response to motion and/or in response to
activation signals including pre-selected transmitter station
codes. Alternatively, it is also possible to program a stand-alone
transmitter station to include alarm instructions including one or
more tag identity codes in the activation signal and causing only
tags having the same tag identity code or codes to generate an
alarm signal when activated in the operating area of that
transmitter station.
[0060] The system shown in FIG. 1 also includes a number of
personal identity tags 49, 50, 51, 52 to be worn by persons in the
building 1, which tags may for instance have the same structure as
the tag shown in FIG. 2. In accordance with the field of
application it may or may not be preferable to include tamper
sensors, motion detectors and acoustic alarms in such tags. Thus,
the shown system also allows tracing the location of persons.
[0061] One particularly advantageous application of such tags is
that they allow modifying or suppressing warning signals if a
predetermined personal (tag) identity code is determined within a
predetermined time period and in combination with the same
transmitter station code as the transmitter station code included
in the signal matching the warning condition. This allows for
instance to distinguish a situation in which an object is carried
through an operating area of a transmitter station by a person
authorized to do so from a situation in which the same object is
carried through the same operating area by a person not authorized
to do so.
[0062] Furthermore, associating the detection of personal identity
codes in an operating area to the detection of tag identity codes
in the same operating area within the same limited time frame
allows to establish which person was last detected in combination
with an object, which may be helpful for finding back the object in
the event tracing alone does not lead to this result.
[0063] According to the present example, the operating areas 23-27
of the transmitter stations 2-6 are spatially separated from each
other. This brings about the advantage that the tags are not
activated when they are located in most areas of the building and
that the tags are activated only when they are located in some
limited areas in the building 1 covered by the transmitter
stations. Thus, the tags are activated only when present in
selected areas of the building 1, which contributes to reducing
energy consumption of the tags and reducing the intensity of
communication. Furthermore, the likelihood of disturbance of other
similar systems operating independent of the shown system is
reduced due to the relatively small operating ranges of the
transmitter stations.
[0064] Preferably, the transmitter stations send activation signals
at a LF frequency of for instance 8.9 kHz and preferably the tags
send reaction signals at a frequency in the UHF range, for instance
433 MHz and more preferably, 868 MHz. UHF frequencies higher than
600 to 700 MHz are advantageous because of relatively little
sensitivity to disturbance and the possibility of using a
relatively small antenna in both the tags and the receiver
stations. Smaller antennas are more suitable for integration in
housings, which is favourable for counteracting damage and sabotage
of the antennas.
[0065] That the operating area of the receiver station 36 includes
the operating areas 23-27 of a plurality of the transmitter
stations 2-6 also enhances the ease of installation of the proposed
system, because only a limited number of receiver stations 36 need
to be installed. This is particularly advantageous because the
receiver stations are to be connected for communication with the
central control station. To limit the number of receiver stations
36 and to obtain a relatively low density of operating areas of the
transmitter stations 2-6 in which the tags 14-20 are activated, the
operating range within which the receiver station 36 is capable of
receiving reaction signals from the tags 14-20 is preferably at
least three, and more preferably at least four or at least five
times as large as the operating range within which the tags 14-20
are activated by the transmitter stations 2-6. Furthermore, the
operating range of the transmitter stations is preferably
adjustable, for instance from 2-6 meters, to accommodate the
operating area to the situation where the passage of objects is to
be monitored.
[0066] According to the present example, the tagged objects 7-13
are each located in an enclosed area, the enclosure of the area
having a passage 5357 allowing entry and exit of the objects. The
operating areas 23-27 of the transmitter stations 2-6 each include
one of the passages 53-57. By including a entry and exit passage of
an enclosed area in a monitored operating area of a transmitter,
tracing of objects in a relatively large area is made possible with
reasonable certainty by monitoring only relatively small areas
including the entry and exit passage of that area. In conjunction
with the present system, this also provides the advantage that the
tags are in principle only activated when entering or leaving the
enclosed area, so that energy consumption of the tags and
communication intensity are further reduced. In turn, the rare
activation and relatively low communication intensity allow the use
of tags having transmitters with a large operating range without
causing too much interfering signals and without undue reduction of
battery life.
[0067] For quick inventory of missing objects and/or inoperative
tags an activation signal receivable by any tag in a monitoring
area can be transmitted and, reaction signals received in response
to the activation signal can be registered and compared with
registered data representing tags in the monitoring area. Then, if
data representing tags in the monitoring area are not matched by
any of the registered reaction signals, a warning signal is
generated indicated that the tag is either missing or inoperative,
for instance due to the battery being empty or due to damage to the
tag. The signal in the monitoring area can for instance be
generated by portable transmitter or by a strong central
transmitter.
[0068] Within the framework of the present invention many other
embodiments than the above-described examples are conceivable. For
instance, instead of sending the reaction signals directly to the
receiver station or stations, it is also possible to use one or
more relay stations for receiving and retransmitting reaction
signals to increase the effective operating area of a receiver
station.
* * * * *