Title: Device for locating trapped victims and a method of operating such a device
Abstract: A locating device, particularly for locating trapped victims under avalanches, under debris or under collapsed buildings, equipped with a receiving unit (6-13) for signals from transmitters and preferably a transmitter (13, 14), as well as optical (6) and/or acoustic (12) display units, whereby the receiving unit is connected to three preferably orthogonally arranged ferrite rod antennas (2, 3, 4). All antennas (2, 3, 4) are disposed in a compact housing (1) together with the receiving unit (6-13) and preferably also the transmitter (13, 14) to ensure accurate locating of the trapped victim across the largest range possible at compact design whereby one antenna (4) is of substantially shorter length than the two other antennas (2, 3). The receiving unit is provided with a DSP module (11) for incoming signals of the antennas (2, 3, 4).
Patent Number: 6,960,996 Issued on 11/01/2005 to Sackl
| Inventors:
|
Sackl; Rudolf (Deutschlandsberg, AT)
|
| Assignee:
|
Seidel Elektronik GmbH NFG. KG (Deutschlandsberg, AT)
|
| Appl. No.:
|
755669 |
| Filed:
|
January 13, 2004 |
Foreign Application Priority Data
| Jan 15, 2003[AT] | A 47/2003 |
| Current U.S. Class: |
340/539.11; 340/539.13; 340/539.21; 340/539.23; 340/573.1 |
| Intern'l Class: |
G08B 001/08 |
| Field of Search: |
340/5391,539.11,539.13,539.21,539.23,573.1,573.5,573.7
342/22,27,51
343/760
455/92,100
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Trieu; Van T.
Attorney, Agent or Firm: Dykema Gossett PLLC
Claims
1. A locating device, particularly for locating trapped victims under avalanches,
under debris or under collapsed buildings, comprising a receiving unit for signals
from transmitters, a transmitter connected to three orthogonally arranged rod antennas,
optical and/or acoustic display units, wherein all antennas are placed in a compact
housing together with the receiving unit and also a transmitter whereby one antenna
is of shorter length than the other two antennas.
2. A locating device according to claim 1, wherein the antenna of shorter length
is maximally half as long as a longest antenna of the locating device.
3. A locating device according to claim 2, wherein the antenna of shorter length
is about one quarter the length of the longest antenna.
4. A locating device according to claim 1, wherein the receiving unit is provided
with a DSP module (digital signal processor module) for incoming signals of the antennas.
5. A locating device according to claim 4, wherein the receiving unit includes
a subassembly for the transformation of incoming signals by way of fast Fourier
transformation whereby said subassembly is integrated in the DSP module.
6. A locating device according to claim 1, wherein additional components selected
from the group consisting of altimeter, thermometer and compass are integrated.
7. A method for the operation of a locating device, particularly for locating
trapped victims under avalanches, under debris or under collapsed buildings whereby
incoming signals of one or several transmitters are monitored by a receiving unit,
wherein all received incoming signals are registered over a predetermined period
whereby discriminating characteristics of at least these incoming signals are registered
and whereby the receiving unit can be tuned to one of these incoming signals with
the aid of said characteristics.
8. A method according to claim 7, whereby an entire duration of one period of
the incoming signal is used as discriminating characteristic.
9. A method according to claim 7, whereby a duration of a pulse or the time of
transmission of the incoming signal is used as discriminating characteristic.
10. A method according to claim 7, whereby a duration of pause of the incoming
signal is used as discriminating characteristic.
11. A method according to claim 7, whereby signal strength or amplitude of the
incoming signal is used as discriminating characteristic.
12. A method according to claim 7, whereby a frequency of the incoming signal
is used as discriminating characteristic.
13. A method according to claim 7, whereby previously monitored incoming signals
are filtered out subsequent to reception of incoming control signals in the receiving unit.
14. A method according to claim 13, whereby the receiving unit is advantageously
tuned to the remaining incoming signals with the aid of discriminating characteristic.
15. A method according to claim 7, whereby the characteristic of signals is determined
by means of fast Fourier transformation.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a locating device, particularly for locating
trapped victims under avalanches, under debris or under collapsed buildings, including
a receiving unit for signals from transmitters, preferably a transmitter connected
to three preferably orthogonally arranged ferrite rod antennas, optical and/or
acoustic display units, as well as a method for the operation of a locating device,
particularly for locating trapped victims under avalanches, under debris or under
collapsed buildings, whereby incoming signals of one or several transmitters are
monitored by a receiving unit.
2. The Prior Art
Current portable devices for locating trapped victims are equipped with devices
to detect and display the magnitude and possibly the direction of the magnetic
field strength of a transmitter. This displayed information is used to advance
toward the trapped victim along field lines. In most cases, one or two ferrite
receiving antennas are provided for this purpose which are mounted in a common
housing together with the processing electronics and the display devices whereby
the possible rod length limits the range of transmission and whereby accurate point
locating is also made difficult in the case of two antennas. The rescuer may reach
positions during the search for a point location at which the field strength is
oriented completely vertical and at which the horizontal plane equals zero. Inexperienced
rescuers cannot determine the exact location of the trapped victim in this case.
In such cases, even devices with a "virtual" antenna are useless as described,
for example, in EP 0 855 600 A2. Otherwise, devices having three identical, preferably
orthogonally oriented actual antennas, as disclosed in EP 0 733 916 A2, for example,
are too bulky and unmanageable or they have too short of a range for a meaningful
search while being designed of small dimensions.
The object of the present invention was therefore to provide a device of the
aforementioned type which makes possible, in a simple manner, locating of a trapped
victim at a range as large as possible without being susceptible to operational
errors and which is nevertheless dimensioned in such a compact manner that is does
not restrict the movement of the operator during the search, and whereby it can
be carried along during other activities. An additional object of the invention
was a method to operate a device of the aforementioned type with which locating
of several trapped victims is possible in succession in a simple and reliable manner.
SUMMARY OF THE INVENTION
It is proposed for the achievement of the first object that all antennas are
placed
in a compact housing together with the receiving unit and preferably also a transmitter
whereby one antenna is of shorter length than the other two antennas. This short
third antenna is sufficient to make three-dimensional position-finding of the transmitter
possible at close range and not confuse the rescuer at the positions with vertical
field orientation but to guide him directly to a specific location where the trapped
victim is located. In addition, this antenna contributes to the increase of signal
strength of the incoming signal at close range.
According to a preferred embodiment of the inventive device, it is advantageously
proposed that the shortest antenna is maximally half as long as the longest antenna
of the locating device, preferably approximately one quarter-length of the longest antenna.
The receiving unit is provided with a DSP module (digital signal processor module)
for incoming signals of the antennas according to an additional characteristic
of the invention. The incoming signal is very weak and hardly noticeable because
of noise interference at some distance from the trapped victim. The extremely weak
transmission signal can be recognized within the noisy incoming signal by means
of a digital signal processor and its range can be considerably increased thereby.
It is advantageously proposed thereby that the receiving unit includes a subassembly
for the transformation of incoming signals by way of fast Fourier transformation
whereby the subassembly is preferably integrated in the DSP module.
According to an additional characteristic of the invention, additional
components such as preferably an altimeter, thermometer or compass may be integrated,
which can give a rescuer additional information during the course of the rescue action.
The secondly cited object is achieved according to the invention in that all
received incoming signals are registered over a predetermined period whereby discriminating
characteristics of at least these incoming signals are registered and whereby the
receiving unit can be tuned to one of these incoming with the aid of the characteristics.
A reliable and rapid search is made possible through these characteristics even
in the case of several trapped victims located within the receiving range so that
the rescuer will not be confused by the high number of incoming signals. The recognition
of several transmitters and the determination of the number of transmitters is
made possible based on the standardized signal characteristic of the avalanche
victim locating device whose transmitters transmit typically at 100 milliseconds
at a constant transmission frequency and which subsequently pauses for at least
400 milliseconds. If a transmitted signal is received within the defined pause,
or if the received pulse surpasses a specific time range, or if the pulses have
a highly different amplitude, then these are indicators for the presence of more
than one transmitter in the receiving range of the device of the rescuer. Small
discriminating signal characteristics exist for different transmitters based on
the predetermined tolerance of the transmitter, and based on these differences,
the receiver recognizes which signal pulses come from which specific transmitter.
Characteristics for transmitter identification can be the entire duration of one
period, time of transmission, length of pauses, amplitude or transmission frequency.
The receiver selects now a transmitter automatically or upon confirmation by the
user, which means the receiver synchronizes to this one specific transmitter.
Furthermore, it can be proposed that the receiver identifies the number
of additionally existing transmitters of the trapped victims.
It is advantageously proposed thereby that the signal strength or amplitude of
the incoming signal is used as discriminating characteristic. This quantity can
be determined very simply and it allows rapid tuning of the device to a specific
incoming signal.
Since there are always differences between the individual transmitters, in
spite of general determination of the signal characteristic, based on tolerance
and other influences on the transmitters, and on the transmitting signals as well,
there can be used as discriminating characteristic the duration of the pulse or
the time of transmission of the incoming signal according to an additional or alternative
embodiment of the method.
The same applies also to the frequency of the signals, which are set at 457 kHz
according to standards; however, from the set value occur small deviation as well
so that the frequency of the incoming signal can also be used as discriminating characteristic.
According to an additional characteristic of the invention, a reliable
search for one of the additionally existing transmitters can be initiated, after
successfully locating the transmitter of the monitored incoming signal, if the
previously monitored incoming signals are filtered out subsequent to the reception
of incoming control signals in the receiving unit. The device can be switched by
the rescuer in such a manner that the signal with the currently synchronized characteristic
is filtered out so that synchronization to another transmitter is made possible
and thus the search for the next trapped victim is made possible as well.
The receiving unit is thereby advantageously tuned to the remaining incoming
signals with the aid of discriminating characteristic.
According to an additional characteristic of the invention, it is proposed
that the characteristic of signals is preferably determined by means of fast Fourier
transformation with the advantage of optimum signal identification and signal discrimination
in case of several existing transmitters, which means, during the search for multiple
trapped victims.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in more detail in the following description with
the aid of the accompanying drawings wherein
FIG. 1 shows a schematic front view of an embodiment for the inventive device;
FIG. 2 is a schematic top view onto the device in FIG. 1;
FIG. 3 is a simplified block diagram of the inventive device; and
FIG. 4 illustrates the field line course in case of a horizontally placed transmission antenna.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Three ferrite antennas
2,
3 and
4 are disposed in the
housing
1 of the inventive locating device. The antennas are preferably
orthogonal to one another and of various lengths to make possible the compact traditional
dimensioning of the housing
1 in terms of its shape. The shortest antenna
4 is maximally half as long as the longest antenna
2 of the locating
device, while the two longer antennas
2 and
3 have lengths of approximately
8 cm or 6 cm. The length of antenna
4 is preferably approximately a quarter-length
of the longest antenna
2, which is approximately 2 cm in absolute numbers.
As can seen in FIG. 2, the two longer antennas
2 and
3 lie essentially
parallel to the lateral side or the face of a printed circuit board
5, which
contains receiving and transmitting electronics and on the optical display unit
6 attached to said printed circuit board as well. Symbols are provided on
the display unit
6 that may be triggered to determine direction and distance
to the incoming transmitter, for example, and possibly additional information such
as the presence of other transmitters, temperature, altitude, compass bearing,
battery condition, etc. The presence of additional transmitters can be detected
as described below while other information is added through preferably electronic
units, such as a thermometer, altimeter or compass provided in the device.
The third and shortest antenna
4 extends preferably through a boring in
the printed circuit board
5.
The basic electronic circuit can be seen with the aid of the block diagram of
FIG. 3 in which components are not show for reason of clarity, which are not part
of the invention, and which common components are known to those skilled in the
art. It is obvious, for example, that the symbols for the antenna
2,
3,
4 include naturally the associated resonating circuits and similar components.
The antennas
2,
3,
4 are individually connected to a antenna
selector switch
7, which switches alternately between the antennas
2,
3,
4 during reception of the device and which transmits the signal
of a respective antenna. An amplifier
8 is provided behind the antenna selector
switch
7 from which amplifier
8 the signal reaches a second amplifier
10 via a mixer
9.
One output of the mixer
9 and the output of the amplifier
10 are
connected to the digital signal processor module
11. An audio signal output
unit
12 can be connected directly to said DSP module
11, which consists
of the actual digital signal processor itself and its peripherals, and which is
designed for signal processing by means of fast Fourier transformation (FFT).
However, in each case there is an optical display unit
6 provided,
which is controlled by a micro-controller
13 and the micro-controller
13
is coupled to the DSP module
11 (as already illustrated in FIG.
2).
The micro-controller
13 also controls a switch that connects a preferably
existing transmitting oscillator
14 preferably to the longest antenna
2,
if the device is to be operated in the transmitting mode.
The locating device is normally held parallel to the snow surface O and the field
strength received mainly by the longer antennas
2,
3 increases continuously
while approaching the transmitter. In case of the unfortunate case in which the
transmitting antenna S lies horizontally in the snow (see FIG. 4) then the field
strength increases also continuously while approaching said transmitter; however,
the direction of the field lines turns increasingly from the horizontal direction
to the vertical direction and subsequently horizontal again (directly on top of
the transmission antenna).
For an inexperienced rescuer who holds his receiving device usually in a horizontal
position and whereby the two longer antennas
2 and
3 are also horizontal
relative to the snow surface O, the circumstances are as follows:
- the field strength increases while approaching the transmitter (=the
distance reading on the display 6 decreases),
- the horizontal component of the field becomes smaller and the distance
reading increases again at some time based on the turning of the field lines.
An inexperienced rescuer believes therefore that the trapped victim is located
under the maximum field strength (a minimum of distance reading), whereas an experienced
operator continues to walk a few meters in the original direction to be on the
safe side and to determine if there can be found yet a greater maximum field strength
after the point of decrease in field strength. Should this occur, then rescuers
search and dig there manually by using an avalanche probe.
The field can be measured in a three-dimensional manner with the short third
antenna
4 in the immediate vicinity of the transmitting antenna S since
the transmitter field strength in the immediate vicinity of the transmitter is
so great that the short third antenna
4 can contribute a sufficient signal
component for a three-dimensional representation—it is in the immediate vicinity
of said transmitting antenna S where the problem of the false maximum (minimum)
exists caused by the vertical field lines. The inventive device guides therefore
even an inexperienced user reliably, without operational errors, clearly and directly
to the specific location of the transmitter and thereby also to the trapped victim
(maximum field strength—lowest distance reading).
*
