U.S. patent application number 15/338016 was filed with the patent office on 2017-02-16 for method and device for searching through collapsed ground.
The applicant listed for this patent is Totalfoersvarets Forskningsinstitut. Invention is credited to Staffan ABRAHAMSON.
Application Number | 20170043220 15/338016 |
Document ID | / |
Family ID | 46830973 |
Filed Date | 2017-02-16 |
United States Patent
Application |
20170043220 |
Kind Code |
A1 |
ABRAHAMSON; Staffan |
February 16, 2017 |
METHOD AND DEVICE FOR SEARCHING THROUGH COLLAPSED GROUND
Abstract
The invention relates to a device and a method for determining
whether a living person has been buried in collapsed ground. The
device consists of a rod provided with a receiver unit and a signal
processing unit. The receiver unit is intended to receive reflected
radar signals transmitted form a radar transmitting antenna and
transfer these signals to the signal processing unit. The signal
processing unit which is provided with specific detection units
determines whether the received signal have been Doppler shifted.
By determining this the device can decide whether the Doppler shift
depends on the moving chest of a breathing person buried alive.
Inventors: |
ABRAHAMSON; Staffan;
(Linkoping, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Totalfoersvarets Forskningsinstitut |
Stockholm |
|
SE |
|
|
Family ID: |
46830973 |
Appl. No.: |
15/338016 |
Filed: |
October 28, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14003556 |
Sep 6, 2013 |
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PCT/SE2012/000030 |
Mar 8, 2012 |
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15338016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A63B 2220/802 20130101;
G01S 13/56 20130101; A63B 2230/00 20130101; G01S 13/885 20130101;
A63B 2225/50 20130101; A63B 29/021 20130101 |
International
Class: |
A63B 29/02 20060101
A63B029/02; G01S 13/56 20060101 G01S013/56; G01S 13/88 20060101
G01S013/88 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 11, 2011 |
SE |
1100177-3 |
Claims
1-5. (canceled)
6. A device for receiving and processing signals reflected from
objects in the ground comprising a rod to be inserted into the
ground, a radar information generating unit including an antenna
provided in the rod for transmitting radar signals into the ground,
at least one signal receiving unit provided in the rod for
receiving radar signals reflected from an object in the ground, and
a signal processing unit connected to the at least one signal
receiving unit and containing as units for main detection i) a
band-pass filter that blocks frequencies outside the interval
0.3-10 Hz, ii) a differential detector that continuously compares
the amplitudes of the received signals that have passed the
band-pass filter to determine the derivative of the amplitudes and
determine an absolute value of the derivative, and iii) a
comparator and decision processor unit that compares the absolute
value of the derivative with a threshold value that corresponds to
the background noise in the collapsed ground and decides whether a
reflected signal has been Doppler shifted in a way that is likely
to be by the breathing movement of a buried person.
7. The device according to claim 6, characterized in that the rod
in its length direction is divided into multiple sections, each
section of the rod having thereon the at least one signal receiving
unit connected to the signal processing unit, the sections
corresponding to different length segments of the rod and providing
indication of the ground depth where a moving object has been
detected.
8. The device according to claim 7, characterized in that each
section is radially divided into sectors disposed peripherally
around the rod, each sector carrying the at least one signal
receiving unit connected to the signal processing unit, whereby
signals received by a specific receiving unit are processed to
determine whether a reflected radar signal has been Doppler shifted
and thereby determine whether an object in the ground is moving,
each sector providing information about angular positioning of the
object relative the rod where the Doppler shift was detected.
9. A method for determining the position of a buried moving object
by using a radar transmitting unit and a device according to claim
6, the method comprising the steps of a) inserting the rod into the
ground, b) generating by the radar information generating unit a
radar signal into the ground, c) receiving by the receiving unit
radar signals reflected from an object in the ground and
transferring these signals to the signal processing unit, d)
blocking by the band-pass filter radar signal frequencies outside
0.03-10 Hz and transferring non-blocked radar signals to the
differential detector, e) determining by the differential detector
the derivative of the amplitudes of the received non-blocked radar
signals and an absolute value of this derivative, f) comparing by
the comparator and decision processor the determined absolute value
of the derivative with a threshold value corresponding to
background noise in the ground, and when the determined absolute
value is larger than the threshold value, finding a Doppler shift
is detected that is likely caused by movement of a buried object,
and g) presenting by a presentation unit the finding of the
previous step.
10. The method according to claim 9, further comprising, with the
rod inserted in the ground at different locations, repeating all
the steps at each location, and determining the position of the
buried object by triangulation using the results obtained by
repeating all the steps at the different locations.
Description
[0001] The present invention relates to a receiver for radar
signals and a method that utilize said receiver for searching
collapsed ground with the intention to decide whether people have
been buried in the collapsed masses. More specifically it relates
to a receiver and a method that uses the Doppler shift of
frequencies and wavelengths to identify movement of possibly buried
persons. In one embodiment of the invention it is also possible to
localize the buried person and hence make it easier for the rescue
crew to excavate the person.
BACKGROUND OF THE INVENTION
[0002] The invention primarily relates to a receiver designed to
detect whether persons are buried in collapsed ground. With
collapsed ground is meant anything from house ruins resulting from
i.e. earthquakes or explosions to avalanches. Since it is a matter
of life and death to quickly excavate persons buried in the masses,
all methods that quickly localize the positions to start excavating
are of great interest. During for example avalanches, where large
amounts of snow are swept away, it is increasingly hard to localize
persons if one does not possess techniques that give a first
indication of where to search. Furthermore, the inaccessibility of
the collapsed ground during for example earthquakes is troublesome
for the rescue crew since it is tough to force ones way through the
surroundings. There is a therefore a need for a device that is both
easy to use and give the rescue crew reliable indications whether
persons are buried in the masses. If the device furthermore is able
to indicate the locations of these persons this would also be a
positive feature. A device according to the present invention
provides for all these positive features.
[0003] The device according to the invention consists of at least
one radar generating and radar transmitting means, a receiver
device and a signal processing unit connected to said receiver
device. The task of giving a first indication whether persons are
buried in the masses is performed by means of transmitting a radar
signal into the ground whereby the receiver is designed to receive
the reflected signal. The reflected signal is subsequently analyzed
in the signal processing unit to decide whether there are
persons/moving objects present in the masses. The analyzing step is
searching for Doppler shifts in the received signal. A Doppler
shift is a phenomenon that emerges when a source is moving relative
the signal transmitting device. This movement will lead to shifts
in the received frequencies or wavelengths relative the transmitted
ones. Since Doppler shifts are relevant when an object is moving
relative the signal source, a detection of a Doppler shift in the
received signal will correspond to the fact that an object in the
collapsed ground is moving. The present invention is searching for
those small Doppler shifts that are present when there are minor
movements from the object. The minor movements could, for example,
be movements pertaining to breathing whereby the chest is moving
relative the signal source. Due to the very small relative
movements there is needed a signal processing that is highly
sensitive. The present invention comprises a signal processing unit
with those features.
BACKGROUND ART
[0004] In attacking the problem of detecting persons buried in
collapsed ground it is known to utilize radar. In the known methods
within the technical field it is taught to equip a helicopter with
a radar device, transmit signals into the ground and receive the
reflected signals. These signals are then analyzed to decide
whether the electromagnetic wave has been scattered against a
discontinuity in the ground. One example of such a discontinuity
could be a buried person. One problem with this particular method
is that the discontinuity could be something else rather than a
person. This method is therefore more suited to applications
relating to the searching of snow since it is likely that the snow
is homogenous and that the discontinuity most probably will be
persons buried in the snow. A problem with radar equipped
helicopters aiming to use the Doppler shifts according to the
present invention is that the movement and vibrations of the
helicopter makes it practically impossible to detect small
movements. Also the problematic shielding of the background would
affect it negatively.
[0005] The present invention overcomes these problems by actively
searching for moving objects in the ground and it does not rely on
the ground being homogenous. Furthermore, the relative smallness of
the device allows for the rescue crew to bring it along during a
rescue mission and thus to control where in the area a search shall
be performed. This makes the device an excellent tool for those
cases when it is not possible to use for example radar equipped
helicopters. This could for example be the case during war
situations. All in all the invention provides for a secure and easy
to use system that can be used both as a complement to helicopter
borne systems and by itself on location.
BRIEF DESCRIPTION OF THE COMPONENTS IN THE INVENTION
[0006] Before a more detailed description of the invention is given
we provide a brief review of those components in the invention that
are necessary to be able to detect the small Doppler shifts that,
for example, relates to the heaving of a chest during breathing.
Since breathing movements leads to very small Doppler shifts,
signal processing functions are used that are designed to detect
small changes and discard Doppler shifted signals relating to
movements that cannot be derived from movements of the chest. For
example, Doppler shifts relating to movements of rats. These
particular signal processing functions are referred to as main
detection and supplementary detection and they will be described in
what follows.
[0007] The components and units in the device according to the
invention will be described functionally and we therefore give
short definitions of the terms used.
[0008] With radar transmitting device is intended an antenna and a
microwave unit according to, for example, FIG. 4. This constitutes
a conventional design. The important parameter for the intended
application is that the device can be adapted to transmit radar of
such frequencies that the intended search depth can be reached. In
general a frequency of 300 MHZ to 10 GHz is needed. The chosen
frequency is preferably adapted to the ground conditions in the
area to be searched. The radar transmitting device and the radar
receiving device are preferably fed by a battery with the
possibility to make the device according to the invention wireless.
Alternatively the rod could be connected to a power source by means
of a cable. This could however lead to problems since the cable
could be damaged by, for example, sharp rocks.
[0009] With band-pass filter, which is incorporated in the
receiving device according to claim 1, is intended a device that
filter out certain specific frequencies. In the present case the
incoming signal (that is, the signal that has been reflected from
the buried object) will be filtered so that only Doppler
frequencies will be processed. Usually these frequencies are in the
range 0.03 to 10 Hz.
[0010] With the term detector or differential detector is intended
a for the detection essential signal processing function which is
designed to continuously compare the amplitude of the signal to
obtain a derivative (slope of the curve) that reflects the
frequency change of the signal. With continuously is meant that the
signal is sampled many times during a short time interval, for
example 100 times during a second. It is based on these samplings
that a comparison is done and a derivative is obtained. The
amplitude of the derivative will be zero, positive or negative. To
obtain information about the derivative that is relevant for the
detection, the signal processing unit creates an absolute value of
the derivative. To lessen the influence of fluctuations of the
derivative and possible faults due to multiple Doppler shifts
relative the sampling frequency this particular signal processing
unit is also designed to create a mean value of the absolute value
(usually 2-5 times).
[0011] With a decision processor is intended a signal processing
unit that sets a threshold level in the processor where said
threshold level corresponds to the fact that the background noise
has been exceeded. To ascertain that it is a person that has been
detected the value of the derivative obtained from the detector
shall exceed said threshold level. This level thereby constitutes a
threshold value for a possible detection.
[0012] With presentation device is intended a device that presents
the results of the signal processing for a user. This device could,
for example, constitute a display but it could also be a
presentation based on sound.
[0013] With DFT is intended Discrete Fourier Transform which
transform the incoming signal to the frequency domain. With FFT is
meant Fast Fourier Transform, which constitutes a quick version of
DFT.
[0014] With frequency/amplitude-detector is intended a device that
detects the changes in the frequency or amplitude of the
signal.
DRAWINGS
[0015] FIG. 1 discloses schematically the device during use.
[0016] FIG. 2 discloses schematically how a person's breathing
affects the reflected radar signals.
[0017] FIG. 3 discloses the division of the rod into sections and
also the division into sectors. In the figure two sectors are
disclosed. In an enlarged view of the section, parts of three
sectors are shown. In the second enlarged segment it is
schematically shown how an alarm informs the user about the
direction and at what depth the detection has been made.
[0018] FIG. 4 discloses a version of the antenna and microwave part
for the radar transmitting device according to the invention.
[0019] FIG. 5 discloses a flow chart giving the signal processing
steps for both main detection and supplementary detection, said
steps are used to determine whether the received reflected signals
are Doppler shifted.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
[0020] The invention consists of a rod provided with a receiver
with a corresponding signal processing unit intended to receive
reflected radar signals transmitted from a radar generating and
radar transmitting antenna located in the rod. The receiver
registers the received signals and transfer these signals to a
specific signal processing unit that performs analyzing steps to
determine whether the signals have been Doppler shifted and whether
these Doppler shifts are likely to depend on the movement of the
chest due do the breathing of a living person buried in the
collapsed ground.
[0021] In addition to the device, the invention also relates to a
method for detecting movements within the collapsed ground. The
method utilizes the device according to claim 1 and the claims
dependent upon this claim. The receiver according to the invention
will be described first and after that a description of the method
will follow.
[0022] In a first embodiment the receiver according to the
invention comprises a rod or a pole (1) intended to be brought into
the ground. Within the rod there is provided a radar transmitting
antenna and a receiving device for receiving and registering radar
signals. Said receiving device could be any well-known receiver
adapted to receive radar signals. The receiver provided in the rod
(1) is electronically connected to a signal processing unit to
which said received and registered radar signals are transferred.
The purpose of the signal processing unit is to analyze the
received radar waves to determine whether there has been a Doppler
shift of the signals relative the known transmitted out-signals. As
has been described earlier a Doppler shift would give an indication
that something in the collapsed ground is moving. Since the
possible movement of a person buried in the masses, such as an
avalanche victim, is severely constrained it is essential that the
signal processing unit is capable of detecting the minute movement
relative the radar transmitting device. To fulfill these high
demands the signal processing unit is provided with a band-pass
filter, a differential detector, a comparator and a decision
processor whose combined purpose is to analyze the received signals
and in a quick and secure way determine whether a Doppler shift is
present in the received signals. The signal processing step
according to the above given is referred to as main detection and
constitutes the fundamental signal processing. Further signal
processing steps, referred to as supplementary detection, can also
be used. Said supplementary detection will be described
separately.
[0023] The band-pass filter in the signal processing unit performs
a first sorting of the incoming data in the form of received radar
signals. By adjusting the band-pass filter so that it discards all
signals that are not likely do derive from humans a first reduction
of the in-data is obtained. Those signals that survive this sorting
step are transferred to a differential detector.
[0024] The purpose of the differential detector is to continuously
compare the amplitudes of the signals that have passed the
band-pass filter to create a derivative (slope of the curve) that
represent the change of the received signals. By continuously is
meant that the signal is sampled many times during a short time
interval, for example 100 times per second. It is from these
samplings that a comparison is made and a measure of the derivative
is obtained. The derivative of the amplitude will take the values,
zero, positive or negative. To obtain the information relevant for
the detection about the derivative the signal processing also
creates an absolute value of the derivative. To lessen the
influence of fluctuations of the derivative and possible faults due
to multiples of the Doppler frequencies relative the sampling
frequency is this specific signal processing unit also designed to
create a mean value of this absolute value (usually based on 2-5
samplings). When this is done the corresponding value of the
derivative is transferred to a comparator/decision processor that
compares the obtained value with a threshold value that corresponds
to the background noise in the collapsed ground. If the value of
the derivative obtained from the differential detector is above the
determined threshold value the signal processing unit judges that a
Doppler shift has been detected in the received radar signals. The
signal processing unit can be provided with a presentation device,
for example a display or a sound device that informs the user that
a Doppler shift has been detected. This is the functionality of the
signal processing unit that makes it possible to detect the very
small signal changes that the device according to the invention
pertains to detect.
[0025] In a second embodiment of the receiver according to the
invention reference is made to FIG. 3, in which drawing there is
shown that the rod (1) is divided into sections (2) in the length
direction. It could for example be four sections evenly distributed
along the rod. Each of these sections contains its own designated
radar receiver. Each of these receivers is electronically connected
to a signal processing unit. The functionality of the signal
processing unit is the same as the one described in the first
embodiment. According to the invention each of these sections can
have its own designated signal processing unit, or as an
alternative there can be used a central signal processing units
that processes data from all sections. The purpose of the division
of the rod into sections is to make it possible to search through
different height levels in the collapsed ground when the rod has
been brought into the ground. With four such sections it is
therefore possible to search through four different height levels
in the ground at the same time. It is obviously possible to use
more or fewer sections depending on how sensitive the search shall
be. The function of each of the sections is identical with the
functions described with regard to the first embodiment. The only
difference is that the received radar signals are treated on its
own and therefore yields more information, namely the depth where
the Doppler shift has been detected. If a certain section receives
a signal that is processed by the signal processing unit the signal
processing unit can be designed to inform whether a Doppler shift
has been detected but also that the receiver on this specific
section was the receiver that received the shifted signal. In this
way it is possible to plan the digging based on the depth level
that the buried person was detected. If the depth is substantial
than automated digging means, such as an excavator, might be used
while at a lesser depth the use of a shovel or some other manually
operated tool might be called for to ascertain that the buried
person won't get hurt.
[0026] In a third preferred embodiment of the invention, which
builds upon the sections described above in the second embodiment,
sectors (3) are provided in each of the sections, see FIG. 3. Each
sector is provided with a receiving device connected to a signal
processing unit. Since a section can be provided with a number of
sectors, provided peripherally on the rod, an indication of the
direction of the detection of the Doppler shift can be obtained. By
designing the presentation unit so that said unit provides out-data
in the form of which specific sector in a specific section that
made a detection this particular embodiment provides for three
essential information parts for the rescue crew, namely, that a
Doppler shift has been detected, which indicate a buried person,
the depth where said detection has been made and in what direction
relative the rod that the source of the Doppler shift has been
detected. This substantial information can then be used so that the
rescue crew can optimize the rescue work by digging at the right
place and with appropriate digging tools. The number of sectors
that shall be used in each section is not decisive but if a smaller
number of sectors are used one obviously get a poorer localization
than would be the case if a larger number were used. In FIG. 3
there is shown, in an enlarged view on the right side of the
figure, that 4 sectors are used. This is however only an example.
In the expanded view in FIG. 3 it is schematically shown how an
alarm can be used to show where a living person is located. The
white triangle gives an indication that a Doppler shift
corresponding to the fact that a living person has been detected in
this particular direction.
[0027] Above the so called main detection has performed the signal
receiving and signal processing steps. A separate and parallel
procedure can also be used in all of these embodiments, namely
supplementary detection. Supplementary detection is not necessary
to make the invention work but it provides for a way to obtain a
more reliable procedure to determine Doppler shifts.
[0028] Common method steps for the supplementary detection and the
main detection are the signal receiving as well as the transfer of
the received signal to the signal processing unit. When the signal
has been transferred to the signal processing unit the common step
of band-pass filtering the signals is performed, this to sort out
Doppler shifts that most probably does not derive from a buried but
alive person. Those signal components that thereby remains for
further signal processing steps are mainly resulting from movements
of the chest during breathing.
[0029] The next step during the supplementary detection transforms
the signals to the frequency domain through DFT (FFT). DFT and FFT
stands for Discrete Fourier Transform and Fast Fourier Transform,
respectively, these are well known transforms within the technical
field.
[0030] Based on the transformed signal there is now instead
performed a frequency/amplitude detection. In this step either the
frequency change or the amplitude change of the signal is
determined in pre-set time intervals that correspond to the
breathing frequency of a human being.
[0031] The value obtained during the above given step is then
compared with a threshold value in a decision processor. As
described earlier the threshold value corresponds to a
predetermined value of the background signal. If the value obtained
from the detected frequency or amplitude change is above the
threshold value a Doppler shift is considered to have been
detected, as before.
[0032] As a possible last step in the supplementary detection the
result of the process is transferred to a presentation unit that
informs the user about the result.
[0033] Main detection and supplementary detection can be performed
in parallel on the same signal, see FIG. 5. It is however also
possible to perform the tasks separately for different received
signals.
[0034] When it comes to the design of the rod in the device
according to the present invention it is preferable if the rod is
hollow to allow for the components and units to be embedded into
the rod, which in turn provides a shielding against wearing and
damp and dust. The rod should be made of a material that is
transparent for radar energy. Possible materials could for example
be plastics.
[0035] Besides the above given relating to a device the invention
also pertains to a method for searching collapsed ground for
victims through the use of a device according to the present
invention. The method steps given in point form are: [0036] 1) The
rod in a device according to the present inventions is brought into
the ground that shall be searched for buried victims. [0037] 2) An
antenna provided in the rod generates a radar signal and transmit
it into the collapsed ground. [0038] 3) The receiver according to
the invention receives the radar signals that have been reflected
from objects in the ground. A band-pass filter in the receiver sort
out those frequencies that most probably does not derive from
buried but living humans. The remaining signals are transferred
from the receiver to a signal processing unit. [0039] 4) A
differential detector in the signal processing unit is used to
obtain a measure of the derivative of the received signals. An
absolute value of the derivative is generated by the differential
detector and transferred to a decision processor or a comparator
unit. The decision processor, or comparator unit, compares the
absolute value of the derivative with a pre-set threshold value
corresponding to the value of the background noise in the ground.
If the measure of the absolute value of the derivative exceeds said
threshold value, the decision processor or the comparator unit
transmit information to a presentation unit which informs the user
of the fact that a Doppler shift has been detected, which fact in
turn corresponds to the situation that a detected object is moving
relative the transmitted radar signals. [0040] 5) Based on the
obtained information the digging is commenced to thereby excavate a
possible victim.
[0041] Finally it is possible to further refine the method by
performing the method steps at various different positions. The
data output from the various positions can then be compared to
obtain a better positioning of the buried moving object by means of
triangulation.
* * * * *