Note: Descriptions are shown in the official language in which they were submitted.
Method and device for generating proximity warnings
Technical Field
The invention relates to a method and device
for generating proximity warnings, in particular for use
in a mining environment.
Background Art
Surface mines and similar sites or areas are
generally operated by means of a large number of vehicles
and staff. Some of the vehicles may be exceedingly large,
heavy, and difficult to control.
It has been proposed to use GNSS-devices
(GNSS = global navigation satellite system, such as GPS)
on board of vehicles and other objects, such as cranes,
to generate proximity warnings in order to reduce the
n risk of collisions between vehicles. Such a system is
e.g. described in WO 2004/047047 and it is based on de-
vices mounted to the objects. Each device comprises a
GNSS receiver, a control unit deriving positional data
using the signal of the GNSS receiver, a radio circuit
n for Tair,=0,,gg 4,xnhrig,m of the positional data with the
other devices, and an output device for outputting prox-
imity warnings.
Such systems allow the driver of a vehicle to
obtain information on some of the obstacles nearby.
Disclosure of the Invention
The problem to be solved by the invention is
to provide a method and a monitoring apparatus of a simi-
lar type that enables improved safety and/or positioning
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accuracy, even in situations with poor or absent GNSS re-
ception.
Accordingly, a method for generating a prox-
imity warning on an area (e.g., in a surface mine) is
carried out by a plurality of monitoring devices mounted
on movable objects like vehicles, persons, etc. on said
n area. At least a first monitoring device at a first posi-
tion and a second monitoring device at a second position
each comprises a radio transceiver for transmitting and
receiving radio pulses and position information. It
should be noted here that the radio receiver is not nec-
15 a single device but can comprise a plurality of
physical devices. The first and the second monitoring de-
vices additionally comprise a receiver for a radio based
positioning system such as a GNSS (e.g., GPS, Galileo,
each. The method comprises the following steps:
20 - A determination of a first position of the
first monitoring device and a determination of a second
position of the second monitoring device using the re-
spective receivers for the radio based positioning sys-
tem. The determined second position is then transmitted
25 (advantageously together with a unique identifier of sec-
ond monitoring device) by means of the radio transceiver
of the second monitoring device such that other monitor-
ing devices in range are aware of the second position.
Specifically, the transmitted second position of the sec-
30 ond monitoring device is received by means of the radio
transceiver of the first monitoring device such that the
first monitoring device knows about the second position.
The method comprises further steps of
a) A transmission of a first radio pulse by
35 said radio transceiver of said first monitoring device.
The first radio pulse advantageously comprises a unique
identifier of the first monitoring device. Furthermore,
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this first radio pulse is advantageously a frequency
chirped pulse (i.e., a radio pulse with a frequency modu-
lation over time). Preferred frequencies of the first ra-
dio pulse are in the range between 0.3 and 6 GHz, par-
ticularly in the range between 868 and 928 MHz, in the
range between 2 and 3 GHz, in the range between 2.3 and
2.5 GHz, or in the range between 5 and 6 GHz. Thus, the
signal-to-noise ratio and radio range can be improved,
e.g., also by means of suitable post-processing steps
lo (e.g., correlation algorithms, filtering, etc.).
b) Then, the first radio pulse from the first
monitoring device is received by means of said radio
transceiver of said second monitoring device. Advanta-
geously, suitable post-processing steps such as, e.g.,
filtering, are applied to the received radio pulse as it
is obvious to the person skilled in the art.
c) Then, after processing, the second moni-
toring device transmits a second radio pulse (reply
pulse) by means of its radio transceiver. As discussed
above, the second radio pulse advantageously also com-
prises a unique identifier of the second monitoring de-
vice such that the first monitoring device is aware that
the reply pulse originates from the second monitoring de-
vice. Furthermore, the second radio pulse is advanta-
geously also a frequency chirped pulse. Preferred fre-
quencies of the second radio pulse are in the range be-
tween 0.3 and 6 GHz, particularly in the range between
868 and 928 MHz, in the range between 2 and 3 GHz, in the
range between 2.3 and 2.5 GHz, or in the range between 5
and 6 GHz.
d) Then, the second radio pulse is received
by means of the radio transceiver of the first monitoring
device, and - again - suitable post-processing is advan-
tageously applied to the received radio pulse. As part of
this, coarse (i.e., 20 degrees) relative bearing infor-
mation can be derived, e.g., using at least one direc-
tional antenna. As discussed below, ambiguities in posi-
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tion determinations using, e.g., triangulation methods,
can be resolved.
e) Then, the first monitoring device measures
a first flight time t_TOF of the first and second radio
pulses between the transmission of the first radio pulse
(from its own radio transceiver) and the receiving of
said second radio pulse which originates from the second
monitoring device.
As an alternative to the bidirectional ex-
change of the first and second radio pulses as discussed
above under the steps a) - d), an unidirectional trans-
mission and receiving of a single first radio pulse is
also possible:
a) The second monitoring device transmits a
n first radio pulse by means of its radio transceiver. This
first radio pulse advantageously comprises a unique iden-
tifier of the second monitoring device such that the
first monitoring device is aware that the first radio
pulse originates from the second monitoring device. Fur-
thermore, the first radio pulse is advantageously a fre-
quency chirped pulse. Preferred frequencies of the first
radio pulse are in the range between 0.3 and 6 GHz, par-
ticularly in the range between 868 and 928 MHz, in the
range between 2 and 3 GHz, in the range between 2.3 and
2.5 GHz, or in the range between 5 and 6 Ghz.
b) Then, the first radio pulse is received by
means of the radio transceiver of the first monitoring
device, and - advantageously - suitable post-processing
is applied to the received first radio pulse. As part of
this, coarse (i.e., 20 degrees) relative bearing infor-
mation can be derived, e.g., using at least one direc-
tional antenna. As discussed below, ambiguities in posi-
tion determinations using, e.g., triangulation methods,
can be resolved.
c) Then, the first monitoring device measures
a first flight time t_TOF of the first radio pulse be-
tween the transmission of the first radio pulse (from the
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radio transceiver of the second monitoring device) and
the receiving of said first radio pulse by means of the
first monitoring device's radio transceiver. For this,
the first radio pulse comprises a synchronized timestamp
5 or equivalent time information. The term "synchronized
timestamp" herein relates to a transmission timestamp at-
tached to the radio pulse, wherein clocks of the first
and the second monitoring device are synchronized. Such
synchronized time information/clocks is/are advanta-
io derived by means of the receiver for the radio
based positioning system, e.g., from information trans-
mitted by GPS satellites. As an alternative to transmis-
sion timestamps, the first radio pulse can also be trans-
mitted at a predefined synchronized time between the
first and the second monitoring device. The term "prede-
fined synchronized time" herein relates to a predefined
transmission time of the radio pulse, wherein clocks of
the first and the second monitoring device are synchro-
nized.
In both scenarios, i.e., the bidirectional
radio pulses scenario (ping-pong-scenario) and the unidi-
rectional radio pulse scenario (pong-scenario), the
method comprises the following further steps:
- The first monitoring device derives a first
distance value d12 or a value indicative of this dis-
tance value between said first and said second monitoring
devices, i.e., between the first and the second posi-
tions. This is achieved using
* said measured first flight time t TOF and
advantageously a known response delay of the second moni-
toring device in the ping-pong-scenario as described
above. This known response delay is due to necessary
processing steps in the second monitoring device between
receiving the first radio pulse and transmitting the sec-
ond radio pulse. Thus, the precision of the derivation of
the first distance value d12 can be improved.
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In addition to solely using radio pulse time-
of-flight measurements as discussed above for deriving
the first distance value d12, also
* the determined first position of the first
monitoring device and the received second position of the
second monitoring device are used.
Both distance derivation schemes, i.e., the
position based and the time-of-flight based scheme, are
weighted and combined to improve the precision and/or re-
liability of the derivation of the first distance value
d12. One possibility of deriving the first distance
value is based on the equation:
d12 = w TOF * d TOF + w POS * d POS
with d TOF and d POS being the time-of-flight
based and the position based distance values, respec-
tively, and with w_TOF and w_POS being associated weight-
ing factors with w_TOF + w_POS = 1. The weighting factors
can be fixed or changed on the fly, e.g., based on the
reliability and/or accuracies of the respective position
determinations (see below).
- Then, an, e.g., acoustic, tactile (vibra-
tional), electric shock, or optical proximity warning or
approach warning is issued to, e.g., a driver of a vehi-
cle or an operator of an object as a function of said
first distance value d12. As an example, an acoustic
beeping can be triggered as soon as the first distance
value decreases below a threshold, e.g., 10 or 50 m. An-
other warning can be triggered as soon as, e.g., a cur-
rent approach speed of the first monitoring device and
the second monitoring device would result in an impact in
less than a threshold time, e.g., 4 s.
In an advantageous embodiment, a first posi-
tioning accuracy of the first position of the first moni-
toring device is determined. The positioning accuracy of
the first position as determined by the receiver for the
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radio based positioning system can vary, e.g., due to
changing satellite reception levels and/or signal reflec-
tions. Thus, a reliability level or precision of the de-
termined first position can be assessed.
In another advantageous embodiment, a second
positioning accuracy of the second position of the second
monitoring device is determined. As discussed above, the
positioning accuracy of the second position as determined
by the receiver for the radio based positioning system
3.0 can also vary, e.g., due to changing satellite reception
levels and/or signal reflections. Thus, a reliability
level of precision of the determined second position can
also be assessed. This second positioning accuracy is
then transmitted by means of the radio transceiver of the
second monitoring device. Then, the transmitted second
positioning accuracy is received by the radio transceiver
of the first monitoring device. Thus, the first monitor-
ing device is aware of the accuracy/precision of the sec-
ond position of the second monitoring device.
Then, preferably, the first positioning accu-
racy of the first position and/or the second positioning
accuracy of the second position are used in the step of
deriving the first distance value d_12 between the first
and the second monitoring device. Thus, e.g., the above
described radio-pulse time-of-flight contribution can be
uprated (i.e., its weighting factor is increased) in the
derivation of the first distance value d_12 in a case
when one or both determined positions have a decreased
reliability. In a border case, when the first and/or the
second position cannot be determined at all, e.g., due to
a lack of satellite reception, a fallback to solely using
the time-of-flight based distance value derivation is
also possible (i.e., with w_TOF = 1 in the above exam-
ple). This improves the reliability of the proximity
warning generation method.
In another advantageous embodiment, the prox-
imity warning issued by, e.g., the first monitoring de-
8
vice, comprises the second position of the second moni-
toring device. Then, an operator of a machine who re-
ceives the proximity warning is aware of the position of
the second monitoring device and can take suitable ac-
tion. Thus, the overall safety is increased.
In an advantageous embodiment, the derived
first distance value d_12 between the first and the sec-
ond monitoring devices is transmitted to all or selected
other monitoring devices in range, such that these moni-
n toring devices are aware of the distance value d_12 be-
tween the first and the second monitoring devices. Thus,
a more complete "picture" of the spatial distribution of
the monitoring devices on the area is derivable. Advanta-
geously, using additional positional data from the re-
m ceiver(s) for said radio based positioning system and,
e.g., triangulation methods (see below), also position
information of monitoring devices without a receiver for
the radio based positioning system are derivable. Thus,
the overall safety is increased.
20 As another aspect of the invention, a moni-
toring device comprises a radio transceiver for transmit-
ting and for receiving a radio pulse. Furthermore, the
monitoring device comprises an interface (e.g., an acous-
tic, tactile, e.g., vibrating, and/or optical user inter-
25 fa=-e. or - in another embodiment - a computer interface)
for issuing a proximity warning as a function of the de-
rived distance value(s). Furthermore, the monitoring de-
vice comprises an analysis and control unit which is
adapted and structured to carry out the steps of a method
8() as described. Specifically, the analysis and control unit
can comprise a computer program element comprising com-
puter program code means for, when executed by the analy-
sis and control unit, implementing a method for generat-
ing a proximity warning as described.
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According to an aspect of the present
invention there is provided a method for generating a
proximity warning on an area, by means of a plurality of
monitoring devices mounted on movable objects on said
area;
wherein at least a first monitoring device
at a first position (P_1) and a second monitoring device
at a second position (P_2) each comprises a radio
transceiver and a receiver for a radio based positioning
n system;
said method comprising the steps of:
determining said first position (P_1) of
said first monitoring device by means of said receiver
for said radio based positioning system of said first
monitoring device;
determining a first positioning accuracy
of said determined first position (P 1) by means of said
first monitoring device;
determining said second position (P_2) of
said second monitoring device by means of said receiver
for said radio based positioning system of said second
monitoring device;
transmitting said determined second
position (P_2) by means of said radio transceiver of said
n second monitoring device;
receiving said transmitted second position
(P_2) of said second monitoring device by means of said
radio transceiver of said first monitoring device,
and comprising the steps of:
a) transmitting a first radio pulse
(P TOP) by means of said radio transceiver of said first
monitoring device;
b) receiving said first radio pulse
(P TOP) from said first monitoring device by means of
15 said radio transceiver of said second monitoring device;
c) transmitting a second radio pulse
(R TOF) by means of said radio transceiver of said second
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monitoring device;
d) receiving said second radio pulse
(R_TOF) by means of said radio transceiver of said first
monitoring device;
e) measuring by means of said first
monitoring device a first flight time (t TOF) between
said transmitting of said first radio pulse (P TOF) and
said receiving of said second radio pulse (R_TOF),
and wherein the method further comprises
n the steps of:
deriving by means of said first monitoring
device a first distance value (d_12) between said first
and said second monitoring devices using said measured
first flight time (t_TOF) and using said determined first
n position (P_1) of said first monitoring device and using
said first positioning accuracy of said determined first
position (P_1) and using said received second position
(P_2) of said second monitoring device; and
issuing by means of said first monitoring
20 device a proximity warning as a function of said first
distance value (d_12) between said first and said second
monitoring devices.
According to another aspect of the present
2.5 invention there is provided a method for generating a
proximity warning on an area, by means of a plurality of
monitoring devices mounted on movable objects on said
area;
wherein at least a first monitoring device
n at a first position (P_1) and a second monitoring device
at a second position (P_2) each comprises a radio
transceiver and a receiver for a radio based positioning
system;
said method comprising the steps of:
35 determining said first position (P 1) of
said first monitoring device by means of said receiver
for said radio based positioning system of said first
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monitoring device;
determining a first positioning accuracy
of said determined first position (P_1) by means of said
first monitoring device;
determining said second position (P_2) of
said second monitoring device by means of said receiver
for said radio based positioning system of said second
monitoring device;
transmitting said determined second
m position (P_2) by means of said radio transceiver of said
second monitoring device;
receiving said transmitted second position
(P_2) of said second monitoring device by means of said
radio transceiver of said first monitoring device,
and the steps of:
a) transmitting a first radio pulse
(P TOP) by means of said radio transceiver of said second
monitoring device, wherein said first radio pulse (P_TOF)
comprises a synchronized timestamp or wherein said first
n radio pulse (P TOP) is transmitted at a predefined
synchronized time;
b) receiving said first radio pulse
(P TOP) by means of said radio transceiver of said first
monitoring device;
c) measuring by means of said first
monitoring device a first flight time (t_TOF) between
said transmitting of said first radio pulse (P_TOF) and
said receiving of said first radio pulse (P_TOF);
and wherein the method further comprises
BO the steps of:
deriving by means of said first monitoring
device a first distance value (d_12) between said first
and said second monitoring devices using said measured
first flight time (t TOP) and using said determined first
m position (P_1) of said first monitoring device and using
said first positioning accuracy of said determined first
position and using said received second position (P_2) of
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said second monitoring device; and
issuing by means of said first monitoring
device a proximity warning as a function of said first
distance value (d_12) between said first and said second
monitoring devices.
According to a further aspect of the
present invention there is provided a monitoring device
comprising:
a radio transceiver for transmitting and
receiving a radio pulse (P_TOF, R_TOF);
an interface for issuing a proximity
warning; and
an analysis and control unit adapted and
m structured to carry out the steps of a method as
described herein.
According to a further aspect of the
present invention there is provided a computer readable
medium on which is stored computer program code means
for, when executed by a processing unit, implementing a
method as described herein.
According to a further aspect of the
n present invention there is provided a computer readable
medium as described herein, wherein the computer program
code means is executable by an analysis and control unit.
According to a further aspect of the
n present invention there is provided an apparatus
comprising:
a processing unit configured to perform a
method as described herein.
35 Note:
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The described embodiments and/or features
similarly pertain to both the apparatuses and the meth-
ods. Synergetic effects may arise from different combina-
tions of these embodiments and/or features although they
might not be described in detail.
Brief Description of the Drawings
The invention and its embodiments will be
more fully appreciated by reference to the following de-
tailed description of presently preferred but nonetheless
illustrative embodiments in accordance with the present
invention when taken in conjunction with the accompanying
n drawings.
Fig. 1 schematically shows a surface mine 100
with a monitoring apparatus comprising three monitoring
devices 1,2,3,
fig. 2 shows a monitoring apparatus 1,2,3
n comprising a radio transceiver 10, an interface 5, an op-
tional receiver for a radio based positioning system 20,
and an analysis and control unit 6.
25 Modes for Carrying Cut the Invention
Definitions:
A "movable object" is any object that can
change and is expected to change its position and/or ori-
30 entation or configuration in space. It may e.g. be a
truck or any other vehicle that moves from place to place
and changes its orientation in respect to the general
north-south direction, e.g., by steering, or it may be an
object positioned at a fixed location but able to rotate
35 about its axis or to change its physical configuration,
e.g. by extending an gripper or shovel, in such a manner
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that The volume of safety space attributed to it varies
in significant manner.
The term GNSS stands for -Global Navigation
Satellite System" and encompasses all satellite 16 based
5 navigation systems, including GPS and Galileo.
The term "radio based positioning system"
stands for a GNSS or for any other type of positioning
system using radio signals, such as a pseudolite system.
The term "monitoring apparatus" as used here-
10 in designates an assembly of monitoring devices distrib-
uted over several locations, with the single monitoring
devices communicating with each other as described. Some
of the monitoring devices are installed on movable ob-
jects while others may be installed at fixed locations,
e.g., fixed obstacles.
The term "mounting a device to a person" can
be understood as affixing the monitoring device to the
person in such a manner that the person will carry it
without requiring the use of his/her hands. For example,
the term expresses that the monitoring device is affixed
to a piece of clothing or equipment, such as a belt or a
helmet, that the person is wearing.
The area:
Fig. 1 schematically depicts an area, such as
a surface mine 100, to be monitored by the present sys-
tem. Typically, such a site covers a large area, in the
case of a surface mine, e.g., in the range of several
square kilometers, with a network of roads (bold lines)
and other traffic ways, such as rails. A plurality of ob-
jects is present in the mine, such as:
- Large vehicles, such as haul trucks 40,
cranes, or diggers. Vehicles of this type may easily
weigh several 100 tons, and they are generally difficult
to control, have very large braking distances, and a
large number of blind spots that the vehicle operator is
unable to visually monitor without monitoring cameras.
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- Medium sized vehicles, such as regular
trucks 50. These vehicles are easier to control, but they
still have several blind spots and require a skilled
driver.
- Small vehicles. Typically, vehicles of this
type weigh 3 tons or less. They comprise passenger vehi-
cles and small lorries.
- Trains.
- Individual persons 8, in particular pedes-
A further type of object within the mine is
comprised of stationary obstacles, such as temporary or
permanent buildings, open pits, boulders, non-movable ex-
cavators, stationary cranes, deposits, etc.
The risk of accidents in such an environment
is high, specifically under adverse conditions as bad
weather, during night shifts, etc. In particular, the
large sized vehicles can easily collide with other vehi-
cles, or obstacles.
For this reason, the mine is equipped with a
monitoring apparatus comprising a plurality of monitoring
devices 1,2,3 that allows to generate proximity warnings
for the personnel of the site, thereby reducing the risk
of collisions and accidents.
The monitoring apparatus:
Basically, the monitoring apparatus comprises
a plurality of monitoring devices 1,2,3 that are affixed
to fixed objects and/or movable objects and/or persons.
Specifically, monitoring device 1 is affixed to haul
truck 40 which is at position P_1, monitoring device 2 is
affixed to truck 50 which is at position P_2, and moni-
toring device 3 is affixed to person 8 who is at position
P3. These components communicate in a wireless manner,
in particular by radio signals by means of integrated ra-
dio transceivers 10. They are described in more detail in
the following sections.
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In addition, the monitoring apparatus can
comprise a central server (not shown), whose role is also
explained below.
The monitoring devices:
As stated above, the monitoring devices 1,2,3
are affixed to different objects in the area.
In general, the larger the number of in-
stalled monitoring devices 1,2,3, the higher the safety
,o level.
The monitoring devices 1,2,3 comprise an
analysis and control unit 6, such as a microprocessor
system, which controls the operations of the monitoring
device and the communication with the other monitoring
is devices.
The monitoring devices 1,2,3 further comprise
a radio transceiver 10 comprising a first and a second
transceiver unit. The second transceiver unit comprises a
digital transceiver for exchanging digital data such as
20 position information, positioning accuracies, distance
values, etc. with other monitoring devices 1,2,3. Due to
the digitally exchanged signals, error detection/ correc-
tion algorithms can be used which increase the reliabil-
ity of the data exchange. The radio transceiver 10, spe-
25 cifically its first transceiver unit, is also adapted to
transmit and receive time-of-flight radio pulses and op-
tionally timestamp information. By measuring a flight
time of these radio pulses (e.g., first pulse P_TOF from
first monitoring device 1 to second monitoring device 2,
30 reply pulse R_TOF from second monitoring device 2 to
first monitoring device 1) between two monitoring devices
1,2, a first distance value d_12 of a distance between
the two monitoring devices, i.e., between the first posi-
tion P1 of the first monitoring device 1 and the second
35 position P__.2 of the second monitoring device 2 can be de-
rived (dotted line and dotted circle segment).
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The monitoring devices 1,2 further comprises
a GNSS receiver 20. Although it is called a GNSS receiver
in the following, it can also he a receiver interoper-
ating with any other radio based positioning system for
determining its position. The present invention can be
used on various types of radio based positioning systems.
Control unit 6 accesses a memory (e.g., RAM,
ROM) that comprises programs as well as various parame-
ters, such as a unique identifiers of the monitoring de-
vices which is transmitted with each message over the ra-
dio transceiver. Thus, the identity or origin of the
transmitted signals can be determined.
An interface 5, here, an acoustic and optical
user interface 5 advantageously comprises an optical dis-
1,5 play 22 as well as an acoustic signal source 23, such as
a loudspeaker. Furthermore, a tactile interface such as a
vibrating unit (not shown) for alerting a user can be
comprised in the interface 5.
The primary purpose of monitoring device
1,2,3 is to generate proximity warnings or approach warn-
ings in case that there is a danger of collision between
two or more objects. This is achieved by a two-step ap-
proach:
a) By receiving position signals through GNSS
receiver 20, a position of the respective monitoring de-
vice(s) is determined. This position(s) is or are advan-
tageously transmitted by means of the radio transceiver
10 to all the other monitoring devices 1,2,3 that are in
range such that all monitoring devices 1,2,3 are aware of
the respective positions, velocities, and probabilities
for collisions.
b) By deriving distance values (e.g., d_12)
between the monitoring devices 1,2,3 using position based
and time-of-flight based measurements of radio pulses
that are exchanged between the two monitoring devices.
Again, advantageously, the distance values are exchanged
with other monitoring devices 1,2,3 in order to calculate
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relative positions, velocities, and probabilities for
collisions. The method for calculating relative positions
is described in the next section, while further informa-
tion about various aspects of the monitoring device fol-
lows later.
The advantage of using such a two-step ap-
proach is that proximity warnings or approach warnings
can also be issued in a case where one or more of the
monitoring devices 1,2,3 do not or only have poor GNSS
reception and thus positioning accuracy and/or where one
or more of the monitoring devices 1,2,3 are not equipped
with a GNSS receiver 20.
In an advantageous embodiment, monitoring de-
vice 1,2,3 can also comprises an acceleration detector
(not shown here). Acceleration values can also be trans-
mitted by means of the radio transceiver 10. This accel-
eration detector can be used to reduce the energy con-
sumption of the monitoring device. Since GNSS receiver 20
is one of the major power drains, GNSS receiver 20 can
have a "disabled mode" where it is not operating and an
"enabled mode" where it is operating. When analysis and
control unit 6 detects an acceleration by means of the
acceleration detector, it puts GNSS receiver 20 into its
enabled state to obtain the current position of the moni-
tering device. Otherwise, it puts GNSS receiver 20, e.g.,
after a predetermined amount of time, into its disabled
state. In addition to this, to account for the unlikely
event that no acceleration is measured even though the
monitoring device 1,2,3 is moving, control unit 6 can be
adapted to put GNSS receiver 20 into its enabled state at
regular intervals in order to perform sporadic position
measurements.
In addition or alternatively to switching
GNSS receiver 20 between a disabled an enabled state,
other parts of monitoring device 1,2,3 can be switched
between an idle and an active state in response to sig-
nals from the acceleration detector. In general terms,
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monitoring device 1,2,3 can have an "idle state" and an
"active state", wherein, in said idle state, monitoring
device 1,2,3 has a smaller power consumption than in said
active state. Control unit 6 is adapted to put monitoring
5 device 1,2,3 into its active state upon detection of an
acceleration by the acceleration detector, while the
monitoring device is, e.g., brought back to its inactive
state if no acceleration has been detected for a certain
period of time.
10 Monitoring device 1,2,3 advantageously com-
prises a rechargeable battery (not shown) for feeding
power to its components. A battery charger comprises cir-
cuitry for charging the battery. The battery charger can
draw power from at least one power source. Such power
15 sources can, e.g., be
- a power plug for directly connecting moni-
toring device 1,2,3 to an external power supply;
- an inductive coupler comprising a coil
adapted to generate electrical current from an alternat-
ing magnetic field generated by an external primary coil;
such inductive power couplers are known to the skilled
person; and/or
- a solar power supply mounted at the outer
surface of the monitoring device 1,2,3 or in a separate
unit electrically connected to the monitoring device
1,2,3.
Relative position determination:
If all monitoring devices 1,2,3 would have a
GNSS receiver 20, the operation of the monitoring devices
could be basically as in conventional systems of this
type, such as, e.g., described in WO 2004/047047 and need
not be described in detail herein.
In such a simple approach, each monitoring
device 1,2, and 3 would obtain information about its re-
spective position P1, P_2, and P3 derived from a signal
from GNSS receiver 20. This data is stored in a 'device
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status dataset". The device status dataset also contains
a unique identifier 0...e. an identifier unique to each of
the monitoring devices 1,2,3 used on the same area 100).
The device status dataset is then transmitted
s as a digital radio signal through radio transceiver 10.
At the same time, the monitoring device receives the cor-
responding signals from neighboring monitoring devices
and, for each such neighboring monitoring device, it cal-
culates the relative distance d_xy (where x and y denote
n) the index of the involved monitoring devices, e.g., d_12
relates to a distance between monitoring device 1 and
monitoring device 2) by subtracting its own coordinates
from those of the neighboring monitoring device.
In the present invention, however, the den-
15 of the distance values d_xy does not simply rely
on the described position based procedure but also on a
radio pulse flight time approach. Both distance deriva-
tion schemes are weighted and combined as described to
improve the reliability and safety of the system, in per-
20 ticular in situations with poor GNSS reception.
Proximity warnings:
Proximity warnings can be generated by means
of various algorithms. Examples of such algorithms are
25 described in the following.
In a very simple approach, it can be tested
if the absolute value of the relative distance d_xy is
below a given threshold. If yes, a proximity warning can
be issued. This corresponds to the assumption that a cir-
30 cular volume in space is reserved for each object. The
radius of the circular volume attributed to an object
can, e.g., be encoded in its device status dataset.
A more accurate algorithm can, e.g., take
into account not only the relative position, but also the
35 driving velocities and directions of the vehicles.
An improvement of the prediction of colli-
sions can be achieved by storing data indicative of the
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size and/or shape of the object that a monitoring device
1,2,3 is mounted to. This is especially true for large
vehicles, e.g., haul truck 40, which may have non-
negligible dimensions. In a most simple embodiment, a ye-
hide can be modeled to have the same size in all direc-
tions, thereby defining a circle/sphere "covered" by the
vehicle. If these circles or spheres of two vehicles are
predicted to intersect in the near future, a proximity
warning can be issued. It should be noted here that it is
also possible to affix more than one monitoring device to
an object which, e.g., enables the monitoring of orienta-
tions. These multiple monitoring devices on the same ob-
ject would then, e.g., be configured not to exchange
time-of-flight radio pulses with each other.
Instead of modeling an object or vehicle by a
simple circle or sphere, a more refined modeling and
therefore proximity prediction can be achieved by storing
the shape (i.e. the bounds) of the vehicle in the data-
set. In addition, not only the shape of the vehicle, but
also the position of the GNSS-receiver 20 (or its an-
tenna) in respect to this shape or bounds can be stored
in memory.
In some cases, the signal strength of a re-
ceived radio signal can be used to determine a range of
distance where the monitoring device may be, thus improv-
ing warning accuracy in such a case. Hence, a first moni-
toring device receiving a signal from a second monitoring
device assesses the signal strength of said signal and
generates a proximity warning based on the assessed sig-
25 nal strength, in particular by comparing it to a maximum
value.
Other functions:
In addition to issuing proximity warnings as
described above, monitoring devices 1,2,3 can provide
other uses and functions.
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In one embodiment, which is particularly use-
ful if monitoring device 1,2,3 is worn on a person, the
monitoring device 1,2,3 can issue a warning when it
leaves the site or enters a "restricted area" of the
site. This can, e.g., happen when a user of the monitor-
ing device forgets to return the apparatus when leaving
the site or tries to steal it, or when a user enters an
area, such as a blast area, that is not safe for him.
This type of warning can be generated by exe-
n outing the following steps:
1) In a first step, analysis and control unit
6 obtains the position of the monitoring device by means
of GNSS receiver 20 or via time-of-flight triangulation
(see below).
2) In a second step, analysis and control
unit 6 compares this position to a predefined geographi-
cal area. This geographical area can, e.g., be stored in
memory and describes the area where the monitoring device
is allowed to be operated. If it is found that the posi-
tion is not within the geographical area, the following
step 3 is executed:
3a) A warning which can comprise one or more
positions of monitoring devices is issued. This warning
can, e.g., be displayed on a display or issued as a sound
by acoustic signal source 23.
3b) Alternatively, or in addition to step 3a,
the warning can be sent, e.g., by means of a cellular
phone transceiver (not shown) integrated into the moni-
toring device 1,2,3 or by means of the radio transceiver
10 to a central monitoring system (i.e. a central
server), together with the current position and identity
of the respective monitoring device 1,2,3. Then, the
warning can be displayed by the central server and
brought to the attention of personnel that can then take
further necessary steps.
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3c) Alternatively or in addition to steps 3a
and/or 3b, the apparatus can be made unusable by blocking
and/or destroying at least part of its functionality.
In general, a cellular phone network (or any
other wireless network) can be used to transmit informa-
tion from the monitoring devices 1,2,3 to the central
server. As mentioned, this information can, e.g., com-
prise any warnings issued by the monitoring devices
1,2,3, and/or it may comprise the position of the morii-
io device.
Another application of a cellular phone tran-
sceiver integrated into monitoring device 1,2,3 is to
send messages from the central server to any monitoring
device 1,2,3. Such messages are received the respective
monitoring device 1,2,3 and displayed or brought to the
operator's attention acoustically. This, e.g., allows to
issue warnings, alerts or information to the person using
the monitoring device 1,2,3.
The monitoring devices 1,2,3 can also be used
for generating automatic response to the presence of a
vehicle or person at a certain location. For example,
when a pedestrian with a monitoring device approaches a
gate, such as door of a building, that door can open
automatically. Similarly, an entry light can switch to
red or to green, depending on the type of object that a
monitoring device is attached to, or a boom can open or
close. This can be achieved by mounting a receiver device
to a selected object (such as a door, a gate, boom or an
entry light). The receiver device is equipped with a ra-
dio receiver adapted to detect the proximity of monitor-
ing devices 1,2,3. When the receiver device detects the
proximity of a monitoring device 1,2,3, it actuates an
actuator (such as the door, gate or entry light) after
testing access rights of the object attributed to the
monitoring device 1,2,3. For example, the actuator may be
actuated depending on the type of the object that the
monitoring device is attached to and/or to its distance
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from the receiver. The type and/or distance information
is transmitted as part of the device status dataset of
the monitoring device 1,2,3.
Furthermore, the control unit of the monitor-
ing device 1,2,3 can have an "alert mode", which can be
activated by a user, e.g., by pressing an alert button en
a keyboard of the monitoring device 1,2,3 and/or by voice
control. It can, e.g., be used to indicate that the per-
son using the monitoring device is in need of urgent help
lo or needs all activity around it to be stopped immedi-
ately. The device status dataset comprises a flag indica-
tive of whether the monitoring device is in alert mode.
Another monitoring device receiving a device status data-
set that indicates that the sender is in alert mode may
n take appropriate action. For example, the central control
room operator can be informed, closeby machinery can be
shut down, etc.
Persons on the site:
20 As mentioned above, the monitoring devices 1,
2, 3 can not only be mounted to vehicles in the area, but
also to individual persons on the site. By using the same
type of device for persons as well as vehicles, costs can
be reduced. In such a situation, the monitoring device
1,2 mounted to vehicles can cooperate with the monitoring
device 3 mounted to a person in such a manner that
a) the drivers of the vehicles are alerted of
the presence of pedestrians, and/or
b) the pedestrians are alerted of the pres-
ence of the vehicles 40,50.
While option a) is the primary purpose of the
present invention, option b) may also have its advan-
tages, too.
In order to alert the drivers of the presence
of a pedestrian, each pedestrian-mounted monitoring de-
vice can transmit a flag indicative of the fact that it
is mounted to a pedestrian, e.g., as part of its device
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status dataset. Thus, all other monitoring devices in
range are aware of this fact and can adapt their warning
strategy accordingly.
Time of flight measurement/triangulation:
Under adverse conditions, e.g. when one or
more satellite signals are partially or fully blocked by
obstacles, GNSS receiver 20 of a given monitoring device
1,2 may not be able to reliably derive its position
n P_1,P_2, or the determined position P_1,P_2 will be inac-
curate. In another situation, one monitoring device 3 may
not equipped with a GNSS receiver 20 at all (therefore,
GNSS receiver 20 is dotted in fig. 2).
Therefore, in order to improve the reliabil-
is and versatility of the proximity warning method, the
monitoring devices 1,2,3 are adapted and structured for
mutual time-of-flight distance derivation. For this, the
monitoring devices 1,2,3 are equipped with radio trans-
ceivers 10 to perform a "time-of-flight (TOF) measurement
20 and/or triangulation". This TOF measurement/triangulation
allows to at least_ approximately determine the mutual
distances and/or positions of several monitoring devices
1,2,3, even if the monitoring device 3 is unable to de-
termine its position P_3 because of the lack of a GNSS
25 receiver 20.
In the given example situation, a first posi-
tion P 1 of the first monitoring device 1 and a second
position P2 of the second monitoring device 2 are deter-
mined using the GNSS receivers 20 of the respective moni-
30 toring devices 1,2. The first and second positions p_l
and P_2 are then transmitted by the monitoring devices
1,2 such that all monitoring devices 1,2,3 are aware of
these positions P_1 and P_2.
Then, using a bidirectional exchange of TOF-
35 pulses P_TOF and R_TOF (see above) between the first and
the second devices 1,2 and using the first and second po-
sitions P1 and P2, the first monitoring device I de-
_
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rives a first distance value d12 (dotted lines and cir-
cle segments in figure 1) between the first and the sec-
ond monitoring devices 1,2. Then, this distance value
d12 is transmitted in a way that all monitoring devices
1,2,3 in range are aware of it.
As another step, by means of a bidirectional
exchange of TOP-pulses P_TOF (i.e., a third radio pulse)
and R TOF (see above) between the second and the third
monitoring devices 2,3, the second monitoring device 2
lo derives a second distance value d 23 (dotted lines and
circle segments in figure 1) between the second and the
third monitoring devices 2,3. It should be noted here
that this distance value d_23 is not derivable because
position P_3 is not (yet) known. Then, the distance value
d23 is also transmitted in a way that all monitoring de-
_
vices 1,2,3 in range are aware of it.
As another step, by means of a bidirectional
exchange of TOP-pulses P_TOF and R TOF (see above) be-
tween the first and the third monitoring devices 1,3, the
first monitoring device 1 derives a third distance value
d13 (dotted lines and circle segments in figure 1) be-
tween the fist and the third of the monitoring devices
1,3. The P TOF pulse can be the first radio pulse which
is also used for deriving d_12 as discussed above or it
can be a fourth radio pulse. It should be noted here that
this distance value d13 is also not derivable from the
respective positions because the third position P_3 is
not yet known. Then, the distance value d_13 is also
transmitted in a way that all monitoring devices 1,2,3 in
lo range are aware of it.
Now, the monitoring apparatus (specifically
all the monitoring devices 1,2,3 in range) are aware of
P_1, P_2, d_12, d_13, and d_23. From this information,
the position P_3 of the third of the monitoring device 3
is derived and optionally transmitted by means of the ra-
dio transceiver(s). An ambiguity between P_3 and an also
possible "mirrored position P_3'" is resolved by means of
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a radio transceiver antenna with directional resolution,
i.e., a direction sensitive antenna, in any of the moni-
toring devices 1,2,3.
Then, a proximity warning can be issued as a
function of the first, the second, and/or the third dis-
tance values d12, d_23, d13 and/or optionally of the
first, second, and/or third position P_1, P_2, P_3.
Thus, even without a GNSS receiver 20 in the
third of the monitoring devices 3, the position P_3 is
n derivable which leads to higher reliability and increased
safety of the monitoring apparatus.
Note:
The above mentioned steps of transmitting a
determined position P_1, P_2, and/or P_3 of a monitoring
device 1,2,3 by means of the radio transceiver 10 of the
respective monitoring device 1,2,3 can comprise absolute
position information, e.g., altitude, longitude, and
latitude and/or relative position information with regard
to a predefined position or regular grid points on the
surface mine 100. Furthermore, an incremental position
information transmission is possible as well in which
only position changes are transmitted.
While there are shown and described presently
preferred embodiments of the invention, it is to be dis-
tinctly understood that the invention is not limited the-
reto but may be otherwise variously embodied and prac-
ticed within the scope of the following claims.
