U.S. patent application number 14/049240 was filed with the patent office on 2015-04-09 for determing an activity of a mobile machine.
This patent application is currently assigned to Caterpillar Inc.. The applicant listed for this patent is Caterpillar Inc.. Invention is credited to David William Smith.
Application Number | 20150097412 14/049240 |
Document ID | / |
Family ID | 52776379 |
Filed Date | 2015-04-09 |
United States Patent
Application |
20150097412 |
Kind Code |
A1 |
Smith; David William |
April 9, 2015 |
DETERMING AN ACTIVITY OF A MOBILE MACHINE
Abstract
Disclosed herein is a method for determining an activity
associated with a mobile machine in an underground mine, and a
system (30) configured to perform the method. The method comprises
communicating by a radio-frequency communication between a first
ranging device (34) at a known location (35) within the mine and a
second ranging device (36) located on the mobile machine (10). The
method further comprises determining a position of the mobile
machine (10) based at least on a time-based characteristic
associated with the radio-frequency communication. The method
further comprises identifying an activity of the mobile machine
(10) based on the determined position in the mine (20).
Inventors: |
Smith; David William; (Upper
Coomera, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Caterpillar Inc. |
Peoria |
IL |
US |
|
|
Assignee: |
Caterpillar Inc.
Peoria
IL
|
Family ID: |
52776379 |
Appl. No.: |
14/049240 |
Filed: |
October 9, 2013 |
Current U.S.
Class: |
299/1.05 |
Current CPC
Class: |
E21C 41/16 20130101;
E21F 17/18 20130101; E02F 9/264 20130101 |
Class at
Publication: |
299/1.05 |
International
Class: |
E21C 41/16 20060101
E21C041/16; E21F 17/18 20060101 E21F017/18 |
Claims
1. A method for determining an activity associated with a mobile
machine in an underground mine, the method comprising:
communicating by a radio-frequency communication between a first
ranging device at a known location within the mine and a second
ranging device located on the mobile machine; determining a
position of the mobile machine based at least on a time-based
characteristic associated with the radio-frequency communication;
and identifying an activity of the mobile machine based on the
determined position in the mine.
2. A method according to claim 1, wherein identifying the activity
is based on a positional correlation between the determined
position and an activity identifier from a plurality of activity
identifiers associated with respective positions in the mine.
3. A method according to claim 2, wherein the determined position
of the machine is a position of a portion of the mobile machine for
carrying earth material; and determining the position of said
portion of the mobile machine is based on said time-based
characteristic and on orientation information associated with said
portion, the orientation information being derived from at least
one orientation sensing device located on the mobile machine.
4. A method according to claim 2, wherein the plurality of activity
identifiers comprise: one or more first activity identifiers
corresponding to respective positions in the mine which are
designated for loading earth material; and wherein in the event
that said determined position of the mobile machine positionally
correlates with a first activity identifier, the activity is
determined to be loading of the earth material.
5. A method according to claim 4, wherein the method further
comprises tracking movement of the mobile machine based on a
time-based characteristic associated with subsequent radio
frequency communications between the first and second signal
devices; and wherein the plurality of activity identifiers further
comprise one or more second activity identifiers corresponding to
respective positions in the mine which are designated for dumping
the earth material; and in the event that a determined position of
the mobile machine positionally correlates with a second activity
identifier, the determined activity is dumping of the earth
material.
6. A method according to claim 5, wherein in the event that the
mobile machine is stationary for longer than a predetermined
time-period while said position of the mobile machine is not
positionally correlated with a first or second position identifier,
the mobile machine is determined to be inactive.
7. A method according to claim 1, wherein the radio frequency
communication comprises at least one round trip, each of the at
least one round trips comprising: transmitting a first radio
frequency signal from one of first and second ranging devices, the
first ranging device being at a known location in the mine and the
second ranging device being on the mobile machine; and receiving a
radio frequency response signal from the other of the first and
second ranging devices; wherein the characteristic is a two-way
time-of-flight.
8. A method according to claim 7, transmitting a first signal and
transmitting a response signal each comprise transmitting data
multiple times, wherein the data is coherently processed to
determine the time of flight.
9. A method according to claim 7, wherein the method comprises
determining the position from a plurality of determined two-way
time-of-flights, for respective round-trip communications, using a
Kalman filter.
10. A method according to claim 1, wherein determining the position
of the mobile machine is further based on information derived from
a motion sensor.
11. The method of claim 7, wherein determining the position of the
mobile machine is further based on information derived from a
motion sensor, and wherein the position is determined from a
plurality of determined time-of-flights, wherein the position is
derived using a particle filter.
12. The method of claim 1, wherein the radio-frequency
communication is an ultra-wideband radio-frequency
communication.
13. The method of claim 1, wherein the method further comprises:
performing a radio-frequency communication between the second
ranging device and a third ranging device, the third ranging device
being at another known location in the mine; and determining the
position of the mobile machine is additionally based on a
time-based characteristic associated with the radio frequency
communication between the second and third ranging devices.
14. A system for determining an activity associated with a mobile
machine in an underground mine, the system comprising: a first
ranging device for positioning at a known location in the mine and
a second ranging device for attaching to the mobile machine, the
first and second ranging devices being configured to perform a
radio-frequency communication therebetween; a memory system for
storing data defining a geographic frame of reference; and a
processing system configured to: determine a position of the mobile
machine based at least on a time-based characteristic associated
with the radio-frequency communication; and identify an activity of
the mobile machine based on the determined position in the mine by
determining a positional correlation between the determined
position of the mobile machine and an activity identifier from a
plurality of activity identifiers associated with respective
positions in the mine, the positional correlation being determined
with respect to the stored data defining a geographic frame of
reference.
15. A system according to claim 14, wherein identifying the
activity comprises is based on a positional correlation between the
determined position of the mobile machine and said activity
identifier from a plurality of activity identifiers.
16. A system according to claim 14, wherein: the system further
comprises an orientation sensing device located on the mobile
machine for determining orientation information associated with a
portion of the mobile machine for carrying the earth material; the
determined position of the machine is a determined position of said
portion of the mobile machine; and the processing system is
configured to determine the position of said portion of the mobile
machine based on said time-based characteristic and on the
orientation information associated with said portion of the mobile
machine.
17. A system according to claim 15, wherein the plurality of
activity identifiers comprise: one or more first activity
identifiers corresponding to respective positions in the mine which
are designated for loading earth material; and wherein in the event
that said determined position of the mobile machine positionally
correlates with a first activity identifier, the activity is
determined to be loading of the earth material.
18. A system according to claim 17, wherein the plurality of
activity identifiers further comprise one or more second activity
identifiers corresponding to respective positions in the mine which
are designated for dumping the earth material; and the processing
system is further configured to track movement of the mobile
machine based at least a time-based characteristic associated with
subsequent radio frequency communications between the first and
second signal devices; wherein in the event that a determined
position of the mobile machine positionally correlates with a
second activity identifier, the activity is determined to be
dumping of the earth material.
19. A system according to claim 14, wherein the first ranging
device and second ranging device are ultra-wideband ranging
devices, and the characteristic is a two-way time-of-flight.
20. A method for determining a plurality of activities associated
with a mobile machine in an underground mine, the method
comprising: performing a first radio-frequency communication
comprising at least one round trip communication, each of the at
least one round-trips comprising: transmitting a first radio
frequency signal from one of first and second ranging devices, the
first ranging device being at a known location in the mine and the
second ranging device being on the mobile machine; receiving a
radio frequency response signal from the other of the first and
second ranging devices; determining a first position of the second
ranging device based at least on a time-of-flight associated the
first radio-frequency communication; receiving first orientation
information associated with a bucket portion of the mobile machine
from an orientation sensing device located on the mobile machine;
determining a first activity based on the determined position and
the received first orientation information; and performing a second
first radio-frequency communication comprising at least one round
trip communication, each of the at one least round-trips
comprising: transmitting a second radio frequency signal from one
of second and third ranging devices, the third ranging device being
at another known location in the mine; receiving a second
ultra-wideband radio frequency response signal from the other of
the second and third ranging devices; determining a second position
of the second ranging device based at least on a time-of-flight
associated with the second radio-frequency communication; receiving
second orientation information associated with the bucket from the
orientation sensing device located on the mobile machine;
determining a second activity based on the second determined
position and the received second orientation information.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to a method and
system for determining an activity of a mobile machine. The method
and system are especially relevant to determining an activity in an
underground mine
BACKGROUND
[0002] Machines such as, for example, haul trucks, drills, loaders,
conveyors, and other types of heavy equipment are commonly used in
underground mining applications to perform a variety of tasks.
Unlike above-ground mining applications, underground mining sites
do not have access to GPS (Global Positioning System) signals, yet
knowledge of a machine's on-site location is desirable, for
example, with respect to the site geography.
[0003] In some underground mining applications, it is desirable to
monitor the specific tasks required of the machine or machine(s) in
the underground mine. For example, in some cases where at least one
machine is assigned to move ore in a mine, it is sometimes
desirable to remotely monitor the movement of ore. This may be
achieved by identifying when and where a machine loads ore and the
location from which it is loaded, and identifying when and where
the machine then dumps the loaded ore. Some systems use RFID tags
and readers to identify the machine's activity. For example, the
machine may have an RFID reader mounted to it, while RFID tags are
mounted at each of one or more drawpoints (at which ore may be
loaded) and each of one or more ore passes (at which ore may be
dumped). The drawpoints and ore passes and their corresponding RFID
tags are stored in a computer readable memory. When the machine
arrives at a drawpoint or ore pass, the RFID reader comes into
proximity with the RFID tag at the drawpoint or ore pass, allowing
the RFID reader to identify the RFID tag. Depending on whether the
RFID tag corresponds to a drawpoint or an ore pass, the system can
thus attribute the activity of loading ore from the drawpoint or
dumping ore at the ore pass. The specific drawpoint or ore pass
associated with the activity may be identified by knowing which
drawpoint or ore pass the identified RFID tag is associated with.
However, the RFID tags need to be stored inside the drawpoint or
inside the ore pass to be sure to identify that the machine has in
fact entered the drawpoint or ore pass. This requires careful
distribution and positioning of the RFID tags within the mine.
Furthermore, the RFID tags can easily become damaged, requiring
replacement. This adds to the costs and reduces the reliability of
the system.
[0004] In some an underground mining applications using a
load-haul-dump (LHD) loader, loading or dumping activities may be
determined by identifying when a bucket for carrying ore on the LHD
loader (or a portion of the bucket) is situated in a position
within the mine that corresponds to drawpoint or orepass,
respectively. The position of the bucket is determined from
information from an articulation sensor and from a tracked position
of a Lidar sensor on the machine. However, Lidar positioning
systems tend to be expensive and, in harsh and dirty underground
mine environments, often have reliability and maintenance issues.
Additionally, some mining applications may not be suitable for
operating Lidar positioning systems, or the use of such systems may
be difficult to implement.
[0005] The disclosed method and system are directed to overcoming
or at least ameliorating one or more of the problems set forth
above.
SUMMARY
[0006] In one aspect, there is disclosed a method for determining
an activity associated with a mobile machine in an underground
mine. The method comprises communicating by a radio-frequency
communication between a first ranging device at a known location
within the mine and a second ranging device located on the mobile
machine. The method further comprises determining a position of the
mobile machine based at least on a time-based characteristic
associated with the radio-frequency communication. The method
further comprises identifying an activity of the mobile machine
based on the determined position in the mine.
[0007] In another aspect, there is disclosed a system for
determining an activity associated with a mobile machine in an
underground mine. The system comprises a first ranging device for
positioning at a known location in the mine and a second ranging
device for attaching to the mobile machine. The first and second
ranging devices are configured to perform a radio-frequency
communication therebetween. The system further comprises a memory
system for storing data defining a geographic frame of reference.
The system further comprises a processing system configured to
determine a position of the mobile machine based at least on a
time-based characteristic associated with the radio-frequency
communication. The processing system is further configured to
identify an activity of the mobile machine based on the determined
position in the mine. This is achieved by determining a positional
correlation between the determined position of the mobile machine
and an activity identifier from a plurality of activity identifiers
associated with respective positions in the mine. The positional
correlation is determined with respect to the stored data defining
a geographic frame of reference.
[0008] As used herein, the term "comprises" (and grammatical
variants thereof) is used inclusively and does not exclude the
existence of additional features, elements or steps.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Various aspects and features of an embodiment of the
invention will be described with reference to the following figures
which are provided for the purposes of illustration and by way of
non-limiting example only.
[0010] FIG. 1 is a pictorial illustration of an exemplary disclosed
machine;
[0011] FIG. 2 is a pictorial illustration of an exemplary system
that may be used to determine an activity of the mobile machine of
FIG. 1, the machine being illustrated in a simplified manner;
[0012] FIG. 3 is a pictorial illustration of a worksite in which
the system of FIG. 2 may operate;
[0013] FIG. 4 is a flowchart depicting an exemplary disclosed
method; and
[0014] FIG. 5 is a flowchart depicting an embodiment of the
exemplary disclosed method.
DETAILED DESCRIPTION
[0015] FIG. 1 illustrates a machine 10 having an exemplary
disclosed system. Machine 10 embodies a mobile machine configured
to perform one or more operations associated with an industry such
as mining, construction, farming, transportation, or any other
industry known in the art. For example, machine 10 may be a
load-moving machine such as a haul truck, a loader, an excavator, a
wheel tractor, a scraper, or any other like machine. Machine 10 may
be used above-ground or underground, but in the present disclosure
the machine 10 is used underground. For example, FIG. 1 more
specifically illustrates an underground mining load-haul-dump (LHD)
loader, which may be used to access a load site in a mine (eg from
a drawpoint), haul a load away from the load site, and release the
load at a dump site (eg at an ore pass). Machine 10 may be manually
controlled, semi-autonomously controlled, or fully-autonomously
controlled. Machine 10 includes one or more traction devices that
propel machine 10. In the exemplified embodiment, machine 10 has
four traction devices in the form of respective wheels 13. The
machine 10 also includes, among other things, movement sensors 14
that sense various movements of machine 10, and a power source 15
orientation sensing devices 16, 17, and a controller 18.
[0016] The machine 10 has an articulation joint 19 which divides
the machine 10 into a front portion 23, including two wheels 13 and
ending in bucket 25, and a rear portion 27, including the
controller 18, another two wheels 13, a cabin 28 for an person, and
a rear end 29 behind the two wheels 13 of the rear portion 27 and
holding the power source 15. The front portion 23 and rear portion
27 pivot about the articulation joint 19 to effect steering of the
machine 10. The orientation sensing devices 16, 17 each measure
information which independently may be used to determine the
orientation of least the front portion 23 of the machine 10. For
example, one of the orientation sensing devices 16 is a digital
compass located on the front portion 23 of the machine 10, forward
of the articulation joint 19. The other of the orientation sensing
devices 17 is an articulation sensor which measures an angle
indicative or other parameter that is indicative of the angle of
rotation of the articulation joint 19, and hence indicates the
disposition of the front portion 23 of the machine 10 with respect
to the rear portion 27 of the machine 10. In the illustrated
embodiment, the articulation sensor is located on the rear portion
27 of the machine, adjacent the articulation joint 19.
[0017] Controller 18 is in communication with movement sensors 14,
orientation sensors 16, 17, power source 15, and/or drive traction
devices 13, and may be configured to regulate operation of power
source 15 in response to various inputs, for example, from an
operator input device and/or movement sensors 14, to drive the
traction devices to propel machine 10 in a desired manner.
Controller 18 may also receive information from movement sensors 14
indicative of, for example, velocity, acceleration, and/or turning
rate of machine 10, and may be configured to compute various
motions, such as distance and direction traversed by machine 10,
based on such information.
[0018] Controller 18 includes a processor (not shown), and a memory
system (not shown) comprised of a memory module and/or a storage
module. Optionally, one or more of the processor, memory module,
and/or storage module may be included together in a single
apparatus. Alternatively, one or more of the processor, memory
module, and/or storage module may be provided separately. The
processor may include one or more known processing devices, such as
a microprocessor. Memory module may include one or more devices,
such as random-access memory (RAM), configured to store information
used dynamically by controller 18 to perform functions related to
the various operations of machine 10. The storage module may
include any type of storage device or computer readable medium
known in the art. For example, the storage module may comprise a
magnetic, semiconductor, tape, optical, removable, non-removable,
volatile, and/or non-volatile storage device. The storage module
may store programs, algorithms, maps, look-up tables, and/or other
information associated with determining a position of machine 10 in
worksite 20. The functions of both the storage module and memory
module may be performed by a single memory/storage device.
[0019] FIG. 2 illustrates machine 10, shown in a simplified manner,
performing a task at in worksite 20. Worksite 20 may be any
worksite having a roadway 22 traversable by machine 10, but
exemplary embodiments are particularly suited to worksites which do
not having access to a GPS navigation system. For the exemplary
embodiments illustrated herein, worksite 20 is an underground mine
site, which does not have access to GPS navigation systems. Roadway
22 is bordered by side walls 24, such as walls of an underground
tunnel, and may have a ceiling, such as a tunnel roof (not shown)
disposed above roadway 22. In some applications, there may also be
objects other than side walls 24 such as other machines, barrels,
poles, geological features, and other like obstacles disposed in
various locations at worksite 20 relative to roadway and/or the
additional objects described above. In various situations, it may
be desirable to ascertain position information of machine 10 in
worksite 20. The position information may be used to monitor and
gather data about how efficiently machine 10 and other machines in
worksite 20 are performing various tasks. Additionally, the
position information may be used by machine 10 in navigating
worksite 20.
[0020] In exemplary embodiments, a position of machine 10 in
worksite 20 is determined by utilizing an monitoring system 30. As
illustrated in FIG. 2, monitoring system 30 includes, among other
things, a processing system 38. The monitoring system 30 further
includes a radio frequency communication system 33, as illustrated
in FIGS. 2 and 4. The monitoring system 30 determines and tracks
the position of the machine 10 at any given time when the machine
10 is in the worksite (or at least operating within an assigned
area of the worksite) based at least on the radio-frequency
communication system 33. In some embodiments, the determined
position includes a coordinate, and optionally an orientation, with
respect to a map of the mine which may be stored in a memory system
of the monitoring system 30, such as memory system 21 in
communication with the processing system 38.
[0021] The radio frequency communication system 33 includes one or
more reference signal devices 34, 37 at respective known locations
within the worksite 20, and a mobile signal device 36 that is
located on the machine. In some embodiments, there may be two,
three, or more of reference signal devices 34, 37. As shown in FIG.
2, a first of the reference signal devices 34 is at a corresponding
known location 35 within the worksite 20. The first signal device
34 may be fixed to a side wall 24 or ceiling (not shown) of the
worksite 20, such as a sidewall 24 or ceiling of the assigned
tunnel 113 within which the machine 10 is assigned to operate. A
second signal device 36 is located on the machine. In some
embodiments, the second signal device 36 is fixed to the rear
portion 27 of the machine 10. For example, in one embodiment, the
second signal device 36 is located on top of cabin 28, while in
another embodiment, the second signal device is located on top of
the rear end 29 of the rear portion 27. A third signal device 37,
being another of the reference signal devices 34, 37, is attached
to the worksite at a different location to the first signal device
34. For example, the third signal device 37 may be fixed to a side
wall 24 or ceiling (not shown) of the worksite 20, such as a
sidewall 24 or ceiling of the assigned tunnel 113 within which the
machine 20 is assigned to operate. The radio frequency
communication system 33 is configured to perform a radio frequency
communication between the mobile signal device 36 and at least one
of the reference signal devices 34, 37.
[0022] Processing system 38 is in communication with one or more of
the mobile signal device 36 and reference signal devices 34, 37 of
the radio-frequency communication system 33, via at least one
communication channel. The processing system 38 may send commands
to, and receive data from, the radio-frequency communication system
33 over the communication channel. In one embodiment, the
communication channel is or includes a wired communication network
39, such as an Ethernet network, with the reference signal
device(s) 34, 37. Alternatively, or additionally, a further
communication channel allows the processing system 38 to
communicate by a wireless network, eg by at least one WiFi
transceiver 40, with the radio-frequency communication system 33.
Such a wireless communication can be used to communicate with the
mobile signal device 36 in cases where at least part of the
processing system 38 is mounted in a fixed position with respect to
the worksite (as in FIG. 2), or to communicate with one or more of
the reference signal device 34, 37 in cases where the processing
system 38 is mounted entirely on the machine 10.
[0023] The processing system 38 may include, or may be, the
controller 18. In embodiments, in which the processing system 38 is
the controller 18, memory system 21 may include additional data
representative of a map of the worksite 20, which may be in
addition to or instead of the worksite map stored on memory system
21. The monitoring system 30 may further include a user interface
(not shown) having a display panel (not shown) for displaying
information to an operator of the monitoring system. In embodiments
in which the processing system 38 includes but is not the same as
controller 18, processing system 38 may include separate processing
device(s), and may use a separate memory system, from the
processing device(s) and memory system of the controller 18. In
such cases, the processing system may store, outside of controller
18, data representative of a map of the worksite 20. The memory
system 21 may be comprised of the same type of components that
constitute the controller 18. Similarly, the processing system 38
may include one or more processors in the same manner and types
described in relation to controller 18. The processing system 38
obtains data relating to the radio frequency communication from the
radio frequency communication system 33. In some embodiments, the
obtained data defines a distance associated with a characteristic
of the radio-frequency communication. For example, the
characteristic may be an time-based characteristic, such as a
time-of-flight, associated with the radio-frequency communication.
Based on the obtained data relating to the radio frequency
communication, the processing system 38 determines position data
that is indicative of the position of machine 10 within the
worksite 20. The position data indicates the position of the
machine 10 within the worksite 20.
[0024] The reference signal device or devices 34, 37 and the mobile
signal device 36 may consist of the same hardware and software.
However, in some embodiments, especially involving multiple
reference signal devices 34, 37 and/or multiple mobile signal
devices 36, each of the reference signal devices 34, 37 and mobile
signal devices 36 has a respective device identifier associated
therewith, such as unique MAC address. In other embodiments the
hardware and/or software of the reference signal devices 34, 37 may
be different to that of the mobile signal device(s) 36 by having
further differences, in addition to the different device
identifiers.
[0025] As described in exemplary embodiments below, the
radio-frequency communication 33 is used by processing system 38 to
determine position based on a time-based characteristic of the
radio-frequency communication. A radial distance to at least one
reference signal device 34, 37 may be determined from the
time-based characteristic associated with the radio frequency
communication. In some embodiments, this radial distance forms the
basis of the determined position of the mobile signal device 36 or
machine 10.
[0026] In one embodiment, the time-based characteristic is
associated with an elapsed time between a transmission of the radio
frequency communication and a reception of the radio frequency
communication. In one embodiment, the elapsed time is the
difference between a time at which a radio-frequency signal is
transmitted, in one direction, from one of (i) a reference signal
device 34 or 37 or (ii) the mobile signal device 36, and received
from the other of the reference signal device 34, 37 or the mobile
signal device 36. The transmitted signal includes a time stamp at
which the signal was transmitted. The receiving device can
therefore determine the time taken for the signal to travel from
the transmitter to the receiver. Since the speed of travel is known
(ie the speed of light), the radial distance can be determined.
However, the internal clock (to which time is measured) on the
transmitting device will drift with time with respect to the
internal clock on the receiving device. This limits the accuracy
with which the travel time, and hence distance and position, can be
determined. Therefore, in one embodiment, a wireless
synchronization protocol is employed to maintain some synchronicity
between the internal clocks.
[0027] In some embodiments, rather than determining an elapsed
time, communication system 33 or processing system 38 determines
the position of the second signal device 36 by using a
time-difference of arrival (TDOA). The time-difference refers to a
difference in arrival times for respective signal transmissions
between the mobile signal device 36 and a plurality of reference
signal devices 34, 37. In this case, the arrival times of the
respective signal transmissions are the characteristic upon which
the position determination is made. For example a signal may be
broadcasted from the mobile signal device 36, and the times of
reception (ie arrival) at each of the reference signal devices 34,
37 may be recorded to derive one or more time-difference
measurements. Conversely, each of the reference signal devices 34,
37 may simultaneously transmit respective signals, and the arrival
time of each of the signals is recorded at the mobile signal device
36. The reference signal devices 34, 37 may be synchronized with
each other so that the time difference calculation removes any
asynchronicity between the mobile signal device 36 and the
reference signal devices 34, 37. Based on the difference in arrival
times, the position of the second signal device 36 may be
derived.
[0028] In other embodiments, the time-characteristic is an elapsed
time relates to a round-trip for a two-way radio frequency
communication. An initiating, first radio-frequency signal is
transmitted from an initiating device to a responding receiving
device. Upon receiving the first signal, the responding device
sends a response radio-frequency signal to the initiating device.
In one embodiment, the first signal may include identification data
that identifies the initiating device that transmitted the first
signal. The response signal may also include the identification
data identifying the initiating device. Thus, when the initiating
device receives the response signal it can determine that the
response signal was a response to the first signal sent by that
initiating device, as opposed to some other possible initiating
devices in the worksite. The responding device may also include in
the response signal identification data that identifies the
responding device. Thus, in embodiments having multiple responding
devices in the worksite 10, the initiating device can determine
which responding device responded to its initiating signal. From
this information, the elapsed time is the time taken for the first
signal to propagate from the initiating device to the responding
device plus the time taken for the response signal to propagate
from the responding device to the initiating device. Processing
delays by the initiating device and responding device are constant
and may be subtracted or otherwise factored out of any time
measurements, and the error due to any clock asynchronicity is
eliminated from the elapsed time calculation, since both the
transmission time and the reception time are referenced to the same
internal clock (ie the clock of the initiating device). The elapsed
time may thus represent a two-way time of flight of the
radio-frequency communication. The radial distance(s) to the
corresponding reference signal device(s) 34, 37 involved in the
radio-frequency communication(s) can be determined as being half of
the time-of-flight multiplied by the speed of light.
[0029] In one embodiment, the signal transmission involves
directional transmission, as opposed to omnidirectional
transmission, so that the radial distance corresponds to a specific
location in the worksite, as opposed being any point on a circle
defined by the radius.
[0030] In another embodiment, the specific location along the
circle 44 or 46 at which the machine 10 is located may be
determined by knowledge of the worksite topology. For example,
based on a worksite map stored in memory, the processing system 38,
in determining the position of machine 10, may exclude locations
along the circle 44 or 46 which are not possible locations for the
machine 10. Such excluded locations may be for example locations
within a wall of the worksite. Additionally or alternatively, as
described above, the processing system 38 can limit the possible
locations to those locations on the circle 44 or 46 which are
within a tunnel 113 in which the machine 10 is known to be located,
eg because it has been assigned to operate in that tunnel.
[0031] In addition or as an alternative to using knowledge of the
worksite topology, monitoring system 30 also determines a radial
distance from a second, third or more reference signal devices 34,
37 at which the machine 10 is located. The distances from the
respective reference signal devices 34, 37 are used by one of the
processing system 38 to determine position by a trilateration
process. In the trilateration process, possible position(s) of the
mobile signal device 36 is limited to the locations of intersection
47, 49 of the notional circles 44, 46 respectively centered the two
or more reference signal devices 34, 37 and having respective radii
equal the corresponding determined radial distances. It is
appreciated that in the case of two reference signal devices, the
trilateration process may be referred to as "bilateration". However
as used herein "trilateration" is intended to refer to determining
location based on the intersection between two or more circles.
[0032] In some embodiments, in addition or instead of using the
worksite topology information and/or a trilateration process, the
accuracy of the position determination may be improved based on a
statistical model, such as a Kalman filter. A Kalman filter
determines position using an iterative process. Specifically, a
Kalman filter determines the most likely position at a time, t, by
using knowledge of one or more past position determinations to
weight, based on a likelihood of being correct, all possible
positions at time, t. The possible positions, may be identified by
the one or more radial distances to respective one or more
reference signal devices 34, 37. For example, the statistical model
may know the position (or a possible positions) at time t-1, and
know the maximum speed of machine 10, or a measured change of speed
of machine 10. Based on this knowledge, the statistical model can
weight, and then rank, the possible positions at time t based on
their distance and/or directional disposition with respect to the
previous position or possible positions at t-1. For example, those
possible positions at time t which are a further than a first
distance from the position or possible positions at time t-1 may be
ranked much lower than those possible positions at time t which are
closer than a second distance from the position or possible
positions at time t-1.
[0033] In addition to or instead of using a Kalman filter to
improve overall position determination as the machine 10 moves in
the worksite, a Kalman filter may also be used to improve the
accuracy each of the distance measurement used in the position
determination. For example, communication system 33 may measure
time-of-flight a number of times, by repetitively transmitting
round trip communications while the machine 10 is at essentially
the same position in the worksite. This may be beneficial in the
underground environments due to a level of noise that may result
from multi-path reflections or from low a low-signal to-noise
ratio. A Kalman filter may in this case be used to improve the
distance measurement by disregarding or giving low weighting to
measurements that are statistical outliers, and giving higher
weighting to measurements which are statistically consistent with
previous measurements. Thus, in one embodiment, a first Kalman
filter may be used in determining the time-of-flight or distance
associated therewith, and second Kalman filter may be used to
determine position within the worksite.
[0034] In some embodiments, in addition to or instead of using the
worksite topology information and/or a trilateration process, the
position determination is based on movement information from one or
more motion sensors 14, and/or orientation information from an
orientation sensor 16 and/or 17. In one embodiment, a velocity
vector or speed is determined from the motion sensor(s) 14. For
example, one motion sensor 14 may be an odometer, from which a
speed is derived. A velocity vector may be derived based on the
speed and orientation information, such as may be provided by a
digital compass 16. Since for the described LHD loader, the digital
compass 16 provides the orientation of the front portion 23 of the
machine 10 only, the orientation of the rear portion 27 of the
machine 10 may be derived based on the determined orientation of
the front portion 23 and the articulation sensor 17, measuring the
rotation of the rear portion 27 with respect the front portion 23.
The velocity vector or speed can then be used to predict a future
position or future set of positions based on a previously
determined position or set of possible positions derived from a
previous radio-frequency communication (eg an elapsed time). The
set of predicted positions can then be narrowed based on their
correlation with a new set of possible positions derived from an
updated radio-frequency communication. The parameters in the
narrowed set of positions is then updated to new predicted values
based on the velocity or speed. This process can repeated
iteratively until only a single predicted position remains, or
until the set of positions is narrowed enough to represent an
acceptable level of positional accuracy.
[0035] The determination of position based on the motion sensors
may include a position simulation based on statistical model such
as a particle filter. Such a particle filter simulation may include
populating a stored map of worksite 20 with one or more virtual
particles. Each particle represents a different possible machine
position and/or orientation. For example, the position may be
represented by an x-coordinate associated with an x-axis and a
y-coordinate associated a y-axis. Orientation of each particle may
be represented by degrees of rotation relative to, for example, the
positive x-axis, or a two-dimensional unit vector characterized by
an x- and y-value. During such a simulation, position system 30
randomly populates a map stored in the memory system 21 with
particles. Each particle has an initial randomly generated position
and orientation. The respective positions and/or orientations of
the particles are then iteratively updated based on information
from position data derived from the elapsed time measurements to
respective reference signal devices 34, 37, until monitoring system
30 is able to determine an accurate position of machine 10
indicated by a spatial convergence of the updated particles.
[0036] For any of the above embodiments based on a time-based
characteristic, the initiating device(s) and the responding
device(s) are Radio-Frequency Ranging (RFR) devices. In one
embodiment, the initiating device(s) are respective active (as
opposed to passive) RFID tags and the responding device(s) may be
respective RFID readers. Alternatively, the initiating device(s)
may be respective RFID readers and the responding devices may be
respective active RFID tags. However, as a further alternative, the
initiating devices and receiving devices are Radio Frequency
Ranging (RFR) comprised of the same hardware configuration, but
which may be selectively commanded by processing system 38 to
initiate the radio-frequency from selected RFR device to any one or
more other RFR devices in the RFR system.
[0037] The accuracy of the position determination may be improved
in a number of ways. In one embodiment, the RFR devices are
ultra-wideband (UWB) radio-frequency devices configured to
determine a distance between respective devices based on an UWB
radio-frequency communication. In some embodiments, the
communicated UWB radio-frequency signals have a bandwidth in the
order of gigahertz. For example, in one embodiment, the frequencies
may range from 3.1 to 5.3 GHz, with a centre frequency of 4.3 GHz,
thus providing a bandwidth of approximately 2 GHz. The radio
frequency signal transmission may be comprised of a train of pulse
waveforms. The pulsed waveforms are short impulses having frequency
components that are, in some embodiments, spread over two or more
gigahertz. In one embodiment, the spread of frequencies has a
centre frequency of around 4 GHz, eg 4.3 GHz. The calculation
relating time-of-flight to distance of travel of the radio
frequency transmission assumes that the path of transmission is
along a straight line. However, in underground mine sites,
radio-frequency transmissions are reflected by the rock bed that
forms the walls of the mine tunnels, so the transmission has
multiple paths between the transmitter and receiver. The multiple
paths result in the signal being received at a multitude of
different times, making it difficult to determine the time of the
direct, straight path. However, the direct path will arrive first,
so can be determined from the leading edge of the received signal,
ie the first received pulse. The use of UWB radio-frequencies can
improve the resolution of the measurement due to high bandwidth,
high frequency composition of the waveform, or put conversely, due
to the short wavelength of the signal. In one embodiment, to enable
the direct path of transmission to reach the receiver, and be
received at an adequate signal strength to accurately detected, the
transmitting and receiving RFR devices are arranged in
line-of-sight of each other.
[0038] In some embodiments, the radio-frequency signal is
transmitted and processed for the coherent signal processing. The
coherent signal processing involves repetitively transmitting the
radio frequency signal in a coherent manner so that same bits of
data transmitted via the communication repetitively transmitted
over multiple transmissions. This allows the amplitude of the
signal transmission to be lower for a given signal-to-noise ratio.
The reduced amplitude and hence, power, of the transmission may in
some instances be of assistance in ensuring that the
radio-frequency communication in within any maximum allowable
electromagnetic emission level. This may assist the monitoring
system 30 in meeting any regulatory electromagnetic compatibility
(EMC) standards which may be required. Additionally or
alternatively, the low signal-to-noise ratio can be used to
increase, for the same power level, the maximum distance over which
the ranging devices may communicate. Accordingly, in some
embodiments, the mobile signal device 36 and the reference signal
devices 34, 37 determine a time-of-flight measurement using
coherent signal processing. Further, in some embodiments, the
coherent signal processing is achieved using UWB radio-frequency
ranging devices as the respective signal devices 34, 36, 37, and
the time of flight measurement is a two-way (round-trip)
time-of-flight measurement. In one embodiment, the UWB coherent
processing radio-frequency ranging devices are PulsON.RTM. 410
(P410) ranging radio devices manufactured by TimeDomain.RTM. (TDC
Acquisition Holdings, Inc.). In another embodiment, the UWB
coherent processing radio-frequency ranging devices are P412
ranging radio devices, and in a further embodiment, the UWB
coherent processing radio-frequency ranging devices are P442
ranging radio devices, also manufactured by TimeDomain.RTM..
[0039] In an exemplary embodiment of a two-way time of flight
measurement involving coherent processing, a data packet may be
transmitted multiple times, at regular intervals (ie a known duty
cycle), in a first signal from the initiating device to the
responding device. The data packet includes a time stamp indicating
the first time that the data is transmitted and an identifier that
identifies the initiating device (eg the initiating device's MAC
address). The responding device receives the transmission, and
identifies the time at which the signal is first arrived at the
responding device. The responding device knows the duty cycle at
which the data packets are transmitted. Thus the responding device
can correlate the packets to integrate corresponding bits within
each packet and thereby improve the signal-to-noise ratio. The
responding device then determines a one-way time of flight based on
the time stamp and the recorded time of arrival. The responding
device then sends a response signal to the initiating device using
the same repetitive transmission method, but encoding in the
response data packets the time of transmitting the response signal,
the calculated one-way time-of-flight, the identifier of the
initiating device and an identifier associated with the responding
device (eg the responding device's MAC address). The initiating
device then receives the response signal and correlates the data
from each data packet to improve the signal to noise ratio. The
initiating device records the time of first receiving the response
signal, and determines the time-of flight for the response signal.
The two-way time-of-flight is then derived by the initiating device
by summing the time-of-flight of the first signal and the
time-of-flight of the response signal.
[0040] FIG. 3 illustrates, on a map of worksite mine 20, an
arrangement of monitoring system 30. The mine has a plurality of
tunnels parallel 113, 115. At a first end of each of the tunnels
113, 115 are respective first signal devices 34, being reference
signal devices as described herein. Machine 10, having a mobile,
second signal device 36, is assigned to operate a tunnel 113 and
portions of the worksite branching therefrom, such as designated
loading locations (eg drawpoints) for loading ore, and at least one
designated dumping location (eg an ore pass) for dumping ore. In
some embodiments, the machine 10 is operated to move earth material
other than ore, in which case the designated loading and dumping
locations may relate to the other earth materials. In some cases,
such other materials may be dirt or waste having no intrinsic
value, yet it may nonetheless be desirable to determine the
activity of the machine in relation to movement of these materials.
Each of the designated loading locations and dumping locations are
assigned a corresponding unique activity identifier 50, 52, which
are mapped to the mine map. Each activity identifier identifies a
specific one of the designated locations. The activity identifiers
50, 52 are stored in the memory system of processing system 38.
Therefore, the activity identifiers 50, 52 act as virtual
identifiers with respect to the stored mine map or other stored
geographic frame of reference, such as one or more geographic
coordinates. Accordingly, as far as the monitoring system is
concerned there is no need for the activity identifiers to occupy
physical space in the mine.
[0041] The activity identifiers 50, 52 comprise first activity
identifiers 50 uniquely identifying each of the designated loading
locations, and second activity identifiers 52 uniquely identifying
each of the designated dumping locations. Associated with each
identifier 50, 52, is a geographic area over which the
corresponding designated location is located. Each geographic area
may be identified in the memory system of processing system 38. For
example the area may be represented by coordinates corresponding to
the mine map. In the embodiment illustrated in FIG. 3, these
geographic areas are indicated on the mine map as shapes indicated
by broken lines. In another embodiment, the area is known by the
processing system 38 in terms being within a maximum radial
distance from the location associated with the corresponding
identifier. In further embodiments, rather than radial distance,
the areas corresponding to the designated locations may be
represented by other dimensional relationships with respect to the
identifier's location or with respect to the mine map. Another
machine 11 operates in another tunnel 115 of the mine, although,
optionally but not shown, the other machine 11 may operate in the
same tunnel 113 as machine 10. Machine 11 may have the same
components as machine 10, and like machine 10, and may also be an
LHD loader. Machine 11 has a corresponding mobile, second signal
device 36 being uniquely identifiable from the mobile device 36 on
machine 10 to due to each of the mobile devices 36 having a
different serial number, MAC address or some other unique
identifier by which the mobile device 36 may be uniquely
identified. At a second end of the tunnels 113, 115, opposite the
first end, are respective third signal devices 37, being reference
signal devices as described herein.
[0042] Each of the reference signal devices 34, 37 have a field of
operation, within the tunnel, over which the reference signal
devices 34, 37 have a line of sight. The field of operation passes
at least two of the designated loading locations. In the embodiment
of FIG. 3, the field of operation extends at least half way down
the corresponding tunnel 113, 115, and optionally, the entire
length of the tunnel 113, 115. Each of the reference signal devices
34, 37 are positioned at intersections of the corresponding tunnel
113 or 115 and a cross-road 119 connecting the respective tunnels
113, 115, so the field of operation also includes part of a cross
road 119. In this way, the reference signal devices 34, 37 so that
mobile machines 10 and 11 are always within a line of sight to at
least one, and in one embodiment two, reference signal devices 34,
37. In one embodiment, the reference signal devices 34, 37 are
positioned on longitudinal centerlines of their corresponding
tunnel. Since the tunnels 113, 115 are relatively narrow, the
signal device 36 will be generally collinear with the signal
devices 34, 37 at either end of the tunnel. This reduces the
position determination to a determination in 1-dimensional space,
thus enabling accurate longitudinal position determination by
bi-lateration.
[0043] Ethernet network 39 connects the processing system 38 to
each of the reference signal devices 34, 37 and, optionally, also
to wireless network transceivers 40, in the form of Wi-Fi
transceivers, located proximal to a corresponding reference signal
device 34, 37. The wireless network transceivers 40 are, in one
embodiment, located at the intersection of the corresponding tunnel
113, 115 and crossroad 119. However, in the embodiment illustrated
in FIG. 3, the wireless transceivers 40 are located adjacent the
intersection, just inside the corresponding tunnel 113 or 115, and
have a line of sight meeting the same criteria as for the reference
signal devices, so that the mobile signal devices 36 are always
within line-of-sight of at least one wireless transceiver 40. The
Ethernet network 39 includes an Ethernet switch (not shown) at or
next to each of the reference signal devices so that the reference
signal devices, and optionally the WiFi transceivers, are connected
in a daisy chain topology. In one embodiment, each Ethernet switch
is included in a corresponding reference signal devices 34, 37. The
Wi-Fi transceivers may be used to send and/or receive operational
data to and/or from a Wi-Fi transceivers (not shown) on the
respective mobile machines 10, 11. The operational data may for
example include information which may be read or entered by an
operator of the mobile machine via a user-interface module (not
shown) in communication with the Wi-Fi transceiver on the mobile
machine 10, 11.
[0044] The respective positions of the machines 10, 11 in the
worksite 20 may be determined based on radio-frequency
communication in accordance to any method and on any system
described herein. However, in one embodiment, particularly suited
to the arrangement of monitoring system 30 in FIG. 3, reference
signal devices 34, 37 are UWB radio-frequency ranging devices
having features and operation as has been previously described.
[0045] The position of the second signal device infers the position
of the machine 10 at the part of the machine 10 at which the second
signal device 36 is mounted. In some embodiments, the second signal
device is mounted on the rear portion 27 of the machine 10. This is
because when the machine 10 is in a drawpoint or ore pass, the rear
portion of the machine remains in the tunnel 113, 115 from which
the drawpoint or ore pass is accessed. By keeping the second signal
device 36 within the tunnel 113, 115, a line-of-sight communication
can be maintained between the second signal device 36 and at least
one of the reference signal devices 34, 37. Thus, for any
operational position of the machine 10, the monitoring system 30
maintains (or may obtain) positional knowledge concerning the
current position of the machine 10 from the signal devices 34, 36,
37.
[0046] An exemplary method 200 for determining an activity
associated with a machine, in accordance with the present
disclosure, is illustrated in FIG. 4. At step 202, monitoring
system 30 performs a radio-frequency communication between
reference signal device 34 at a known location and a mobile signal
device 36 on the machine 10. In some other embodiments, the
communication involves one or more round-trips between the mobile
signal device 36 and the reference signal device 34. In the case of
the communication involving at least one round trip, at step 204 a
first radio frequency signal is transmitted from an initiating
device, being one of the first reference signal device 34 and
mobile signal device 36, to the responding device, the responding
device being the other of the first reference signal device 34 and
the mobile signal device 36. At step 206, after receiving the first
signal, the responding device transmits a response signal back to
the initiating device. The initiating device, upon receiving the
response signal determines the position of the machine 10 in a
manner as described herein, based on a time-of-flight. In other
embodiment, the radio-frequency communication at step 202 is a
one-way communication. In this case, the position may be determined
based on some other time-based metric such as
time-difference-of-arrival, provided positioning system 30 takes
into account an arrival time with respect to a communication
between the mobile device and a further reference signal device 37,
as described herein. In either case, the position of the second
ranging device 36 and thus machine 10, is determined in step 210,
based on at least on a time-based characteristic associated the
radio-frequency communication. At step 218, the processing system
38 identifies an activity of the mobile machine 10 based on a
positional correlation between the determined position of the
mobile machine 10 and one of a plurality of activity identifiers
associated with respective positions in the mine 20. In addition to
identifying a type of activity, the monitoring system 30 may
identify the location associated with the activity. The monitoring
system 30 may further identify a time or time period at which the
activity is determined to have occurred. The positional correlation
is determined with respect to a geographic frame of reference (eg
the worksite map) stored in the memory system 21. In one
embodiment, the processing system 38 of the monitoring system is
configured to display the worksite map, the activity identifiers,
and the determined position of the machine 10 on the display panel
of the user interface, for example, as illustrated in FIG. 3.
[0047] There will now be described exemplary embodiments for
determining an activity associated with machine 10, based on the
determined position of the machine 10. In some of these
embodiments, the activity determination is more specifically based
on position of a portion of the machine.
[0048] In some embodiments, processing system 38 determines or
infers the position of the front bucket 25 of the front portion 23
of machine 10 based on the determined position of the second signal
device 36, and an inferred position of the rear portion 27 of the
machine 10. The position of the front bucket 25 may be determined
by using the orientation information from the digital compass 16
and/or articulation sensor 17 to determine the position of the
front bucket 25 with respect to the second signal device 36. In one
embodiment, the monitoring system 30 determines that the machine 10
is in a drawpoint or ore pass if: (i) the articulation sensor
indicates that the front portion 23 (and therefore the bucket 25)
of machine 10 is rotated by more than a threshold angle with
respect the rear portion of the machine; and (ii) the position of
the second signal device 36 is adjacent an ore pass or drawpoint.
This conclusion is derived from an assumption in some situations
that, for the machine 10 to access the ore pass or drawpoint, the
machine 10 must be oriented in a sufficiently bent manner.
Accordingly it is concluded that the bucket 25 is positionally
correlated with the ore pass or drawpoint adjacent the machine. In
one embodiment the threshold angle is 25 degrees. In some
embodiments, this bent orientation is required due the tunnel being
relatively narrow, which limits the range of positions of the
machine 10 from which the ore pass or drawpoint may be accessed. By
contrast, if the articulation sensor 17 indicates that the rotation
is less than the threshold angle, the monitoring system 30
determines that the orientation of the machine 10 is substantially
straight, or at least not sufficiently bent to indicate loading or
dumping at a drawpoint or ore pass.
[0049] In other embodiments, the position of mobile signal device
36 may be combined with historical data regarding the orientation
of machine 10 in order to determine the correlation with an
activity identifier 50, 52. This may be useful in instances where
the machine 10 turns to enter a designated activity location, but
has straightened up by the time the machine 10 reaches a positional
correlation with the associated activity identifier 50, 52. Recent
orientation data indicating the turn may be used in this case to
infer the positional correlation of the bucket 25 with the activity
identifier.
[0050] In some positions along the tunnel 113 there are more than
one designated loading or dumping locations for the same
longitudinal position along the tunnel 113. For example, for the
same position along the tunnel's length, there may be two
drawpoints 54, 56, one each side of the tunnel. Drawpoint 54 is on
the left side of the tunnel 113 as the machine 10 drives along a
longitudinal centerline of the tunnel 113, along path 90, toward
reference end 91 of the tunnel 113. The other drawpoint 56 will be
on the right side of the tunnel 113 as the machine drives towards
the reference end 91. In FIG. 3, drawpoints 54 and 56 are slightly
offset from each other, with respect to the longitudinal axis of
tunnel 113. However, for the position of the second signal device
36, the bucket 25 of machine 10 could potentially be in either of
the drawpoints 54 or 56, depending on the rotation at the
articulation joint 19. Further, in some mines, drawpoints on either
side of a tunnel may be directly opposite each other, ie with no
longitudinal offset, making it harder to distinguish which
drawpoint the machine 10 is positionally correlated with.
[0051] The uncertainty over which side of the tunnel 113 the bucket
is located may, in some cases, be exacerbated if the monitoring
system 30 is unable to sufficiently determine the position of the
second signal device 36 across the tunnel 113, ie how the second
signal device 36 or machine 10 is positioned laterally from the
longitudinal centerline of the tunnel 113. For example, with one
reference signal device 34 at one end of tunnel 113, and one other
reference signal device 36 at the other end of tunnel 113,
positioning based on the radio-frequency communication alone may
not provide sufficient accuracy or positional resolution to
determine the lateral position.
[0052] One way to determine the lateral position is to use a
time-of-flight or time of arrival measurement (the latter being for
a time-distance of arrival measurement) associated with a reference
signal device located in an adjacent tunnel 115. However, a
reference signal device from an adjacent tunnel 115 will not have a
line of sight to the second signal device 36 of machine 10, so the
measurement may be unreliable. However, based on the determined
position of the second sensing device 36 and the angle and
direction of rotation of the articulation joint 19, as measured by
articulation sensor 17, monitoring system 30 can conclude which of
the left or right drawpoints 54 or 56 the bucket 25 is positionally
correlated with, based on their respective positions as indicated
by their associated activity identifiers 50. If the angular
orientation indicated by articulation sensor 17 is very small (ie
the machine 10 is substantially straight), monitoring system 30 can
conclude that the bucket 25 is somewhere between but not in the
drawpoints 54, 56. Put another way, bucket 25 is not positionally
correlated with either of the drawpoints 54, 56.
[0053] By determining whether the machine is positionally
correlated with an activity identifier, the monitoring system 30
can also infer instances when the machine is inactive, which may
indicate a fault with the machine or a problem experienced by an
operator (i.e. a person) on the machine. Typically, if the machine
10 is stationary for longer than some short period of time, eg 10
seconds, it may be concluded that the machine 10 is either loading
ore, dumping ore or is inactive. However, when the machine is near
a loading or dumping location it may be difficult to determine
whether the machine is inactive or, alternatively, loading or
dumping. However, when the machine 10 is not loading or dumping it
should be moving between loading and dumping locations. Taking this
into account, in one embodiment, monitoring system 30 determines
that the machine is in an inactive state if the machine 10 is
stationary for longer than the predetermined time-period, eg 3
minutes, while the mobile machine is not positionally correlated
with a first or second position identifier 50, 52 for loading or
dumping. The monitoring system 30 may indicate to an operator of
the monitoring system 30 that an inactive status has been
determined, so that the operator may act in response to the
inactive status determination. In some applications loading and
dumping activities only take 10-20 seconds. In such applications
monitoring system 30 may determine an inactive status if the
machine 10 is correlated with a loading or dumping activity
identifier for longer than a predetermined period of time, eg 5
minutes, as this may indicate a problem with the machine 10.
[0054] Additionally, or alternatively to using the orientation
information from the articulation sensor 17, the positional
correlation can be determined from the position of the second
sensing device 36 and orientation information from digital compass
16. Digital compass 16 measures the orientation, in terms of
direction, along which the front portion 23 of machine 10 is
aligned. By tracking the position of machine 10, which generally
travels in a forward direction, the monitoring system 30 can
determine the orientation of the rear portion 27 of machine 10, on
which second signal device 36 is mounted. As an alternative to
assuming that the machine travels in the forward direction, the
monitoring system 30 may determine whether the machine 10 is moving
forward or in reverse along tunnel 113 based on information from
the motion sensing device 14. Knowing the orientation of the rear
portion 27 and the orientation of the front portion 23, monitoring
system 30 can determine whether the bucket 25 is positionally
correlated with any activity identifiers 50, 52 respectively
identifying the positions of the designated loading or dumping
location(s), either side of the tunnel 113.
[0055] For example, in the embodiment illustrated in FIG. 3, the
tunnel runs from a south-west end to a north-east end (reference
end 91). It may be known, eg by tracking movement of machine 10,
that the rear end 29 of rear portion 27 is facing south west. If
the directional orientation of the front portion 23 is north-south
aligned, it may be concluded that the bucket 25 is positionally
correlated with a designated dumping/loading location on the left
or western side of the tunnel, as shown in FIG. 3, illustrating the
bucket 25 being positionally correlated with the north-western
drawpoint 54. On the other hand, if the digital compass 16
indicates that the front portion 23 is east-west aligned,
monitoring system 30 can conclude that the bucket 25 is
positionally correlated with south-eastern drawpoint 56.
[0056] The orientation information in terms of both directional
orientation (from digital compass 16) and angular orientation (from
articulation sensor 17) can be used to determine the precise
location of the bucket 25 with respect to the mine map, for a
determined position of second signal device 36 or the machine 10 to
which the second signal device is mounted. Alternatively, the
precise location of the bucket 25 with respect to the mine map can
be determined based on the information from either one of the
digital compass 16 and articulation sensor 17, by taking into
account the how the current position of machine 10 and how the
machine's position along tunnel 113 has changed with time (eg by
using a particle filter or Kalman filter or any other position
tracking method). The position of the front bucket 25 is derived
with respect to a map of the mine which is stored in a memory
system of the processing system 38. In one embodiment, the position
is stored as a coordinate, such as an x (eg north/south) and y (eg
east/west) coordinate, with respect to the map of the mine. In
other embodiments the position may be stored a memory address which
corresponds to a particular position on the map. The positional
correlation of bucket 25 with respect to any one or more the
activity identifiers 50, 52 for the designated loading and dumping
locations can then be calculated or otherwise determined.
[0057] In one embodiment, the distance from the bucket 25 to any or
all of the positions associated with the activity identifiers 50,
52 is calculated by measuring the distance between x and y
positional coordinates of the bucket 25 and x and y positional
coordinates for the respective activity identifiers. If the
distance with respect to any one activity identifier is less than a
threshold distance, eg 3 meters, then the bucket is determined to
be positionally correlated with that activity identifier.
Accordingly, the activity performed by machine 10 is then
determined to be the activity associated with the activity
identifier.
[0058] In another embodiment, as indicated in FIG. 3, each activity
identifier is associated with a specific area, which is indicated
on, or with respect to, a map of the mine. In FIG. 3, each of these
areas are illustrated by triangular shapes. However, any shape may
be used to indicate the area associated with an activity identifier
50, 52. In one embodiment, if the position of the bucket 25 is
within the area associated with an activity identifier, then the
machine 10 is then determined to be performing the activity
associated with the activity identifier. In some cases, the
activity may be performed if the bucket is partially within the
area. For such cases, monitoring system 30 is configured to
minimize false activity determinations by determining how much of
the bucket is within the area and makes a decision on the whether
the activity is being performed based on a threshold area
measurement. For example, the machine may be determined to be
performing the activity if minimum percentage or amount of the
bucket 25 is within the area associated with the activity
identifier 50, 52. In another embodiment, positioning system 30
determines if two points on the machine 10 (eg two points on the
front of the bucket) are within the area.
[0059] In further embodiments the mobile machine 10 may be a truck
(not shown) that operates in a truck level or haulage layer (not
shown) of the mine 20. The truck may have the same features as the
LHD loader, but might not have an articulation joint 19 or
articulation sensor 17. Alternatively, the truck may have an
articulation joint 19 and articulation sensor 17, but the joint 19
and sensor 17 might not be of assistance in identifying the truck's
activity. Like the case of an LHD loader, the truck may have a
bucket 25 adapted for carrying ore. Alternatively, in place of
bucket 25, some other portion of the truck may be adapted for
carrying ore, eg a rear portion of the truck. The system 30 may
thus determine the activity of the truck based on the positional
correlation of the bucket 25 (or some other portion of the truck
for carrying ore) and an activity identifier in the mine 20. In
this case the first activity identifiers 50, corresponding to a
designated loading location, may be associated with a corresponding
chute that receives ore from an associated orepass. Second activity
identifiers 52, corresponding with designated dumping locations,
may be associated corresponding crushers.
[0060] Regardless of whether the mobile machine (10) is an LHD
loader, a truck or some other vehicle, in some embodiments, the
positional correlation between the mobile machine 10 and an
activity identifier 50, 52 may be determined without reference to
the orientation of the machine 10 or the portion of the machine 10
for carrying ore. For example, in one embodiment, if the entire
mobile machine 10 is determined to be within an area defined by an
activity identifier, system 30 determine that the machine is
performing the activity associated with the positionally correlated
activity identifier. In other embodiments the positional
correlation with the activity identifiers may be determined with
respect to the second signal device 36, alone. Thus, in such cases
the orientation of the machine 10 need not be considered. Such
embodiments may be employed especially in cases where an activity
identifier corresponds to a relatively large, spread out area, in
comparison with the size of the machine 10.
[0061] In further embodiments, the orientation of machine 10 may be
utilized to determination the positional correlation of the machine
with an activity identifier but the orientation is derived by
tracking the movement of the mobile signal device 36 on the mobile
machine. The orientation of the mobile machine 10 can then be
inferred based on the movement of the mobile signal device 36 and
known behaviors of the machine 10 and/or limitations on the
machine's locomotion.
[0062] In addition to loading and dumping activity identifiers 50,
52, other activity identifiers may be used by monitoring system 30.
For example, an activity identifier may correspond with a parking
bay to allow for identification of the machine 10 as being in a
"parked" activity state when it is in the parking bay. In other
example, the activity identifier may correspond with a workshop for
identifying when the machine is in a non-operational state, and
undergoing repairs, modifications or servicing.
[0063] Monitoring system 30 can also determine the activity of the
machine 10 based on the determined position of the machine, taking
into account a previously determined activity or previous
correlation between the mobile machine (or a portion thereof) and
an activity identifier. For example, if the machine position had
been correlated with a loading location, and the machine's position
is subsequently determined to be moving away (or to have moved
away) from the loading location 50, the monitoring system 30 may
determine the machine's position to be `travelling full`, ie
travelling full of ore or other earth material, as the case may be.
Similarly, when the position of the machine is determined to be
travelling away from (or to have just left) a designated dumping
location 52, the monitoring system 30 may determine the machine's
activity to be `travelling empty`, since it can be assumed that the
machine 10 has just emptied its contents at the dumping location
52. When the monitoring system has determined that the machine 10
has been travelling empty, loaded, traveled full, dumped, the
monitoring system can determine that the machine 10 has completed a
cycle. Such cycles may be accumulatively tracked by the monitoring
system.
INDUSTRIAL APPLICATION
[0064] FIG. 5 illustrates an method 220, which is an embodiment of
the method 200. Steps 202, the communication system 33 performs an
ultra-wideband radio-frequency communication. The communication
involves, at step 224, repetitive transmission of data packets from
an initiating signal device (a reference signal device 34, 37 or
the mobile signal device 36) to a responding signal device (the
other of reference signal device 34, 37 or the mobile signal device
36). The data packets are coherently processed at the responding
device to determine the propagation time (time-of-flight) from the
initiating device to the responding device. At step 206, the
responding device then repetitively transmits a response packet
back the initiating device, which coherently processes the response
packet to determine the propagation time from the response device
to the initiating device. The initiating device, then sums the
determined two propagation times to determine a two-way time of
flight at step 228. The two-way time of flight is determined for a
plurality of round-trip communications and fed into a Kalman filter
(not shown) to improve the accuracy of the two way time of flight
measurement. From the Kalman filter's time of-flight measurement, a
distance measurement is derived and fed into a statistical filter
at 229 which determines the position of the mobile signal device 36
with respect to the mine 20, based on the distance measurement and
the known location of the reference signal device 34, 37 associated
with the distance measurement. The communication system repeats
steps 224 to 208 to derive further distance measurements for
subsequent positions of the machine 10. In one embodiment, the
statistical filter is another Kalman filter. Based on these
iteratively derived distance measurements the Kalman filter
determines the position of the machine 10, at step 230. In an
alternative embodiment, the statistical filter is a particle
filter, which receives the iteratively derived distance
measurements and also orientation information from an orientation
sensing device 16, 17 to derive the position of the machine 10. At
step 236, the processing system 38 evaluates the positional
correlation between the machine (or ore-carrying portion thereof,
such as bucket 25) with activity identifiers to identify whether
there is an activity identifier that is positionally correlated
with the machine 10 or portion thereof. If the machine is
positionally correlated with an activity identifier, the processing
system 38 determines that the machine is performing the activity
associated with the correlated activity identifier, at step 238.
The communication system 30 continues to perform
radio-communications to track the position of the machine as it
moves in the mine and identify further activities as the machine
moves into a positional correlation with further activity
identifiers.
[0065] In some embodiments, monitoring system 30 need not indicate
or record which specific machine in the mine performed the
activity. Rather, the monitoring system 30 may merely indicate, or
record in a memory system, that the activity has been performed.
For example, if a machine is involved in a loading activity,
monitoring system 30 might only record that the activity of loading
ore has occurred and, optionally record the specific loading
location from which the ore was loaded. Similarly, if a machine is
involved in a dumping activity, the monitoring system 30 may also
record that ore has been dumped, and optionally record the dumping
location at which the dumping occurred. Such information may be
used, for example, to track the movement of ore within the
mine.
[0066] By using a time based characteristic to determine the
position of machine 10, the machine's position can be tracked even
when the machine 10 is outside of the designated loading or dumping
locations. The use of a time-based characteristic may allow the
machine 10 to be relatively accurately determined and/or tracked
using referencing hardware (reference signal devices 34, 37)
located at one or both ends of the tunnel. It can thus be
determined when the machine 10 is at a designated loading/dumping
location without requiring RFID hardware to be installed and
maintained at the designated loading/dumping locations.
Furthermore, the tracking function enabled by the time-based
position determination enables other activity states of the machine
to be determined when the machine 10 is not at a designated
loading/dumping location.
[0067] It will be understood that the disclosure in this
specification extends to all alternative combinations of two or
more of the individual features mentioned or evident from the text
or drawings. All of these different combinations constitute various
alternative aspects of the disclosure.
* * * * *