Note: Descriptions are shown in the official language in which they were submitted.
CA 02318686 2000-09-12
BP #5568-51
BERESKIN ~ PARR CANADA
Title: METHOD OF AND APPARATUS FOR GUIDANCE OF AUTOMATED
VEHICLES
Inventors: ROSS POOLE
JACK PURCHASE
ROBERT WARD
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Titte: METHOD OF AND APPARATUS FOR GUIDANCE OF AUTOMATED
VEHICLES
FIELD OF THE INVENTION
This invention relates to guidance systems for automated
vehicles. More specifically, the invention relates to a method of and an
apparatus for use in the guidance of automated vehicles in a mine
environment.
BACKGROUND OF THE INVENTION
The use of automated or driverless vehicles is becoming more
widespread. Such vehicles are commonly used in a variety of industrial
settings, where it is desired to have one or more vehicles travel a set route,
or in a defined network of routes. In such situations, automated vehicles
offer considerable advantages and cost savings.
Automated guidance systems for these vehicles have been
developed for use in factories and the like. To keep the design of the
guidance system simple and robust, a common element of most systems
is to provide some clear indication of the path or route along which the
vehicle is to travel. The route or routes are usually fixed or set, and it is
simply a matter of making a single installation of some device marking the
route. One known technique is to provide a wire or cable embedded onto
the floor of a factory. A guidance system then uses the electromagnetic
characteristics of this cable to guide the vehicle so that the vehicle follows
the path of the cable. It is also known to use optical techniques and a strip
painted on the floor. All of these systems have the advantage that the fixed
element defining the intended path is simple, robust and passive, i.e. it
does not require power nor is maintenance required for an active device.
Automated vehicle guidance systems have also been
developed for use in mines. A mining environment poses a wholly different
set of problems from a conventional industrial setting. Firstly, the whole
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environment is much harsher than a conventional factory. Frequently, there
are high levels of dust, and any path or route rather than being a smooth,
concrete floor or the like may well be along the rough floor of a tunnel or
drift.
Further, the pathways of the vehicle in a mine are often irregular, both
vertically and horizontally, and are subject to constant change. In a factory
setting, the initial cost of the system defining the route or path of the
vehicle
is not usually critical, since it is a one-time cost. In a mine, on the other
hand, where the route or path must be constantly changed and updated, the
cost of installing devices or equipment to define the route is an extremely
important factor. Additionally, in a mine, it may be difficult and costly to
maintain a supply of electrical power throughout the mine.
One example of a system used to guide automated vehicles in
a mining environment is disclosed in Canadian Patent No. 2,041,073. The
system provides a guide for a vehicle in the form of an elongate reflective
strip suspended above the desired path for the vehicle. This provides a so-
called coded longitudinal reference means, which more specifically is
retroreflective. There are various proprietary tapes available which provide
such retroreflective capability. The reflective strip would be detected by
lasers. The lasers are oscillated from side to side, and the position of the
laser is noted when a reflected beam is returned to the vehicle.
As a further example, Canadian Patent No. 2,145,731
discloses an automated guidance system for a vehicle which provides a
guide in the form of a continuous source of light arranged parallel to the
intended path and above the vehicle. Such a source of light can be what is
known as a "light rope". This is a commercially available product
comprising numerous small bulbs encapsulated to form, in effect, a
continuous rope or string. It provides a continuous, bright source of light,
which is easily recognised by a vision guidance system. Some sort of
vision guidance system is provided, so that an on-board vehicle guidance
system can determine the lateral position of the vehicle relative to the
"light
rope", to guide the vehicle.
Still further, pending United States Application No. 09/060,134,
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filed by the applicant, discloses a guidance system comprising a guide in
the form of a fluorescent elongate element mounted along a desired path
capable of absorbing radiation at a first frequency and radiating radiation at
a different, lower frequency. The elongate element may comprise several
portions which may be used to define different paths, each portion capable
of radiating radiation at a frequency different from the radiation radiated by
any other portion upon absorbing radiation of the first frequency. A portion
of
the elongate element is illuminated with radiation of the first frequency, and
the radiated radiation is detected by a detector mounted on the vehicle. This
provides positional information to the control unit, which can enable
guidance means to steer the vehicle along the desired path.
To date, the automation of mine vehicles in particular has been
achieved by starting with a conventionally designed vehicle and adding to it
the: necessary automated control system. There are a number of reasons
for this. Often, any automation scheme will only provide guide paths along
high traffic routes, e.g. from a work face to a location for dumping ore.
Consequently, there will always be occasions when a vehicle has to be
manually driven, e.g. when it is to be taken to a service centre for routine
maintenance. Additionally, many mine managers are reluctant to dispense
2o with manual controls and rely solely on what may be perceived to be
unproven automation technology. A further consideration is that automation
equipment, with modern electronics, is relatively compact and lightweight,
so that it is a simple matter to add this, in addition to standard manual
controls.
Accordingly, many of the vehicles used today in conjunction
with automated guidance systems such as those mentioned above are still
built with manual control mechanisms (i.e., controls to be used by a human
operator) despite the fact that the vehicles are used primarily in a mode
w'iere vehicle movement is automated and no on-vehicle manual control is
required. The manual control mechanisms are thus used infrequently,
typically only in situations where a vehicle is required to travel along a
path
where a guide is unavailable, and where it is either inconvenient, expensive,
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or otherwise undesirable to install a guide along the path. As noted, the
manual control mechanisms may be used by an on-board driver to steer the
vehicle to a garage or repair centre for maintenance or refuelling. The
manual control mechanisms may also be used to move a vehicle from one
set of paths where automated movement is possible, to a separate set of
paths at a different location.
Unfortunately, building or equipping automated vehicles with
the capability of being operated manually can be costly. In particular, a mine
environment can be very harsh, and providing suitable protection and at
i0 least some degree of comfort for the operator is costly. For example, it is
common to provide special seats to prevent spine injuries, and the cost of
the seat can be 15% of the total cost of the manual controls, which
themselves can cost on the order of CAN $100,000. Thus, there is the
possibility of substantial savings by building automated vehicles without
manual controls. Accordingly, the present invention has realized that there
is a need for a system and method to allow for automated vehicles not
equipped with manual controls to move along on a path where the normal
guide (e.g., reflective strip, light rope, or elongate element as described
above) is unavailable.
SUMMARY OF THE INVENTION
One aspect of the invention relates to an assembly for
providing a simulated towing action for automated vehicles comprising a
towing vehicle, an automated vehicle including drive means, steering
actuation means and a controller connected to the drive and steering
actuation means for control thereof, a tow frame towed behind the towing
vehicle, and guiding means mounted on the tow frame and the automated
vehicle for providing information to the controller on the relative spacing
and
orientation of the automated vehicle relative to the tow frame, whereby the
controller controls the automated vehicle to cause the automated vehicle to
follow the path travelled by the towing vehicle, and wherein the tow frame
ensures adequate spacing between the towing vehicle and the automated
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vehicle.
The invention also provides for a tow frame for use in an
assembly comprising a towing vehicle and an automated vehicle intended
to follow the towing vehicle in a manner of a simulated tow. The tow frame
comprises a tow frame, a coupling element at the forward end of the tow
frame, at least two wheels supporting the tow frame, and signalling means
for' providing a signal to the automated vehicle enabling a controller on the
automated vehicle to determine the relative position between the towing
vehicle and the automated vehicle.
The invention also provides for a method of providing
simulated towing for an automated vehicle, the automated vehicle having
drive means for driving the vehicle, steering actuation means for steering
the vehicle and a controller connected to the drive means and the steering
actuation means for the control thereof, comprising:
(a) providing a towing vehicle and driving the towing vehicle
over a desired path;
(b) towing a tow frame behind the towing vehicle; and
(c) providing on the towing frame and the automated vehicle
guiding means, for providing an indication to the
automated vehicle of the relative spacing between the
automated and towing vehicles and relative orientation
between the towing and automated vehicles, whereby the
controller controls the automated vehicle to maintain a
desired spacing at a desired orientation between the
towing and automated vehicles.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
For a better understanding of the present invention and to
show more clearly how it may be carried into effect, reference will now be
made by way of example, to the accompanying drawings, which show a
preferred embodiment of the present invention and in which:
Figure 1 is a perspective view of the present invention in a
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preferred embodiment;
Figure 2 is a perspective view of a guiding tow bar mounted on
a T-shaped tow frame;
Figures 3a and 3b are perspective views of a guiding tow bar
mounted on alternative tow frame designs; and
Figures 4a, 4b and 4c illustrate the operation of signalling
means on a tow frame in a variant embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Figure 1, a system for guiding automated vehicles
10 is shown. Preferably, system 10 operates to guide automated vehicles
in a mining environment along paths which are not equipped with guides
used for tracking by the automated vehicles. However, system 10 can
operate on any path on which a vehicle can travel.
System 10 comprises a towing vehicle 20, one or more tow
frames 30, and an automated vehicle 40. System 10 may also comprise
additional components to aid in the transport of automated vehicles 40 to a
desired destination.
The towing vehicle 20 is operated so as to lead an automated
vehicle 40 to a desired destination. More specifically, the towing vehicle 20
2o is driven on a path to the desired destination while the automated vehicle
40
follows behind the towing vehicle 20. The towing vehicle 20 is preferably a
jeep, but can be any manually-driven or automated vehicle including an
automobile, a truck, a cart, a hauling vehicle, etc.
In the preferred embodiment of the invention, the system 10
comprises at least one tow frame 30 which is hitched to or is otherwise
pulled by the towing vehicle 20. Several tow frames 30 may be connected or
hitched together in series, in known manner and as shown. The primary
purpose of the tow frames 30 is to provide a safety zone between the towing
vehicle 20 and the automated vehicle 40 following behind the towing vehicle
20. In the event that the automated vehicle 40 is unable to stop in sufficient
time to prevent a collision with one or more tow frames 30 and the towing
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vehicle 20, the presence of the tow frames 30 makes damage to the towing
vehicle 20 and injury to any occupants of the towing vehicle 20 less likely.
In this context, a typical automated mining machine might be a
Load Haul Dump (LHD) vehicle with a weight of, for example, 26,000 to
45,000 kilograms. Such vehicles are not very manoeuvrable and it is
desirable to maintain a significant safety distance from a lightweight
guidance vehicle. Note that simply setting a larger distance between the
two vehicles is inadequate. In a mine environment, with narrow drifts, in
order to ensure that the automated vehicle takes a proper path around
corners, the vehicle must closely follow some guiding element.
The tow frame 30 which is furthest away from towing vehicle 20
is equipped with a guiding tow bar 50. The guiding tow bar 50 comprises
signalling means 52 which provide guiding elements and can be detected
by one or more guide detectors 60 on the automated vehicle 40. For
instance, the signalling means 52 can comprise radiation sources, where
the radiated radiation can be detected by a guide detector 60. As a further
example, guiding tow bar 50 may be equipped with a signalling means 52
which is a continuous source of light, where the light can be detected by the
guide detector 60. Still further, guiding tow bar 50 may be equipped with a
signalling means 52 comprising reflective or fluorescent means, which can
be detected by the guide detector 60. Guiding tow bar 50 may also be
equipped with signalling means 52 for emitting, for example, radio
microwaves or other electromagnetic radiation, which can be detected by
the guide detector 60. Guiding tow bar 50 may also be equipped with
signalling means 52 capable of emitting a combination of the above
signals.
As noted, the automated vehicle 40 is equipped with the guide
detector 60, and is also equipped with a controller 62 connected to the
guide detector 60. The guide detector can be a camera looking axially or
longitudinally; preferably there are two such cameras looking forwardly and
rearwardly, for operation in either direction. Commonly such vehicles have
two generally vertically directed cameras for following a light rope or the
like
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and two cameras mounted for detecting falls.
The controller 62 analyzes signals emitted by the signalling
means 52 on the guiding tow bar 50 (for example, light, radiation, radio
waves) and subsequently detected by the guide detector 60. The controller
62 uses this information to control the steering actuation means and the
drive and transmission systems of the automated vehicle 40. The controller
62 determines from the signals detected by the guide detector 60 the
relative longitudinal position of the guiding tow bar 50 with respect to the
automated vehicle 40. This is done simply by determining the observed
1o spacing of the signalling means 52 in the image taken by the camera 60. If
the signalling means are too close together, indicative that the vehicles are
too far apart, then the vehicle 40 is accelerated; if the signalling means or
sources are observed to be too far apart, this is interpreted to mean that the
vehicles are too close together and the vehicle 40 is slowed, either by
simply decreasing power provided by the engine and/or by braking as
required. Further, the positional information allows the controller 62 to
steer left, right, or straight relative to the direction the automated vehicle
40
is currently moving, so that it follows essentially the same path traversed by
the guiding tow bar 50. This is done by detecting the lateral location of the
signalling means 52 in the field of view or image from the camera 60, and
steering the vehicle 40, to keep the signalling means 52 centred. Therefore,
as the tow frames 30 are attached to the towing vehicle 20, the automated
vehicle 40 effectively follows the towing vehicle 20. This allows automated
vehicles 40 to be moved without the need for on-board manual operation
along paths for which guides are not installed. Hence, an automated
vehicle 40 to be used in system 10 may be built without manual controls.
In variant embodiments of the invention, the guiding tow bar 50
may be equipped with signalling means 52 which emits light or radiating
radiation in pulses, at a specified frequency, to be detected by one or more
3o guide detectors 60. This permits the controller 62 to distinguish between
light being emitted or radiation being radiated by the signalling means 52
on guiding tow bar 50 from other sources of light (for example, natural light,
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headlights, flashlights, drift lighting, machinery equipment lights, or other
reflective objects) that may interfere with the system 10 and cause the
automated vehicle 40 to follow the wrong light or radiation source.
In one embodiment of the invention, the signalling means 52
on the guiding tow bar 50 comprises two light or radiation sources
separated at a specified distance on the guiding tow bar 50. As detailed,
information relating to the distance separating the two sources can be used
by the controller 62 in determining exactly how far automated vehicle 40 is
from the guiding tow bar 50 at any particular time.
The controller 62 is also able to stop or slow down the
automated vehicle 40 (and to perform any other pre-determined desired
actions) if the camera 60 fails to detect a signal (or fails to detect one of
a
number of detectable signals) from signalling means 52 after a specified
period of time. For instance, if signalling means 52 is comprised of a light
source, and the path from the light source to the camera 60 is interrupted
(for example, if a person or vehicle crosses this path), the controller 62 may
cause the automated vehicle 40 to stop. It is anticipated that there will be
some form of communication between the automated vehicle 40 and the
towing vehicle 20, if only to enable an emergency stop to be signalled to the
automated vehicle 40. This communication link can also provide for the
towing vehicle 20 to restart the automated vehicle 40. It can also enable the
automated vehicle 40 to signal that it has lost contact with the signalling
means 52, indicating that the towing vehicle 20 needs to back up.
Also preferably, the towing vehicle 20 itself is equipped with
means to stop or otherwise disable the automated vehicle 40, which may be
useful if it is necessary to stop the automated vehicle quickly in an
emergency situation. This can be implemented, for example, by connecting
a radio receiver to controller 62 and providing a corresponding transmitter in
the towing vehicle 20. Then, the receiver can cause the automated vehicle
40 to stop upon receiving a signal from the radio transmitter. In particular,
thc~ transmitter can include an emergency stop button, so that a driver of the
towing vehicle 20 can signal the automated vehicle 40 to stop, for any
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desired reason. This radio transmitter can also be designed to maintain
continuous communication (e.g. a signal indicating the status of the towing
operation) with the controller 62. In the event that such radio communication
is interrupted or becomes unavailable for a specified period of time, the
controller 62 can cause the automated vehicle 40 to automatically stop.
The radio transmitter and the radio receiver may also be
adapted to communicate information regarding the distance between the
towing vehicle 20 (or signalling means 52) and the automated vehicle 40. A
display may be installed in the towing vehicle 20 which indicates the current
distance between the two vehicles.
In the event that the towing vehicle 20 is able to stop more
quickly than the automated vehicle 40, the automated vehicle may tend to
overshoot its desired position. For this situation, a low profile signalling
means could be provided that enables the automated vehicle 40 to ride over
the signalling means 52 without damaging it.
Referring to Figure 2, details of the tow frame 30 having a T-
shape are shown. A tow frame 30 comprises the guiding tow bar 50 and an
elongate shaft 54. The forward end of the shaft 54 includes an aperture or
coupling element 56 for coupling to a complementary coupling element. As
shown, on an extension of the elongate shaft 54, there is such a
complementary coupling element 58. Commonly, the coupling element 58
is some sort of a projecting ball or pin or the like, and the coupling element
56 is a corresponding socket. It will be understood that, for the rear most
tow frame 30, the extension of the shaft 54 and the coupling element 58 can
be eliminated. However, for convenience, it is preferable for the tow frames
to be similar. This enables any number of tow frames 30 to be coupled
together, in any order, which can be useful for maintenance and other
purposes.
The signalling means 52 are mounted on top of the guiding
3o tow bar 50 as shown. However, it is possible that the signalling means 52.
be otherwise integral with the tow bar 50.
Where the tow frame 30 omits the coupling element 58, the
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tow frame 30 must necessarily be the last tow frame. All intermediate tow
frames 30 would need both coupling elements 56, 58. It will also be
understood that the use of an intermediate tow frame 30 is optional. It is
possible that just one tow frame 30 be provided, which need include just the
coupling element 56 for attachment to the towing vehicle 20.
Although the signalling means 52 are shown, schematically,
mounted on the guiding tow bar 50, it will be understood that the signalling
means 52 could be mounted as required for a particular installation. Thus,
in some applications, it may be desirable to mount the signalling means 52
at the same height as a vision system on the automated vehicle 40.
Additionally, the relative location of the signalling means 52 may depend on
their nature. For example, as noted, the signalling means 52 can comprise
a variety of radiation sources (e.g. conventional light sources, laser
sources,
radio sources), or can simply comprise some form of reflector.
Preferably, the signalling means 52 mounted on the guiding
tow bar 50 would be very low to the ground to enable the automated vehicle
40 to ride over it without damage, as detailed above.
Reference can now be made to Figures 3a and 3b, which
show two alternative embodiments of the tow frames designated as 80 and
90 respectively. Simplistic, like components are given the same reference
numbers in Figures 3a and 3b, and the description of these components is
not repeated.
In Figure 3a, the tow frame 80 has a generally triangular shape
and comprises elements 82 forming a triangular frame, with the guiding tow
bar 50 forming or mounted on one end of the frame. Here, in addition to the
two rear wheels 70, there is a single, front wheel 84 mounted as a cast
wheel, so as to follow the direction determined by the vehicle 20. The wheel
84 is rotatively mounted in an inverted U-shaped frame 86, the U-shaped
frame 86 being pivotedly mounted below a short elongate shaft 88
extending from the front of the triangular frame and on which the
accompanying element 56 is mounted.
Referring to Figure 3b, the tow frame 90 here includes a
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generally rectangular frame having side elements 92 and a front element
94. The rear element of the rectangular frame is again provided by the
guiding tow bar 50. A short elongate shaft 96 is provided at the front,
extending from the front element 94, and again providing the coupling
element 56.
In this embodiment of Figure 3b, the tow frame 90 now
comprises rear wheels 70, and in addition, a pair of forward wheels 98 are
provided. It will be understood that the wheels 98 are mounted for a
steering action, so as again to permit the frame 90 to freely follow the path
taken by the towing vehicle 20.
It will be also understood that, in the tight confines of a mine, it
is desirable that the guiding tow bar 50 closely follow the same path as the
towing vehicle 20. Where conditions require the guiding tow bar 50 to be
located some distance from the towing vehicle 20, and where the towing
vehicle 20 has to traverse relatively tight turns, then, in known manner, the
guiding tow bar 50 on the rearmost tow frame will tend to track radially
inwards on turns. If this effect is significant, then the tow frames can be
modified to allow for this.
Thus, in known manner, a steering mechanism can be
incorporated into the tow frames, to cause the wheels to steer, so as to
cause each tow frame to accurately follow the path taken by the towing
vehicle 20, without any tendency to track radially inwards. Such
mechanisms are well known, and are commonly used, for example, in
baggage carts and the like used at airports, where commonly a large
number of baggage carts are towed as a train behind a vehicle, and for the
same reasons as here, it is desirable that these baggage carts follow
substantially the same path.
Additionally, where tight turns are involved, this can impair the
effect of the signalling means 52. In traversing a tight corner, the elements
3o which comprise the signalling means 52 as viewed by a vision system on
the automated vehicle 40, will appear to move closer together, since the
vision system will be observing the tow bar 50 and the elements which
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comprise the signalling means 52 at an angle. The control system on the
automated vehicle 40 should interpret this as meaning that the elements
comprising the signalling means 52 have moved away from the automated
vehicle 40, which will, erroneously, cause the automated vehicle 40 to
accelerate towards the towing vehicle 20 and the guiding tow bar 50.
Bearing in mind that the towing vehicle 20 may, when entering a turn, be
decelerating anyway, this could have disastrous consequences, in that the
automated vehicle 40 may overrun the rear left tow frame 30 at least. Again,
to compensate for this, the signalling means 52 may be mounted on the
frame element that is mounted for rotation on a vertical axis which is steered
so as to always direct the signalling means 52 towards a location in which
the automated vehicle 40 is anticipated to be.
Bends and corners in the path may also prevent the automated
vehicle 40 from successfully following the towing vehicle 20, if the camera
60 loses sight of the signalling means 52 as the towing vehicle 20 and rear
tow frame 30 disappear around a bend or corner. A short stretch of
conventional guidance light rope may be installed on the bend or the corner
of the path to guide the automated vehicle 40 around the corner until the
signalling means 52 is once again in view. The light rope would be visible
to the camera 60. The controller 62 would automatically direct the
automated vehicle 40 to follow the light rope if it loses sight of the
signalling
means 52, and would switch back to directing the automated vehicle 40 to
follow the signalling means 52 once it is again in view.
In Figures 3a and 3b, the additional coupling element 58 is
provided. It will be appreciated that, for a tow frame 80, 90 including
signalling means 52 which is always intended for use with the terminal or
rearmost tow frame, then this coupling element 58 may not be provided.
However, as mentioned, there are advantages in always providing it, to
enable complete flexibility in the coupling of various tow frames.
It will also be understood that for tow frames intended as
intermediate tow frames, the coupling element 58 necessarily must be
provided, but the signalling means 52 could be omitted, to simplify the tow
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frame and cheapen the costs of the tow frame.
It will also be understood that while Figures 2, 3a and 3b show
exemplary profiles of the tow frames, any geometric configuration is
possible, and also any wheel arrangement is possible, which provides the
necessary function.
As noted, it is believed that for many applications, a camera on
the vehicle may be used as the guide detector 60. The camera is connected
to a controller 62 on the automated vehicle. The controller 62 is used during
normal operation of the automated vehicle 40, for controlling and guiding the
1o vehicle 40 along routes with guide elements extending along the routes.
The controller 62 will have already been programmed, or should be
programmed, to cause the automated vehicle 40 to follow the signalling
means 52 in the manner described above, i.e. so as to maintain a specified
constant spacing between the two signalling elements 52 and to maintain
the signalling elements 52 in the centre of the field of view.
It is also conceivable that, instead of using a separate camera
for towing operations, the same camera used in other vehicle operations
can be utilized. In particular, it may be possible to provide one camera for
use in normal automated guidance where guide elements are provided,
and for towing operations. For switching between the two modes of
operation, it may be simply a matter of re-orienting the camera from a
generally upwardly facing orientation to a generally horizontally directed
orientation. Similarly, it is anticipated that it may be necessary to provide
both forward and rearward facing cameras, if it is desired to have the
automated vehicle 40 follow the towing vehicle 20 in either the forward or
rearward direction. Again, this may prove unnecessary, at least for some
vehicles; for example, it may be possible to have a single camera mounted,
generally centrally on the vehicle, which can be switched between forward
and rearward facing orientations. In variant embodiments of the invention,
mirrors or other similar means may be used to "re-orient" the view of a
camera without having to move the camera itself.
In a variant embodiment of the invention, as shown in Figures
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4a, 4b, and 4c, the signalling means 52 comprises a horizontal array of
three lights 101, 102, 103, with each pair of adjacent lights being separated
by a specified distance, S. The lights 101, 102, 103 are placed on the
guiding tow bar 50 such that the centre light 102 is centred horizontally with
respect to the back of the tow frame on which the guiding tow bar 50 is
mounted. When a vehicle is being towed, the centre light 102 is
permanently on. The outside lights 101, 103 alternate between being on
and off, as shown in Figures 4a and 4b, at a rate between 5 Hz and 10 Hz for
example.
This variant embodiment anticipates providing a variety of
unique identifiers embedded in the signals transmitted by signalling means
52. For example, where there are three lights 101, 102, 103 comprising
signalling means 52, the signalling means 52 can alternate between
transmitting the signal pattern in Figure 4a ("A"), the signal pattern in
Figure
4b ("B"), and a signal pattern ("C") as shown in Figure 4c to embed a unique
identifier in the transmitted signals. Embedding the unique identifier in the
transmitted signals requires the insertion of the signal pattern C at various
times during the sequence of signal patterns A and B being transmitted.
Such a unique identifier can be used to distinguish between different towing
vehicles, so that any given automated vehicle can be controlled so as to only
follow the tow frame having signalling means transmitting signals
containing the unique identifier.
Each signal pattern A, B, or C, is transmitted for a fixed
duration. Suppose a synchronization string is defined as ABAB (where the
letters refer to equal time period of the signal patterns A and B). A unique
identifier is created by inserting signal pattern C in the signalling sequence
such that the synchronization string never occurs in the middle of a code
string. The light pattern must always change at a regular time interval. Here
are some examples of unique patterns that could be used:
ABABCABAB
ABABCBABAB
ABABCACABAB
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ABABCBCBABAB
ABABCABACABAB
ABABCBABCBABAB
ABABCACBCABAB
ABABCBCACBABAB
ABABCACABACABAB
ABABCBCBABCBABAB
ABABCACBCACABAB
ABABCBCACBCBABAB etc.
1o As noted, in this example, ABAB represents the
synchronization string. The coding is based on a simple binary tree.
Variant embodiments of the invention may also include a
remote control system for controlling the operation of the automated vehicle '
in a remotely-controlled mode. The remote control system can be used by
an operator of a towing vehicle to initially line up the automated vehicle
with
the tow frame (on which the signalling means is mounted) being towed by
the towing vehicle. The remote control system can also be used to start the
engine of the automated vehicle. The remote control system is equipped
with a device controlled by the operator of the towing vehicle, that can
2o communicate with the controller of the automated vehicle to switch the
operation mode of the automated vehicle from a remotely-controlled mode,
to the towing mode. The controller of the automated vehicle (e.g.
StrongBox~ device) operates the front facing camera of the automated
vehicle to search for the signalling means (or more specifically, the
signalling means transmitting a sequence of signals with the desired
unique identifier as determined by the operator through the remote control
system, where applicable) in its field of view. If the signalling means is
detected and the distance between the signalling means and the
automated vehicle is separated by a pre-defined minimum distance (the
distance being determined by the controller as measured by the apparent
separation of the individual lights in the field of view), a "lock" light will
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illuminate on the remote control device controlled by the operator of the
towing vehicle. The towing vehicle can move slowly away while the operator
uses the remote control device to initiate forward motion of the automated
vehicle, thus initiating a simulated tow. The automated vehicle begins to
move forward following the towing vehicle.
The controller steers the automated vehicle to keep the centre
light (where there are three lights as in Figures 4a, 4b, and 4c) in the
centre
of the automated vehicle camera's field of view (adjusting for camera angle
and offset), and continually calculates the distance between the automated
vehicle and the tow frame equipped with the signalling means. If this
distance falls outside a pre-defined maximum distance, the automated
vehicle will stop, and the "lock" light on the remote control device will
cease
to illuminate.
The "lock" light may be replaced with one or more lights
designed to indicate the status or "health" of the towing operation. For
example, in a normal towing operation which is being executed
successfully, a status light can be illuminated in green to indicate this.
Where the automated vehicle is not following the towing vehicle, the status
light can be illuminated in red or can be off to indicate this. A variety of
other
colours or indicators may be used to indicate other situations, for example,
when the automated vehicle is having difficulties following or keeping speed
with the towing vehicle.
The automated vehicle will stop if the controller loses radio
contact with the remote control device. The remote control system may also
comprise a means for the operator of the towing vehicle to stop the
automated vehicle at any time. Thus, the automated vehicle will also be
directed to stop if the operator has transmitted a "STOP" signal to the
controller using the remote control device. The automated vehicle will also
stop if the array of lights being followed are not detected for a pre-defined
period of time. The controller may also be programmed to stop the vehicle if
any other lights appear in the vicinity of the light array (e.g. brake
lights).
The remote control system may also comprise a display (e.g. a
CA 02318686 2000-09-12
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miniature television) which would allow an operator to view what is seen by
the front facing camera on the automated vehicle.
The remote control system may also comprise a display
indicating the distance between the towing vehicle (or the signalling means)
and the automated vehicle.
The remote control system may also be adapted to
communicate the speed of the towing vehicle to the controller of the
automated vehicle to assist in the control of the operation of the automated
vehicle. For example, if the towing vehicle's speed is zero, the automated
vehicle may be directed to stop.
At any time, the operator can terminate the towing mode and
revert to a mode of remotely-controlled operation.
It will also be well understood by those skilled in the art that,
while a load haul dump vehicle has been shown, the invention has
applicability to many different vehicles. For example, in a mining
environment, it can also be applied to blasting machines and other vehicles.
A load haul dump vehicle typically has a speed of 25
kilometres per hour and requires a 4 meter stopping distance. Accordingly,
the tow frame 30 should be dimensioned so as to provide at least that
distance and a suitable safety margin between the towing vehicle 20 and
the towed vehicle 40. A typical LHD machine is a 26,000 to 45,000 kg
machine, so that clearly a collision with the towing vehicle 20 of any force
could, at a minimum, cause significant damage.
It is also to be appreciated that, while the present invention has
been described with signalling means on a tow frame or trailer and some
sort of detector on the automated vehicle, other configurations are possible.
Thus, these elements could be reversed, with a detector provided on the tow
frame and some sort of signalling device on the vehicle. Whatever
configurations are adopted, it may also be desirable to provide some sort of
proximity detector mounted on the rearmost tow frame 30, as a safety
feature. This proximity detector would continuously note the relative position
of the automated vehicle 40, and if the automated vehicle 40 comes too
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close to the tow frame 30, the proximity detector would automatically
transmit a stop signal to the automated vehicle 40 and provide an indicator
to the driver of the towing vehicle 20 of the situation and the transmission
of
the stop signal.
Similarly, a single detection means 60 can be used both
during normal operation of the automated vehicle 40 where the vehicle
travels along paths following guides which are installed along the paths,
and during towing operations where the automated vehicle 40 follows a
towing vehicle 20. However, separate detection means may instead be
used for the two operations, with both detection means connected to at least
one controller on the automated vehicle 40.
In a variant embodiment of the invention, the invention provides
for a means to teach the controller of the automated vehicle about the path
on which it travels and the desired velocity profile over that path while the
automated machine is being towed. This would allow the controller of the
automated vehicle to anticipate intersections and changes of direction,
slope, tilt, etc. in the path, and to make adjustments to its speed and
movement accordingly.
In a variant embodiment of the invention, a light rope or a strip
of material (e.g. plastic) embedded with a fluorescent or reflective
substance may be attached to the back of a towing vehicle or a tow frame,
and dragged behind the towing vehicle or the tow frame. Again, the tow
frame could be provided with a low profile, to prevent damage should the
automated vehicle accidentally ride over it. The light rope or strip could
accordingly follow the path of the towing vehicle. An automated vehicle
would detect the light rope or strip and follow the towing vehicle,
maintaining
the light rope or strip between the automated vehicle's wheels. The light
rope or strip would be equipped with a desired point as well as position
markings that would give an indication of the amount and direction of
longitudinal deviation from the desired position (i.e. whether the machines
were too close or too far apart). For instance, the light rope or strip could
be
equipped with light sources around a center white light region (indicative of
CA 02318686 2000-09-12
a desired point where the automated vehicle 40 should be positioned),
where the light sources could change to red if the automated vehicle was
too close and to green if the automated vehicle was too far away, and where
the light sources may also indicate when the towing vehicle is accelerating
or decelerating.
In variant embodiments of the invention, a physical bar may be
connected to a tow frame in the event that the automated vehicle is an
electric vehicle that requires power. The guiding tow bar can provide the
automated vehicle through a connection on the physical bar with power to
operate. Alternatively, a motor generator may be attached to an electric
automated vehicle to provide the necessary power to allow the vehicle to
follow the guiding tow bar. For example, the motor generator itself is often a
vehicle of substantial size. In such a case, the motor generator vehicle
could act as the towing vehicle and an electric cable would be provided
between the two vehicles for transfer of electric power. The motor generator
vehicle would then be equipped with signalling means in accordance with
the present invention, to enable control of the two vehicles by one operator.
