Note: Descriptions are shown in the official language in which they were submitted.
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Title: GUIDANCE SYSTEM FOR AUTOMATED VEHICLES, AND
GUIDANCE STRIP FOR USE THEREWITH
FIELD OF THE INVENTION
This invention relates to a guidance ~yslem for automated
5 vehicles. It is more particularly concerned with some elongate device or
means which will define a path along which an automated vehicle is to
travel. Even more particularly, this invention is concerned with 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 defined network of routes. In such situations, automated
vehicles offer considerable advantages and cost savings.
By automating vehicle operation, the cost of having an
individual operator for each vehicle is avoided. Where the vehicles are
repeatedly traversing relatively short routes, this is tedious for the operator,and operator boredom and fatigue can be a problem. By automating
guidance of the vehicle, in many cases, the vehicle can be guided more
20 consistently and accurately, and this can be useful in environments where
there are tight clearances.
Such automated guidance systems 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
25 clear indication of the path or route along which the vehicle is to travel.
This avoids having to provide the vehicle with any complex computer
~y~ , artificial intelligence or the like, which enables it to determine the
route to take.
In factories and the like, defining a route for the vehicle is
30 a relatively simple matter. More importantly, the route or routes are
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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 into the floor of a factory. A guidance system then
uses the electromagnetic characteristics of this cable to guide the vehicle so
5 that the vehicle follows the path of the cable. It is also known to use optical
techniques and a strip painted on the floor.
More recently, there have been proposals to provide such
automated vehicle guidance systems for use in a mine. A mining
environment poses a wholly different set of problems from a conventional
10 industrial setting. Firstly, the whole environment is much harsher than a
conventional factory. Frequently, there are high levels of dust, and any
path or route rather than being along a smooth, concrete floor or the like
may well be a long rough floor of a tunnel or drift.
Additionally, in a mine, there are problems of electrical
15 power supply. Again, in a conventional industrial plant, electrical power is
usually readily available.
A further factor is that, in a mine, by its very nature, the
pathways of the vehicle are irregular and subject to constant change. In a
factory setting, the initial installation cost of the system defining the route
20 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.
Nonetheless, despite these numerous differences between
25 an industrial setting and a mining environment, many guidance ~yslell-s
proposed for mines make little or no allowance for these differences. Thus,
one technique is to borrow the optical guidance technique used elsewhere.
It is recognized that providing some sort of path along the floor of a drift is
impractical in mind, and it would often be subject to severe damage or
30 simply covered in debris.
Instead, it has been proposed to provide an elongate
reflective strip suspended above the desired path for a vehicle. Such an
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arrangement is taught in Canadian Patent 2,041,373 (Mintronics Systems
Corporation). 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.
5 While this solution may appear relatively simple and practical, it does not
totally solve all of the problems. The strip itself still needs to be hung at
regular intervals, and must be oriented downwardly to a reasonable degree
of accuracy.
The intention is that the reflective strip would be detected
10 by lasers. The lasers are oscillated from side to side, and the position of the
laser is noted when a beam is retumed to the vehicle.
However, this arrangement has numerous disadvantages.
Firstly, it requires lasers and a relatively delicate mechanism for causing the
lasers to oscillate. Providing such a mechanism that is robust enough to
15 withstand the typical working conditions of a mine is extremely difficult,
and many mechanical failures have been encountered.
A more significant problem is that a retroreflective strip
does not, in fact, provide an adequately bright return signal to enable it to
provide a positive and accurate guidance system for the vehicle. In
20 particular, as a vehicles speed increases, it is standard practice to cause the
guidance system to look further ahead, so as to anticipate tums in the path.
In a mine, a drift will have the minimum height possible,
so that a laser has to be shone forward so that is strikes the reflective strip at
a fairly shallow acute angle. This in turn gives a poor reflected signal.
25 Additionally, mine environments are typically cluttered. Along many
drifts or tunnels, there are numerous other linear objects, e.g. pipes, duct
work, cabling etc, all of which are capable of acting in a reflective manner. Itis therefore quite easy for the guidance system to be confused by all the other
objects suspended from the roof of a drift, which provide background
30 clutter.
This problem has been recognized, and others have
proposed solutions to it. In particular, Canadian Patent Application
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2,145,731 discloses an automated guidance system for a vehicle which
provides 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
5 numerous small bulbs encapsulated to form, in effect, a continuous rope or
string.
This system certainly has a number of advantages. It
provides a continuous, bright source of light, which is easily recognised by a
vision and guidance system. It avoids all of the problems of inlelLerence by
10 reflectance from background objects.
However, such a system is extremely costly both to install
and to maintain. At current prices, it can cost around C$10.00 per foot and
requires about 5 W of power per foot. In one large installation of which the
applicants are aware, the installation cost was of the order of $300,000.00,
15 and the completed installation required 100 kW of power.
Providing power at this sort of level down a mine is
extremely difficult, complex and costly. In sizable installations, it results instrategies requiring sections of the available routes to be turned on and off
as required, so as to minimize power requirements. This leads to
20 complications, and stranding of vehicles, if the power is accidently turned
off. It imposes a significant maintenance burden, since the light rope must
be monitored, and sections replaced as bulbs fail.
To this end, to maximize the life of the light rope, some
unusual precautions are taken. The voltage is reduced. Additionally, it has
25 been discovered that in a blasting environment, the bulb filaments are
much more robust when warm and much less susceptible to failure, so that
the lights are maintained switched on when blasting occurs.
As noted, by its very nature, a mine environment requires
continuous creation of new drifts and routes, and closure of old ones. This
30 requires constant installation and removal of a guidance ~y~lem. Where
this light rope ~yslelll is used, this requires the light rope and associated
transformers, power supplies etc., all to be moved and relocated.
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This light rope approach has enjoyed some considerable
commercial success, but this only serves to underscore the limitations of the
retroreflective tape approach. What is really required is some technique for
defining a route for a vehicle in a mine, or other environment, which
5 enables a route to be quickly and accurately defined, which is inexpensive to
maintain and install, and which ensures accurate tracking of the route by a
vehicle.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is
10 provided a vehicle guidance system, for use with a vehicle which includes
at least one steerable wheel and steering actuation means for steering each
steerable wheel, the vehicle guidance system comprising: an elongate
element aligned with a desired path for the vehicle, mounted along the
path and including a fluorescent material which absorbs radiation at a first
15 frequency and radiates radiation at a second, lower frequency; illumination
means for mounting on the vehicle and for illuminating the elongate
element with radiation at the first frequency; detection means, for
mounting on the vehicle, and for receiving and detecting radiation from
the elongate element at the second frequency to provide positional
20 information, indicating a position of the vehicle relative to the elongate
element; a main control unit for determining the location of the vehicle
relative to the desired path from the positional information from the
detection means, and for controlling the steering actuation means to cause
the vehicle to follow the desired path, the main control unit being adapted
25 for connection to the detection means and the steering actuation means.
Preferably, the elongate element is flexible and adapted to
be suspended from at least one of a roof and a wall around the desired path,
more preferably from the roof directly above the desired path. The elongate
element can comprise a tube formed from plastics material with the
30 fluorescent material embedded in the plastics material.
Advantageously, the elongate element includes a first
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portion which radiates radiation at the second, lower frequency, and at least
one other portion which absorbs the radiation at the first frequency and
radiates radiation at another frequency different from the second frequency
and the frequency of radiation emitted from each other portion. The
5 detection means and the main control unit are then adapted to distinguish
between the different frequencies emitted by the different portions of the
elongate element. Then, a plurality of different portions of the elongate
element having different radiation frequencies can be configured to provide
information to the main control unit, at desired locations. For example,
10 each portion of the elongate element can be associated with a respective
path, and the main control unit can utilize the different frequencies
received from the different portions of the elongate element to distinguish
the different paths from one another and to guide the vehicle along the
desired path.
Another aspect of the present invention provides an
excitation means for driving the illumination means, which excitation
means causes the illumination means to provide a series of pulses at a
known, control frequency, and wherein the system includes a filter means
for filtering out signals outside the control frequency, thereby to remove
any inlelrering signals. The filter means being connected between the
detector means and the main control unit.
Preferably, the detection means comprises a video camera
means, which provides control information to the main control unit in the
form of data representing an image indicating the relative location of the
elongate element to the vehicle, and two cameras can be provided for
forward and rearward movement.
In accordance with another aspect of the present
invention, there is provided a method of remotely guiding a vehicle, the
method comprising the steps of:
(a) providing an elongate element aligned with a desired
path for the vehicle and including a fluorescent material which absorbs
radiation of a first frequency and radiates radiation at a second, lower
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frequency;
(b) propelling a vehicle along the desired path;
(c) illuminating the elongate element with radiation of the
first frequency;
(d) detecting radiation of the second frequency emitted
from the elongate element, to determine the position of the vehicle relative
to the elongate element and thereby to determine the vehicle's position
relative to the desired path; and
(e) in dependence upon the vehicle's relative position to
the desired path, steering the vehicle, so that the vehicle travels along the
desired path.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, and to
15 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 plan view of an exemplary mine plan;
Figure 2 is a side view of a mining vehicle travelling down
a drift utilizing a guidance system in accordance with the present invention;
and
Figure 3 is a schematic of a control circuit for the vehicle
shown in Figure 2.
DETAILED DESCRIPTION OF THE INVENTION
Referring first to Figure 1, there is shown an exemplary
schematic of a mine or part of a mine. It should be appreciated that this
mine plan is purely exemplary, and that the invention is generally
applicable to any mine layout. Moreover, the invention is not restricted to
use in underground mines, but is applicable to guidance of vehicles in any
30 situation, particulary in harsh conditions where the ground surface tends to
be rough and cluttered.
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In Figure 1, the section of the mine shown has an entrance
10 and a dumping point 12. Shown adjacent the dumping point 12 is a
garage 14 for a load haul dump (LHD) vehicle, which may be a Scooptram
(Registered Trademark) as manufactured by Wagner Inc. From the entrance
5 10, a main drift 16 extends, and there are numerous branch drifts or tunnels
18 branching off from the main drift 16. A typical LHD vehicle 20 is shown
in greater detail in Figure 2. Its key elements are described in detail below.
Now, in accordance with the present invention, there is
provided an elongate fluorescent element 30 extending along the routes or
10 pathways that it is desired for the LHD vehicle 20 to follow. The elongate
element 30 includes a material that is fluorescent and/or phosphorescent.
Desirably, it is fluorescent, i.e. it absorbs radiation of one wave length and
essentially immediately reradiates it as a radiation of a second, longer wave
length. This, as detailed below, enables a vehicle guidance system to follow
15 the element 30.
It is additionally desirable that the element 30 have some
phosphorescent properties, that is to say it reradiates radiation of a certain
wave length, some time after having been radiated itself. The reradiated
radiation should be in the visible spectrum. This has the advantage that,
20 some time after a vehicle has passed, the element will still continue to
glow. At least in the confines of an underground mine, only a very low
level of radiation is necessary from the element 30 for it to be visible by a
miner. This has considerable safety advantages. If a miner walking along a
drift notices that the element 30 has some residual glow or
25 phosphorescence, then this indicates that a vehicle has passed that way
recently, and is likely to be returning along that drift again. In other words,
a miner should only feel comfortable walking along a drift where the
guidance element 30 is essentially dark.
The element 30 comprises numerous separate portions.
30 For ease of reference, these are designated below as 30a, 30b etc. Thus, there
is a portion 30a at the entrance to the mine. This extends to the dumping
point 12 and into the garage 14. From the dumping point 12, a main
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portion 30b extends along the main drift 16. Extending off from the main
portion 30b are various branch portions 30c, 30d and 30e.
Guidance and recognition of the individual branch
portions can be provided in various ways. Thus, one simple technique is to
5 provide some distance markers along the length of the main branch portion
30b, so that the guidance system aboard the LHD vehicle 20 knows, at all
times, where the vehicle is to the required degree of accuracy. These
distance markers could be additional portions of the element 30 provided
adjacent the main guidance portion, so as to be capable of being "read" by a
10 guidance system.
However, a further aspect of the present invention
provides a fluorescent element 30 that is provided in different types, each of
which reradiates a different frequency or wave length, all in response to
radiation of a single frequency. Thus, the main portion 30b could reradiate
15 radiation at a second frequency, the branch portion 30c could radiate
radiation at a third frequency, the branch portion 30d could radiate radiation
at a fourth frequency and so on, with all the second and additional
frequencies being different.
Then, it is not necessary for the vehicle guidance system to
20 know exactly where the vehicle is. Rather, in order to instruct the vehicle
to follow a particular branch, it is simply necessary to instruct the guidance
system to look for a branch with a certain frequency characteristic. In other
words, if it is desired for the vehicle to travel down the branch portion 30d,
then the guidance system is instructed to follow the main branch 30b until
25 it encounters a branch portion showing the fourth frequency. This branch
portion 30d is then followed.
It will also be appreciated that this provision of a
fluorescent element 30 having different radiation characteristics enables
various information to be encoded along the length of say the main branch
30 30a in a completely linear fashion. In other words, it is not necessary to
provide any additional pieces of the element 30 adjacent the main piece,
forming a sort of bar code, as has been proposed elsewhere. It is noted that
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the provision of such additional pieces could confuse the guidance system.
By way of example, if it is desired to have some distance
indications, distance markers could be provided by alternating the different
types of fluorescent element in short lengths. Thus, a first distance marker
5 could comprise two short pieces of the element 30 radiating at the second
frequency interposed into the main portion 30b, which otherwise radiates at
the first frequency. Ideally, these pieces should be short enough that they
can be read, in a digital-type fashion, while at the same time not being long
enough to confuse the guidance system into thinking it has encountered a
10 branch portion showing the second frequency. Where fluorescent element
is available radiating at third, fourth or other frequencies, then clearly the
possibilities for encoding information into the fluorescent element 30 are
greatly increased.
Reference will now be made to Figure 2, which shows an
15 exemplary LHD vehicle 20. The LHD vehicle 20 is largely conventional, and
accordingly is described in outline only. The vehicle 20 has a front portion
40 and a rear portion 42, which are articulated together by a central pivot 44.
A scoop or bucket 46 is mounted at the front end and can be lifted, raised,
tipped etc., by way of hydraulic cylinders. At the rear of the rear portion 42,
20 there is a drive unit. Head lamps 48 are provided for illuminating a drift
along which the vehicle is travelling.
Now in accordance with the present invention, an
ultraviolet lamp 50 is provided and mounted generally centrally on the
vehicle 20. As shown, the lamp 50 is pivotable between a position 50a
25 pointing forward and a position 50b pointing rearwards. A length of the
fluorescent element or rope 30 is shown in Figure 2. The lamp 50
illuminates a substantial length of the element 30. In known manner, it is
highly desirable to illuminate a substantial length of the element 30 ahead
of the direction of travel. Thus, the lamp 50 is directed into position 50a for
30 forward travel.
Then, the element 30 fluoresces and radiates visible light,
for example of an orange colour.
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Forward and rearward television cameras 52 and 54 are
provided, for use during forward movement and rearward movement
respectively. For forward motion, the length of the element 30 radiating the
orange light ahead of the vehicle is picked up by the camera 52. The camera
5 52 is provided with a filter to filter out other frequencies, and in particular
to filter out the ultraviolet light.
Accordingly, as no other piece of equipment in the drift of
the mine should fluoresce in the same manner, the image received by the
television camera 52 or 54 is essentially a wholly dark background showing
a bright strip where the elongate element 30 is present. This provides an
extremely clear and precise guidance line for the guidance system, and there
should be no difficulty with inleLrer~l,ce from unwanted objects or signals.
The cameras 52 and 54 thus provide detection means that provide
positional information, indicating the position of the vehicle 20 relative to
the element 30. Where various portions of the element are provided which
radiate in different frequencies, then the cameras 52, 54 should be filtered so
as to filter out the excitation frequency of the ultraviolet light, but to permit
reception of all the possible frequencies. The different branches can then be
identified, by electronically filtering the resultant image.
Where it is desired to have the headlights 48 operational,
this may possibly cause inl~lfeL~l-ce. Thus, if the frequencies radiated by the
element 30 are in the visible spectrum, them there may be strong
intelferellce signals caused by lamps 48; for example, there may be duct
work, cabling etc., which presents a strong linear image and which may
25 accidentally be coloured so as to reflect an interfering frequency or wave
length.
To allow for this, a further aspect of the invention, detailed
below in relation to the control circuitry, is to pulse the light from the
ultraviolet lamp 50 at a certain excitation frequency. This excitation
30 frequency should be chosen bearing in mind the properties of the element
30. In particular, the spacing between the pulses should be sufficient to
permit all the radiation from the element 30 to be radiated, and to allow for
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any phosphorescent characteristics of the material used. Then, the
television camera 52 or 54 will receive, for each of the radiated frequencies
of the element 30, a series of spaced pulses. These can be passed through a
filter, so as to filter out any continuous interfering signals, as any such
5 interfering signals caused by the continuously running headlights 48 will
similarly be continuous.
Referring now to Figure 3, a control circuit is shown
schematically. It will be appreciated that the basic principles of controlling
such LHD vehicles 20 are well known and can be conventional. The
10 present invention is solely concerned with the issue of providing a clear
indication of the path that the vehicle should follow. The control circuit is
indicated generally by the reference 60, and is shown with the ultraviolet
lamp 50 and the television cameras indicated generally at 52, 54. A main
control unit 62 controls an ultraviolet lamp actuator 64 and a television
15 camera select a switch 66. Thus, a signal from the control unit 62 is used toswitch the ultraviolet lamp 50 between its forward and rearward positions
50a, 50b, and simultaneously switch the selector switch 66 between the
forward and rear video cameras 52, 54.
The lamp 50 is driven by an excitation unit 68, which like
20 all elements in the control circuitry is powered by the vehicle electrical
system.
The selector switch 66 has an output connected to a first
filter 70, for filtering out the ultraviolet frequency provided by the lamp 50.
This filter may alternatively be provided by an optical filter. This filter 70 is
25 connected through to the main control unit 62.
Where the excitation units 68 pulses the ultraviolet lamp,
then a second filter 72 is provided, to filter out frequencies below that
excitation frequency, and particularly any constant or DC component. It
may well be possible to combine the filter 70, 72 together as a single filter, as
30 a single bandpass filter that rejects the ultraviolet frequency, and low
frequencies including a DC component, while passing all possible
frequencies that may be radiated by the different fluorescent elements. For
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some applications, it may prove advantageous to have a feed from the
excitation signal from the unit 68 connected through to the filter 72, to
provide improved filtering.
The effect of the processing through the filters 70, and 72 as
5 present, is to provide an image in the direction of which the vehicle is
travelling showing a clear indication of the different branches ahead. The
control unit 62 processes these image signals and drives a steering actuation
unit 74 accordingly. It can also be connected to a vehicle engine control unit
76 as shown. The main purpose of this is to enable the vehicle speed to be
10 controlled, so that the vehicle can be slowed when approaching sharp
corners, and then accelerated again once the corner has past. In known
manner, the steering control unit drives hydraulic actuators that cause the
front and rear portions 40,42 to pivot relative to one another.
The elongate fluorescent element 30 can be formed of any
15 suitable material. Conveniently, it comprises an elongate plastic tube
formed from? and having an external diameter of 12 mm with a thickness
of approximately 2 mm. Such material is inexpensive and readily available,
and is commonly used in the entertainment industry. It will be appreciated
that, depending upon the particular environment, other materials could be
used. Thus, the elongate element could be in the form of a woven rope.
The elongate fluorescent element should preferably be flexible, so as being
capable of being provided as a continuous reel, and readily mounted where
required.
The element 30 is attached to the roof of a mine and any
length between support points for the element 30 should be chosen
depending upon its characteristics and the nature of the installation. In
other words, the resultant hanging loop should be such as to not be large
enough to interfere with travel of the vehicle or affect the guidance of the
vehicle.
While it is preferred for the element 30 to be suspended
along the roof of a mine, this is not essential. It could certainly be
suspended along the wall of a drift or tunnel, and the vehicle guided so as
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to maintain a fixed distance from the element 30. This arrangement is also
suitable for installations other than closed mines, e.g. in open cast mines or
other industrial settings.
In less harsh environments, particularly where the surface
5 will not be so cluttered or subject to coverage with debris, it is conceivablethat the element could be provided on the ground, preferably embedded. In
factories and the like, it could be provided as a painted strip on a floor. For
many applications this may be suitably durable, and may simply need to be
repainted at required intervals.
