U.S. patent application number 09/776277 was filed with the patent office on 2001-09-13 for anti-rut system for autonomous-vehicle guidance.
Invention is credited to Burns, Ray L., Parfenov, Vadim.
Application Number | 20010021888 09/776277 |
Document ID | / |
Family ID | 25106937 |
Filed Date | 2001-09-13 |
United States Patent
Application |
20010021888 |
Kind Code |
A1 |
Burns, Ray L. ; et
al. |
September 13, 2001 |
Anti-rut system for autonomous-vehicle guidance
Abstract
In a vehicle traffic system, the predetermined nominal
trajectory for an autonomous vehicle is varied periodically within
acceptable boundaries which define a permitted travel corridor. The
corridor's boundaries ensure the continued safe and controlled
operation of the vehicle within the system. In an embodiment of the
invention, alternative trajectories are selected randomly; in
another, they are parallel to one another. In yet another,
preferred embodiment, judiciously-selected, alternative
trajectories are repeated periodically according to a predetermined
schedule designed to avoid repetitive travel over the same precise
path, and possibly also selected for optimal results under
different terrain, environmental, and/or operational conditions.
According to another aspect of the invention, the shape and size of
the corridor defining the boundaries for safe operation are varied
in response to changed conditions to increase operational
flexibility. Thus, by avoiding repeated passage precisely over the
path of the nominal trajectory, rutting on the road is greatly
reduced and a more uniform surface is maintained for travel.
Inventors: |
Burns, Ray L.; (St. David,
AZ) ; Parfenov, Vadim; (Tucson, AZ) |
Correspondence
Address: |
Antonio R. Durando
Durando Birdwell & Janke, P.L.C.
2929 E. Broadway Blvd.
Tucson
AZ
85716
US
|
Family ID: |
25106937 |
Appl. No.: |
09/776277 |
Filed: |
February 2, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09776277 |
Feb 2, 2001 |
|
|
|
09521436 |
Mar 7, 2000 |
|
|
|
Current U.S.
Class: |
701/23 ;
701/26 |
Current CPC
Class: |
G05D 2201/021 20130101;
G05D 1/0278 20130101; G05D 1/0297 20130101; G05D 2201/0202
20130101 |
Class at
Publication: |
701/23 ;
701/26 |
International
Class: |
G05D 001/00 |
Claims
We claim:
1. In an autonomous vehicle system wherein traffic control
apparatus guides a vehicle along a corresponding nominal travel
trajectory on a roadway, a method for reducing the formation of
ruts in the roadway, the method comprising the following steps: (a)
generating alternative paths for travel by the vehicle along said
nominal travel trajectory; and (b) sequentially guiding the vehicle
to travel along a plurality of said alternative paths.
2. The method of claim 1, further including the step of
establishing a corridor defining boundaries available for travel by
the vehicle around said nominal trajectory; wherein said
alternative paths are contained within the corridor.
3. The method of claim 2, wherein said boundaries are variable.
4. The method of claim 1, wherein said step (a) is carried out by
randomly selecting said alternative paths.
5. The method of claim 2, wherein said step (a) is carried out by
randomly selecting said alternative paths within the corridor.
6. The method of claim 3, wherein said step (a) is carried out by
randomly selecting said alternative paths within the corridor.
7. The method of claim 1, wherein said step (a) is carried out by
selecting said alternative paths in parallel to the nominal
trajectory.
8. The method of claim 2, wherein said step (a) is carried out by
selecting said alternative paths in parallel to the nominal
trajectory within the corridor.
9. The method of claim 3, wherein said step (a) is carried out by
selecting said alternative paths in parallel to the nominal
trajectory within the corridor.
10. The method of claim 3, wherein said boundaries are variable as
a function of vehicle dimensions.
11. The method of claim 3, wherein said boundaries are variable as
a function of vehicle dynamic parameters.
12. The method of claim 3, wherein steps (a) and (b) are repeated
periodically after said boundaries have been varied.
13. The method of claim 1, wherein said autonomous vehicle system
is implemented in a surface mine.
14. In an autonomous vehicle system wherein traffic control
apparatus guides a vehicle along a corresponding nominal travel
trajectory on a roadway, apparatus for reducing the formation of
ruts in the roadway, the apparatus comprising the following: (a)
means for generating alternative paths for travel by the vehicle
along said nominal travel trajectory; and (b) and means for
sequentially guiding the vehicle to travel along a plurality of
said alternative paths.
15. The apparatus of claim 14, further including means for
establishing a corridor defining boundaries available for travel by
the vehicle around said nominal trajectory; wherein said
alternative paths are contained within the corridor.
16. The apparatus of claim 14, wherein said boundaries are
variable.
17. The apparatus of claim 14 wherein said autonomous vehicle
system is implemented in a surface mine.
Description
RELATED APPLICATIONS
[0001] This is a continuation-in-part application of U.S. Ser. No.
09/521,436, filed on Mar. 7, 2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention is related in general to autonomous vehicles
operating in a surface facility, such as a surface mine. In
particular, the invention relates to a method for avoiding the
formation of ruts and similar road damage caused by the repetitive
passage of autonomously-guided vehicles over prescribed travel
trajectories.
[0004] 2. Description of the Related Art
[0005] Autonomous vehicles operating in a surface facility such as
a mine are controlled by tracking the position of each vehicle in
the system and by guiding the vehicle safely along a predetermined
course. Guidance control signals may be generated from a central
location, a peripheral position, other vehicles, or directly from
within the vehicle. Typically, the position of the vehicle is
continuously monitored and controlled by a central or satellite
center transmitting control signals to the vehicle's on-board
computer, based on current mine conditions and in response to
position information communicated by the vehicle. Alternatively,
the vehicles's own on-board computer can produce appropriate
control signals to the vehicle as a function of its position and
additional information received from external components of the
guidance system. Knowing the current position of the vehicle with
respect to known fixed obstacles and other mine equipment, the
vehicle can be maneuvered to its destinations by the continuous
control of its operating functions (for example, steering-wheel,
accelerator and brake position of a truck). An on-board
satellite-based positioning system (such as GPS) or an equivalent
positioning unit (either of which can be supplemented with an
inertial navigation system or the like) can be used to determine
the current position of the vehicle, with an on-board
transmitter/receiver unit to communicate with the control center,
and on-board microprocessing and storage modules with appropriate
hardware and software can also be used to effect the actual
movement and guidance of the vehicle. Every operating function is
manipulated to cause the vehicle to follow a predetermined
trajectory that can be modified by current control instructions to
meet particular up-to-date traffic conditions. Hazards are avoided
by implementing a predetermined control response when a hazard is
identified by the system. For example, if a potential obstacle is
detected within a certain distance of the vehicle being monitored,
the path of the vehicle is modified to avoid collision. Thus, for
the purposes of this disclosure, the term "autonomous" is intended
to refer to the availability of either on-board or off-board
automated supervisory systems for controlling the movement of a
vehicle.
[0006] Surface mines utilize a variety of work machines for
excavating and transporting ore, grading and stabilizing roadways
and slopes in the mine pit, and for providing all support functions
necessary for the operation of a mine. In the past, most work and
haulage machines have been human-operated, mobile pieces of
equipment constantly being moved around the surface of the mine.
Skilled operators ensure that each machine or vehicle is positioned
in the right place and optimally oriented to perform its intended
function while avoiding accidents and injury to people and
property. In order to improve efficiency, much effort is currently
under way to develop automated systems for controlling the
operation of such work machines in surface mines and other
environments. Therefore, this invention is described in the context
of a surface mine operation, but its concept is applicable to any
operation involving moving equipment (such as at waste sites and in
underground mining, or in digging, shipping, trucking, and
automotive operations) and should not be understood to be limited
to surface mines.
[0007] As mentioned, the function of each autonomous vehicle in a
surface mine is performed according to a predetermined trajectory
related to its particular task and implemented by a guidance system
through on-board GPS and two-way communication hardware. The
roadways of mines are typically temporary and subject to frequent
changes to adapt to varied operating conditions. Therefore, such
roads normally consist of unpaved dirt routes that are easily
damaged by vehicle traffic. In particular, the repetitive passage
of autonomous vehicles over the same predetermined trajectories
unavoidably causes ruts in the roads that can affect the efficiency
and operation of the roads. Operators of manned vehicles can try
and minimize this problem by avoiding existing cuts as they begin
to appear on the road, thereby reduce the formation of deep ruts.
Unmanned vehicles, on the other hand, are programmed to follow a
preselected trajectory as precisely as possible, and much effort is
dedicated, primarily for safety concerns and work efficiency, to
ensure that deviations from that trajectory are minimized during
the course of autonomous operation. Given the current state of the
art, autonomous vehicles can be controlled to follow a path with
maximum deviations in the order of centimeters. Thus, the formation
of ruts is an inherent problem of autonomous-vehicle traffic on
dirt roads. This invention is directed at reducing the rutting
caused by the operation of such vehicles.
BRIEF SUMMARY OF THE INVENTION
[0008] The primary objective of this invention is a guidance
control system for reducing the formation of ruts in roadways
travelled by autonomous vehicles in a mining or similar
operation.
[0009] Another objective is an approach that can be integrated with
existing guidance systems for autonomous-vehicle operation on dirt
roads of industrial facilities, in particular surface mines.
[0010] Another goal is a system that is suitable for automated
implementation with current autonomous equipment, in particular
surface-mine haulage and mining equipment.
[0011] A final objective is a system that can be implemented
economically according to the above stated criteria.
[0012] Therefore, according to these and other objectives, the
present invention involves linking each autonomous vehicle and/or
other moving equipment in a surface-mine facility to a control
center for communicating data and control signals. The function of
each autonomous vehicle is performed automatically by causing it to
track a predetermined nominal trajectory related to its particular
task and is implemented using on-board GPS and two-way
communication hardware. The current position of the vehicle is
continuously monitored and correlated to the position of potential
hazards along its path, so that corrective action can be taken by
implementing appropriate, predetermined control strategies.
[0013] According to the invention, the predetermined nominal
trajectory for each vehicle is varied periodically within
acceptable boundaries which define a travel corridor that ensures
the continued safe and controlled operation of the vehicle within
the system while avoiding the formation of ruts in the roadway. In
an embodiment of the invention, the deviation is selected randomly
from alternative trajectories that ensure a continuous and steady
travel within the corridor containing the original nominal
trajectory. By avoiding repeated passage precisely over the path of
the nominal trajectory, wear on the road is greatly reduced and a
more uniform surface is maintained for travel.
[0014] According to another embodiment of the invention, the
guidance system may provide for multiple trajectories consisting of
parallel paths to be used alternatively in order to avoid rutting
of the roadway. In yet another, preferred embodiment,
judiciously-selected, alternative trajectories are repeated
periodically according to a predetermined schedule designed to
avoid repetitive travel over the same precise path, and possibly
also selected for optimal results under different terrain,
environmental, and/or operational conditions.
[0015] According to another aspect of the invention, the shape and
size of the corridor defining the boundaries for safe operation
along the nominal trajectory are varied dynamically to increase
operational flexibility within the safety requirements for current
traffic conditions facing the vehicle as it performs its autonomous
function along its predetermined path. For example, the width of
the corridor may be increased when the autonomous vehicle is
traveling alone, or decreased when it is in a high-traffic zone.
Thus, the corridor may be dynamically adjusted for each vehicle as
circumstances change during the performance of its autonomous
function.
[0016] Various other purposes and advantages of the invention will
become clear from its description in the specification that follows
and from the novel features particularly pointed out in the
appended claims. Therefore, to the accomplishment of the objectives
described above, this invention consists of the features
hereinafter illustrated in the drawings, fully described in the
detailed description of the preferred embodiment and particularly
pointed out in the claims. However, such drawings and description
disclose but one of the various ways in which the invention may be
practiced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 illustrates in plan view a sample portion of a
prior-art map of a surface mine property including routes between
typical destination points.
[0018] FIG. 2 illustrates schematically the selection of a
reference point within a vehicle's physical structure to establish
a nominal position for the vehicle within a selected coordinate
system.
[0019] FIG. 3 illustrates the concept of a corridor defining a
space around the nominal trajectory of an autonomous vehicle,
wherein alternative travel paths are provided by the
guidance-control system of the vehicle.
[0020] FIG. 4 illustrates a randomly-generated alternative path to
the nominal trajectory within the corridor of the invention.
[0021] FIG. 5 is a flow chart showing the steps of the
invention.
[0022] FIG. 6 is a schematic illustration of the apparatus required
to implement the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0023] The heart of this invention lies in the idea of introducing
variations in the precisely-controlled path followed by autonomous
vehicles traveling on the roadways of a surface mine. By avoiding
repetitive passage over the same trajectory, the formation of
undesirable ruts is prevented, or at least greatly reduced.
[0024] For the purposes of this disclosure, it is understood that
every reference to a vehicle is intended to apply as well to any
other movable piece of equipment that may be found in a surface
mine or other facility employing autonomous vehicles. The term
"trajectory" of a vehicle is intended to mean the predetermined
path assigned to the vehicle so that it can perform its intended
task. Accordingly, it refers to the set of x, y, z positions
defining a trajectory to be followed by a reference point on the
vehicle as it travels between an origin and a destination.
[0025] Referring to the drawings, wherein like parts are designated
throughout with like numerals and symbols, FIG. 1 illustrates in
plan view a sample portion of a map of a surface mine property
including exemplary routes between typical destination points.
Specifically, excavators 10 are illustrated as mining at two
loading sites 12, 14 which are connected to a crusher 16 at a site
18 through mine roadways associated with predetermined vehicle
trajectories 20, 22, 24, 26, 28, 30. Each trajectory represents a
predetermined optimal travel path along which an autonomous vehicle
32, such as a haulage truck, is intended to be guided between end
destinations (12, 14, 18) by an autonomous guidance system in order
to effect a particular task. Additional alternative trajectories
34, 36, 38, 40 are provided within the sites 12, 14, 18 to control
the approach and departure of the vehicle 32 to and from the
excavators 10 and the crusher 16. In essence, based on current
vehicle-position data generated by an on-board GPS or other
equivalent positioning unit and using known feedback-control servo
mechanisms, the mine's autonomous guidance system controls the
motion of the vehicle 32 by performing steering, braking,
acceleration, and other functions so as to closely track the
trajectory of interest (i.e., the path of trajectory 20, in the
case illustrated in the figure). Since present positioning systems
have accuracies of the order of a few centimeters, it is possible
to obtain very close adherence to the target trajectory. To that
end, the pertinent trajectory (selected from the applicable
trajectories 20-30), or portion of a trajectory, currently being
traveled by the vehicle 32 is stored in the controller's storage
unit of the vehicle's microprocessor and used as a target
trajectory by the guidance system. Note that these features are
well known in the art and do not constitute a novel aspect of the
invention.
[0026] In practice, a nominal vehicle position within a selected
coordinate system is chosen to correspond to the position of a
reference point 42 within the vehicle's physical structure, such as
its geometric center or the location of a communication antenna, as
illustrated in FIG. 2, and the guidance system is programmed to
cause that particular point to track the desired trajectory (path
20 in FIG. 1, for example). Obviously, though, the physical
dimensions of the vehicle 32 extend beyond the point 42 and a
correspondingly larger clear path along the trajectory 20 must be
present as the vehicle passes through in order to avoid collisions
with nearby obstacles. For example, the length and width of the
vehicle 32 define its minimum physical operating space required
when the vehicle is at rest. As the vehicle moves along the
trajectory 20 under the control of the autonomous guidance system,
additional factors must be accounted for to ensure safety, such as
steering error, navigational guidance margins, and stopping
distance variations due to load, equipment condition, road surface
and grade, etc. Thus, the actual physical space required by the
vehicle 32 to ensure its safe operation is greater than its size.
These variables further contribute to the estimation of the space
required by the vehicle to ensure its safe operation. Companion
application U.S. Ser. No. 09/521,436 describes a system whereby the
vehicle 32 is assigned a safety zone that allows for the vehicle's
actual physical presence and for all pertinent operating tolerances
defined by a variable safety envelope 44 around the autonomous
vehicle 32.
[0027] According to the present invention, the guidance system
provides for a modified, expanded trajectory (as defined below)
consisting of multiple paths to be used alternatively in order to
avoid rutting of the roadway. For example, the target position for
point 42 of vehicle 32 may be shifted to the left or right of the
nominal trajectory 20 by a predetermined offset, thereby defining
different paths substantially codirectional with the nominal
trajectory 20. Accordingly, a trajectory, in an expanded
definition, may also refer to alternative path options within a
corridor which may be allowed, instead of a single linear path, in
order to achieve the particular operational goals of avoiding rut
formation.
[0028] FIG. 3 illustrates a corridor 46 defining a space 48 within
which the reference point 42 of vehicle 32 is allowed to move while
traveling along the nominal trajectory 20 in order to implement the
anti-rut procedure of the invention. As shown, the width of the
corridor 46 may vary along the nominal trajectory to account for
different terrain, environmental, operational, and other
conditions. The corridor 46 may be enlarged, for example, to
accommodate bad weather conditions that may more readily cause
rapid formation of ruts in the roadways. A wider travel area,
assuming that roadway space is available and other operating
conditions permit it, makes it possible to reduce travel over any
particular precise path, thereby minimizing wear and tear on the
road. Simply by shifting the travel path of the vehicle 32 to the
right or left of the nominal trajectory 20 to alternative paths 50
or 52, for instance, the guidance control system implements an
anti-rut procedure according to the invention.
[0029] According to one embodiment of the invention, as the vehicle
32 is guided along its nominal trajectory 20, new paths are
continually followed by allowing the random shifting of the
vehicle's reference point 42 to any position within the corridor 46
so long as a continuous and smooth travel toward the intended
destination is maintained. That is, the vehicle is allowed to
continue in its travel without the imposition of further
directional controls so long as it remains within the boundaries of
the corridor 46. While this random control strategy would appear to
ensure the most even travel distribution over the width of the
corridor 46 (because of its random nature), in fact it may still
lead to the formation of ruts because any pre-existing cut in the
road tends to produce a preferential travel path along its
trajectory. Therefore, as soon as an initial groove is formed, the
free selection of a path is no longer random but, rather,
conditioned by the existence of the groove, which in turn leads to
the development of a deep rut.
[0030] According to another embodiment of the invention,
alternative paths within the corridor 46 are generated randomly,
but then they are imposed upon the vehicle 46 by its guidance
system. That is, for example, an alternative path 54 to the nominal
trajectory 52 is generated by a computer ensuring that it remains
within the boundaries of the corridor 46, as illustrated in FIG. 4,
but on the basis of random steps constrained only by parameters
that maintain the general direction and continuity of motion. Thus,
the alternative path should not require unusual steering of the
vehicle that would affect its normal travel parameters, such as
speed and general direction. Once such an alternative path is
generated, it is imposed on the vehicle by the guidance controls of
the system. Therefore, these alternative trajectories are
sequentially imposed by the system and, because they are randomly
generated, they are very unlikely to ever repeat themselves.
[0031] According to yet another embodiment of the invention,
alternative paths are selected not randomly but pursuant to a
particular strategy deemed most appropriate for the type of vehicle
and road involved. For example, parallel paths may be preferable on
corridors having substantially uniform width, while crisscrossing
paths may be needed to take full advantage of wider spaces in
nonuniform corridors.
[0032] It is noted that the invention is implemented through
computer software that establishes a corridor along the nominal
trajectory of each autonomous vehicle. Once the boundaries of the
corridor are established, alternative anti-rut paths are generated,
as explained. If desired, the boundaries of the corridor can be
updated to account for changes in the road condition of the
premises or other operating factors (such as differences in vehicle
size or shape, speed or other dynamic parameters, and
guidance-control errors and/or tolerances). Thus, according to
another aspect of the invention, the corridor may be updated
between vehicle iterations or from vehicle to vehicle to provide
different space solutions for new alternative anti-rut paths. For
example, a corridor may be enlarged under wet conditions to provide
a larger area over which to spread the wear and tear of the
resulting softer terrain; or the corridor's width may be reduced
when dry conditions improve the hardness and durability of dirt
roads.
[0033] In essence, the novel concept of the invention resides in
the idea of allocating a corridor around the nominal trajectory of
each vehicle operating in an autonomous system. The space within
the corridor is then used to generate alternative paths to the
nominal trajectory to be followed by the vehicle in order to
minimize rutting. If desired, the corridor boundaries are changed
as a function of operating parameters.
[0034] The invention is one of several features of a collision
avoidance system applied to a conventional guidance system for
autonomous vehicles in operations that may also include manned
vehicles.
[0035] The guidance system and other components of the collision
avoidance approach are not part of this invention and, therefore,
are not described here. In practice, the invention can be
implemented within an existing autonomous system as follows. As
illustrated in the flow chart of FIG. 5, each course to be traveled
by one or more vehicles between points in the facility is assigned
a nominal trajectory with a corresponding corridor defining an area
of permitted travel along the nominal trajectory. Alternative paths
are generated for travel within the boundaries of the corridor and
assigned to each vehicle for sequential use during the course of
its operation. If desired, the boundaries of the corridor
associated with each nominal trajectory may be changed and new
alternative paths correspondingly generated for each vehicle.
[0036] FIG. 6 is a schematic illustration of the apparatus required
to implement the anti-rut system of the invention within the
autonomous-vehicle traffic-control system of a surface mine. Each
excavator 10 and haulage vehicle 32 within the system is equipped
with two-way communication apparatus 70 and with a positioning
system unit 72 (such as a GPS unit). Mine roadway maps, vehicle
nominal trajectories, corresponding corridors and alternative
paths, as well as appropriate software to implement the various
functions required for the invention, are stored in digital form in
a computer 74 (or, equivalently, in a unit of a computer network)
housed in a base station 76 which is also equipped with two-way
communication apparatus 70. Thus, the precise location of the
vehicle 32 can be determined periodically, using its positioning
system unit and an on-board processor 78 (with appropriate
hardware, software and control modules 80), and communicated to the
computer 74 at the base station together with identifying
information regarding the particular vehicle 32 being guided. Upon
processing of this information, the computer 74 transmits the
appropriate set of instructions to the on-board processor 78 to
guide the vehicle to the intended destination according to the
invention using appropriate hardware and guidance software
incorporated within the vehicle. The control mechanisms and related
processing hardware and software required to implement the various
steps of the invention are well known in the art.
[0037] Various changes in the details, steps and components that
have been described may be made by those skilled in the art within
the principles and scope of the invention herein illustrated and
defined in the appended claims. For example, the invention has been
illustrated, and for simplicity it is currently preferably
implemented, in terms of two-dimensional nominal trajectories and
alternative paths, but the concept would apply in equivalent
fashion to a three-dimensional implementation. In practice, the
approximation introduced by a 2-D model does not affect the system
sufficiently to warrant the additional complication of a 3-D model,
although the latter could be implemented successfully with modern
positioning systems. Therefore, while the present invention has
been shown and described herein in what is believed to be the most
practical and preferred embodiments, it is recognized that
departures can be made therefrom within the scope of the invention,
which is not to be limited to the details disclosed herein but is
to be accorded the full scope of the claims so as to embrace any
and all equivalent apparatus and procedures.
* * * * *