Automated continuous haulage system

• US 20040054434A1
• Filed: 10/22/2003
• Published: 03/18/2004
• Est. Priority Date: 10/10/2000
• Status: Active Grant

• Current Assignee: Caterpillar Global Mining America LLC (Caterpillar Incorporated), Virginia Tech Intellectual Properties, Inc.
• Original Assignee: DBT America, Inc. (Caterpillar Incorporated), Virginia Tech Intellectual Properties, Inc.
• Inventors: Twigger, Michael, Sturges, Robert H., Kanarat, Amnart
• Granted Patent: US 7,076,346 B2
• Time in Patent Office: Days
• US Class Current: 700/213
• CPC Class Codes: E21F 13/08 Shifting conveyors or other transport devices from one location at the working face to another guiding mining machines along conveyors for the cut mineral E21C35/12; in combination with mine roof supports for step-by-step movement E21D23/00
• CPC Class Codes: E21F 13/083 Conveyor belts removing methods or devices
• CPC Class Codes: G01S 17/931 of land vehicles

Abstract

The present invention relates to an automated continuous haulage apparatus and method designed for use in underground environment. Each mobile bridge carrier (10) contains distance measurement (70) and angular position (74) means for determining the mobile bridge carrier'"'"'s (10) position and the angular position of attached piggyback conveyors (30). Means for determining the ceiling height (76) are utilized to adjust the height of the piggyback conveyors (30). On each mobile bridge carrier (10), input from the various sensors is received by an electronic controller (80) that calculates the position and orientation of the bridge carrier (10) and attached piggyback conveyors (30). The controller then plans an optimal path of movement for the bridge carrier (10) and computes the rate of movement for each independently operated track assembly on the bridge carrier such that the bridge carrier (10) and piggyback conveyors (30) arrive as close as possible to the planned path.

Claims

1. A method of controlling an automated two track or wheel vehicle through a maze, wherein the vehicle includes a track controller having a control cycle period, the vehicle having a front portion pivotally coupled to an elongated adjacent front structure via a first trolley, and a rear portion pivotally coupled to an elongated adjacent rear structure, the elongated rear structure coupled to a second trolley, each trolley providing at any given point in time a minimum available travel distance between the vehicle and the corresponding structure, the maze defined by walls which open to intersections, the intersections each having an angle of substantially the same number of degrees, wherein the number of the degrees is known, the method comprising:

obtaining a first set of range data from a sensor located on the left side of the vehicle;

obtaining a second set of range data from a sensor located on the right side of the vehicle;

determining, for each set of range data, the biggest group defined by consecutive distances having a difference less than a setting threshold;

dividing, for each set of range data, the biggest group into subgroups using recursive line-splitting technique, each subgroup defining a line;

selecting, for each set of range data, the two subgroups which define the two longest lines, whereby a wall on each side of the vehicle is represented by the respective selected subgroups;

defining a global coordinate frame based on the two longest lines;

determining the width of the maze between the walls adjacent the vehicle;

selecting from a table, based on the width and the number of degrees, a polynomial curve which minimizes a cost function, whereby the selected polynomial curve represents the path which provides the greatest assurance that the vehicle and the front and rear structures will not collide with the walls of the maze;

determining the point along the polynomial path having the shortest distance to a center of the vehicle;

determining the angle between the longitudinal axis of the vehicle as measured from a line tangent to the closest point;

determining the shortest of the two travel distances;

determining the travel velocity required for the vehicle to move the shortest travel distance during the control cycle period;

determining, based on the travel velocity, the angular velocity of the vehicle towards the closest point;

determining the left and right track or wheel velocities based on the travel velocity and angular velocity; and

accelerating the vehicle, via the controller, in accordance with the left and right velocities, whereby the vehicle is directed towards the closest point along the polynomial path.

2. A control system for controlling an automated two track or wheel vehicle through a maze, the vehicle having a front portion pivotally coupled to an elongated adjacent front structure via a first trolley, and a rear portion pivotally coupled to an elongated adjacent rear structure, the elongated rear structure coupled to a second trolley, each trolley providing at any given point in time a minimum available travel distance between the vehicle and the corresponding structure, the maze defined by walls which open to intersections, the intersections each having an angle of substantially the same number of degrees, wherein the number of the degrees is known, the system comprising:

a track or wheel controller having a control cycle period;

a first sensor located on the left side of the vehicle for obtaining a first set of range data;

a second sensor located on the right side of the vehicle for obtaining a second set of range data, the first and second sensor for determining the width of the maze between the walls adjacent the vehicle;

means for determining, for each set of range data, the biggest group defined by consecutive distances having a difference less than a setting threshold;

means for dividing, for each set of range data, the biggest group into subgroups using recursive line-splitting technique, each subgroup defining a line;

means for selecting, for each set of range data, the subgroup which defines the longest line, whereby a wall on each side of the vehicle is represented by the respective selected subgroup;

means for selecting from a table, based on the width and the number of degrees, a polynomial curve which minimizes a cost function, whereby the selected polynomial curve represents the path which provides the greatest assurance that the vehicle and the front and rear structures will not collide with the walls of the maze;

means for determining the point along the polynomial path having the shortest distance to a center of the vehicle;

means for determining the angle between the longitudinal axis of the vehicle as measured from a line tangent to the closest point;

means for determining the shortest of the two travel distances;

means for determining the travel velocity required for the vehicle to move the shortest travel distance during the control cycle period;

means for determining, based on the travel velocity, the angular velocity of the vehicle towards the closest point;

means for determining the left and right track or wheel velocities based on the travel velocity and angular velocity; and

means for activating the controller for accelerating the vehicle, in accordance with the left and right velocities, whereby the vehicle is directed towards the closest point along the polynomial path.

3. The control system of claim 2, wherein the vehicle is a mobile bridge carrier having a left track and a right track, the front portion having a slidable first trolley which is pivotally coupled to the front structure which is a first bridge conveyor, and the rear structure is a second bridge conveyor coupled to another mobile bridge carrier having a second trolley, the system further comprising:

two PIC servo controller boards coupled to the left and right tracks;

the first and second sensors are each an infrared laser scanner;

a means for filtering range data which represents an adjacent bridge conveyor in view of the first or second sensor, wherein the adjacent bridge conveyor is not interpreted as part of the walls of the maze, the filtering means includes an angular potentiometer coupled between the mobile bridge carrier and an adjacent bridge conveyor; and

the means for determining the shortest of the two travel distances includes a first linear potentiometer coupled between the first trolley and the mobile bridge carrier, and a second linear potentiometer coupled between the rear structure and the second trolley.

4. A method of determining the position and orientation of an automated vehicle with respect to a wall adjacent the vehicle, the method comprising the steps of:

obtaining range data from a sensor on the vehicle;

determining the biggest group defined by consecutive distances having a difference less than a setting threshold;

dividing the biggest group into subgroups using recursive line-splitting technique, each subgroup defining a line; and

selecting the subgroup which defines the longest line, whereby the wall is represented by the selected subgroup.

5. The method of claim 4, further comprising, prior to the step of determining, the step of filtering out potentially erroneous data.

6. The method of claim 5, wherein the vehicle is pivotally coupled to an adjacent structure, wherein the step of filtering includes determining the position of the adjacent structure, and discarding data which corresponds to the area the adjacent structure is located.

7. The method of claim 6, wherein the position of the other vehicle is obtained by determining the angle of the adjacent structure with respect to the vehicle.

8. The method of claim 4, further comprising, prior to the step of dividing, the step of filtering out potentially erroneous data includes ignoring data having a measured distance greater than a specified limit.

9. The method of claim 4, wherein the step of obtaining range data includes measuring the distance from a point at the vehicle to any object located adjacent the vehicle within a substantially horizontal plane, the step of measuring including measuring a plurality of distances within an arc extending from the point and within the substantially horizontal plane, whereby the range data consists of a plurality of consecutive measured distances between the point at the vehicle and any object located within the substantially horizontal plane.

10. The method of claim 9, wherein the step of determining includes determining the difference of measured distance between adjacent measurements, determining if the difference is greater than a setting threshold, and dividing the range data between two adjacent measurements if the difference between the two adjacent measurements is greater than the setting threshold.

11. The method of claim 4, wherein the selecting step includes selecting the two subgroups which define the two longest lines, whereby the wall is represented by the selected two subgroups.

12. The method of claim 11, further comprising, after the selecting step, the step of defining a global coordinate frame based on the two longest lines.

13. The method of claim 4, wherein the automated vehicle is a mining vehicle located in a mine, and the method determines the position and orientation of the mining automated vehicle with respect to a wall adjacent both sides of the vehicle, the method comprising the steps of:

obtaining a first set of range data from a sensor located on a first side of the vehicle;

obtaining a second set of range data from a sensor located on a second side of the vehicle;

determining, for each set of range data, the biggest group defined by consecutive distances having a difference less than a setting threshold;

dividing the biggest group, for each set of range data, into subgroups using recursive line-splitting technique, each subgroup defining a line; and

selecting the subgroup, for each set of range data, which defines the longest line, whereby the mine environment is represented by the selected subgroup from the first and second range data.

14. A method of path planning for an automated vehicle through a maze, the vehicle having a front portion pivotally coupled to an elongated adjacent front structure, and a rear portion pivotally coupled to an elongated adjacent rear structure, the maze defined by walls which open to intersections, the intersections each having an angle of substantially the same number of degrees, wherein the number of the degrees is known and the position and orientation of the vehicle is known with respect to the maze, the method comprising:

determining the width of the maze between the walls adjacent the vehicle; and

selecting from a table, based on the width and the number of degrees, a polynomial curve which minimizes a cost function, whereby the selected polynomial curve represents the path which provides the greatest assurance that the vehicle and the front and rear structures will not collide with the walls of the maze.

15. The method of claim 14, wherein the table is generated offline, the method further comprising the steps of:

generating a polynomial curve, for a maze with a first width and a first angle, based on parameters representing an allowable position and orientation of the vehicle and rear and front structures, and on a set of random coefficients;

repeat the above step a plurality of times, each time with a different set of random coefficients;

determine the coefficients of a polynomial curve having the minimum cost function;

storing the coefficients of the curve, representing the minimized cost function, and the corresponding first width and angle in the table; and

repeat the above steps for a further width and angle, whereby a table is created having coefficients representing the minimized cost function for a given width and angle.

16. The method of claim 14,.flrther comprising the steps of:

weighting a cost function as minimized if the angles between the vehicle and the adjacent structures are minimized;

weighting a cost function as minimized if the clearance between the structures and the maze, through the turn, are maximized; and

weighting a cost function as minimized if the error tolerances for the vehicle to track the curve is maximized.

17. A method of path tracking for a two-track or two wheel vehicle, wherein the vehicle includes a track or wheel controller having a control cycle period, the vehicle coupled to at least one structure via a trolley, the trolley providing at any given point in time a minimum available travel distance between the vehicle and the structure, wherein the vehicle position and orientation within a global coordinate frame is known, and the coefficients of a polynomial path plotted within the global coordinate frame is known, the method comprising:

determining the point along the polynomial path having the shortest distance to a center of the vehicle;

determining the angle between the longitudinal axis of the vehicle as measured from a line tangent to the closest point;

determining the travel distance;

determining the travel velocity required for the vehicle to move the travel distance during the control cycle period;

determining, based on the travel velocity, the angular velocity of the vehicle towards the closest point;

determining the left and right track or wheel velocities based on the travel velocity and angular velocity; and

accelerating the vehicle, via the controller, in accordance with the left and right velocities, whereby the vehicle is directed towards the closest point along the polynomial path.