Front-wheel drive steering compensation method and system

• US 7,325,636 B2
• Filed: 08/30/2004
• Issued: 02/05/2008
• Est. Priority Date: 08/30/2004
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Claytor, Kevin Lynn, Lunzman, Stephen Victor, Yeoman, John Andrew, Strnad, Michael Dan
• Primary Examiner(s): Morris; Lesley D.
• Assistant Examiner(s): ARCE, MARLON ALEXANDER
• Application Number:
  US10/928,167
• Publication Number:
  US 20060042838A1
• Time in Patent Office: 1,254 Days
• Field of Search: 180/62, 180/6.24, 180/6.26, 180/6.3, 180/6.48, 180/419
• US Class Current: 180/62
• CPC Class Codes: B62D 12/00 Steering specially adapted for vehicles operating in tandem or having pivotally connected frames steering endless tracks or the like B62D11/00; steering specially adapted for trailers B62D13/00
• CPC Class Codes: B62D 9/002 combined with means for differentially distributing power on the deflectable wheels during cornering
• CPC Class Codes: E02F 3/7663 Graders with the scraper blade mounted under a frame supported by wheels, or the like
• CPC Class Codes: E02F 9/0841 Articulated frame, i.e. having at least one pivot point between two travelling gear units tractor-trailer combinations B62D53/00

Abstract

A method of controlling the speed of a right front wheel and a left front wheel on a work machine includes receiving a speed command based at least partially on an operator input and monitoring at least one wheel steering angle of at least one front wheel. A first front wheel speed command may be determined based at least partially on the at least one wheel steering angle. In addition, a second front wheel speed command may be determined based at least partially on the at least one wheel steering angle. The first front wheel speed command and the second front wheel speed command may be output to independently control the speed of the right and the left front wheels.

Claims

1. A method of controlling the speed of a right wheel and a left wheel on a machine, comprising:

receiving a speed command based at least partially on an operator input;

monitoring an articulation angle between a front frame section and a rear frame section of the machine;

monitoring at least one wheel steering angle of at least one wheel;

determining a first wheel speed command based at least partially on the at least one wheel steering angle;

determining a second wheel speed command based at least partially on the at least one wheel steering angle; and

outputting the first wheel speed command and the second wheel speed command to independently control the speed of the right and the left wheels.

2. The method of claim 1, including

receiving the first wheel speed command at a first hydrostatic transmission controller for controlling a first hydrostatic transmission to drive the right wheel;

and

receiving the second wheel speed command at a second hydrostatic transmission controller for controlling a second hydrostatic transmission to drive the left wheel.

3. The method of claim 1, including:

sensing a speed of the right wheel with a first wheel speed sensor; and

sensing a speed of the left wheel with a second wheel speed sensor,

wherein determining the first wheel speed command and determining the second wheel speed command include consideration of the respective sensed speed of the right and left wheels.

4. The method of claim 1,

wherein the first wheel speed command and the second wheel speed command are based upon the monitored articulation angle.

5. The method of claim 1, wherein determining the first wheel speed command and determining the second wheel speed command are accomplished using a mapping function based on the speed command and the wheel steering angle.

6. The method of claim 1, wherein determining the first wheel speed command and determining the second wheel speed command are accomplished using trigonometry based on the machine configuration and the wheel steering angle.

7. The method of claim 1, wherein monitoring the wheel steering angle includes monitoring the wheel steering angle of the wheel that is inside during a turn.

8. The method of claim 7, including determining whether a right wheel or a left wheel is on the inside during a turn.

22. The method of claim 1, further including:

determining an aggression factor based on desired speeds of at least one front wheel and at least one rear wheel;

generating a desired speed ratio by multiplying the aggression factor with a rear transmission speed ratio; and

generating an adjusted speed ratio, based on the desired speed ratio and an articulation angle.

9. A system for controlling the speed of a right wheel and a left wheel on a machine, comprising:

an operator input device;

a speed module configured to generate a speed command based at least partially on a signal from the input device;

at least one frame sensor configured to monitor an articulation angle between a front frame section and a rear frame section of the machine;

at least one wheel angle sensor associated with at least one of the right and the left wheels, the at least one wheel angle sensor being configured to monitor at least one wheel steering angle of the at least one of the right and left wheels; and

a steering compensation module configured to determine a first wheel speed command based at least partially on the at least one wheel steering angle and to determine a second wheel speed command based at least partially on the at least one wheel steering angle, the steering compensation module being configured to output the first wheel speed command and the second wheel speed command to independently control the speed of the right and the left wheels.

10. The system of claim 9, including

a first hydrostatic transmission associated with the right wheel and configured to drive the right wheel;

a second hydrostatic transmission associated with the left wheel and configured to drive the left wheel; and

wherein the first and second hydrostatic transmission controllers are configured to respectively receive the first and second wheel speed commands to drive the right and left wheels.

11. The system of claim 9, including:

a first speed sensor associated with the right wheel and configured to sense a speed of the right wheel; and

a second speed sensor associated with the left wheel and configured to sense a speed of the left wheel,

wherein the steering compensation module is configured to determine the first wheel speed command and determine the second wheel speed command based at least partially on the respective sensed speed of the right and left wheels.

12. The system of claim 9, including the at least one frame sensor being in communication with the steering compensation module,

wherein the steering compensation module is configured to determine the first and second wheel speed commands based at least partially on the articulation angle and the steering angle.

13. The system of claim 9, wherein the steering compensation module is configured to use a mapping function to determine the first and second wheel speed commands based at least partially on the speed command and the steering angle.

14. The system of claim 9, wherein the steering compensation module is configured to use trigonometric equations to determine the first and second wheel speed commands based at least partially on the machine configuration and the wheel steering angle.

15. The system of claim 9, wherein the steering compensation module is configured to determine the first and second wheel speed commands based on the wheel steering angle of the left or right wheel that is on the inside of a turn.

16. The system of claim 15, including a sensor processing configured to monitor signals from the at least one wheel angle sensor and filter signals associated with the wheel steering angle of the wheel that is on the outside of a turn.

17. A method of controlling the speed of a right front wheel and a left front wheel on an all-wheel drive, articulating motor grader, comprising:

receiving a speed command based at least partially on an operator input;

monitoring a wheel steering angle of at least one front wheel;

monitoring an articulation angle between a front frame section and a rear frame section of the motor grader; and

determining a right front wheel speed command based at least partially on the wheel steering angle and the articulation angle;

determining a left front wheel speed command based at least partially on the wheel steering angle and the articulation angle; and

outputting the right front wheel speed command and the left front wheel speed command to independently control the speed of the right and the left front wheels.

18. The method of claim 17, including

receiving the right front wheel speed command at a right hydrostatic transmission controller for controlling a right hydrostatic transmission to drive the right front wheel;

and

receiving the left front wheel speed command at a left hydrostatic transmission controller for controlling a left hydrostatic transmission to drive the left front wheel.

19. The method of claim 17, including:

sensing a speed of the right front wheel with a right wheel speed sensor; and

sensing a speed of the left front wheel with a left wheel speed sensor,

wherein determining the right front wheel speed command and determining the left front wheel speed command include consideration of the respective sensed speed of the right and left front wheels.

20. The method of claim 17, wherein determining the right front wheel speed command and determining the left front wheel speed command are accomplished using one of

a mapping function based on the speed command, the articulation angle, and the wheel steering angle, and

trigonometry based on distance between front wheels of the motor grader, the distance between front and rear wheels of the motor grader, and the wheel steering angle.

21. The method of claim 17, further including:

determining an aggression factor based on desired speeds of at least one front wheel and at least one rear wheel;

generating a desired speed ratio by multiplying the aggression factor with a rear transmission speed ratio; and

generating an adjusted speed ratio, based on the desired speed ratio and the wheel steering angle and the articulation angle.