System for Determining Error in a Sensed Machine Position

• US 20140303923A1
• Filed: 04/03/2013
• Published: 10/09/2014
• Est. Priority Date: 04/03/2013
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Friend, Paul
• Granted Patent: US 9,541,420 B2
• Time in Patent Office: Days
• US Class Current: 702/94
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices
• CPC Class Codes: G01D 3/022 having an ideal characteristic, map or correction data stored in a digital memory
• CPC Class Codes: G01D 5/2448 Correction of gain, threshold, offset or phase control
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

A system for determining an error in a sensed position of a machine includes a position sensing system, a dead reckoning system, and a controller. The controller is configured to determine a difference between a sensed position and a calculated position determined by dead reckoning. The difference is compared to an error threshold defining a maximum acceptable distance between the sensed position of the machine and the calculated position of the machine and an error signal generated if the difference exceeds the error threshold. A pair of offset dead reckoning processes may be used.

Claims

1. A system for determining an error in a sensed position of a machine, comprising:

a position sensing system associated with the machine for determining a sensed position of the machine;

a dead reckoning system associated with the machine for determining a calculated position of the machine; and

a controller configured to;

store an error threshold defining a maximum acceptable distance between the sensed position of the machine and the calculated position of the machine;

determine an initialization position based upon the position sensing system;

determine a calculated position based upon the initialization position and the dead reckoning system;

determine a sensed position based upon the position sensing system;

determine a difference between the calculated position and the sensed position;

compare the difference to the error threshold; and

generate an error signal if the difference exceeds the error threshold.

2. The system of claim 1, wherein the dead reckoning system includes an acceleration sensor, the acceleration sensor being configured to provide an acceleration signal indicative of an acceleration of the machine, and the controller is further configured to receive an acceleration signal from the acceleration sensor and determine the calculated position based upon the acceleration signal.

3. The system of claim 2, wherein the dead reckoning system further includes a pitch rate sensor mounted on the machine, the pitch rate sensor being configured to provide a pitch rate signal indicative of a pitch rate of the machine, and the controller is further configured to receive a pitch rate signal from the pitch rate sensor and determine the calculated position based upon the pitch rate signal.

4. The system of claim 3, wherein the acceleration sensor and the pitch rate sensor are part of an inertial measurement unit.

5. The system of claim 1, wherein the dead reckoning system includes a pitch rate sensor, the pitch rate sensor being configured to provide a pitch rate signal indicative of a pitch rate of the machine, and the controller is further configured to receive a pitch rate signal from the pitch rate sensor and determine the calculated position based upon the pitch rate signal.

6. The system of claim 1, wherein the position sensing system includes a GPS sensor.

7. The system of claim 1, wherein the controller is further configured to stop the machine upon generating an error signal.

8. The system of claim 1, wherein the controller is further configured to slow the machine upon generating an error signal.

9. The system of claim 1, wherein the controller is further configured to delay determining the difference until passage of a predetermined period of time after determining the initialization position.

10. The system of claim 1, wherein the controller is further configured to determine a second initialization position of the machine based upon the position sensing system, the second initialization position being spaced from the initialization position, determine a second calculated position based upon the second initialization position and the dead reckoning system, determine a second difference between the second calculated position and the sensed position, compare the second difference to the error threshold, and generate an error signal if the second difference exceeds the error threshold.

11. A controller-implemented method for determining an error in a sensed position of a machine, comprising:

storing an error threshold defining a maximum acceptable distance between a sensed position of the machine based upon a position sensing system and a calculated position of the machine based upon a dead reckoning system;

determining an initialization position based upon the position sensing system;

determining a calculated position based upon the initialization position and the dead reckoning system;

determining a sensed position based upon the position sensing system;

determining a difference between the calculated position and the sensed position;

comparing the difference to the error threshold; and

generating an error signal if the difference exceeds the error threshold.

12. The method of claim 11, further including providing an acceleration signal from an acceleration sensor indicative of an acceleration of the machine, and determining the calculated position based upon the acceleration signal.

13. The method of claim 12, further including providing a pitch rate signal from a pitch rate sensor indicative of a pitch rate of the machine, and determining the calculated position based upon the pitch rate signal.

14. The method of claim 11, further including providing a pitch rate signal from a pitch rate sensor indicative of a pitch rate of the machine, and determining the calculated position based upon the pitch rate signal.

15. The method of claim 11, wherein further including providing GPS signals from a GPS sensor of a position sensing system.

16. The method of claim 11, further including stopping the machine upon generating an error signal.

17. The method of claim 11, further including slowing the machine upon generating an error signal.

18. The method of claim 11, further including delaying determining the difference until passage of a predetermined period of time after determining the initialization position.

19. The method of claim 11, further including determining a second initialization position of the machine based upon the position sensing system, the second initialization position being spaced from the initialization position, determining a second calculated position based upon the second initialization position and the dead reckoning system, determining a second difference between the second calculated position and the sensed position, comparing the second difference to the error threshold, and generating an error signal if the second difference exceeds the error threshold.

20. An autonomously operated machine comprising:

a propulsion system;

a steering system;

a position sensing system associated with the machine for determining a sensed position of the machine;

a dead reckoning system associated with the machine for determining a calculated position of the machine;

an accuracy verification system for determining an error in the sensed position; and

a controller configured to;

store an error threshold defining a maximum acceptable distance between the sensed position of the machine and the calculated position of the machine;

determine an initialization position based upon the position sensing system;

determine a calculated position based upon the initialization position and the dead reckoning system;

determine a sensed position based upon the position sensing system;

determine a difference between the calculated position and the sensed position;

compare the difference to the error threshold; and

generate an error signal if the difference exceeds the error threshold.