TILT SENSOR AND METHOD FOR DETERMINING THE TILT OF A VEHICLE

• US 20130041577A1
• Filed: 08/12/2011
• Published: 02/14/2013
• Est. Priority Date: 08/12/2011
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Puhalla, Jeffrey S., Tevs, Nikolai R.
• Granted Patent: US 8,548,722 B2
• Time in Patent Office: Days
• US Class Current: 701/124
• CPC Class Codes: B60W 2030/041 about the pitch axis
• CPC Class Codes: B60W 2030/043 about the roll axis
• CPC Class Codes: B60W 2050/0051 combined with averaging
• CPC Class Codes: B60W 2300/152 Tractors
• CPC Class Codes: B60W 2520/105 Longitudinal acceleration
• CPC Class Codes: B60W 2520/125 Lateral acceleration
• CPC Class Codes: B60W 40/11 Pitch movement
• CPC Class Codes: B60W 40/112 Roll movement

Abstract

A tilt sensor and method comprises a first accelerometer for measuring a first acceleration level associated with a first axis of the vehicle. A second accelerometer measures a second acceleration level associated with a second axis of the vehicle that is generally perpendicular to the first axis. A data processor is capable of determining an arcsine-derived tilt based on an arcsine equation and the determined first acceleration level. The data processor is capable of determining an arc-cosine-derived tilt based on an arccosine equation and the determined second acceleration level. The data processor comprises a selector for selecting the arcsine-derived tilt as the final tilt of the vehicle if the determined arcsine-derived tilt is lesser than the determined arccosine derived tilt such that the final tilt compensates for vertical acceleration associated with changes in the terrain in the direction of travel of the vehicle.

Claims

1. A method for determining the tilt of a vehicle, the method comprising:

measuring a first acceleration level associated with a first axis of the vehicle;

measuring a second acceleration level associated with a second axis of the vehicle that is generally perpendicular to the first axis, the second axis generally aligned with or coincident with a vertical axis of the vehicle;

determining an arcsine-derived tilt based on an arcsine equation and the determined first acceleration level;

determining an arc-cosine-derived tilt based on an arccosine equation and the determined second acceleration level; and

selecting the arcsine-derived tilt as the final tilt of the vehicle if the determined arcsine-derived tilt is lesser than the determined arccosine derived tilt such that the final tilt compensates for vertical acceleration associated with changes in the slope terrain in the direction of travel of the vehicle.

2. The method according to claim 1 further comprising:

selecting the arccosine-derived tilt as the final tilt of the vehicle if the determined arsine-derived tilt is not lesser than the determined arccosine derived tilt such that the final tilt such that the final tilt compensates for lateral acceleration changes of the vehicle.

3. The method according to claim 1 wherein, the first axis comprises the X-axis or the Y-axis of the vehicle and the second axis comprises the Z-axis of the vehicle.

4. The method according to claim 1 wherein T_ASY=arcsine(A_Y), where T_ASY is the arcsine-derived tilt angle and A_Y is the measured Y-axis acceleration or the measured first acceleration level.

5. The method according to claim 1 wherein T_ASX=arcsine(A_X), where T_ASX is the arcsine-derived tilt angle and A_X is the measured X-axis acceleration or the measured first acceleration level.

6. The method according to claim 1 wherein T_AC=arccosine(A_Z), where T_FAC is the arccosine-derived tilt angle and A_Z is the Z-axis acceleration or the measured second acceleration level.

7. The method according to claim 1 wherein the measuring of the first acceleration level and the second acceleration level is accomplished during a sampling interval at a sampling rate, such that the selecting of the final tilt may change between adjacent calculation intervals, where each calculation interval has a greater duration than the sampling interval.

8. The method according to claim 1 wherein the measuring of the first acceleration level and the second acceleration level are filtered or averaged over an averaging period or sliding window prior to the determining of the arcsine-derived tilt and the arccosine-derived tilt.

9. The method according to claim 1 wherein determining the arc-cosine-derived tilt based on an arccosine equation and the determined second acceleration level further comprises setting the arccosine to zero if the arccosine numerator is greater than an acceleration of 1 G.

10. The method according to claim 1 further comprising:

measuring a third acceleration level associated with a third axis of the vehicle that is generally perpendicular to the first axis and the second axis of the vehicle; and

determining the arcsine-derived tilt based on the arcsine equation and the determined first acceleration level and the determined third acceleration level.

11. The method according to claim 10 wherein the arcsine-derived tilt comprises T_XY, which is the two-axis, arcsine-derived tilt angle, determined in accordance with the following equation:

T_XY=arcsin√

{square root over (A_x²+A_y²)}, where A_X is a measured X-axis acceleration or the first acceleration level, where A_y is a measured Y-axis acceleration or the third acceleration level.

12. A system for determining the tilt of a vehicle, the system comprising:

a first accelerometer for measuring a first acceleration level associated with a first axis of the vehicle;

a second accelerometer for measuring a second acceleration level associated with a second axis of the vehicle that is generally perpendicular to the first axis, the second axis generally aligned with or coincident with a vertical axis of the vehicle;

a data processor for determining an arcsine-derived tilt based on an arcsine equation and the determined first acceleration level, the data processor configured to determine an arc-cosine-derived tilt based on an arccosine equation and the determined second acceleration level; and

the data processor comprising a selector for selecting the arcsine-derived tilt as the final tilt of the vehicle if the determined arcsine-derived tilt is lesser than the determined arccosine derived tilt such that the final tilt compensates for vertical acceleration associated with changes in the slope terrain in the direction of travel of the vehicle.

13. The system according to claim 12 further comprising:

the selector configured to select the arccosine-derived tilt as the final tilt of the vehicle if the determined arsine-derived tilt is not lesser than the determined arccosine derived tilt such that the final tilt such that the final tilt compensates for lateral acceleration changes of the vehicle.

14. The system according to claim 12 wherein, the first axis comprises the X-axis or the Y-axis of the vehicle and the second axis comprises the Z-axis of the vehicle.

15. The system according to claim 12 wherein the arc-sine tilt is determined in accordance with the following equation:

T_ASY=arcsine(A_Y), where T_FAS is the arcsine-derived tilt angle and A_Y is the measured Y-axis acceleration or the measured first acceleration level.

16. The system according to claim 12 wherein the arc-sine derived tilt is determined in accordance with the following equation:

T_ASX=arcsine(A_X), where T_FAS is the arcsine-derived tilt angle and A_X is the measured X-axis acceleration or the measured first acceleration level.

17. The system according to claim 12 wherein the arccosine-derived tilt is determined in accordance with the following equation:

T_AC=arccosine(A_Z), where T_FAC is the arccosine-derived tilt angle and A_Z is the Z-axis acceleration or the measured second acceleration level.

18. The system according to claim 12 wherein the first accelerometer is configured to measure the first acceleration level and second accelerometer is configured to measure the second acceleration level during a sampling interval at a sampling rate, such that the selecting of the final tilt may change between adjacent calculation intervals of the data processor, where each calculation interval has a greater duration than the sampling interval.

19. The system according to claim 12 wherein the first accelerometer is adapted to filter or average the first acceleration level and the second acceleration level over an averaging period or sliding window prior to the determining of the arcsine-derived tilt and the arccosine-derived tilt.

20. The system according to claim 12 wherein data processor determines the arc-cosine-derived tilt by setting the arccosine to zero if the arccosine numerator is greater than an acceleration of 1 G.

21. The system according to claim 12 further comprising:

a third accelerometer for measuring a third acceleration level associated with a third axis of the vehicle that is generally perpendicular to the first axis and the second axis;

where the arcsine-derived tilt is determined in accordance with the following equation;

T_CAS=(W_Yarcsine(A_Y)+W_Xarcsine(A_X))/2, T_CAS is the arcsine-derived tilt;

A_Y is the measured Y-axis acceleration or third acceleration level;

A_X is the measured X-axis acceleration or first acceleration level;

W_Y is the weighting factor for Y-axis acceleration;

W_x is the weighting factor for the X-axis acceleration; and

W_Y+W_x=1.

22. The system according to claim 12 further comprising:

a third accelerometer for measuring a third acceleration level associated with a third axis of the vehicle that is generally perpendicular to the first axis and the second axis of the vehicle;

where the arcsine-derived tilt comprises T_XY, which is the two-axis, arcsine-derived tilt angle, in accordance with the following equation;

T_XY=arcsin√

{square root over (A_x²+A_y²)}, where A_X is a measured X-axis acceleration or first acceleration level, where A_y is a measured Y-axis acceleration or second acceleration level.

23. A method for determining the tilt of a vehicle, the method comprising:

measuring a first acceleration level associated with a first axis of the vehicle;

measuring a second acceleration level associated with a second axis of the vehicle that is generally perpendicular to the first axis, the second axis generally aligned with or coincident with a vertical axis of the vehicle;

measuring a third acceleration level associated with a third axis of the vehicle that is generally perpendicular to the first axis and the second axis of the vehicle;

determining an arcsine-derived tilt based on an arcsine equation and the determined first acceleration level and the determined third acceleration level;

determining an arc-cosine-derived tilt based on an arccosine equation and the determined second acceleration level; and

selecting the arcsine-derived tilt as the final tilt of the vehicle if the determined arcsine-derived tilt is lesser than the determined arccosine derived tilt such that the final tilt compensates for vertical acceleration associated with changes in the slope terrain in the direction of travel of the vehicle.

24. The method according to claim 23 wherein arcsine-derived tilt comprises T_XY , which is the two-axis, arcsine-derived tilt angle determined in accordance with the following equation:

T_XY=arcsin√

{square root over (A_x²+A_y²)}, where A_Y is a measured third axis acceleration level along the Y-axis and A_X is the measured first axis acceleration level along the X-axis.

25. The method according to claim 23 wherein the arcsine-derived tilt is determined in accordance with the following equation:

T_CAS=(W_Yarcsine(A_Y)+W_Xarcsine(A_X))/2, T_CAS is the arcsine-derived tilt;

A_Y is the measured Y-axis acceleration or the third acceleration level;

A_X is the measured X-axis acceleration or the first acceleration level;

W_Y is the weighting factor for Y-axis acceleration;

W_x is the weighting factor for the X-axis acceleration; and

W_Y+W_x=1.

26. The method according to claim 23 wherein the arcsine-derived tilt is determined in accordance with the following equation:

T_XY=arcsin√

{square root over (A_x²+A_y²)}, where T_XY is the two-axis, arcsine-derived tilt angle;

A_Y is the measured Y-axis acceleration or third acceleration level;

A_X is the measured X-axis acceleration or first acceleration level.