Inclinometer with calibration

• US 8,566,034 B1
• Filed: 12/02/2010
• Issued: 10/22/2013
• Est. Priority Date: 06/11/2008
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Van Wyck Loomis, Peter
• Primary Examiner(s): Black, Thomas
• Assistant Examiner(s): LOUIE, WAE LENNY
• Application Number:
  US12/928,038
• Time in Patent Office: 1,055 Days
• Field of Search: 342/357.14, 342/357.06, 702/154, 702/96, 702/141, 701/70, 701/34, 701/41
• US Class Current: 701/480
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01C 5/00 Measuring height; Measuring distances transverse to line of sight; Levelling between separated points; Surveyors' levels G01C3/20, G01C3/30 take precedence
• CPC Class Codes: G01C 9/08 Means for compensating acceleration forces due to movement of instrument
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled

Abstract

An inclinometer using a forward speed, a yaw angle rate, a forward acceleration and external altitude information in order to calculate an inclination angle. The inclinometer performs an automatic calibration of an accelerometer bias. The inclinometer may also perform an automatic calibration of an accelerometer position offset. The external altitude information is not required to be continuous.

Claims

1. An inclinometer, comprising:

an estimator configured to use a forward speed, a yaw angle rate, a forward acceleration and external altitude information in order to estimate an error in said acceleration due to an accelerometer bias without a requirement for an initial estimate of said accelerometer bias; and

an output converter configured to use said forward speed, said yaw angle rate, said forward acceleration and said estimated accelerometer bias to calculate an inclination angle.

2. The inclinometer of claim 1, wherein:

the estimator and the output converter are configured to provide new calculations of said inclination angle based on said estimated accelerometer bias and new information for said forward speed, said yaw angle rate and said forward acceleration for a time period when said external altitude information is not continuous.

3. The inclinometer of claim 1, wherein:

the estimator is further configured to use said forward speed, said yaw angle rate, said forward acceleration and said external altitude information to estimate a position offset with respect to a turn center of a vehicle carrying an accelerometer configured to provide said acceleration without a requirement for an initial estimate of said position offset; and

the output converter is further configured to use said estimated position offset to calculate of said inclination angle.

4. The inclinometer of claim 3, wherein:

the output converter is configured to use a product of said estimated position offset times a square of said yaw angle rate to calculate said inclination angle.

5. The inclinometer of claim 3, wherein:

the estimator is configured to use said forward speed, said yaw angle rate, said forward acceleration and said external altitude information to estimate a model altitude for said external altitude information, and use said estimated model altitude to estimate said accelerometer bias and said position offset.

6. The inclinometer of claim 5, wherein:

said external altitude information is an external altitude or an external altitude rate from an external positioning source.

7. The inclinometer of claim 3, wherein:

the estimator includes a propagator and updater to make recursive estimates of states of said estimated position offset and said estimated accelerometer bias;

said propagator configured to use said forward speed, said yaw angle rate and said forward acceleration with said states to propagate said states; and

said updater configured to use said external altitude information with said states to update said states.

8. The inclinometer of claim 3, wherein:

the estimator includes a propagator and updater to make recursive estimates of states of said estimated position offset, said estimated accelerometer bias and a model altitude for said external altitude information;

said propagator configured to use said forward speed, said yaw angle rate and said forward acceleration with said states to propagate said states; and

said updater configured to use said external altitude information with said states to update said states.

9. The inclinometer of claim 1, wherein:

the estimator includes a propagator and updater to make recursive estimates of a state of said estimated accelerometer bias;

said propagator configured to use said forward speed, said yaw angle rate and said forward acceleration with said state to propagate said state; and

said updater configured to use said external altitude information with said state to update said state.

10. The inclinometer of claim 1, further comprising:

a yaw rate sensor to provide information for said yaw angle rate;

a linear accelerometer to provide information for said acceleration; and

an external positioning source to provide said external altitude information.

11. A method for determining inclination angle, compromising:

using a forward speed, a yaw angle rate, a forward acceleration and external altitude information for estimating an error in said acceleration due to an accelerometer bias without a requirement for an initial estimate of said accelerometer bias; and

using said forward speed, said yaw angle rate, said forward acceleration and said estimated accelerometer bias for determining an inclination angle.

12. The method of claim 11, wherein:

the step of estimating includes providing new determinations of said inclination angle based on said estimated accelerometer bias and new information for said forward speed, said yaw angle rate and said forward acceleration for a time period when said external altitude information is not continuous.

13. The method of claim 11, wherein:

the step of estimating includes using said forward speed, said yaw angle rate, said forward acceleration and said external altitude information for estimating a position offset with respect to a turn center of a vehicle carrying an accelerometer configured for providing said acceleration without a requirement for an initial estimate of said position offset; and

the step of determining includes using said estimated position offset for determining said inclination angle.

14. The method of claim 13, wherein:

the step of determining includes calculating a product for said estimated position offset times a square of said yaw angle rate and using said product for determining said inclination angle.

15. The method of claim 13, wherein:

the step of estimating includes using said forward speed, said yaw angle rate, said forward acceleration and said external altitude information for estimating a model altitude for said external altitude information, and using said estimated model altitude for estimating said accelerometer bias and said position offset.

16. The method of claim 15, wherein:

said external altitude information is an external altitude or an external altitude rate from an external positioning source.

17. The method of claim 13, wherein:

the step of estimating includes making recursive estimates of said estimated position offset and said estimated accelerometer bias by using said forward speed, said yaw angle rate and said forward acceleration with said states for propagating said states; and

using said external altitude information with said states for updating said states.

18. The method of claim 13, wherein:

the step of estimating further includes making recursive estimates of said estimated position offset, said estimated accelerometer bias and a model altitude for said external altitude information by using said forward speed, said yaw angle rate and said forward acceleration with said states for propagating said states; and

using said external altitude information with said states for updating said states.

19. The method of claim 11, wherein:

the step of estimating includes making recursive estimates of a state of said estimated accelerometer bias by using said forward speed, said yaw angle rate and said forward acceleration with state for propagating said state, and using said external altitude information with said state for updating said state.

20. The method of claim 11, further comprising:

receiving information for said yaw angle rate from a yaw rate sensor;

receiving information for said acceleration from a linear accelerometer; and

receiving said external altitude information from an external positioning source.