Self-calibration for an inertial instrument based on real time bias estimator

• US 7,103,477 B1
• Filed: 02/28/2006
• Issued: 09/05/2006
• Est. Priority Date: 08/08/2005
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Corporation
• Inventors: Lee, Charles A.
• Primary Examiner(s): Camby, Richard M.
• Application Number:
  US11/364,316
• Time in Patent Office: 189 Days
• Field of Search: 701/220, 701/221, 701/222, 701/207, 701/216, 701/217, 340/990, 34235701-35717, 734/88, 734/90
• US Class Current: 701/220
• CPC Class Codes: G01C 21/183 Compensation of inertial measurements, e.g. for temperature effects
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38

Abstract

An exemplary inertial measurement apparatus incorporates self-calibrating bias correction signals. First and second inertial instruments generate respective input signals representative of an inertial attribute to be measured. A bias estimator generates first and second bias correction signals. First and second summation nodes receive the respective input signals and the respective first and second bias correction signals. The first and second summation nodes provide respective summed signals to the first and second inertial instruments. The first and second inertial instruments generate respective output signals representative of a value of the inertial attribute based on the respective summed signals. The bias estimator calculates the first and second bias correction signals based on first and second measurements made during respective first and second time intervals where a sign of one of the first and second bias error signals changes from one state during the first time interval to the other state during the second time interval.

Claims

1. An inertial measurement apparatus comprising:

first and second inertial instruments adapted to generate respective sensed signals representative of an inertial attribute to be measured;

means adapted to combine first and second bias error signals with the respective sensed signals thereby generating respective output signals;

bias estimator adapted to receive said output signals and generate respective first and second bias correction signals corresponding to the first and second inertial instruments;

the bias estimator calculating the first and second bias correction signals based on first and second measurements made during respective first and second time intervals where a sign of one of the first and second bias error signals changes from one state during the first time interval to the other state during the second time interval;

bias estimator adapted to generate first and second corrected output signals based on a combination of the first and second bias correction signals with the respective output signals.

2. The apparatus of claim 1 wherein the bias estimator calculates the first and second bias correction signals based on first and second measurements made during respective first and second time intervals where a sign of the other of the first and second bias correction signals does not change state during the first and second time intervals.

3. The apparatus of claim 2 wherein the bias estimator calculates the first and second bias correction signals based on equations Eq3, Eq4, Eq5 and Eq6.

4. The apparatus of claim 1 wherein the first and second inertial instruments have the same physical orientation relative to the inertial attribute to be measured, so that the first and second inertial instruments are measuring the same inertial attribute.

5. The apparatus of claim 1 wherein the bias estimator generates a third corrected output signal representative of a value of the inertial attribute, where the third output signal is an average of the respective output signals of the first and second inertial instruments when the sign of neither of the first and second bias correction signals is changing, the third corrected output signal being selected to represent the inertial attribute of one of the first and second inertial instruments when the other of the first and second inertial instruments has a respective bias correction signal with its sign undergoing a change of states.

6. An inertial measurement apparatus comprising:

first and second means for generating respective sensed signals representative of an inertial attribute to be measured;

means adapted to combine first and second bias error signals with the respective sensed signals thereby generating respective output signals;

bias estimator means, adapted to receive said output signals, for generating respective first and second bias correction signals corresponding to the first and second means;

the bias estimator means calculating the first and second bias correction signals based on first and second measurements made during respective first and second time intervals where a sign of one of the first and second bias error signals changes from one state during the first time interval to the other state during the second time interval;

bias estimator means adapted to generate first and second corrected output signals based on a combination of the first and second bias correction signals with the respective output signals.

7. The apparatus of claim 6 wherein the bias estimator means calculates the first and second bias correction signals based on first and second measurements made during respective first and second time intervals where a sign of the other of the first and second bias correction signals does not change state during the first and second time intervals.

8. The apparatus of claim 7 wherein the bias estimator means calculates the first and second bias correction signals based on equations Eq3, Eq4, Eq5 and Eq6.

9. The apparatus of claim 6 wherein the first and second means each comprise inertial instruments that have the same physical orientation relative to the inertial attribute to be measured, so that the first and second means are measuring the same inertial attribute.

10. The apparatus of claim 6 wherein the bias estimator means generates a third corrected output signal representative of a value of the inertial attribute, where the third output signal is an average of the respective output signals of the first and second means when the sign of neither of the first and second bias correction signals is changing, the third corrected output signal being selected to represent the inertial attribute of one of the first and second means when the other of the first and second means has a respective bias correction signal with its sign undergoing a change of states.

11. A method for utilizing self-calibrating bias signals in an inertial measurement apparatus comprising:

generating first and second sensed signals each representative of a same inertial attribute to be determined, where each of the first and second sensed signals is generated based on the same parameters sensed at the same location;

combining first and second bias error signals with the respective first and second sensed signals to generate respective first and second output signals;

generating first and second bias correction signals that correspond to the respective first and second output signals;

calculating the first and second bias correction signals based on measurements made during first and second time intervals where a sign of the first bias error signal is changed from one state during the first time interval to another state during the second time interval;

generating first and second corrected output signals representative of a value of the inertial attribute based on the first and second output signals and the first and second bias correction signals, respectively.

12. The method of claim 11 wherein the calculating step comprises calculating the first and second bias correction signals based on first and second measurements made during respective first and second time intervals where a sign of the second bias correction signal does not change state during the first and second time intervals.

13. The method of claim 12 wherein the calculating step comprises calculating the first bias correction signal based on equations Eq3, Eq4, Eq5 and Eq6.

14. The method of claim 11 further comprising the step of generating a third corrected output signal representative of a value of the inertial attribute, where the third corrected output signal is an average of the first and second corrected output signals when the sign of neither of the first and second bias correction signals is changing, the third corrected output signal being selected to represent the inertial attribute of one of the first and second corrected outputs when the other of the of the first and second corrected output signals has a corresponding bias correction signal with its sign undergoing a change of state.