Compensation for mounting misalignment of a navigation device

• US 8,086,405 B2
• Filed: 06/28/2007
• Issued: 12/27/2011
• Est. Priority Date: 06/28/2007
• Status: Active Grant

• Current Assignee: CSR Technology Holdings Inc. (Qualcomm, Inc.)
• Original Assignee: SiRF Technology Holdings Incorporated (Qualcomm, Inc.)
• Inventors: Han, Shaowei, Niu, Xiaoji, Ma, Changlin
• Primary Examiner(s): Elchanti, Hussein A.
• Assistant Examiner(s): Khatib, Rami
• Application Number:
  US11/823,964
• Publication Number:
  US 20090254279A1
• Time in Patent Office: 1,643 Days
• Field of Search: 701/207, 701/214, 701/216, 701/217, 701/220, 701/221, 73/13.7, 73/13.8, 73/17.7, 735/03, 735/033, 735/040.2, 735/040.3, 735/11, 735/140.1, 342/357.14
• US Class Current: 701/216
• CPC Class Codes: G01C 21/185 for gravity
• CPC Class Codes: G01C 21/265 constructional aspects of navigation devices, e.g. housings, mountings, displays G01C21/3688 takes precedence
• CPC Class Codes: G01C 21/28 with correlation of data from several navigational instruments

Abstract

Compensating for the misalignment of a navigation device with respect to a vehicle is described. In one example, the compensation is made by applying a high pass filter to a measured acceleration of the vehicle to produce a motion acceleration signal, weighting the motion acceleration signal with a measured steering rate of the vehicle, and deriving misalignment parameters for the navigation device with respect to the vehicle using the weighted motion acceleration signal.

Claims

1. A method to determine a misalignment of a navigation device with respect to a vehicle comprising:

applying a high pass filter to a measured acceleration of the vehicle to produce a motion acceleration signal;

weighting the motion acceleration signal with a measured steering rate of the vehicle; and

deriving, using a processor, misalignment parameters for the navigation device with respect to the vehicle using the weighted motion acceleration signal.

2. The method of claim 1, further comprising:

determining if the vehicle is moving;

applying a low pass filter to the measured acceleration while the vehicle is moving to produce a gravity signal; and

wherein deriving misalignment parameters comprises also using the gravity signal.

3. The method of claim 1, wherein deriving misalignment parameters comprises applying a Kalman filtering system.

4. The method of claim 1, wherein weighting comprises;

generating a proportional weighting factor from the measured steering rate; and

multiplying the motion acceleration signal with the proportional weighting factor to produce a centrifugal acceleration component of the motion acceleration signal.

5. The method of claim 1, wherein weighting comprises;

generating an inverse proportional weighting factor from the measured steering rate; and

multiplying the motion acceleration signal with the inverse proportional weighting factor to produce a forward acceleration component of the motion acceleration signal.

6. The method of claim 2, wherein weighting comprises using the measured steering rate to weight the motion acceleration signal so that a centrifugal acceleration and a forward acceleration are produced, and wherein deriving misalignment parameters comprises using a Kalman filtering system to produce three misalignment angles based on the gravity signal, the centrifugal acceleration signal and the forward acceleration signals.

7. The method of claim 1, further comprising correcting raw sensor data using correction angles obtained from the derived misalignment parameters.

8. The method of claim 7, further comprising determining new misalignment parameters after correcting the raw sensor data and correcting the raw sensor data again using the new misalignment parameters.

9. The method of claim 8, further comprising determining the location of the vehicle after correcting.

10. The method of claim 9 wherein determining the location comprises determining the location using a satellite positioning system.

11. The method of claim 1, further comprising using odometer signals from the vehicle to determine whether the motion acceleration signal corresponds to the vehicle being in motion.

12. The method of claim 1, further comprising measuring the acceleration along three orthogonal axes using a three axis accelerometer to produce the measured acceleration.

13. The method of claim 1, further comprising receiving a measured acceleration from an external sensor.

14. The method of claim 1, further comprising measuring the steering rate using a vertical gyroscope.

15. The method of claim 1, wherein the misalignment parameters comprise misalignment correction angles corresponding to the misalignment between the navigation device and the vehicle.