Systems and methods for 3-axis accelerometer calibration

• US 9,217,757 B2
• Filed: 09/19/2012
• Issued: 12/22/2015
• Est. Priority Date: 09/20/2011
• Status: Active Grant

• Current Assignee: CalAmp Corporation
• Original Assignee: CalAmp Corporation
• Inventors: Hergesheimer, Peter, Sprague, Todd, Dlagnekov, Alexandre
• Primary Examiner(s): Beaulieu, Yonel
• Assistant Examiner(s): KLEINMAN, LAIL A
• Application Number:
  US13/622,844
• Publication Number:
  US 20130073142A1
• Time in Patent Office: 1,189 Days
• Field of Search: 701/33.1
• US Class Current: 1/1
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups

Abstract

Systems and methods for calibrating the alignment of 3-axis accelerometers in accordance embodiments of the invention are disclosed. In one embodiment of the invention, a telematics system includes a global positioning system (GPS) receiver. an accelerometer, and a processor, wherein the GPS receiver is configured to determine velocity information, wherein the accelerometer is configured to determine accelerometer acceleration information along one or more accelerometer axes, and wherein the processor is configured to receive a velocity information sample using the GPS receiver, determine GPS acceleration information along one or more vehicle axes using the velocity information sample, receive accelerometer acceleration information samples using the accelerometer, and calibrate one of the vehicle axes to an accelerometer axis in the one or more accelerometer axes using the GPS acceleration information sample and the accelerometer acceleration information sample.

Claims

1. A telematics system, comprising:

a global positioning system (GPS) receiver;

an accelerometer; and

a processor;

wherein the GPS receiver determines velocity information;

wherein the accelerometer determines accelerometer acceleration information along a set of accelerometer axes comprising a first accelerometer axis in a first vector;

wherein the telematics system is located in a vehicle having one or more vehicle axes;

where;

the vehicle axes comprise a first vehicle axis in a forward vector, a second vehicle axis in a lateral vector, and a third vehicle axis in a vertical vector; and

the orientation of the accelerometer axes is independent of the orientation of the vehicle axes; and

wherein the processor;

receives a velocity information sample using the GPS receiver;

determines GPS acceleration information along the one or more vehicle axes using the velocity information sample;

receives accelerometer acceleration information samples using the accelerometer; and

maps the first accelerometer axis to one of the one or more vehicle axes based on the GPS acceleration information sample and the accelerometer acceleration information sample, where the first vector of the calibrated first accelerometer axis corresponds to the vectors forward vector of the vehicle, by computing orthogonal vectors based on the cross product of every combination of the GPS acceleration information along the one or more vehicle axes, thereby calibrating the orientation of the accelerometer so that the first accelerometer axis corresponds to the forward vector of the vehicle.

2. The telematics system of claim 1, wherein:

the accelerometer is a 3-axis accelerometer further comprising a second accelerometer axis in a second vector and a third accelerometer axis in a third vector; and

the processor further;

maps the second accelerometer axis to the lateral vector of the vehicle by analyzing the GPS acceleration information in the forward vector of the vehicle and the acceleration information samples corresponding to the first accelerometer axis, thereby calibrating the orientation of the accelerometer so that the second accelerometer axis corresponds to the lateral vector of the vehicle; and

maps the third accelerometer axis to the vertical vector of the vehicle by processing the GPS acceleration information along the forward vector of the vehicle and the vertical vector of the vehicle, thereby calibrating the orientation of the accelerometer so that the third accelerometer axis corresponds to the vertical vector of the vehicle and the third vector is distinct from the first vector and the second vector.

3. The telematics system of claim 1, wherein:

the accelerometer comprises a first sampling rate; and

the telematics system further comprises an accelerometer accumulator accumulating a plurality of accelerometer acceleration information samples taken at the first sampling rate.

4. The telematics system of claim 3, wherein:

The GPS receiver comprises a second sampling rate; and

the telematics system further comprises a GPS accumulator accumulating a plurality of velocity information samples taken at the second sampling rate.

5. The telematics system of claim 4, wherein the processor is matches the first sampling rate to the second sampling rate.

6. The telematics system of claim 1, wherein the processor calibrates a vehicle axis to the first accelerometer axis using a least squares method.

7. The telematics system of claim 6, wherein the processor performs the least squares method using a Gaussian elimination solver.

8. The telematics system of claim 7, further comprising motion sample storage storing a plurality of motion samples, where motion samples are selected from the group consisting of GPS location information samples and accelerometer acceleration information samples.

9. The telematics system of claim 8, wherein the processor performs the least squares method using at least one motion sample in the plurality of motion samples.

10. The telematics system of claim 1, wherein the processor further:

detects the vertical vector in the calibrated vehicle axes; and

recalibrates the calibrated vehicles axes using the using the GPS acceleration information sample, the accelerometer acceleration information sample, and the detected vertical vector.

11. The telematics system of claim 1, wherein the processor further:

detects the lateral vector in the calibrated vehicle axes; and

recalibrates the calibrated vehicles axes using the using the GPS acceleration information sample, the accelerometer acceleration information sample, and the detected lateral vector.

12. A method for calibrating an accelerometer, comprising:

receiving velocity information samples using a telematics system, where the telematics system is located in a vehicle having one or more vehicle axes comprising a first vehicle axis in a forward vector, a second vehicle axis in a lateral vector, and a third vehicle axis in a vertical vector;

determining vehicle acceleration information samples along a vehicle axis in the one or more vehicle axes using the velocity information and the telematics system;

receiving accelerometer acceleration information samples along a set of accelerometer axes using the telematics system, where the orientation of the accelerometer axes is independent of the orientation of the vehicle axes and the set of accelerometer axes comprises a first accelerometer axis in a first vector; and

mapping the first accelerometer axis to one of vehicle axes based on using the vehicle acceleration information samples, the accelerometer acceleration information samples, and the telematics system, where the first vector of the calibrated first accelerometer axis corresponds to the forward vector of the vehicle by computing orthogonal vectors based on the cross product of every combination of the GPS acceleration information along the one or more vehicle axes, the lateral vector, and the vertical vector thereby calibrating the orientation of the accelerometer so that the first accelerometer axis corresponds to the forward vector of the vehicle.

13. The method of claim 12, wherein receiving velocity information samples using the telematics system further includes receiving the velocity information samples at a first sampling rate.

14. The method of claim 13, wherein receiving accelerometer acceleration information samples at a second sampling rate.

15. The method of claim 14, further comprising matching the first sampling rate to the second sampling rate using the telematics system.

16. The method of claim 12, wherein calibrating a vehicle axis to the first accelerometer axis includes performing a least squares method using the telematics system.

17. The method of claim 16, wherein performing the least squares method includes performing a Gaussian elimination solver using the telematics system.

18. The method of claim 17, further comprising storing a plurality of motion samples using the telematics system, where motion samples are selected from the group consisting of velocity information samples and accelerometer acceleration information samples.

19. The method of claim 17, further comprising performing the least squares method using at least one motion sample in the plurality of motion samples and the telematics system.

20. The method of claim 12, further comprising:

detecting the vertical vector in the calibrated vehicle axes using the telematics system; and

recalibrating the calibrated vehicles axes using the using the GPS acceleration information sample, the accelerometer acceleration information sample, the detected vertical vector, and the telematics system.

21. The method of claim 12, further comprising:

detecting the lateral vector in the calibrated vehicle axes using the telematics system; and

recalibrating the calibrated vehicles axes using the using the GPS acceleration information sample, the accelerometer acceleration information sample, the detected lateral vector, and the telematics system.