TELEMATICS SYSTEM AND ASSOCIATED METHOD

• US 20150094977A1
• Filed: 09/26/2014
• Published: 04/02/2015
• Est. Priority Date: 09/28/2013
• Status: Active Grant

• Current Assignee: Quartix Limited (Quartix Technologies Plc)
• Original Assignee: Quartix Limited (Quartix Technologies Plc)
• Inventors: Dobra, Thomas, Bentham, Jeremy
• Granted Patent: US 10,082,522 B2
• Time in Patent Office: Days
• US Class Current: 702/104
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices
• CPC Class Codes: G01P 15/00 Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 19/52 Determining velocity
• CPC Class Codes: G07C 5/08 Registering or indicating performance data other than driving, working, idle, or waiting time, with or without registering driving, working, idle or waiting time
• CPC Class Codes: G08G 1/0112 from the vehicle, e.g. floating car data [FCD]
• CPC Class Codes: G08G 1/052 with provision for determining speed or overspeed speed measuring in general G01P

Abstract

Telematics system wherein a data processor is configured to: calculate a first rotation to isolate horizontal components of orientation data obtained from a three-axis accelerometer; calculate a second rotation of the orientation data dependent on acceleration data obtained from the velocity measuring device; and perform the first and second rotations on the orientation data to calibrate the orientation of the accelerometer relative to a vehicle on which the accelerometer is mounted. An associated method of calibrating the orientation of accelerometer is also provided.

Claims

1. A telematics system comprising a three-axis accelerometer associated with a moving object and configured to generate orientation data, a velocity measuring device, and a data processor, wherein the data processor is configured to:

calculate a first rotation to isolate horizontal components of orientation data;

calculate a second rotation of the orientation data dependent on acceleration data obtained from the velocity measuring device; and

perform the first and second rotations on the orientation data to calibrate the orientation of the accelerometer relative to the moving object.

2. The telematics system according to claim 1, wherein the first and second rotations are combined to apply a single transformation to the orientation data.

3. The telematics system according to claim 1, wherein the data processor is configured to identify at least one first value representative of a first angle of orientation of the accelerometer relative to a first axis and at least one second value representative of a second angle of orientation of the accelerometer relative to a second axis, the first axis being orthogonal to the second axis, and to use the first value and the second value to calculate the first rotation.

4. The telematics system according to claim 3, wherein the first angle is between the gravity vector and an x-axis and the second angle is between the gravity vector and a z-axis.

5. The telematics system according to claim 3, wherein the first and second angles are calculated to provide the first and second values.

6. The telematics system according to claim 3, wherein the at least one first value representative of the first angle and the at least one second value representative of the second angle are trigonometric functions only.

7. The telematics system according to claim 3, wherein the first and second angles are obtained from look-up tables to provide the first and second values.

8. The telematics system according to claim 1, wherein the orientation data represents a gravity vector.

9. The telematics system according to claim 1, wherein the second rotation is calculated using vector and scalar products of the accelerometer data with acceleration data obtained from the velocity measuring device.

10. The telematics system according to claim 1, wherein the first and second rotations are calculated rotational matrices to be applied to original data.

11. The telematics system according to claim 1, wherein the data processor is configured to accumulate orientation data and/or velocity data when moving between 5 km/h and 80 km/h.

12. The telematics system according to claim 1, wherein the data processor accumulates data for a set period of time.

13. The telematics system according to claim 1, wherein the velocity measuring device and the accelerometer are each sampled at a different frequency.

14. The telematics system according to claim 1, wherein the velocity measuring device is a GPS device.

15. A method of calibrating the orientation of a three-axis accelerometer associated with a moving object, the method comprising acquiring orientation data from the accelerometer, acquiring velocity data from a velocity measuring device, and supplying the orientation data and velocity data to a data processor, wherein the method further comprises:

calculating a first rotation to isolate horizontal components of the orientation data;

calculating a second rotation of the orientation data dependent on acceleration data derived from the velocity data; and

performing the first and second rotations on the orientation data to calibrate the orientation of the accelerometer relative to the moving object.

16. The method of calibrating the orientation of a three-axis accelerometer according to claim 15, further comprising combining the first and second rotations to apply a single transformation to the orientation data.

17. The method of calibrating the orientation of a three-axis accelerometer according to claim 15, wherein the orientation data represents a gravity vector.

18. The method of calibrating the orientation of a three-axis accelerometer according to claim 17, wherein the first angle is between the gravity vector and an x-axis and the second angle is between the gravity vector and a z-axis.

19. The method of calibrating the orientation of a three-axis accelerometer according to claim 17, comprising calculating the sines and cosines of the angles between the orientation vector and x and z axes by normalising vector components, and calculating the first rotation as a combination of rotation by the first angle about the z-axis followed by a rotation by the second angle about the axis.

20. The method of calibrating the orientation of a three-axis accelerometer according to claim 15, further comprising identifying at least one first value representing a first angle of orientation of the accelerometer relative to a first axis and identifying at least one second value representing a second angle of orientation of the accelerometer relative to a second axis, the first axis being orthogonal to the second axis, and using the first value and the second value to calculate the first rotation.

21. The method of calibrating the orientation of a three-axis accelerometer according to claim 20, further comprising calculating the first and second angles to provide the first and second values.

22. The method of calibrating the orientation of a three-axis accelerometer according to claim 20, further comprising calculating at least one first value representative of the first angle and the at least one second value representative of the second angle as trigonometric functions only.

23. The method of calibrating the orientation of a three-axis accelerometer according to claim 20, further comprising obtaining the first and second angles from look-up tables to provide the first and second values.

24. The method of calibrating the orientation of a three-axis accelerometer according to claim 15, further comprising calculating the second rotation using vector and scalar products of the accelerometer data with the acceleration data obtained from the velocity measuring device.

25. The method of calibrating the orientation of a three-axis accelerometer according to claim 15, further comprising calculating the first and second rotations as rotational matrices to be applied to original data.

26. The method of calibrating the orientation of a three-axis accelerometer according to claim 15, further comprising accumulating orientation data and/or velocity data when moving between 5 km/h and 80 km/h.

27. The method of calibrating the orientation of a three-axis accelerometer according to claim 15, further comprising accumulating data for a set period of time.

28. The method of calibrating the orientation of a three-axis accelerometer according to claim 15, further comprising sampling each of the velocity measurement device and the accelerometer at a different frequency.

29. The method of calibrating the orientation of a three-axis accelerometer according to claim 15, wherein the velocity measuring device is a GPS device.