ELECTRONIC COMPASS SYSTEM

• US 20070124076A1
• Filed: 11/07/2006
• Published: 05/31/2007
• Est. Priority Date: 03/01/2002
• Status: Active Grant

• Current Assignee: Gentex Corporation
• Original Assignee: Gentex Corporation
• Inventors: Ockerse, Harold, Bechtel, Jon, Bugno, Mark
• Granted Patent: US 7,266,452 B2
• Time in Patent Office: Days
• US Class Current: 701/224
• CPC Class Codes: G01C 17/28 Electromagnetic compasses with north seeking magnetic elements and having electric pick-offs G01C17/26
• CPC Class Codes: G01C 17/30 Earth-inductor compasses
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

An electronic compass system includes a magnetic sensor circuit having at least two sensing elements for sensing perpendicular components of the Earth'"'"'s magnetic field vector. A processing circuit is coupled to the sensor circuit to filter, process, and compute a heading. The processing circuit may determine whether too much noise is present in the output signals received from said magnetic sensor circuit as a function of the relative strength of the Earth'"'"'s magnetic field vector. The magnetic sensor circuit may include three magnetic field sensing elements contained in a common integrated package having a plurality of leads extending therefrom for mounting to a circuit board. The sensing elements need not be perpendicular to each other or parallel or perpendicular with the circuit board. The electronic compass system is particularly well suited for implementation in a vehicle rearview mirror assembly.

Claims

12. An electronic compass system for use in a vehicle having at least one vehicle accessory capable of adversely effecting the operation of the compass system, said electronic compass system comprising:

a magnetic sensor circuit for sensing at least two components of the Earth'"'"'s magnetic field vector and generating output signals representing the at least two sensed components;

a processing circuit coupled to the magnetic sensor circuit for sampling the output signals from the magnetic sensor circuit, computing a heading of the vehicle as a function of the sensed components, and generating a heading signal representing the computed heading; and

wherein said processing circuit immediately compensates for the effect of the vehicle accessory on the magnetic field sensed by the magnetic sensor circuit upon detection of the effect of the vehicle accessory on the magnetic field without requiring a signal from the vehicle accessory.

13. The electronic compass system of claim 12, wherein said compensating means comprises a monitoring circuit that monitors the output of the magnetic sensor circuit to identify changes in the levels of the output signals in a manner consistent with that caused by the vehicle accessory.

14. The electronic compass system of claim 13, wherein said monitoring circuit is a digital signal processor.

15. The electronic compass system of claim 13, wherein said monitoring circuit is a portion of said processing circuit.

16. The electronic compass system of claim 13, wherein said magnetic sensor circuit comprises three sensing elements for supplying three output signals representing three orthogonal components of the Earth'"'"'s magnetic field, wherein said monitoring circuit monitors the output signals of all three of said sensing elements to identify changes in the levels of the output signals in a manner consistent with that caused by the vehicle accessory.

17. The electronic compass system of claim 13, wherein said magnetic sensor circuit comprises two sensing elements for supplying two output signals representing two orthogonal components of the Earth'"'"'s magnetic field, wherein said monitoring circuit monitors the output signals of both of said sensing elements to identify changes in the levels of the output signals in a manner consistent with that caused by the vehicle accessory.

18. The electronic compass system of claim 13, wherein said processing circuit selects a first approximating geometric pattern based on a first set of reference data points derived from the sensed components, and computes a heading of the vehicle as a function of at least two of the sensed components while referencing the first approximating geometric pattern.

19. The electronic compass system of claim 18, wherein said compensating means includes a portion of said processing circuit, wherein, during such time that said monitoring circuit identifies changes in the levels of the output signals in a manner consistent with that caused by the vehicle accessory, said portion of said processing circuit selects a second approximating geometric pattern based on reference data points received and utilizes the second approximating geometric pattern to compute the heading of the vehicle.

20. The electronic compass system of claim 19, wherein during such time that said monitoring circuit does not identify changes in the levels of the output signals in a manner consistent with that caused by the vehicle accessory, said portion of said processing circuit utilizes the first approximating geometric pattern to compute the heading of the vehicle.

21. The electronic compass system of claim 18, wherein said compensating means includes a portion of said processing circuit, wherein, during such time that said monitoring circuit identifies changes in the levels of the output signals in a manner consistent with that caused by the vehicle accessory, said portion of said processing circuit shifts the first approximating geometric pattern by an offset corresponding to a shift in the levels of the output signals caused by the vehicle accessory when activated.

22. The electronic compass system of claim 12, wherein said compensating means immediately compensates for the effect of an electric field caused by the opened or closed state of the vehicle equipment on the magnetic field sensed by the magnetic sensor circuit upon detection of the activation of the change in the vehicle accessory.

23. The electronic compass system of claim 13, wherein said monitoring circuit monitors the voltage of the vehicle'"'"'s battery and monitors the output of the magnetic sensor circuit to identify changes in the levels of the output signals in a manner consistent with that caused by the vehicle accessory taken as a function of the voltage of the vehicle'"'"'s battery.

24. In a vehicle having a conductive glass windshield with an electrically conductive material incorporated therein and an electronic compass system having a magnetic sensor circuit located in proximity to the conductive glass windshield, the magnetic sensor circuit senses at least two components of the Earth'"'"'s magnetic field vector and generates output signals representing the at least two sensed components, an improvement comprising:

a processing circuit coupled to the magnetic sensor circuit for sampling the output signals from the magnetic sensor circuit, computing a heading of the vehicle as a function of the sensed components, and generating a heading signal representing the computed heading; and

compensating means for compensating for the effect of an electric field caused by a conductive glass windshield on the magnetic field sensed by the magnetic sensor circuit.

1. An electronic compass system for use in a vehicle having vehicle equipment consisting of one of a convertible top and sunroof, said electronic compass system comprising:

a magnetic sensor circuit for sensing at least two components of the Earth'"'"'s magnetic field vector and generating output signals representing the at least two sensed components;

a processing circuit coupled to the magnetic sensor circuit for sampling the output signals from the magnetic sensor circuit, computing a heading of the vehicle as a function of the sensed components, and generating a heading signal representing the computed heading; and

compensating means for compensating for the effect of a change in the opened or closed state of the vehicle equipment on the magnetic field sensed by the magnetic sensor circuit.

2. The electronic compass system of claim 1, wherein said compensating means comprises a monitoring circuit that monitors the output of the magnetic sensor circuit to identify changes in the levels of the output signals in a manner consistent with that caused by the opened or closed state of the vehicle equipment.

3. The electronic compass system of claim 2, wherein said monitoring circuit is a digital signal processor.

4. The electronic compass system of claim 2, wherein said monitoring circuit is a portion of said processing circuit.

5. The electronic compass system of claim 2, wherein said magnetic sensor circuit comprises three sensing elements for supplying three output signals representing three orthogonal components of the Earth'"'"'s magnetic field, wherein said monitoring circuit monitors the output signals of all three of said sensing elements to identify changes in the levels of the output signals in a manner consistent with that caused by the opened or closed state of the vehicle equipment.

6. The electronic compass system of claim 2, wherein said magnetic sensor circuit comprises two sensing elements for supplying two output signals representing two orthogonal components of the Earth'"'"'s magnetic field, wherein said monitoring circuit monitors the output signals of both of said sensing elements to identify changes in the levels of the output signals in a manner consistent with that caused by the opened or closed state of the vehicle equipment.

7. The electronic compass system of claim 2, wherein said processing circuit selects a first approximating geometric pattern based on a first set of reference data points derived from the sensed components, and computes a heading of the vehicle as a function of at least two of the sensed components while referencing the first approximating geometric pattern.

8. The electronic compass system of claim 7, wherein said compensating means includes a portion of said processing circuit, wherein, during such time that said monitoring circuit identifies changes in the levels of the output signals in a manner consistent with that caused by the opened or closed state of the vehicle equipment, said portion of said processing circuit selects a second approximating geometric pattern based on reference data points received and utilizes the second approximating geometric pattern to compute the heading of the vehicle.

9. The electronic compass system of claim 8, wherein during such time that said monitoring circuit does not identify changes in the levels of the output signals in a manner consistent with that caused by the opened or closed state of the vehicle equipment, said portion of said processing circuit utilizes the first approximating geometric pattern to compute the heading of the vehicle.

10. The electronic compass system of claim 7, wherein said compensating means includes a portion of said processing circuit, wherein, during such time that said monitoring circuit identifies changes in the levels of the output signals in a manner consistent with that caused by the opened or closed state of the vehicle equipment, said portion of said processing circuit shifts the first approximating geometric pattern by an offset corresponding to a shift in the levels of the output signals caused by the conductive glass windshield when activated.

11. The electronic compass system of claim 1, wherein said compensating means immediately compensates for the effect of an electric field caused by the opened or closed state of the vehicle equipment on the magnetic field sensed by the magnetic sensor circuit upon detection of an activation signal that causes the change in the opened or closed state of the vehicle equipment.

25. The vehicle improvement of claim 24, wherein said compensating means comprises a controller for supplying a pulsed activation signal to the electrically conductive material incorporated in the conductive glass windshield when the conductive glass windshield is to be activated, the pulsed activation signal being pulsed between high and low power activation states, said controller supplies a signal to said processing circuit that identifies when the pulsed activation signal is in a low power activation state, wherein said processing circuit times the sampling of the output signals from the magnetic sensor circuit such that samples are not taken when the pulsed activation signal is in a low power activation state so as to prevent the reading of samples of the output signals of the magnetic sensor circuit when noise is produced by the conductive glass windshield.

26. The vehicle improvement of claim 24, wherein said compensating means comprises a coil provided in proximity to the compass sensor circuit to create a magnetic field that nulls a magnetic field produced by the conductive glass windshield when the conductive glass windshield is activated.

27. The vehicle improvement of claim 24, wherein said compensating means comprises a pattern of conductive strips of the electrically conductive material of the conductive glass windshield, wherein at least adjacent first and second conductive strips extending in close proximity to the compass sensor circuit are patterned such that current passes through the first conductive strip in an opposite direction from the current passing through the adjacent second conductive strip so as to create magnetic fields that null one another.

28. The vehicle improvement of claim 24, wherein said compensating means comprises a pattern of very thin wires, wherein at least adjacent first and second wires extending in close proximity to the compass sensor circuit are positioned such that current passes through the first wire in an opposite direction from the current passing through the adjacent second wire so as to create magnetic fields that null one another.

29. The vehicle improvement of claim 24, wherein the electrically conductive material on the conductive glass window is provided in at least two portions and said compensating means comprises a window controller that periodically alternates the direction in which current is applied to the portions.

30. The vehicle improvement of claim 24, wherein said compensating means comprises a magnetic shielding coating placed between the conductive glass windshield and the compass sensor circuit.

31. The vehicle improvement of claim 24, wherein said compensating means comprises a monitoring circuit that monitors the output of the magnetic sensor circuit to identify rising and falling of levels of the output signals in a manner consistent with that caused by a magnetic field caused by the conductive glass windshield.

32. The vehicle improvement of claim 31, wherein the monitoring circuit prevents the sampling of the output signals by the processing circuit when such rising and falling of the levels of the output signals is identified.

33. The vehicle improvement of claim 31, wherein said monitoring circuit is a digital signal processor.

34. The vehicle improvement of claim 31, wherein said monitoring circuit is a portion of said processing circuit.

36. The vehicle improvement of claim 31, wherein said magnetic sensor circuit comprises three sensing elements for supplying three output signals representing three orthogonal components of the Earth'"'"'s magnetic field, wherein said monitoring circuit monitors the output signals of all three of said sensing elements to identify rising and falling of levels of the output signals in a manner consistent with that caused by a magnetic field caused by the conductive glass windshield.

37. The vehicle improvement of claim 31, wherein said processing circuit selects a first approximating geometric pattern based on a first set of reference data points derived from the sensed components, and computes a heading of the vehicle as a function of at least two of the sensed components while referencing the first approximating geometric pattern.

38. The vehicle improvement of claim 37, wherein said compensating means includes a portion of said processing circuit, wherein, during such time that said monitoring circuit identifies rising and falling of levels of the output signals in a manner consistent with that caused by a magnetic field caused by the conductive glass windshield, said portion of said processing circuit selects a second approximating geometric pattern based on reference data points received and utilizes the second approximating geometric pattern to compute the heading of the vehicle.

39. The vehicle improvement of claim 38, wherein during such time that said monitoring circuit does not identify rising and falling of levels of the output signals in a manner consistent with that caused by a magnetic field caused by the conductive glass windshield, said portion of said processing circuit utilizes the first approximating geometric pattern to compute the heading of the vehicle.

40. The vehicle improvement of claim 37, wherein said compensating means includes a portion of said processing circuit, wherein, during such time that said monitoring circuit identifies rising and falling of levels of the output signals in a manner consistent with that caused by a magnetic field caused by the conductive glass windshield, said portion of said processing circuit shifts the first approximating geometric pattern by an offset corresponding to a shift in the levels of the output signals caused by the conductive glass windshield when activated.

41. The vehicle improvement of claim 24, wherein said compensating means comprises a controller that activates the conductive glass windshield using a periodic activation signal having a predetermined frequency, wherein said processing circuit samples the output signals of the compass sensor circuit at twice the predetermined frequency of the activation signal, said processing circuit averages the samples of the output signals and subtracts any DC offset to eliminate the effect of the noise produced by the conductive glass windshield.

42. The vehicle improvement of claim 24, wherein the electrically conductive material incorporated within the conductive glass windshield is provided in the form of very thin wires or transparent strips.

43. The vehicle improvement of claim 24, wherein the electrically conductive material incorporated within the conductive glass windshield is provided in the form of transparent strips.

44. The vehicle improvement of claim 24, wherein said compensating means immediately compensates for the effect of an electric field caused by a conductive glass windshield on the magnetic field sensed by the magnetic sensor circuit upon detection of the activation of the conductive glass windshield.

36-1. The vehicle improvement of claim 31, wherein said magnetic sensor circuit comprises two sensing elements for supplying two output signals representing two orthogonal components of the Earth'"'"'s magnetic field, wherein said monitoring circuit monitors the output signals of both of said sensing elements to identify rising and falling of levels of the output signals in a manner consistent with that caused by a magnetic field caused by the conductive glass windshield.