Compensation system for electronic compass

Claim 3

The method as defined in claim 1 wherein said first predetermined fractional part is equal to one-fourth and said second predetermined fractional part is equal to one-half.

Claim 4

A compensated electronic compass system suitable for use in a vehicle comprising: a two-axis compass sensor comprising a first magnetoresistive sensor and a second magnetoresistive sensor for detecting an external magnetic field and developing electronic signals representative of the strength and direction of said magnetic field, said external magnetic field being a combination of the earth magnetic field and a deviating magnetic field of the vehicle; each of said first and second sensors comprising at least one magnetoresistive field sensing element having a magnetic field sensitive axis and having an output which provides an output signal representative of a component of said external magnetic field along said sensitive axis, said first and second sensors being orientated with their sensitive axes in a predetermined angular relation with each other; a digital electronic circuit including a microcomputer coupled with said output of said first sensor and said output of said second sensor; said compass system providing a direction indicating signal to a compass heading display located within the vehicle, said direction indicating signal compensated for the deviating magnetic field of the vehicle so as to be representative of the magnetic heading of the vehicle; said compass system having an initial calibration mode to determine an initial deviation compensation for a particular vehicle installation and a normal calibration mode which is operative during normal compass operation, said compass system provided with a manual actuation to set said system into said initial calibration mode, said compass system automatically exiting said initial calibration mode into said normal calibration mode after said initial deviation compensation is complete.

Claim 5

A compensated electronic compass system suitable for use in a vehicle comprising: a two-axis compass sensor comprising a first magnetoresistive sensor and a second magnetoresistive sensor for detecting an external magnetic field and developing electronic signals representative of the strength and direction of said magnetic field, said external magnetic field being a combination of the earth magnetic field and a deviating magnetic field of the vehicle; each of said first and second sensors comprising at least one magnetoresistive field sensing element having a magnetic field sensitive axis and having an output which provides an output signal representative of a component of said external magnetic field along said sensitive axis, said first and second sensors being orientated with their sensitive axes in a predetermined angular relation with each other; a digital electronic circuit including a microcomputer coupled with said output of said first sensor and said output of said second sensor; said compass system providing a direction indicating signal to a compass heading display located within the vehicle, said direction indicating signal compensated for the deviating magnetic field of the vehicle so as to be representative of the magnetic heading of the vehicle; said compass system having an initial calibration mode to determine an initial deviation compensation for a particular vehicle installation and a normal calibration mode which is operative during normal compass operation, said compass system provided with a manual actuation to set said system into said initial calibration mode, said compass system automatically exiting said initial calibration mode into said normal calibration mode after said initial deviation compensation is complete.

Claim 6

The compass system of claim 3 wherein said compass system exits said initial calibration mode into said normal calibration mode after a plurality of cardinal compass points is sensed by said two-axis sensor.

Claim 7

The compass system of claim 4 wherein said plurality of cardinal points is at least six cardinal points.

Claim 8

The compass system of claim 3 wherein said manual actuation comprises manual closure of a switch for a predetermined time.

Claim 9

The compass system of claim 6 wherein said predetermined time is about a half second.

Claim 10

The compass system of claim 3 wherein said direction indicating signal is automatically compensated for any change in said deviating field of said vehicle at least once during each ignition cycle of the vehicle when said compass system is in said normal calibration mode.

Claim 11

The compass system of claim 8 wherein said direction indicating signal is automatically compensated for any change in said deviating field of said vehicle at least twice during each ignition cycle of the vehicle when said compass system is in said normal calibration mode.

Claim 12

The compass system of claim 8 wherein said compass system includes a warm-up delay whereby compensation of said compass system while in said normal calibration mode is delayed for a period after the ignition switch of the vehicle is turned on.

Claim 13

The compass system of claim 10 wherein said warm-up delay period is at least five minutes.

Claim 14

The compass system of claim 3 wherein said microcomputer operates under a control program that computes the magnetic heading of the vehicle.

Claim 15

The compass system of claim 3 wherein said magnetoresistive field sensing elements are deposited as thin films on a substrate.

Claim 16

The compass system of claim 13 wherein said substrate comprises a silicon substrate.

Claim 17

The compass system of claim 14 wherein said thin films comprise a ferromagnetic material.

Claim 18

The compass system of claim 3 wherein said compass heading display comprises an alphanumeric display.

Claim 19

The compass system of claim 16 wherein said alphanumeric display comprises a vacuum fluorescent display.

Claim 20

The compass system of claim 3 wherein said two-axis compass sensor is mounted on an inside rearview mirror assembly of the vehicle.

Claim 21

The compass system of claim 18 wherein said two-axis compass sensor is mounted on said inside rearview mirror assembly so that its position is fixed with respect to the vehicle.

Claim 22

The compass system of claim 18 wherein said two-axis compass sensor and said digital electronic circuit are located in a module that is secured to a mounting bracket of said inside rearview mirror assembly.

Claim 23

The compass system of claim 20 wherein said module communicates with a compass heading display located on said inside rearview mirror assembly.

Claim 24

The compass system of claim 21 wherein said compass heading display is located behind the mirror of said inside rearview mirror assembly and viewable through an area thereof.

Claim 25

The compass system of claim 21 wherein said compass heading display is displayed above the mirror of said inside rearview mirror assembly.

Claim 26

The compass system of claim 21 wherein said compass heading display is displayed below the mirror of said inside rearview mirror assembly.

Claim 27

The compass system of claim 20 wherein said compass heading display is displayed at a position in the vehicle remote from the location of the inside rearview mirror.

Claim 28

The compass system of claim 20 wherein said inside rearview mirror assembly comprises a prismatic mirror.

Claim 29

The compass system of claim 20 wherein said inside rearview mirror assembly comprises an electrochromic mirror.

Claim 30

The compass system of claim 3 wherein said magnetic field sensitive axis of said first magnetoresistive sensor is orientated orthogonal to said magnetic field sensitive axis of said second magnetoresistive sensor when said two-axis compass sensor is mounted in the vehicle.

Claim 31

The compass system of claim 28 wherein said magnetic field sensitive axis of said first magnetoresistive sensor is orientated parallel to the longitudinal axis of the vehicle when said two-axis compass sensor is mounted in the vehicle.

Claim 32

A rearview mirror mounted compensated electronic compass system suitable for use in a vehicle comprising: an inside rearview mirror assembly, said assembly including a mirror mounting bracket for mounting said assembly in the vehicle; a two-axis compass sensor comprising a first magnetoresistive sensor and a second magnetoresistive sensor for detecting an external magnetic field and developing electronic signals representative of the strength and direction of said magnetic field, said external magnetic field being a combination of the earth magnetic field and a deviating magnetic field of the vehicle; each of said first and second sensors comprising at least one magnetoresistive field sensing element having a magnetic field sensitive axis and having an output which provides an output signal representative of a component of said external magnetic field along said sensitive axis, said first and second sensors being orientated with their sensitive axes in a predetermined angular relation with each other; a digital electronic circuit including a microcomputer coupled with said output of said first sensor and said output of said second sensor; said compass system providing a direction indicating signal to a compass heading display located within the vehicle, said direction indicating signal compensated for the deviating magnetic field of the vehicle so as to be representative of the magnetic heading of the vehicle; said compass system having an initial calibration mode to determine an initial deviation compensation for a particular vehicle installation and a normal calibration mode which is operative during normal compass operation, said compass system automatically exiting said initial calibration mode into said normal calibration mode after said initial deviation compensation is complete and; wherein said two-axis compass sensor and said digital electronic circuit are located in a module that is secured to said mounting bracket of said inside rearview mirror assembly.

Claim 33

A rearview mirror mounted compensated electronic compass system suitable for use in a vehicle comprising: an inside rearview mirror assembly, said assembly including a mirror mounting bracket for mounting said assembly in the vehicle; a two-axis compass sensor comprising a first magnetoresistive sensor and a second magnetoresistive sensor for detecting an external magnetic field and developing electronic signals representative of the strength and direction of said magnetic field, said external magnetic field being a combination of the earth magnetic field and a deviating magnetic field of the vehicle; each of said first and second sensors comprising at least one magnetoresistive field sensing element having a magnetic field sensitive axis and having an output which provides an output signal representative of a component of said external magnetic field along said sensitive axis, said first and second sensors being orientated with their sensitive axes in a predetermined angular relation with each other; a digital electronic circuit including a microcomputer coupled with said output of said first sensor and said output of said second sensor; said compass system providing a direction indicating signal to a compass heading display located within the vehicle, said direction indicating signal compensated for the deviating magnetic field of the vehicle so as to be representative of the magnetic heading of the vehicle; said compass system having an initial calibration mode to determine an initial deviation compensation for a particular vehicle installation and a normal calibration mode which is operative during normal compass operation, said compass system automatically exiting said initial calibration mode into said normal calibration mode after said initial deviation compensation is complete and; wherein said two-axis compass sensor and said digital electronic circuit are located in a module that is secured to said mounting bracket of said inside rearview mirror assembly.

Claim 34

The compass system of claim 30 wherein said compass system exits said initial calibration mode into said normal calibration mode after a plurality of cardinal compass points is sensed by said two-axis sensor.

Claim 35

The compass system of claim 31 wherein said plurality of cardinal points is at least six cardinal points.

Claim 36

The compass system of claim 30 wherein said compass system is provided with a manual actuation to set said system into said initial calibration mode.

Claim 37

The compass system of claim 33 wherein said manual actuation comprises manual closure of a switch for a predetermined time.

Claim 38

The compass system of claim 30 wherein said direction indicating signal is automatically compensated for any change in said deviating field of said vehicle at least once during each ignition cycle of the vehicle when said compass system is in said normal calibration mode.

Claim 39

The compass system of claim 35 wherein said direction indicating signal is automatically compensated for any change in said deviating field of said vehicle at least twice during each ignition cycle of the vehicle when said compass system is in said normal calibration mode.

Claim 40

The compass system of claim 35 wherein said compass system includes a warm-up delay whereby compensation of said compass system while in said normal calibration mode is delayed for a period after the ignition switch of the vehicle is turned on.

Claim 41

The compass system of claim 37 wherein said warm-up delay period is at least five minutes.

Claim 42

The compass system of claim 30 wherein said microcomputer operates under a control program that computes the magnetic heading of the vehicle.

Claim 43

The compass system of claim 30 wherein said magnetoresistive field sensing elements are deposited as thin films on a substrate.

Claim 44

The compass system of claim 40 wherein said substrate comprises a silicon substrate.

Claim 45

The compass system of claim 41 wherein said thin films comprise a ferromagnetic material.

Claim 46

The compass system of claim 30 wherein said compass heading display comprises an alphanumeric display.

Claim 47

The compass system of claim 43 wherein said alphanumeric display comprises a vacuum fluorescent display.

Claim 48

The compass system of claim 30 wherein said two-axis compass sensor is mounted on an inside rearview mirror of the vehicle.

Claim 49

The compass system of claim 45 wherein said two-axis compass sensor is mounted on said inside rearview mirror assembly so that its position is fixed with respect to the vehicle.

Claim 50

The compass system of claim 45 wherein said two-axis compass sensor and said digital electronic circuit are located in a module that is secured to a mounting bracket of said inside rearview mirror assembly.

Claim 51

The compass system of claim 47 wherein said module communicates with a compass heading display located on said inside rearview mirror assembly.

Claim 52

The compass system of claim 48 wherein said compass heading display is located behind the mirror of said inside rearview mirror assembly and viewable through an area thereof.

Claim 53

The compass system of claim 48 wherein said compass heading display is displayed above the mirror of said inside rearview mirror assembly.

Claim 54

The compass system of claim 48 wherein said compass heading display is displayed below the mirror of said inside rearview mirror assembly.

Claim 55

The compass system of claim 30 wherein said compass heading display is displayed at a position in the vehicle remote from the location of the inside rearview mirror.

Claim 56

The compass system of claim 30 wherein said inside rearview mirror assembly comprises a prismatic mirror.

Claim 57

The compass system of claim 30 wherein said inside rearview mirror assembly comprises an electrochromic mirror.

Claim 58

The compass system of claim 30 wherein said magnetic field sensitive axis of said first magnetoresistive sensor is orientated orthogonal to said magnetic field sensitive axis of said second magnetoresistive sensor when said two-axis compass sensor is mounted in the vehicle.

Claim 59

The compass system of claim 55 wherein said magnetic field sensitive axis of said first magnetoresistive sensor is orientated parallel to the longitudinal axis of the vehicle when said two-axis compass sensor is mounted in the vehicle.

Claim 60

A compensated electronic compass system suitable for use in a vehicle comprising: a two-axis compass sensor comprising a first magnetoresistive sensor and a second magnetoresistive sensor for detecting an external magnetic field and developing electronic signals representative of the strength and direction of said magnetic field, said external magnetic field being a combination of the earth magnetic field and a deviating magnetic field of the vehicle; each of said first and second sensors comprising at least one magnetoresistive field sensing element having a magnetic field sensitive axis and having an output which provides an output signal representative of a component of said external magnetic field along said sensitive axis, said first and second sensors being orientated with their sensitive axes in a predetermined angular relation with each other; a digital electronic circuit including a microcomputer coupled with said output of said first sensor and said output of said second sensor; said compass system providing a direction indicating signal to a compass heading display located within the vehicle, said direction indicating signal compensated for the deviating magnetic field of the vehicle so as to be representative of the magnetic heading of the vehicle; said compass system having an initial calibration mode to determine an initial deviation compensation for a particular vehicle installation and a normal calibration mode which is operative during normal compass operation and; wherein said magnetic field sensitive axis of said first magnetoresistive sensor is orientated orthogonal to said magnetic field sensitive axis of said second magnetoresistive sensor and wherein said magnetic field sensitive axis of said first magnetoresistive sensor is orientated parallel to the longitudinal axis of the vehicle when said two-axis compass sensor is mounted in the vehicle.

Claim 61

A compensated electronic compass system suitable for use in a vehicle comprising: a two-axis compass sensor comprising a first magnetoresistive sensor and a second magnetoresistive sensor for detecting an external magnetic field and developing electronic signals representative of the strength and direction of said magnetic field, said external magnetic field being a combination of the earth magnetic field and a deviating magnetic field of the vehicle; each of said first and second sensors comprising at least one magnetoresistive field sensing element having a magnetic field sensitive axis and having an output which provides an output signal representative of a component of said external magnetic field along said sensitive axis, said first and second sensors being orientated with their sensitive axes in a predetermined angular relation with each other; a digital electronic circuit including a microcomputer coupled with said output of said first sensor and said output of said second sensor; said compass system providing a direction indicating signal to a compass heading display located within the vehicle, said direction indicating signal compensated for the deviating magnetic field of the vehicle so as to be representative of the magnetic heading of the vehicle; said compass system having an initial calibration mode to determine an initial deviation compensation for a particular vehicle installation and a normal calibration mode which is operative during normal compass operation and; wherein said magnetic field sensitive axis of said first magnetoresistive sensor is orientated orthogonal to said magnetic field sensitive axis of said second magnetoresistive sensor and wherein said magnetic field sensitive axis of said first magnetoresistive sensor is orientated parallel to the longitudinal axis of the vehicle when said two-axis compass sensor is mounted in the vehicle.

Claim 62

The compass system of claim 57 wherein said compass system is provided with a manual actuation to set said system into said initial calibration modes.

Claim 63

The compass system of claim 58 wherein said manual actuation comprises manual closure of a switch for a predetermined time.

Claim 64

The compass system of claim 57 wherein said compass system automatically exits said initial calibration mode into said normal calibration mode after a plurality of cardinal compass points is sensed by said two-axis sensor.

Claim 65

The compass system of claim 57 wherein said direction indicating signal is automatically compensated for any change in said deviating field of said vehicle at least once during each ignition cycle of the vehicle when said compass system is in said normal calibration mode.

Claim 66

The compass system of claim 61 wherein said direction indicating signal is automatically compensated for any change in said deviating field of said vehicle at least twice during each ignition cycle of the vehicle when said compass system is in said normal calibration mode.

Claim 67

The compass system of claim 57 wherein said microcomputer operates under a control program that computes the magnetic heading of the vehicle.

Claim 68

The compass system of claim 57 wherein said magnetoresistive field sensing elements are deposited as thin films on a substrate.

Claim 69

The compass system of claim 57 wherein said compass heading display comprises an alphanumeric display.

Claim 70

The compass system of claim 57 wherein said two-axis compass sensor is mounted on an inside rearview mirror assembly of the vehicle.

Claim 71

The compass system of claim 66 wherein said two-axis compass sensor is mounted on said inside rearview mirror assembly so that its position is fixed with respect to the vehicle.

Claim 72

The compass system of claim 66 wherein said two-axis compass sensor and said digital electronic circuit are located in a module that is secured to a mounting bracket of said inside rearview mirror assembly.

Claim 73

The compass system of claim 68 wherein said module communicates with a compass heading display located on said inside rearview mirror assembly.

Claim 74

The compass system of claim 69 wherein said compass heading display is located behind the mirror of said inside rearview mirror assembly and viewable through an area thereof.

Claim 75

The compass system of claim 69 wherein said compass heading display is displayed above the mirror of said inside rearview mirror assembly.

Claim 76

The compass system of claim 69 wherein said compass heading display is displayed below the mirror of said inside rearview mirror assembly.

Claim 77

The compass system of claim 69 wherein said compass heading display is displayed at a position in the vehicle remote from the location of the inside rearview mirror.

Claim 78

The compass system of claim 68 wherein said inside rearview mirror assembly comprises a prismatic mirror.

Claim 79

The compass system of claim 68 wherein said inside rearview mirror assembly comprises an electrochromic mirror.