Vehicle compass system with automatic calibration
DCFirst Claim
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1. An electrical quick calibration compass system for use in a vehicle such as an automobile comprising:
- a magnetic field sensor for detecting the earth'"'"'s magnetic field and for providing electrical signals representing the direction of the vehicle in relation to the earth'"'"'s magnetic field;
a processing circuit coupled to said sensor for processing signals from said sensor and for providing display output signals in response thereto;
a display circuit coupled to said processing circuit and responsive to said display output signals for displaying the vehicle heading; and
said processing circuit responsive to signals from said sensor, during which time the change of direction of the vehicle is less than a closed loop, for determining that the detected signal levels from said sensor, corresponding to the effect of the earth'"'"'s magnetic field and the effect of vehicle magnetism on said sensor, have shifted such that said signal levels are outside a predetermined threshold, said processing circuit responsive to said determination that said signal levels are outside said threshold for recalibrating said compass system using the detected signal levels output from said sensor during the time in which the vehicle direction changed less than a closed loop;
wherein said processing circuit adjusts the detected signal levels after determining that the vehicle'"'"'s direction of travel has changed a predetermined amount corresponding to a plot of said detected signal levels from said sensor creating an arc spanning a predetermined angle, said arc has a starting point and an ending point that are used to determine the center of said arc, the center of the arc being determined by assuming a radius and identifying at least one center candidate point that is spaced apart from the starting point and the ending point by the assumed radius.
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Abstract
An electrical system providing automatic calibration of a vehicle compass for abrupt and significant changes in vehicle magnetism. The system includes a magnetic field sensor providing signal information representing the magnetic field sensed within the vehicle. Coupled to the sensor is an electrical circuit for processing the signal information from the sensor to determine if a shift in vehicle magnetism has occurred and for calculating compensation signal information to provide a corrected heading display.
715 Citations
38 Claims
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1. An electrical quick calibration compass system for use in a vehicle such as an automobile comprising:
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a magnetic field sensor for detecting the earth'"'"'s magnetic field and for providing electrical signals representing the direction of the vehicle in relation to the earth'"'"'s magnetic field; a processing circuit coupled to said sensor for processing signals from said sensor and for providing display output signals in response thereto; a display circuit coupled to said processing circuit and responsive to said display output signals for displaying the vehicle heading; and said processing circuit responsive to signals from said sensor, during which time the change of direction of the vehicle is less than a closed loop, for determining that the detected signal levels from said sensor, corresponding to the effect of the earth'"'"'s magnetic field and the effect of vehicle magnetism on said sensor, have shifted such that said signal levels are outside a predetermined threshold, said processing circuit responsive to said determination that said signal levels are outside said threshold for recalibrating said compass system using the detected signal levels output from said sensor during the time in which the vehicle direction changed less than a closed loop; wherein said processing circuit adjusts the detected signal levels after determining that the vehicle'"'"'s direction of travel has changed a predetermined amount corresponding to a plot of said detected signal levels from said sensor creating an arc spanning a predetermined angle, said arc has a starting point and an ending point that are used to determine the center of said arc, the center of the arc being determined by assuming a radius and identifying at least one center candidate point that is spaced apart from the starting point and the ending point by the assumed radius. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An electrical quick calibration compass system for use in a vehicle such as an automobile comprising:
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a magnetic field sensor for detecting the earth'"'"'s magnetic field and for providing electrical signals representing the direction of the vehicle in relation to the earth'"'"'s magnetic field; a processing circuit coupled to said sensor for processing signals from said sensor and for providing display output signals in response thereto; a display circuit coupled to said processing circuit and responsive to said display output signals for displaying the vehicle heading; and said processing circuit responsive to signals from said sensor, for adjusting the detected signal levels after determining that the vehicle'"'"'s direction of travel has changed a predetermined amount corresponding to a plot of said detected signal levels from said sensor creating an arc spanning a predetermined angle, said arc has a starting point and an ending point that are used to determine the center of said arc, the center of the arc being determined by assuming a radius and identifying at least one center candidate point that is spaced apart from the starting point and the ending point by the assumed radius. - View Dependent Claims (15)
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16. An electrical quick calibration compass system for use in a vehicle such as an automobile comprising:
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a magnetic field sensor for detecting the earth'"'"'s magnetic field and for providing electrical signals representing the direction of the vehicle in relation to the earth'"'"'s magnetic field; a processing circuit coupled to said sensor for processing signals from said sensor and for providing display output signals in response thereto; a display circuit coupled to said processing circuit and responsive to said display output signals for displaying the vehicle heading; and said processing circuit responsive to signals from said sensor for determining that the detected signal levels from said sensor, corresponding to the effect of the earth'"'"'s magnetic field and the effect of vehicle magnetism on said sensor, have shifted such that said signal levels are outside a predetermined threshold for a predetermined distance of travel of the vehicle, said processing circuit responsive to said determination for calculating compensation signals to adjust said detected signal levels such that said detected signal levels are within said predetermined threshold and for correcting said display output signals to display the vehicle heading. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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24. An electrical quick calibration compass system for use in a vehicle such as an automobile comprising:
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sensing means for detecting the earth'"'"'s magnetic field and for providing electrical signals representing the direction of the vehicle in relation to the earth'"'"'s magnetic field; circuit means coupled to said sensing means for processing signals therefrom and for providing display output signals in response thereto; display means coupled to said circuit means and responsive to said display output signals for displaying the vehicle heading; and said circuit means including determining means responsive to signals from said sensing means, during which time the change of direction of the vehicle is less than a closed loop, for determining when the detected signal levels from said sensing means, corresponding to the effect of the earth'"'"'s magnetic field and the effect of vehicle magnetism on said sensing means, have changed such that said signal levels exceed a predetermined threshold, said circuit means further including means for recalibrating said compass system using the detected signal levels output from said sensing means during the time in which the vehicle direction changed less than a closed loop, wherein said determining means determines that said detected signal levels from said sensing means are outside said predetermined threshold for a predetermined distance of travel of the vehicle before calculating compensation data. - View Dependent Claims (25, 26, 27, 28, 31)
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29. An electrical quick calibration compass system for use in a vehicle such as an automobile comprising:
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a magnetic field sensor for detecting the earth'"'"'s magnetic field and for providing electrical signals representing the direction of the vehicle in relation to the earth'"'"'s magnetic field; a processing circuit coupled to said sensor for processing signals therefrom and for providing display output signals in response thereto; a display circuit coupled to said processing circuit and responsive to said display output signals for displaying the vehicle heading; and said processing circuit responsive to signals from said sensor, during which time the change of direction of the vehicle is less than a closed loop, for monitoring signals from said sensor which correspond to the effect of the earth'"'"'s magnetic field and the effect of vehicle magnetism on said sensor for determining when the detected signal levels have shifted such that said signal levels are outside a predetermined threshold for a predetermined distance of travel of the vehicle, said processing circuit responsive to said determination for calculating compensation signals to adjust said detected signal levels after said processing circuit detects that the vehicle'"'"'s direction of travel has changed a predetermined amount such that said detected signal levels are within said threshold and substantially coincide with stored signal levels before the shift occurred. - View Dependent Claims (30, 32)
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33. An electrical compass system for use in a vehicle, said system including a sensor for sensing a magnetic field and for providing output signals representative thereof, a processing circuit coupled to said sensor for processing said signals and for providing display output signals in response thereto, and a display circuit coupled to said processing circuit and responsive to said display output signals for displaying the vehicle heading, said processing circuit continuously monitoring signal information from said sensor when the vehicle has travelled through a path for determining the maximum and minimum detected signal levels from said sensor, corresponding to the effect of the earth'"'"'s magnetic field and the effect of vehicle magnetism on said sensor, and during the course of movement of the vehicle through the path calculating from said maximum and minimum detected signal levels an offset signal for providing compensating signals to display the correct vehicle heading;
- wherein the improvement comprises;
said processing circuit programmed to compensate for large changes in vehicle magnetism caused by local magnetic field interference by detecting, during which time the change of direction of the vehicle is less than a closed loop, when sensor signal levels have shifted such that said signal levels are outside a predetermined threshold indicating an abnormal change in vehicle magnetism, said processing circuit responsive to said detection for recalibrating said compass system using the detected signal levels output from said sensor during the time in which the vehicle direction changed less than a closed loop, wherein said processing circuit is responsive to said sensor for determining that signal levels from said sensor are outside said predetermined threshold for a predetermined distance of travel of the vehicle. - View Dependent Claims (34, 35, 36, 37, 38)
- wherein the improvement comprises;
Specification