Vehicle compass with automatic continuous calibration
DCFirst Claim
1. In an electronic compass system for use in a vehicle such as an automobile comprising:
- sensing means for detecting the earth'"'"'s magnetic field and for providing electrical signals representative of the direction of movement of the vehicle with respect to the earth'"'"'s magnetic field;
circuit means coupled to said sensing means for providing display output signals representing heading information corresponding to the detected direction;
display means coupled to said circuit means for displaying the vehicle heading in response to said display output signals, wherein the improvement comprises;
said circuit means including means responsive to the direction representative signals for detecting the rate of change of said direction representative signals, and for determining if the rate of change exceeds a predetermined level thereby indicating the existence of invalid detected direction information; and
means for providing an error output signal for display in response to said determining means determining that said rate of change exceeds said predetermined level.
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Accused Products
Abstract
A vehicle compass includes a magnetic field sensor for mounting within a vehicle and providing two output channels of information representing orthogonal direction sensing of the earth'"'"'s magnetic field within the vehicle. The sensor is coupled to an electrical circuit including a microprocessor for sampling the data from each of the two channels and providing a plurality of tests to determine if the rate of change of data is within a prescribed limit thereby indicating valid data is being received. Further, the data is tested to determine the maximum and minimum signal levels during movement of the vehicle through a completed 360° path of travel and for calculating therefrom the compass compensation information used to provide a corrected heading display.
495 Citations
20 Claims
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1. In an electronic 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 representative of the direction of movement of the vehicle with respect to the earth'"'"'s magnetic field; circuit means coupled to said sensing means for providing display output signals representing heading information corresponding to the detected direction; display means coupled to said circuit means for displaying the vehicle heading in response to said display output signals, wherein the improvement comprises; said circuit means including means responsive to the direction representative signals for detecting the rate of change of said direction representative signals, and for determining if the rate of change exceeds a predetermined level thereby indicating the existence of invalid detected direction information; and
means for providing an error output signal for display in response to said determining means determining that said rate of change exceeds said predetermined level. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An electrical 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 for processing said signals 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 first determining means responsive to said sensing means for determining that the vehicle has been moved through a closed loop, second determining means responsive to said first determining means and said direction representative signals for determining during the course of movement of the vehicle through a closed loop, the maximum and minimum detected signal level from said sensing means corresponding to the effect of the earth'"'"'s magnetic field and the magnetic properties of the vehicle on said sensing means;
said circuit means further including means for calculating from said maximum and minimum detected signal level an offset signal representing the static flux field due to the vehicle magnetism and means for correcting said display output signals to display the vehicle heading. - View Dependent Claims (8)
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9. An electrical compass system for a vehicle, said system including sensing means for sensing a magnetic field and providing output signals representative thereof, circuit means coupled to said sensing means for providing display output signals, and display means coupled to said circuit means and responsive to said display output signals for displaying the sensed magnetic field;
- wherein the improvement comprises automatic compensation means for continuously correcting the sensed and displayed magnetic field for local magnetic field interference which varies with vehicle use;
said compensation means comprising;said circuit means including means for continuously monitoring signal information from said sensing means first determining means responsive to said output signals for determining that the vehicle has traveled through a closed loop, and second determining means for determining the value of an offset signal during a closed loop of travel of the vehicle said circuit means includes means responsive to said offset signal to provide a compensated heading display, and wherein said circuit means includes means for updating the offset signal value with successive loops of travel of the vehicle. - View Dependent Claims (10, 11, 12, 13, 14, 15)
- wherein the improvement comprises automatic compensation means for continuously correcting the sensed and displayed magnetic field for local magnetic field interference which varies with vehicle use;
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16. A digital compass system for a vehicle comprising:
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a magnetic field sensor; a microprocessor and interface circuit means coupling said microprocessor to said sensor for providing display output signals representative of the magnetic direction of orientation of said sensor; display means coupled to said microprocessor for displaying said magnetic direction; and wherein said microprocessor is programmed to provide means for compensating said output signals for local magnetic field interference which otherwise causes said sensor to provide output signals which deviate from the actual magnetic orientation of said sensor with respect to the earth'"'"'s magnetic field such that the actual magnetic orientation of said sensor will be displayed, said compensating means including means for continuously monitoring signal information from said sensor circuit as the vehicle travels during use, for determining that the vehicle has traveled through a closed loop and, after each completed loop of travel of the vehicle, for determining an updated correction to the sensed field, said compensating means further including means responsive to said updated correction for modifying the signal applied to said display means to correct for the local field interference.
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17. An electrical 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 for processing said signals and for providing display output signals during a period of time in which the vehicle travels through a closed loop circumscribing 365°
of movement in one direction;display means coupled to said circuit means and responsive to said display output signals for displaying the vehicle heading; means for determining that the vehicle has moved through a closed loop, means for determining, during the course of movement of the vehicle through the closed loop, the maximum and minimum detected signal level from said sensing means corresponding to the effect of the earth'"'"'s magnetic field and the magnetic properties of the vehicle on said sensing means;
said circuit means including means for calculating from the signal information during each completed loop of travel of the vehicle, an offset signal representing the static flux field due to the vehicle magnetism and for correcting the display output signals to display the vehicle heading; andsaid circuit means further including means for detecting the rate of change of said direction representative signals to determine if the rate of change exceeds a predetermined level thereby indicating the existence of invalid detected direction information and for providing an error output signal for display in the event the rate of change exceeds said predetermined level. - View Dependent Claims (18, 19, 20)
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Specification