Method and apparatus for calibrating a vehicle compass system
First Claim
1. A vehicle compass system comprising magnetic sensing means including a magnetic sensing device having first and second sensing coils positioned within the vehicle and adapted for producing first and second output signals that vary in accordance with changes in the directional heading of the vehicle, a control circuit including a microcomputer for producing first and second compensation signals that are supplied to said first and second sensing coils, respectively, to compensate for the remnant magnetic fields associated with the vehicle and for processing said first and second output signals from said magnetic sensing means and determining therefrom the heading direction of the vehicle and producing display output signals that are supplied to a display means adapted to display the heading direction of the vehicle;
- the improvement comprising;
memory means for storing predetermined values corresponding to the desired values for said first and second output signals when the vehicle is positioned in a single predetermined location and orientation;
initiation means for initiating an initial calibration process when the vehicle is in said predetermined location and orientation; and
wherein said microcomputer is programmed to be responsive to said initiation means for initially calibrating the compass system by reading said desired values from said memory means and generating appropriate compensation signals for both said first and second sensing coils to cause the actual output signals from said magnetic sensing means to bear a determined relationship to said desired values, and storing the values of said appropriate compensation signals.
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Accused Products
Abstract
A vehicle compass system that is adapted to be calibrated in the assembly plant during final assembly of the vehicle. In particular, two factory calibration modes are disclosed: an automatic factory calibration mode wherein the calibration sequence is automatically initiated upon the occurrence of a uniquely definable event on the assembly line, and a manual factor calibration mode wherein a calibration button sequence is actuated at a specified location on the assembly line. In addition, an automatic adaptive calibration process is disclosed which continuously updates the calibration constants each time valid new heading data is obtained. In particular, heading vectors for the four main N, S, E, and W heading directions are calculated and stored in memory when the system is initially calibrated. Thereafter, whenever new heading direction data is obtained, the value of the new heading vector is used to update the value of the closest of the four main heading vectors. A new center calculation is also performed using the updated values and if the result is outside a tolerance window, the calibration constants are changed accordingly.
65 Citations
38 Claims
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1. A vehicle compass system comprising magnetic sensing means including a magnetic sensing device having first and second sensing coils positioned within the vehicle and adapted for producing first and second output signals that vary in accordance with changes in the directional heading of the vehicle, a control circuit including a microcomputer for producing first and second compensation signals that are supplied to said first and second sensing coils, respectively, to compensate for the remnant magnetic fields associated with the vehicle and for processing said first and second output signals from said magnetic sensing means and determining therefrom the heading direction of the vehicle and producing display output signals that are supplied to a display means adapted to display the heading direction of the vehicle;
- the improvement comprising;
memory means for storing predetermined values corresponding to the desired values for said first and second output signals when the vehicle is positioned in a single predetermined location and orientation;
initiation means for initiating an initial calibration process when the vehicle is in said predetermined location and orientation; and
wherein said microcomputer is programmed to be responsive to said initiation means for initially calibrating the compass system by reading said desired values from said memory means and generating appropriate compensation signals for both said first and second sensing coils to cause the actual output signals from said magnetic sensing means to bear a determined relationship to said desired values, and storing the values of said appropriate compensation signals. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- the improvement comprising;
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8. A vehicle compass system comprising a magnetic sensing device having first and second sensing coils positioned within the vehicle and adapted for producing output signals that vary in accordance with changes in the directional heading of the vehicle, a control circuit including signal processing means having associated therewith a gain factor for processing the output signals from the sensing coils and producing corresponding actual sensor signals, a microcomputer for producing compensation signals that are supplied to said sensing coils to compensate for the remnant magnetic fields associated with the vehicle, for determining from said actual sensor signals the directional heading of the vehicle, and for producing display output signals that are supplied to a display means adapted to display the directional heading of the vehicle;
- the improvement comprising;
memory means for storing a predetermined value corresponding to the desired value for at least one of said actual sensor signals when the vehicle is oriented in a predetermined position;
initiation means for initiating an initial calibration process when the vehicle is oriented in said predetermined position; and
wherein said microcomputer is programmed to be responsive to said initiation means for initially calibrating the compass system by reading said desired sensor signal value, determining the actual gain factor of said signal processing means, adjusting the value of said desired sensor signal value in accordance with the difference between said actual gain factor and a predetermined gain factor, generating an appropriate compensation signal to cause said one actual sensor signal to correspond to said adjusted desired sensor signal, and storing in said memory means said determined actual gain factor. - View Dependent Claims (9)
- the improvement comprising;
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10. A method of initially calibrating a vehicle compass system comprising a magnetic sensing device having first and second sensing coils positioned within the vehicle and adapted for producing output signals that vary in accordance with changes in the directional heading of the vehicle, a control circuit including signal processing means for processing the output signals from the sensing coils and producing corresponding actual sensor signals, memory means, and a microcomputer for producing first and second compensation signals that are supplied to said first and second sensing coils respectively to compensate for the remnant magnetic fields associated with the vehicle and for determining from said actual sensor signals the heading direction of the vehicle and producing display output signals that are supplied to a display means adapted to display the heading direction of the vehicle;
- the method comprising the steps of;
selecting a relatively magnetically stable location along the final portion of the assembly line where the vehicle is assembled; storing in said memory means predetermined values corresponding to the desired values for said actual sensor signals when the vehicle is located at said selected location; and initiating an initial calibration process when the vehicle reaches said selected location, said initial calibration process comprising the further steps of obtaining the actual sensor signals for both of said first and second sensing coils, comparing said actual sensor signals to said desired values, and adjusting the values of both of said compensation signals until said actual sensor signals bear a determinable relationship to said desired values. - View Dependent Claims (11, 12, 13, 14)
- the method comprising the steps of;
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15. A method of dynamically calibrating a vehicle compass system during normal operation of the vehicle in which the compass system is installed wherein the compass system comprises a magnetic sensing device having first and second sensing coils positioned within the vehicle and adapted for producing output signals that vary in accordance with changes in the directional heading of the vehicle, a control circuit including memory means and a microcomputer for producing first and second compensation signals that are supplied to said first and second sensing coils respectively to compensate for the remnant magnetic fields associated with the vehicle and for processing the output signals from the sensing coils and determining therefrom the heading direction of the vehicle and producing display output signals that are supplied to a display means adapted to display the heading direction of the vehicle;
- the method comprising the steps of;
establishing desired heading data corresponding to each of the N, S, E, W main heading directions; obtaining new output signals from said sensing coils sufficient to determine the current heading direction of the vehicle; processing said new output signals and determining therefrom new heading data representative of the current heading direction of the vehicle; producing new display output signals in accordance with said new heading data and displaying the current heading direction on said display means; and determining from said new heading data whether to change the value of either of said first and second compensation signals by comparing said new heading data with said desired main heading data for the main heading direction closest to said current heading direction and updating the closest of said desired main heading data based upon said comparison. - View Dependent Claims (16, 17, 18, 19, 20, 21)
- the method comprising the steps of;
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22. A vehicle compass system comprising magnetic sensing means including a magnetic sensing device having first and second sensing coils positioned within the vehicle and adapted for producing first and second output signals that vary in accordance with changes in the directional heading of the vehicle, a control circuit including a microcomputer for processing said first and second output signals from said magnetic sensing means and determining therefrom the heading direction of the vehicle and producing display output signals that are supplied to a display means adapted to display the heading direction of the vehicle;
- the improvement comprising;
memory means for storing predetermined values corresponding to the desired values for said first and second output signals when the vehicle is positioned in a single predetermined location and orientation;
initiation means for initiating an initial calibration process when the vehicle is in said predetermined location and orientation; and
wherein said microcomputer is programmed to be responsive to said initiation means for initially calibrating the compass system by reading said desired values from said memory means, determining the differences between said desired values and said first and second output signals from said magnetic sensing means when the vehicle is positioned in said predetermined location and orientation, and using said differences to correct said display output signals. - View Dependent Claims (23, 24, 25, 26, 27, 28)
- the improvement comprising;
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29. A method of initially calibrating a vehicle compass system comprising a magnetic sensing device having first and second sensing coils positioned within the vehicle and adapted for producing output signals that vary in accordance with changes in the directional heading of the vehicle, a control circuit including signal processing means for processing the output signals from the sensing coils and producing corresponding actual sensor signals, memory means, and a microcomputer for determining from said actual sensor signals the heading direction of the vehicle and producing display output signals that are supplied to a display means adapted to display the heading direction of the vehicle;
- the method comprising the steps of;
selecting a relatively magnetically stable location along the final portion of the assembly line where the vehicle is assembled; storing in said memory means predetermined values corresponding to the desired values for said actual sensor signals when the vehicle is located at said selected location; and initiating an initial calibration process when the vehicle reaches said selected location, said initial calibration process comprising the further steps of obtaining the actual sensor signals for both of said first and second sensing coils, comparing said actual sensor signals to said desired values, and correcting said display output signals in accordance with the differences between said actual sensor signals and said desired values. - View Dependent Claims (30, 31, 32)
- the method comprising the steps of;
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33. A method of dynamically calibrating a vehicle compass system during normal operation of the vehicle in which the compass system is installed wherein the compass system comprises a magnetic sensing device having first and second sensing coils positioned within the vehicle and adapted for producing output signals that vary in accordance with changes in the directional heading of the vehicle, a control circuit including memory means and a microcomputer for determining the appropriate compensation factors to compensate for the remnant magnetic fields associated with the vehicle, processing the output signals from the sensing coils, and determining therefrom the heading direction of the vehicle and producing display output signals that are supplied to a display means adapted to display the heading direction of the vehicle;
- the method comprising the steps of;
establishing desired heading data corresponding to each of the N, S, E, W main heading directions; obtaining new output signals from said sensing coils sufficient to determine the current heading direction of the vehicle; processing said new output signals and determining therefrom new heading data representative of the current heading direction of the vehicle; producing new display output signals in accordance with said new heading data and displaying the current heading direction on said display means; and determining from said new heading data whether to change the value of said compensation factors by comparing said new heading data with said desired main heading data for the main heading direction closest to said current heading direction and updating the closest of said desired main heading data based upon said comparison. - View Dependent Claims (34, 35, 36, 37, 38)
- the method comprising the steps of;
Specification