Vehicle compass with electronic sensor
First Claim
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1. An electronic compass for use in a vehicle comprising:
- a magnetoresistive sensor for detecting an external magnetic field and developing electronic signals representative of said external magnetic field, said external magnetic field being a combination of the earth magnetic field and a deviating field of the vehicle,a digital electronic circuit for determining the strength and direction of the vehicle deviating magnetic field,said sensor including means for nullifying said deviating magnetic field in said sensor,said nullifying means being coupled with said electronic circuit and energized thereby in accordance with the strength and direction of said deviating magnetic field whereby said sensor develops a deviation compensated signal corresponding to the earth field.
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Abstract
An electronic compass is described for use in vehicles. The compass employs a magnetoresistive sensor for sensing the earth magnetic field and the sensor is operated in alternate set/reset bias modes. The compass is provided with deviation compensation by a closed loop system including measurement of the sensor output signals and an offset current strap for nullifying the vehicle deviation field.
448 Citations
25 Claims
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1. An electronic compass for use in a vehicle comprising:
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a magnetoresistive sensor for detecting an external magnetic field and developing electronic signals representative of said external magnetic field, said external magnetic field being a combination of the earth magnetic field and a deviating field of the vehicle, a digital electronic circuit for determining the strength and direction of the vehicle deviating magnetic field, said sensor including means for nullifying said deviating magnetic field in said sensor, said nullifying means being coupled with said electronic circuit and energized thereby in accordance with the strength and direction of said deviating magnetic field whereby said sensor develops a deviation compensated signal corresponding to the earth field. - View Dependent Claims (2, 3)
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4. A method for compensating for the effect of a deviating magnetic field in a vehicle compass, said compass comprising:
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a magnetic field sensing means which produces an output signal representative of an external magnetic field impinging on said sensing means, said external magnetic field having a component due to the earth magnetic field and a component due to a deviating magnetic field, said method comprising the steps of; determining whether the actual value of the signal is different from a reference value which is approximately equal to that which would be produced by the earth magnetic field, if it is, generating an increment of compensating magnetic field impinging on said sensor in opposition to the deviating magnetic field, and repeating, alternately, the step of determining whether the actual value is different from the reference value and the step of generating an increment of compensating magnetic field until the actual value is substantially equal to the reference value.
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5. An electronic compass for use in a vehicle, said compass comprising:
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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 external 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 connected in an electrical network, said network 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 oriented with their sensitive axes in a predetermined angular relation with each other, and a digital electronic circuit coupled with said output of said first sensor and said output of said second sensor and responsive to said electronic signals for producing compensated electronic signals representative of the magnetic heading of the vehicle.
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6. An electronic compass for use in a vehicle, said compass comprising:
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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 external magnetic field, said external 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 connected in an electrical network, said network 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 oriented with their sensitive axes in a predetermined angular relation with each other, and a digital electronic circuit coupled with said output of said first sensor and said output of said second sensor and responsive to said electronic signals for modifying said electronic signals in accordance with the value of said deviating magnetic field whereby modified electronic signals are produced which are representative of the magnetic heading of said vehicle.
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7. An electronic compass for use in a vehicle, said compass comprising:
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a magnetoresistive sensor for detecting an external magnetic field and developing electronic signals representative of the strength and direction of said external magnetic field, said external magnetic field being a combination of the earth magnetic field and a deviating magnetic field of the vehicle, a digital electronic circuit coupled with said sensor and responsive to said electronic signals, and electromagnetic means coupled with said sensor and with said electronic circuit for producing modified electronic signals which are compensated for said deviating magnetic field and representative of the magnetic heading of said vehicle.
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8. In a magnetoresistive sensor for determining orientation with respect to an external magnetic field, said sensor being of the type comprising magnetoresistive sensing means having a sensitive axis for producing an output signal representative of an external magnetic field, and means for applying a bias magnetic field to said sensing means, the improvement comprising:
a magnetic field generating means for applying an offset magnetic field to said sensing means in a direction aligned with the sensitive axis of said sensing means. - View Dependent Claims (9)
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10. A compass for a vehicle comprising:
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a first sensor and a second sensor, each of said sensors comprising magnetic field sensing means having a sensitive axis and having an output providing an output signal representative of an external magnetic field and having an offset field generating means for applying an offset magnetic field in a direction aligned with the sensitive axis of said sensing means, said first and second sensors being oriented with their sensitive axes in a predetermined angular relation with each other, and being aligned in a predetermined angular relation with respective axes of said vehicle, and said offset field generating means of said first sensor being coupled with said offset field generating means of said second sensor for energization from a second common source of energization. - View Dependent Claims (11, 12, 13, 14)
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15. A compass for a vehicle comprising:
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a first sensor and a second sensor, said sensors being oriented with their sensitive axes in a predetermined angular relation with each other and being aligned in a predetermined angular relation with respective axes of said vehicle, a multiplexer having a first input coupled with the output of said first sensor and having a second input coupled with the output of said second sensor, a circuit having a dc reference voltage output, an analog-to-digital converter having an input coupled with the output of said multiplexer, and including means for determining the magnitude of the output signal of said first sensor and the output signal of said second sensor relative to said reference voltage, and a digital electronic circuit having an input coupled with the output of said analog-to-digital converter for obtaining direction information of said vehicle. - View Dependent Claims (16, 17, 18)
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19. A compass for a vehicle comprising:
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first and second sensors, each of said sensors comprising magnetoresistive magnetic field sensing means having a sensitive axis and having an output providing an output signal representative of an external magnetic field, an electrical conductor means for applying a bias magnetic field to said sensing means, and an electromagnetic offset field generating means for applying with the sensitive axis of said sensing means, said sensors being oriented with their sensitive axes in a predetermined angular relation with each other and being aligned in a predetermined angular relation with respective axes of said vehicle, a multiplexer having a first input coupled with the output of said first sensor and a second input coupled with the output of said second sensor, an analog-to-digital converter having an input coupled with the output of said multiplexer for measuring the output signals of each of said sensors, said analog-to-digital converter having a full scale measurement substantially equal to the value of said output signals corresponding to the maximum earth field to be sensed by said sensors, and a digital electronic circuit having an input coupled with the output of said analog-to-digital converter for processing said electrical signals produced by said first and second sensors to obtain direction information of said vehicle, said electronic circuit being operative to incrementally change the value of current in said offset field generating means when the output signal of said first sensor differs from said full scale measurement and when the output signal of said second sensor differs from said full scale measurement. - View Dependent Claims (20, 21, 22, 23)
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24. A compass for a vehicle comprising:
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first and second sensors, each of said sensors comprising magnetoresistive magnetic field sensing means having a sensitive axis and having an output providing an output signal representative of an external magnetic field, means for applying an alternate-polarity bias magnetic field to each of said sensing means whereby the output signal of each sensor has an AC and a DC component, said sensors being oriented with their sensitive axes in a known angular relationship with each other and being oriented in a predetermined angular relationship with the axes of said vehicle, and a digital electronic circuit for processing said electrical signals produced by said sensors to obtain direction information of said vehicle, said output of each of said sensors being coupled with said digital electronic circuit by a capacitor whereby the DC component of each of said output signals is suppressed. - View Dependent Claims (25)
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Specification