Azimuth sensor which corrects azimuth circle diameter and center for temperature variation

• US 4,739,560 A
• Filed: 10/09/1986
• Issued: 04/26/1988
• Est. Priority Date: 10/09/1985
• Status: Expired due to Fees

• Current Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Inventors: Ichikawa, Hitoshi, Akutsu, Kazushi
• Primary Examiner(s): Martin, Jr., William D.
• Application Number:
  US06/917,594
• Time in Patent Office: 565 Days
• Field of Search: 33/349, 33/361, 33/362, 374/142, 324/224
• US Class Current: 33/361
• CPC Class Codes: G01C 17/30 Earth-inductor compasses
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

An azimuth calculation apparatus includes an azimuth sensor mounted on a moving body for detecting a direction of the moving body, the azimuth sensor having an excitation winding wound on an annular magnetic core and a pair of output windings wound on the core perpendicularly relative to one another to produce first and second output signals therefrom in response to energization of the excitation winding. The calculation apparatus is arranged to detect a temperature of the azimuth sensor and to determine a pair of correction values based on the detected temperature of the azimuth sensor so as to correct each value of the first and second output signals from the output windings to an optimal value for calculating the direction of the moving body in dependence upon the corrected output signals from the output windings.

Claims

1. An azimuth calculation apparatus responsive to first and second output signals from an azimuth sensor, adapted to be mounted on a moving body, for detecting a direction of said moving body relative to the earth'"'"'s magnetism, said azimuth sensor being of a type having an annular magnetic core, an exitation winding wound on said core, and a pair of output windings wound on said core perpendicularly to one another and connected to a common voltage source and which produce first and second output signals in response to energization of said excitation winding, the azimuth calculation apparatus comprising:

a temperature sensor for detecting a temperature of said azimuth sensor, and producing a temperature signal indicative thereof;

means, responsive to said temperature signal, for determining a diameter of an azimuth circle and correcting said diameter of said azimuth circle in accordance with a change of said temperature signal based on a relation indication of a thermal characteristic of said azimuth sensor;

means, responsive to the first and second output signals from said azimuth sensor and to a voltage signal from said voltage source, for correcting values of said first and second output signals such that an azimuth circle diameter for said corrected signals will coincide with an optimal diameter for said azimuth sensor, the center of which is defined by voltage signal; and

means for calculating the direction of said moving body based on said corrected values of said output signals.

2. An azimuth calculation apparatus as claimed in claim 1, wherein said means responsive to the first and second output signals from said azimuth sensor and said voltge signal includes means for calculating first and second correction values Xa and Ya of said output signals respectively based on the following equations:

space="preserve" listing-type="equation">Xa=(X-COM)K/R(t)+COM

space="preserve" listing-type="equation">Ya=(Y-COM)K/R(t)+COM

wherein X is a value of said first output signal from said azimuth sensor, COM is a value of said voltage signal from said voltage source, K is said optimal diameter, R(t) is the calculated diameter of the azimuth circle, and Y is a value of said second output signal from said azimuth sensor.

3. An azimuth calculation apparatus as claimed in claim 1, wherein said temperature sensor is a thermistor with a negative temperature coefficient, mounted on said azimuth sensor.

4. An azimuth calculation apparatus responsive to first and second output signals from an azimuth sensor that is adapted to be mounted on a moving body for detecting a direction of said moving body relative to earth'"'"'s magnetism, said azimuth sensor being of a type having an annular magnetic core, an excitation winding wound on said core, and a pair of output windings wound on said core perpendicularly to one another and connected to a common voltage source, to produce said first and second output signals therefrom in response to energization of said excitation winding, the azimuth calculation apparatus comprising:

first and second temperature sensors located adjacent said azimuth sensor and connected respectively in series with said output windings of said azimuth sensor, said temperature sensors each having a negative temperature coefficient;

first and second resistors, each connected in parallel with one of said temperature sensors, to adjust respective internal resistance values of said temperature sensors in accordance with a change of the abient temperature of said azimuth sensor; and

means for calculating the direction of said moving body based on each value of said output signals from said azimuth sensor.

5. A calculation apparatus as in claim 4 wherein said means for calculating a diameter of an azimuth circle includes means for calculating an actual temperature of said azimuth sensor based on a restored relationship between said temperature signal and an actual temperature.

6. An azimuth calculation apparatus, comprising:

an azimuth sensor, adapted to be mounted on a moving body whose azimuth is to be calculated, of a type having an annular magnetic core, an excitation winding wound on said core, and first and second output windings wound on said core in a perpendicular fashion to one another, said excitation winding coupled to receive a voltage signal, and said first and second output windings producing first and second output signals in response to said excitation winding receiving said voltage signal, and in response to movement of said azimuth sensor;

means for detecting a temperature indicative of a temperature of said azimuth sensor, and producing a temperature signal indicative thereof;

memory means for storing a plurality of prestored information, said prestored information including a relationship between a change in diameter of an azimuth circle and a temperature of said azimuth sensor, and an optimal diameter of said azimuth sensor; and

processing means, coupled to said first and second outputs of said azimuth sensor, said temperature signal of said temperature sensing means, and to an output of said memory means, for;

(1) calculating a diameter of an azimuth circle of said azimuth sensor in relation to said temperature based on said stored relation,

(2) calculating correction values based on a value of said voltage signal, said optimal diameter, and said first and second output signals,

(3) correcting said first and second output signals in a way such that they are indicative of output signals coinciding with an azimuth sensor having said optimal diameter a center of which being defined by said voltage signal; and

(4) calculating a direction of movement of said moving body based on said corrected values.

7. An apparatus as in claim 6 wherein said processing means includes

analog to digital converting means, receiving said voltage signal, said first and second output signals and said temperature signals, for converting said signals into digital signals, and

sample and hold means connected between said output of said azimuth sensor and said analog to digital converter, for sampling and holding said first and second output signals.

8. Apparatus as in claim 6 wherein said read only memory means also includes means for storing a correction relation between said temperature signal and an actual temperature of said azimuth sensor.

9. Apparatus as in claim 6 wherein said processing means calculating correction value function includes means for calculating output signals based on the following equations:

space="preserve" listing-type="equation">Xa=(X-COM)K/R(t)+COM

space="preserve" listing-type="equation">Ya=(Y-COM)K/R(t)+COM

where X is a value of said first output signal from said azimuth sensor, COM is a value of said voltage signal from said voltage source, K is said optimal diameter, R(t) is the calculated diameter of the azimuth circle, and Y is a value of said second output signal from said azimuth sensor.

10. A method of calculating azimuth which is responsive to first and second output signals from an azimuth sensor that is adapted to be mounted on a moving body for detecting a direction of said moving body relative to earth'"'"'s magnetism, the azimuth sensor being of a type having an annular magnetic core, an excitation winding wound on said core, a pair of output windings wound on said core perpendicularly to one another and connected to a common voltage source, and which produce first and second output signals in response to energization of said excitation winding, comprising the steps of:

detecting a temperature of said azimuth sensor and producing a temperature signal indicative thereof;

determining a characteristic curve based on a relation between a thermal characteristic of said azimuth sensor and a change in azimuth circle diameter;

calculating a diameter of an azimuth circle based on said temperature signal and said charascteristic curve, thereby obtaining a corrected said diameter of said azimuth circle in accordance with a change of said temperature signal;

receiving said first and second output signals form said azimuth sensor and said voltge signal from the voltage source, and correcting values of the first and second output signals such that an azimuth circle diameter of said corrected values coincides with an optimal diameter for said azimuth sensor, the center of said optimal diameter being defined by said voltage signal; and

calculating a direction of movement of said moving body based on said corrected values.