Electronic compass
First Claim
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1. An electronic compass providing a directional bearing, comprising:
- a base for mounting thereto in a mutually orthogonal relationship, a first, second and third magnetic field sensor, said first and second magnetic field sensors arranged for measuring respectively orthogonal magnetic field components in a plane associated with the electronic compass;
said third magnetic field sensor arranged for measuring a magnetic component of the magnetic field orthogonal to the plane determined by the first and second sensors;
a roll sensor for sensing angular roll orientations of said electronic compass about an axis aligned in a direction of intended travel and for providing output roll angle data; and
a programmed processor for calculating a vertical magnetic field component in conjunction with the measured magnetic field components of the first and second magnetic field sensors and programmed for reprojecting the measured first and second magnetic field components onto a reference plane using said roll angle data to thereby remove effects of roll orientations of the electronic compass on the measured magnetic field components.
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Abstract
An electronic compass (10) for use in a boring tool (12) which will provide an orientation of the boring tool relative to the earth'"'"'s magnetic field. In addition, a more straightforward left or right deviation from an initial bearing can be determined. The invention can correct for pitch angle and roll angle variation as well. The magnetic field is sensed by an axial magnetic field (12), a radial magnetic field sensor (18) and a plane-normal magnetic sensor (24) which are preferably magnetoresistive sensors.
247 Citations
74 Claims
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1. An electronic compass providing a directional bearing, comprising:
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a base for mounting thereto in a mutually orthogonal relationship, a first, second and third magnetic field sensor, said first and second magnetic field sensors arranged for measuring respectively orthogonal magnetic field components in a plane associated with the electronic compass; said third magnetic field sensor arranged for measuring a magnetic component of the magnetic field orthogonal to the plane determined by the first and second sensors; a roll sensor for sensing angular roll orientations of said electronic compass about an axis aligned in a direction of intended travel and for providing output roll angle data; and a programmed processor for calculating a vertical magnetic field component in conjunction with the measured magnetic field components of the first and second magnetic field sensors and programmed for reprojecting the measured first and second magnetic field components onto a reference plane using said roll angle data to thereby remove effects of roll orientations of the electronic compass on the measured magnetic field components. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 67, 68, 69, 70)
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23. A method of calculating a directional bearing of a movable object using an electronic compass, comprising the steps of:
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mounting the electronic compass to the object; fixing an axial component magnetic field sensor and radial component magnetic field sensor orthogonally with respect to each other so as to prevent relative movement of said sensors; mounting a pitch angle sensor and a roll angle sensor orthogonally with respect to each other; mounting a processor and memory for receiving magnetic field measurement data, angular roll data and angular pitch data from the respective sensors; and programming the processor to process the magnetic field measurement data and the angular roll and pitch data to provide an output defining compass rose indications of directional bearing. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31)
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32. An electronic compass, comprising:
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a radial, axial and plane-normal magnetic field component sensor, each mounted orthogonal to each other to measure respective X, Y and Z magnetic field components of the earth'"'"'s magnetic field; a roll angle sensor fixed in a predefined orientation with respect to said magnetic field component sensors, for measuring roll angle displacements of the electronic compass with respect to a reference plane; a pitch angle sensor for measuring pitch angles of the electronic compass with respect to the reference plane; an AID converter for converting analog measurements of the sensors to respective digital data; and a programmed processor for receiving the digital data and for processing the measured magnetic field components to correct for angular pitch and roll displacements of said electronic compass from the reference plane, and for providing output indications of directional bearing from 0-360 degrees of a compass rose. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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43. An electronic compass, comprising:
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a circuit board for mounting thereto electronic components; an axial, radial and plane-normal magnetoresistive sensor mounted to said circuit board, each said sensor mounted with a magnetic sensitive axis thereof orthogonal to each other according to a three-axis coordinate system, said sensors each providing respective output axial, radial and plane-normal analog signals representative of a magnetic field component associated with a respective axis of the coordinate system; a roll sensor mounted to said circuit board and responsive to roll orientations of angular movement of the electronic compass about an axis of the circuit board, said roll sensor providing output indications of the extent of roll of said electronic compass; an analog-to-digital (A/D) converter for converting output analog signals of said magnetoresistive sensors and said roll sensor, and providing corresponding output digital signals; and a processor for receiving the digital signals from the A/D converter and programmed to calculate an axial, radial and plane-normal magnetic field component of an external magnetic field with respect to the coordinate system, and programmed to reproject the axial, radial and plane-normal components of the coordinate system into another three-axis coordinate system using output indications of said roll sensor, and programmed to determine a directional bearing of the electronic compass with respect to said external magnetic field. - View Dependent Claims (44, 45, 46, 47, 48)
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49. A method of constructing an electronic compass for underground boring, comprising the steps of:
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mounting a magnetoresistive magnetic field measuring arrangement including an axial, a radial and a plane-normal magnetic field sensor so that a respective sensitive axis thereof is orthogonal to each other and corresponds to a three-axis coordinate system associated with the electronic compass; mounting a roll measuring sensor to said magnetic field measuring arrangement; fixing the magnetic field measuring arrangement to an underground boring tool so that the magnetic field measuring arrangement undergoes the same linear and angular movements as does said boring tool;
coupling an analog-to-digital (A/D) converter to said magnetoresistive sensor arrangement and to said roll sensor to convert analog signals to corresponding digital signals, andprogramming a processor to process the digital signals to determine a first directional bearing as a function of the radial and axial magnetoresistive sensors, and processing the digital signals of the plane-normal magnetoresistive sensor and the roll measuring sensor to provide a second directional bearing corrected for effects of a roll angle of the boring tool that is different from a reference roll angle. - View Dependent Claims (50, 51, 52, 53, 54, 55, 56, 57)
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58. A method of measuring deviation of an object from an intended path using an electronic compass, comprising the steps of:
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storing in a memory of the electronic compass a parameter of an intended path indicating a desired directional bearing; measuring at periodic times during movement of the object a deviation of the object from the intended path; processing the measured deviation at the periodic times and summing the measured deviations; and comparing the summed deviations with the stored parameter and providing output signals for indicating deviation of the object from said intended path. - View Dependent Claims (59, 60, 61, 62, 63, 64, 65, 66)
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72. A method of providing a directional bearing using an electronic compass, comprising the steps of:
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mounting axial, radial and plane-normal magnetic field sensors so as to be immovable with respect to each other and undergo the same movements as said electronic compass; providing a pitch and roll sensor with said electronic compass to sense pitch and roll movements of said electronic compass from respective zero-pitch and zero-roll references; programming a processor with an algorithm to process axial, radial and plane-normal magnetic field data as measured by said axial, radial and plane-normal magnetic field sensors; programming said processor to reproject measured axial and radial magnetic field components onto a reference plane when said electronic compass experiences an orientation departing from said zero-pitch and zero-roll references; and processing reprojected axial magnetic field and reprojected radial magnetic field component data according to a programmed algorithm to provide a directional bearing corrected for any departure of movements of said electronic compass from said zero-pitch or zero-roll references. - View Dependent Claims (71, 73, 74)
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Specification