Angular position sensor for a downhole tool
First Claim
1. A downhole tool comprising:
- first and second members disposed to rotate about a common axis with respect to one another;
first and second circumferentially spaced magnets deployed on the first member the first and second magnets being configured to emit a magnetic field having a radial component that varies in strength substantially linearly with an angular position about the second member for a range of at least 30 degrees in angular position;
a plurality of circumferentially spaced magnetic field sensors deployed on the second member, at least one of the magnetic field sensors in sensory range of magnetic flux emanating from at least one of the magnets; and
a controller disposed to calculate an angular position of the first member with respect to the second member from magnetic flux measurements at the magnetic field sensors.
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Accused Products
Abstract
Aspects of this invention include a downhole tool having an angular position sensor disposed to measure the relative angular position between first and second members disposed to rotate about a common axis. A plurality of magnetic field sensors are deployed about the second member and disposed to measure magnetic flux emanating from first and second magnets deployed on the first member. A controller is programmed to determine the relative angular position based on magnetic measurements made by the magnetic field sensors. In a one exemplary embodiment, a downhole steering tool includes first and second magnets circumferentially spaced on the shaft and a plurality of magnetic field sensors deployed about the housing.
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Citations
29 Claims
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1. A downhole tool comprising:
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first and second members disposed to rotate about a common axis with respect to one another; first and second circumferentially spaced magnets deployed on the first member the first and second magnets being configured to emit a magnetic field having a radial component that varies in strength substantially linearly with an angular position about the second member for a range of at least 30 degrees in angular position; a plurality of circumferentially spaced magnetic field sensors deployed on the second member, at least one of the magnetic field sensors in sensory range of magnetic flux emanating from at least one of the magnets; and a controller disposed to calculate an angular position of the first member with respect to the second member from magnetic flux measurements at the magnetic field sensors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A downhole tool comprising:
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a shaft deployed to rotate substantially freely in a housing; first and second arc-shaped magnets circumferentially spaced on the shaft, the first and second magnets being tapered, having a thin end and a thick end, such that a radial thickness of the magnets increases from the thin end to the thick end, the first magnet having a magnetic north pole on an outer surface and a magnetic south pole an inner surface thereof, the second magnet having a magnetic south pole on an outer surface and a magnetic north pole on an inner surface thereof; a plurality of circumferentially spaced magnetic field sensors deployed in the housing, at least one of the magnetic field sensors in sensory range of magnetic flux emanating from at least one of the magnets; and a controller deployed in the housing and disposed to determine a relative angular position between the housing and the shaft from magnetic flux measurements made by the magnetic field sensors. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method for determining a relative angular position between first and second members of a downhole tool, the method comprising:
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(a) deploying a downhole tool in a borehole, the downhole tool including first and second members disposed to rotate about a common axis with respect to one another, first and second circumferentially spaced magnets deployed on the first member, a plurality of circumferentially spaced magnetic field sensors deployed on the second member wherein the first and second magnets are configured to emit a magnetic field having a radial component that varies in strength substantially linearly with an angular position about the second member for a range of at least 30 degrees in angular position; (b) causing each of the magnetic field sensors to measure a magnetic flux; and (c) processing the magnetic flux measurements to calculate the relative angular position between the first and second members. - View Dependent Claims (24, 25, 26, 27)
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28. A downhole tool comprising:
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first and second members disposed to rotate about a common axis with respect to one another; first and second arc-shaped magnets circumferentially spaced on the shaft, the first magnet having a magnetic north pole on an outer surface and a magnetic south pole an inner surface thereof, the second magnet having a magnetic south pole on an outer surface and a magnetic north pole on an inner surface thereof; first and second tapered, arc-shaped magnetic lenses deployed radially between the first and second magnets and selected ones of the magnetic field sensors, the magnetic lenses being fabricated from a magnetic material; a plurality of circumferentially spaced magnetic field sensors deployed on the second member, at least one of the magnetic field sensors in sensory range of magnetic flux emanating from at least one of the magnets; and a controller disposed to calculate an angular position of the first member with respect to the second member from magnetic flux measurements at the magnetic field sensors.
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29. A downhole tool comprising:
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first and second members disposed to rotate about a common axis with respect to one another; first and second circumferentially spaced sets of discrete magnets deployed on the first member, each set including a plurality of discrete magnets circumferentially spaced about a unique circumferential portion of the first member, a magnetic strength of the discrete magnets increasing from one end of each set to an opposing end; a plurality of circumferentially spaced magnetic field sensors deployed on the second member, at least one of the magnetic field sensors in sensory range of magnetic flux emanating from at least one of the magnets; and a controller disposed to calculate an angular position of the first member with respect to the second member from magnetic flux measurements at the magnetic field sensors.
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Specification