Position encoder utilizing fluxgate sensors
First Claim
1. A position encoder for providing a substantially linear output signal representative of a position of a movable magnetic element, relative to a reference position, comprising:
- said magnetic element having opposing magnetic poles disposed along a polar axis and producing a magnetic field;
a first spatially orthogonal fluxgate sensor pair for detecting said magnetic field, said first sensor pair including a first tangential field sensor and a first radial field sensor, and being disposed adjacent to said polar axis at a first predetermined distance and fixed with respect to said reference position, and a second spatially orthogonal fluxgate sensor pair for detecting said magnetic field, said second pair including a second tangential field sensor and a second radial field sensor, and being disposed adjacent to said polar axis at a second predetermined distance and fixed with respect to said reference position, wherein said first tangential field sensor and said second tangential field sensor are electrically connected in series opposition so as to produce a composite tangential signal, and said first radial field sensor and said second radial field sensor are electrically connected in series opposition so as to produce a composite radial signal; and
, a signal processor for receiving said composite tangential signal and said composite radial signal, and for producing said output signal as a function of said said composite tangential signal and said composite radial signal.
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Accused Products
Abstract
An improved position encoder system for providing an output signal representative of the position of a movable body, relative to a reference position, includes at least one magnetic element fixedly attached to the movable body. The system further includes a first spatially orthogonal fluxgate sensor pair and a second spatially orthogonal fluxgate sensor pair for detecting the magnetic field. The first sensor pair is disposed adjacent to the polar axis at a first predetermined distance, and the second pair is disposed adjacent to the polar axis at a second predetermined distance, preferably twice the first predetermined distance. The system further includes a signal processor for receiving a signal from the first sensor pair and a signal from the second sensor pair. The signal processor produces an output signal that corresponds to a predetermined combination of the signal from the first sensor pair and the signal from the second pair, such that a resulting relationship between the output signal and the position of the movable body is substantially linear. Motion of the movable body may be rotational or linear, such that the encoded position is angular or linear. Proper placement of the sensors along the magnetic element of a linear position encoder enables a range of motion significantly beyond the total length of the magnetic element. Eccentric placement of the magnetic element on a rotatably movable body provides a substantially linear position-to-output signal relationship with relatively little processing of the resulting sensor signals.
53 Citations
31 Claims
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1. A position encoder for providing a substantially linear output signal representative of a position of a movable magnetic element, relative to a reference position, comprising:
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said magnetic element having opposing magnetic poles disposed along a polar axis and producing a magnetic field;
a first spatially orthogonal fluxgate sensor pair for detecting said magnetic field, said first sensor pair including a first tangential field sensor and a first radial field sensor, and being disposed adjacent to said polar axis at a first predetermined distance and fixed with respect to said reference position, and a second spatially orthogonal fluxgate sensor pair for detecting said magnetic field, said second pair including a second tangential field sensor and a second radial field sensor, and being disposed adjacent to said polar axis at a second predetermined distance and fixed with respect to said reference position, wherein said first tangential field sensor and said second tangential field sensor are electrically connected in series opposition so as to produce a composite tangential signal, and said first radial field sensor and said second radial field sensor are electrically connected in series opposition so as to produce a composite radial signal; and
,a signal processor for receiving said composite tangential signal and said composite radial signal, and for producing said output signal as a function of said said composite tangential signal and said composite radial signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A position encoder for providing a substantially linear output signal representative of a position of a movable body, relative to a reference position, comprising:
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a plurality of magnetic elements, each having opposing magnetic poles disposed along a polar axis so as to define a polar orientation, and each of said magnetic elements producing a magnetic field, said elements being uniformly distributed about, and fixedly attached to, said movable body, such that adjacent magnetic elements alternate said polar orientation;
a pair of fluxgate sensors substantially aligned with adjacent poles of respectively two adjacent ones of said magnetic elements, and fixed with respect to said reference position; and
,a signal processor for receiving at least a first signal and a second signal from said pair of fluxgate sensors, said first signal representing said magnetic field from a first magnetic element of said two adjacent ones of said magnetic elements, said second signal representing said magnetic field from a second magnetic element of said two adjacent ones of said magnetic elements, and for producing said output signal corresponding to a predetermined combination of said first signal and said second signal. - View Dependent Claims (17, 18, 19, 20)
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21. A position encoder for providing an output signal representative of a position of a movable body along an axis of motion, relative to a reference point, comprising:
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an elongated magnetic element having a length L and having opposing magnetic poles disposed along a polar axis and producing a magnetic field, said magnetic element being fixedly attached to said movable body;
a first fluxgate sensor and a second fluxgate sensor disposed along a first sensor axis extending through and substantially normal to said polar axis, said first sensor being disposed at a first predetermined distance R1 from said polar axis and said second sensor being disposed at a second predetermined distance R2 from said polar axis;
a third fluxgate sensor and a fourth fluxgate sensor disposed along a second sensor axis extending through and substantially normal to said polar axis and parallel to said first sensor axis, said third sensor being disposed at a third predetermined distance R3 from said polar axis and said fourth sensor being disposed at a fourth predetermined distance R4 from said polar axis, said first sensor axis being a predetermined distance D from said second sensor axis measured along said polar axis, wherein said distance D is substantially equal to L/3; and
a signal processor for receiving a plurality of signals from said first, second, third and fourth fluxgate sensors, and for producing said output signal corresponding to a predetermined combination of said plurality of signals, such that said output signal is representative of said position of said movable body and said range of motion of said movable body is substantially greater than said length L. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29)
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30. A position encoder for providing an output signal representative of an angular position of a rotatably movable body having an axis of rotation, relative to a reference point, comprising:
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at least one magnetic element having opposing magnetic poles disposed along a polar axis and producing a magnetic field, said at least one magnetic element being fixedly attached to said movable body, offset from said axis of rotation, such that said magnetic element rotates eccentrically with respect to said movable body;
a radial fluxgate sensor for detecting a radial component of said magnetic field, said radial sensor being disposed adjacent to said polar axis at a first predetermined distance, and a tangential fluxgate sensor for detecting a tangential component of said magnetic field, said tangential sensor being disposed adjacent to said polar axis at a second predetermined distance; and
,a signal processor for receiving at least one signal from said radial sensor and at least one signal from said tangential sensor, and for producing said output signal corresponding to a predetermined combination of said at least one signal from said radial sensor and said at least one signal from said tangential sensor, such that a resulting relationship between said output signal and said position of said movable body is substantially linear for a range of said angular position. - View Dependent Claims (31)
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Specification