Position sensor
First Claim
1. A position encoder comprising:
- first and second members which are relatively movable along a measurement path;
an excitation winding and one or more a sensor windings, at least one of the excitation winding and the one or more sensor windings being carried by the first member;
a DC magnetic field generator carried by the second member and operable to generate a DC magnetic field which varies with position along the measurement path;
a film of magnetizable material which is located, in use, within said positionally varying DC magnetic field to cause the film to have a positionally varying magnetization state along the measurement path;
wherein the excitation and sensor windings are arranged relative to said film so that a mutual electromagnetic coupling between them varies in dependence upon the positionally varying magnetization state of said film of magnetizable material, so that when said excitation winding is energized with an excitation signal, a sensor signal is generated in the one or more sensor windings that varies with the relative position between said first and second members;
an excitation circuit operable to generate an excitation signal having an excitation frequency for energizing the excitation winding to cause the excitation winding to generate an excitation electromagnetic field; and
a processing circuit operable to process sensor signals generated in the one or more sensor windings which are at substantially the same frequency as said excitation frequency, to determine a value of a ratiometric function, which value is indicative of the relative position between the first and second relatively movable members,wherein said excitation electromagnetic field comprises a first component which is orthogonal to the surface of the film and a second component which is parallel to the surface of the film and wherein the excitation winding and the excitation circuit are arranged so that the magnitude of said second component is insufficient to drive the film into and out of saturation in the vicinity of said one or more sensor windings.
2 Assignments
0 Petitions
Accused Products
Abstract
A position encoder is provided for indicating the relative position between first and second relatively move members. One of the members carries a magnetic field generator which generates a magnetic field whose magnitude and direction vary with position. In a preferred embodiment, the other member carries an excitation winding, one or more sensor windings and a film of magnetizable material. The arrangement is such that the positionally varying magnetic field interacts with the film to change the mutual coupling between the excitation winding and the or each sensor winding. Excitation and processing circuitry is provided for energising the excitation winding and for processing the sensor signals to determine a value indicative of the relative position between the first and second relatively movable members.
30 Citations
25 Claims
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1. A position encoder comprising:
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first and second members which are relatively movable along a measurement path; an excitation winding and one or more a sensor windings, at least one of the excitation winding and the one or more sensor windings being carried by the first member; a DC magnetic field generator carried by the second member and operable to generate a DC magnetic field which varies with position along the measurement path; a film of magnetizable material which is located, in use, within said positionally varying DC magnetic field to cause the film to have a positionally varying magnetization state along the measurement path; wherein the excitation and sensor windings are arranged relative to said film so that a mutual electromagnetic coupling between them varies in dependence upon the positionally varying magnetization state of said film of magnetizable material, so that when said excitation winding is energized with an excitation signal, a sensor signal is generated in the one or more sensor windings that varies with the relative position between said first and second members; an excitation circuit operable to generate an excitation signal having an excitation frequency for energizing the excitation winding to cause the excitation winding to generate an excitation electromagnetic field; and a processing circuit operable to process sensor signals generated in the one or more sensor windings which are at substantially the same frequency as said excitation frequency, to determine a value of a ratiometric function, which value is indicative of the relative position between the first and second relatively movable members, wherein said excitation electromagnetic field comprises a first component which is orthogonal to the surface of the film and a second component which is parallel to the surface of the film and wherein the excitation winding and the excitation circuit are arranged so that the magnitude of said second component is insufficient to drive the film into and out of saturation in the vicinity of said one or more sensor windings.
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2. A position encoder comprising:
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first and second members which are relatively movable along a measurement path; an excitation winding and one or more a sensor windings, at least one of the excitation winding and the one or more sensor windings being carried by the first member; a DC magnetic field generator carried by the second member and operable to generate a DC magnetic field which varies with position along the measurement path; a film of magnetizable material which is located, in use, within said positionally varying DC magnetic field to cause the film to have a positionally varying magnetization state along the measurement path; wherein the excitation and sensor windings are arranged relative to said film so that a mutual electromagnetic coupling between them varies in dependence upon the positionally varying magnetization state of said film of magnetizable material, so that when said excitation winding is energized with an excitation signal, a sensor signal is generated in the one or more sensor windings that varies with the relative position between said first and second members; an excitation circuit operable to generate an excitation signal having an excitation frequency for energizing the excitation winding to cause the excitation winding to generate an excitation electromagnetic field; and a processing circuit operable to process sensor signals generated in the one or more sensor windings which are at substantially the same frequency as said excitation frequency, to determine a value of a ratiometric function, which value is indicative of the relative position between the first and second relatively movable members, wherein said magnetic field generated by said magnetic field generator creates an in-homogeneity spot in said film, the position of which varies with the relative position between the first and second relatively movable members and wherein said excitation and sensor windings are arranged so that the mutual electromagnetic coupling between them varies in dependence upon the position of said in-homogeneity spot in the film. - View Dependent Claims (3, 4)
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5. A position encoder comprising:
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first and second members which are relatively movable along a measurement path; an excitation winding and one or more a sensor windings, at least one of the excitation winding and the one or more sensor windings being carried by the first member; a DC magnetic field generator carried by the second member and operable to generate a DC magnetic field which varies with position along the measurement path; a film of magnetizable material which is located, in use, within said positionally varying DC magnetic field to cause the film to have a positionally varying magnetization state along the measurement path; wherein the excitation and sensor windings are arranged relative to said film so that a mutual electromagnetic coupling between them varies in dependence upon the positionally varying magnetization state of said film of magnetizable material, so that when said excitation winding is energized with an excitation signal, a sensor signal is generated in the one or more sensor windings that varies with the relative position between said first and second members; an excitation circuit operable to generate an excitation signal having an excitation frequency for energizing the excitation winding to cause the excitation winding to generate an excitation electromagnetic field; and a processing circuit operable to process sensor signals generated in the one or more sensor windings which are at substantially the same frequency as said excitation frequency, to determine a value of a ratiometric function, which value is indicative of the relative position between the first and second relatively movable members, wherein said at least one winding which is carried by said first member is arranged along said measurement path in a geometrically varying manner. - View Dependent Claims (6)
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7. A position encoder comprising:
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first and second members which are relatively movable along a measurement path; an excitation winding and one or more a sensor windings, at least one of the excitation winding and the one or more sensor windings being carried by the first member; a DC magnetic field generator carried by the second member and operable to generate a DC magnetic field which varies with position along the measurement path; a film of magnetizable material which is located, in use, within said positionally varying DC magnetic field to cause the film to have a positionally varying magnetization state along the measurement path; wherein the excitation and sensor windings are arranged relative to said film so that a mutual electromagnetic coupling between them varies in dependence upon the positionally varying magnetization state of said film of magnetizable material, so that when said excitation winding is energized with an excitation signal, a sensor signal is generated in the one or more sensor windings that varies with the relative position between said first and second members; an excitation circuit operable to generate an excitation signal having an excitation frequency for energizing the excitation winding to cause the excitation winding to generate an excitation electromagnetic field; and a processing circuit operable to process sensor signals generated in the one or more sensor windings which are at substantially the same frequency as said excitation frequency, to determine a value of a ratiometric function, which value is indicative of the relative position between the first and second relatively movable members, wherein a winding carried by said first member comprises at least two loops of conductor which extend along the measurement direction and which are connected in series in a figure of eight arrangement.
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8. A position encoder comprising:
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first and second members which are relatively movable along a measurement path; an excitation winding and one or more a sensor windings, at least one of the excitation winding and the one or more sensor windings being carried by the first member; a DC magnetic field generator carried by the second member and operable to generate a DC magnetic field which varies with position along the measurement path; a film of magnetizable material which is located, in use, within said positionally varying DC magnetic field to cause the film to have a positionally varying magnetization state along the measurement path; wherein the excitation and sensor windings are arranged relative to said film so that a mutual electromagnetic coupling between them varies in dependence upon the positionally varying magnetization state of said film of magnetizable material, so that when said excitation winding is energized with an excitation signal, a sensor signal is generated in the one or more sensor windings that varies with the relative position between said first and second members; an excitation circuit operable to generate an excitation signal having an excitation frequency for energizing the excitation winding to cause the excitation winding to generate an excitation electromagnetic field; and a processing circuit operable to process sensor signals generated in the one or more sensor windings which are at substantially the same frequency as said excitation frequency, to determine a value of a ratiometric function, which value is indicative of the relative position between the first and second relatively movable members. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 23, 24, 25)
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21. A position encoder comprising:
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first and second members which are relatively movable along a measurement path; an excitation winding and one or more a sensor windings, at least one of the excitation winding and the one or more sensor windings being carried by the first member; a DC magnetic field generator carried by the second member and operable to generate a DC magnetic field which varies with position along the measurement path; a film of magnetizable material which is located, in use, within said positionally varying DC magnetic field to cause the film to have a positionally varying magnetization state along the measurement path; wherein the excitation and sensor windings are arranged relative to said film so that a mutual electromagnetic coupling between them varies in dependence upon the positionally varying magnetization state of said film of magnetizable material, so that when said excitation winding is energized with an excitation signal, a sensor signal is generated in the one or more sensor windings that varies with the relative position between said first and second members; an excitation circuit operable to generate an excitation signal having an excitation frequency for energizing the excitation winding to cause the excitation winding to generate an excitation electromagnetic field; and a processing circuit operable to process sensor signals generated in the one or more sensor windings which are at substantially the same frequency as said excitation frequency, to determine a value of a ratiometric function, which value is indicative of the relative position between the first and second relatively movable members, wherein said processing circuit is operable to combine said sensor signals with a signal having the same frequency as said excitation frequency. - View Dependent Claims (22)
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Specification