Patent EP0378351A2 successfully refreshed from Google Patents.
EP0378351A2
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EP
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Relative position transducer
Assignee: Gemalto Terminals Ltd
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Filing: 1990-01-09
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Granted: —
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Expires: 2010-01-09
Abstract
Abstract A relative position transducer (10) for determining the angular position of a first member (20) angularly movable relative to a second member (18) includes a coded track (22) on the first member, a read head (30) mounted on the second member, drive means (not shown) for oscillating the read head to scan over and read a limited region of the coded track, and a mircrocomputer (not shown) for interpreting the code read by the read head as the position. A first sensor (60, 62) detects when the read head is in a predetermined reference position, and a second sensor (103, 104) detects the end points and direction of the read head scan. The sensor outputs are connected to the computer for correct interpretation of the read head output. An interpolation is used to improve the accuracy of the position determination.
Inventors
- 👤 Teresa Mary Roberts
- 👤 Adrian Vivian Lewis
- 👤 Graham Kenneth Thornton
- 👤 Jolyon Peter Willson
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 09:04
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/12; G01D5/244; G01D5/249; G01D5/2492; G01D5/2495; H; H03; H03M; H03M1/00; H03M1/12; H03M1/22; H03M1/24; H03M1/245; H03M1/28; H03M1/282
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
85 words
Apparatus for detecting the position of a first member (20) movable relative to a second member, comprising a coded track (22) on the first member, and extending in the direction of the relative movement, characterised in that it further comprises a photosensitive read head (30) mounted on the second member, means (32, 52) for oscillating the read head to scan over and read a limited region of the coded track, and means (116,120,122,124,126,128,130,134,138,140) for interpreting the code read by the read head as the position.
Claim 2
Dependent Claim
85 words
Apparatus for detecting the position of a first member (20) movable relative to a second member, comprising a coded track (22) on the first member, and extending in the direction of the relative movement, characterised in that it further comprises a photosensitive read head (30) mounted on the second member, means (32, 52) for oscillating the read head to scan over and read a limited region of the coded track, and means (116,120,122,124,126,128,130,134,138,140) for interpreting the code read by the read head as the position.
Claim 3
Dependent Claim
35 words
Apparatus according to claim 1, characterised in that the position is an angular position, and the first member is a rotatable disc (20), the coded track (22) being formed as a circle on the disc.
Claim 4
Dependent Claim
17 words
Apparatus according to claim 1 or 2, characterised in that the code is a binary data code.
Claim 5
Dependent Claim
19 words
Apparatus according to claim 3, characterised in that the binary data code is arranged sequentially along the track (22).
Claim 6
Dependent Claim
51 words
Apparatus according to claim 4, characterised in that each bit of the data code is represented on the track as a sequence of binary features, namely a first feature corresponding to a logical 1, a second feature corresonding to the data bit, and a third feature corresponding to a logical 0.
Claim 7
Dependent Claim
69 words
Apparatus according to any of claims 3 to 5, characterised in that the binary data code is a continuous pseudo random code having the property that any selected group of N adjacent bits of the code is not repeated in any other group of N adjacent bits, N being a positive integer and the amplitude of the oscillation being sufficient to scan a region encompassing at least N bits.
Claim 8
Dependent Claim
27 words
Apparatus according to any of the preceding claims, characterised in that the code is read sequentially in both directions of travel of the oscillating read head (30).
Claim 9
Dependent Claim
47 words
Apparatus according to claim 7, characterised in that it further comprises means (116) for selectively inverting the output signal from the read head whereby, for one direction of scan the output signal is not inverted and, for the other direction of scan the output signal is inverted.
Claim 10
Dependent Claim
66 words
Apparatus according to any of the preceding claims, in which the first member is moving relative to the second member, characterised in that the apparatus further comprises means (116) for controlling the interpreting means such that the code is only interpreted from the track during a scan in the opposite direction to the direction of movement of the first member (20) relative to the second member.
Claim 11
Dependent Claim
53 words
Apparatus according to claim 9, characterised in that the means (116) for controlling the interpreting means are responsive to the speed of movement of the first member to cause the code to be interpreted only during a scan in the said opposite direction only when the speed of movement exceeds a predetermined level.
Claim 12
Dependent Claim
35 words
Apparatus according to any of the preceding claims, characterised in that the means for oscillating the read head comprises a magnet and a coil, the coil being excited electrically to attract and repel the magnet.
Claim 13
Dependent Claim
29 words
Apparatus according to any of the preceding claims, characterised in that the read head (30) is mounted on an assembly (32) supported by means of a torsion bar (52).
Claim 14
Dependent Claim
24 words
Apparatus according to claim 12, characterised in that the read head (30) is movably oscillated at the resonant frequency of the torsion bar (52).
Claim 15
Dependent Claim
19 words
Apparatus according to claim 13, characterised in that the resonant frequency is in the range of 50Hz to 250Hz.
Claim 16
Dependent Claim
36 words
Apparatus according to any of the preceding claims, charcterised in that it further comprises means (103, 104, 106, 107, 108) for detecting the end points of travel of the oscillatory movement of the read head (30).
Claim 17
Dependent Claim
56 words
Apparatus according to claim 15, characterised in that the read head (30) is movably oscillated at the resonant frequency of the torsion bar (52), and the output from the detecting means ( 103, 104, 106, 107, 108) is applied in a positive feedback manner to the means for oscillating the read head, to maintain resonant oscillation.
Claim 18
Dependent Claim
36 words
Apparatus according to claim 15 or 16, characterised in that the detecting means comprise a magnet (103) attached to the read head assembly (30, 32), and a magnetic pick up (104) mounted on the second member.
Claim 19
Dependent Claim
38 words
Apparatus according to claim 15 or 16, characterised in that the detecting means comprise a linear variable differential transformer displacement sensor having a core axially movable in the direction of scan withing the coils of a differential transformer
Claim 20
Dependent Claim
63 words
Apparatus according to any of the preceding claims, characterised in that it further comprises means (60, 62, 112, 114) for detecting when the read head (30) is in a predetermined reference position relative to the second member, whereby the code read on either side of the reference position can be aligned to ensure that it corresponds to a reading at the reference position.
Claim 21
Dependent Claim
39 words
Apparatus according to claim 19, characterised in that the reference position detecting means comprise an optical detector (60) and an optical reference mark (62), mounted on the read head assembly (30, 32) and the other on the second member.
Claim 22
Dependent Claim
162 words
Apparatus according to claim 19 or 20, characterised in that the optical detector (60) comprises a first optical fibre (68) for delivering light from a source to illuminate the reference mark (62), and second (64) and third (66) optical fibres for receiving light reflected back from the reference mark (62) and delivering the light to respective light detectors, the second (64) and third (66) optical fibres being positioned on either side of the first optical fibre (68), the arrangement being such that, in use during the oscillatory movement of the read head assembly, when the reference mark is in the reference position, light is reflected equally down the second (64) and third (66) optical fibres, when the reference mark is offset to one side of the reference position, light is reflected mostly down the second optical fibre (64), when the reference mark is offset to the other side of the reference position, light is reflected mostly down the third optical fibre (66).
Claim 23
Dependent Claim
41 words
Apparatus according to claim 21, characterised in that it further comprises an electronic circuit (112) for obtaining a signal corresponding to the difference between the outputs of the light detectors, such that in the reference position the difference signal is zero.
Claim 24
Dependent Claim
53 words
Apparatus according to claims 20, 21 or 22, characterised in that the optical reference mark (62) is a chrome line formed on glass, the width of the line being less than the distance (E) between outermost parts of the light transmissive cores (64′, 66′) of the second and third optical fibres (64, 66).
Claim 25
Dependent Claim
121 words
Apparatus according to any of the preceding claims, characterised in that the code on the track consists of binary features, further comprising means (120, 122, 124, 126, 128, 130, 132, 134, 138) for determining the relative positions of the reference position and the beginning and end of the coded data bit during which the reference position is detected, the means comprising a first timer (126) for timing the period between the instant that the reference position is detected and the end of the coded data bit during which the detection occurs, and a second timer (120, 122, 124) for timing the period between the instants that the beginning and end of the coded data bit are read by the read head.
References Cited (Backward Citations)
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