EP0470558B1 - Positionsmessvorrichtung - Google Patents

Positionsmessvorrichtung Download PDF

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Publication number
EP0470558B1
EP0470558B1 EP19910113143 EP91113143A EP0470558B1 EP 0470558 B1 EP0470558 B1 EP 0470558B1 EP 19910113143 EP19910113143 EP 19910113143 EP 91113143 A EP91113143 A EP 91113143A EP 0470558 B1 EP0470558 B1 EP 0470558B1
Authority
EP
European Patent Office
Prior art keywords
signal
excitation
signals
transducer
excitation signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19910113143
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English (en)
French (fr)
Other versions
EP0470558A2 (de
EP0470558A3 (en
Inventor
Harold A. Morser
Thomas E. Nead
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Milacron Inc
Original Assignee
Milacron Inc
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Filing date
Publication date
Application filed by Milacron Inc filed Critical Milacron Inc
Publication of EP0470558A2 publication Critical patent/EP0470558A2/de
Publication of EP0470558A3 publication Critical patent/EP0470558A3/en
Application granted granted Critical
Publication of EP0470558B1 publication Critical patent/EP0470558B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08C—TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS
    • G08C19/00—Electric signal transmission systems
    • G08C19/38—Electric signal transmission systems using dynamo-electric devices
    • G08C19/46—Electric signal transmission systems using dynamo-electric devices of which both rotor and stator carry windings

Definitions

  • This invention relates generally to apparatus for position measurement.
  • this invention relates to interface circuits used with electromagnetic position transducers.
  • Position transducers which are of interest herein include resolvers and slider and scale systems producing AC output signals in response to AC excitation signals wherein a phase shift between the excitation signals and the output signals is introduced by the relative position of a transducer armature and stator. The position of the armature relative to the stator is measured by detecting this phase difference.
  • phase discrimination technique wherein the excitation signals are applied to pairs of windings arranged in quadrature, and the position induced phase shift is detected by phase comparison of the output signal with a reference from which the excitation signals are derived
  • amplitude technique wherein the output signals are produced by the quadrature windings and the position induced phase shift is detected from the ratio of the instantaneous magnitudes of the output signals.
  • Fig. 1a illustrates an arrangement used with the amplitude technique employing a resolver to measure position of a moveable member of, for example, machine tools, robots or other position controlled equipment.
  • the resolver 10 includes a rotor 12 having an armature coil 14, and a stator having stator coils 16 and 18.
  • the rotor 12 is rotated relative to the stator by, for example, a motor 28.
  • the transducer 10 is located remotely from a control device 20 wherein a drive amplifier 22 produces an AC excitation signal applied to the armature coil 14. Output signals appearing at the stator coils 16 and 18 are returned to differential amplifiers 24 and 26 located in control 20.
  • Conducting cables 30, 32, and 34 typically twisted pairs, provide connection of excitation and output signals between the interface circuits of control 20 and the resolver 10.
  • Fig. 1b illustrates an arrangement used with the phase discrimination technique employing a resolver to measure position of a moveable member.
  • excitation signals are produced by drive amplifiers 23 and 25 and applied to the resolver stator coils 17 and 19.
  • An output signal appears at resolver armature coil 13 and is returned to differential amplifier 21 in control 19.
  • the excitation signals are derived from a single reference signal and are phased displaced one from the other by ⁇ /2 radians.
  • Fig. 2 illustrates capacitive coupling between an excitation signal cable and an output signal cable which will exist as a result of proximity of the conducting cables 30, 32 and 34 of Fig. la or cables 29, 36 and 38 of Fig. 1b.
  • capacitors C1, C2, C3, and C4 represent lumped values of the coupling capacitances distributed over the lengths of the conducting cables; source SD represents the source of excitation signals; and, load LD represents the load impedance presented to an output signal.
  • Inductive coupling of the rotor and stator windings is intentionally omitted to simplify the analysis of the capacitive coupling in the conducting cables. It will be appreciated from Fig. 2 that by virtue of the grounded return paths only capacitance C1 contributes an error component to the output signal appearing across the load.
  • the voltage error component in the output signals arising from capacitive coupling as shown in Fig. 2 has a magnitude equal to the excitation signal magnitude and is phase displaced ⁇ /2 radians therefrom.
  • the current due to this error component is added algebraically to the output signal current magnitude, resulting in a position error repeated over the range of position measured by the resolver.
  • Such errors are referred to as "cyclic errors.” It is common practice to provide individual shields for each conducting cable, such as shields 31, 33, and 35 to reduce or eliminate capacitive coupling between the excitation and output signal cables. The cost of such shielding significantly increases the material and labor costs associated with the installation of such cables.
  • the present invention provides an excitation signal source for use with electromagnetic position transducers producing an AC excitation signal symmetrical with respect to ground.
  • a first AC signal is inverted to produce a second AC signal and the excitation signal is taken as the difference between the first and second AC signals.
  • a receiver for use with electromagnetic position transducers is provided having matched impedances for signal and return lines of an output signal.
  • Figs. 1a and 1b illustrate prior art circuits for position measurement using a resolver.
  • Fig 2 illustrates capacitive coupling between excitation and output signal conducting cables.
  • Fig. 3 illustrates circuits of the present invention as applied to a resolver.
  • Figs. 4a, 4b and 4c are equivalent circuits illustrating the effects of the circuits of Fig. 3 on the capacitive coupling illustrated by Fig. 2.
  • Fig 5 illustrates circuits of the present invention as applied to a slider and scale system.
  • electromagnetic position transducer interface circuits of a motor control device developed for Cincinnati Milacron Inc., the assignee of the present invention shall be described in detail. While the interface circuits to be described constitute a preferred embodiment, it is not the intention of applicants to limit the scope of the invention to the details thereof.
  • a resolver 40 mechanically coupled to motor 50, is shown remotely located from motor controller 60. None of the details of motor controller 60 pertaining to control of motor 50 are pertinent to the present invention and these details shall not be described herein.
  • Motor 50 under control of controller 60, effects rotation of rotor 42 relative to a resolver stator.
  • Stator coils 46 and 48 are fixed relative to the resolver stator and produce AC output signals in response to an AC excitation signal impressed on rotor coil 44.
  • the output signals F1 and F2 are expressed as functions of the excitation signal and the relative angular position of the rotor 42 and stator as follows:
  • F1 E * sine( ⁇ ) * sine(Wt)
  • F2 E * cosine ( ⁇ ) * sine(Wt)
  • the excitation signal may in fact be inductively coupled thereto from the stator in brushless resolvers.
  • the signal and return paths of the excitation signal are provided by twisted pair conductor cable 52.
  • the signal and return paths for the output signals F1 and F2 are provided in, respectively, twisted pair conductor cables 54 and 56.
  • the excitation signal V1 is taken across the outputs of amplifiers 62 and 64.
  • Amplifier 62 receives a sinusoidal AC signal S1 of constant frequency W derived from a square wave.
  • the output of amplifier 62 is inverted by amplifier 64.
  • Series inductors 66 and 68 are provided to reduce the possibility of high frequency oscillation appearing at the outputs of amplifiers 62 and 64 when connected to cables presenting relatively high capacitive loads.
  • Gain setting resistors R1 and R2 are of equal value within a moderately close tolerance as may be readily achieved, for example, using 1% components.
  • the excitation signal V1 is symmetrical about ground due to the inversion of the output of amplifier 62 by amplifier 64.
  • output signals F1 and F2 are received by differential amplifiers 70 and 72 which amplify the potential difference appearing across the signal and return paths of the twisted pair conductor cables 56 and 54.
  • the use of differential amplifiers provides high rejection of noise signals common to the amplifier inputs.
  • Gain determining components R4, R7, and R6, R9 are chosen to have equal values within a component tolerance of 0.1% to facilitate analogue to digital conversion with an accuracy of 12 binary digits.
  • Gain determining components R8 and R3 of amplifier 70 and resistors R10 and R5 of amplifier 72 are also chosen to be equal within a component tolerance of 0.1%.
  • impedance matching resistors R11 and R12 are connected between the return path input and ground at respectively, amplifier 70 and amplifier 72.
  • the resistor R11 has a value equal to half the product of the sum of the values of resistors R7 and R8 multiplied by the ratio of R7 to R8 and the resistor R12 has a value equal to half the product of the sum of the values of resistors R9 and R10 and the ratio of R9 to R10.
  • Fig. 5 shows the use of a symmetrical excitation signal and balanced impedance receivers for the output signals as applied to a slider and scale measuring system 80.
  • a scale excitation signal output by scale amplifier 88 is applied to a scale 82.
  • Scale 82 has a formed conductor defining pole segments SP I having a pitch I.
  • Slider output signals are induced in slider formed conductors 85 and 86 by the scale excitation signal.
  • the slider formed conductors 85 and 86 define pole segments APS I and APC I having the same pitch I as the scale pole segments.
  • the slider pole segments are arranged relative to one another so as to be spatially separated by I/4.
  • the slider output signals are transmitted to line amplifiers 89 proximate the slider 84 via conducting cables 118 and 120.
  • Line amplifiers 89 produce AC output signals which are transmitted to control 90 via conducting cables 112 and 114.
  • An excitation signal generated at control 90 is transmitted to scale amplifier 88 proximate the scale 82 via conducting cable 110.
  • Scale amplifier 88 produces the scale excitation signal conducted by cable 116 to scale 82.
  • Relative position of the slider 84 and scale 82 may be determined from the slider output signals using the amplitude technique described for use with resolvers. Because of the low impedance of the interface between the slider and scale system and of the amplifiers 88 and 89, capacitive coupling between the scale excitation signal and the slider output signals does not generally give rise to an appreciable error component in the measured position. Conversely, the interface between the control 90 and the amplifiers 88 and 89 is susceptible to the same capacitive effects discussed with reference to Fig. 2. Therefor, the use of an excitation signal symmetrical with respect to ground and matched impedances in the signal and return lines of the output signals provide the same advantages as previously discussed thereby permitting the inclusion of cables 110, 112 and 114 within a single shield 130.
  • the circuits of control 90 used in this application are the same as shown in Fig. 3.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)
  • Arrangements For Transmission Of Measured Signals (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Claims (5)

  1. Vorrichtung zur Positionsmessung, wobei leitende Kabel (52, 54, 56) Wechselspannungs-Erregungssignale und Wechselspannungs-Wandlerausgangssignale zwischen einem elektromagnetischen Positionswandler (40) und zugehörigen Schnittstellenschaltkreisen (60), die von diesem entfernt sind, führen, wobei die Schnittstellenschaltkreise Mittel zum Erzeugen eines Erregungssignals und Empfänger zum Aufnehmen der Ausgangssignale des Wandlers aufweisen, wobei die Vorrichtung charakterisiert ist durch eine Verschaltung des Signals und des Rückflusses zum Reduzieren der effektiven Kopplungskapazität (C1, C2, C32, C4) zwischen den leitenden Kabeln, wobei die Schaltung Mittel zum Erzeugen des Erregungssignals mit einem Verstärker (62) zum Erzeugen eines ersten Wechselspannungssignals, Mittel (64) zum Invertieren des ersten Wechselspannungs-Signals zum Erzeugen eines zweiten Wechselspannungs-Signals in Gegenphase relativ zu dem ersten Wechselspannungs-Signal aufweist und das Erregungssignal als die Potentialdifferenz zwischen dem ersten Wechselspannungs-Signal und dem zweiten Wechselspannungs-Signal genommen wird.
  2. Die Vorrichtung von Anspruch 1, weiter gekennzeichnet durch Empfänger für das Ausgangssignal mit Signalempfangsmitteln (70, R3, R4, R7, R8, R11; 72, R5, R6, R9, R10, R12), die einen Signal- und Rückflußweg für die Ausgangssignale (F1, F2) des Wandlers bilden, bei denen die Impedanz des Signal- und Rückflußweges zur Masse gleich sind.
  3. Vorrichtung zur Positionsmessung, wobei leitende Kabel (52, 50) Wechselspannungs-Erregungssignale und Wechselspannungs-Wandlerausgangssignale zwischen einem elektromagnetischen Positionswandler (40) und zugehörigen Schnittstellenschaltungen (60), die von diesem entfernt sind, führen, die Schnittstellenschaltungen Mittel zum Erzeugen eines Erregungssignals und Empfänger zum Empfangen eines Wandlerausgangs-Signals aufweisen, und die Vorrichtung gekennzeichnet ist durch eine Signal- und Rückf lußverschaltung zum Verringern der effektiven Kopplungskapazität (C1, C2, C2, C4) zwischen den leitenden Kabeln, wobei die Verschaltung Empfangsmittel (70, R3, R4, R7, R8, R11; 72, R5, R6, R9, R10, R12) für das Wandlerausgangs-Signal aufweist, das Signal- und Rückführungswege für die Wandlerausgangs-Signale (F1, F2) schafft, bei denen die Impedanzen des Signalwegs und des Rückflußweges zur Masse gleich sind.
  4. Die Vorrichtung nach Anspruch 3, dadurch gekennzeichnet, daß das das Erregungssignal erzeugende Mittel einen ersten Verstärker (62) zum Erzeugen eines ersten Wechselspannungs-Signals und einen zweiten Verstärker (64) zum Invertieren des ersten Wechselspannungs-Signals zum Erzeugen eines zweiten Wechselspannungs-Signals, das gegenüber dem ersten Wechselspannungs-Signal gegenphasig ist, aufweist, wobei das Erregungssignal als die Potentialdifferenz zwischen dem ersten Wechselspannungs-Signal und dem zweiten Wechselspannungs-Signal genommen wird.
  5. Vorrichtung nach einem der vorangehenden Ansprüche, weiter dadurch gekennzeichnet, daß der Wandler ein Drehmelder mit einem Rotor (42) mit einer Rotorspule (44) und Statorwicklungen (46, 48) zum Auflösen von Wechselspannungs-Erregungssignale in ein erstes Wechselspannungs-Ausgangssignal in der Form E * sin (ϑ * sin (Wt) und ein zweites Wechselspannungs-Ausgangssignal in der Form E * cos (ϑ) * sin (Wt) ist, wobei E die Größe des Erregungssignals, ϑ die relative Winkelposition des Stators und des Ankers, W die Frequenz des Erregungssignals und t die Zeit angibt.
EP19910113143 1990-08-06 1991-08-05 Positionsmessvorrichtung Expired - Lifetime EP0470558B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US58348090A 1990-08-06 1990-08-06
US583480 1990-08-06

Publications (3)

Publication Number Publication Date
EP0470558A2 EP0470558A2 (de) 1992-02-12
EP0470558A3 EP0470558A3 (en) 1992-05-27
EP0470558B1 true EP0470558B1 (de) 1995-10-18

Family

ID=24333280

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19910113143 Expired - Lifetime EP0470558B1 (de) 1990-08-06 1991-08-05 Positionsmessvorrichtung

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EP (1) EP0470558B1 (de)
JP (1) JPH04233699A (de)
CA (1) CA2048382C (de)
DE (1) DE69113916T2 (de)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106092150B (zh) * 2016-06-01 2018-07-03 同济大学 旋转变压器的位置信息获取方法、系统及电子设备

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4207505A (en) * 1977-05-09 1980-06-10 Sundstrand Corporation Measuring system
US4270061A (en) * 1978-11-03 1981-05-26 The Singer Company Current transformer input system for AC conversion devices
US4270077A (en) * 1980-03-10 1981-05-26 Sperry Corporation Demodulatorless synchro position sensor apparatus utilizing square wave excitation

Also Published As

Publication number Publication date
EP0470558A2 (de) 1992-02-12
DE69113916T2 (de) 1996-04-04
CA2048382A1 (en) 1992-02-07
CA2048382C (en) 1997-01-14
DE69113916D1 (de) 1995-11-23
EP0470558A3 (en) 1992-05-27
JPH04233699A (ja) 1992-08-21

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