Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
  • G01B7/30—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring angles or tapers; for testing the alignment of axes
  • G01B7/31—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes

Definitions

• the present invention relates to a method for measuring an axial deviation in a tensioned wire alignment system. It also relates to a measuring device implementing this method, as well as a tensioned wire alignment system including such measuring devices.
• Another tensioned wire alignment system is also known in which a tungsten wire with a diameter of 125 ⁇ m and having a resistivity of 40 ⁇ .m is subjected to a high frequency alternating voltage. Capacitive sensor rings are arranged between guard segments connected to ground. These rings and the electronics are arranged in a shielded housing.
• the conductivity of the tensioned wire is used to carry out axial deviation measurements which excludes using for the production of these wires, materials having a high electrical resistivity.
• the object of the invention is to remedy these drawbacks by proposing a method for measuring an axial gap in an alignment system comprising a tensile resistive wire which can in particular be made of a material having higher mechanical characteristics than the materials used. currently in wire distance meters.
• the method comprises: applying an alternating voltage signal to a measurement electrode provided with a guard electrode, this measurement electrode being arranged in a measurement plane on a support fixed to an element to align and close to the tensioned wire, this tensioned wire being dyncimically connected to the ground, a measurement by a capacitive bridge comprising a first capacity constituted by the measurement electrode and the wire and a second predetermined capacity, to provide a measurement signal representative of an axial position of the measurement electrode with respect to the wire stretched along a first measurement axis normal to said measurement plane, and a processing of this measurement signal to provide information representative of an axial deviation of the element to be aligned with respect to a predetermined alignment position.
• first and second alternating voltage signals are applied respectively to a first and a second measurement electrodes respectively provided with guard electrodes and disposed respectively in a first and a second measurement planes located on either side of the reference axis
• the method further comprises, for each measurement electrode, a measurement by capacitive bridge to provide a signal representative of the capacitance between the measurement electrode and the wire, and a differential processing of said first and second signals representative of the capacities corresponding respectively to the first and second measuring electrodes to deliver information representative of an axial deviation of the element to be aligned with respect to a predetermined alignment positioning along a first measurement axis.
• the first and second measurement planes are substantially parallel, and information is obtained on the axial deviation of the element to be aligned with respect to a predetermined alignment position along a measurement axis normal to said first and second measurement planes. measured.
• the method according to the invention further comprises at least one application of an alternating voltage signal to at least one other measuring electrode arranged near the wire stretched in another measurement plane not parallel to the first measurement plane, a measurement by capacitive bridge to provide at least one other measurement signal representative of an axial position of the other measurement electrode along another axis normal measurement to said other measurement plane, and processing of this other signal to deliver information representative of an axial deviation of the element to be aligned with respect to a predetermined alignment position along said other measurement axis.
• the other measurement plane is not parallel to the first measurement plane, and can for example be orthogonal to the latter.
• a device for measuring an axial gap in a tensioned wire alignment system comprising a support fixed to an element to align along a reference axis, characterized in that it comprises: at least one measurement electrode provided with a guard electrode and disposed in a measurement plane located near a taut conductive wire connected to a ground, means for generating and applying to this measuring electrode an alternating voltage signal, relative to the guard electrode, capacitive bridge means for delivering a measuring signal representative of an axial position of the measuring electrode with respect to wire stretched along a measurement axis normal to said measurement plane, and means for processing this measurement signal in order to deliver information representative of an axial deviation of the element to be aligned by relative to a predetermined alignment position.
• the measurement device comprises at least two measurement electrodes disposed respectively in two substantially orthogonal measurement planes.
• the measurement device according to the invention comprises at least two measurement electrodes respectively disposed in two substantially parallel measurement planes on either side of the reference axis.
• this further comprises a central recess for receiving the tensioned wire, around which are arranged several measuring elements, each measuring element comprising an insulating support on which the measuring electrode is arranged in the form of a thin layer.
• each measuring element comprises a piece of insulating material comprising on its outer face the measuring electrode and fixed to a metal support acting as a guard for this measuring electrode which can have various geometric shapes.
• the generation means and the capacitive bridge means can be housed within the device, in the immediate vicinity of the measurement electrodes, and arranged at least partially in a shielded enclosure which can be brought to a floating potential.
• all of the electronic equipment is offset by several meters, the measurement device then being passive.
• FIG. 1 is a descriptive view of an alignment system using axial displacement measuring devices according to the invention
• - - Figure 2 is a sectional view of a first embodiment of a measuring device according to the invention
• FIG. 2A is a partial view of a capacitive module within the device shown in Figure 2;
• FIG. 3 is a sectional view of a second embodiment of a measuring device according to the invention.
• a tensioned wire alignment system 1 according to 1
• the invention comprises a set of deviation measuring devices 10, 11, hereinafter referred to as deviometers, a wire 2 preferably made from carbon fibers, having a high electrical resistivity and stretched in both directions.
• traction equipment 5, 6 comprising for example pulleys and weights, electronic processing equipment 100, 110 and a central unit 120 for collecting the information of axial deviation delivered by each variometer 10, 11 and for emitting control instructions 130 to positioning actuators (not shown) in order to obtain the desired alignment.
• the distance meters 10, 11 are securely fixed to elements 3, 7 whose alignment is sought, for example on vertical lateral faces 4, 8 of these elements.
• the wire 2 is stretched along a reference axis AR but in practice describes a chain because of its own weight. It should however be noted that the use of a low density carbon fiber yarn made possible by the method according to the invention contributes to considerably reducing this chain effect.
• Wire 2 is electrically connected to earth or to a reference ground, either directly or dynamically by capacitive coupling. One can for example provide a connection 12 to earth at a pulley 6.
• a distance meter 10 comprises a support 280 conductor connected to the ground and fixed to a lateral external face 4 of an element to be aligned 2, a piece 290 of insulating material and a guard piece metallic 200 having a U-shaped cross-section and receiving on its internal faces 261, 262 capacitive measuring elements 260, 270 between which passes the tensioned wire 2 which is electrically connected to earth by suitable electrical connection means 12.
• the two capacitive measuring elements 260, 270, separated by a spacer element 201, are arranged in opposition on the two inner faces of the guard piece 200.
• Each capacitive measuring element 260, 270 may for example comprise, as shown in FIG. 2A, a measurement electrode 20, 22 deposited on a layer of insulating material 26, 27, for example alumina, arranged on the internal faces 261, 262 which act as a guard for the two measurement electrodes 20, 22
• the measurement electrodes are of substantially rectangular shape on guard pieces of round shape. However, many other geometric shapes can be envisaged both for the measurement electrodes and for the guard pieces.
• each capacitive measurement element 260, 270 defines a measurement plane P, P 'including the measurement electrode 20, 22.
• the two measurement planes P, P' are preferably parallel and, on the one hand, there is associated a first measurement axis X normal to the measurement planes and on the other hand, a second measurement axis Z parallel to the measurement planes. In a configuration with two parallel measurement planes such as that shown in FIG. 2, only the axial deviations along the first measurement axis X are measured.
• the distanceometer 10 may include in situ an electronic excitation and processing unit 24 included in the within the support 200, in order to guarantee high measurement accuracy. Furthermore, it is advantageous to provide on the base of the variometer 10 a temperature sensor 240 in order to compensate by calculation for the thermal expansion of the base.
• a deviation measurement device or devometer 30 comprises, with reference to the figure 3, a frame 300 fixed via an electrically insulating support to an accessible face 4 of an element to be aligned 3, this frame 300 made of electrically conductive material, comprising a central recess 350 in which the tensioned wire 2 passes and on the interior walls which are arranged capacitive measuring elements 312, 322, 332, 342 which may have a geometry similar to that which has just been described.
• First and second capacitive measurement elements 322, 332 are arranged in two parallel measurement planes P, P 'for measuring an axial deviation x along a first measurement axis X, while a third and a fourth capacitive measurement elements 312, 342 are arranged in two other parallel measurement planes P ", P"'to measure an axial deviation z along a second measurement axis Z perpendicular to the first measurement axis Z.
• Each capacitive measurement element 312, 322, 332, 342 comprises a support 31, 32, 33, 34 of insulating material, for example ceramic, on which have been deposited, for example by screen printing, a central measurement electrode 310, 320, 330, 340 and a guard electrode 311, 321, 331, 341.
• the measuring electrodes may for example be rectangular in shape and surrounded by guard electrodes having the shape of a rectangular frame.
• a remote box 370 comprises electronic processing units 40 associated with each capacitive measurement element and connected to these by shielded connection cables 371, 372. These cables are at least coaxial cables whose core is connected to the measuring electrode and the shield is connected to the corresponding guard. It is also possible to provide triaxial cables comprising an additional shield connected to earth.
• Each capacitive measurement element 400 is associated with an electronic excitation and processing unit 40 to deliver information representative of an axial deviation of an element to be aligned with respect to a desired predetermined alignment position.
• This unit 40 may comprise, according to known techniques, floating oscillators 43 and a guard enclosure 50 comprising a capacitive bridge produced from an operational amplifier 42 having its negative input connected via the floating oscillators 43 to the measurement electrode 20, its positive input connected to earth, and its output connected through a feedback capacitor 41 to its negative input.
• the guard enclosure 50 connected to earth, also includes a demodulator 45 disposed at the output of a level amplifier 44 downstream of the charge amplifier 42, and a modulator 47 disposed at the output of an integrator 46 in downstream of the demodulator 45.
• the output of the modulator 47 is applied to the negative input of the charge amplifier 42 through a reference capacitor 49.
• the modulator 47 and the demodulator 45 are synchronized from the floating oscillators 43.
• the signal of the output voltage Vs, taken at the output of the integrator 46, is generally digitized and is the subject of a processing using for example a 3rd order linear regression.
• a distance meter according to the invention comprising two capacitive measurement sensors such as that illustrated in FIG.
• the following metrological characteristics have been obtained experimentally: travel along the X axis: ⁇ 1.25 mm, zero being in the center of the two sensors 260, 270; displacement along the Z axis: ⁇ 2 mm, the zero being placed 14 mm from the spacer 201; average sensitivity: 4 mV / ⁇ m; measurement noise: 0.1 ⁇ m / VHz peak to peak, - bandwidth: 80 Hz, -
• the wire used in this embodiment has a diameter of 0.3 mm and a total resistance of 50 k ⁇ . In maximum use, corresponding to a deviation of the wire over the entire two strokes along the X axis and the Z axis: natural linearity: ⁇ 8 ⁇ m; residual errors after a 3rd order regression: ⁇ 0.5 ⁇ m;
• the measurement and guard electrodes can have different geometries from that which has just been described.
• the electrodes can also be produced in printed circuit or by mechanical assembly.
• the deviation measurement devices according to the invention can be arranged with respect to the elements to be aligned using any fixing techniques.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
• Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

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• 1995
  • 1995-11-13 FR FR9513420A patent/FR2741147B1/fr not_active Expired - Fee Related
• 1996
  • 1996-11-13 EP EP96946368A patent/EP0888520A1/de not_active Withdrawn
  • 1996-11-13 US US09/068,518 patent/US6246244B1/en not_active Expired - Fee Related
  • 1996-11-13 WO PCT/FR1996/001787 patent/WO1997018438A1/fr not_active Application Discontinuation
  • 1996-11-13 JP JP51862697A patent/JP4073484B2/ja not_active Expired - Fee Related

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