Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
  • G01P13/00—Indicating or recording presence, absence, or direction, of movement
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
  • G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
  • G01B11/18—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge using photoelastic elements

Definitions

• the invention relates to a movement measuring device with two bodies which can be moved relative to one another, between which a deformation body made of transparent material is attached, which carries polarization filters on both sides at at least one measuring point and has at least one light source and a photocell which is connected to an electronic evaluation circuit.
• induced voltage result in transparent bodies to a change in optical properties, they are transparent bodies, which are optically isotropic when no voltage is anisotropically under the influence of voltages. This behavior is used in stress optics to visualize stresses in transparent model bodies that occur under certain loads; For this purpose, the transparent body is illuminated with polarized light.
• the deformation body consists of a single crystal of gallium phosphide or gallium arsenide.
• anisotropy changes the optical permeability of the deformation body. The change in brightness of the polarized light falling through the deformation body is measured and provides a signal for the size of the deformation.
• the device is therefore only suitable for a simple force measuring device, in particular a pressure measuring device, in which the direction of the force occurring is predetermined.
• the object of the invention is therefore to provide a movement measuring device of the type mentioned at the outset which enables a differentiation between tensile and compressive forces and is suitable for the construction of even complex force measuring devices.
• the transparent deformation body consists of amorphous material and an optically active filter is rotated by 45 ° on both sides, that a mirror layer is applied to the outside of one filter that on the outside of the other Filters a circular polarizing filter layer is arranged, on the outside of which the light source and the photocell are arranged, and that a device is provided which detects a change in the color of the light falling on the photocell.
• the anisotropy that occurs during the deformation of the deformation body has different effects on the different wavelengths of the light during expansion or compression. If white light is used, the color of the emerging light changes in opposite directions during compression and expansion. If monochromatic light of different wavelengths is used, the changes in brightness occurring during compression and stretching are different.
• This optical behavior makes it possible in a simple manner to infer not only the size but also the direction of the deformation carried out from the signal of the photocell. In this way, force measuring devices can be built in which the deformations are determined according to size and direction at several points on a deformation body, so that even complex forces and / or moments can be detected.
• the device for detecting a change in the color of the light is preferably formed by arranging at least two light sources close to one another at the measuring point, which emit monochromatic light of different wavelengths and each of which is assigned a separate photocell, the output signals of which are detected separately in the evaluation circuit and be compared in a comparator. Depending on the direction of the deformation, the change in brightness will be stronger in one or the other photocell. This phenomenon can be recorded and evaluated.
• Advantageous embodiments of the inventive concept are the subject of further dependent claims.
• 1 is a longitudinal section of a motion measuring device with a deformation body with several measuring points
• FIGS. 1 and 3 are end views of the deformation body of the motion measuring device according to FIGS. 1 and 3 with a block diagram of the evaluation circuit
• Fig. 5 is a simplified partial circuit diagram for a measuring point
• Fig. 6 + 7 other embodiments of the deformation body each in an end view.
• the movement measuring device shown in FIGS. 1 and 3 has a disk-shaped deformation body 1, which is arranged in a housing 2, which is designed as a tubular sleeve.
• An elongated glass transmission body 3 is connected at one end to the housing 2. At its other end, it is connected to the central region of the deformation body 1.
• the outer region of the deformation body 1 is connected to the housing 2.
• a circuit board 4 arranged in front of the deformation body 1 carries light sources, photocells and parts of the evaluation circuit, which are connected to a transmission coil 5 at the end of the housing 2.
• This transmission coil 5 is inductively connected to an associated transmission coil, not shown, outside the housing 2.
• the deformation body 1 consists of transparent, amorphous material, for example glass, but any other substance which is optically isotropic in the de-energized state can also be used, for example. All transparent amorphous solid bodies.
• the deformation body 1 On both sides, the deformation body 1 carries in the area of a measuring point an optically active filter 6 or 7 rotating the light through 45 °.
• a mirror layer 8 is applied to the outside of the one filter 7.
• a filter layer 9 which circularly polarizes the light is arranged on the outside of the other filter 6.
• the light emanating from a light source 10, for example a photodiode enters the deformation element 1 through the circularly polarizing filter layer 9 and the optically active filter 6 rotating through 45 °. It passes through the optically active filter 7 rotating through 45 ° to the mirror layer 8, is reflected there and passes through the filter 7, the deformation element 1, the filter 6 and the circularly polarizing filter layer 9 to a photocell 11, which delivers a signal depending on the brightness.
• the deformation body 1 If the deformation body 1 is undeformed, the light is simply reflected.
• the emerging light has the same wavelength as the incoming light. If white light is used and the deformation body 1 is deformed, the emerging light changes color. There is a different absorption depending on the wavelength. Which wavelengths are absorbed and how strongly this happens depends on the direction and strength of the deformation. With compression under compression there is a discoloration in the direction of blue or green, while with expansion under a tensile stress there is discoloration in the direction of yellow and red.
• the deformation body 1 has a central disk 12 and concentrically at a radial distance from it a ring 13 which are connected to one another by measuring webs 14.
• the measuring points are located in the area of the measuring webs 14.
• three measuring points 14 are arranged a three evenly distributed on the circumference, which are approximately at an angle of 45 ° to the radial direction. 3639
• Fig. 5 shows schematically the structure of a measuring arrangement for a measuring point.
• Arranged on the measuring web 14 are three pairs of light sources 10 and photocells 11, for example photodiodes, which each work with different light and measure the changes in brightness of the different colors.
• the signals supplied by the individual “photo cells” are sent to a microprocessor 17 of the evaluation circuit via analog-digital converter 15 and a decoder 16 as the signals representing the size and direction of the movement that has occurred.
• the deformation of the entire movement measuring device (FIG. 1) can be determined from the measured deformations at the six measuring points of the exemplary embodiment shown in FIG. 4 with the aid of the microprocessor 17 by means of trigonometric calculations.
• Appropriate programming can ensure that, in addition to the respective state of deformation, other variables can also be monitored, for example variables derived from the deformation and its duration and limit violations.
• the microprocessor 17 is programmed so that it can be calibrated at any time and the zero point can be set; Limit values or quantities derived from the deformations can also be specified.
• the data required for this are stored in an EEPROM 18.
• the output signals reach the transmission coil 5 via a decoder 19, which is connected to a voltage supply device 20. If the motion measuring device or the sensor is installed, for example, in a tool holder, a corresponding command is first given to the motion measuring device for calibration. This is then ready for calibration. A few deformations of the tool holder are then carried out and the direction and magnitude of the movement are transmitted to the movement measuring device. Later, the movement measuring device can convert its relative movement into the absolute deformations of the tool holder. The data required for this are stored in the EEPROM 18. ⁇ r
• the instantaneous deformation is stored again in the EEPROM 18 as a reference.
• the limit values are transmitted to the motion measuring device.
• the movement measuring device issues a message when the specified limit values are exceeded. It is also possible to query current values with a corresponding command, not only the deformation itself but also the quantities derived from it.
• Fig. 4 the six measuring points A-D have been designated. At these measuring points, for example, the following values were determined according to size and direction, the size of the deformation being given in arbitrarily defined units.
• An elongation is marked with +, a compression with -:
• Embodiment according to FIG. 7 both radial measuring webs 14 'and tangential measuring webs 14' 'are formed at the three circumferential points.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Length Measuring Devices By Optical Means (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

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ID=6313605

Family Applications (1)

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Citations (4)

• 1986
  • 1986-11-10 DE DE19863638338 patent/DE3638338A1/de not_active Withdrawn
• 1987
  • 1987-11-04 EP EP87907221A patent/EP0288523A1/de not_active Withdrawn
  • 1987-11-04 JP JP62506768A patent/JPH01501341A/ja active Pending
  • 1987-11-04 WO PCT/EP1987/000669 patent/WO1988003639A1/de not_active Application Discontinuation
  • 1987-11-04 AU AU81779/87A patent/AU8177987A/en not_active Abandoned
• 1988
  • 1988-06-15 KR KR1019880700677A patent/KR890700232A/ko not_active Application Discontinuation

Patent Citations (4)

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