SU1747875A1 - Optical fiber displacement transducer - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure displacements. The aim of the invention is to improve the accuracy when exposed to destabilizing factors. Rotation of the disk 16 when measuring displacements leads to reciprocating movement of the rods 14 and 15, which is registered by means of two pairs of optical fiber sensors 2 and 3 displacement. The signals from the outputs of the fiber-optic sensors of the electronic unit 20 determine the amount of movement. 2 Il.

Description

The invention relates to a measurement technique and can be used to measure mechanical reversing movements in a wide range.

A displacement sensor is known, which contains a radiation source, a fiber-optic LINR-optical communication, a sensitive element in the form of a half-turn fiber and a photodetector.

The disadvantage of this sensor is its relatively low sensitivity.

A fiber optic displacement sensor is known, comprising a housing, a differentiated sensing element mounted therein in the form of two multi-turn sections of optical fibers optically coupled to corresponding radiation sources and photo-detectors, used in a velocity head meter.

The disadvantage of this sensor is the small range of measured displacements, in the order of units of millimeters.

The closest in technical essence to the present invention is a device for measuring displacements, comprising a housing, a roller mounted in the housing so that it can be rotated around its axis, a rotation angle sensor, kinematically l. entered with a roller, a processing unit, the input of which is connected to the output of a rotation angle sensor.

The specified device has a photoelectric sensor angle of rotation of the roller, made in the form of a disk with a circular diffraction grating. During the rotation of the disk, ultimately, pulses are generated, the number of which is proportional to the angle of rotation of the measuring roller associated with the linear movement of the object. These pulses are counted by an electronic counter.

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This device allows one to measure linear movements of a controlled object in a wide range of movements. However, in the known technical solution, there are high demands on the accuracy of fabrication of the diffraction grating, and, with an increase in the measurement accuracy, the dimensions of the grating also grow.

In the known device, the photoelectric converter comprises an open channel of the photoradiation and the photodetector, which are sensitive to contamination by dust and aerosols. The known technical solution does not allow it to be used in dusty, corrosive, explosive and flammable transients, as well as under the influence of electromagnetic interference, since the electrical elements of the photoelectric converter are directly in the meter. In a known solution, a position is always calculated only from the origin of coordinates. To determine a different position, it is necessary to return the entire system to the origin and start the measurement from there. Positioning when reversing the movement of an object is impossible. In this device, it is not possible to judge the angular position of the roller when it is at rest or moving at low speed. This makes it impossible to introduce corrections for the angular position in the case of an eccentricity of the measuring roller.

These disadvantages can significantly reduce the accuracy of measuring linear displacements.

The purpose of the invention is to improve the accuracy of measuring linear displacements.

This goal is achieved by the fact that in the displacement sensor comprising a housing, a roller mounted in the housing can be rotated around its axis, a rotation angle sensor connected kinematically with a roller, a processing unit whose input is connected to the output of the rotation angle sensor, the rotation angle sensor made in the form of a disc eccentrically bonded to the roller, two rods installed in the housing with the possibility of displacement along the axis of their symmetry so that these axes are perpendicular to each other and the axis of rotation of the roller, two pairs of fiber-optic displacement sensors, each of which is associated with a corresponding rod, the outputs of the fiber-optic sensors in each pair are connected to the corresponding inputs of the processing unit in a differential circuit, and each fiber-optic sensor is made in the form of a fiber light guide with a multi-turn section , a radiator optically coupled to the input end of the optical fiber, and a photodetector optically coupled to the output end of the optical fiber.

A new feature of the present invention is the implementation of a rotation angle sensor in the form of a disk eccentrically bonded to a roller, two rods installed in the housing with the possibility of displacement along the axis of their symmetry so that these axes are perpendicular to each other and the axis of rotation of the roller optical displacement sensors, each of which is associated with a corresponding rod, the outputs of the fiber-optic sensors in each pair are connected to the corresponding inputs of the processing unit in a differential circuit, and each fiber The o-optical sensor is made in the form of an optical fiber with a multi-turn section, an emitter optically coupled to the input end of the optical fiber, and a photodetector optically coupled to the output end of the optical fiber.

And it is precisely this device performance that ensures the achievement of a positive effect - an increase in the accuracy of movement measurement.

FIG. Figure 1 shows the simplified design of the proposed sensor; in fig. 2 shows the geometry of the mutual arrangement of the component parts of the angle sensor.

The sensor (Fig. 1) contains a housing 1 in which two pairs of fiber-optic displacement sensors 2 and 3 are placed. Each of them is made in the form of multi-turn sections of optical fibers 4 and 5, which optically interconnect the respective emitters

6,8, 10 and 12 and photodetectors 7, 9, 11 and 13. Both multi-turn sections 4 and 5 of displacement sensors 2 and 3 are mechanically coupled with spring-loaded rods 14 and 15. placed perpendicular to each other and both perpendicular to the eccentric axis The disk 16. The disk 1 is fixed on the same axis with the roller 17, which is in contact with the surface 18 of the object being monitored. Emitters 6, 8, 10 and 12, as well as photodetectors

7.9, 11 and 13 are electrically connected to the input of the conversion unit 19, and the output of the flea 19 is informationally connected to the input of the processing unit 20, which calculates the current position of the sensor. The rods 14 and 15 are equipped with springs 21 to eliminate the backlash. The disk 16 is made in the form of a cylindrical cam eccentrically fixed on the axis of rotation of the roller 17. The electronic conversion unit 19 contains the power of the emitters and an amplifier that performs large-scale conversion of signals from the pair of differentially-activated photoreceivers 7 and 9, 11 and 13 for matching them with the input of the processing unit 20, which is intended to perform mathematical operations in order to obtain information about the measured movement by corresponding In the initial state, when there is no movement of the sensor body 1 relative to the surface 18, the rods 14 and 15 are stationary. The degree of deformation of the turns of the sections of the optical fibers 4 and 5 does not change, their light transmission remains constant, and the signals from the outputs of the photodetectors 7. 9, 11, 13 remain unchanged. In the processing unit 20, the initial value of the initial coordinate of the sensor is fixed.

The movement sensor operates as follows.

When the sensor body 1 moves relative to the surface 18, the roller 17 rolls along the surface 18 without sliding, converting the linear movement of the body 1 into the rotational movement of the disk 16. The rotation of the disk 16 leads to reciprocating movement of the rods 14 and 15, which receive the ends with a spring 21 are pressed against the surface of the disk 16.

The reciprocating movement of the rods 14 and 15 causes a periodic alternating deformation of the turns of the sections of the optical fibers 4 and 5 of the displacement sensors 2 and 3, which leads to a corresponding change in the light transmission of the latter and to a change in the differential signal at the output of the photodetectors 7 and 9, 11 and 13. The selected location and design of the displacement sensors 2 and 3 ensure that the signals from the output of the conversion electronic unit 19, when linearly moving the housing 1 relative to the surface 18, represent the voltage These values vary according to the law of sine and cosine depending on the movement of the rods 14 and 15, respectively.

The processing unit 20 converts the electrical signals from the output of the block 19 to the coordinate of the current position of the sensor housing 1 relative to the surface 18.

The perpendicular arrangement of the displacement sensors 2 and 3 relative to each other and perpendicular to the axis of the disk 16 allows measuring the magnitude of the displacement and determining the direction of the displacement.

To clarify the principle of operation of the motion sensor, we obtain its conversion function (Fig. 2).

A roller 17 of radius R without sliding rolls along the surface 18. A disk 16 is fixed on the same axis O with the roller 17. The displacement (eccentricity) of the axis of rotation of the disk relative to its geometric axis 0 is a, and the radius of disk 16 is RL

The point of contact between the disk 16 and the receiving end of the rod 15 is denoted by A, the distance from the end of the axis OX-hy. and the angle between the OO and OX through p0. Then: + a. .

When the roller 17 is moved to the right from the position Si to the position Zg by a small distance A, the roller 17 will turn clockwise at a small angle. herewith, the receiving end of the rod 15 is moved to a small height A hy. Magnitude

AAI oAt

2jrTT W rad. Then the value Ahy is determined by the expression:

Any a (sin ((pQ + Ay) -sin p0) 2a-sln

А (2 р0 + Dos) Duz-cos,

For the stem 14, located perpendicular to the stem 15, the distance from the end to the axis Oy we denote h Then,

hx Ri-a cos (p0

And a small change in this distance A hx when moving roller 17 from position Si to position S will be:

Ahx -a (cos (po +) -cos) 2a. sin {ysln

If we now take the ratio of A p to A hx, then we get:

Ahy / A hx tg ();

Without loss of generality, we can assume that in the initial state p0 0, then we have:

A hy / A hx;

From here we get the expression for the small displacement D1:

A 2Rarctg (1)

Thus, the small displacement And I of the housing 1. relative to the surface 18 can be measured by recalculating the small displacements of the rods 14 and 15 according to the formula (1).

It can be assumed that to measure the displacement, D | it is sufficient to measure the movement of one of the rods 14 and 15 (only A They or only Ahy). However, since in the region of maxima (minima) of the functions sin p or cos p, changing the argument p to + Dy leads to a change in the function of one sign, this makes it impossible to determine the direction of movement of housing 1 or the increment sign A.

The calculation of the arc tangent allows the direction and magnitude of the displacement vector to be determined.

Large movements AL are calculated by the accumulator, integrating (digital or analog) small movements D1.

AL LO + j Ah.

i 1.

(2)

Or

when exposed to electrical interference, since the radiation source, photodetectors and electronic circuit are completely removed from the converter at

The length of optical fiber lines that can reach several hundred meters. In this device, it is possible to determine the position of a controlled object for any, including reversible,

moving the object. This device allows you to continuously determine the current angular positions of the measuring roller, also in the case when the roller is stationary, which is essential for the introduction of trigger points to angular positions in the case of an eccentricity of the measuring roller.

Thus, the proposed sensor avoids a decrease in the accuracy of the measurement of movement.

In the implemented sensor layout, the range of motion measurement from 0 to 400 mm was obtained with an error not exceeding 1%.

tn

(2a)

AL U + / Ai (t) dt, tu

where Lo is the initial, initial value of the position of the sensor housing 1 relative to the surface 18;

n is the number of counts of elementary displacements Ah;

to - the initial moment of time;

tn is the instant of the sensor position reference time.

Thus, having a linear dependence of the voltage at the output of the conversion unit 19 on the position of the sensing ends of the perpendicularly located rods 14 and 15, the processing coordinates of the position of the sensor body 1 relative to the surface 18, i.e. measured displacement.

A comparative analysis of the proposed solution and the known one allows us to reveal the following advantages of the proposed one.

In the proposed solution, there is no expensive and difficult to manufacture infraction lattice. In addition, the optical channels of the fiber optic converter are completely isolated from the environment.

The proposed device can be used in dusty, aggressive explosive and fire hazardous environments, as well as

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Claims (1)

Invention Formula Fiber optic displacement sensor, comprising a housing, a roller mounted in the housing with the possibility of rotation around its axis, a rotation angle sensor, kinematically associated with a roller, is a processing unit whose input is connected to the output of a rotation angle sensor, characterized in that, in order to increase accuracy. The rotation angle sensor is made in the form of a disk, eccentrically bonded to the roller, of two rods installed in the housing with the possibility of displacement along the axis of their symmetry so that these axes are perpendicular to each other. a friend and roller rotation axis, two pairs of fiber-optic displacement sensors, each of which is associated with a corresponding rod, the outputs of the fiber-optic sensors in each pair are connected to the corresponding inputs of the processing unit in a differential circuit, and each fiber-optic sensor fiber with multi-turn section, emitter, optically coupled to the input end of the optical fiber; and a photodetector optically coupled to the output end of the optical fiber. 777/7 // 7/7 / G7 / 7F // 7/77777 / t / U /, g //////// 17 W 18 14 21 Fig. /