RU2335736C2 - Reflex photoelectric angular displacement control system - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: reflex photoelectric angular displacement control system contains two light sources, reflector in the form of mirror plate with two opposite reflecting surfaces and fixed on torsion suspension, two-way electric circuit including two photodetectors, two amplifiers and matching computing unit. Light sources are mounted so that beams lie in plane perpendicular to torsion suspension rotation axis, move to reflector along the same straight line in reverse direction. And reflected beams lie in the same plane and move to associated photodetectors photodetecting planes of which are mutually parallel. Photodetectors generate voltage proportional to beam displacement on their photodetecting planes supplied to matching computing unit generating voltage proportional to difference of two voltages.

EFFECT: higher control accuracy of system angular displacement and vibration resistance, and extended applicability of proposed device.

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Description

The invention relates to instrumentation, recording equipment of electrical and non-electrical quantities and can be used in optical systems of torsion pendulums of various types, torsion scales, including precision (see, for example: Postnikov BC, Ammer S.A., Belyaev AM Internal Friction, Shear Modulus, and Strength of Copper Whiskers // Physics of Metals and Metallurgy, Volume 19, Issue 2, 1965, pp. 268-273).

The invention can also be used in various types of galvanometers when registering electrical and non-electrical quantities to increase the vibration stability of devices.

Known optical measuring device, which is part of a torsion balance (Laboratory workshop on physics // Edited by A.S. Akhmatova. - M .: Higher school., 1980, 360 S. Figure 27 on page 53), containing a torsion wire, a mirror mounted on a twisting wire, light source, linear one-dimensional scale. The value of the twist angle of the twist wire in this device is determined by the translational displacements of the light "bunny" on the scale. The light "bunny" is formed by the reflection of a ray of light (light source) from a mirror (Laboratory practical work in physics // Edited by A.S. Akhmatov. - M.: Higher school., 1980, 360 pp. See p. 54, second and third paragraphs).

However, the indicated optical measuring device has the disadvantage that not only angular displacements (rotations) of the twisting wire, but also translational displacements of the wire together with the mirror in the horizontal plane can lead to displacements of the “bunny” on the scale of the device. In fact, in this device it is impossible to separate the angular and translational displacements of the mirror on the wire. This leads to an increase in errors in measuring the angle of rotation. Also, this device is poorly protected from vibration interference. The authors indicate the only method of combating vibration interference: "... the wire should be slightly stretched ...". The authors note that “This sufficiently avoids the torsional body oscillations from side to side”, indirectly indicating the presence of problems in the fight against vibration interference in this device (Laboratory Workshop on Physics // Edited by A.S. Akhmatov - M .: Higher school, 1980, 360 pp. See p. 53). Weak immunity to vibration interference leads to limitations in the use of this device.

Known optical reading device, which is part of a common measuring mechanism of electrical measuring instruments (Analog electrical measuring instruments // E.G. Bishard, E.A. Kiseleva, G.P. Lebedev and others - 2nd ed. Revised and add. - M .: Higher school, 1991, 415 pp. Figures: 4.4 (c) on page 67; 4.6 (d) on page 72) containing a light source, an optical system that forms a long beam of light, a mirror, fixed on a thin bronze ribbon (with a moving part), a mechanical scale. The value of the twist angle of a thin bronze ribbon (with a moving part) in this device is determined by the translational displacements of the light "spot with index" on the scale of the device. According to the readings on the scale of the device determine the measured electrical quantity. The scale of the device can be calibrated directly in the appropriate units of measurement of electrical quantities.

However, the indicated optical reading device has the disadvantage that not only the angular displacements (rotations) of the thin bronze tape (with the moving part), but also the translational displacements of the thin bronze tape (with the moving part) in the horizontal and vertical planes. In fact, in this device it is impossible to separate the angular and translational displacements of a mirror mounted on a thin bronze ribbon. This leads to an increase in measurement errors and, consequently, to a decrease in the measurement accuracy of the corresponding electrical quantity.

Also, this device is poorly protected from vibration interference. In the literature describing similar measuring mechanisms (Fundamentals of Metrology and Electrical Measurements // Edited by E.M. Dushin. - 6th ed. Revised and enlarged. - L .: Energoatomizdat, 1987, - 480 p. See page .122, Fig. 5-13), indicate the easiest way to protect against "mechanical shocks": installing the device "on a solid wall". This limits the applicability of this device.

The closest in technical essence to the claimed technical solution is an optical reading device (prototype) of a vibration-stable P.Doll system (Meyer E., Merder K. Mirror galvanometers and devices with a light indicator. - M. and L .: Gosenergoizdat, 1959, 568 p. See p. 497, Fig. 59-5), containing the light source, two separate frames (moving part), each with its own mirror, recording the tape. The entire system is immersed in liquid so that the angle between the mirrors remains constant. To compensate for the rotational accelerations around the axis of rotation of the system, the property of the light ray is used in sequential reflection from two mirrors not to change the direction of the ray "after turning them as a single system by a certain angle." The process is recorded simultaneously by two systems that are identical in their mechanical, electrical and optical properties. According to P.Doll, systems are used in two versions: 1) current is passed through only one system, while the second is used only as compensation; 2) current flows through both systems and deflects them in opposite directions.

However, this optical reading device has the disadvantage that both angular displacements (rotations) of the frame and translational displacements lead to displacements of the light beam on the recording tape. Moreover, since there are two mirrors, on two different suspensions and frames, the amount of displacement will depend on the uncontrolled displacement of each mirror in both the first version and the second version. In fact, in this device it is impossible to separate the angular and translational displacements of the mirrors. This leads to an increase in errors in measuring the angle of rotation of the frame and, as a consequence, to a decrease in the accuracy of measurement of the corresponding electrical quantity.

The use of fluid partially increases the vibration resistance of the system, but at the same time leads to an increase in the mass and moment of inertia of the moving part, both for one frame and for another. This also leads to an increase in measurement errors.

The use of two systems at the same time by P. Dollem leads to the fact that vibrations affect both one and the other system, reducing the vibration resistance of the device. This limits the applicability of this device.

The technical result of the invention: improving the accuracy of control of angular displacements, increasing the vibration resistance of the system, expanding the application of the proposed device.

The specified technical result is achieved by the fact that the proposed device contains two light sources, a reflector mounted on a torsion suspension, an indicator, and the reflector is made in the form of a mirror plate with two opposite reflective surfaces and is oriented with respect to the light rays so that the rays lie in a plane, perpendicular to the axis of rotation of the torsion suspension, and two photodetectors, two amplifiers and a matching one are additionally included in the two-channel electrical circuit of each reflective surface calculation block.

Compared with the closest similar solution (prototype), the claimed technical solution has the following distinctive features:

- the reflector is made in the form of a mirror plate with two opposite reflective surfaces;

- the reflector is oriented with respect to the rays of light so that the rays lie in a plane perpendicular to the axis of rotation of the torsion suspension;

- two photodetectors, two amplifiers and a matching computing unit are additionally included in the two-channel electrical circuit of each reflective surface.

Therefore, the claimed technical solution meets the requirement of "novelty."

Using the reflector in the proposed device in the form of a mirror plate with two opposite reflecting surfaces onto which light beams fall, two photodetectors, two amplifiers and a matching computing unit that generates a difference electric signal proportional to the angular displacement of the system, allows you to separate the translational and angular displacements of the reflector ( consequently, of the entire system associated with it), to control the actual angular displacements of the system and, ultimately, to increase the accuracy l measuring angular displacements, increase the vibration resistance of the entire system, expand the capabilities of the device.

Therefore, the claimed technical solution meets the requirement of "positive effect".

In the claimed technical solution, the shape of the reflector, its orientation with respect to the incident light rays, the formation of the reflected rays using two photodetectors, two amplifiers of two photo signals and the receipt in the matching computing unit of a voltage proportional to the difference of the two photo signals leads to an unexpected effect - the final voltage applied to indicator proportional only to the angle of rotation of the mirror reflector together with the system. A separation (separate effect) of translational and angular displacements of the reflector is achieved. Thus, the influence of translational displacements of the reflector on the readings of the device is excluded.

Analysis of existing technical solutions showed that the listed features are absent in these solutions.

Therefore, the listed distinguishing features ensure compliance of the claimed technical solution to the requirement of "significant differences".

Figure 1 shows a mirror photoelectric device for controlling angular displacements; figure 2 illustrates the offset of the reflected light rays on the photodetector planes FP1 and FP2 with translational displacements of the reflector in the horizontal plane along the axis OX; figure 3 illustrates the offset of the reflected light rays on the photodetector planes FP1 and FP2 at translational displacements of the reflector in the horizontal plane along the axis OY; figure 4 illustrates the nature of the displacement of the reflected light rays on the photodetector planes FP1 and FP2 with angular rotation of the reflector around a vertical axis passing through point O.

The mirror photoelectric device for controlling angular displacements shown in Fig. 1 contains a reflector 1, two light sources Is1 and Is2, two photodetectors (for example, single-axis) 2 and 3, two amplifiers 4, matching computing unit 5, indicator 6.

The mirror reflector 1 represents the fastened two opposite reflecting mirror planes Z1 and Z2. The mirror reflector 1 is mounted on a twisting thread 7, to which a torque of forces M is applied. The twisting thread 7 can be of a wire type (metal wire) in a torsion pendulum, it can be an object of study, for example, a whisker, it can be a suspension with a frame in the magnetic field of a galvanometer or any similar system experiencing angular displacements (turns). The light source Is1 is located so that the light beam from it falls on the reflecting surface Z1 and, being reflected, falls on the photodetector 2. The light source Is1 is located so that the light beam from it falls on the reflecting surface З2 and, being reflected, is incident on the photodetector 3. Beam1 and beam2, the lines of the photodetectors lie in the same XOY plane (usually a horizontal plane) perpendicular to the torsional filament 7. The photodetector planes of the photodetectors 2 and 3 are parallel to each other and are oriented along the same OY axis, as shown in Fig. 1.

The purpose of the matching computing unit 5 is to generate a differential electric signal ΔU from the amplified signals U ₁ and U ₂ introduced into it from photodetectors 2 and 3.

The purpose of indicator 6 is to register values proportional to the angle of rotation of the system associated with the torsional thread 7. As an indicator, electrical measuring instruments, an oscilloscope, a loop oscilloscope, a recorder, etc. can be used.

The device operates as follows.

Beam 1 from the light source Is1 is directed in the XOY plane (usually a horizontal plane) to the reflecting surface Z1 of the reflector 1. The reflected beam 1 then hits the photodetector plane of the photodetector 2. At the same time, beam 2 from the light source Is2 is sent to the plane XOY (usually a horizontal plane ) on the reflecting surface Z2 of the reflector 1. The reflected beam 2 then hits the photodetector plane of the photodetector 3. In the absence of movement of the reflector 1, the electrical signals from the photodetectors are equal to zero. When the reflector 1 moves at angular or translational displacements of the filament 7, the reflected rays are displaced respectively on the photodetector planes of the photodetectors 2 and 3. Photodetectors generate voltages U ₁ (expression (1)) and U ₂ (expression (2)), respectively, which are supplied to amplifiers 4 The amplified signals U ' ₁ and U' ₂ are supplied to a matching computing unit 5 in which a signal ΔU is generated proportional to the voltage difference U ₁ and U ₂ (expressions (3) and (4)). The voltage ΔU is supplied to indicator 6, in which the angular displacement of the system associated with the thread 7, or any other value associated with the rotation angle of the thread 7, is recorded. Indicator 6 can be calibrated directly in units of the measured value.

In the proposed device to achieve the declared technical result, first of all, special properties of the behavior of two reflected rays from a mirror plate with two opposite reflecting surfaces are used: when translational displacements of the mirror plate in the horizontal plane, the reflected rays, the first and second, on the photodetector planes experience the same displacements sign (same directions) and the same size; at angular displacements (rotations) of the same mirror plate around the vertical axis, the reflected rays on photodetector planes experience displacements of different signs (different directions).

Therefore, when subtracting photosignals from reflected rays from photodetectors, the difference signal is proportional only to the magnitude of the angular displacement of the mirror plate, and therefore to the angular displacements of the entire torsion system or suspension system, for example, together with the frame.

Figure 2 presents one of the possible cases of displacement of the rays, when the beam 1 from the light source Is1 and the beam 2 from the light source Is2 go towards each other in a straight line, and the angles of incidence on the mirror plate Zn (reflector 1 from figure 1) of the rays equal to 45 °. Beam 1 is reflected from the mirror surface Z1 of the mirror plate Zn and propagates along the axis OX of the horizontal plane. The reflected beam 1 falls on the photodetector plane Фп1 (photodetector 2 of FIG. 1) and can move along the axis OY of the horizontal plane. Beam 2 is reflected from the opposite mirror surface 32 of the mirror plate Zn and propagates against the axis OX in the same horizontal plane. The reflected beam 2 falls on the photodetector plane Фп2 (photodetector 3 from Fig. 1) and can move along the axis OY of the horizontal plane.

The suspension line is vertical, passes through point O and is perpendicular to the plane of the picture (horizontal plane) of FIG. 2.

With translational displacements of the mirror plate Zn along or against the axis OX in the horizontal plane during vibrations, the mirror plate occupies new positions, characterized by points O 'or O''. The bias value ΔX, and beam 1 and beam 2 are shifted along the OY axis by the same amount (dashed lines in figure 2) and the photodetectors produce the same, both in magnitude and sign of voltage, U _x1 and U _x2 , proportional to the bias value ΔX. In Fig.2, the magnitude of the displacement of the rays along the OY axis is represented (calibrated) directly in units of the generated voltage.

Figure 3, similarly to figure 2, presents the case of displacements of the reflected rays (beam 1 and beam 2) on the photodetector planes Фп1 and Фп2 along the axis OY with translational displacements of the mirror plate Зп in the horizontal plane along the other axis - the axis OY.

The suspension line is vertical, passes through point O and is perpendicular to the plane of the picture (horizontal plane) of FIG. 3.

With translational displacements of the mirror plate Zn along or against the OY axis in the horizontal plane during vibrations, the mirror plate occupies new positions characterized by points O 'or O. The displacement ΔY, while beam 1 or beam 2 are shifted along the OY axis by the same amount ( the dotted lines in Figure 3) and photodetectors generate the same both in magnitude and in sign to the voltage U U _y1 and _y2 proportional displacement ΔY. 2, the quantity of rays displaced along OY axis represents (calibrate) directly expressed in units atyvaemogo voltage.

Any arbitrary translational displacements of the mirror plate Zn during vibrations in the horizontal plane can be represented (expanded) as the sum of two independent translational displacements along the axes OX and OY. Therefore, the photodetectors of the corresponding photodetector planes Фп1 and Фп2 will generate voltages equal to the sum of the voltages proportional to the displacements of the mirror plate along the OX and OY axes, i.e. ΔX and ΔY. These voltages, as can be seen from figure 2 and figure 3, are the same in magnitude and have the same signs.

Figure 4 presents the case of the displacement of the reflected rays 1 and 2 from the reflecting planes Z1 and Z2 of the mirror plate Зп only when turning (angular displacements) of the entire system around a vertical axis (suspension line) passing through point O and perpendicular to the plane of the picture (horizontal plane ) figure 4. When the entire system is rotated through an angle α, the mirror plate Зп rotates through an angle α (thick dashed line in FIG. 4), and the reflected rays (dashed lines in FIG. 4), in accordance with well-known laws of geometric optics, rotate in a horizontal plane by an angle 2α. As can be seen from figure 4, the reflected beam 1, beam 2 are displaced along the photodetector planes FP1 and FP2 by the same amount, but these are displacements of different signs. Therefore, the photodetectors in this case generate the same voltage (modulus) voltage U _α1 and U _α2 , but of different signs. In Fig.4, the magnitude of the displacement of the rays along the OY axis is represented (calibrated) directly in units of the generated voltage.

In the proposed device, according to the value of the angle of rotation α, caused precisely by the angular displacements of the entire system, any value associated with the angle of rotation α can be measured. In torsion scales, torsion pendulums it can be, for example, the moment of torsion forces, the magnitude of internal friction. In galvanometers, these can be electrical quantities (current, voltage), causing the frame to rotate, for example, on a suspension in a magnetic field.

From figure 4 it follows that the stresses U _α1 and U _{α2 are} proportional to the value (tg2α) · l. At small rotation angles, as is usually observed, the voltages U _α1 and U _{α2 are} proportional to (2α) · l (where l is the distance from the reflector axis to the photodetector plane of the device, the so-called "optical beam arm").

Summarizing the results of the description of FIG. 2, FIG. 3, FIG. 4, it can be concluded that, with the necessary rotations of the entire system, the translational vibration displacements, which are random in nature, contribute to the voltage value from the photodetectors. The resulting voltage from the photodetectors 2 and 3 (see figure 1) have the form

where U ₁ is the voltage from the output of the photodetector 2 (see figure 1).

where U ₂ is the voltage from the output of the photodetector 3 (see figure 1).

As can be seen from the figures of figure 2 and figure 3, U _x1 = U _x2 ; U _y1 = U _y2 . As can be seen from the figure of FIG. 4, | U _α1 | = | U _α2 |, i.e. are equal in absolute value but have different signs, i.e. U _α1 = -U _α2 .

If voltages U ₁ and U _{2 are} applied to a computing unit in which only two signals are subtracted (such blocks, electrical circuits are well known), then the resulting voltage ΔU equal to

The value of ΔU is equal to (proportional): ΔU ~ 2 · (tg2α) · l.

.At small rotation angles of the entire system:

.

This voltage is recorded by indicator 6 (see figure 1), allowing you to determine both the angle of rotation of the entire system, and any necessary value associated with the angle of rotation of the entire system.

Analytical expressions (1) - (4) emphasize that in the proposed device, on the one hand, the translational and angular displacements are separated, and, on the other hand, only the angular displacements of the entire system are distinguished, for example, on a suspension.

Thus, in this device, the influence of vibration disturbances associated with random translational displacements of the reflector (as well as the entire system) in the horizontal plane is eliminated. This increases the vibration resistance of the entire system, the accuracy of measuring the magnitude of the angular displacement.

Separation of translational and angular displacements provides another opportunity to control vibration displacements.

If it is necessary to isolate precisely the translational displacements of the reflector, then this can be done by summing the signals from photodetectors 2 and 3 (see Fig. 1). As follows from expressions (1) and (2), when summing the stresses U ₁ and U _{2, the} resulting voltage is proportional to the sum of the displacements of the system along the OX and OY axes of the horizontal plane. In this case, the influence of angular displacements and so-called rotational accelerations around the axis of the system is excluded.

In Fig. 2, Fig. 3, Fig. 4, the mirror plate Zn has a zero thickness, i.e. mirror reflective surfaces Z1 and Z2 are adjacent to each other from opposite sides. However, the reflector may have a finite thickness other than zero. This thickness value can be taken into account on the photodetector planes Фп1 and Фп2 by shifting the reference point by a value corresponding to the thickness. The calculated relations (1) - (4) will remain unchanged.

The angles of incidence of the rays can differ from 45 ° and even be different for beam 1 and beam 2, since the effect of separation of translational and angular displacements of the reflector in the proposed device is due primarily to the fact that the reflected rays are displaced in the same direction with translational displacements of the system , and at angular displacements (turns) they are displaced in opposite directions. In this case, the calculated ratios will become somewhat more complicated, but the calculation scheme based on the laws of geometric optics will remain the same and, ultimately, the device detects the angular displacement of the reflector by the difference of the two signals from the photodetectors or extracts translational displacements of the reflector by the sum of the two signals from the photodetectors .

Well-known optical systems that increase the optical arm (length) of the reflected beam can also be used in this device. As can be seen from expression (4), in the proposed device, in fact, the optical arm increases by 2 times, which increases the accuracy of measuring the magnitude of the angular displacement.

The use of a reflector in the proposed device in the form of a mirror plate with two opposite reflecting surfaces, its orientation with respect to incident light beams, the use of two photodetectors, two amplifiers, a matching computing unit that generates a difference electric signal proportional to the angular displacement of the system, allows, firstly, to separate the angular and translational displacements of the system into threads, and secondly, to control the actual angular displacements of the system. Therefore, this device allows to achieve the declared technical result: to increase the accuracy of control of angular displacements, to increase the vibration resistance of the device and, therefore, to expand the possibilities of its application.

Claims (1)

A mirror photoelectric device for controlling angular displacements, containing two light sources, a reflector made in the form of a mirror plate with two opposite reflecting surfaces and mounted on a torsion suspension oriented with respect to the light rays so that the rays lie in a plane perpendicular to the axis of rotation of the torsion suspension , a two-channel electrical circuit comprising two photodetectors, two amplifiers and a matching computing unit, characterized in that the light sources are installed so that the rays go to the reflector in a straight line in the opposite direction, and the reflected rays lie in the same plane and fall on the corresponding photodetectors, the photodetector planes of which are oriented parallel to each other, and the photodetectors generate voltages proportional to the displacement of the rays on their photodetector planes, which amplify in amplifiers and served on the matching computing unit, forming a voltage proportional to the difference between the two voltages, which is fed to the indicator.

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