JP3118058B2 - Speed detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting the number of revolutions of a rotating body, and more particularly to an apparatus capable of contactlessly detecting the number of revolutions of a rotating body flying while rotating in the air.

[0002]

2. Description of the Related Art FIGS. 4 and 5 conceptually show a conventional rotational speed detecting system. As shown in FIG. 4, an encoder 21 is attached to a rotating shaft 20a of a rotating body 20 such as a motor, and an output signal of the encoder 21 is input to a computer 22 via a wire. The computer 22 detects the number of rotations (rotational speed) of the rotating body 20 by calculating the input signal.

As shown in FIG. 5, a variable resistor 24 is mounted on a rotating shaft 23a of a rotating body 23. Then, a voltage is applied from a predetermined power supply 25 to the variable resistor 24 via a wire, a change in the resistor 24 is converted into a voltage, and this is output to the frequency counter 26 via the wire. Frequency counter 26
Detects the number of rotations of the rotating body 23 based on the frequency at which the voltage changes.

[0004] In the case of a long distance, an electric signal can be transmitted wirelessly by a telemeter or the like instead of a wire.

[0005]

As described above, in the conventional detection system, a sensor such as an encoder for directly detecting the rotation of the rotating shaft must be attached to the rotating body. Moreover, it is necessary to send the detection signal of this sensor to the computer 22 or the like via a wire or wirelessly. Therefore, 1) a rotating body having no space for mounting a sensor for directly detecting rotation such as an encoder, or a rotating body having a structure in which rotation cannot be detected by these sensors in the first place; 2) a wire is connected to fly in the air. In the case of a rotating body whose mechanical resistance cannot be ignored, 3) In the case of a rotating body where a transmitter such as a telemeter cannot be mounted due to induction disturbance by radio waves, the conventional detection system should be applied as it is. Therefore, it was not possible to detect the rotation speed of the rotating body.

The present invention has been made in view of such a situation, and reliably detects the number of rotations even in a rotating body in which the conventional detection system as described in 1) to 3) above is difficult to apply. It is an object of the present invention to provide a rotational speed detecting device capable of detecting a rotational speed.

[0007]

Accordingly, in the present invention,
In a rotation speed detection device that detects the rotation speed of a rotating body that rotates around a predetermined axis, the rotation speed detection device has a rotatable polarization element that polarizes light, and by rotating the polarization element, the polarization plane of the light First polarizing means for rotating at a rotation speed and projecting light in the axial direction of the rotating body; and second polarizing means provided on the rotating body and polarizing light projected from the first polarizing means. A reflecting unit provided on the rotating body, for reflecting light polarized by the second polarizing unit; a frequency detecting unit for detecting a frequency of a change in intensity of the light reflected by the reflecting unit; Calculating means for calculating the number of revolutions of the rotating body based on the number of revolutions of the surface and the frequency detected by the frequency detecting means.

[0008]

The light polarized by the first polarizing means is polarized by the second polarizing means of the rotator. At this time, the angle formed by the polarization plane of the light by the second polarization unit with respect to the polarization plane of the light by the first polarization unit changes according to the rotation of the rotating body. Then, the light intensity of the reflected light changes according to the angle formed by these two polarization planes. That is, when the polarization planes are parallel to each other, the intensity of the reflected light is maximized, and when the polarization planes are orthogonal, the intensity of the reflected light is minimized. Therefore, the rotation speed of the rotating body is detected by detecting the frequency of the intensity change of the reflected light.

Here, it is only necessary to attach a second polarizing means for polarizing the projected light and a reflecting means for reflecting the light polarized by the second polarizing means to the rotating body. For example, since a sensor for directly detecting rotation is not attached, a mounting space can be reduced, and the present invention can be applied to a rotating body having a structure in which rotation of a shaft cannot be directly detected.

Further, since the number of rotations of the rotating body can be detected by projecting and reflecting light, even a rotating body which flies in the air or a rotating body which may cause an induction trouble due to radio waves can be accurately obtained. The number of rotations can be detected.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a rotational speed detecting device according to the present invention; FIG. 1 is a diagram showing the overall configuration of the embodiment apparatus.

As shown in FIG. 1, the apparatus according to the embodiment includes a ground apparatus 1 disposed on the ground and a rotating body 11 to be detected. Here, the rotating body 11
For example, a shell that flies in the air while rotating around a predetermined axis C is assumed. This is because the performance of the shell, such as ballistic flight motion, differs depending on the number of revolutions around the axis C, and therefore, detecting the number of revolutions is significant. Unlike a motor or the like, the shell has a structure in which the shaft rotates relative to the main body.
Rotation cannot be detected, and there is no room for mounting them. In addition, a transmitter such as a telemeter cannot be used because there is a possibility that an induction trouble may occur due to radio waves. Therefore, the rotation speed is detected in a non-contact manner without using a sensor such as an encoder or using a transmitter such as a telemeter.

That is, a laser beam L having a predetermined frequency is oscillated from the laser oscillator 2 of the ground apparatus 1 and applied to the beam expander 3. In this beam expander 3, the spread angle of the laser light L is adjusted. This divergence angle, even when the rotating body 11 is moving at high speed,
The size is adjusted so that the reflector 13 of the rotating body 11 described below is irradiated with the laser beam L.

Then, the laser beam L beam expanded by the beam expander 3 is applied to a polarization plane rotating unit 4. In the polarization plane rotation unit 4, the laser light L is polarized, and the polarization plane is rotated at a predetermined rotation number F (Hz). For example, the laser light L is polarized by a polarization element such as a polarization filter, and the polarization plane is rotated by rotating the polarization element. The rotation number F of the polarization plane is detected by a sensor (not shown), and a detection signal is sent to the computer 9.

The polarized laser light L is applied to the converging mirror 5 with an off-axis hole, passes through the hole 5a, and projects the optical axis of the laser light L toward the reflector 13 of the rotating body 11. .
In addition, the ground apparatus 1 has a theodolite 10 for adjusting the projection direction of the laser light L. This theodolite 10 is manually
Alternatively, the horizontal azimuth and the elevation angle of the laser beam L are adjusted by operating automatically, and the laser beam L is
Irradiate the reflector 13.

On the other hand, the rotating body 11 is provided with a polarizing filter 12 for polarizing the laser light L incident on the reflector 13. A reflector 13 that reflects only the polarized light component transmitted through the polarizing filter 12 is provided.
As the reflector 13, a corner cube, a retroreflector or the like can be used, and the incident light L is reflected in the same direction as the incident direction. As a result, the reflected light L 'always returns to the ground apparatus 1. When the projected laser light L is a point light source (a light source having a spread angle), the size of the reflected light L' is reflected by the ground apparatus 1. The size is twice as large as when the light enters the vessel 13. The reflected laser light L ′ is condensed by the converging mirror 5 having an off-axis hole and passes through the interference filter 6.
In the interference filter 6, components other than the signal wavelength in the reflected light L ′ are cut, and this is input to the sensor 7. Sensor 7
Then, the frequency f (Hz) of the intensity change of the transmitted laser light L '
Is detected. This detection signal is amplified by the amplifier 8 and input to the computer 9. In the computer 9, the rotation speed X (Hz) of the rotating body 11 is determined based on the rotation speed F of the polarization plane input from the polarization plane rotation unit 4 and the frequency f of the intensity change of the laser light L ′ input from the amplifier 8. Is calculated.

Here, the contents of the arithmetic processing performed by the computer 9 will be described.

FIG. 2 shows the relationship between the frequency f of the intensity change of the reflected laser light L ′ detected by the sensor 7 and the number of rotations X of the rotating body 11 using the polarization plane rotation unit 4 for the polarization plane of the projection laser light L. Are not rotated.

The intensity of the reflected laser beam L 'is maximum when the plane of polarization of the polarization filter 12 is parallel to the plane of polarization set at a predetermined angle by the plane-of-polarization rotator 4 in accordance with the rotation of the rotator 11. Become. Further, when the two polarization planes are orthogonal to each other in accordance with the rotation of the rotator 11, the intensity of the reflected laser beam L 'becomes minimum. Since the change between the “maximum” and the “minimum” gradually changes, the intensity change of the reflected laser light L ′ becomes a sine wave as shown in FIG. Here, since the angle of the polarization plane set by the polarization plane rotation unit 4 is fixed, the polarization filter 12 of the rotator 11 is
The plane of polarization by “” repeats “parallel” and “orthogonal” every time the rotation angle of the rotating body 11 changes by 90 degrees. Therefore, the intensity of the reflected laser light L ′ repeats “maximum” and “minimum” every 90-degree rotation of the rotating body 11. Therefore, when the cycle of one rotation of the rotating body 11 is T, the cycle of the intensity change of the reflected laser beam L 'is half the cycle T / 2, and the rotation speed X of the rotating body 11 and the intensity of the reflected laser beam L' The relationship f = 2X (1) is established with the change frequency f (see FIGS. 2A and 2B).

Therefore, when the polarization plane of the projection laser light L is not rotated by the polarization plane rotation unit 4, the rotator 1 is obtained from the above equation (1) based on the frequency f detected by the sensor 7.
The rotation speed X of 1 can be calculated and detected.

Conversely, the same applies to the case where the rotating body 11 is not rotating, and the case where the projection laser light L is being rotated by the polarization plane rotating unit 4. The relationship f = 2F (2) holds between the frequency f of the intensity change of 'and the rotation number F of the polarization plane by the polarization plane rotation unit 4.

Therefore, when the polarization plane of the projection laser beam L is rotated by the rotation plane F by the polarization plane rotation unit 4, and the rotator 11 is rotated by the rotation number X in the same direction as the polarization plane rotation unit 4. In this case, f <2F, and the relationship obtained by superimposing the above equations (1) and (2) holds: f = 2F−2X (3). Therefore, from the above equation, the rotation speed X of the rotation pair 11 is as follows: X = (2F−f) / 2 (where f <2F) (4)

When the rotating body 11 is rotating in the direction opposite to that of the changing surface rotating unit 4 at the rotation speed X, f> 2F, and the relation obtained by superposing the above equations (1) and (2) is obtained. , F = 2F + 2X (5). Therefore, from the above equation, the rotation speed X of the rotating body 11 is as follows: X = − (2F−f) / 2 (where f <2F) (6) Based on these equations (4) and (6), the computer 9 can calculate and detect the rotation speed X of the rotating body 11. FIG. 3 illustrates the relationship between the rotation speed X of the rotating body 11, the rotation speed F of the polarization plane of the projection laser light L, and the frequency f of the intensity change of the reflected light, in the case of the above equation (5). It is. As is clear from FIG. 2, if the angle of the polarization plane in the polarization plane rotation unit 4 is fixed, if the angle of the polarization plane is known, the angle of the rotator 11 and the angle of the rotator 11 according to the intensity of the reflected laser beam L 'are known. Angular velocity can be detected. However, since the period of the intensity change of the reflected laser light L 'is half of the period of the rotating body 11, the condition is that the rotation range of the rotating body 11 is smaller than 180 degrees. Further, as described above, the intensity of the reflected laser beam L 'becomes maximum when the plane of polarization of the projected laser beam L and the plane of polarization of the polarization filter 12 of the rotator 11 are parallel. Therefore, when the polarization plane of the projection laser light L is rotated by the polarization plane rotation unit 4, the polarization direction of the polarization filter 12 attached to the rotation body 11 is adjusted to the reference position of the rotation body 11 in advance. Then, when the intensity of the reflected laser light L ′ is maximum, the projected laser light L rotated by the polarization plane rotation unit 4
And the rotation angle of the rotator 11 coincide with each other. Therefore, the rotation angle of the rotating body 11 can be detected by detecting the rotation angle of the polarization plane of the projection laser light L by the polarization plane rotation unit 4. Also, by setting the rotation speed of the polarization plane of the laser beam L, that is, the rotation speed of the polarization plane rotation unit 4 sufficiently higher than the rotation speed of the rotator, the rotation angle of the rotator can be detected with high accuracy. Rotating body 1
Even when 1 is not rotating, the rotation angle of the rotating body 11 can be detected by rotating the polarization plane of the projection laser light L by the polarization plane rotation unit 4.

In the embodiment, the laser beam is used. However, the present invention is not limited to this, and it is possible to project polarized light toward the rotating body, and to further polarize and reflect the polarized light by the rotating body. Any light can be applied as long as it can receive the reflected light and detect the frequency of the intensity change.

[0025]

As described above, according to the present invention, polarized light is projected toward the rotating body, the polarized light is further reflected and reflected by the rotating body, and the reflected light is received to change the intensity. The number of rotations of the rotating body is detected by detecting the frequency.Therefore, there is no space for mounting a sensor such as an encoder that directly detects rotation, or a structure that cannot detect rotation in the first place with these sensors. Because there is a rotating body or a rotating body that flies in the air, the mechanical resistance will not be negligible when wired,
Even if the rotating body cannot be equipped with a transmitter such as a telemeter, the number of rotations can be reliably and accurately detected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a rotation speed detecting device according to the present invention.

FIG. 2 is a waveform diagram used to explain arithmetic processing performed by the computer shown in FIG. 1;

FIG. 3 is a waveform diagram used to explain arithmetic processing performed by the computer shown in FIG. 1;

FIG. 4 is a diagram conceptually showing a configuration of a conventional rotation speed detecting device.

[Explanation of symbols]

 Reference Signs List 2 laser oscillator 4 polarization plane rotating unit 7 sensor 9 computer 11 rotating body 12 polarizing filter 13 reflector

Claims (1)

(57) [Claims] An apparatus for detecting the number of rotations of a rotator rotating about a predetermined axis, comprising a rotatable polarizing element for polarizing light, and rotating the polarizing element to rotate the light. First polarizing means for rotating a polarization plane at a predetermined number of revolutions and projecting light in the axial direction of the rotator; and provided on the rotator for polarizing light projected from the first polarizing means. A second polarization unit, a reflection unit provided on the rotator, for reflecting light polarized by the second polarization unit, and a frequency detection unit for detecting a frequency of a change in intensity of the light reflected by the reflection unit. Means for calculating the number of rotations of the rotator based on the number of rotations of the polarization plane and the frequency detected by the frequency detection means.