JPS59147202A - Displacement measuring method - Google Patents

Abstract

PURPOSE:To permit easy and prompt displacement measurement even in places under adverse environmental conditions by a method wherein laser beams from two light sources at different positions are focused to the same point on the object to be measured to measure the separation distance between two radiant points which are produced due to displacement of the measured object. CONSTITUTION:First, a screw 1 is rotated at a low speed so that no cavitation will occur. In this state, angles of laser projectors 6a, 6b are controlled to focus laser beams to the same irradiation point on the screw surface. This operation is repeatedly carried out over the entire length of the screw 1, and angles of the laser projectors 6a, 6b are displayed on and stored in a laser angle display 9. When the number of revolutions of the screw 1 is so increased as to generate cavitation, two radiant points are produced. A separation distance between those radiant points is measured by a video scaler 17 thereby compute a depth of cavitation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a displacement measuring method capable of measuring the amount of displacement without contact.

Generally, in order to measure the amount of displacement in a place with poor environmental conditions, non-contact displacement measurement is performed by taking stereo photographs and analyzing the photographic results.

However, analyzing stereo photographs takes a long time,
Moreover, it required difficult work and was not efficient.

SUMMARY OF THE INVENTION An object of the present invention is to provide a displacement measuring method that can immediately and easily measure the amount of displacement.

In order to achieve this purpose, the present invention irradiates laser beams from two light sources onto the same irradiation point on the object to be measured, and when a displacement occurs, the irradiation point splits into two bright spots. The amount of displacement is determined from the distance between the bright spots (this distance is defined as the separation distance) and the position of the light source. Hereinafter, the present invention will be described in detail using drawings showing embodiments.

As an application example of the present invention, a device for measuring the thickness of cavitation generated by the rotation of a ship's propeller will be described. Cavitation is a group of air bubbles that occur near the screw when the rotational speed of the screw reaches a certain level.When cavitation occurs intensely, the metal parts become severely corroded, so screw design is important. In this case, consideration is given to making cavitation less likely to occur. This device examines the amount of cavitation generated by a designed screw.

FIG. 1 is a block diagram of a displacement measuring device to which the method of the present invention is applied. In the figure, 1 is a screw, which is connected to an engine (not shown) via a shaft 2. A disc 3 is provided on the shaft 2, and around the disc 3 there is one long pin 4a, which is short. 179 pins 4b are attached at equal intervals. A light emitter 5a and a light receiver 5b, which are provided to sandwich the pins 4a and 4b, constitute a rotational pulse detection device. The light receiver 5b has two light receiving elements, one of which is placed at the tip of the pin 4a, and outputs an output signal only when the pin 4a blocks the light from the emitter 5a. , and other light receiving elements generate output signals even when any pin blocks the light from the light emitter 5a. 6a and 6b are laser projectors serving as light sources, which project laser light supplied from a laser shutter 7 into the water, and whose projection angles are controlled by a laser angle controller 8. This projection angle is displayed on the laser angle display 9 and is also stored there. 10 is a preset counter, and among the signals supplied from the light receiver 5b, the signal generated by the long pin 4a is input to the input terminal 1.
It is reset by being supplied to 0a, and the signal generated by short pin 4b is supplied to input terminal 1iob, which counts this signal and generates an output signal when the divisor value reaches a predetermined value. It looks like this. The output signal of the preset counter 10 is counted by a strobe flash controller 11 in order to ensure a sufficient amount of strobe light, which will be described later, and an output signal is generated after the counted value reaches a predetermined value. Reference numeral 12 denotes a strobe power source, which supplies a signal to the strobe flash 13 and the laser shutter 7 when a signal is supplied from the strobe flash controller 11. Here, the strobe flash 13 serves as a light source for monitoring the shape of the screw 1 with a monitor to be described later, and the laser shutter γ generates laser light in response to a signal supplied from the strobe power source 12. 14 is a television camera whose zoom up and imaging direction are controlled in accordance with signals supplied from a camera controller 15.

In addition to performing the operations described above, the camera controller 15 is also configured to send a video signal supplied from the television camera 14 to the video memory 16.

Laser projector 6a, 6b and strobe flash 1
Since the light generated from 3 is intermittent, video memory 1
Since the video signal supplied to the monitor 6 is also intermittent, the video memory 16 converts this signal into a continuous signal so that an easy-to-see video can be displayed on a monitor, which will be described later. 17 is a video scaler which supplies the video signal supplied from the video memory 16 to the monitor 19 and measures the thickness of the capitulation, which is the amount of displacement of the object to be measured, by a method to be described later. . 19 is a VTR for recording images.

The operation of the device configured in this way is as follows. When the screw 1 is rotated, a signal corresponding to the rotation speed is supplied from the light receiver 5b to the preset counter 10. At this time, the preset counter 10 is reset by the signal supplied to the input terminal 10a, counts the signal supplied to the input terminal 10b, and generates an output signal when the counted value reaches a predetermined value. This output signal is generated once every rotation of the screw 1, but as mentioned above, when the number of pulses supplied from the preset counter 10 is supplied a predetermined number of times, the strobe flash controller 11 outputs an output signal to the strobe power supply 12. supply.

As a result, the strobe power supply 12 supplies a signal to the laser shutter 7 and the strobe flash 13.

The laser shutter I is a laser projector 6a.

Since the laser beam is supplied to 6b, the laser projector 6a,
A laser beam is emitted from 6b, and a strobe light is emitted from a strobe flash 13 in synchronization with this. At this time, if the preset value of the preset counter 10 is set appropriately, a specific wing surface of the screw 1 can be set to the laser projectors 6a, 6b and the strobe flash 13.
It is possible to emit laser beams and strobe beams when the beam crosses the optical axis of the beam. Note that the strobe flash controller 11 generates an output signal after the input signal is supplied a predetermined number of times, and this is to ensure a sufficient amount of light from the strobe flash 13.

Next, screw 1 is rotated at low speed to prevent cavitation, and laser angle controller 8
By adjusting the angles of the laser projectors 6a and 6b, the laser beam is focused on the same irradiation point on the wing surface. When this operation is performed over the entire blade span of the screw 1, the laser angle indicator 9 changes to the laser projector 6a at this time.

The angle of 6b is displayed and memorized. This operation is performed while monitoring the video signal from the television camera 14 on the monitor 18. Then, in response to this operation, the camera controller 15 performs zoom-up and swing control of the television camera 14, and this control operation is stored in the camera controller 15.

After the following operations are completed, cavitation occurs when the rotational speed of the screw 1 is increased.

When cavitation occurs, the laser beam is scattered in the bubble group 20 of FIG. 2, and two bright spots 21a and 21b are generated at the interface between the bubble group 20 and water.

Therefore, the video scaler 17 measures the separation distance DF between the bright spots 21a and 21b from the image signal, and calculates the cavitation thickness BE based on the predetermined positions of the laser projectors 6a and 6b. and,
The laser angle display 9 and the camera controller 15 control the laser projectors 6a, 6b and the television camera 14 based on the previously stored data.
The cavitation thickness is measured over the entire span of the blade. In this case, the cavitation thickness is calculated as follows, for example. First, the bright spots 21a and 21b in FIG.
is scanned, the separation distance DF is measured from the time at which both bright spots are scanned. And laser projectors 6a, 6b
Since the position of point B, the position of point B, and the lengths of sides BC and AG are known, and triangle DBF and triangle ABC are congruent, the cavitation thickness BE can be easily calculated from these conditions. In this way, the thickness of keyer biting can be measured without contact.

In addition, although the thickness of the keyer biting was measured in the following examples, this can be considered to be due to the displacement of the blade surface position of the screw 1, which means that the amount of displacement of the object to be measured can be measured. means.

As explained above, the displacement measuring method according to the present invention uses 2! where the position is known in advance. A laser beam is focused on a point on the object to be measured from a light source, and the separation distance between the two bright spots that appear on the object when the object is displaced is measured to determine the amount of displacement of the object to be measured. Since the device is designed to measure the displacement of the object to be measured without contact, it has the excellent effect of being able to easily and quickly measure the amount of displacement in a place with poor environmental conditions.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a diagram for explaining a displacement calculation method. 1...screw, 4...fist/bottle, 5a...
Emitter, 5b...Receiver, 6a, 6b...Fist laser emitter, 7...Laser shutter, 8...Laser angle controller, 9...Laser angle indicator, 10
... Preset counter, No. 13... Strobe flash, 15...-Camera controller, 17. E-video scaler. Patent applicant: Ministry of Transport, Ship Technology Research Institute

Claims (1)

[Claims] Laser beams are irradiated from two light sources in different locations to the same irradiation point on the object to be measured so as to be focused, and the separation distance between the irradiation points caused by the displacement of the object to be measured is measured. 7. Displacement measuring method, characterized in that the amount of displacement of the object to be measured is calculated from the distance data and the light source position data.