A method for measuring laser reflection wave height

Abstract

The present invention discloses a method for measuring the height of laser reflection waves, which includes a wave-making board, upper and lower brackets, metal support rods, hemispherical foam floats, stainless steel protective shells, a data processor, a linear CCD camera, a laser emitter, and fixing bolts. The wave-making board is fixed on the side wall of the pool. The upper and lower brackets are fixed on the wave-making board using the fixing bolts. The upper and lower ends of the metal support rod are respectively connected to the upper and lower brackets and are installed perpendicular to the water surface. A circular hole is provided in the center of the hemispherical foam float, and it is sleeved on the metal support rod through the central circular hole. The stainless steel protective shell is installed on the upper bracket, and the data processor, linear CCD camera, and laser emitter are arranged inside it. By using the method of the present invention, the height change of waves in the pool can be accurately reflected in real time, thereby ensuring the stability of active wave absorption.

Description

Technical Field

[0001] The present invention relates to a method for measuring wave height in a wave-making experiment, and particularly to a method for measuring wave height based on laser reflection. Background Art

[0002] The wave-making flume test system is an important means to simulate natural ocean waves and study their interaction with structures, and has wide applications in the fields of hydraulic engineering, port and coastal engineering, and ocean engineering. In addition, the coupled simulation of flow generation, wave generation, wind generation, earthquake and other effects can study more complex extreme natural environments and provide strong support for engineering design and disaster prevention and mitigation.

[0003] In a wave-making experiment, due to the limited scope and environment of the test flume, it is impossible to be as infinite as the ocean. Therefore, after the progressive wave hits the side wall in the wave-making experiment, reflected waves and secondary reflected waves will be generated. At this time, the data of the wave-making experiment cannot accurately reflect the action of the waves on the building. For this reason, researchers have proposed a method of using a wave-making machine to absorb the reflected wave while generating waves, which is called "active absorption". This type of wave-making method can, according to the feedback information of hydrodynamics, drive the movement of the wave-making board through a control system with a mathematical model to achieve the effect of separating the incident wave and eliminating the reflected wave. Moreover, the active absorption technology can also effectively avoid the generation of resonance phenomena in the flume and the pool, greatly shorten the still water time between two experiments, and reduce the generation of pseudo-harmonics.

[0004] The core of the active absorption technology is to receive the wave height situation in real time. The control system needs to separate the wave components of the incident wave according to the current wave height situation, and then control the wave-making board to generate the target wave and absorb the reflected wave simultaneously.

[0005] Existing wave height sensors based on capacitance and force, etc., because the sensor probe is immersed in water during use, the sensor is greatly affected by the environment. For example, the force wave height sensor is affected by the water temperature, and the capacitance sensor will swing due to the impact of the waves on the capacitance wire of the probe, resulting in large measurement errors. Traditional force and capacitance sensors use analog current transmission as the data feedback method. Since the range of the wave-making test flume is large, the measurement domain of the sensor also needs to be large, and the inability to transmit over long distances is also a major disadvantage. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a method for measuring wave height based on laser reflection that can accurately reflect the change of wave height in the pool in real time, thereby ensuring the stability of active absorption wave-making.

[0007] A method for measuring wave height based on laser reflection of the present invention includes the following steps:

[0008] Step 1. Install the measuring device. The measuring device includes an upper bracket and a lower bracket that are fixedly spaced up and down on the wave-making board of an existing wave maker. The upper and lower ends of a metal support rod vertically arranged on the water surface are fixedly connected to the upper bracket and the lower bracket respectively. A hemispherical foam float is sleeved on the metal support rod through a central circular hole and can slide up and down along the metal support rod. A stainless-steel protective shell is fixed on the upper bracket. A data processor, a linear CCD camera, and a laser emitter are installed in the stainless-steel protective shell. The light beam emitted by the laser emitter is parallel to the central axis of the metal support rod and can irradiate the top surface of the hemispherical foam float. The lens surface of the linear CCD camera is flat and can obtain an image of the hemispherical foam float. The linear CCD camera is connected to the data processor through a data cable;

[0009] Step 2. Start the wave maker. The wave-making board of the wave maker generates a reciprocating motion to push the water body in front of the board during the wave-making experiment, thereby causing the required water level change on the water surface and forming waves in the entire pool. The change in the water level in front of the wave-making board causes the hemispherical foam float floating on the water surface to move linearly along the metal support rod. The light beam emitted by the laser emitter is vertically irradiated on the upper surface of the hemispherical foam float and undergoes diffuse reflection. A very small amount of the reflected light beam enters the linear CCD camera and is received by the photosensitive element. The linear CCD camera outputs the received optical signal to the data processor. The data processor uses a built-in formula to calculate and process to obtain the wave height y, and outputs the calculation result to the user's signal acquisition device using the IO-Link protocol;

[0010] The built-in formula is:

[0011] In the formula:

[0012] y: the distance from the upper surface of the hemispherical foam float to the zero position;

[0013] Zero position: the dividing line of the minimum measurement range measured by the linear CCD camera;

[0014] x: the position where the reflected light from the upper surface of the hemispherical foam float irradiates on the linear CCD camera, and this value changes with the movement of the hemispherical float;

[0015] a: the length of the lens of the linear CCD camera;

[0016] b: the distance from the zero position to the lens surface of the linear CCD camera;

[0017] β: the angle between the reflected light of the laser at the zero position and the lens surface of the linear CCD camera;

[0018] δ: the angle between the incident light and the reflected light of the laser at the zero position.

[0019] The beneficial effects of the present invention:

[0020] 1. Make the wave height measurement more accurate and rapid by using the method of laser reflection;

[0021] 2. The non-contact measurement device keeps the electronic structure involved in data processing away from the water body, avoiding damage to and influence on the measurement device by environmental factors such as water quality, water temperature, and water electrification;

[0022] 3. The modular mechanical structure is applicable to wave-making plates of different sizes and facilitates the installation and replacement of components;

[0023] 4. The device adopts the communication method of digital IO-Link, which is more convenient for accurately and rapidly setting and reading the device data parameters, and can also achieve a longer-distance connection with the control device. Description of the Drawings

[0024] Figure 1 is a schematic diagram of the device adopted by a wave height measurement method based on laser reflection according to the present invention;

[0025] Figure 2 is the schematic diagram of the method of the present invention. Detailed Embodiment

[0026] The present invention will be further described in detail below in conjunction with the drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the protection scope of the present invention.

[0027] A wave height measurement method based on laser reflection according to the present invention as shown in the drawings includes the following steps:

[0028] Step 1. Install the measurement device. The measurement device includes an upper bracket 2 and a lower bracket 10 that are fixedly spaced up and down on a wave-making plate 1 of an existing wave-making machine. The upper bracket 2 and the lower bracket 10 can be fixed on the wave-making plate 1 by fixing bolts 3. The upper end and the lower end of a metal support rod 9 vertically arranged on the water surface are respectively fixedly connected to the upper bracket 2 and the lower bracket 10. As Figure 1 shown, they can be fixedly connected by bolts 11. A hemispherical foam float 8 is sleeved on the metal support rod 9 through a central circular hole and can slide up and down along the metal support rod 9. The lower surface of the hemispherical foam float 8 is hemispherical, which will increase the buoyancy of the hemispherical foam float 8 and make it not easy to shake. Preferably, the upper surface edge of the hemispherical foam float is lower than the center and is conical. The taper is further preferably 3 degrees. The upper surface is also coated with a hydrophobic coating to prevent water accumulation on the upper surface from tilting the float and affecting the wave height measurement. Preferably, the surface of the central circular hole of the hemispherical foam float is smoothed, and the surface roughness of the central circular hole is between 1.6 and 3.2, so that the friction force between it and the metal support rod 9 is smaller.

[0029] A stainless steel protective shell 7 is fixed on the upper support 2. A data processor 4, a linear CCD camera 5 and a laser emitter 6 are installed inside the stainless steel protective shell. The beam emitted by the laser emitter 6 is parallel to the central axis of the metal support rod 9 and can irradiate the top surface of the hemispherical foam float. The lens surface of the linear CCD camera is flat and can obtain an image of the hemispherical foam float 8. The linear CCD camera is connected to the data processor 4 through a data cable.

[0030] Step 2: Start the wave maker (an existing device can be used, and the structure of the wave maker can be referred to CN201910228207, a liftable wave-making system). The wave-making plate 1 of the wave maker generates a reciprocating motion to push the water body in front of the plate during the wave-making experiment, so as to cause the required water level change on the water surface and form waves in the entire pool. The change in the water level in front of the wave-making plate 1 causes the hemispherical foam float 8 floating on the water surface to move linearly along the metal support rod 9. The beam emitted by the laser emitter 6 is perpendicularly irradiated on the upper surface of the hemispherical foam float 8 and undergoes diffuse reflection. A very small amount of the reflected light beam enters the linear CCD camera 5 and is received by the photosensitive element. The linear CCD camera 5 outputs the received optical signal to the data processor 4. The data processor 4 uses a built-in formula to calculate and process to obtain the wave height y, and outputs the calculation result to the user's signal acquisition device using the IO-Link protocol.

[0031] The built-in formula is as follows:

[0032] As Figure 2 shown,

[0033] In the formula:

[0034] y: The distance from the upper surface of the hemispherical foam float to the zero position;

[0035] Zero position: The dividing line of the minimum measurement range position measured by the linear CCD camera;

[0036] x: The position where the reflected light from the upper surface of the hemispherical foam float irradiates on the linear CCD camera, and this value changes with the movement of the hemispherical float;

[0037] a: The length of the lens of the linear CCD camera;

[0038] b: The distance from the zero position to the lens surface of the linear CCD camera;

[0039] β: The angle between the reflected light of the laser at the zero position and the lens surface of the linear CCD camera;

[0040] δ: The angle between the incident light and the reflected light of the laser at the zero position;

[0041] The derivation process of the above formula is as follows:

[0042] The present invention utilizes the water level change in front of the wave-making board in the wave field to drive the hemispherical buoy to move in a direction perpendicular to the horizontal plane, and measures the wave height by the position change of the reflected laser spot in the linear CCD camera. As Figure 2 shown, according to the laser reflection principle, the laser is incident perpendicular to the horizontal plane. The lens center of the linear CCD camera is O. The minimum range position measured by the linear CCD camera is called the 0 position. The reflected light less than the 0 position is beyond the linear CCD camera. The distance between the 0 position and the upper surface of the hemispherical foam buoy is the wave height y. The point where the laser spot shines on the hemispherical foam buoy is point B, and the point where it passes through the lens center of the CCD camera and is reflected onto the linear array of the linear CCD module is point B'. At the 0 position, the included angle between the incident light and the reflected light is δ, and at the linear array, the included angle between the reflected light and the lens surface of the linear CCD camera is β. To construct similar triangles for the built-in formula calculation, perpendiculars are drawn from point B and point B' to the reflected light of the laser at the 0 position, intersecting the reflected light at point A and point A' respectively.

[0043] According to the similarity of triangles, we can get:

[0044]

[0045] Among them:

[0046] AB = y·sinδ

[0047] A'B' = x·sinβ

[0048]

[0049]

[0050] Simplifying the above formula, we get:

[0051]

[0052] The working process of adopting this device is as follows:

[0053] When the linear CCD camera 5 and the laser emitter 6 are fixed in the stainless steel protective shell 7, the parameters a, b, δ, and β are all fixed values. When the wave height changes, the height of the hemispherical foam buoy will also move accordingly. This height corresponds to the y value in the above formula. When y changes, the position x of the reflected light spot on the linear CCD camera also changes synchronously, and the x value will be generated by the linear CCD camera. The linear CCD camera transmits the generated x value to the data processor. The data processor substitutes the x value into the above-mentioned built-in formula, and then can calculate the wave height value y, and outputs the wave height value y through the IO-Link data transmission protocol. This data transmission protocol is an internationally common protocol, and users can use this protocol to read the required wave height value y from this device, so as to measure the wave height.

[0054] It should be noted that although the preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, the present invention is not limited solely to the above specific embodiments. The above embodiments are merely illustrative and not restrictive. Those skilled in the relevant art, inspired by the present invention, can make many forms without departing from the spirit of the present invention and the scope of protection of the claims. These all fall within the scope of protection of the present invention.

Claims

1. A method for measuring the height of a laser reflection wave, characterized in that Including the following steps: Step 1: Install the measuring device. The measuring device includes an upper bracket and a lower bracket that are fixedly arranged at intervals above and below on the wave-making board of an existing wave maker. The upper and lower ends of a metal support rod vertically arranged on the water surface are fixedly connected to the upper bracket and the lower bracket respectively. A hemispherical foam float is sleeved on the metal support rod through a central circular hole and can slide up and down along the metal support rod. A stainless-steel protective shell is fixed on the upper bracket. A data processor, a linear CCD camera, and a laser emitter are installed in the stainless-steel protective shell. The light beam emitted by the laser emitter is parallel to the central axis of the metal support rod and can irradiate the top surface of the hemispherical foam float. The lens surface of the linear CCD camera is flat and can obtain an image of the hemispherical foam float. The linear CCD camera is connected to the data processor through a data cable; Step 2: Start the wave maker. The wave-making board of the wave maker generates a reciprocating motion to push the water body in front of the board during the wave-making experiment, so as to cause the required water level change on the water surface and form waves in the entire pool. The change in the water level in front of the wave-making board causes the hemispherical foam float floating on the water surface to move linearly along the metal support rod. The light beam emitted by the laser emitter is vertically irradiated on the upper surface of the hemispherical foam float and undergoes diffuse reflection. A very small amount of the reflected light beam enters the linear CCD camera and is received by the photosensitive element. The linear CCD camera outputs the received optical signal to the data processor. The data processor uses a built-in formula to calculate and process to obtain the wave height y, and outputs the calculation result to the user's signal acquisition device using the IO-Link protocol; The built-in formula is as follows: In the formula: y: The distance from the upper surface of the hemispherical foam float to the 0 position; 0 position: The dividing line of the minimum range position measured by the linear CCD camera; x: The position where the reflected light from the upper surface of the hemispherical foam float irradiates on the linear CCD camera, and this value changes with the movement of the hemispherical float; a: The length of the lens of the linear CCD camera; b: The distance from the 0 position to the lens surface of the linear CCD camera; β: The angle between the reflected light of the laser at the 0 position and the lens surface of the linear CCD camera; δ: The angle between the incident light and the reflected light of the laser at the 0 position.

2. The method for measuring the height of a laser reflection wave according to claim 1, wherein: The edge of the upper surface of the hemispherical foam float is lower than the center and is conical.

3. The method for measuring the height based on the laser reflection wave according to claim 2, wherein: The taper of the cone is 3 degrees.

4. The method for measuring the height of a laser reflection wave according to claim 3, characterized in that: The upper surface of the hemispherical foam float is coated with a hydrophobic coating.

5. The method for measuring the height based on the laser reflection wave according to claim 4, wherein: The surface of the central circular hole of the hemispherical foam float is smoothed, and the surface roughness of the central circular hole is between 1.6 and 3.2.

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