WO2023035544A1 - Laboratory spatial wave real-time measurement method based on visual edge detection - Google Patents

Abstract

A laboratory spatial wave real-time measurement method based on visual edge detection, comprising the following steps: S1: calibrating a camera (4); S2: photographing a wave surface image under wave motion by means of the camera (4), and sending the wave surface image to a digital signal processing system (5); S3: the digital signal processing system (5) performing visual edge detection on the received wave surface image; S4: the digital signal processing system (5) detecting a water level line (2) and a wave surface feature in the wave surface image; S5: the digital signal processing system (5) performing coordinate conversion on the detected water level feature; and S6: storing the coordinate conversion result, and displaying the coordinate conversion result on a wave surface identification display interface in real time. The problem that existing measurement techniques cannot realize real-time detection of a spatial wave surface and real-time measurement of a water level for wave motion is solved.

Description

A real-time measurement method of laboratory space waves based on visual edge detection technical field

The invention belongs to the field of marine engineering, in particular to a method for real-time measurement of laboratory space waves based on visual edge detection.

Background technique

In order to study the characteristics of wave elements in hydraulic experiments, relevant research departments at home and abroad need to take measures to monitor the wave motion in the laboratory. Commonly used wave motion measurement methods mainly include artificial visual observation, video monitoring, wave height sensors and other sensors. Device contact measurement, etc. Manual visual observation can be used to simply and roughly observe changes in water level and wave surface, but this method is time-consuming and labor-intensive and lacks the accuracy of observation, so it is difficult to be widely used in experiments and engineering; video monitoring can remotely observe wave motion, but it can only measure the wave motion Real-time observation and recording of video cannot record the height and wave surface characteristics of the water level in real time; electronic devices such as wave height sensors, ultrasonic liquid level gauges, and radar level gauges can measure the water level and wave height in real time through the conversion of electrical or acoustic signals. change, but the spatial form of the wave cannot be obtained. The above methods are commonly used in wave motion observation, but none of them can realize real-time and automatic measurement of spatial wave motion.

In recent years, computer vision technology and graphics processing technology have developed rapidly by virtue of the advantages of high precision, high efficiency, and low cost. More and more researchers have begun to apply computer vision technology to the research field of wave motion.

Contents of the invention

In view of this, the present invention proposes a real-time measurement method of laboratory space waves based on visual edge detection to solve the problem that the existing measurement technology cannot realize real-time detection of space wave surface and real-time measurement of water level for wave motion.

In order to achieve the above object, technical solution of the present invention is achieved in that way:

A method for real-time measurement of laboratory space waves based on visual edge detection, comprising the following steps:

S1: Calibrate the camera;

S2: The wave surface image under the wave motion is captured by the camera, and the wave surface image is sent to the digital signal processing system;

S3: The digital signal processing system performs visual edge detection on the received wavefront image;

S4: The digital signal processing system detects the water level line and wavefront features in the wavefront image;

S5: The digital signal processing system performs coordinate transformation on the detected water level features;

S6: Store the water coordinate transformation result and display it on the wave surface identification display interface in real time.

Further, the method for calibrating the camera in step S1 is Zhang Zhengyou's calibrating method.

Further, the visual edge detection described in step S3 includes the following steps:

S31: Using wavelet transform to filter and denoise the collected wavefront image to obtain a denoised wavefront image A;

S32: Binarize the wavefront image A after filtering and denoising, so as to highlight the spatial wavefront features of the image;

S33: Gaussian filtering is performed on the binarized wavefront image to obtain a smooth wavefront image B;

S34: Calculate the gradient value and gradient direction of the wavefront image B through the smooth wavefront image B, and obtain the contour features of the wavefront image B;

S35: According to the gradient direction obtained by the gradient calculation in step S34, traverse all points in the wavefront image B, each point is set as a central point, and compare the central point and other pixel points in the gradient direction The size of the gradient value. If the gradient value of the center point is the largest, the center point will be kept, otherwise the point will be discarded, so as to obtain a thinner contour edge;

S36: Set two thresholds, high and low, if there is a point greater than the high threshold at the center pixel or in the neighborhood of the center pixel, then judge that this point is the edge point of the wavefront image B and keep it, otherwise discard this point, so as to obtain a more For detailed edge contours.

Further, step S34 obtains the contour feature method of wavefront image B as follows:

S341: Filter the wavefront image B through a Sobel horizontal edge detection operator to obtain a gradient value Gx in the horizontal direction of the wavefront image B;

S342: Filter the wavefront image B through the Sobel vertical edge detection operator to obtain the gradient value Gy in the vertical direction of the wavefront image B;

S343: Calculate the gradient value of the wavefront image according to the Pythagorean theorem:

The gradient direction is:

In this way, the contour features of the wavefront image B are obtained.

Further, the detection of the water level line and wavefront feature described in step S4 is performed by traversing the contour features of the wavefront image from top to bottom at the origin of the image coordinate system, and when the water level is scanned, it is obtained sequentially from left to right The data information of the entire water level line, and then obtain the contour characteristics of the wave surface.

Further, the coordinate transformation method described in step 5 includes the following steps:

S51: Before the experiment, spray a scale on the wall of the tank along the vertical direction, and the range of the scale includes the range of wave motion;

S52: Obtain the pixel ordinate value x ₁ of the highest point of the scale on the wavefront image, the actual height value y ₁ of the point, obtain the pixel ordinate value x ₂ of the lowest point of the scale, and the actual height value y ₂ of the point, Calculate the following equation

Obtain constant b, constant k, obtain coordinate conversion function y=kx+b;

S53: Bring the pixel height x of the feature point on the collected wavefront image into the coordinate conversion function, so as to calculate the actual height value y, and complete the coordinate conversion.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The present invention adopts the edge detection method in the image processing technology to realize the segmentation of the wave front video image, and can obtain the spatial form of the wave motion and the height of the water level in real time, overcoming the difficulty in determining the spatial form information of the wave motion in the traditional measurement method ;

(2) the present invention provides a kind of laboratory tank space wave measurement method based on visual edge detection, through the scale sprayed on the wall of the laboratory tank, the water level value on the wave surface image can be converted into the actual water level value;

(3) A method for measuring waves in a laboratory tank space based on visual edge detection provided by the present invention can identify the water level in real time, and display the actual height of the water level at a fixed point in the video image.

Description of drawings

The drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments and descriptions of the present invention are used to explain the present invention, and do not constitute an improper limitation of the present invention. In the attached picture:

Fig. 1 is a schematic diagram of a real-time measurement method for laboratory space waves based on visual edge detection according to an embodiment of the present invention;

Fig. 2 is an experimental layout diagram of a real-time measurement method for space waves in a laboratory tank based on visual edge detection according to an embodiment of the present invention.

Explanation of reference signs:

1. Scale; 2. Water level line; 3. Spatial wave surface shape; 4. Camera; 5. Visual edge detection digital signal processing system.

Detailed ways

It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

In describing the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", " The orientations or positional relationships indicated by "vertical", "horizontal", "top", "bottom", "inner" and "outer" are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and Simplified descriptions, rather than indicating or implying that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and thus should not be construed as limiting the invention. In addition, the terms "first", "second", etc. are used for descriptive purposes only, and should not be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, a feature defined as "first", "second", etc. may expressly or implicitly include one or more of that feature. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it can be mechanically connected or electrically connected; it can be directly connected or indirectly connected through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention based on specific situations.

The present invention will be described in detail below with reference to the accompanying drawings and examples.

As shown in Figure 1, a real-time measurement method for laboratory space waves based on visual edge detection includes the following steps:

S1: Calibrate the camera 4;

S2: taking a wave surface image under wave motion through the camera 4, and sending the wave surface image to a digital signal processing system;

S3: The digital signal processing system performs visual edge detection on the received wavefront image;

S4: The digital signal processing system detects the water level line 2 and the wavefront features in the wavefront image;

S5: The digital signal processing system performs coordinate transformation on the detected water level features;

S6: Store the water coordinate transformation result and display it on the wave surface identification display interface in real time.

The calibration method described in step S1 is the Zhang Zhengyou calibration method.

The visual edge detection described in step S3 comprises the following steps:

S31: Using wavelet transform to filter and denoise the collected wavefront image to obtain a denoised wavefront image A;

S32: Binarize the wavefront image A after filtering and denoising, so as to highlight the spatial wavefront features of the image;

S33: Gaussian filtering is performed on the binarized wavefront image to obtain a smooth wavefront image B;

S34: Calculate the gradient value and gradient direction of the wavefront image B through the smooth wavefront image B, and obtain the contour features of the wavefront image B;

S35: According to the gradient direction obtained by the gradient calculation in step S34, traverse all points in the wavefront image B, each point is set as a central point, and compare the central point and other pixel points in the gradient direction The size of the gradient value. If the gradient value of the center point is the largest, the center point will be kept, otherwise the point will be discarded, so as to obtain a thinner contour edge;

S36: Set two thresholds, high and low, if there is a point greater than the high threshold at the center pixel or in the neighborhood of the center pixel, then judge that this point is the edge point of the wavefront image B and keep it, otherwise discard this point, so as to obtain a more For detailed edge contours.

Further, step S34 obtains the contour feature method of wavefront image B as follows:

S341: Filter the wavefront image B by the Sobel horizontal edge detection operator to obtain the gradient value Gx on the wavefront image B horizontal direction;

S342: Filter the wavefront image B through the Sobel vertical edge detection operator to obtain the gradient value Gy in the vertical direction of the wavefront image B;

S343: According to the Pythagorean theorem, calculate the magnitude of the gradient value of the wavefront image as , and the gradient direction as , so as to obtain the contour feature of the wavefront image B.

The water level line 2 and wave surface feature detection described in step S4 is to traverse the contour features of the wave surface image from top to bottom at the origin of the image coordinate system. When the water level is scanned, the entire line is obtained from left to right. Water level 2 data information, and then obtain the contour features of the wave surface.

The coordinate transformation method described in step 5 comprises the following steps:

S51: Before the experiment, spray scale 1 along the vertical direction on the wall of the tank, and the range of scale 1 includes the range of wave motion;

S52: Obtain the pixel ordinate value of the highest point of scale 1 on the wavefront image, the actual height value of this point, obtain the pixel ordinate value of the lowest point of scale 1, the actual height value of this point, and calculate the following equation, Obtain the constant b, constant k, and obtain the coordinate conversion function;

S53: Bring the pixel height x of the feature point on the collected wavefront image into the coordinate conversion function, so as to calculate the actual height value y, and complete the coordinate conversion.

The laboratory tank is 456 meters long, 5 meters wide, and 8-12 meters deep, of which the wave generation section is 42 meters long, the test section is 116 meters long, and the wave generation section and energy dissipation section are 298 meters in total. The present invention is provided with 8 cameras 4 altogether in the test section, and each camera 4 is sprayed with a scale 1 on the wall of the water tank opposite to each other, and the division value of the scale 1 is 2 cm. 2 The position is centered on the image screen, as shown in Figure 3, to ensure that the camera 4 can collect both the wavefront shape and the scale information on the wall of the tank, and the digital signal processing system for visual edge detection performs edge detection processing on the collected images , save the detection result and display it in the video image in real time, as shown in Figure 4. The digital signal processing system for visual edge detection has a processing speed of about 36 milliseconds for a single-frame wavefront image and a measurement accuracy of 4 mm, which can meet the speed and accuracy requirements of real-time measurement in the sink laboratory.

The invention adopts the edge detection method in the image processing technology to realize the segmentation of the video image of the wave surface, and can obtain the spatial form of the wave motion and the height of the water level in real time, overcoming the difficulty in determining the spatial form information of the wave motion in the traditional measurement method;

The invention provides a method for measuring waves in a laboratory water tank space based on visual edge detection. The water level value on the wave surface image can be converted into an actual water level value through the scale 1 sprayed on the wall of the laboratory water tank;

The invention provides a method for measuring waves in a laboratory tank space based on visual edge detection, which can identify the water level in real time, and display the actual height of the water level at a fixed point in the video image.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (6)

1. A method for real-time measurement of laboratory space waves based on visual edge detection, characterized in that: comprising the following steps:

   S1: Calibrate the camera;

   S2: The wave surface image under the wave motion is captured by the camera, and the wave surface image is sent to the digital signal processing system;

   S3: The digital signal processing system performs visual edge detection on the received wavefront image;

   S4: The digital signal processing system detects the water level line and wavefront features in the wavefront image;

   S5: The digital signal processing system performs coordinate transformation on the detected water level features;

   S6: Store the water coordinate transformation result and display it on the wave surface identification display interface in real time.
2. A real-time measurement method for laboratory space waves based on visual edge detection according to claim 1, characterized in that: the method for calibrating the camera in step S1 is Zhang Zhengyou's calibration method.
3. A kind of laboratory space wave real-time measurement method based on visual edge detection according to claim 1, is characterized in that: the visual edge detection described in step S3 comprises the following steps:

   S31: Using wavelet transform to filter and denoise the collected wavefront image to obtain a denoised wavefront image A;

   S32: Binarize the wavefront image A after filtering and denoising, so as to highlight the spatial wavefront features of the image;

   S33: Gaussian filtering is performed on the binarized wavefront image to obtain a smooth wavefront image B;

   S34: Calculate the gradient value and gradient direction of the wavefront image B through the smooth wavefront image B, and obtain the contour features of the wavefront image B;

   S35: According to the gradient direction obtained by the gradient calculation in step S34, traverse all points in the wavefront image B, each point is set as a central point, and compare the central point and other pixel points in the gradient direction The size of the gradient value. If the gradient value of the center point is the largest, the center point will be kept, otherwise the point will be discarded, so as to obtain a thinner contour edge;

   S36: Set two thresholds, high and low, if there is a point greater than the high threshold at the center pixel or in the neighborhood of the center pixel, then judge that this point is the edge point of the wavefront image B and keep it, otherwise discard this point, so as to obtain a more For detailed edge contours.
4. A kind of laboratory space wave real-time measurement method based on visual edge detection according to claim 3, is characterized in that: step S34 obtains the method for the profile feature of wave surface image B as follows:

   S341: Filter the wavefront image B through a Sobel horizontal edge detection operator to obtain a gradient value Gx in the horizontal direction of the wavefront image B;

   S342: Filter the wavefront image B through the Sobel vertical edge detection operator to obtain the gradient value Gy in the vertical direction of the wavefront image B;

   S343: Calculate the gradient value of the wavefront image according to the Pythagorean theorem:

   

   The gradient direction is:

   

   In this way, the contour features of the wavefront image B are obtained.
5. A kind of laboratory space wave real-time measurement method based on visual edge detection according to claim 1, it is characterized in that: the water level line and wave surface feature detection described in step S4 is by at the origin of the image coordinate system, the wave surface image The contour features of the wave surface are traversed from top to bottom. When the water level is scanned, the data information of the entire water level line is obtained sequentially from left to right, and then the contour features of the wave surface are obtained.
6. A kind of laboratory space wave real-time measurement method based on visual edge detection according to claim 1, is characterized in that: the coordinate conversion method described in step 5 comprises the following steps:

   S51: Before the experiment, spray a scale on the wall of the tank along the vertical direction, and the range of the scale includes the range of wave motion;

   S52: Obtain the pixel ordinate value x ₁ of the highest point of the scale on the wavefront image, the actual height value y ₁ of the point, obtain the pixel ordinate value x ₂ of the lowest point of the scale, and the actual height value y ₂ of the point, Calculate the following equation

   

   Obtain constant b, constant k, obtain coordinate conversion function y=kx+b;

   S53: Bring the pixel height x of the feature point on the collected wavefront image into the coordinate conversion function, so as to calculate the actual height value y, and complete the coordinate conversion.

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