Image-based drop hammer impact speed measuring device and measuring method

Abstract

The invention provides an image-based drop hammer impact speed measuring device and method, the device comprises a drop hammer unit, a calibration scale, an image acquisition unit and an image processing unit, the drop hammer unit comprises two guide rails, and a drop hammer falls along the two guide rails; the calibration graduated scale is located in a plane formed by the axes of the two guide rails of the drop hammer unit; the angle of the image obtained by the image obtaining unit is perpendicular to a plane formed by the axes of the two guide rails of the drop hammer unit, the drop hammer and the calibration graduated scale can be located in the same frame of image, and the obtained image is transmitted to the image processing unit; and the image processing unit calculates the speed of the drop hammer according to the falling high speed of the drop hammer in the two frames of images and the time difference between the two frames of images. According to the invention, the number of equipment required for realizing high-precision measurement of the impact speed is small, the device is not limited by space in use, and the device is suitable for measuring the falling speed of various objects.

Description

Technical Field

[0001] The present invention belongs to the technical field of drop hammer impact speed measurement, and particularly relates to an image-based drop hammer impact speed measurement device and a measurement method. Background Art

[0002] The drop hammer impact test is an essential test link for testing the impact resistance of materials. When using the drop hammer impact test to evaluate the impact resistance of materials, not only the impact force-time change curve during the impact process needs to be concerned, but also the velocity-time change curve during the drop of the drop hammer needs to be collected.

[0003] In the existing drop hammer impact tests, an optoelectronic switch is usually used to obtain the speed of the drop hammer at a certain position during the drop process. This method sets checkpoints with a fixed distance during the drop of the drop hammer, records the time required for the drop hammer to pass through these two checks, and calculates the average speed of the drop hammer over this distance as the instantaneous speed of the drop hammer. Due to the limitations of the optoelectronic switch itself, the distance between the two checkpoints is difficult to be very small, the calculation accuracy is low, and only the speed information at a certain position can be obtained, and it is difficult to obtain the velocity-time change curve during the drop of the drop hammer. Moreover, most of the devices such as optoelectronic switches used for measuring the drop hammer impact speed are specially made based on specific drop hammer units, and the installation and use are restricted by the structure of the drop hammer unit, and it is difficult to have general applicability. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an image-based drop hammer impact speed measurement device and a measurement method. The solution of the present invention can solve the problems existing in the above prior art.

[0005] The technical solution of the present invention:

[0006] According to the first aspect, an image-based drop hammer impact speed measurement device is provided, including a drop hammer unit, a calibration scale, an image acquisition unit, and an image processing unit. The drop hammer unit includes two guide rails, and the drop hammer drops along the two guide rails; the calibration scale is located in the plane formed by the axes of the two guide rails of the drop hammer unit; the image acquisition unit acquires images at an angle perpendicular to the plane formed by the axes of the two guide rails of the drop hammer unit, and can make the drop hammer and the calibration scale be in the same frame of image, and transmits the acquired image to the image processing unit; the image processing unit calculates the speed of the drop hammer according to the speed of the drop hammer falling in the two frames of images obtained and the time difference between the two frames of images.

[0007] Further, the image acquisition unit is a high-speed camera or a video camera.

[0008] Further, the drop hammer unit further includes a base, and the guide rail and the calibration scale are both installed on the base.

[0009] According to a second aspect, there is provided the above-mentioned method for measuring the impact velocity of a drop hammer based on an image, including the following steps:

[0010] Install a device for measuring the impact velocity of a drop hammer based on an image;

[0011] Obtain images including the drop hammer and the calibration scale during the falling process of the drop hammer;

[0012] Calculate the velocity of the drop hammer based on the relative displacement between the drop hammer and the calibration scale in two frames of images and the time interval between the two frames of images.

[0013] Further, the two frames of images are two adjacent frames.

[0014] Further, to improve the accuracy of calculating the instantaneous velocity of the drop hammer, it is necessary to shorten the time interval between two frames of images.

[0015] Advantages of the present invention compared with the prior art:

[0016] (1) The equipment of the present invention is simple, the number of equipment required to achieve high-precision measurement of the impact velocity is small, the use of the device is not limited by space, and it is applicable to the measurement of the falling velocity of various objects:

[0017] (2) The present invention calculates the impact velocity based on the high-frame-rate photos taken by the high-speed image acquisition unit, and has a relatively high measurement range and measurement accuracy. Description of the Drawings

[0018] The accompanying drawings included are used to provide a further understanding of the embodiments of the present invention, which form a part of the specification, are used to illustrate the embodiments of the present invention, and are used to explain the principles of the present invention together with the text description. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0019] Figure 1 Shows a schematic structural diagram of a device for measuring the impact velocity of a drop hammer based on an image provided by an embodiment of the present invention;

[0020] Figure 2 Shows a schematic diagram for calculating the instantaneous velocity of a drop hammer falling provided by an embodiment of the present invention.

[0021] The above-mentioned accompanying drawings include the following reference numerals:

[0022] 1 - Drop hammer unit, 2 - Calibration scale, 3 - High - speed camera, 4 - Image processing unit, h1 - Drop hammer height 1, h2 - Drop hammer height 2. Detailed implementation manners

[0023] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The description of at least one exemplary embodiment below is actually only illustrative and in no way restricts the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0024] It should be noted that the terms used herein are only for describing the specific implementation manners and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or their combinations.

[0025] Unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps described in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for the sake of convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and devices should be regarded as part of the authorized specification. In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0026] Such as Figure 1As shown, according to an embodiment of the first aspect of the present invention, there is provided an image-based drop hammer impact speed measuring device, including a drop hammer unit, a calibration scale, an image acquisition unit, and an image processing unit. The drop hammer unit includes two guide rails, and the drop hammer falls along the two guide rails; the calibration scale is located in the plane formed by the axes of the two guide rails of the drop hammer unit; the angle at which the image acquisition unit acquires the image is perpendicular to the plane formed by the axes of the two guide rails of the drop hammer unit, and can make the drop hammer and the calibration scale be in the same frame of image, and transmits the acquired image to the image processing unit; the image processing unit calculates the speed of the drop hammer according to the high speed of the drop hammer falling in the two acquired frames of images and the time difference between the two frames of images.

[0027] With this setting, the number of devices required to achieve high-precision measurement of the impact speed is small, the use of the device is not restricted by space, and it is suitable for measuring the falling speeds of various objects.

[0028] Further, in one embodiment, the image acquisition unit is a high-speed camera or a video camera. By increasing the frame rate of the high-speed camera or the video camera, the accuracy of calculating the instantaneous speed of the drop hammer is improved.

[0029] Preferably, in one embodiment, the image acquisition unit is fixed on a support frame. Ensure that there is no movement during the shooting process and no unnecessary errors are introduced.

[0030] Further, in one embodiment, the drop hammer unit further includes a base, and the guide rails and the calibration scale are both installed on the base.

[0031] According to an embodiment of the second aspect, there is provided the above-mentioned image-based drop hammer impact speed measuring method, including the following steps:

[0032] Install the image-based drop hammer impact speed measuring device;

[0033] Acquire images including the drop hammer and the calibration scale during the falling process of the drop hammer;

[0034] Calculate the speed of the drop hammer according to the relative displacement between the drop hammer and the calibration scale in the two frames of images and the time interval between the two frames of images.

[0035] Further, in one embodiment, the two frames of images are two adjacent frames. Selecting two adjacent frames of images for calculation means selecting the distance that the drop hammer falls within the shortest time interval for calculating the instantaneous speed of the drop hammer, and at this time, the highest calculation accuracy is obtained. Preferably, in one embodiment, to improve the accuracy of calculating the instantaneous speed of the drop hammer, the time interval between the two frames of images needs to be shortened.

[0036] In order to have a further understanding of the image-based drop hammer impact speed measuring device and method provided by the present invention, the following will be described in detail with specific examples and drawings.

[0037] The present invention provides a measuring device for the impact velocity of a drop hammer based on images, including a drop hammer unit 1, a calibration scale 2, a high-speed camera 3, an image processing device unit 4, a drop hammer height h1, and a drop hammer height h2.

[0038] The calibration scale 2 is installed on the drop hammer unit and is used to calibrate and measure the height of the drop hammer during its fall. To reduce measurement errors, it should be ensured that the calibration scale does not tilt, and the scale surface should be located within the plane formed by the axes of the two guide rails of the drop hammer unit. Before the drop hammer test begins, the shooting work of the high-speed camera should be prepared in advance. It should be ensured that the shooting angle of the high-speed camera is perpendicular to the calibration scale surface, that is, within the plane formed by the axes of the two guide rails of the drop hammer unit, to prevent the influence of the viewing angle tilt on the accuracy of the calculation results. When in use, it should be noted that the velocity measurement method of the present invention is calculated based on the height difference of the drop hammer positions in two consecutive frames of images, and the displacement of the high-speed camera during the measurement process should be avoided as much as possible to introduce unnecessary errors.

[0039] When using this method to measure the velocity of the drop hammer, assuming that the instantaneous falling velocity of the drop hammer at position 1 is to be measured, the height information h1 of the drop hammer in this frame of image when the drop hammer is at position 1 can be obtained through the image processing device unit, and at the same time, the height information h2 of the next frame, that is, the drop hammer position 2, can be obtained. Then the falling height of the drop hammer within this frame of time can be obtained. The instantaneous falling velocity of the drop hammer at position 1 can be calculated by the following formula:

[0040] v = (h1 - h2)·k = Δh·k

[0041] In the formula, Δh is the height difference between two consecutive frames when the drop hammer is falling, and k is the frame rate used by the high-speed camera to shoot the falling process of the drop hammer.

[0042] A measuring method for measuring the impact velocity of a drop hammer based on image processing, the method comprising the following steps:

[0043] (1) Install and fasten the impact test piece in the drop hammer device, and install the calibration scale 2, the high-speed camera 3, and the image processing unit 4;

[0044] (2) Turn on the high-speed camera for shooting, and operate the drop hammer device to conduct a drop hammer impact test;

[0045] (3) Obtain a high-frame-rate video of the drop hammer falling process, and output the video frame by frame in the form of pictures through the image processing device;

[0046] (4) By reading the position of the drop hammer in one frame of image and the position of the drop hammer in the next frame of image, calculate the instantaneous falling velocity v of the drop hammer at this position according to the formula.

[0047] The calculation method of the instantaneous falling velocity of the drop hammer in step (4) is:

[0048] v = Δh·k

[0049] Wherein, Δh is the height difference between two consecutive frames when the drop hammer is falling, and k is the frame rate used by the high-speed camera to capture the falling process of the drop hammer.

[0050] In summary, a measuring device and method for the impact velocity of a drop hammer based on images provided by the present invention have at least the following advantages compared with the prior art:

[0051] (1) The device of the present invention is simple, the number of devices required to achieve high-precision measurement of the impact velocity is small, the use of the device is not limited by space, and it is suitable for measuring the falling velocity of various objects:

[0052] (2) The present invention calculates the impact velocity based on the high-frame-rate photos captured by the high-speed image acquisition unit, and has a relatively high measurement range and measurement accuracy.

[0053] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An image-based drop hammer impact velocity measurement device, characterized in that, it includes a drop hammer unit, a calibration scale, an image acquisition unit and an image processing unit. The drop hammer unit includes two guide rails, and the drop hammer falls along the two guide rails; the calibration scale is located in the plane formed by the axes of the two guide rails of the drop hammer unit; the image acquisition unit acquires images at an angle perpendicular to the plane formed by the axes of the two guide rails of the drop hammer unit, and can make the drop hammer and the calibration scale be in the same frame of image, and transmits the acquired image to the image processing unit; the image processing unit calculates the velocity of the drop hammer according to the high speed of the drop hammer falling in two acquired frames of images and the time difference between the two frames of images.

2. The image-based drop hammer impact velocity measurement device according to claim 1, characterized in that, the image acquisition unit is a high-speed camera or a video camera.

3. The image-based drop hammer impact velocity measurement device according to claim 2, characterized in that, the drop hammer unit further includes a base, and the guide rails and the calibration scale are both installed on the base.

4. The image-based drop hammer impact velocity measurement device according to claim 2, characterized in that, the image acquisition unit is fixed on a support frame.

5. An image-based drop hammer impact velocity measurement method using the image-based drop hammer impact velocity measurement device according to any one of claims 1-4, characterized in that, the method includes the following steps: installing the image-based drop hammer impact velocity measurement device; acquiring images during the fall of the drop hammer, including the images of the drop hammer and the calibration scale; calculating the velocity of the drop hammer according to the relative displacement between the drop hammer and the calibration scale in two frames of images and the time interval between the two frames of images.

6. The image-based drop hammer impact velocity measurement method according to claim 5, characterized in that, the two frames of images are two adjacent frames.

7. The image-based drop hammer impact velocity measurement method according to claim 6, characterized in that, to improve the accuracy of calculating the instantaneous velocity of the drop hammer, it is necessary to shorten the time interval between the two frames of images.

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