CN112245893A - Method and device for measuring rotation speed of table tennis - Google Patents
Method and device for measuring rotation speed of table tennis Download PDFInfo
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- CN112245893A CN112245893A CN202011225260.0A CN202011225260A CN112245893A CN 112245893 A CN112245893 A CN 112245893A CN 202011225260 A CN202011225260 A CN 202011225260A CN 112245893 A CN112245893 A CN 112245893A
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- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B71/00—Games or sports accessories not covered in groups A63B1/00 - A63B69/00
- A63B71/06—Indicating or scoring devices for games or players, or for other sports activities
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- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B2102/00—Application of clubs, bats, rackets or the like to the sporting activity ; particular sports involving the use of balls and clubs, bats, rackets, or the like
- A63B2102/16—Table tennis
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- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B2220/00—Measuring of physical parameters relating to sporting activity
- A63B2220/30—Speed
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- General Health & Medical Sciences (AREA)
- Physical Education & Sports Medicine (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
The invention discloses a method and a device for measuring the rotation speed of table tennis, comprising the following steps: constructing a coordinate system, setting an image acquisition range, and acquiring an image; identifying the mark of the table tennis, and acquiring the main direction of the mark; calculating an included angle alpha between the main direction and an x axis of a coordinate system; acquiring an included angle beta between the main direction of the mark of the table tennis ball in the image after the time interval T and the x axis of the coordinate system; acquiring the rotation direction of the table tennis according to the angle difference between the included angle alpha and the included angle beta; and calculating the rotation speed omega of the table tennis according to the angle difference and the time interval T. According to the invention, the image acquisition range is set to analyze the characteristics of the table tennis in the small-range image, so that the defects of large data transmission quantity and low speed in the traditional high-speed vision field are overcome, and the rotation speed of the table tennis can be calculated in a very short time.
Description
Technical Field
The invention relates to the technical field of computer vision, in particular to a method and a device for measuring the rotation speed of a table tennis ball.
Background
In recent years, computer vision technology has been increasingly used to assist in educational training of athletic activities, and is also widely used in sporting events. In the application of computer vision in table tennis, the observation of the rotary ball is a big difficulty, and a system capable of calculating the rotation direction and the rotation speed of the table tennis in real time can facilitate the process of the repeated training or the match of athletes and coaches, and enhance the teaching effect of the rotary ball.
In the prior art, the observation of the motion state of the table tennis is generally realized by observing the rotation of the table tennis through a high-speed camera, but the table tennis needs to be covered on the whole table tennis field to obtain a complete table tennis motion track, the equipment needs to be deployed in a large range and the scheme is very complex, and the requirement on the high-speed camera is very high, a plurality of groups of high-speed cameras are needed, and the local details of the table tennis need to be clearly observed. The scheme in the prior art has extremely high requirements on site range and equipment, the equipment deployment in a large range has very high requirements on the signal transmission speed between equipment, and the scheme is complex, the signal transmission efficiency is not high and the cost is too high on the whole.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method and a device for measuring the rotating speed of a table tennis ball, which solve the defects of large data transmission quantity and low speed in the traditional high-speed vision field and ensure that the rotating speed of the table tennis ball can be calculated in a very short time by setting an image acquisition range to analyze the characteristics of the table tennis ball in a small-range image. To achieve the above objects and other advantages in accordance with the present invention, there is provided a method of measuring a rotation speed of a table tennis ball, comprising:
(1) constructing a coordinate system, setting an image acquisition range, and acquiring an image;
(2) identifying the mark of the table tennis, and acquiring the main direction of the mark;
(3) calculating an included angle alpha formed by the main direction and an x-axis of a coordinate system, wherein the x-axis of the coordinate system is parallel to a plane where the table tennis table is located;
(4) repeating the steps (2) to (3), and obtaining an included angle beta formed by the main direction of the mark of the table tennis ball in the image after the time interval T and the x axis of the coordinate system;
(5) acquiring the rotation direction of the table tennis according to the angle difference between the included angle alpha and the included angle beta;
(6) calculating the rotation speed omega of the table tennis ball according to the angle difference and the time interval T:
the time interval T is determined by the frame rate of the images.
Preferably, the image acquisition range is an image of a table tennis ball in the process of moving after passing through a table tennis table middle net, a first distance is set after the table tennis ball passes through the table tennis table middle net, and the setting range of the first distance is 20 cm-40 cm.
Preferably, the frame rate of the image is set in a range of 2000fps to 4000 fps.
Preferably, in the step (3), the principal direction of the label is obtained by a principal component analysis method.
The device for measuring the rotation speed of the table tennis is characterized by comprising an image acquisition module, a sensor module, a light source module, a data set transmission module and a processing module, wherein the processing module comprises a storage unit and a processing unit, and the processing unit is used for executing instructions in the storage unit;
the image acquisition module is used for shooting images of the table tennis flying through the vicinity of the net in the table tennis table;
the sensor module is used for providing a trigger signal to enable the image acquisition module to acquire images simultaneously;
the light source module is used for providing the brightness requirement of a shooting area;
the data transmission module is used for transmitting the image data to the processing module;
the processing module is used for operating a ping-pong ball rotation direction and speed algorithm to calculate the ping-pong ball rotation direction and speed.
Preferably, the image acquisition module comprises at least two high-speed cameras, and the high-speed cameras are hung right in front of the trainer and used for acquiring the image acquisition range.
Preferably, the sensor module is an infrared grating trigger, and the infrared grating trigger is arranged in an area above the middle net of the table and used for providing a trigger signal to start the image acquisition module to acquire the image in the image acquisition range.
Preferably, the infrared grating trigger is used for monitoring a shooting area 110cm above the middle net in real time, when a table tennis ball passes through the infrared grating, the infrared grating is triggered to generate a pulse signal, the pulse signal is transmitted to the high-speed cameras, and the transmission time of the infrared signal is less than 50us, so that the two high-speed cameras synchronously acquire images.
Preferably, the processing module is an industrial personal computer, the light source module comprises 6 100W non-stroboscopic light sources and a first suspender used for fixing the light sources, and the light sources are located right above the middle net of the table tennis table through the first suspender.
Preferably, the data set transmission module comprises a USB optical modem, an optical fiber wire and a USB3.0 wire, wherein one end of the optical fiber wire is connected with the high-speed camera, the other end of the optical fiber wire is connected with the USB optical modem, the USB optical modem is connected with the USB3.0 wire, and the USB3.0 wire is connected with the processing module.
Compared with the prior art, the invention has the beneficial effects that:
(1) the binocular high-speed image acquisition system simultaneously uses two high-speed cameras to simultaneously acquire images, and can ensure that the identification on the table tennis ball always exists in the field of view of the cameras.
(2) The binocular high-speed image acquisition system records the process image of the table tennis passing through the net in the table and moving within the distance range of 30cm, transmits a small amount of data to realize near real-time data transmission, and avoids the real-time transmission of large-flow data and the limitation of the current data transmission bandwidth.
(3) The supplementary lighting light source system provides enough light intensity to enable the exposure time of the camera to be as short as possible so as to meet the shooting requirement;
(4) the synchronous automatic trigger system of the camera solves the problem that the ultra-high speed camera simultaneously acquires the image of the table tennis.
(5) According to the data transmission system, the optical fiber signal and the USB3.0 signal are converted mutually by using the USB optical modem, and long-distance transmission and high-speed transmission of images are realized simultaneously.
(6) The ping-pong ball rotating direction and speed algorithm can quickly and accurately calculate the ping-pong ball rotating direction and speed.
Drawings
FIG. 1 is a block flow diagram of the steps of a method for measuring the rotational speed of a table tennis ball according to the present invention;
fig. 2 is a block flow diagram of a method and apparatus for measuring ping-pong ball rotation speed according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1-2, a method of measuring a ping-pong ball rotation speed includes:
(1) constructing a coordinate system, setting an image acquisition range, and acquiring an image;
(2) identifying the mark of the table tennis, and acquiring the main direction of the mark;
(3) calculating an included angle alpha formed by the main direction and an x-axis of a coordinate system, wherein the x-axis of the coordinate system is parallel to a plane where the table tennis table is located;
(4) repeating the steps (2) to (3), and obtaining an included angle beta formed by the main direction of the mark of the table tennis ball in the image after the time interval T and the x axis of the coordinate system;
(5) acquiring the rotation direction of the table tennis according to the angle difference between the included angle alpha and the included angle beta;
(6) calculating the rotation speed omega of the table tennis ball according to the angle difference and the time interval T:
the time interval T is determined by the frame rate of the images.
Specifically, the image acquisition module is the high-speed camera of two 200W pixel 3000 frames in this embodiment, and the high-speed camera passes through the jib fixed erection for acquire the real-time image in the image acquisition scope, so that the mark on the table tennis can be shot clearly to the high-speed camera, this mark is the trade mark or the artificial mark of table tennis, use two mesh high-speed cameras simultaneously promptly two high-speed cameras simultaneously to gather the image simultaneously, the camera field of vision covers 80% surface of table tennis, can guarantee that the sign on the table tennis exists all the time in the camera field of vision.
The processing module is an industrial personal computer, the industrial personal computer is used for storing the image acquired by the image acquisition module into a solid state disk in the industrial personal computer, the solid state disk is selected from a Pcie 3.0 interface NVME protocol solid state disk, the theoretical read-write speed of the solid state disk can reach 3000MB/s, and the write-in time of 90MB data is about 0.03s, so that the total time required by storing the image shot by a ping-pong ball through the network once is 0.26s, and the real-time requirement of the system on the signal is met.
Further, the image acquisition range is an image of a table tennis ball moving process after passing through the table tennis table middle net, a first distance is arranged after the table tennis ball passes through the table tennis table middle net, and the setting range of the first distance is 20 cm-40 cm.
Further, the frame rate of the image is set in a range of 2000fps to 4000 fps.
Further, in the step (3), the principal direction of the marker is obtained by a principal component analysis method.
The device for measuring the rotation speed of the table tennis is characterized by comprising an image acquisition module, a sensor module, a light source module, a data set transmission module and a processing module, wherein the processing module comprises a storage unit and a processing unit, and the processing unit is used for executing instructions in the storage unit;
the image acquisition module is used for shooting images of the table tennis flying through the vicinity of the net in the table tennis table;
the sensor module is used for providing a trigger signal to enable the image acquisition module to acquire images simultaneously;
the light source module is used for providing the brightness requirement of a shooting area;
the data transmission module is used for transmitting the image data to the processing module;
the processing module is used for operating a ping-pong ball rotation direction and speed algorithm to calculate the ping-pong ball rotation direction and speed.
Furthermore, the image acquisition module comprises at least two high-speed cameras, and the high-speed cameras are hung right in front of the trainer and used for acquiring the image acquisition range.
Further, the sensor module is an infrared grating trigger, and the infrared grating trigger is arranged in an area above the middle net of the table and used for providing a trigger signal to start the image acquisition module to acquire the image in the image acquisition range.
Furthermore, the infrared grating trigger is used for monitoring a shooting area 110cm above the middle net in real time, when a table tennis ball passes through the infrared grating, the infrared grating is triggered to generate a pulse signal, the pulse signal is transmitted to the high-speed cameras, the transmission time of the infrared signal is less than 50us, and the two high-speed cameras can synchronously acquire images.
Further, the light source module comprises 6 100W non-stroboscopic light sources and a first suspender used for fixing the light source, and the light source is positioned right above the middle net of the table tennis table through the first suspender.
Further, data set transmission module includes USB optical modem, optic fibre wire rod and USB3.0 wire rod, optic fibre wire rod one end links to each other with high-speed making a video recording, the other end with USB optical modem links to each other, USB optical modem is connected with USB3.0 wire rod, USB3.0 wire rod is connected with processing module, and communication between the module adopts following mode, and high-speed camera passes through optic fibre and is connected with USB optical modem, and the industrial computer passes through USB3.0 wire rod and is connected with USB optical modem, uses optic fibre to solve the speed decay problem of USB3.0 wire rod when remote transmission, and the actual real-time transmission speed of USB3.0 is about 380MB/S, uses USB3.0 transmission 80MB data needs 0.23S.
The method comprises the steps that a player hits a ball, when a table tennis ball moves to a position above a middle net of a table tennis table, an infrared grid trigger is triggered, two high-speed cameras start to synchronously acquire images after receiving a trigger signal of the infrared grid trigger, then the high-speed cameras transmit the images to an industrial personal computer and store the images into a storage unit of the industrial personal computer, a processing unit of the industrial personal computer obtains the position of the table tennis ball in a first image to be processed in a plurality of images according to a background difference method, then a mark of the table tennis ball is obtained, then the main direction of the mark of the table tennis ball is obtained according to a main component analysis method, and the main direction is obtained through analysis. And after the main direction is obtained, calculating an included angle alpha between the main direction and the x axis of the coordinate system.
Calculating to obtain an included angle alpha of the processed first image, selecting images separated by one frame or several frames, obtaining an included angle beta between the main direction of the marker of the table tennis ball in the image and the x axis of the coordinate system, wherein the time interval between the image and the processed first image is a time interval T, and if the two images are separated by one frame, shooting at a frame rate of 3000fps according to the premise that a high-speed camera shoots, the value of T is
And after the included angle alpha and the included angle beta are obtained, the rotation direction of the table tennis is obtained according to the angle difference of the two included angles.
Then, based on the time interval T, the rotation speed ω of the table tennis ball is calculated:
so as to obtain the speed and rotation information of the table tennis in the hitting.
The system further comprises a light source module, the light source module is arranged above the table tennis table and used for providing a stable light source for the image acquisition module, and the accuracy of image acquisition of the image acquisition module is improved. In this embodiment, the light source module is a 6-station 100W stroboflash-free light source and a suspension rod for suspending the light source, the light source is installed right above a middle net of a table tennis table through the suspension rod, if the table tennis moving speed is 20m/s, the transverse view field of the high-speed camera is about 1.5m, and the transverse resolution is 1920, the precision of a single pixel is 0.78mm, and the shooting exposure time of the camera cannot be more than 40 us. Through the actual measurement of the illuminometer, when the exposure of the camera is 40us, the illumination intensity needs 10000lux to shoot a clear picture, namely the average brightness of a shooting area needs to be about 10000lux, and if the brightness of the working environment of the system is poor, the light source module is started to supplement illumination required by the system.
In the above embodiment, the image acquisition range is an image of a movement process of the table tennis after passing through the table tennis net, and the first distance is set after the table tennis passes through the table tennis net. As another embodiment, the first distance is set to be 20cm to 40cm, and when the first distance is set to be 20cm, the image acquisition module with a higher shooting frame rate is required to shoot at a frame rate of 4000 fps. When the first distance is set to 40cm, the shooting frame rate of the image acquisition module needs to be reduced, and shooting is performed at a frame rate of 2000 fps. That is, in the above embodiment, the high-speed camera takes a picture at a frame rate of 3000fps, and if the frame rate of the high-speed camera is increased, the setting of the first distance is decreased accordingly. If the frame rate of the high speed camera is decreased, the setting of the first distance is correspondingly increased.
In the above embodiment, the coordinate system is constructed in a manner that the desktop is used as the xy plane, and the vertical upward direction is used as the positive direction of the z axis. As another embodiment, another common method may also be adopted to construct the coordinate system, for example, directly construct the coordinate system on the image acquired by the image acquisition module by using the image edge or construct the coordinate system in the image, the construction principle is that the x-axis of the coordinate system is parallel to the plane where the table tennis table is located and the x-axis of the coordinate system is parallel to the middle net of the table tennis table as much as possible, and the main direction of the marker of the table tennis and the reference mode of the coordinate system are changed accordingly.
The number of devices and the scale of the processes described herein are intended to simplify the description of the invention, and applications, modifications and variations of the invention will be apparent to those skilled in the art.
While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.
Claims (10)
1. A method for measuring the rotation speed of a table tennis ball is characterized by comprising the following steps:
(1) constructing a coordinate system, setting an image acquisition range, and acquiring an image;
(2) identifying the mark of the table tennis, and acquiring the main direction of the mark;
(3) calculating an included angle alpha formed by the main direction and an x-axis of a coordinate system, wherein the x-axis of the coordinate system is parallel to a plane where the table tennis table is located;
(4) repeating the steps (2) to (3), and acquiring an included angle beta between the main direction of the mark of the table tennis ball in the image after the time interval T and the x axis of the coordinate system;
(5) acquiring the rotation direction of the table tennis according to the angle difference between the included angle alpha and the included angle beta;
(6) calculating the rotation speed omega of the table tennis ball according to the angle difference and the time interval T:
the time interval T is determined by the frame rate of the images.
2. The method for measuring ping-pong rotation as claimed in claim 1, wherein the image capturing range is an image of a process of the ping-pong ball moving after passing through the net in the table, the ping-pong ball passing through the net in the table is provided with a first distance, and the first distance is provided in a range of 20cm to 40 cm.
3. The method of claim 1, wherein a frame rate of the image is set in a range of 2000fps to 4000 fps.
4. The method of claim 1, wherein in step (3), the principal direction of the mark is obtained by principal component analysis.
5. The apparatus for measuring rotational speed of table tennis ball according to claim 1, comprising an image acquisition module, a sensor module, a light source module, a data set transmission module and a processing module, wherein the processing module comprises a storage unit and a processing unit, and the processing unit is used for executing instructions in the storage unit;
the image acquisition module is used for shooting images of the table tennis flying through the vicinity of the net in the table tennis table;
the sensor module is used for providing a trigger signal to enable the image acquisition module to acquire images simultaneously;
the light source module is used for providing the brightness requirement of a shooting area;
the data transmission module is used for transmitting the image data to the processing module;
the processing module is used for operating a ping-pong ball rotation direction and speed algorithm to calculate the ping-pong ball rotation direction and speed.
6. The apparatus according to claim 5, wherein the image capturing module comprises at least two high-speed cameras, and the high-speed cameras are mounted right in front of the trainer and used for acquiring the image capturing range.
7. The apparatus for measuring rotational velocity of table tennis as claimed in claim 5, wherein the sensor module is an infrared grid trigger disposed in an area above the net in the table and configured to provide a trigger signal to activate the image capturing module to capture the image of the image capturing area.
8. The apparatus for measuring the rotation speed of table tennis as claimed in claim 7, wherein the infrared grid trigger is used for monitoring a shooting area 110cm above the middle net in real time, when the table tennis passes through the infrared grid, the infrared grid trigger generates a pulse signal, the pulse signal is transmitted to the high-speed cameras, the transmission time of the infrared signal is less than 50us, and the two high-speed cameras synchronously acquire images.
9. The apparatus of claim 5, wherein the processing module is an industrial personal computer, the light source module is a first boom comprising 6 100W strobeless light sources and a fixed light source, and the light source is located directly above the net in the table tennis table through the first boom.
10. The apparatus for measuring ping-pong ball rotation speed according to claim 5, wherein the data set transmission module comprises a USB optical modem, an optical fiber wire and a USB3.0 wire, one end of the optical fiber wire is connected with the high-speed camera, the other end of the optical fiber wire is connected with the USB optical modem, the USB optical modem is connected with the USB3.0 wire, and the USB3.0 wire is connected with the processing module.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011225260.0A CN112245893A (en) | 2020-11-05 | 2020-11-05 | Method and device for measuring rotation speed of table tennis |
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| CN202011225260.0A CN112245893A (en) | 2020-11-05 | 2020-11-05 | Method and device for measuring rotation speed of table tennis |
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| CN202011225260.0A Pending CN112245893A (en) | 2020-11-05 | 2020-11-05 | Method and device for measuring rotation speed of table tennis |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114612522A (en) * | 2022-05-09 | 2022-06-10 | 广州精天信息科技股份有限公司 | Table tennis sport parameter detection method and device and table tennis training auxiliary system |
-
2020
- 2020-11-05 CN CN202011225260.0A patent/CN112245893A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114612522A (en) * | 2022-05-09 | 2022-06-10 | 广州精天信息科技股份有限公司 | Table tennis sport parameter detection method and device and table tennis training auxiliary system |
| CN114612522B (en) * | 2022-05-09 | 2023-01-17 | 广东金融学院 | Table tennis sport parameter detection method and device and table tennis training auxiliary system |
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