Photoelectric detection-based squash hit judgment and integration system

Abstract

The invention relates to the technical field of sports intelligent analysis, and discloses a squash hit judgment and integration system based on photoelectric detection, the system accurately measures the impact speed and impact point of a squash while judging effective hit through a photoelectric detection unit with an inner and outer double-light-curtain structure; through a laser speckle rotation analysis module, a sphere surface speckle image is collected at the impact moment, and a three-dimensional angular velocity vector is calculated. The signal processing unit integrates the initial conditions, calls an aerodynamic model containing Magnus force, and predicts a complete rebound trajectory in real time. According to the method, the limitation of single information of a traditional scoring mode is overcome, effective hit can be accurately judged in real time, multi-dimensional dynamic parameters including the ball hitting speed, the rotation intensity and the complete flight path are provided for a user, and comprehensive and quantitative data support is provided for competition scoring and athlete technical analysis.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sports intelligent analysis, in particular to a squash hit determination and scoring system based on photoelectric detection. BACKGROUND

[0002] In fast-paced ball games such as squash, the determination of whether the ball hit the effective area and the quantitative analysis of the player's technical action are the core links in the competition and professional training. The traditional competition scoring mainly relies on the manual observation and judgment of the referee. This method not only has subjectivity and is easy to cause disputes, but also cannot provide objective and quantitative technical data such as hitting speed and rotation strength for the players.

[0003] In order to overcome the limitations of manual determination, some video image analysis systems based on conventional cameras have appeared in the prior art. These systems track the ball position by processing video streams to assist in determining whether it is hit or not. However, such technical solutions usually focus on trajectory tracking and landing point determination, and have limited ability to reveal the key physical characteristics of the ball at the moment of impact (such as impact speed and angular velocity of spin). In addition, complex image recognition algorithms require high computing resources, which may result in high system cost and delayed response, making it difficult to meet the demand for instant feedback.

[0004] Especially important is that the rotation state (i.e. angular velocity) of the squash is a key factor determining its rebound trajectory, which directly affects the difficulty and line of the return ball. The existing technical means generally lack effective methods for accurate and rapid measurement of this core dynamic parameter. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a squash hit determination and scoring system based on photoelectric detection, which solves the problem that the existing squash scoring system based on photoelectric detection can only provide static information such as hit position, cannot obtain the impact speed and rotation characteristics of the squash, and leads to the problem of single dimension of the system in providing sports analysis.

[0006] To achieve the above purpose, the present application realizes the following technical scheme: a squash hit determination and scoring system based on photoelectric detection.

[0007] The system comprises: a photoelectric detection unit for detecting the passage of the squash through a predetermined spatial region; a laser speckle rotation analysis module for measuring the rotation characteristics of the squash; a signal processing unit in communication connection with the photoelectric detection unit and the laser speckle rotation analysis module, for determining effective hit events, calculating dynamic parameters of the squash and predicting its rebound flight trajectory; A score display unit, connected to the signal processing unit, for displaying the game score and the dynamic parameters.

[0008] In an alternative embodiment, the photoelectric detection unit comprises an inner light curtain arranged on the rebound wall of the squash court, and an outer light curtain arranged in parallel with the inner light curtain and maintaining a known precise distance with the inner light curtain. The inner light curtain is used to detect the squash ball hitting the wall, and the outer light curtain is used to measure the speed in cooperation with the inner light curtain.

[0009] In an alternative embodiment, the signal processing unit comprises a hit determination unit, a dynamic parameter calculation unit and a trajectory prediction unit.

[0010] The hit determination unit is used to determine the valid hit event based on the light blocking signal received from the photoelectric detection unit, and to determine the impact point coordinates. While determining the valid hit event, the hit determination unit sends a synchronous trigger signal to the laser speckle rotation analysis module.

[0011] The dynamic parameter calculation unit is used to calculate the speed and rotation characteristics of the squash ball.

[0012] Specifically, the dynamic parameter calculation unit performs the following functions: Records the time difference between the squash ball crossing the outer light curtain and the inner light curtain .

[0013] Based on the known precise distance and the time difference , the impact speed of the squash ball is calculated by the following formula :

[0014] Based on the impact speed and the elastic recovery coefficient of the wall material, the rebound speed of the squash ball is determined .

[0015] Processes the image data collected by the laser speckle rotation analysis module to calculate the angular velocity vector representing the rotation characteristics of the squash ball .

[0016] The trajectory prediction unit is used to predict the rebound trajectory of the squash ball based on the dynamic parameters. Specifically, the trajectory prediction unit receives the impact point coordinates determined by the hit determination unit, and the rebound speed and the angular velocity vector determined by the dynamic parameter calculation unit. Based on an aerodynamic model containing Magnus force, the rebound flight trajectory of the squash ball is obtained by numerically solving the following motion equation : ; wherein: is the mass of the squash ball, is the acceleration vector of the squash ball at time t; is the gravity; is the air resistance, which is proportional to the square of the velocity of the squash ball and is opposite to the direction of the velocity; is the Magnus force, which is calculated by: ; wherein, is the lift coefficient, is the instantaneous velocity vector of the squash ball.

[0017] In an optional embodiment, the trajectory prediction unit is further configured to predict a second collision event of the squash ball with other walls of the court using the rebound flight trajectory.

[0018] In an optional embodiment, the laser speckle rotation analysis module comprises a laser emitter and a high-speed image sensor. The laser emitter projects laser light onto the surface of the squash ball upon receiving a synchronization trigger signal from the hit determination unit. The high-speed image sensor is configured to synchronously capture a plurality of continuous frames of laser speckle images formed by the surface of the squash ball. The dynamic parameter calculation unit calculates the angular velocity vector by processing the plurality of continuous frames of laser speckle images. .

[0019] In an optional embodiment, the scoring display unit is further configured to display the rebound flight trajectory calculated by the trajectory prediction unit in a visualized form.

[0020] The present application provides a squash hit determination and scoring system based on photoelectric detection. The present application has the following advantages: 1. The present application comprises an inner light curtain and an outer light curtain which are parallel to each other. The signals generated by the inner light curtain and the outer light curtain are processed by a dynamic parameter calculation unit, so that the impact velocity of the squash ball can be accurately calculated. Meanwhile, the laser speckle rotation analysis module is triggered by a hit determination unit to work at the moment of impact, so that the angular velocity vector of the squash ball can be obtained. This makes the system obtain two key dynamic parameters, i.e. velocity and rotation, in addition to the traditional hit positioning, thereby solving the technical problem of the prior art that only static hit information can be provided and the analysis dimension is single.

[0021] 2、The application uses a trajectory prediction unit, taking the rebound speed, angular velocity vector measured by the dynamic parameter calculation unit and the impact point coordinates determined by the hit determination unit as initial conditions, and applying an aerodynamics model containing Magnus force to solve. This enables the system to scientifically predict the squash rebound flight trajectory with the rotation effect, and visualizes it through the scoring display unit, providing intuitive and quantitative technical feedback to the players and improving the training assistance value of the system.

[0022] 3、The application uses a synchronous trigger signal generated by the hit determination unit to start the work of the laser speckle rotation analysis module. This cooperative working mechanism ensures that high-speed imaging and data processing for rotation analysis are only performed at the key moment of effective hit, avoiding continuous, high-power acquisition and analysis of sensor data. This not only significantly improves the operation efficiency and response speed of the system, but also ensures the accuracy and reliability of dynamic parameter capture. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The structural block diagram of a squash hit determination and scoring system based on photoelectric detection according to an embodiment of the application; Figure 2 The structural schematic diagram of a photoelectric detection unit according to an embodiment of the application; Figure 3 The structural schematic diagram of a laser speckle rotation analysis module according to an embodiment of the application; Figure 4 The internal functional block diagram of a signal processing unit according to an embodiment of the application.

[0024] Among them, 10, photoelectric detection unit; 11, inner light curtain; 12, outer light curtain; 20, laser speckle rotation analysis module; 21, laser emitter; 22, high-speed image sensor; 30, signal processing unit; 31, hit determination unit; 32, dynamic parameter calculation unit; 33, trajectory prediction unit; 40, scoring display unit. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the specification of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the application.

[0026] Referring to the drawings Figure 1 , Figure 1is a structure diagram of a photoelectric detection-based ping pong hitting determination and scoring system according to an embodiment of the present application. The present application provides a photoelectric detection-based ping pong hitting determination and scoring system, which can include a photoelectric detection unit 10, a laser speckle rotation analysis module 20, a signal processing unit 30, and a scoring display unit 40.

[0027] The photoelectric detection unit 10 functions to detect the passing of a ping pong through a preset space region and generate a corresponding detection signal. This unit is the physical basis for the system to obtain the position of the ping pong and the basic motion timing information.

[0028] The laser speckle rotation analysis module 20 functions to optically image the surface of the ping pong at a specific time to obtain image data for analyzing the rotation characteristics thereof. This module is the core sensing component of the system for measuring the rotation parameters of the ping pong.

[0029] The signal processing unit 30 is the processing core of the system. It is communicatively connected with the photoelectric detection unit 10 and the laser speckle rotation analysis module 20, and is used to receive and process the raw data collected by these two units. Based on the received data, the signal processing unit 30 performs all operations and logical judgments for determining valid hitting events, calculating dynamic parameters of the ping pong, and predicting the rebound flight trajectory thereof.

[0030] The scoring display unit 40 is connected with the signal processing unit 30. Its function is to receive the result data processed by the signal processing unit 30, and present the game scores and the dynamic parameters to the user in a visual or audible manner.

[0031] In the working of the system, the connection and data flow among the units are as follows: the photoelectric detection unit 10 sends the real-time detected ping pong passing event signal to the signal processing unit 30. Based on this signal, the signal processing unit 30 performs analysis, and when a hitting event is determined to occur, it sends a synchronous trigger instruction to the laser speckle rotation analysis module 20 on one hand, and receives accurate timing information from the photoelectric detection unit 10 on the other hand.

[0032] After receiving the synchronous trigger instruction, the laser speckle rotation analysis module 20 performs its imaging function, and returns the collected image data to the signal processing unit 30.

[0033] After receiving all the required data (including the timing signal from the photoelectric detection unit 10 and the image data from the laser speckle rotation analysis module 20), the signal processing unit 30 completes all calculation and prediction tasks, and sends the finally generated score, speed, rotation parameter, and trajectory data, etc. information to the scoring display unit 40 for output. This structure and connection mode ensures the collaborative work among the functional modules of the system to complete the complete process from data acquisition to result presentation.

[0034] Refer to the attached drawings Figure 2 , Figure 2 is a schematic diagram of a photoelectric detection unit 10 according to an embodiment of the present application. The photoelectric detection unit 10 can include: an inner light curtain 11 and an outer light curtain 12.

[0035] The inner light curtain 11 is installed on the effective scoring area of the rebound wall of the squash court, or is arranged close to the surface of the wall.

[0036] In a specific embodiment, the inner light curtain 11 is composed of multiple pairs of infrared emitters and infrared receivers, which are linearly arranged along two orthogonal directions (for example, horizontal and vertical directions) of the effective scoring area, thereby forming an invisible two-dimensional infrared grating or matrix in front of the wall. When the squash ball hits the wall, the ball will block one or more beams in the grating, and the inner light curtain 11 generates corresponding light blocking signals accordingly, which are used for subsequent hit event judgment and impact point coordinate positioning.

[0037] The outer light curtain 12 has a similar structure to the inner light curtain 11 and is also composed of multiple pairs of infrared emitters and infrared receivers. The outer light curtain 12 is installed in front of the inner light curtain 11 and ensures that the sensing plane formed thereby is strictly parallel to the sensing plane of the inner light curtain 11.

[0038] A rigid mechanical support structure is used to fix the inner light curtain 11 and the outer light curtain 12, so as to ensure that a known and accurately calibrated vertical distance is maintained between the two. The constancy of the distance is the basis for accurately calculating the impact speed of the squash ball. The function of the outer light curtain 12 is to detect the passing of the ball before the inner light curtain 11 during the process of the squash ball flying towards the wall, thereby providing a first time marker point for speed calculation.

[0039] Refer to the attached drawings Figure 3 , Figure 3 is a schematic diagram of a laser speckle rotation analysis module 20 according to an embodiment of the present application. The laser speckle rotation analysis module 20 can include: a laser emitter 21 and a high-speed image sensor 22.

[0040] The function of the laser emitter 21 is to project a laser beam onto the surface of the squash ball that is about to hit or is hitting the wall after receiving a synchronization trigger signal from the signal processing unit 30.

[0041] In a specific embodiment, the laser emitter 21 is a low-power semiconductor laser. Its working wavelength can be selected as visible light or near-infrared band, for example, 650 nanometers, to form a speckle pattern with clear contrast on the surface of the ball. Its output power is controlled within a safe level.

[0042] a high-speed image sensor 22, which is configured to synchronously capture a series of laser speckle images formed by the laser light reflected from the rough surface of the cue ball, and transfer the image data to a signal processing unit 30. In one embodiment, the high-speed image sensor 22 is a high frame rate CMOS image sensor. To ensure that the surface displacement of the cue ball at the moment of impact can be captured, the frame rate of the high-speed image sensor 22 can be set to 1000 frames per second or higher.

[0043] In terms of physical layout, the laser emitter 21 and the high-speed image sensor 22 are jointly integrated and installed at a predetermined position close to the bounce wall, such as above or aside the playing field. The installation direction is calibrated so that the projection area of the laser beam and the field of view of the high-speed image sensor both cover the expected range of cue ball impact points.

[0044] In one preferred embodiment, the projection direction of the laser beam forms a preset angle with the optical axis direction of the high-speed image sensor 22. Such a non-coaxial arrangement is intended to enable the high-speed image sensor 22 to effectively capture the speckle pattern caused by the tangential motion of the cue ball surface, while avoiding the saturation of the sensor caused by the reception of too strong specular reflection light, thereby improving the signal-to-noise ratio of the image data.

[0045] Please refer to the accompanying drawings Figure 4 , the accompanying drawings Figure 4 is an internal functional block diagram of the signal processing unit 30 according to one embodiment of the present application. In one embodiment, the signal processing unit 30 can be implemented in hardware by one or more processing devices, such as a microcontroller (MCU), a digital signal processor (DSP), or a field programmable gate array (FPGA). The processing device is capable of performing data processing, numerical calculation, and logic control.

[0046] In terms of logic functions, the signal processing unit 30 can include a hit determination unit 31, a dynamic parameter calculation unit 32, and a trajectory prediction unit 33.

[0047] The hit determination unit 31 is configured to process the signals from the photodetector unit 10. Specifically, the unit determines whether an effective hit event occurs based on the light blocking signal generated by the inner light curtain 11, and calculates the impact point coordinates of the cue ball according to the position information of the blocked infrared receivers , . At the same time, the unit outputs a synchronization trigger signal to the laser speckle rotation analysis module 20 at the moment when the effective hit event occurs.

[0048] A dynamic parameter calculation unit 32, which is responsible for calculating the key dynamic parameters of the cue ball. This unit receives the time difference data measured by the photodetector unit 10, and calculates the impact speed of the cue ball. This unit also receives the multi-frame laser speckle images collected by the laser speckle rotation analysis module 20, and solves the angular velocity vector representing the rotation characteristics of the cue ball through image processing algorithms. In addition, this unit determines the rebound speed of the cue ball based on the impact speed and the preset wall elasticity recovery coefficient.

[0049] A trajectory prediction unit 33, which is responsible for predicting the subsequent trajectory of the cue ball. This unit receives the impact point coordinates provided by the hit determination unit 31, as well as the rebound speed and angular velocity vector provided by the dynamic parameter calculation unit 32 as initial conditions. Based on these initial conditions, this unit solves the rebound flight trajectory of the cue ball by numerically solving an aerodynamic model that includes Magnus force.

[0050] It should be noted that the hit determination unit 31, the dynamic parameter calculation unit 32, and the trajectory prediction unit 33 are logical divisions based on function. In a specific physical implementation, they can be different program modules, functions or threads running on the same processor, or different logical function areas implemented in FPGA.

[0051] Please refer to the attached Figure 1 The scoring display unit 40 is responsible for receiving and outputting the result data processed by the signal processing unit 30. In a specific embodiment, the scoring display unit 40 can include a display screen, a voice broadcast module, and a data interface.

[0052] The display screen can be a liquid crystal display (LCD) screen, a light-emitting diode (LED) panel, or a projector for projecting information onto a designated surface in the venue. The screen is used to visually present data in the form of numbers and graphics. Its display content can include the real-time scores of both parties, the specific values of impact speed and angular velocity calculated by the dynamic parameter calculation unit 32, and the rebound flight trajectory of the cue ball depicted in a visual form solved by the trajectory prediction unit 33.

[0053] The voice broadcast module can be composed of a voice synthesis chip and a speaker. The function of this module is to provide information feedback in the form of sound. For example, it can broadcast the current score, the speed value or rotation intensity of the effective cue ball, and other key performance indicators in real time, so that users can obtain feedback information without continuously observing the display screen.

[0054] The data interface can be a wireless communication module, such as a Bluetooth module or a Wi-Fi module. The function of this interface is to transmit all data collected and processed by the system, including scoring history, dynamic parameters of each shot, and trajectory data, to an external computing device, such as a smartphone, tablet, or personal computer. This provides a channel for long-term data storage, detailed post-match technical analysis, and individual progress tracking for athletes.

[0055] The collaborative workflow of the system of this invention within a complete working cycle is as follows: First, as the squash ball flies towards the rebound wall, it will successively pass through the sensing planes of the outer light curtain 12 and the inner light curtain 11. The signal processing unit 30 will accurately record the moments when the squash ball triggers the outer light curtain 12 and the inner light curtain 11 respectively, and calculate the time difference between them. The time difference data is temporarily stored for subsequent speed calculations.

[0056] Immediately afterwards, when the squash ball hits the wall and triggers the inner light curtain 11, the hit determination unit 31 analyzes the light-blocking signal sent by the inner light curtain 11. If the signal characteristics meet the preset criteria for a valid hit, the unit immediately performs two parallel operations: First, determine the coordinates of the squash ball's impact point based on the array position of the blocked infrared transceivers. , ); Second, a synchronization trigger signal is sent to the laser speckle rotation analysis module 20.

[0057] Upon receiving the synchronization trigger signal, the laser speckle rotation analysis module 20 immediately projects a laser beam onto the surface of the squash ball using its laser emitter 21. Simultaneously, its high-speed image sensor 22 is activated, continuously acquiring multiple frames of laser speckle images formed on the squash ball's surface. After acquisition, these image data containing squash ball rotation information are immediately transmitted to the signal processing unit 30.

[0058] At this time, the dynamic parameter calculation unit 32 of the signal processing unit 30 begins to execute the core operation. It calls the previously stored time difference. The impact velocity of the squash ball is calculated based on the preset distance D between the inner and outer light curtains. And based on this, determine its rebound speed. Simultaneously, it processes multiple consecutive frames of speckle images received from the laser speckle rotation analysis module 20 to calculate the angular velocity vector characterizing the squash ball's rotation state. .

[0059] After the dynamic parameter calculation unit 32 completes the calculation, the trajectory prediction unit 33 immediately calls up all the necessary initial conditions: the coordinates of the impact point ( , rebound speed and angular velocity vector The unit calculates the complete rebound flight trajectory of the wall ball after impact by numerically solving a pre-set aerodynamic model.

[0060] Finally, the signal processing unit 30 integrates and sends all the calculation and prediction results, including the updated game score, the impact speed of this shot, the angular velocity vector, and the predicted flight trajectory data, to the score display unit 40. The score display unit 40 then presents this information to the user through its display screen, voice broadcast module, or data interface, thereby completing a complete hit determination and scoring process.

[0061] In a specific embodiment, the calculation of the wall ball impact speed and rebound speed is performed by the dynamic parameter calculation unit 32 in the signal processing unit 30. The physical model and mathematical principles on which this calculation process is based are described as follows.

[0062] The dynamic parameter calculation unit 32 obtains the precise time stamps of the wall ball triggering the outer light curtain 12 and the inner light curtain 11 from the system's timing module, and calculates the time difference Δt between the two. At the same time, the vertical distance D between the inner and outer light curtains is stored in the memory of the signal processing unit 30 as a known, pre-calibrated system constant.

[0063] Based on the above two parameters, the dynamic parameter calculation unit 32 calculates the impact speed of the wall ball before hitting the wall surface by the following formula (1) This speed mainly represents the velocity component of the wall ball perpendicular to the wall surface.

[0064] (1); After determining the impact speed , the dynamic parameter calculation unit 32 further determines the rebound speed of the wall ball. This determination process is based on the collision physics model and can be represented by the following formula (2): (2) In formula (2), is the coefficient of restitution between the wall ball and the rebound wall surface. This coefficient is an empirical parameter that depends on the material of the wall ball, the internal air pressure, and the material properties of the wall surface. In a specific embodiment, the value of is obtained through experimental calibration and stored as a pre-set parameter in the signal processing unit 30. The dynamic parameter calculation unit 32 calls this pre-set value during operation to calculate the size of the rebound speed . This rebound speed is a key initial condition for subsequent trajectory prediction calculations.

[0065] In one specific embodiment, the calculation of the wall ball angular velocity vector is performed by a dynamic parameter calculation unit 32 in the signal processing unit 30. The input data for this calculation process is the two or more consecutive frames of laser speckle images at the instant of impact acquired by the high-speed image sensor 22 of the laser speckle rotation analysis module 20.

[0066] The calculation principle is based on the Digital Image Correlation (DIC) method. The dynamic parameter calculation unit 32 first selects two consecutive images from the image sequence, denoted as the first frame image and the second frame image , where is the inter-frame time interval of the high-speed image sensor 22, which is the inverse of the frame rate.

[0067] In this calculation process, the dynamic parameter calculation unit 32 selects a reference sub-region of M x M pixels in the central region (i.e., the laser speckle coverage area) of the first frame image . Then, within a predetermined search range of the second frame image , the dynamic parameter calculation unit 32 finds the target sub-region of M x M pixels with the highest similarity to the reference sub-region by calculating the normalized cross-correlation coefficient. The position where the cross-correlation coefficient reaches the peak value is the new position of the reference sub-region in the second frame image. By comparing the center point coordinates of the reference sub-region in the two frames of images, a two-dimensional pixel displacement vector , is obtained.

[0068] After obtaining the pixel displacement vector, the dynamic parameter calculation unit 32 converts the pixel displacement to a physical displacement vector of the ball surface on the imaging plane using a pre-calibrated scale conversion coefficient (unit: meters / pixel). Accordingly, the translation velocity vector of the speckle pattern can be calculated using the following equation (3), which is the projection of the tangential velocity of the ball surface on the imaging plane: (2); This two-dimensional surface velocity vector is related to the three-dimensional angular velocity vector of the wall ball. Assuming that the coordinate system is established such that the Z-axis points to the wall ball along the optical axis direction of the high-speed image sensor 22, and the X-axis and Y-axis are in the imaging plane. When the laser beam illumination point is close to the vertex of the ball directly opposite the sensor, the following relationship (4) can be established to solve the components of the angular velocity in the X and Y directions: , (4), where R is the radius of the wall ball, which is a known physical parameter.

[0069] For the rotational component along the Z axis (i.e. "compound" rotation), which does not cause a global translation of the speckle pattern, but rather a rotation of itself. To solve for , the dynamic parameter calculation unit 32 performs polar coordinate transformation on the reference sub-region and the target sub-region in the two consecutive images, converting them from the Cartesian coordinate system to the polar coordinate system. By performing one-dimensional cross-correlation operation on the transformed images in the angle dimension, the rotation angle Δθ of the speckle pattern itself can be obtained. The rotation angle can be converted from the following formula (5) , whose calculation formula is (5).

[0070] Finally, the dynamic parameter calculation unit 32 integrates the three components calculated into a complete three-dimensional angular velocity vector , and provides it to the trajectory prediction unit 33 for use.

[0071] In a specific embodiment, the prediction of the trajectory of the rebound of the cue ball is performed by the trajectory prediction unit 33 in the signal processing unit 30. This unit integrates the calculation results from the hit determination unit 31 and the dynamic parameter calculation unit 32 as initial conditions for its solution.

[0072] The starting point of the trajectory prediction is the moment when the cue ball separates from the wall surface, denoted as t = 0. The initial conditions at this time include: Initial position r(0), whose value is the impact point coordinates , , ) determined by the hit determination unit 31, where the coordinates are usually 0 (assuming the wall surface is = 0 plane).

[0073] Initial velocity v(0), whose value is the rebound velocity determined by the dynamic parameter calculation unit 32, which is a three-dimensional vector whose magnitude has been determined by formula (2) and whose direction is perpendicular to the wall surface outward.

[0074] Angular velocity vector , whose value is the three-dimensional angular velocity vector solved by the dynamic parameter calculation unit 32, which can be assumed to decay slowly in the air and be approximately constant during the duration of the trajectory prediction.

[0075] The trajectory prediction unit 33 obtains the flight trajectory of the cue ball by solving a dynamic model describing the motion of the cue ball in the air. This model is based on Newton's second law, and its core motion equation is shown in the following formula (6): (6); where: Let be the mass of the squash ball, and be a known physical parameter.

[0076] Let be the acceleration vector of the squash ball at time t.

[0077] The net external force acting on the squash ball, in this embodiment, is mainly composed of gravity. air resistance And Magnus It consists of three parts.

[0078] The specific calculation methods for each of the forces are as follows: Gravity For a constant force, it is determined by the following formula (7): (7), where, This is the gravitational acceleration vector, and its direction is vertically downward.

[0079] air resistance It is a force related to the instantaneous velocity of the squash ball, whose magnitude is proportional to the square of the velocity, and whose direction is always opposite to the velocity vector. Conversely, it can be calculated using the following formula (8): (8), where, air density, The cross-sectional area of ​​the squash ball ( ), The air drag coefficient is given. These are all parameters that can be obtained by consulting reference materials or experimental calibration. v(t) is the instantaneous velocity vector of the squash ball at time t.

[0080] Magnus The lift is generated by the interaction between the squash ball's rotation and the air, and its direction is perpendicular to the angular velocity vector. and instantaneous velocity vector The plane formed by the forces. This force is determined by the vector cross product of the following formula (9): (9); in, The lift coefficient is related to the air density. , sphere radius These factors are related and can be obtained through experimental calibration.

[0081] Since equation (6) is a nonlinear system of second-order ordinary differential equations and has no analytical solution, the trajectory prediction unit 33 uses a numerical integration method to solve it. In a specific implementation, the fourth-order Runge-Kutta method (RK4) can be used for the solution. The trajectory prediction unit 33 uses a small time step. ,from Starting with the initial conditions r(0) and v(0) at time t=0, the position r(t+) at each subsequent time step is iteratively calculated. ) and velocity v(t+ In each iteration step, the unit is recalculated based on the current instantaneous velocity v(t). and and update the combined external forces Then, the acceleration is calculated based on this, and the velocity and position are updated for the next moment.

[0082] By continuously executing the above iterative process, the trajectory prediction unit 33 can generate a series of discrete position coordinate points. Connecting these points forms the three-dimensional flight trajectory of the squash ball after its bounce. This trajectory data is finally sent to the scoring and display unit 40 for visualization.

[0083] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A squash hit determination and integration system based on photoelectric detection, characterized in that, include: The photoelectric detection unit is used to detect the squash ball passing through a preset spatial area; Laser speckle rotation analysis module, used to measure the rotational characteristics of a squash ball; The signal processing unit is communicatively connected to the photoelectric detection unit and the laser speckle rotation analysis module, and is used to determine valid hit events, calculate the dynamic parameters of the squash ball, and predict its bounce trajectory. The scoring display unit, connected to the signal processing unit, is used to display the competition score and the dynamic parameters.

2. The squash hit determination and integration system based on photoelectric detection according to claim 1, characterized in that, The photoelectric detection unit includes: An internal light screen, installed on the rebound wall of a squash court, is used to detect squash balls hitting the wall. The outer light curtain is set parallel to the inner light curtain and maintains a known precise distance from it.

3. The squash hit determination and integration system based on photoelectric detection according to claim 1, characterized in that, The signal processing unit includes: A hit determination unit is used to determine a valid hit event based on a signal received from the photoelectric detection unit; The dynamic parameter calculation unit is used to calculate the speed and rotation characteristics of the squash ball; The trajectory prediction unit is used to predict the bounce trajectory of the squash ball based on dynamic parameters.

4. The squash hit determination and integration system based on photoelectric detection according to claim 3, characterized in that, The dynamic parameter calculation unit is further used for: Record the time difference between the squash ball passing through the inner and outer light curtains in the photoelectric detection unit; The impact velocity of the squash ball is calculated based on the known precise distance between the inner light curtain and the outer light curtain and the time difference. The rebound speed of the squash ball is determined based on the impact speed.

5. The squash hit determination and integration system based on photoelectric detection according to claim 4, characterized in that, The hit determination unit is further used for: The valid hit event is determined based on the light-blocking signal received from the photoelectric detection unit, and the coordinates of the impact point are determined. And at the same time as determining the valid hit event, a synchronous trigger signal is sent to the laser speckle rotation analysis module.

6. The squash hit determination and integration system based on photoelectric detection according to claim 5, characterized in that, The laser speckle rotation analysis module includes: Upon receiving the synchronization trigger signal, the laser emitter projects a laser beam onto the surface of the squash ball. A high-speed image sensor is used to simultaneously acquire multiple consecutive frames of laser speckle images formed on the surface of a squash ball.

7. The squash hit determination and integration system based on photoelectric detection according to claim 6, characterized in that, The dynamic parameter calculation unit is further used for: The continuous multi-frame laser speckle images acquired by the high-speed image sensor are processed to calculate the angular velocity vector characterizing the rotational properties.

8. The squash hit determination and integration system based on photoelectric detection according to claim 7, characterized in that, The trajectory prediction unit is further used for: Receive the impact point coordinates, rebound velocity, and angular velocity vector calculated by the dynamic parameter calculation unit; Based on an aerodynamic model incorporating Magnus forces, the rebound trajectory of the squash ball was calculated.

9. The squash hit determination and integration system based on photoelectric detection according to claim 8, characterized in that, The trajectory prediction unit is further used for: Using the rebound trajectory, secondary collision events between the squash ball and other walls of the court can be predicted.

10. The squash hit determination and integration system based on photoelectric detection according to claim 8, characterized in that, The scoring and display unit is further used for: The rebound flight trajectory calculated by the trajectory prediction unit is displayed in a visual form.

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