System for determining a hit and scoring points in a game of squash based on photodetection

Abstract

The present application relates to the technical field of sports intelligent analysis, and discloses a squash hitting judgment and scoring system based on photoelectric detection, which is characterized by the following: a photoelectric detection unit with an inner and outer double curtain structure is used to accurately measure the impact speed and impact point of a squash ball while judging an effective hit; a laser speckle rotation analysis module is used to collect the speckle image on the surface of the ball at the moment of impact and calculate the three-dimensional angular velocity vector; and a signal processing unit integrates these initial conditions and calls an aerodynamic model containing Magnus force to real-time predict the complete rebound trajectory. The present application overcomes the limitation of single information in the traditional scoring method, can accurately judge an effective hit in real time, and provides multi-dimensional dynamic parameters including the hitting speed, rotation intensity and complete flight trajectory for the user, thereby providing comprehensive and quantitative data support for the game 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 appear 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 lead to 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 trajectory after rebound, 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:

[0008] a photoelectric detection unit for detecting the passage of the squash through a predetermined spatial region;

[0009] a laser speckle rotation analysis module for measuring the rotation characteristics of the squash;

[0010] a signal processing unit, in communication with the photodetection unit and the laser speckle rotation analysis module, for determining valid hit events, calculating dynamic parameters of the cue ball and predicting its rebound trajectory;

[0011] a score display unit, in communication with the signal processing unit, for displaying the score and the dynamic parameters.

[0012] In an alternative embodiment, the photodetection unit comprises an inner light curtain disposed on the rebounding wall of the cue sport court, and an outer light curtain disposed 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 cue ball hitting the wall, and the outer light curtain is used in conjunction with the inner light curtain for speed measurement.

[0013] In an alternative embodiment, the signal processing unit comprises a hit determination unit, a dynamic parameter calculation unit and a trajectory prediction unit.

[0014] The hit determination unit is configured to determine valid hit events based on the light blocking signals received from the photodetection unit, and determine the hitting point coordinates. The hit determination unit sends a synchronization trigger signal to the laser speckle rotation analysis module while determining the valid hit events.

[0015] The dynamic parameter calculation unit is configured to calculate the speed and rotation characteristics of the cue ball.

[0016] Specifically, the dynamic parameter calculation unit performs the following functions:

[0017] records the time difference between the cue ball crossing the outer light curtain and the inner light curtain .

[0018] based on the known precise distance and the time difference , the impact speed of the cue ball is calculated by the following formula :

[0019] based on the impact speed and the elastic recovery coefficient of the wall material, the rebound speed of the cue ball is determined .

[0020] processes the image data collected by the laser speckle rotation analysis module to calculate the angular velocity vector representing the rotation characteristics of the cue ball .

[0021] The trajectory prediction unit is configured to predict the rebound trajectory of the cue ball based on the dynamic parameters. Specifically, the trajectory prediction unit receives the hitting point coordinates determined by the hit determination unit, and the rebound speed and the angular velocity vector determined by the dynamic parameter calculation unit It is based on an aerodynamic model containing Magnus force, and the rebound flight trajectory of the wall ball is obtained by numerically solving the following motion equation :

[0022] ;

[0023] Wherein: is the mass of the wall ball, is the acceleration vector of the wall ball at time t; is the gravity; is the air resistance, which is proportional to the square of the wall ball speed, and the direction is opposite to the speed direction; is the Magnus force, which is calculated by the following formula:

[0024] ;

[0025] Wherein, is the lift coefficient, is the instantaneous speed vector of the wall ball.

[0026] In an optional embodiment, the trajectory prediction unit is further used to predict the second collision event of the wall ball with other walls of the court by using the rebound flight trajectory.

[0027] In an optional embodiment, the laser speckle rotation analysis module includes a laser emitter and a high-speed image sensor. The laser emitter projects laser light onto the surface of the wall ball after receiving a synchronization trigger signal from the hit determination unit. The high-speed image sensor is used to synchronously collect continuous multiple frames of laser speckle images formed by the surface of the wall ball. The dynamic parameter calculation unit calculates the angular velocity vector by processing the continuous multiple frames of laser speckle images .

[0028] In an optional embodiment, the scoring display unit is further used to display the rebound flight trajectory calculated by the trajectory prediction unit in a visual form.

[0029] The present application provides a wall ball hit determination and scoring system based on photoelectric detection. It has the following advantages:

[0030] 1、The present application can accurately calculate the impact speed of the wall ball by setting the inner light curtain and the outer light curtain parallel to each other and processing the signals generated by the dynamic parameter calculation unit in sequence; at the same time, the laser speckle rotation analysis module is triggered by the hit determination unit to work at the moment of impact, so as to obtain the angular velocity vector of the wall ball. This makes the system obtain two key dynamic parameters of speed and rotation in addition to the traditional hit positioning, solving the technical problem of the prior art that only static hit information can be provided and the analysis dimension is single.

[0031] 2、The application uses the trajectory prediction unit to take 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 applies the air dynamics model containing Magnus force to solve. This enables the system to scientifically predict the squash rebound flight trajectory with the rotation effect, and visualizes the presentation through the scoring display unit, providing intuitive and quantitative technical feedback for the players, and improving the training assistance value of the system.

[0032] 3、The application uses the 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 the high-speed imaging and data processing for rotation analysis are only performed at the key moment when the effective hit occurs, 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

[0033] Figure 1 The structural block diagram of the squash hit determination and scoring system based on photoelectric detection for an embodiment of the application;

[0034] Figure 2 The structural schematic diagram of the photoelectric detection unit for an embodiment of the application;

[0035] Figure 3 The structural schematic diagram of the laser speckle rotation analysis module for an embodiment of the application;

[0036] Figure 4 The internal function block diagram of the signal processing unit for an embodiment of the application.

[0037] 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

[0038] 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 the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0039] Refer to the drawings Figure 1 , Figure 1is a structural block 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.

[0040] The photoelectric detection unit 10 functions to detect the passage 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.

[0041] 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.

[0042] 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 for receiving and processing 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 the dynamic parameters of the ping pong, and predicting the rebound flight trajectory thereof.

[0043] 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.

[0044] In the operation of the system, the connections and data flow among the units are as follows: the photoelectric detection unit 10 sends the real-time detected ping pong passage event signal to the signal processing unit 30. Based on this signal, the signal processing unit 30 performs analysis and, upon determining the occurrence of a hitting event, sends a synchronous trigger instruction to the laser speckle rotation analysis module 20 on one hand and receives the accurate timing information from the photoelectric detection unit 10 on the other hand.

[0045] Upon 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.

[0046] Upon 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 ensure the collaborative work among the functional modules of the system to complete the complete process from data collection to result presentation.

[0047] Referring to the 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.

[0048] 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.

[0049] In a specific embodiment, the inner light curtain 11 is composed of a plurality of 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.

[0050] The outer light curtain 12 has a similar structure to the inner light curtain 11 and is also composed of a plurality of 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.

[0051] 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.

[0052] Referring to the 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.

[0053] 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.

[0054] 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, so as to form a speckle pattern with clear contrast on the surface of the ball. Its output power is controlled within a safe level.

[0055] A high-speed image sensor 22 is configured to synchronously capture a series of laser speckle images formed by the rough surface of the cue ball after the laser light is reflected by the cue ball, and transfer the image data to the 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.

[0056] 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 impact point range of the cue ball.

[0057] 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 movement of the cue ball surface, while avoiding the saturation of the sensor due to the reception of too strong specular reflection light, thereby improving the signal-to-noise ratio of the image data.

[0058] 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 has the ability to perform data processing, numerical calculation and logic control.

[0059] 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.

[0060] The hit determination unit 31 is configured to process the signals from the photoelectric detection 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 is determined to occur.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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. The display content can include the real-time scores of both teams, 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.

[0066] 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.

[0067] The data interface can be a wireless communication module, such as a Bluetooth module or a Wi-Fi module. The function of the interface is to transmit all the data collected and processed by the system, including the score history, the dynamic parameters of each shot, and the trajectory data, to an external computing device, such as a smartphone, a tablet computer, or a personal computer. This provides a channel for long-term storage of data, detailed post-game technical analysis, and personal progress tracking of athletes.

[0068] The cooperative workflow of the system in a complete working cycle is as follows:

[0069] Firstly, during the process of the squash ball flying towards the rebound wall, its body will pass through the sensing planes of the outer curtain 12 and the inner curtain 11 in turn. The signal processing unit 30 will accurately record the time when the squash ball triggers the outer curtain 12 and the inner curtain 11, respectively, and calculate the time difference between the two The time difference data is temporarily stored for subsequent speed calculation.

[0070] Then, when the squash ball hits the wall and triggers the inner curtain 11, the hit determination unit 31 analyzes the light blocking signal sent by the inner curtain 11. If the signal characteristics meet the preset standard of valid hit, the unit immediately performs two parallel operations:

[0071] First, according to the array position of the blocked infrared transceiver, the impact point coordinates of the squash ball are determined , ;

[0072] Second, a synchronous trigger signal is sent to the laser speckle rotation analysis module 20.

[0073] The laser speckle rotation analysis module 20 immediately projects laser light onto the surface of the squash ball when it receives the synchronous trigger signal, and its high-speed image sensor 22 starts synchronously, continuously collecting multiple frames of laser speckle images formed by the surface of the squash ball. After the collection is completed, these image data containing the rotation information of the squash ball are immediately transmitted to the signal processing unit 30.

[0074] At this time, the dynamic parameter calculation unit 32 of the signal processing unit 30 begins to perform core operations. It calls the previously stored time difference and the preset distance D between the inner and outer curtains, calculates the impact speed of the squash ball , and determines its rebound speed accordingly. At the same time, it processes the continuous multiple frames of speckle images received from the laser speckle rotation analysis module 20, and solves the angular velocity vector characterizing the rotation state of the squash ball.

[0075] Upon completion of the calculation by the dynamic parameter calculation unit 32, the trajectory prediction unit 33 immediately calls all the necessary initial conditions: the impact point coordinates , , the rebound speed and the angular velocity vector . This unit solves the complete rebound flight trajectory of the cue ball after impact by numerically solving a pre-set aerodynamic model.

[0076] 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 scoring display unit 40. The scoring display unit 40 then presents these information to the user through its display screen, voice broadcast module or data interface, thereby completing a complete hit determination and scoring process.

[0077] In a specific embodiment, the calculation of the cue 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.

[0078] The dynamic parameter calculation unit 32 obtains the precise time stamps of the cue 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.

[0079] Based on the above two parameters, the dynamic parameter calculation unit 32 calculates the impact speed of the cue ball before it hits the wall surface by the following formula (1):

[0080] (1);

[0081] After determining the impact speed , the dynamic parameter calculation unit 32 further determines the rebound speed of the cue ball. This determination process is based on the collision physics model and can be characterized by the following formula (2): (2);in formula (2), is the coefficient of restitution between the cue ball and the rebound wall surface. This coefficient is an empirical parameter that depends on the material of the cue ball, the internal air pressure and the material properties of the wall surface. In a specific embodiment, The value of the rebound speed is obtained by calibration experiment and stored as a preset parameter in the signal processing unit 30. The dynamic parameter calculation unit 32 calls the preset value during operation to calculate the size of the rebound speed, which is a key initial condition for subsequent trajectory prediction calculation.

[0082] In a specific embodiment, the calculation of the wall ball angular velocity vector is performed by the dynamic parameter calculation unit 32 in the signal processing unit 30. The input data received by the calculation process is the continuous two or more frames of laser speckle images at the moment of impact collected by the high-speed image sensor 22 of the laser speckle rotation analysis module 20.

[0083] 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, and its value is the inverse of the frame rate.

[0084] In this calculation process, the dynamic parameter calculation unit 32 selects a reference sub-region of MxM pixels in the central region (i.e. the laser speckle coverage region) of the first frame image . Then, in a preset search range of the second frame image , the MxM pixel target sub-region with the highest similarity to the reference sub-region is found 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 , ) can be obtained.

[0085] 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 speed vector of the speckle pattern can be calculated by the following formula (3), which is the projection of the tangential velocity of the ball surface on the imaging plane: (2);

[0086] The two-dimensional surface velocity vector and the three-dimensional angular velocity vector of the wall ball.Related. Assume the coordinate system is established as follows: the Z-axis points towards the sphere along the optical axis of the high-speed image sensor 22, and the X and Y axes lie in the imaging plane. When the laser beam irradiation point is close to the vertex of the sphere directly opposite the sensor, the following relationship (4) can be established to solve for the components of the angular velocity in the X and Y directions: , (4), where R is the radius of the squash ball, which is a known physical parameter.

[0087] For the rotational component along the Z-axis (i.e., "recursive" rotation), which does not cause a global translation of the speckle pattern, but rather rotates it itself. For solving... The dynamic parameter calculation unit 32 performs polar coordinate transformation on the reference sub-region and the target sub-region in the two consecutive frames of images, transforming them from the Cartesian coordinate system to the polar coordinate system. By performing a one-dimensional cross-correlation operation on the transformed image in the angular dimension, the rotation angle Δθ of the speckle pattern itself can be obtained. This rotation angle can be calculated by the following formula (5). Its calculation formula is (5).

[0088] Finally, the dynamic parameter calculation unit 32 calculates the three components. Combined into a complete three-dimensional angular velocity vector And provide it to the trajectory prediction unit 33 for use.

[0089] In one specific implementation, the prediction of the squash ball's bounce trajectory 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 the initial conditions for its solution.

[0090] The trajectory prediction begins at the instant the squash ball separates from the wall, denoted as t=0. The initial conditions at this point include:

[0091] The initial position r(0) is the coordinate of the impact point determined by the hit determination unit 31. , , ),in The coordinates are usually 0 (assuming the wall surface is...). =0 plane).

[0092] The initial velocity v(0) is the rebound velocity determined by the dynamic parameter calculation unit 32. , is a three-dimensional vector whose size has been determined by formula (2) and whose direction is perpendicular to the wall and outward.

[0093] angular velocity vector Its value is the three-dimensional angular velocity vector calculated by the dynamic parameter calculation unit 32. During the duration of trajectory prediction, it can be assumed that the value decays slowly in the air and is approximately a constant.

[0094] The trajectory prediction unit 33 obtains the flight trajectory by solving a dynamic model describing the motion of a squash ball in the air. This model is based on Newton's second law, and its core equation of motion is shown in the following formula (6):

[0095] (6);

[0096] in:

[0097] Let be the mass of the squash ball, and be a known physical parameter.

[0098] Let be the acceleration vector of the squash ball at time t.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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):

[0103] (9);

[0104] wherein, is the lift coefficient, which value is related to air density , ball radius and other factors, and can be obtained by calibration experiments.

[0105] Since formula (6) is a nonlinear second-order ordinary differential equation system, there is no analytical solution, therefore the trajectory prediction unit 33 solves it by numerical integration method. In a specific embodiment, the fourth-order Runge-Kutta method (RK4) can be used for solving. The trajectory prediction unit 33 starts from the initial conditions r(0) and v(0) at time t = 0, and iteratively calculates the position r(t+Δt) and velocity v(t+Δt) at each subsequent time t+Δt with a small time step . From the initial conditions r(0) and v(0) at time t = 0, the unit iteratively calculates the position r(t+Δt) and velocity v(t+Δt) at each subsequent time t+Δt with a small time step . At each iteration step, the unit recalculates and according to the current instantaneous velocity v(t), and updates the resultant force , and then calculates the acceleration, and finally updates the velocity and position at the next time.

[0106] By continuously performing the above iteration process, the trajectory prediction unit 33 can generate a series of discrete position coordinate points, which, when connected, form the three-dimensional flight trajectory of the cue ball after the bounce. The trajectory data is finally sent to the scoring display unit 40 for visual display.

[0107] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application 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, The application relates to a wall ball game scoring system, comprising: a photoelectric detection unit for detecting a wall ball crossing a preset space region; the photoelectric detection unit comprises: an inner light curtain arranged on a rebound wall surface of a wall ball court for detecting a wall ball hitting the wall surface; an outer light curtain arranged in parallel with the inner light curtain and maintaining a known accurate distance with the inner light curtain; a laser speckle rotation analysis module for measuring rotation characteristics of the wall ball; the laser speckle rotation analysis module comprises: a laser emitter for projecting laser light to a surface of the wall ball after receiving a synchronous trigger signal; a high-speed image sensor for synchronously collecting continuous multiple frames of laser speckle images formed by the surface of the wall ball; a signal processing unit in communication connection with the photoelectric detection unit and the laser speckle rotation analysis module, for determining an effective hitting event, calculating dynamic parameters of the wall ball and predicting a rebound flight trajectory of the wall ball; the signal processing unit comprises: a hitting judgment unit for determining the effective hitting event based on a signal received from the photoelectric detection unit; the hitting judgment unit is further used for: judging the effective hitting event based on a light shielding signal received from the photoelectric detection unit and determining a hitting point coordinate; and sending a synchronous trigger signal to the laser speckle rotation analysis module while judging the effective hitting event; a dynamic parameter calculation unit for calculating a speed and rotation characteristics of the wall ball; a trajectory prediction unit for predicting a rebound trajectory of the wall ball based on the dynamic parameters; a scoring display unit connected with the signal processing unit for displaying game scores and the dynamic parameters.

2. The photodetector-based racquetball hit determination and scoring system of claim 1, wherein, the dynamic parameter calculation unit is further used for: recording a time difference of the wall ball successively crossing the inner light curtain and the outer light curtain in the photoelectric detection unit; and calculating an impact speed of the wall ball based on the known accurate distance between the inner light curtain and the outer light curtain and the time difference; and determining a rebound speed of the wall ball based on the impact speed.

3. The photodetector-based racquetball hit determination and scoring system of claim 2, wherein, the dynamic parameter calculation unit is further used for: processing the continuous multiple frames of laser speckle images collected by the high-speed image sensor to calculate an angular velocity vector representing the rotation characteristics.

4. The photodetector-based racquetball hit determination and scoring system of claim 3, wherein, the trajectory prediction unit is further used for: receiving the hitting point coordinate, the rebound speed and the angular velocity vector calculated by the dynamic parameter calculation unit; and solving the rebound flight trajectory of the wall ball based on an aerodynamic model containing Magnus force.

5. The photodetector-based racquetball hit determination and scoring system of claim 4, wherein, the trajectory prediction unit is further used for: predicting a second collision event of the wall ball with other wall surfaces of the court by using the rebound flight trajectory.

6. The photodetector-based racquetball hit determination and scoring system of claim 4, wherein, the scoring display unit is further used for: displaying the rebound flight trajectory solved by the trajectory prediction unit in a visual form.

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