Spinning Ball Research Articles

Table tennis ball landing control in a robotic system by cameras

Abstract Controlling the landing position of a spinning ball is difficult when using a table tennis robot. A complete physical model requires the factoring in of aerodynamic elements and object collisions, and inaccurate environmental coefficients would increase the landing position error. This study proposed a landing position control method based on a cascade neural network (CNN) that consists of forward and recurrent neural networks (RNNs). The forward NNs are used to estimate the velocity of the outgoing ball according to the velocity and acceleration of the incoming ball captured by cameras and the desired velocity of the outgoing ball. The RNN is employed to reverse-predict ball displacement based on the state of the incoming ball, desired landing point, and ball flight duration. The experiments verified that the method proposed in this study achieved control of differently spinning balls more effectively than the locally weighted regression (LWR)-based model did. The success rate of the CNN at two of six desired landing points was 25.9% and 32.9% higher, respectively, compared with use of the LWR-based model.

Correction to: Analysis of point-contact models of the bounce of a hard spinning ball on a compliant frictional surface

Correction to: Analysis of point-contact models of the bounce of a hard spinning ball on a compliant frictional surface

A Mobile App Driven Smart Ball Launch System for Solo Sports Training

Abstract: In today's world, athletes face intense competition in a variety of sports, but there are few opportunities for them to practice or evaluate their performance on their own, making it difficult for them to grow. Thus, a system is proposed in this paper that allows players to conveniently practice alone without requiring human assistance and may also help them in analyzing their skills. The method mostly concentrates on tennis game. The automatic ball launches for practice is the main aim of the system. With the assistance of a Node MCU that can interact over the internet, the system gives the user exact control over when to launch balls, what kind of ball to launch, and how to launch them remotely. Which is possible on mobile devices due to Blynk app interface. Typically, the system offers three different ball launch types: over spin, backspin, and rapid ball launch. It also allows for exact speed control of the motors used to make the ball launch.

The effect of multimedia-assisted sport education model on teaching tennis lessons in colleges and universities

Abstract The development of information technology is accelerating the development of network multimedia-assisted teaching modes. In this regard, this paper studies the influence of multimedia-assisted sports education on the teaching of tennis classes in colleges and universities. The first step is to analyze the applicable fields and characteristics of network multimedia CAI. Then, the TLBO algorithm focuses on analyzing the “teaching” and “learning” phases of tennis teaching and finds that the TLBO algorithm has defects. To overcome the local optimal situation of the TLBO algorithm, a grouping mechanism is implemented to optimize the TLBO algorithm and maintain the diversity of the population. Finally, the influence of multimedia-assisted teaching was studied in terms of learning motivation, physical fitness, and learning effect. From the perspective of liking tennis sport, the number of experimental classes is 20, which is 15 more than the number of control classes. The mean score of the experimental class in the forehand hitting spinning ball test was 19 points higher than that of the control class.

Analysis of point-contact models of the bounce of a hard spinning ball on a compliant frictional surface

Abstract Inspired by the turf–ball interaction in golf, this paper seeks to understand the bounce of a ball that can be modelled as a rigid sphere and the surface as supplying a viscoelastic contact force in addition to Coulomb friction. A general formulation is proposed that models the finite time interval of bounce from touch-down to lift-off. Key to the analysis is understanding transitions between slip and roll during the bounce. Starting from the rigid-body limit with an energetic or Poisson coefficient of restitution, it is shown that slip reversal during the contact phase cannot be captured in this case, which generalizes to the case of pure normal compliance. Yet, the introduction of linear tangential stiffness and damping does enable slip reversal. This result is extended to general weakly nonlinear normal and tangential compliance. An analysis using the Filippov theory of piecewise-smooth systems leads to an argument in a natural limit that lift-off while rolling is non-generic and that almost all trajectories that lift off do so under slip conditions. Moreover, there is a codimension-one surface in the space of incoming velocity and spin which divides balls that lift off with backspin from those that lift off with topspin. The results are compared with recent experimental measurements on golf ball bounce and the theory is shown to capture the main features of the data.

Pengembangan Alat Spin Ball Untuk Batting Softball

The purpose of this research is that in practicing softball games the hitting technique is more efficient and effective because it does not go back and forth to take the ball when it has been hit by an athlete during practice. This study uses research and development methods. The research sample uses two validations, namely the validation of material experts and media experts, and uses two variables, namely small scale and large scale. Material experts get a percentage of the spin ball tool for softball batting of 87.5% that the spin ball tool is feasible to use. While media experts get a percentage of 81.2% which means it is said to be suitable for use. Small-scale respondents amounted to 7 people with a percentage of 72.8. This large-scale study involved 15 respondents from 3 universities in Semarang city with a percentage of 77.3%. The study concludes that the 4 variables categorize the spin ball tool for softball batting as feasible to use

The drift motion of a spinning ball on carpet

A ball that rolls on carpet while also spinning around a vertical axis will experience a drift force that acts perpendicular to its velocity, opposite to the tangential velocity component of the front point of the ball. Here, we present a model of this motion based on three assumptions: the ball rolls without slipping around the point of contact directly below its center of mass; the ball experiences rolling resistance due to a forward-shifted normal force; and the ball experiences a forward-shifted kinetic friction (drift) force. This model produces a simple analytic solution that is consistent with experimental data. Our measurements suggest that the kinetic friction force acts near the front of the contact patch between the ball and carpet.

Relationships Between Lower Extremity Power and Fastball Spin Rate and Ball Velocity in Professional Baseball Pitchers.

Wong, R, Laudner, K, Amonette, W, Vazquez, J, Evans, D, and Meister, K. Relationships between lower extremity power and fastball spin rate and ball velocity in professional baseball pitchers. J Strength Cond Res 37(4): 823-828, 2023-Lower extremity power has been hypothesized to increase ball spin and velocity during pitching in baseball. Therefore, the purpose of this study was to determine the relationship between lower extremity power and fastball spin rate in professional baseball pitchers. A secondary purpose was to determine the relationship between lower extremity power and ball velocity. Fifty-three asymptomatic professional pitchers participated (24.5 ± 3.6 years; 189.9 ± 6.1 cm; 92.6 ± 10.3 kg). Each athlete performed 3 separate bilateral jump tests on force plates: countermovement jump (CMJ), squat jump (SJ), and drop jump (DJ). The average fastball spin rate and ball velocity for each pitcher was calculated using a 3-dimensional Doppler radar and video system over the course of a competitive season. Standard multiple regression analyses ( p ≤ 0.05) revealed significant relationship between ball spin and summation of variables for the CMJ (peak force, peak power, rate of power development, and jump height) ( R2 = 0.20, F = 3.1, p = 0.03). However, no individual variable was significantly associated ( p > 0.09). There was also a significant amount of variance in ball spin explained by summation of variables for the SJ (peak force, peak power, rate of power development, and jump height) ( R2 = 0.19, F = 2.8, p = 0.04); rate of power development was the only variable that significantly predicted ball spin within this model ( B = 0.27; 95% confidence interval [CI]: 0.003-0.75, p = 0.05). Ball spin was not associated with summation of DJ variables (peak power, rate of power development, jump height, reactive strength index, and total peak power in watts) ( R2 = 0.18, F = 2.0, p = 0.09). For ball velocity, there were no significant relationships for the summation of either the CMJ variables ( R2 = 0.10, p = 0.28) or the SJ variables ( R2 = 0.07, p = 0.44). However, there was a significant amount of variance in ball velocity explained by summation of variables for the DJ ( R2 = 0.30, F = 3.93, p = 0.005). The reactive strength index was the sole unique contribution to this model ( B = 1.18; 95% CI: -10.34 to 2.36, p = 0.002). These findings highlight the relevance of increased lower extremity power on increasing fastball spin rate and ball velocity.

Magnus-Forces Analysis of Pitched-Baseball Trajectories Using YOLOv3-Tiny Deep Learning Algorithm

This study analyzed the characteristics of pitched baseballs from TV broadcast videos to understand the effects of the Magnus force on a pitched-baseball trajectory using aerodynamic theory. Furthermore, an automatic measurement and analysis system for pitched-baseball trajectories, ball speeds, and spin rates was established, capturing the trajectory of the baseball thrown by the pitcher before the catcher catches it and analyzing its related dynamic parameters. The system consists of two parts: (1) capturing and detecting the pitched baseball in all frames of the video using the YOLOv3-tiny deep learning algorithm and automatically recording the coordinates of each detected baseball position; (2) automatically calculating the average speed and spin rate of the pitched baseball using aerodynamic theory. As the baseball thrown by the pitcher is fast, and live-action TV videos like sports and concerts are typically at least 24 fps or more, this study used YOLOv3-tiny algorithm to speed up the calculation. Finally, the system automatically presented pitching data on the screen, and the pitching information in the baseball game was easily obtained and recorded for further discussion. The system was tested using 30 videos of pitched baseballs and could effectively capture the baseball trajectories, throw points, catch points, and vertical displacements. Compared with the values from the TV broadcast, the average errors on the calculated ball speed and spin rate were 1.88% and 7.51%, respectively. Using the ratio of the spin rate and ball speed as a parameter to analyze the pitching state of the pitcher’s four-seam fastball in the Nippon Professional Baseball and Major League Baseball matches, it was observed that when this ratio increased, the Magnus displacement of the ball increased, thereby decreasing its late break. Therefore, the developed system provides scientific pitching data to improve the performance of baseball pitchers.

Simulation of Tennis Spinning Ball Flight Path Based on Fuzzy Reasoning Algorithm

Topspin is one of the most widely used hitting techniques in a tennis match and it is an effective tool to win over the opponent. Hence, flight path simulation of a spinning ball can be a tremendous analysis tool to help tennis players perfect their game. This article proposes a fuzzy logic model based on the principles of kinematics and mechanics. This study analyzes the physical characteristics of a spinning ball during the flight process, which are divided into two categories: the characteristics of the ball on impact (including the floating and rotating it causes) and the landing rebound characteristics. These two characteristics are considered as the constraints of the flight path simulation and the inputs of the fuzzy logic model. Fuzzy logic is used to fuzzify the impact and landing rebound information of the ball based on the knowledge base, solve the problem, and finally defuzzify the results into crisp outputs, that is, accurate flight trajectory. The simulation results show that the estimation error of the proposed model is lower than 3.7 cm/s and 0.9°, and the success rate of accurate topspin execution is 100%, indicating that the proposed model is effective to train tennis players.

Liquid-metal embedded sponge-typed triboelectric nanogenerator for omnidirectionally detectable self-powered motion sensor

With the increasing number of devices that require electrical energy, various types of triboelectric nanogenerators (TENGs), a promising technology for energy harvesting, have been developed in recent years. However, conventional TENGs show relatively low mechanical flexibility because each layer of the conventional TENGs is composed of rigid materials. Low mechanical flexibility produces electrical energy in one-way operation and limits the utilization of TENGs in a variety of applications. In this work, we develop the liquid-metal embedded sponge-typed TENG (LMST). Liquid-metal and silicon rubber are utilized to fabricate the LMST with a peculiar sponge shape, which is inherently including the randomly distributed pores with dispersed liquid-metal droplets. Hence, the LMST can be bent 180° and stretched 300%, which indicates the great flexibility and stretchability of the LMST. The LMST with size of the 1.5 cm × 1.5 cm × 1.5 cm generated a short-circuit current ( I SC ) of 188 nA and an open-circuit voltage ( V OC ) of 24 V. Also, the 2.48 W/m 2 of power density is generated from the proposed LMST by simply inserting wires into the LMST without any conventional processes for fabricating electrodes. Interestingly, the electrical power can be used simply by connecting wires to the LMS, and power can be greatly improved by increasing the number of wires connected to the LMST. Additionally, various shapes of the LMST are facilely designed using 3D printing technology for a wide spectrum of applications. To prove the applicability of the LMST with the unique porous structure, three types of self-powered sensor systems are demonstrated, which are detecting the pressure, the direction of a spinning ball, and real-time detecting malfunction of motor faults. The flexible advantages of the liquid-metal embedded sponge structure triboelectric nanogenerator device, allow us to extend its applicability to battery-free sensors that can be used in various locations. • Using liquid metal, sugar and silicone elastomer, conductive sponges can be produced through a simple manufacturing process. • Electrical power can be generated using the principle of a single electrode TENG by simply connecting a wire to a sponge. • Due to the elasticity of porous sponges, electrical power can be collected from various directions. • The direction of rotation of the ball and motor defects can be detected using LMST.

Simulating the flight of an oval football

The flight of a spinning rugby ball is difficult to describe mathematically but easy to observe experimentally. The flight can be simulated by dropping an egg into a water tank and observing or filming the outcome. Differences between a spinning and a non-spinning wooden egg are presented as supplementary videos.

The effect of spin level and ball exit speed on forearm muscle activity in the tennis forehand stroke

Elbow tendinopathy injuries are very common in tennis players. One of the commonly accepted theories describing the development of elbow tendinopathy in tennis is based on stiffness of the forearm skeletal muscle units and their repetitive overuse in the forehand stroke. Our objective was to use a novel microcontroller based wearable device to compare the influence of different forehand spin levels (flat, topspin and lob) and ball exit speed on forearm muscle activity in the potential onset of elbow tendinopathy in experienced adult tennis players. Peak normalised extensor carpi radialis (ECR) and flexor carpi radialis (FCR) muscle activity corresponding to each forehand shot and ball exit speed were determined and analysed. For the ECR shots (flat = 121, topspin = 272 and lob = 273) by 8 players, Kruskal-Wallis test (p < 0.001) and Post-Hoc tests revealed a significant difference between the flat and topspin spin levels (p < 0.01) and flat and lob spin levels (p < 0.001). For the FCR shots (flat = 125, topspin = 301 and lob = 303) by 9 players, Kruskal-Wallis test showed no significant difference between the three spin levels. For the corresponding ball speed, the Kruskal-Wallis (p < 0.001) and subsequent Post-Hoc (p < 0.001) showed that flat hits had the significantly highest ball speed followed by topspin then lob accordingly for both muscles included shots. Our results suggest that coaches could consider recommending players to hit forehands with topspin in order to potentially reduce the risk of developing lateral elbow tendinopathy.

Aerodynamic Characteristics of Baseball and Tennis Ball using CFD Analysis

The objective of the project is to determine the aerodynamic characteristics of baseballs and tennis balls using Computational Fluid Dynamics (CFD) methods. Most realistic initial and boundary conditions are used to simulate each type of ball and to identify key design aspects that can be applied and modified to enhance the performance of the ball and hence improve the game. The basic conservation equations in fluid dynamics are applied to the domain of study to plot the results. For the inlet, different values of velocity based on the motion of the ball in the game were given. A moderate value of surface roughness was given to model the effects of change in the surface between the two balls and the delay in boundary layer separation subsequently affecting the distance travelled by the ball was seen. By observing the values of lift and drag coefficients we can validate computational results with experimental results obtained from reference journals, thus proving that computational simulation has a place in predicting the trajectory and behaviour of moving balls in real-time.The integration of spin in the simulation also yielded results that showcased the Magnus effect, this visualization is generally not observable on experimental methods since it involves complex processes to simulate spin, hence the trajectory of balls under different shots and pitches has been observed. We further developed an idea that could also be used to determine the trajectory of a dual-axis spinning ball. This would help in building the performance of athletes in the game.

Vertical bounce of a spinning ball

An experiment is described where three different spinning balls were dropped vertically on a horizontal surface, and the bounce was filmed with a video camera. The change in spin and horizontal speed of each ball was estimated theoretically, using equations familiar to physics students. The experiment provides an extension of the usual student exercise where a non-spinning ball is dropped vertically on a surface to measure the coefficient of restitution.

Analysis of the Movement Track of Top Spinning Ball and Biomechanics in the Process of Hitting Tennis Ball

The aim of this study is to analyze the movement track of top spinning tennis ball and the biomechanics characteristics of tennis players. This study took ten tennis players as an example. The hitting process of the top spinning ball was captured by two PULNIX high-speed cameras. The images were processed by APAS motion analysis system. The results showed that the top spinning ball moved forward while rotating in the hitting process and showed a large attack force after rebounding from the land. In biomechanics, A and B had larger angles of upper limb joints and larger joint speed. The center of gravity was on the right. The knee joint flexed, obtained the reactive force through pedaling and stretching, and transferred the power to the racket. At the moment of hitting, the racket head speed of A and B was the largest, 18.3 m/s and 18.5 m/s, respectively. At the end of the follow-through, the shoulder and elbow angle angles of A and B were small. Larger power was provided to the racket by the rapid internal rotation. The power of hitting the ball should be increased to improve the hitting effect and speed. Corresponding guidance can be provided to players to improve their technical level.

Off-Axis Dipole Forces in Optical Tweezers by an Optical Analog of the Magnus Effect.

It is shown that a circular dipole can deflect the focused laser beam that induces it and will experience a corresponding transverse force. Quantitative expressions are derived for Gaussian and angular top hat beams, while the effects vanish in the plane wave limit. The phenomena are analogous to the Magnus effect, pushing a spinning ball onto a curved trajectory. The optical case originates in the coupling of spin and orbital angular momentum of the dipole and the light. In optical tweezers the force causes off-axis displacement of the trapping position of an atom by a spin-dependent amount up to λ/2π, set by the direction of a magnetic field. This suggests direct methods to demonstrate and explore these effects, for instance, to induce spin-dependent motion.

Complete order equivalence of spin unitaries

This paper is a study of linear spaces of matrices and linear maps on matrix algebras that arise from spin systems, or spin unitaries, which are finite sets S of selfadjoint unitary matrices such that any two unitaries in S anticommute. We are especially interested in linear isomorphisms between these linear spaces of matrices such that the matricial order within these spaces is preserved; such isomorphisms are called complete order isomorphisms, which might be viewed as weaker notion of unitary similarity. The main result of this paper shows that all m-tuples of anticommuting selfadjoint unitary matrices are equivalent in this sense, meaning that there exists a unital complete order isomorphism between the unital linear subspaces that these tuples generate. We also show that the C⁎-envelope of any operator system generated by a spin system of cardinality 2k or 2k+1 is the simple matrix algebra M2k(C). As an application of the main result, we show that the free spectrahedra determined by spin unitaries depend only upon the number of the unitaries, not upon the particular choice of unitaries, and we give a new, direct proof of the fact [13] that the spin ball Bmspin and max ball Bmmax coincide as matrix convex sets in the cases m=1,2. We also derive analogous results for countable spin systems and their C⁎-envelopes.

Oxidative degradation behavior of irradiated GO/UHMWPE nanocomposites immersed in simulated body fluid

In this study, the artificial joint substrate material of ultra-high molecular weight polyethylene (UHMWPE) is modified by irradiation cross-linking and graphene oxide (GO). The aim of the study is to evaluate the oxidative degradation behavior of GO/UHMWPE nanocomposites immersed in the simulated body fluid (SBF) atmosphere for a long term at 37 °C, using SBF absorption rate, Fourier transform infrared spectroscopy, electron spin resonance and ball indentation hardness. The results demonstrated that both methods of irradiation cross-linking and GO mixing can effectively improve the physicochemical properties and mechanical properties of UHMWPE matrix. After all the samples were immersed for 12 months, the value of ball indentation hardness of UHMWPE, R-UHMWPE, GO/UHMWPE and R-GO/UHMWPE was decreased by 19.6%, 23.18%, 34.58% and 31.88%, respectively. The GO/UHMWPE nanocomposites suffer from severe oxidative degradation compared to the original UHMWPE. Particularly, the pre-degradation rate was accelerated when mixed with GO. However, irradiated GO/UHMWPE (R-GO/UHMWPE) still exhibited optimal physical performance after oxidative degradation. This study highlights the importance of using more realistic solutions to characterize the performance of the modified UHMWPE nanocomposites, and reveals the mechanism of GO addition and irradiation cross-linking treatment on the UHMWPE nanocomposites immersed in SBF for a long time.

Model trajectories for a spinning tennis ball: III. The effect of a light wind on ground strokes

Theoretical models are presented for the trajectory of a rotating spherical projectile appropriate to the ground stroke in tennis, the ball being delivered in the presence of a light head wind, tail wind or side wind. The aim of the study is to determine, quantitatively, the amount of movement due to such light winds which are known to be present even in enclosed stadiums. The ball is assumed to be struck without spin (i.e., a ‘flat’ stroke), with top-spin or with under-spin (i.e., ‘slice’), with the ball being hit directly down the court or ‘cross-court’. Forces considered are the drag force, the lift force and gravity. It is found that a very modest wind can move the ball/court impact point by large amounts, of the order of tens of centimeters compared to the no-wind case. For example, a wind of 5 km h−1 (1.39 m s−1) may move the impact point by up to 1 m. The direction of movement of the impact point is, not surprisingly, normally in the direction to which the wind is blowing, although the exact direction depends, in-part, on the spin. An under-spun ball, for example, in the presence of a head wind can have its ‘range’ to the impact point actually increased, and in the presence of a tail wind the range can be decreased, a seemingly anomalous behaviour which at first sight seems surprising. Explanations for this behaviour are given. Actual movements due to the wind are compared with the product of the flight time and wind speed, since this quantity might be expected to provide an upper limit to such wind-induced movements. For a head or tail wind of 5 km h−1 and a 150 km h−1 full-court-length flat ground stroke with a flight time of 0.765 s, this product is 1.06 m and the shift in the impact point is 42.5% of this value, with larger shifts of up to 75% occurring for top-spin shots.