Search

This study investigates the determination of the centre of pressure (COP) on spherical sports objects such as cricket balls and footballs using gyroscope data from Inertial Measurement Units (IMUs). Conventional pressure sensors are not suitable for capturing the tangential forces responsible for torque generation. This research presents a novel method to calculate the COP solely from gyroscope data and avoids the complexity of isolating user-induced accelerations from IMU data. The COP is determined from the cross-product of consecutive torque vectors intersecting the surface of the sphere. Effective noise management techniques, including filtering and data interpolation, were employed to improve COP visualisation. Experiments were conducted using a smart cricket ball and a smart football. Validation tests using spin rates between 7.5 and 12 rps and torques ranging from 0.08 to 0.12 Nm confirmed consistent COP clustering around the expected positions. Further analysis extended to various spin bowling deliveries recorded using a smart cricket ball, and a curved football kick recorded using a smart football demonstrated the wide applicability of the method. The COPs of various spin bowling deliveries showed adjacent positions on the surface of the ball, traversing through backspin, sidespin and topspin, excluding the flipper and doosra deliveries. The calculation of the COP on the surface of the soccer ball could only be achieved by increasing the data sampling frequency sevenfold using curve fitting. Knowledge and use of the COP position offers significant advances in understanding and analysing ball dynamics in sports. [ABSTRACT FROM AUTHOR]

This study investigates the determination of the centre of pressure (COP) on spherical sports objects such as cricket balls and footballs using gyroscope data from Inertial Measurement Units (IMUs). Conventional pressure sensors are not suitable for capturing the tangential forces responsible for torque generation. This research presents a novel method to calculate the COP solely from gyroscope data and avoids the complexity of isolating user-induced accelerations from IMU data. The COP is determined from the cross-product of consecutive torque vectors intersecting the surface of the sphere. Effective noise management techniques, including filtering and data interpolation, were employed to improve COP visualisation. Experiments were conducted using a smart cricket ball and a smart football. Validation tests using spin rates between 7.5 and 12 rps and torques ranging from 0.08 to 0.12 Nm confirmed consistent COP clustering around the expected positions. Further analysis extended to various spin bowling deliveries recorded using a smart cricket ball, and a curved football kick recorded using a smart football demonstrated the wide applicability of the method. The COPs of various spin bowling deliveries showed adjacent positions on the surface of the ball, traversing through backspin, sidespin and topspin, excluding the flipper and doosra deliveries. The calculation of the COP on the surface of the soccer ball could only be achieved by increasing the data sampling frequency sevenfold using curve fitting. Knowledge and use of the COP position offers significant advances in understanding and analysing ball dynamics in sports.

Background: In previous studies that analyzed the biomechanics of spin bowling with a smart cricket ball, it was evident that not all the torque applied to the ball was converted into spin rate, with varying losses among different bowlers. This study aims to investigate the factors contributing to these losses. Methods: Developed in 2011, the world's first intelligent cricket ball features five physical and five skill performance parameters. Our study correlates five skill parameters with the ratio of total torque to spin rate to determine the most influential skill parameter. Results: The parameter that most affected the conversion of torque to spin rate was the ratio of maximum angular acceleration to maximum angular velocity. Since the unit of the latter ratio is measured in s–1 or Hz, we hypothesized that the duration of a time-window in which the torque is generated could be a factor in determining the effectiveness of torque to spin conversion. Upon closer examination of the data, we discovered that the spin torque (the torque component that boosts the spin rate) generated earlier in relation to the release point led to greater conversion of total torque into spin rate. Paradoxically, this occurred at smaller peak spin torques. As the time-window of the spin torque widens despite its decreasing magnitude, the angular impulse increases. Conclusions: As the skill parameter calculated from the ratio of maximum angular acceleration to maximum angular velocity correlates well with the time-window during which torque is generated, it can serve as a good indicator of skillful torque to spin conversion, and a potential parameter for talent identification. [ABSTRACT FROM AUTHOR]

BACKGROUND: Analytics, to quantify baseball pitch metrics, take on many forms and are unlike earlier methods to assess performance. OBJECTIVE: Quantify associations of flight kinematic and anthropometric variables on pitch release speed. METHODS: Male college-age pitchers (n = 182) from 2021 Division I games provided data. A 3D radar system collected data. Fixed effects regression OLS models analyzed data for sliders, changeups, curveballs, and fastballs. RESULTS: Spin rate (r = 0.017–0.514, p < 0.05) and vertical break (r = 0.374–0.703, p < 0.05) were positively associated with pitch release speed per pitch type. Release height (r = - 0.286–0.051, p < - 0.05) and pitch extension (r = - 0.176–0.43, p < 0.05) were negatively associated with pitch release speed per pitch type except sliders. Spin axis had a negative association with pitch release speed for fastballs (r = - 0.235, p < 0.05) and sliders (r = - 0.311, p < 0.05), and a positive association (r = 0.029, p < 0.05) with curveball pitch release speed. Weight only related to pitch release speed for fastballs (r = - 0.315, p < 0.05). Height did not impact pitch release speed. CONCLUSIONS: Results refute long-held beliefs of anthropometry's influence on performance and instead reveal flight kinematics' impact on baseball pitch release speed. [ABSTRACT FROM AUTHOR]

ObjectivesThe purpose of this study was to deepen our understanding of pitches and to obtain basic knowledge about pitches by comparing 4-seam and other pitches in Major League Baseball (MLB).MethodsWe analyzed big data for 1,820 professional baseball pitchers of MLB on release speed, spin rate, release point 3D coordinates (X, Y, and Z axes), amount of change for 4-seam, and seven changing ball types (sinker, slider, changeup, cutter, curve, split finger, and knuckle curve), using PITCHf/x and TrackMan. We also evaluated three relationships: (1) between the release points and the ball types of pitch; (2) between the amount of change in the ball and the release speed; and (3) between the release speed and the spin rate.ResultsThe release speed was significantly slower in seven changing ball types than in the 4-seam (p

Spin bowling deliveries in cricket, finger spin and wrist spin, are usually (Type 1, T1) performed with forearm supination and pronation, respectively, but can also be executed with opposite movements (Type 2, T2), specifically forearm pronation and supination, respectively. The aim of this study is to identify the differences between T1 and T2 using an advanced smart cricket ball, as well as to assess the dynamics of T1 and T2. With the hand aligned to the ball’s coordinate system, the angular velocity vector, specifically the x-, y- and z-components of its unit vector and its yaw and pitch angles, were used to identify time windows where T1 and T2 deliveries were clearly separated. Such a window was found 0.44 s before the peak torque, and maximum separation was achieved when plotting the y-component against the z-component of the unit vector, or the yaw angle against the pitch angle. In terms of physical performance, T1 deliveries are easier to bowl than T2; in terms of skill performance, wrist spin deliveries are easier to bowl than finger spin. Because the smart ball allows differentiation between T1 and T2 deliveries, it is an ideal tool for talent identification and improving performance through more efficient training.

This study had two objectives: (a) estimating the force exerted by pitchers in generating the spin of a fastball and (b) examining the factors that influence the spin rate of a fastball. Thirteen baseball pitchers participated in this study. The resultant forces acting on the ball was measured using an accelerometer placed in the baseball, and the force was decomposed into two frequency components using maximal overlap discrete wavelet transform. The intraclass correlation coefficients (ICC) between the integration of the high-frequency component of acceleration and the variation in the tangential velocity was high (ICC(3,1) = 0.64 ± 0.16). The ball spin per velocity (SPV) was significantly correlated with the peak value of the high-frequency component of the resultant forces (r = 0.66, p < 0.01). The high-frequency component of the resultant forces reflected the force in the tangential direction, and this force was one of the factors that adjusted the ball spin rate. The SPV did not significantly correlate with the peak value of the low-frequency component of the resultant forces (r = 0.50, p > 0.05). This indicates that decomposing the resultant forces into two frequency components is necessary to investigate the function of the finger during pitching. [ABSTRACT FROM AUTHOR]

Background: Ulnar collateral ligament reconstruction (UCLR) is commonly performed in Major League Baseball (MLB) pitchers, with variable reported effects on velocity and traditional rate statistics. Currently, no studies have evaluated spin rate in the context of return to play (RTP) after injury. Greater spin rate has become increasingly sought after in the baseball community, as it is believed to be a vital aspect of pitch effectiveness. Purpose/Hypothesis: The purpose was to evaluate the effect of primary UCLR on fastballs (FB) and sliders (SL) of MLB pitchers in terms of spin rate, velocity, hard-hit rate, and whiff rate. It hypothesized that the post-UCLR FB and SL spin rates, velocity, and whiff rate would be significantly decreased versus their pre-UCLR levels, while the FB and SL hard-hit rates would be higher in comparison with pre-UCLR levels. Study Design: Case series; Level of evidence, 4. Methods: In total, 42 pitchers who underwent UCLR and returned to MLB play were identified from public records from 2016 to 2019. The Statcast system was used to collect spin rate, velocity, hard-hit rate, and whiff rate for 4-seam FB (4FB), 2-seam FB (2FB), and SL for pitchers in the preinjury year as well as the 2 years after return from UCLR. Data were analyzed using the appropriate statistical tests. Results: A total of 36 pitchers met the inclusion criteria, and 31 of the eligible 36 players (86.1%) were able to return to MLB pitching (RTP). There were no significant decreases for 4FB, 2FB, or SL in spin rate, measured in revolutions per minute (rpm), when comparing preinjury levels with the first and second seasons after return. There was a significant decrease in velocity for the 2FB in the first season (92.9 vs 93.7 miles per hour [mph]; P =.045) but not the second season (93 mph; P =.629) after RTP in comparison with pre-UCLR levels. For the 2FB, there was a significant increase in spin rate between preinjury and RTP season 2 (2173.5 vs 2253 rpm; P =.022). For the SL, there was a significant increase in spin rate between preinjury and RTP season 2 (2245.1 vs 2406 rpm; P =.016). Conclusion: A cohort of MLB pitchers who underwent UCLR and returned to the MLB level demonstrated no significant decreases in the spin rate, velocity, whiff rate, or hard-hit rate of 4FB, 2FB, or SL at 2 years after UCLR. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study aimed to investigate how high school baseball pitchers throw different pitch types with attention to the ball kinematics, to reveal the kinematic characteristics of each pitch type, and to reveal whether the relationship between the speed and spin rate of fastballs thrown by high school pitchers is different from that of fastballs thrown by collegiate, semi-professional, and professional pitchers (mature pitchers). Eighteen high school baseball pitchers were asked to throw all the pitch types they would normally throw in a game. Among all pitches, this study specifically focused on fastballs, changeups, sliders, and curveballs. First, the kinematics of balls thrown by high school pitchers were compared between each pitch type. Second, the ball kinematics of each pitch type observed in this study were compared with those observed in previous studies investigating mature pitchers. Third, the relationship between the speed and spin rate of fastballs observed in this study was compared with that observed in previous studies. As a result, it was revealed that high school pitchers could throw different pitch types by changing the speed, spin rate, and/or spin axis. In addition, it was indicated that high school pitchers threw different sliders and curveballs compared to mature pitchers. On the other hand, in this study, it could not be asserted that high school pitchers threw different fastballs compared to the mature pitchers. It was revealed that the relationship between the speed and spin rate of fastballs for high school pitchers is similar to that for mature pitchers. [ABSTRACT FROM AUTHOR]

This paper investigates the spin rate bounds, the configuration stability subject to the solar wind fluctuations, and sail angle control of an electric solar wind sail (E-sail) by a high-fidelity tether dynamic model. This model describes the elastic deformation of tethers with inter-connected 2-noded tensile elements discretized by the nodal position finite element method. The E-sail is assumed to be an axisymmetric system spinning in the plane normal to the heliocentric ecliptic plane. The upper and lower spin rate bounds are revisited to reveal the physics that dictates these bounds and analytic expressions are provided to ensure the proper operation of E-sail. Then, the influences of the solar wind fluctuations on the configuration stability of the E-sail are investigated by parametric analysis with different E-sail configurations, sail angles, and spin rates. Finally, an alternative sail angle control strategy for the E-sail is proposed by applying control force at the remote units with a simple PD control. Numerical analysis demonstrates that the sail angle of E-sail can be controlled quickly by the control law at the remote units with a high-precision. • Derived a new theoretical lower bound of spin rate for E-sail with auxiliary tethers. • Analyzed structural dynamics of E-sail by a high-fidelity tether dynamic model. • Revealed necessity and effectiveness of auxiliary tethers by tether dynamic perspective. • Controlled sail angle by applying control forces at remote units only. [ABSTRACT FROM AUTHOR]

Background: There are limited data on the performance or pitching metrics of Major League Baseball (MLB) pitchers who returned to play after ulnar collateral ligament reconstruction (UCLR). Purpose: To describe MLB pitcher performance after return from primary UCLR, compare the velocity and pitch characteristics against the preoperative season, and determine if performance analytics can predict successful return to pitching after UCLR. Study Design: Case-control study; Level of evidence, 3. Methods: This study included 63 pitchers who underwent primary UCLR between 2015 and 2019. Publicly available advanced analytics and pitch metrics from the first 2 postoperative seasons were compared with the preoperative (index) season as well as with an uninjured control group. Results: Overall, 57% of the pitchers successfully returned to the MLB level. Although they threw significantly fewer pitches (P =.012) and innings (P =.022) in postoperative year 1 as compared with the index season, there were no significant differences in pitch velocity, release extension, perceived velocity, or performance as measured by advanced analytics. Also, as compared with the index season, returners demonstrated increased postoperative spin rates on curveballs (P =.001) and sliders (P =.010), and curveball horizontal movement was significantly increased (P =.007); however, horizontal movement was significantly decreased for 4-seam fastballs (P =.026), changeups (P =.005), and sinkers (P =.019). The vertical movement on 4-seam fastballs was greater (P <.001) in postoperative year 1, and the vertical movement on curveballs (P =.031) and sinkers (P =.010) was greater in postoperative year 2 when compared with the index season. Pitchers who failed to return to the MLB level had a lower preoperative strikeout percentage (P =.047), fewer strikeouts per 9 innings pitched (P =.046), fewer wins above replacement ([WAR]; P =.026), and lower player value (P =.030) than the pitchers who returned. Conclusion: Pitchers returning to the MLB level after UCLR demonstrated changes in pitch movement profiles and spin rates postoperatively, but there were no differences in velocity or many advanced analytics upon return. Pitchers with lower strikeout metrics, fewer WAR, and less player value before surgery may have an elevated risk of failing to return to the MLB level. [ABSTRACT FROM AUTHOR]

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.

Measuring the motion state of space non-cooperative targets is in the fields of space on-orbit services and debris removal. This paper proposes a method for the measurements of the spin rate of fast-swirl non-cooperative targets through a monocular camera, for image features that have been degraded at a medium and long distance. First, the coordinate system between the tracking satellite and the target is established, and the relationship between the target spin period and its image projection angle is deduced. An image processing method which can extract the projection angle of the target image stably under complex illumination conditions is then proposed. Next, considering the characteristics of the sequence projection angle of the fast-spinning target at a long distance, the spin rate of the target is calculated using a sinusoidal polynomial fitting method. The proposed method is validated by simulated and on-orbit data. Experiment results show that the method has strong adaptability, measurement reliability and practical engineering application prospects. • Measuring the spin rate of non-cooperative targets through monocular camera images. • Proving the mathematical principle of the spin rate measurement. • Applied to long-distance, image feature degradation and fast spin small targets. • Fora 60°/s fast-spinning target, the measuring standard deviation is 0.05°/s. • Giving ground simulation and space images data verification test results. [ABSTRACT FROM AUTHOR]

A pitcher’s action, when delivering a fastball, was analyzed from the data provided by a smart baseball. The spin rate at the release of the ball was merely 15.7 rps, however, the peak torque was excessively high, namely 0.396 Nm. The reason why the pitcher was not able to translate the torque entirely to angular kinetic energy and this to the spin rate was that the spin axis changed its direction suddenly three times when moving across the ball’s surface. This resulted in angles between torque and angular velocity vectors of greater than 90°, high precession and precession torque, and negative spin torques, causing a very low efficiency (5.4%) and a slow spin rate at the release of the ball.

A Frisbee with a mass of 0.21 kg, diameter of 0.27 m and moment of inertia (MOI) of 0.002 kg·m2 was instrumented with a triaxial gyroscope. The Frisbee was thrown at low angular velocities as the measurement limit of a single gyroscope was at 6.065 rps. The angular velocities of the triaxial gyroscope were analysed to study the attitude of a Frisbee before and after release. The angular velocities measured were post-processed and the following data were obtained: spin rate at release—3.9–6.14 rps; user-induced peak torque—0.483–0.9 Nm, and peak angular acceleration—204–358 rad/s2; and power input 7.53–19.56 W. The Frisbee wobbled at release which decreased during the flight due to a damping effect. This affected the spin decay, the reduction of wobble lead to a reduced drag force and thus to a smaller spin decay, which was initially 1.12–0.31 rev/s2 and then asymptoted to 0.11–0.01 rev/s2.

Profiling of spin bowlers is currently based on the assessment of translational velocity and spin rate (angular velocity). If two spin bowlers impart the same spin rate on the ball, but bowler A generates more spin rate than bowler B, then bowler A has a higher chance to be drafted, although bowler B has the potential to achieve the same spin rate, if the losses are minimized (e.g., by optimizing the bowler’s kinematics through training). We used a smart cricket ball for determining the spin rate and torque imparted on the ball at a high sampling frequency. The ratio of peak torque to maximum spin rate times 100 was used for determining the ‘spin bowling potential’. A ratio of greater than 1 has more potential to improve the spin rate. The spin bowling potential ranged from 0.77 to 1.42. Comparatively, the bowling potential in fast bowlers ranged from 1.46 to 1.95.

The aim of this study was to identify the key kinematic parameters which contribute to higher spin rates in elite finger spin bowling. Kinematic data were collected for twenty-three elite male finger spin bowlers with thirty kinematic parameters calculated for each delivery. Stepwise linear regression and Pearson product moment correlations were used to identify kinematic parameters linked to spin rate. Pelvis orientation at front foot contact (r = 0.674, p < 0.001) and ball release (r = 0.676, p < 0.001) were found to be the biggest predictors of spin rate, with both individually predicting 43% of the observed variance in spin rate. Other kinematic parameters correlated with spin rate included: shoulder orientation at ball release (r = 0.462, p = 0.027), and pelvis-shoulder separation angle at front foot contact (r = 0.521, p = 0.011). The bowlers with the highest spin rates adopted a mid-way pelvis orientation angle, a larger pelvis-shoulder separation angle and a shoulder orientation short of side-on at front foot contact. The segments then rotated sequentially, starting with the pelvis and finishing with the pronation of the forearm. This knowledge can be translated to coaches to provide a better understanding of finger spin bowling technique. [ABSTRACT FROM AUTHOR]

In this study, three-dimensional baseball kinematics are described including spin characteristics batted toward the left field (same field), center field, and right field (opposite field) in baseball. The study also discusses the effects of these kinematics on the flight distance. Six collegiate male baseball players performed free-batting and were instructed to hit the ball as far as possible. The balls just before, at, and after bat-ball impact were recorded with three high-speed video cameras. Eighty-one trials (same field: 25 trials, center field: 30 trials, and opposite field: 26 trials) were analyzed, and the ball kinematics among the three hitting directions were compared. Although there were no significant differences in the initial velocities and launch angles along the vertical plane of batted balls for the three hitting directions, the flight distance for the opposite field was significantly shorter than that for the other fields. The magnitude of the side spin components for the opposite field was significantly greater than that for the other fields. We conjecture that the balls batted toward the opposite field experienced a larger Magnus force along the horizontal direction; moreover, the trajectories were relatively more curved than in the cases towards the other fields. Therefore, a straight-line distance to the batted ball landing point in the opposite field tended to be shorter despite the similar initial velocity and launch angle. The results demonstrated that the spin characteristics, especially the side spin component, were different for different batting directions, and indicated that these characteristics affected the ball trajectory and flight distance. [ABSTRACT FROM AUTHOR]

The effect of air processed polymer solar cells fabricated from conjugated polymers and fullerene derivatives poly (3-hexylthiophene) and [6, 6]-phenyl-C61-butyric acid methyl ester functioning as donor and acceptor materials. The device architecture was (Cs2CO3/P3HT: PCBM/V2O5/Al). The spin rate of the Cs2CO3 and P3HT: PCBM layer was subjected to be varied and its device performance were evaluated. The basic characterizations such as UV-Vis spectrum, PL spectra, FTIR, XRD, FESEM, EDAX, AFM and I-V studies were performed for all the materials used for fabricating the devices. The performance of the device demonstrated under air-processed conditions delivers a photo-conversion efficiency of 0.1% initially. The scaling up of the self-organized active layer can be achieved by varying and controlling the spin casting and the evaporation rate at room temperature. After varying the spin conditions the fabricated devices were tested under the same conditions and photo-conversion efficiency enhances from 0.1 to 1.43% with the Jsc of 5.6 mA cm−2; Voc of 0.55 V and FF of 0.454. The device performance can be further enhanced by controlling the exposure of the electrode materials by masking. [ABSTRACT FROM AUTHOR]

Ball shooting machine (pitching machine) is used for practicing ball sports, and it is widely prevalent. However, there are few pitching machines that can throw a ball with a gyro spin, such as a football or rifle bullet, in which the axis of the ball spins in the same direction as the ball travels. In this study, a new ball shooting machine, which can throw in the ball in a wide range of speeds and all pitch types (no, top, down, side and gyro spin balls) was invented by introducing a launch mechanism using four rollers (two launch and two gyro rollers). The shooting machine is able to arbitrarily change the rotational speed of the four rollers and the crossing angle of both gyro rollers. Shooting tests were conducted using the prototype shooting machine to confirm the ability of its performance. From the experiment results, the prototype machine had a maximum ball speed of 42.5 m/s, a spin rate of exceeding 5000 rpm, and a ball of any pitch type could also be shot. In addition, the position accuracy (shot accuracy) at the targeted fall position in the opponent's court was high because the gyro spin and other pitch types (no, top and side spins) were less than 140 mm and 40 mm (the diameter of one table tennis ball), respectively. The prototype machine had the necessary launching performance for table tennis practice of a college student level.

Satellite thermal control ensures safe operating temperature ranges for satellite components throughout the mission life. Effects of altitude, spin, and position of satellite radiator(s) on the thermal control of a small Low Earth Orbit (LEO) satellite have been studied. Results show that change in satellite altitude, in the range considered here, does not produce critical thermal conditions. However, satellite spin rate has a marked influence on the satellite temperatures. Also, comparison of results for the satellite configurations considered in this study suggests that a radiator at top provides better thermal design conditions. Results also indicate the adequacy of the discussed considerations for use in the design of satellites of similar configurations, missions and orbital parameters.

This study aims to examine the mechanism by which the ball spin rate during fastball pitching is controlled by synergistic joint torque. The participants were seven baseball players. The kinematics and kinetics of the fingers, wrist, elbow, and shoulder were calculated using the inverse dynamics method. The synergistic relationship between the joint torques was calculated using singular value decomposition. The similarity of the spatial pattern of the joint torque in each participant was evaluated using cosine similarity. The results indicated that there were three types of synergistic torque control: (1) two pitchers had a synergistic torque control that was primarily based on shoulder internal rotation torque, (2) two pitchers had a synergistic torque control that was primarily based on elbow extension torque, and (3) three pitchers had a synergistic torque control that was primarily based on shoulder horizontal adduction torque. In particular, pitchers with a high spin rate relative to the ball velocity (SPV) had a torque control of the shoulder internal rotation type. In contrast, pitchers with a low SPV had a torque control of the shoulder horizontal adduction type. It is considered that pitchers with a high SPV execute shoulder internal rotation torque, which has the same direction as that of ball spin, based on hierarchical control to increase the ball spin rate. These results suggest that pitchers with high and low SPVs exhibit different motor patterns. Pitchers and coach need to focus on the shoulder joint as well as the fingers when they throw fastball. [ABSTRACT FROM AUTHOR]

Spin rate of a high-speed spinning-rotor gyroscope will make a significant impact on angular rate sensor performances such as the scale factor, resolution, measurement range, and bias stability. This paper presents the spin rate effects on performance indicators of a microelectromechanical systems (MEMS) gyroscope where a free-spinning rotor is electrostatically suspended in an evacuated vacuum cavity and functions as a dual-axis angular rate sensor. Theoretical models of the scale factor and measurement range of such a spinning-rotor gyroscope are derived. The experimental results indicate that the measured scale factors at different settings of the spin rate match well with the theoretical predication. In order to separate the disturbance component of the rotation control loop on the gyroscope output, a testing strategy is proposed by operating the gyroscope at different spin rates. Experimental results on a prototype gyroscope show that the squared drive voltage generated by the rotation control loop is approximately proportional to the noise of the gyroscope output. It was further investigated that an improved performance of such spinning-rotor gyroscopes can be achieved by operating the gyroscope rotor at an optimal spin rate.

In the off-spin bowling grip, the ball is clamped between index and middle fingers. Spin bowlers attempt to select a spread angle between these two fingers that achieves comfort and optimises performance. The aim of this paper was to investigate whether the standard grip is superior to narrow and wide grips. The bowling performance parameters were obtained from a smart cricket ball. Smart ball data revealed that the performance parameters varied with grip type. The following parameters were optimum at the standard grip: spin rate, resultant torque, spin torque, peak angular acceleration, and peak power. The following parameters were optimum at standard and wide grips: efficiency. The following parameters were optimum at standard and narrow grips: pitch angle of spin axis. The following parameters were optimum at the wide grip: precession and the precession torque. In general, the data tended to show that the standard grip is most effective for spin bowling. However, more research is needed to confirm this result, because the precession and precession torque were optimum at the wide grip, suggesting that this may have a superior performance over the standard and narrow grips.

A smart cricket ball was used to investigate the influence of increased spin rate on the bowling performance parameters. In three spin bowlers, the performance parameters were compared before and after increasing the spin rate. The first bowler increased the spin rate by 22%, decreased the normalised precession the angle at which the spin rate vector moves into the torque vector—the lower the more efficient), and increased the torque, angular acceleration and power, showing an improvement in all performance parameters. The second bowler showed no improvement in any performance parameters. The third bowler increased the spin rate marginally, but insignificantly; but improved the normalised precession dramatically (reducing it by 50%). The research results suggest that the mere intention to improve the spin rate changes bowling technique in way that optimises normalised precession, even if the spin rate does not actually increase.

As torque is imparted on a cricket ball before release, the spin vector precesses into the torque vector. Normalising the precession speed to the torque and the angular velocity yields the ‘normalised precession’, i.e. the angle between the spin vector and the torque vector. The maximal normalised precession was analysed in spin bowling, specifically in finger- and wrist spin, and topspin, sidespin and backspin deliveries. The data were recorded with a smart cricket ball and a Cortex motion analysis system. The maximal normalised precession at the beginning of the finger torque increased from topspin to backspin. The reason for this behaviour is that the motion of the bowling arm imparts a topspin on the ball, and therefore the spin axis does not have to change its direction if the fingers impart further topspin on the ball. [ABSTRACT FROM AUTHOR]

Cricket bowling requires high level of skills in many ways (e.g. physically and mentally). The ball delivery technique is one of these important skills which can be optimised with advanced training methods. These training methods hinge on advanced performance parameters. Development of a low cost smart cricket ball will address the shortcomings of the existing systems and discover and explore cricket bowling kinematics and dynamics. In the past cricket bowling kinematics has not been properly studied using instrumented balls due to technical limitations of sensor system and electronics design. The aim of the project was to develop a highly portable instrumented cricket ball for recording the ball's kinematics and calculating dynamic performance parameters from kinematic data. The ball is designed in such a way that it exactly feels and looks (i.e. mass and material) as a real cricket ball. The ball is constructed from leather hemispheres, an impact proof Nylon6/6 nutshell, a shock damping foam material, and miniaturized electronics circuit. [ABSTRACT FROM AUTHOR]

Abstract: In seam bowling, the spin vector precesses rapidly into the torque vector, thereby crossing from one hemisphere to the other once torque is imparted onto the ball. However, the spin axis reaches the torque vector only at large times. If the spin axis does not coincide with the pole of the ball, the seam wobbles and introduces another roughness element. Thus, if the seam is angled toward the smooth side (for half a period per spin revolution) then the flow is turbulent on both sides of the ball and the aerodynamic side force decreases and vanishes, thereby disturbing the swing. The aim of this study was to investigate how accurate is the placement of the spin axis at release of the ball. A smart cricket ball instrumented with three high-speed MEMS gyroscopes was used for this purpose and the data of four spin bowlers were analysed. It was found that the spin axis can under- and overshoot the optimal position of the ball as well as deviate off the pole. The spin rates recorded were 15-20 rps produced by peak torques of 0.29-0.39 Nm. The deviation of the spin axis correlated with the torque, indicating that too much torque imparted onto the ball worsens the accuracy of bowling. Undershooting the optimal position is due to equal torques imparted by index and middle fingers. The optimal position of the spin axis can be achieved if the middle finger is closer to the seam than the index. This causes an overshooting torque vector and allows the spin axis to be placed at the pole of the ball at release. [Copyright &y& Elsevier]