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1.
Flight dynamics of the screw kick in rugby   总被引：1，自引：1，他引：0  
This paper describes the aerodynamic forces and the flight trajectory for the screw (spiral) kick in rugby. The screw kick is defined as that which causes the ball to spin on its longitudinal axis. The aerodynamic forces acting on a rugby ball spinning on its longitudinal axis were measured in a wind tunnel using a six-component strut type balance. It was found that the drag, the lift and the pitching moment depend on the angle of attack, while the side force (Magnus force) depends on both the spin rate and the angle of attack in the range where the wind speed lies between 15 and 30 m s-1 and the spin rate is between 1 and 10 revolutions per second. Moreover, the flight trajectory was obtained by integrating the full nonlinear six degrees of freedom equations of motion on the basis of aerodynamic data. In a simulation, a ball spinning on its longitudinal axis tended to hook toward or away from the touchline even if the velocity and angular velocity vectors were parallel to the touchline. The direction of the hook depends on the direction of the angular velocity vector. The initial direction of the hook depends on the relationship between the flight path angle and the pitch angle as well as the direction of the angular velocity vector.  相似文献   

2.
This paper describes the use of Pareto-optimal solutions for the screw kick in rugby. We attempted to optimise the initial conditions for a screw kick. The optimisation was carried out using an elitist non-dominated sorting genetic algorithm. Distance achieved in flight is considered as an objective function, as well as the lateral deviation between the ball and the touchline, or the flight time. Six initial conditions were defined as control parameters: the magnitude of the velocity vector, the flight path angle, the azimuth angle, the spin rate, the pitch angle and the yaw angle. The results are summarised as follows: it is impossible for both objective functions to be satisfied simultaneously, although the greatest distance achieved in flight and the smallest value of the lateral deviation between the ball and the touchline, or the least flight time, is the ideal situation. This kind of conflicting solution is called a ‘Pareto-optimal solution’. The optimal kick in Pareto-optimal solutions made by the leg nearest the touchline produces a greater flight distance than the optimal kick in Pareto-optimal solutions made using the leg furthest from the touchline. The initial pitch angle, which is the angle between the longitudinal axis of the ball and the horizontal plane, should be comparable to or slightly greater than the initial flight path angle in order to satisfy the Pareto-optimal solutions.  相似文献   

3.
To investigate non-kicking-side arm motion during rugby place kicking, five experienced male kickers performed trials under two conditions, both with an accuracy requirement but one with an additional maximal distance demand. Joint centre coordinates were obtained at 120 Hz during kicking trials and a three-dimensional model was created to enable the determination of segmental contributions to whole-body angular momentum. All kickers possessed minimal non-kicking-side arm angular momentum about the global medio-lateral axis. The more accurate kickers exhibited greater non-kicking-side arm angular momentum about the global antero-posterior axis. This augmented the whole-body antero-posterior angular momentum, and altered the whole-body lateral lean at ball contact. The accurate kickers also exhibited greater non-kicking-side arm angular momentum about the global longitudinal axis, which opposed the kicking leg longitudinal angular momentum and attenuated the whole-body longitudinal angular momentum. All participants increased the longitudinal angular momentum of the non-kicking-side arm in the additional distance demand condition, except for one participant whose accuracy decreased, suggesting that the longitudinal angular momentum of the non-kicking-side arm assists maintenance of accuracy in maximum distance kicking. Goal kickers should be encouraged to produce non-kicking-side arm rotations about both the antero-posterior and longitudinal axes, as these appear important for both the initial achievement of accuracy, and for maintaining accuracy during distance kicking.  相似文献   

4.
Contributions of the non-kicking-side arm to rugby place-kicking technique   总被引：1，自引：0，他引：1  
To investigate non-kicking-side arm motion during rugby place kicking, five experienced male kickers performed trials under two conditions, both with an accuracy requirement but one with an additional maximal distance demand. Joint centre coordinates were obtained at 120 Hz during kicking trials and a three-dimensional model was created to enable the determination of segmental contributions to whole-body angular momentum. All kickers possessed minimal non-kicking-side arm angular momentum about the global medio-lateral axis. The more accurate kickers exhibited greater non-kicking-side arm angular momentum about the global antero-posterior axis. This augmented the whole-body antero-posterior angular momentum, and altered the whole-body lateral lean at ball contact. The accurate kickers also exhibited greater non-kicking-side arm angular momentum about the global longitudinal axis, which opposed the kicking leg longitudinal angular momentum and attenuated the whole-body longitudinal angular momentum. All participants increased the longitudinal angular momentum of the non-kicking-side arm in the additional distance demand condition, except for one participant whose accuracy decreased, suggesting that the longitudinal angular momentum of the non-kicking-side arm assists maintenance of accuracy in maximum distance kicking. Goal kickers should be encouraged to produce non-kicking-side arm rotations about both the antero-posterior and longitudinal axes, as these appear important for both the initial achievement of accuracy, and for maintaining accuracy during distance kicking.  相似文献   

5.
Many slo-pitch coaches and players believe that generating spin on a ball can affect its trajectory. The influence of air resistance on a ball that is thrown at a moderate speed and spin is unclear. The aim of this study was to examine the influence of spin on the ball's trajectory in slo-pitch pitching using both experimental results and ball flight simulations. Fourteen pitchers participated in the study, each of whom threw five backspin and topspin pitches each. Data were collected using standard three-dimensional videography. The horizontal velocity, vertical velocity, angular velocity, release height, and horizontal displacement of the backspin pitches were significantly higher than those of the topspin pitches. The ball flight simulations were developed to examine the influence of the ball spin, and it was concluded that the spin of the ball had a significant effect on the ball's vertical and horizontal displacements. Furthermore, our results suggest that a backspin pitch that reaches the maximum height allowable and lands in the front edge of the strike zone has the steepest slope. The present results add to our understanding of projectile motion and aerodynamics.  相似文献   

6.
Many slo-pitch coaches and players believe that generating spin on a ball can affect its trajectory. The influence of air resistance on a ball that is thrown at a moderate speed and spin is unclear. The aim of this study was to examine the influence of spin on the ball's trajectory in slo-pitch pitching using both experimental results and ball flight simulations. Fourteen pitchers participated in the study, each of whom threw five backspin and topspin pitches each. Data were collected using standard three-dimensional videography. The horizontal velocity, vertical velocity, angular velocity, release height, and horizontal displacement of the backspin pitches were significantly higher than those of the topspin pitches. The ball flight simulations were developed to examine the influence of the ball spin, and it was concluded that the spin of the ball had a significant effect on the ball's vertical and horizontal displacements. Furthermore, our results suggest that a backspin pitch that reaches the maximum height allowable and lands in the front edge of the strike zone has the steepest slope. The present results add to our understanding of projectile motion and aerodynamics.  相似文献   

7.
Recreational tennis players tend to have higher incidence of tennis elbow, and this has been hypothesised to be related to one-handed backhand technique and off-centre ball impacts on the racket face. This study aimed to investigate for a range of participants the effect of off-longitudinal axis and off-lateral axis ball–racket impact locations on racket and forearm joint angle changes immediately following impact in one-handed tennis backhand groundstrokes. Three-dimensional racket and wrist angular kinematic data were recorded for 14 university tennis players each performing 30 “flat” one-handed backhand groundstrokes. Off-longitudinal axis ball–racket impact locations explained over 70% of the variation in racket rotation about the longitudinal axis and wrist flexion/extension angles during the 30 ms immediately following impact. Off-lateral axis ball–racket impact locations had a less clear cut influence on racket and forearm rotations. Specifically off-longitudinal impacts below the longitudinal axis forced the wrist into flexion for all participants with there being between 11° and 32° of forced wrist flexion for an off-longitudinal axis impact that was 1 ball diameter away from the midline. This study has confirmed that off-longitudinal impacts below the longitudinal axis contribute to forced wrist flexion and eccentric stretch of the wrist extensors and there can be large differences in the amount of forced wrist flexion from individual to individual and between strokes with different impact locations.  相似文献   

8.
ABSTRACT

When executed correctly, swing bowling has the potential to influence the outcome of a cricket match, yet little is known about the required bowling action and ball flight characteristics. This study aimed to describe the bowling action and initial ball flight characteristics as well as to identify variables that may be associated with increased swing in pathway and high-performance medium and fast pace bowlers. A 17-camera Vicon motion analysis system captured retro-reflective markers placed on the upper-body of participants and new cricket balls to quantify bowling action and initial ball flight kinematics. Bowlers delivered the ball with their forearm and hand angled in the direction of intended swing with an extended wrist flexing through the point of ball release. Bowlers who produced more swing had increased seam stability, possibly linked to a lower wrist and ball angular velocity. It is believed that swing increases with seam stability, however, optimal ranges may exist for seam azimuth angle, ball angular velocity and release speed. These findings may assist coaches to optimise the performance of bowlers, however, future research should use bowlers who play at higher levels to investigate swing bowling at greater speeds.  相似文献   

9.
Direction of spin axis and spin rate of the pitched baseball   总被引：1，自引：0，他引：1  
In this study, we aimed to determine the direction of the spin axis and the spin rate of pitched baseballs and to estimate the associated aerodynamic forces. In addition, the effects of the spin axis direction and spin rate on the trajectory of a pitched baseball were evaluated. The trajectories of baseballs pitched by both a pitcher and a pitching machine were recorded using four synchronized video cameras (60 Hz) and were analyzed using direct linear transform (DLT) procedures. A polynomial function using the least squares method was used to derive the time-displacement relationship of the ball coordinates during flight for each pitch. The baseball was filmed immediately after ball release using a high-speed video camera (250 Hz), and the direction of the spin axis and the spin rate (omega) were calculated based on the positional changes of the marks on the ball. The lift coefficient was correlated closely with omegasinalpha (r = 0.860), where alpha is the angle between the spin axis and the pitching direction. The term omegasinalpha represents the vertical component of the velocity vector. The lift force, which is a result of the Magnus effect occurring because of the rotation of the ball, acts perpendicularly to the axis of rotation. The Magnus effect was found to be greatest when the angular and translational velocity vectors were perpendicular to each other, and the break of the pitched baseball became smaller as the angle between these vectors approached 0 degrees. Balls delivered from a pitching machine broke more than actual pitcher's balls. It is necessary to consider the differences when we use pitching machines in batting practice.  相似文献   

10.
This study investigated ball release speed and performance kinematics between elite male and female cricket fast bowlers. Fifty-five kinematic parameters were collected for 20 male and 20 female elite fast bowlers. Group means were analysed statistically using an independent samples approach to identify differences. Significant differences were found between: ball release speed; run-up speed; the kinematics at back foot contact (BFC), front foot contact (FFC), and ball release (BR); and the timings between these key instants. These results indicate that the female bowlers generated less whole body linear momentum during the run-up than the males. The male bowlers also utilised a technique between BFC and FFC which more efficiently maintained linear momentum compared to the females. As a consequence of this difference in linear momentum at FFC, the females typically adopted a technique more akin to throwing where ball release speed was contributed to by both the whole body angular momentum and the large rotator muscles used to rotate the pelvis and torso segments about the longitudinal axis. This knowledge is likely to be useful in the coaching of female fast bowlers although future studies are required to understand the effects of anthropometric and strength constraints on fast bowling performance.  相似文献   

11.
Three-dimensional simulations of the frictional collision between solid balls moving on a rough surface are analyzed in this paper. The analysis is performed in the context of pool and snooker, two popular games in the pocket billiards family. Accurate simulations of ball motion in billiard games are useful for television broadcasts, training systems and any robotic game playing systems. Studying solid ball collisions in a three-dimensional space requires careful consideration of the different phenomena involved in ball motion such as rolling, sliding and ball spin about a general axis. A set of differential equations are derived describing ball dynamics during collisions. In the absence of explicit analytical solutions to the differential equations, a numerical procedure is performed to determine post-collision ball velocities and spins after collision. In addition, the paper also presents a methodology to analyze the curved, slip trajectories of balls immediately after impact. The results presented here, when compared with some experimental shots, show that the percentile errors in post-collision velocities are reduced by the proposed method. The prediction accuracies for ball travel direction are increased twofold by the proposed impact simulation algorithm.  相似文献   

12.
A dynamic model for motion of a basketball on the rim is derived. The model is used to investigate shot success sensitivity to initial conditions and to search for initial conditions that lead to long rim contact times. Nonlinear ordinary differential equations describe three components of ball angular velocity and contact point position on the toroidal rim. The model includes radial ball compliance and dissipation and contains three sub-models describing slipping contact, nonslipping contact and purely gravitational flight. Switching between the three sub-models depends on contact point velocity and friction forces. Equivalent radial stiffness and damping constants are estimated using experimental ball force-deflection hysteresis data. General initial conditions almost always involve slip of the ball on the rim. Bouncing on the rim can also occur. After contact it is possible for the ball to enter the rim with its centre passing significantly below the rim plane before rising and ultimately escaping. Exotic quasi-equilibrium periodic circular trajectories exist inside but below the rim plane, relying for their existence on a combination of centripetal force, friction and gyroscopic precession of radial spin about the contact point. Trajectories, and consequent ball capture or escape, are extremely sensitive to initial conditions, especially rim contact position and backspin angular velocity. Backspin aids capture on longrolling trajectories.  相似文献   

13.
The appropriate determination of performance outcome is critical when appraising a performer’s technique. Previous studies of rugby place kicking technique have typically assessed performance based on ball velocity, but this is not the sole requirement. Therefore, a mathematical model of rugby place kick ball flight was developed to yield a single measure more representative of true performance. The model, which requires only initial ball flight kinematics, was calibrated and validated using empirical place kick data, and found to predict ball position with a mean error of 4.0% after 22 m of ball flight. The model was then applied to the performances of 33 place kickers. The predicted maximum distance, a single performance measure which accounted for initial ball velocity magnitude and direction, and spin, was determined using the model and was compared against ball velocity magnitude. A moderate association in the rank-order of the kicks between these two measures (ρ = 0.52) revealed that the relative success of the kicks would be assessed differently with each measure. The developed model provides a representative measure of place kick performance that is understandable for coaches, and can be used to predict changes in performance outcome under different ball launch or environmental conditions.  相似文献   

14.
Modelling the flight of a soccer ball in a direct free kick   总被引：2，自引：0，他引：2  
This study involved a theoretical and an experimental investigation of the direct free kick in soccer. Our aim was to develop a mathematical model of the ball's flight incorporating aerodynamic lift and drag forces to explore this important 'set-play'. Trajectories derived from the model have been compared with those obtained from detailed video analysis of experimental kicks. Representative values for the drag and lift coefficients have been obtained, together with the implied orientation of the ball's spin axis in flight. The drag coefficient varied from 0.25 to 0.30 and the lift coefficient from 0.23 to 0.29. These values, used with a simple model of a defensive wall, have enabled free kicks to be simulated under realistic conditions, typical of match-play. The results reveal how carefully attackers must engineer the dynamics of a successful kick. For a central free kick some 18.3 m (20 yards) from goal with a conventional wall, and initial speed of 25 m x s(-1), the ball's initial elevation must be constrained between 16.5 degrees and 17.5 degrees and the ball kicked with almost perfect sidespin.  相似文献   

15.
Spin bowling plays a fundamental role within the game of cricket yet little is known about the initial ball kinematics in elite and pathway spin bowlers or their relationship to performance. Therefore, the purpose of this study was to record three-dimensional ball kinematics in a large and truly high level cohort of elite and pathway finger-spin (FS) and wrist-spin (WS) bowlers, identifying potential performance measures that can be subsequently used in future research. A 22-camera Vicon motion analysis system captured retro-reflective markers placed on the seam (static) and ball (dynamic) to quantify ball kinematics in 36 FS (12 elite and 24 pathway) and 20 WS (eight elite and 12 pathway) bowlers. Results indicated that FS bowlers delivered the ball with an increased axis of rotation elevation, while wrist-spin bowlers placed greater amounts of revolutions on the ball. It also highlighted that ball release (BR) velocity, revolutions and velocity/revolution index scores for both groups and seam stability for FS bowlers, and seam azimuth angle and spin axis elevation angle for WS bowlers, were discriminators of playing level. As such these variables could be used as indicators of performance (i.e. performance measures) in future research.  相似文献   

16.
This study involved a theoretical and an experimental investigation of the direct free kick in soccer. Our aim was to develop a mathematical model of the ball's flight incorporating aerodynamic lift and drag forces to explore this important 'set-play'. Trajectories derived from the model have been compared with those obtained from detailed video analysis of experimental kicks. Representative values for the drag and lift coefficients have been obtained, together with the implied orientation of the ball's spin axis in flight. The drag coefficient varied from 0.25 to 0.30 and the lift coefficient from 0.23 to 0.29. These values, used with a simple model of a defensive wall, have enabled free kicks to be simulated under realistic conditions, typical of match-play. The results reveal how carefully attackers must engineer the dynamics of a successful kick. For a central free kick some 18.3 m (20 yards) from goal with a conventional wall, and initial speed of 25 m·s?1, the ball's initial elevation must be constrained between 16.5° and 17.5° and the ball kicked with almost perfect sidespin.  相似文献   

17.
The displacement of the golf ball struck by a driving club is affected by several player characteristics and equipment parameters and their interrelationships. Some modelling and simulation studies have shown a relationship between shaft length and clubhead speed, supported by a few experimental studies. The aim of the present study was to examine the relationship between driver length and ball launch conditions in an indoor test facility using a ball launch monitor. Nine males considered to be skilled golfers participated in the study. Four driving clubs of total length 117, 119, 124, and 132 cm were assembled from commercially available components and were used to strike golf shots while initial ball velocity, backspin rate, and launch angles were measured. Statistical analysis identified a significant difference in initial launch speed due to club length, a significant difference between participants, but no difference between the trials for a given golfer. A positive trend was noted between backspin and launch angle for all four clubs, and significant inverse associations between initial launch speed and backspin rate and launch angle. However, the combined launch conditions associated with increasing length were not considered optimal, with uncontrolled swingweight and moment of inertia effects considered to be limiting factors.  相似文献   

18.
Abstract

The displacement of the golf ball struck by a driving club is affected by several player characteristics and equipment parameters and their interrelationships. Some modelling and simulation studies have shown a relationship between shaft length and clubhead speed, supported by a few experimental studies. The aim of the present study was to examine the relationship between driver length and ball launch conditions in an indoor test facility using a ball launch monitor. Nine males considered to be skilled golfers participated in the study. Four driving clubs of total length 117, 119, 124, and 132 cm were assembled from commercially available components and were used to strike golf shots while initial ball velocity, backspin rate, and launch angles were measured. Statistical analysis identified a significant difference in initial launch speed due to club length, a significant difference between participants, but no difference between the trials for a given golfer. A positive trend was noted between backspin and launch angle for all four clubs, and significant inverse associations between initial launch speed and backspin rate and launch angle. However, the combined launch conditions associated with increasing length were not considered optimal, with uncontrolled swingweight and moment of inertia effects considered to be limiting factors.  相似文献   

19.
A mechanical field-goal kicking machine was used to investigate toppling ball flight in American football place-kicking, eliminating a number of uncontrollable impact variables present with a human kicker. Ball flight trajectories were recorded using a triangulation-based projectile tracking system to account for the football’s 3-dimensional position during flight as well as initial launch conditions. The football flights were described using kinematic equations relating to projectile motion including stagnant air drag and were compared to measured trajectories as well as projectile motion equations that exclude stagnant air drag. Measured football flight range deviations from the non-drag equations of projectile motion corresponded to deficits between 9 and 31%, which is described by a football toppling compound drag coefficient of 0.007 ± 0.003 kg/m. Independent variables including impact location and impact angle orientation resulted in 15 impact conditions. We found that an impact location of 5.5 cm from the bottom of the ball maximized trajectory height and distance. At the 5.5-cm impact location, alterations in impact angle produced minimal change in football trajectory, including launch angle (range = 1.96 deg), launch speed (range = 1.06 m/s), and range (range = 0.94 m).  相似文献   

20.
Despite many coaching and biomechanical texts describing how the kinematics of the club-head at impact lead to distance and accuracy of the ball flight, there is limited quantitative evidence supporting these assertions. The purpose of this study was to quantify the relationships between club-head kinematics and subsequent early ball flight characteristics during the golf drive. An opto-reflective system operating at 400 Hz was used to capture the swings of 21 male golfers using their own drivers. The 3D displacement data permitted the calculation of club-head kinematics at impact, as well as subsequent early ball flight characteristics. Using regression analyses, club-head kinematics at impact (velocity, orientation, path, and centeredness) were used to explain the variability in five dependent variables of early ball flight characteristics (resultant velocity, launch angle, side angle, back spin, and side spin). The results of the study indicated that club-head kinematics at impact explained a significant proportion of early ball flight characteristics (adjusted r 2 = 0.71–0.82), even when generalized across individual clubs.  相似文献   

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