Characterisation of football trajectories for assessing flight performance
Characterisation of football trajectories for assessing flight performance
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DOI：
10.1177/1754337118774414
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发表时间：
2019-03-01
影响因子：
1.5
通讯作者：
Harland, Andy
中科院分区：
文献类型：
--
作者：
Ward, Matthew;Passmore, Martin;Harland, Andy
许多讨论围绕着协会足球（足球）的飞行，特别是在飞行可能被认为是不规则的地方。由于摄像机覆盖率和公众监督的增加，这种情况在备受瞩目的比赛中尤为普遍。所有足球在飞行中的表现并不相同。这篇文章开发了一些方法来描述飞行的重要特征，使球设计之间的直接，定量的比较成为可能。用于生成飞行轨迹的系统包括在风洞中收集气动力系数数据，这些数据在各种实际条件下输入飞行模型。从这些轨迹中推导出参数，以确定飞行范围内的飞行偏差，并对不同球的空气动力学性能进行统计比较。飞行中的横向移动量通过计算与初始射击向量的最终横向偏差来确定。为了量化飞行的总体形状，将多项式函数的阶数递增地拟合到飞行轨迹，直到获得良好的拟合，其中高阶多项式指示不太一致的飞行。在每次飞行中的拐点的数量也被记录，以进一步定义的飞行路径。通过比较真实的投篮，第二个飞行路径，而不考虑方向相关的力量，球的方向依赖性进行了评估。这些飞行之间的差异隔离了与方向有关的气动力的影响。文章提供了一种方法，定量描述一个球的空气动力学行为在一个定义和强大的数学过程。关于哪些球是好的和坏的，并没有得出结论;这些都是主观的术语，只能通过全面的球员感知研究来分析。
Much discussion surrounds the flight of association footballs (soccer balls), particularly where the flight may be perceived as irregular. This is particularly prevalent in high-profile competitions due to increased camera coverage and public scrutiny. All footballs do not perform in an identical manner in flight. This article develops methods to characterise the important features of flight, enabling direct, quantitative comparisons between ball designs. The system used to generate the flight paths included collection of aerodynamic force coefficient data in a wind tunnel, which were input into a flight model across a wide range of realistic conditions. Parameters were derived from these trajectories to characterise the in-flight deviations across the range of flights from which the aerodynamic performance of different balls were statistically compared. The amount of lateral movement in flight was determined by calculating the final lateral deviation from the initial shot vector. To quantify the overall shape of the flight, increasing orders of polynomial functions were fitted to the flight path until a good fit was obtained with a high-order polynomial indicating a less consistent flight. The number of inflection points in each flight was also recorded to further define the flight path. The orientation dependency of a ball was assessed by comparing the true shot to a second flight path without considering orientation-dependent forces. The difference between these flights isolated the effect of orientation-dependent aerodynamic forces. The article provides the means of quantitatively describing a ball's aerodynamic behaviour in a defined and robust mathematical process. Conclusions were not drawn regarding which balls are good and bad; these are subjective terms and can only be analysed through comprehensive player perception studies.