The profiles were analyzed to describe ball roundness and seam height separately.
A bespoke, non-contact, ball surface profiler, was used to measure ball radius, including seam height. The aim of this work was to quantify the effect of seam height and roundness on ball lift and drag, which, to our understanding, has never been done outside of a wind tunnel. Ball diameter, weight, seam height, surface roughness, and shape influence lift and drag, and therefore carry distance. Little is known concerning the causes of variation in ball drag. Past work has shown large variation in the drag of baseballs. The results indicate that FL could be accurately explained from ESp and also that seam orientation (four-seam or two-seam) did not produce a uniform effect on estimating FL from ESp. Equations were derived to estimate the FL using the effective spin parameter (ESp) which is a spin parameter calculated using a component of angular velocity of the ball with the exception of the gyro-component. The initial angular velocity of the ball was determined using a custom-made apparatus. The linear kinematics of the ball was determined at 0.008sintervals during the flight, and the resultant fluid force acting on the ball was calculated with an inverse dynamics approach. Four high-speed video cameras were used to record flight trajectory and spin for seven types of pitches. The purpose of this study was to describe the relationship between FL and spin for different types of pitches thrown by collegiate pitchers. This work benefits several important application areas including the monitoring of sensor calibration systems and the definition of ball specifications that constrain trajectories to acceptable ranges.Īlthough the lift force (FL) on a spinning baseball has been analyzed in previous studies, no study has analyzed such forces over a wide variety of spins. We demonstrate the statistical significance of the results.
Previous methods based on smaller sets of laboratory measurements have been unable to discern changes in the lift coefficient in response to changes in seam height of 0.02 inches. We also demonstrate the ability to predict increases in the lift coefficient in response to changes in seam height on the order of a thousandth of an inch. By applying this methodology to a set of over two million trajectory measurements, we achieve unprecedented accuracy in the characterization of the lift force.We show that the lift coefficient is more than six percent greater than measured by previous laboratory experiments. Fine-grained weather data is associated with each radar measurement to enable compensation for the local air density. The optimization accounts for the uncertainty in the different data sources while exploiting the size and diversity of the radar measurements to mitigate the effects of systematic biases, outliers, and the lack of geometric information that is typically available in laboratory experiments. A new optimization method is developed that incorporates domain knowledge and constraints derived from optical measurements. The reduced degree of standardization in the measurements is countered by several elements of the approach. The methodology addresses this task from the novel perspective of considering a large set of radar measurements acquired outside of a laboratory setting. We develop a new method for characterizing the lift force on a baseball.
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