加速度センサを用いた飛翔中の野球ボールの回転特性計測

抄録

In order to accurately and easily measure the rotational property of a ball in flight, we attempt to use a baseball with a built-in acceleration sensor unit which consists of one three-axis sensor for Low G and three sensors for High G. Two approaches for obtaining the rotational speed and its axis of the ball from outputs of the sensors are investigated; one is based on rotational acceleration component in the outputs and the other is based on translational one. In flight experiments, we obtain the time series data of acceleration for two kinds of flight trajectory of straight and curve balls. By using these experimental data, we measure the rotational speed and rotation axis with the present two algorithms. As the results, in each algorithm it is shown that the rotational speed is decreasing with time, and also that the rotation axis keeps almost constant during the flight. These results indicate the effectiveness of the present algorithms. In particular, the latter result means the validity of our assumption on rotation axis. The estimated rotational speeds are 15.0 rps and 22.4 rps in average for straight and curve ball, and the difference between the results of the two algorithms shows 0.6 rps and 0.03 rps, respectively. On the other hand, the difference in rotation axis is approximately 19 degrees in the case of straight ball while that is 16 degrees in curve ball.