Pitcher training aided by instrumented baseball

Proper pitching mechanics are imperative for developing different types of pitches (e.g., fastball vs. breaking ball) and for preventing injury. Different pitch types are distinguished by the path (i.e. break) and speed of the ball which, in turn, are dictated by the angular velocity of the ball and the velocity of the ball center at the instant of release from the pitcher's hand. While radar guns effectively measure ball speed, they provide no information about the direction of the velocity of the ball center, the angular velocity of the ball, or the way in which these quantities change during the throw. These quantities can, in principle, be calculated using high-speed video-based motion capture (mocap), but doing so requires measurements in a controlled lab environment taken by a skilled technician. Moreover, mocap is unlikely to accurately resolve the angular velocity of the ball which is crucial to understanding pitching. This paper addresses these shortcomings by presenting an instrumented ball containing a miniature, wireless inertial measurement unit (IMU) to measure ball dynamics on the field of play. Measurements reveal that this technology can deduce the magnitude and direction of the ball's velocity at release to within 4% when benchmarked against mocap. Moreover, the IMU directly measures the angular velocity of the ball for pitches that remain within the measurement range of the associated angular rate gyros.