Quantification of a Ball-Speed Generating Mechanism of Baseball Pitching Using IMUs

Abstract

The purpose of this study was to propose a methodology which quantifies the ball-speed generating mechanism of baseball pitching with the use of inertial measurement units (IMUs). IMUs were attached to the upper trunk, upper arm, forearm, and hand segments. The initial orientation parameters of each segment were identified using the differential iteration method from the acceleration and angular velocity of the sensor coordinate system output by IMUs attached to each segment. The motion of each segment was calculated and the dynamic contributions were then calculated. The motion of a baseball pitcher, who was instructed to throw at the target, was measured with a motion capture (mocap) system and IMUs. The results show that quantitative analysis of the ball-speed generation mechanism by the proposed method is almost similar to that conducted by the mocap system. In the future, this method will be employed to evaluate the ball-speed generation mechanism outside controlled laboratory conditions in an effort to help understand and improve the player’s motion.

Keywords

• baseball pitching
• motion-dependent term
• ball speed generation
• dynamic contribution
• differential iteration method
• whip-like effect