Design of a full degree-of-freedom baseball pitching machine

Abstract

The design, implementation, and experimental validation of a new kind of baseball pitching machine is discussed. This machine provides accurate and repeatable release conditions with full degree-of-freedom control over the linear and angular velocity vectors, by using separate mechanisms to impart each. It provides a research tool for use in understanding the aerodynamic effects of linear and angular velocity variations on the ball’s trajectory as well as providing a potentially more robust training tool to athletes who play the game. Design of the pneumatic propulsion system is based on a thermodynamic model of the gas flow in the plenum and barrel. Release speeds up to 45 m · s–1 and spin rates up to 40 revolutions per second are achieved. The direction of the angular velocity vector is fully adjustable relative to the translational velocity vector, which itself may be controlled in pitch and yaw. High-speed video experiments used to validate the machine’s performance show that speed and spin rate are controllable to ≈2% and 5%, respectively.