Position estimation of ball impact in baseball batting using PVDF films

Abstract

In this study, we present a position estimation of ball impact in baseball batting using PVDF films. A vibration sensor consisted of two PVDF films in a cross shape was developed. The outputs from the PVDF films were normalized and filtered. We calculated the largest peak of the normalized and filtered outputs to eliminate the effect of intensity of the impact and extract a primary vibration mode, and the amplitude ratio between two outputs. The largest peak and the amplitude ratio were used as the parameters for the estimation. Fundamental experiments on the different impact intensities and the different positions showed that the largest peak well reflected the longitudinal impact position of the impact and the amplitude ratio reflected both longitudinal and circumferential impact positions of the impact. Then, we proposed an estimation method in which the longitudinal position was estimated firstly, then the circumferential position was estimated. The validation test showed that the estimation errors were small around the sweet spot, indicating that our sensor has the capability of determining the longitudinal and circumference positions of the ball impact in baseball batting.