Ryozo Ishiwata

Image processing of rotation of a pitching ball in baseball

To make clear the principle of a breaking pitching of baseball, we have developed a image processing system of pitching ball. This system can detect a rotation speed and a direction of rotation axis of ball from images taken by a high-speed video camera. These images were taken at frame rate of 500 or 1000fps and shutter speed of 1/2000 or 1/5000s. The velocity of ball was determined by its position in 6 continuous flames. The rotation speed and axis of rotation were determined from the pattern of seam. The pitching balls of test pitchers were analyzed by the present system, and discussed. The present system will be used in an analysis of the pitching ball, a training of pitcher, a development of new breaking pitching and so on.

Flow around a Swinging Circular Cylinder in a Stationary Fluid

It is known that manipulators of marine robots are oscillated by Karman-vortex shed from themselves when they move in a water. To analyze fundamentally this, flows around a circular cylinder turned round its end have been visualized by means of hydrogen-bubble method in this study.The separation vortices generated in the neighborhood of the other end of cylinder were periodically shed from it. The vortex shedding made continuously progress toward the center of rotation, and vortex filaments like ox-horn were formed. They were not continued to the center of rotation but broken off in the middle of the cylinder. The locations of breakaway point were scattered in every vortex shedding. Therefore the shedding frequency was higher in outer region than in inner.