和弓発射の運動力学:リンクモデルによる角見の解析

抄録

This paper describes the dynamics of Japanese bows and arrows. In "kyudo" (Japanese archery), archers twist the grip at the moment of shooting, to avoid the "archers' paradox" which is a change of trajectory of the arrow caused by the structure of the bow and the arrow. To investigate the relation between the trajectory of an arrow and the twisting force on the grip, we proposed a dynamic model simplifying three rigid limbs and two elastic hinge. And we made an experimental apparatus that can give a force to twist the grip, and performed a shooting experiment. We measured with a strain gauge the twisting force on the grip, the tension of the string, bending moment at the center of arrow, and the compressive force of the neck. After that, we performed a computer simulation with the model we suggested and compared its result with the result of the experiment. As a result of comparison we proved that the tendency of computer simulation is consistent with the experiment. Then using this model, we investigated the relation between the twisting force and the trajectory of an arrow. As a result of simulation, twisting force is shown to be specially important during the term from taking a stance to the beginning of the shooting.