著者

酒井 忍 保富 大輔 史 金星 浦上 晃 溝口 正人

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.85, no.877, pp.19-00118, 2019 (Released:2019-09-25)

参考文献数

19

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In rubber baseball games, when the rubber ball is hit by a baseball bat, the rubber ball is deformed greatly comparing to an official baseball ball, and the batted ball speed decreases due to the energy loss during the deformation. Since the new rubber ball has been applied in games from 2018, the material properties and the restitution characteristics of the new rubber ball attract plenty of attention among scholars. In this study, the difference of the material properties and the restitution characteristics between the new and old rubber balls is investigated deeply by the static compression and collision tests. According to the static compression test, we find that the new rubber ball is harder and more difficult to generate deformation than the old one. In the collision test, the rebound ball speeds of both of the new and the old balls become faster when using a smaller diameter of steel cylinder instead of baseball bat, and the rebound ball speed of the new ball is slower than that of the old one under the same experimental conditions. Furthermore, to develop high performance baseball bats adapting to the new rubber baseball, the diameter of the baseball bat is studied by the impact simulation based on the finite element analysis. In the simulation, the batted ball speed under the analytical conditions of different offset heights and different barrel diameters of the bat are evaluated considering the initial spin. As a result, the batted ball speed generated by the bat with diameter φ55 mm is faster than generated by the bat with diameter φ70 mm when the offset height range is smaller than 14.6 mm, so that the bat diameter φ55 mm is recommended according to the present work.

著者

酒井 忍 尾田 十八 米村 茂 坂本 二郎

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 A編 (ISSN:03875008)

巻号頁・発行日

vol.73, no.734, pp.1177-1182, 2007-10-25 (Released:2011-03-02)

参考文献数

10

被引用文献数

2 1

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In the United States and Japan, baseball is a very popular sport played by many people. However, the ball used is hard and moves fast. A professional baseball pitcher in good form can throw a ball at up to 41.7 m/s (150km/hr). If a ball at this speed hits the batter, serious injury is quite likely. In this paper we will describe our investigations on the impact of a baseball with living tissues by finite element analysis. Baseballs were projected at a load cell plate using a specialized pitching machine. The dynamic properties of the baseball were determined by comparing the wall-ball collision experimentally measuring the time history of the force and the displacement using dynamic finite element analysis software (ANSYS/LS-DYNA). The finite element model representing a human humerus and its surrounding tissue was simulated for balls pitched at variable speeds and pitch types (knuckle and fast ball). In so doing, the stress distribution and stress wave in the bone and soft tissue were obtained. From the results, the peak stress of the bone nearly yielded to the stress caused by a high fast ball. If the collision position or direction is moved from the center of the upper arm, it is assumed that the stress exuded on the humerus will be reduced. Some methods to reduce the severity of injury which can be applied in actual baseball games are also discussed.

著者

尾田 十八 山崎 光悦 坂本 二郎 北山 哲士 酒井 忍 金井 亮 李 鵬 李 鵬

出版者

金沢大学

雑誌

基盤研究(A)

巻号頁・発行日

2006

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本研究は,自然・生態系と調和した新しい材料,構造,機器,システム等の創生法を,生物に学ぶことによって確立することを目的としている.その方法は多様な生物の中で,特異性を有する生物にまず注目する.本研究では動物の例として繰返し衝撃負荷に耐える「キツツキ」を,植物の例としては,軽量であるが不燃性を示す「桐材」に注目した.そしてこれらの特性がどのようなメカニズムによって生じているのかを,主として力学的視点より明らかにした.これらの結果と,代表者らがすでに行って来ている竹や卵殻の構造・組織分析結果を含め,新しい構造設計および材料設計法の基本原理を提示した.

著者

酒井 忍 北出 侑也

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.856, pp.17-00225-17-00225, 2017 (Released:2017-12-25)

参考文献数

17

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Ball shooting machine (pitching machine) is used for practicing ball sports, and it is widely prevalent. However, there are few pitching machines that can throw a ball with a gyro spin, such as a football or rifle bullet, in which the axis of the ball spins in the same direction as the ball travels. In this study, a new ball shooting machine, which can throw in the ball in a wide range of speeds and all pitch types (no, top, down, side and gyro spin balls) was invented by introducing a launch mechanism using four rollers (two launch and two gyro rollers). The shooting machine is able to arbitrarily change the rotational speed of the four rollers and the crossing angle of both gyro rollers. Shooting tests were conducted using the prototype shooting machine to confirm the ability of its performance. From the experiment results, the prototype machine had a maximum ball speed of 42.5 m/s, a spin rate of exceeding 5000 rpm, and a ball of any pitch type could also be shot. In addition, the position accuracy (shot accuracy) at the targeted fall position in the opponent's court was high because the gyro spin and other pitch types (no, top and side spins) were less than 140 mm and 40 mm (the diameter of one table tennis ball), respectively. The prototype machine had the necessary launching performance for table tennis practice of a college student level.

著者

酒井 忍 北出 侑也

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

pp.17-00225, (Released:2017-11-15)

参考文献数

17

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Ball shooting machine (pitching machine) is used for practicing ball sports, and it is widely prevalent. However, there are few pitching machines that can throw a ball with a gyro spin, such as a football or rifle bullet, in which the axis of the ball spins in the same direction as the ball travels. In this study, a new ball shooting machine, which can throw in the ball in a wide range of speeds and all pitch types (no, top, down, side and gyro spin balls) was invented by introducing a launch mechanism using four rollers (two launch and two gyro rollers). The shooting machine is able to arbitrarily change the rotational speed of the four rollers and the crossing angle of both gyro rollers. Shooting tests were conducted using the prototype shooting machine to confirm the ability of its performance. From the experiment results, the prototype machine had a maximum ball speed of 42.5 m/s, a spin rate of exceeding 5000 rpm, and a ball of any pitch type could also be shot. In addition, the position accuracy (shot accuracy) at the targeted fall position in the opponent's court was high because the gyro spin and other pitch types (no, top and side spins) were less than 140 mm and 40 mm (the diameter of one table tennis ball), respectively. The prototype machine had the necessary launching performance for table tennis practice of a college student level.

著者

尾田 十八 酒井 忍 羽場 吉博

出版者

一般社団法人電子情報通信学会

雑誌

電子情報通信学会技術研究報告. NC, ニューロコンピューティング (ISSN:09135685)

巻号頁・発行日

vol.101, no.94, pp.47-51, 2001-05-18

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従来使用されているアーム式または, 2ローラ式のピッチングマシンでは投球の速度とコースを同時かつ即座に変更することはきわめて困難である. そこで本研究では, 3個のローラを用いそのローラの回転数を各々独立に制御することにより, 従来得ることのできなかった様々なコース, 速度を極めて正確に投げ分けることのできるピッチングマシンを試作した. なお, その制御法にはニューラルネットワークを用い, 的の各コースおよび速度を入力データ, 各ローラの回転数を出力データとして学習を行い, 使用者(バッター)が希望する投球をピッチングマシン自身が適応して投げ分けてくる. このような機械は知的機械と呼ばれており, ここでは, そのようなピッチングマシンのシステムとその性能について記述する.