对乒乓球发球动作违规风险的研究——以2012年伦敦奥运会乒乓球女子单打决赛争议发球为例

Irregularity Risk of Service in Table Tennis: Taking Debatable Service of Table Tennis Women's Singles Final in 2012 London Olympic Games for Example

在2012年伦敦奥运会女子乒乓球单打决赛中,丁宁的发球被判罚不仅影响了比赛胜负的结果,而且引发了人们对发球判罚的争议。通过在比赛录像截图中建立二维直角坐标系,对乒乓球在直角坐标系中进行定位,对丁宁两个被判发球抛球的出手角度和抛球高度进行定量研究。结果表明,丁宁被判罚的两个发球的抛球高度都大于40cm,出手角度在80o左右,反映出裁判员判罚尺度过分严格,丁宁抛球前不执拍手从远离身体向靠近身体的水平移动是被裁判认为抛球不够垂直的主要原因。同时,丁宁抛球后不执拍手臂未能从球和球网之间的空间移开存在违规风险。

In Table Tennis Women＇s Singles Final of 2012 London Olympic Games ,the penalties of Ding Ning＇ s service not only affected the result of match but also caused debate on the service penalty. By building up twodimensional rectan gular coordinate system in the screenshots of video,locating de ball in the twodimensional rectangular coordinate system, a quantitative research was done about toss angles and heights of Ding Ning＇ s two services which were penalized. The re suits indicated that the heights Ding Ning＇ s services were more than 40cm,and the angles were about 80° ,reflecting that the umpire was over strict. The main reason why the umpire thought Ding Ning＇ s toss was not vertical is the free hand moved from far to near before toss. At the same time, after projecting the ball, Ding Ning＇ s free arm didn＇ t remove from the space between the ball and the net which has the irregularity risk.