無線微機電感測器應用於網球開放式正拍上旋球之球拍振動分析

THE RACKET VIBRATION ANALYSIS OF WIRELESS MEMS SENSORS USED IN TENNIS OPEN FOREHAND TOP SPIN

目的：本研究探索運用無線微機電感測器，分析優秀和次優秀選手在網球開放式正拍上旋球的球拍振動差異。對象：受測優秀選手目前全國男子單打排名第9名；次優選手目前為全國排名賽會前賽選手。方法：將無線微機電感測器放在球拍上，內含有三軸加速規，取樣頻率為3333Hz，並搭配高速攝影機拍攝，當擊正拍上旋球時無線擷取運動學資料，並作統計分析。結果：(1)兩位選手個人在無配戴與有配戴感測器在球速方面，經比對t檢定後，無顯著差異。(2)在球拍加速度頻譜振動頻率次數分佈中，優秀選手的Y、Z軸，均在高頻率有較多的振動現象，而次優秀選手卻無明顯振動。優秀選手的X軸，均有較無明顯振動，而次優秀選手卻在高頻率有明顯振動。(3)球拍振動時間經檢定後發現優秀與次優秀選手在X、Y、Z軸均有顯著差異(顯著差異α為0.05)。(4)在球拍加速度的時域分析，優秀選手在X、Y、Z軸最大和最小平均值與次優秀選手有顯著差異，得知優秀選手擊到球時，明顯集中於甜區，且揮拍速度較快，擊球力量較大。結論：(1)配戴感測器不會影響選手的表現。(2)優秀選手擊到球時，明顯集中於甜區，且揮拍速度較快，擊球力量較大。(3)在振動時間中，優秀選手明顯時間高於次優秀選手，代表優秀選手在擊球時能夠緊握球拍至將整個正拍上旋球擊球動作完成，讓擊出的上旋球質較紮實穩定。(4)球拍時域資料，經F和t檢定後，發現在三軸的最大和最小平均值有顯著差異，所以優秀選手瞬間施力較大，且上旋球轉速較快，球質較穩定。

Purpose: This research explored the use of Wireless Micro Electro Mechanical Systems (MEMS) sensors to analysis the difference of tennis open forehand top spin. Subjects: The elite athlete is ranked number 9 of man single in Taiwan and the sub-elite is ranked the third of group in Taiwan. Methods: Underneath the racket is placed a wireless Micro Electro Mechanical Systems (MEMS) sensors which includes a tri-axis accelerometer. The sample is taken on the frequency of 3333Hz. When athletes strike forehand cut racket， sensors capture measuring point of numerical data， and statistical analysis. Results: 1. Two of the contestants not worn and wear sensors in ball speed， paired t testing， no significant differences. 2. Number of vibration frequency distribution in the Y， Z axes of the elite athlete， at high frequencies there are more vibration phenomena in the racket acceleration spectrum， while the sub-elite athlete， there was no vibration. The elite athlete of the X-axis， are less obvious vibration sub-elite athlete in the high frequency vibration. 3. From the test of racket vibration time， verification revealed that the elite athlete and the sub-elite have obviously difference. 4. The analysis of racket time zone， it indicates that athletes have obviously difference during the max and min average values on X， Y and Z axis. The result showed that the elite athlete hit the tennis obviously on the center of the racket，the striking speed was faster and the hitting power was stronger. Discussions: 1.Wear sensors will not affect the athletes’ performance. 2. The elite athlete hit the ball obviously focused on the sweet spot， and a faster swing speed， hitting power. 3. In the vibration time， it indicates that the elite athlete has longer period than the sub-elite. It means that the elite athletes are significantly better than the sub-elite. 4. From the time zone of the racket， the max and min average in tri-axis get obviously difference paired F and t test. The elite athlete gets more power in a flash hitting the speed of the top spin was faster and gets better control in striking.