| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 101 === Baseball is one of the most popular sports in Taiwan. In recent years, there are already many baseball players establishing their position as major league starters, such as Chien-Ming Wang, Wei-Yin Chen etc. They have been showing their talent on the U.S. Major League Baseball and helped bringing Taiwan to the international stage. A pitcher plays the major role in a baseball game. A good pitcher has to control his pitch precisely. But the strike zone is up to the chief umpire. In crucial time, whether a pitched ball is a strike or a ball could decide the result in a game. In MLB, the K-Zone system is used to show whether the pitch ball is a strike or a ball to provide viewers to check the umpire call. This system is attracting people who love baseball. We try to implement such a system with low-cost. With the concept of low-cost, our system can reconstruct baseball three-dimensional trajectory and show whether a pitched ball is a strike or a ball.
This system uses low-cost high-speed cameras. We also use easily produced chessboard as calibration board and use external signal lighting device for synchronization. To get the baseball trajectory, we set up two cameras to take the videos. After the videos are saved to Wi-Fi SD card, the video sequences are transferred to computer by Wi-Fi internet for the image processing. The image processing program does camera’s calibration, selects strike zone, and detects baseball. Our system mainly detects baseballs from both cameras and uses projection transform matrix to calculate the world 3D coordinates of the detected baseballs. First, we calibrate two cameras to get their intrinsic parameters and extrinsic parameters. Once we have intrinsic parameters and extrinsic parameters, we can calculate projection matrix. Second, we select four corners of strike zone and calculate their three-dimension world coordinates. Third, we get the baseball trajectory, drawing 3D trajectory with gnuplot software.
Our system can build 3D trajectory successfully and observe whether the baseball pass through strike zone. Furthermore, we improve our system performance on execution speed with OpenMP which is a parallel execution library, making the processing of baseball candidates and baseball trajectory fast. OpenMP implementation doubles computation speed than we without using OpenMP. The differences between the measured values of strike zone border and actual values of border are 6.13% and 7.91% respectively, which is quite precise.
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