發送短信 : On repetitive learning control for periodic tracking tasks

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 |__  //   /_   _//  |__  //  | || | ||  /_   _// 
   / //     -| ||-     / //   | || | ||  `-| |,-  
  / //__    _| ||_    / //__  | \\_/ ||    | ||   
 /_____||  /_____//  /_____||  \____//     |_||   
 `-----`   `-----`   `-----`    `---`      `-`'