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標題: | 自主式水面載具於衝浪帶波浪中位置保持之研究 Station Keeping in Surf Zone Waves of an Autonomous Surface Craft |
作者: | Yu-Cheng Lin 林祐成 |
指導教授: | 郭振華 |
關鍵字: | 影像處理,雙眼立體視覺,相機校正,影像切割,色彩空間轉換,無人載具,特徵對應,近岸波浪調查,導航, Image processing,stereo camera,camera calibration,image clustering,autonomous surface craft,feature correspondence,surf zone waves,navigation, |
出版年 : | 2013 |
學位: | 碩士 |
摘要: | 本文發展水上自主式無人載具用於自主蒐集衝浪帶之觀測資料。近年來,衝浪帶之觀測資料多用近岸觀測值與海洋觀測值內插而得,故發展一套自主衝浪帶觀測載具有其必要性。載具於衝浪帶執行觀測時,受衝浪帶波浪影響其定位產生極大誤差。故此本論文發展無人水上載具,須在指定的範圍內必須擁有好的起伏與定位表現。GPS訊號用來將無人水上載具導航至指定區域,接下來利用影像處理以及雙眼立體視覺來監測載具周圍之波浪場。為了取得波浪場,首先,本文介紹一般雙眼視覺攝影機的校正方法,經由校正後的影像,接著將左攝影機影像之RGB色彩空間轉換到L*a*b*的色彩空間,利用K-means 演算法將波峰下的陰暗處切割出來,並且利用累積計算找到相連陰暗處最大區塊而後找出上緣邊界,接著找出左右攝影機影像的對應關係,最後利用座標轉換關係可得空間中波峰與自主無人載具之間的關係。有了上述的關係,就可以在自主式無人載具位置保持的導航中考慮此因素。最後,本論文展示其實驗數據,以驗證當載具執行位置保持於一地區的任務中,考慮波的漂流效果來降低載具起伏與飄移的可行性。 An autonomous surface craft (ASC) is designed to perform autonomous survey missions mainly in surf zone waters. In recent years, the survey data in surf zone has been made by interpolation between the offshore survey and the coastal survey. Therefore, it is necessary to develop the autonomous survey craft in surf zone. There are great position errors when the craft operates the localization and keeping station. In order to do station keeping in surf zone waves, the ASC is designed to have a good heaving and localization performance in a specific range of the surf zone wave period. GPS signals are utilized to navigate the ASC into a way-point area, and then a wave crest measurement system using stereo cameras on the ASC are developed to monitor wave fields surrounding the ASC. To facilitate the wave field monitoring, stereo images were calibrated and rectified. The corresponding epipolar lines become collinear and parallel to the image scanning lines. L*a*b* color spaces and k-means techniques were adopted to find the wave crest shadow. Wave fronts are found by the Hough transform in the images. Normalized cross correlation is then used to find the correspondence between left and right images. Stereo visions of the wave crest are then transformed by the space relation to the coordinate of the ASC. Information of the wave crest is taken into account for the ASC as the vehicle is inside the way-point area resisting waves. Finally, the wave crest detection and the navigation strategies were verified by experimental data using the ASC station-kept in a surf zone area. The feasibility to reduce the ASC drifting as the vehicle is under station keeping mode was discussed. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/62951 |
全文授權: | 有償授權 |
顯示於系所單位: | 工程科學及海洋工程學系 |
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