Friedman C, Leftwich M C
Department of Mechanical and Aerospace Engineering, School of Engineering and Applied Sciences, The George Washington University, 801 22nd St, NW Washington, DC 20052, USA.
Bioinspir Biomim. 2014 Nov 7;9(4):046010. doi: 10.1088/1748-3182/9/4/046010.
To determine the two-dimensional kinematics of the California sea lion foreflipper during thrust generation, a digital, high-definition video is obtained using a non-research female sea lion at the Smithsonian National Zoological Park in Washington, DC. The observational videos are used to extract maneuvers of interest--forward acceleration from rest using the foreflippers and banked turns. Single camera videos are analyzed to digitize the flipper during the motions using 10 points spanning root to tip in each frame. Digitized shapes were then fitted with an empirical function that quantitatively allows for both comparison between different claps, and for extracting kinematic data. The resulting function shows a high degree of curvature (with a camber of up to 32%). Analysis of sea lion acceleration from rest shows thrust production in the range of 150-680 N and maximum flipper angular velocity (for rotation about the shoulder joint) as high as 20 rad s⁻¹. Analysis of turning maneuvers indicate extreme agility and precision of movement driven by the foreflipper surfaces.
为了确定加州海狮在产生推力时前鳍肢的二维运动学，我们使用华盛顿特区史密森国家动物园的一只非研究用雌性海狮，获取了一段数字高清视频。这些观测视频用于提取感兴趣的动作——利用前鳍肢从静止状态向前加速以及倾斜转弯。通过分析单摄像头视频，在每个帧中使用从鳍肢根部到尖端的10个点来数字化鳍肢。然后，将数字化的形状与一个经验函数拟合，该函数能够定量地比较不同的拍打动作，并提取运动学数据。所得函数显示出高度的曲率（最大拱度达32%）。对海狮从静止状态开始加速的分析表明，推力产生范围在150 - 680 N之间，鳍肢绕肩关节旋转的最大角速度高达20 rad s⁻¹。对转弯动作的分析表明，前鳍肢表面驱动的运动具有极高的灵活性和精确性。
