Research on quadrupedal robots inspired by canids or felids have been widely reported and demonstrated. However, none of these legged robots can deal with difficult environments that include water, such as small lakes, streams, rain, mud, flooded terrain, etc. In this paper, we present for the first time a kinematic analysis and a hydrodynamic model of dog paddling motion in a robotic system. The quadrupedal paddling gait of dogs was first analyzed based on underwater video recording. Hydrodynamic drag force analysis in a paddling gait cycle was conducted for a prototype robotic dog. The prototype robotic dog was developed using four pre-charged pneumatics soft actuators with consideration of relative positions of CG (center of gravity) and CB (center of buoyancy) and their dynamic variation in paddling. It was found that such soft actuators have great potential in developing amphibious legged robots, because they are inherently water-tight, anti-rusty, simple in structural design, and have large hydrodynamic advantage due to their mostly hemi-cylindrical shape design. Trotting and paddling of the prototype robotic dog was also demonstrated. It is believed that our findings reported in this research will provide useful guidance in future development of amphibious robotic dogs.

中文翻译：

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受生物启发的机器狗划桨：运动学和流体动力学分析。

受犬科动物或猫科动物启发的四足机器人研究已经得到广泛报道和证明。但是，这些腿式机器人都无法应对包括水在内的困难环境，例如小湖，溪流，雨水，泥泞，洪水泛滥的地形等。在本文中，我们首次提出了运动分析和流体动力学模型。狗在机器人系统中划桨运动。首先基于水下视频记录来分析狗的四足步态。在原型步态狗中进行了步行步态的水动力阻力分析。原型机器狗是使用四个预充气的气动软执行器开发的，其中考虑了CG（重心）和CB（浮力中心）的相对位置及其在划水时的动态变化。已经发现，这种软致动器在开发两栖有腿机器人方面具有很大的潜力，因为它们固有地是水密的，防锈的，结构设计简单的，并且由于其主要是半圆柱形的形状设计而具有很大的流体动力优势。还演示了原型机器狗的小跑和划桨。可以相信，我们在这项研究中报告的发现将为两栖机器狗的未来发展提供有用的指导。