Realizing Efficient Front Crawl Stroke With a Wheel-Paddle-Integrated Mechanism: Inspired by Human Competitive Swimming

Oscillating propulsion is widely used in underwater robots, which is inspired by the fin of fish. However, the negative force generated during the locomotion is affecting the propelling efficiency. To tackle such a problem, a swimming mode called front crawl stroke, which gets inspiration from human competitive swimming, has been proposed in this paper. It was implemented in a wheel-paddle-integrated mechanism. This mechanism is capable of flexible transformation among various locomotion modes, permitting more choices when facing complex application environment. The proposed front crawl stroke was studied both theoretically and experimentally. The results suggest that when generating the same maximum propelling force, the front crawl stroke can produce less negative force than the oscillating mode, so as to larger effective net thrust. Furthermore, the propelling efficiency of the front crawl stroke is 2.7 times higher than the oscillating mode. The stroke was also explored with various periods and duty factors. It was found that shorter period and lower duty factor can generate larger net thrust, whereas the force of longer stroke period and higher duty factor is comparatively stable.