Swimming Performance Improvement of a Compliant Bio-fish Robot with Flexible Driving Mechanism

Bio-fish robots have better swimming performance than traditional propeller-based vehicles, because they can replicate a real fish motion. However, most of prototypes cannot move as smooth and efficient as a real fish for their complicated multilink driving mechanism. Although a few of robots have adopted soft or smart mechanism to mimic fish driving, their performance hasn't improved much either. In this paper, a compliant bio-fish robot with flexible driving mechanism is presented. Because the swimming speed of the fish was influenced by the swing amplitude and frequency through their different body structure, the different motion and structure parameters on the swimming performance of the robot was analyzed through theoretical equation and experiment via the established propulsion force measuring platform. Then, a wire driven robot was designed imitating the fly fish with an elastic plate caudal stalk and a passive component to connect the caudal fin. Also, an incomplete gear was adopted to realize an efficient reverse during caudal fin swing. The performance of the robot was investigated in the pool and a widely used indicator is chosen to evaluate the swimming performance of our robot. The results show that our robot has a great improvement in swimming efficiency compared with other robots.