A kind of bionic robofish with swaying flexible tail fin

Focusing on solving the problem of swaying propulsion, a design of bionic robofish with swaying flexible tail fin is presented. In this design, according to the principle of crank-rocker, a special four-bar linkage swaying mechanism combined with the flexible tail fin is adopted to guarantee the stable swimming of robofish. The skillful application of hall position sensors achieves the detection of critical position of the swing link, which makes it possible to detect the position of the tail fin and control the turning of robofish. For effective raising and lowering, a mechanism using a cylinder as a pump to imitate the swimming bladder is developed. Experiments show that the robofish with our new swaying mechanism gets the desired performance. It can be applied to various fields, including underwater tasks, military reconnaissance and entertainments.