Research on flexible collapsible fluid-driven bionic robotic fish.

Hydraulic drive is one of the main driving methods of traditional bionic fish, which has the disadvantages of high driving pressure and significant radial expansion of the fishtail. In this research, two innovative structures are introduced in the fishtail design to overcome these drawbacks. Firstly, high-flexible origami technology is applied to the fishtail, significantly reducing the unwanted radial expansion of the fishtail and improving energy efficiency. Based on the experiments, the origami-structured fishtail can save up to 92.3% energy compared with the traditional fishtail. Secondly, according to the bionic principles, the hybrid neutral layer of the fishtail which is sandwich-structured with knitting methods was designed. The test results show that this novel hybrid neutral layer could save up to 56.7% energy compared to the fishtail with a rigid neutral layer. A bionic fish in BCF model (Body and/or Caudal Fin propulsion) is fabricated and tested in a water tank. The results prove that the new bionic fish with the innovative fishtail obtain a good straight-line swimming direction and turning ability. This study could provide an important reference for the bionic design to mimic real fish. • A new type of fishtail is designed with an origami-style driven structure and a neutral layer that mimics a real fish's bone. • The structure of the elastic fluid driver adopts the folding paper structure to expand and contract efficiently. • Inspired by traditional Chinese knot structure, the neutral layer of the original rigid body structure was scattered first and then connected by knot structure to form a whole structure. • The novel fishtail shows excellent energy efficiency in experiments. [ABSTRACT FROM AUTHOR]