Review of multi-fin propulsion and functional materials of underwater bionic robotic fish

Abstract

At present, single-fin propulsion modes, such as pectoral fins and caudal fins, cannot ensure the mobility and forward speed of bionic robotic fish, whereas a multi-fin and flexible body can better ensure a high propulsion efficiency – particularly with low-speed mobility and high-speed stability. Therefore, the cooperative propulsion mode of the pectoral fin and caudal fin has become a research hotspot in recent years. This paper systematically introduces various actuators of robotic fish, including traditional actuators and functional materials. The functional materials include shape-memory alloy wires, ionic polymer–metal composites and piezoelectric ceramics, and their performance characteristics and limitations are discussed. Functional materials can reduce the volume and weight of a robot and reduce noise. Underwater robots have the advantages of flexibility and the ability to perform complex motions. Therefore, flexible robotic fish that combine the flexible behaviour of real fish with robot technology are gradually emerging. Finally, future research directions for bionic robotic fish are presented.

A Survey on Unmanned Underwater Vehicles: Challenges, Enabling Technologies, and Future Research Directions

“…To move through water, UUVs use navigation and control systems. An inertial navigation system, a GPS system, and a sonar system are a few examples [20,21,23,28,37,43,44,54,55,59].…”

“…The propulsion system also controls the vehicle's buoyancy, usually using a ballast system, which absorbs or releases water to regulate the vehicle's buoyancy, as well as control systems to control dives and ascents [18]. UUVs can also be propelled by wings, fins, and hydrojets [19][20][21][22].…”

A Comparative and Collaborative Study of the Hydrodynamics of Two Swimming Modes Applicable to Dolphins

“…In previous studies, individual fins were distinguished and studied to help eliminate confusion and clarify their respective quantitative contribution [ 29 , 30 , 31 , 32 ], but it is generally believed that the interaction between various parts of the fish body may potentially improve thrust generation and propulsive efficiency [ 33 ]. Wang summarized the characteristics of collaborative work of pectoral and caudal fins, and pointed out that there were few studies on multifin collaboration in fish [ 34 ]. Tytell used particle image velocimetry to visualize the 3D wake interaction between various fins around the bluegill sunfish and quantified the contribution of each fin to the wake [ 35 ].…”