翻译：传统水下航行器大多采用螺旋桨推进器有笨重、环境适应性差、噪声大等缺点而软体仿生机器鱼小型轻巧结构柔软度高等特点特别是以离子聚合物-金属复合材料Ionic Polymer Metallic Composites简称IPMC驱动的软体机器人驱动电压小易于操作、灵活、不会发出噪音可以承受大变形在海军防务、水下勘测、生活娱乐等领域有潜在的应用前景。目前软体机器鱼还存在驱动力不足机动性薄弱运动控制不精

Traditional underwater vehicles mostly use propellers as propulsion, which have the disadvantages of being bulky, having poor environmental adaptability, and producing loud noise. However, soft biomimetic robotic fish are small, lightweight, and highly flexible, especially those driven by Ionic Polymer Metallic Composites (IPMC), which have a low driving voltage, are easy to operate, flexible, noiseless, and able to withstand large deformations. They have potential applications in naval defense, underwater exploration, and entertainment. Currently, soft robotic fish still have problems such as insufficient driving force, weak maneuverability, and imprecise motion control. Therefore, it is necessary to combine the propulsion methods of fish and conduct hydrodynamic research to improve the comprehensive performance of robotic fish.

To simulate the swimming of fish more realistically, this study designs a soft robotic fish modeled after the Carangidae family of fish, with IPMC-driven flexible pectoral fins and caudal fins. Overlapping mesh technology is used to simulate the direct swimming propulsion of the flexible tail fin and the combined driving of the flexible pectoral and caudal fins. The hydrodynamic performance is studied, including:

(1) Defining the contour dimensions of the Carangidae fish body according to the reference literature and designing IPMC pectoral and caudal fins. Extracting the relevant motion parameters of the IPMC pectoral and caudal fins through underwater experiments, using the BCF fish flapping motion model to analyze the kinematics of the IPMC pectoral and caudal fins, and establishing the swinging equation of the flexible pectoral and caudal fins. Simplifying the fish body into a slender body according to the Lighthill slender body theory, analyzing the forces acting on the robotic fish in water. Since the speeds of the points on the pectoral fin surface are different during the swinging process, the pectoral fin is divided into several microelements along the chordwise direction for force analysis. Using the Kutta-Joukowski formula and the Blasius formula to calculate the normal force and tangential resistance acting on the pectoral fin when it is flapping up and down. Using the integration method to solve the total fluid dynamic force acting on the object and establish the whole fish dynamic equation.

(2) Since it is difficult to obtain analytical solutions for the dynamic equations, this study uses numerical simulation methods and overlapping mesh technology to simulate the motion of the soft robotic fish. Under different frequencies and amplitudes of pectoral and caudal fin driving, the hydrodynamic performance of the direct swimming state of the soft robotic fish with flexible tail fin driving and the combined driving of flexible pectoral and caudal fins is analyzed through fluid dynamics simulation. The displacement, velocity, and hydrodynamic coefficients are analyzed to reveal the driving frequency and amplitude of the optimal pectoral and caudal fins.

(3) Finally, a robotic fish experimental platform is constructed to measure the combined force of the direct swimming state under the flexible tail fin driving mode and the combined driving mode of flexible pectoral and caudal fins, and to verify the numerical simulation results. Based on the numerical simulation and experimental results, the hydrodynamic performance of the soft robotic fish under the IPMC tail fin driving mode and the IPMC pectoral and caudal fins combined driving mode for direct swimming propulsion is compared and analyzed.

Keywords: soft robotic fish; IPMC; flexible pectoral and caudal fins; overlapping mesh; hydrodynamic performance.