Water hydraulic actuator for bionic fish pectoral fin: Optimization and implementation

The utilization of soft actuators in robotics is progressively expanding, particularly for intricate tasks like grasping and exploration in complex environments. However, conventional rigid actuators driven by motors often prove unsuitable for underwater applications due to their intricate structure. This paper introduces a novel underwater twisting water hydraulic artificial muscle (TWHAM) specifically designed for biomimetic flexible robotic fish, such as pectoral fins. A mathematical model for TWHAM is developed using Gaussian Process Regression (GPR), and the parameters are optimized through Harris Hawks Optimization (HHO). Experimental results demonstrate that TWHAM can achieve an impressive torsion angle of 49.5 degrees and generate a substantial torque of 0.848 N & sdot;m under a pressure of 1.0 MPa. The incorporation of bionic pectoral fins enables the robotic fish to achieve precise steering with a radius of 0.65 m at a speed of 0.32 m/s. These findings highlight the significant potential application of water hydraulics in areas such as environmental protection, water quality testing, and ocean exploration.