Soft Manta Ray Robot Based on Bilateral Bionic Muscle Actuator

The pectoral fins of manta rays are driven by bilateral muscles to generate up-down flapping movements that allow for efficient and flexible swimming. However, current soft underwater biomimetic flapping robots are mostly driven by unilateral muscle actuators, and the pectoral fin can only realize simple downward bending motion, the biomimicry, motion flexibility, and swimming speed of these robots need to be further enhanced. Here, a soft manta ray robot driven by bilateral dielectric elastomer bionic muscle actuators is proposed. The bilateral muscle-driven pectoral fin can not only achieve a larger bending angle (37°), but also present a 3D morphology similar to that of a natural manta ray during the swimming process. Compared to the simple downward flapping used by most robots, the simulation shows that the pectoral fins driven by bilateral muscles can obtain larger vortex intensity, flow field velocity, and thrust. The fastest swimming speed of the designed manta ray robot driven by a bilateral bionic actuator is 42 mm/s (0.76 body length per second BL/s), which is about 0.7 times higher than the swimming speed of the robot driven by a unilateral bionic muscle actuator (25 mm/s). What's more, by strategically controlling multiple actuating units of the actuators, the manta ray robot can achieve more flexible swimming motions, including continuous turns, C-shaped, and S-shaped swimming trajectories. This study not only reveals the effectiveness of the bidirectional flapping mode in improving the performance of underwater swimming robots but also the proposed bilateral muscle-driven mode can be applied to other soft robots and flexible electronic devices.