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Watch: This robot swims like a manta ray

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Researchers have created an aquatic robot called MantaDroid that mimics the swimming locomotion of manta rays.

The robotic manta ray, which swims at the speed of twice its body length per second and can operate for up to 10 hours, could potentially be employed for underwater surveillance in future.

Manta rays are considered one of nature’s most graceful and efficient swimmers. Unlike most underwater species, manta rays possess a unique propulsion mechanism that enables them to cruise through turbulent seas by flapping their pectoral fins effortlessly. This distinctive feature has sparked great interests in understanding the science behind the mechanism and to incorporate similar mechanisms into autonomous underwater vehicles (AUVs).

Motivated to develop a bio-inspired AUV, researchers developed MantaDroid, which resembles a juvenile manta ray. The robot measures 35cm in length and 63cm in width and weighs just 0.7kg.

The researchers designed and optimized MantaDroid over two years after an in-depth study of fluid dynamics and multiple experiments which included testing of 40 different fin designs. The fins that researchers eventually installed on the robot are a pair of flexible pectoral fins made using PVC sheets. The fins achieved good maneuverability and swimming capability when researchers tested them in a swimming pool.

“Unlike other flapping-based underwater robots that replicate manta ray’s flapping kinematics by using multiple motors to achieve active actuations throughout the fins, MantaDroid is powered by only one electric motor on each fin. We then let the passive flexibility of the fins interact naturally with the fluid dynamics of the water to propel the subsequent motions,” explains Chew Chee Meng, an associate professor in the mechanical engineering department at National University of Singapore Faculty of Engineering.

MantaDroid makes a promising alternative to traditional propeller-based thrusters used in conventional AUVs, and could potentially operate for a longer range. Like a real manta ray, MantaDroid has a flat, wide body that can accommodate a range of sensors that could be utilized for different purposes such as studying marine biodiversity, measuring hydrographic data, and performing search operations.

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Next, the team will be testing MantaDroid in the sea to investigate its swimming capability at different depths and its ability to withstand underwater current. The team is also working to incorporate more modes of movement into the robot’s fin mechanism.

Yeo Khoon Seng, an associate professor from the mechanical engineering department at NUS Faculty of Engineering, led the research with Chew.

Source: National University of Singapore

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