An aquatic robot that emulates the swimming locomotion of manta rays could be put to use as an underwater surveillance platform.
Developed by researchers at the National University of Singapore (NUS), the so-called MantaDroid, measures 35cm in length, 63cm in width and can swim at a speed of 0.7m per second for up to 10 hours.
Manta rays are of interest because they possess a unique propulsion mechanism that enables them to cruise through turbulent seas by flapping their pectoral fins. This distinctive feature has led researchers to investigate the science behind manta ray locomotion and incorporate similar mechanisms into autonomous underwater vehicles (AUVs).
MantaDroid, which weighs 0.7kg, was designed and optimised 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 were eventually installed on the robot are a pair of flexible pectoral fins made using PVC sheets, giving the device favourable manoeuvrability and swimming capabilities in pool tests.
The MantaDroid was developed by a team led by Associate Professor Chew Chee Meng and Associate Professor Yeo Khoon Seng from the Department of Mechanical Engineering at NUS Faculty of Engineering.
“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,” said Assoc Prof Chew.
MantaDroid makes a promising alternative to traditional propeller-based thrusters used in conventional AUVs, and could potentially operate for a longer range.
Like the real manta ray, NUS’ aquatic robot also has a flat and wide body that can accommodate a range of sensors and be utilised for different purposes such as studying marine biodiversity, measuring hydrographic data and performing search operations.
The NUS team will next test their aquatic robot 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 in the robot’s fin mechanism.