Robotic designers continue to improve their mimicry of the speed and efficiency with which manta rays glide through the water. An autonomous underwater vehicle (AUV) designed by researchers from the National University of Singapore is the latest, most advanced iteration of manta ray-inspired robotics.
The MantaDroid emulates the manta ray not only in appearance, but in function. Manta rays’ efficiency of movement is derived largely from a propulsion mechanism which makes them unique among swimming sea life. After testing 40 fin models over the course of two years, MantaDroid designers chose flexible PVC sheets as the material that best re-creates the pectoral fins on a real manta ray. The result is an AUV that can swim approximately 2.3 feet per second, or twice its body length, for up to ten hours. The MantaDroid mimics the dimensions of a juvenile manta ray, as it is 35 cm long and 64 cm wide, weighing about a 1.5 lbs.
The MantaDroid distinguishes itself from prior manta ray-inspired AUVs by incorporating a single electric motor per fin. This creates a propulsion system that is more reminiscent of the manta ray’s fluid motion. This, its designers explain, allows it to swim greater distances more efficiently than robotic predecessors.
“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,” explained associate professor Chew Chee Mang, leader of the MantaDroid team.
Potential uses for the MantaDroid include search and rescue missions, underwater surveying and inspection, mapping, and military recon, with the potential for groups of these AUVs to be deployed simultaneously. The wide, flat design of the MantaDroid’s body means that it holds the capability to anchor several sensors utilized for these purposes, eventually gaining fully autonomous functionality. Further, the propeller-less propulsion system poses less risk of entanglement in aquatic plants while also producing less turbulence than its propeller-dependent counterparts.
The team is working on a larger, 14-inch version of the MantaDroid that is twice the size of the original, continuing to employ biomimetics – applied learning about natural systems in robotics – in its design and development processes.