India develops undetectable underwater robot
The Indian Institute of Technology Madras has designed the nation's first bio-inspired underwater robot. Operating at a maximum of 100 metres below sea level, the machine is undetectable due to its biologically-inspired movements. Thus, it may be used for stealth observations by the military as well as for inspections of offshore oil and gas rigs, ships, bridges, dams and ports.

The robotic fish Duli' (means turtle in Sanskrit) has biologically inspired caudal (tail) fin and conventional rotary thrusters.

Chennai: A student from IIT-Madras and his professor have designed the country’s first bio-inspired underwater robot which can be used for various operations like stealth observations in the military operations and to monitor the bio-environment in the sea.

The robotic fish ‘Duli’ (means turtle in Sanskrit) has biologically inspired caudal (tail) fin and conventional rotary thrusters. Santhosh Ravichandran, a second year MS student (machine design) from the department of mechanical engineering, has designed the robot with the guidance of his professor Prabhu Rajagopal.

"The remotely operated underwater vehicle can be camouflaged as fish. It can go undetected as nobody will be able to get a signature of it," said Rajagopal, associate professor, IIT-Madras and director, Planys Technologies Pvt Ltd, Chennai.

The bio-inspired fins can be used for long distance straight travel (with lesser manoeuverability requirements) and conventional rotary thrusters for complex local motions like turning.

"The bio-inspired vehicle is the future worldwide and in the robotics, the trend is more and more bio-inspired. We want to design the robot with all the fins like in the fish which can go much deeper but its very difficult to control," he said.

"The vehicle is difficult to control. Lot more research is required before making it commercially available," he added.

The highly versatile vehicle can also be used for inspecting the structural stability of the ports, ships, offshore oil and gas rigs, bridges and dams. It can go up to 100 metres under the water.

"We moved into bio-inspired vehicles because we found that it is more efficient than the conventional vehicles," said Ravichandran. "Soon we realised that efficient bio-inspired vehicles are not really manoeuverable. Then we came up with the idea to integrate both the conventional thrusters and bio-inspired propulsions for both manoeuvrability and efficiency, " he said.

"In nature, there is a lot of mechanisms we can copy. Only very few people in the world are working in the bio-inspired vehicles. The efficiency of the conventional underwater vehicle is only around 40 per cent. This bio-inspired vehicle’s efficiency will be more than 60 per cent," he said.

He studied types of fish ranging from sharks to tuna before settling in on the tail fin. The type of tail they have come up is having the resemblance of dolphins.

"There are vehicles with fish tails but this type of configuration using both the fish tail and conventional had not been done before. We also researched on how to make the fish fin to flap. We have got the provisional patent for design configuration and functionality of the vehicle," he said. "Our immediate goal is to make it more controllable and to make it commercially available," Ravichandran said.