Football sized underwater robot to provide port security

An Indian-origin researcher at MIT has developed an oval-shaped submersible robot, smaller than a football, that can skim discreetly along a ship's hull to seek hollow compartments concealing contraband.
Researchers at the Massachusetts Institute of Technology (MIT) unveiled the robot with a flattened panel on one side that it can slide along an underwater surface to perform ultrasound scans.
Originally designed to look for cracks in nuclear reactors' water tanks, the robot could also inspect ships for the false hulls and propeller shafts that smugglers frequently use to hide contraband.
Because of its small size and unique propulsion mechanism - which leaves no visible wake - the robots could, in theory, be concealed in clumps of algae or other camouflage.

Fleets of them could swarm over ships at port without alerting smugglers and giving them the chance to jettison their cargo, researchers said.
"It's very expensive for port security to use traditional robots for every small boat coming into the port," said Sampriti Bhattacharyya, a graduate student in mechanical engineering, who designed the robot together with her adviser, Ford Professor of Engineering Harry Asada.

"If this is cheap enough - if I can get this out for USD 600, say - why not just have 20 of them doing collaborative inspection? And if it breaks, it's not a big deal. It's very easy to make," said Bhattacharyya.

Bhattacharyya built the main structural components of the robot using a 3-D printer. Half of the robot - the half with the flattened panel - is waterproof and houses the electronics.
The other half is permeable and houses the propulsion system, which consists of six pumps that expel water through rubber tubes.
Two of those tubes vent on the side of the robot opposite the flattened panel, so they can keep it pressed against whatever surface the robot is inspecting. The other four tubes vent in pairs at opposite ends of the robot's long axis and control its locomotion.
As Bhattacharyya explained, the elliptical shape of the robot is inherently unstable - by design.

"It's very similar to fighter jets, which are made unstable so that you can manoeuvre them easily. If I turn on the two jets (at one end), it won't go straight. It will just turn," she said.
That tendency to turn is an asset when the robot is trying to execute tight manoeuvres, but it's a liability when it's travelling in a straight line.
In the robot's watertight chamber are its control circuitry, its battery, a communications antenna, and an inertial measurement unit, which consists of three accelerometers and three gyroscopes that can gauge the robot's motion in any direction.

The control algorithm constantly adjusts the velocity of the water pumped through each of the six jets to keep the robot on course.