• A screen shot from an animated video shows how the robot could be used to perform ultrasound scans.

    A screen shot from an animated video shows how the robot could be used to perform ultrasound scans.

    Courtesy of the researchers

    Full Screen
  • Half of the robot 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. The main structural components of the robot were made with a 3-D printer.

    Half of the robot 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. The main structural components of the robot were made with a 3-D printer.

    Courtesy of the researchers

    Full Screen
  • 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.

    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.

    Courtesy of the researchers

    Full Screen

Underwater robot for port security

A screen shot from an animated video shows how the robot could be used to perform ultrasound scans.

Football-size robot can skim discreetly along a ship’s hull to seek hollow compartments concealing contraband.


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Last week, at the International Conference on Intelligent Robots and Systems, MIT researchers unveiled an oval-shaped submersible robot, a little smaller than a football, 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.

“It’s very expensive for port security to use traditional robots for every small boat coming into the port,” says Sampriti Bhattacharyya, a graduate student in mechanical engineering, who designed the robot together with her advisor, Ford Professor of Engineering Harry Asada. “If this is cheap enough — if I can get this out for $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.”

Indeed, Bhattacharyya built the main structural components of the robot using a 3-D printer in Asada’s lab. 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.

Courting instability

As Bhattacharyya explains, 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 maneuver them easily,” she says. “If I turn on the two jets [at one end], it won’t go straight. It will just turn.”

That tendency to turn is an asset when the robot is trying to execute tight maneuvers, but it’s a liability when it’s traveling in a straight line scanning the hull of a ship. So all the tubes exit the robot at different angles, which Bhattacharyya calculated to provide the greatest degree of control over the robot’s instabilities.

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.

In their initial experiments, the researchers were just testing the robot’s ability to navigate to an underwater surface and stay in contact with it while traveling in a straight line, so the prototype is not yet equipped with an ultrasound sensor.

The rechargeable lithium batteries used in the prototype, Bhattacharyya says, last about 40 minutes. Since the robot can travel between half a meter and a meter per second while pressed against a surface, that should give it ample time to inspect multiple small craft before being recharged. The researchers envision that teams of the robots could be kept in rotation, some returning to port to recharge just as others are going back on duty.

Their next prototype, Bhattacharyya says, will feature wirelessly rechargeable batteries. And modifications to the propulsion system, she says, should increase the robot’s operation time on a single charge to 100 minutes.

Keep your distance

Bhattacharyya notes that while she and Asada have demonstrated the robot’s ability to travel along a smooth surface, the hulls of many ships will have encrustations that might prevent continuous contact. Ultrasound, however, works only when the emitter is in direct contact with the object to be scanned — or when its distance is a specific multiple of the wavelength of sound.

Maintaining that precise distance is a tall order, but in ongoing work, Bhattacharyya and Asada are exploring mechanical systems that would create hydrodynamic buffers of just the right depth to enable the robot to perform ultrasound scans without surface contact.

Nathan Betcher, a special-tactics officer in the U.S. Air Force, has followed Bhattacharyya and Asada’s work closely. “I have a great deal of interest in seeing if this type of technology can have a substantive impact on a number of missions or roles which I might be charged with in the future,” he says. “I am particularly interested to see if this type of technology could find use in domestic maritime operations ranging from the detection of smuggled nuclear, biological, or chemical agents to drug interdiction, discovery of stress fractures in submerged structures and hulls, or even faster processing and routing of maritime traffic.”

The MIT research was funded by the National Science Foundation.


Topics: Robotics, Autonomous Underwater Vehicles (AUV), School of Engineering, Mechanical engineering, Research

Comments

great product

Technology yet to be invented and for which there is a real need is AUV capable of operation at extreme depths. A bot which can check radiation levels at subduction zones, follow the Fukushima leak, look in on the multiple radioactive material ocean bottom dump sites. Lots of money in imagined or future threats but let's get real.

To underwater robot team,

Good day,

I. Am interested to learn more and if cost is feasible can consider hiring same.

Brgds
Capt Nitin

In order to decrease the absorptive rate of ultrasound in water, one must use a subharmonic or suboctave carrier wave. The beneficial effects of this will be increased distance of the ultrasound wave traversal. The detrimental effects will be increased penetration and cavitation induced by the ultrasound, due to the altered pressure from the suboctave carrier wave.

As an example, let us consider a 48 kilo hertz wave. This 48 kilo hertz wave will be strongly absorbed in water, and if at a sufficient amplitude, cavitate the water. In order to increase the distance of propagation, a carrier wave must be introduced along the same vector pathway. This carrier wave, in order to have constructive interference with the 48 Khz wave, must be a sub octave, or subharmonic. So, a 12 KHz wave would be sufficient to increase the distance of propagation of the 48 KHz wave, however, utilizing this will also cause an increased peak at 12KHz, so if one used a wave that caused resonation to the material, it would cause it to cavitate, warp, or other vibrational damage. However, if one used a 16 KHz wave, then varied it +-5 % of frequency, once could test and see which would be a applicable carrier wave for the current application.

I can get into more detail if you would like.

Dear Mr. Hardesty, I think this is very innovative technology. This is not academic question. Could you export this product commercially? Of course, except hostile countries. We have potential customers and sales network for this product in here.

To whom it may concern,

I'd like to ask, what is the device that is used in this robot to connect to the monitor/screen so that the server or the one that controls the robot will be able to see the contraband's? Is there a wireless connector from the robot to the monitor or a camera recorder that is directed to the monitor/screen to view/detect the ultrasound waves? I'm really curious. My another question is, Is this robot available to the market? If not yet, when do you think it would be available to the public or for the government to use? This is really a great new discovered technology. I wish you could answer all my curiosities.

What is the device that is used to connect the robot to the monitor/screen so that the server/the one who controls the robot can see the ultrasound waves? Is it wireless or there are some kind of recording device in it?

Where was it made

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