More and more torpedo-shaped robots are plying the oceans to sniff out mines, gather environmental data, and scan the ocean floor for famous wrecks. But these underwater vehicles struggle with the same problem that heavy smartphone users have: short battery life.
With a typical run time of about 24 hours, autonomous underwater vehicles, or AUVs as they are known, have so far been limited in use. If the industry can come up with a way to repower them at sea, these underwater robots could give the military powerful new tools and take on a broader range of commercial and scientific jobs.
Bluefin Robotics’s solution is much like what the auto industry is developing for electric cars: charging stations. Instead of being yanked out of the water for recharging, the robot would pull up to a refueling station on the ocean bottom.
Bluefin, on the Fore River in Quincy, has built a docking station that communicates directly with underwater vehicles, guiding them to where they can recharge and transfer data. The refueling station resembles a cage roughly 5 by 15 feet with a cone-shaped entrance. Once it’s inside, the robot is recharged wirelessly through inductive coils — the same technology used for charging electric toothbrushes. The refueling itself could rely on a bank of larger batteries if it’s a remote location, or a power cable from an external source, either on land or a surface buoy.
Any data the robot has gathered, such as images of the sea bed or boat traffic, could be uploaded to the docking station and transmitted to home base, which could wire new instructions to the robot. “Launch and recovery from a boat is a very difficult process. This way you have a garage,” said Robert Geoghegan, department manager for ocean engineering for Battelle Memorial Institute, a research organization that owns Bluefin Robotics. “So instead of doing launch and recovery every day, you can do it once a week or longer.” With a continuous supply of electricity, an AUV could work for months at a time, recharging daily, Bluefin executives said.
The Navy already has hundreds in service, usually for security-oriented missions, but has a multiyear master plan to expand the fleet. It envisions networks of AUVs gathering military intelligence, such as about enemy submarine movements, or neutralizing or arming mines. These vehicles could also be launched from submarines and pilot themselves while carrying weapons. But the Navy wants 60-day missions, rather than the day-long trips underwater robots take now. Navy officials were in Quincy last month, scoping out the new docking station.
Oil and gas companies, which have been using remote-controlled underwater vehicles for years, are looking at autonomous robots to reduce costs and danger to people from inspecting pipelines after hurricanes. A single rechargable AUV could test the structural integrity of equipment over a vast area and report back to a drilling platform. And for scientists, a longer-running AUV would be able to collect more data, such as from tracking pollutants over several weeks, and give researchers flexibility to change missions without the expense of a recovery boat.
An AUV could also be positioned at a remote docking station and be activated on demand — for example, when underwater volcanic activity near Hawaii increases, said Alan Beam of the Lee, N.H.-based Autonomous Underwater Vehicle Application Center and a former program manager for UUVs at DARPA. “People have been working on the pieces to this for a long time. The key trick is to integrate it all to make it work,” Beam said.
Woods Hole Oceanographic Institution in Falmouth has been researching underwater docking stations for more than a decade and has two projects underway. The Naval Postgraduate School will install a docking station made by Woods Hole in the coming months in the waters off Monterey, Calif. Like Bluefin Robotics’ machine, the Woods Hole device has a funnel-shaped “entrance nozzle” to guide entering vehicles. The metal frame that holds AUVs in place is mounted on sleds anchored by lead weights. The station will use an undersea cable for power and transferring data, allowing Naval researchers to keep the vehicles in the water for long stretches.
“When you attach a subsea cable and run power through it, it means you can power and point the vehicle [out] for multiple missions. You have it recharge without bringing it back in, so you greatly minimize the expenses for ship operations,” said Ben Allen, a senior engineer at Woods Hole Oceanographic Institution. “Within the research community, there’s a lot of interest.”
Woods Hole is also involved in a major scientific expedition, the National Science Foundation’s Ocean Observatories Initiative, that will deploy docking stations at sea. The Pioneer Array on the edge of the Continental Shelf south of Martha’s Vineyard will use a combination of surface moorings and unmanned vehicles to collect environmental data and high-resolution images.
Three AUVs, supplied by Hydroid LLC in Pocasset, will take measurements in concert with six self-propelled underwater gliders in 500 feet of water over 2,500 square miles. Having the docking stations will allow researchers to collect data over long periods of time and, using a two-way satellite link, send instructions to the AUVs to modify their sampling plans.
The surface moorings will also provide energy to the docking stations using a combination of solar panels, wind turbines, and fuel cells.
In some applications, refueling stations can help keep up with the considerable power demands for transmitting data. The underwater engineering company Phoenix International used a Bluefin Robotics vehicle in the search this year for the downed plane of missing aviatrix Amelia Earhart in the South Pacific.
A 20-hour mission can generate a terabyte of data of high-resolution images, sonar, and video, said Christopher Moore, AUV manager at Largo, Md.-based Phoenix International, creating bottlenecks in transmission and a drain on power. “The limitations of these machines is power,” he said. “You need power to move a lot of data in an efficient amount of time, recharge the batteries, and accept a new mission.”
For its docking station, Bluefin Robotics last fall ran an eight-hour demonstration in which an AUV was launched outside of Boston Harbor, rose to the surface to get its position using GPS, and then docked at the refueling station, which was erected on a scaffold about three meters off the bottom.
One challenge was getting the AUV to enter the snug interior of the docking station on its own. To make the demonstration work, engineers needed to fine-tune the homing capabilities to ensure the robot approached the intake cone at the right angle and made a reliable connection inside, said Steve Somlyody, a senior systems engineer at Bluefin.
The system communicates via acoustic waves, which can be easily disrupted by other objects in the water, he said. Bluefin Robotics and Battelle said they will target the refueling station at applications that demand longer missions, such as where a network of AUVs monitor one area continuously.
The docking stations are coming along at an opportune moment for the young industry. Many operators had kept their robots on a tight leash, out of fear of losing one, said Duane Fotheringham, vice president of operations at Hydroid.
“The interest in docking stations is to move the autonomy one step further and remove the men from the loop and take advantage of the robotics as much as possible,” Fotheringham said. “It’s an evolution of the technology as people become more and more comfortable with underwater robotics.”