"Our ideal batteries would cost similar to lead acid, charge as quickly as ultracapacitors and last as long as possible," he said.
Shooting for the moon -- or a better vacuum
Such ideal batteries are a long way off, but that hasn't stopped researchers today from pushing the limits of battery storage. The U.S. military is interested in autonomous robots that can operate for 10 hours on batteries, and NASA's space missions would hugely benefit from longer-lasting batteries, said Allen Sirota, the supervisor of the robotic hardware group at NASA's Jet Propulsion Lab.
The lab developed the robotic rovers, named Spirit and Opportunity, that are currently roaming around the surface of Mars -- years past when NASA expected them to fail. While rigged with solar panels, the rovers remain dependent on batteries, as the meager solar energy they receive needs to be gathered for energy-intensive operations.
"It's kind of like making deposits in the battery bank," Sirota said.
His team is also developing a large, six-legged robot to be used on the moon, if NASA does indeed return there. The energy demands of legged robots is especially high compared with their wheeled peers. But while wheels are efficient in their energy use, they are limited to hard, smooth surfaces like roads. When obstacles come into play -- say, a field of mines or the craggy lunar surface -- then "legs are really king," Hong added.
The current breed of mobile robots is limited also in their strength. The Roomba is a perfect example of this, Christensen said. Its actual vacuum is underpowered compared with plugged-in robots, simply because it cannot spare the charge. Improved batteries will bring truly mobile vacuums and lawnmowers, able to do substantial work for extended periods.
Power problems become even more severe as robots scale down in size. As Mel Siegel, a roboticist at Carnegie Mellon points out, even the Energizer Bunny runs for only three or four minutes before its batteries give out (according to the creator of the animatronic). At microscopic levels batteries, no matter how good, won't be the solution. Energy will instead have to be extracted from the environment, he said, the way microbes do.
In the coming years, people are most likely to begin directly interacting with mobile, autonomous robots in more familiar settings, like the hospital and road. Health care in particular is pushing the industry forward with robot-assisted surgery, which is used in delicate operations on the heart, brain and prostate, for example. In the United States, some 200,000 robot-assisted surgeries were conducted last year, Christensen said.
While many of these medical robots served as extensions of surgeons, robots are now being developed that can conduct surgery on their own and learn from previous operations. Trials on a system that will use a robot to decide the best route for an operation are set to begin next year in Europe, according to a recent report from the U.K.'s Royal Society of Engineering.
And in the home, mobile robotics systems that monitor the elderly and infirm are being developed that will learn from their subjects' typical habits to flag odd behavior such as too much time spent in the bathroom, or not enough eating. Much research is being conducted on designing systems that convey emotions, and already in Japan robots serve as babysitters in shopping centers.
People talk to their cats, and soon, they will be talking to their robots, said Chris Elliott, a contributor to the Royal Society report.
As a society, we have done very little work in conceiving the ethical, moral and legal implications of autonomous robots, Elliott said. In the case of a robotic surgeon that has learned from its previous 50 operations, "What happens in the 51st case when it kills someone?" he said. Can a business be held liable for a machine that learns? And what if the success rate remains higher for the robot than human surgeon? Will we allow robots to make mistakes?