Monday, July 27, 2009

Robots Take Wing

In many ways, autonomous robots are like toddlers. They need to learn their limits. They must also discover how to play nice with others. And, like toddlers, they often fall down trying.
Nowhere was this more on evident than the Hanover Fair display of German automation specialist, Festo AG & Co. One side of the company's long space was crammed with pneumatic and electrical actuators and control systems similar to those in the booths around it. The other side contained the toys. These included a wall of lightweight pylons that interacted by moving as people walked by and a huge aquarium containing three mechanical penguins that interacted with one another as they swam.
Festo has a history of producing audacious autonomous robots for Hanover Fair, and these displays were no exception. Yet the company's most impressive display was taking place above the heads of the onlookers, where three flying penguins interacted with one another in tight airspace above Festo's booth.
Penguins, of course, cannot fly. Festo's AirPenguins, however, are balloons with bodies made of carbon fiber rod and extruded polyurethane foam under metalized foil. Each one measures 3.7 meters long and 0.9 meter deep with a 2.5-meter wingspan. Each flying penguin carries a complete control system, battery pack, an assortment of sensors, and servos to power the wings, nose, and tail. The entire ensemble weighs one kilogram.
Providing consistent yet autonomous behaviors to Festo's AirPenguin proved a major challenge for Kristof Jebens and Agalya Nagarathinam, an engineering team based in Gärtringen, Germany.
To enable the AirPenguins to interact with one another in their confined airspace—just 3.5 meters above the area of the Festo booth—Jebens first had to synchronize their wing movements through use of a wireless timing signal. "Without synchronization, if they came close, the turbulence would suck them in and they would crash," Jebens said. By eliminating a turbulence sensor, Jebens and Nagarathinam could concentrate on what was really important: avoiding the AirPenguin's most feared predator—the building's air conditioning system.
Festo had been down this road before. One year at Hanover Fair, the company featured manta ray-like balloons with wings that moved up and down. The large, flat surfaces made a perfect target for a downdraft. When the balloons flew under an air conditioning vent, any downdraft would push them into the booth.
The AirPenguins are far more versatile. Their wings not only move up and down, but also pivot to propel them forward like a swimmer doing the breaststroke. Their nose and tail bend also, allowing them to lean into turns like a real penguin in the water for faster response.
To take advantage of this mechanical flexibility, Jebens and Nagarathinam designed the AirPenguins to carry an array of sensors. For instance, a receiver enables the balloons to triangulate their position in space by listening to three ultrasonic stations located around the Festo booth. They are also equipped with a compass and three-axis accelerometer, which tell the AirPenguin if it is level or tilted, and allow the robot to calculate yaw for more-precise quick turns.
The AirPenguins also contain an air pressure sensor sensitive enough to calculate altitude to within 10 centimeters. When Jebens and Nagarathinam tested the system in Festo's high-roofed corporate lounge, that sensor worked fine. At Hanover Fair, where Festo's booth is always crowded, updrafts from the body heat of visitors and drafts from open doors made it harder for the AirPenguins to use pressure data to determine their height. The AirPenguins, however, could deduce their height from the ultrasonic beacons around the booth.
The ultrasonic receiver and pressure sensors alert the AirPenguin when a draft of cold air from the air conditioner is pushing it down. The robot might try to fly around the flow of cold air or dive into it to increase its speed and then turn sharply away.
Sometimes it works. Other times, the AirPenguins crash. When the balloons are flying, Festo technicians hold backup controls in case anything goes wrong. In the end, while Festo's AirPenguins show complex behaviors, they also have a lot of conventional automation safeguards built in as well. "
You have to do that if you want to have a nice show," Jebens said. "Sometimes, if you try to make them more adaptive, it doesn't work as well. For the software to adapt, you need lots of cycles. We don't want it to start learning while all the visitors are coming to the booth."
In other words, clean the toddlers up before company comes and hope that in a few years, they will have learned how to behave and play nice with others on their own.

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