The little robot's big round eyes glow a happy green, and its antennae lean forward. "Hello, I'm Quasi!" it chirps to a small crowd at an exhibition held this past fall at Carnegie Mellon University, in Pittsburgh. "What's your name?"
"I'm Chelsea," calls out a young woman. Quasi swivels its head to face her and leans back slightly, as if to get a better view. "He's so cute!" Chelsea whispers to her friend, who also seems enchanted with the 76-centimeter-tall bot.
"Hi, Chelsea!" Quasi exclaims, giggling a little as its eyes flash purple-pink for a second. "Do you want to see my Halloween costume?" Chelsea says yes.
"Okay! Watch this!" The little robot's body suddenly goes rigid, its eyes glowing red. "Luke, I am your father," the voice of Darth Vader proclaims.
The onlookers, mostly science journalists, laugh nervously. Then the animated machine seems to relax, and its eyes revert to their friendly green hue. It resumes working the crowd, waving its knobby arms, cocking its head, swiveling its antennae like the ears of a dog.
While most robots are designed to serve a single dull, utilitarian function, Quasi's reason for being is charm. The machine's creators, all graduate students at Carnegie Mellon's Entertainment Technology Center, wanted to build a captivating character that would go well beyond the standard animatronic amusement park figures that spew out canned patter to bored preschoolers. They wanted to build a robot that would make people forget it's a robot.
To do that, they programmed Quasi to mimic the slightly snarky, moody personality of a 12-year-old boy. Quasi's five "moods" [see photos, " Mood Indigo"] are conveyed most obviously by the color of its light-emitting-diode eyes and antennae: green for happy, blue for sad, red for angry, yellow for confused, and purple-pink for embarrassed. Quasi's got lots of expressive moves, too: the bot hunches its shoulders, gesticulates with its hands, shifts its weight, and looks you straight in the eye.
All this is done so convincingly that you probably wouldn't even notice that Quasi's feet are bolted to a fixed base that houses 32 industrial off-the-shelf servos--2 for each antenna, 4 for each eye, and 24 for limbs and posture--that control the little robot's every move. Additional hardware, including microphone preamplifiers, a mixer, a sound processor, wireless audio receivers and transmitters, and four custom PCs that serve as Quasi's "brains," is stored in a separate case.
Originally designed as an attraction for the hallway of the Entertainment Technology Center, Quasi lured visitors with offers of candy and then would chat for a minute or two. A motion detector and infrared sensors mounted alongside its body notified Quasi when a person was approaching, and a video camera and face-tracking software helped the robot identify when the person was within greeting distance.
Quasi's "moods" are controlled by a finite-state machine, a software-based behavioral model that triggers certain actions when specific conditions are met. If, for example, a passerby ignores Quasi, the robot's mood shifts to a sadder state: its eyes and antennae turn blue, its head hangs down, and it becomes stingy with its offers of candy.
Each mood, in turn, has a range of intensities. So if Quasi plays a game of tic-tac-toe with a visitor and the visitor keeps winning, the robot's state shifts to anger: the antennae lie back, the eyes glow red. Continued losses will trigger additional anger states and finally an ignore state, in which Quasi refuses to play or even acknowledge the visitor. But, as with most 12-year-old boys, the mood doesn't last long: after a few minutes, the state reverts to a less angry one, and Quasi begins interacting again.
Last year, Quasi's designers created a second operating mode for the robot, as a puppet controlled by a human operator. The operator guides Quasi using a wireless tablet PC interface; the tablet controls three digital multiplex boards of the sort used in theatrical lighting, which in turn control the servos and the colored LEDs. Puppet Quasi has all the same "moods" and gestures as autonomous Quasi, plus a conversational repertoire as wide as that of the operator who's doing the talking.
The bot's big break came last summer, when it was selected to appear in the Emerging Technologies Conference of SIGGRAPH 2005, in Los Angeles, probably the world's most prestigious gathering for computer graphics and interactive technology. Quasi caused a sensation with its clever antics and impersonations of Star Wars droid C-3PO and other famous robots. The robot's creators have since started their own company, Interbots, in Pittsburgh, to develop other interactive characters. The company is now tackling its biggest gig to date: building an animatronic character for PNC Park, where the Pittsburgh Pirates play baseball.
About the Author
Kim Krieger is a science writer based in Washington, D.C.