They have names as endearing as "Sparky" and as confounding as the "Double-Taker (Snout)."
Some are snakelike, designed to look for survivors beneath collapsed buildings. Others are built to haul construction material in space, deliver snacks around the office or play soccer.
Over the years, people at Carnegie Mellon University have done just about everything imaginable with their robots.
Everything, that is, but count them.
Enter Heather Knight, a first-year doctoral student in robotics from Boston who arrived this fall from the Massachusetts Institute of Technology.
More than a little zealous on the subject, she wasn't satisfied to simply guess how many robots might be taking up floor space in campus labs, resting atop classroom shelves or residing in file cabinet drawers.
Instead, she resolved to count every last one, embarking on the university's first-ever Robot Census.
She's at 547 robots after several weeks of counting.
Dozens of faculty and students have filled out a two-page census form asking them to specify their robot's type, building location and address, degree of intelligence and freedom, primary language, and whether it has wireless Internet connectivity.
Next to a question about their robot's job status, census participants are asked to check one of four options: "working," "learning," "retired" or "under construction."
At CMU, robots seem to be everywhere -- in theater productions, art studios and research labs.
Some are humanoid and semi-humanoid. Others look like toy trucks, construction cranes or dogs.
Ms. Knight's research interests lie in human-robot interaction. She said she does not want to impose on census participants a rigid definition of what constitutes a robot.
"That's one of the exciting things about this," she said. "I leave it 100 percent up to them."
That said, there are some obvious prerequisites that include, she said, "some sort of actuation or ability to affect the world, some sort of sensor and ability to perceive the world and some internal computation capability."
If she manages to get a complete campuswide count, CMU will be able to tell the world with authority not only that its undergraduate-to-faculty ratio is 11.5-to-1, or that 59 percent of those undergraduates are male, but also this -- the ratio of robots to humans on campus.
That statistic might well become a point of pride at a place that went so far as to establish a Robot Hall of Fame and once spawned a Human-Robot Interaction Reading Group, a weekly gathering for those interested in sharing relevant research.
The campus is home to the Carnegie Mellon Robotics Institute, founded in 1979 and considered to be among the world's biggest centers for robotics research and education.
The institute's director, Matt Mason, said it's odd that the campus has never gotten a grip on its robot population. Then again, he said, faculty have wide autonomy to conduct their research, so it's not easy to know every robot being developed.
"Some of us are working on robots for education; some of us are working on robots for mines or agriculture," he said. "We get some of our funding from the Defense Department, so there are robots for reconnaissance, surveillance and all kinds of defense applications."
He said one of the most mind-bending projects he saw upon taking the job was work on a machine that watches lab mice and takes detailed recordings of their behavior, so humans can be liberated from that work.
Some robots tallied so far in the census are from Howie Choset, an associate professor of robotics, who counts among his research efforts "Modsnakes" or modular snakes, slender locomotive devices 2 or 3 feet long made of aluminum and rubber, enabling them to crawl through collapsed buildings or inside pipes.
He said he saw nothing unusual about a robot census, then qualified those words: "I come to work every day and walk by a robot receptionist, so that tells you what my sense of normal would be."
He was referring to "Tank," a talking "roboceptionist" that greets visitors to Newell Simon Hall.
Its cartoonlike face on a flat-screen monitor has eyes that move left and right, and it can answer questions typed into a keyboard.
Where's the elevator, Tank? "Go past my desk and turn right," comes the reply.
How's your father? "It's painful. We don't speak much anymore."
Another robot in the census, "Snackbot," may not be chatty about family matters but nonetheless should be popular doing what it's designed to do: Traverse hallways, delivering food to office workers.
There's more than hunger behind the project, a collaboration between the Robotics Institute and CMU's Human-Computer Interaction Institute. It enables researchers to explore social interaction and how robots respond to people.
Some are interactive art installations.
One example, "Double-taker (Snout)," is an 8-foot-long industrial robot arm. Its creators say it was built to look like a gigantic inchworm or an elephant's trunk and has an oversized eye at one end. Its design allows it to swing in response to human movements, creating an impression it is doing "double takes" at passers-by who approach.
It was installed in 2008 above an entrance to the Pittsburgh Center for the Arts.
Those on campus say the robots in Ms. Knight's census are a mix of originals developed at Carnegie Mellon, duplicates and others purchased to help with research and teaching.
Ms. Knight said she plans to buy her own robot and would like to see her campus count eventually blossom into a nationwide tally of robots.
Along with providing a head count, the census should yield insight into the varied types of research and what the school's "robot culture" is.
In her view, robots are anything but bit players at the university.
"As much as we're here for the professors," she said in remarks posted on the university's website. "We're also here for the robots."
Bill Schackner: firstname.lastname@example.org or 412-263-1977.