June 12, 2006 — A novel, walling-climbing robot could cut thousands of dollars off building inspection fees and one day work to survey urban war zones, where corners, rooftops and building materials thwart otherwise capable robots.
The City Climber rover, being developed by Jizhong Xiao and his team at the City College of New York, uses a vacuum chamber to get vertical. The robot is part of a project that aims to automate mandatory building inspections.
"New York City mandates that the facades of buildings be inspected every five years," said Xiao. "But the current manual inspection is time-consuming and the cost is very high — about $5,000 for one day."
Xiao thinks his robot, which costs less than one day’s work, can do the job faster, cheaper, and more thoroughly than trained technicians, who typically perform their gravity-defying work from suspended scaffolding.
Robotic wall climbers typically employ more superhero-like methods: sticky feet, suction cups, claws, or magnets. But those grippers are only as good as the surface they make contact with.
Suction cups or sticky feet, for example, work best on smooth surfaces such as glass or marble, but not so well on brick. Clawed toes clamber well over rock and brick but slip on glass.
What’s more, such devices tend to move tentatively and cannot navigate over a variety of textured surfaces.
Getting a robot to both cling to a wall and maneuver effortlessly over it are among the two biggest challenges that face researchers focused on wall-climbing robots, said Ning Xi, director of the Laboratory of Robotics and Automation at Michigan State University.
"In both aspects, the City Climber is probably the best in the world right now," said Xi, who is not associated with the project.
The 1-kilogram device clings to the wall by way of a vacuum rotor located in the center of its underbelly. The rotor’s impeller draws air in from the center of the device and spews it out toward the edges.
The column of circulating air creates a region of low air pressure inside the vacuum chamber. Because the surrounding air pressure is higher, it pushes down on the device, keeping it tight to the wall.
Small wheels on the underbelly of the device drive the robot forward and back.
By linking two triangular-shaped modules with a hinged arm, the researchers were able to make the City Climber maneuver around 90-degree angle corners and transition from a wall to a roof — all with the strength to pull or carry a payload four times its weight.
"They have achieved one of the highest payloads reported in the literature," said
professor Nikos Papanikolopoulos of the University of Minnesota.
Xiao will be capitalizing on his rover’s payload capabilities this summer by equipping it with a high-resolution digital camera to conduct a mock building inspection.
