Duke Robot Climbs to Victory in Madrid

January 1, 2004

From left to right: Andrew Meyerson, Brian Burney, Kevin Parker, and Julien Finlay. Parker holds "Wallter" the wall-climbing robot during the robotics conference in Madrid.

A wall-climbing, book-sized autonomous vehicle made by a Duke University team drove up a challenging vertical course to win first prize in an international competition Sept. 22-24 in Madrid.

The student competition was part of the seventh annual International Conference on Climbing and Walking Robots.

Jason Janet, an adjunct professor in Duke’s electrical and computer engineering department and faculty adviser on the robotics project, said the Madrid competition shows the growing importance of climbing robots.

"Robots that climb walls and cross ceilings can go where humans can’t," Janet said. "They can do security and safety jobs like looking for bombs or finding cracks in a support beam or the wing of a jumbo jet."

The Duke team’s leader was Brian Burney, a staff member at Duke’s Pratt School of Engineering and graduate student at North Carolina State University. The other team members were Pratt School undergraduates Kevin Parker, Andrew Meyerson and Julien Finlay.

"Our robot Wallter was the only one that could start flat on the floor and climb the wall on its own, go over a barrier across the wall or stop itself after crossing the finish line," Burney said.

"As the smallest, fastest and most novel robot, Wallter was one of the most popular exhibits," Meyerson said. "I was interviewed for Spanish national television for a story about the conference featuring the Duke robot."

According to Burney, the Duke vehicle set itself apart when it rolled to the foot of a metallic wall, reared up on its hind wheels, and used a "tornado in a cup" to hug the wall and start its ascent.

The "tornado" is generated by a patented device from Vortex HC, LLC of Morrisville, N.C., said Janet, who is vice president of development at the company. The device uses air currents swirling in a cylinder, about the size of an upside-down tuna can, to exert suction on a wall or ceiling. An impeller in the cylinder spins like a propeller but recirculates captive air rather than sucking air in one end and blasting it out the other.

"It’s a tornado in a cup, but no ordinary tornado," Janet said. "Two vortexes swirl simultaneously, one in a spiral and the other in a toroidal path, like a donut. The forces generated hold the vehicle to the wall and yet allow free movement because the cup never touches the surface."

Parker said the Madrid competition required performing five tasks: starting on the metal competition wall and climbing as high as possible; climbing after the addition of randomly placed obstacles; crossing a barrier placed on the wall; starting from the floor and then climbing; and stopping after crossing the finish line.

"We faced stiff competition from German and Italian teams," Parker said. "The robot from the University of Catania was amazingly good at detecting and avoiding all the obstacles. Our robot brushed against a couple of obstacles, but it was the only one that completed all five tasks."

Janet said the Duke team combined the "tornado in a cup" technology with an original control system. "A human operates Vortex’s commercial robots by remote control," Janet said. "The students added sensors and wrote software that enables their robot to operate on its own."

Parker said they added ultrasonic and infrared sensors across the front and programmed a tiny computer, called a microcontroller, to navigate based on information from the sensors. Ultrasonic sensors detect objects by bouncing sonar-like sound waves off them. Infrared sensors, used in television remote controls, detect light outside the range of human vision.

Burney provided an initial basic design for the Duke vehicle, Janet said. Meyerson and Parker, both biomedical engineering students, focused on writing software and incorporating the sensors.

When tests showed the centimeter-high barrier broke the hold of the Vortex technology, Janet called in Finlay to solve the problem of crossing the barrier without falling off the wall. Finlay is a mechanical engineering student and a veteran of the team that produced Duke’s prize-winning autonomous underwater vehicle Charybdis.

Finlay said he tried to design a solution that would work with or without the metal wall at the competition.

"We tried adding treads," Finlay said. "We tried a wheelie bar to keep the rear end of the robot flat against the wall and prevent the front from lifting up. Unfortunately, the results were disappointing. Time was running out so we had to add magnets and take advantage of the metal."

According to Finlay, the magnets were successfully tested only one day before the team flew to Spain.

In Madrid, Meyerson and Parker had to adapt the robot's software for the competition wall. "The traction was different from what we were used to," Meyerson said.

With software tuned and magnets added, Wallter crossed the centimeter barrier without difficulty in practice runs. However, in the first competition runs, Wallter slipped down the wall when attempting to cross.

"There were 15 minutes of pure terror and panic," Parker said. "We didn’t know what was wrong."

Burney said, "We finally realized we had the brackets for the magnets on wrong. The magnets were upside down, and the magnetism was too weak that way."

With the magnets positioned correctly, Wallter negotiated the barrier, reached the top of the wall, and won the first prize of about $250.

The team members were exhausted by the end of the competition, mostly because they kept Spanish hours, said Meyerson. "Restaurants don't open for dinner until 9 and a meal takes hours," Meyerson said. "Everyone stays out until 4 a.m. and that's without even trying to go clubbing."

Janet said Duke’s robotics efforts include teaming with a group from Carnegie Mellon University for the DARPA (Defense Advanced Research Projects Agency) Grand Challenge to design a full-sized autonomous land vehicle and continuing the development of autonomous underwater vehicles.

In addition, computer science professor Ronald Parr and graduate student Austin Eliazar are developing software that enables a mobile robot to map its surroundings as it moves and simultaneously locates itself on the map. Such "simultaneous localization and mapping" is a longstanding challenge in robotics research.

The Duke wall-climbing robot was funded by a grant from the Lord Foundation. Janet said the Vortex technology was developed by Vortex HC on a grant from the DARPA Microsystems Technology Office.