Discover Magazine Awards for Technological Innovation, 1997


Northwestern University's Cobots


Auto-assembly workers must often install heavy, unwieldy parts smoothly and precisely, and it's never been an easy task. Conventional robots aren't much help -- they're lousy teamworkers and dangerous for humans to work alongside. So when Northwestern University mechanical engineers J. Edward Colgate and Michael Peshkin were asked by officials at General Motors to devise a better assembly tool, they quickly focused on the issue of guidance. And the solution they came up with was virtual walls. A conventional robot would hold the bulky part, but the robot would be programmed to keep the part within a certain area contained by invisible walls. A worker putting in a door, seat, or windshield would use the virtual walls as invisible guide rails to maneuver the part into the correct spot, in the same way that a ruler helps you draw a straighter line.

Colgate and Peshkin quickly ran into a couple of problems. "Robots aren't good at making the walls feel smooth," Colgate says. "There is a jerkiness or bumpiness to a robot's motion." More important, they still felt uneasy about allowing powerful motor-and-gear-driven robots to hoist heavy parts close to human workers. After pondering their dilemma, Colgate and Peshkin came up with a rather unconventional robot, designed specifically to work side by side with humans.

Their "cobots," for collaborative robots, have no strong motors or gears and won't move unless pushed. Their only moving parts, in fact, are the wheels (the same ones used on Rollerblades), and the motors that steer the wheels along the virtual walls. Inside the walls created by the cobot's computer, those wheels move smoothly and freely, like the casters of an office chair. At the wall boundary, however, the computer takes over, turning the wheels parallel to the wall and allowing movement only along the periphery.

The Northwestern team has developed a variety of cobots, including a simple one-wheeled machine, first displayed publicly at a robotics conference in April 1996. Since then the engineers have built three-wheeled cobots to help GM assembly-line workers install automobile doors. These cobots, fitted with gripper arms to hold the doors, will be tested this fall.