(Press release, November 1996)
EVANSTON, Ill. --- Popular imagination has long delighted in the specter of robots gone awry. As real robots have invaded America's factories injuries have been few, but if robots have turned out to be good neighbors, much of the credit goes to the fences that keep people safely out of reach.
Soon, robots and humans may truly work hand-in-hand. Researchers at Northwestern University have invented a new kind of collaborative robot, or "cobot." Cobots don't have the powerful motors that drive conventional robots, and that make robots dangerous.
"Cobots can work safely with people, and yet you'll never see them replacing people, because cobots simply can't move on their own at all" says inventor J. Edward Colgate, associate professor of mechanical engineering at Northwestern's Robert R. McCormick School of Engineering and Applied Science.
Colgate described a prototype cobot on Thursday, Nov. 21, at the International Mechanical Engineering Congress and Exposition in Atlanta.
Cobots are being developed under a grant from the General Motors Foundation in response to a need in automobile assembly. Assembly workers must maneuver and attach bulky components such as seats, windshields, and doors, without damaging the auto body. Conventional hoists can reduce the burden of weight, but they add bulk that makes the process slower, and collisions more likely.
Colgate and co-inventor Michael Peshkin, also an associate professor of mechanical engineering, foresee a cobot and a person working together to install an auto component. The cobot offers support against gravity, but its main purpose is to provide guidance. The human worker supplies all the force necessary to move the component, while taking advantage of the cobot's guidance to push it along quickly and easily without fear of collisions.
The researchers are working with General Motors on a cobot for installation of complete instrument panels, which barely fit through the door opening of a truck cab. The cobot will provide what the researchers call "virtual surfaces" guarding the door frame and interior surfaces of the cab. These surfaces are defined and controlled by the computer that operates the cobot.
Virtual surfaces are invisible, but their presence cannot fail to be noticed. "The virtual surfaces extend out of the cab door like an invisible funnel" says Peshkin. "Workers can maneuver the instrument panel down the middle of the funnel if they wish, but more likely they will prefer to push it up against a virtual surface and just slide it along into the cab."
The virtual surfaces must be strong enough to deflect and redirect the motion of an auto part pushed by a human worker. Cobots do not use motors for this purpose, which would require motors of at least human strength. Instead, cobots use free-rolling wheels. The inventors have found rollerblade wheels to be ideal.
"A few rollerblade wheels, appropriately oriented, can change the direction of motion of a 200 pound skater in a fraction of a second" says Colgate. "That's exactly what a cobot does -- it redirects motion by steering."
The Northwestern team has built a three-wheeled cobot, nicknamed Scooter. Scooter is a low, sturdy triangle with a rollerblade wheel at each corner, each wheel remaining firmly in contact with the ground. The wheels are independently steered, under control of a computer.
True to the passive nature of cobots, Scooter can't move on its own. "You can push it around whatever direction you want until you hit a virtual surface" says graduate student Witaya Wannasuphoprasit, who built Scooter. As the cobot approaches a virtual surface, the control computer steers Scooter's wheels so that only motion parallel to the virtual surface is possible.
"It feels like you've run into a wall" says Peshkin. "It's an invisible wall, and a slippery one. Suddenly you and the cobot are just going in a new direction, yet nothing is physically there."
The future may hold cobots of other shapes. Scooter is able to move about in what is known as a planar workspace, such as a factory floor. The researchers are also designing an arm-like cobot, the shape that many robots have. It could be used in computer-assisted surgery. Like automobile assembly, computer-assisted surgery requires cooperation between a human and a machine.
The researchers note that often the benefit of conventional robots is not their strength or autonomy, but rather the fact that they are directed by computers. "You can think of a cobot as a physical interface for a person to collaborate with a computer" says Colgate.
More information about the Laboratory for Intelligent Mechanical Systems is available at http://lims.mech.nwu.edu
Professor Michael Peshkin may be reached at 847 491 4630
Professor J. Edward Colgate may be reached at 847 491 4264
Comments from General Motors:
"The human operator, with his/her ability to see, feel and react, is a critical contributor to the successful operation of our assembly operations. Whenever possible, we provide our line workers with assist devices for moving large components around. We are also very interested in adapting recent technological advances to develop newer intelligent assist devices. GM is therefore working with Northwestern University to develop a new generation of assist devices.
We are excited by the possibilities that these technologies present," says GM lead engineer and co-principal investigator, Dr. Prasad Akella. "It is important to ensure the operator's safety while creating these new devices. Cobots, inherently, ensure this while facilitating the performance of the operator's task." says Akella. "The fact that they afford the operator greater freedom in performing his/her task while requiring less effort concentrating on moving the modules around helps ensure the quality of our products. We will be testing these devices in our labs and on the plant floor as we continue to develop them."
(Dr. Prasad Akella may be reached at 810-602-8252.)