Mechanical Advantage

Two Northwestern University engineers are developing cobots -- machines that, unlike robots, cooperate with workers without displacing them

Michael Peshkin, left, and Edward Colgate, who teach mechanical engineering at Northwestern University, work in their laboratory on machines to make it easier and safer for assembly line workers to install parts of cars.

(Tribune Photo by Charles Osgood)

By Jon Van
TRIBUNE STAFF WRITER
Web-posted: Wednesday, December 11, 1996

aneuvering 22 pounds of heating and cooling apparatus into the opening of a dashboard while scrunched inside a truck cab as it moves down an assembly line is a great way to wrench your back, researchers have found.

The two Northwestern University faculty members who made this discovery did not do so by taking surveys or analyzing medical reports, but by actually working on the factory floor of General Motors Corp.'s pickup truck assembly plant in Ft. Wayne, Ind.

"It got very tiring very quickly,'' said Michael Peshkin, associate professor at Northwestern's Robert R. McCormick School of Engineering and Applied Sciences.

While Peshkin and his colleague, Edward Colgate, also a Northwestern associate professor of mechanical engineering, didn't become proficient at building trucks during their stint in the plant, they learned enough about the problems workers face to design some new equipment intended to help.

Perhaps even more important, the experience enabled the two to develop a new concept in robotics: the "cobot," a machine designed not to replace a worker and take his job, but to help him do the job more efficiently and with reduced risk of injury.

The collaboration between Northwestern and GM is an unusual one. Instead of inventing something in their university lab and then offering it to private industry, Colgate and Peshkin started by asking people at GM what kinds of problems they would like addressed.

"This project is very different from the usual mode,'' said Prasad Akella, GM lead engineer and co-principal investigator with Colgate and Peshkin. ``Instead of taking a new technology and looking for problems it might solve, we've flipped that whole thing. We at GM have been focusing and distilling our problems to the core issues. Then with the help of our friends at Northwestern we look for technology that might help."

The collaboration has yielded a new type of hoist that lifts a pickup's heating and air-conditioning unit so that it may be guided into place by the assembly worker. Older versions of such hoists are commonly used and also commonly disliked by workers, said Peshkin.

"Workers don't want something that forces them to do their job the same way every time,'' he said. ``They have to install these units once every 57 seconds on average. But sometimes they like to do it faster, to move up the line to get started early and get ahead so they can have a little break."

In designing the new hoist, the Northwestern researchers called upon experience from robotics engineering, which has devised many tricks to minimize the effects of errors that inevitably occur in automated systems. One example of this approach is revealed in the way the new hoist is built to move up and down.

Most hoists come equipped with motorized pulleys that enable workers to raise or lower the unit as needed using a hand-held controller, but the one designed by Colgate and Peshkin works differently.

"Pulleys are great for raising something a foot or so, but they're terrible for going up a fraction of an inch,'' said Colgate. ``We put garage door springs on our hoist so the worker can nudge the unit up or down a little to make the fit."

A prototype of the assist device was tested first by GM workers who visited Northwestern's Evanston lab and then on the assembly line in Fort Wayne. The design is now being built into full-fledged assist devices that will be installed in GM factories.

While this device apparently will be a welcome help to GM workers, it really was only a practice run for full-fledged cobots that the researchers are now working to develop.

The cobot will be a computer-controlled device able to hold a heavy, bulky component such as a control panel or a door that must be loaded into a tight space, often at an odd angle, for assembly. The cobot, which is mounted on coaster wheels, will have no power itself but will depend upon the worker to push it.

While the worker will have complete freedom to move the cobot around most of the time, as he approaches the truck chassis, the computer will direct the coaster wheels as if they were on tracks so that the unit can slide into place only the right way, no matter how the worker applies force needed to push it.

"We're looking for a way to reduce the ergonomic strain on the worker,'' said Colgate. ``Originally, we were looking at a system where the robot would have powerful motors and brakes. But after working ourselves on the factory floor, we realized that such a thing would be too dangerous. You couldn't have workers in close body contact with such equipment."

The cobot concept not only reduces dangers, it also eliminates costs inherent in powering a robot with a series of motors.

GM executives who have visited the Northwestern campus for a demonstration of primitive cobot technology have come away enthusiastic.

"I think my management wants cobots tomorrow,'' said Akella. ``The demand is there."

Cobots won't be delivered that soon because they are still being developed. But because GM is part of the development process, it can incorporate the cobot concept into its design of future assembly lines, Akella said.

Peshkin and Colgate said that working so closely with one company on a particular problem hasn't damaged their academic status at all. In fact, the concept of cobots they've developed has been embraced as an exciting new area for basic research in robotics.

At an international meeting of robotics researchers last spring, a report on cobots presented by the Northwestern engineers was honored as the best paper of the meeting.