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A backhoe.

Backhoes equipped with the most advanced fluid-power technology could improve efficiency by 30 percent. Backhoes are just one type of machinery that could benefit from research at a new University-led center to study fluid power.

New fluid power center has faculty pumped

Fluid-powered hybrid vehicles and machines could save even more energy than electric hybrids

By Deane Morrison

May 26, 2006

As the population ages, there will be a huge market for personal service robots to help the elderly and infirm. Unfortunately, even today's state-of-the-art robots run out of juice after only about 20 minutes. But an extra jolt of energy from a compact, efficient source of fluid power could ameliorate that shortcoming and allow this technology to blossom. That scenario is just one vision that came a step closer to reality when the University, along with several other institutions, received a five-year, $15 million grant from the National Science Foundation (NSF) for a center devoted to reviving and rejuvenating the science and technology of fluid power. Besides robots, optimal use of fluid power could allow all sorts of vehicles and power machinery, from dentists' drills to jaws of life to backhoes, to cut their energy consumption between 10 and 30 percent, says Kim Stelson, a University mechanical engineering professor and director of the new Engineering Research Center for Compact and Efficient Fluid Power. The center will be based in 1701 University Avenue, on the Twin Cities campus.The University got the nod for lead institution because its faculty did the heavy lifting in organizing the long list of participants and making the case to NSF that investment in fluid power could pay big dividends. Besides the NSF grant, industry partners have chipped in $3 million, which the seven universities involved in the center have matched, bringing the total endowment to $21 million. "Back in the 1950s and 1960s, the United States led the world in fluid-power research, but now Europe and Asia have passed us by," says Stelson. "We hope that this new center will get us back on track in this growing field." Researchers at the center will study ways to used fluid power to improve efficiency in equipment for agriculture, mining, construction, and equipment for manufacturing, such as injection-molding machines. Fluid-powered hybrid vehicles are now in development by Eaton Corp., one of the center's industry partners. The first applications of the technology will be in garbage trucks, other heavy trucks, and buses, all of which make frequent stops and starts and are big enough to hold a fluid-powered apparatus. The system uses a "regenerative braking" scheme to capture the kinetic energy of the vehicle as it slows down; with standard brakes, that energy would be lost as heat. "In a fluid-powered system, when you brake, a pump pumps fluid from a low-pressure reservoir to a high-pressure reservoir," says Stelson. "This requires energy, which is stored in the high-pressure reservoir. When you release the brake, fluid flows out of the reservoir and drives the pump backward, turning it into a hydraulic motor to help power the car. "The challenge is downsizing this stuff to get it into cars. It's hard to decrease the size to fit a car and get the energy reservoirs to fit."

"Back in the 1950s and 1960s, the United States led the world in fluid-power research, but now Europe and Asia have passed us by," says Stelson. "We hope that this new center will get us back on track in this growing field."

A trial of fluid-powered regenerative braking will soon get under way in the Chinese cities of Beijing and Shanghai. In preliminary tests, Eaton, which is conducting the trials, has shown that 80 percent of the braking energy is recovered and reused, resulting in a 30 percent fuel saving. Different savings will be realized in different types of machinery, but Stelson estimates at least $100 million of energy savings in each application. For example, backhoes equipped with fluid-powered technology developed at the center could improve efficiency by 30 percent, and in the big kahuna-passenger cars--perhaps 10 percent, saving $10 billion of the $100 billion now spent on fuel. As with its other grants, NSF places a high value on getting research out of the laboratory and into the minds and markets of the nation. One of the country's greatest successes in that field is another center member, the Science Museum of Minnesota. Mechanical engineering professor Will Durfee, the education and outreach director for the center, says the museum will take the lead on two projects. "We'll have an interactive exhibit on the fundamentals of fluid power," he says. "We want people to recognize that fluid power is useful because it can generate a lot of power for a small weight. In the exhibit, people will watch fluid flow from chamber to chamber and see the effects of the flow. Most people have the capacity to understand fluid power if it's presented in the right way. We hope clones of the exhibit will tour the country." The fluids in the exhibit will be the ones used in real life: oil, for heavy equipment, and air, for applications like dentists' drills and the machines that whisk lug nuts off car wheels. In the second project, the museum's Youth Science Center will have teenage staffers present talks to museum visitors. They will also go to high schools to conduct experiments involving fluid power. "It's called peer teaching and guidance," says Durfee. "Also, we'll help Project Lead the Way [a national, New York-based nonprofit organization that develops pre-engineering courses for middle and high schools] develop modules for teaching. Project Lead the Way is also part of the center. Other university members of the center are the University of Illinois at Urbana-Champaign, Georgia Institute of Technology, Purdue University, Vanderbilt University, the Milwaukee School of Engineering and North Carolina A&T State University. Besides the Science Museum and Project Lead the Way, the other nonuniversity institution is the National Fluid Power Association. Twin Cities area industry partners are Caterpillar, Toro, Eaton Corp., R.T. Dygert International, Sauer-Danfoss, and Tennant Co.

Read more about the center in a recent news release.