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Innovative vehicle suspension system wins R&D 100 award

R&D Magazine names SwRI project one of the 100 most significant technical accomplishments of 1997

August 22, 1997 -- San Antonio, Texas -- A new energy efficient, ride enhancing, active vehicle suspension system, designed and developed by engineers at Southwest Research Institute® (SwRI®) , has been named one of the 100 most significant technical accomplishments of 1997 by R&D Magazine.

Originally conceived through an internally funded research project, the SwRI regenerative active vehicle suspension system offers both increased ride quality and better handling. Conventional suspension systems cannot offer both because ride quality is associated with spring stiffness -- the softer the spring, the better the ride -- and soft springs contribute to more body roll and pitch, thus sacrificing good handling.

One application of the suspension system is for large vehicles, such as a passenger bus. Although conventional hydraulic systems can require as much as 30 horsepower for activation in a large vehicle, the SwRI system requires as little as 7 horsepower even during demanding maneuvering conditions because the regenerative pump allows recovery of 75 percent of the energy required to activate the system.

The SwRI-developed suspension system counteracts compression and extension of vehicle hydropneumatic struts during turns by recovering hydraulic energy from the inside struts and transferring hydraulic energy to the outside struts. This energy transfer occurs through a combination of computer-controlled hydraulic pumps/motors, one per strut on the vehicle, all engine driven and mechanically coupled to each other.

By recovering most of the actuation energy, a design engineer can improve ride quality by softening the suspension spring and damping rates while maintaining control of the vehicle chassis during turns, braking events, and operation over undulating surfaces. Currently, no other active suspension system allows actuation energy to be recovered during operation.

For large vehicles such as buses, conventional hydraulic systems can require a total of 30 horsepower for activation. Tests show the SwRI regenerative suspension system requires only 7 horsepower to maintain chassis control while recovering more than 75 percent of actuation energy during demanding maneuvers.

"The improvement in ride that results from reduced spring and damping accompanied by improved control makes this system ideally suited for large passenger vehicles such as buses and recreational vehicles," says Gary Stecklein, director of Vehicle Systems Research in SwRI's Engine and Vehicle Research Division and co-inventor of the suspension system. "This system has been installed and demonstrated on a 30,000-pound bus with exceptional results. Ride was improved by reducing the spring rate by 50 percent, and chassis motions during steering and braking events were reduced by 50 percent when compared to conventional bus suspension systems."

Other applications for the suspension system include emergency vehicles such as ambulances, where a smooth ride can be critical to the care of the injured, and military vehicles that must travel at high speeds over rough terrain.

Design and development concepts of the SwRI suspension system are contained in U.S. Patent 5,020,826, "Vehicle Suspension System," issued June 4, 1991, Gary L. Stecklein and Glenn Wendel, inventors. Wendel is manager of Hydraulic Systems Development in SwRI's Engine and Vehicle Research Division.

The R&D 100 awards will be presented September 25 at a banquet and ceremony to be held in Chicago at the Museum of Science and Industry.


For more information about SwRI's R&D 100 award, contact Deborah Deffenbaugh, Communications Department, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas 78228-0510, Phone (210) 522-2046, Fax (210) 522-3547.

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