16 April 2009

Smart speed bump moves vehicles faster

By driving over a speed bump-like “diagnostic cleat” containing sensors, it is possible to detect damage to critical suspension components in a vehicle.

“Our aim is to save time and maintenance costs, but more importantly to reduce downtime by catching damage before it leads to failure in the field,” said Douglas Adams, an associate professor of mechanical engineering and director of Purdue University’s Center for Systems Integrity.

They drive the vehicles over the “tactical wheeled vehicle diagnostic cleat,” which is like a rubber-jacketed speed bump equipped with sensors called triaxial accelerometers. The system measures vibrations created by forces that a vehicle’s tires apply to the cleat. They can find damage in the tires, wheel bearings, and suspension components by using signal processing software to interpret the sensor data. Purdue is working with the U.S. Army and Honeywell International Inc. to develop the technology.

“Let’s say one of the tires is severely under pressure,” Adams said. “The cleat tells you to turn around and fill up that tire because you are about to embark on a 10-hour mission with this vehicle. Or, you are returning the vehicle to the depot, and the cleat tells you that the right rear suspension has a problem in the shock absorber or a critical bolt in the front suspension is broken. The maintenance personnel don’t have to troubleshoot the vehicle. They know what to fix.”

The system also could work in commercial applications to test civilian vehicles, Adams said.

“The diagnostic cleat is designed to be quick and easy to use,” said Joseph Gothamy, acting team leader for the reliability and durability modeling and simulation team at the U.S. Army center. “The last thing we want to do is take time from already overburdened soldiers and maintenance officers. The cleat is a quick first check to determine what’s mechanically wrong with a vehicle before wasting time hunting for potentially simple problems.”

“Operating and maintenance costs for military weapon systems accounted for about 60% of the $500 billion U.S. Department of Defense budget in 2006,” Adams said. “Better diagnostic and prognostic technologies could reduce this expense and ensure readiness of ground vehicle fleets.”

By using the instrumented cleat and other “condition-based” maintenance methods, the military could reduce costs by performing work on vehicles when needed based on the condition of parts instead of performing scheduled maintenance on vehicles regardless of whether they need the work.

“Some vehicles may be used at checkpoints while others may be hauling supplies hundreds of miles,” Gothamy said. “Even if the same vehicle variant is used, they are on very different missions and trying to use the same regular maintenance schedule for both isn’t always efficient or effective.”

The researchers tested their system in experiments with high-mobility multipurpose wheeled vehicles, or Humvees, and also developed a computational model to simulate how the system works.

“Our simulated model showed us that we were capable of using the system accurately to detect damage to vehicle components, and our experiments with actual vehicles validated the model,” said Adams. “The system was sensitive to as little as a 5% change in the stiffness of the suspension.”

For related information, go to www.isa.org/sensors.