The Johns Hopkins Gazette: July 20, 1998
July 20, 1998
VOL. 27, NO. 40


The Evolution Of Smarter Dummies

Research: APL scientists engineer the next generation of crash test dummies

Greg Rienzi
The Gazette

Johns Hopkins Gazette Online Edition

Researchers at the Applied Physics Laboratory think they can learn a lot from a dummy, or at least more than what the dummy now tells them.

A team of APL scientists, using existing technology, is helping the National Highway Traffic Safety Administration develop "smarter" crash test dummies that will be able to quickly and more accurately record injury-related data during automobile crash tests.

Specifically, the multidisciplinary research team is working with optical and magnetic sensors and 3-D imaging that will enhance its ability to measure chest compression and head injury during the crash tests. The new sensors would either replace or supplement the mechanical sensors inside the dummies that are currently used.

In the driver's seat: APL's research team hopes the crash-test dummy it is developing will lead the way to improved safety measures in automobiles. Optical and magnetic sensors and 3-D imaging will enhance the dummy's ability to measure chest compression and head injury during tests. From the left, Matt Bevan, Jack Roberts, Bryan Jacobs and Bryan Pfister; not pictured, Carl Nelson.

The innovations constitute a major step forward in crash test technology, which has changed very little in the past 20 years, according to Jack Roberts, co-principal investigator of the magnetic sensor research being developed with APL internal research and development funding.

"The sensors now being used are mechanically oriented and only give us a gross idea of what injuries have occurred," Roberts says. "But our magnetic sensors are five times faster, and two to five times more sensitive in registering displacement."

The displacement recorded during a crash test is currently measured on the chest by rotary potentiometers at five specific spots: the aorta, heart, spleen, liver and lungs. Following a crash test, the compression of these points, measured to within only 2 to 3 millimeters, can tell roughly if any of these organs have been injured.

But by using the magnetic sensors, which would be placed on a vest, Roberts says the researchers will now be able to measure compression to within two-tenths of a millimeter so that they could determine if, for example, the liver had been bruised or lacerated during the crash.

Although the electromagnetic principles behind the system have been known for over 100 years, the signal processing uses the same state-of-the-art techniques employed in many Global Positioning System receivers.

"The magnetic sensors work by simultaneously measuring the magnetic fields generated by several transmitters mounted at known locations," says Roberts. "Since the magnetic field strength varies with the transmitter-sensor separation distance, a method similar to triangulation can be used to determine the sensors' location."

Carl Nelson, co-principal investigator, is working also on high-speed, high-accuracy optical sensors that would be placed on the rib cage and spine of the dummies to detect displacement. Nelson's research is being sponsored by the National Highway Traffic Safety Administration.

The origin of the dummy research came from a conversation that Roberts, a research professor in the Mechanical Engineering Department, had with a former student, who now works as a contractor with the U.S. Department of Transportation. Roberts says the two were involved in a discussion about strain gauges that ultimately led to the topic of crash test dummy technology, an interest of his that stems from his work developing dummies for the Michigan-based Transportation Research Institute during the 1970s.

Roberts says his former student then introduced him to a biomechanics expert at the Department of Transportation, who was very interested in developing new crash test sensors. That meeting led to the National Highway Traffic Safety Administration to approve funding for the APL research, which is being supplemented by internal APL funding. Currently, the research team is looking for additional funding to develop a prototype for the magnetic sensor crash test dummy.

"DOT sets the standards for crash tests. And the scientists there were looking into new and different ways of improving the technology," Roberts says.

The first anthropomorphic crash test dummy was invented in 1949 for the U.S. Air Force in order to evaluate aircraft ejection seats. Since the late 1950s, crash test dummies have been used by the automobile industry to determine the extent of human injury during a crash so that modifications can be made to automobile design to enhance passenger safety. The injury data is recorded by mechanical sensors inside the dummy, which are connected to wires that come out its back like an umbilical cord, which is in turn attached to a computer. Black and yellow stickers on the side of the head are used as a reference point so that special cameras can record the motion of the dummy.

Roberts says that dummy technology has advanced very little since the 1970s, which is one of the reasons, he says, that the leading supplier of crash test dummies in the United States, First Technology Safety Systems, of Ann Arbor, Mich., has expressed interest in the magnetic sensor technology being developed at APL.

In addition to recording chest compression and injuries, the magnetic sensors can be used to measure shearing deformation of the brain during a crash. The magnetic sensors implanted into a dummy's skull--filled with a special silicon gel to simulate brain tissue--can give researchers, who will use an advanced 3-D positioning system, a clearer picture of how much the brain has been deformed during an accident.

Bryan Pfister, a doctoral student in the Mechanical Engineering Department and member of the APL research team concerned with head injuries, says that the existing accelerators inside the dummy's head don't give researchers the whole picture.

"They're not telling us a whole lot. They don't tell us exactly what displacement has occurred and what kind of force was needed for that displacement," Pfister says. "We would like to know exactly what kind of brain injuries have occurred."

Roberts says the research team is still working out problems with the technology, mainly the interference on the magnetic sensors caused by the metal parts inside the dummies.

If this new technology is implemented, Pfister says, it could lead to better seat belt and head rest designs for cars, improved designs for helmets like those worn by motorcyclists and even basic structural changes in automobiles.