Here in the cavernous sled lab, staff work intensively over the cab section of a pickup truck. Window glass has been removed and the windshield has been replaced by plexiglass, but the interior is present, and a crash test dummy is belted into the seat. Angelo Adler is Senior Manager Systems Engineering at ZF TRW’s Occupant Safety Systems (OSS) test center in Washington Township, Michigan. He says it takes about twice as long to correctly set up a test event as it does to analyze the immense amount of data that is generated. Firing mechanisms, lighting and dummy test circuits all must be checked for accuracy, timing and functionality.
As one of the last steps, the precisely positioned crash test dummies are given a chalk makeup job. The use of different colors allow exact analysis of how a chin, nose, forehead or cheek contact the deploying airbag. When all is ready, the ServoSled (short for servo-hydraulic sled) simulates a 35-mph collision impact involving an acceleration of over 50 Gs, knocking the vehicle sled weighing up to 3,000 pounds backward down a 100-foot-long tunnel. From four to 12 technicians and engineers cluster in the control room, which then is carefully locked and the lab entrances sealed for safety. A technician says “Here we go”; a voice counts down – “five, four, three, two, one” – and with a blast like a cannon being fired, the working cylinder thrusts the test rig backward. The noise comes not only from the piston, but also from as many as four airbags and seat belt pretensioners deploying simultaneously.
Like any collision impact event, the action takes place in milliseconds. Six to 12 high-speed cameras document the event at rates of 1,000, 3,000 or 10,000 frames per second. The data can show everything from the precise deployment track of an airbag to the interaction between test dummy, seat belt and active restraint system.
The ServoSled (short for servo-hydraulic sled) isn’t the only impressive feature at Washington Township. In the bottom of the building several labs thump, shake and rattle things. Unlike the spacious carpeted lobby or the architectural smoothness of the office atrium, passages down here are narrow and utilitarian. Different labs and test suites crop up at unexpected levels. Included are areas for sled, linear-impactor and out-of-position testing; dynamic testing that includes a 35-mile-per-hour bungee sled decelerator used to test seat belts and side-impact airbag systems; and a seat-belt reliability lab.
“Testing and simulation is a highly technical area, and we bring our customers the best possible safety evaluations. Our facilities are an investment in validating the future of occupant safety. We’re not just testing restraints, we’re simulating those restraints’ performance in the vehicle environment”, says Steven J. Peterson, Vice President Engineering, North America Region, Global Systems.
Located 37 miles north of Detroit’s riverfront city center, the OSS engineering development center and test facility were built at a time when the lab could be remote and somewhat isolated from casual observation. The nearest neighbors were fruit farmers whose apple orchards spread around the small city of Romeo. TRW was one of the first automotive suppliers to invest in extensive vehicle sled testing in a specialized facility when the center was constructed in 1988.
The center in Washington Township is one of four global testing facilities that are part of the OSS product line that includes airbags, seat belts and steering wheel technologies. Peterson says the goal is to support OEM customers in North America, Germany, Japan and most recently China, where ZF TRW in April 2016 opened a new crash sled lab at its Anting Technical Center in Shanghai. “We are supporting vehicle restraints development in North America. The focus is on the customer we have right here. The most important thing in testing is that we need to do it the same way – how we set up and run a test – so that we can run the same test in China and have the same results. The intent is to have consistent validation of products, and it’s a big challenge,” Peterson says.
New safety standards
It’s a challenge that the test center willingly undertakes. Adler, who heads the performance teams at Washington Township, has 28 years of experience at the center. “The fast pace of the auto industry means there’s never a dull moment, never a time when you sit and wait,” he says. Safety regulations accumulate – there’s rarely one that goes away – and new safety standards coupled with new technology create a constant demand to test everything, from individual components to entire vehicles. Technical employees in Washington work jointly with those at a sister facility located just six miles north in Romeo.
New standards and measurements will soon change the way light vehicles are given their five-star safety ratings in the U.S. Among them, the New Car Assessment Program (NCAP) will include a frontal oblique crash test to see how well occupants are protected in an angled collision, and a modified frontal crash test will measure how rear-seat occupant safety can be improved. Just getting rear-seat occupants to use the existing seat belts should provide some immediate benefit; unlike Europe, where usage of rear restraints is mandatory, most American states have no law requiring adults to buckle up when sitting in back. “We see rear-seat safety improvement as the next horizon. There was a point in time when the rear seat was the safe place to be – that’s why we put our children back there,” says Adler. While the rear seat is still the place for properly restrained children in age- and weight-appropriate child seat systems, though, the front seat typically has more available safety features to help protect larger passengers. Front-seat designs help to keep occupants centered during a crash; they also include components like seatbelt pretensioners and load limiters to help position the belt correctly. Rear-seat systems are more limited. However, that’s likely to change soon.
“Correctly setting up a test event takes about twice as long as analyzing the resulting data.”Angelo Adler, Senior Manager Systems Engineering
ZF TRW has a whole range of Hybrid III dummies in various sizes. Children’s dummies are tested not only in correctly restrained seating but also in child out-of-position postures
“The answer to rear seat safety may not just be the restraints, it may be the seat itself,” says Adler. Carmakers have been contemplating the addition of small airbags to help protect rear passengers, and the design of such systems may be complex. Side curtain airbags running the full length of the vehicle currently help to improve both side-impact protection and restrain occupants from being ejected, but must be made to interact with any comprehensive rear-safety program.
Romeo is where such airbag development takes place. “For airbags, it’s all about the fabric,” says Adler, “and being able to sew and fold our products in a repeatable way. They’re difficult parts because, unlike other parts, they’re soft, they move, and even installing them can be a challenge.”
As is sometimes seen with human drivers, the dummies can be set up out of position, including with chin-on-wheel and torso-on-wheel configurations. Children’s dummies are tested not only in correctly restrained seating but also in child out-of-position postures – kneeling on a seat to look out, or standing in front of the instrument panel. The Hybrid III dummies have taken hard knocks, but have gathered lots of useful information in the process.
“Our facilities are an investment in validating the future of occupant safety.”Steven J. Peterson, Vice President Engineering, North America Region, Global Systems
“You probably won’t see people from here leaving the parking lot without their seat belts on,” says Adler of ZF TRW employees who have viewed the dummies in action. Soon they will be joined by new and more complex dummies. THOR, for Test Device for Human Occupant Restraint, will bring both more instrumentation and more realistic human movement and articulation to the test environment. New WorldSID dummies, meanwhile, will be added to optimize side-impact data gathering.
Testing has come a long way since the 1980s, but ZF TRW’s test facility is ready for the road ahead. “We have the components and systems. We are what helps to protect the occupant. The seat belts and airbags, all of this is occupant protection. One thing that’s clear is that we are going to have to do more,” says Peterson of the test center’s overall mission.