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How exactly does a crash-test dummy work?

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31/01/2019
 

Driver assistance and safety systems help prevent accidents. At VisionZeroWorld we explain how ABS, airbags and other safety-related technologies work. This time it’s the turn of the crash-test dummy.


Thor’s new job is not for the faint-hearted. It involves sitting in a car and waiting to be crashed into a wall. At 1.78 meters tall, and weighing 80 kilos, Thor has the physique of the average adult male. He is the strong, silent type, and utterly fearless. That’s just as well, of course, considering he’s got probably the car industry’s toughest job – not to mention one of the most important. Because Thor is a crash-test dummy, and his mission is to help pave the way for a future with zero accident fatalities. There is one thing, though, that sets Thor apart from the other members of his extensive family: he’s the first dummy to be specially adapted for autonomous vehicle testing.

 

Thor (Test device for Human Occupant Restraint) was built by Humanetics, a company based near Detroit in the USA. Thor is successor to the previous Hybrid III dummy, which was selected as the official standard for crash testing back in 1997. Humanetics has been building mannequin-type test dummies for over 65 years. To this day it supplies three quarters of all crash-test dummies used in the auto industry. For several decades, crash-test dummies conformed to a single standard format, but all that has now changed. Today, Humanetics produces a whole family of these humanoid figures, including babies, infants, and male and female children, teenagers and adults. There are replicas of obese and elderly people too. The new dummy on the block, Thor AV (Alpha Version) to give him his full title, is even more talented than his predecessors, since unlike earlier models, which had a rigid pelvis, he can also lie down. This is important because when autonomous vehicles take to the road, occupant sitting positions are expected to change as well. That said, whether working with autonomous vehicles of tomorrow or compact cars of today, all dummies are committed to one and the same goal: Vision Zero. So how do these inanimate super-heroes of the auto industry actually work?

Keeping it in the family … the standard Hybrid III crash-test dummies come in all shapes and sizes.

 

Fifty years ago, the dummies used in the auto industry didn’t look much different from the average shop-window mannequin. The crash-test dummy of today, however, is quite a different proposition. It is a highly sophisticated high-tech device that is modeled almost exactly on the human anatomy. In order to deliver as much data as possible about what happens to vehicle occupants in an accident, the dummies are equipped with around 200 sensors at all of the most critical points on the body. These sensors measure all of the forces acting on the dummy’s body during crash-testing. To ensure that the results are as accurate and comparable as possible, the tests always follow standardized procedures.

 

Prior to testing, the dummies are calibrated to ensure that all the sensors are supplying correct readings. First of all, in order to calibrate the instruments inside the skull, the head assembly is detached and dropped from a height of 40 centimeters. This is followed by a test to determine the flexibility of the neck. In this case the test object, comprising a head assembly attached to a shoulder assembly, is accelerated, then subjected to sudden braking. If this test too is successful, the shoulders and head are attached to the torso. The dummy is dressed in yellow clothes and liquid paint is applied – not, of course, to make it look pretty but so that the paint will mark all the points at which it comes into contact with the vehicle. Now the dummy is ready for its big moment – a short ride ending in a wall.

All in a day’s work for a crash-test dummy. Photo: Global NCAP

 

When the dummy has taken a seat, the car accelerates to exactly 64 km/h – then collides head-on into a wall or other obstacle. This impact subjects the dummies to forces of up to 40 g. While the vehicle is moving and during the impact itself, sensors record and store all the relevant data. With newer, digital dummies, the data is saved to a measurement system inside the dummy, while older dummies are fitted with wires that relay the data to a measuring system inside the car. The simulation is filmed by high-speed cameras, whose high-resolution slow-motion images allow every second in real time to be extended during playback to as much as several minutes. To confirm the reliability of the data obtained, the test is repeated several times. Once the engineers have evaluated all the sensor data, along with the camera images, the interior impact sites and the condition of the test vehicle itself, they are finally able to say exactly how safe the car is – or indeed isn’t.

 

Crash-test dummies are produced in virtually every shape and size, as well as in different versions for use in different types of accident situation. For example, there are special dummies for side impacts, rear impacts and frontal impacts. Crash tests are conducted by various different bodies across the world – among them the member organizations of Global NCAP (New Car Assessment Program). Global NCAP awards ratings of between zero and five stars to the vehicles it tests, based on their performance. And while these crash tests are not actually mandatory for automakers, these days a low rating is nevertheless very bad news for any new car about to be launched on the market. According to David Ward, Secretary General of Global NCAP, speaking in a recent interview with VisionZeroWorld, the NCAP tests promote “competition for greater safety that benefits everyone.” One of the tasks of the NCAP organizations, he says, is to act “as catalysts and accelerators of the shift towards greater safety, quite simply by making the crash tests as transparent as possible for the general public.” Thor too is set to help accelerate this shift towards greater safety in the coming years - and marks yet another milestone on the road to Vision Zero.