Autoliv optimizes vehicle safety equipment using LMS testing solutions

Although cars today are much safer than 20 years ago, traffic accidents kill thousands of people every year and seriously injure nearly five million. The mission of Autoliv is to continuously increase vehicle occupant protection by introducing breakthrough safety innovations and extending its specialized safety equipment offering. To evaluate the performance of airbag and seat belt systems – and reduce the noise they generate – Autoliv uses LMS test systems to measure noise levels that test dummies face during crash simulation tests. 



LMS test systems are also used to evaluate individual safety products, such as seat belts, seat frames and steering column assemblies. Overall, LMS Test.Lab guarantees maximum measurement reliability and reduces testing throughput substantially.

Autoliv is a worldwide leader in automotive safety systems – a pioneer in both airbags and seat belts – and a technology leader that offers an extensive portfolio of vehicle occupant protection products. Its latest contributions to automotive safety include an anti-whiplash seat, a side-impact airbag for chest protection, and an inflatable head-protection curtain designed for lateral impact. Currently, Autoliv is in the forefront of developing roll-over protection, night vision and pedestrian protection systems. Autoliv is a supplier to all major vehicle manufacturers and most vehicle brands, and every year its products save over thousands of lives and prevent many more severe injuries.

In the event of a car accident, a predefined sequence of actions is initiated to protect the occupants of the vehicle. Thomas Norberg, Laboratory Manager at Autoliv in Vårgårda, Sweden, describes what happens starting at the onset of a crash, “A small pyrotechnic charge activates belt pre-tensioners, which tighten the belts and restrain the occupants as early as possible. After this action, load limiters make sure the load on the occupant’s chest does not become too high. In this way, the excessive energy is absorbed more uniformly by the frontal airbag, which by that time is fully inflated. The primary purpose of the airbag is to cushion head and chest and prevent both from striking hard surfaces in the front of the vehicle, such as steering wheel, dashboard and windshield. Seat belts and airbags significantly reduce the risk of serious injuries and occupant fatalities in frontal crashes. To protect driver and passengers against side-impact accidents, Autoliv offers dedicated head, pelvis and thorax airbags to be integrated in the vehicle interior.”

As part of the development of new safety products, Autoliv invests significant research and development effort in reducing the noise generated by pyrotechnic initiator mechanisms. It is desirable to reduce this explosive noise level, as it may increase the risk of hearing damage. Apart from sound pressure levels, the human ear is very sensitive to the timing sequence of the initiation of the safety devices. In general, a firm sound, for example from a pyrotechnic belt pre-tensioner initiator, activates the Stapidus reflex of occupants’ ears. This ear reflex is a self-protective reaction that temporarily inactivates hearing capability after approximately 10 milliseconds. This means that during this period, it is likely that occupants suffer less from subsequent airbag initiator noise.

In dedicated acoustic test facilities, Autoliv engineers perform noise measurements inside vehicles equipped with a series of fully-integrated seat belt and airbag prototypes, occupied by up to five crash test dummies. A dedicated trigger unit precisely executes a predefined trigger sequence to activate seat belt restrainers and airbag detonation. Microphones, integrated in all dummies’ ear positions, capture the noise generated by successively exploding initiator mechanisms and transfer them to an LMS SCADAS III front-end. 


Autoliv engineers use LMS Test.Lab and LMS CADA-X test software to manage the communication with the trigger unit and to process the acquired data. The complete sequence of such tests is often recorded with dedicated video cameras.

Thomas Norberg explains that the recorded noise time signals form the basis for running dedicated frequency analyses that provide insight into maximum amplitudes and most dominating frequency components. “The main purpose of these kinds of investigations is to examine the noise performance of different types of explosive materials as well as to fine-tune the mechanics of airbag initiator designs during the final stages of development. A specific proprietary algorithm is developed to convert the acquired test data of each microphone into one single numerical value that reliably reflects the risk of hearing damage. The use of this algorithm increases the efficiency and consistency of the evaluation process of the noise measurements, as it allows the noise performance of new design modifications to be quickly interpreted and compared with previous results.”

At the Autoliv noise test laboratories, engineers also focus on eliminating undesired sounds generated by other safety-related equipment, such as seat belts and seat frames, during their normal operation. Even the weakest noises produced by such systems negatively influence the comfort of driver as well as passengers. To reduce noise disturbances, Autoliv engineers execute environmental noise measurements on specific safety equipment. While a unidirectional shaker system mechanically excites a newly-developed seat belt assembly or a folding steering column with integrated airbag assembly, for example, the resulting noise is measured and analyzed. 

These environmental tests can be quite relentless because the shaker system is able to excite over half a ton of weight with accelerations up to 60g. In addition, the ambient temperature present can vary between -50 and +110 degrees Celsius. The purpose of these tests is to execute safety system benchmark tests and to further drive development innovation. Autoliv engineers compile the vibrations they apply to test specimens on the basis of accelerometer measurements taken on identical or similar safety equipment during test vehicle investigations on roads and test tracks. 

Using LMS Test.Lab, they perform random Power Spectral Density (PSD) calculations to accurately convert the acquired vibration measurements into a representative and effective shaker table control spectrum. To further increase the test capability and turnover of its noise test facilities, Autoliv extended its existing LMS CADA-X installed base with LMS Test.Lab. Thomas Norberg summarizes how this affects his testing operations, “Already for many years, we rely on LMS test systems to accommodate for our dedicated and varying testing requirements. Our experience with LMS Test.Lab clearly demonstrates that testing throughput times are compressed drastically. The associated productivity gains mainly result from the software’s higher flexibility and efficiency standards that help speed up test setup and post-processing stages. Also LMS Test.Lab’s process-driven application workbooks accelerate our repetitive benchmark testing activities and increase the involved data consistency significantly. Autoliv engineers consider high data acquisition accuracy, custom calculation flexibility and reliable external interaction as the core to further step up testing productivity and strengthen their commitment to realize optimum occupant protection.”