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Abstract
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27th International Technical Conference on the Enhanced Safety of Vehicles (ESV): Enhanced and Equitable Vehicle Safety for All: Toward the Next 50 Years
https://www-esv.nhtsa.dot.gov/Proceedings/27/27ESV-000067.pdf
Pre-crash occupant dynamics change more and more with the broad usage of advanced driver assistance systems (ADAS) and automated driving (AD) functions. Occupant interaction with pre-crash activated seatbelt systems (SBS) represent a challenge and an opportunity at the same time for providing restraint solutions tailored to the individual passenger and to the actual driving situation. To fully understand the dynamics, and to design robust control parameters, the increased complexity can eventually only be assessed by means of a virtual approach. Consequently, this requires compulsory realistic advanced physical tests and development targets to ensure that integrity and functionality of all system components are fully understood and modeled appropriately. Focusing on the most frequent crash types: frontal and rear end crashes, allows to use a specially designed, stripped-down Anthropomorphic Test Device (ATD) to dynamically load the seatbelt system in a representative way. In addition, a high-precision surrogate with different selectable upper body moments of inertia, seated on a generic steel seat with an adjustable backrest is available to extend the range of the applicable load. In both cases the retaining effect caused by friction on a real vehicle seat is accounted for by an adjustable viscous damper, retarding the motion of the lower body. These reduced setups guaranty by design a direct and accurate positioning of the ATD, minimizing test setup variability. As a novum, a seamless transition from initial pre-crash dynamics to the final crash pulse loading can be realized when mounting these ATDs on an innovative test bench using closed-loop controlled electric linear motors to accelerate a linear ball bearing guided carbon sled along a 6-meter track for achieving a maximum in reliability and in repeatability. This physical bench test represents the foundation not only for demonstrating benefits of pre-crash activation on seat belt systems but also for validating functional SBS simulation models, so that numerical simulations become its digital twin. Reliable digital SBS simulation will be the key to generate more and advanced seat belt functions. However, the capability to measure efficiently and accurately via physical tests the performance of these SBS products throughout the entire range of their functional design space, will promote not only the product, but further raises the credibility of simulation. A new rating criterion Characteristic Shoulder Force Level (CFL) evaluating the SBS performance virtually is proposed, which assess the performance of the SBS intervention up to force-closure and demonstrates the strength of a hybrid approach. Different vehicle configurations, crash pulses, load scenarios and SBS activation strategies can be rated and directly compared to each other. This supports improved integrated safety systems solutions and allows detailed analyses of active safety pre-crash interventions as triggered by ADAS or AD. The combined virtual-physical approach is illustrated via load cases combining braking intervention with conventional and actively controlled seatbelt systems. The potential benefit to occupant safety of different combination of braking and SBS activation is measured and discussed.
Language: en |