Concept Study of Adaptive Seatbelt Load Limiter Using Magnetorheological Fluid

Most current seatbelt load limiter technologies could only offer three or fewer predetermined patterns of seatbelt restraint force. However, researches have shown that, to better realize adaptive protection to different occupants under different crash severities, a continuously and real-time adjustable load limiter may be one step further. This concept could be especially favorable to vulnerable occupants such as small stature females and elderly people. Ideas have emerged suggesting possibility of using magnetorheological fluid (MRF) to realize such load limiter (MR-LL). This paper presents a concept study of MR-LL, aiming at evaluating its feasibility and establishing basic guidelines for prototype development. Configuration of an MR damper integrated with seatbelt retractor is selected in the study, in which the seatbelt force can be controlled by varying the strength of magnetic field exerted on the MRF inside the damper. The MR damper is numerically modeled and validated against experimental data found in the literature. Then by merging the MR damper model with a simplified occupant and seatbelt model subjected to sled impact loading, the performance of MR-LL under different parameter settings is studied and optimized. The simulation results demonstrate proof of the concept, indicating that the proposed MR-LL can generate various seatbelt force patterns with a wide adjusting range, thus to meet the requirement of both occupant adaptability and crash severity adaptability. Possible limitations of the proposed MR-LL are also discussed.