Institute of Fundamental Technological Research

This short communication is aimed at indication of a significant problem to be solved by researchers working in the field of engineering structures. The contribution concerns a very important application of a rescue cushion, which is an airbag system devoted to the impact mitigation appearing during evacuation of people from heights. Although, a very similar in the principle of their operation, car airbags have been thoroughly tested, rescue cushions have not received sufficient attention. It should be emphasized that the performance of the actually operated devices is far from sufficient and even fatal accidents occur. The authors identified the problem and have initiated a study, which includes numerical simulation and experimental validation of the impact absorption process, as well as the elaboration of a suitable adaptive solution.

adaptive airbag, Adaptive Impact Absorption, inflatable structure, pneumatic absorber, rescue air cushion

Small drones with total mass of a few kilograms are becoming more and more popular in many applications increasing the probability of occurrence of emergency situations caused by an equipment failure or a human error. In case of a fall from a high altitude very often it is possible to use parachute rescue systems, which however require relatively long time for deployment and development of braking forces. The touchdown velocity may be large enough to exceed limit accelerations for UAV equipment. The paper presents the concept of deployable airbag systems, in particular with adaptive flow control, which provides a possible solution to the above-mentioned problems. The paper discusses the overall control and adaptation strategy. Simplified methods for mathematical modeling are proposed and formulated for an example on a cylindrical airbag. The conceptual part is concluded with the presentation of the methodology of experimental verification and results of initial tests of the integrated airbag system.

Despite the fact that airbag systems are well-known and used in safety engineering for many years the growth of research and development activities and increasing number of new applications of airbags are observed. Advances in the field includes among others: development of advanced car airbags, analyses of airbag cushioning for landing on Mars, elaboration of emergency landing system for drones. Another field of airbags application and simultaneously the main motivation for the study presented in the paper is the evacuation of people conducted by the fire brigade. When people are forced to leave the building by jump from the window or roof the rescue cushion is placed on the ground in order to mitigate the impact and safe life of evacuated people. The aim of the study is to develop the relevant adaptation strategy for the system and provide efficient operation of the airbag in case of different impact velocities and different masses of the landing person. Several approaches to the system adaptation are analyzed and they include semi-active as well as semi-passive solutions. Also possibility of implementing the concept of self-adaptive impact absorption is assessed. Technical and operational requirements for the rescue cushion are considered and based on them the final adaptation principles are selected. Evaluation of the system performance is conducted with the use of numerical models of dummies provided in the LS Dyna software environment. In Fig. 1. the overloads acting on pelvis of three different dummies dropped from assumed height are shown. The obtained mitigation of the impact loading is significant for all considered cases.