Flexible airbag cushioning for Martian landing based on discrete element method

Abstract

With the exploration missions to Mars gradually turning from detection of the surroundings to landing patrol, an airbag cushion system has become a new research area. A large number of researchers have simulated the airbag landing buffering process through numerical calculation methods, and applied the simulation results to optimise the airbag system parameters. According to a summary of previous studies, the researchers have all used a continuous geometry to simulate an impacted surface. Such a model cannot truly reflect the discrete morphological features of the Martian surface, however, and cannot predict the actual airbag cushion characteristics of the Martian subsurface. Based on this problem, this work proposes the use of discrete elements to study the cushioning characteristics of an airbag. This method has certain advantages in simulating the discrete surface of Mars and the dynamic characteristics of discrete surfaces after an impact. At the same time, to simulate the cushioning process of an airbag on the discrete ground, it is necessary to focus on a method of modelling the airbag based on the discrete element theory. We establish a three-dimensional particle-spring equivalent model of an inflatable airbag microelement based on the discrete element idea, and the model parameters are matched based on theory and a simulation. Finally, the discrete element simulation model of a spherical inflatable airbag is established using the discrete element simulation software EDEM, and the reliability of the model is verified by comparing the experimental and simulation values. Based on a theoretical derivation, the physical quantities that affect the airbag acceleration are obtained; these physical quantities are used as variables to perform a multi-condition simulation analysis, and the preliminary variation law between the acceleration and physical quantities is obtained. Further, a multi-ball model for a multi-state simulation analysis is described, along with the simulation results used to predict the cushioning characteristics of the airbag landing in the Martian environment.