Nonparametric Terrain Estimation Based on the Interaction Simulation Between Planetary Penetrator and Soil

Penetration detection is an important way to method for in-situ scientific exploration of planets, which is used to indirectly detect the mechanical properties of the planetary subsurface soil. In this paper, four ovoid-nosed penetrators with different radius penetrating different compactness of planetary soil under different impact velocity were simulated using nonlinear finite element (FE) method through Hypermesh/Ls-dyna. A nonparametric estimation method for estimating the mechanical properties of planetary soil is presented. Three main characteristic parameters in the process of penetrator penetration were adopted in the method, including maximum acceleration am, penetration depth z, and maximum deflection angle θm. Twenty identification parameters for identifying planetary soils properties were derived based on these three characteristic parameters. The terrain consisted of simulant soil classified nonparametrically and artificially defined as three states (low, medium and high compactness) based on different harnesses, and five identification criteria (slack, ideal, partially strict, relatively strict and strict) were put forward. Four superior identification parameters were derived through the analysis of the evaluation indexes (recognition rate, accurate rate and conservative rate) under different identification criteria. and are selected as the optimal identification parameters and verified by simulation test, the accurate success rate and conservative success rate of the final estimation are 58.3% and 91.7%, respectively, which indicated that the nonparametric estimation method in this work can be used to evaluate the mechanical properties of planetary soil effectively.