We propose to calibrate the DEM microparameters in our YADE soil model to match the stress-strain responses measured from geotechnical laboratory tests. These calibrated DEM inputs will then be used to simulate a known wheel geometry under controlled terramechanics testing conditions to evaluate the predictive capabilities of our models. Following thorough validation of these modeling methods and of our calibrated DEM inputs, additional predictive models will be run to evaluate the tractive performance of wheels with varying geometries operating under different loads and soil conditions. Two primary innovations come from this proposed Phase II work: 1) a grain-based DEM soil model which has been calibrated to the unique behaviors of lunar soil and 2) an automated calibration routine for DEM which can function on a highly generalizable calibration tool for multiple software packages. These innovations add to the existing state of the art in numerical modeling which lacks calibrated grain-based models of lunar soil with realistic grain shape and generalizable calibration tools for DEM.
These proven and proposed modeling advancements mark a dramatic improvement over existing terramechanics models for simulating the lunar soil response during slip conditions and large plastic deformations. These methods incorporate the unique factors at the lunar poles which increase risk of entrapment such as potentially low soil compaction due to reduced diurnal temperature swings. Open source software will be used for all modeling efforts and the majority of our routines will be publicly released to encourage other researchers to use the numerical tools developed through Phase II. Commercialization of our efforts will come in the form of an automated DEM calibration tool which can be licensed by customers through a paid, subscription-based service which will increase ease of use, accuracy of results, and user confidence in selected input parameters for DEM software.
The goals outlined in this Phase II proposal directly support NASA’s Moon-to-Mars campaign and complement NASA’s Strategic Goal 1 to expand human knowledge through new scientific discoveries and Strategic Goal 2 to extend human presence deeper into space and to the Moon for sustainable long-term exploration and utilization. Additional development of this tool will enable more accurate simulations of soil-wheel interactions, de-risk future missions to the Moon, and act as tool for assisting laboratory testing.
The proposed Phase II benefits the broader DEM modeling community by integrating an automated DEM calibration routine into an open-source simulation platform to enable more accurate DEM models and a far simpler user experience. Open source software will be used for all modeling efforts to encourage other researchers to use the numerical tools developed through this project.