Measuring and modelling of soil displacement from a horizontal penetrometer and a sweep using an IMU sensor fusion and DEM

Abstract

When simulating soil tillage processes using the discrete element method (DEM), it is essential to know the discrete element micromechanical parameters that describe the soil model, and this requires calibration. The formulation of a model that accurately reflects the behaviour of the soil from several perspectives is only possible by employing several different measurement procedures and DEM simulations. For this reason, four different measurements were used in this study for the purpose of calibrating the DEM model’s micromechanical parameters for sandy soil with a dry based moisture content of 4.1 %. The cone penetration resistance was measured with a horizontal penetrometer that was developed in-house and a vertical penetrometer, while a displacement sensor placed in the soil provided information on the internal movement of the soil, and the draught force of a sweep tool was also monitored. The DEM models of the measurements were defined in Altair EDEM® software using the hysteretic spring contact model. To model the soil, spherical elements and clump elements were examined. The displacement sensor was modelled with a clump element, whereas the sweep tool and the horizontal and vertical penetrometers were taken into account as rigid surface models. Based on the simulations, it was determined that the clump elements examined are not suitable for proper calibration with the hysteretic-spring contact model, because, as a consequence of the large coordination number, they excessively increased the draught force by getting stuck in front of the tools and measuring devices. By studying sweep tool simulations, it was observed that, in terms of the particle sizes used, particles with a higher density and higher bulk density resulted in a higher draught force, but at the same time, they moved at a lower speed. Finally, by taking vertical penetrometer measurements and running simulations, the soil model created with spherical elements was validated with a relative error of 8.7 % which can describe the sandy soil with sufficient accuracy in all the examined aspects.