Terra-22: an aerial soil sampling in densely compacted agricultural fields

Abstract

Soil sampling is used in agriculture to monitor fields and plan fertilizer application. This task is typically performed manually, but ground robots have recently been introduced. However, ground robots are often slow and heavy, which contributes to soil compaction. Fast-flying drones could provide an interesting alternative to ground robots. However, drones are severely limited in their payload and in the forces that they can apply to the soil. This paper presents the Terra-22, the first airborne system capable of sampling densely compacted agricultural soils. To do so, many challenges were addressed, including the development of (i) a high-power density drilling system that outperforms typical brushed DC gear motor by 39%, (ii) a drill design that is 48% lighter than traditional steel auger drills and that keeps cross-contamination under 4%, and (iii) a drill penetration rate controller that reduces the torque requirement by 33% and the axial force requirement by eight folds when compared to a constant penetration speed controller. Outdoor soil sampling tests in a corn field (sandy loam soil, compaction between 0.8 and 2 MPa) demonstrated a 94% success rate on flat terrain and a sampling duration under one minute.