Design and testing of a precision seeding device for aerial sowing of pelleted forest seeds from a UAV

Aerial sowing of forest seeds using unmanned aerial vehicles (UAVs) is an effective method for rapid and inexpensive reforestation, which is particularly relevant in the face of modern environmental challenges. A review of research and technical equipment in this field revealed that domestically produced sowing device for UAVs capable of precisely sowing pelleted forest seeds and incorporating them into the surface soil layer are currently lacking. The objective of this study is to develop and test a precision sowing device for aerial sowing of pelleted forest seeds from a UAV, as well as to study its operating modes to determine the parameters for effective seed placement. The research materials and methods include 3D modeling of the sowing device geometry using computer-aided design (CAD) systems. The modeling is performed using the discrete element method (DEM), representing the soil as spherical particles of varying degrees of cohesion and the indenter as a solid sphere with specified physical properties (mass, position, velocity, force). Particle interaction is described by a contact model with a spring and damper. Impact interaction occurs at indenter velocities of 25, 50, and 75 m/s with cohesionless, moderately cohesive, and cohesive soils. A laboratory experiment is conducted on cohesionless soils at an indenter speed of 75 m/s. The results showed that, according to the 3D model, the mass of the sowing device was 1140 g, while the mass of the manufactured experimental sample was 1074 g. DEM modeling revealed that indenter penetration was observed only in cohesionless soils at speeds of 75 m/s. However, a speed of 25 m/s was sufficient to prevent the indenter from being ejected from the resulting crater. In the case of moderately cohesive and cohesive soils, only minor lateral coverage of the indenter by soil particles or its presence on the surface within the formed depression was observed. Experimental verification revealed several discrepancies with the modeling data: the penetration depth in the modeling was 17.5 mm, while in the laboratory experiment it was 24.6 mm. Moreover, the average diameter of the formed craters in the upper part was, conversely, larger for the modeling data and amounted to 53.5 mm, while for the experimental data it was 19.3 mm. To reduce discrepancies in the future, it is necessary to modify the model taking into account the influence of moisture, particle size distribution and bulk density of natural soils.