# Simulation of Sowing Precision in Laboratory Conditions
## 2 Materials and Methods
### Tests under Laboratory Conditions  
The determination of souring precision under laboratory conditions was made by means of a fully automated stand, which ensured testing conditions for all types of precision planter row units, consisting of the following components:  
1. A frame with the possibility of simulating the slope of the terrain between 0-11\({}^{\circ}\);
2. Two 5.5 kW variable speed motors: the first being used to drive the row units with an individual transmission, and the second for driving the seed meters of the row units with a centralized transmission, both being able to simulate working speeds between 2 and 12 km\(\cdot\)h\({}^{-1}\);
3. Three SICK laser transducers, model FLG2-20025011, with a response time of <0.1 ms and a detection surface of 250 mm\(\times\)200 mm. Their role was to measure and transform \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Plot** & **Soil Fractions, (mm)** & **Weight of Soil Fraction, (kg)** & \(G_{ms}\)**, (\%)** & \(SD\)**, (\%)** \\ \hline \multirow{4}{*}{P1} & \(>\)100 & 1.67 & 0.96 & 0.62 \\  & 50–100 & 37.00 & 21.22 & 3.58 \\  & 20–50 & 68.40 & 39.23 & 2.61 \\  & \(<\)20 & 67.30 & 38.60 & 2.98 \\  & **Sample total weight** & **174.37** & & \\  & \(>\)100 & - & - & \\  & 50–100 & 19.90 & 10.86 & 0.28 \\  & 20–50 & 82.90 & 45.23 & 2.03 \\  & \(<\)20 & 80.47 & 43.91 & 2.86 \\  & **Sample total weight** & **183.27** & & \\  & \(>\)100 & 4.40 & 2.29 & 1.43 \\  & 50–100 & 45.47 & 23.65 & 2.11 \\ P3 & 20–50 & 81.17 & 42.22 & 7.77 \\  & \(<\)20 & 61.23 & 31.85 & 12.30 \\  & **Sample total weight** & **192.27** & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Degree of soil grinding. the fall time interval between two seeds in space (multiplying the fall time by the forward speed) which, then, was compared with the reference space between the seeds in the row;
4. A vacuum generator that could create a maximum depression of 5883 Pa (depression measured by means of a Prandtl-Pitot tube), the nominal speed being 4000 rev-min\({}^{-1}\);
5. A control panel with an operating terminal that processed the data received from the laser transducers and controlled the speed of the two electric motors. Figure 7 shows the basic scheme of the stand for determining the sowing precision. To simulate, in the laboratory, the real operating conditions corresponding to the three plots where the sowing work was carried out, the drums and rubber bands, provided with two rows of holes in the contact area between them and compaction wheels with zero pressure tires, were mounted on the stand to determine the sowing precision. PCB accelerometers (model 356B10) were mounted on the row units (on the SO row unit in the horizontal direction, on the SV row unit in the vertical direction, and on the BV row unit, on its support bar, in the vertical direction) and the seed meters were connected to the centralized transmission of the stand to determine the sowing precision. Rubber hemispheres, with diameters ranging from \(\Phi\) 30 to 100 mm, were randomly mounted on the rubber belt, until the power spectrum of the vibrations measured on the row units resembled the one measured in the field, when the belt was driven with speeds corresponding to the travel speeds of 4, 6, and 8 km\(\cdot\)h\({}^{-1}\) (Figure 8). Figure 8: Seed meter drive belt provided with rubber hemispheres: (1) hemispheres with \(\Phi\) 100 mm; (2) hemispheres with \(\Phi\) 80 mm; (3) hemispheres with \(\Phi\) 50 mm; and (4) hemispheres with \(\Phi\) 30 mm. Figure 7: The basic scheme of the stand for determining the sowing precision: (1) frame; (2) depression hose; (3) operating terminal; (4) individual transmission row unit; (5) rubber belt; (6) electric motor driving the individual transmission row unit; (7) electric motor for driving the centralized transmission row units; (8) seed meter drive shaft; (9) laser transducer; (10) centralized transmission row unit; and (11) support legs (adjustable).