# Analysis and Assessment of a Brushless DC Outrunner Motor for Agriculture Drones Using JMAG
## 4 Results and Discussion
### Implementation  
The implementation of the selected propulsion system is shown in Figure 27 with the conditions imposed in Table 12. The vehicle was flown in autonomous mode after defining a trajectory characteristic of agriculture applications (Figure 28). The peak power consumed corresponds to take-off (Figure 29): demanding up to 22% more power than the rest of the trajectory. From Figure 30, it is in the turning points that the rest of the local maximum power demands occur. In order to examine the agricultural UAV trajectory, points one and four were subjected to analysis, representing take-off and the maximum power consumption state immediately after. Assuming equal conditions for all six motors, Table 13 presents the results and simulation inputs for take-off. A DT6236B digital tachometer was used in the static thrust tests to obtain the required simulation speed for the angular velocity definition on the rotor in JMAG. Additionally, the coupled motor-propeller system via the motor shaft transfers the mechanical power from the motor to the propeller; thus, the torque and mechanical power from the CFD analysis and electromagnetic analysis are compared in Table 13, showing a maximum variation of 3.5% from the manufacturer's data. The motor torque and phase currents from JMAG are shown in Figures 31 and 32, respectively. Figure 28: Trajectory for autonomous flight mode emulating an agriculture application. Figure 29: Power consumption evolution throughout the imposed trajectory. The simulation inputs, experimental electrical measurements, and numerical results corresponding to point four are presented in Table 14. The overall efficiency of the motor-propeller combination goes down to 7.075 g/W, while the mechanical power between the manufacturer's data, the propeller simulation, and electromagnetic analysis of the BLDC motor results in a maximum variation of 5.4%. In the context of multi-rotor UAVs for agriculture applications, these deviations represent a subtle contribution to the overall performance of the vehicle. From Figures 29 and 30, it is clear that the larger effective propeller area and high inertia of the drone reduce the need for high dynamics and pronounced accelerations even in complex scenarios such as agriculture application trajectories, whereas in small multi-rotors, the reduced propeller area and high thrust-to-weight ratios entail a higher dependency on motor and propeller dynamics. The torque ripple amplitude result of the magnetic configuration is observed in Figure 33.  
The qualitative comparison between numerical and experimental currents and voltages is introduced in Figures 34 and 35. The amplitude of the square waveform shows good agreement. Figure 36 shows the current evolution for a hover autonomy test with the parameters defined in Table 15. The current draw between translational flight and hover presents a maximum variation of 5.2 A at any time instant after take-off, reaching 11.6 min of flight time. \begin{table}
\begin{tabular}{l c c c} \hline \hline  & **Propeller** & \multicolumn{2}{c}{**Motor**} \\ \hline
**Parameter** & \multicolumn{2}{c}{**Simulation**} & \multicolumn{2}{c}{**Experimental**} \\ \hline Speed & 2548 rpm & 2548 rpm & 2548 rpm \\ Thrust & 51.26 N & - & - \\ Torque & 2.092 Nm & 1.95 Nm & 1.93 Nm \\ Phase current RMS & - & 22.6 A & 21.4 A \\ Bus current & - & 11.2 A & 11.2 A \\ Mechanical power & 542.71 W & 520.29 W & 514.9 W \\ Efficiency & 9.31 g/W & 76\% & - \\ \hline Overall efficiency & \multicolumn{2}{c}{7.075 g/W} & - \\ \hline \hline \end{tabular}
\end{table} 
Table 14: Motor–propeller conditions and results for point four in the specified trajectory. Figure 33: Motor torque from JMAG corresponding to point four conditions.