## 3 Results and Discussion
### Rotary Tillage Cycle  
Rotary tillage is another common working condition of tractors with medium tractive work and heavy power demand. The traction resistance, tractor speed, and PTO power were measured in the previous field rotary tillage, as shown in Figure 15.  
In rotary tillage operation, tractors overcome traction resistance to maintain their forward speed while providing stable output power for the power take-off (PTO), thus maintaining an approximately constant speed which requires two motors in a DICPS to drive independently, one of which provides the power required for DMET driving, and the other providing the power demand of the PTO. When rotary tillage is carried out, the PTO needs more power, so the PTO should be connected to the high-power motor. When PDR = 0.2-0.5, PTO is connected to EM_R, and when PDR = 0.5-0.8, PTO is connected  
Figure 14: Overall efficiency comparison under plowing cycle. Figure 13: Working points of EM_T in SMPS. to EM_S. This section mainly studied the effects of different PDR and k values and PTO connection locations (connected to EM_S or EM_R) on the efficiency performance of the DICPS under a rotary tillage cycle. The overall efficiency at the end of the rotary tillage cycle for different PDR and k values is shown in Table 5. With the increase in k, the overall efficiency showed a decreasing trend, as it did under the ploughing cycle. As can be seen from Table 5, when the PTO was connected to EM_R, the overall efficiency decreased with the increase in PDR, and the overall efficiency had the same trend as PTO, connecting to EM_S. The maximum efficiency of the system occurred at PDR = 0.2. The reason for this trend is that with the increase of PDR, \(i_{s}\) decreased and \(i_{r}\) increased (as shown in Table 3). A smaller \(i_{s}\) makes EM_S work in the low-speed and high-torque region, and a larger \(i_{r}\) makes EM_R work in the high-speed and low-torque region. Both motors deviate from the high-efficiency region. However, even for the worst-case (PDR = 0.8, \(k\) = 3.6) of the DICPS, the efficiency was still much higher than the best case of the SMPS. When a tractor is working in rotary tillage, the power demand of the driving wheels is small and stable and the overall efficiency is mainly affected by the motor connected to the PTO. Therefore, this section mainly comprised a comparative study of the working points of the PTO motor with different PDR values. Figure 16a-c shows the working points of EM_S and EM_R with different PDR values under a rotary tillage cycle. Figure 16a shows the working point distribution of the motors when PDR was 0.8 or 0.2, and it can be seen that when PTO was connected to EM_R (PDR = 0.2), more working points were located in a higher efficiency region. When PTO was connected to EM_S, with the decrease in PDR, the working points of the motor shifted to the high-speed and low-torque area and gradually to the high-efficiency region; when PTO was connected to EM_R, with the increase in PDR, the working points of the motor were further away from the high-efficiency region, as shown in Figure 16b,c. Figure 15: Rotary tillage cycle for an agricultural tractor. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **PDR = 0.2** & **PDR = 0.35** & **PDR = 0.5** & **PDR = 0.5** & **PDR = 0.65** & **PDR = 0.8** \\ \hline \(k\) = 1.6 & 86.1 & 84.2 & 82.8 & 85.8 & 85.2 & 84.3 \\ \(k\) = 3.6 & 82.7 & 82 & \(\times\) & 80.8 & 79.9 & 79.2 \\ \(k\) = 5.6 & 81.8 & 80.9 & \(\times\) & \(\times\) & \(\times\) & \(\times\) \\ \(k\) = 7.6 & 81.4 & 80.2 & \(\times\) & \(\times\) & \(\times\) & \(\times\) \\ \hline \hline \end{tabular} \(\times\) indicates that the motors cannot meet the power demand.  
\end{table} 
Table 5: The overall efficiency of rotary tillage cycle.