## 5 Conclusions  
This study was conducted to develop an automated manual transmission for agricultural tractors. Shuttle shifting and clutch actuators, which are of the electric type, were designed for the automation \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \begin{tabular}{c} **Shifting** \\ **Condition** \\ \end{tabular} & \begin{tabular}{c} **Range Shift** \\ \end{tabular} & \begin{tabular}{c} **Driving Shift** \\ \end{tabular} & \begin{tabular}{c} **Total Duration** \\ **Time (s)** \\ \end{tabular} & \
\begin{tabular}{c} **RPM Reaching** \\ **Time (s)** \\ \end{tabular} &
\begin{tabular}{c} **Transmission RPM** \\ **(rpm)** \\ \end{tabular} \\ \hline \multirow{8}{*}{Neutral} & \multirow{3}{*}{2 nd} & 1 st & 2.40 \(\pm\) 0.04 & 2.63 \(\pm\) 0.05 & 66.3 \(\pm\) 0.05 \\ \cline{3-6}  & & 2 nd & 2.35 \(\pm\) 0.05 & 2.59 \(\pm\) 0.04 & 79.1 \(\pm\) 0.10 \\ \cline{3-6}  & & 3 rd & 2.40 \(\pm\) 0.04 & 2.65 \(\pm\) 0.03 & 93.1 \(\pm\) 0.13 \\ \cline{3-6}  & & 4 th & 2.38 \(\pm\) 0.07 & 2.65 \(\pm\) 0.08 & 124.1 \(\pm\) 0.15 \\ \cline{3-6}  & & 1 st & 2.29 \(\pm\) 0.03 & 2.62 \(\pm\) 0.04 & 147.1 \(\pm\) 0.03 \\ \cline{3-6}  & & 2 nd & 2.36 \(\pm\) 0.03 & 2.69 \(\pm\) 0.03 & 174.0 \(\pm\) 0.20 \\ \cline{3-6}  & & 3 rd & 2.37 \(\pm\) 0.03 & 2.75 \(\pm\) 0.03 & 204.8 \(\pm\) 0.25 \\ \cline{3-6}  & & 4 th & 2.43 \(\pm\) 0.06 & 2.88 \(\pm\) 0.05 & 274.0 \(\pm\) 0.22 \\ \hline \multirow{8}{*}{Neutral} & \multirow{3}{*}{2 nd} & 1 st & 2.39 \(\pm\) 0.05 & 2.61 \(\pm\) 0.08 & 55.0 \(\pm\) 0.15 \\ \cline{3-6}  & & 2 nd & 2.33 \(\pm\) 0.06 & 2.55 \(\pm\) 0.06 & 65.0 \(\pm\) 0.10 \\ \cline{3-6}  & & 3 rd & 2.38 \(\pm\) 0.04 & 2.60 \(\pm\) 0.03 & 75.8 \(\pm\) 0.65 \\ \cline{3-6}  & & 4 th & 2.37 \(\pm\) 0.06 & 2.63 \(\pm\) 0.08 & 102.0 \(\pm\) 0.06 \\ \cline{3-6}  & & 1 st & 2.29 \(\pm\) 0.04 & 2.58 \(\pm\) 0.03 & 121.6 \(\pm\) 0.47 \\ \cline{3-6}  & & 2 nd & 2.36 \(\pm\) 0.03 & 2.63 \(\pm\) 0.03 & 143.6 \(\pm\) 0.32 \\ \cline{3-6}  & & 3 rd & 2.37 \(\pm\) 0.04 & 2.73 \(\pm\) 0.05 & 168.2 \(\pm\) 0.36 \\ \cline{3-6}  & & 4 th & 2.41 \(\pm\) 0.03 & 2.81 \(\pm\) 0.05 & 225.1 \(\pm\) 0.30 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Results of performance evaluation for automatic shuttle shifting control according to shifting conditions and each gear stage. Figure 14: Results of automatic shuttle shifting control (range shift: 3 rd, driving shift: 2 nd). of shuttle shift and clutch control. An AMT control system for the tractor was developed using TCU hardware and a PID controller. For the PID controller design, the PID coefficients were determined by using the Z-N method and simulation tests. An experimental test-bed for performance evaluation of the AMT was constructed using a tractor powertrain, clutch housing, a motor (instead of an engine), a three-phase inverter to control the motor speed, and two actuators. The experimental tests were conducted by shifting gear level. In order to evaluate the performance of the AMT for agricultural tractors, the transmission of the experimental test-bed was shifted from the neutral to forward and from neutral to reverse in all gear stages. The PID coefficient combination of \(\text{K}_{\text{P}}=1.45\), \(\text{K}_{\text{I}}=3.45\), and \(\text{K}_{\text{D}}=0.190\) was chosen because it showed low overshoot, settling time, and steady-state error. The results of the performance of the actuator position control indicated that the shuttle shifting actuator was controlled appropriately to achieve a maximum overshoot of less than 5%, settling time of less than 0.500 s, and steady-state error of less than 1%. In the case of the clutch actuator, it was controlled appropriately to achieve a maximum overshoot of less than 0%, settling time of less than 1.50 s, and steady-state error of less than 1%. The automatic F/R control performance showed a shift control time of less than 2.50 s and target RPM reaching time of less than 3.00 s under all conditions (i.e., gear stages and F/R).