## 4 Experiment and Analysis
### Mechanical Performance Test of the TRUMs  
In order to study the influence of high overload on the performance of TRUM, the mechanical performance test of the four TRUMs before and after high impact are carried out. Figure 14 shows the experimental setups. The driving voltage is generated by a function generator (AFG 3022B; Tektronix Inc., Beaverton, AL, USA) and amplified to 400 V\({}_{\text{P-P}}\) by two power amplifiers (HFVA-153; Foneng Technology Co., Ltd., Nanjing, China). The end of the test motor shaft is connected to a torque sensor (CYT-303; Tianyu Sensor Co., Ltd., Beijing, China), through which speed and output torque of the motor are measured. The results are finally displayed on the monitor of the data collector.  
Figure 14: Performance test setups for the TRUMs.  
\begin{table}
\begin{tabular}{c c c} \hline
**TRUM Number** & \
\begin{tabular}{c} **Plastic Deformation of the stator** \\ **Web (\(\upmu\)m)** \\ \end{tabular} &
\begin{tabular}{c} **Plastic Deformation of the Motor** \\ **Web (\(\upmu\)m)** \\ \end{tabular} \\ \hline TRUM-1 & 17 & 296 \\ TRUM-2 & 24 & 13 \\ TRUM-3 & 19 & 232 \\ TRUM-4 & 27 & 10 \\ \hline \end{tabular}
\end{table}
Table 3: Plastic deformation of the stator and rotor webs after high impact test (10,000 g).  
According to the mechanical performance data of each motor obtained from the experiment, the relationship between torque and speed is plotted, as shown in Figure 15.  
Comparing the TRUMs in group 1, TRUM-1 performs well before the high-impact test with the maximum speed reaching 280 rpm and the stalling torque 0.16 N\(\cdot\)m. However, after the high-impact test, the motor is damaged with no performance. For TRUM-2, the performance decreases after the impact test, the maximum speed decreases from 280 rpm to 270 rpm, and the stalling torque reduces from 0.25 N\(\cdot\)m to 0.21 N\(\cdot\)m. At the torque of 0.15 N\(\cdot\)m, the speed decreases about 21.3%. This performance is acceptable. Comparing this with TRUMs in group 2, the maximum speed of TRUM-3 reaches 285 rpm and the stalling torque is 0.3 N\(\cdot\)m. After the impact test, the motor performance drops severely. The maximum speed is 70 rpm and the speed drops rapidly to 0 until the torque is 0.15 N\(\cdot\)m. Among the four motors, TRUM-4 has the lowest performance degradation after impact. The maximum speed decreases from 288 rpm to 280 rpm, and the stalling torque reduces from 0.3 N\(\cdot\)m to 0.25 N\(\cdot\)m. At the torque of 0.15 N\(\cdot\)m, the speed decreases only 1.6%. The good performance of TRUM-4, indicating that the high acceleration of 10,000 g applied to this type of motor has little influence on its performance and the structure, means that it can be considered of high-overload resistance. Comprehensive analysis of the simulation and experimental results leads to the conclusion that the performance of the TRUMs with the disc spring is much less affected by the high overload than that without the disc spring, which indirectly proves that the disc spring applied to the structure of a TRUM acts as a good buffer and protects the motor from high overload.  
Figure 15: The TRUMs’ performance before and after high-impact test: (**a**) TRUM-**1**; (**b**) TRUM-**2**; (**c**) TRUM-**3**; (**d**) TRUM-**4**.