## 3 Results and Analysis of the Ground Test
### Performance Test of the Orthographic Stabilization Platform
#### 3.1.2 Test Method and Results of the Stability Accuracy  
The test of stability accuracy is achieved through optical path bending and an inclinometer scheme. The optical path turning test is designed with a two-axis manual swing table and a photoelectric bending device--that is, a 45\({}^{\circ}\) flat mirror is placed below the lens, the monitored target directly below it is converted into the target directly in front by bending the light path (Figure 3). The swing table is shaken with a swinging range and a swinging period, and the trajectory data of the target in front is recorded and imaged in the camera. Its peak is then taken as the stable accuracy. On 8 September 2020, after setting up the optical path bending test conditions, different swing conditions were applied to the manual swing device. The test results are shown in Table 3. When the swinging period is 20 s and the amplitude is \(\pm\)15 \({}^{\circ}\), the stability accuracy  
Figure 2: Schematic diagram of stable accuracy calculation principle. \(a\) is the coverage distance, \(L\) is the target distance, \(\alpha_{targ}\) is the FOV angle, and \(\beta\) is the stable accuracy threshold. is the best, only \(\pm 0.04^{\circ}\). When the swinging period is 15 s and the amplitude is \(\pm 15^{\circ}\), the stability accuracy is \(\pm 0.045^{\circ}\). When the swinging period is 7 s and the amplitude is \(\pm 10^{\circ}\), the stability accuracy is \(\pm 0.05^{\circ}\). All results are better than the calculated stability accuracy threshold of 0.535\({}^{\circ}\) mentioned above, which indicates that the stability accuracy test on ground under simulated airborne conditions meets the usage requirements. The inclinometer scheme involves installing an inclinometer on the inner frame. When the swinging table shakes, the inclinometer data is collected and analyzed. This scheme is easy to operate. However, due to the poor performance of the inclinometer in dynamic environments, the inclinometer can only maintain accuracy in a stationary environment. When the equipment has high stability, the inclinometer on the stable surface is approximately in a stationary environment. At this time, the credibility of the test data is high, otherwise the data error is large. In general, the inclinometer scheme is a mutually influencing scheme. In the case of poor test results, the actual indicators of the equipment may not necessarily be worse than the test results. However, if the test results meet the requirements of the indicators, the actual indicators of the equipment must exceed the required indicators. On 8 September 2020, the load was equipped with an inclinometer and the manual swing device was subjected to the same swing conditions as the optical path bending test. The test results are shown in Table 3. When the swinging period is 20 s and the amplitude is \(\pm 15^{\circ}\), the stability accuracy is the best, only \(\pm 0.035^{\circ}\). When the swinging period is 15 s and the amplitude is \(\pm 15^{\circ}\), the stability accuracy is \(\pm 0.042^{\circ}\). When the swinging period is 7 s and the amplitude is \(\pm 10^{\circ}\), the stability accuracy is \(\pm 0.045^{\circ}\). All results are better than  
Figure 3: Layout diagram of the testing environment for the orthographic stabilization platform. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{2}{c}{**Swing Conditions**} & \multicolumn{2}{c}{**Stability Accuracy**} \\ \hline
**Swinging Period** & **Amplitude** & **Optical Path Bending Test** & **Inclinometer Scheme** \\ \hline
20 s & \(\pm 15^{\circ}\) & \(\pm 0.04^{\circ}\) & \(\pm 0.035^{\circ}\) \\
15 s & \(\pm 15^{\circ}\) & \(\pm 0.045^{\circ}\) & \(\pm 0.042^{\circ}\) \\
7 s & \(\pm 10^{\circ}\) & \(\pm 0.05^{\circ}\) & \(\pm 0.047^{\circ}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Stability accuracy test results of the orthographic stabilization platform. the results from optical path bending test, also indicating that its stability accuracy met the requirements of the usage conditions.