# Correction Strategy of Online Midcourse Guidance for High-Speed Gliding Target Interceptor
## 4 Simulation Verification
### Simulation Scenario 1: Online Correction Algorithm for Single PIP  
The position coordinate of the PIP in the East-North-Up coordinate system is \([641572,50000,50000]\)m, the initial position coordinate of the mid-course guidance is \([94369,45000,0]\)m, the remaining flight time of the interceptor is 150 s, the initial speed of the interceptor is 3210 m/s, and the thrust of the orbit control engine on the interceptor is 30 kN. The correction ability of the interceptor against a single PIP under the initial inclination angle \(\vartheta_{0}=0,3,5,10,15,20\) deg is verified. Figures 9 and 10 demonstrate the changes in the interceptor's maneuvering trajectory and speed guided by the velocity gain, respectively. It can be seen from Figure 9 that, under the guidance of velocity gain, the interceptor trajectory is smooth, which belongs to the high-drop reentry trajectory. Table 1 shows that the PIP can be reached with high accuracy under different initial trajectory inclination angles. At the same time, in Figure 10, the change in the magnitude of the velocity gain shows a convergence trend. There is a  
Figure 8: The diagram illustrates the work content of this paper. The main objective of this paper is to correct the interceptor during the midcourse guidance stage, in order to more effectively cope with constantly updated PIPs while saving fuel as much as possible. The primary work is divided into two parts: Section 3.3 mainly addresses the issue of ensuring that the missile accurately reaches the final true PIP, while Section 3.4 aims to prevent frequent engine start-up and optimize the fuel consumption as much as possible in the context of PIP updates. certain fluctuation between 70 s and 100 s in Figure 10. This is caused by the interceptor's declining flight altitude and increased aerodynamic effects. Although some adjustments are necessary, they are minor. It is necessary to adjust the required velocity, but the adjustment is only a small amount. Therefore, it can be concluded that the guidance of velocity gain effectively resolves the aforementioned issue. Simulation Scenario 2: The Online Correction Effect of the Designed Correction Algorithm for Multiple PIP Updates  
Firstly, the staged threshold setting method is not adopted, and the starting threshold of the whole engine is \(\varepsilon=20\) m/s. In the simulation, the update period of the PIP is set to 5 s, and a total of 30 updates occur in 150 s. The 3-fold variance of the PIP distribution at the initial instant is 10 km, which means \(3\sigma_{x}=3\sigma_{y}=3\sigma_{z}=10\) km. With the interceptor flying, the PIP converges to the real PIP in the error domain \([641572,50000,5000]\), and the initial inclination angle \(\phi_{0}=0,3,5,10,15,20\) deg is verified. It can be seen from Figure 11 that the trajectory of the interceptor conforms to the trajectory characteristics of high throw-reentry, and the blue points are PIPs for the update \begin{table}
\begin{tabular}{c c c} \hline
**Initial Inclination Angle \((\theta_{0}\)/deg)** & **Guidance Error (km)** & **Working Time of Engine (s)** \\ \hline
0 & 0.0066 & 53.57 \\ \hline
3 & 0.0051 & 48.49 \\ \hline
5 & 0.0038 & 45.99 \\ \hline
10 & 0.0046 & 42.49 \\ \hline
15 & 0.0081 & 43.52 \\ \hline
20 & 0.0182 & 48.69 \\ \hline
25 & 0.0014 & 56.80 \\ \hline \end{tabular}
\end{table} 
Table 1: Guidance error and starting time under different initial inclination angles. Figure 10: Change in the speed gain under different initial inclination angles. Figure 9: Trajectory under different initial inclination angles. process, red points are the final PIPs. However, the interceptor still flies to the final PIP after correction. The overall correction trajectory is relatively smooth, and there is no large-scale trajectory change. The final miss distance is 0.633 km, and the continuous start-up time of the engine is 62.28 s. It can be seen from Figures 11 and 12 that the velocity gain guidance method can complete the midcourse guidance interception task.