## 4 Simulation Results and Discussion  
The purpose of this paper is to combine the innovation of variable-swept configuration and the ADSC method so as to achieve the plunge-dive and trans-media locomotion of HAUVs. In this section, means of simulations are conducted and results are presented to illustrate the effectiveness of the ADSC for the longitudinal model of the variable-swept HAUV based on RBF. As for the geometrics of the HAUV, in order to achieve research objectives and simplify the paper's work content, there is no influence that makes the model parameters and aerodynamic coefficients during the variable-swept process the same as [30]. The simulation design parameter values in Section 3 are given as \(v_{o}=100\) m/s, \(\alpha_{o}=0\), and the other parameters are listed in Table 1.  
The maneuverability of the bird-like HAUV entering water has been analyzed in Section 2.1, which is also a prominent advantage of using the oblique water-entry method to achieve trans-media locomotion. In order to verify the effectiveness of the ADSC controller for the HAUV oblique water-entry process, this paper tested three different flight-path angle changes. According to the sequence of the variable sweepback adjustments and plunge-dive actions, two HAUV oblique entry-water cases have been formed. One is to perform a variable sweep during the plunge-dive process after completing the max  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Variable** & **Numerical Value** & **Variable** & **Numerical Value** \\ \hline \(\Delta_{1}\) & \(\left\{ \begin{array}{l}0.001\sin(\frac{\pi}{6}t),t\leq 20\\ 0.2\sin(\frac{\pi}{6}t),t>20\end{array} \right.\) & \(\Delta_{2}\) & \(\left\{\begin{array}{l}0.001\cos(\frac{\pi}{6}t),t\leq 20\\ 0.5\cos(\  
adjustment process of the flight-path angle; the second is to complete the variable-swept process fully during the level flight in the air, followed by plunge-diving. This section further analyzes the control performance of the controller under different water ingress strategies through two sets of simulations. At the same time, in order to simulate the process of HAUV ingressing the water more closely to the actual situation, the disturbance term is designed as the parameters shown in Table 1. The start time of water contact is 20 s, and after the dive begins, the disturbance rapidly increases and changes. _Case 1: During plunge-diving, complete the change in variable sweepback fully and then ingress the water._  
The relationship between ideal flight-path angle and sweepback over time are as follows:  
\[x_{1d}= \begin{cases}0^{\circ}&t\leq 5\\ -\gamma_{\epsilon}\sin(\frac{\pi}{10}t-\frac{\pi}{2})&5<t\leq 10\text{ and } \chi=\begin{cases}\frac{\pi}{12}&t\leq 11\\ \frac{\pi}{6}\lg(t-10)+\frac{\pi}{2}&11<t\leq 20\\ \frac{\pi}{4}&t>20\end{cases}\end{cases}  \tag{57}\]  
where \(\gamma_{\epsilon}=\frac{\pi}{12},\frac{\pi}{6},\frac{\pi}{4}\). Figure 5 shows the trajectory tracking results of the HAUV with a variable-sweep configuration during the water-entry process. The three subgraphs in Figure 5 all have upper and lower parts, where the upper half represents the tracking trajectory of the flight-path angle, and the lower half represents the tracking error of the control algorithm. Conduct simulation tests on three different flight-path angle change rates. From the simulation results above, it can be conducted that the overall trend is roughly the same for the three change rates. Within the initial 5 s, there is a trajectory error between the flight-path angle \(x_{1}\) and the ideal flight-path angle \(x_{1d}\), which gradually decreases to a certain small range. As the flight-path angle begins to change after 5 s, the controller's tracking of the ideal trajectory undergoes jittering. However, when the process of changing the flight-path angle is completed after 10 s, the tracking error gradually decreases and remains within the absolute value of 0.25\({}^{\circ}\).