## 5 Simulations Results and Analysis
### Results of Switch Control Strategy
#### 5.2.1 J-Turn Maneuver
The spring mass, vehicle speed, and suspension damping were used as the internal uncertain disturbance of the system. Taking the working conditions in Figure 13 as the initial conditions without disturbance, and the road disturbance signal is shown in Figure 15, which is imposed on the left tire. It can be seen from Figure 15, two road disturbances are imposed on the system respectively, and disturbance-2 is more serve than disturbance-1. On the one hand, the acceleration curves of the three conditions are roughly similar in the aspects of amplitude and trend in Figure 16a. On the other hand, the roll angle curves in Figure 16b show almost no difference compared with the initial system without disturbance. In other words, the ride comfort and the stability are stable, and the suspension system has excellent immunity to external disturbances. Taking into account the typical non-linear characteristics of the suspension system, the following three parameters of the suspension system, unspring mass, damping, and vehicle speed, are used as internal uncertainties to validate the system robustness. The corresponding simulation results are shown from Figures 17-19. Figure 16: The robustness simulation curves with the road disturbance: (**a**) the vehicle body vertical acceleration in time domain; (**b**) the roll angle acceleration in time domain. Figure 15: The road disturbance imposed on the system. The systems with three different unspring masses are compared in Figure 17. The black curve represents the initial condition with a sprung mass of 1525 kg, and the red and blue curves represent an increase and decrease of 20% of the sprung mass on the basis of the initial condition, respectively. As shown in Figure 16a, the differences between the three curves are small both in terms of trend and  
Figure 19: The robustness simulation curves with the uncertainty of vehicle speed: (**a**) the vehicle body vertical acceleration in time domain; (**b**) the roll angle acceleration in time domain. Figure 17: The robustness simulation curves with uncertainty of unspring mass: (**a**) the vehicle body vertical acceleration in time domain; (**b**) the roll angle acceleration in time domain. Figure 18: The robustness simulation curves with the uncertainty of suspension damping: (**a**) the vehicle body vertical acceleration in time domain; (**b**) the roll angle acceleration in time domain. amplitude. The roll angle curves in Figure 17b show that the trends of the three conditions are basically the same, and the amplitude is slightly different. As shown in Figure 18, the red and blue curves represent an increase and decrease of 20% of the damping comparing to the black curve of the initial condition, respectively. Obviously, changes in suspension damping in this range have almost no effect on the acceleration and roll angle of the vehicle system. As a result, the suspension system in this paper has a good anti-interference ability to the parameter uncertainty of suspension damping. Figure 19 shows the impact of vehicle speed changes on the suspension system. The vehicle speed under the initial condition is 70 km/h, which is the maximum speed of the rescue vehicle in this paper. Therefore, reducing vehicle speed by 20% and 30%, respectively, was used to verify the interference caused by the uncertainties of vehicle speed on the system. As can be seen from the two diagrams in Figure 19, the system has a strong anti-interference ability to vehicle speed uncertainty. As a result, it can be seen from the above simulation results and analysis that the suspension system has strong ability to resist the disturbances, which were caused by both the external uncertainty and parametric uncertainty. In other words, the suspension system of the rescue vehicle built in this paper has good stability and robustness.