## 5 Simulation Results and Analysis
### Gear Shift Performance Analysis  
The simulation conditions used in this study are shown in Figure 20. In the shift process of 01-11, the sign of the shift start was that the driven end of CL2 began to generate rotary velocity (when the rotary velocity was not zero). According to the rotary velocity curves of the active and driven ends of CL2, given in Figure 21, the starting time of shifting was 10.38 s. To better analyze the dynamic change law of each variable in the shift process, an interval of 10-12 s was selected for display and analysis. Figure 22 shows the shift simulation results, from 01-11, when the gear shift coordinated control strategy, based on the common PID control algorithm, was used to regulate the motor rotary velocity. It can be seen in Figure 22a that the time from the generation of rotary velocity at the driven end of CL2 to the complete equality of the rotary velocities at the active and driven ends of CL2 was 0.42 s (10.38 s to 10.80 s). At the same time, the initial oil pressure of CL2 was established during the process of EM1, regulating the rotary velocity of the driven end of CL2. As shown in Figure 22b, before shifting (before 10.38 s), EM2 independently output torque to drive the vehicle. At 10.38 s, EM1 started and output torque. The torque presented a trend of first increasing and then decreasing, and there was a certain degree of fluctuation, which was mainly due to the instability of the PID control algorithm. The dynamic response effect of the PID controller is unstable, mainly  
Figure 19: Comparison of different control algorithms. Figure 20: Simulation conditions. because it does not have the ability to adaptively adjust the control parameters. It is worth noting that, in the EM1 rotary velocity regulation stage, CL2 was not engaged. Thus, the torque fluctuation of EM1 would not cause a disturbance in the driving of the vehicle. For CL2, the torque changed to \(-20\) Nm, mainly because CL2 had the initial oil pressure in its empty stroke stage, which led to a certain friction torque. When CL2 reached the sliding friction stage, the friction torque further increased to \(-40\) Nm. After the shift, the torque of EM1 could be transmitted to the input shaft of the gearbox, reducing the torque of EM2. However, the sum of the torques of EM1 and EM2 was basically the same as that of EM2 driven alone before the shift. Figure 22c shows that the output torque of the gearbox was always positive, and there was no power interruption during the shift process. Figure 22d shows that, under the gear shift coordinated control strategy, based on the PID control algorithm, during the whole shift process, the maximum value of jerk was \(1.46\) m/s\({}^{3}\), and the slipping friction work, generated by CL2, was \(1017\) J. Figure 23 shows the results when the gear shift coordinated control strategy proposed in this study, based on the PID-bang-bang-fuzzy compound intelligent algorithm, was used to regulate the rotary velocity of EM1, and the shift process from \(01\) to \(11\) was simulated. It can be seen, in Figure 23a, that the time from the generation of rotary velocity at the driven end of the CL2 to the complete equality of the rotary velocities at the active and driven ends of CL2 was \(0.27\) s (\(10.38\) s to \(10.65\) s). Meanwhile, the initial oil pressure of CL2 was established during the process of EM1, regulating the rotary velocity of the driven end of CL2, which showed that the coordinated control strategy of the EM1 rotary velocity and CL2 oil pressure had a significant control effect. It can be seen, from Figure 23b, that the torque variation law of the power source and CL2 was consistent with Figure 22b. The difference was that the output torque of EM1 steadily increased in the rotary velocity regulation stage, which was mainly due to the stable control effect of the PID-bang-bang-fuzzy intelligent control algorithm.