# Optimization of Mode-Switching Quality of Hybrid Tractor Equipped with HMCVT
## 3 Optimization of Control Policy for Driver Source Switching
### SimulationX and Matlab/Simulink Interact Analysis  
SimulationX software can co-simulate with Matlab/simulink software through TCP/IP protocol [24]. The schematic diagram of interact is shown in Figure 12.  
SimulationX 3.5 and Matlab/Simulink 2018a software are used for interact. When starting the simulation, Simulink should be started first, and S-Function should wait for ITI SimulationX to start calculation. When the pure electric mode is switched to the speed-coupling mode, the control strategy of \"clutch oil pressure fuzzy control + motor torque compensation\" is not implemented, as shown in Figure 13. According to Formula (8), the velocity reduction of the output shaft is 21.875%. After the control strategy is added, the speed reduction of the output shaft is 18.755%. The results show that the control strategy reduces the velocity drop by 3.12%. The pure electric mode is switched to the speed-coupling mode when it is not coordinated, as shown in Figure 14. The maximum output torque of the output shaft is 847.29 N-m, and the dynamic load coefficient of the output shaft is 8.473, according to Formula (9). After the control strategy is implemented, the maximum output torque of the output shaft is 757.29 N-m, and the corresponding dynamic load coefficient is 7.573. The results show that the dynamic load coefficient of the output shaft decreases from 8.473 to 7.573 after the control strategy is implemented, and the optimization effect of the control strategy for the dynamic load coefficient of the output shaft is 10.622%. Figure 12: Interact diagram. Figure 13: Simulation and comparison of the output shaft velocity drop amplitude. The whole simulation time was set to 30 s; 20 s was used as the just-in-time switching point; and the three levels were 0.5 s in advance, 0.5 s in time switching, and 0.5 s in delay switching of each clutch. Output shaft velocity drop, dynamic load coefficient of output shaft, impact strength, and switching time were used as evaluation indexes I, II, III, and IV, respectively. Using L\({}_{27}\)(3\({}^{\circ}\)) orthogonal table to arrange the simulation, a total of 27 simulations needed to be completed, and MINITAB was used for range analysis [26]. The analysis results of the velocity drop amplitude of the output shaft by the range method are shown in Figure 16, where R represents the range value. The analysis results show that the switching sequence of clutch C6 had the greatest influence on the velocity drop amplitude of the output shaft, and the switching sequence of clutch C7 had the least influence. The optimal scheme was E\({}_{1}\)C\({}_{3}\)A\({}_{2}\)D\({}_{3}\)B\({}_{1}\)F\({}_{3}\). From the point of view of the range value, clutches C6, C3, C0, and C4 played a major role, and clutches C2 and C7 played a certain role. Therefore, the combination of E\({}_{1}\)C\({}_{3}\)A\({}_{2}\)D\({}_{3}\) can meet most of the working conditions, and the speed reduction can be reduced from 18.755% to 1.217%, which indicates that the gear shift without speed fluctuation can be achieved at a certain time. The analysis results of the dynamic load coefficient of the output shaft by the range method are shown in Figure 17, where R represents the range value. The analysis results show that the switching time sequence of clutch C6 had the greatest influence on the dynamic load coefficient of output shaft, and the switching time sequence of clutch C2 had the least influence. The optimal scheme was E\({}_{1}\)C\({}_{3}\)D\({}_{3}\)F\({}_{2}\)A\({}_{3}\)B\({}_{3}\). From the point of view of the range value, clutches C6, C3, C4, and C7 played a major role, and clutches C0 and C2 played a certain role. Therefore, the combination of E\({}_{1}\)C\({}_{3}\)D\({}_{3}\)F\({}_{2}\) can meet most of the working conditions, and the dynamic load coefficient can be reduced from 7.573 to 2.715. The impact strength analysis results of the range method on the output shaft are shown in Figure 18, where R represents the range value.