## 2 Configuration and Working Principles of Novel HEV  
This study considered a novel HEV as the research object. A schematic of its configuration is shown in Figure 1, and the main parameters of the vehicle are listed in Table 1. The power sources of the novel HEV included an internal combustion engine (ICE), electric motor 1 (EM1), and electric motor 2 (EM2). A gearbox with three gear pairs was used as the power coupling and power transfer device. Three wet clutches, namely clutch 1 (CL1), clutch 2 (CL2), and clutch 3 (CL3), and a synchronizer (SY) were used as the executive parts for speed ratio switching (mode switching). None of the three wet clutches had the function of driving the vehicle to start by sliding. This study focused on the control of motor and shift actuator (wet clutch) in the powertrain system. Meanwhile, the dynamic coordinated control strategy, for various mechanisms during the shift process, was equally concerned.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Component** & **Item** & **Value/Unit** \\ \hline \multirow{5}{*}{Vehicle} & Vehicle mass & 1545 kg \\  & Wheel radius & 0.347 m \\  & Drag coefficient & 0.36 \\  & Rolling resistance coefficient & 0.008 \\  & Windward area & 2.638 m2 \\ \hline \multirow{3}{*}{ICE} & Maximum power & 110 kW \\  & Maximum torque & 210 Nm \\  & Operating speed range & 700–5500 rpm \\ \hline \multirow{3}{*}{EM1} & Peak torque & 160 Nm \\  & Peak power & 55 kW \\  & Peak speed & 6200 rpm \\ \hline \multirow{3}{*}{EM2} & Peak torque & 155 Nm \\  & peak power & 70 kW \\  & Peak speed & 12,000 rpm \\ \hline \multirow{3}{*}{Gearbox} & First gear ratio & 2.03 \\  & Second gear ratio & 1.1 \\  & Three gear ratio & 0.63 \\ \hline Main reducer & Gear ratio & 3.9 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Main parameters of novel HEV.  
Figure 1: Schematic of structure of novel HEV.  
An analysis of the structure and working principle of the novel HEV shows that, in the steady-state mode, each power source in the power system had two working states of running and stopping, and each shift actuator (wet clutch and synchronizer) in the transmission system had two working states of engagement and disengagement. Cooperation between the power source and shift actuator caused the gearbox system of the novel HEV to have nine working modes of combined gears, as listed in Table 2, where ID represents the engaged gear(s), regardless of the power flow. It is worth noting that, for the novel hybrid power system proposed in this manuscript, the shift execution components that affect the power transmission path of the gear include the CL2, the CL3, and the synchronizer. The CL1 only determines whether the vehicle works in a pure electric working mode or a hybrid working mode. Therefore, from the perspective of gear analysis, the working state of the CL1 doesn't need to be taken into consideration.  
From the perspective of the control of the powertrain system for an HEV, in order to improve the smoothness, comfort, and power performance of the shift process, it is necessary to focus on solving the control problem of motor active rotary velocity regulation to assist in the clutch engagement and the problem of dynamically coordinating the control of multiple mechanisms in the powertrain system. Therefore, this study considered the 01-11 shift process as a typical shift scheme.