A shift point optimization method for a multi-gear electromechanical composite transmission system

Abstract

The application discloses a kind of multi-gear electromechanical composite transmission system shift point optimization method, belong to the field of hybrid electric vehicle transmission.Selecting certain parallel plug-in hybrid electric vehicle with multi-gear electromechanical composite transmission system as research object, with vehicle speed, pedal opening, operating mode as control parameter, considering the influence of engine, motor dual power source and battery state of charge, on the basis of initial shift rule, with system working efficiency optimal as target, for pure electric mode EV, hybrid electric vehicle mode HEV, engine alone driving mode Eng, different mode under different pedal opening under shift speed of driving charging mode Chg, using the global optimization method of DIRECT to carry out offline optimization.Compared with other global optimization algorithms, the method can find the optimal solution in fewer iteration times, improve the calculation efficiency, thereby significantly improve the fuel economy of multi-gear hybrid electric vehicle.

Description

Technical Field

[0001] This invention relates to hybrid vehicle transmission technology, specifically to a method for optimizing shift points in a multi-speed electromechanical hybrid transmission system. Background Technology

[0002] Hybrid electric vehicles (HEVs), as an ideal product in the transition from traditional cars to pure electric vehicles, are significantly superior to traditional vehicles in terms of energy saving and power supply capabilities. This is primarily influenced by two factors: optimized energy management strategies and a rational shifting strategy to ensure the engine and motor operate within their high-efficiency range. The quality of this shifting strategy largely depends on the transmission system, also known as the electromechanical hybrid transmission system. Currently, the use of multi-speed integrated electromechanical hybrid transmission systems in plug-in hybrid electric vehicles (PHEVs) not only significantly improves driving performance but also energy efficiency, becoming a trend in hybrid vehicle development. Increasing the number of gears in the electromechanical hybrid transmission system of PHEVs makes the vehicle structure more compact, performs better, and is easier to control, while simultaneously allowing the engine and motor to operate within their high-efficiency range. Therefore, a rational shifting strategy is crucial for improving the overall vehicle's economy, power, and comfort.

[0003] Traditional shift control typically relies on static, offline shift tables for the power source, manually determined based on past experience or bench test calibration results. This method, employing extensive heuristic testing and adjustments to achieve optimal transmission control, is highly effective and robust, playing a crucial role in industrial implementation. However, this process is time-consuming and costly, often dependent on expert knowledge, and requires significant calibration work before being applied to real vehicles. Furthermore, it struggles to fully leverage the potential of integrated electromechanical hybrid powertrains to improve overall performance, leading to limitations in optimizing fuel economy and driving performance. For electromechanical hybrid powertrains integrating the motor and transmission, shifting requires identifying operating modes and ensuring smooth shifting. The entire process involves changes in operating modes and alterations in system state within a specific mode, resulting in typical coupling characteristics between the operating mode switching and shifting strategies of plug-in hybrid electric vehicles (PHEVs). This poses a challenge to developing shifting patterns for multi-gear hybrid systems. Summary of the Invention

[0004] The purpose of this invention is to improve the economy, power, and comfort of the entire vehicle. To this end, this invention proposes a method for optimizing the shift points of a multi-speed electromechanical hybrid transmission system. Addressing the need for a reasonable shifting strategy in a multi-speed parallel plug-in hybrid electric vehicle equipped with an integrated electromechanical hybrid transmission system, this invention takes optimal overall system efficiency and battery charge-discharge balance as its starting point. Based on the analysis of the efficiency models of each component, it establishes efficiency models under different operating modes and leverages the advantages of the DIRECT global optimization algorithm to propose an economical shifting strategy design method that couples energy management and shifting strategy. This improves the vehicle's fuel economy and provides a new approach to economical shifting strategies for plug-in hybrid electric vehicles based on an integrated electromechanical hybrid transmission system.

[0005] The technical solution adopted in this invention is a method for optimizing shift points in a multi-speed electromechanical composite transmission system, comprising: a vehicle demand torque module, a mode discrimination module, a torque distribution module, a system comprehensive efficiency calculation module for each mode, a module for determining economical shift rules for each mode, a DIRECT algorithm shift rule optimization module, and a gear decision module. The vehicle demand torque module analyzes the accelerator pedal opening and vehicle speed signals. The drive mode discrimination module determines whether the vehicle is in pure electric mode (EV), hybrid electric mode (HEV), engine-only drive mode (Eng), or driving-charging mode (Chg) based on the vehicle demand torque and battery SOC. The torque distribution module further calculates the output torque of each component based on the torque thresholds of different components and the vehicle operating mode signal determined by the mode discrimination module. The system comprehensive efficiency calculation module calculates the system comprehensive efficiency for each operating mode based on the torque distribution in each mode. By traversing the mechanical path gears, electric path gears, and accelerator pedal opening, initial economical shift rules for each mode are established. The DIRECT algorithm-optimized economic shifting pattern module corrects the initial economic shifting pattern using the DIRECT algorithm and outputs the optimized pattern to the gear selection decision module. The gear selection decision module then uses the optimized economic shifting pattern to switch gears between the mechanical and electric circuits in each mode.

[0006] Preferably, due to the presence of mixed gears in the multi-speed electromechanical composite transmission system, the transmission ratio of the mechanical circuit and the electric circuit in the whole vehicle torque demand module is related to the working mode and gear. At the same time, the torque output by the engine and the motor is coupled inside the gearbox. Therefore, the demand torque needs to be analyzed to the front end of the main reducer and converted into a function of vehicle speed and pedal opening.

[0007] Preferably, the input required by the drive mode determination module is the vehicle's required torque T. r Battery SOC, vehicle speed v, mechanical road speed ratio i ge And electric road speed ratio i gmThe vehicle's operating modes are divided into five modes: Pure Electric (EV), Hybrid Electric (HEV), Engine-Only Drive (Eng), Driving and Charging (Chg), and Braking Mode. Based on the required torque T... r The system determines whether the vehicle is in drive mode or braking mode, and divides the drive mode into charge consumption mode (CD) and charge maintenance mode (CS) based on the change in the state of charge (SOC) of the power battery.

[0008] Preferably, the torque distribution module, due to the presence of mixed gears in the multi-gear electromechanical composite transmission system, needs to consider the mechanical speed ratio i. ge And electric road speed ratio i gm The coupling characteristics of energy management and shifting strategy are achieved by using the torque thresholds of the engine and motor, as well as the difference between the engine's optimal fuel economy curve and the required torque.

[0009] Preferably, the system overall efficiency calculation module for each mode calculates the power flow of the multi-speed electromechanical hybrid transmission system under EV mode, HEV mode, Eng mode, and Chg mode. The overall efficiency of the vehicle system is defined as the ratio of system output power to input power. The efficiency under different modes is calculated based on the different power flow directions when the vehicle is running in different modes.

[0010] Preferably, the module for determining the economic shifting pattern for each mode obtains the shifting speed by traversing the gears and solving for the intersection of the overall system efficiency of adjacent gears in each mode. Simultaneously, it traverses the pedal opening to obtain the shifting speed at different pedal openings, thus determining the pedal opening-up shifting pattern curve for different modes. An equal-delay downshifting strategy is adopted, using a downshifting speed difference of 6 km / h to obtain the downshifting pattern. The shifting pattern curve is then corrected based on simulation results to determine the initial economical upshifting and downshifting pattern.

[0011] Preferably, optimizing the economical gear shifting pattern based on the DIRECT global optimal algorithm includes the following steps:

[0012] (1) Determine the topology and working mode of the multi-speed electromechanical composite transmission system, and establish the torque distribution of the engine and motor under the vehicle driving mode;

[0013] (2) Determine the hybrid vehicle working mode judgment method of the mode discrimination module based on the accelerator pedal and vehicle speed signal, and transmit the determined vehicle driving mode signal to the torque distribution module;

[0014] (3) Establish a comprehensive efficiency model of the system under each working mode based on the working torque distributed by the engine and motor;

[0015] (4) Traverse the gears and pedal openings, solve for the intersection of the system's overall efficiency curves in adjacent gears, and obtain the initial shifting and upshifting rules;

[0016] (5) An equal-delay downshifting strategy is adopted, and the downshifting pattern is obtained with a downshifting speed difference of 6 km / h. The shifting pattern curve is corrected according to the simulation results to obtain the initial economic upshifting and downshifting pattern.

[0017] (6) Based on the economic shifting pattern, the shifting speed of adjacent gears under different modes and pedal openings is used as the optimization variable, with the goal of optimizing system efficiency. The upshift and downshifting thresholds of the initial shifting pattern are used as constraints for each optimization variable under different pedal openings, and an objective function is established. The constraints include the speed and torque limits of different power sources such as the engine and motor, the threshold of the shifting speed under the initial economic shifting pattern, and the working current and voltage limits of the battery;

[0018] (7) The DIRECT method is used to perform optimization within the feasible region to obtain the speed range for reasonable gear operation and further update the economical gear shifting law;

[0019] Preferably, in step (7), the shift speed under different modes and pedal openings is used as the optimization variable, and the difference in efficiency before and after shifting is optimized with the goal of maximizing system efficiency. At the same time, the optimization process must limit the engine, motor and other components to their physical constraints. In order to improve the optimization efficiency, the optimal economic shift curves under each mode are used as the upper and lower limits of the constraints of each optimization variable under different pedal openings.

[0020] Preferably, the shift decision module takes engine speed ratio, motor speed ratio, mode, and vehicle speed as inputs. It first converts the mechanical speed ratio and electric speed ratio into gears for each mode, then compares the current vehicle speed with the offline-defined shift speed, and gradually shifts up or down to achieve gear decision.

[0021] The beneficial effect of this invention lies in meeting the needs of a reasonable shifting strategy for multi-speed parallel plug-in hybrid electric vehicles equipped with an integrated electromechanical hybrid transmission system. Taking the optimization of overall system efficiency and battery charge-discharge balance as the starting point, an economical shifting point optimization method for multi-speed electromechanical hybrid transmission systems is proposed. Based on the analysis of the efficiency models of each component, by establishing efficiency models under different working modes, and combining the advantages of the DIRECT global optimization algorithm, an economical shifting strategy design method coupling energy management and shifting strategy is proposed to further improve the fuel economy of the vehicle. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the economical shift point optimization of a multi-speed electromechanical composite transmission system.

[0023] Figure 2 This is a schematic diagram illustrating the formulation of the economic shift pattern curve.

[0024] Figure 3 This is a diagram illustrating the shifting patterns in each mode;

[0025] Among them, (a) - pure electric mode, (b) - engine drive mode, (c) - hybrid mode, and (d) - driving and charging mode.

[0026] Figure 4 This is a schematic diagram of the topology of a multi-speed electromechanical composite transmission system.

[0027] Figure 5 This is a schematic diagram of the DIRECT algorithm optimization.

[0028] Figure 6 A diagram illustrating economical gear shifting decisions. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0030] Figure 1 This is a schematic diagram illustrating the economic shift point optimization proposed in this invention. The shift point optimization process includes: a vehicle torque demand module, a drive mode determination module, a torque distribution module, a system comprehensive efficiency calculation module for each mode, a module for determining the economic shift rules for each mode, a DIRECT algorithm shift rule optimization module, and a gear decision module.

[0031] Due to the presence of mixed gears in the multi-speed electromechanical hybrid transmission system, the transmission ratio of the mechanical and electric circuits in the vehicle's torque demand module is related to the operating mode and gear. Simultaneously, the torque output from the engine and motor is coupled within the transmission. Therefore, the required torque needs to be analyzed and routed to the front end of the final drive, and converted into a function of vehicle speed and pedal opening, expressed as:

[0032] (1);

[0033] (2);

[0034] (3);

[0035] In the formula, T final_in The input torque of the main reducer, T e T is the engine output torque. m T is the output torque of the motor. r For the torque required at the wheel end, i ge For the mechanical path speed ratio, i gm For the electric path speed ratio, i0 is the speed ratio of the main reducer, and n is the speed ratio of the electric path speed ratio. i Main reducer input shaft speed, T max (n i) represents the maximum torque value corresponding to the input shaft speed, acc represents the accelerator pedal opening, and f represents the maximum torque value corresponding to the input shaft speed. r (acc) is a monotonically increasing function with respect to the accelerator pedal opening, and satisfies: ;

[0036] This study will f r (acc) is taken as a linear relationship, that is: (4);

[0037] Based on the vehicle speed, mechanical path gear, and electric path gear, the input shaft speed of the main reducer can be determined as follows: (5);

[0038] In the formula, n i The main reducer input shaft speed, v is the vehicle speed, i gi These are the speed ratios of the mechanical and electric paths corresponding to the input shaft speeds, respectively. i0 is the speed ratio of the main reducer, and r is the wheel radius.

[0039] Substituting equation (5) into equation (4), we get: (6);

[0040] The input required by the drive mode determination module is the vehicle's required torque T. r Battery SOC, vehicle speed v, mechanical road speed ratio i ge And electric road speed ratio i gm The vehicle's operating modes are divided into five modes: Pure Electric (EV), Hybrid Electric (HEV), Engine-Only Drive (Eng), Driving and Charging (Chg), and Braking Mode. Based on the required torque T... r Determine whether the vehicle enters drive mode and braking mode, when the required torque T r When the torque is greater than zero, the mode determination module determines that the vehicle is operating in drive mode, and when the required torque T... r When the SOC is less than zero, the vehicle is determined to be operating in braking mode. Simultaneously, based on the change in the SOC of the power battery, the driving mode is divided into charge consumption mode (CD) and charge sustaining mode (CS). When the SOC is greater than zero... obj When the battery is in power consumption mode, and the SOC is less than or equal to the SOC, the battery will be in power consumption mode. obj At this time, the battery is in power maintenance mode.

[0041] To further illustrate the economical shift point method proposed in this invention, a plug-in hybrid electric vehicle based on a multi-speed electromechanical composite transmission system is taken as the research object. Its transmission system structure is as follows: Figure 4As shown, this configuration mainly consists of an engine, an electric motor, a single clutch, and an AMT (Automated Manual Transmission) gearbox arranged in P2.5. The engine and electric motor are connected to the AMT via two shafts, providing two independent torque transmission paths to the wheels: a mechanical path connected to the engine and an electric path connected to the motor. The motor remains connected to the output shaft at all times. This type of AMT achieves torque coupling while changing speed and torque, with alternating upshifts between the mechanical and electric gear paths, enabling continuous power output. (The last sentence appears to be incomplete and possibly refers to a specific configuration or feature.) Figure 4 The shift point optimization method used in the hybrid vehicle powertrain shown includes the following steps:

[0042] (1) Determine the topology of the multi-speed electromechanical composite transmission system, and solve for the output torque of other components based on the torque thresholds of different components and the vehicle operating mode signal determined by the mode discrimination module. Simultaneously, the mechanical speed ratio i needs to be considered. ge And electric road speed ratio i gm This achieves the coupling characteristics of energy management and shifting strategies, establishing the torque distribution between the engine and motor in vehicle drive mode as follows:

[0043] Table 1 shows the torque distribution strategy:

[0044] ;

[0045] Wherein, SOC > 0.3 indicates that the remaining battery charge is greater than 30%, SOC ≤ 0.3 indicates that the remaining battery charge is less than or equal to 30%, CD / CS-EV indicates the pure electric drive mode under energy consumption CD and energy maintenance mode CS, CD / CS-HEV indicates the hybrid drive mode under energy consumption CD and energy maintenance mode CS, CS-Eng indicates the pure engine drive mode under energy maintenance mode CS, CS-Chg indicates the driving charging mode under energy maintenance mode CS, Braking indicates the braking mode, T r For the torque required for vehicle drive, T mmax The maximum output torque of the motor, T emax For the engine's maximum output torque, T eopt To minimize engine fuel consumption, i is the optimal output torque. ge For the mechanical path speed ratio, i gm This is the speed ratio of the electric path.

[0046] (2) The system comprehensive efficiency calculation module for each mode calculates the system comprehensive efficiency under each working mode based on the torque distribution in each mode. By traversing the mechanical path gears, electric path gears, and pedal opening, the initial economic shifting rules for each mode are established. The process for establishing the economic shifting rule curve is as follows: Figure 2 And a diagram illustrating the shifting patterns in each mode, as shown below. Figure 3As shown. The system overall efficiency calculation module for each mode calculates the power flow based on the EV mode, HEV mode, Eng mode, and Chg mode, η. EV η HEV η Eng η Chg The efficiency figures are as follows: pure electric mode, hybrid mode, engine-only drive mode, and charging mode.

[0047] (7),

[0048] (8),

[0049] (9),

[0050] (10);

[0051] In the formula, P e For engine power, P m For motor power, η e For engine efficiency, η m_motor For the electric motor efficiency, η m_charge The charging efficiency of the motor is calculated or obtained from the operating points of the engine and motor, η. bat For battery charge and discharge efficiency, η T The efficiency of the transmission system is defined as 0.9.

[0052] (3) Traverse the gears and pedal openings, solve the intersection of the system comprehensive efficiency curves under adjacent gears, and obtain the initial shifting and upshifting rules; adopt the equal delay downshifting strategy, obtain the downshifting rules with a downshifting speed difference of 6km / h, and correct the shifting rules curves according to the simulation results to obtain the initial economic shifting rules.

[0053] (4) Based on the economical shifting pattern, the shifting speed of adjacent gears under different modes and pedal openings is used as the optimization variable, with the goal of optimizing the system's working efficiency. The upshifting and downshifting thresholds of the initial shifting pattern are used as constraints on each optimization variable under different pedal openings. The objective function is as follows:

[0054] (11),

[0055] (12);

[0056] In the formula, J is the objective function for optimizing system efficiency, and cost is... η For the cost function of efficiency, u i The shift point is where i represents pedal opening, j represents gear position, and P represents the shift point. bThe battery power is represented by EV / Eng / HEV, which respectively indicate pure electric drive, engine-only drive, and hybrid drive modes. Chg indicates the driving and charging mode. The combination of shift points in each mode reflects the speed range in which each gear operates. A reasonable speed range allows multi-gear parallel plug-in hybrid electric vehicles to operate in an efficient range.

[0057] The constraints include speed and torque limits for different power sources such as engines and motors, as well as battery operating current and voltage limits. Due to the large number of optimization variables, to reduce the computational load, quickly obtain the optimal solution, and improve optimization efficiency, the optimal economic upshift curves for each mode are used as the upper and lower limits of the constraints for each optimization variable under different pedal openings. The constraints are expressed as follows:

[0058] (13);

[0059] ω e For engine speed, ω m T is the motor speed. e T represents engine torque. m I is the motor torque. bat U is the battery's operating current. bat The operating voltage of the battery is indicated by the subscript "". ,min "" indicates the lower limit of the value, and the subscript "" indicates the lower limit of the value. ,max "" indicates the upper limit of the value.

[0060] (5) The DIRECT algorithm is used to perform optimization within the feasible region, such as... Figure 5 As shown, the values ​​of the shift points are normalized, thus transforming the variable space into an n-dimensional hypercube. First, the function value at the center point of the variable space is calculated. Then, the variable space is continuously divided, and the function values ​​at the center points of the divided subspaces are compared to obtain the local optimal efficiency value. Finally, the global optimal efficiency value is obtained, thereby determining the speed range for reasonable gear operation.

[0061] (6) Using engine speed ratio, motor speed ratio, mode, and vehicle speed as inputs, the mechanical and electric speed ratios are first converted into gears for each mode. Then, the current vehicle speed is compared with the offline shift speed, and gears are gradually shifted up or down to achieve gear selection. Figure 6 As shown.

[0062] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0063] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for optimizing shift points in a multi-speed electromechanical composite transmission system, characterized in that, include: The system includes a vehicle torque demand module, a drive mode determination module, a torque distribution module, a system comprehensive efficiency calculation module for each mode, a shift pattern determination module for each mode, a shift pattern optimization module using the DIRECT algorithm, and a gear decision module. The vehicle torque demand module analyzes the accelerator pedal opening and vehicle speed signals. The drive mode discrimination module divides the vehicle operation mode into 5 modes based on the input. The torque distribution module further calculates the output torque of each component based on the torque threshold of different components and the vehicle working mode signal determined by the mode discrimination module. The system comprehensive efficiency calculation module calculates the system comprehensive efficiency of each working mode based on the torque distribution in each mode. By traversing the mechanical path gear, electric path gear, and accelerator pedal opening, the initial economic shifting rules for each mode are established. The DIRECT algorithm optimization economic shifting rule module corrects the initial economic shifting rules through the DIRECT algorithm and outputs the optimized economic shifting rules to the gear decision module. The gear decision module realizes the gear switching between mechanical and electric paths in each mode based on the optimized economic shifting rules. The initial economical shifting pattern is corrected using the DIRECT algorithm, and the optimized economical shifting pattern is output to the gear decision module, including the following steps: (1) Determine the topology and working mode of the multi-speed electromechanical composite transmission system, and establish the torque distribution of the engine and motor under the vehicle driving mode; (2) Determine the hybrid vehicle working mode judgment method of the mode discrimination module based on the accelerator pedal and vehicle speed signal, and transmit the determined vehicle driving mode signal to the torque distribution module; (3) Establish a comprehensive efficiency model of the system under each working mode based on the working torque distributed by the engine and motor; (4) Traverse the gears and pedal openings, solve for the intersection of the system's overall efficiency curves in adjacent gears, and obtain the initial shifting and upshifting rules; (5) An equal-delay downshifting strategy is adopted, and the downshifting pattern is obtained with a downshifting speed difference of 6 km / h. The shifting pattern curve is corrected according to the simulation results to obtain the initial economic upshifting and downshifting pattern. (6) In view of the economic shifting pattern, the shifting speed of adjacent gears under different modes and pedal openings is used as the optimization variable, the system working efficiency is optimized as the goal, and the shifting threshold of the initial shifting pattern is used as the constraint condition for each optimization variable under different pedal openings. The objective function is established, and the constraint conditions include the speed and torque limits of different power sources of the engine and motor, the shifting speed threshold under the initial economic shifting pattern, and the working current and voltage limits of the battery. (7) The DIRECT method is used to optimize the solution within the feasible region, obtain the speed range of reasonable gear operation, and further update the economical gear shifting law.

2. The method according to claim 1, characterized in that, Due to the presence of mixed gears in the multi-speed electromechanical composite transmission system, the transmission ratio of the mechanical path and the electric path is related to the working mode and gear. At the same time, the torque output by the engine and the motor is coupled inside the gearbox. Therefore, the required torque needs to be analyzed to the front end of the main reducer and converted into a function of vehicle speed and pedal opening.

3. The method according to claim 1, characterized in that, The mode discrimination module determines the required torque T of the vehicle based on the input torque T. r Battery SOC, vehicle speed v, mechanical road speed ratio i ge And electric road speed ratio i gm The vehicle operating mode is divided into five modes: pure electric mode (EV), hybrid electric mode (HEV), engine-only drive mode (Eng), driving and charging mode (Chg), and braking mode; among them, the drive mode determination module is based on the vehicle's required torque T. r Determine whether the vehicle enters drive mode and braking mode, when the vehicle's required torque T r When the value is greater than 0, the vehicle enters the driving mode; when the total vehicle torque demand Tr is less than or equal to 0, the vehicle enters the braking mode; at the same time, the driving mode discrimination module divides the battery charge SOC into charge consumption mode CD and charge maintenance mode CS according to the change process of the battery charge SOC; among them, charge consumption mode CD is divided into CD-EV mode and CD-HEV mode, and charge consumption mode CS is divided into CS-EV mode, CS-HEV mode, CS-Eng mode and CS-Chg mode.

4. The method according to claim 1, characterized in that, Due to the presence of mixed gears in the multi-speed electromechanical composite transmission system, the torque distribution module needs to consider the mechanical speed ratio i. ge And electric road speed ratio i gm It achieves the coupling characteristics of energy management and shifting strategy by using the torque thresholds of the engine and motor, as well as the engine's optimal fuel economy curve and demand torque.

5. The method according to claim 1, characterized in that, The system comprehensive efficiency calculation module for each mode calculates the power flow of the multi-speed electromechanical composite transmission system under EV mode, HEV mode, Eng mode, and Chg mode. The definition of the overall efficiency of the vehicle system is: the ratio of system output power to input power. The efficiency of different modes is calculated based on the flow direction of different power flows when the vehicle is running in different modes.

6. The method according to claim 1, characterized in that, The module for determining the economic shifting rules for each mode obtains the shifting speed by traversing the gears and solving the intersection of the overall system efficiency of adjacent gears in each mode. At the same time, it traverses the pedal opening to obtain the shifting speed under different pedal openings, and formulates the pedal opening-up rule curve for different modes. It adopts an equal-delay downshifting strategy with a downshifting speed difference of 6 km / h to obtain the downshifting rule, and corrects the shifting rule curve based on the simulation results to formulate and obtain the initial economic upshifting and downshifting rules.

7. The method according to claim 1, characterized in that, The shift decision module takes engine speed ratio, motor speed ratio, mode, and vehicle speed as inputs. It first converts the mechanical and electric speed ratios into gears for each mode, then compares the current vehicle speed with the offline shift speed, and gradually shifts up or down to achieve gear decision.

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