Method for acceleration process control for a hybrid electric vehicle

Abstract

This invention discloses an acceleration process control method for hybrid electric vehicles. It optimizes the critical points for switching control stages during the acceleration process of a hybrid electric vehicle, obtaining the optimal critical point of vehicle speed at the transition between the first and second stages under constraints of acceleration time, total fuel consumption during acceleration, and total pollutant emissions. Specifically, when constructing the solver model, the work done by the drive motor during acceleration is converted into fuel consumption and pollutant emissions generated under the steady-state power generation condition of the engine, thereby calculating the total fuel consumption and total pollutant emissions during acceleration. In the actual complete solution process, given input parameters such as acceleration time, the optimal solution for total fuel consumption and total pollutant emissions can be obtained by adjusting the critical vehicle speed. This invention enables the acceleration process control of hybrid electric vehicles to better meet energy conservation and emission reduction requirements while ensuring sufficient acceleration time.

Description

Technical Field

[0001] This invention relates to the field of hybrid vehicle technology, and more particularly to an acceleration process control method for hybrid electric vehicles. Background Technology

[0002] For the acceleration process control of plug-in hybrid electric vehicles, the acceleration process can generally be divided into two stages. In the first stage, the drive motor drives the vehicle from a standstill to a certain speed. When this speed is reached, the second stage begins, in which the engine participates in the acceleration process. The engine and drive motor work together to drive the acceleration, which ends when the preset speed limit for the acceleration process is reached.

[0003] The drive motor of a hybrid electric vehicle uses electrical energy from an onboard energy storage device (battery) as input and converts it into mechanical energy as output. The engine uses the thermal energy (or internal energy) of fuel as input and converts it into mechanical energy as output. The electrical energy in the onboard energy storage device can be obtained from a charging station or generated by the hybrid electric vehicle's engine through an onboard generator, converting the internal energy of the fuel.

[0004] Existing acceleration control strategies prioritize minimizing acceleration time. When the vehicle speed reaches the engine's idle speed, the engine engages in acceleration, and the entire acceleration process is completed according to the power output characteristics of the engine and drive motor. In other words, existing technologies only consider completing the acceleration process in the shortest possible time, without considering energy efficiency or emissions during acceleration. Both engine-driven acceleration and the drive motor's use of electricity converted from engine energy can yield specific fuel consumption (g / kWh). Calculations show that neither drive mode is fuel-efficient under all operating conditions, nor does it consistently meet emission standards. Summary of the Invention

[0005] In view of the above, the present invention aims to provide an acceleration process control method for hybrid electric vehicles to solve the aforementioned technical problems.

[0006] The technical solution adopted in this invention is as follows:

[0007] This invention provides a method for acceleration process control of a hybrid electric vehicle, comprising:

[0008] A calculation model for motor fuel consumption is established when a hybrid electric vehicle uses generators to generate electricity and converts it into the output mechanical energy of a drive motor to propel the vehicle.

[0009] Establish a calculation model for engine fuel consumption during the entire acceleration and driving process;

[0010] Establish a calculation model for the motor pollutant emissions during the acceleration process of the drive motor;

[0011] Establish a calculation model for engine pollutant emissions during engine acceleration;

[0012] Define the starting speed, ending speed, acceleration time, and critical speed for the acceleration process used as input, whereby the acceleration time characterizes the total time of the acceleration process.

[0013] A solver is constructed based on the motor fuel consumption calculation model, the engine fuel consumption calculation model, the motor pollutant emission calculation model, the engine pollutant emission calculation model, and the preset vehicle kinematics model, and the starting vehicle speed, the ending vehicle speed, the acceleration time, and the critical vehicle speed are used as inputs to the solver.

[0014] After the initial vehicle speed, the final vehicle speed, and the acceleration time are given to the solver, different critical vehicle speeds are input, and the solver calculates the corresponding motor fuel consumption, engine fuel consumption, motor pollutant emissions, and engine pollutant emissions.

[0015] The total fuel consumption is calculated using the motor fuel consumption and the engine fuel consumption; the total pollutant emissions are calculated using the motor pollutant emissions and the engine pollutant emissions.

[0016] Based on the total pollutant emissions and the total fuel consumption, corresponding change curves are fitted; the intersection of the two curves is the optimal solution, and the critical speed corresponding to the optimal solution is the target critical speed point.

[0017] During vehicle acceleration, the target critical speed point is used to switch between different stages of control.

[0018] In at least one possible implementation, the engine fuel consumption calculation model includes:

[0019] ;

[0020] Among them, Q e P represents the engine's fuel consumption during the entire acceleration and driving process. x q represents the power output of the engine during acceleration. ex (n,P x ( ) is the engine speed n and output power P x The corresponding fuel consumption value at that time.

[0021] In at least one possible implementation, the motor pollutant emission calculation model includes:

[0022] ;

[0023] in, This refers to the amount of pollutants emitted during the acceleration process of the drive motor. The pollutant emissions under steady-state operating conditions of the engine generating electricity; This refers to the power output of the drive motor. This refers to the output power of the engine under steady-state operating conditions. The generator's operating efficiency when the engine is generating electricity under steady-state conditions; The efficiency of the power battery when it outputs electrical energy; The efficiency of the drive motor when outputting power at a certain operating point, and It is a dynamic change associated with the operating point of the drive motor during the acceleration process, and is obtained by interpolation based on the drive motor efficiency MAP.

[0024] In at least one possible implementation, the engine pollutant emission calculation model includes:

[0025] ;

[0026] in, H represents the concentration of pollutants emitted when the engine is running; H represents the volume of exhaust gas emitted per engine revolution; and n represents the engine speed.

[0027] In at least one of the possible implementations, the acceleration time is related to the maximum output power of the vehicle's powertrain.

[0028] In at least one possible implementation, the vehicle kinematic model includes:

[0029] ;

[0030] ;

[0031] ;

[0032] Where f0, f1, and f2 are the coasting drag coefficients; Px is the engine output power; P M denoted as _n_, where n is the output power of the drive motor; _n_, where n is the speed of the drive wheels; _R_, where R is the tire radius; _m_, where m is the total mass of the vehicle; and _a_, where a is the acceleration.

[0033] In at least one possible implementation, fitting the corresponding change curve includes: fitting the change curves of the total pollutant emissions and the total fuel consumption value with preset weights, wherein the weights are used to characterize whether the solution tends to be low in emissions or low in fuel consumption when seeking the optimal solution.

[0034] The main design concept of this invention lies in optimizing the critical point for switching between control stages during the acceleration process of a hybrid electric vehicle. Under constraints of acceleration time, total fuel consumption during acceleration, and total pollutant emissions during acceleration, the optimal critical point for the vehicle speed at the transition between the first and second stages is obtained. Specifically, when constructing the solver model, the work done by the drive motor during acceleration is converted into fuel consumption and pollutant emissions generated under the steady-state power generation condition of the engine, thereby calculating the total fuel consumption and total pollutant emissions during acceleration. In the actual complete solution process, given input parameters such as acceleration time, the optimal solution for the total fuel consumption and total pollutant emissions during acceleration can be obtained by adjusting the critical vehicle speed. This invention enables the acceleration process control of hybrid electric vehicles to better meet energy conservation and emission reduction requirements while ensuring sufficient acceleration time.

[0035] Furthermore, the present invention preferably introduces weight allocation in the calculation of the optimal solution, providing optional control factors for setting the optimal solution, that is, the optimal solution can be made more inclined towards low fuel consumption or more inclined towards low emissions as needed. Attached Figure Description

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings, wherein:

[0037] Figure 1 A flowchart of an acceleration process control method for a hybrid electric vehicle provided in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the topology of the solver provided in an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the dual variation curves provided in an embodiment of the present invention. Detailed Implementation

[0040] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0041] Before proceeding with the following embodiments of the present invention, it should be emphasized that the scenario addressed by the present invention is the acceleration and driving process under full throttle and full powertrain load conditions, without considering power distribution, and both the drive motor and the engine output maximum external characteristic power. Furthermore, for ease of explanation, the present invention assumes that the efficiency of the power battery's output energy remains constant during a single acceleration process (i.e., temperature remains constant, and SOC changes are minimal).

[0042] Furthermore, the universal characteristics of the engine involved in this invention are common knowledge in the field, as shown in the table below:

[0043]

[0044] In this table, column 1 represents engine speed, column 2 represents engine output power, column 3 represents engine fuel consumption rate, and column 4 represents the concentration of nitrogen oxides, CO, sulfides, etc., emitted by the engine. Based on the data in the table, a MAP chart of engine specific fuel consumption and an MAP chart of engine emissions can be generated.

[0045] Similarly, the universal characteristics of drive motors are common knowledge, and a table of universal characteristic parameters for drive motors can be pre-constructed. The first row of this table represents the speed of the drive motor, the first column represents the output torque of the drive motor, and the cells at the intersection of the row and column represent the corresponding energy conversion efficiency of the drive motor (conversion of electrical energy into mechanical energy). A MAP diagram of the motor can be generated based on the table of universal characteristic parameters of the drive motor.

[0046] Furthermore, as those skilled in the art will understand, during the discharge process of a power battery, there will be energy efficiency loss due to the internal resistance of the battery cell itself. This invention simplifies this problem by considering the heat consumption during the discharge process of the power battery as the efficiency loss. The internal resistance of the power battery cell has a corresponding relationship under different temperatures and different SOC values, which will not be elaborated upon in this invention.

[0047] Based on the above, this invention proposes an embodiment of an acceleration process control method for hybrid electric vehicles, specifically, as follows: Figure 1 As shown, it includes:

[0048] Step S1: Set up a calculation model for the motor fuel consumption of a hybrid electric vehicle when the motor generates electricity and converts it into the output mechanical energy of the drive motor to drive the vehicle.

[0049] Step S2: Set up a calculation model for engine fuel consumption during the entire acceleration process. It should be noted that the engine fuel consumption during the entire acceleration process can be calculated by multiplying the fuel consumption value by the power and integrating over time, as illustrated in the following formula:

[0050] ;

[0051] Q e P represents the engine's fuel consumption during the entire acceleration and driving process; x This represents the power output of the engine during acceleration (this value is a continuously changing dynamic value); q ex (n,P x () represents the engine speed n and output power P. x The corresponding specific fuel consumption value is obtained from the preset engine specific fuel consumption MAP map by interpolation (as described above).

[0052] Step S3: Set up a calculation model for the motor pollutant emissions during acceleration; the model can be referenced as follows:

[0053] ;

[0054] in, This represents the amount of pollutants emitted during the acceleration process of the drive motor (i.e., this mechanical energy is provided by the engine generating electricity, and pollutants are emitted during the engine generating electricity). This represents the pollutant emissions under steady-state operating conditions when the engine is generating electricity (which can be converted to L / kW). This represents the power output of the drive motor; This represents the output power of the engine under steady-state operating conditions. This represents the generator's operating efficiency when the engine is generating electricity under steady-state conditions. This represents the efficiency of the power battery when it outputs electrical energy, and is related to the battery's SOC value and ambient temperature. This represents the efficiency of the drive motor when it outputs power at a certain operating point. The operating point of the drive motor changes dynamically throughout the acceleration process. It is also changing dynamically. In actual operation, the efficiency MAP of the drive motor (as mentioned above) can be obtained by interpolation.

[0055] Integrating the result obtained from the power conversion relationship over time yields the pollutant emissions generated by the motor's output mechanical energy during the entire acceleration process.

[0056] Step S4: Set up a calculation model for engine pollutant emissions during acceleration; the model can be referenced as follows:

[0057] ;

[0058] in, The pollutant emission concentration represents the concentration of pollutants emitted when the engine is running. It can be obtained by interpolation from the engine emission MAP chart based on the engine speed n and power P. H represents the volume of exhaust gas emitted per engine revolution. n represents the engine speed. The method involves calculating the volume of pollutants emitted per unit time based on the exhaust gas volume, engine speed, and pollutant emission concentration. Integrating this value over time yields the pollutant emission amount when the engine is running continuously.

[0059] Step S5: Define the starting vehicle speed V0 and the ending vehicle speed V during the acceleration process. t Acceleration time and critical speed are V x (i.e., the vehicle speed at the boundary between the first and second stages), the acceleration time represents the total time of the acceleration process;

[0060] This is set based on the performance requirements of the vehicle itself. For example, the starting speed is set to 0 km / h, the ending speed to 80 km / h, and the acceleration time to 12 seconds. The acceleration time setting must be reasonable to ensure that the maximum output power of the powertrain is sufficient. Otherwise, if an unrealistically fast acceleration time is set, the existing powertrain will not be able to meet the requirements, and the powertrain components will need to be reselected.

[0061] Vehicle speed between V0 and V x In the first stage, acceleration is achieved solely by the drive motor; in V x -V t The second stage involves acceleration driven by both the engine and the drive motor.

[0062] Step S6: Based on the motor fuel consumption calculation model, the engine fuel consumption calculation model, the motor pollutant emission calculation model, the engine pollutant emission calculation model, and the preset vehicle kinematics model, construct as follows: Figure 2 The solver shown takes the initial vehicle speed, the final vehicle speed, the acceleration time, and the critical vehicle speed as inputs to the solver.

[0063] It should be noted here that the preset vehicle kinematics model includes the following:

[0064] ;

[0065] ;

[0066] ;

[0067] Where f0, f1, and f2 are the coasting drag coefficients; Px represents the engine output power; P Mrepresents the output power of the drive motor; n represents the speed of the drive wheels; R represents the tire radius; m represents the total mass of the vehicle; a represents the acceleration, and the vehicle speed is the integral of acceleration a over time.

[0068] Step S7: After giving the initial vehicle speed, the final vehicle speed and the acceleration time to the solver, input different critical vehicle speeds, and the solver calculates the corresponding motor fuel consumption, engine fuel consumption, motor pollutant emissions and engine pollutant emissions.

[0069] Step S8: Calculate the total fuel consumption using the motor fuel consumption and the engine fuel consumption; calculate the total pollutant emissions using the motor pollutant emissions and the engine pollutant emissions.

[0070] In other words, by inputting different critical vehicle speeds into the solver (i.e., changing the initial engine speed at which acceleration is engaged), the solver calculates the total pollutant emissions Exh = Exh at different critical vehicle speeds.

[0071] e +Exh M Total fuel consumption Q = Q e +Q M .

[0072] Step S9: Fit the corresponding change curves based on the total pollutant emissions and the total fuel consumption; wherein, the intersection of the two curves is the optimal solution, and the critical speed corresponding to the optimal solution is the target critical speed point;

[0073] Figure 3 The fitted curve and optimal solution are shown. A key characteristic of this curve is that the two constraints—total fuel consumption and total pollutant emissions during acceleration—have opposite monotonicity. Therefore, it can be understood that the horizontal axis of the curve represents several critical speeds, and the vertical axis represents total pollutant emissions and total fuel consumption. Total pollutant emissions (Exh) decrease as the critical speed increases (because the engine's involvement time during acceleration shortens), while total fuel consumption (Q) increases with increasing critical speed because the energy loss from acceleration driven entirely by the drive motor is greater. Furthermore, as the critical speed increases, the engine's involvement time during acceleration decreases, resulting in less power output from the powertrain throughout the acceleration process. Consequently, the acceleration value decreases, affecting the acceleration time constraint. Therefore, while multiple critical speeds can be set, they cannot be increased indefinitely.

[0074] In practice, after calculating several total pollutant emissions Exh and total fuel consumption values ​​Q using a solver, it is preferable to fit the aforementioned two change curves with preset weights. The weights are used to characterize whether the solution tends to be low in emissions or low in fuel consumption when seeking the optimal solution.

[0075] Step S10: During vehicle acceleration, different stages of control are switched using the target critical speed point.

[0076] In summary, the main design concept of this invention lies in optimizing the critical point for switching between control stages during the acceleration process of a hybrid electric vehicle. Under constraints of acceleration time, total fuel consumption during acceleration, and total pollutant emissions during acceleration, the optimal critical point for the vehicle speed at the transition between the first and second stages is obtained. Specifically, when constructing the solver model, the work done by the drive motor during acceleration is converted into fuel consumption and pollutant emissions generated under the steady-state power generation condition of the engine, thereby calculating the total fuel consumption and total pollutant emissions during acceleration. In the actual complete solution process, given input parameters such as acceleration time, the optimal solution for the total fuel consumption and total pollutant emissions during acceleration can be obtained by adjusting the critical vehicle speed. This invention enables the acceleration process control of hybrid electric vehicles to better meet energy conservation and emission reduction requirements while ensuring sufficient acceleration time.

[0077] In this embodiment of the invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, A and B simultaneously, or B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0078] The above description of the structure, features, and effects of the present invention is based on the embodiments shown in the figures. However, the above are only preferred embodiments of the present invention. It should be noted that the technical features involved in the above embodiments and their preferred methods can be reasonably combined and matched by those skilled in the art to form a variety of equivalent solutions without departing from or changing the design concept and technical effects of the present invention. Therefore, the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A method for acceleration process control in a hybrid electric vehicle, characterized in that, include: A calculation model for motor fuel consumption is established when a hybrid electric vehicle uses generators to generate electricity and converts it into the output mechanical energy of a drive motor to propel the vehicle. Establish a calculation model for engine fuel consumption during the entire acceleration and driving process; Establish a calculation model for the motor pollutant emissions during the acceleration process of the drive motor; Establish a calculation model for engine pollutant emissions during engine acceleration; Define the starting speed, ending speed, acceleration time, and critical speed for the acceleration process used as input, whereby the acceleration time characterizes the total time of the acceleration process. A solver is constructed based on the motor fuel consumption calculation model, the engine fuel consumption calculation model, the motor pollutant emission calculation model, the engine pollutant emission calculation model, and the preset vehicle kinematics model, and the starting vehicle speed, the ending vehicle speed, the acceleration time, and the critical vehicle speed are used as inputs to the solver. After the initial vehicle speed, the final vehicle speed, and the acceleration time are given to the solver, different critical vehicle speeds are input, and the solver calculates the corresponding motor fuel consumption, engine fuel consumption, motor pollutant emissions, and engine pollutant emissions. The total fuel consumption value is calculated using the motor fuel consumption and the engine fuel consumption. The total pollutant emissions are calculated using the pollutant emissions from the electric motor and the pollutant emissions from the engine. Based on the total pollutant emissions and the total fuel consumption, corresponding change curves are fitted; the intersection of the two curves is the optimal solution, and the critical speed corresponding to the optimal solution is the target critical speed point. During vehicle acceleration, the target critical speed point is used to switch between different stages of control.

2. The acceleration process control method for a hybrid electric vehicle according to claim 1, characterized in that, The engine fuel consumption calculation model includes: ； Among them, Q e P represents the engine's fuel consumption during the entire acceleration and driving process. x q represents the power output of the engine during acceleration. ex (n,P x ( ) is the engine speed n and output power P x The corresponding fuel consumption value at that time.

3. The acceleration process control method for a hybrid electric vehicle according to claim 1, characterized in that, The calculation model for motor pollutant emissions includes: ； in, This refers to the amount of pollutants emitted during the acceleration process of the drive motor. The pollutant emissions under steady-state operating conditions of the engine generating electricity; This refers to the power output of the drive motor. This refers to the output power of the engine under steady-state operating conditions. The generator's operating efficiency when the engine is generating electricity under steady-state conditions; The efficiency of the power battery when it outputs electrical energy; The efficiency of the drive motor when outputting power at a certain operating point, and It is a dynamic change associated with the operating point of the drive motor during the acceleration process, and is obtained by interpolation based on the drive motor efficiency MAP.

4. The acceleration process control method for a hybrid electric vehicle according to claim 1, characterized in that, The engine pollutant emission calculation model includes: ； in, H represents the concentration of pollutants emitted when the engine is running; H represents the volume of exhaust gas emitted per engine revolution; and n represents the engine speed.

5. The acceleration process control method for a hybrid electric vehicle according to claim 1, characterized in that, The acceleration time is related to the maximum output power of the vehicle's powertrain.

6. The acceleration process control method for a hybrid electric vehicle according to any one of claims 1 to 5, characterized in that, The fitting of the corresponding change curves includes: fitting the change curves of the total pollutant emissions and the total fuel consumption value with preset weights, wherein the weights are used to characterize whether the solution tends to be low in emissions or low in fuel consumption when seeking the optimal solution.

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