A method for optimizing control of instantaneous efficiency of a P4 configuration hybrid vehicle during driving

Abstract

The application provides a P4 configuration hybrid vehicle driving charging instantaneous efficiency optimal control method, and aims to solve the problem of energy secondary conversion and additional power loss caused by using the traditional engine optimal control thought. The control method comprises the following steps: S1, discrete vehicle speed and driver demand torque; S2, establishing a power distribution relationship; S3, solving the working point instantaneous charging efficiency, that is, establishing an optimization objective function; S4, extracting the driving charging instantaneous efficiency optimal map and curve; S5, driving charging instantaneous efficiency optimal control. The application breaks through the traditional engine optimal control thought, realizes the highest instantaneous energy utilization efficiency of the power system of the whole vehicle in the driving charging mode, simultaneously does not need prior conditions as input, has the real-time performance required by the actual controller application, can fully exert the multi-mode advantages of the P4 configuration hybrid vehicle, and improves the driving economy of the P4 configuration hybrid vehicle.

Description

Technical Field

[0001] This invention relates to the field of hybrid vehicle control, and specifically to a method for optimizing the instantaneous charging efficiency of a P4 configuration hybrid vehicle. Background Technology

[0002] With the increasing number of hybrid vehicles entering the market, hybrid vehicles, due to their diverse operating modes, have a stronger adaptability to various operating conditions than traditional gasoline vehicles. Among the different hybrid configurations, the P4 configuration hybrid vehicle has a more complex structure compared to the mainstream P2 configuration. Its rear-wheel electric drive system in the powertrain is coupled with the traditional engine power in a timely manner, providing all-wheel drive. This makes the P4 configuration hybrid commercial vehicle more adaptable and capable of handling complex and rough roads, exhibiting a more significant driving advantage under harsh operating conditions. The driving modes of the P4 configuration hybrid vehicle mainly include pure electric drive, engine direct drive, driving-charging, and combined drive. The switching between these four modes depends on the current state of the vehicle. Traditional control strategies employ the idea of ​​optimal engine control, which uses dynamic compensation and peak shaving by the drive motor to stably control the engine operating point near the optimal curve. Therefore, when the vehicle's required torque is below the engine's optimal curve, the vehicle operates in driving-charging mode. While this ensures optimal engine fuel consumption at the current moment, the charging process involves secondary energy conversion, which may actually reduce the overall energy utilization efficiency of the vehicle. Therefore, research on the optimal control method for instantaneous charging efficiency of P4 configuration hybrid vehicles is beneficial to ensuring the highest comprehensive energy utilization rate of the power system in the vehicle charging mode, thereby improving the overall vehicle economy.

[0003] In existing technologies, such as the invention patent published on January 15, 2021 (Publication No.: CN112224210A), "Dynamic Adjustment Method for Driving Charging Power of Planetary Hybrid Vehicle and Vehicle," this patent provides a solution for adjusting the driving charging power of planetary hybrid vehicles. However, due to significant differences between different hybrid system configurations and the fact that this method is based on the control concept of constant battery state, it cannot guarantee the best energy utilization effect of the entire vehicle. Therefore, it is not applicable to the problem of optimal driving charging efficiency for P4 configurations. Another example is the invention patent published on April 29, 2015 (Publication No.: CN104578267A), "A Driving Charging System for Pure Electric Vehicles." This patent describes a charging system only for pure electric vehicles charging while parked, not for driving charging modes. Furthermore, the innovation of this invention mainly includes hardware facilities such as charging equipment and charging lines, but does not include software aspects such as control algorithms. In summary, there are currently no existing technologies that can achieve optimal instantaneous efficiency of the power system in driving charging mode for P4 configuration hybrid vehicles. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention presents a method for optimal instantaneous charging efficiency control based on P4 hybrid vehicles. This method involves traversing the feasible regions of vehicle speed, driver-demanded torque, and drive motor load rate to extract and form an optimal instantaneous charging efficiency map and curve. When the driver-demanded torque is lower than the optimal instantaneous charging efficiency curve, the vehicle enters a charging drive mode. The optimal drive motor load rate for the current moment is determined by looking up the optimal instantaneous charging efficiency map, ultimately achieving optimal instantaneous charging efficiency control. This method breaks through the traditional engine optimal control concept, enabling the highest instantaneous energy utilization efficiency of the power system in charging mode, reducing additional power losses caused by secondary energy conversion. Furthermore, this method has real-time application capabilities, contributing to further improvement in the economic performance of P4 hybrid vehicles during actual driving.

[0005] To achieve the above objectives, the present invention employs the following technical solution.

[0006] Step 1: Discrete vehicle speed and driver's required torque.

[0007] A P4 hybrid vehicle is described, wherein the central axle is driven by an engine, with engine power transmitted to the central axle drive axle via a multi-speed automatic transmission, and the rear axle is driven by an electric drive axle. When the P4 hybrid vehicle operates in a charging mode, the driver's required torque should be lower than the engine's optimal torque curve, and the actual engine output torque T... eng It is mainly divided into two parts. One part is used to drive the whole vehicle and meet the driver's torque T. dri The other part is used to power the drive motor to generate electricity, i.e., the motor's generating torque T. isg ,

[0008] First, set the vehicle speed V to the minimum stable vehicle speed V. min Up to maximum speed V max The range is discrete at equal intervals, and the engine torque T is... eng At minimum torque T eng_min To maximum torque T eng_max The range is discretely spaced at equal intervals. The current gear i of the mid-axle multi-gear automatic transmission is obtained by looking up the shifting rules of the mid-axle multi-gear automatic transmission in the table by looking up the vehicle speed V. gm And obtain the current gear i of the electric drive axle by looking up the shift rules of the electric drive axle transmission. gr This allows us to obtain a discrete engine speed sequence n. e As shown in equation (1), and the discrete drive motor speed sequence n m As shown in equation (2), and let the driver demand torque sequence T dri As shown in expression (3),

[0009]

[0010]

[0011] T dri =[T eng_min :dT:T eng_max ]·i gm i fdm η gm η fdm (3)

[0012] In the formula, dV and dT represent the distance between vehicle speed and step size and the distance between engine torque and step size, respectively. fdm i fdr R represents the speed ratio of the central shaft main reducer and the speed ratio of the electric drive axle main reducer, respectively. m R r η represents the rolling radius of the center axle wheel and the rolling radius of the rear axle wheel, respectively. gm η fdm These represent the transmission efficiency of the multi-speed automatic transmission on the central shaft and the transmission efficiency of the central shaft final reducer, respectively.

[0013] Step 2: Establish the power distribution relationship.

[0014] With the peak torque T of the drive motor m_max As a reference value, the discrete drive motor generating torque T is selected from the drive motor load rate sequence δ. m As shown in equation (5), the expression for the drive motor load rate sequence δ is shown in equation (4), and the drive motor generating torque sequence T is... m With the driver's required torque sequence T dri Summing these values ​​will give the actual torque T required by the engine. eng As shown in equation (6),

[0015] δ=[0:dδ:1] (4)

[0016] T m =T m_max ·δ (5)

[0017]

[0018] To prevent the torque demanded by the power source from exceeding its operating range, the torque demand of the power source is limited, that is, the actual torque demand sequence T of the engine is required to be limited. eng The maximum torque limit of the engine T must not be exceeded. eng_max (n e As shown in equation (7), the generator torque sequence T of the drive motor is... m The maximum torque limit T of the drive motor must not be exceeded.m_chg_max (n m As shown in equation (8),

[0019] T eng_min ≤T eng ≤T eng_max (n e (7)

[0020] 0≤T m ≤T m_chg_max (n m (8)

[0021] Step 3: Solve for the instantaneous charging efficiency at the operating point, i.e., establish the optimization objective function.

[0022] Based on the actual torque demand T of the engine eng Engine speed n e By looking up the engine universal characteristic map, the fuel consumption rate b at the current operating point can be obtained. e The generator produces torque T by driving the motor. m Drive motor speed n m By looking up the efficiency characteristic map of the drive motor, the power generation efficiency η of the drive motor at the current operating point can be obtained. m Then, the fuel energy demand Q of the engine at the current moment can be calculated from equations (9), (10), and (11). eng Energy generated by the drive motor Q m Aggregate demand drives energy Q dri ,

[0023]

[0024]

[0025]

[0026] In the formula, q represents the calorific value of fuel oil, MJ / kg, and n dri The output speed of the central shaft main reducer is represented by the discrete sequence of the speed, which can be calculated by equation (12).

[0027]

[0028] The expression for the instantaneous charging efficiency at the operating point is shown in equation (13), thus establishing the optimization objective function.

[0029]

[0030] Step 4: Extract the map and curve showing the optimal instantaneous charging efficiency while driving.

[0031] Through computer programming, the vehicle speed sequence V and the driver's required torque sequence T are iteratively generated.dri Given the drive motor load rate sequence δ, iterate through all feasible operating points, calculate and record the instantaneous charging efficiency η at each operating point. tot And record it at every vehicle speed and driver-demanded torque to achieve instantaneous charging efficiency η tot The maximum drive motor load rate δ, i.e. the optimal drive motor load rate δ opt ;

[0032] Based on equations (1) and (3), the current vehicle speed and the driver's required torque are converted to the engine output, which are then converted into engine speed and engine torque. The optimal drive motor load rate δ corresponding to each engine speed and engine torque is plotted. opt The image is built in a three-dimensional coordinate system, with the x-axis and y-axis corresponding to engine speed and engine torque, respectively, and the z-axis corresponding to the optimal drive motor load rate. The projection of the image onto the xy plane is the map of the optimal instantaneous charging efficiency while driving.

[0033] Connect the optimal drive motor load rate δ in the instantaneous charging efficiency map of the vehicle. opt The boundary between zero and greater than zero is used to extract the optimal curve for instantaneous charging efficiency of the vehicle by polynomial fitting and smoothing.

[0034] Step 5: Optimal control of instantaneous charging efficiency while driving.

[0035] During vehicle operation, the vehicle control unit (HCU) monitors the current vehicle speed and driver-demanded torque in real time, and translates these values ​​into engine output. When the driver-demanded torque falls below the optimal instantaneous charging efficiency curve, the vehicle enters the charging drive mode. The optimal drive motor load rate δ is then determined by consulting the optimal instantaneous charging efficiency map. opt The driving motor generating torque is determined according to equation (5), and the engine demand torque can be determined according to equation (6). When the driver's demand torque is higher than the optimal curve of instantaneous charging efficiency, the vehicle exits the charging drive mode.

[0036] Compared with the prior art, the beneficial effects of this invention are as follows:

[0037] 1. The P4 configuration hybrid vehicle instantaneous charging efficiency optimal control method described in this invention breaks through the traditional engine optimal control concept, and can achieve the highest instantaneous energy utilization efficiency of the power system in the vehicle's driving charging mode. It reduces the secondary energy conversion caused by the traditional driving charging mode strategy, thereby reducing the additional power loss. It can give full play to the multi-mode advantages of the P4 configuration hybrid vehicle and improve the economic performance of the P4 configuration hybrid vehicle.

[0038] 2. The method for optimal instantaneous charging efficiency control of P4 configuration hybrid vehicles described in this invention does not require prior operating conditions as input. After rule extraction, the optimal control rules can be quickly determined using only a two-dimensional lookup table, and it has the real-time performance required for practical controller applications. Attached Figure Description

[0039] The following description of the embodiments, taken in conjunction with the accompanying drawings, will make the embodiments readily understood, wherein:

[0040] Figure 1 A schematic diagram of the optimal control process for instantaneous charging efficiency of a P4 configuration hybrid vehicle according to an embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the powertrain structure of a P4 configuration hybrid vehicle according to an embodiment of the present invention.

[0042] Figure 2 Explanation of the reference numerals: 1-Front axle steering wheel, 2-Power domain controller PDU, 3-Middle axle drive wheel, 4-Rear axle drive wheel, 5-Drive motor, 6-Rear axle 2-speed automatic transmission, 7-Final reducer and differential assembly, 8-Power battery, 9-Final reducer and differential assembly, 10-Universal joint, 11-Middle axle 12-speed automatic transmission, 12-Engine. Detailed Implementation

[0043] 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.

[0044] The following description, with reference to the accompanying drawings, illustrates a method for optimal instantaneous charging efficiency control of a P4 configuration hybrid vehicle, but the invention is not limited to these embodiments.

[0045] Reference Appendix Figure 1 The implementation of this invention specifically includes five steps:

[0046] Step 1: Discrete vehicle speed and driver's required torque.

[0047] For a P4 configuration hybrid vehicle, see attached... Figure 2 The P4 hybrid vehicle is driven by engine 12 on the central axle, and the power of engine 12 is transmitted to the central axle drive axle through a multi-speed automatic transmission 11. The rear axle is driven by an electric drive axle. When the P4 hybrid vehicle is operating in driving-charging mode, the torque required by the driver should be lower than the engine's optimal torque curve, and the actual output torque T of engine 12 is... engIt is mainly divided into two parts. One part is used to drive the whole vehicle and meet the driver's torque T. dri The other part is used to power the drive motor 5 to generate electricity, i.e., the motor's generating torque T. isg ,

[0048] First, set the vehicle speed V to the minimum stable vehicle speed V. min Up to maximum speed V max The range is discrete at equal intervals, and the engine torque T is... eng At minimum torque T eng_min To maximum torque T eng_max The range is discretely spaced at equal intervals. The current gear i of the mid-axle multi-gear automatic transmission is obtained by looking up the shifting rules of the mid-axle multi-gear automatic transmission in the table by looking up the vehicle speed V. gm And obtain the current gear i of the electric drive axle by looking up the shift rules of the electric drive axle transmission. gr This allows us to obtain a discrete engine speed sequence n. e As shown in equation (1), and the discrete drive motor speed sequence n m As shown in equation (2), and let the driver demand torque sequence T dri As shown in expression (3),

[0049]

[0050]

[0051] T dri =[T eng_min :dT:T eng_max ]·i gm i fdm η gm η fdm (3)

[0052] In the formula, dV and dT represent the distance between vehicle speed and step size and the distance between engine torque and step size, respectively. fdm i fdr R represents the speed ratio of the central shaft main reducer and the speed ratio of the electric drive axle main reducer, respectively. m R r η represents the rolling radius of the center axle wheel and the rolling radius of the rear axle wheel, respectively. gm η fdm These represent the transmission efficiency of the multi-speed automatic transmission on the central shaft and the transmission efficiency of the central shaft final reducer, respectively.

[0053] Step 2: Establish the power distribution relationship.

[0054] With the peak torque T of the drive motor m _ max As a reference value, the discrete drive motor generating torque T is selected from the drive motor load rate sequence δ. mAs shown in equation (5), the expression for the drive motor load rate sequence δ is shown in equation (4), and the drive motor generating torque sequence T is... m With the driver's required torque sequence T dri Summing these values ​​will give the actual torque T required by the engine. eng As shown in equation (6),

[0055] δ=[0:dδ:1] (4)

[0056] T m =T m_max ·δ (5)

[0057]

[0058] To prevent the torque demanded by the power source from exceeding its operating range, the torque demand of the power source is limited, that is, the actual torque demand sequence T of the engine is required to be limited. eng The maximum torque limit of the engine T must not be exceeded. eng_max (n e As shown in equation (7), the generator torque sequence T of the drive motor is... m The maximum torque limit T of the drive motor must not be exceeded. m_chg_max (n m As shown in equation (8),

[0059] T eng_min ≤T eng ≤T eng_max (n e (7)

[0060] 0≤T m ≤T m_chg_max (n m (8)

[0061] Step 3: Solve for the instantaneous charging efficiency at the operating point, i.e., establish the optimization objective function.

[0062] Based on the actual torque demand T of the engine eng Engine speed n e By looking up the engine universal characteristic map, the fuel consumption rate b at the current operating point can be obtained. e The generator produces torque T by driving the motor. m Drive motor speed n m By looking up the efficiency characteristic map of the drive motor, the power generation efficiency η of the drive motor at the current operating point can be obtained. m Then, the fuel energy demand Q of the engine at the current moment can be calculated from equations (9), (10), and (11). eng Energy generated by the drive motor Q m Aggregate demand drives energy Q dri ,

[0063]

[0064]

[0065]

[0066] In the formula, q represents the calorific value of fuel oil, MJ / kg, and n dri The output speed of the central shaft main reducer is represented by the discrete sequence of the speed, which can be calculated by equation (12).

[0067]

[0068] The expression for the instantaneous charging efficiency at the operating point is shown in equation (13), thus establishing the optimization objective function.

[0069]

[0070] Step 4: Extract the map and curve showing the optimal instantaneous charging efficiency while driving.

[0071] Through computer programming, the vehicle speed sequence V and the driver's required torque sequence T are iteratively generated. dri Given the drive motor load rate sequence δ, iterate through all feasible operating points, calculate and record the instantaneous charging efficiency η at each operating point. tot And record it at every vehicle speed and driver-demanded torque to achieve instantaneous charging efficiency η tot The maximum drive motor load rate δ, i.e. the optimal drive motor load rate δ opt ;

[0072] Based on equations (1) and (3), the current vehicle speed and the driver's required torque are converted to the engine output, which are then converted into engine speed and engine torque. The optimal drive motor load rate δ corresponding to each engine speed and engine torque is plotted. opt The image is built in a three-dimensional coordinate system, with the x-axis and y-axis corresponding to engine speed and engine torque, respectively, and the z-axis corresponding to the optimal drive motor load rate. The projection of the image onto the xy plane is the map of the optimal instantaneous charging efficiency while driving.

[0073] Connect the optimal drive motor load rate δ in the instantaneous charging efficiency map of the vehicle. opt The boundary between zero and greater than zero is used to extract the optimal curve for instantaneous charging efficiency of the vehicle by polynomial fitting and smoothing.

[0074] Step 5: Optimal control of instantaneous charging efficiency while driving.

[0075] During vehicle operation, the vehicle control unit (HCU) monitors the current vehicle speed and driver-demanded torque in real time, and translates these values ​​into engine output. When the driver-demanded torque falls below the optimal instantaneous charging efficiency curve, the vehicle enters the charging drive mode. The optimal drive motor load rate δ is then determined by consulting the optimal instantaneous charging efficiency map. opt The driving motor generating torque is determined according to equation (5), and the engine demand torque can be determined according to equation (6). When the driver's demand torque is higher than the optimal curve of instantaneous charging efficiency, the vehicle exits the charging drive mode.

Claims

1. A method for optimal control of instantaneous charging efficiency during driving in a P4 configuration hybrid vehicle, characterized in that... Includes the following steps: Step 1: Discrete vehicle speed and driver's required torque. A P4 hybrid vehicle is described, wherein the central axle is driven by an engine, with engine power transmitted to the central axle drive axle via a multi-speed automatic transmission, and the rear axle is driven by an electric drive axle. When the P4 hybrid vehicle operates in a charging mode, the driver's required torque should be lower than the engine's optimal torque curve, and the actual engine output torque T... eng It is divided into two parts. One part is used to drive the entire vehicle, which satisfies the driver's torque T. dri The other part is used to power the drive motor to generate electricity, i.e., the motor's generating torque T. isg , First, set the vehicle speed V to the minimum stable vehicle speed V. min Up to maximum speed V max The range is discrete at equal intervals, and the engine torque T is... eng At minimum torque T eng_min To maximum torque T eng_max The range is discretely spaced at equal intervals. The current gear i of the mid-axle multi-gear automatic transmission is obtained by looking up the shifting rules of the mid-axle multi-gear automatic transmission in the table by looking up the vehicle speed V. gm And obtain the current gear i of the electric drive axle by looking up the shift rules of the electric drive axle transmission. gr This allows us to obtain a discrete engine speed sequence n. e As shown in equation (1), and the discrete drive motor speed sequence n m As shown in equation (2), and let the driver demand torque sequence T dri As shown in expression (3), T dri =[T eng_min :dT:T eng_max ]·i gm i fdm η gm η fdm (3) In the formula, dV and dT represent the distance between vehicle speed and step size and the distance between engine torque and step size, respectively. fdm i fdr R represents the speed ratio of the central shaft main reducer and the speed ratio of the electric drive axle main reducer, respectively. m R r η represents the rolling radius of the center axle wheel and the rolling radius of the rear axle wheel, respectively. gm η fdm These represent the transmission efficiency of the multi-speed automatic transmission on the central shaft and the transmission efficiency of the central shaft final reducer, respectively. Step 2: Establish the power distribution relationship. With the peak torque T of the drive motor m _ max As a reference value, the discrete drive motor generating torque T is selected from the drive motor load rate sequence δ. m As shown in equation (5), the expression for the drive motor load rate sequence δ is shown in equation (4), and the drive motor generating torque sequence T is... m With the driver's required torque sequence T dri Summing these values ​​will give the actual torque T required by the engine. eng As shown in equation (6), δ=[0:dδ:1] (4) T m =T m_max ·δ (5) To prevent the torque demanded by the power source from exceeding its operating range, the torque demand of the power source is limited, that is, the actual torque demand sequence T of the engine is required to be limited. eng The maximum torque limit of the engine T must not be exceeded. eng_max (n e As shown in equation (7), the generator torque sequence T of the drive motor is... m The maximum torque limit T of the drive motor must not be exceeded. m_chg_max (n m As shown in equation (8), T eng_min ≤T eng ≤T eng_max (n e ) (7) 0≤T m ≤T m_chg_max (n m ) (8) Step 3: Solve for the instantaneous charging efficiency at the operating point, i.e., establish the optimization objective function. Based on the actual torque demand T of the engine eng Engine speed n e By looking up the engine universal characteristic map, the fuel consumption rate b at the current operating point can be obtained. e The generator produces torque T by driving the motor. m Drive motor speed n m By looking up the efficiency characteristic map of the drive motor, the power generation efficiency η of the drive motor at the current operating point can be obtained. m Then, the fuel energy demand Q of the engine at the current moment can be calculated from equations (9), (10), and (11). eng Energy generated by the drive motor Q m Aggregate demand drives energy Q dri , In the formula, q represents the calorific value of fuel oil, MJ / kg, and n dri The output speed of the central shaft main reducer is represented by the discrete sequence of the speed, which can be calculated by equation (12). The expression for the instantaneous charging efficiency at the operating point is shown in equation (13), thus establishing the optimization objective function. Step 4: Extract the map and curve showing the optimal instantaneous charging efficiency while driving. Through computer programming, the vehicle speed sequence V and the driver's required torque sequence T are iteratively generated. dri Given the drive motor load rate sequence δ, iterate through all feasible operating points, calculate and record the instantaneous charging efficiency η at each operating point. tot And record it at each vehicle speed and the driver's required torque to make the instantaneous charging efficiency η tot The maximum drive motor load rate δ, i.e. the optimal drive motor load rate δ opt ; Based on equations (1) and (3), the current vehicle speed and the driver's required torque are converted to the engine output, which are then converted into engine speed and engine torque. The optimal drive motor load rate δ corresponding to each engine speed and engine torque is plotted. opt The image is built in a three-dimensional coordinate system, with the x-axis and y-axis corresponding to engine speed and engine torque, respectively, and the z-axis corresponding to the optimal drive motor load rate. The projection of the image onto the xy plane is the map of the optimal instantaneous charging efficiency while driving. Connect the optimal drive motor load rate δ in the map of the instantaneous efficiency of vehicle charging. opt The boundary between zero and greater than zero is used to extract the optimal curve for instantaneous charging efficiency of the vehicle by polynomial fitting and smoothing. Step 5: Optimal control of instantaneous charging efficiency while driving. During vehicle operation, the vehicle control unit (HCU) monitors the current vehicle speed and driver-demanded torque in real time, and translates these values ​​into engine output. When the driver-demanded torque falls below the optimal instantaneous charging efficiency curve, the vehicle enters the charging drive mode. The optimal drive motor load rate δ is then determined by consulting the optimal instantaneous charging efficiency map. opt The driving motor generating torque is determined according to equation (5), and the engine demand torque can be determined according to equation (6). When the driver's demand torque is higher than the optimal curve of instantaneous charging efficiency, the vehicle exits the charging drive mode.

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