Energy recovery torque distribution control method, system and vehicle for pure electric four-wheel drive vehicle

Abstract

The present application relates to electric vehicle power distribution technical field, especially to a kind of pure electric four-wheel drive car energy recovery torque distribution control method, system and vehicle. Specifically including obtaining the vehicle condition parameter when target vehicle travels, obtaining driver demand torque and calculating dynamic vertical load;According to the dynamic vertical load, the road adhesion coefficient and the level of the four wheels of target vehicle are calculated, the corrected driver demand torque is obtained by adjusting, the front axle torque distribution coefficient before and after correction is calculated and adjusted, the front axle torque is obtained, and is transferred to motor controller and executes distribution.The present application combines road conditions and vehicle state, and actively adjusts energy recovery torque under different road conditions, so that the vehicle can obtain better energy recovery performance and stability margin.According to the road adhesion level and vehicle state, the front axle torque distribution coefficient before and after correction is actively adjusted, so that the vehicle obtains better energy recovery performance, handling performance and stability performance.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle power distribution technology, and in particular to a method, system and vehicle for energy recovery torque distribution control of a pure electric four-wheel drive vehicle. Background Technology

[0002] Developing new energy vehicles has become an international consensus and a national strategy. The development of new energy vehicles is driving the transformation of automobiles from traditional hardware-driven to software-driven mobile intelligent terminals. Compared to two-wheel drive vehicles, four-wheel drive vehicles offer better acceleration, handling, and stability. Pure electric four-wheel drive vehicles eliminate the transmission and transfer case of traditional gasoline vehicles, achieving hardware decoupling between the front and rear axles through a dual-motor arrangement, resulting in superior four-wheel drive performance. Torque distribution control is a key technology in pure electric four-wheel drive vehicles.

[0003] When a pure electric four-wheel drive vehicle decelerates and regenerates energy, the vehicle's center of gravity shifts forward, resulting in a greater load on the front axle tires than the rear axle tires. Based on the friction circle theory, the torque distribution between the front and rear axles needs to be adjusted to ensure sufficient stability margin for both axles, thereby improving vehicle handling stability. The total torque and torque distribution ratio between the front and rear axles also need to be adjusted when driving on different road surfaces to ensure sufficient stability margin and improve handling stability. Currently, mass-produced pure electric four-wheel drive models primarily distribute the energy recovery torque between the front and rear axles using a fixed distribution coefficient. The torque is only passively adjusted via ESP intervention when tires slip on the road surface. This prevents the vehicle from optimally utilizing the road surface adhesion coefficient, reducing its handling performance and stability.

[0004] Existing torque distribution control methods either focus solely on economy without considering vehicle acceleration performance or energy recovery torque distribution, or they focus solely on acceleration performance while ignoring the impact of road conditions on the vehicle and neglecting energy recovery torque distribution. There is a lack of a comprehensive control method that integrates road conditions and vehicle status to actively adjust the total energy recovery torque and front-to-rear axle torque distribution to achieve better energy recovery performance, handling performance, and stability performance in pure electric four-wheel drive vehicles. Summary of the Invention

[0005] This invention aims to at least improve one of the technical problems existing in the prior art. To this end, this invention proposes a method, system, and vehicle for energy recovery torque distribution control of a pure electric four-wheel drive vehicle.

[0006] A method for controlling the energy recovery torque distribution of a pure electric four-wheel drive vehicle according to a first aspect of the present invention includes: Step S100: Obtain vehicle condition parameters when the target vehicle is in motion. The vehicle condition parameters include vehicle speed, longitudinal acceleration, accelerator pedal opening, road slope, energy recovery level, actual torque of the front and rear axle motors, and actual wheel speed of the four wheels. Step S200: Obtain the first driver's required torque by looking up a table based on the vehicle speed, accelerator pedal opening and energy recovery level; Step S300: Calculate the dynamic vertical loads on the front and rear axles of the target vehicle based on the vehicle's longitudinal acceleration and road slope. Step S400: Calculate the road adhesion coefficient and road adhesion level of the four wheels of the target vehicle based on the dynamic vertical load of the front and rear axles and the tire ground force. Step S500: Adjust the first driver's required torque according to the road surface adhesion level to obtain the corrected second driver's required torque; Step S600: Calculate the first front and rear axle torque distribution coefficient based on the second driver's required torque and energy recovery level; Step S700: Adjust the first front and rear axle torque distribution coefficient according to the road surface adhesion level and vehicle condition to obtain the second front and rear axle torque distribution coefficient, wherein the vehicle condition includes vehicle speed, longitudinal acceleration and road slope. Step S800: Calculate the front and rear axle torques based on the second driver's required torque and the second front and rear axle torque distribution coefficient, and transmit the torques to the motor controller for distribution. The energy recovery torque distribution control method for pure electric four-wheel drive vehicles according to embodiments of the present invention, combined with road conditions and vehicle status, actively adjusts the energy recovery torque under different road conditions, thereby enabling the vehicle to obtain better energy recovery performance and stability margin. It also actively adjusts the front-to-rear torque distribution coefficient based on the road surface adhesion level and vehicle status, thereby enabling the vehicle to obtain better energy recovery performance, handling performance, and stability performance.

[0007] In one possible implementation of the first aspect, the energy recovery levels include Level 1, Level 2, and Level 3. A two-dimensional MAP (which can be calibrated) is set up for each of these three energy recovery levels and driving modes, with the horizontal axis representing throttle opening, the vertical axis representing vehicle speed, and the elements in the table representing energy recovery torque values. Different preset MAPs are selected according to different energy recovery levels, and the required torque for the first driver is obtained by looking up the table based on the current vehicle speed and throttle pedal opening. The intermediate value is calculated using a linear interpolation method.

[0008] In one possible implementation of the first aspect, in step S300, when the vehicle accelerates, the vehicle's center of gravity shifts rearward, resulting in a greater load on the rear axle tires than on the front axle tires. Similarly, when the vehicle goes uphill, the vehicle's center of gravity shifts rearward, resulting in a greater load on the rear axle tires than on the front axle tires. The calculation of the dynamic vertical loads on the front and rear axles of the target vehicle includes the following formulas: , , In the formula, Indicates the dynamic vertical load on the front axle. This indicates the dynamic vertical load on the rear axle. This indicates the overall vehicle weight of the target vehicle. This is the distance from the front axle to the center of gravity. This is the distance from the rear axle to the center of mass. It is the acceleration due to gravity. For road slope angle, For the longitudinal acceleration of the vehicle, The height of the vehicle's center of gravity above the ground.

[0009] In one possible implementation of the first aspect, in step S400, the formula for calculating the tire ground force is as follows: , in Indicates the tire's ground force. Indicates the driving torque at the wheels. This represents the moment of inertia of the tire. This represents the tire's angular acceleration. This represents the tire radius, where the radius is used when calculating the ground forces on the front axle tires. Equal to the actual output torque of the front axle motor Half of, that is When calculating the ground force on the rear axle tires, Equal to the actual output torque of the rear axle motor Half of, that is ; Tire angular velocity is calculated from wheel speed. ,in Indicates the actual wheel speed of the tire. This represents the tire radius. The tire angular acceleration is calculated from the change in tire angular velocity per unit time. ; The formula for calculating the road surface adhesion coefficient is as follows: , This is used to calculate the road adhesion coefficient for each of the four wheels separately, and the minimum road adhesion coefficient of the four wheels is taken as the estimated road adhesion coefficient. For dynamic vertical loads on the front and rear axles; Based on the estimated road surface adhesion coefficient, road surface adhesion levels are defined into three types: good, low adhesion, and very low adhesion. When the estimated road surface adhesion coefficient is greater than the first threshold (0.45), it is considered to be a good road condition; When the estimated road surface adhesion coefficient is greater than the second threshold (0.25) and less than the first threshold (0.4), it is considered to be a low adhesion road condition. When the estimated road surface adhesion coefficient is less than the second threshold (0.22), it is considered to be an extremely low adhesion road condition.

[0010] In one possible implementation of the first aspect, when the road surface adhesion level is good, the torque demanded by the second driver is equal to the torque demanded by the first driver, i.e. ; When the road surface adhesion level is low adhesion, the torque required by the second driver is equal to the torque required by the first driver multiplied by the low adhesion correction factor. ,Right now ; When the road surface adhesion level is extremely low, the torque required by the second driver is equal to the torque required by the first driver multiplied by the extremely low adhesion correction factor. ,Right now .

[0011] The low-adjustment and ultra-low-adjustment correction factors are adjusted according to a preset one-dimensional lookup table, the input of which is the driver's required torque. The value is output as the corresponding correction coefficient.

[0012] In one possible implementation of the first aspect, in step S600, when the energy recovery level is Level 1, Level 2, or Level 3, the first front-to-rear axle torque distribution coefficient can be calculated using the most efficient method for the electric drive system. Specifically, based on the driver's required torque and vehicle speed, the distribution coefficient that minimizes the sum of electrical losses of the front and rear motors is calculated. To save chip processing time, this method typically involves offline calculation of a two-dimensional MAP table, where the horizontal axis represents vehicle speed, the vertical axis represents the driver's required torque, and the elements in the table are the front motor distribution coefficients. Front motor distribution coefficient and the motor distribution coefficient The sum is 1.

[0013] Alternatively, you can choose to distribute the torque between the front and rear axles using a fixed distribution coefficient, for example, a fixed front and rear axle distribution coefficient of 0.5 and 0.5.

[0014] In one possible implementation of the first aspect, step S700 specifically includes the following: When the road surface adhesion level is good, the first front axle torque distribution coefficient... Up, shift forward by a preset value. The adjusted second front axle torque distribution coefficient is obtained. ; When the road surface adhesion level is low-adhesion, the first front axle torque distribution coefficient... Up, shift forward by a preset value. The adjusted second front axle torque distribution coefficient is obtained. ; When the road surface adhesion level is extremely low, the torque distribution coefficient of the first front axle is... Up, shift forward by a preset value. The adjusted second front axle torque distribution coefficient is obtained. ; Based on the vertical load of the vehicle's front and rear axles and A vertical load transfer factor ratio was calculated. The adjusted second front axle torque distribution coefficient is obtained. ; The adjusted second front axle torque distribution coefficient calculated above It needs to satisfy the constraint condition 0 < <1, Adjusted second rear axle torque distribution coefficient The constraint condition 0 < must be met. <1.

[0015] In one possible implementation of the first aspect, step S800 includes: Front axle torque equals the second driver's required torque multiplied by the second front axle torque distribution factor. The rear axle torque equals the second driver's required torque multiplied by the second rear axle torque distribution coefficient. ; The front axle torque and rear axle torque are respectively processed by the drivability filtering module to obtain the required torque for the front axle and the required torque for the rear axle, and then transmitted to the motor controller for execution output.

[0016] According to a second aspect of the present invention, a pure electric four-wheel drive vehicle energy recovery torque distribution control system is provided for implementing the pure electric four-wheel drive vehicle energy recovery torque distribution control method as described above, wherein the system includes: The data acquisition module is used to collect vehicle condition parameters when the target vehicle is in motion. These parameters include vehicle speed, longitudinal acceleration, accelerator pedal opening, road gradient, energy recovery level, actual torque of the front and rear axle motors, and actual wheel speed of the four wheels. The acquisition module is used to look up the required torque for the first driver based on the vehicle speed, accelerator pedal opening and energy recovery level. The first calculation module is used to calculate the dynamic vertical loads on the front and rear axles of the target vehicle based on the vehicle's longitudinal acceleration and the road slope. The second calculation module is used to calculate the road adhesion coefficient and road adhesion level of the four wheels of the target vehicle based on the dynamic vertical load of the front and rear axles and the tire ground force. The first correction module adjusts the first driver's required torque according to the road surface adhesion level to obtain the corrected second driver's required torque. The third calculation module calculates the first front and rear axle torque distribution coefficient based on the second driver's required torque and energy recovery level. The second correction module adjusts the first front and rear axle torque distribution coefficient according to the road surface adhesion level and vehicle status to obtain the second front and rear axle torque distribution coefficient. The vehicle status includes vehicle speed, longitudinal acceleration and road slope. The distribution module calculates the front and rear axle torques based on the second driver's required torque and the second front and rear axle torque distribution coefficient, and transmits the results to the motor controller for distribution.

[0017] A vehicle according to a third aspect of the present invention, wherein the vehicle includes the energy recovery torque distribution control system described above.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of an energy recovery torque distribution control method for a pure electric four-wheel drive vehicle according to an embodiment of the present invention. Detailed Implementation

[0021] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0022] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] The terms "first," "second," "third," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects and not to describe a particular order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, it may include a series of steps or units, or optionally, steps or units not listed, or other steps or units inherent to these processes, methods, products, or devices.

[0025] The accompanying drawings show only the portions relevant to this application, not all of them. Before discussing exemplary embodiments in more detail, it should be noted that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe operations (or steps) as sequential processes, many of these operations may be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations may be rearranged. The process may be terminated when its operation is completed, but may also have additional steps not included in the drawings. The process may correspond to a method, function, procedure, subroutine, subprogram, etc.

[0026] The terms “component,” “module,” “system,” “unit,” etc., used in this specification are used to refer to computer-related entities, hardware, firmware, combinations of hardware and software, software, or software in execution. For example, a unit can be, but is not limited to, a process running on a processor, a processor, an object, an executable file, a thread of execution, a program, and / or distributed between two or more computers. Furthermore, these units can be executed from various computer-readable media on which various data structures are stored. Units can communicate, for example, via local and / or remote processes based on signals having one or more data packets (e.g., data from a second unit interacting with another unit between a local system, a distributed system, and / or a network; for example, the Internet interacting with other systems via signals).

[0027] Example 1 See Figure 1 As shown, this embodiment provides a method for controlling the energy recovery torque distribution of a pure electric four-wheel drive vehicle, which includes: Step S100: Obtain vehicle condition parameters when the target vehicle is in motion. The vehicle condition parameters include vehicle speed, longitudinal acceleration, accelerator pedal opening, road slope, energy recovery level, actual torque of the front and rear axle motors, and actual wheel speed of the four wheels. Step S200: Based on the vehicle speed, accelerator pedal opening, and energy recovery level, the required torque for the first driver is obtained by looking up a table. The energy recovery levels include Level 1, Level 2, and Level 3. A two-dimensional MAP table (which can be calibrated) is set up for each of these three energy recovery levels, with accelerator pedal opening on the horizontal axis, vehicle speed on the vertical axis, and energy recovery torque values ​​as the table elements. Different preset MAP tables are selected according to different energy recovery levels, and the required torque for the first driver is obtained by looking up the table based on the current vehicle speed and accelerator pedal opening. This embodiment illustrates a MAP table for one type of Level 1 capacity recovery torque value, as shown in Table 1 below: Table 1: Primary Energy Recovery Map Table The intermediate value was calculated using a linear interpolation method.

[0028] Step S300: Calculate the dynamic vertical loads on the front and rear axles of the target vehicle based on the vehicle's longitudinal acceleration and road slope.

[0029] When a vehicle accelerates, its center of gravity shifts rearward, resulting in a greater load on the rear axle tires than the front axle tires. Similarly, when a vehicle goes uphill, its center of gravity shifts rearward, leading to a greater load on the rear axle tires than the front axle tires. The dynamic vertical loads on the front and rear axles of the target vehicle are calculated using the following formulas: , , In the formula, Indicates the dynamic vertical load on the front axle. This indicates the dynamic vertical load on the rear axle. This indicates the overall vehicle weight of the target vehicle. This is the distance from the front axle to the center of gravity. This is the distance from the rear axle to the center of mass. It is the acceleration due to gravity. For road slope angle, For the longitudinal acceleration of the vehicle, The height of the vehicle's center of gravity above the ground.

[0030] Step S400: Calculate the road adhesion coefficient and road adhesion level of the four wheels of the target vehicle based on the dynamic vertical loads of the front and rear axles and the tire ground force. The formula for calculating the tire ground force is as follows: , in Indicates the tire's ground force. Indicates the driving torque at the wheels. This represents the moment of inertia of the tire. This represents the tire's angular acceleration. This represents the tire radius, where the radius is used when calculating the ground forces on the front axle tires. Equal to the actual output torque of the front axle motor Half of, that is When calculating the ground force on the rear axle tires, Equal to the actual output torque of the rear axle motor Half of, that is ; Tire angular velocity is calculated from wheel speed. ,in Indicates the actual wheel speed of the tire. This represents the tire radius. The tire angular acceleration is calculated from the change in tire angular velocity per unit time. ; The formula for calculating the road surface adhesion coefficient is as follows: , This is used to calculate the road adhesion coefficient for each of the four wheels separately, and the minimum road adhesion coefficient of the four wheels is taken as the estimated road adhesion coefficient. For dynamic vertical loads on the front and rear axles; Based on the estimated road surface adhesion coefficient, road surface adhesion levels are defined into three types: good, low adhesion, and very low adhesion. When the estimated road surface adhesion coefficient is greater than the first threshold (preferably 0.45 in this embodiment), it is considered to be a good road condition; When the estimated road surface adhesion coefficient is greater than the second threshold (preferably 0.25 in this embodiment) and less than the first threshold (preferably 0.4 in this embodiment), it is considered to be a low-adhesion road condition. When the estimated road surface adhesion coefficient is less than the second threshold (preferably 0.22 in this embodiment), it is considered to be an extremely low adhesion road condition.

[0031] Step S500: Adjust the first driver's required torque according to the road surface adhesion level to obtain the corrected second driver's required torque. When the road surface adhesion level is good, the torque required by the second driver is directly equal to the torque required by the first driver, that is... ; When the road surface adhesion level is low adhesion, the torque required by the second driver is equal to the torque required by the first driver multiplied by the low adhesion correction factor. (This is the calibration value), that is ; This embodiment illustrates a low-adjustment correction factor under one type of calibration. The intermediate values ​​were calculated using a linear interpolation method, as shown in Table 2 below.

[0032] Table 2 When the road surface adhesion level is extremely low, the torque required by the second driver is equal to the torque required by the first driver multiplied by the extremely low adhesion correction factor. (This is the calibration value), that is ; This embodiment illustrates a low-adjustment correction factor under one type of calibration. The intermediate values ​​were calculated using a linear interpolation method, as shown in Table 3 below.

[0033] Table 3 The low-adjustment and ultra-low-adjustment correction factors are adjusted according to a preset one-dimensional lookup table, the input of which is the driver's required torque. The value is output as the corresponding correction coefficient.

[0034] Step S600: Calculate the first front-to-rear axle torque distribution coefficient based on the second driver's required torque and energy recovery level. When the energy recovery level is Level 1, 2, or 3, the first front-to-rear axle torque distribution coefficient can be calculated using the most efficient method for the electric drive system. Specifically, this involves calculating the distribution coefficient that minimizes the sum of electrical losses between the front and rear motors based on the driver's required torque and vehicle speed. To save chip processing time, this method typically involves offline calculation of a two-dimensional MAP table. The horizontal axis of this table represents vehicle speed, the vertical axis represents the driver's required torque, and the elements in the table are the front motor distribution coefficients. Front motor distribution coefficient and the motor distribution coefficient The sum is 1.

[0035] Alternatively, you can choose to distribute the torque between the front and rear axles using a fixed distribution coefficient, for example, a fixed front and rear axle distribution coefficient of 0.5 and 0.5.

[0036] Step S700: Adjust the first front-to-rear axle torque distribution coefficient according to the road surface adhesion level and vehicle condition to obtain the second front-to-rear axle torque distribution coefficient. The vehicle condition includes vehicle speed, longitudinal acceleration, and road gradient. When the road surface adhesion level is good, the first front axle torque distribution coefficient... Up, shift forward by a preset value. The adjusted second front axle torque distribution coefficient is obtained. For example It can be a fixed value of 0.1, or it can be obtained by looking up a table using a one-dimensional MAP with vehicle speed as the input and transfer coefficient as the output; When the road surface adhesion level is low-adhesion, the first front axle torque distribution coefficient... Up, shift forward by a preset value. The adjusted second front axle torque distribution coefficient is obtained. For example It can be a fixed value of 0.2, or it can be obtained by looking up a table using a one-dimensional MAP with vehicle speed as the input and transfer coefficient as the output; When the road surface adhesion level is extremely low, the torque distribution coefficient of the first front axle is... Up, shift forward by a preset value. The adjusted second front axle torque distribution coefficient is obtained. For example It can be a fixed value of 0.3, or it can be obtained by looking up a table using a one-dimensional MAP with vehicle speed as the input and transfer coefficient as the output; Based on the vertical load of the vehicle's front and rear axles and A vertical load transfer factor ratio was calculated. The adjusted second front axle torque distribution coefficient is obtained. ; The adjusted second front axle torque distribution coefficient calculated above It needs to satisfy the constraint condition 0 < <1, Adjusted second rear axle torque distribution coefficient The constraint condition 0 < must be met. <1; Step S800: Calculate the front and rear axle torques based on the second driver's required torque and the second front and rear axle torque distribution coefficient, and transmit the result to the motor controller for distribution. Front axle torque equals the second driver's required torque multiplied by the second front axle torque distribution factor. The rear axle torque equals the second driver's required torque multiplied by the second rear axle torque distribution coefficient. ; The front axle torque and rear axle torque are respectively processed by the drivability filtering module to obtain the required torque for the front axle and the required torque for the rear axle, and then transmitted to the motor controller for execution output. The energy recovery torque distribution control method for pure electric four-wheel drive vehicles according to embodiments of the present invention, combined with road conditions and vehicle status, actively adjusts the energy recovery torque under different road conditions, thereby enabling the vehicle to obtain better energy recovery performance and stability margin. It also actively adjusts the front-to-rear torque distribution coefficient based on the road surface adhesion level and vehicle status, thereby enabling the vehicle to obtain better energy recovery performance, handling performance, and stability performance.

[0037] Example 2 A pure electric four-wheel drive vehicle energy recovery torque distribution control system is provided to implement the above-described pure electric four-wheel drive vehicle energy recovery torque distribution control method, comprising: The data acquisition module is used to collect vehicle condition parameters when the target vehicle is in motion. These parameters include vehicle speed, longitudinal acceleration, accelerator pedal opening, road gradient, energy recovery level, actual torque of the front and rear axle motors, and actual wheel speed of the four wheels. The acquisition module is used to look up the required torque for the first driver based on the vehicle speed, accelerator pedal opening and energy recovery level. The first calculation module is used to calculate the dynamic vertical loads on the front and rear axles of the target vehicle based on the vehicle's longitudinal acceleration and the road slope. The second calculation module is used to calculate the road adhesion coefficient and road adhesion level of the four wheels of the target vehicle based on the dynamic vertical load of the front and rear axles and the tire ground force. The first correction module adjusts the first driver's required torque according to the road surface adhesion level to obtain the corrected second driver's required torque. The third calculation module calculates the first front and rear axle torque distribution coefficient based on the second driver's required torque and energy recovery level. The second correction module adjusts the first front and rear axle torque distribution coefficient according to the road surface adhesion level and vehicle status to obtain the second front and rear axle torque distribution coefficient. The vehicle status includes vehicle speed, longitudinal acceleration and road slope. The distribution module calculates the front and rear axle torques based on the second driver's required torque and the second front and rear axle torque distribution coefficient, and transmits the results to the motor controller for distribution.

[0038] Example 3 A vehicle comprising the energy recovery torque distribution control system described above.

[0039] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention.

[0040] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0041] Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The reference to "embodiment" herein means that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily indicate the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0042] 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 controlling the energy recovery torque distribution of a pure electric four-wheel drive vehicle, characterized in that, include: Step S100: Obtain vehicle condition parameters when the target vehicle is in motion. The vehicle condition parameters include vehicle speed, longitudinal acceleration, accelerator pedal opening, road slope, energy recovery level, actual torque of the front and rear axle motors, and actual wheel speed of the four wheels. Step S200: Obtain the first driver's required torque by looking up a table based on the vehicle speed, accelerator pedal opening and energy recovery level; Step S300: Calculate the dynamic vertical loads on the front and rear axles of the target vehicle based on the vehicle's longitudinal acceleration and road slope. Step S400: Calculate the road adhesion coefficient and road adhesion level of the four wheels of the target vehicle based on the dynamic vertical load of the front and rear axles and the tire ground force. Step S500: Adjust the first driver's required torque according to the road surface adhesion level to obtain the corrected second driver's required torque; Step S600: Calculate the first front and rear axle torque distribution coefficient based on the second driver's required torque and energy recovery level; Step S700: Adjust the first front and rear axle torque distribution coefficient according to the road surface adhesion level and vehicle condition to obtain the second front and rear axle torque distribution coefficient, which specifically includes the following: When the road surface adhesion level is good, the first front axle torque distribution coefficient... Up, shift forward by a preset value. The adjusted second front axle torque distribution coefficient is obtained. ; When the road surface adhesion level is low-adhesion, the first front axle torque distribution coefficient... Up, shift forward by a preset value. The adjusted second front axle torque distribution coefficient is obtained. ; When the road surface adhesion level is extremely low, the torque distribution coefficient of the first front axle is... Up, shift forward by a preset value. The adjusted second front axle torque distribution coefficient is obtained. ; Based on the dynamic vertical load of the vehicle's front axle and rear axle dynamic vertical load A vertical load transfer factor ratio was calculated. The adjusted second front axle torque distribution coefficient is obtained. ; The adjusted second front axle torque distribution coefficient calculated above It needs to satisfy the constraint condition 0 < <1, Adjusted second rear axle torque distribution coefficient The constraint condition 0 < must be met. <1; The vehicle status includes vehicle speed, longitudinal acceleration, and road gradient; Step S800: Calculate the front and rear axle torques based on the second driver's required torque and the second front and rear axle torque distribution coefficient, and transmit the torques to the motor controller for distribution.

2. The energy recovery torque distribution control method for a pure electric four-wheel drive vehicle according to claim 1, characterized in that, Energy recovery levels include Level 1, Level 2, and Level 3. A two-dimensional map is created for each of these three energy recovery levels and driving modes, with the horizontal axis representing throttle opening and the vertical axis representing vehicle speed. The elements in the map represent the energy recovery torque values. Different preset two-dimensional map tables are selected based on the different energy recovery levels, and the driver's required torque is obtained by looking up the table based on the current vehicle speed and throttle pedal opening. The intermediate values ​​were calculated using linear interpolation.

3. The energy recovery torque distribution control method for a pure electric four-wheel drive vehicle according to claim 1, characterized in that, In step S300, when the vehicle accelerates, its center of gravity shifts rearward, resulting in a greater load on the rear axle tires than on the front axle tires. Similarly, when the vehicle goes uphill, its center of gravity shifts rearward, causing the rear axle tires to bear a greater load than the front axle tires. The calculation of the dynamic vertical loads on the front and rear axles of the target vehicle includes the following formulas: ， ， In the formula, Indicates the dynamic vertical load on the front axle. This indicates the dynamic vertical load on the rear axle. This indicates the overall vehicle weight of the target vehicle. This is the distance from the front axle to the center of gravity. This is the distance from the rear axle to the center of mass. It is the acceleration due to gravity. For road slope angle, For the longitudinal acceleration of the vehicle, The height of the vehicle's center of gravity above the ground.

4. The energy recovery torque distribution control method for a pure electric four-wheel drive vehicle according to claim 1, characterized in that, In step S400, the formula for calculating tire ground force is as follows: ， in Indicates the tire's ground force. Indicates the driving torque at the wheels. This represents the moment of inertia of the tire. This represents the tire's angular acceleration. This represents the tire radius, where the radius is used when calculating the ground forces on the front axle tires. Equal to the actual output torque of the front axle motor Half of, that is When calculating the ground force on the rear axle tires, Equal to the actual output torque of the rear axle motor Half of, that is ; Tire angular velocity is calculated from wheel speed. ,in Indicates the actual wheel speed of the tire. This represents the tire radius. The tire angular acceleration is calculated from the change in tire angular velocity per unit time. ; The formula for calculating the road surface adhesion coefficient is as follows: ， This is used to calculate the road adhesion coefficient for each of the four wheels separately, and the minimum road adhesion coefficient of the four wheels is taken as the estimated road adhesion coefficient. For dynamic vertical loads on the front and rear axles; Based on the estimated road surface adhesion coefficient, road surface adhesion levels are defined into three types: good, low adhesion, and very low adhesion. When the estimated road surface adhesion coefficient is greater than the first threshold, it is considered to be a good road condition; When the estimated road surface adhesion coefficient is greater than the second threshold and less than the first threshold, it is considered a low adhesion road condition. When the estimated road surface adhesion coefficient is less than the second threshold, it is considered to be an extremely low adhesion road condition.

5. The energy recovery torque distribution control method for a pure electric four-wheel drive vehicle according to claim 4, characterized in that, When the road surface adhesion level is good, the torque required by the second driver is equal to the torque required by the first driver, that is... ; When the road surface adhesion level is low adhesion, the torque required by the second driver is equal to the torque required by the first driver multiplied by the low adhesion correction factor. ,Right now ; When the road surface adhesion level is extremely low, the torque required by the second driver is equal to the torque required by the first driver multiplied by the extremely low adhesion correction factor. ,Right now .

6. The energy recovery torque distribution control method for a pure electric four-wheel drive vehicle according to claim 1, characterized in that, In step S600, when the energy recovery level is level one, level two, or level three, the first front and rear axle torque distribution coefficient is calculated according to the efficiency of the electric drive system. Specifically, the distribution coefficient with the minimum sum of electrical losses of the front and rear motors is calculated based on the driver's required torque and vehicle speed.

7. The energy recovery torque distribution control method for a pure electric four-wheel drive vehicle according to claim 1, characterized in that, Step S800 includes: Front axle torque equals the second driver's required torque multiplied by the second front axle torque distribution factor. The rear axle torque equals the second driver's required torque multiplied by the second rear axle torque distribution coefficient. .

8. A pure electric four-wheel drive vehicle energy recovery torque distribution control system, used to implement the pure electric four-wheel drive vehicle energy recovery torque distribution control method as described in any one of claims 1 to 7, characterized in that, include: The data acquisition module is used to collect vehicle condition parameters when the target vehicle is in motion. These parameters include vehicle speed, longitudinal acceleration, accelerator pedal opening, road gradient, energy recovery level, actual torque of the front and rear axle motors, and actual wheel speed of the four wheels. The acquisition module is used to look up the required torque for the first driver based on the vehicle speed, accelerator pedal opening and energy recovery level. The first calculation module is used to calculate the dynamic vertical loads on the front and rear axles of the target vehicle based on the vehicle's longitudinal acceleration and the road slope. The second calculation module is used to calculate the road adhesion coefficient and road adhesion level of the four wheels of the target vehicle based on the dynamic vertical load of the front and rear axles and the tire ground force. The first correction module adjusts the first driver's required torque according to the road surface adhesion level to obtain the corrected second driver's required torque. The third calculation module calculates the first front and rear axle torque distribution coefficient based on the second driver's required torque and energy recovery level. The second correction module adjusts the first front-to-rear axle torque distribution coefficient based on the road surface adhesion level and vehicle condition to obtain the second front-to-rear axle torque distribution coefficient. The vehicle condition includes vehicle speed, longitudinal acceleration, and road gradient, specifically including the following: When the road surface adhesion level is good, the first front axle torque distribution coefficient... Up, shift forward by a preset value. The adjusted second front axle torque distribution coefficient is obtained. ; When the road surface adhesion level is low-adhesion, the first front axle torque distribution coefficient... Up, shift forward by a preset value. The adjusted second front axle torque distribution coefficient is obtained. ; When the road surface adhesion level is extremely low, the torque distribution coefficient of the first front axle is... Up, shift forward by a preset value. The adjusted second front axle torque distribution coefficient is obtained. ; Based on the dynamic vertical load of the vehicle's front axle and rear axle dynamic vertical load A vertical load transfer factor ratio was calculated. The adjusted second front axle torque distribution coefficient is obtained. ; The adjusted second front axle torque distribution coefficient calculated above It needs to satisfy the constraint condition 0 < <1, Adjusted second rear axle torque distribution coefficient The constraint condition 0 < must be met. <1; The distribution module calculates the front and rear axle torques based on the second driver's required torque and the second front and rear axle torque distribution coefficient, and transmits the results to the motor controller for distribution.

9. A vehicle, characterized in that, The vehicle includes the energy recovery torque distribution control system as described in claim 8.

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