WO2022104601A1 - 电动车四驱扭矩分配方法、系统及车辆 - Google Patents

电动车四驱扭矩分配方法、系统及车辆 Download PDF

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Publication number
WO2022104601A1
WO2022104601A1 PCT/CN2020/129825 CN2020129825W WO2022104601A1 WO 2022104601 A1 WO2022104601 A1 WO 2022104601A1 CN 2020129825 W CN2020129825 W CN 2020129825W WO 2022104601 A1 WO2022104601 A1 WO 2022104601A1
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Prior art keywords
torque distribution
rear axle
distribution coefficient
vehicle
axle torque
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PCT/CN2020/129825
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English (en)
French (fr)
Inventor
胡本波
张荡
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浙江吉利控股集团有限公司
宁波吉利汽车研究开发有限公司
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Application filed by 浙江吉利控股集团有限公司, 宁波吉利汽车研究开发有限公司 filed Critical 浙江吉利控股集团有限公司
Priority to CN202080106295.4A priority Critical patent/CN116490393A/zh
Priority to PCT/CN2020/129825 priority patent/WO2022104601A1/zh
Priority to JP2023518364A priority patent/JP7471517B2/ja
Priority to US18/037,083 priority patent/US20230415583A1/en
Priority to EP20961892.5A priority patent/EP4249312A1/en
Publication of WO2022104601A1 publication Critical patent/WO2022104601A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
    • B60L15/20—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K6/00—Arrangement or mounting of plural diverse prime-movers for mutual or common propulsion, e.g. hybrid propulsion systems comprising electric motors and internal combustion engines ; Control systems therefor, i.e. systems controlling two or more prime movers, or controlling one of these prime movers and any of the transmission, drive or drive units Informative references: mechanical gearings with secondary electric drive F16H3/72; arrangements for handling mechanical energy structurally associated with the dynamo-electric machine H02K7/00; machines comprising structurally interrelated motor and generator parts H02K51/00; dynamo-electric machines not otherwise provided for in H02K see H02K99/00
    • B60K6/20—Arrangement or mounting of plural diverse prime-movers for mutual or common propulsion, e.g. hybrid propulsion systems comprising electric motors and internal combustion engines ; Control systems therefor, i.e. systems controlling two or more prime movers, or controlling one of these prime movers and any of the transmission, drive or drive units Informative references: mechanical gearings with secondary electric drive F16H3/72; arrangements for handling mechanical energy structurally associated with the dynamo-electric machine H02K7/00; machines comprising structurally interrelated motor and generator parts H02K51/00; dynamo-electric machines not otherwise provided for in H02K see H02K99/00 the prime-movers consisting of electric motors and internal combustion engines, e.g. HEVs
    • B60K6/50—Architecture of the driveline characterised by arrangement or kind of transmission units
    • B60K6/52—Driving a plurality of drive axles, e.g. four-wheel drive
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
    • B60L15/20—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
    • B60L15/2036—Electric differentials, e.g. for supporting steering vehicles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L3/00—Electric devices on electrically-propelled vehicles for safety purposes; Monitoring operating variables, e.g. speed, deceleration or energy consumption
    • B60L3/10—Indicating wheel slip ; Correction of wheel slip
    • B60L3/106—Indicating wheel slip ; Correction of wheel slip for maintaining or recovering the adhesion of the drive wheels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/10—Vehicle control parameters
    • B60L2240/12—Speed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/10—Vehicle control parameters
    • B60L2240/24—Steering angle
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/40—Drive Train control parameters
    • B60L2240/42—Drive Train control parameters related to electric machines
    • B60L2240/423—Torque
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/40—Drive Train control parameters
    • B60L2240/46—Drive Train control parameters related to wheels
    • B60L2240/465—Slip
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/60—Navigation input
    • B60L2240/64—Road conditions
    • B60L2240/645—Type of road
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/60—Navigation input
    • B60L2240/64—Road conditions
    • B60L2240/647—Surface situation of road, e.g. type of paving
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2250/00—Driver interactions
    • B60L2250/26—Driver interactions by pedal actuation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2250/00—Driver interactions
    • B60L2250/26—Driver interactions by pedal actuation
    • B60L2250/28—Accelerator pedal thresholds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2260/00—Operating Modes
    • B60L2260/20—Drive modes; Transition between modes
    • B60L2260/28—Four wheel or all wheel drive
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/72—Electric energy management in electromobility

Definitions

  • the present application relates to the field of vehicle power distribution, and in particular to a torque distribution method for four-wheel drive of an electric vehicle, and a system and a vehicle to which the method for four-wheel drive torque distribution of an electric vehicle is applied.
  • the four-wheel drive system can provide better power performance and handling performance. Therefore, more and more electric vehicles adopt the power system of four-wheel drive structure.
  • Electric four-wheel drive vehicles usually have independent front axle electric drive system and rear axle electric drive system. -1) The distribution of the driver's vehicle demand torque is carried out. Different from two-wheel drive electric vehicles, electric four-wheel drive vehicles require torque distribution on the front and rear axles, and an effective torque distribution control strategy is required to give full play to the advantages of the four-wheel drive system, which has high control complexity.
  • the current torque distribution control technology for the front and rear axles of four-wheel drive vehicles is still a difficult and hot spot in vehicle control technology.
  • Different terrains, different road adhesion coefficients, different vehicle motion states and different driving operations of the driver have different requirements for the torque distribution of the front and rear axles of the vehicle.
  • Different front and rear axle torque distributions affect the driving efficiency, stability and handling of the vehicle. and other performance, and the front and rear axle torque distribution is also limited to the limitations of the front and rear axle electric drive system. Therefore, how to reasonably distribute the torque distribution ratio of the front and rear axles according to the actual driving conditions of the electric four-wheel drive vehicle to achieve the highest driving efficiency is a technical problem to be solved by those skilled in the art.
  • the purpose of the present application is to provide a four-wheel drive torque distribution method for an electric vehicle, and a system and a vehicle applying the four-wheel drive torque distribution method for an electric vehicle, which can realize the torque distribution of the front and rear axles with the best road adhesion performance and the highest driving efficiency .
  • the present application provides a torque distribution method for an electric vehicle four-wheel drive.
  • the torque distribution method for an electric vehicle four-wheel drive includes:
  • the demand state includes the highest driving efficiency
  • outputting the front and rear axle torque distribution coefficient corresponding to the demand state of the entire vehicle includes: according to the mathematical model of the front and rear axle driving force based on the simultaneous slippage of the front and rear wheels and the total demand torque of the entire vehicle the obtained first front and rear axle torque distribution coefficient; the front and rear axle torque distribution coefficient is obtained according to the first front and rear axle torque distribution coefficient;
  • the target torque of the front and rear drive systems is obtained according to the torque distribution coefficient of the front and rear axles and the total required torque of the entire vehicle.
  • the step of obtaining the total vehicle demand torque includes:
  • the total vehicle demand torque is calculated according to the vehicle speed and the accelerator pedal opening by looking up a table.
  • the step of obtaining the total vehicle demand torque includes:
  • the total vehicle demand torque is calculated according to the driving mode, the vehicle speed and the accelerator pedal opening by looking up a table.
  • the method for obtaining the mathematical model of the driving force of the front and rear axles based on the simultaneous slippage of the front and rear wheels includes the steps:
  • the first formula group corresponding to the moment is obtained from the ground contact points of the front and rear axle tires;
  • the road surface adhesion coefficient is eliminated, and the mathematical model based on the front and rear axle driving force distribution when the front and rear wheels simultaneously slip is obtained.
  • the first formula group is:
  • the second formula group is:
  • the third formula group is:
  • the step of obtaining the target torque of the front and rear drive systems according to the front and rear axle torque distribution coefficient and the total vehicle demand torque further includes:
  • the final target torque is sent to the front and rear drive systems.
  • the demand state further includes vehicle steering instability control, and obtaining the front and rear axle torque distribution coefficients according to the first front and rear axle torque distribution coefficients includes:
  • the front and rear axle torque distribution coefficient is obtained by adding the first front and rear axle torque distribution coefficient and the second front and rear axle torque distribution coefficient.
  • the vehicle dynamics analysis is to simplify the vehicle into a two-degree-of-freedom model, analyze the force relationship between the lateral and lateral motion of the vehicle when turning, and use the resultant force of the external vehicle force perpendicular to the driving direction of the vehicle and the center of mass of the vehicle.
  • the torque and the force equation are established to obtain the desired yaw rate of the driver, and then the vehicle steering state is obtained by the difference between the desired yaw rate and the actual yaw rate, and the vehicle steering state is used as PID control
  • the input parameters of the algorithm, and then the torque distribution coefficient of the second front and rear axles is obtained according to the relationship between the input parameters and the preset steering distribution coefficient; wherein, the force equation is:
  • V is the speed of the vehicle
  • M is the mass of the vehicle
  • Izz is the moment of inertia around the z-axis
  • D 1 and D 2 are the cornering stiffnesses of the tires on the front and rear axles, respectively
  • a 1 and a 2 are the distances from the center of mass to the front and rear axles, respectively.
  • ⁇ is the slip angle
  • yaw rate is the tire angle, that is, the product of the steering wheel angle and the angular transmission ratio.
  • the demand state further includes gradeability, and obtaining the front and rear axle torque distribution coefficient according to the first front and rear axle torque distribution coefficient includes:
  • the front and rear axle torque distribution coefficient is obtained according to the product of the third front and rear axle torque distribution coefficient and the first front and rear axle torque distribution coefficient.
  • obtaining the front-rear axle torque distribution coefficient according to the product of the third front-rear axle torque distribution coefficient and the first front-rear-axle torque distribution coefficient includes:
  • the fourth front and rear axle torque distribution coefficient based on the axle slip control is obtained through the relationship between the axle slip state parameter and the preset distribution coefficient based on the axle slip state parameter;
  • the demand state further includes demand maneuverability, and obtaining the front and rear axle torque distribution coefficient according to the first front and rear axle torque distribution coefficient includes:
  • the fifth front and rear axle torque distribution coefficient is obtained by comparing the steering wheel angle with the preset distribution coefficient calibration scale based on the steering wheel angle;
  • the front and rear axle torque distribution coefficient is obtained according to the product of the fifth front and rear axle torque distribution coefficient and the first front and rear axle torque distribution coefficient.
  • obtaining the front and rear axle torque distribution coefficient according to the product of the fifth front and rear axle torque distribution coefficient and the first front and rear axle torque distribution coefficient includes:
  • the front and rear axle torque distribution coefficient is obtained by multiplying the fifth front-rear axle torque distribution coefficient, the sixth front-rear axle torque distribution coefficient, and the first front-rear axle torque distribution coefficient.
  • the demand state further includes vehicle steering instability control, gradeability and demand maneuverability, and obtaining the front and rear axle torque distribution coefficients according to the first front and rear axle torque distribution coefficients includes:
  • the vehicle steering state is obtained through vehicle dynamics analysis, and then the second front and rear axle torque distribution coefficient is obtained according to the relationship between the vehicle steering state and the preset steering distribution coefficient.
  • the quantitative table is compared to obtain the third front and rear axle torque distribution coefficient based on the slope gradient, and the fourth front and rear axle torque distribution coefficient based on the axle slip control is obtained through the relationship between the axle slip state parameter and the preset distribution coefficient based on the axle slip state parameter.
  • the fifth front and rear axle torque distribution coefficient is obtained by comparing the steering wheel angle with the preset steering wheel angle-based distribution coefficient calibration scale, and the sixth front and rear axle torque distribution is obtained by comparing the vehicle speed with the preset vehicle speed-based distribution coefficient calibration scale.
  • the present application also provides a four-wheel drive torque distribution system for an electric vehicle.
  • the four-wheel drive torque distribution system for an electric vehicle includes:
  • the memory stores at least one program instruction
  • a processor where the processor loads and executes the at least one program instruction to implement the four-wheel drive torque distribution method for an electric vehicle according to any one of the foregoing embodiments.
  • the present application further provides a vehicle, as an embodiment, the vehicle includes the four-wheel drive torque distribution system for an electric vehicle described in the above embodiment.
  • the four-wheel-drive torque distribution method for an electric vehicle provided by the present application, as well as a system and a vehicle applying the four-wheel-drive torque distribution method for an electric vehicle, by establishing a mathematical model of the front and rear axle driving torques when the front and rear wheels of the vehicle slip simultaneously, according to the mathematical model, it is possible to obtain The ideal front and rear axle driving force distribution curves of different road adhesion coefficients are obtained.
  • the required torque and the corresponding front and rear axle torque distribution coefficients obtain the target torque of the front and rear drive systems with the best road adhesion and the highest driving efficiency.
  • FIG. 1 is a schematic flowchart of an embodiment of a torque distribution method for an electric vehicle four-wheel drive according to the present application.
  • FIG. 2 is a schematic diagram of a vehicle driving force analysis when the mathematical model of the application is constructed.
  • Figure 3 is a schematic diagram of the ideal front and rear axle driving force distribution curve obtained by the application through a mathematical model.
  • FIG. 4 is a logical structural block diagram of an embodiment of an electric vehicle four-wheel drive torque distribution method according to the present application.
  • FIG. 5 is a schematic structural diagram of an embodiment of an electric vehicle four-wheel drive torque distribution system according to the present application.
  • A, B or C or “A, B and/or C” means “any of the following: A; B; C; A and B; A and C; B and C; A, B and C” . Exceptions to this definition arise only when combinations of elements, functions, steps, or operations are inherently mutually exclusive in some way.
  • FIG. 1 is a schematic flowchart of an embodiment of a torque distribution method for an electric vehicle four-wheel drive according to the present application.
  • the four-wheel-drive torque distribution method for an electric vehicle in this embodiment may include, but is not limited to, the following steps:
  • Step S1 Obtain the total vehicle demand torque.
  • the total required torque of the entire vehicle represents the torque required by the entire vehicle under different driving states.
  • it is determined by the opening degree of the accelerator pedal, that is, the current total vehicle demand torque is calculated by looking up the table of the accelerator pedal opening degree.
  • step S1: obtaining the total vehicle demand torque includes:
  • step S1: obtaining the total vehicle demand torque includes:
  • vehicle speed and accelerator pedal opening look up the table to calculate the total required torque of the vehicle.
  • Step S2 determining the vehicle demand state according to the driving parameter information, and outputting the front and rear axle torque distribution coefficients corresponding to the vehicle demand state;
  • the demand state includes the highest driving efficiency
  • the output torque distribution coefficient of the front and rear axles corresponding to the demand state of the whole vehicle includes: according to the mathematical model of the front and rear axle driving force based on the simultaneous slippage of the front and rear wheels and the total demand torque of the vehicle, the first front and rear axles are obtained.
  • Torque distribution coefficient P1; the front and rear axle torque distribution coefficient P is obtained according to the first front and rear axle torque distribution coefficient P1.
  • the demand state of the whole vehicle refers to the different functional requirements of the vehicle in different motion scenarios, and the different functional requirements can be transformed into different front and rear axle torque distributions.
  • the most basic functional requirement is that the driving efficiency of the vehicle is the highest.
  • the demand state of the vehicle in different special situations such as the stability of the vehicle when the vehicle is running on a gradient, is to be adjusted corresponding to the front and rear axle torque distribution coefficient corresponding to the special situation when the vehicle is running.
  • the driving parameter information of the vehicle corresponding to different demand states requires different driving parameter information, which may include steering wheel angle, four-wheel speed, vehicle speed, yaw rate, lateral acceleration, longitudinal acceleration, driving mode, and slope gradient.
  • the highest driving efficiency of the vehicle is particularly important.
  • the road surface adhesion performance of the vehicle tires is the best, and the driving efficiency is the highest. Therefore, by establishing a mathematical model of the driving torque of the front and rear axles when the front and rear wheels of the vehicle slip at the same time, according to the mathematical model, the ideal distribution curve of the front and rear axle driving force on the road surface with different road adhesion coefficients can be obtained.
  • the front and rear axle torque distribution coefficients under different required torques are calibrated, and the first front and rear axle torque distribution coefficient P1 corresponding to the highest driving efficiency can be obtained from the calibration chart.
  • the torque distribution coefficient of the front and rear axles mentioned in this article represents the proportion of the front axle torque to the total demand torque, or the proportion of the rear axle torque to the total demand torque. When one of them is determined, the other parameter is Of course it can be determined.
  • step S2 the method for obtaining the mathematical model of the driving force of the front and rear axles when the front and rear wheels slip simultaneously includes the steps:
  • the first formula group corresponding to the moment is obtained from the ground contact points of the front and rear axle tires;
  • the road adhesion coefficient is eliminated, and the mathematical model based on the front and rear axle driving force distribution when the front and rear wheels are slipping at the same time is obtained.
  • FIG. 2 is a schematic diagram of a vehicle driving force analysis when the mathematical model of the present application is constructed.
  • the first formula group is obtained by taking the moment at the contact points of the front and rear axle tires of the vehicle:
  • the vehicle's adhesion performance is best utilized.
  • the condition when the front and rear wheels are slipping at the same time is that the front and rear axle driving forces are equal to the adhesion force, and the front and rear axle driving forces are respectively equal to their respective adhesion forces , so the second formula group is:
  • the third formula group representing the driving force of the front and rear axles is obtained:
  • the ideal driving force distribution curve can be obtained for different adhesion coefficient road surfaces, that is, the ideal front and rear axle torque distribution curve.
  • FIG. 3 is a schematic diagram of an ideal front and rear axle driving force distribution curve obtained by a mathematical model of the present application. It can be seen from Figure 3 that when the total required torque of the whole vehicle is determined, the corresponding torques of the front and rear axles are also determined, that is to say, the torque distribution coefficient P1 of the first front and rear axles is determined. The distribution coefficient P1 is obtained by looking up the table of the total required torque of the whole vehicle, and the table is obtained through the above analysis, that is, the final application of the mathematical model.
  • step S2 the demand state further includes vehicle steering instability control, and obtaining the front and rear axle torque distribution coefficient according to the first front and rear axle torque distribution coefficient P1 includes:
  • the front and rear axle torque distribution coefficient P is obtained by adding the first front and rear axle torque distribution coefficient P1 and the second front and rear axle torque distribution coefficient P2.
  • the torque distribution of the front and rear axles is particularly important. It can be understood that when the vehicle is in a state of excessive steering, the lateral force load on the rear tires is relatively large. At this time, if the driving torque distribution control is applied to the rear wheels , increasing the torque will easily lead to the deterioration of the vehicle's excessive steering state, which is not conducive to vehicle stability control. When the vehicle is in a neutral or understeer state, by controlling the torque distribution to the rear wheels and increasing the torque, it is beneficial to improve the steering response of the vehicle and weaken the understeer characteristics.
  • the steering state of the vehicle is judged, and then the torque distribution coefficient of the front and rear axles under different steering states is obtained according to the relationship between different steering states and the preset steering distribution coefficient, that is, the quantified steering state is used as the input parameter.
  • the preset steering distribution coefficient relationship may be a calibration table or a calculation formula, which is not limited here.
  • the vehicle dynamics analysis is to simplify the vehicle into a two-degree-of-freedom model, analyze the force relationship between the lateral and lateral motion of the vehicle when turning, and use the resultant force of the vehicle's external force perpendicular to the vehicle's driving direction and the moment around the center of mass and
  • the force equation is established to obtain the desired yaw rate of the driver, and then the vehicle steering state is obtained by the difference between the desired yaw rate and the actual yaw rate, and the vehicle steering state is used as the input parameter of the PID control algorithm, and then according to the input
  • the relationship between the parameters and the preset steering distribution coefficient obtains the corresponding torque distribution coefficient P2 of the second front and rear axles; wherein, the force equation is:
  • V is the speed of the vehicle
  • M is the mass of the vehicle
  • Izz is the moment of inertia around the z-axis
  • D 1 and D 2 are the cornering stiffnesses of the tires on the front and rear axles, respectively
  • a 1 and a 2 are the distances from the center of mass to the front and rear axles, respectively.
  • ⁇ is the slip angle
  • yaw rate is the tire angle, that is, the product of the steering wheel angle and the angular transmission ratio.
  • the vehicle is simplified to a two-degree-of-freedom model, and according to the force equation obtained by the model, when the driver inputs a certain steering wheel angle, the driver's expected yaw rate can be calculated, and then the The actual yaw angular velocity values detected by the yaw angular velocity sensor installed on the vehicle are compared. When the actual yaw angular velocity is greater than the expected yaw angular velocity, the vehicle is oversteered, otherwise it is understeered.
  • the difference between the expected yaw angular velocity and the actual yaw angular velocity is used as the input parameter of the closed-loop PID (proportion, integral, differential) control algorithm, according to the preset steering distribution coefficient relationship.
  • the second front and rear axle torque distribution coefficient P2 is determined.
  • the demand state further includes gradeability
  • the front and rear axle torque distribution coefficient obtained according to the first front and rear axle torque distribution coefficient P1 includes:
  • the third front and rear axle torque distribution coefficient P3 based on the slope gradient is obtained by comparing the gradient gradient with the preset calibration scale of the distribution coefficient based on the gradient gradient;
  • the front-rear axle torque distribution coefficient P is obtained according to the product of the third front-rear axle torque distribution coefficient P3 and the first front-rear-axle torque distribution coefficient P1.
  • the demand state is gradeability, which may include torque distribution adjustment for front and rear axles when driving on a slope.
  • torque adjustment for front and rear axles in other situations may also be added.
  • the slope of the ramp is used as a variable.
  • a look-up table with the slope of the ramp as an input parameter is preset.
  • the corresponding slope of the look-up table has a corresponding distribution coefficient, and the distribution coefficient is used as the third front and rear.
  • the axle torque distribution coefficient P3, and then the front and rear axle torque distribution coefficient P is obtained according to the product of the third front and rear axle torque distribution coefficient P3 and the first front and rear axle torque distribution coefficient P1.
  • the front and rear axle torque distribution coefficient P obtained according to the product of the third front and rear axle torque distribution coefficient P3 and the first front and rear axle torque distribution coefficient P1 includes:
  • the fourth front and rear axle torque distribution coefficient P4 based on the axle slip control is obtained through the relationship between the axle slip state parameter and the preset distribution coefficient based on the axle slip state parameter;
  • the preset distribution coefficient relationship based on the shaft slip state parameter may be a corresponding calibration scale or a corresponding calculation formula.
  • the demand state further includes demand maneuverability, and obtaining the front and rear axle torque distribution coefficient P according to the first front and rear axle torque distribution coefficient P1 includes:
  • the fifth front and rear axle torque distribution coefficient P5 is obtained by comparing the steering wheel angle with the preset distribution coefficient calibration scale based on the steering wheel angle;
  • the front-rear axle torque distribution coefficient P is obtained according to the product of the fifth front-rear axle torque distribution coefficient P5 and the first front-rear-axle torque distribution coefficient P1.
  • the torque distribution of the front and rear axles is revised according to the steering wheel angle, so as to achieve rapid and precise control of vehicle handling.
  • the front and rear axle torque distribution coefficient P obtained according to the product of the fifth front and rear axle torque distribution coefficient P5 and the first front and rear axle torque distribution coefficient P1 includes:
  • the sixth front and rear axle torque distribution coefficient P6 is obtained by comparing the vehicle speed with the preset vehicle speed-based distribution coefficient calibration scale;
  • the front and rear axle torque distribution coefficient P is obtained by multiplying the fifth front and rear axle torque distribution coefficient P5, the sixth front and rear axle torque distribution coefficient P6, and the first front and rear axle torque distribution coefficient P1.
  • the demand state further includes vehicle steering instability control, gradeability and demand maneuverability, and obtaining the front and rear axle torque distribution coefficient P according to the first front and rear axle torque distribution coefficient P1 includes:
  • the steering state of the vehicle is obtained through the analysis of vehicle dynamics, and then the second front and rear axle torque distribution coefficient P2 is obtained according to the relationship between the steering state of the vehicle and the preset steering distribution coefficient.
  • the calibration scale is compared to obtain the third front and rear axle torque distribution coefficient P3 based on the slope gradient, and the fourth front and rear axle torque distribution based on axle slip control is obtained through the relationship between the axle slip state parameter and the preset distribution coefficient based on the axle slip state parameter.
  • Coefficient P4 the fifth front and rear axle torque distribution coefficient P5 is obtained by comparing the steering wheel angle with the preset distribution coefficient calibration scale based on the steering wheel angle, and the sixth torque distribution coefficient P5 is obtained by comparing the vehicle speed with the preset vehicle speed-based distribution coefficient calibration scale.
  • FIG. 4 is a logical structural block diagram of an embodiment of a torque distribution method for an electric vehicle four-wheel drive of the present application.
  • the vehicle driving parameters are used as input signals, including the steering wheel.
  • Front and rear axle torque distribution coefficient P3, fourth front and rear axle torque distribution coefficient P4 based on axle slip control, fifth front and rear axle torque distribution coefficient P5 based on steering wheel angle, sixth front and rear axle torque distribution coefficient P6 based on vehicle speed, and then by formula P P1*P3*P5*P6+P2+P4, where P is the torque distribution coefficient of the front and rear axles, and then the front and rear axle torque distribution coefficient P is multiplied by the total vehicle demand torque to obtain the target front axle torque and the target rear axle torque, It is then sent to the vehicle's front and rear drive systems to request execution.
  • Step S3 Obtain the target torque of the front and rear drive systems according to the front and rear axle torque distribution coefficient P and the total vehicle demand torque.
  • step S3 after the step of obtaining the target torque of the front and rear drive systems according to the torque distribution coefficient of the front and rear axles and the total required torque of the vehicle, it further includes:
  • the actual front and rear axle torque distribution cannot be completely consistent with the ideal driving force distribution curve.
  • the ideal distribution is carried out within the range of the road adhesion coefficient, which is reflected in the accelerator pedal or the total required torque of the whole vehicle, that is, only reasonable distribution can be carried out within a certain range of required torque. Therefore, in the present embodiment, the final target torque of the front and rear drive system is obtained by revising the front and rear axle torque distribution coefficient P in consideration of the actual motor conditions.
  • the weight of the front and rear axles can be evaluated in real time, and a dynamic driving model can be established to achieve optimal road adhesion utilization.
  • the ideal front and rear axle driving force distribution curves of the road surface with different road adhesion coefficients can be obtained.
  • the ideal front and rear axle driving force distribution curve calibrates the front and rear axle torque distribution coefficients under different demand torques, so that the best road adhesion performance can be obtained according to the total vehicle demand torque and the corresponding front and rear axle torque distribution coefficients when the vehicle is running. Target torque for the most efficient front and rear drive systems.
  • the present application also provides an electric vehicle four-wheel drive torque distribution system.
  • FIG. 5 is a schematic structural diagram of an embodiment of the electric vehicle four-wheel drive torque distribution system of the present application.
  • the four-wheel-drive torque distribution system 10 for an electric vehicle includes a memory 11 and a processor 12 , the memory 11 stores at least one program instruction, and the processor 12 loads and executes at least one program instruction to implement any of the above-mentioned embodiments.
  • Four-wheel drive torque distribution method for electric vehicles includes a memory 11 and a processor 12 , the memory 11 stores at least one program instruction, and the processor 12 loads and executes at least one program instruction to implement any of the above-mentioned embodiments.
  • the present application also provides a vehicle, which includes the four-wheel drive torque distribution system 10 for an electric vehicle described in the above embodiments.
  • vehicle may also include various network interfaces, power supplies and other components.
  • the ideal front and rear axle driving force distribution curves of the road surface with different road adhesion coefficients can be obtained,
  • the front and rear axle torque distribution coefficients under different demand torques are calibrated, so that the best road adhesion performance can be obtained according to the total vehicle demand torque and the corresponding front and rear axle torque distribution coefficients when the vehicle is running.
  • the target torque for the front and rear drive systems with the best driving efficiency is a mathematical model of the driving torque of the front and rear axles when the front and rear wheels of the vehicle slip simultaneously.
  • the four-wheel-drive torque distribution method for electric vehicles of the present application as well as the system and vehicle applying the four-wheel-drive torque distribution method for electric vehicles, by establishing a mathematical model of the driving torque of the front and rear axles when the front and rear wheels of the vehicle slip at the same time, according to the mathematical model, it can be obtained
  • the ideal front and rear axle driving force distribution curve of the road surface with different road adhesion coefficients According to the ideal front and rear axle driving force distribution curve, the front and rear axle torque distribution coefficients under different demand torques are calibrated, so that the total vehicle demand is based on the real-time demand of the vehicle when the vehicle is running.
  • the torque and the corresponding front and rear axle torque distribution coefficients obtain the target torque of the front and rear drive system with the best road adhesion and the highest driving efficiency.

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Abstract

一种电动车四驱扭矩分配方法、系统及车辆，包括：获取整车总需求扭矩；根据行驶参数信息确定整车需求状态，并输出与整车需求状态对应的前后轴扭矩分配系数；其中，需求状态包括驱动效率最高，输出与整车需求状态对应的前后轴扭矩分配系数包括：根据基于前后轮同时打滑时的前后轴驱动力数学模型和整车总需求扭矩得到的第一前后轴扭矩分配系数；根据第一前后轴扭矩分配系数得到前后轴扭矩分配系数；根据前后轴扭矩分配系数和整车总需求扭矩得到前后驱动系统的目标扭矩。通过该电动车四驱扭矩分配方法，可以实现车辆路面附着性能最好、驱动效率最高。

Description

电动车四驱扭矩分配方法、系统及车辆 技术领域
本申请涉及汽车动力分配领域，具体涉及一种电动车四驱扭矩分配方法，以及应用所述电动车四驱扭矩分配方法的系统及车辆。
背景技术
随着全球环境问题和能源危机的不断加重，环保节能成为全球的热点话题，电动汽车由于具有节能、高效以及零排放等优点，越来越多的国家开始致力于推进纯电动汽车的研发和普及。
在节能和环保的基础上，通过四驱动力系统能够提供更好的动力性能和操控性能。因此，越来越多的电动汽车采用了四驱结构的动力系统，电动四驱汽车通常具备独立的前轴电驱动系统和后轴电驱动系统，前、后轴电驱动系统均可以在(0-1)的占比范围内进行驾驶员的整车需求扭矩的分配。与两驱电动汽车不同，电动四驱汽车需要在前后轴进行扭矩分配，需要有效的扭矩分配控制策略才能充分发挥四驱动力系统的优势，具有较高的控制复杂性。
技术问题
由于四驱汽车前后轴扭矩分配需要考虑不同的地形和行驶工况，目前对于四驱汽车前后轴的扭矩分配控制技术仍然是整车控制技术的难点及热点。不同地形、不同路面附着系数，不同车辆运动状态以及驾驶员不同的驾驶操作，对车辆的前后轴扭矩分配的要求均不同， 不同的前后轴扭矩分配影响到车辆的驱动效率、稳定性和操控性等性能，并且前后轴扭矩分配时还限于前后轴电驱系统的自身限制。因此，如何根据电动四驱车辆的实际行驶状况合理分配前后轴的扭矩分配比例实现驱动效率最高是本领域技术人员亟待解决的技术问题。
技术解决方案
本申请的目的在于，提供一种电动车四驱扭矩分配方法，以及应用所述电动车四驱扭矩分配方法的系统及车辆，可以实现路面附着性能最好、驱动效率最高的前后轴的扭矩分配。
为解决上述技术问题，本申请提供一种电动车四驱扭矩分配方法，作为其中一种实施方式，所述电动车四驱扭矩分配方法包括：
获取整车总需求扭矩；
根据行驶参数信息确定整车需求状态，并输出与所述整车需求状态对应的前后轴扭矩分配系数；
其中，所述需求状态包括驱动效率最高，输出与所述整车需求状态对应的前后轴扭矩分配系数包括：根据基于前后轮同时打滑时的前后轴驱动力数学模型和所述整车总需求扭矩得到的第一前后轴扭矩分配系数；根据所述第一前后轴扭矩分配系数得到所述前后轴扭矩分配系数；
根据所述前后轴扭矩分配系数和所述整车总需求扭矩得到前后驱动系统的目标扭矩。
作为其中一种实施方式，所述获取整车总需求扭矩的步骤包括：
获取车速和油门踏板开度；
根据所述车速和所述油门踏板开度查表计算出所述整车总需求扭矩。
作为其中一种实施方式，所述获取整车总需求扭矩的步骤包括：
获取驾驶模式、车速及油门踏板开度；
根据所述驾驶模式、所述车速和所述油门踏板开度查表计算出所述整车总需求扭矩。
作为其中一种实施方式，所述基于前后轮同时打滑时的前后轴驱动力数学模型的得到方法包括步骤：
对前、后轴轮胎接地点取力矩得到对应的第一公式组；
根据前、后轴驱动力之和等于总的路面附着力，且前、后轴驱动力分别等于各自的路面附着力，得到对应的第二公式组；
根据所述第一公式组和所述第二公式组得到代表前、后轴驱动力的第三公式组；
在所述第三公式组的基础上消除其中的路面附着系数，得到所述基于前后轮同时打滑时的前后轴驱动力分配的数学模型。
作为其中一种实施方式，所述第一公式组为：
F Z1L＝(G*b-m*du/dt*Hg)
F Z2L＝(G*a+m*du/dt*Hg)
所述第二公式组为：
F f+F r＝φ*G
F f＝φ*F Z1
F r＝φ*F Z2
所述第三公式组为：
F f＝φ(W f*g-φ*m*g*Hg/L)
F r＝φ(W r*g+φ*m*g*Hg/L)
所述基于前后轮同时打滑时的前后轴驱动力分配的数学模型为：
Figure PCTCN2020129825-appb-000001
其中，m＝W f+W r，L＝a+b，G＝m*g，
Figure PCTCN2020129825-appb-000002
m为满载质量，W f为前轴质量，W r为前轴质量，F Z1为前轮地面法向力，F Z2为后轮地面法向力，Hg为质心高度，L为轴距，a为质心到前轴的距离，b为质心到后轴的距离，r为轮胎滚动半径，
Figure PCTCN2020129825-appb-000003
为所述路面附着系数，G为汽车重力，du/dt为汽车加速度，F f为所述前轴驱动力，F r为所述后轴驱动力，M f为前轴扭矩，M r为后轴扭矩。
作为其中一种实施方式，所述根据所述前后轴扭矩分配系数和所述整车总需求扭矩得到前后驱动系统的目标扭矩的步骤后还包括：
获取所述前后驱动系统的最大扭矩参数；
将所述目标扭矩与所述最大扭矩参数进行比较，取其中的较小值作为前后驱动系统的最终目标扭矩；
将所述最终目标扭矩发送至所述前后驱动系统。
作为其中一种实施方式，所述需求状态还包括车辆转向失稳控制，根据所述第一前后轴扭矩分配系数得到所述前后轴扭矩分配系数包括：
通过车辆动力学分析得到车辆转向状态，然后根据所述车辆转向状态与预先设置的转向分配系数关系获取第二前后轴扭矩分配系数；
将所述第一前后轴扭矩分配系数与所述第二前后轴扭矩分配系数相加得到所述前后轴扭矩分配系数。
作为其中一种实施方式，所述车辆动力学分析为将车辆简化为二自由度模型，分析车辆在转弯时侧向与横向运动受力关系，以车辆外力在垂直于车辆行驶方向合力与绕质心的力矩和建立受力方程式，得到驾驶员的期望横摆角速度，然后通过所述期望横摆角速度与实际横摆角速度的差值得到所述车辆转向状态，并将所述车辆转向状态作为PID控制算法的输入参数，然后根据所述输入参数和预先设置的转向分配系数关系得到所述第二前后轴扭矩分配系数；其中，所述受力方程式为：
Figure PCTCN2020129825-appb-000004
Figure PCTCN2020129825-appb-000005
其中，V为车速，M为整车质量，Izz为绕z轴的转动惯量，D 1、D 2分别为前后轴轮胎的侧偏刚度，a 1、a 2分别为质心到前后轴的距离，β为侧偏角，
Figure PCTCN2020129825-appb-000006
为横摆角速度，δ为轮胎转角，即方向盘转角与角传动比的乘积。
作为其中一种实施方式，所述需求状态还包括爬坡能力，根据所述第一前后轴扭矩分配系数得到所述前后轴扭矩分配系数包括：
通过坡道坡度与预设的基于坡道坡度的分配系数标定量表比对得到基于坡道坡度的第三前后轴扭矩分配系数；
根据所述第三前后轴扭矩分配系数与所述第一前后轴扭矩分配系数的乘积得到所述前后轴扭矩分配系数。
作为其中一种实施方式，根据所述第三前后轴扭矩分配系数与所述第一前后轴扭矩分配系数的乘积得到所述前后轴扭矩分配系数包括：
通过轴打滑状态参数与预先设置的基于轴打滑状态参数的分配系数关系得到基于轴打滑控制的第四前后轴扭矩分配系数；
将所述第三前后轴扭矩分配系数与所述第一前后轴扭矩分配系数相乘，并将相乘得到的结果与所述第四前后轴扭矩分配系数相加得到所述前后轴扭矩分配系数。
作为其中一种实施方式，所述需求状态还包括需求操控性，根据所述第一前后轴扭矩分配系数得到所述前后轴扭矩分配系数包括：
通过方向盘转角与预设的基于方向盘转角的分配系数标定量表比对得到第五前后轴扭矩分配系数；
根据所述第五前后轴扭矩分配系数与所述第一前后轴扭矩分配系数的乘积得到所述前后轴扭矩分配系数。
作为其中一种实施方式，所述根据所述第五前后轴扭矩分配系数与所述第一前后轴扭矩分配系数的乘积得到所述前后轴扭矩分配系 数包括：
通过车速与预设的基于车速的分配系数标定量表比对得到第六前后轴扭矩分配系数；
将所述第五前后轴扭矩分配系数、所述第六前后轴扭矩分配系数以及所述第一前后轴扭矩分配系数相乘得到所述前后轴扭矩分配系数。
作为其中一种实施方式，所述需求状态还包括车辆转向失稳控制、爬坡能力以及需求操控性，根据所述第一前后轴扭矩分配系数得到所述前后轴扭矩分配系数包括：
通过车辆动力学分析得到车辆转向状态，然后根据所述车辆转向状态与预先设置的转向分配系数关系获取第二前后轴扭矩分配系数，通过坡道坡度与预设的基于坡道坡度的分配系数标定量表比对得到基于坡道坡度的第三前后轴扭矩分配系数，通过轴打滑状态参数与预先设置的基于轴打滑状态参数的分配系数关系得到基于轴打滑控制的第四前后轴扭矩分配系数，通过方向盘转角与预设的基于方向盘转角的分配系数标定量表比对得到第五前后轴扭矩分配系数，通过车速与预设的基于车速的分配系数标定量表比对得到第六前后轴扭矩分配系数；
将所述第一前后轴扭矩分配系数、所述第三前后轴扭矩分配系数、所述第五前后轴扭矩分配系数以及所述第六前后轴扭矩分配系数相乘，并将相乘所得与所述第二前后轴扭矩分配系数和所述第四前后轴扭矩分配系数相加以获得所述前后轴扭矩分配系数。
为解决上述技术问题，本申请还提供一种电动车四驱扭矩分配系统，作为其中一种实施方式，所述电动车四驱扭矩分配系统包括：
存储器，所述存储器存储有至少一条程序指令；
处理器，所述处理器通过加载并执行所述至少一条程序指令以实现上述任一实施方式所述的电动车四驱扭矩分配方法。
为解决上述技术问题，本申请还提供一种车辆，作为其中一种实施方式，所述车辆包括上述实施方式所述的电动车四驱扭矩分配系统。
有益效果
本申请提供的电动车四驱扭矩分配方法，以及应用所述电动车四驱扭矩分配方法的系统及车辆，通过建立车辆前后轮同时打滑时的前后轴驱动力矩数学模型，根据该数学模型可以得出不同路面附着系数路面理想的前后轴驱动力分配曲线，根据该理想的前后轴驱动力分配曲线标定不同需求扭矩下的前后轴扭矩分配系数，从而在车辆行驶时根据车辆实时需求的整车总需求扭矩和相应的前后轴扭矩分配系数得到路面附着性能最好、驱动效率最高的前后驱动系统的目标扭矩。
附图说明
图1为本申请电动车四驱扭矩分配方法一实施方式的流程示意图。
图2为本申请数学模型构建时的车辆驱动受力分析示意图。
图3为本申请通过数学模型得到的理想前后轴驱动力分配曲线 示意图。
图4为本申请电动车四驱扭矩分配方法一实施方式的逻辑结构框图。
图5为本申请电动车四驱扭矩分配系统一实施方式结构示意图。
本发明的实施方式
以下由特定的具体实施例说明本申请的实施方式，熟悉此技术的人士可由本说明书所揭露的内容轻易地了解本申请的其他优点及功效。
在下述描述中，参考附图，附图描述了本申请的若干实施例。应当理解，还可使用其他实施例，并且可以在不背离本申请的精神和范围的情况下进行机械组成、结构、电气以及操作上的改变。下面的详细描述不应该被认为是限制性的，并且本申请的实施例的范围仅由公布的专利的权利要求书所限定。这里使用的术语仅是为了描述特定实施例，而并非旨在限制本申请。虽然在一些实例中术语第一、第二等在本文中用来描述各种元件，但是这些元件不应当被这些术语限制。这些术语仅用来将一个元件与另一个元件进行区分。
再者，如同在本文中所使用的，单数形式“一”、“一个”和“该”旨在也包括复数形式，除非上下文中有相反的指示。应当进一步理解，术语“包含”、“包括”表明存在所述的特征、步骤、操作、元件、组件、项目、种类、和/或组，但不排除一个或多个其他特征、步骤、操作、元件、组件、项目、种类、和/或组的存在、出现或添加。此处使用的术语“或”和“和/或”被解释为包括性的，或意味着任一个或任何组合。因此，“A、B或C”或者“A、B和/或C”意味着“以 下任一个：A；B；C；A和B；A和C；B和C；A、B和C”。仅当元件、功能、步骤或操作的组合在某些方式下内在地互相排斥时，才会出现该定义的例外。
请参阅图1，图1为本申请电动车四驱扭矩分配方法一实施方式的流程示意图。
需要说明的是，本实施方式的电动车四驱扭矩分配方法可以包括但不限于如下几个步骤：
步骤S1：获取整车总需求扭矩。
具体地，整车总需求扭矩代表车辆在不同的行驶状态下整车所需要的扭矩。一般情况下，通过油门踏板的开度进行确定，也就是通过油门踏板开度查表计算出当前的整车总需求扭矩。
在一实施方式中，步骤S1：获取整车总需求扭矩包括：
获取车速和油门踏板开度；
根据车速和油门踏板开度查表计算出整车总需求扭矩。
值得一提的是，不同级别的车辆具有不同的整车性能调节，例如对于具备驾驶模式调节的车辆，可以调节运动、舒适等不同的驾驶模式，而在不同的驾驶模式下，不同油门踏板开度下所需的整车扭矩是不同的，也就是不同的驾驶模式下具有不同的油门踏板开度查表。因此，在一实施方式中，步骤S1：获取整车总需求扭矩包括：
获取驾驶模式、车速和油门踏板开度；
根据驾驶模式、车速和油门踏板开度查表计算出整车总需求扭矩。
步骤S2：根据行驶参数信息确定整车需求状态，并输出与整车需求状态对应的前后轴扭矩分配系数；
其中，需求状态包括驱动效率最高，输出与整车需求状态对应的 前后轴扭矩分配系数包括：根据基于前后轮同时打滑时的前后轴驱动力数学模型和整车总需求扭矩得到的第一前后轴扭矩分配系数P1；根据第一前后轴扭矩分配系数P1得到所述前后轴扭矩分配系数P。
具体地，整车的需求状态指车辆在不同的运动场景下不同的功能需求，而不同的功能需求可以转化为不同的前后轴扭矩分配。例如在整个车辆的行驶过程中，最基础的功能需求为车辆的驱动效率最高，在驱动效率最高的基础上可能还需要实现车辆转向失稳时的失稳控制，还可能要实现在车辆上坡时的车辆坡度行驶时的稳定性等不同特殊情形下的车辆的需求状态，也就是对应车辆行驶时的特殊情形具有对应的前后轴扭矩分配系数的调整。其中，车辆的行驶参数信息对应不同的需求状态所需的行驶参数信息不同，可以包括方向盘转角、四轮轮速、车速、横摆角速度、横向加速度、纵向加速度、驾驶模式、坡道坡度等。
其中，作为最基础的车辆需求状态，车辆的驱动效率最高尤为重要。当车辆的前后轮同时打滑时，车辆轮胎的路面附着性能最好，驱动效率最高。因此，通过建立车辆前后轮同时打滑时的前后轴驱动力矩数学模型，根据该数学模型可以得出不同路面附着系数路面理想的前后轴驱动力分配曲线，根据该理想的前后轴驱动力分配曲线可以标定不同需求扭矩下的前后轴扭矩分配系数，从该标定图表可以得出驱动效率最高对应的第一前后轴扭矩分配系数P1。
值得一提的是，本文中所说的前后轴扭矩分配系数，表示前轴扭矩对于总需求扭矩的占比，或者是后轴扭矩对于总需求扭矩的占比，当其中一个确定后另外一个参数当然也就得以确定。
在一实施方式中，步骤S2中，基于前后轮同时打滑时的前后轴驱动力数学模型的得到方法包括步骤：
对前、后轴轮胎接地点取力矩得到对应的第一公式组；
根据前、后轴驱动力之和等于总的路面附着力，且前、后轴驱动力分别等于各自的路面附着力，得到对应的第二公式组；
根据第一公式组和第二公式组得到代表前、后轴驱动力的第三公式组；
在第三公式组的基础上消除其中的路面附着系数，得到基于前后轮同时打滑时的前后轴驱动力分配的数学模型。
具体地，请参考图2，图2为本申请数学模型构建时的车辆驱动受力分析示意图。如图2所示，对车辆的前、后轴轮胎接地点取力矩得到第一公式组：
F Z1L＝(G*b-m*du/dt*Hg)
F Z2L＝(G*a+m*du/dt*Hg)
当前后轮同时打滑时，车辆附着性能利用最好，在任何附着系数的路面上，前后轮同时打滑时的条件是前后轴驱动力之后等于附着力，并且前后轴驱动力分别等于各自的附着力，因此，第二公式组为：
F f+F r＝φ*G
F f＝φ*F Z1
F r＝φ*F Z2
根据第一公式组和第二公式组得到代表前、后轴驱动力的第三公式组：
F f＝φ(W f*g-φ*m*g*Hg/L)
F r＝φ(W r*g+φ*m*g*Hg/L)
最后在第三公式组的基础上消除其中的路面附着系数
Figure PCTCN2020129825-appb-000007
得到基于前后轮同时打滑时的前后轴驱动力分配的数学模型：
Figure PCTCN2020129825-appb-000008
其中，m＝W f+W r，L＝a+b，G＝m*g，
Figure PCTCN2020129825-appb-000009
m为满载质量，W f为前轴质量，W r为前轴质量，F Z1为前轮地面法向力，F Z2为后轮地面法向力，Hg为质心高度，L为轴距，a为质心到前轴的距离，b为质心到后轴的距离，r为轮胎滚动半径，
Figure PCTCN2020129825-appb-000010
为所述路面附着系数，G为汽车重力，du/dt为汽车加速度，F f为所述前轴驱动力，F r为所述后轴驱动力，M f为前轴扭矩，M r为后轴扭矩。
根据上述分析可以得出不同附着系数路面，理想的驱动力分配曲线，即理想的前后轴扭矩分配曲线。请参考图3，图3为本申请通过数学模型得到的理想前后轴驱动力分配曲线示意图。从图3可以看出，当整车的总需要扭矩确定后，相应的前后轴的扭矩也就得到确定，也就是说第一前后轴扭矩分配系数P1得到确定，实质上该第一前后轴扭矩分配系数P1是通过整车总的需求扭矩查表得出，而该表则是通过上述分析得到，也即该数学模型的最终应用。例如，图3中，路面附着系数
Figure PCTCN2020129825-appb-000011
为0.1时对应的后轴扭矩为400N.m，前轴扭矩为500N.m，因此总的需求扭矩为900N.m，此时的第一前后轴扭矩分配系数P1为前轴扭矩或后轴扭矩与总扭矩的比值。
在一实施方式中，步骤S2中，需求状态还包括车辆转向失稳控制，根据第一前后轴扭矩分配系数P1得到前后轴扭矩分配系数包括：
通过车辆动力学分析得到车辆转向状态，然后根据车辆转向状态与预先设置的转向分配系数关系获取第二前后轴扭矩分配系数P2；
将第一前后轴扭矩分配系数P1与第二前后轴扭矩分配系数P2相加得到前后轴扭矩分配系数P。
具体地，车辆在转向时，前后轴扭矩分配尤为重要，可以理解的是，车辆在过多转向状态时，后轮轮胎的侧向力负荷较大，此时如果在后轮施加驱动扭矩分配控制，增加扭矩，则容易导致车辆过多转向状态恶化，不利于车辆稳定控制。而车辆在中性或不足转向状态下，通过对后轮进行扭矩分配控制，增加扭矩，则有利于提升车辆转向响应和减弱不足转向特性。因此，通过车辆动力学分析，对车辆的转向状态进行判断，然后根据不同的转向状态与预先设置的转向分配系数关系获取不同转向状态下前后轴扭矩分配系数，即量化的转向状态作为输入参数，获取按照预先设置的转向分配系数关系得到的第二前后轴扭矩分配系数。其中，预先设置的转向分配系数关系可以是标定量表或计算公式，此处不做限定。
在一实施方式中，车辆动力学分析为将车辆简化为二自由度模型，分析车辆在转弯时侧向与横向运动受力关系，以车辆外力在垂直于车辆行驶方向合力与绕质心的力矩和建立受力方程式，得到驾驶员的期望横摆角速度，然后通过期望横摆角速度与实际横摆角速度的差值得到车辆转向状态，并将车辆转向状态作为PID控制算法的输入参数，然后根据该输入参数和预先设置的转向分配系数关系得到相应的第二前后轴扭矩分配系数P2；其中，受力方程式为：
Figure PCTCN2020129825-appb-000012
Figure PCTCN2020129825-appb-000013
其中，V为车速，M为整车质量，Izz为绕z轴的转动惯量，D 1、D 2分别为前后轴轮胎的侧偏刚度，a 1、a 2分别为质心到前后轴的距离，β为侧偏角，
Figure PCTCN2020129825-appb-000014
为横摆角速度，δ为轮胎转角，即方向盘转角 与角传动比的乘积。
具体地，根据车辆动力学分析，将车辆简化为二自由度模型，根据该模型得到的受力方程式，当驾驶员输入某个方向盘转角时，可以计算出驾驶员期望的横摆角速度，然后通过安装在整车上的横摆角速度传感器检测的实际横摆角速度数值进行对比，当实际横摆角速度大于期望的横摆角速度时，车辆为过多转向，反之为不足转向。在量化计算方面，通过将期望横摆角速度与实际横摆角速度差值作为闭环PID(比例(proportion)、积分(integral)、微分(differential))控制算法输入参数，根据预先设置的转向分配系数关系决策出第二前后轴扭矩分配系数P2。
在一实施方式中，需求状态还包括爬坡能力，根据第一前后轴扭矩分配系数P1得到前后轴扭矩分配系数包括：
通过坡道坡度与预设的基于坡道坡度的分配系数标定量表比对得到基于坡道坡度的第三前后轴扭矩分配系数P3；
根据第三前后轴扭矩分配系数P3与第一前后轴扭矩分配系数P1的乘积得到前后轴扭矩分配系数P。
具体地，该需求状态为爬坡能力，该状态可以包括对于坡道行驶时的前后轴扭矩分配调节，当然根据稳定性需求，还可以加入其他情形时的前后轴扭矩调节。本实施方式中，坡道的坡度作为一个变量，对应的，预设有以坡道坡度为输入参数的查表，查表中对应坡道坡度具有对应的分配系数，该分配系数作为第三前后轴扭矩分配系数P3，然后根据第三前后轴扭矩分配系数P3与第一前后轴扭矩分配系数P1的乘积得到前后轴扭矩分配系数P。
在一实施方式中，根据第三前后轴扭矩分配系数P3与第一前后轴扭矩分配系数P1的乘积得到前后轴扭矩分配系数P包括：
通过轴打滑状态参数与预先设置的基于轴打滑状态参数的分配系数关系得到基于轴打滑控制的第四前后轴扭矩分配系数P4；
将第三前后轴扭矩分配系数P3与第一前后轴扭矩分配系数P1相乘，并将相乘得到的结果与第四前后轴扭矩分配系数P4相加得到前后轴扭矩分配系数P。
具体地，预先设置的基于轴打滑状态参数的分配系数关系可以是相应的标定量表或相应的计算公式。
在一实施方式中，需求状态还包括需求操控性，根据第一前后轴扭矩分配系数P1得到前后轴扭矩分配系数P包括：
通过方向盘转角与预设的基于方向盘转角的分配系数标定量表比对得到第五前后轴扭矩分配系数P5；
根据第五前后轴扭矩分配系数P5与第一前后轴扭矩分配系数P1的乘积得到前后轴扭矩分配系数P。
具体地，同前述稳定性相类似，本实施方式中通过针对方向盘转角对前后轴扭矩分配进行修订，实现快速精准控制车辆操控性。
在一实施方式中，根据第五前后轴扭矩分配系数P5与第一前后轴扭矩分配系数P1的乘积得到前后轴扭矩分配系数P包括：
通过车速与预设的基于车速的分配系数标定量表比对得到第六前后轴扭矩分配系数P6；
将第五前后轴扭矩分配系数P5、第六前后轴扭矩分配系数P6以及第一前后轴扭矩分配系数P1相乘得到前后轴扭矩分配系数P。
在一实施方式中，需求状态还包括车辆转向失稳控制、爬坡能力以及需求操控性，根据第一前后轴扭矩分配系数P1得到前后轴扭矩分配系数P包括：
通过车辆动力学分析得到车辆转向状态，然后根据所述车辆转向 状态与预先设置的转向分配系数关系获取第二前后轴扭矩分配系数P2，通过坡道坡度与预设的基于坡道坡度的分配系数标定量表比对得到基于坡道坡度的第三前后轴扭矩分配系数P3，通过轴打滑状态参数与预先设置的基于轴打滑状态参数的分配系数关系得到基于轴打滑控制的第四前后轴扭矩分配系数P4，通过方向盘转角与预设的基于方向盘转角的分配系数标定量表比对得到第五前后轴扭矩分配系数P5，通过车速与预设的基于车速的分配系数标定量表比对得到第六前后轴扭矩分配系数P6；
将第一前后轴扭矩分配系数P1、第三前后轴扭矩分配系数P3、第五前后轴扭矩分配系数P5以及第六前后轴扭矩分配系数P6相乘，并将相乘所得与第二前后轴扭矩分配系数P2和第四前后轴扭矩分配系数P4相加以获得前后轴扭矩分配系数P。
具体地，请参考图4，图4为本申请电动车四驱扭矩分配方法一实施方式的逻辑结构框图。如图4所示，为了满足车辆的路面附着性能利用最好、驱动效率最高、转向失稳控制以及快速精准控制车辆操控性和稳定性，本实施方式中通过车辆行驶参数作为输入信号，包括方向盘转角、四轮轮速、车速、横摆角速度、横向加速度、纵向加速度、驾驶模式、坡道坡度以及油门踏板开度，通过上述输入信号，获得整车总需求扭矩，并通过基于前后轮同时打滑时的前后轴驱动力数学模型和整车总需求扭矩得到的第一前后轴扭矩分配系数P1，基于横摆偏差量的PID控制的第二前后轴扭矩分配系数P2，基于坡道坡度的第三前后轴扭矩分配系数P3，基于轴打滑控制的第四前后轴扭矩分配系数P4，基于方向盘转角的第五前后轴扭矩分配系数P5，基于车速的第六前后轴扭矩分配系数P6，然后通过公式P＝P1*P3*P5*P6+P2+P4，其中P为前后轴扭矩分配系数，然后通过前 后轴扭矩分配系数P与整车总需求扭矩相乘，得到目标前轴扭矩与目标后轴扭矩，然后发送给车辆的前后驱动系统请求执行。
需要说明的是，图4中P1-P6前的文字均为其对应的实质内容，例如基于坡道坡度的扭矩分配系数P3，也就是第三前后轴扭矩分配系数P3。
步骤S3：根据前后轴扭矩分配系数P和整车总需求扭矩得到前后驱动系统的目标扭矩。
在一实施方式中，步骤S3：根据前后轴扭矩分配系数和整车总需求扭矩得到前后驱动系统的目标扭矩的步骤后还包括：
获取前后驱动系统的最大扭矩参数；
将目标扭矩与前后驱动系统的最大扭矩参数进行比较，取其中的较小值作为前后驱动系统的最终目标扭矩；
将最终目标扭矩发送至前后驱动系统。
具体地，实际应用中，当车辆的前后驱动系统的前后电机参数(功率/峰值扭矩)确定后，实际的前后轴扭矩分配无法做到完全和理想的驱动力分配曲线一致，只能在一定的路面附着系数范围内进行理想分配，反应在油门踏板或整车总的需求扭矩，也即只能在一定范围的需求扭矩范围内进行合理的分配。因此，本实施方式中，通过结合实际的电机情况，修订前后轴扭矩分配系数P得到最终的前后驱动系统的目标扭矩。
值得一提的是，还可以通过增加高度传感器，实时评估前后轴的重量，建立动态的驱动模型，以期达到最优的路面附着利用。
本申请的电动车四驱扭矩分配方法，通过建立车辆前后轮同时打滑时的前后轴驱动力矩数学模型，根据该数学模型可以得出不同路面附着系数路面理想的前后轴驱动力分配曲线，根据该理想的前后轴驱 动力分配曲线标定不同需求扭矩下的前后轴扭矩分配系数，从而在车辆行驶时根据车辆实时需求的整车总需求扭矩和相应的前后轴扭矩分配系数得到路面附着性能最好、驱动效率最高的前后驱动系统的目标扭矩。
本申请还提供一种电动车四驱扭矩分配系统，请参考图5，图5为本申请电动车四驱扭矩分配系统一实施方式结构示意图。如图5所示，电动车四驱扭矩分配系统10包括存储器11和处理器12，存储器11存储有至少一条程序指令，处理器12通过加载并执行至少一条程序指令以实现上述任一实施方式的电动车四驱扭矩分配方法。
本申请还提供一种车辆，该车辆包括上述实施方式所述的电动车四驱扭矩分配系统10。当然该车辆还可以包括各种网络接口、电源等组件。
本申请的电动车四驱扭矩分配系统及车辆，通过建立车辆前后轮同时打滑时的前后轴驱动力矩数学模型，根据该数学模型可以得出不同路面附着系数路面理想的前后轴驱动力分配曲线，根据该理想的前后轴驱动力分配曲线标定不同需求扭矩下的前后轴扭矩分配系数，从而在车辆行驶时根据车辆实时需求的整车总需求扭矩和相应的前后轴扭矩分配系数得到路面附着性能最好、驱动效率最高的前后驱动系统的目标扭矩。
需要说明的是，本说明书中的各个实施例均采用递进的方式进行描述，每个实施例重点说明的都是与其他实施例的不同之处，各个实施例之间相同相似的部分互相参见即可。
上述实施例仅例示性说明本申请的原理及其功效，而非用于限制本申请。任何熟悉此技术的人士皆可在不违背本申请的精神及范畴下，对上述实施例进行修饰或改变。因此，举凡所属技术领域中具 有通常知识者在未脱离本申请所揭示的精神与技术思想下所完成的一切等效修饰或改变，仍应由本申请的权利要求所涵盖。
工业实用性
本申请的电动车四驱扭矩分配方法，以及应用所述电动车四驱扭矩分配方法的系统及车辆，通过建立车辆前后轮同时打滑时的前后轴驱动力矩数学模型，根据该数学模型可以得出不同路面附着系数路面理想的前后轴驱动力分配曲线，根据该理想的前后轴驱动力分配曲线标定不同需求扭矩下的前后轴扭矩分配系数，从而在车辆行驶时根据车辆实时需求的整车总需求扭矩和相应的前后轴扭矩分配系数得到路面附着性能最好、驱动效率最高的前后驱动系统的目标扭矩。

Claims (15)

  1. 一种电动车四驱扭矩分配方法，其特征在于，包括：
    获取整车总需求扭矩；
    根据行驶参数信息确定整车需求状态，并输出与所述整车需求状态对应的前后轴扭矩分配系数；
    其中，所述需求状态包括驱动效率最高，输出与所述整车需求状态对应的前后轴扭矩分配系数包括：根据基于前后轮同时打滑时的前后轴驱动力数学模型和所述整车总需求扭矩得到的第一前后轴扭矩分配系数；根据所述第一前后轴扭矩分配系数得到所述前后轴扭矩分配系数；
    根据所述前后轴扭矩分配系数和所述整车总需求扭矩得到前后驱动系统的目标扭矩。
  2. 根据权利要求1所述的电动车四驱扭矩分配方法，其特征在于，所述获取整车总需求扭矩的步骤包括：
    获取车速和油门踏板开度；
    根据所述车速和所述油门踏板开度查表计算出所述整车总需求扭矩。
  3. 根据权利要求1所述的电动车四驱扭矩分配方法，其特征在于，所述获取整车总需求扭矩的步骤包括：
    获取驾驶模式、车速及油门踏板开度；
    根据所述驾驶模式、所述车速和所述油门踏板开度查表计算出所述整车总需求扭矩。
  4. 根据权利要求1-3任一项所述的电动车四驱扭矩分配方法，其特征在于，所述基于前后轮同时打滑时的前后轴驱动力数学模型的得 到方法包括步骤：
    对前、后轴轮胎接地点取力矩得到对应的第一公式组；
    根据前、后轴驱动力之和等于总的路面附着力，且前、后轴驱动力分别等于各自的路面附着力，得到对应的第二公式组；
    根据所述第一公式组和所述第二公式组得到代表前、后轴驱动力的第三公式组；
    在所述第三公式组的基础上消除其中的路面附着系数，得到所述基于前后轮同时打滑时的前后轴驱动力分配的数学模型。
  5. 根据权利要求4所述的电动车四驱扭矩分配方法，其特征在于，
    所述第一公式组为：F Z1L＝(G*b-m*du/dt*Hg)
    F Z2L＝(G*a+m*du/dt*Hg)
    所述第二公式组为：F f+F r＝φ*G
    F f＝φ*F Z1
    F r＝φ*F Z2
    所述第三公式组为：F f＝φ(W f*g-φ*m*g*Hg/L)
    F r＝φ(W r*g+φ*m*g*Hg/L)
    所述基于前后轮同时打滑时的前后轴驱动力分配的数学模型为：
    Figure PCTCN2020129825-appb-100001
    其中，m＝W f+W r，L＝a+b，G＝m*g，
    Figure PCTCN2020129825-appb-100002
    m为满载质量，W f为前轴质量，W r为前轴质量，F Z1为前轮地面法向力，F Z2为后轮地面法向力，Hg为质心高度，L为轴距，a为质心到前轴的距离，b为质心到后轴的距离，r为轮胎滚动半径，
    Figure PCTCN2020129825-appb-100003
    为所述路面附着系数，G 为汽车重力，du/dt为汽车加速度，F f为所述前轴驱动力，F r为所述后轴驱动力，M f为前轴扭矩，M r为后轴扭矩。
  6. 根据权利要求1所述的电动车四驱扭矩分配方法，其特征在于，所述根据所述前后轴扭矩分配系数和所述整车总需求扭矩得到前后驱动系统的目标扭矩的步骤后还包括：
    获取所述前后驱动系统的最大扭矩参数；
    将所述目标扭矩与所述最大扭矩参数进行比较，取其中的较小值作为前后驱动系统的最终目标扭矩；
    将所述最终目标扭矩发送至所述前后驱动系统。
  7. 根据权利要求1所述的电动车四驱扭矩分配方法，其特征在于，所述需求状态还包括车辆转向失稳控制，根据所述第一前后轴扭矩分配系数得到所述前后轴扭矩分配系数包括：
    通过车辆动力学分析得到车辆转向状态，然后根据所述车辆转向状态与预先设置的转向分配系数关系获取第二前后轴扭矩分配系数；
    将所述第一前后轴扭矩分配系数与所述第二前后轴扭矩分配系数相加得到所述前后轴扭矩分配系数。
  8. 根据权利要求7所述的电动车四驱扭矩分配方法，其特征在于，所述车辆动力学分析为将车辆简化为二自由度模型，分析车辆在转弯时侧向与横向运动受力关系，以车辆外力在垂直于车辆行驶方向合力与绕质心的力矩和建立受力方程式，得到驾驶员的期望横摆角速度，然后通过所述期望横摆角速度与实际横摆角速度的差值得到所述车辆转向状态，并将所述车辆转向状态作为PID控制算法的输入参数，然后根所述该输入参数和预先设置的转向分配系数关系得到所述第二前后轴扭矩分配系数；其中，所述受力方程式为：
    Figure PCTCN2020129825-appb-100004
    Figure PCTCN2020129825-appb-100005
    其中，V为车速，M为整车质量，Izz为绕z轴的转动惯量，D 1、D 2分别为前后轴轮胎的侧偏刚度，a 1、a 2分别为质心到前后轴的距离，β为侧偏角，
    Figure PCTCN2020129825-appb-100006
    为横摆角速度，δ为轮胎转角，即方向盘转角与角传动比的乘积。
  9. 根据权利要求1所述的电动车四驱扭矩分配方法，其特征在于，所述需求状态还包括爬坡能力，根据所述第一前后轴扭矩分配系数得到所述前后轴扭矩分配系数包括：
    通过坡道坡度与预设的基于坡道坡度的分配系数标定量表比对得到基于坡道坡度的第三前后轴扭矩分配系数；
    根据所述第三前后轴扭矩分配系数与所述第一前后轴扭矩分配系数的乘积得到所述前后轴扭矩分配系数。
  10. 根据权利要求9所述的电动车四驱扭矩分配方法，其特征在于，根据所述第三前后轴扭矩分配系数与所述第一前后轴扭矩分配系数的乘积得到所述前后轴扭矩分配系数包括：
    通过轴打滑状态参数与预先设置的基于轴打滑状态参数的分配系数关系得到得到基于轴打滑控制的第四前后轴扭矩分配系数；
    将所述第三前后轴扭矩分配系数与所述第一前后轴扭矩分配系数相乘，并将相乘得到的结果与所述第四前后轴扭矩分配系数相加得到所述前后轴扭矩分配系数。
  11. 根据权利要求1所述的电动车四驱扭矩分配方法，其特征在于，所述需求状态还包括需求操控性，根据所述第一前后轴扭矩分配系数得到所述前后轴扭矩分配系数包括：
    通过方向盘转角与预设的基于方向盘转角的分配系数标定量表比对得到第五前后轴扭矩分配系数；
    根据所述第五前后轴扭矩分配系数与所述第一前后轴扭矩分配系数的乘积得到所述前后轴扭矩分配系数。
  12. 根据权利要求11所述的电动车四驱扭矩分配方法，其特征在于，所述根据所述第五前后轴扭矩分配系数与所述第一前后轴扭矩分配系数的乘积得到所述前后轴扭矩分配系数包括：
    通过车速与预设的基于车速的分配系数标定量表比对得到第六前后轴扭矩分配系数；
    将所述第五前后轴扭矩分配系数、所述第六前后轴扭矩分配系数以及所述第一前后轴扭矩分配系数相乘得到所述前后轴扭矩分配系数。
  13. 根据权利要求1所述的电动车四驱扭矩分配方法，其特征在于，所述需求状态还包括车辆转向失稳控制、爬坡能力以及需求操控性，根据所述第一前后轴扭矩分配系数得到所述前后轴扭矩分配系数包括：
    通过车辆动力学分析得到车辆转向状态，然后根据所述车辆转向状态与预先设置的转向分配系数关系获取第二前后轴扭矩分配系数，通过坡道坡度与预设的基于坡道坡度的分配系数标定量表比对得到基于坡道坡度的第三前后轴扭矩分配系数，通过轴打滑状态参数与预先设置的基于轴打滑状态参数的分配系数关系得到基于轴打滑控制的第四前后轴扭矩分配系数，通过方向盘转角与预设的基于方向盘转角的分配系数标定量表比对得到第五前后轴扭矩分配系数，通过车速与预设的基于车速的分配系数标定量表比对得到第六前后轴扭矩分配系数；
    将所述第一前后轴扭矩分配系数、所述第三前后轴扭矩分配系数、所述第五前后轴扭矩分配系数以及所述第六前后轴扭矩分配系数 相乘，并将相乘所得与所述第二前后轴扭矩分配系数和所述第四前后轴扭矩分配系数相加以获得所述前后轴扭矩分配系数。
  14. 一种电动车四驱扭矩分配系统，其特征在于，包括：
    存储器，所述存储器存储有至少一条程序指令；
    处理器，所述处理器通过加载并执行所述至少一条程序指令以实现如权利要求1-13任一项所述的电动车四驱扭矩分配方法。
  15. 一种车辆，其特征在于，包括如权利要求14所述的电动车四驱扭矩分配系统。
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