Composite brake slip rate control system and method based on hub motor and EMB

Abstract

The invention discloses a composite braking slip rate control system and method based on a hub motor and an EMB. The method comprises the steps that vehicle information is obtained; calculating a target slip rate according to the vehicle information; according to the target slip rate, calculating a slip rate threshold value for opening and exiting the ABS; according to the vehicle speed, the opening degree of a brake pedal, the actual slip rate and the slip rate threshold value, an ABS start-stop mark is given; according to the vehicle speed, parameters of a slip rate tracking controller are calculated through the attachment coefficient, the slip rate and the slip rate change rate, and then the total target braking torque is calculated; selecting a braking torque distribution mode according to a motion mode switch, gradient and the like, and distributing target braking torque to the hub motor and the EMB; and the hub motor and the EMB execute the target braking torque command, and connection between the inverter and the battery is cut off in time. According to the method, the slip rate can be calculated more finely, the target slip rate and controller parameters are adaptively adjusted according to working conditions, the road adhesion coefficient utilization rate can be effectively improved, and the braking efficiency and stability are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle braking, and in particular to a composite braking slip rate control system and method based on a wheel hub motor and an EMB. Background Art

[0002] The vehicle anti-lock braking system (ABS) prevents wheel lock by controlling the slip rate and is an important technology to ensure vehicle braking safety. After years of exploration and iteration, traditional ABS technology still has problems such as poor adaptability to working conditions. With the improvement of braking performance requirements and the development of vehicle braking technology, the forms of braking systems have gradually diversified, and electro-hydraulic composite braking, electrical composite braking, and dual-electric composite braking based on wheel hub motors and electromechanical brakes (EMB) have appeared one after another. Some scholars have conducted some exploration and research on the braking torque distribution method for electro-hydraulic composite braking systems and electrical composite braking systems, but there are few ABS technical solutions for dual-electric composite braking based on wheel hub motors and EMBs. On the one hand, the traditional problems such as poor adaptability to working conditions have not been solved. On the other hand, the supporting ABS solutions for electro-hydraulic composite braking systems and electrical composite braking systems cannot be directly applied to dual-electric composite braking systems, and the unique advantages of dual-electric braking systems have not been fully utilized.

[0003] Therefore, it is urgent to develop a composite braking slip rate control technology based on wheel hub motor and EMB. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0005] To this end, the present invention proposes a composite braking slip rate control system based on wheel hub motor and EMB, so that ABS can perform well under different working conditions, and can give full play to the unique advantages of the dual electric braking system to further improve braking efficiency and stability.

[0006] Another object of the present invention is to provide a composite braking slip rate control method based on a hub motor and an EMB.

[0007] To achieve the above-mentioned purpose, the present invention proposes a composite braking slip rate control system based on wheel hub motor and EMB, comprising: an information acquisition module, a fusion perception module, a target slip rate calculation module, a slip rate threshold calculation module, an ABS start-stop module, a slip rate tracking module, a braking torque distribution module and an execution module; wherein,

[0008] The information acquisition module is used to process the measured signal and transmit it to the fusion perception module;

[0009] The fusion perception module is used to receive the combined sensing information sent by the information acquisition module, obtain the vehicle dynamic parameters after filtering and fusion processing, calculate the actual longitudinal speed, slip rate and utilization adhesion coefficient of each wheel based on the vehicle dynamic parameters, and package them into vehicle information;

[0010] The target slip ratio calculation module is used to calculate the target slip ratio according to the vehicle information sent by the fusion perception module, and send the target slip ratio to the slip ratio threshold calculation module and the slip ratio tracking module;

[0011] The slip ratio threshold calculation module is used to calculate the slip ratio threshold for ABS on and off according to the target slip ratio sent by the target slip ratio calculation module, and send the slip ratio threshold to the ABS start-stop module;

[0012] The ABS start-stop module is used to determine whether to start and exit the ABS based on the vehicle information transmitted by the fusion perception module and the slip rate threshold sent by the slip rate threshold calculation module, and send the ABS start-stop flag to the slip rate tracking module;

[0013] The slip rate tracking module is used to calculate controller parameters based on the vehicle information sent by the fusion perception module, calculate the required total target braking torque, and send the total target braking torque to the braking torque distribution module;

[0014] The braking torque distribution module is used to receive the total target braking torque transmitted by the slip rate tracking module, and judge and select the braking torque distribution mode according to the vehicle information sent by the fusion perception module, distribute the hub motor target braking torque and the EMB target braking torque, judge whether the inverter and the battery are connected or disconnected, and send the hub motor target braking torque, the EMB target braking torque and the opening and closing command between the inverter and the battery to the execution module;

[0015] The execution module is a dual electric brake system composed of a hub motor and an EMB and a first switch between an inverter and a battery. It executes the target braking torque command issued by the braking torque distribution module and disconnects the connection between the inverter and the battery in a timely manner.

[0016] The composite braking slip rate control system based on the wheel hub motor and EMB in the embodiment of the present invention may also have the following additional technical features:

[0017] In one embodiment of the present invention, the information acquisition module includes multiple types of cameras, radars, inertial measurement units, wheel speed sensors, and wheel steering angle sensors.

[0018] In one embodiment of the present invention, the vehicle dynamic parameters include multiple ones of vehicle longitudinal acceleration, vehicle lateral acceleration, wheel speed, front wheel steering angle, road surface type, hub motor force, EMB braking force, vehicle longitudinal speed, battery SOC, driver sports mode switch, and slope.

[0019] To achieve the above object, the present invention proposes a composite braking slip rate control method based on a hub motor and an EMB, comprising:

[0020] The combined sensing information is filtered and fused to obtain vehicle dynamic parameters, and the actual longitudinal speed, slip rate and utilized adhesion coefficient of each wheel are calculated based on the vehicle dynamic parameters;

[0021] Calculate the target slip ratio based on the adhesion coefficient, the longitudinal speed of the wheel, the steering angle of the wheel and the road type;

[0022] The slip rate threshold for ABS activation and deactivation is calculated based on the target slip rate;

[0023] Determine and output the ABS start / stop flag based on vehicle speed, brake pedal opening, slip rate and slip rate threshold;

[0024] Calculate the parameters of the slip rate tracking controller according to the vehicle speed, the adhesion coefficient, the slip rate and the slip rate change rate, and calculate the total target braking torque;

[0025] According to the sport mode switch, slope and total target braking torque, the braking torque distribution mode is judged and selected, and the target braking torque command of the hub motor and EMB is output;

[0026] The hub motor and EMB receive and execute the target braking torque command, and disconnect the inverter and battery in a timely manner through the braking system until the braking process is completed.

[0027] The composite braking slip rate control system and method based on the hub motor and EMB of the embodiment of the present invention can calculate the slip rate more accurately, adaptively adjust the target slip rate and controller parameters according to the working conditions, and with richer torque distribution modes, can effectively improve the utilization rate of the road adhesion coefficient and improve the braking efficiency and stability.

[0028] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0030] Figure 1 is a structural schematic diagram of a composite braking slip rate control system based on a wheel hub motor and an EMB according to an embodiment of the present invention;

[0031] Figure 2 is a flow chart of a composite braking slip rate control method based on a hub motor and an EMB according to an embodiment of the present invention;

[0032] Figure 3 is a flow chart of a determination process for turning on a wheel ABS according to an embodiment of the present invention;

[0033] Figure 4 is a flow chart of a determination process for exiting a wheel ABS according to an embodiment of the present invention;

[0034] Figure 5 4 is a flow chart of a braking torque distribution mode determination process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0036] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0037] A composite braking slip ratio control system and method based on a hub motor and an EMB according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0038] Figure 1 A composite braking slip rate control system based on a wheel hub motor and an EMB according to an embodiment of the present invention is provided. Figure 1 As shown, it includes an information acquisition module, a fusion perception module, a target slip rate calculation module, a slip rate threshold calculation module, an ABS start-stop module, a slip rate tracking module, a braking torque distribution module and an execution module; wherein,

[0039] The information acquisition module includes cameras, radars, inertial measurement units, wheel speed sensors, wheel steering angle sensors, etc. The measured signals are processed and then transmitted to the fusion perception module.

[0040] The fusion perception module receives the combined sensing information transmitted by the information acquisition module, filters and fuses the vehicle longitudinal acceleration, vehicle lateral acceleration, each wheel speed, front wheel steering angle, road type, wheel hub motor force, EMB braking force, vehicle longitudinal speed, battery SOC, driver sports mode switch, slope, etc., and further calculates the actual longitudinal speed of each wheel, the slip rate of each wheel and the utilization adhesion coefficient of each wheel. The filtered, fused and calculated information is packaged as vehicle information and transmitted to the target slip rate calculation module, ABS start-stop module, slip rate tracking module and braking torque distribution module.

[0041] The target slip ratio calculation module calculates the target slip ratio according to the vehicle information transmitted by the fusion perception module, and transmits the target slip ratio to the slip ratio threshold calculation module and the slip ratio tracking module.

[0042] The slip ratio threshold calculation module calculates the slip ratio threshold for ABS activation and deactivation according to the target slip ratio transmitted by the target slip ratio calculation module, and transmits the slip ratio threshold to the ABS start-stop module.

[0043] The ABS start-stop module receives the vehicle information transmitted by the fusion perception module, receives the slip rate threshold transmitted by the slip rate threshold calculation module, determines whether to start and exit the ABS, and transmits the ABS start-stop flag to the slip rate tracking module.

[0044] The slip rate tracking module receives the vehicle information transmitted by the fusion perception module, calculates the controller parameters, and further calculates the required total target braking torque, and transmits it to the braking torque distribution module.

[0045] The braking torque distribution module receives the total target braking torque transmitted by the slip rate tracking module, receives the vehicle information transmitted by the fusion perception module, determines and selects the braking torque distribution mode, reasonably distributes the hub motor target braking torque and the EMB target braking torque, determines whether the inverter and the battery should be connected or disconnected, and transmits the hub motor target braking torque, the EMB target braking torque and the opening and closing commands between the inverter and the battery to the execution module.

[0046] The execution module is a dual electric braking system composed of a hub motor and an EMB and a first switch between the inverter and the battery. It receives and executes the target braking torque command issued by the braking torque distribution module and disconnects the connection between the inverter and the battery in a timely manner.

[0047] The composite braking slip rate control system based on the hub motor and EMB according to the embodiment of the present invention can calculate the slip rate more accurately, adaptively adjust the target slip rate and controller parameters according to the working conditions, and with richer torque distribution modes, it can effectively improve the utilization rate of the road adhesion coefficient and improve the braking efficiency and stability.

[0048] In order to implement the above embodiment, Figure 2 As shown, this embodiment also provides a composite braking slip rate control method based on the wheel hub motor and the EMB, including:

[0049] S1, obtaining vehicle dynamic parameters by filtering and fusing the combined sensor information, and calculating the actual longitudinal speed, slip rate and utilized adhesion coefficient of each wheel based on the vehicle dynamic parameters;

[0050] S2, calculates the target slip ratio based on the adhesion coefficient, the longitudinal speed of the wheel, the steering angle of the wheel and the road type;

[0051] S3, calculating the slip rate threshold for ABS activation and deactivation according to the target slip rate;

[0052] S4, judging and outputting the start / stop flag of the ABS according to the vehicle speed, brake pedal opening, slip rate and slip rate threshold;

[0053] S5, calculating the parameters of the slip rate tracking controller according to the vehicle speed, the adhesion coefficient, the slip rate and the slip rate change rate, and calculating the total target braking torque;

[0054] S6, judging and selecting a braking torque distribution mode according to the sport mode switch, the slope and the total target braking torque, and outputting target braking torque commands for the hub motor and the EMB;

[0055] In S7, the wheel hub motor and EMB receive and execute the target braking torque command, and disconnect the inverter and the battery in a timely manner through the braking system until the braking process is completed.

[0056] In one embodiment of the present invention, the actual longitudinal speed v of each wheel is calculated. i (i=1,2,3,4), slip rate s of each wheel i (i=1,2,3,4) and the utilization coefficient of each wheel

[0057] The longitudinal speed v at the center of mass and the front wheel steering angle δ i (i=1,2) Calculate the actual longitudinal speed of each wheel:

[0058]

[0059] Where L is the wheelbase; B is the track width; ω r is the vehicle yaw angular velocity.

[0060] Considering the relative movement of the wheel caused by tire deformation, the slip rate of each wheel is calculated by correcting the actual longitudinal velocity of the wheel:

[0061]

[0062] In the formula, v Ri (i=1,2,3,4) is the longitudinal speed of the wheel relative to the ground caused by tire deformation; s Ri (i=1,2,3,4) is the longitudinal displacement of the wheel relative to the ground caused by tire deformation; C and D are the elastic stiffness and damping of the tire respectively; F Ii (i=1,2,3,4) is the motor power of each wheel hub; F Ei (i=1,2,3,4) is the EMB braking force of each wheel; r i (i=1,2,3,4) is the radius of each wheel; n i (i=1,2,3,4) is the rotation speed of each wheel.

[0063] Calculate the utilization adhesion coefficient of each wheel. First, use the vehicle longitudinal acceleration a x and the vehicle lateral acceleration a y Calculate the vertical force on the wheel:

[0064]

[0065] Where m is the mass of the vehicle; a and b are the distances from the center of mass to the front and rear axles respectively; and h is the height of the center of mass of the vehicle.

[0066] Then, the utilization adhesion coefficient is calculated based on the wheel braking force and the wheel vertical force:

[0067]

[0068] In one embodiment of the present invention, the target slip ratio is calculated based on the adhesion coefficient, the longitudinal speed of the wheel, the steering angle of the wheel, and the road type.

[0069]

[0070] Where o is the target wheel slip rate; f v (·),f δ (·),f ay (·),f ξ (·) are the functions of the target wheel slip rate with respect to the utilized adhesion coefficient, wheel longitudinal speed, wheel steering angle and road surface type, respectively.

[0071] In one embodiment of the present invention, the slip ratio threshold for ABS activation and deactivation is calculated based on the target slip ratio transmitted by the target slip ratio calculation module. In order to avoid frequent activation and deactivation of ABS and ensure the stability of the slip state, the activation and deactivation of ABS are delayed, and the ABS activation threshold is respectively formulated. H and ABS exit threshold o L as follows:

[0072]

[0073] In the formula, r H 、r L They are the coefficients for delaying ABS on and delaying ABS off, respectively.

[0074] In one embodiment of the present invention, the start / stop flag of the ABS is determined and given according to the vehicle speed, the brake pedal opening, the actual slip ratio, the slip ratio threshold, etc.

[0075] The judgment process of wheel ABS activation is as follows Figure 3 As shown: When the vehicle speed v exceeds the minimum vehicle speed threshold v min And the brake pedal opening u B Exceeding the minimum brake pedal opening threshold u Bmin When the basic conditions for ABS activation are met, the subsequent judgment process is entered, otherwise the ABS start / stop flag of the wheel is directly output as 0. If the actual wheel slip rate s exceeds the wheel ABS activation threshold o H , a certain time t H After that, confirm again whether the actual wheel slip rate exceeds the wheel ABS opening threshold. If yes, the wheel ABS start-stop flag is set to 1, otherwise it is 0.

[0076] The judgment process of wheel ABS exit is as follows Figure 4 As shown: When the vehicle speed v exceeds the minimum speed threshold v min And the brake pedal opening u B Exceeding the minimum brake pedal opening threshold u Bmin When the basic conditions for ABS activation are met, the subsequent judgment process is entered, otherwise the ABS start / stop flag of the wheel is directly output as 0. If the actual wheel slip rate s is lower than the wheel ABS exit threshold o L , a certain time t L After that, confirm again whether the actual wheel slip rate is lower than the wheel ABS exit threshold. If so, the wheel ABS start-stop flag is set to 0, otherwise it is 1.

[0077] In one embodiment of the present invention, the parameter K of the slip rate tracking controller is calculated according to the vehicle speed, the adhesion coefficient, the slip rate and the slip rate change rate. P , K I , K D, and then calculate the total target braking torque T d .

[0078]

[0079] In the formula, f P (·) is K P Function of vehicle speed, adhesion coefficient and slip rate; f I (·) is K I Function of slip rate; f D (·) is K D A function of slip rate and slip rate change rate; e is the difference between the target slip rate and the actual slip rate.

[0080] In one embodiment of the present invention, the braking torque distribution mode is judged and selected according to the sport mode switch and the slope, and the hub motor target braking torque and the EMB target braking torque are reasonably distributed.

[0081] The braking torque distribution mode is divided into the normal mode Mode = 0, the sports mode Mode = 1 and the long downhill mode Mode = 2. The judgment process of the braking torque distribution mode is as follows: Figure 5 As shown: the default braking torque distribution mode is the normal mode; when it is detected that the driver turns on the sport mode switch, the sport mode flag Sport=1, and the braking torque distribution mode is switched to the sport mode, otherwise it enters the subsequent judgment process; when it is detected that it is in a long downhill condition, the long downhill condition flag LDH=1, and the braking torque distribution mode is switched to the long downhill mode, otherwise the braking torque distribution mode remains in the normal mode.

[0082] In normal mode, in order to achieve the highest energy utilization, the braking torque is allocated to the wheel hub motor first, and the part exceeding the maximum torque of the motor is shared by the EMB. At the same time, when the battery SOC is greater than 85% or the charging power exceeds the maximum charging power that the battery can withstand, the braking torque is fully allocated to the EMB.

[0083] In the sports mode, in order to achieve the shortest braking response time and braking distance, the braking torque is shared by the hub motor and EMB, and the torque distribution ratio is divided according to the performance of the two. Let the proportion of the hub motor braking torque in the sports mode be α I The wheel hub motor bears α of the total braking torque I , and the rest is borne by EMB. At the same time, when the battery SOC is greater than 85% or the charging power exceeds the maximum charging power that the battery can withstand, the connection between the inverter and the battery is disconnected.

[0084] In long downhill mode, in order to avoid thermal failure of the brake system caused by long-term frequent braking, the braking torque is borne by the hub motor and EMB in turn, and the duration of each bearing is divided according to the braking performance maintenance ability of the two. ltI When the wheel hub motor is withdrawn, the EMB starts braking alone. When the EMB continues braking alone for more than t ltE When the battery SOC is greater than 85% or the charging power exceeds the maximum charging power that the battery can withstand, the connection between the inverter and the battery is disconnected.

[0085] In one embodiment of the present invention, the execution module executes the target braking torque command.

[0086] The hub motor and EMB receive and execute the target braking torque command issued by the braking torque distribution module, and disconnect the connection between the inverter and the battery at the appropriate time until the braking process is completed.

[0087] In summary, in recent years, vehicles are developing rapidly towards electrification, intelligence and unmanned operation. At the same time, the demands for unmanned operation, intelligence and energy saving have put forward higher requirements on the adaptability, response speed and stability of the vehicle body. The composite braking system based on wheel hub motor and EMB has a fast response speed and has the potential to adjust the wheel slip rate at the millisecond level and greatly improve the braking safety and stability. The implementation of this composite braking slip rate control method based on wheel hub motor and EMB can not only significantly improve the adaptability of the slip controller and provide safety protection for the vehicle and passengers, but also take into account the advantages of high energy recovery, short braking distance and high reliability. This technology has broad application prospects in electric vehicles, autonomous driving and high-performance vehicles, and is expected to play an important role in future automotive braking systems, promoting the automotive industry to develop in a more intelligent, efficient and environmentally friendly direction.

[0088] The composite braking slip rate control method based on the hub motor and EMB according to the embodiment of the present invention can calculate the slip rate more accurately, adaptively adjust the target slip rate and controller parameters according to the working conditions, and with richer torque distribution modes, can effectively improve the utilization rate of the road adhesion coefficient and improve the braking efficiency and stability.

[0089] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0090] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

Claims

1. A composite braking slip rate control system based on wheel hub motor and EMB, characterized in that: include: Information collection module, fusion perception module, target slip rate calculation module, slip rate threshold calculation module, ABS start-stop module, slip rate tracking module, braking torque distribution module and execution module; wherein, The information acquisition module is used to process the measured signal and transmit it to the fusion perception module; The fusion perception module is used to receive the combined sensing information sent by the information acquisition module, obtain the vehicle dynamic parameters after filtering and fusion processing, calculate the actual longitudinal speed, slip rate and utilization adhesion coefficient of each wheel based on the vehicle dynamic parameters, and package them into vehicle information; The target slip ratio calculation module is used to calculate the target slip ratio according to the vehicle information sent by the fusion perception module, and send the target slip ratio to the slip ratio threshold calculation module and the slip ratio tracking module; The slip ratio threshold calculation module is used to calculate the slip ratio threshold for ABS on and off according to the target slip ratio sent by the target slip ratio calculation module, and send the slip ratio threshold to the ABS start-stop module; The ABS start-stop module is used to determine whether to start and exit the ABS based on the vehicle information transmitted by the fusion perception module and the slip rate threshold sent by the slip rate threshold calculation module, and send the ABS start-stop flag to the slip rate tracking module; The slip rate tracking module is used to calculate controller parameters based on the vehicle information sent by the fusion perception module, calculate the required total target braking torque, and send the total target braking torque to the braking torque distribution module; The braking torque distribution module is used to receive the total target braking torque transmitted by the slip rate tracking module, and judge and select the braking torque distribution mode according to the vehicle information sent by the fusion perception module, distribute the hub motor target braking torque and the EMB target braking torque, judge whether the inverter and the battery are connected or disconnected, and send the hub motor target braking torque, the EMB target braking torque and the opening and closing command between the inverter and the battery to the execution module; The execution module is a dual electric brake system composed of a hub motor and an EMB and a first switch between an inverter and a battery. It executes the target braking torque command issued by the braking torque distribution module and disconnects the connection between the inverter and the battery in a timely manner.

2. The system according to claim 1, characterized in that The information collection module includes multiple types of cameras, radars, inertial measurement units, wheel speed sensors and wheel steering angle sensors.

3. The system according to claim 1, characterized in that The vehicle dynamic parameters include vehicle longitudinal acceleration, vehicle lateral acceleration, wheel speed, front wheel steering angle, road surface type, wheel hub motor force, EMB braking force, vehicle longitudinal speed, battery SOC, driver sports mode switch, and slope.

4. A composite braking slip rate control method based on wheel hub motor and EMB, characterized in that: include: The combined sensing information is filtered and fused to obtain vehicle dynamic parameters, and the actual longitudinal speed, slip rate and utilized adhesion coefficient of each wheel are calculated based on the vehicle dynamic parameters; Calculate the target slip ratio based on the adhesion coefficient, the longitudinal speed of the wheel, the steering angle of the wheel and the road type; The slip rate threshold for ABS activation and deactivation is calculated based on the target slip rate; Determine and output the ABS start / stop flag based on vehicle speed, brake pedal opening, slip rate and slip rate threshold; Calculate the parameters of the slip rate tracking controller according to the vehicle speed, the adhesion coefficient, the slip rate and the slip rate change rate, and calculate the total target braking torque; According to the sport mode switch, slope and total target braking torque, the braking torque distribution mode is judged and selected, and the target braking torque command of the hub motor and EMB is output; The hub motor and EMB receive and execute the target braking torque command, and disconnect the inverter and battery in a timely manner through the braking system until the braking process is completed.

5. The method according to claim 4, characterized in that The longitudinal speed v at the center of mass and the front wheel steering angle δ i Calculate the actual longitudinal velocity v of each wheel i : Where L is the wheelbase; B is the track width; ω r is the vehicle yaw angular velocity.

6. The method according to claim 4, characterized in that Based on the relative movement of the wheel caused by tire deformation, the slip rate s of each wheel is calculated by correcting the actual longitudinal speed of the wheel. i : In the formula, v Ri is the longitudinal speed of the wheel relative to the ground caused by tire deformation; s Ri is the longitudinal displacement of the wheel relative to the ground caused by tire deformation; C and D are the elastic stiffness and damping of the tire respectively; F Ii Powering the wheel hub motors; F Ei is the EMB braking force of each wheel; r i is the radius of each wheel; n i is the speed of each wheel.

7. The method according to claim 4, characterized in that Using the vehicle longitudinal acceleration a x and the vehicle lateral acceleration a y Calculate the vertical force on the wheel: Where m is the mass of the vehicle; a and b are the distances from the center of mass to the front and rear axles respectively; h is the height of the center of mass of the vehicle; The adhesion coefficient is calculated based on the wheel braking force and the wheel vertical force.

8. The method according to claim 4, characterized in that The target slip ratio is calculated based on the adhesion coefficient, wheel longitudinal speed, wheel steering angle and road type: Where o is the target wheel slip rate; f v (·),f δ (·),f ay (·),f ξ (·) are the functions of the wheel target slip ratio with respect to the utilized adhesion coefficient, wheel longitudinal velocity, wheel steering angle and road surface type, respectively.

9. The method according to claim 4, characterized in that Set the ABS opening threshold respectively. H and ABS exit threshold o L : In the formula, r H 、r L They are the coefficients for delaying ABS on and delaying ABS off, respectively.

10. The method according to claim 4, characterized in that The parameter K of the slip rate tracking controller is calculated based on the vehicle speed, adhesion coefficient, slip rate and slip rate change rate. P , K I , K D , and calculate the total target braking torque T d : In the formula, f P (·) is K P Function of vehicle speed, adhesion coefficient and slip rate; f I (·) is K I Function of slip rate; f D (·) is K D A function of slip rate and slip rate change rate; e is the difference between the target slip rate and the actual slip rate.

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