Wheel-hub motor and EMB-based composite braking slip rate control system and method

Abstract

The application discloses a compound brake slip rate control system and method based on a wheel hub motor and EMB, and the method comprises the following steps: acquiring vehicle information; calculating a target slip rate according to the vehicle information; calculating a slip rate threshold for starting and exiting ABS according to the target slip rate; giving an ABS start-stop flag according to the vehicle speed, brake pedal opening degree, actual slip rate and slip rate threshold; calculating parameters of a slip rate tracking controller according to the vehicle speed, using the adhesion coefficient, slip rate and slip rate change rate, and then calculating a total target braking torque; selecting a braking torque distribution mode according to a motion mode switch and a slope, and distributing the target braking torque to the wheel hub motor and EMB; the wheel hub motor and EMB execute the target braking torque command, and timely disconnect the connection between the inverter and the battery. The application can more finely calculate the slip rate, adaptively adjust the target slip rate and the controller parameters according to the working conditions, effectively improve the utilization rate of the road adhesion coefficient, and improve the braking efficiency and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle braking, in particular to a compound braking slip rate control system and method based on wheel hub motor and EMB. BACKGROUND

[0002] The Anti-lock braking system (ABS) prevents wheel lock by controlling slip rate, which is an important technology to ensure vehicle braking safety. After years of exploration and iteration, the traditional ABS technology still has problems such as poor working condition adaptability. With the improvement of braking performance requirements and the development of vehicle braking technology, the forms of braking systems are gradually diversified, and electric-hydraulic compound braking, electric compound braking, and double-electric compound braking based on wheel hub motor and electromechanical brake (EMB) have appeared. Some scholars have carried out some research on braking torque distribution methods for electric-hydraulic compound braking systems and electric compound braking systems, but there are few ABS technology solutions for double-electric compound braking based on wheel hub motor and EMB. On the one hand, the traditional problems of poor working condition adaptability have not been solved, and on the other hand, the supporting ABS solutions for electric-hydraulic compound braking systems and electric compound braking systems cannot be directly applied to double-electric compound braking systems, and the unique advantages of double-electric braking systems are not fully utilized.

[0003] Therefore, it is urgent to develop a compound braking slip rate control technology based on wheel hub motor and EMB. SUMMARY

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

[0005] To this end, the present application proposes a compound braking slip rate control system based on wheel hub motor and EMB, which enables ABS to perform well in different working conditions and fully utilizes the unique advantages of double-electric braking systems to further improve braking efficiency and stability.

[0006] Another object of the present application is to propose a compound braking slip rate control method based on wheel hub motor and EMB.

[0007] To achieve the above-mentioned purpose, the present application proposes a compound 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 configured to transmit the processed measured signals to the fusion perception module.

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

[0010] The target slip ratio calculation module is configured 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 configured to calculate the slip ratio threshold for starting and exiting the ABS 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 configured to determine whether to start and exit the ABS based on the vehicle information sent by the fusion perception module and the slip ratio threshold sent by the slip ratio threshold calculation module, and send the start-stop flag of the ABS to the slip ratio tracking module.

[0013] The slip ratio tracking module is configured to calculate the controller parameters based on the vehicle information sent by the fusion perception module, and 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 configured to receive the total target braking torque sent by the slip ratio tracking module, determine 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, determine 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 double-electric braking system composed of the hub motor and the EMB and the first switch between the inverter and the battery, which executes the target braking torque command sent by the braking torque distribution module, and timely disconnects the connection between the inverter and the battery.

[0016] The hub motor and EMB-based composite braking slip ratio control system according to the embodiment of the application can have the following additional technical features:

[0017] In an embodiment of the application, 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 application, the vehicle dynamic parameters include multiple parameters selected from the group consisting of vehicle longitudinal acceleration, vehicle lateral acceleration, wheel rotational speed, front wheel steering angle, road type, wheel motor braking force, EMB braking force, vehicle longitudinal speed, battery SOC, driver sport mode switch, and slope.

[0019] To achieve the above object, another aspect of the present application provides a wheel motor and EMB-based compound braking slip ratio control method, comprising:

[0020] The vehicle dynamic parameters are obtained by filtering and fusing the combined sensing information, and the actual longitudinal speed, slip ratio and utilization coefficient of adhesion of each wheel are calculated based on the vehicle dynamic parameters.

[0021] The target slip ratio is calculated according to the utilization coefficient of adhesion, wheel longitudinal speed, wheel steering angle and road type.

[0022] The slip ratio threshold for starting and exiting ABS is calculated according to the target slip ratio.

[0023] The start-stop flag of output ABS is determined according to the vehicle speed, brake pedal opening degree, slip ratio and slip ratio threshold.

[0024] The parameters of the slip ratio tracking controller are calculated according to the vehicle speed, utilization coefficient of adhesion, slip ratio and slip ratio change rate, and the total target braking torque is calculated.

[0025] The braking torque distribution mode is determined and selected according to the sport mode switch, slope and total target braking torque, and the target braking torque commands of the wheel motor and EMB are output.

[0026] The wheel motor and EMB receive and execute the target braking torque commands, and timely disconnect the connection between the inverter and the battery through the braking system until the braking process is completed.

[0027] The wheel motor and EMB-based compound braking slip ratio control system and method of the embodiments of the present application can more accurately calculate the slip ratio, adaptively adjust the target slip ratio and controller parameters according to the working conditions, and match more abundant torque distribution modes, which can effectively improve the utilization rate of road adhesion coefficient and improve the braking efficiency and stability.

[0028] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0029] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, taken in conjunction with the accompanying drawings, in which:

[0030] Figure 1 is a structure diagram of a wheel hub motor and EMB-based composite brake slip ratio control system according to an embodiment of the present application;

[0031] Figure 2 is a flowchart of a wheel hub motor and EMB-based composite brake slip ratio control method according to an embodiment of the present application;

[0032] Figure 3 is a flowchart of a process of determining whether to start wheel ABS according to an embodiment of the present application;

[0033] Figure 4 is a flowchart of a process of determining whether to exit wheel ABS according to an embodiment of the present application;

[0034] Figure 5 is a flowchart of a process of determining a brake torque distribution mode according to an embodiment of the present application. DETAILED DESCRIPTION

[0035] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application 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 present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present application.

[0037] The wheel hub motor and EMB-based composite brake slip ratio control system and method according to the embodiments of the present application will be described below with reference to the accompanying drawings.

[0038] Figure 1 is a wheel hub motor and EMB-based composite brake slip ratio control system according to an embodiment of the present application, as shown in Figure 1 , which comprises an information acquisition module, a fusion perception module, a target slip ratio calculation module, a slip ratio threshold calculation module, an ABS start-stop module, a slip ratio tracking module, a brake torque distribution module and an execution module; wherein,

[0039] The information acquisition module comprises a camera, a radar, an inertial measurement unit, a wheel speed sensor, a wheel steering angle sensor and the like. 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 collection module, filters and fuses to obtain the vehicle longitudinal acceleration, vehicle lateral acceleration, wheel speed, front wheel steering angle, road type, hub motor braking force, EMB braking force, vehicle longitudinal speed, battery SOC, driver sport mode switch, slope, etc., and further calculates the actual longitudinal speed of each wheel, the slip ratio of each wheel and the utilization adhesion coefficient of each wheel. The information obtained by filtering, fusing and calculating is packaged as vehicle information and transmitted to the target slip ratio calculation module, the ABS start-stop module, the slip ratio tracking module and the brake 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 it 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 starting and exiting ABS according to the target slip ratio transmitted by the target slip ratio calculation module, and transmits it 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 ratio threshold transmitted by the slip ratio threshold calculation module, judges whether to start and exit ABS, and transmits the start-stop flag of ABS to the slip ratio tracking module.

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

[0045] The brake torque distribution module receives the total target brake torque transmitted by the slip ratio tracking module, receives the vehicle information transmitted by the fusion perception module, judges and selects the brake torque distribution mode, reasonably distributes the hub motor target brake torque and the EMB target brake torque, judges whether the inverter and the battery should be connected or disconnected, and transmits the hub motor target brake torque, the EMB target brake torque and the open-close command between the inverter and the battery to the execution module.

[0046] The execution module, for the dual-electric braking system composed of the hub motor and the EMB and the first switch between the inverter and the battery, receives and executes the target brake torque command issued by the brake torque distribution module, and timely disconnects the connection between the inverter and the battery.

[0047] The wheel hub motor and EMB-based composite brake slip ratio control system according to the embodiment of the present application can more finely calculate the slip ratio, adaptively adjust the target slip ratio and the controller parameters according to the working conditions, and match more abundant torque distribution modes, so as to effectively improve the utilization rate of the road adhesion coefficient and improve the braking efficiency and stability.

[0048] To achieve the above-mentioned embodiments, as Figure 2 indicated, the present embodiment also provides a wheel hub motor and EMB-based composite brake slip ratio control method, comprising:

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

[0050] S2, calculating the target slip ratio according to the utilization adhesion coefficient, wheel longitudinal speed, wheel steering angle and road type;

[0051] S3, calculating the slip ratio threshold for starting and exiting ABS according to the target slip ratio;

[0052] S4, judging the start-stop flag of output ABS according to the vehicle speed, brake pedal opening degree, slip ratio and slip ratio threshold;

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

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

[0055] S7, the wheel hub motor and EMB receive and execute the target braking torque commands, and timely disconnect the connection between the inverter and the battery through the braking system until the braking process is completed.

[0056] In an embodiment of the present application, the actual longitudinal speed v i (i=1, 2, 3, 4) of each wheel, the slip ratio s i (i=1, 2, 3, 4) of each wheel and the utilization adhesion coefficient

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

[0058]

[0059] where L is the wheel base; B is the track; ω r is the vehicle yaw rate.

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

[0061]

[0062] where v Ri is the longitudinal velocity 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, D are the tire stiffness and damping, respectively; F Ii is the EMB braking force of each wheel; F Ei is the EMB braking force of each wheel; r i is the radius of each wheel; n i is the rotational speed of each wheel.

[0063] The utilization adhesion coefficient of each wheel is calculated. First, the wheel vertical force is calculated using the vehicle longitudinal acceleration a x and the vehicle lateral acceleration a y

[0064]

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

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

[0067]

[0068] In an embodiment of the present application, the target slip ratio is calculated according to the utilization adhesion coefficient, the wheel longitudinal velocity, the wheel steering angle, and the road type.

[0069]

[0070] where o is the target slip ratio of the wheel; f v (·), f δ (·), f ay (·), f ξ (·) are functions of the target slip ratio of the wheel with respect to the utilization adhesion coefficient, the wheel longitudinal velocity, the wheel steering angle, and the road type, respectively.

[0071] ​In one embodiment of the present application, the ABS opening and exiting slip rate threshold values are calculated according to the target slip rate calculated by the target slip rate calculation module. In order to avoid frequent starting and stopping of ABS and ensure stable slip state, the starting and stopping actions of ABS are delayed, and the ABS opening threshold value o H and the ABS exiting threshold value o L are respectively determined as follows:

[0072]

[0073] wherein r H and r L are the coefficients of delayed ABS opening and delayed ABS exiting respectively.

[0074] In one embodiment of the present application, the ABS starting and stopping flag is determined and given according to the vehicle speed, brake pedal opening, actual slip rate, slip rate threshold value, etc.

[0075] The judgment flow of wheel ABS opening is shown in Fig. 2: Figure 3 When the vehicle speed v exceeds the minimum vehicle speed threshold value v min and the brake pedal opening u B exceeds the minimum brake pedal opening threshold value u Bmin , the basic condition for ABS opening is met, and the subsequent judgment flow is entered, otherwise the ABS starting and stopping flag of the wheel is directly output as 0. If the actual slip rate s of the wheel exceeds the wheel ABS opening threshold value o H , after a certain time length t H , it is again confirmed whether the actual slip rate of the wheel exceeds the wheel ABS opening threshold value, yes or no. If yes, the ABS starting and stopping flag of the wheel is given as 1, otherwise as 0.

[0076] The judgment flow of wheel ABS exiting is shown in Fig. 3: Figure 4 When the vehicle speed v exceeds the minimum vehicle speed threshold value v min and the brake pedal opening u B exceeds the minimum brake pedal opening threshold value u Bmin , the basic condition for ABS opening is met, and the subsequent judgment flow is entered, otherwise the ABS starting and stopping flag of the wheel is directly output as 0. If the actual slip rate s of the wheel is lower than the wheel ABS exiting threshold value o L , after a certain time length t L , it is again confirmed whether the actual slip rate of the wheel is lower than the wheel ABS exiting threshold value, yes or no. If yes, the ABS starting and stopping flag of the wheel is given as 0, otherwise as 1.

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

[0078]

[0079] wherein f P (·) is a function of K P about the vehicle speed, using the adhesion coefficient and the slip ratio; f I (·) is a function of K I about the slip ratio; f D (·) is a function of K D about the slip ratio and the slip ratio change rate; and e is the difference between the target slip ratio and the actual slip ratio.

[0080] In an embodiment of the application, the braking torque distribution mode is determined 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 a normal mode Mode = 0, a sport mode Mode = 1 and a long downhill mode Mode = 2. The determination process of the braking torque distribution mode is shown in Fig. 2: the default braking torque distribution mode is the normal mode; when it is monitored that the driver turns on the sport mode switch, the flag of the sport mode is Sport = 1, the braking torque distribution mode is switched to the sport mode, otherwise the subsequent determination process is entered; when it is monitored that the vehicle is in the long downhill working condition, the flag of the long downhill working condition is LDH = 1, the braking torque distribution mode is switched to the long downhill mode, otherwise the braking torque distribution mode remains the normal mode. Figure 5 In the normal mode, in order to achieve the highest energy utilization rate, the braking torque is preferentially distributed to the hub motor, 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 bear, the braking torque is entirely distributed to the EMB.

[0082] In the sport mode, in order to achieve the shortest braking response time and braking distance, the braking torque is shared by the hub motor and the 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 sport mode be α I , the hub motor bears α I of the total braking torque, and the remaining part is borne 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 bear, the connection between the inverter and the battery is disconnected.

[0083]

[0084] ​In long downhill mode, to avoid thermal failure of the brake system caused by long-term frequent braking, the braking torque is taken by the hub motor and EMB in turn, and the duration of each 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 exceeds 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 inverter and battery at the appropriate time until the braking process is completed.

[0087] In summary, in recent years, vehicles have been rapidly developing towards electrification, intelligence, and unmanned operation. At the same time, these demands for unmanned operation, intelligence, and energy conservation place higher demands on the adaptability, responsiveness, and stability of the vehicle itself. The hybrid braking system based on in-wheel motors and EMBs offers a fast response speed, with the potential to adjust wheel slip in milliseconds and significantly improve braking safety and stability. Implementing this hybrid braking slip control method based on in-wheel motors and EMBs not only significantly improves the adaptability of the slip controller, ensuring vehicle and occupant safety, but also balances 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 a vital role in future automotive braking systems, driving the automotive industry towards 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 precisely, adaptively adjust the target slip rate and controller parameters according to the working conditions, and with a richer torque distribution mode, can effectively improve the utilization rate of the road adhesion coefficient and improve the braking efficiency and stability.

[0089] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. Furthermore, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction.

[0090] In addition, the terms "first", "second", are used only for descriptive purposes and cannot be understood to indicate or imply relative importance or imply the number of the indicated technical features. Thus, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly specified.

Claims

1. A slip ratio control system for a hybrid brake system based on a hub motor and an EMB, characterized by, The information acquisition module, the fusion perception module, the target slip rate calculation module, the slip rate threshold calculation module, the ABS start-stop module, the slip rate tracking module, the brake torque distribution module and the execution module are included. The information acquisition module is configured to transmit the processed measured signals to the fusion perception module. The fusion perception module is configured to receive the combined sensing information transmitted by the information acquisition module, obtain vehicle dynamic parameters after filtering and fusion processing, and calculate the actual longitudinal speed, slip rate and utilization adhesion coefficient of each wheel based on the vehicle dynamic parameters, and pack the vehicle information. The target slip rate calculation module is configured to calculate the target slip rate based on the vehicle information transmitted by the fusion perception module, and transmit the target slip rate to the slip rate threshold calculation module and the slip rate tracking module. The slip rate threshold calculation module is configured to calculate the slip rate threshold for starting and exiting the ABS based on the target slip rate transmitted by the target slip rate calculation module, and transmit the slip rate threshold to the ABS start-stop module. The ABS start-stop module is configured 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 transmitted by the slip rate threshold calculation module, and transmit the start-stop flag of the ABS to the slip rate tracking module. The slip rate tracking module is configured to calculate the controller parameters based on the vehicle information transmitted by the fusion perception module, and calculate the required total target brake torque, and transmit the total target brake torque to the brake torque distribution module. The brake torque distribution module is configured to receive the total target brake torque transmitted by the slip rate tracking module, determine and select the brake torque distribution mode based on the vehicle information transmitted by the fusion perception module, distribute the hub motor target brake torque and the EMB target brake torque, determine whether the inverter and the battery are connected or disconnected, and transmit the hub motor target brake torque, the EMB target brake torque and the opening and closing command between the inverter and the battery to the execution module. The execution module is a double-electric braking system composed of the hub motor and the EMB and a first switch between the inverter and the battery, which executes the target brake torque command issued by the brake torque distribution module and timely disconnects the connection between the inverter and the battery. The information acquisition module includes multiple types of cameras, radars, inertial measurement units, wheel speed sensors and wheel steering angle sensors.

2. The system of claim 1, wherein, The vehicle dynamic parameters include multiple types of vehicle longitudinal acceleration, vehicle lateral acceleration, wheel speed, front wheel steering angle, road type, hub motor braking force, EMB braking force, vehicle longitudinal speed, battery SOC, driver sport mode switch and slope.

3. The system of claim 1, wherein, The combined sensing information is filtered and fused to obtain vehicle dynamic parameters, and the actual longitudinal speed, slip rate and utilization adhesion coefficient of each wheel are calculated based on the vehicle dynamic parameters.

4. A slip ratio control method for a hybrid brake based on a hub motor and an EMB, characterized by, The target slip rate is calculated based on the utilization adhesion coefficient, wheel longitudinal speed, wheel steering angle and road type. The slip rate threshold for starting and exiting the ABS is calculated based on the target slip rate. ​ ​ According to the vehicle speed, brake pedal opening, slip ratio and slip ratio threshold, the start-stop flag of the ABS is determined; According to the vehicle speed, the utilization coefficient of adhesion, the slip ratio and the slip ratio change rate, the parameters of the slip ratio tracking controller are calculated, and the total target braking torque is calculated; According to the sport mode switch, the slope and the total target braking torque, the braking torque distribution mode is determined and selected, and the target braking torque commands of the in-wheel motor and the EMB are outputted; The in-wheel motor and the EMB receive and execute the target braking torque commands, and timely disconnect the connection between the inverter and the battery through the braking system until the braking process is completed.

5. The method of claim 4, wherein, By means of the longitudinal vehicle speed v at the center of mass and the front wheel steering angle δ i The actual longitudinal speed v of each wheel is calculated i : In the formula, L is the wheelbase; B is the track; ω r is the vehicle yaw rate.

6. The method of claim 4, wherein, Based on the motion of the wheel relative to the ground caused by the tire deformation, the slip ratio s of each wheel is calculated by correcting the actual longitudinal speed of the wheel i : where v Ri is the longitudinal velocity of the wheel relative to the ground due to tire deformation; s Ri is the longitudinal displacement of the wheel relative to the ground due to tire deformation; C, D are the tire's elastic stiffness and damping, respectively; F Ii is the braking force of each wheel hub motor; F Ei is the braking force of each wheel EMB; r i is the radius of each wheel; n i is the rotational speed of each wheel.

7. The method of claim 4, wherein, Using the vehicle longitudinal acceleration a x and the vehicle lateral acceleration a y Calculating the wheel vertical force: In the formula, m is the vehicle mass; a and b are the distances from the mass center to the front and rear axles respectively; h is the mass center height of the vehicle; According to the wheel braking force and the wheel vertical force calculation using the adhesion coefficient 8. The method of claim 4, wherein, According to the utilization coefficient of adhesion, the wheel longitudinal speed, the wheel steering angle and the road type, the target slip ratio is calculated: where o is the wheel target slip ratio; f v (·), f δ (·), f ay (·), f ξ (·) are functions of the wheel target slip ratio with respect to the adhesion coefficient, the wheel longitudinal velocity, the wheel steering angle and the road type, respectively.

9. The method of claim 4, wherein, ABS on threshold o H and ABS off threshold o L : where r H , r L are coefficients for delaying ABS on and off, respectively.

10. The method of claim 4, wherein, According to the vehicle speed, the parameters K of the slip ratio tracking controller are calculated using the adhesion coefficient, the slip ratio, and the slip ratio change rate P , I , D The total target brake torque T d is calculated. where f P (·) is K P a function of vehicle speed, using the adhesion coefficient and slip ratio; f I (·) is K I a function of slip ratio; f D (·) is K D a function of slip ratio and slip ratio rate of change; e is the difference between target slip ratio and actual slip ratio.

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