Auxiliary steering system for automobile and automobile

Abstract

According to the auxiliary steering system for the automobile and the automobile, under the emergency conditions that a steer-by-wire system is in complete failure and the like, braking force of left and right wheels can be electrically and actively distributed, steering torque is generated, emergency steering is achieved, and it is guaranteed that the automobile avoids obstacles or maintains a running path in the speed reduction process; the safety when the steer-by-wire system fails under the extreme working condition is improved, steering control is independently achieved through the braking system, the emergency backup effect can be achieved without mechanical backup of the steer-by-wire system, and the complexity of the component structure can be reduced; an inherent executing mechanism of the braking system is utilized, the response speed can reach the millisecond level and is better than mechanical transmission delay of traditional mechanical backup, and the emergency response time can be shortened; by dynamically adjusting the left and right braking force difference, accurate direction correction can be achieved under the scenes such as linear driving, curves and wet and slippery road surfaces, the limitation of single deceleration parking is reduced, and the method adapts to various complex road conditions. The invention is widely applied to the technical field of automobiles.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automotive technology, and in particular to an auxiliary steering system for a vehicle and a vehicle. BACKGROUND

[0002] Currently, advanced steering systems, such as steer-by-wire systems, are widely used in vehicles. The principle of these steering systems is to replace the mechanical system to some extent by an electronic system, and to transmit the steering intention of the driver through an electrical signal, so as to achieve a more relaxed steering feel.

[0003] However, the above-mentioned steering system relies more on the electronic system, although the electronic system itself has relatively high device reliability, and the electronic system also has multiple electronic redundancy designs (such as dual power supply, dual communication architecture, multiple sensor backup, etc.), but in extreme working conditions such as electromagnetic interference and multiple hardware failures, the steering system may still fail. Once the steering system fails, the steering system will not be able to respond to the steering intention of the driver in time to generate enough steering force on the steering wheel, or even completely unable to output steering force, so as to adjust the driving direction of the vehicle, which is easy to cause collision risk if encountering a curve or an obstacle. Although using a mechanical system as a backup on the basis of the electronic system can reduce the risk caused by the failure of the electronic system, however, this will increase the structural complexity, which is not economically feasible. SUMMARY

[0004] In view of at least one of the above technical problems, the purpose of the present application is to provide an auxiliary steering system for a vehicle and a vehicle.

[0005] In one aspect, an embodiment of the present application includes an auxiliary steering system for a vehicle, the auxiliary steering system for a vehicle comprising: a left brake module, the left brake module being configured to controllably apply a braking force to a left rear wheel of the vehicle; a right brake module, the right brake module being configured to controllably apply a braking force to a right rear wheel of the vehicle; a control module, the control module being configured to, when a steering demand event is detected, obtain a base braking force, distribute the base braking force to obtain a left rear braking force and a right rear braking force, control the left brake module according to the left rear braking force, and control the right brake module according to the right rear braking force.

[0006] Further, the steering demand event includes a steer-by-wire system failure and a brake operating member being operated, or a component of a steering force output part of the steer-by-wire system being failed and a component of a steering demand detection part being normal and being operated.

[0007] Further, the distributing the base braking force to obtain the left rear braking force and the right rear braking force comprises: Real-time acquisition of the target yaw moment of the vehicle; Real-time acquisition of the vehicle's actual yaw rate; The yaw moment requirement of the vehicle is calculated in real time based on the target yaw moment and the actual yaw rate. Based on the yaw moment requirement, the difference in braking force between the left and right rear wheels of the vehicle is calculated in real time. The left rear braking force and the right rear braking force are obtained by distributing the braking force according to the basic braking force and the difference between the left and right rear braking forces.

[0008] Furthermore, the real-time acquisition of the target yaw moment of the vehicle includes: Real-time acquisition of the vehicle's current speed, steering wheel angle, wheelbase, and lane departure level; According to the formula

[0009] Calculate the target yaw moment ;in, The current vehicle speed, The steering wheel angle, The wheelbase is... The stability coefficient is determined by the degree of lane deviation.

[0010] Furthermore, the stability coefficient It is negatively correlated with the degree of lane deviation.

[0011] Furthermore, the step of calculating the vehicle's yaw moment requirement in real time based on the target yaw moment and the actual yaw rate includes: Obtain the vehicle's moment of inertia; According to the formula

[0012] Calculate the required yaw moment ;in, Let the moment of inertia of the vehicle be . The actual yaw rate, This indicates the derivative with respect to time.

[0013] Furthermore, the step of calculating the difference in braking force between the left and right rear wheels of the vehicle in real time based on the yaw moment requirement includes: Get the rear wheel track width of the car; According to the formula

[0014] Calculate the difference in braking force between the left and right rear wheels ;in, The rear wheel track is the distance between the two wheels.

[0015] Further, the step of distributing the left rear braking force and the right rear braking force based on the base braking force and the difference in braking forces between the left and right rear wheels includes: When the steering demand event indicates a left turn, according to the formula According to the formula

[0016]

[0017] Calculate the left rear braking force and the right rear braking force ;in, This refers to the basic braking force.

[0018] Further, the step of distributing the left rear braking force and the right rear braking force based on the base braking force and the difference in braking forces between the left and right rear wheels includes: When the steering demand event indicates a right turn, according to the formula... According to the formula

[0019]

[0020] Calculate the left rear braking force and the right rear braking force ;in, This refers to the basic braking force.

[0021] On the other hand, embodiments of the present invention also include a vehicle, the vehicle including the auxiliary steering system for the vehicle described in the embodiments.

[0022] The beneficial effects of this invention are as follows: The assisted steering system for automobiles in the embodiments can generate steering torque to achieve emergency steering by actively distributing braking force between the left and right wheels in emergency situations such as the complete failure of the steer-by-wire system. This ensures that the vehicle avoids obstacles or maintains its driving path during deceleration, improving safety when the steer-by-wire system fails under extreme conditions. Steering control is achieved independently through the braking system, filling the gap in direction adjustment capability after the complete failure of the steer-by-wire system. It can achieve emergency backup without the need for a mechanical backup of the steer-by-wire system, which can reduce the complexity of component structures. Utilizing the inherent actuator of the braking system, the response speed can reach the millisecond level, which is better than the mechanical transmission delay of traditional mechanical backup, thus shortening the emergency response time. By dynamically adjusting the difference in braking force between the left and right wheels, precise direction correction can be achieved in scenarios such as straight driving, curves, and slippery roads, reducing the limitations of single deceleration and stopping, and adapting to various complex road conditions. Attached Figure Description

[0023] Figure 1 This is a partial structural diagram of a car equipped with an auxiliary steering system, as shown in the embodiment. Figure 2 This is a schematic diagram illustrating the steps executed by the control module in the embodiment. Detailed Implementation

[0024] In this embodiment, a portion of the structure of the vehicle equipped with the assisted steering system is as follows: Figure 1 As shown. (Refer to...) Figure 1 A car equipped with an auxiliary steering system includes wheels such as the left front wheel, left rear wheel, right front wheel, and right rear wheel, as well as steer-by-wire system and braking components such as foot pedals. The auxiliary steering system includes a control module, a left brake module, and a right brake module. The control module is a component with data acquisition, processing, and control functions; for example, an electronic control unit (ECU) can be used as the control module. The left brake module is specifically installed on the left rear wheel of the car and includes components such as a wheel-end controller, hydraulic calipers, and hydraulic clamps. The wheel-end controller is connected to the control module via a data cable. The control module can send control commands to the wheel-end controller, which responds to the control commands by controlling the hydraulic calipers to clamp the brake disc of the left rear wheel. This applies a clamping force to the left rear wheel. Specifically, under the same conditions, the braking force exerted on the left rear wheel by the ground is positively correlated with the clamping force applied by the left brake module (it can be considered a direct proportional relationship). Therefore, the clamping force applied by the left brake module to the brake disc of the left rear wheel can be regarded as the braking force exerted on the left rear wheel. The right brake module is specifically a brake module installed on the right rear wheel of the car. The structure of the right brake module is the same as that of the left brake module, including components such as wheel end controller, hydraulic caliper and hydraulic caliper. The right brake module can apply braking force to the right rear wheel under the control of the control module.

[0025] In this embodiment, the braking control component is a foot pedal. When the driver intends to brake, the driver can press the foot pedal, causing the foot pedal to generate an operation signal. This operation signal contains information such as the depth and timing of the driver pressing the foot pedal. The foot pedal sends the operation signal to the control module, which can trigger the control module to control the left and right braking modules. Specifically, the control module controls the left and right braking modules simultaneously. This can be symmetrical, meaning that the left and right braking modules apply the same braking force at the same time, or asymmetrical, meaning that the left and right braking modules apply different braking forces at the same time.

[0026] In this embodiment, refer to Figure 2 The control module performs the following steps: S1. Upon detecting a steering demand event, acquire the basic braking force; S2. Distribute the basic braking force to obtain the left rear braking force and the right rear braking force; S3. Control the left braking module based on the left rear braking force, and control the right braking module based on the right rear braking force.

[0027] In step S1, the control module detects steering demand events in real time. In this embodiment, a steering demand event is an event indicating that the driver has a braking need. For example, a steering demand event can be defined as "the brake control element is operated". Thus, when the driver presses the brake pedal, the pedal generates an operation signal and sends the operation signal to the control module. The control module then determines that a steering demand event has been detected and executes steps S1-S3.

[0028] In this embodiment, a steering demand event can be defined as "the brake actuator is activated, and the steer-by-wire system fails." The steer-by-wire system failure includes software malfunctions such as the inability to respond promptly to the control module's control due to software errors, and hardware malfunctions such as insufficient steering force output due to damage to the hydraulic or electric power steering components. Thus, even if the brake actuator is activated, triggering the control module to control the steer-by-wire system, the system will still be unable to properly control the rotating wheels (typically the left and right front wheels) for steering.

[0029] In this embodiment, even if only the components of the steering force output section of the steer-by-wire system (such as the hydraulic or electric power steering components) are damaged, while the components of the steering demand detection section (such as the sensor that detects the steering wheel rotation amplitude) are functioning normally, i.e., when the steer-by-wire system is only partially malfunctioning, a steering demand event can still be determined. In this case, the driver can operate the components of the steering demand detection section, for example, by turning the steering wheel when it is necessary to control the car to turn. In this way, the steer-by-wire system can output information indicating the steering wheel rotation amplitude indicating the steering demand, but it cannot actually drive the steering wheels to turn.

[0030] In this embodiment, when the control module detects a steering demand event that "the brake control element is operated and the steer-by-wire system fails", the control module executes steps S1-S3, thereby enabling the auxiliary steering system to operate and allowing the car to steer.

[0031] In this embodiment, refer to Figure 2The control module executes steps S1-S3 dynamically in real time. For example, if a steering demand event persists (e.g., the steer-by-wire system continues to fail), the control module continuously executes each cycle of steps S1-S3, forming a loop. That is, after each round of steps S1-S3 is completed, the next round of steps S1-S3 is executed. The base braking force in each round of steps S1-S3 is acquired in real time, therefore the allocated left and right rear braking forces are also updated in real time. This ultimately achieves real-time control of the left and right braking modules. In other words, the left rear braking force generated by the left braking module and the right rear braking force generated by the right braking module are dynamically updated in different rounds of steps S1-S3, enabling dynamic response to road conditions. Since the principle of steps S1-S3 is the same for all rounds, this embodiment will use any one round of steps S1-S3 as an example for explanation.

[0032] In step S1, when the steering-by-wire system completely fails, the driver, while steering according to traffic rules, will operate the braking mechanism (e.g., depress the pedal) to slow down. This operation triggers the control module to generate braking control commands to control the left and right braking modules to apply braking force. This operation itself triggers the control module to control the left and right braking modules to apply braking force symmetrically, that is, to control both the left and right braking modules to output a magnitude of... In this embodiment, the force... This is the basic braking force obtained in step S1.

[0033] In step S1, when the online steering system partially fails (only the components of the steering force output section are damaged, while the components of the steering demand detection section are normal), the steering wheel rotation amplitude in the steering demand event represents the steering demand. According to traffic rules and safe driving technical standards, a specific steering wheel rotation amplitude represents a steering demand that requires the vehicle to stably reduce its speed to a specific speed value. The reduction of the vehicle's current speed to a specific speed value corresponds to a specific acceleration, i.e., a specific braking force. Therefore, in this embodiment, the steering demand event itself corresponds to a specific magnitude (magnitude) that the left and right braking modules need to output. In this embodiment, the force of ) The basic braking force obtained in step S1.

[0034] In this embodiment, when the control module executes step S2, which is to allocate the basic braking force and obtain the left rear braking force and the right rear braking force, it can specifically perform the following steps: S201. Real-time acquisition of the target yaw moment of the vehicle; S202. Real-time acquisition of the vehicle's actual yaw rate; S203. Calculate the vehicle's yaw moment requirement in real time based on the target yaw moment and the actual yaw rate; S204. Calculate the difference in braking force between the left and right rear wheels of the vehicle in real time based on the yaw moment requirement; S205. Distribute the braking force based on the basic braking force and the difference in braking force between the left and right rear wheels to obtain the left rear braking force and the right rear braking force.

[0035] In step S201, the control module acquires the vehicle's current speed in real time. Steering wheel angle (rotation range) Wheelbase And the degree of lane departure. The control module can detect the current vehicle speed in real time by calling relevant sensors. and steering wheel angle Parameters, wheelbase of the car It is a fixed value, and the wheelbase can be preset. The wheelbase is stored in the control module, which reads it during step S2. .

[0036] In this embodiment, the lane departure degree is determined by the stability coefficient. This indicates that the stability coefficient is... It is negatively correlated with the degree of lane departure, i.e., the stability coefficient. The smaller the value, the greater the lane departure. Specifically, the control module can invoke the vehicle's lane departure monitoring system to detect the distance between the vehicle body and the lane lines (specifically, the distance between the current side of the vehicle and the lane line closest to the vehicle body), using this distance value as a stability coefficient. .

[0037] In step S201, the control module follows the formula.

[0038] The target yaw moment was calculated. Target yaw moment It represents the yaw moment required for the auxiliary steering system to turn the car while maintaining vehicle stability and safety.

[0039] In step S202, the control module can call the sensors installed on the car body to detect the actual yaw rate of the car. Actual yaw rate This indicates the car's current actual yaw rate.

[0040] In step S203, the control module determines the yaw rate based on the actual yaw rate. yaw moment with target The deviation between them is calculated by PID control to achieve the target yaw moment. Required yaw moment, i.e., yaw moment demand Specifically, the control module can pre-store the vehicle's moment of inertia. (This is a constant related to the vehicle body structure), and the vehicle's moment of inertia is read during step S203. According to the formula

[0041] Calculate the yaw moment requirement .in, This indicates the derivative with respect to time.

[0042] In step S204, the control module can pre-store the rear wheel track of the car. (This represents the distance between the left and right rear wheels, a constant related to the vehicle body structure.) The rear wheel track is read during step S204. According to the formula

[0043] Calculate the difference in braking force between the left and right rear wheels Difference in braking force between the left and right rear wheels It represents the difference between the braking force obtained by the left rear wheel and the braking force obtained by the right rear wheel required for the auxiliary steering system to make a turn while maintaining the car's stability and safety.

[0044] In step S205, the control module determines the basic braking force. and the difference in braking force between the left and right rear wheels Distribute the force to obtain left rear braking force. and right rear braking force Specifically, the left rear braking force is the braking force applied to the left rear wheel by the left braking module during the current execution cycle (steps S1-S3), and the right rear braking force is the braking force applied to the right rear wheel by the right braking module during the current execution cycle. After the allocation is performed in step S205, the left rear braking force... and right rear braking force They are respectively in basic braking force The left rear braking force was obtained by adjusting the existing system. and right rear braking force The sum is the basic braking force This allows the car to obtain the braking force needed for turning, specifically the left rear braking force. and right rear braking force Relative to basic braking force When a deviation occurs, the left and right sides of the car receive different braking forces. The resultant force of these two braking forces forms a certain angle with respect to the car's axis, causing the car to turn. This allows the car to turn even in situations where the steering system fails, thus meeting the turning needs in emergency situations, ensuring the controllability of the car body, and ultimately guaranteeing driving safety.

[0045] Specifically, when the control module executes step S205, which involves allocating braking force based on the base braking force and the difference in braking force between the left and right rear wheels to obtain the left and right rear braking forces, it can first determine whether the steering request event indicates a left or right turn. For example, if the components of the steering request detection part of the on-line steering system are functioning normally and being operated, the driver's steering wheel rotation amplitude can be detected to determine whether the driver needs to turn left or right, thus determining whether the steering request event indicates a left or right turn. In the event of a failure of the on-line steering system, the control module can use the vehicle's microphone to detect the driver's voice commands and determine whether the steering request event indicates a left or right turn based on the voice commands. In the event of a failure of the on-line steering system, the control module can use the lidar to detect the position of obstacles outside the vehicle, determine a safe driving route for the vehicle, and determine whether the steering request event indicates a left or right turn based on the safe driving route.

[0046] When the steering demand event indicates a left turn, meaning the driver's intention or safe driving requirement is for the vehicle to turn left, the control module, when executing step S205, calculates according to the formula...

[0047]

[0048] Calculate the left rear braking force and right rear braking force Thus, when the control module executes step S3, it determines the left rear braking force... Control the left braking module according to the right rear braking force Controlling the right brake module will result in a relatively larger braking force on the left rear wheel and a relatively smaller braking force on the right rear wheel. This will create a left-turning torque on the car body, thus satisfying the steering requirements of the steering event. Furthermore, the left rear braking force... and right rear braking force The sum equals the basic braking force This allows the car to decelerate steadily when turning, ensuring driving safety.

[0049] When a steering demand event indicates a right turn, meaning the driver's intention or safe driving requirement is for the vehicle to turn right, the control module, during step S205, calculates according to the formula...

[0050]

[0051] Calculate the left rear braking force and right rear braking force Thus, when the control module executes step S3, it determines the left rear braking force... Control the left braking module according to the right rear braking force Controlling the right brake module will result in a relatively smaller braking force on the left rear wheel and a relatively larger braking force on the right rear wheel. This will create a right-turning torque on the car body, thus fulfilling the steering requirements of the steering event. Furthermore, the left rear braking force... and right rear braking force The sum equals the basic braking force This allows the car to decelerate steadily when turning, ensuring driving safety.

[0052] In this embodiment, by continuously executing multiple rounds of cyclical processes, the left rear braking force can be maintained. and right rear braking force The system makes real-time dynamic adjustments to prevent wheel lock-up or oversteering.

[0053] Reference Figure 2 After each cycle is completed, the system can detect whether the steering request event has ended. If the steering system returns to normal or the vehicle has safely pulled over, the control module confirms the steering request event has ended and stops executing the cycle. Otherwise, it executes the next cycle.

[0054] The assisted steering system for automobiles in this embodiment can generate steering torque and achieve emergency steering by actively distributing braking force to the left and right wheels in emergency situations such as complete failure of the steer-by-wire system. This ensures that the vehicle avoids obstacles or maintains its driving path during deceleration, improving safety when the steer-by-wire system fails under extreme conditions. Steering control is achieved independently through the braking system, filling the gap in direction adjustment capability after complete failure of the steer-by-wire system. It can achieve emergency backup without the need for a mechanical backup of the steer-by-wire system, which can reduce the complexity of component structure. Utilizing the inherent actuator of the braking system (such as an electro-hydraulic brake EHB or a mechanical braking unit), the response speed can reach the millisecond level, which is better than the mechanical transmission delay of traditional mechanical backups, and can shorten the emergency response time. By dynamically adjusting the difference in braking force between the left and right wheels, precise direction correction can be achieved in scenarios such as straight driving, curves, and slippery roads, reducing the limitations of single deceleration and stopping, and adapting to various complex road conditions.

[0055] It should be noted that, unless otherwise specified, when a feature is referred to as "fixed" or "connected" to another feature, it can be directly fixed or connected to the other feature, or indirectly fixed or connected to the other feature. Furthermore, the descriptions of "upper," "lower," "left," and "right" used in this disclosure are only relative to the relative positional relationships of the components of this disclosure in the accompanying drawings. The singular forms "a," "an," and "the" used in this disclosure are also intended to include the plural forms, unless the context clearly indicates otherwise. Moreover, unless otherwise defined, all technical and scientific terms used in this embodiment have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this embodiment specification is only for describing particular embodiments and is not intended to limit the invention. The term "and / or" as used in this embodiment includes any combination of one or more of the associated listed items.

[0056] It should be understood that although the terms first, second, third, etc., may be used to describe various elements in this disclosure, these elements should not be limited to these terms. These terms are only used to distinguish elements of the same type from each other. For example, a first element may also be referred to as a second element without departing from the scope of this disclosure, and similarly, a second element may also be referred to as a first element. The use of any and all instances or exemplary language (“e.g.,” “such as,” etc.) provided in this embodiment is intended only to better illustrate embodiments of the invention and, unless otherwise required, does not impose a limitation on the scope of the invention.

[0057] It should be recognized that embodiments of the present invention can be implemented or carried out by computer hardware, a combination of hardware and software, or by computer instructions stored in a non-transitory computer-readable storage medium. The method can be implemented using standard programming techniques—including a non-transitory computer-readable storage medium configured with a computer program, wherein such a storage medium causes the computer to operate in a specific and predefined manner—according to the methods and drawings described in the specific embodiments. Each program can be implemented in a high-level procedural or object-oriented programming language to communicate with the computer system. However, if desired, the program can be implemented in assembly or machine language. In any case, the language can be a compiled or interpreted language. Furthermore, for this purpose, the program can run on a programmed application-specific integrated circuit (ASIC).

[0058] Furthermore, the procedures described in this embodiment can be performed in any suitable order unless otherwise indicated by this embodiment or clearly contradicted by the context. The procedures (or variations and / or combinations thereof) described in this embodiment can be executed under the control of one or more computer systems configured with executable instructions, and can be implemented by hardware or a combination thereof as code (e.g., executable instructions, one or more computer programs, or one or more applications) that commonly executes on one or more processors. A computer program includes multiple instructions executable by one or more processors.

[0059] Furthermore, the method can be implemented in any suitable type of computing platform, including but not limited to personal computers, minicomputers, mainframes, workstations, networked or distributed computing environments, standalone or integrated computer platforms, or in communication with charged particle tools or other imaging devices, etc. Aspects of the invention can be implemented as machine-readable code stored on a non-transitory storage medium or device, whether removable or integrated into a computing platform, such as a hard disk, optical read and / or write storage medium, RAM, ROM, etc., such that it is readable by a programmable computer, and when the storage medium or device is read by the computer, it can be used to configure and operate the computer to perform the processes described herein. Furthermore, the machine-readable code, or portions thereof, can be transmitted via wired or wireless networks. The invention of this embodiment includes these and other different types of non-transitory computer-readable storage media when such media comprises instructions or programs that implement the steps above in conjunction with a microprocessor or other data processor. When programmed according to the methods and techniques of the invention, the invention also includes the computer itself.

[0060] A computer program can be applied to input data to perform the functions of this embodiment, thereby transforming the input data to generate output data stored in non-volatile memory. The output information can also be applied to one or more output devices, such as a display. In a preferred embodiment of the invention, the transformed data represents physical and tangible objects, including specific visual depictions of physical and tangible objects generated on the display.

[0061] The above are merely preferred embodiments of the present invention. The present invention is not limited to the above-described embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention, as long as they achieve the technical effects of the present invention by the same means, should be included within the scope of protection of the present invention. Within the scope of protection of the present invention, the technical solutions and / or implementation methods can have various modifications and variations.

Claims

1. An assist steering system for a vehicle, characterized by, The auxiliary steering system for the vehicle comprises: a left brake module, configured to apply a left rear wheel braking force to the vehicle in a controlled manner; a right brake module, configured to apply a right rear wheel braking force to the vehicle in a controlled manner; a control module, configured to, when a steering demand event is detected, acquire a basic braking force, distribute the basic braking force, obtain a left rear braking force and a right rear braking force, control the left brake module according to the left rear braking force, and control the right brake module according to the right rear braking force.

2. The assist steering system for a vehicle according to claim 1, characterized by, The steering demand event comprises a failure of a steer-by-wire system and an operation of a brake operating member, or a failure of a component of a steering force output part of the steer-by-wire system and a normal operation of a component of a steering demand detection part.

3. The assist steering system for a vehicle according to claim 1 or 2, characterized by, The distribution of the basic braking force to obtain the left rear braking force and the right rear braking force comprises: acquiring a target yaw moment of the vehicle in real time; acquiring an actual yaw angular velocity of the vehicle in real time; calculating a yaw moment demand of the vehicle in real time according to the target yaw moment and the actual yaw angular velocity; calculating a left-right rear wheel braking force difference of the vehicle in real time according to the yaw moment demand; and distributing the basic braking force and the left-right rear wheel braking force difference to obtain the left rear braking force and the right rear braking force.

4. The assist steering system for a vehicle according to claim 3, characterized by, The acquisition of the target yaw moment of the vehicle in real time comprises: acquiring a current vehicle speed, a steering wheel angle, a wheelbase and a lane deviation degree of the vehicle in real time; and calculating the target yaw moment according to a formula calculating the target yaw moment ; wherein is the current vehicle speed, is the steering wheel angle, is the wheelbase, is a stability coefficient determined by the lane departure degree.

5. The assist steering system for a vehicle according to claim 4, characterized by, the stability coefficient is negatively correlated with the degree of lane deviation.

6. The assist steering system for a vehicle according to claim 4, characterized by, The calculation of the yaw moment demand of the vehicle in real time according to the target yaw moment and the actual yaw angular velocity comprises: acquiring a vehicle rotational inertia of the vehicle; and calculating the yaw moment demand according to a formula calculating the yaw moment demand ; wherein is the vehicle moment of inertia, is the actual yaw rate, denotes the derivation with respect to time.

7. The assist steering system for a vehicle according to claim 5, characterized by, The calculation of the left-right rear wheel braking force difference of the vehicle in real time according to the yaw moment demand comprises: acquiring a rear wheel track of the vehicle; and calculating the left-right rear wheel braking force difference according to a formula calculating the left-right rear wheel braking force difference ; wherein is the rear wheel track.

8. The assist steering system for a vehicle according to claim 7, characterized by, The distribution of the basic braking force and the left-right rear wheel braking force difference to obtain the left rear braking force and the right rear braking force comprises: when the steering demand event indicates a left turn, distributing the basic braking force and the left-right rear wheel braking force difference according to a formula distributing the basic braking force and the left-right rear wheel braking force difference according to a formula calculating the left rear braking force and the right rear braking force ; wherein is the base braking force.

9. The assist steering system for a vehicle according to claim 7, characterized by, The distribution of the basic braking force and the left-right rear wheel braking force difference to obtain the left rear braking force and the right rear braking force comprises: when the steering demand event indicates a right turn, distributing the basic braking force and the left-right rear wheel braking force difference according to a formula distributing the basic braking force and the left-right rear wheel braking force difference according to a formula calculating the left rear braking force and the right rear braking force ; wherein is the base braking force.

10. An automobile characterized by comprising: The vehicle comprises: the auxiliary steering system for the vehicle according to any one of claims 1-9.

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