Vehicle stability control method for single-wheel braking failure of double-electric-braking automobile

Abstract

The invention discloses a vehicle stability control method for single-wheel braking failure of a double-electric-braking automobile. According to the vehicle stability control method, stability control after failure can be more fully achieved on the basis of an overdrive system of a double-electric-braking system. In the light braking process, the influence of yawing is small in consideration, and tracking control can be carried out through closed-loop feedback electro-mechanical braking (EMB); the influence of moderate braking yaw is relatively large, and wheel end feedback motor braking and electronic mechanical braking need to be coordinated for common control; under heavy braking, longitudinal braking deceleration is not expected to be reduced, and stability control needs to be achieved by combining steering intervention and braking. Compared with the prior art, the method has the advantages that on the premise of double-electric braking, the requirements of vehicle stability under different braking strengths are considered, the characteristics of the overdrive system are combined, stability control over the vehicle after braking failure of the single-wheel feedback motor can be met, and longitudinal deceleration does not need to be sacrificed.

Description

Vehicle stability control method for single-wheel braking failure in dual-electric braking vehicles Technical Field

[0001] This invention relates to the fields of automotive braking systems and intelligent vehicle technology, and in particular to a vehicle stability control method for single-wheel braking failure in dual-electric braking vehicles. Background Technology

[0002] Compared to traditional hydraulic braking systems, electromechanical hybrid braking systems offer advantages such as faster response, higher integration, and independent decoupling of the four wheels. They can also effectively address the issue of insufficient braking force provided by regenerative motor braking during emergency braking, thus resolving the problem of simultaneous braking failure when regenerative motor braking is the only option.

[0003] In addition, another advantage of electromechanical hybrid braking systems is their energy recovery strategy, which can balance a high level of energy recovery at stable vehicle speeds with a rapid braking response in emergency situations. However, there is currently no systematic understanding of how to utilize distributed electromechanical braking and the remaining regenerative motor for fault-tolerant control after the failure of the regenerative motor; in particular, there is a lack of in-depth research on how to combine steering to achieve stability control when tire braking margin is insufficient in emergency braking situations. Summary of the Invention

[0004] This invention proposes a dual-electric braking system and its control strategy. The system includes a hub motor and its controller, and a complete electromechanical braking (EMB) system. The system employs a cooperative control strategy to achieve energy recovery under normal braking conditions, with the regenerative braking motor participating throughout the braking process. Failure occurs when the regenerative braking motor alone loses braking force. The main objective of this invention is to provide a vehicle stability control method for vehicles with dual-electric braking systems experiencing single-wheel braking failure. This method can achieve vehicle stability control under different braking intensities and road surface adhesion conditions, based on different control strategies, even after a regenerative motor failure during braking.

[0005] Another objective of this invention is to propose a vehicle stability control system for single-wheel braking failure in dual-electric braking vehicles.

[0006] A third objective of this invention is to provide a non-transitory computer-readable storage medium.

[0007] To achieve the above objectives, a first aspect of the present invention proposes a vehicle stability control method for single-wheel braking failure in dual-electric braking vehicles, comprising:

[0008] The system acquires the driver's brake pedal opening input signal and the road surface adhesion estimation signal, calculates the total braking force demand based on the vehicle's mass, and classifies the braking intensity according to a preset threshold to determine whether the current braking condition is light, moderate, or heavy. Based on the determined braking condition and the failure state of the single-wheel regenerative motor braking, corresponding control strategies are adopted. The control results based on the control strategies are input into the four-wheel braking distribution module, which dynamically adjusts the distribution ratio of the regenerative motor braking torque and the electromechanical braking clamping force based on the vehicle's dynamic state parameters to ensure that the braking torque of each wheel meets the tire adhesion limit constraint. The electromechanical braking clamping force is corrected in real time through a slip ratio closed-loop feedback controller, matching the actual braking torque with the target value and eliminating control errors caused by the nonlinear characteristics of the actuator.

[0009] In one embodiment of the present invention, the process of acquiring the driver's brake pedal opening input signal and the road surface adhesion estimation signal, calculating the total braking force requirement based on the vehicle mass, and classifying the braking intensity according to a preset threshold to determine whether the current braking condition is light, moderate, or heavy includes: receiving a braking intensity command signal issued by the autonomous driving domain controller or the driver, and calculating the total braking force requirement by multiplying the braking intensity command signal by the vehicle mass and taking the negative value, in conjunction with the vehicle mass parameter; receiving the road surface adhesion estimation signal from the vision module, and calculating the theoretical maximum longitudinal braking force by multiplying the road surface adhesion estimation signal by the vehicle mass and the gravitational acceleration parameter and taking the negative value; comparing the ratio of the absolute value of the total braking force requirement to the absolute value of the maximum longitudinal braking force with a preset first threshold and a second threshold: when the ratio is less than or equal to the first threshold, the current braking condition is determined to be light; when the ratio is greater than the first threshold and less than or equal to the second threshold, the current braking condition is determined to be moderate; when the ratio is greater than the second threshold, the current braking condition is determined to be heavy.

[0010] In one embodiment of the present invention, corresponding control strategies are adopted according to the determined braking conditions and the failure state of the single-wheel regenerative motor braking, including: under light braking conditions, adjusting the electromechanical braking clamping force through closed-loop feedback to compensate for the unexpected yaw moment generated by the failed wheel; under moderate braking conditions, coordinating the residual regenerative motor power and the electromechanical braking system, establishing a quadratic constraint quadratic programming optimization model based on the tire adhesion ellipse constraint, and solving the optimal braking torque distribution scheme that meets the longitudinal braking force requirements; under heavy braking conditions, maintaining the longitudinal braking force requirements unchanged, and calculating the front wheel steering angle compensation amount through a two-degree-of-freedom model in conjunction with the steering system to offset the unexpected yaw rate.

[0011] In one embodiment of the present invention, the control results based on the control strategy are input into the four-wheel brake distribution module to obtain the solution results of the optimization model. The distribution ratio of the regenerative electric motor torque and the electromechanical braking clamping force is dynamically adjusted based on vehicle dynamics state parameters to ensure that the braking torque of each wheel meets the tire adhesion limit constraint. This includes: the four-wheel brake distribution module receiving the optimized distribution results of the regenerative electric motor torque and electromechanical braking torque of each wheel output by the optimization model; acquiring vehicle dynamics state parameters provided by the dynamics state calculation module, including vehicle speed signal, wheel speed signal, yaw rate, lateral velocity, braking deceleration, vertical force of each wheel, and lateral force of each wheel; and dynamically adjusting the regenerative electric motor torque and electromechanical braking clamping force of each wheel according to the state parameters. The distribution ratio of braking torque generated by the braking clamping force is defined, wherein the electromechanical braking clamping force is converted into actual braking torque through a closed-loop feedback controller; a longitudinal braking torque constraint is applied to each wheel, the constraint condition being that the square of the longitudinal braking torque does not exceed the difference between the square of the product of the road adhesion coefficient and the wheel vertical force and the square of the wheel lateral force, wherein the longitudinal braking torque is determined by dividing the sum of the feedback electromechanical braking torque and the electromechanical braking torque of the corresponding wheel by the wheel radius; a closed-loop correction of the electromechanical braking torque is performed based on slip ratio feedback, specifically by calculating the deviation between the slip ratio of the wheel on the electromechanical braking side and the reference slip ratio, and generating a torque correction amount using a proportional-integral control method to compensate for the mapping error of the electromechanical braking actuator and improve control accuracy.

[0012] In one embodiment of the present invention, the electromechanical braking clamping force is corrected in real time by a slip ratio closed-loop feedback controller to match the actual braking torque with the target value and eliminate control errors caused by the nonlinear characteristics of the actuator. This includes: acquiring the real-time vehicle speed signal and wheel speed signals output by the dynamic state calculation module; calculating the braking slip ratio of each wheel based on the ratio of the difference between vehicle speed and wheel speed to the vehicle speed; for the wheel controlled by the electromechanical braking clamping force, using the average slip ratio of the non-failed wheels or the slip ratio of the wheels on the opposite side of the same axle as a reference target value, calculating the deviation between the current wheel slip ratio and the reference target value; inputting the slip ratio deviation into a proportional-integral controller, generating an electromechanical braking torque correction amount through a weighted combination of proportional and integral terms, wherein the proportional gain and integral gain are dynamically adjusted according to the braking conditions and road surface adhesion conditions; superimposing the torque correction amount onto the original target value of the electromechanical braking torque to obtain a corrected clamping force control command, which is then transmitted to the electromechanical braking actuator. The closed-loop feedback is continuously adjusted until the error between the actual braking torque and the target braking torque converges to a preset accuracy range.

[0013] In one embodiment of the present invention, stability control after single-wheel failure is performed according to the three classified working conditions; under the light braking condition, the braking intensity is relatively small, and the longitudinal braking force distributed to the four wheels is as follows:

[0014]

[0015] in, This is a command for four-wheel braking force. This is the front axle braking force distribution coefficient; at this time, braking only includes regenerative braking, and the additional yaw moment caused by single wheel failure is calculated as follows:

[0016] in: c represents the unexpected yaw moment caused by the failure; c is the vehicle track width. The braking force is the force applied to the wheel on the other side of the same axle as the failed wheel; the initial electromechanical braking torque of the failed wheel is:

[0017] in: The initial braking torque for the electromechanical braking of the failed wheel; Let the wheel radius be denoted by ; the slip ratio is calculated based on the vehicle speed and wheel speed signals, using the following formula:

[0018] in: The braking slip ratio of the wheel on the other side of the same axle as the failed wheel; u is the vehicle speed. Let be the angular velocity of the wheel; the closed-loop correction formula for the braking torque feedback of the failed wheel is:

[0019]

[0020] In passing Correct the original This allows the vehicle to achieve stable yaw moment compensation through electromechanical braking when the single-wheel regenerative motor fails under light braking conditions, thus ensuring vehicle driving stability.

[0021] To achieve the above objectives, a second aspect of the present invention proposes a vehicle stability control system for single-wheel braking failure in dual-electric braking vehicles, comprising: a basic sensor module and a vision module with road surface adhesion estimation function, used to collect vehicle state and road surface adhesion information; an autonomous driving domain controller module, used to generate drive, braking and steering control commands according to the environment and driving intention; a chassis domain controller module, used to parse braking commands from the autonomous driving domain controller or the driver, and generate total braking force requirements; execute steering angle commands under normal operating conditions, and respond to corrective steering angle commands during heavy braking; calculate the overall vehicle dynamic state; calculate unexpected yaw moment based on the dynamic state and generate corrective braking yaw moment; distribute braking force in combination with vehicle speed and battery SOC during normal braking, and dynamically distribute four-wheel electromechanical composite braking force by integrating braking intensity, road surface adhesion, corrective yaw moment and corrective steering angle when feedback braking fails and stability control is triggered; and an electromechanical composite braking control module, wherein each wheel's electromechanical composite braking system has a separate EMB control module and motor control module, which receives braking commands from the four-wheel braking distribution module during braking and controls the corresponding wheel's motor braking module and friction braking module.

[0022] This invention relates to a vehicle stability control method and system for single-wheel braking failure in dual-electric braking vehicles. The method is specifically designed for electro-mechanical composite braking systems with energy feedback strategies, primarily addressing fault scenarios involving the failure of the regenerative braking motor in the braking system. Specifically, it categorizes braking conditions into three types based on the driver's brake pedal input and road surface adhesion: light braking, moderate braking, and heavy braking. A single-wheel regenerative braking motor failure during braking can lead to unexpected vehicle yaw. This invention, based on an overdrive system within a dual-electric braking system, can more effectively achieve stability control after the failure. For light braking, considering the relatively small yaw impact, closed-loop feedback electro-mechanical braking (EMB) can be used for tracking and control. For moderate braking, the yaw impact is relatively large, requiring coordinated control of wheel-end regenerative braking motor braking and electro-mechanical braking. Under heavy braking, to avoid reducing longitudinal braking deceleration, a combination of steering intervention and braking is needed to achieve stability control. Compared with existing technologies, this invention, based on dual-electric braking, considers the vehicle stability requirements under different braking intensities and combines the characteristics of the overdrive system. It can meet the vehicle stability control requirements after the failure of a single-wheel regenerative braking motor without sacrificing longitudinal deceleration. Furthermore, this invention considers the mapping relationship between the clamping force and braking torque of the electromechanical brake and incorporates closed-loop feedback regulation, improving control accuracy and ensuring the feasibility of solving the overdrive system under moderate and heavy braking conditions.

[0023] To achieve the above objectives, a third aspect of this application provides a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the vehicle stability control method for single-wheel braking failure of a dual-electric braking vehicle as described in the first aspect embodiment.

[0024] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments in conjunction with the accompanying drawings, in which: Figure 1 is a structural diagram of a vehicle stability control system for single-wheel braking failure of a dual-electric braking vehicle provided by an embodiment of the present invention; Figure 2 is a flowchart of a vehicle stability control method for single-wheel braking failure of a dual-electric braking vehicle provided by an embodiment of the present invention; Figure 3 is a detailed architecture diagram of a vehicle stability control method for single-wheel braking failure of a dual-electric braking vehicle provided by an embodiment of the present invention. Detailed Implementation

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0028] The following description, with reference to the accompanying drawings, describes a vehicle stability control method and system for single-wheel braking failure in dual-electric braking vehicles, based on an embodiment of the present invention.

[0029] This embodiment provides a vehicle stability control system for single-wheel braking failure in dual-electric braking vehicles. As shown in Figure 1, it includes: a basic sensor module 10, containing sensors that measure various vehicle state information for state analysis and control adjustment; a vision module 11 with road adhesion estimation, used to estimate road adhesion conditions and analyze which control strategy to adopt; an autonomous driving domain controller module 20, mainly containing an algorithm analysis chip, which sends operation commands required for vehicle operation to the drive, braking, and steering modules; a battery module 30, mainly containing a battery, electrical system, and related sensors, mainly realizing energy recovery and transmitting battery state signals to the four-wheel braking distribution module 43; and a chassis domain controller module 40, containing braking, drive, and steering modules for vehicle operation, wherein the braking... The braking module 41 receives braking intensity commands from the autonomous driving domain controller 20 or the driver, analyzes the braking intent, generates the total braking force demand, and transmits it to the four-wheel brake distribution module 43. The steering module 42 receives steering angle commands from the autonomous driving domain controller 20 or the driver during normal steering, and receives corrective steering angle commands from the autonomous driving domain controller 20 under heavy braking control to achieve vehicle stability control. The braking stability control module 44 calculates the unexpected yaw moment generated by the vehicle based on the current vehicle dynamics state, and obtains the corrective braking yaw moment to be applied accordingly, which is finally transmitted to the four-wheel brake distribution module 43 for electromechanical composite braking system braking force. The four-wheel brake distribution module 43, under normal braking conditions, distributes the braking force of the four-wheel electromechanical composite braking system according to the braking force demand and in combination with the vehicle speed and the SOC status signal transmitted from the battery module 30, performing normal braking distribution; after the regenerative motor braking fails and triggers the braking stability control module 44, it distributes the braking force of the four-wheel electromechanical composite braking system according to the braking intensity signal, road surface adhesion signal, correction braking yaw moment command, correction steering angle signal, and distribution demand; the dynamic state calculation module 45 receives the raw signals transmitted from the basic sensor module 10 and the vision module 11 and performs calculations based on the whole vehicle dynamics model to obtain the wheel states during the whole vehicle braking process. The system includes vehicle dynamics signals such as the maximum value of the longitudinal and lateral forces of the tires, yaw rate, lateral velocity, braking deceleration, and vehicle speed; an electromechanical composite braking control module 50, where each wheel's electromechanical composite braking system has a separate EMB control module and motor control module, which receives braking commands from the four-wheel braking distribution module during braking and controls the corresponding wheel's motor braking module 60 and friction braking module 70. In addition, considering the mapping characteristics of the clamping force and braking torque of the EMB, a closed-loop feedback controller 71 exists between the friction braking module 70 and the electromechanical composite braking control module 50, which corrects the applied braking clamping force through feedback to ensure that the braking torque generated by the friction braking module 70 meets the actual requirements.

[0030] The second aspect of this invention provides a vehicle stability control method for single-wheel braking failure in dual-electric braking vehicles, as shown in Figures 2 and 3. The process is as follows: S1, acquire the driver's brake pedal opening input signal and the road surface adhesion estimation signal, calculate the total braking force demand based on the vehicle mass, and classify the braking intensity according to a preset threshold to determine whether the current braking condition is light, moderate, or heavy; S2, adopt corresponding control strategies according to the determined braking condition and the single-wheel regenerative motor braking failure state; S3, input the solution results of the optimization model into the four-wheel braking distribution module based on the control results of the control strategy, dynamically adjust the distribution ratio of the regenerative motor braking torque and the electromechanical braking clamping force based on the vehicle dynamics state parameters, ensuring that the braking torque of each wheel meets the tire adhesion limit constraint; S4, correct the electromechanical braking clamping force in real time through a slip ratio closed-loop feedback controller, matching the actual braking torque with the target value and eliminating control errors caused by the nonlinear characteristics of the actuator.

[0031] In one embodiment of the present invention, a braking intensity command signal issued by an autonomous driving domain controller or driver is received. Combined with vehicle mass parameters, the total braking force requirement is calculated by multiplying the braking intensity command signal by the vehicle mass and taking the negative value. A road surface adhesion estimation signal from a vision module is received. Combined with gravitational acceleration parameters, the theoretical maximum longitudinal braking force is calculated by multiplying the road surface adhesion estimation signal by the vehicle mass and gravitational acceleration and taking the negative value. The ratio of the absolute value of the total braking force requirement to the absolute value of the maximum longitudinal braking force is compared with a preset first threshold and a second threshold. If the ratio is less than or equal to the first threshold, the current braking condition is determined to be light; if the ratio is greater than the first threshold and less than or equal to the second threshold, the current braking condition is determined to be moderate; if the ratio is greater than the second threshold, the current braking condition is determined to be heavy.

[0032] Specifically, in step S1, the braking intensity command signal issued by the automatic driving controller is received. Combined with the overall vehicle weight Calculate the total braking force command The specific calculation formula is as follows:

[0033] Simultaneously receiving the road adhesion estimation signal μ from the vision module, and combining it with the gravitational acceleration g, the theoretically maximum longitudinal braking force can be calculated. The specific calculation formula is as follows:

[0034] in accordance with The value is compared with the designed first threshold and second threshold. When it is less than or equal to the first threshold, it is a light braking condition. When it is greater than the first threshold and less than or equal to the second threshold, it is a moderate braking condition. When it is greater than the second threshold, it is a heavy braking condition.

[0035] In one embodiment of the present invention, under light braking conditions, the electromechanical braking clamping force is adjusted through closed-loop feedback to compensate for the unexpected yaw moment generated by the failed wheel; under moderate braking conditions, the residual feedback electromechanical power and the electromechanical braking system are coordinated, and a quadratic constraint quadratic programming optimization model is established based on the tire adhesion ellipse constraint to solve the optimal braking torque distribution scheme that meets the longitudinal braking force requirements; under heavy braking conditions, the longitudinal braking force requirements are kept constant, and the front wheel steering angle compensation is calculated through a two-degree-of-freedom model in conjunction with the steering system to offset the unexpected yaw rate.

[0036] Specifically, in step S2, stability control after single-wheel failure is performed according to the three working conditions classified in step S1. Under the light braking condition, the braking intensity is relatively low, and the longitudinal braking force distributed to the four wheels is as follows:

[0037]

[0038] in, Command for four-wheel braking force ( (These represent the front left, front right, rear left, and rear right wheels, respectively). This is the front axle braking force distribution coefficient.

[0039] At this point, braking only includes regenerative braking. The additional yaw moment caused by single wheel failure is calculated as follows:

[0040] in: c represents the unexpected yaw moment caused by the failure; c is the vehicle track width. The braking force is applied to the wheel on the opposite side of the same axle as the failed wheel. The initial electromechanical braking torque value of the failed wheel is:

[0041] in: The initial braking torque for the electromechanical braking of the failed wheel; The radius is the wheel radius.

[0042] Since the braking torque input needs to be applied through the electromechanical braking actuator to apply clamping force, there is a certain degree of error. Therefore, closed-loop feedback is needed to adjust the braking torque, and the design uses slip ratio as the target for correction. Based on the vehicle speed and wheel speed signals transmitted from the dynamics calculation state module 45, the slip ratio can be calculated using the following formula:

[0043] in: The braking slip ratio of the wheel on the other side of the same axle as the failed wheel; u is the vehicle speed. Let be the angular velocity of the wheel. The closed-loop correction formula for the braking torque feedback of the failed wheel is:

[0044]

[0045] In passing Correct the original This allows the vehicle to achieve stable yaw torque compensation through electromechanical braking when the single-wheel regenerative motor fails under light braking conditions, ensuring vehicle driving stability.

[0046] In one embodiment of the present invention, the four-wheel brake distribution module receives the optimized distribution results of the regenerative electric motor torque and electromechanical braking torque of each wheel output by the optimization model; acquires vehicle dynamic state parameters provided by the dynamic state calculation module, including vehicle speed signal, wheel speed signal, yaw rate, lateral velocity, braking deceleration, vertical force of each wheel, and lateral force of each wheel; and dynamically adjusts the distribution ratio between the regenerative electric motor torque and the braking torque generated by the electromechanical braking clamping force of each wheel according to the state parameters, wherein the electromechanical braking clamping force is converted into actual braking force through a closed-loop feedback controller. A longitudinal braking torque constraint is applied to each wheel, wherein the constraint condition is that the square of the longitudinal braking torque does not exceed the difference between the square of the product of the road adhesion coefficient and the vertical force of the wheel and the square of the lateral force of the wheel. The longitudinal braking torque is determined by dividing the sum of the feedback electromechanical braking torque and the electromechanical braking torque of the corresponding wheel by the wheel radius. The electromechanical braking torque is corrected in a closed loop based on the slip ratio feedback. Specifically, the deviation between the slip ratio of the wheel on the electromechanical braking side and the reference slip ratio is calculated, and a proportional-integral control method is used to generate the torque correction amount to compensate for the mapping error of the electromechanical braking actuator and improve the control accuracy.

[0047] Specifically, under moderate braking conditions, due to the high braking intensity, the unexpected yaw moment generated by the failure of a single-wheel regenerative braking motor cannot be ignored. Therefore, it is necessary to coordinate the control of the remaining regenerative braking motor and the EMB system. The specific method is as follows: Determine the control objectives of the regenerative braking motor and EMB: The regenerative braking motor aims to reduce the force exerted by the regenerative braking motor at the diagonal of the failed wheel to reduce the unexpected yaw moment. The EMB aims to minimize the use of EMB (including the magnitude of the braking torque and the number of wheels involved) while ensuring tire adhesion conditions. Theoretically, braking torque can be applied in the following ways: applying EMB braking force only to the failed wheel; or applying EMB braking force to the failed wheel and the two wheels on the same side.

[0048] The left front wheel regenerative motor of the vehicle failed, and the braking torque... For example, braking torque vector

[0049] The longitudinal braking force constraint conditions are:

[0050] in These represent the regenerative electric motor torques of the four wheels. This represents the EMB braking torque of the front and rear wheels on the left side.

[0051]

[0052] The lateral yaw moment constraint condition is:

[0053]

[0054] Considering the case under the constraint of tire adhesion ellipse, the vertical braking forces of each wheel are as follows:

[0055]

[0056]

[0057]

[0058] Longitudinal braking force needs to meet The longitudinal braking forces of each wheel are as follows:

[0059]

[0060]

[0061]

[0062] in The lateral forces on the four wheels, The vertical force on the four wheels, and These represent the distances from the front axle to the center of gravity and the rear axle to the center of gravity, respectively; L is the vehicle's wheelbase. For the height of the vehicle's center of gravity, and These represent the vehicle's longitudinal and lateral accelerations, respectively.

[0063] Based on the objectives of minimizing EMB usage and tire adhesion utilization, the following objective function is established:

[0064] Therefore, a quadratically constrained quadratic programming (QCQP) problem can be designed and solved:

[0065]

[0066]

[0067]

[0068] in

[0069]

[0070]

[0071]

[0072] By optimizing the solution to the minimum value, the required braking torque of the regenerative motor and EMB can be obtained. While maintaining a constant longitudinal braking force, adjusting the additional yaw torque eliminates unexpected yaw. Furthermore, the braking torque of the EMB accounts for a relatively small proportion and involves fewer wheels. However, closed-loop feedback correction using the slip ratio is still necessary. The specific formula is shown in the light braking condition formula, which only requires that the slip ratio on the EMB braking side be referenced to the other side.

[0073] In one embodiment of the present invention, the real-time vehicle speed signal and wheel speed signals of each wheel output by the dynamic state calculation module are acquired, and the braking slip ratio of each wheel is calculated based on the ratio of the difference between the vehicle speed and the wheel speed to the vehicle speed. For the wheel controlled by the electromechanical braking clamping force, the average slip ratio of the non-failed wheel or the slip ratio of the wheel on the opposite side of the same axle is used as a reference target value, and the deviation between the current wheel slip ratio and the reference target value is calculated. The slip ratio deviation is input into the proportional-integral controller, and the electromechanical braking torque correction amount is generated by the weighted combination of the proportional term and the integral term, wherein the proportional gain and the integral gain are dynamically adjusted according to the braking conditions and road adhesion conditions. The torque correction amount is superimposed on the original target value of the electromechanical braking torque to obtain the corrected clamping force control command and transmit it to the electromechanical braking actuator. The closed-loop feedback is continuously adjusted until the error between the actual braking torque and the target braking torque converges to the preset accuracy range.

[0074] Specifically, under heavy braking conditions, the tire force is close to the adhesion limit, and simply adjusting the braking force is insufficient to simultaneously meet the requirements of longitudinal braking force and yaw stability. Therefore, steering is considered for coordinated control. In principle, priority is given to coordinating the remaining regenerative braking motor and all EMBs for braking control; when the road surface adhesion coefficient is high, the degree of steering intervention can be reduced; optimal control is achieved through drive system optimization analysis.

[0075] At this point, the state vector is 8-dimensional, where a certain vector in the feedback motor ( The value is 0 at the time of the fault.

[0076] The longitudinal braking force constraint conditions remain as follows:

[0077] in These represent the regenerative electric motor torques of the four wheels. EMB torque representing the four wheels.

[0078]

[0079] Because the lateral yaw moment is difficult to converge to zero at this point, and steering control is required with an unexpected yaw rate, the yaw moment is used as the objective function for optimization.

[0080]

[0081] Longitudinal braking force still needs to be met The longitudinal braking forces of each wheel are as follows:

[0082]

[0083]

[0084]

[0085] At this point, we can design a solution to a quadraticly constrained quadratic programming (QCQP) problem, where the objective function is a linear function and the constraints contain quadratic terms:

[0086]

[0087]

[0088] By optimizing the solution to the minimum value, the required braking torque of the residual feedback motor and EMB can be obtained. The torque of the EMB also needs to be adjusted through closed-loop feedback. The adjustment method is to take the average slip ratio of the vehicles that have not failed as the target value for tracking control. Under the condition that the longitudinal braking force remains unchanged, the minimum value of the unexpected yaw moment is found, and this value is recorded as [value]. It meets the following conditions:

[0089] From the vehicle dynamics conditions, the following relationship can be derived between the unexpected yaw moment and the unexpected yaw acceleration of the vehicle:

[0090] in Let be the moment of inertia of the vehicle about the z-axis. The unexpected yaw rate is generated; by integrating the angular acceleration, the unexpected yaw rate can be obtained, and further, the front wheel steering angle compensation can be obtained from the two-degree-of-freedom vehicle model:

[0091]

[0092] in Let be the longitudinal speed of the vehicle. This refers to the vehicle's wheelbase. The steering angle of the vehicle's front wheels. For the vehicle's understeer gradient, For the front axle lateral stiffness of the vehicle, This refers to the rear axle lateral stiffness of the vehicle.

[0093] At this point, the intervention of steering can alleviate the yaw stability problem caused by the failure of the regenerative motor braking under heavy braking conditions to some extent.

[0094] In summary, the dual-electric braking system described above, while meeting energy recovery requirements and incorporating sensor information, achieves the following effects: 1) It achieves full coverage of three braking conditions through a hierarchical control strategy; 2) Combining dual-electric braking with steering control solves the stability control problem under heavy braking conditions; 3) Optimization algorithms ensure that longitudinal braking force requirements are met while minimizing unexpected yaw moments; 4) Closed-loop control compensates for EMB actuator errors, improving control accuracy; 5) It comprehensively considers how to coordinate the distribution of regenerative braking and EMB braking; 6) It provides a feasible approach for the design of braking systems in intelligent dual-electric braking vehicles.

[0095] To implement the above embodiments, this application also proposes a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the method described in the foregoing embodiments.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0097] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0098] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

Claims

1. A vehicle stability control method for single-wheel braking failure in dual-electric braking vehicles, characterized in that, include: The system acquires the driver's brake pedal opening input signal and the road surface adhesion estimation signal, calculates the total braking force demand based on the vehicle's mass, and classifies the braking intensity according to a preset threshold to determine whether the current braking condition is light, moderate, or heavy. Based on the determined braking condition and the failure state of the single-wheel regenerative motor braking, corresponding control strategies are adopted. The control results based on the control strategies are input into the four-wheel braking distribution module, which dynamically adjusts the distribution ratio of the regenerative motor braking torque and the electromechanical braking clamping force based on the vehicle's dynamic state parameters to ensure that the braking torque of each wheel meets the tire adhesion limit constraint. The electromechanical braking clamping force is corrected in real time through a slip ratio closed-loop feedback controller, matching the actual braking torque with the target value and eliminating control errors caused by the nonlinear characteristics of the actuator.

2. The method according to claim 1, characterized in that, The system acquires the driver's brake pedal opening input signal and the road surface adhesion estimation signal, calculates the total braking force requirement based on the vehicle's mass, and classifies the braking intensity according to preset thresholds to determine whether the current braking condition is light, moderate, or heavy. This includes: receiving a braking intensity command signal from the autonomous driving domain controller or the driver, and calculating the total braking force requirement by multiplying the braking intensity command signal by the vehicle mass and taking the negative value, in conjunction with vehicle mass parameters; receiving the road surface adhesion estimation signal from the vision module, and calculating the theoretical maximum longitudinal braking force by multiplying the road surface adhesion estimation signal by the vehicle mass and gravitational acceleration parameters and taking the negative value; comparing the ratio of the absolute value of the total braking force requirement to the absolute value of the maximum longitudinal braking force with preset first and second thresholds: when the ratio is less than or equal to the first threshold, the current braking condition is determined to be light; when the ratio is greater than the first threshold and less than or equal to the second threshold, the current braking condition is determined to be moderate; when the ratio is greater than the second threshold, the current braking condition is determined to be heavy.

3. The method according to claim 1, characterized in that, Based on the determined braking conditions and the failure state of the single-wheel regenerative motor brake, corresponding control strategies are adopted, including: under light braking conditions, adjusting the electromechanical braking clamping force through closed-loop feedback to compensate for the unexpected yaw moment generated by the failed wheel; under moderate braking conditions, coordinating the remaining regenerative motor power and the electromechanical braking system, establishing a quadratic constraint quadratic programming optimization model based on the tire adhesion ellipse constraint, and solving the optimal braking torque distribution scheme that meets the longitudinal braking force requirements; under heavy braking conditions, maintaining the longitudinal braking force requirements unchanged, and calculating the front wheel steering angle compensation amount through a two-degree-of-freedom model in conjunction with the steering system to offset the unexpected yaw rate.

4. The method according to claim 1, characterized in that, The control results based on the control strategy are input into the four-wheel brake distribution module, which dynamically adjusts the distribution ratio of the regenerative electric motor torque and the electromechanical braking clamping force based on the vehicle dynamics state parameters. This ensures that the braking torque of each wheel meets the tire adhesion limit constraints. The process includes: the four-wheel brake distribution module receiving the optimized distribution results of the regenerative electric motor torque and electromechanical braking torque for each wheel output from the optimization model; acquiring the vehicle dynamics state parameters provided by the dynamics state calculation module, including vehicle speed signal, wheel speed signal, yaw rate, lateral velocity, braking deceleration, vertical force of each wheel, and lateral force of each wheel; and dynamically adjusting the regenerative electric motor torque and electromechanical braking clamping force of each wheel according to the state parameters. The distribution ratio among the generated braking torques is determined by converting the electromechanical braking clamping force into actual braking torque through a closed-loop feedback controller. A longitudinal braking torque constraint is applied to each wheel, where the square of the longitudinal braking torque does not exceed the difference between the square of the product of the road adhesion coefficient and the wheel's vertical force and the square of the wheel's lateral force. The longitudinal braking torque is determined by dividing the sum of the corresponding wheel's feedback electromechanical braking torque and the electromechanical braking torque by the wheel radius. A closed-loop correction is performed on the electromechanical braking torque based on slip ratio feedback. Specifically, the deviation between the slip ratio of the wheel on the electromechanical braking side and the reference slip ratio is calculated, and a proportional-integral control method is used to generate the torque correction amount to compensate for the mapping error of the electromechanical braking actuator and improve control accuracy.

5. The method according to claim 1, characterized in that, The electromechanical braking clamping force is corrected in real time by a slip ratio closed-loop feedback controller to match the actual braking torque with the target value, eliminating control errors caused by the nonlinear characteristics of the actuator. This includes: acquiring the real-time vehicle speed signal and wheel speed signal of each wheel output from the dynamic state calculation module; calculating the braking slip ratio of each wheel based on the ratio of the difference between the vehicle speed and wheel speed to the vehicle speed; for the wheel controlled by the electromechanical braking clamping force, using the average slip ratio of the non-failed wheel or the slip ratio of the wheel on the opposite side of the same axle as the reference target value, calculating the deviation between the current wheel slip ratio and the reference target value; inputting the slip ratio deviation into the proportional-integral controller, generating the electromechanical braking torque correction amount through a weighted combination of proportional and integral terms, where the proportional gain and integral gain are dynamically adjusted according to the braking conditions and road adhesion conditions; superimposing the torque correction amount onto the original target value of the electromechanical braking torque to obtain the corrected clamping force control command, which is then transmitted to the electromechanical braking actuator. The closed-loop feedback is continuously adjusted until the error between the actual braking torque and the target braking torque converges to the preset accuracy range.

6. The method according to claim 1, characterized in that, Stability control after single-wheel failure is performed according to the three classified operating conditions. Under light braking conditions, the braking intensity is relatively low, and the longitudinal braking force distributed to the four wheels is as follows: in, This is a command for four-wheel braking force. This is the front axle braking force distribution coefficient; at this time, braking only includes regenerative braking, and the additional yaw moment caused by single wheel failure is calculated as follows: in: c represents the unexpected yaw moment caused by the failure; c is the vehicle track width. The braking force is the force applied to the wheel on the other side of the same axle as the failed wheel; the initial electromechanical braking torque of the failed wheel is: in: The initial braking torque for the electromechanical braking of the failed wheel; Let the wheel radius be denoted by ; the slip ratio is calculated based on the vehicle speed and wheel speed signals, using the following formula: in: The braking slip ratio of the wheel on the other side of the same axle as the failed wheel; u is the vehicle speed. Let be the angular velocity of the wheel; the closed-loop correction formula for the braking torque feedback of the failed wheel is: In passing Correct the original This allows the vehicle to achieve stable yaw moment compensation through electromechanical braking when the single-wheel regenerative motor fails under light braking conditions, thus ensuring vehicle driving stability.

7. A vehicle stability control system for single-wheel braking failure in dual-electric braking vehicles, characterized in that, include: The basic sensor module and the vision module with road surface adhesion estimation function are used to collect vehicle status and road surface adhesion information; The autonomous driving domain controller module is used to generate drive, braking and steering control commands based on the environment and driving intentions; The chassis domain controller module is used to parse braking commands from the autonomous driving domain controller or the driver, and generate total braking force requirements; execute steering angle commands under normal operating conditions, and respond to corrective steering angle commands during heavy braking; calculate the vehicle dynamics state; calculate unexpected yaw moment based on the dynamics state and generate corrective braking yaw moment; distribute braking force in combination with vehicle speed and battery SOC during normal braking; and dynamically distribute four-wheel electromechanical composite braking force by integrating braking intensity, road adhesion, corrective yaw moment, and corrective steering angle when regenerative braking fails and stability control is triggered. The electromechanical composite braking control module has a separate EMB control module and motor control module for each wheel's electromechanical composite braking system. During braking, it receives braking commands from the four-wheel braking distribution module and controls the corresponding wheel's motor braking module and friction braking module.

8. The system according to claim 7, characterized in that, The system further includes a battery module, which includes at least a battery, an electrical system, and related sensors, for realizing energy recovery and transmitting battery status signals to the four-wheel braking distribution module.

9. The system according to claim 7, characterized in that, The chassis domain controller module specifically includes: a braking module, which receives braking intensity commands from the autonomous driving domain controller or the driver, parses the braking intent, generates the total braking force demand, and transmits it to the four-wheel brake distribution module; a steering module, which receives steering angle commands from the autonomous driving domain controller or the driver during normal steering, and receives corrective steering angle commands from the autonomous driving domain controller under heavy braking control, to achieve vehicle stability control; and a braking stability control module, which calculates the unexpected yaw moment generated by the vehicle based on the current vehicle dynamics state, and accordingly obtains the corrective braking yaw moment to be applied, ultimately transmitting it to the four-wheel brake distribution module for the distribution of braking force in the electromechanical hybrid braking system; and four-wheel brake distribution. The module performs conventional braking distribution based on braking force requirements and vehicle speed and SOC status signals under normal braking conditions. When regenerative braking fails and triggers the braking stability control module, it distributes braking force according to braking intensity signals, road surface adhesion signals, corrected braking yaw moment commands, corrected steering angle signals, and distribution requirements. The dynamics state calculation module receives raw signals from the basic sensor module and vision module and performs calculations based on the vehicle dynamics model to obtain vehicle dynamics state signals such as the maximum value of tire longitudinal and lateral forces, yaw rate, lateral velocity, braking deceleration, and vehicle speed during the braking process.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements a vehicle stability control method for single-wheel braking failure of a dual-electric braking vehicle as described in any one of claims 1-6.

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