Vehicle braking anti-sideslip control system and method

Abstract

The invention provides a vehicle braking anti-sideslip control system and method, and relates to the technical field of vehicle safety control. Comprising a vehicle control unit VCU used for calculating expected and actual yaw velocity and judging whether a current vehicle does not trigger an ABS, whether vehicle speed data is larger than a first set value, whether the opening degree of a brake pedal is larger than a second set value and whether brake energy recovery is activated; if yes, whether the slippage rate of any driving wheel is larger than a third set value or whether the difference value between the actual yaw velocity and the expected yaw velocity is larger than a fourth set value is judged; if yes, the VCU enters a braking anti-sideslip function, the braking energy recovery torque is controlled through a logic threshold method, and exiting is carried out till the vehicle triggers an ABS or the wheel slip rate of a driving wheel is smaller than a fifth set value or the vehicle speed data is smaller than a sixth set value or the yaw velocity is smaller than a seventh set value or the opening degree of a brake pedal is smaller than an eighth set value and is kept for a certain time. The sideslip trend can be recognized, the motor torque is controlled in advance, and the braking safety and stability are improved.

Description

Technical Field

[0001] This invention belongs to the field of vehicle dynamics, and specifically relates to a vehicle braking anti-skid control system and method. Background Technology

[0002] According to data released by the National Bureau of Statistics, the number of cars in China has exceeded 300 million, and traffic accidents are also on the rise. Therefore, car safety is receiving increasing attention from consumers. ABS, or Anti-lock Braking System, is an active safety technology whose core function is to prevent the wheels from locking up completely during emergency braking. The ABS system rapidly increases and decreases the pressure in the brake wheel cylinders to control wheel slip within a reasonable range, maintaining the vehicle's steering ability and enhancing braking stability.

[0003] While ABS systems are highly effective at preventing longitudinal lock-up and slippage, their effectiveness in improving a vehicle's anti-skid capability is limited. Due to cost considerations, vehicles equipped only with ABS systems often lack acceleration and yaw rate sensors to assess lateral motion. Furthermore, the drive motor suffers from delayed feedback torque response due to hardware limitations, making the development of control strategies quite challenging.

[0004] Therefore, in order to reduce the risk of vehicle sideslip, this paper proposes a vehicle braking anti-slip control system and method. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a vehicle braking anti-skid control system and method, which improves the braking safety and stability of the vehicle by identifying the vehicle in a condition that is about to skid or is prone to skidding and intervening in the torque of the drive motor in advance.

[0006] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0007] The first aspect of the present invention provides a vehicle braking anti-skid control system, comprising:

[0008] Brake pedal opening sensor, which is used to collect brake pedal opening signal and send it to the vehicle control unit (VCU);

[0009] Steering wheel angle sensor, which is used to collect steering wheel angle signals and send them to the vehicle control unit (VCU);

[0010] Wheel speed sensors are used to collect wheel speed signals and send them to the ABS controller;

[0011] The ABS controller is used to estimate the vehicle speed based on the wheel speed data and send the wheel speed data and vehicle speed data to the vehicle control unit (VCU).

[0012] The vehicle control unit (VCU) receives brake pedal opening signals, steering wheel angle signals, wheel speed data, and vehicle speed data. It calculates the desired yaw rate and estimates the actual yaw rate. It then determines whether the vehicle has not triggered ABS, whether the vehicle speed data is greater than a first set value, whether the brake pedal opening is greater than a second set value, and whether regenerative braking is activated. If so, it determines whether the slip ratio of any drive wheel is greater than a third set value or whether the difference between the actual yaw rate and the desired yaw rate is greater than a fourth set value. If so, the VCU enters the anti-skid braking function, using a logic threshold method to control the regenerative braking torque until the vehicle triggers ABS, or the slip ratio of the drive wheels is less than a fifth set value, or the vehicle speed data is less than a sixth set value, or the yaw rate is less than a seventh set value, or the brake pedal opening is less than an eighth set value, and maintains this condition for a certain period of time before exiting the function.

[0013] The setting value when exiting the function is different from the setting value when entering it. The setting value when exiting the function should be smaller than the setting value when entering it to avoid frequent entry and exit, which would affect the control effect.

[0014] The motor controller MCU is used to receive torque reduction commands sent by the vehicle controller VCU and control the motor torque.

[0015] Preferably, the vehicle controller (VCU) is also used to determine whether the conditions for activating the regenerative braking function are met and when the regenerative braking torque is negative, the current vehicle state is in the regenerative braking function activated state.

[0016] Preferably, the vehicle control unit (VCU) is also used to calculate the desired yaw rate using a vehicle dynamics model based on the steering wheel angle signal and wheel speed data.

[0017] Preferably, the vehicle control unit (VCU) controls and intervenes in the regenerative braking torque through logic threshold control.

[0018] Preferably, the upper limit of the regenerative braking torque and the slope should not exceed the capacity of the motor and battery.

[0019] The second aspect of the present invention provides a vehicle braking anti-skid control method, including a method for calculating the driver's desired yaw rate, a method for estimating the actual yaw rate, and a method for the VCU to intervene in the braking energy recovery torque control.

[0020] The preferred method for calculating the driver's desired yaw rate specifically includes:

[0021]

[0022] In the formula, The yaw rate is the driver's desired yaw rate. For vehicle speed, For the front wheel steering angle, Wheelbase For vehicle quality, This is the distance from the center of gravity to the front axle. This is the distance from the center of mass to the rear axle. For the front wheel lateral stiffness, This refers to the rear wheel lateral stiffness.

[0023] Steering wheel angle The front wheel steering angle can be calculated. :

[0024]

[0025] In the formula, This is the steering system transmission ratio.

[0026] The preferred method for estimating yaw rate calculation yields two equations based on the wheel speeds of the four wheels and the front wheel steering angle, specifically including:

[0027]

[0028] In the formula, For the estimated yaw rate, The speed of the outer wheel on the front axle. The speed of the inner wheel on the front axle. For the wheel radius, For the front wheel steering angle, The wheelbase is the distance between the wheels. The speed of the outer wheel on the front axle. This refers to the wheel speed of the inner wheel on the front axle.

[0029] Then, the Kalman filter was used to fuse the estimated yaw rate equation, which is more accurate than using the difference in wheel speed between the front axle or the rear axle to estimate the yaw rate.

[0030] Preferably, the method by which the VCU intervenes in the torque control of regenerative braking adopts a logic threshold control method, specifically including:

[0031] The system determines whether the vehicle has not triggered ABS, whether the vehicle speed data is greater than the first set value, whether the brake pedal opening is greater than the second set value, and whether regenerative braking is activated. If so, it determines whether the slip ratio of any drive wheel is greater than the third set value or whether the difference between the actual yaw rate and the expected yaw rate is greater than the fourth set value. If so, the VCU enters the anti-skid braking function and uses a logic threshold method to control the regenerative braking torque until the vehicle triggers ABS, or the slip ratio of the drive wheel is less than the fifth set value, or the vehicle speed data is less than the sixth set value, or the yaw rate is less than the seventh set value, or the brake pedal opening is less than the eighth set value and remains so for a certain period of time before exiting the function.

[0032] The setting value when exiting the function is different from the setting value when entering it. The setting value when exiting the function should be smaller than the setting value when entering it to avoid frequent entry and exit, which would affect the control effect.

[0033] Preferably, the target slip ratio threshold must be less than the ABS trigger threshold slip ratio and consist of a base target slip ratio and a correction factor:

[0034]

[0035] In the formula, For the target slip ratio, Based on slip ratio, This is a correction factor.

[0036] Preferably, the factors influencing the basic target slip ratio are: ① the higher the vehicle speed, the lower the target slip ratio, improving yaw stability; ② the lower the vehicle speed, the higher the target slip ratio, shortening the braking distance. Therefore, the basic target slip ratio is:

[0037]

[0038] In the formula, Based on slip ratio, It is the basic target slip ratio as a function of vehicle speed.

[0039] Preferably, the factors influencing the correction factor are: ① The greater the proportion by which the rear axle speed is less than the front axle speed, the smaller the correction factor; ② The larger the vehicle speed and the lower the rear axle speed, the smaller the correction factor; ③ The greater the yaw rate, the smaller the correction factor; ④ The smaller the road surface adhesion coefficient, the smaller the correction factor; ⑤ The greater the braking deceleration and the smaller the rear axle normal force, the smaller the correction factor. Therefore, the correction factor is:

[0040]

[0041] In the formula, As a correction factor, , , , , These are functions of the correction factor with respect to wheel speed, vehicle speed, yaw rate, adhesion coefficient, and braking deceleration, respectively.

[0042] Preferably, based on the target slip ratio threshold, additional torque-increasing slip ratio thresholds and torque-decreasing slip ratio thresholds are added to avoid wheel vibration caused by repeated increases and decreases in motor feedback torque around the target threshold. The torque-increasing slip ratio threshold and torque-decreasing slip ratio threshold are:

[0043]

[0044] In the formula, For the target slip ratio, To increase the torsional slip ratio threshold, To reduce the torsional slip ratio threshold, and This is a coefficient related to factors such as vehicle speed.

[0045] Preferably, when the slip ratio of the drive wheel is less than the torque slip ratio threshold. When the braking energy recovery torque is increased; when the slip ratio of the drive wheels exceeds the torque-increasing slip ratio threshold... And less than the target slip ratio threshold When the braking energy recovery torque remains constant; when the drive wheel slip ratio exceeds the target slip ratio threshold... And less than the torque slip ratio threshold. If the drive wheel slip ratio shows a decreasing trend, the regenerative braking torque remains constant; otherwise, the regenerative braking torque decreases slowly. When the drive wheel slip ratio exceeds the torque reduction slip ratio threshold... At that time, the regenerative braking torque decreases rapidly.

[0046] The above one or more technical solutions have the following beneficial effects:

[0047] This invention proposes a vehicle braking anti-skid control system and method. By calculating the vehicle yaw rate expected by the driver and estimating the actual vehicle yaw rate, it identifies whether the vehicle is in a skidding tendency or in a skidding-prone condition, intervenes in advance to recover braking energy torque, and controls the slip ratio of the drive wheels to be near the target slip ratio. This solves the problem of untimely feedback torque response without increasing hardware costs and enhances the braking stability of the vehicle.

[0048] Advantages of additional aspects 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

[0049] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0050] Figure 1 This is a system structure diagram for an example.

[0051] Figure 2 The flowchart illustrates the braking energy recovery stage control method in this embodiment.

[0052] Figure 3 This is a schematic diagram of the braking energy recovery stage control method in an embodiment.

[0053] Figure 4 This is a schematic diagram of the ideal control process during the braking energy recovery stage of an embodiment. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0055] A vehicle braking anti-skid control system and method according to an embodiment of the present invention will now be described with reference to the accompanying drawings.

[0056] This embodiment discloses a vehicle braking anti-skid control system.

[0057] like Figure 1 As shown, a vehicle braking anti-skid control system specifically includes:

[0058] This includes a brake pedal opening sensor, wheel speed sensor, steering wheel angle sensor, ABS controller, vehicle control unit (VCU), and motor control unit (MCU).

[0059] Brake pedal opening sensor, which is used to collect brake pedal opening signal and send it to the vehicle control unit (VCU);

[0060] Steering wheel angle sensor, which is used to collect steering wheel angle signals and send them to the vehicle control unit (VCU);

[0061] Wheel speed sensors are used to collect wheel speed signals and send them to the ABS controller;

[0062] The ABS controller is used to estimate the vehicle speed based on the wheel speed data and send the wheel speed data and vehicle speed data to the vehicle control unit (VCU).

[0063] The vehicle control unit (VCU) receives brake pedal opening signals, steering wheel angle signals, wheel speed data, and vehicle speed data. It calculates the desired yaw rate and estimates the actual yaw rate. It then determines whether the vehicle has not triggered ABS, whether the vehicle speed data is greater than a first set value, whether the brake pedal opening is greater than a second set value, and whether regenerative braking is activated. If so, it determines whether the slip ratio of any drive wheel is greater than a third set value or whether the difference between the actual yaw rate and the desired yaw rate is greater than a fourth set value. If so, the VCU enters the anti-skid braking function, using a logic threshold method to control the regenerative braking torque until the vehicle triggers ABS, or the slip ratio of the drive wheels is less than a fifth set value, or the vehicle speed data is less than a sixth set value, or the yaw rate is less than a seventh set value, or the brake pedal opening is less than an eighth set value, and maintains this condition for a certain period of time before exiting the function.

[0064] The setting value when exiting the function is different from the setting value when entering it. The setting value when exiting the function should be smaller than the setting value when entering it to avoid frequent entry and exit, which would affect the control effect.

[0065] The motor controller MCU is used to receive torque reduction commands sent by the vehicle controller VCU and control the motor torque.

[0066] This embodiment discloses a vehicle braking anti-skid control method.

[0067] like Figure 2 The flowchart shown illustrates a vehicle braking anti-skid control method, which specifically includes:

[0068] The system determines whether the vehicle has not triggered ABS, whether the vehicle speed data is greater than the first set value, whether the brake pedal opening is greater than the second set value, and whether regenerative braking is activated. If so, it determines whether the slip ratio of any drive wheel is greater than the third set value or whether the difference between the actual yaw rate and the expected yaw rate is greater than the fourth set value. If so, the VCU enters the anti-skid braking function and uses a logic threshold method to control the regenerative braking torque until the vehicle triggers ABS, or the slip ratio of the drive wheel is less than the fifth set value, or the vehicle speed data is less than the sixth set value, or the yaw rate is less than the seventh set value, or the brake pedal opening is less than the eighth set value and remains so for a certain period of time before exiting the function.

[0069] The setting value when exiting the function is different from the setting value when entering it. The setting value when exiting the function should be smaller than the setting value when entering it to avoid frequent entry and exit, which would affect the control effect.

[0070] The target slip ratio threshold must be less than the ABS trigger threshold slip ratio and consist of a base target slip ratio and a correction factor.

[0071]

[0072] In the formula, For the target slip ratio, Based on slip ratio, This is a correction factor.

[0073] The factors affecting the basic target slip ratio are: ① The higher the vehicle speed, the smaller the target slip ratio, improving yaw stability; ② The lower the vehicle speed, the larger the target slip ratio, shortening the braking distance. Therefore, the basic target slip ratio is:

[0074]

[0075] In the formula, Based on slip ratio, It is the basic target slip ratio as a function of vehicle speed.

[0076] The factors affecting the correction factor are: ① The greater the proportion by which the rear axle speed is lower than the front axle speed, the smaller the correction factor; ② The higher the vehicle speed and the lower the rear axle speed, the smaller the correction factor; ③ The greater the yaw rate, the smaller the correction factor; ④ The smaller the road surface adhesion coefficient, the smaller the correction factor; ⑤ The greater the braking deceleration and the smaller the rear axle normal force, the smaller the correction factor. Therefore, the correction factor is:

[0077]

[0078] In the formula, As a correction factor, , , , , These are functions of the correction factor with respect to wheel speed, vehicle speed, yaw rate, adhesion coefficient, and braking deceleration, respectively.

[0079] Based on the target slip ratio threshold, additional torque-increasing and torque-decreasing slip ratio thresholds are added to prevent wheel vibration caused by repeated increases and decreases in motor feedback torque around the target threshold. The torque-increasing and torque-decreasing slip ratio thresholds are:

[0080]

[0081] In the formula, For the target slip ratio, To increase the torsional slip ratio threshold, To reduce the torsional slip ratio threshold, and This is a coefficient related to factors such as vehicle speed.

[0082] A schematic diagram of a vehicle braking anti-skid control method is shown below. Figure 3As shown, the desired yaw rate is first calculated based on the steering wheel angle and wheel speed. Then, a Kalman filter is used to fuse the difference between the steering wheel angle and wheel speed to estimate the actual yaw rate. After that, based on the desired yaw rate, the estimated actual yaw rate, vehicle speed, steering wheel angle, etc., it is determined whether there is a tendency for fishtailing. If so, the drive motor torque is adjusted.

[0083] A diagram of a vehicle braking anti-skid control process is shown below. Figure 4 As shown, when the slip ratio of the drive wheel is less than the torque slip ratio threshold... When the braking energy recovery torque is increased; when the slip ratio of the drive wheels exceeds the torque-increasing slip ratio threshold... And less than the target slip ratio threshold When the braking energy recovery torque remains constant; when the drive wheel slip ratio exceeds the target slip ratio threshold... And less than the torque slip ratio threshold. If the drive wheel slip ratio shows a decreasing trend, the regenerative braking torque remains constant; otherwise, the regenerative braking torque decreases slowly. When the drive wheel slip ratio exceeds the torque reduction slip ratio threshold... At that time, the regenerative braking torque decreases rapidly.

[0084] In the description of this specification, the reference to the term "preferred" means that a specific feature or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the 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 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 the different embodiments or examples.

[0085] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A vehicle braking anti-skid control system, characterized in that, include: Brake pedal opening sensor, which is used to collect brake pedal opening signal and send it to the vehicle control unit (VCU); Steering wheel angle sensor, which is used to collect steering wheel angle signals and send them to the vehicle control unit (VCU); Wheel speed sensors are used to collect wheel speed signals and send them to the ABS controller; The ABS controller is used to estimate the vehicle speed based on the wheel speed data and send the wheel speed data and vehicle speed data to the vehicle control unit (VCU). The vehicle control unit (VCU) receives brake pedal opening signals, steering wheel angle signals, wheel speed data, and vehicle speed data. It calculates the desired yaw rate and estimates the actual yaw rate. It then determines whether the vehicle has not triggered ABS, whether the vehicle speed data is greater than a first set value, whether the brake pedal opening is greater than a second set value, and whether regenerative braking is activated. If so, it determines whether the slip ratio of any drive wheel is greater than a third set value or whether the difference between the actual yaw rate and the desired yaw rate is greater than a fourth set value. If so, the VCU enters the anti-skid braking function, using a logic threshold method to control the regenerative braking torque until the vehicle triggers ABS, or the slip ratio of the drive wheels is less than a fifth set value, or the vehicle speed data is less than a sixth set value, or the yaw rate is less than a seventh set value, or the brake pedal opening is less than an eighth set value, and maintains this condition for a certain period of time before exiting the function. The setting value when exiting the function is different from the setting value when entering it. The setting value when exiting the function should be smaller than the setting value when entering it to avoid frequent entry and exit, which would affect the control effect. The motor controller MCU is used to receive torque reduction commands sent by the vehicle controller VCU and control the motor torque. The vehicle controller (VCU) is also used to determine whether the conditions for the activation of the regenerative braking function are met and when the regenerative braking torque is negative, the current vehicle state is in the regenerative braking function activated state. The vehicle control unit (VCU) is also used to calculate the desired yaw rate using a vehicle dynamics model based on the steering wheel angle signal and wheel speed data. The vehicle control unit (VCU) controls the regenerative braking torque through logic threshold control, and the upper limit and slope of the regenerative braking torque cannot exceed the capacity of the motor and battery.

2. A vehicle braking anti-skid control method, characterized in that, A vehicle braking anti-skid control system based on claim 1 includes a method for calculating the driver's desired yaw rate, a method for estimating the actual yaw rate, and a method for the VCU to intervene in the braking energy recovery torque control. The method for calculating the driver's desired yaw rate includes: In the formula, The yaw rate is the driver's desired yaw rate. For vehicle speed, For the front wheel steering angle, Wheelbase For vehicle quality, This is the distance from the center of gravity to the front axle. This is the distance from the center of mass to the rear axle. For the front wheel lateral stiffness, Rear wheel lateral stiffness; From the steering wheel angle The front wheel steering angle can be calculated. : In the formula, This refers to the steering system gear ratio; The method for estimating yaw rate calculation yields two equations based on the wheel speeds of the four wheels and the front wheel rotation angle, specifically including: In the formula, For the estimated yaw rate, The speed of the outer wheel on the front axle. The speed of the inner wheel on the front axle. For the wheel radius, For the front wheel steering angle, The wheelbase is the distance between the wheels. The speed of the outer wheel on the front axle. This refers to the wheel speed of the inner wheel on the front axle. Then, the Kalman filter was used to fuse the estimated yaw rate equation, which is more accurate than using the wheel speed difference between the front axle or the rear axle alone to estimate the yaw rate. The VCU intervenes in the torque control of regenerative braking using a logic threshold control method, specifically including: The system determines whether the vehicle has not triggered ABS, whether the vehicle speed data is greater than the first set value, whether the brake pedal opening is greater than the second set value, and whether regenerative braking is activated. If so, it determines whether the slip ratio of any drive wheel is greater than the third set value or whether the difference between the actual yaw rate and the expected yaw rate is greater than the fourth set value. If so, the VCU enters the anti-skid braking function and uses a logic threshold method to control the regenerative braking torque until the vehicle triggers ABS, or the slip ratio of the drive wheel is less than the fifth set value, or the vehicle speed data is less than the sixth set value, or the yaw rate is less than the seventh set value, or the brake pedal opening is less than the eighth set value and remains so for a certain period of time before exiting the function. The setting value when exiting the function is different from the setting value when entering it. The setting value when exiting the function should be smaller than the setting value when entering it to avoid frequent entry and exit, which would affect the control effect. The target slip ratio threshold must be less than the ABS trigger threshold slip ratio and consist of a base target slip ratio and a correction factor. In the formula, For the target slip ratio, Based on slip ratio, As a correction factor; The factors affecting the basic target slip ratio are: ① The higher the vehicle speed, the smaller the target slip ratio, which improves yaw stability; ② The lower the vehicle speed, the larger the target slip ratio, which shortens the braking distance. Therefore, the basic target slip ratio is: In the formula, Based on slip ratio, The basic target slip ratio is a function of vehicle speed; The factors affecting the correction factor are: ① The larger the proportion by which the rear axle speed is less than the front axle speed, the smaller the correction factor; ② When the vehicle speed is high and the rear axle speed is low, the correction factor is smaller; ③ The greater the yaw rate, the smaller the correction factor; ④ The smaller the road surface adhesion coefficient, the smaller the correction factor; ⑤ The greater the braking deceleration and the smaller the rear axle normal force, the smaller the correction factor. Therefore, the correction factor is: In the formula, As a correction factor, , , , , These are functions of the correction factor with respect to wheel speed, vehicle speed, yaw rate, adhesion coefficient, and braking deceleration, respectively. Based on the target slip ratio threshold, additional torque-increasing and torque-decreasing slip ratio thresholds are added to prevent wheel vibration caused by repeated increases and decreases in motor feedback torque around the target threshold. The torque-increasing and torque-decreasing slip ratio thresholds are: In the formula, For the target slip ratio, To increase the torsional slip ratio threshold, To reduce the torsional slip ratio threshold, and A coefficient related to factors such as vehicle speed; When the slip ratio of the drive wheel is less than the torque slip ratio threshold When the braking energy recovery torque is increased; when the slip ratio of the drive wheels exceeds the torque-increasing slip ratio threshold... And less than the target slip ratio threshold When the braking energy recovery torque remains constant; when the drive wheel slip ratio exceeds the target slip ratio threshold... And less than the torque slip ratio threshold. If the drive wheel slip ratio shows a decreasing trend, the regenerative braking torque remains constant; otherwise, the regenerative braking torque decreases slowly. When the drive wheel slip ratio exceeds the torque reduction slip ratio threshold... At that time, the regenerative braking torque decreases rapidly.

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