One-box based vehicle front wheel brake control method and system in a ramp environment

Abstract

The present application relates to the field of vehicle braking, in particular to a front wheel braking control method for a vehicle based on one-box in a slope environment, which is suitable for low-speed reversing of a vehicle on a slope with a slope percentage greater than 40%, and comprises: judging whether the vehicle enters a braking function intervention mode according to a preset condition; after the vehicle enters the braking function intervention mode, calculating and correcting a feedforward braking force of the front wheel, calculating a braking force correction amount of the left front wheel and the right front wheel, and obtaining target braking forces of the left front wheel and the right front wheel; filtering the target braking forces, and executing the target braking forces or executing limit values in a preset range. The present application can effectively prevent the occurrence of dangerous conditions caused by axle load transfer when the vehicle reverses downhill on a slope, and further ensures the personal safety of drivers and passengers in various situations.

Description

Technical Field

[0001] This invention relates to the field of vehicle braking, specifically to a one-box-based method and system for front wheel braking control of vehicles in slope environments. Background Technology

[0002] With the continuous development of automotive technology, new energy vehicles (pure electric and hybrid) are developing towards higher range and higher safety. As a core safety component, the integration, lightweighting and efficiency of the braking system have become the focus of industry research and development.

[0003] EHB (Electronic Brake Assist) is based on a traditional hydraulic braking system. It uses electronic sensors to detect the driver's braking intentions and the vehicle's driving status, transmitting these signals to the ECU (Electronic Control Unit). The ECU calculates and analyzes the received signals, then controls the hydraulic actuators to precisely adjust the brake fluid pressure, thereby achieving precise control of the vehicle's braking. Depending on the degree of integration between the power assist system and ESP (Electronic Stability Program), EHB offers two-box and one-box options.

[0004] The one-box braking system integrates core components such as the master cylinder, electro-hydraulic unit (EHCU), and motor drive mechanism into a single module. Compared with the split braking system, it has advantages such as smaller size, lower weight, higher assembly efficiency, faster and more precise pressure control, and lower operating noise, and has gradually become the mainstream configuration for new energy passenger vehicles.

[0005] For most vehicles, the ratio of front axle load to rear axle load is close to 50:50. When a vehicle is on a slope, due to inertia, axle load transfer occurs during braking. Especially when reversing downhill on a slope with a gradient greater than 40%, this axle load transfer can easily cause the front wheels to lock up before the rear wheels. At this point, the rear wheels are still rotating while the front wheels are locked, and the vehicle continues to move downhill, causing it to lose steering ability. This situation is extremely dangerous and can threaten the safety of the driver and passengers.

[0006] In existing technologies, when controlling vehicle braking, factors such as wheel speed, ground friction coefficient, and road slope are generally considered to adjust braking force to ensure stable and safe vehicle operation. Examples include functions such as ABS (Anti-lock Braking System) and EBD (Electronic Brakeforce Distribution).

[0007] However, there is currently no solution for adjusting the braking force on the front wheels of a vehicle when it is reversing downhill at low speed on a slope with a gradient greater than 40%. This solution addresses the technical problems in this scenario by providing a targeted solution. Summary of the Invention

[0008] The purpose of this invention is to provide a one-box-based method and system for front wheel braking control of vehicles in slope environments, in order to solve the problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a one-box-based method for front wheel braking control of vehicles in a slope environment, applicable to low-speed reversing of vehicles on slopes with a gradient greater than 40%, specifically including the following steps: The system obtains driving information and slope percentage when the vehicle is reversing downhill. Based on preset conditions, it determines whether the vehicle should enter the braking function intervention mode. If any preset condition cannot be met in the subsequent process, the vehicle exits the braking function intervention mode. After the vehicle enters the braking function intervention mode, the feedforward braking force of the front wheels is calculated and corrected. The braking force correction amount of the left front wheel and the right front wheel is calculated according to the PID control algorithm. The target braking force of the left front wheel and the right front wheel is obtained based on the feedforward braking force and the braking force correction amount. The target braking force is filtered and it is determined whether it falls within a preset range. If it falls within the preset range, the target braking force is executed. If it does not fall within the preset range, the limit value of the preset range is used as the target braking force.

[0010] Preferably, the preset conditions for the vehicle to enter the braking function intervention mode are: ① The vehicle is reversing downhill; ② The vehicle speed is lower than its preset value; ③ The slope percentage is greater than its preset value; ④ The driver has already pressed the brake pedal.

[0011] Preferably, if any condition cannot be met, the vehicle exits the braking function intervention mode.

[0012] Preferably, gradient limiting is activated when the vehicle enters the braking function intervention mode, and the gradient limiting is used to limit the change in vehicle braking force.

[0013] Preferably, the formula for calculating the feedforward braking force of the front wheel is as follows:

[0014] in, The front wheel pressure is calculated using feedforward, and the unit is bar. The braking force for the rear wheel cylinder model is a known input quantity, in bar. The distance from the center of mass to the front axle, in meters (m). The distance from the center of mass to the rear axle, in meters (m). The height of the center of mass, in meters (m). Slope percentage; The front axle CP value. This is the CP value for the rear axle.

[0015] Preferably, the correction formula for the feedforward braking force of the front wheel is as follows:

[0016] in, It is a correction factor for the feedforward calculation value, and its value is used as a calibration value, which can be calibrated through actual vehicle testing.

[0017] Preferably, the formulas for calculating the braking force correction of the left and right front wheels are as follows:

[0018] in, This is the difference between the front wheel speed and the rear axle speed. This refers to the speed of the left front wheel or the speed of the right front wheel, in m / s. This refers to the rear axle speed, in m / s.

[0019] in, The dynamic component of the target value calculated for term P is in bar. The GAIN value of the P term is used as the standard value;

[0020]

[0021] in, To The value obtained by integration; The dynamic component of the target value calculated for item I, in bar; The GAIN value of item I is used as the standard value;

[0022]

[0023] in, To The value obtained by performing differential calculations; The target value dynamic component calculated for option D is in bar. The GAIN value in option D is used as the standard value; Based on the above formula, the formula for the front wheel braking force correction is as follows:

[0024] when When the speed of the left front wheel is given, the braking force correction of the left front wheel is given. ;when When the speed of the right front wheel is given, the braking force correction of the right front wheel. .

[0025] Preferably, the formula for calculating the target braking force of the left front wheel is:

[0026] The formula for calculating the target braking force of the right front wheel is:

[0027] in, The front wheel pressure obtained from the corrected feedforward calculation is in bar. This is the braking force correction amount for the left front wheel. This is the braking force correction amount for the right front wheel.

[0028] The present invention also provides a one-box-based front wheel braking control system for vehicles in slope environments, including a sensor module, a one-box ECU module, and an execution module; The sensor module includes a wheel speed sensor, an IMU sensor, and a brake pedal position sensor, which collect vehicle driving information. The ECU module receives vehicle information collected by the sensor module and performs braking force analysis, then transmits the target braking force to the execution module; The execution module includes a one-box HCU module and a vehicle brake, and executes the received target braking force.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention uses the braking system of onebox to brake the front wheels of the vehicle, which can effectively prevent dangerous situations caused by axle load transfer when the vehicle is reversing downhill on a slope, and further protect the personal safety of the driver and passengers in various situations. Attached Figure Description

[0030] Figure 1 This is a schematic flowchart of the front wheel braking control method of the present invention; Figure 2 This is a flowchart of the process for determining whether a vehicle has entered the braking function intervention mode according to the present invention. Figure 3 This is a schematic diagram of the vehicle system modules upon which the front wheel braking control method of the present invention is based. Detailed Implementation

[0031] To address the issue of front wheel lock-up being more likely during traditional braking processes, this invention discloses a one-box-based front wheel braking control method and system for vehicles in incline environments. This method is suitable for low-speed reversing on slopes with a gradient greater than 40%. The method includes the following steps, detailed in the documentation. Figure 1 : The system obtains driving information and slope percentage when the vehicle is reversing downhill. Based on preset conditions, it determines whether the vehicle should enter the braking function intervention mode. If any preset condition cannot be met in the subsequent process, the vehicle exits the braking function intervention mode. After the vehicle enters the braking function intervention mode, the feedforward braking force of the front wheels is calculated and corrected. The braking force correction amount of the left front wheel and the right front wheel is calculated according to the PID control algorithm. The target braking force of the left front wheel and the right front wheel is obtained based on the feedforward braking force and the braking force correction amount. The target braking force is filtered and it is determined whether it falls within a preset range. If it falls within the preset range, the target braking force is executed. If it does not fall within the preset range, the limit value of the preset range is used as the target braking force.

[0032] The specific details of the above steps are as follows: The preset conditions for the vehicle to enter braking intervention mode are: ① The vehicle is reversing downhill; ② The vehicle speed is lower than its preset value; ③ The slope percentage is greater than its preset value, which is 40%.

[0033] ④ The driver has already pressed the brake pedal.

[0034] For example, the vehicle can be determined by the vehicle being in reverse downhill, the vehicle being in reverse, and the longitudinal acceleration being positive. The vehicle gear is obtained from the current gear of the vehicle's transmission, and whether the driver has pressed the brake pedal is collected by the brake pedal position sensor.

[0035] If any preset condition cannot be met during subsequent braking force analysis, the vehicle will exit the braking function intervention mode. See details... Figure 2 : A. The vehicle was not detected reversing downhill; B. The vehicle speed is higher than the preset value; C. The slope percentage is less than or equal to the preset value; D. The driver was detected to have released the brake pedal.

[0036] When the vehicle enters the braking function intervention mode, gradient limitation is activated. The gradient limitation is used to limit the change in vehicle braking force and can be specifically set according to different vehicle models.

[0037] The specific process of braking force analysis is as follows: ① Calculate the feedforward braking force of the front wheels:

[0038] in, The front wheel pressure is calculated using feedforward, and the unit is bar; here It is a general term for "front axle". (Front Left) (Front Right) is A specific subset of. The braking force for the rear wheel cylinder model is a known input quantity, in bar. The distance from the center of mass to the front axle, in meters (m). The distance from the center of mass to the rear axle, in meters (m). The height of the center of mass, in meters (m). Slope percentage; The front axle CP value. This is the CP value for the rear axle.

[0039] ② Correct the feedforward braking force of the front wheels:

[0040] in, It is a correction factor for the feedforward calculation value, and its value is used as a calibration value, which can be calibrated through actual vehicle testing.

[0041] ③ Calculate the braking force correction for the front wheels:

[0042] in, This is the difference between the front wheel speed and the rear axle speed. This refers to the rear axle speed, in m / s. The front wheel speed is measured in m / s and is obtained through wheel speed sensors mounted on the vehicle. The left front wheel speed (denoted as...) ) or right front wheel speed (denoted as All can be brought in The following formula contains and The symbols correspond to the calculation parameters of the left front wheel and the right front wheel, respectively, and their physical meanings are related to... The symbols are consistent.

[0043]

[0044] in, The dynamic component of the target value calculated for term P is in bar. The GAIN value of the P term is used as the standard value;

[0045]

[0046] in, To The value obtained by integration; The dynamic component of the target value calculated for item I, in bar; The GAIN value of item I is used as the standard value;

[0047]

[0048] in, To The value obtained by performing differential calculations; The target value dynamic component calculated for option D is in bar. The GAIN value in option D is used as the standard value; Based on the above formula, the formula for the front wheel braking force correction is as follows:

[0049] When calculating the braking force correction for the left front wheel, the formula in the front group should be used. Replace with left front wheel speed With the definitions and calculation logic of the remaining parameters unchanged, the braking force correction of the left front wheel is obtained:

[0050] in, , and The calculation methods are respectively different from those in the previous set of formulas. , Consistent.

[0051] Similarly, when calculating the braking force correction for the right front wheel, the formula in the first set of equations should be used... Replace with the right front wheel speed With the definitions and calculation logic of the remaining parameters unchanged, the braking force correction for the right front wheel is obtained:

[0052] in, , and The calculation methods are respectively different from those in the previous set of formulas. , Consistent.

[0053] ④ The target braking forces for the left and right front wheels can be obtained by combining the feedforward braking force and braking force correction amount obtained above. The specific calculation formula is as follows: Target braking force of the left front wheel:

[0054] Target braking force of the right front wheel:

[0055] in, The corrected front wheel braking force is expressed in bar. This is the braking force correction amount for the left front wheel. This is the braking force correction amount for the right front wheel.

[0056] ⑤ Filter the obtained target braking forces of the left and right front wheels and determine whether they fall within the preset range; if they fall within the preset range, execute the target braking force; if they do not fall within the preset range, use the limit value of the preset range as the target braking force. The specific limit value of which end of the range is selected is calibrated according to different vehicle models.

[0057] The aforementioned front wheel braking control method in a slope environment is based on the following modules in the vehicle system, see below. Figure 3 The system includes a sensor module, a one-box ECU module, and an execution module.

[0058] The sensor module includes wheel speed sensors, an IMU sensor, and a brake pedal position sensor. It collects vehicle driving information to determine whether the vehicle has entered braking intervention mode or to provide data for subsequent braking force analysis. Specifically, the wheel speed sensors collect wheel speed values ​​for the left and right front wheels and the rear axle speed; the IMU sensor collects acceleration signals, angular velocity signals, etc.; and the brake pedal position sensor determines whether the driver has pressed the brake pedal.

[0059] The ECU module receives vehicle information collected by the sensor module, performs braking force analysis according to the pre-set program, and transmits the target braking force to the execution module.

[0060] The execution module includes a one-box HCU module and a vehicle brake, which executes the received target braking force. Specifically, the execution method is to adjust the braking force applied to the wheels by opening and closing valves.

[0061] Based on the above technical solution, the following embodiment of front wheel braking control for a vehicle in a slope environment based on a one-box is provided: This embodiment uses a certain new energy SUV model as the application object. This model is equipped with a one-box braking system, and the vehicle parameters are as follows: distance from center of gravity to front axle. Distance from center of gravity to rear axle Center of mass height Front axle CP value Rear axle CP value The scenario involves a vehicle on a slope with a percentage gradient. Reverse at low speed on a continuous slope (greater than 40% of the preset value), initial reversing speed (lower than) (Speed ​​preset value), the driver needs to control the vehicle's backward movement distance, so he continuously and lightly presses the brake pedal, triggering the braking function intervention requirement.

[0062] The following information is collected by the sensor module to determine the braking function intervention mode: 1. Gear position signal: The transmission is in reverse (R) gear. Combined with the reverse rotation signal from the wheel speed sensor, the vehicle is determined to be in reverse. The IMU sensor collects the longitudinal acceleration as follows: (Positive value, consistent with downhill acceleration characteristics), confirming that the vehicle is reversing downhill.

[0063] 2. Speed ​​Information: The wheel speed sensor collects the rear axle speed. (correspond ), lower than ( The default value.

[0064] 3. Slope information: The IMU sensor calculates the slope percentage through acceleration decomposition and outputs 45%, which is greater than the preset value of 40%.

[0065] 4. Brake pedal signal: The brake pedal position sensor detects that the pedal travel is 15mm, indicating that the driver has pressed the brake pedal.

[0066] When all four conditions are met, the vehicle enters the braking function intervention mode and simultaneously activates the gradient limiting function, setting the braking force change rate to no more than 5 bar / s to avoid sudden changes in braking force that could lead to vehicle instability.

[0067] After the vehicle enters braking intervention mode, braking force analysis is performed: 1. Calculate the feedforward braking force Known braking force of the rear wheel cylinder model (Calculated by the one-box ECU module based on pedal travel), substituting into the feedforward braking force calculation formula:

[0068] Substitute the parameters:

[0069]

[0070]

[0071] but:

[0072] 2. Correct feedforward braking force Through real-vehicle testing and calibration, the feedforward calculation correction factor K=1.05 for this model in a 40%-50% slope reversing scenario. Substituting this into the correction formula:

[0073] 3. Calculate the PID braking force correction. (1) Error acquisition: The wheel speed sensor collects the speed of the left front wheel in real time. Right front wheel speed Rear axle speed .

[0074] Calculate the speed error of the left front wheel:

[0075] Calculate the speed error of the right front wheel:

[0076] (2) PID parameter setting: Through actual vehicle debugging, the PID parameters in this scenario are calibrated as follows: , , The integration time window is set to 0.5s, and the derivative time window is set to 0.1s.

[0077] (3) Calculation of item P: Left front wheel P component:

[0078] Right front wheel P component:

[0079] (4) Calculation of item I: Integrate the velocity error over 0.5s. Left front wheel error integral:

[0080] Left front wheel component I:

[0081] Right front wheel error integral:

[0082] Right front wheel component I:

[0083] (5) Calculation in option D: Differentiate the velocity error by 0.1s (assuming the rate of change of error is constant) Left front wheel error differential:

[0084] Left front wheel, component D:

[0085] Right front wheel error differential:

[0086] Right front wheel, component D:

[0087] (6) Summary of corrections: Left front wheel braking force correction:

[0088] Right front wheel braking force correction:

[0089] 4. Calculate the target braking force: Target braking force of the left front wheel:

[0090] Target braking force of the right front wheel:

[0091] 5. Filtering and range determination of the above results: First-order low-pass filtering (filtering time constant 0.1s) was applied to the target braking forces of the left and right front wheels. After filtering, the target braking force of the left front wheel was 5.95 bar and the target braking force of the right front wheel was 6.18 bar. The preset range of front wheel braking force of the one-box braking system of this model is 3 bar-8 bar. The filtered target braking forces all fall within the range and do not need to be replaced with extreme values.

[0092] The ECU module transmits the filtered target braking force signals for the left and right front wheels to the execution module: (1) After receiving the signal, the HCU module of the one-box controls the hydraulic valve group to adjust the pressure of the front wheel cylinder. The pressure of the left front wheel cylinder is gradually increased to 5.95 bar, and the pressure of the right front wheel cylinder is gradually increased to 6.18 bar. The pressure change rate is controlled at 4.5 bar / s (below the gradient limit of 5 bar / s).

[0093] (2) The vehicle brake responds to the pressure signal and generates the corresponding braking force, so that the vehicle reverse speed is stabilized in the range of 2.8km / h-3.0km / h, and the front wheels are prevented from locking up due to axle load transfer.

[0094] When the vehicle reverses to a gentle section of the slope, the IMU sensor detects that the slope percentage drops to 38% (less than or equal to the preset value of 40%), which meets the conditions for exiting the braking function intervention mode. The system automatically exits the intervention mode and restores the normal braking control logic, with the front wheel braking force directly controlled by the driver's pedal travel.

[0095] In summary, the present invention can effectively prevent dangerous situations caused by axle load transfer when a vehicle is reversing downhill on a slope, and further protect the personal safety of drivers and passengers in various situations.

[0096] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A one-box-based method for front wheel braking control of a vehicle in a slope environment, characterized in that, This method is applicable for low-speed reversing of vehicles on slopes with a gradient greater than 40%, and includes the following steps: Obtain vehicle driving information and slope percentage when reversing downhill; The system determines whether the vehicle should enter the braking function intervention mode based on preset conditions. If any preset condition cannot be met in the subsequent process, the vehicle will exit the braking function intervention mode. After the vehicle enters the braking function intervention mode, the feedforward braking force of the front wheels is calculated and corrected. The calculation of the feedforward braking force is based on the distance from the vehicle's center of gravity to the front / rear axle, the height of the center of gravity, the percentage of the slope, and the CP value of the front and rear axles. Based on the PID control algorithm, the braking force correction of the left front wheel and the right front wheel is calculated based on the difference between the front wheel speed and the rear axle speed. The target braking forces for the left and right front wheels are obtained based on the feedforward braking force and the braking force correction. The target braking force is filtered and it is determined whether it falls within a preset range. If it falls within the preset range, the target braking force is executed. If it does not fall within the preset range, the limit value of the preset range is used as the target braking force.

2. The control method according to claim 1, characterized in that, The preset conditions for the vehicle to enter the braking function intervention mode are: ① The vehicle is reversing downhill; ② The vehicle speed is lower than its preset value; ③ The slope percentage is greater than its preset value; ④ The driver has already pressed the brake pedal.

3. The control method according to claim 1, characterized in that, When the vehicle enters the braking function intervention mode, gradient limiting is activated, which is used to limit changes in the vehicle's braking force.

4. The control method according to claim 1, characterized in that, The formula for calculating the feedforward braking force of the front wheel is as follows: in, The front wheel pressure is calculated using feedforward, and the unit is bar. The braking force for the rear wheel cylinder model is a known input quantity, in bar. The distance from the center of mass to the front axle, in meters (m). The distance from the center of mass to the rear axle, in meters (m). The height of the center of mass, in meters (m). Slope percentage; The front axle CP value. This is the CP value for the rear axle.

5. The control method according to claim 4, characterized in that, The correction formula for the feedforward braking force of the front wheel is as follows: in, It is a correction factor for the feedforward calculation value, and its value is used as a calibration value, which can be calibrated through actual vehicle testing.

6. The control method according to claim 5, characterized in that, The formulas for calculating the braking force correction of the left and right front wheels are as follows: in, This is the difference between the front wheel speed and the rear axle speed. This refers to the speed of the left front wheel or the speed of the right front wheel, in m / s. This refers to the rear axle speed, in m / s. in, The dynamic component of the target value calculated for term P is in bar. The GAIN value of the P term is used as the standard value; in, To The value obtained by integration; The dynamic component of the target value calculated for term I is in bar. The GAIN value of item I is used as the standard value; in, To The value obtained by performing differential calculations; The target value dynamic component calculated for option D is in bar. The GAIN value in option D is used as the standard value; Based on the above formula, the formula for the front wheel braking force correction is as follows: when When the speed of the left front wheel is given, the braking force correction of the left front wheel. ;when When the speed of the right front wheel is given, the braking force correction of the right front wheel. .

7. The control method according to claim 6, characterized in that, The formula for calculating the target braking force of the left front wheel is: The formula for calculating the target braking force of the right front wheel is: in, The front wheel pressure obtained from the corrected feedforward calculation is in bar. This is the braking force correction amount for the left front wheel. This is the braking force correction amount for the right front wheel.

8. A one-box-based front wheel braking control system for vehicles in slope environments, characterized in that, This includes a sensor module, a one-box ECU module, and an execution module; The sensor module includes a wheel speed sensor, an IMU sensor, and a brake pedal position sensor, which collect vehicle driving information. The ECU module receives vehicle information collected by the sensor module and performs braking force analysis, then transmits the target braking force to the execution module. The analysis process employs the one-box-based front wheel braking control method for vehicles in a slope environment as described in any one of claims 1-7. The execution module includes a one-box HCU module and a vehicle brake, and executes the received target braking force.

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