Brake control method and system

Abstract

The invention discloses a brake control method and system.The method comprises the steps that brake pressure and vehicle speed are obtained, and when the brake pressure is larger than a pressure threshold value and the vehicle speed is larger than a first vehicle speed threshold value, a return function closing instruction is triggered; after the return function closing instruction is triggered, if braking is relieved, a return function activating instruction is triggered after specified time delay or when the vehicle speed is smaller than a second vehicle speed threshold value; the return function is used for return control of the steering gear, and the brake pressure represents the brake fluid pressure of the brake system. By means of the method, the active aligning function can be temporarily closed in the braking period, the superimposed effect of the aligning torque and the deformation torque of the plate spring is eliminated, and therefore deviation is restrained.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of vehicles, and in particular, to a braking control method and system. Background Art

[0002] When a commercial vehicle brakes under the existing technology, the leaf spring generates an S-shaped deformation due to load transfer, which causes an asymmetric steering torque and results in vehicle braking deviation. The active return function of the electro-hydraulic power steering system (EHPS) will further amplify the deviation amount under braking conditions, threatening driving safety. The existing return control strategy does not consider the coupling effect of braking conditions and suspension deformation, resulting in poor deviation suppression effect.

[0003] During the braking process, the target torque of the return function conflicts with the actual vehicle attitude requirements, and a dynamic intervention strategy needs to be developed to balance the steering return requirements and braking stability. Therefore, a decoupling control method for the active return torque and the braking deviation torque is required. Summary of the Invention

[0004] The present invention provides a braking control method and system to achieve the purpose of solving at least one defect existing in the prior art.

[0005] In a first aspect, an embodiment of the present invention provides a braking control method, including:

[0006] Obtain the braking pressure and vehicle speed. When the braking pressure is greater than the pressure threshold and the vehicle speed is greater than the first vehicle speed threshold, a return function closing instruction is triggered;

[0007] After triggering the return function closing instruction, if the braking is released, after a specified time delay, or when the vehicle speed is less than the second vehicle speed threshold, an activation return function instruction is triggered;

[0008] The return function is used for the return control of the steering gear, and the braking pressure represents the brake fluid pressure of the braking system.

[0009] Optionally, before triggering the return function closing instruction, it further includes:

[0010] Obtain the steering wheel angle. When the steering wheel angle is within the first angle range, the return function is allowed to be closed;

[0011] Obtain the braking pressure and vehicle speed. When the braking pressure is greater than the pressure threshold and the vehicle speed is greater than the first vehicle speed threshold, if the return function is allowed to be closed, a return function closing instruction is triggered.

[0012] Optionally, triggering the return function closing instruction includes:

[0013] If the braking pressure is within the first pressure range, the straightening function shutdown command is used to reduce the gain of the straightening control.

[0014] Optionally, triggering the straightening function shutdown command includes:

[0015] If the braking pressure is within the second pressure range, the straightening function shutdown command is used to turn off the straightening control.

[0016] Optionally, triggering the straightening function shutdown command includes:

[0017] If the braking pressure is within the third pressure range, the straightening function shutdown command is used to turn off the straightening control and enable the steering resistance torque compensation and the coordinated control of the electronic stability system.

[0018] Optionally, it further includes dynamically updating the pressure threshold and the first vehicle speed threshold by using a self-learning model.

[0019] Optionally, it further includes dynamically updating the time delay by using a self-learning model.

[0020] Optionally, it further includes that when the anti-lock braking system is activated, the straightening control is turned off and the steering resistance torque compensation and the coordinated control of the electronic stability system are enabled.

[0021] Optionally, after the braking is released, if the steering wheel angle is within the second angle range, the activation straightening function command is immediately triggered.

[0022] In a second aspect, an embodiment of the present invention further provides a braking control system, including an electronic control unit, and the electronic control unit is configured to execute any one of the braking control methods recorded in the embodiments of the present invention.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention proposes a braking control method. In this method, the active straightening function is temporarily turned off during braking to eliminate the superposition effect of the straightening torque and the leaf spring deformation torque, thereby suppressing vehicle deviation. This solution directly monitors the brake fluid pressure by using the pressure sensor of the ESC system. This pressure is a direct reflection of the actual working state of the braking system, can accurately reflect the braking intensity and the presence or absence of braking action, effectively avoid false alarms caused by insufficient accuracy of the pedal opening sensor, and ensure the reliability of braking state determination. Based on the accurate braking state determination, this solution timely turns off the straightening function during braking to avoid conflict with the braking torque and improve braking stability; after the braking is released, according to the specified time delay or vehicle speed threshold, the straightening function is activated in a timely manner to ensure the rapid recovery of steering controllability and achieve the efficient coordination of the braking and steering systems. Description of the Drawings

[0024] Figure 1It is the flowchart of the braking control method in the embodiment;

[0025] Figure 2 It is the schematic diagram of the force on the steering component in the embodiment;

[0026] Figure 3 It is the flowchart of another braking control method in the embodiment;

[0027] Figure 4 It is the structural block diagram of the braking control system in the embodiment. Specific implementation mode

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. In addition, it should be noted that, for the sake of description, only parts related to the present invention rather than all structures are shown in the accompanying drawings.

[0029] Embodiment 1

[0030] Figure 1 It is the flowchart of the braking control method in the embodiment. Refer to Figure 1 , the braking control method includes:

[0031] S101. Obtain the braking pressure and vehicle speed. When the braking pressure is greater than the pressure threshold and the vehicle speed is greater than the first vehicle speed threshold, a return-to-neutral function closing instruction is triggered.

[0032] In this solution, the braking pressure represents the braking fluid pressure of the braking system. The braking pressure can be measured by a pressure sensor in the ESC (Electronic Control Suspension) system, and specifically, it can be the braking fluid pressure in the braking system pipeline.

[0033] After the driver steps on the brake pedal, the braking fluid pressure generated by the master cylinder piston squeezing the braking fluid is the direct power to drive the wheel brakes (such as the brake calipers of disc brakes and the brake shoes of drum brakes) to clamp the brake disc / drum.

[0034] In this solution, the return-to-neutral function is a function of dynamically adjusting the active return-to-neutral of the electro-hydraulic steering under braking conditions. In active return-to-neutral control, by sensing the force change of the vehicle during braking, the return-to-neutral torque of the steering system is adjusted in real time to balance braking stability and steering response.

[0035] Exemplarily, in this solution, the assisted return-to-neutral can be realized through the Electric Power Steering (EPS) system. The EPS controller drives the motor to apply a torque opposite to the steering direction according to the steering wheel angle sensor and vehicle speed signal, and provides the return-to-neutral torque through motor assistance.

[0036] In this solution, when the instruction to turn off the return-to-center function is triggered, the (active) return-to-center function is prohibited. At this time, the vehicle still has the passive return-to-center function, which is realized by the mechanical structure of the vehicle. Through the design of the geometric parameters of the chassis suspension and steering system, when the vehicle is driving, the force acting on the wheels from the road surface can automatically generate a return-to-center moment.

[0037] Exemplarily, in this solution, the design of geometric parameters may include caster angle, kingpin inclination, wheel camber angle, etc. Among them, the kingpin provides the axis of rotation for the wheel to steer, enabling the wheel to deflect around it to achieve steering.

[0038] The kingpin is usually a cylindrical metal rod, with its upper end installed on the frame / axle through a bushing or bearing, and its lower end hinged to the steering knuckle. The wheel is installed on the steering knuckle through the hub, and the deflection of the kingpin directly changes the steering angle of the wheel.

[0039] One end of the steering knuckle arm is fixed to the kingpin, and the other end is connected to the steering drag link. When the steering drag link transmits the steering force, the steering knuckle arm rotates around the kingpin, driving the axis of the kingpin to deflect, thereby pushing the wheel to steer. If the steering knuckle arm is deformed, it will cause the axis of the kingpin to shift, resulting in abnormal steering angle of the wheel and vehicle pulling to one side.

[0040] S102. After the instruction to turn off the return-to-center function is triggered, if the braking is released, then after a specified time delay, or when the vehicle speed is less than the second vehicle speed threshold, the instruction to activate the return-to-center function is triggered.

[0041] Exemplarily, in this solution, the pedal stroke can be monitored in real time by a position sensor (such as a potentiometer, Hall sensor) installed on the brake pedal. When the pedal returns from the depressed state to the initial position (stroke = 0), it is determined that the braking is released.

[0042] Exemplarily, in this solution, the change in brake fluid pressure can be monitored by a pressure sensor installed at the master cylinder. When the pressure drops from above the initial value (such as > 0.5 bar) to below the set threshold (such as ≤ 0.2 bar), it is determined that the braking is released.

[0043] In this solution, when the instruction to activate the return-to-center function is triggered, the (active) return-to-center function is reactivated. At this time, the vehicle has both the active return-to-center function and the passive return-to-center function.

[0044] Figure 2 It is the schematic diagram of the forces on the steering components in the embodiment. Refer to Figure 2 , the steering drag link 1 is used to connect the steering gear and the steering knuckle arm 2, and it is used to transmit the steering force. One end of the steering knuckle arm 2 is connected to the kingpin 3, and the other end is connected to the steering drag link 1. The steering knuckle arm 2 drives the kingpin 3 to deflect under the drive of the steering drag link 1, directly controlling the steering of the wheel.

[0045] The eye 4 connects the front leaf spring 6 to the vehicle frame, allowing the spring to oscillate slightly as it deforms, transmitting vertical force. It also allows the leaf spring to oscillate forward and backward (rotate around the eye pin) as it deforms, relieving the lateral force generated by the spring's expansion and contraction.

[0046] The front axle 5 is the installation base of the wheels (including tires, wheel hubs, etc.), rigidly supports the front wheels, and is connected to the steering system (steering knuckle arm 2, steering trailing rod 1, etc.) through the steering knuckle and kingpin 3.

[0047] One end of the front leaf spring 6 is hinged to the frame through the lifting lug 4, and the other end is rigidly connected to the front axle 5 (or through a skateboard structure). It is an elastic supporting component responsible for buffering road impact and transmitting vertical force.

[0048] The wheels are mounted on the steering knuckles of the front axle 5 through wheel hub bearings, directly contacting the ground to transmit braking force, vertical force, and lateral force.

[0049] For example, during braking, the wheels are subjected to a rearward braking force from the ground (opposite to the direction of travel), and this force is transmitted upward to the suspension system through the wheel hub, the steering knuckle, and the front axle 5 .

[0050] The front axle 5 transmits the wheel braking force rigidly to the front leaf spring 6. At the same time, as the center of gravity of the vehicle moves forward, the vertical load borne by the front axle increases sharply (the load originally distributed to the rear axle is transferred to the front axle due to inertia).

[0051] The forward movement of the center of gravity compresses the front leaf spring 6, and the spring deforms to absorb the vertical load while storing elastic potential energy (which will act in reverse on the front axle and wheels).

[0052] The braking force is transmitted to the leaf spring through the front axle, causing the spring to bear a backward tension / compression force (depending on the spring installation method), driving the spring to swing forward around the eye 4 (because the braking force is backward, the spring needs to pull the front axle, so the eye will swing toward the front of the vehicle).

[0053] The lifting eye 4 serves as the hinge point between the leaf spring and the vehicle frame. When the spring is deformed by braking force and vertical force, it swings around its own pin to release the lateral force generated by the expansion and contraction of the spring.

[0054] In the figure, the blue part represents the ideal straight-line driving condition of a left-hand drive vehicle (the driver holds the steering wheel tightly with his hands). Under the braking condition, the steering knuckle arm 2 is deformed as shown in the red part, and the tire turns left.

[0055] However, in actual driving conditions, it is difficult for the driver to hold the steering wheel, and the entire steering system does not deform only due to the deformation of the steering knuckle arm 2. Therefore, the drop arm will swing backward a certain angle as the steering knuckle arm 2 deforms, causing the steering wheel to deflect to the right. At this time, if the active return function is activated, the steering wheel will return to the left, exacerbating the braking deviation.

[0056] Exemplarily, in an ideal state, during braking, the front wheels are subject to ground braking force, which is transmitted through the front axle 5 to the steering knuckle arm 2, causing it to have a tendency to bend and deform to the left. The steering knuckle arm 2 drives the kingpin 3, and then causes the wheel to deflect to the left.

[0057] At this time, the vehicle should simply deviate to the left. If the driver tightly holds the steering wheel, the steering drag link 1 is locked in the neutral position of the steering wheel, and only the steering knuckle arm 2 deforms as a single component in the system.

[0058] Under actual working conditions, when the steering knuckle arm 2 deforms to the left, it pulls the drag link (not marked in the figure) through the steering drag link 1, causing the drag link to swing backward and rotate around the output shaft of the steering gear.

[0059] At the same time, the forward shift of the braking center of gravity causes the front leaf spring 6 to compress, and the hanger 4 swings at a small angle as the spring deforms, indirectly changing the relative position between the front axle 5 and the frame, and amplifying the force on the steering knuckle arm.

[0060] The backward swing of the drag link pushes the steering wheel to deflect to the right through the internal gear-rack / recirculating ball mechanism of the steering gear (mechanical transmission characteristic of a left-hand drive vehicle: the backward swing of the drag link causes the steering wheel to turn to the right). At this time, if the driver does not tightly hold the steering wheel, the steering wheel will lose the neutral locking state.

[0061] After the steering wheel deflects to the right, the angle sensor of the electro-hydraulic steering gear recognizes the non-neutral position and activates the active return-to-center function, and the hydraulic power assist pushes the steering wheel to return to the left.

[0062] The return force acts on the steering knuckle arm 2 again through the steering drag link 1, superimposing on the initial leftward deformation force, causing the kingpin 3 to drive the wheel to deflect to the left by a larger angle. At the same time, the deformation of the front leaf spring 6 caused by the load transfer magnifies the difference in vertical force and braking force between the left and right wheels, and finally the deviation amplitude increases sharply.

[0063] In this solution, the active return-to-center function is temporarily turned off during braking to eliminate the superimposed effect of the return torque and the leaf spring deformation torque, thereby suppressing deviation.

[0064] This embodiment proposes a braking control method. In this method, the active return-to-center function is temporarily turned off during braking to eliminate the superimposed effect of the return torque and the leaf spring deformation torque, thereby suppressing deviation. This solution directly monitors the brake fluid pressure using the pressure sensor of the ESC system. This pressure is a direct reflection of the actual working state of the braking system, can accurately reflect the braking intensity and the presence or absence of braking action, effectively avoid false alarms caused by insufficient accuracy of the pedal opening sensor, and ensure the reliability of braking state determination. Based on the accurate braking state determination, this solution timely turns off the return function during braking to avoid conflict with the braking torque and improve braking stability; after braking is released, according to the specified time delay or vehicle speed threshold, the return function is activated in a timely manner to ensure the rapid recovery of steering controllability and achieve the efficient coordination of the braking and steering systems.

[0065] On the basis of any of the foregoing solutions, in an implementable solution, before triggering the instruction to turn off the return-to-center function, it further includes: obtaining the steering wheel angle, and when the steering wheel angle is in the first angle range, allowing the return-to-center function to be turned off.

[0066] In this solution, obtain the braking pressure and vehicle speed. When the braking pressure is greater than the pressure threshold and the vehicle speed is greater than the first vehicle speed threshold, if the return-to-center function is allowed to be turned off, then trigger the instruction to turn off the return-to-center function.

[0067] In this solution, when the steering wheel angle θ is in the neutral range (the first angle range), allowing the return-to-center function to be turned off can avoid accidentally triggering the turning off of the return-to-center function. The neutral range can be |θ| < θ0. The neutral range represents a state close to straight-line driving.

[0068] In this solution, before triggering the instruction to turn off the return-to-center function, add a judgment condition for the steering wheel angle. First, judge whether the steering wheel angle is in the preset first angle range. Only when the steering wheel angle is within this range is the return-to-center function allowed to be turned off; if it exceeds this range, the return-to-center function is maintained to work normally.

[0069] Turning off the return-to-center function during the steering process (when the steering wheel angle is large) may cause the steering wheel to get out of control or abnormal return, increasing the risk of vehicle sideslip and fishtailing. Through the angle judgment, it can be ensured that the return-to-center function is only turned off when going straight or slightly correcting the direction, ensuring steering safety.

[0070] When braking, if the vehicle is in a turning state, the return-to-center function can assist the driver in correcting the direction and avoid oversteering or understeering. This solution realizes the dynamic balance between braking and steering control through the angle condition.

[0071] On the basis of any of the foregoing solutions, in an implementable solution, triggering the instruction to turn off the return-to-center function includes: if the braking pressure is in the first pressure range, the instruction to turn off the return-to-center function is used to reduce the gain of the return-to-center control.

[0072] Exemplarily, in this solution, the braking pressure corresponding to the first pressure range is set to P1 to P2 (for example, 2 to 4 MPa), and the first pressure range corresponds to light braking.

[0073] In this solution, when triggering the instruction to turn off the return-to-center function, introduce a judgment of the braking pressure range. When it is detected that the braking pressure is in the preset first pressure range, the system does not completely turn off the return-to-center function, but weakens the return-to-center force by reducing the gain of the return-to-center control (such as reducing the output of the active return-to-center torque to 50% of the normal value).

[0074] During light braking (such as slow driving or normal following - vehicle braking), the vehicle may still need to make fine steering adjustments (such as avoiding obstacles). Completely turning off the return - to - center function at this time will affect the steering feel, while reducing the gain can retain some return - to - center ability and avoid the return - to - center torque interfering with the braking operation.

[0075] In this solution, through pressure range division, progressive control of the return - to - center function from partial weakening to complete shutdown is achieved, making the system response more in line with actual driving needs and improving control accuracy.

[0076] Exemplarily, in this solution, the first pressure range (P1 - P2) can be determined through vehicle tests. For example, P1 = 2 MPa and P2 = 4 MPa, covering the conventional light - braking pressure range.

[0077] The return - to - center control gain can be calibrated according to the steering characteristics of the vehicle model. For example, an output ratio of 50% can weaken the return - to - center torque while retaining the basic return - to - center ability.

[0078] In this solution, during light braking, part of the return - to - center function is retained to prevent the steering wheel from becoming heavy or losing feedback due to the complete loss of the return - to - center torque, maintaining a natural steering feel and improving driving comfort. The driver can still easily make fine steering adjustments (such as lane - changing, avoidance) during braking, and the system will not be interfered by an overly strong return - to - center torque.

[0079] Based on any of the above solutions, in an implementable solution, triggering the return - to - center function shutdown instruction includes: if the braking pressure is in the second pressure range, the return - to - center function shutdown instruction is used to turn off the return - to - center control.

[0080] Exemplarily, in this solution, the braking pressure corresponding to the second pressure range is set as P3 - P4 (for example, 4 - 6 MPa), and the second pressure range corresponds to medium braking.

[0081] In this solution, it is judged whether the braking pressure is in the medium - braking range (P3 - P4). When the pressure enters this range, the system determines that the vehicle is in a medium - braking condition. At this time, the active return - to - center function is completely turned off, and no additional compensation mechanism (such as mechanical return - to - center enhancement or electronic auxiliary compensation) is enabled. This strategy aims to avoid the return - to - center torque interfering with the braking force transmission during medium braking, while maintaining basic steering stability and ensuring the balance between braking and steering.

[0082] During medium braking, the vehicle's center - of - gravity transfer and tire force changes are relatively obvious. The active return - to - center function may cause abnormal steering wheel feedback (such as excessive return - to - center, deviation) due to superposition with the braking force. Turning off this function can eliminate such interference. Not enabling the compensation mechanism simplifies the control logic, reduces the algorithm complexity and hardware cost, and at the same time avoids the misjudgment risk that may be caused by the compensation strategy (such as over - compensation leading to steering out of control).

[0083] Exemplarily, in this solution, the medium braking interval (P3 - P4) can be determined through on-vehicle braking tests, which need to cover the conventional medium braking pressure range (e.g., P3 = 4 MPa, P4 = 6 MPa), forming a clear demarcation from the light and heavy braking intervals.

[0084] Exemplarily, in this solution, a first vehicle speed threshold (e.g., 30 km / h) is set to avoid false triggering at low speeds; a second vehicle speed threshold (e.g., 10 km / h) is used as the activation condition for the return-to-center function after braking is released.

[0085] In this solution, when the braking pressure is in the medium braking interval, the active return-to-center function is turned off to avoid its superposition with the braking torque, preventing abnormal return or deviation of the steering wheel during braking, ensuring that the vehicle decelerates stably in a straight line, and improving braking stability. The compensation mechanism is not enabled, relying on mechanical structures (such as caster angle) to provide the basic return ability, which not only reduces interference but also retains the driver's direct control of steering and maintains the steering feel.

[0086] Based on any of the above solutions, in an implementable solution, the trigger for the return-to-center function off command includes: if the braking pressure is in the third pressure interval, the return-to-center function off command is used to turn off the return-to-center control, and the steering resistance torque compensation and the electronic stability system cooperative control are enabled.

[0087] In this solution, the steering resistance torque compensation can be: increasing the damping of the steering system through an electro-hydraulic servo valve or a motor to keep the steering wheel stable during emergency braking and reduce the risk of driver misoperation.

[0088] In this solution, the electronic stability system (ESC) cooperative control can be: ESC real-time monitors the vehicle's yaw rate and lateral acceleration, and corrects the vehicle's body attitude through unilateral wheel braking, jointly maintaining vehicle stability with the steering resistance torque compensation.

[0089] In this solution, when the braking pressure is in the third pressure interval (corresponding to emergency braking, e.g., P > P4, P4 ≈ 6 MPa), the system executes the return-to-center control off, disables the active return-to-center function to avoid its conflict with the braking torque; enables the steering resistance torque compensation to prevent excessive rotation of the steering wheel by increasing the damping of the steering system; enables the electronic stability system (ESC) cooperation, and ESC actively intervenes in braking distribution to suppress vehicle sideslip or spin, forming a resultant force with the steering resistance torque compensation.

[0090] Exemplarily, in this solution, when the steering resistance torque compensation is enabled, the controller increases the resistance torque of the steering system by adjusting the hydraulic valve opening of the electro-hydraulic steering system or the current of the EPS motor, making the steering wheel feel heavy.

[0091] The magnitude of the resistance torque is directly proportional to the vehicle speed and the braking pressure, providing greater damping during high-speed emergency braking. When the driver actively applies a steering force (such as for an avoidance maneuver), the system dynamically reduces the resistance torque to ensure steering responsiveness.

[0092] Exemplarily, in this solution, when ESC collaborative control is enabled, when ESC monitors that the vehicle's yaw rate or lateral acceleration exceeds a threshold (such as yaw rate > 8° / s), it is determined that there is a risk of sideslip. At this time, the inner rear wheel is slightly braked (such as with a pressure of 0.5 - 1 MPa) to generate a torque opposite to the direction of sideslip and suppress fishtailing. If understeer occurs, the outer front wheel is braked to assist the vehicle in steering.

[0093] When ESC performs braking intervention, the steering resistance torque compensation synchronously increases the damping to prevent the steering wheel from deflecting violently due to uneven unilateral braking force and improve the driver's controllability of steering.

[0094] Exemplarily, in this solution, the steering resistance torque compensation and ESC collaborative control can also be: superimposing the (steering resistance torque) compensation current and the ESC braking pulse signal to form a control signal, and realizing assisting the vehicle in steering through this control signal.

[0095] In this solution, when steering and avoiding while performing emergency braking, the system dynamically adjusts the steering resistance torque to reduce the driver's burden. The steering resistance torque compensation simulates the stable feel of traditional hydraulic power steering to avoid the steering wheel feeling floaty or suddenly returning to the straight position during emergency braking. The collaborative control of ESC and the steering resistance torque makes the vehicle's response more linear during emergency braking and steering, reducing the risk of oversteering or understeering.

[0096] Based on any of the foregoing solutions, in an implementable solution, it further includes dynamically updating the pressure threshold and the first vehicle speed threshold using a self-learning model.

[0097] Exemplarily, in this solution, by collecting multi-dimensional data such as braking pressure, vehicle speed, steering wheel angle, and ESC system status during vehicle driving, the pressure threshold (P1 - P4 for distinguishing light, medium, and heavy braking) and the first vehicle speed threshold (the vehicle speed threshold for triggering the closing of the return-to-center function) are dynamically adjusted using a self-learning model (such as machine learning algorithms or reinforcement learning algorithms).

[0098] By dynamically updating the pressure threshold and the first vehicle speed threshold, the system can adapt to different driving styles, vehicle wear levels, and environmental conditions (such as changes in road surface adhesion) and continuously optimize the braking and steering collaborative control strategy.

[0099] Exemplarily, in this solution, for aggressive drivers (frequent hard braking) or conservative drivers (gentle braking), by dynamically adjusting the pressure threshold or the first vehicle speed threshold, their driving habits can be matched to avoid mis-triggering or missing the instruction to close the return-to-center function.

[0100] Exemplarily, after long-term use of the vehicle, when the performance of the braking system deteriorates (such as brake pad wear) or the load transfer characteristics change due to the aging of the suspension, the self-learning model can automatically correct the threshold to ensure that the control strategy is always effective.

[0101] Exemplarily, in this solution, it is possible to configure the use of a brake pressure sensor, a wheel speed sensor, a steering wheel angle sensor, and ESC system sensors (such as yaw rate and lateral acceleration sensors) to collect real-time data.

[0102] A database is established in the vehicle ECU (Electronic Control Unit) or in the cloud to store historical data such as brake pressure sequences, vehicle speeds, steering operations, and braking results (such as whether there is deviation, whether ABS is triggered), which are used as model training samples.

[0103] Based on the historical data, the braking condition types (light / medium / severe braking) are marked, and a classification model (such as random forest, support vector machine) is trained to predict the braking intensity, and the pressure threshold and the first vehicle speed threshold are deduced inversely.

[0104] The control strategy effect (such as braking stability score, steering response time) is used as a reward function, and the threshold parameters are optimized by continuous trial and error to maximize the system performance.

[0105] The cloud data is regularly downloaded to the local ECU, and the model is trained using in-vehicle computing power. New data is received in real time, and an incremental learning algorithm (such as online gradient descent) is used to dynamically update the model parameters to ensure that the threshold adapts to the working condition changes in a timely manner.

[0106] When the amount of newly collected data reaches a set threshold (such as 1000 braking records), the model update is started. If there are multiple occurrences of braking deviation or incorrect triggering of the return-to-center function in a row, the threshold is forcibly updated.

[0107] After each update, the system enters the verification stage, comparing the braking control effects (such as braking distance, steering wheel return accuracy) under the old and new thresholds. If the performance deteriorates, it rolls back to the original parameters and retrains.

[0108] In this solution, the self-learning model can correct the threshold in real time as the vehicle ages, brake pads are replaced, or under different road conditions (such as ice and snow, dry roads), ensuring that braking and steering control are always in the optimal state. By learning typical false triggering scenarios (such as bumpy roads being misjudged as braking) through historical data, the threshold logic is optimized, unnecessary functional intervention is reduced, and system stability is improved. Reasonable threshold settings can avoid excessive intervention in the braking and steering systems (such as frequently closing / opening the return function), reduce the wear frequency of actuators (such as electro-hydraulic servo valves, EPS motors), and extend the life of the hardware. The self-learning model can continuously optimize the control strategy, reduce the need for fault repairs due to parameter mismatches, and indirectly reduce the maintenance cost of the vehicle throughout its life cycle.

[0109] Based on any of the aforementioned solutions, in one possible implementation, it further includes using a self-learning model to dynamically update the delay.

[0110] In this solution, by collecting driving data after the vehicle brakes are released (such as vehicle speed changes, steering wheel angle, road conditions, driving style, etc.), a self-learning model (such as machine learning and reinforcement learning algorithms) is used to analyze the optimal delay value in different scenarios.

[0111] In this solution, the system no longer uses a fixed time delay, but dynamically adjusts according to real-time working conditions to ensure that the return function can be reactivated at the most appropriate time after the brake is released, balancing the steering response speed and vehicle stability.

[0112] Driving requirements after brake release vary significantly in different scenarios. For example, after high-speed braking, a longer delay is required to prevent premature return to centering and disrupting the vehicle's coasting; while after low-speed following braking, a shorter delay is required to quickly restore steering flexibility. The self-learning model accurately adapts to various operating conditions.

[0113] Exemplarily, in this solution, measurement data from a brake pressure sensor, a wheel speed sensor, a steering wheel angle sensor, an acceleration sensor, and a GPS (Global Positioning System) may be collected.

[0114] Each brake release event is labeled with an optimal delay reference value. For example, if there is no steering action within 2 seconds after the brake is released, then 2 seconds is marked as a high-quality delay sample for this scenario, taking into account the driver's subsequent steering operation.

[0115] Eliminate abnormal data (such as sensor failure fluctuation values) and classify according to driving scenarios (high speed / low speed, dry / wet road surface, etc.).

[0116] Use historical data to train a regression model (such as random forest regression and neural network), input features such as vehicle speed, pressure, and road conditions when the brake is released, and output the predicted optimal delay.

[0117] Taking vehicle stability (such as yaw rate fluctuation) and driver operation comfort (such as the degree of sudden change in steering resistance) as the reward function, the model is allowed to continuously try and error in the simulation environment to optimize the time delay strategy.

[0118] Regularly upload the data accumulated by the vehicle to the cloud, train the model using a high-performance server, and then push it to the in-vehicle ECU through OTA (Over-the-Air Technology).

[0119] The ECU receives new data in real time and fine-tunes the model parameters using an incremental learning algorithm (such as online gradient descent) to quickly adapt to new working conditions.

[0120] When 500 pieces of newly collected brake release data are reached, start the model retraining and parameter update. If there are multiple consecutive steering abnormalities caused by improper time delay (such as the steering wheel shaking caused by premature straightening), force the update of the time delay.

[0121] After the brake is released, the ECU calls the self-learning model to predict the time delay value based on characteristics such as the current vehicle speed, road surface conditions, and driving style, and activates the straightening function after the end of this time period. For example, after braking on a high-speed dry road surface, the model predicts a time delay of 1.5 seconds; after braking on a low-speed wet and slippery road surface, the time delay is shortened to 0.8 seconds.

[0122] In this solution, the dynamic time delay ensures that the straightening function is activated after the vehicle state is stable, preventing premature intervention from interfering with the driver's control of the steering wheel (such as the mis-triggering of straightening during inertial sliding after high-speed braking), and reducing the risk of loss of control. Whether it is high-speed emergency braking, low-speed creeping, or rain, snow, and wet road surfaces, the self-learning model can give accurate time delays based on historical data and real-time working conditions to ensure that the straightening function matches the driving requirements.

[0123] On the basis of any of the foregoing solutions, in an implementable solution, the method further includes that if the anti-lock braking system is activated, the straightening control is turned off, and the steering resistance torque compensation and the electronic stability system cooperative control are enabled.

[0124] In this solution, when the ABS system detects that the wheels are about to lock and activates the anti-lock function, the straightening control is simultaneously turned off and the active straightening function is disabled to avoid conflicts with the ABS braking torque and prevent the vehicle from losing control due to the interference of the straightening force; the steering resistance torque compensation is enabled, and the steering damping is increased through an electro-hydraulic servo valve or an electric power steering (EPS) system to improve the steering operation stability of the steering wheel and prevent the driver from misoperating the steering wheel due to the high-frequency vibration during the operation of the ABS; the electronic stability system (ESC) cooperative control is enabled, and the ESC monitors parameters such as the vehicle yaw rate and lateral acceleration in real time, and corrects the vehicle attitude through unilateral wheel braking intervention, forming a resultant force with the steering resistance torque compensation to suppress dangerous situations such as sideslip and tail swing.

[0125] In this solution, when the ABS is working, the braking force is adjusted frequently. If the return-to-center function continues to act, it may exacerbate the uneven force on the wheels and cause the vehicle to deviate. Turning off the return-to-center control can ensure the maximization of the ABS efficiency.

[0126] The steering resistance torque compensation simulates the damping feeling of traditional hydraulic power steering to help the driver firmly hold the steering wheel during the high-frequency vibration of the ABS; the ESC collaborative braking actively corrects the vehicle body posture and reduces the risk of loss of control.

[0127] In this solution, when the ABS is enabled, turning off the return-to-center control avoids its conflict with the ABS braking torque. The steering resistance torque compensation stabilizes the steering wheel operation, and the ESC actively corrects the vehicle body posture. The three work together to effectively suppress vehicle sideslip and fishtailing, especially on slippery roads. When steering and avoiding while the ABS is working, the stable steering resistance torque and the braking intervention of the ESC help the driver more accurately control the vehicle trajectory and improve the success rate of emergency obstacle avoidance.

[0128] Based on any of the above solutions, in an implementable solution, after the braking is released, it further includes that if the steering wheel angle is in the second angle range, an instruction to activate the return-to-center function is immediately triggered.

[0129] Exemplarily, in this solution, the second angle range means that the steering wheel angle deviates from the neutral position. At this time, the steering wheel angle θ satisfies |θ| > θ1.

[0130] In this solution, the second angle range can be determined through vehicle tests. θ1 can be 15°, to avoid too small an interval resulting in delayed return-to-center.

[0131] In this solution, after the braking operation ends, the system continuously monitors the steering wheel angle θ. If it is detected that the steering wheel angle deviates from the neutral position by more than the set threshold θ1, an instruction to restore the steering return-to-center function is immediately triggered, and a return-to-center torque is applied through the electro-hydraulic steering system or the electric power steering system (EPS) to assist the driver in returning the steering wheel to the neutral position, thereby correcting the vehicle deviation trend and ensuring driving straightness.

[0132] In this solution, with the steering wheel angle as the core judgment basis, the dynamic activation of the return-to-center function is realized, making the vehicle control system more in line with the actual driving needs and reflecting the intelligent characteristics.

[0133] Figure 3 It is another flowchart of the braking control method in the embodiment. Refer to Figure 3 , based on any of the above solutions, in an implementable solution, the method includes:

[0134] S201. Obtain the steering wheel angle. When the steering wheel angle is in the first angle range, the return-to-center function is allowed to be turned off.

[0135] S202. Obtain the braking pressure and vehicle speed. When the braking pressure is greater than the pressure threshold and the vehicle speed is greater than the first vehicle speed threshold, if the function of closing the return is allowed, then trigger the instruction to close the return function.

[0136] In this solution, if the braking pressure is in the first pressure range, the instruction to close the return function is used to reduce the gain of the return control.

[0137] In this solution, if the braking pressure is in the second pressure range, the instruction to close the return function is used to turn off the return control.

[0138] In this solution, if the braking pressure is in the third pressure range or the anti-lock braking system is activated, the instruction to close the return function is used to turn off the return control, and the steering resistance torque compensation and the coordinated control of the electronic stability system are enabled.

[0139] After triggering the instruction to close the return function, if the braking is released, after a specified time delay, or when the vehicle speed is less than the second vehicle speed threshold, trigger the instruction to activate the return function; after the braking is released, if the steering wheel angle is in the second angle range, immediately trigger the instruction to activate the return function.

[0140] In this solution, the method further includes dynamically updating the pressure threshold, the first vehicle speed threshold, and the time delay by using a self-learning model.

[0141] In this solution, the ESC braking pressure sensor signal is used as the basis for determining the braking state, and the corresponding pressure threshold is set. The method collects the braking signal, vehicle speed, and steering wheel angle in real time; when the braking pressure exceeds the threshold and the vehicle speed is higher than the set value, execute the instruction to close the return function; after the braking ends, reactivate the return function according to the preset conditions.

[0142] Exemplarily, in this solution, it is set that the return function recovery delay time T (time delay) is negatively correlated with the braking duration.

[0143] In this solution, by using the above method, the braking deviation can be reduced by 50% - 60%, the overall design scheme of the braking deviation and the interference hard point position of the leaf spring suspension can be coordinated, and the limitation of the hard point position on the braking deviation performance can be reduced; the braking stability and the return comfort in the normal working condition can be taken into account; no hardware modification is required, the forging and casting dies can be saved, and the development cycle and development cost can be reduced.

[0144] Exemplarily, the above solution is applicable to the prohibition and activation control of the active return function of the electro-hydraulic power steering (EHPS). The physical characteristics, response speed, and force transmission methods of different steering gears (electro-hydraulic / electric) and suspensions (leaf spring / air, etc.) are significantly different, and the extended application can be realized through the adaptive adjustment of the robust design parameters.

[0145] Exemplarily, robust design dynamically matches hardware characteristics by establishing a general control framework and combining a parameter adaptive adjustment mechanism. For example, for differences in steering gears, electro-hydraulic steering gears rely on the response of the hydraulic system, and electric steering gears are directly driven by motors, so different power assist characteristics need to be adapted; for differences in suspensions, the stiffness of leaf spring suspensions is fixed, and air suspensions can be adjusted dynamically, which have different impacts on vehicle attitude changes and force transmission.

[0146] Exemplarily, data can be collected in real time through sensors, and the system automatically adjusts control parameters (such as the return torque gain and steering resistance compensation coefficient) to ensure that the strategy runs stably on various types of hardware.

[0147] Exemplarily, a model can be constructed through specified hardware characteristic parameters, and the adaptive adjustment coefficient can be determined through the model. The hardware characteristic parameters can include: characteristics such as hydraulic pump pressure fluctuations, solenoid valve response time, position sensor feedback delay, suspension stiffness and damping coefficient, air spring pressure sensor, height sensor data, etc.

[0148] Based on the above hardware characteristic parameters, a steering-suspension system dynamics model can be established as the basis for parameter adjustment.

[0149] Exemplarily, in an implementable embodiment, an active return adjustment strategy with multi-parameter coupling (including but not limited to load distribution, leaf spring deformation, road surface adhesion coefficient, etc. as auxiliary determination parameters) can be introduced to achieve a more precise turn-off / activation strategy.

[0150] Compared with relying on single parameters such as braking pressure and vehicle speed to control the return function, this solution introduces auxiliary parameters such as load distribution, leaf spring deformation, and road surface adhesion coefficient, and constructs a multi-parameter coupling decision model in combination with the main parameter (such as braking pressure).

[0151] Regarding load distribution, when braking, the vehicle's center of gravity moves forward, and the change in the front and rear axle loads affects the tire adhesion and the demand for return torque, so the intensity of the return function needs to be adjusted accordingly. Regarding the leaf spring deformation, the compression deformation amount of the leaf spring suspension during braking directly reflects the change in the vehicle body attitude and can assist in judging whether the return function needs to be delayed or enhanced. Regarding the road surface adhesion coefficient, the adhesion coefficient of wet, slippery, and icy road surfaces is low, and too strong a return torque is likely to cause sideslip, so the return function gain needs to be reduced or the activation needs to be delayed.

[0152] Through multi-parameter collaborative analysis, the system can more accurately identify the working conditions and dynamically optimize the switch strategy of the return function.

[0153] Exemplarily, in an implementable embodiment, based on the closed-loop compensation mechanism of the steering resistance torque, after turning off the active return function, by calculating the difference in the steering system resistance torque ΔT in real time, a more precise turn-off / activation strategy can be achieved.

[0154] In this solution, by introducing a closed-loop compensation mechanism for steering resistance torque, after turning off the active return function, the resistance torque difference is used as the core adjustment variable to achieve precise control of the return function.

[0155] For example, in this solution, when the active self-centering function is turned off, the system monitors the actual resistance torque (actual) of the steering system in real time, compares it with the target resistance torque (target) under ideal working conditions, and calculates the difference between the two (actual target). Based on the size and change trend of ΔT, the compensation strategy of the steering system is dynamically adjusted to optimize the steering feel and more accurately determine the activation time of the self-centering function.

[0156] After turning off the return function, the vehicle's steering characteristics change, and the resistance torque closed-loop compensation can maintain a stable steering feel to prevent the steering wheel from being too light or too heavy.

[0157] In this solution, the resistance torque difference is used as a reference indicator for activating the self-centering function. Compared with single parameter judgment (such as vehicle speed and brake pressure), it can more directly reflect the actual state of the steering system and reduce the risk of misjudgment.

[0158] For example, in this solution, when |ΔT|>ΔT 阈值 When ΔT is negative, the controller can be configured to send compensation instructions to the actuator according to the positive and negative and size of ΔT:

[0159] For example, if ΔT>0 (the actual resistance torque is too large), reduce the power-assist motor current or reduce the electro-hydraulic servo valve opening to reduce the resistance torque; if ΔT<0 (the actual resistance torque is too small), increase the power-assist motor current or increase the electro-hydraulic servo valve opening to increase the resistance torque.

[0160] For example, in one possible implementation scheme, braking and steering can be controlled in a coordinated manner, linked with the brake pressure pedal service sensor, ESC, ABS and other sensors, and can synchronously share the data bus during emergency braking, thereby achieving a more precise shutdown / activation strategy.

[0161] In this solution, the real-time data of key sensors such as the brake pressure pedal opening sensor, ESC, and ABS are integrated through the data bus to build a decision-making model based on multi-source information fusion.

[0162] During emergency braking, the system comprehensively judges the vehicle status (such as braking intensity, wheel slip rate, and vehicle posture) based on shared data and dynamically adjusts the turning return function's off / on strategy. For example:

[0163] When ABS detects that a wheel is about to lock and the brake pressure pedal opening reaches a threshold, the system immediately turns off the return function and adjusts the steering resistance torque compensation intensity according to the yaw angular velocity monitored by ESC to prevent the vehicle from skidding.

[0164] After the brakes are released, the system uses the data from various sensors to determine whether the vehicle is stable (such as whether the speed, steering wheel angle, and body posture have returned to normal), and accurately triggers the activation command for the return-to-center function.

[0165] This solution avoids single-sensor misjudgments (e.g., relying solely on brake pressure, which may overlook the risk of wheel lock) and improves decision accuracy through cross-validation of multi-source data. In high-risk scenarios like emergency braking, it achieves millisecond-level coordination between the braking and steering systems, maximizing vehicle stability and controllability.

[0166] Example 2

[0167] This embodiment proposes a braking control system, including an electronic control unit, which is configured to execute any one of the braking control methods recorded in Example 1. The implementation process and beneficial effects of the method are the same as the corresponding contents recorded in Example 1, and the specific contents will not be described in detail.

[0168] Figure 4 This is a structural diagram of the braking control system in the embodiment, refer to Figure 4 In one possible implementation, the system includes:

[0169] The electronic control unit 100 , and the brake pressure sensor 201 , the steering wheel angle sensor 202 , the leaf spring deformation sensor 203 , the CAN bus 204 , the EHPS 301 , and the ESC 302 connected to the electronic control unit 100 .

[0170] In this solution, the brake pressure sensor 201 is used to measure the brake pressure, the steering wheel angle sensor 202 is used to measure the steering wheel angle, the leaf spring deformation sensor 203 can be a wheel center height sensor / strain gauge, which is used to monitor the leaf spring deformation in real time, and the CAN bus 204 is used to transmit the vehicle speed signal.

[0171] Based on the contents recorded in Example 1, illustratively, in this solution, the electronic control unit 100 (ECU) is used for multi-sensor data fusion, integrating information such as steering force, leaf spring deformation, vehicle speed, and brake pressure, running a multi-parameter coupling return strategy and a resistance torque closed-loop compensation algorithm, and determining when the return function is turned off / activated.

[0172] Send torque control instructions to EHPS 301 and synchronously share data with ESC 302 to achieve deep braking and steering coordination; continuously iterate control parameters (such as return threshold and compensation coefficient) to adapt to different scenarios and hardware characteristics.

[0173] In this solution, the EHPS 301 is used to provide power assistance to the steering system and can actively apply a return torque or a resistance torque compensation.

[0174] The EHPS 301 executes the steering control instructions of the electronic control unit 100, such as turning off active return, enhancing resistance torque compensation, etc.; the EHPS 301 can also be configured to dynamically adjust the assist level in combination with vehicle speed, leaf spring deformation, etc. (stable at high speeds and light at low speeds), optimizing the driving experience.

[0175] Exemplarily, in this solution, the leaf spring deformation can dynamically adjust the assist characteristics of the EHPS 301 (such as enhancing the steering resistance compensation when the leaf spring is compressed too much to prevent excessive pitching of the vehicle body from affecting handling), adapting to different suspension types (leaf spring, air suspension, etc.).

[0176] The ESC 302 is used to suppress vehicle sideslip and fishtailing by adjusting the wheel braking force (intervening in the ABS) and engine torque, ensuring driving stability.

[0177] The ESC 302 can be configured to provide data such as yaw rate, wheel slip ratio, and vehicle body attitude to the electronic control unit 100, supporting multi-parameter coupling decision-making (such as jointly judging the sideslip risk during emergency braking);

[0178] In cooperation with the EHPS 301, when braking emergently, the ESC adjusts the wheel braking force distribution, and the EHPS 301 synchronously corrects the steering torque, doubly suppressing pulling to one side and sideslip; combining with the steering system data, it realizes brake-steering joint control (such as when making an emergency avoidance, the ESC 302 assists in adjusting the vehicle body attitude, and the EHPS 301 optimizes the steering assist).

[0179] Note that the above is only the preferred embodiment of the present invention and the applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described here, and various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments only. Without departing from the concept of the present invention, it can also include more other equivalent embodiments, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A braking control method, characterized in that, Comprising: Obtain the braking pressure and vehicle speed. When the braking pressure is greater than the pressure threshold and the vehicle speed is greater than the first vehicle speed threshold, trigger a command to turn off the return-to-center function; After triggering the command to turn off the return-to-center function, if the braking is released, after a specified time delay, or when the vehicle speed is less than the second vehicle speed threshold, trigger a command to activate the return-to-center function; The return-to-center function is used for the return-to-center control of the steering gear, and the braking pressure represents the brake fluid pressure of the braking system.

2. The braking control method according to claim 1, wherein Before triggering the command to turn off the return-to-center function, it also includes: Obtain the steering wheel angle. When the steering wheel angle is in the first angle range, allow the return-to-center function to be turned off; Obtain the braking pressure and vehicle speed. When the braking pressure is greater than the pressure threshold and the vehicle speed is greater than the first vehicle speed threshold, if the return-to-center function is allowed to be turned off, trigger a command to turn off the return-to-center function.

3. The braking control method according to claim 1, characterized in that, Triggering the command to turn off the return-to-center function includes: If the braking pressure is in the first pressure range, the command to turn off the return-to-center function is used to reduce the gain of the return-to-center control.

4. The braking control method according to claim 1, characterized in that, Triggering the command to turn off the return-to-center function includes: If the braking pressure is in the second pressure range, the command to turn off the return-to-center function is used to turn off the return-to-center control.

5. The braking control method according to claim 1, characterized in that, Triggering the command to turn off the return-to-center function includes: If the braking pressure is in the third pressure range, the command to turn off the return-to-center function is used to turn off the return-to-center control, and enable the steering resistance torque compensation and the coordinated control of the electronic stability system.

6. The braking control method according to claim 1, characterized in that, It also includes dynamically updating the pressure threshold and the first vehicle speed threshold using a self-learning model.

7. The braking control method according to claim 1, characterized in that, It also includes dynamically updating the time delay using a self-learning model.

8. The braking control method according to claim 1, wherein It also includes that if the anti-lock braking system is activated, turn off the return-to-center control, and enable the steering resistance torque compensation and the coordinated control of the electronic stability system.

9. The braking control method according to claim 1, wherein, After the braking is released, it also includes that if the steering wheel angle is in the second angle range, immediately trigger the command to activate the return-to-center function.

10. A braking control system, characterized in that, Comprising an electronic control unit, which is configured to execute the braking control method according to any one of claims 1 to 9.

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