Brake control method and apparatus based on rear axle load

Abstract

The application discloses a brake control method and device based on rear axle load. The method estimates the current rear axle load of a vehicle based on vehicle operating parameters and pre-stored vehicle basic parameters during vehicle braking, compares the estimated rear axle load with a pre-set rear axle load target threshold range, matches a corresponding brake pedal feel mode according to the threshold range into which the rear axle load falls, each brake pedal feel mode is pre-set with a corresponding relationship between brake pedal stroke and brake master cylinder pressure, and finally controls an electronic hydraulic brake system to output corresponding brake force according to the corresponding relationship of the selected brake pedal feel mode. The method automatically matches a corresponding brake pedal feel mode of the rear axle load through dynamic estimation, realizes adaptive adjustment of the brake pedal feel according to the vehicle load state without manual switching operation, and adopts hierarchical differentiated master cylinder pressure mapping logic, so that the brake force demand under different working conditions can be matched.

Description

Technical Field

[0001] This application relates to the field of automotive braking technology, and in particular to a braking control method and device based on rear axle load. Background Technology

[0002] Electro-hydraulic braking systems are the mainstream solution for brake-by-wire in commercial vehicles. They feature independently calibrated brake pedal feel and can flexibly adjust braking force output by pre-setting the mapping relationship between pedal travel and master cylinder pressure. Commercial vehicles experience large load fluctuations during operation, with significant differences in rear axle load under different load conditions. The compatibility between brake pedal feel and actual load directly affects braking safety and ride comfort.

[0003] Currently, there are three main ways to implement brake pedal feel control in commercial vehicle electro-hydraulic braking systems (EHB): a fixed calibration scheme using a single set of mapping curves, a multi-mode scheme where the driver manually switches between modes, and a scheme that automatically matches the brake pedal feel by adding a dedicated load sensor.

[0004] Fixed calibration schemes cannot adapt to the load fluctuation characteristics of commercial vehicles, and are prone to problems such as overly sensitive braking when unloaded and insufficient braking force when fully loaded. Manual switching schemes have poor matching reliability and increase hardware costs, while dedicated load sensor schemes have high material costs and many failure points. Existing solutions are all difficult to achieve fully automatic and accurate matching between brake pedal feel and rear axle load at low cost. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a braking control method and device based on rear axle load.

[0006] The embodiments of this application disclose the following technical solutions: In a first aspect, embodiments of this application provide a braking control method based on rear axle load, the method comprising: During vehicle braking, the current rear axle load of the vehicle is estimated based on the vehicle's operating parameters and pre-stored basic vehicle parameters. The rear axle load is compared with a preset target threshold range for the rear axle load to determine the comparison result. The target threshold range for the rear axle load includes a first threshold range corresponding to the no-load condition, a second threshold range corresponding to the half-load condition, and a third threshold range corresponding to the full-load condition. Based on the comparison results, the threshold range into which the rear axle load falls is determined, and the brake pedal feel mode corresponding to the threshold range is selected. The brake pedal feel mode includes an unloaded mode, a half-loaded mode, and a full-loaded mode. Each of the brake pedal feel modes has a preset correspondence between the brake pedal travel and the brake master cylinder pressure. Under the same brake pedal travel, the brake master cylinder pressure corresponding to the unloaded mode is less than the brake master cylinder pressure corresponding to the half-loaded mode, and the brake master cylinder pressure corresponding to the half-loaded mode is less than the brake master cylinder pressure corresponding to the full-loaded mode. Based on the correspondence between the brake pedal travel and the brake master cylinder pressure corresponding to the selected brake feel mode, the electro-hydraulic braking system is controlled to output the corresponding braking force.

[0007] In one possible implementation, estimating the current rear axle load of the vehicle based on vehicle operating parameters and pre-stored basic vehicle parameters includes: Calculate vehicle speed and braking deceleration based on wheel speed signals; The total braking force is obtained by calculating the braking force at the front and rear wheels based on the current master cylinder pressure and the pre-stored braking system parameters. Calculate the total mass of the vehicle based on the total braking force and the braking deceleration; The rear axle load is calculated based on the total mass of the vehicle and the pre-stored wheelbase and center of gravity position parameters.

[0008] In one possible implementation, the formula for calculating the total mass of the vehicle is M=Fb / a, where Fb is the total braking force and a is the braking deceleration. The formula for calculating the rear axle load is F=M×b / L, where L is the wheelbase and b is the distance from the center of mass to the rear axle.

[0009] In one possible implementation, the second threshold range is determined based on a reference value for the rear axle load at half load. The first threshold range is a range that is less than the lower limit of the second threshold range and greater than the preset minimum rear axle load value; The third threshold range is a range greater than the upper limit of the second threshold range.

[0010] In one possible implementation, controlling the electro-hydraulic braking system to output corresponding braking force based on the correspondence between the brake pedal travel and the brake master cylinder pressure corresponding to the selected brake feel mode includes: The master cylinder pressure is established by driving the push rod with a motor; The feedback signal of the master cylinder pressure is collected in real time, and the feedback signal is compared with the preset calibration pressure of the corresponding pedal stroke in the selected mode. The motor current is corrected by a PID control algorithm so that the actual master cylinder pressure tracks the preset calibration pressure.

[0011] In one possible implementation, the method further includes: Real-time monitoring of the working status of wheel speed sensors, brake pedal travel acquisition components, and pressure actuators of the electro-hydraulic braking system; When any of the wheel speed sensor, the brake pedal travel acquisition component, or the pressure actuator is detected to be malfunctioning and unable to work properly, the system automatically switches to the brake pedal feel mode corresponding to the preset highest load level to output fixed pressure.

[0012] In one possible implementation, the method further includes: After the vehicle is powered on and before the rear axle load is estimated, braking control is performed using the brake pedal feel corresponding to the half-load mode.

[0013] Secondly, embodiments of this application disclose a braking control device based on rear axle load, the device comprising: The estimation module is used to estimate the current rear axle load of the vehicle during braking, based on the vehicle's operating parameters and pre-stored basic vehicle parameters. The comparison module is used to compare the rear axle load with a preset rear axle load target threshold range and determine the comparison result. The rear axle load target threshold range includes a first threshold range corresponding to no-load conditions, a second threshold range corresponding to half-load conditions, and a third threshold range corresponding to full-load conditions. The switching module is used to determine the threshold range into which the rear axle load falls based on the comparison result, and select the brake pedal feel mode corresponding to the threshold range. The brake pedal feel mode includes an unloaded mode, a half-loaded mode, and a full-loaded mode. Each of the brake pedal feel modes has a preset correspondence between the brake pedal travel and the brake master cylinder pressure. Under the same brake pedal travel, the brake master cylinder pressure corresponding to the unloaded mode is less than the brake master cylinder pressure corresponding to the half-loaded mode, and the brake master cylinder pressure corresponding to the half-loaded mode is less than the brake master cylinder pressure corresponding to the full-loaded mode. The control module is used to control the electro-hydraulic braking system to output the corresponding braking force based on the correspondence between the brake pedal travel and the brake master cylinder pressure corresponding to the selected brake pedal feel mode.

[0014] In one possible implementation, the estimation module is specifically used to calculate the vehicle speed and braking deceleration based on the wheel speed signal; calculate the front and rear wheel-end braking forces based on the current brake master cylinder pressure and pre-stored braking system parameters to obtain the total braking force; calculate the total vehicle mass based on the total braking force and the braking deceleration; and calculate the rear axle load based on the total vehicle mass and pre-stored wheelbase and center of gravity position parameters.

[0015] In one possible implementation, the formula for calculating the total mass of the vehicle is M=Fb / a, where Fb is the total braking force and a is the braking deceleration; the formula for calculating the rear axle load is F=M×b / L, where L is the wheelbase and b is the distance from the center of gravity to the rear axle.

[0016] In one possible implementation, the second threshold range is determined based on the rear axle load reference value at half load; the first threshold range is a range that is less than the lower limit of the second threshold range and greater than the preset minimum rear axle load value; and the third threshold range is a range that is greater than the upper limit of the second threshold range.

[0017] In one possible implementation, the control module is specifically used to establish master cylinder pressure by driving a push rod with a motor; to collect feedback signals of master cylinder pressure in real time, and to compare the feedback signals with the preset calibration pressure of the corresponding pedal stroke in the selected mode; and to correct the motor current through a PID adjustment algorithm so that the actual master cylinder pressure tracks the preset calibration pressure.

[0018] In one possible implementation, the device further includes a detection module, which is used to detect the working status of the wheel speed sensor, the brake pedal travel acquisition component, and the pressure actuator of the electro-hydraulic braking system in real time; when any of the wheel speed sensor, the brake pedal travel acquisition component, and the pressure actuator is detected to be malfunctioning and unable to work properly, the device automatically switches to the brake pedal feel mode corresponding to the preset highest load level to output fixed pressure.

[0019] In one possible implementation, the switching module is further configured to perform braking control using the brake pedal feel corresponding to the half-load mode after the vehicle is powered on and before the rear axle load estimation is completed.

[0020] Thirdly, embodiments of this application disclose a control device, including a processor and a memory, wherein the memory is used to store programs, instructions or code, and the processor is used to execute the programs, instructions or code in the memory to perform the braking control method based on rear axle load as described in any of the first aspects.

[0021] Fourthly, embodiments of this application disclose a computer-readable storage medium, characterized in that it stores a computer program, which is loaded by a processor to execute the braking control method based on rear axle load as described in any of the first aspects.

[0022] This application provides a braking control method and device based on rear axle load. During vehicle braking, the method estimates the current rear axle load based on vehicle operating parameters and pre-stored basic vehicle parameters. The estimated rear axle load is compared with preset target threshold ranges for unloaded, half-loaded, and fully loaded rear axle loads. The method matches the corresponding brake pedal feel mode according to the threshold range the rear axle load falls into. Each brake pedal feel mode has a preset correspondence between brake pedal travel and master cylinder pressure. Under the same brake pedal travel, the master cylinder pressure in the unloaded mode is lower than that in the half-loaded mode, and the master cylinder pressure in the half-loaded mode is lower than that in the fully loaded mode. Finally, the method controls the electro-hydraulic braking system to output the corresponding braking force based on the correspondence of the selected brake pedal feel mode.

[0023] This method automatically matches the corresponding level of brake pedal feel mode by dynamically estimating the rear axle load. It can achieve adaptive adjustment of brake pedal feel according to vehicle load status without manual switching. At the same time, it adopts a graded and differentiated master cylinder pressure mapping logic, which can match the braking force requirements under different working conditions such as no load, half load, and full load. It not only alleviates the problem of overly sensitive braking under no load conditions, but also ensures braking efficiency under full load conditions, effectively balancing braking comfort and braking safety under different load conditions. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 An architecture diagram of an EHB system provided in this application embodiment; Figure 2 A flowchart of a braking control method based on rear axle load provided for an embodiment of this application; Figure 3 A schematic diagram of a master cylinder pressure-pedal stroke calibration curve provided for an embodiment of this application; Figure 4 This is a schematic diagram of a braking control device based on rear axle load, provided as an embodiment of this application. Detailed Implementation

[0026] As described earlier, electro-hydraulic braking systems are the mainstream technology in the field of brake-by-wire for commercial vehicles. Compared with traditional hydraulic braking systems, they feature fast braking response, high pressure control precision, and independently calibrated brake pedal feel. They can flexibly adjust braking force output characteristics by pre-setting the mapping relationship between brake pedal travel and master cylinder pressure to adapt to different driving needs. Commercial vehicles, as the main freight vehicles, frequently switch between empty, half-load, and fully loaded operating conditions. The load on the rear axle of the vehicle varies significantly under different load conditions, resulting in a large difference in the braking force amplitude required to achieve the same braking deceleration. The compatibility of the brake pedal feel with the actual vehicle load directly affects the vehicle's braking safety performance and driving experience.

[0027] Currently, the industry's commercial vehicle electro-hydraulic brake pedal feel control mainly adopts either fixed calibration or manual switching schemes. The fixed calibration scheme pre-sets a unique mapping relationship between brake pedal travel and master cylinder pressure at the vehicle's factory, and the vehicle outputs braking force according to this mapping relationship under all operating conditions. The manual switching scheme pre-calibrates multiple brake pedal feel curves, allowing the driver to manually select the corresponding feel mode via in-vehicle control buttons. In addition, some load-integrated braking control schemes directly acquire rear axle load information by adding dedicated detection components such as load sensors and suspension displacement sensors to the vehicle's rear axle, and then match the corresponding braking output characteristics based on this load information.

[0028] Fixed calibration schemes cannot adapt to the significant load fluctuations characteristic of commercial vehicles. If the manual pedal feel is calibrated based on a fully loaded condition, the braking force corresponding to the same pedal travel is too large under unloaded conditions, resulting in a hard braking feel that can easily lead to wheel lock-up and vehicle skidding, resulting in poor driving comfort. If the calibration is based on an unloaded condition, the braking force output is insufficient under full load conditions, resulting in a longer braking distance and making it difficult to guarantee braking safety under heavy load conditions. While manual switching can cover various load conditions, it relies entirely on the driver's subjective judgment of the vehicle's load status, which is prone to misjudgment of the load condition and forgetting to switch, making it impossible to guarantee that the pedal feel mode always matches the actual load. The additional operation buttons also increase the overall vehicle hardware cost and assembly complexity. Although the solution of using dedicated sensors to detect the load can achieve automatic matching between load and pedal feel, the additional hardware components increase the overall vehicle material cost and wiring difficulty, and also increase the system's potential failure points, which is not conducive to cost control and reliability assurance of mass-produced models.

[0029] To address this technical problem, this application provides a braking control method and device based on rear axle load. During vehicle braking, the method estimates the current rear axle load based on vehicle operating parameters and pre-stored basic vehicle parameters. The estimated rear axle load is compared with preset target threshold ranges for unloaded, half-loaded, and fully loaded rear axle loads. A corresponding brake pedal feel mode is matched according to the threshold range the rear axle load falls into. Each brake pedal feel mode has a preset correspondence between brake pedal travel and master cylinder pressure. Under the same brake pedal travel, the master cylinder pressure in the unloaded mode is lower than that in the half-loaded mode, and the master cylinder pressure in the half-loaded mode is lower than that in the fully loaded mode. Finally, the electronic hydraulic braking system is controlled to output the corresponding braking force based on the correspondence of the selected brake pedal feel mode.

[0030] This method automatically matches the corresponding level of brake pedal feel mode by dynamically estimating the rear axle load. It can achieve adaptive adjustment of brake pedal feel according to vehicle load status without manual switching. At the same time, it adopts a graded and differentiated master cylinder pressure mapping logic, which can match the braking force requirements under different working conditions such as no load, half load, and full load. It not only alleviates the problem of overly sensitive braking under no load conditions, but also ensures braking efficiency under full load conditions, effectively balancing braking comfort and braking safety under different load conditions.

[0031] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0032] The control method provided in this application can be directly applied to the existing hardware architecture of commercial vehicles equipped with electro-hydraulic braking systems. It does not require additional dedicated detection hardware such as rear axle load sensors and suspension displacement sensors. It only reuses the wheel speed sensors that are standard on the vehicle, as well as the master cylinder pressure sensor, push rod stroke sensor, EHB controller and brake master cylinder pressure actuator built into the electro-hydraulic braking system. All functions can be realized by embedding load estimation algorithms and foot feel mode matching logic in the controller. The hardware modification cost is low and the mass production adaptability is strong.

[0033] This method is applicable to commercial vehicle usage scenarios such as urban distribution logistics and intercity freight where there are frequent switching between no-load, half-load, and full-load operating conditions. It covers various commercial vehicle types such as light trucks and vans. When the load changes after loading and unloading, the driver does not need to manually switch modes. The method automatically matches the corresponding brake pedal feel characteristics based on the real-time rear axle load to adapt to the braking force requirements under different load conditions.

[0034] The EHB system will now be described with reference to the accompanying diagrams. Figure 1 As shown, the EHB system adopts an electro-hydraulic drive architecture, which consists of three parts: a core control unit, a signal acquisition unit, and a brake master cylinder pressure actuator. The rear axle load estimation module is integrated into the core controller. The entire system can achieve load-adaptive braking control based on the vehicle's original sensing hardware without the need for additional dedicated load detection components.

[0035] The EHB controller is the core of the entire system's computation and control. It is responsible for receiving signals collected by various sensor modules, performing load estimation logic calculations, determining load conditions, and deciding on braking pedal feel modes. It also outputs precise pressure control commands to the actuators. The rear axle load estimation module is embedded in the EHB controller. Based on the collected wheel speed signals, it can perform step-by-step calculations of vehicle speed, braking deceleration, total vehicle mass, and rear axle load. It reuses the vehicle's existing sensor resources throughout the process, effectively reducing system hardware costs and wiring complexity.

[0036] The EHB system's signal acquisition unit includes wheel speed sensors and pedal travel acquisition components. The wheel speed sensor, corresponding to the independent component in the upper right corner of the attached diagram, is used to acquire the wheel rotational angular velocity signal in real time and transmit it to the rear axle load estimation module inside the EHB controller, providing vehicle motion state data for load calculation. The brake pedal travel acquisition reuses the displacement sensor inside the EHB, corresponding to the displacement sensor in the attached diagram. This sensor is linked with the input push rod and push rod fork, and the brake pedal travel signal is calculated by acquiring the displacement of the push rod, synchronously transmitted to the EHB controller, providing the pedal input basis for braking force output.

[0037] The brake master cylinder pressure actuator is the hydraulic output terminal of the system, such as... Figure 1 The actuator comprises components such as a motor, ball screw, return spring, master cylinder, pressure sensor, and brake fluid reservoir. After receiving control commands from the EHB controller, the actuator outputs power from the motor, which converts the rotational motion into linear thrust via the ball screw, driving the master cylinder piston to establish brake master cylinder pressure. The integrated pressure sensor on the master cylinder collects the current pressure value in real time and feeds it back to the EHB controller, forming a closed-loop pressure control system to ensure accurate pressure output. The brake fluid reservoir stores brake fluid, providing hydraulic replenishment to the master cylinder. The return spring pushes the piston back to its original position when the brake is released. The entire actuator can accurately output brake master cylinder pressures of different amplitudes according to control commands, matching the output requirements of different pedal feel modes.

[0038] See Figure 2 , Figure 2This is a flowchart illustrating a braking control method based on rear axle load, provided in an embodiment of this application. The execution subject of this method can be a server, desktop computer, or other electronic device capable of computation. The following description uses an EHB controller as the execution subject, and the method includes: S201: During vehicle braking, the EHB controller estimates the current rear axle load of the vehicle based on vehicle operating parameters and pre-stored basic vehicle parameters.

[0039] When the vehicle enters braking mode, the EHB controller performs real-time estimation of the axle load using existing available vehicle parameters, without requiring additional dedicated detection hardware. Vehicle operating parameters refer to dynamic operating data collected in real-time by standard vehicle sensors during braking, such as wheel speed signals output from wheel speed sensors and master cylinder pressure signals monitored in real-time by the electro-hydraulic braking system. These vehicle operating parameters change dynamically with the vehicle's driving and braking states. Pre-stored basic vehicle parameters refer to inherent vehicle attribute parameters pre-written into the controller during vehicle development, such as braking force conversion coefficients, wheelbase, and distances from the center of gravity to the front and rear axles. These basic vehicle parameters are fixed structural parameters and remain unchanged throughout the entire process.

[0040] In one possible implementation, the EHB controller first converts the wheel speed signal to obtain the real-time vehicle speed during braking. Based on the speed difference before and after braking and the corresponding time interval, it calculates the braking deceleration. Braking deceleration, the reduction in vehicle speed per unit time, characterizes the deceleration intensity of the current braking process. The EHB controller calculates the wheel-end braking force of the front and rear wheels from the current master cylinder pressure and braking system parameters, summing them to obtain the total vehicle braking force. Subsequently, based on fundamental dynamic relationships, the EHB controller calculates the total vehicle mass from the total braking force and braking deceleration. Finally, the EHB controller, combining wheelbase and center of gravity position parameters, calculates the current rear axle load according to the static load distribution ratio.

[0041] This application embodiment achieves dynamic estimation of axle load by reusing existing vehicle sensor resources and inherent parameters, eliminating the need for additional dedicated load or displacement sensors, effectively reducing the hardware cost and system complexity of load sensing. Simultaneously, the estimation process is executed synchronously with braking actions, updating the estimation results in real time to follow changes in the vehicle's load state. This provides a reliable load judgment basis for subsequent adaptive matching of the brake pedal feel mode, ensuring the accuracy of the matching between the pedal feel mode and the actual load state.

[0042] To further clarify the specific execution steps of rear axle load estimation and improve the feasibility and consistency of load estimation logic, this application also provides a step-by-step rear axle load refinement estimation method.

[0043] In one possible implementation, estimating the current rear axle load of the vehicle based on vehicle operating parameters and pre-stored basic vehicle parameters includes: Calculate vehicle speed and braking deceleration based on wheel speed signals; The total braking force is obtained by calculating the braking force at the front and rear wheels based on the current master cylinder pressure and the pre-stored braking system parameters. Calculate the total mass of the vehicle based on the total braking force and the braking deceleration; The rear axle load is calculated based on the total mass of the vehicle and the pre-stored wheelbase and center of gravity position parameters.

[0044] First, the vehicle's motion state and braking force state are calculated from the vehicle's operating parameters. Vehicle speed and braking deceleration are calculated based on wheel speed signals, which are collected in real-time by the vehicle's existing wheel speed sensors, reflecting the real-time angular velocity of the wheels. Combined with pre-stored tire rolling radius parameters, the vehicle's real-time speed can be calculated. During braking, the vehicle speed at the start and end of braking is selected, and the speed decay rate is calculated based on the corresponding time intervals to obtain the current braking deceleration. The total braking force is calculated based on the current master cylinder pressure and pre-stored braking system parameters. These parameters are inherent structural parameters of the vehicle's braking system, including wheel cylinder piston area, brake caliper braking efficiency, and effective radius of the brake disc. The front and rear wheel-end braking forces are obtained through the conversion relationship between the master cylinder pressure and these parameters. Summing the front and rear wheel-end braking forces yields the total vehicle braking force.

[0045] Based on the total braking force and braking deceleration, the derivation of the total vehicle mass and rear axle load is completed sequentially. The total vehicle mass is calculated based on the total braking force and braking deceleration, which is based on the fundamental principles of dynamics. Specifically, during vehicle braking, the total braking force is used to overcome vehicle inertia and produce a deceleration effect; the ratio of these two forces is the total vehicle mass. The formula for calculating the total vehicle mass can be M = Fb / a, where Fb is the total braking force and a is the braking deceleration.

[0046] After obtaining the total vehicle mass, the rear axle load is calculated based on pre-stored wheelbase and center of gravity position parameters. The wheelbase is the distance between the front and rear axles, and the center of gravity position parameter is the horizontal distance from the vehicle's center of gravity to the rear axle. According to the static axle load distribution ratio, the weight of the total vehicle mass distributed to the rear axle along the wheelbase direction based on the center of gravity position is the current rear axle load. The formula for calculating the rear axle load is, for example, F = M × b / L, where L is the wheelbase and b is the distance from the center of gravity to the rear axle. This calculation process ignores dynamic load transfer during braking, significantly simplifying the calculation logic while ensuring the estimation accuracy meets the requirements of foot-feel mode switching, and adapting to the real-time computing capabilities of the vehicle controller.

[0047] In the EHB system, the rear axle load estimation process is completed by the rear axle load estimation module integrated in the EHB controller. After the vehicle is powered on, the wheel speed sensor enters the real-time acquisition state and continuously transmits the wheel rotation angular velocity ω to the estimation module. The module synchronously completes the calculation of basic motion parameters such as vehicle speed, deceleration, and wheel dynamics, providing real-time motion data support for subsequent load estimation.

[0048] The estimation module first calculates the vehicle's motion state based on the wheel speed signal: combining the pre-stored tire rolling radius r, the wheel speed is converted into the vehicle's real-time driving speed using the formula V=rω; the rate of change of vehicle speed over time is calculated to obtain the braking deceleration a=dV / dt, reflecting the deceleration intensity of the current braking process; further, the rate of change of deceleration is calculated to obtain the wheel dynamic J=da / dt, which is used to characterize the rate of change of braking intensity and assist in judging the effectiveness and smoothness of the braking condition.

[0049] Under braking conditions, the rear axle load estimation module further combines braking system parameters to derive the total braking force and the total vehicle mass. The module obtains the master cylinder pressure P corresponding to the current push rod stroke, and calculates the front wheel end braking force Fbf and the rear wheel end braking force Fbr respectively by combining the pre-stored braking system structural parameters. The sum of the two is used to obtain the total vehicle braking force Fb = Fbf + Fbr. At the same time, the vehicle speeds V1 and V2 at two moments during the braking process and the corresponding time points S1 and S2 are selected to calculate the average braking deceleration during this period. Then, the total vehicle mass M is estimated according to the dynamic formula M = Fb / a.

[0050] Finally, the rear axle load estimation module calculates the rear axle load based on the vehicle's total mass and chassis structural parameters. The module retrieves pre-stored parameters such as wheelbase L, distance from the center of gravity to the front axle, and distance from the center of gravity to the rear axle. Ignoring dynamic load transfer during braking, it uses static axle load distribution logic to calculate the rear axle load, with the formula F=M. a / L, where 'a' in the formula represents the horizontal distance from the center of gravity to the front axle. This estimation scheme fully reuses the vehicle's existing wheel speed sensors and EHB internal sensing resources, eliminating the need for additional position or load sensors. While meeting the accuracy requirements for brake pedal feel adjustment, it effectively reduces system hardware costs.

[0051] S202: The EHB controller compares the rear axle load with the preset target threshold range for the rear axle load and obtains the comparison result.

[0052] The EHB controller classifies vehicle load conditions by comparing the rear axle load with a preset target threshold range, providing a basis for selecting the subsequent brake pedal feel mode. The target threshold range for the rear axle load is a pre-calibrated load value range stored in the electro-hydraulic brake system controller, used to classify continuously changing rear axle loads into different operating conditions. The first, second, and third threshold ranges correspond to three typical operating conditions: unloaded, half-loaded, and fully loaded, respectively. The boundary values ​​of each threshold range are set based on the rear axle load reference values ​​under these conditions, covering all possible rear axle load ranges.

[0053] Specifically, the computing device compares the estimated current rear axle load value with the boundary values ​​of three preset threshold ranges sequentially to determine the range in which the current rear axle load falls. The three threshold ranges are divided in a continuous manner, with the second threshold range corresponding to the half-load condition as the middle interval. The upper limit of the first threshold range connects to the lower limit of the second threshold range, and the upper limit of the second threshold range connects to the lower limit of the third threshold range, ensuring that all rear axle load values ​​correspond to a unique operating range and that there are no blind spots in load determination.

[0054] This application embodiment uses a tiered threshold comparison method to transform continuously changing rear axle loads into three distinct load conditions. This not only accurately distinguishes different load states of the vehicle but also effectively avoids frequent mode switching caused by small fluctuations in load values ​​due to road bumps and estimation errors, thus improving the stability of brake pedal feel. At the same time, the threshold comparison calculation logic is simple and direct, consuming very little computing power from the vehicle controller, and can complete the condition determination in a very short time, ensuring the real-time response performance of the entire braking control process.

[0055] To further clarify the division logic of the target threshold range of the rear axle load and the matching rules of the corresponding brake pedal feel mode, and to improve the rationality of the load condition judgment and the adaptability of the braking force output, this application embodiment also provides a refined calibration implementation method for the threshold range and brake pedal feel mode.

[0056] The three target threshold ranges for rear axle load are arranged with the second threshold range corresponding to the half-load condition as the core benchmark. The first threshold range corresponds to the unloaded condition, and the third threshold range corresponds to the fully loaded condition. The first threshold range's value is lower than the lower limit of the second threshold range, and its lower bound is a preset minimum rear axle load value, covering the rear axle load fluctuation range under unloaded conditions. The second threshold range is the intermediate load range, covering the normal load deviation range under half-load conditions. The third threshold range's value is higher than the upper limit of the second threshold range, covering the rear axle load range under fully loaded conditions. The three ranges are numerically continuous, completely covering all rear axle load values ​​under legal operating conditions, with no blind spots. Each threshold range uniquely corresponds to a specific brake pedal feel mode.

[0057] The specific boundary values ​​of the three threshold ranges are set based on the rear axle load reference value under half-load conditions. During the setting process, the reference values ​​of the unloaded rear axle load f1, the half-loaded rear axle load f2, and the fully loaded rear axle load f3 are first obtained. The half-loaded rear axle load f2 is used as the calibration reference value. 0.8 times the reference value is taken as the lower limit F2 of the second threshold range, and 1.2 times the reference value is taken as the upper limit F3 of the second threshold range. Thus, the second threshold range corresponding to the half-load condition is determined to be F2≤F≤F3. Based on this, combined with the minimum rear axle load F1 considering weight deviation under unload conditions, the interval greater than F1 and less than F2 is defined as the first threshold range corresponding to the unloaded condition, and the interval greater than F3 is defined as the third threshold range corresponding to the fully loaded condition. This setting takes the half-load condition, which is frequently used by commercial vehicles, as the intermediate anchor point. By extending the interval to the high and low load ends by a fixed ratio, it can clearly distinguish the three typical operating conditions of no load, half load, and full load, while also accommodating normal deviations in vehicle load. This avoids frequent mode switching caused by small load fluctuations and ensures the stability of the braking feel.

[0058] Each threshold range corresponds to a calibrated brake pedal feel mode. The mapping relationship between brake pedal travel and brake master cylinder pressure for the three modes is pre-stored in the EHB controller. When the rear axle load falls into the first threshold range, the EHB controller controls the brake master cylinder pressure actuator to adopt an unloaded mode, outputting a correspondingly smaller brake master cylinder pressure to provide a smaller braking force. When the rear axle load falls into the second threshold range, a half-load mode is adopted to output a medium brake master cylinder pressure to provide a medium braking force. When the rear axle load falls into the third threshold range, a full-load mode is adopted to output a larger brake master cylinder pressure to provide a larger braking force. The calibration of the three modes is based on the half-load mode. Under the same brake pedal travel, the brake master cylinder pressure in the no-load mode is 60% to 95% of that in the half-load mode, and the brake master cylinder pressure in the full-load mode is 105% to 120% of that in the half-load mode. For example, when the brake pedal travel is 40mm, the master cylinder pressure in the half-load mode is calibrated to 8MPa, the no-load mode to 6.4MPa, and the full-load mode to 9.6MPa. The braking force output of all modes meets the braking rate requirements of commercial vehicles, and the calibration process can be achieved by adjusting the EHB motor operating current without the need for additional hardware structure, which simplifies the calibration process and reduces calibration costs.

[0059] S203: Based on the comparison results, the EHB controller determines the threshold range into which the rear axle load falls and selects the brake pedal feel mode corresponding to the threshold range.

[0060] The brake pedal feel modes include an unloaded mode, a half-loaded mode, and a full-loaded mode. Each of the brake pedal feel modes has a preset correspondence between the brake pedal travel and the brake master cylinder pressure. Under the same brake pedal travel, the brake master cylinder pressure corresponding to the unloaded mode is less than the brake master cylinder pressure corresponding to the half-loaded mode, and the brake master cylinder pressure corresponding to the half-loaded mode is less than the brake master cylinder pressure corresponding to the full-loaded mode.

[0061] The EHB controller matches the corresponding braking control strategy based on the load condition determination result. The brake pedal feel mode is a pre-calibrated mapping rule between brake pedal travel and master cylinder pressure stored in the controller. Each mode corresponds to an independent master cylinder pressure-pedal travel calibration curve, determining the braking force output intensity under the same pedal operation. This application embodiment includes three modes: no-load mode, half-load mode, and full-load mode, corresponding to no-load, half-load, and full-load load conditions, respectively.

[0062] The EHB controller determines the threshold range into which the rear axle load falls based on the comparison results, and selects the corresponding brake pedal feel mode. When the rear axle load falls into the first threshold range corresponding to the no-load condition, the no-load mode is selected; when the rear axle load falls into the second threshold range corresponding to the half-load condition, the half-load mode is selected; and when the rear axle load falls into the third threshold range corresponding to the full-load condition, the full-load mode is selected. The pressure output of the three modes is gradient-distributed. Under the same brake pedal travel, the brake master cylinder pressure corresponding to the no-load mode is lower than that of the half-load mode, and the brake master cylinder pressure corresponding to the half-load mode is lower than that of the full-load mode. This matches the braking force requirements under different loads and adapts to the comfort requirements under no-load conditions and the braking performance requirements under full load conditions.

[0063] This application embodiment achieves automatic matching of brake pedal feel to vehicle load status through a one-to-one mapping mechanism between load range and pedal feel mode, eliminating the need for manual mode switching by the driver and improving the automation level and adaptability of braking control. Furthermore, this application embodiment adopts a tiered mode design, rather than continuous stepless adjustment, which not only covers the load requirements of the main operating conditions of commercial vehicles but also effectively simplifies the control logic, reduces the computational load on the controller, and ensures the response speed and operational stability of braking control.

[0064] To further refine the matching and determination logic between rear axle load and brake pedal feel mode, and to clarify the braking force output characteristics corresponding to each working condition, this application embodiment also provides a refined implementation method for brake pedal feel mode selection based on three-level threshold determination.

[0065] The EHB controller compares the estimated rear axle load F with the preset target threshold ranges for unloaded, half-loaded, and fully loaded rear axle loads one by one to accurately determine the load condition and match the mode. When the rear axle load F is between F1 and F2, satisfying F1 < F < F2, the vehicle is determined to be in an unloaded condition, and the unloaded mode is selected as the effective braking pedal feel mode. When the rear axle load F is between F2 and F3, satisfying F2 ≤ F ≤ F3, the vehicle is determined to be in a half-loaded condition, and the half-loaded mode is selected as the effective braking pedal feel mode. When the rear axle load F is greater than F3, satisfying F > F3, the vehicle is determined to be in a fully loaded condition, and the fully loaded mode is selected as the effective braking pedal feel mode.

[0066] Three brake pedal feel modes correspond to different levels of braking force output, presenting a gradient pressure output characteristic under the same brake pedal travel. The unloaded mode controls the brake master cylinder pressure actuator to output a smaller brake master cylinder pressure, providing less braking force to suit the low braking force requirements of unloaded vehicles, avoiding wheel lock-up and a harsh driving experience caused by excessive braking. The half-loaded mode outputs a medium-amplitude brake master cylinder pressure, providing a moderate level of braking force, balancing smooth braking response and braking efficiency. The fully loaded mode outputs a larger brake master cylinder pressure, providing greater braking force to match the high braking force requirements of heavily loaded vehicles, ensuring braking distance and driving safety under heavy load conditions.

[0067] Once the brake pedal feel mode is selected, the brake master cylinder pressure is output through a mechanical structure that drives the push rod via a motor. To ensure the accuracy and stability of the pressure output, the EHB controller simultaneously employs a PID closed-loop control mechanism to regulate the master cylinder pressure. The controller collects feedback signals from the brake master cylinder pressure sensor in real time, compares them with the preset calibrated pressure corresponding to the pedal travel in the current mode, and dynamically corrects the motor operating current through a PID adjustment algorithm. This, in turn, adjusts the push rod thrust and master cylinder pressure output, effectively suppressing hydraulic fluctuations and execution errors, ensuring consistent brake pedal feel and safe brake control.

[0068] To further visually demonstrate the differences in braking force output among the three braking pedal feel modes and to clarify the pressure mapping characteristics under different load conditions, this application embodiment combines the brake master cylinder pressure-pedal stroke calibration curve to specifically explain the pressure output characteristics corresponding to the modes.

[0069] like Figure 3 As shown, the horizontal axis of the calibration curve represents the brake pedal travel in millimeters, and the vertical axis represents the brake master cylinder pressure in megapascals. Figure 3 The three curves, from top to bottom, correspond to the full-load mode, half-load mode, and no-load mode, respectively. The overall trend of the three curves is consistent, all showing a non-linear increase with the increase of brake pedal travel. In the initial stage of braking, the master cylinder pressure increases slowly, and as the pedal travel continues to increase, the pressure increase rate gradually increases. Overall, it fits the driver's expected pedal feel during normal braking operation, ensuring the linear feel and controllability of braking operation.

[0070] Under the same brake pedal travel, the master cylinder pressure corresponding to the three curves exhibits a stable gradient distribution. The master cylinder pressure is highest in the fully loaded mode, followed by the half-load mode, and lowest in the unloaded mode. When the system determines that the vehicle is in an unloaded condition, it calls the calibration curve corresponding to the unloaded mode to execute the pressure output, outputting lower master cylinder pressure and braking force under the same pedal operation, avoiding excessive braking and a hard pedal feel in the unloaded state, and reducing the risk of wheel lock-up. When the system determines that the vehicle is in a half-loaded condition, it calls the half-loaded mode curve to output a moderate level of master cylinder pressure, balancing braking response smoothness and ride comfort. When the system determines that the vehicle is in a fully loaded condition, it calls the fully loaded mode curve to output a higher master cylinder pressure, providing sufficient braking torque to ensure braking performance and driving safety under heavy load conditions.

[0071] The corresponding parameters of the three calibration curves are pre-stored in the EHB controller. The system automatically switches and calls up the curves based on the real-time estimated rear axle load, achieving adaptive matching between braking force output and actual vehicle load state without manual operation by the driver.

[0072] To further cover the braking control conditions during the initial power-on phase of the vehicle, fill the control gap before the initial estimation of the rear axle load, and improve the braking reliability of the system throughout its entire operating cycle, this application embodiment also provides a default braking pedal feel control method during the initial power-on phase.

[0073] In one possible implementation, the method further includes: After the vehicle is powered on and before the rear axle load is estimated, braking control is performed using the brake pedal feel corresponding to the half-load mode.

[0074] This braking mode takes effect after the vehicle is powered on and the system initialization is completed, but before the first effective rear axle load estimation result is output. During this stage, the system has not yet obtained real-time load data that can be used for condition determination, and cannot complete the adaptive matching of the brake pedal feel mode. The EHB controller defaults to selecting the half-load mode as the initial effective brake pedal feel mode, and calls the mapping relationship between the brake pedal travel and the brake master cylinder pressure corresponding to the half-load mode. When the driver presses the brake pedal, the system directly controls the brake master cylinder pressure actuator to output braking force according to the calibration parameters of the half-load mode. Only after the rear axle load estimation module completes the first effective load calculation and completes the condition determination will the system automatically switch to the brake pedal feel mode that matches the current load, and subsequent braking processes will be controlled according to the matched mode.

[0075] This initial control method resolves the mode matching blind spot issue caused by missing load data during the initial power-on phase of the vehicle, ensuring a stable and controllable braking feel from the very first braking action after vehicle start-up. Selecting a half-load mode as the default initial mode leverages its moderate braking force output characteristics, simultaneously addressing the initial braking needs of both unloaded and fully loaded conditions. Compared to the default unloaded mode, it avoids the safety risks of insufficient braking force and excessively long braking distance during the initial full-load phase; compared to the default fully loaded mode, it alleviates the discomfort of overly sensitive and stiff braking during the initial unloaded phase, significantly improving the balance and reliability of braking performance during the initial vehicle operation phase without requiring additional hardware.

[0076] S204: The EHB controller controls the electro-hydraulic braking system to output the corresponding braking force based on the correspondence between the brake pedal travel and the brake master cylinder pressure corresponding to the selected brake pedal feel mode.

[0077] The EHB controller translates preset mapping rules into actual braking force output, serving as the final execution vehicle for achieving load-adaptive braking feel. The correspondence between brake pedal travel and master cylinder pressure is a pre-calibrated mapping rule stored in the EHB controller. This is reflected in the target master cylinder pressure value corresponding to different brake pedal travels. Different braking feel modes each have their own independent mapping relationship, directly determining the braking force output intensity under the same pedal operation.

[0078] During execution, the system collects real-time data on the driver's brake pedal travel. Based on the currently selected brake feel mode, it retrieves the corresponding pedal travel-master cylinder pressure mapping relationship to match the target master cylinder pressure value under the current pedal travel. The EHB controller then outputs control commands to the brake master cylinder pressure actuator, which uses a drive motor to move the master cylinder push rod to establish brake master cylinder pressure. This hydraulic pressure is then transmitted to the brake ends of each wheel, outputting braking force matching the current operating conditions. During execution, the controller collects real-time feedback signals from the master cylinder pressure sensor and dynamically adjusts the actuator's output parameters to ensure the actual master cylinder pressure matches the calibrated target value, improving the accuracy and stability of the braking force output.

[0079] This application embodiment utilizes a differentiated mode mapping mechanism to dynamically adapt braking force output to vehicle load conditions. Under no-load conditions, a lower pressure output is used to avoid excessive braking, ensuring braking smoothness and ride comfort. Under fully loaded conditions, a higher pressure output ensures braking efficiency, shortens braking distance, and guarantees driving safety. The entire control logic relies on the existing electronic control output characteristics of the electro-hydraulic braking system, requiring no additional hardware structure. It features fast control response and high pressure regulation accuracy, effectively balancing braking safety and driving experience under full load conditions for commercial vehicles.

[0080] To further clarify the specific control logic of the braking force output of the electro-hydraulic braking system and improve the control accuracy and output stability of the master cylinder pressure, this application embodiment also provides a master cylinder pressure control implementation method based on PID closed-loop regulation.

[0081] In one possible implementation, controlling the electro-hydraulic braking system to output corresponding braking force based on the correspondence between the brake pedal travel and the brake master cylinder pressure corresponding to the selected brake feel mode includes: The master cylinder pressure is established by driving the push rod with a motor; The feedback signal of the master cylinder pressure is collected in real time, and the feedback signal is compared with the preset calibration pressure of the corresponding pedal stroke in the selected mode. The motor current is corrected by a PID control algorithm so that the actual master cylinder pressure tracks the preset calibration pressure.

[0082] The EHB controller, based on the selected brake pedal feel mode and the current brake pedal travel, matches the target master cylinder pressure and then outputs a control signal to the drive motor of the brake actuator. The rotational torque output by the motor is converted into linear thrust through the transmission mechanism, which drives the push rod forward to push the master cylinder piston, compressing the brake fluid in the master cylinder, thereby establishing the corresponding brake master cylinder pressure and transmitting hydraulic power to the brake ends of each wheel to generate braking force.

[0083] During the pressure build-up process, the system simultaneously performs pressure feedback and deviation comparison. The EHB controller collects the feedback signal of the actual master cylinder pressure in real time through the pressure sensor integrated on the master cylinder. At the same time, it retrieves the preset calibration pressure corresponding to the current pedal travel under the current brake pedal feel mode as the target value. The difference between the real-time feedback actual pressure and the preset calibration pressure is compared to obtain the current pressure deviation, providing a basis for subsequent adjustment.

[0084] Ultimately, the EHB system completes closed-loop pressure correction through a PID control algorithm. The controller inputs the calculated pressure deviation into the PID control algorithm, which performs proportional, integral, and derivative operations to output a corrected motor control current. By adjusting the magnitude of the motor operating current, the motor output thrust is dynamically changed, thereby adjusting the piston thrust and pressure amplitude of the master cylinder. This ensures that the actual master cylinder pressure continuously tracks the preset calibration pressure, ultimately achieving precise and stable pressure output. This closed-loop control method effectively compensates for pressure errors caused by hydraulic system leakage, mechanical friction, and load fluctuations, ensuring the accuracy and consistency of pressure output under different braking feel modes and preventing pressure fluctuations from affecting the smoothness of the braking feel and braking safety.

[0085] To further improve the operational reliability of the braking control system and cover braking safety protection under critical component failure scenarios, this application embodiment also provides an emergency braking control method under failure conditions.

[0086] In one possible implementation, the method further includes: Real-time monitoring of the working status of wheel speed sensors, brake pedal travel acquisition components, and pressure actuators of the electro-hydraulic braking system; When any of the wheel speed sensor, the brake pedal travel acquisition component, or the pressure actuator is detected to be malfunctioning and unable to work properly, the system automatically switches to the brake pedal feel mode corresponding to the preset highest load level to output fixed pressure.

[0087] During system operation, the EHB controller monitors the working status of three core components in real time: wheel speed sensors, brake pedal travel acquisition components, and pressure actuators of the electro-hydraulic braking system. Wheel speed sensors provide basic motion data for rear axle load estimation, brake pedal travel acquisition components provide driver input for braking force output, and pressure actuators are the final execution unit for braking force output. All three are critical hardware components for the normal operation of load adaptive braking control; failure of any component will lead to inaccurate load estimation or abnormal braking force output.

[0088] When any of the aforementioned components malfunctions, fails to acquire signals, or execute control commands, the EHB controller immediately terminates the adaptive load matching logic and automatically switches to the brake pedal feel mode corresponding to the preset highest load level to execute fixed pressure output. The highest load level corresponds to the brake pedal feel mode under full load conditions. In this mode, the brake master cylinder pressure is the highest and the braking force is the most sufficient for the same pedal travel, prioritizing ensuring that the vehicle has sufficient braking performance under fault conditions. This avoids prolonged braking distance and potential traffic accidents due to insufficient braking force, prioritizing safety in handling component failure scenarios.

[0089] Simultaneously with switching to emergency braking mode, the EHB controller triggers a fault alarm mechanism. This is achieved by illuminating the EHB fault indicator light on the vehicle's instrument panel and triggering an onboard buzzer, alerting the driver that the braking system is in emergency operation and requires immediate inspection. This emergency braking solution requires no additional hardware; it can be implemented solely through the controller's built-in fault diagnosis and mode switching logic, effectively enhancing the fault tolerance and operational safety of the entire braking control system.

[0090] The following section uses a light truck application scenario as an example to explain the specific implementation process of this solution in detail.

[0091] Before the vehicle leaves the factory, the axle load threshold range and brake pedal feel mode are pre-calibrated, and all mapping parameters are stored in the EHB controller. Specifically, the first threshold range for unloaded conditions is 728kg < F < 1400kg, the second threshold range for half-loaded conditions is 1400kg ≤ F ≤ 2000kg, and the third threshold range for fully loaded conditions is F > 2000kg. Corresponding to the calibration of the three brake pedal feel modes, within the brake pedal travel range of 0~100mm, the brake master cylinder pressure range for unloaded mode is 4~8MPa, for half-loaded mode it is 6~10MPa, and for fully loaded mode it is 8~12MPa. The pedal travel-master cylinder pressure mapping relationship for all three modes meets the braking rate requirements for light trucks in GB18565-2016.

[0092] After the vehicle is powered on, the system defaults to half-load mode for braking control. At the same time, the wheel speed sensor enters real-time acquisition mode and continuously outputs the wheel rotation angular velocity ω. The rear axle load estimation module combines the pre-stored tire rolling radius parameters and calculates the real-time vehicle speed using the formula V=rω. It also simultaneously calculates the braking deceleration a=dV / dt and wheel dynamics J=da / dt, providing complete motion state data for subsequent rear axle load estimation.

[0093] When the vehicle is under half-load and braking is performed, the initial braking speed is 50 km / h. The EHB push rod travel sensor collects a push rod travel of 8 mm, which is converted internally to a brake pedal travel of 32 mm. At this time, the system defaults to a braking pressure of 5 MPa in half-load mode. After braking for 2 seconds, the vehicle speed drops to 20 km / h. The calculated braking deceleration is a = (50-20) km / h ÷ 2s = 30 / 3.6 ÷ 2 ≈ 4.166 m / s². Combining the braking pressure and preset braking system structural parameters, the total braking force of the vehicle is calculated to be Fb = 7900 N. Further derivation shows that the total vehicle mass M = Fb / a ≈ 7900 ÷ 4.166 ≈ 1890 kg, corresponding to a rear axle load of approximately 1890 kg. Comparing the estimated rear axle load with the preset threshold range, this value falls within the 1400 kg to 2000 kg range corresponding to half-load conditions. The EHB controller determines that the current condition is half-load and maintains the half-load mode. When the driver depresses the brake pedal to a travel of 32mm, the EHB controller controls the actuator to output a brake master cylinder pressure of 5MPa, providing a moderate level of braking force, balancing braking comfort and braking performance under half-load conditions, and preventing wheel lock-up.

[0094] When the vehicle is under no-load conditions and braking is applied, the initial braking speed is also 50 km / h, which translates to a brake pedal travel of 32 mm. Under the default half-load mode, this corresponds to a braking pressure of 5 MPa. After braking for 1.6 seconds, the vehicle speed drops to 10 km / h. Calculations show that the braking deceleration a = (50-10) km / h ÷ 1.6s = 40 / 3.6 ÷ 1.6 ≈ 6.944 m / s²; the total braking force Fb = 7900 N, resulting in a total vehicle mass M ≈ 7900 ÷ 6.944 ≈ 1138 kg, corresponding to a rear axle load of approximately 1138 kg. This rear axle load falls within the 728 kg to 1400 kg range corresponding to the no-load condition, and the EHB controller immediately switches the brake pedal feel mode to no-load mode. When the driver presses the brake pedal to a travel of 32mm, the EHB controller outputs a brake master cylinder pressure of 4MPa, which is adapted to the low braking force requirements under no-load conditions, ensuring a smooth and comfortable braking feel and effectively preventing excessive braking force under no-load conditions from causing wheel lock-up.

[0095] When the vehicle is fully loaded and braking is applied, the initial braking speed is 50 km / h, which translates to a brake pedal travel of 32 mm. Under the default half-load mode, this corresponds to a braking pressure of 5 MPa. After 2.6 seconds of braking, the vehicle speed drops to 20 km / h. Calculations show that the braking deceleration a = (50-20) km / h ÷ 2.6 s = 30 / 3.6 ÷ 2.6 ≈ 3.205 m / s²; the total braking force Fb = 7900 N, resulting in a total vehicle mass M ≈ 7900 ÷ 3.205 ≈ 2465 kg, corresponding to a rear axle load of approximately 2465 kg. This rear axle load exceeds 2000 kg, falling within the threshold range corresponding to the full-load condition. Therefore, the EHB controller immediately switches the brake pedal feel mode to full-load mode. When the driver depresses the brake pedal to a travel of 32mm, the EHB controller outputs a brake master cylinder pressure of 6MPa, providing sufficient braking force to meet the braking performance requirements under full load conditions and ensure braking distance and driving safety under heavy load conditions.

[0096] When the system detects a malfunction in the brake pedal travel sensor or wheel speed sensor, preventing the normal acquisition of travel and wheel speed signals, the EHB controller immediately terminates the adaptive load matching logic, automatically switches to emergency mode, and outputs a fixed brake master cylinder pressure of 10MPa adapted to full-load conditions, prioritizing braking performance under fault conditions; at the same time, it illuminates the EHB fault indicator on the vehicle's instrument panel to remind the driver to go for maintenance in time.

[0097] This application also provides a braking control device based on rear axle load, such as... Figure 4 As shown, the device includes: The estimation module 401 is used to estimate the current rear axle load of the vehicle during vehicle braking based on the vehicle operating parameters and pre-stored basic vehicle parameters. The comparison module 402 is used to compare the rear axle load with a preset rear axle load target threshold range and determine the comparison result. The rear axle load target threshold range includes a first threshold range corresponding to no-load conditions, a second threshold range corresponding to half-load conditions, and a third threshold range corresponding to full-load conditions. The switching module 403 is used to determine the threshold range into which the rear axle load falls based on the comparison result, and select the brake pedal feel mode corresponding to the threshold range. The brake pedal feel mode includes an unloaded mode, a half-loaded mode, and a full-loaded mode. Each of the brake pedal feel modes has a preset correspondence between the brake pedal travel and the brake master cylinder pressure. Under the same brake pedal travel, the brake master cylinder pressure corresponding to the unloaded mode is less than the brake master cylinder pressure corresponding to the half-loaded mode, and the brake master cylinder pressure corresponding to the half-loaded mode is less than the brake master cylinder pressure corresponding to the full-loaded mode. The control module 404 is used to control the electro-hydraulic braking system to output the corresponding braking force according to the correspondence between the brake pedal travel and the brake master cylinder pressure corresponding to the selected brake pedal feel mode.

[0098] In one possible implementation, the estimation module 401 is specifically used to calculate the vehicle speed and braking deceleration based on the wheel speed signal; calculate the front and rear wheel-end braking forces based on the current brake master cylinder pressure and pre-stored braking system parameters to obtain the total braking force; calculate the total vehicle mass based on the total braking force and the braking deceleration; and calculate the rear axle load based on the total vehicle mass and pre-stored wheelbase and center of gravity position parameters.

[0099] In one possible implementation, the formula for calculating the total mass of the vehicle is M=Fb / a, where Fb is the total braking force and a is the braking deceleration; the formula for calculating the rear axle load is F=M×b / L, where L is the wheelbase and b is the distance from the center of gravity to the rear axle.

[0100] In one possible implementation, the second threshold range is determined based on the rear axle load reference value at half load; the first threshold range is a range that is less than the lower limit of the second threshold range and greater than the preset minimum rear axle load value; and the third threshold range is a range that is greater than the upper limit of the second threshold range.

[0101] In one possible implementation, the control module 404 is specifically used to establish master cylinder pressure by driving a push rod with a motor; to collect feedback signals of master cylinder pressure in real time, and to compare the feedback signals with the preset calibration pressure of the corresponding pedal stroke in the selected mode; and to correct the motor current through a PID adjustment algorithm so that the actual master cylinder pressure tracks the preset calibration pressure.

[0102] In one possible implementation, the device further includes a detection module, which is used to detect the working status of the wheel speed sensor, the brake pedal travel acquisition component, and the pressure actuator of the electro-hydraulic braking system in real time; when any of the wheel speed sensor, the brake pedal travel acquisition component, and the pressure actuator is detected to be malfunctioning and unable to work properly, the device automatically switches to the brake pedal feel mode corresponding to the preset highest load level to output fixed pressure.

[0103] In one possible implementation, the switching module 403 is further configured to perform braking control using the brake pedal feel corresponding to the half-load mode after the vehicle is powered on and before the rear axle load estimation is completed.

[0104] This application also provides a control device. The control device may include a memory and a processor. The processor is used to execute the braking control method based on rear axle load as described in any of the above embodiments. The memory may be random access memory (RAM), flash memory, read-only memory (ROM), non-volatile read-only memory (EPROM), registers, hard disk, removable disk, etc.

[0105] The memory can store computer instructions, which, when executed by the processor, can be used to implement braking control methods based on rear axle load. The memory can also store data.

[0106] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape) or a semiconductor medium (e.g., solid-state disk (SSD)).

[0107] This application also provides a readable storage medium for storing the methods provided in the above embodiments. For example, RAM, flash memory, ROM, EPROM, registers, hard disk, removable disk, or any other form of storage medium in the art.

[0108] In the embodiments of this application, the terms "first" and "second" (if they exist) are used only as name identifiers and do not represent the order of first and second.

[0109] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the methods disclosed in the embodiments, since they correspond to the product embodiments disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the description of the product embodiments.

[0110] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A braking control method based on rear axle load, characterized in that, include: During vehicle braking, the current rear axle load of the vehicle is estimated based on the vehicle's operating parameters and pre-stored basic vehicle parameters. The rear axle load is compared with a preset target threshold range for the rear axle load to determine the comparison result. The target threshold range for the rear axle load includes a first threshold range corresponding to the no-load condition, a second threshold range corresponding to the half-load condition, and a third threshold range corresponding to the full-load condition. Based on the comparison results, the threshold range into which the rear axle load falls is determined, and the brake pedal feel mode corresponding to the threshold range is selected. The brake pedal feel mode includes an unloaded mode, a half-loaded mode, and a full-loaded mode. Each of the brake pedal feel modes has a preset correspondence between the brake pedal travel and the brake master cylinder pressure. Under the same brake pedal travel, the brake master cylinder pressure corresponding to the unloaded mode is less than the brake master cylinder pressure corresponding to the half-loaded mode, and the brake master cylinder pressure corresponding to the half-loaded mode is less than the brake master cylinder pressure corresponding to the full-loaded mode. Based on the correspondence between the brake pedal travel and the brake master cylinder pressure corresponding to the selected brake feel mode, the electro-hydraulic braking system is controlled to output the corresponding braking force.

2. The method according to claim 1, characterized in that, The estimation of the current rear axle load of the vehicle based on vehicle operating parameters and pre-stored basic vehicle parameters includes: Calculate vehicle speed and braking deceleration based on wheel speed signals; The total braking force is obtained by calculating the braking force at the front and rear wheels based on the current master cylinder pressure and the pre-stored braking system parameters. Calculate the total mass of the vehicle based on the total braking force and the braking deceleration; The rear axle load is calculated based on the total mass of the vehicle and the pre-stored wheelbase and center of gravity position parameters.

3. The method according to claim 2, characterized in that, The formula for calculating the total mass of the vehicle is M=Fb / a, where Fb is the total braking force and a is the braking deceleration. The formula for calculating the rear axle load is F=M×b / L, where L is the wheelbase and b is the distance from the center of mass to the rear axle.

4. The method according to claim 1, characterized in that, The second threshold range is determined based on the reference value of the rear axle load at half load. The first threshold range is a range that is less than the lower limit of the second threshold range and greater than the preset minimum rear axle load value; The third threshold range is a range greater than the upper limit of the second threshold range.

5. The method according to claim 1, characterized in that, The step of controlling the electro-hydraulic braking system to output corresponding braking force based on the correspondence between the brake pedal travel and the brake master cylinder pressure corresponding to the selected brake feel mode includes: The master cylinder pressure is established by driving the push rod with a motor; The feedback signal of the master cylinder pressure is collected in real time, and the feedback signal is compared with the preset calibration pressure of the corresponding pedal stroke in the selected mode. The motor current is corrected by a PID control algorithm so that the actual master cylinder pressure tracks the preset calibration pressure.

6. The method according to claim 1, characterized in that, The method further includes: Real-time monitoring of the working status of wheel speed sensors, brake pedal travel acquisition components, and pressure actuators of the electro-hydraulic braking system; When any of the wheel speed sensor, the brake pedal travel acquisition component, or the pressure actuator is detected to be malfunctioning and unable to work properly, the system automatically switches to the brake pedal feel mode corresponding to the preset highest load level to output fixed pressure.

7. The method according to claim 1, characterized in that, The method further includes: After the vehicle is powered on and before the rear axle load is estimated, braking control is performed using the brake pedal feel corresponding to the half-load mode.

8. A braking control device based on rear axle load, characterized in that, The device includes: The estimation module is used to estimate the current rear axle load of the vehicle during braking, based on the vehicle's operating parameters and pre-stored basic vehicle parameters. The comparison module is used to compare the rear axle load with a preset rear axle load target threshold range and determine the comparison result. The rear axle load target threshold range includes a first threshold range corresponding to no-load conditions, a second threshold range corresponding to half-load conditions, and a third threshold range corresponding to full-load conditions. The switching module is used to determine the threshold range into which the rear axle load falls based on the comparison result, and select the brake pedal feel mode corresponding to the threshold range. The brake pedal feel mode includes an unloaded mode, a half-loaded mode, and a full-loaded mode. Each of the brake pedal feel modes has a preset correspondence between the brake pedal travel and the brake master cylinder pressure. Under the same brake pedal travel, the brake master cylinder pressure corresponding to the unloaded mode is less than the brake master cylinder pressure corresponding to the half-loaded mode, and the brake master cylinder pressure corresponding to the half-loaded mode is less than the brake master cylinder pressure corresponding to the full-loaded mode. The control module is used to control the electro-hydraulic braking system to output the corresponding braking force based on the correspondence between the brake pedal travel and the brake master cylinder pressure corresponding to the selected brake pedal feel mode.

9. A control device, characterized in that, It includes a processor and a memory, the memory being used to store programs, instructions, or code, and the processor being used to execute the programs, instructions, or code in the memory to perform the braking control method based on rear axle load as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The system contains a computer program that is loaded by a processor to execute the braking control method based on rear axle load as described in any one of claims 1-7.

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