An abs emergency brake assist control system, method, and computer program product for an electromechanical brake system

Abstract

The application provides an ABS emergency braking auxiliary control system, method and computer program product of an electromechanical braking system, and the method comprises the following steps: determining whether to activate an emergency braking auxiliary function according to a set condition; after the emergency braking auxiliary function is turned on, performing differentiated torque control on wheels in different ABS activation states until all the wheels are in the ABS activation state; and after all the wheels are in the ABS activation state, performing optimal slip ratio adjustment on all the wheels so that the slip ratios of all the wheels are maintained in a preset optimal slip ratio interval. The application can maximize the utilization rate of road adhesion in an emergency braking condition, significantly shorten the braking distance, and enhance the active safety performance of the vehicle.

Description

Technical Field

[0001] This invention belongs to the field of automotive braking technology, specifically relating to an ABS emergency braking assist control system, method, and computer program product for an electromechanical braking system. Background Technology

[0002] With the rapid development of advanced autonomous driving and drive-by-wire chassis technology, electro-mechanical braking systems (EMB) have become the mainstream technology for next-generation vehicle braking systems due to their core advantages of zero hydraulic delay, rapid response, and high precision in independent four-wheel control. Braking distance and deceleration performance under emergency braking conditions are core indicators for measuring a vehicle's active safety capabilities and are also the core optimization direction for EMB system control algorithms.

[0003] Existing EMB systems mostly employ an ideal braking force distribution strategy, adjusting the braking force distribution between the front and rear wheels to ensure that the front and rear wheels reach their maximum traction as simultaneously as possible. However, due to the combined effects of multiple factors such as dynamic transfer of axle and wheel loads, uneven road surface adhesion coefficient, fluctuations in road surface smoothness, differences in caliper braking performance, and time-varying characteristics of the friction coefficient, the four wheels cannot simultaneously enter the critical state of locking. This can easily lead to a situation where some wheels have entered the full cycle of ABS anti-lock braking while the other wheels have not yet activated ABS. The braking force of the wheels that have not activated ABS has not reached the road surface adhesion limit, resulting in wasted road surface adhesion margin and hindering the improvement of emergency braking safety performance of the vehicle's EMB braking system. Summary of the Invention

[0004] To address the issues of four wheels not entering a state of lock-up synchronously under emergency braking conditions, insufficient braking deceleration due to wasted road adhesion margin, and excessively long braking distance, this invention proposes an ABS emergency braking auxiliary control system, method, and computer program product for an electromechanical braking system.

[0005] An ABS emergency braking assist control system for an electromechanical braking system, which achieves one of the objectives of this invention, includes: The emergency braking assist activation module is used to determine whether to activate the emergency braking assist function based on set conditions. The wheel-specific differential control module is used to perform differentiated torque control on wheels in different ABS activation states after the emergency braking assist function is activated, until all wheels are in the ABS activation state. The all-wheel slip ratio control module is used to adjust the optimal slip ratio of each wheel after all wheels are in ABS activated, maintaining the slip ratio of each wheel within a preset optimal slip ratio range. For different wheels, the preset optimal slip ratio ranges are independent of each other. Each wheel corresponds to its own target slip ratio based on its estimated road surface adhesion coefficient. This target slip ratio lies within the slip ratio range corresponding to the peak longitudinal adhesion coefficient. Different wheels may have different optimal slip ratio ranges due to differences in their adhesion coefficients. The peak longitudinal adhesion coefficient refers to the maximum value reached by the longitudinal adhesion coefficient at the tire-road contact interface as the slip ratio increases, corresponding to the operating point with the highest braking performance. The slip ratio range corresponding to this maximum value is the preset optimal slip ratio range.

[0006] Furthermore, the wheel-specific differential control module includes a first control unit, which is used to estimate the road adhesion coefficient corresponding to a wheel that is already in the ABS activated state based on the wheel speed, actual braking torque and angular deceleration signals; using the road adhesion coefficient as an index, matching the target slip ratio corresponding to the wheel from a preset slip ratio calibration mapping relationship, and matching the PID control coefficient corresponding to the wheel from a preset gain scheduling table. The wheel speed is typically derived from a wheel speed sensor, the actual braking torque is typically derived from the EMB caliper, and the angular deceleration is typically calculated from the wheel speed derivative. The target slip ratio is used to provide the all-wheel slip ratio control module with the closed-loop target value of the wheel's slip ratio. The incremental PID control coefficients are used in the all-wheel slip ratio control module. In the preset slip ratio calibration mapping relationship, the target slip ratio adaptively matches the change in the road surface adhesion coefficient, and the target slip ratio corresponding to each road surface adhesion coefficient is taken from the calibration optimal slip ratio range of 10%-20%. In the preset gain scheduling table, the incremental PID control coefficients are segmented according to the numerical range of the road surface adhesion coefficient, with different numerical ranges corresponding to different gain parameter groups to address the differentiated requirements for control response speed and stability on roads with different adhesion coefficients. The estimation method for the road surface adhesion coefficient can be implemented using methods known in the art, such as an observer method based on a wheel braking dynamics model combined with wheel speed and braking torque signals, or a recursive calculation method based on the relationship between wheel angular deceleration and braking torque. The specific implementation method does not affect the core inventive concept of this invention.

[0007] Furthermore, in the all-wheel slip ratio control module, the PID control coefficients corresponding to each wheel are used as the PID control coefficients of the incremental PID control algorithm, and the deviation between the target slip ratio and the actual slip ratio of each wheel is used as the input of the incremental PID control algorithm. The incremental PID control algorithm outputs the target braking torque correction amount of each wheel to update the target braking torque of each wheel.

[0008] Furthermore, the wheel-specific differential control module includes a second control unit, used to cause the electromechanical brake caliper of a wheel not in ABS activation state to exit the conventional braking torque following logic, continuously increasing the target braking torque at a calibrated incremental rate until the wheel is in ABS activation state. The preferred range of the calibrated incremental rate is 50-150 Nm / s. "Valid setting" refers to the state where the ABS activation flag simultaneously meets three verification conditions: the original ABS activation flag is in position, the EMB caliper is operating normally, and the wheel speed sensor and braking torque signal are fault-free. This is used to distinguish false flag positions caused by sensor or actuator malfunctions. "Conventional braking torque following logic" refers to the control mode in which, under non-emergency braking conditions, the wheel-side electromechanical brake controller executes a torque closed-loop tracking control mode according to the target braking torque command issued by the upper-level controller (such as the EMB main controller) based on the ideal braking force distribution strategy or the driver's braking request. In this mode, the braking force distribution of each wheel follows the conventional braking force distribution curve, without involving active ABS triggering or forcibly increasing the braking torque of a single wheel to the adhesion limit.

[0009] Furthermore, during the process of increasing the target braking torque, the second control unit pauses torque increase when it detects that the wheel's angular deceleration exceeds a preset lock-up warning threshold. Torque increase resumes once the wheel's angular deceleration returns to below the preset lock-up warning threshold. The preset lock-up warning threshold is a pre-calibrated wheel angular deceleration threshold value used to determine whether the wheel is approaching a lock-up critical state during active boost. When the wheel angular deceleration exceeds this threshold, it indicates that the wheel is close to the lock-up critical point, and torque increase must be paused to prevent sudden wheel lock-up. Once the wheel angular deceleration falls below the threshold, it indicates that the wheel's operating state has recovered, and boost can continue. This threshold can be determined through bench or vehicle calibration tests, and its specific value is related to vehicle parameters, tire characteristics, and road conditions.

[0010] Furthermore, in the emergency braking assist activation module, the set conditions include: the vehicle's longitudinal deceleration continuously exceeds a preset deceleration threshold, and the ABS of at least one wheel is activated. Even further, it includes redundancy verification of the vehicle's longitudinal deceleration. The verification method includes: when the deviation between the vehicle's longitudinal acceleration sensor signal and the vehicle reference deceleration signal calculated based on wheel speed is less than a calibration threshold, the vehicle's longitudinal acceleration sensor signal is used as the vehicle's longitudinal deceleration; when the deviation exceeds the limit, the smaller of the two values ​​is taken as the vehicle's longitudinal deceleration.

[0011] Furthermore, it also includes a function exit control module, which, when a preset exit condition is detected, gradually reduces the weight value corresponding to the target braking torque output by the emergency braking assist control through linear interpolation within a calibrated transition time, and simultaneously increases the weight value corresponding to the target braking torque output by the normal braking request. The sum of the two weights is always 1, thereby achieving a smooth switch to the conventional braking torque following logic.

[0012] Furthermore, in the function exit control module, the actual target braking torque output to the wheels is calculated according to the following formula: T out =T aux ×k+T norm ×(1-k) Among them, T out T is the actual output target braking torque. aux T is the target braking torque output for emergency braking assist control. norm The target braking torque is the one required for normal braking, and k is the weight value corresponding to the target braking torque output by the emergency braking assist control. The value of k decreases linearly from 1 to 0 within the calibrated transition time.

[0013] The emergency braking assist function enable flag is a register flag bit inside the EMB main controller used to identify the activation status of the emergency braking assist function. It is broadcast to each wheel-side EMB controller via the bus and serves as a trigger signal for the wheel-side controller to switch control logic.

[0014] A second objective of this invention is an ABS emergency braking auxiliary control method for an electromechanical braking system, comprising: Whether to activate the emergency braking assist function is determined based on the set conditions; After the emergency braking assist function is activated, differentiated torque control is performed on the wheels that are in different ABS activation states until all wheels are in ABS activation state. After all wheels are in ABS activated state, the optimal slip ratio is adjusted for each wheel to keep the slip ratio of each wheel within the preset optimal slip ratio range.

[0015] A computer program product for achieving the third objective of the present invention includes a computer program / instruction, which, when executed by a processor, implements the steps of the ABS emergency braking auxiliary control method of the electromechanical braking system.

[0016] The beneficial effects of this invention include: This invention maximizes road surface adhesion utilization during emergency braking, significantly shortens braking distance, and enhances vehicle active safety performance. By using a function exit control module to linearly interpolate and gradually reduce the weight value corresponding to the target braking torque output of the emergency braking assist control within a calibrated transition time, while simultaneously increasing the weight value corresponding to the target braking torque output of the normal braking request, a smooth transition of braking force output is achieved, avoiding braking shocks and deterioration of ride comfort caused by sudden changes in braking force during function exit. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an embodiment of the method described in this invention; Figure 2 This is a schematic diagram illustrating the steps of an embodiment of the method described in this invention; Figure 3 This is a flowchart of the round-by-round differentiated control stage in an embodiment of the method described in this invention; Figure 4 This is a schematic diagram showing the relationship between wheel slip ratio and adhesion. Detailed Implementation

[0018] The following detailed embodiments are provided to explain the technical solutions of the present invention, so that those skilled in the art can understand the present invention. The scope of protection of the present invention is not limited to the following specific embodiments. Any modifications or improvements made by those skilled in the art that incorporate the technical solutions of the present invention but differ from the following detailed embodiments are also within the scope of protection of the present invention.

[0019] This invention relates in particular to an emergency braking assist control method for an anti-lock braking system of a four-wheel distributed electromechanical braking system, applicable to pure electric, hybrid, and autonomous vehicles equipped with four-wheel independent EMB actuators.

[0020] This invention leverages the characteristics of the EMB system, such as independent four-wheel control, fast response speed, and high torque control accuracy, to construct a multi-level control logic under emergency braking conditions. By forcing non-locked wheels to trigger ABS and uniformly locking the peak adhesion range of all wheels, it maximizes the utilization rate of the vehicle's road surface adhesion, significantly shortens the emergency braking distance, and enhances the vehicle's active safety performance.

[0021] Based on tire dynamics, the longitudinal adhesion coefficient and slip ratio exhibit a strongly nonlinear relationship: as the slip ratio increases, the longitudinal adhesion coefficient rises rapidly, reaching its maximum value in the slip ratio range of 10%-20% (hereinafter referred to as the peak longitudinal adhesion coefficient). At this point, the road surface adhesion utilization rate reaches its highest level, and the maximum output braking torque reaches its limit. When the slip ratio exceeds 20%, the longitudinal adhesion coefficient continues to decrease with increasing slip ratio, while the lateral adhesion coefficient decays rapidly. This leads to a decrease in braking efficiency and a significant deterioration in vehicle lateral stability. Figure 4As shown. The formula for calculating the wheel slip ratio is: , where v ref For reference speed of the whole vehicle, v w This is the linear velocity of the wheel center corresponding to the wheel speed.

[0022] Example 1 The ABS emergency braking auxiliary control method for the electromechanical braking system described in this invention, such as... Figure 1 and Figure 2 As shown, the process includes: determining whether to activate the emergency braking assist function based on set conditions; after the emergency braking assist function is activated, performing differentiated torque control on wheels in different ABS activation states until all wheels are in ABS activation state; and after all wheels are in ABS activation state, performing optimal slip ratio adjustment on each wheel to maintain the slip ratio of each wheel within a preset optimal slip ratio range. The specific execution steps are as follows: S0: Program initialization and standby After the vehicle is powered on, the emergency braking assist control program integrated into the EMB main controller initializes and synchronously collects vehicle signals in real time, including: longitudinal deceleration signals from the vehicle's longitudinal acceleration sensor, wheel speed signals from the four-wheel wheel speed sensors, brake pedal opening signals, ABS activation flag signals for each wheel, and the operating status and actual braking torque signals of the four-wheel EMB calipers. Simultaneously, the EMB main controller calculates the vehicle reference speed, vehicle reference deceleration, real-time slip ratio of each wheel, wheel angular deceleration, and the original ABS activation flag signals based on the collected wheel speed signals. After completing signal acquisition and filtering, the program enters a standby loop, waiting for the function activation conditions to be determined.

[0023] S1: Vehicle deceleration condition determination The EMB main controller performs real-time judgment on the filtered vehicle longitudinal deceleration signal, and simultaneously uses the vehicle reference deceleration calculated from the four-wheel wheel speeds for signal redundancy verification: when the deviation between the vehicle longitudinal deceleration and the vehicle reference deceleration is less than the calibration threshold (e.g., 0.5 m / s²), the signal redundancy is checked. 2 When the vehicle's longitudinal acceleration is exceeded, the signal from the vehicle's longitudinal acceleration sensor is used as the judgment benchmark. When the deviation exceeds the limit, the smaller of the two values ​​is taken as the judgment basis to improve the accuracy and reliability of the deceleration signal. When the vehicle's longitudinal deceleration is greater than the preset deceleration threshold for more than 10ms of anti-shake duration, the deceleration condition is determined to be met, and the process proceeds to step S2. If the condition is not met, signal acquisition and judgment are continuously maintained, and the process returns to step S to execute the vehicle signal synchronous acquisition standby process.

[0024] S2: ABS Trigger Condition Determination The EMB main controller determines the validity of the ABS activation flags on all four wheels in real time. When it detects that the ABS activation flag is validly set on at least one of the four wheels of the vehicle, it determines that the ABS triggering condition is met and proceeds to step S3. If no validly set ABS activation flag is detected, it jumps to step S0 to execute the signal acquisition standby process. This prevents the emergency braking assist function from being falsely triggered under conditions of only large deceleration and when none of the wheels have reached their adhesion limits, thus avoiding meaningless active boosting that could cause braking shocks and deterioration of ride comfort.

[0025] S3: Emergency Braking Assist Function Activation and Active Boost Control The EMB master controller immediately sets the internal emergency braking assist function enable flag and broadcasts the emergency braking assist function enable flag signal to the four wheel-side EMB controllers. After receiving the flag signal, each wheel-side EMB controller executes the control logic in parallel according to the effective activation status of the ABS of its corresponding wheel in the following two ways: For wheels that have been effectively activated by ABS: the wheel-side EMB controller maintains its original basic control logic of the ABS anti-lock braking closed loop to ensure that the wheel does not lock up deeply; at the same time, it collects wheel speed, actual braking torque, and angular deceleration signals in real time and reports them to the EMB main controller; the EMB main controller estimates the road adhesion coefficient corresponding to the wheel based on the reported signals, completes the initialization of target parameters and configuration of control gain for optimal slip ratio closed-loop control, and prepares the state for the subsequent unified optimal slip ratio control mode switching of the four wheels; For wheels that have not triggered effective ABS activation: After receiving the enable signal, the wheel-side EMB controller immediately exits the original conventional braking torque following logic based on the ideal braking force distribution curve and executes active braking torque increment control: continuously increasing the target braking torque of the EMB caliper at a calibrated increment rate of 50-150 Nm / s, while simultaneously collecting the wheel speed, slip ratio, and angular deceleration signals of the wheel in real time, continuously approaching the wheel's road adhesion limit. If the wheel angular deceleration is detected to exceed the preset lock-up warning threshold during the increment process, the torque increment is paused, and pressure is resumed after the wheel's operating state is restored, until the ABS activation flag of the wheel is effectively set, completing the forced triggering of ABS for the wheel.

[0026] S4: Four-wheel optimal slip ratio closed-loop control and exit condition determination Once the ABS activation flags on all four wheels of the vehicle are effectively set, the EMB main controller switches from the wheel-specific differentiated transition control mode of stage S3 to the unified optimal slip ratio closed-loop control mode for all wheels. It then uniformly schedules the four wheel-side EMB controllers to execute the optimal slip ratio closed-loop control. A specific implementation of this closed-loop control is as follows: A robust incremental PID control algorithm for tire-road nonlinear systems is proposed. The algorithm inputs the deviation between the target slip ratio and the actual slip ratio of each wheel, and the outputs the target braking torque correction for each wheel. The target slip ratio for each wheel is taken from a calibrated optimal range of 10%-20%, with specific values ​​adaptively matched based on real-time estimated road adhesion coefficients or using preset fixed calibration values. During control, the EMB main controller calculates the target braking torque adjustment for each wheel in real-time according to a calibrated fixed control cycle and sends it to the corresponding wheel-side EMB controller to execute torque closed-loop control. This dynamically adjusts the braking torque output, maintaining the real-time slip ratio of each wheel within the slip ratio range corresponding to the peak adhesion coefficient, thereby maximizing road adhesion utilization and ultimately improving the vehicle's braking deceleration.

[0027] During optimal slip ratio control, the main controller monitors the function exit conditions in real time. If any of the following conditions are met, it is determined that the function exit conditions are met, and the process proceeds to step S5 to execute the smooth exit procedure. If none of the conditions are met, the optimal slip ratio closed-loop control continues, maintaining the loop of this step: 1. The brake pedal opening decreases by 10% or more from the maximum opening when the function is activated, corresponding to the condition where the driver actively reduces the braking input and the normal braking request is significantly cancelled; 2. When the vehicle's reference speed is lower than the ABS minimum speed threshold of 5 km / h, the ABS system will automatically disengage when the vehicle is about to stop due to insufficient wheel speed detection accuracy. 3. If any wheel speed sensor or EMB caliper malfunctions, or if the ABS activation flag fails the validity check, the fail-safe exit mechanism will be triggered.

[0028] S5: Smooth Exit of Functionality The EMB main controller executes a smooth exit strategy for the emergency braking assist function, setting a calibration transition time of 100ms. Within this 100ms transition time, a linear interpolation method is used to gradually reduce the torque weight of the emergency braking assist control while simultaneously increasing the torque weight of the normal braking request. During the transition, the actual target torque output to the wheels is calculated according to the following formula: T out =T aux ×k+T norm ×(1-k), where T aux T is the target braking torque output for emergency braking assist control. normThe target braking torque for normal braking request output is given by k, which is the weight value corresponding to the target braking torque output by emergency braking assist control. The value of k decreases linearly from 1 to 0 within the calibrated transition time to achieve a smooth transition of braking force output and avoid braking shock caused by sudden changes in braking force. After the transition is completed, the four-wheel EMB calipers completely exit the emergency braking assist function and switch to following the normal braking request torque sent by the EMB main controller. The program ends and returns to the initialization standby loop in step S0.

[0029] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0030] Example 2 The ABS emergency braking assist control system of the electromechanical braking system of the present invention is integrated into the EMB main controller and four wheel-side EMB controllers, including an emergency braking assist activation module, a wheel-specific differential control module and an all-wheel slip ratio control module.

[0031] The EMB main controller is responsible for executing vehicle-level control logic, signal fusion calculation, road adhesion coefficient estimation, target slip ratio matching, PID control coefficient matching, and the main control computation of the all-wheel slip ratio closed-loop control algorithm. The four wheel-side EMB controllers correspond to the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, and are used to execute closed-loop braking torque control, signal acquisition and reporting, and active torque increment control for their respective wheels. The EMB main controller communicates with each wheel-side EMB controller via an onboard bus (such as a CAN bus or FlexRay bus).

[0032] After the vehicle is powered on, the system completes initialization and begins real-time synchronous acquisition of vehicle signals, including: longitudinal deceleration signals from the vehicle's longitudinal acceleration sensor, wheel speed signals from the four-wheel wheel speed sensors, brake pedal opening signals, ABS activation flag signals for each wheel, and the operating status and actual braking torque signals of the four-wheel EMB calipers. Simultaneously, the EMB main controller calculates the vehicle reference speed, vehicle reference deceleration, real-time slip ratio of each wheel, wheel angular deceleration, and the original ABS activation flag signals based on the acquired wheel speed signals. After completing signal acquisition and filtering, the system enters standby mode, awaiting the activation determination of the emergency braking assist function.

[0033] In one embodiment, the emergency braking assist activation module is used to determine whether to activate the emergency braking assist function based on preset conditions. Specifically, the emergency braking assist activation module continuously monitors the vehicle's longitudinal deceleration signal and the four-wheel ABS activation flag signal. When the preset conditions are met, the emergency braking assist function is activated. The preset conditions include: the vehicle's longitudinal deceleration is continuously greater than a preset deceleration threshold, and the ABS of at least one wheel is activated.

[0034] In one embodiment, the emergency braking assist activation module performs real-time determination of the filtered vehicle longitudinal deceleration signal. Specifically, the emergency braking assist activation module continuously monitors the vehicle longitudinal deceleration signal collected by the vehicle longitudinal acceleration sensor and compares this signal with a preset deceleration threshold (e.g., 9.5 m / s²). 2 This is compared to a braking deceleration of approximately 0.97g. Simultaneously, to improve the accuracy and reliability of the judgment results, the emergency braking assist activation module also uses the vehicle reference deceleration signal calculated from the four wheel speeds for signal redundancy verification: when the deviation between the vehicle's longitudinal deceleration and the vehicle reference deceleration is less than a calibrated threshold (e.g., 0.5m / s²),... 2 When the vehicle's longitudinal acceleration is greater than the preset deceleration threshold for a period exceeding the preset anti-shake duration (e.g., 10ms), the emergency braking assist activation module determines that the deceleration condition is met.

[0035] In one embodiment, the emergency brake assist activation module determines the validity of the ABS activation flag position of the four wheels in real time. Specifically, the emergency brake assist activation module reads the original ABS activation flag position signal of each wheel and verifies the validity of the signal. A valid activation flag position means that the ABS activation flag position simultaneously meets the following three verification conditions: (1) the original ABS activation flag position is active; (2) the EMB caliper is operating normally (i.e., the caliper is fault-free, communication is normal, and the motor drive is normal); (3) the wheel speed sensor and braking torque signal are fault-free (i.e., the signal value is within the valid range, there is no communication timeout, and there are no reasonable errors). The above three verification conditions are used to distinguish false flag positions caused by sensor or actuator malfunctions, avoiding accidental triggering of the emergency brake assist function due to fault signals. When the emergency brake assist activation module detects that the ABS activation flag position of at least one of the four wheels of the vehicle is validly active, it determines that the ABS triggering condition is met. When both the vehicle deceleration condition and the ABS trigger condition are met simultaneously, the emergency braking assist activation module determines that the emergency braking assist function activation condition is met, generates an emergency braking assist function enable flag (i.e., a register flag bit inside the EMB main controller used to identify the activation status of the emergency braking assist function), and broadcasts this emergency braking assist function enable flag signal to the four wheel-side EMB controllers, triggering the wheel-specific differential control module to start working. If no validly set ABS activation flag bit is detected, the emergency braking assist activation module does not activate the emergency braking assist function, and the system remains in standby mode to prevent the emergency braking assist function from being falsely triggered under conditions of only high deceleration and when none of the wheels have reached their adhesion limits, thus avoiding meaningless active boosting that could cause braking shock and deterioration of ride comfort.

[0036] The wheel-specific differential control module is used to perform differentiated torque control on wheels in different ABS activation states after the emergency braking assist function is activated, until all wheels are in the ABS activation state.

[0037] After receiving the emergency braking assist function enable signal from the emergency braking assist activation module, the wheel-specific differential control module performs differentiated control on the wheels that are in the ABS activated state and the wheels that are not in the ABS activated state respectively, based on the effective activation state of each wheel's ABS, through the parallel control logic of the first control unit and the second control unit.

[0038] In one embodiment, the first control unit is used to estimate the road adhesion coefficient corresponding to a wheel that is already in ABS activation state, based on the wheel speed, actual braking torque, and angular deceleration signals. Using the road adhesion coefficient as an index, it matches the target slip ratio corresponding to the wheel from a preset slip ratio calibration mapping relationship and matches the PID control coefficient corresponding to the wheel from a preset gain scheduling table. Specifically, for a wheel that has completed effective ABS activation, the wheel-side EMB controller maintains its original basic control logic of the ABS anti-lock braking closed loop to ensure that the wheel does not lock up deeply; simultaneously, it collects wheel speed, actual braking torque, and angular deceleration signals in real time and reports them to the EMB main controller. The EMB main controller estimates the road adhesion coefficient corresponding to the wheel based on the reported wheel speed, actual braking torque, and angular deceleration signals. This estimation can be implemented using any suitable method known in the art, such as an observer method based on a wheel braking dynamics model combined with wheel speed and braking torque signals, or a recursive calculation method based on the relationship between wheel angular deceleration and braking torque. As an optional implementation, the EMB main controller calculates the wheel angular acceleration from the wheel speed signal based on the wheel dynamics equation, and then, combined with the actual braking torque, calculates the ground braking force. Finally, it calculates the road adhesion coefficient based on the relationship between the ground braking force, the road adhesion coefficient, and the wheel vertical load. The specific method for estimating the road adhesion coefficient does not affect the core inventive concept of this invention.

[0039] The EMB main controller uses the estimated road adhesion coefficient as an index to match the target slip ratio corresponding to the wheel from a preset slip ratio calibration mapping relationship. The preset slip ratio calibration mapping relationship refers to a table or fitted curve establishing a correspondence between the road adhesion coefficient and the optimal target slip ratio through bench or real-vehicle calibration tests. Different road adhesion coefficients correspond to different optimal target slip ratios; for example, the optimal target slip ratio for high-adhesion dry asphalt pavements is usually higher, while the optimal target slip ratio for low-adhesion icy or snowy pavements is usually lower. Specific values ​​are determined through calibration tests. The EMB main controller uses the real-time estimated road adhesion coefficient to look up a table or interpolate to obtain the optimal target slip ratio for the wheel under the current road conditions.

[0040] Simultaneously, the EMB main controller uses the estimated road adhesion coefficient as an index to match the corresponding PID control coefficient for that wheel from a preset gain scheduling table. The preset gain scheduling table refers to a correspondence table between the road adhesion coefficient and the incremental PID control coefficient, established beforehand through bench or vehicle calibration tests. Different road adhesion coefficient ranges in the table correspond to different sets of proportional, integral, and derivative control coefficients. Higher proportional and derivative gains are used for high-adhesion roads to achieve rapid response, while lower proportional and derivative gains are used for low-adhesion roads to avoid control oscillations. Specific values ​​are determined through calibration tests. Through this gain scheduling, adaptive scheduling of control parameters is achieved according to road conditions to address the differentiated requirements for control response speed and stability on roads with different adhesion coefficients.

[0041] The target slip ratio and incremental PID control coefficients obtained from the matching are temporarily stored in the EMB main controller to prepare the state for the start-up of the all-wheel slip ratio control module.

[0042] In one embodiment, the second control unit is used to cause the electromechanical brake caliper of a wheel that is not in the ABS activated state to exit the conventional braking torque following logic, so as to continuously increase the target braking torque at a calibrated incremental rate until the wheel is in the ABS activated state. Figure 3 This example illustrates the process of four wheels independently executing active braking torque increment control. The control logic for all four wheels is identical, but they execute independently and in parallel. Due to varying road surface adhesion conditions, the time it takes for each wheel to reach ABS activation differs. Specifically, for wheels that have not triggered effective ABS activation, the wheel-side EMB controller, upon receiving the emergency braking assist function enable signal, immediately exits the conventional braking torque following logic based on the ideal braking force distribution curve. In this mode, the braking force distribution of each wheel follows the conventional braking force distribution curve, without involving active ABS triggering or forcibly increasing the braking torque of a single wheel to the adhesion limit. After exiting the conventional braking torque following logic, the wheel-side EMB controller switches to the active braking torque increment control mode. In this mode, the wheel-side EMB controller continuously increases the target braking torque of the electromechanical brake caliper of that wheel at a calibrated increment rate, while simultaneously acquiring the wheel speed, slip ratio, and angular deceleration signals in real time, continuously approaching the wheel's road surface adhesion limit. The preferred range for the calibration rate of increase is 50-150 Nm / s. The specific value is determined through bench or vehicle calibration tests. Too low a rate of increase will result in too long a time required for the wheel to reach the adhesion limit, affecting the response speed of emergency braking; too high a rate of increase may cause a sharp increase in wheel angular deceleration, leading to sudden wheel lock-up and vehicle instability.

[0043] During the increase of the target braking torque, the EMB main controller continuously monitors the wheel's angular deceleration signal and compares it with a preset lock-up warning threshold. The preset lock-up warning threshold is a pre-calibrated wheel angular deceleration threshold used to determine whether the wheel is approaching a lock-up critical state during active boost. This threshold can be determined through bench or vehicle calibration tests, and its specific value is related to vehicle parameters, tire characteristics, and road conditions; for example, it can be calibrated to -80 to -120 rad / s. 2 The threshold value is defined as follows: When the wheel angular deceleration exceeds this threshold (i.e., the absolute value of the angular deceleration is greater than the threshold), it indicates that the wheel is close to the lock-up critical point, and torque increase needs to be paused to prevent sudden wheel lock-up; after the wheel angular deceleration falls back below the threshold, it indicates that the wheel's operating state has recovered, and torque can continue to be increased. Specifically, when the EMB main controller detects that the wheel's angular deceleration exceeds the preset lock-up warning threshold, the second control unit sends a pause command to the wheel-side EMB controller, which responds to the command by pausing torque increase and maintaining the current target braking torque unchanged; after the EMB main controller detects that the wheel's angular deceleration has recovered to below the preset lock-up warning threshold, the second control unit sends a recovery command to the wheel-side EMB controller, which responds to the command by resuming torque increase. The above pause and recovery process can be repeated multiple times until the ABS activation flag of the wheel is effectively set, completing the forced triggering of ABS for that wheel. When the ABS activation flags of all four wheels are effectively set, the wheel-specific differential control module completes its control task and triggers the all-wheel slip ratio control module to start working.

[0044] In one embodiment, the all-wheel slip ratio control module is used to adjust the optimal slip ratio of each wheel after all wheels are in the ABS activated state, so that the slip ratio of each wheel is maintained within a preset optimal slip ratio range. When the ABS activation flags of all four wheels of the vehicle are effectively set, the EMB main controller switches to the all-wheel unified optimal slip ratio closed-loop control mode, uniformly scheduling the four wheel-side EMB controllers to execute all-wheel optimal slip ratio closed-loop control. The specific implementation of this all-wheel slip ratio control module is as follows: The deviation between the target slip ratio and the actual slip ratio of each wheel is used as the input to the incremental PID control algorithm. That is, for each wheel, the EMB main controller calculates the deviation e(k)=s between the target slip ratio (the value matched by the first control unit from the slip ratio calibration mapping relationship, or a preset fixed calibration value, both taken from the 10%-20% calibration optimal slip ratio range) and the actual slip ratio (the current slip ratio of the wheel calculated in real time during the system initialization phase). target -s actual .

[0045] The EMB main controller uses the incremental PID control coefficients obtained from the gain scheduling table by the first control unit as the PID control coefficients to execute the incremental PID control algorithm on the aforementioned deviation value. The incremental PID control coefficients include three parameters: proportional coefficient Kp, integral coefficient Ki, and derivative coefficient Kd. Kp is used to proportionally amplify the current deviation to determine the speed of response; Ki is used to eliminate steady-state deviation; and Kd is used to predict the deviation change trend to suppress oscillation. These three coefficients constitute a complete set of PID control parameters. Different combinations of coefficients correspond to different road surface adhesion coefficient ranges. High-adhesion roads typically use larger Kp and Kd to achieve a fast response, while low-adhesion roads typically use smaller Kp and Kd to avoid control oscillation. The output of the incremental PID control algorithm is the target braking torque correction amount ΔT for each wheel. b ( k The calculation formula is as follows: Where e(k) is the slip ratio deviation of the current control cycle, e(k-1) is the slip ratio deviation of the previous control cycle, and e(k-2) is the slip ratio deviation of the control cycle before that.

[0046] The EMB master controller sends the calculated target braking torque correction amount to the corresponding wheel-side EMB controller. The wheel-side EMB controller adjusts the current target braking torque (T) according to the received correction amount. target_new =T target_current +ΔT b ( k The wheel-side EMB controller performs closed-loop torque control based on the updated target braking torque, dynamically adjusting the braking torque output to gradually converge the slip ratio deviation to zero, thus achieving optimal slip ratio adjustment for each wheel. During the control process, the EMB main controller calculates the target braking torque adjustment for each wheel in real time according to a calibrated fixed control cycle (e.g., 10ms) and sends it out for execution, maintaining the real-time slip ratio of each wheel within the slip ratio range corresponding to the peak adhesion coefficient (i.e., the calibrated optimal slip ratio range of 10%-20%). For different wheels, the preset optimal slip ratio ranges are independent of each other. Each wheel corresponds to its own target slip ratio based on its estimated road adhesion coefficient, which is located within the slip ratio range corresponding to the peak longitudinal adhesion coefficient. Due to different adhesion coefficients, the optimal slip ratio ranges may differ for different wheels. Through the above control, the road adhesion utilization rate of each wheel is maximized, ultimately improving the overall vehicle braking deceleration.

[0047] During the operation of the all-wheel slip ratio control module, the EMB main controller also monitors the function exit conditions in real time. When any of the following conditions are met, it is determined that the function exit condition has been met, triggering the function exit control module to initiate a smooth exit process; if none of the conditions are met, the all-wheel slip ratio control module continues to operate: When the brake pedal opening decreases by 10% or more relative to the maximum opening when the function is activated, it corresponds to the condition where the driver actively reduces the braking input and the normal braking request is significantly cancelled. When the vehicle's reference speed is lower than the set speed threshold (such as the minimum ABS speed threshold of 5 km / h), the ABS system will automatically disengage when the vehicle is about to stop due to insufficient wheel speed detection accuracy. If any wheel speed sensor or EMB caliper malfunctions, or if the ABS activation flag fails to pass validity verification, the fail-safe exit mechanism will be triggered.

[0048] In one embodiment, the function exit control module is used to, when a preset exit condition is detected, gradually reduce the weight value corresponding to the target braking torque output by the emergency braking assist control through linear interpolation within a calibrated transition time, and simultaneously increase the weight value corresponding to the target braking torque output by the normal braking request.

[0049] After the EMB main controller detects that the preset exit conditions are met, it activates the function exit control module and executes the smooth exit strategy for the emergency braking assist function. Specifically, the function exit control module sets a calibration transition time (preferably 100ms). Within this calibration transition time, it gradually decreases the weight value k corresponding to the target braking torque output by the emergency braking assist control through linear interpolation, while simultaneously increasing the weight value corresponding to the target braking torque output by the normal braking request. The sum of the two weights is always 1. That is, the value of k decreases linearly from 1 to 0, while the weight value (1-k) of the normal braking request increases linearly from 0 to 1.

[0050] During the transition, the function exit control module calculates the actual target braking torque output to the wheels according to the following formula: T out =T aux ×k+T norm ×(1-k) T out T is the actual output target braking torque. aux T is the target braking torque output for emergency braking assist control. normThe target braking torque for normal braking request output is the conventional braking torque request calculated by the EMB main controller based on the driver's brake pedal opening and ideal braking force distribution strategy; k is the weight value corresponding to the target braking torque output by the emergency braking assist control, and the value of k decreases linearly from 1 to 0 within the calibrated transition time. (1-k) is the weight value corresponding to the target braking torque output by normal braking request, which changes synchronously with k. When k=1, T out =T aux The wheels operate entirely according to the emergency braking assist control output; when k=0, T out =T norm The wheels fully switch to normal braking request. During the transition, T out For T aux and T norm The weighted sum achieves a smooth transition in braking force output, avoiding braking shocks caused by sudden changes in braking force. After the transition is complete, the four-wheel EMB calipers completely disengage from the emergency braking assist function and switch to following the normal braking request torque sent by the EMB master controller. The system returns to the initialization standby state, waiting for the next activation determination of the emergency braking assist function.

[0051] This invention also provides a computer program product, including a computer program / instructions that, when executed by a processor, implement the various steps of the method described in this invention.

[0052] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. An ABS emergency braking assist control system for an electromechanical braking system, characterized in that, include: The emergency braking assist activation module is used to determine whether to activate the emergency braking assist function based on set conditions. The wheel-specific differential control module is used to perform differentiated torque control on wheels in different ABS activation states after the emergency braking assist function is activated, until all wheels are in the ABS activation state. The all-wheel slip ratio control module is used to perform optimal slip ratio adjustment on each wheel after all wheels are in the ABS activated state, so that the slip ratio of each wheel is maintained within the preset optimal slip ratio range.

2. The ABS emergency braking assist control system of the electromechanical braking system as described in claim 1, characterized in that, The wheel-specific differential control module includes a first control unit, which is used to estimate the road adhesion coefficient corresponding to a wheel that is already in the ABS activated state based on the wheel speed, actual braking torque and angular deceleration signals; using the road adhesion coefficient as an index, matching the target slip ratio corresponding to the wheel from a preset slip ratio calibration mapping relationship, and matching the PID control coefficient corresponding to the wheel from a preset gain scheduling table.

3. The ABS emergency braking assist control system of the electromechanical braking system as described in claim 2, characterized in that, In the all-wheel slip ratio control module, the PID control coefficients corresponding to each wheel are used as the PID control coefficients of the incremental PID control algorithm, and the deviation between the target slip ratio and the actual slip ratio of each wheel is used as the input of the incremental PID control algorithm. The incremental PID control algorithm outputs the target braking torque correction amount of each wheel to update the target braking torque of each wheel.

4. The ABS emergency braking assist control system of the electromechanical braking system as described in claim 1, characterized in that, The wheel-specific differential control module includes a second control unit, which is used to cause the electromechanical brake caliper of a wheel that is not in the ABS activated state to exit the conventional braking torque following logic, so as to continuously increase the target braking torque at a calibrated incremental rate until the wheel is in the ABS activated state.

5. The ABS emergency braking assist control system of the electromechanical braking system as described in claim 4, characterized in that, During the process of increasing the target braking torque, the second control unit pauses the torque increase when it detects that the angular deceleration of the wheel exceeds the preset lock-up warning threshold. The torque increase is resumed after the angular deceleration of the wheel returns to below the preset lock-up warning threshold.

6. The ABS emergency braking assist control system of the electromechanical braking system as described in claim 1, characterized in that, In the emergency braking assist activation module, the set conditions include: the longitudinal deceleration of the vehicle is continuously greater than a preset deceleration threshold, and the ABS of at least one wheel is activated.

7. The ABS emergency braking assist control system of the electromechanical braking system as described in claim 1, characterized in that, It also includes a function exit control module, which, when a preset exit condition is detected, gradually reduces the weight value corresponding to the target braking torque output by the emergency braking assist control through linear interpolation within a calibrated transition time, and simultaneously increases the weight value corresponding to the target braking torque output by the normal braking request.

8. The ABS emergency braking assist control system of the electromechanical braking system as described in claim 7, characterized in that, In the function exit control module, the actual target braking torque output to the wheels is calculated according to the following formula: T out =T aux ×k+T norm ×(1-k) Among them, T out T is the actual output target braking torque. aux T is the target braking torque output for emergency braking assist control. norm The target braking torque is the output for normal braking request, and k is the weight value corresponding to the target braking torque output for emergency braking assist control. The value of k decreases linearly from 1 to 0 within the calibrated transition time.

9. An ABS emergency braking auxiliary control method applied to the electromechanical braking system of the system described in claim 1, characterized in that, include: Whether to activate the emergency braking assist function is determined based on the set conditions; After the emergency braking assist function is activated, differentiated torque control is performed on the wheels that are in different ABS activation states until all wheels are in ABS activation state. After all wheels are in ABS activated state, the optimal slip ratio is adjusted for each wheel to keep the slip ratio of each wheel within the preset optimal slip ratio range.

10. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instruction is executed by the processor, it implements the steps of the ABS emergency braking auxiliary control method of the electromechanical braking system as described in claim 9.

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