Brake pad wear state-based clamping force compensation method

Abstract

The application provides a clamping force compensation method based on brake friction plate wear state evaluation, and relates to the technical field of electromechanical sensing control.The application screens and obtains effective brake samples and matching mechanical data through brake cycle time interval determination conditions, normalizes vehicle speeds and pedal stroke curves under different working conditions to a standard working condition, extracts deviation characteristics by comparing factory reference brake response curves, further calculates initial wear of the friction plate, compensates errors of the initial wear by using actuator return gaps and ball screw displacements, obtains real wear values, calls pre-calibration mapping relationship to match motor parameter correction coefficients, corrects motor control parameters, and finally drives a brake motor to complete clamping force compensation, which can effectively compensate brake force attenuation problems caused by friction plate wear.

Description

Technical Field

[0001] This invention relates to the field of electromechanical sensing and control technology, specifically to a clamping force compensation method based on the assessment of brake friction pad wear condition. Background Technology

[0002] EMB (Electromechanical Brake) systems rely on a direct-drive motor-screw transmission structure, abandoning the traditional hydraulic brake pipeline structure. With advantages such as fast response, high control precision, and strong integration, they are widely used in the brake-by-wire systems of new energy vehicles. However, brake pads, as core wear-prone friction components, experience continuous wear and tear under long-term vehicle braking conditions. This directly alters the closed-loop braking response characteristics, the internal clearance of the brake, and the load on the ball screw transmission, leading to defects such as brake clamping force attenuation and brake response deviation. Currently, most vehicle EMB brake pad wear assessment and clamping force compensation schemes directly collect vehicle braking sensor data across the entire range without setting tiered thresholds to filter effective braking cycles. This easily introduces invalid disturbance data such as accidental pedal touches, short-term spot braking, and low-speed micro-braking. Furthermore, they fail to perform condition normalization calibration on original braking timing samples with different initial vehicle speeds and different pedal travel distances. The measured braking samples are inconsistent with the factory-standard braking condition benchmark, resulting in high levels of interference from mixed operating conditions.

[0003] In existing technologies, traditional friction pad wear assessments lack stratified threshold screening on existing braking data and cannot eliminate invalid disturbance braking cycles. This results in problems such as disordered braking sample timing and the inability to bind mechanical data and braking data from the same source. Furthermore, traditional solutions rely solely on curve deviation to calculate the initial wear amount, failing to separate actuator return clearance and secondary mechanical errors caused by ball screw displacement. The initial wear amount calculation of the friction pad is mixed with structural pseudo-errors, leading to assessment results that deviate from the true wear value. Additionally, there is no differentiated compensation coefficient to match the mechanical error interference weights.

[0004] Therefore, it is necessary to provide a clamping force compensation method based on brake friction pad wear condition assessment to solve the aforementioned problem.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a clamping force compensation method based on the assessment of brake friction pad wear condition, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A clamping force compensation method based on brake friction pad wear condition assessment, comprising the following steps: Step 1: Set the time interval determination conditions for the vehicle braking cycle. Based on the time interval determination conditions, obtain the braking sample data and braking mechanical data corresponding to several historical braking cycles before the current moment. The braking sample data includes the vehicle speed change curve and the brake pedal travel curve. The braking mechanical data includes the brake actuator return clearance and the absolute displacement of the ball screw. Step 2: Normalize the braking sample data corresponding to each braking cycle, and map the vehicle speed curve and brake pedal travel curve under different working conditions to the target standard vehicle speed and target standard brake pedal travel working conditions to obtain standardized braking samples and obtain the benchmark braking response curve calibrated by the vehicle factory. Step 3: Compare and analyze the standardized braking sample with the reference braking response curve, extract the curve deviation characteristics of the actual braking response relative to the reference braking response, and determine the initial wear of the current friction pad based on the preset curve deviation characteristics and the correspondence between the initial wear of the friction pad. Step 4: Combine the brake actuator return clearance and the absolute displacement of the ball screw to perform error compensation on the initial wear amount and obtain the actual wear amount of the friction plate at present; Step 5: Retrieve the pre-calibrated mapping relationship between the wear amount of the friction pad and the correction coefficient of the brake motor parameters, and combine it with the actual wear amount of the current friction pad to obtain the corresponding correction coefficient of the brake motor parameters; Step 6: Based on the brake motor parameter correction coefficient, match and correct the original control parameters of the brake motor to obtain the corrected brake motor control parameters. Drive the brake motor to complete the brake clamping force compensation according to the corrected brake motor control parameters.

[0008] Furthermore, the method for determining the time interval of the vehicle braking cycle is as follows: The time interval determination condition for the vehicle braking cycle is obtained from the calibration of the front frame before the vehicle leaves the factory and is pre-stored in the EMB controller. The time interval determination condition is jointly set based on the collected signals of the original vehicle brake pedal position sensor and wheel speed sensor. The time interval determination conditions are divided into three types of fixed thresholds: start determination threshold, end determination threshold, and invalid cycle elimination threshold. The effective braking time interval is divided based on these three types of fixed thresholds. Among them, the start determination threshold includes the minimum effective brake pedal travel threshold and the lower limit of the initial braking speed threshold, and the end determination threshold includes the brake pedal travel zero threshold and the vehicle braking deceleration zero threshold. Based on the start and end times of the braking cycle locked by three types of fixed thresholds, the standard effective braking cycle time interval satisfies the following formula: in, The starting time of the braking cycle is determined by the following conditions: the real-time brake pedal travel of the vehicle is greater than the preset minimum effective brake pedal travel threshold and the real-time vehicle speed is greater than the preset initial braking speed threshold lower limit. The braking cycle is determined to start when both conditions are met simultaneously. The braking cycle ends when the braking cycle is terminated. The triggering conditions are: the real-time travel of the brake pedal returns to zero, the vehicle speed change curve tends to be stable and the real-time vehicle speed remains constant. The braking cycle ends when both conditions are met simultaneously. The standard effective braking cycle time interval after filtering out invalid disturbances.

[0009] Furthermore, the vehicle speed curves and brake pedal travel curves under different operating conditions are uniformly mapped to standard vehicle speed and standard brake pedal travel conditions to obtain standardized braking samples. The method used is as follows: Preset, unified braking condition parameters are retrieved, including standard initial vehicle speed and standard brake pedal travel. Based on a time-series data linear mapping normalization algorithm, full-domain condition calibration is performed on the discrete vehicle speed time-series curves and brake pedal travel time-series curves corresponding to each historical braking cycle. This eliminates data interference caused by differences in initial vehicle speed and initial pedal travel in different braking cycles. All original vehicle speed curves and original brake pedal travel curves are uniformly mapped to the same benchmark condition with standard initial vehicle speed and standard brake pedal travel. This completes the condition alignment and data reconstruction of the two types of braking time-series curves, generating standardized braking samples with unified condition dimensions.

[0010] Furthermore, the standardized braking samples are compared and analyzed with the reference braking response curve to extract the curve deviation characteristics of the actual braking response relative to the reference braking response. The method used is as follows: Standardized braking samples and benchmark braking response curves are coupled and matched on a time-series node-by-time basis to unify time-series variables. Using the reference axis, extract the time difference between the standardized vehicle speed and standardized brake pedal travel and the reference vehicle speed and reference brake pedal travel at the same time node; Among them, the vehicle speed timing deviation value and the brake pedal travel timing deviation value are used as curve deviation characteristics; Among them, the vehicle speed timing deviation value and the brake pedal travel timing deviation value are calculated using a timing point-to-point difference algorithm, and the corresponding deviation value calculation formula is as follows: in, , They are time points The timing deviation between the standardized vehicle speed and the reference vehicle speed, and the timing deviation between the standardized brake pedal travel and the reference pedal travel. , These are the time intervals after normalization. Corresponding standardized vehicle speed and standardized brake pedal travel, , They are time points The corresponding reference vehicle speed and reference brake pedal travel.

[0011] Furthermore, based on the preset relationship between the curve deviation characteristics and the initial wear of the friction plate, the initial wear of the current friction plate is determined. The method used is as follows: Retrieve the curve deviation feature-friction pad initial wear correlation mapping model that is pre-calibrated at the factory and stored in the EMB controller. Input the extracted curve deviation features consisting of vehicle speed timing deviation and brake pedal travel timing deviation into the correlation mapping model. Based on the linear correlation fitting relationship of the pre-trained fitting, the initial wear value of the friction pad is obtained by matching and solving. After completing the working condition matching correction by combining the standardized braking sample and the benchmark braking response curve, the initial wear value corresponding to the current braking friction pad is output. The correlation mapping model is obtained offline based on multiple sets of friction pads with different wear levels and matching the corresponding braking response curve deviation samples. The model input is the curve deviation feature, and the model output is the initial wear amount of the friction pad.

[0012] Furthermore, by combining the brake actuator return clearance and the absolute displacement of the ball screw, error compensation is applied to the initial wear amount to obtain the current actual wear amount of the friction plate. The formula used is as follows: in, This indicates the actual wear of the friction pads. This represents the initial wear of the friction plate. This is the return clearance of the brake actuator. For the absolute displacement of the ball screw, , These are the error compensation coefficients for the brake actuator return clearance and the absolute displacement of the ball screw, respectively. .

[0013] Furthermore, the corrected brake motor control parameters were obtained using the following method: Retrieve the original factory reference control parameters of the brake motor stored in the EMB controller. The original reference control parameters include the motor drive current and the target feed stroke of the lead screw. The brake motor parameter correction coefficients obtained by matching are coupled with the original reference control parameters in a global proportional coupling operation. The original reference control parameters are adjusted upwards based on the proportional correction algorithm. Finally, the corrected brake motor control parameters are calculated and output based on the actual wear state of the friction pad. Among them, the proportional coupling operation is a direct proportional multiplication correction operation. The matching brake motor parameter correction coefficient is used as the proportional reference to perform a uniform proportional amplification operation on the motor drive current and the target feed stroke of the lead screw.

[0014] Furthermore, the brake motor is driven to complete the brake clamping force compensation based on the corrected brake motor control parameters. The method used is as follows: The EMB controller calls the corrected brake motor control parameters and issues drive commands, synchronously driving the brake motor based on the corrected motor drive current and the target feed stroke of the lead screw. The brake motor drives the ball screw to move axially, corresponding to the offsetting of two types of mechanical errors: the lead screw displacement compensation offsets the wear and loss thickness of the friction pads, and the clearance compensation offsets the return clearance of the brake actuator. This eliminates the brake clamping force attenuation caused by the absolute displacement of the ball screw and the return clearance of the brake actuator, and adaptively compensates for the attenuated brake clamping force. Thus, under the current braking condition, the actual brake clamping force returns to the vehicle's factory reference clamping force standard, completing the adaptive compensation of brake clamping force under the condition of friction pad wear.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention obtains braking sample data and braking mechanical data corresponding to several historical braking cycles before the current moment based on time interval determination conditions, eliminates the differences in the original braking sample working conditions and the interference of sampling disturbance noise, accurately extracts two types of curve deviation features: vehicle speed time sequence deviation and brake pedal travel time sequence deviation, and quickly solves the initial wear of the friction pad by relying on the factory pre-calibrated correlation mapping model. At the same time, it couples the brake actuator return clearance and the ball screw absolute displacement to match the corresponding error compensation coefficient to complete the closed-loop error compensation of the initial wear amount, and removes the inherent pseudo-errors of EMB brake mechanical assembly offset and transmission displacement, which greatly improves the accuracy of friction pad wear state assessment and avoids the defects of traditional single curve deviation calculation of wear amount, wear assessment distortion caused by the failure to eliminate mechanical errors, and large calculation error. Furthermore, this invention is based on a pre-calibrated mapping relationship between friction pad wear and brake motor parameter correction coefficients. It matches the actual wear amount to retrieve the corresponding brake motor parameter correction coefficients, and performs matching correction on the original control parameters of the brake motor. Based on the corrected brake motor control parameters, it drives the brake motor to complete brake clamping force compensation. This adapts to the actuator load changes and screw feed requirements after friction pad wear, accurately compensating for brake force loss caused by wear and mechanical clearance deviations. This ensures that the brake clamping force returns to the vehicle's factory benchmark standard under all life cycle operating conditions, effectively improving the problems of brake clamping force attenuation and brake response lag after friction pad wear, and enhancing the overall vehicle braking stability and driving safety. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall method flow of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0018] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0019] Example: Please see Figure 1 A clamping force compensation method based on brake friction pad wear condition assessment, comprising the following steps: Step 1: Set the time interval determination conditions for the vehicle braking cycle. Based on the time interval determination conditions, obtain the braking sample data and braking mechanical data corresponding to several historical braking cycles before the current moment. The braking sample data includes the vehicle speed change curve and the brake pedal travel curve. The braking mechanical data includes the brake actuator return clearance and the absolute displacement of the ball screw.

[0020] In a specific embodiment of the present invention, setting the time interval determination condition for the vehicle braking cycle is a crucial step. Since the entire braking cycle of a vehicle includes the processes of feeding, contacting, holding pressure, and returning, and given the complex and variable actual driving conditions of the vehicle, incomplete braking behavior is very likely to occur during driving. Such fragmented disturbance behavior does not meet the requirements of the standard braking condition of the whole vehicle. If the original sensor data of vehicle speed, brake pedal travel, actuator return clearance, and ball screw absolute displacement are directly collected in the whole domain without locking the timing boundary of the braking cycle, a large amount of invalid disturbance data and fragmented half-stroke braking data will be mixed in. On the one hand, this will cause subsequent curve normalization timing misalignment and distortion of curve deviation feature extraction, resulting in interference with the accuracy of friction pad wear calculation. On the other hand, the brake actuator return clearance and ball screw absolute displacement can only be accurately collected under steady-state conditions when braking ends and the actuator is fully returned. Without the determination of the cycle boundary, it is impossible to match the steady-state mechanical sampling time.

[0021] Therefore, this invention relies on the joint calibration of the pedal position sensor and wheel speed sensor to determine the layered threshold, and divides the braking cycle into three categories of judgment rules: start, end, and invalid rejection, so as to accurately lock the start and end time interval of the standard effective braking cycle.

[0022] Furthermore, the method for determining the time interval of the vehicle braking cycle is as follows: The time interval determination condition for the vehicle braking cycle is obtained from the calibration of the front frame before the vehicle leaves the factory and is pre-stored in the EMB controller. The time interval determination condition is jointly set based on the collected signals of the original vehicle brake pedal position sensor and wheel speed sensor. The time interval determination conditions are divided into three types of fixed thresholds: start determination threshold, end determination threshold, and invalid cycle elimination threshold. The effective braking time interval is divided based on these three types of fixed thresholds. Among them, the start determination threshold includes the minimum effective brake pedal travel threshold and the lower limit of the initial braking speed threshold, and the end determination threshold includes the brake pedal travel zero threshold and the vehicle braking deceleration zero threshold. The method used to set the three types of fixed thresholds is as follows: The minimum effective brake pedal travel threshold is used to distinguish various non-braking interference conditions in simulated real vehicles: slight pedal touch, foot mis-press, short-stroke trial operation, parking micro-movement, etc. A large amount of raw pedal travel data is continuously collected, and the maximum value of all invalid micro-movement travel is calculated. Based on the maximum value of invalid micro-movement travel, a safety margin is added, and 1%-3% of the original vehicle's total pedal travel is usually taken to obtain the minimum effective brake pedal travel threshold. The lower limit of the initial braking speed threshold is used to distinguish between three states of a vehicle: static, low-speed maneuvering, and normal driving. A chassis dynamometer is used to simulate different steady-state vehicle speeds, gradually increasing the speed from 0 km / h while simultaneously triggering braking. The minimum driving speed is determined in conjunction with the vehicle design specifications. Using the minimum driving speed defined by the vehicle as a benchmark, and considering the braking system design requirements, this value is the lower limit of the speed threshold. It should be noted that for passenger vehicles, this value is typically 5-10 km / h. The purpose of setting the brake pedal travel zero threshold is to accurately identify the state of the brake pedal being fully released, while compensating for sensor zero drift and pedal mechanical return play, and avoiding misjudging a slight pedal rebound as not returning to its original position. The zero-position reference is collected: when the vehicle is turned off and the pedal returns to its original position naturally, the original zero-position signal of the brake pedal position sensor is collected, and the reference travel value corresponding to the complete return of the pedal is recorded. The "press-release" of the brake pedal is repeated multiple times, and the maximum travel offset caused by mechanical play, sensor temperature drift, and assembly tolerance after the pedal returns to its original position is counted. The maximum travel offset is superimposed on the reference travel of the pedal returning to its original position as the center as the allowable range, and the travel zero threshold is set. That is, if the pedal travel falls within this range, it is judged as "travel zero". The purpose of setting the vehicle braking deceleration zero threshold is to determine when the vehicle has finished decelerating and entered a steady state of uniform speed, avoiding premature termination of the braking cycle while the vehicle is still decelerating, and ensuring the integrity of the braking timing curve. The specific setting method is as follows: relying on wheel speed sensors to calculate the real-time deceleration of the vehicle, the test bench simulates the braking process under all working conditions, and collects deceleration data from the start of braking, continuous deceleration, deceleration stop, and uniform speed driving. The steady state judgment rule is specified. When the vehicle is driving at a uniform speed, the theoretical deceleration is 0. Affected by road bumps and wheel speed sampling fluctuations, there will be small noise in reality. The maximum noise deceleration value under the uniform speed state of the vehicle is counted, and the maximum value of the noise is used as the vehicle braking deceleration zero threshold. When the real-time deceleration is less than or equal to the threshold, it is determined that the vehicle deceleration has ended and the vehicle speed tends to be stable.

[0023] Based on the start and end times of the braking cycle locked by three types of fixed thresholds, the standard effective braking cycle time interval satisfies the following formula: in, The starting time of the braking cycle is determined by the following conditions: the real-time brake pedal travel of the vehicle is greater than the preset minimum effective brake pedal travel threshold and the real-time vehicle speed is greater than the preset initial braking speed threshold lower limit. The braking cycle is determined to start when both conditions are met simultaneously. The braking cycle ends when the braking cycle is terminated. The triggering conditions are: the real-time travel of the brake pedal returns to zero, the vehicle speed change curve tends to be stable and the real-time vehicle speed remains constant. The braking cycle ends when both conditions are met simultaneously. The standard effective braking cycle time interval after filtering out invalid disturbances.

[0024] It should be noted that the method used to obtain braking sample data and braking mechanical data corresponding to several braking cycles before the current moment based on the time interval determination condition is as follows: based on the locked time intervals of each historical effective braking cycle, all continuous time-series sampling signals within each time interval are extracted, time-series vehicle speed sampling points are extracted and fitted to generate the speed curve of the corresponding braking cycle, time-series brake pedal travel sampling points are extracted and fitted to generate the brake travel curve of the corresponding braking cycle, thus completing the extraction of braking sample data; Synchronously match the start and end time interval of the same braking cycle, and under the steady-state condition of the brake actuator fully returning to its position at the end of a single braking cycle, collect two types of braking mechanical data: the brake actuator return gap and the absolute displacement of the ball screw for the corresponding cycle. The speed curves, braking stroke curves, brake actuator return clearance, and ball screw absolute displacement corresponding to the same braking cycle time interval are periodically bound and archived. Unqualified braking cycle data groups with timing misalignment, missing sampling, or abnormal operating conditions are removed. Finally, several sets of braking sample data and braking mechanical data that are time-matched and have unified operating conditions before the current moment are obtained.

[0025] Step 2: Normalize the braking sample data corresponding to each braking cycle, and map the vehicle speed curve and brake pedal travel curve under different working conditions to the target standard vehicle speed and target standard brake pedal travel working conditions to obtain standardized braking samples, and obtain the benchmark braking response curve calibrated by the vehicle at the factory.

[0026] In a specific embodiment of the present invention, all original braking samples are uniformly mapped to the same benchmark condition with the target standard vehicle speed and the target standard brake pedal travel, eliminating external interference caused by differences in driver operation and differences in initial driving conditions, and eliminating differences in cross-cycle operating condition variables. The multiple sets of historical braking cycles obtained after screening in step 1 were all collected during vehicle operation. Due to differences in driver pedaling habits, road conditions, and initial driving state, there are significant individual differences in the initial braking speed, maximum brake pedal travel, and braking input conditions of the original braking samples in different braking cycles. The factory-calibrated reference braking response curve retrieved by this invention is generated offline under standard rated conditions on the vehicle test bench, with a fixed initial speed and a fixed standard pedal travel, and is only compatible with a single standard braking reference condition. If the original vehicle speed curve and original brake pedal travel curve with chaotic conditions are directly compared with the reference braking response curve, the curve deviation value will be mixed with a large number of working condition interference deviations caused by differences in initial vehicle speed and human pedal travel. This type of working condition disturbance deviation is much greater than the actual braking response deviation induced by friction pad wear, which ultimately leads to redundant noise in the vehicle speed time sequence deviation and pedal travel time sequence deviation extracted in step 3. This results in the distortion of the input parameters of the deviation feature-wear amount mapping model, and the calculation result of the initial wear amount of the friction pad is seriously deviated from the true value. This processing ensures that the measured braking sample's operating condition dimension and timing dimension are fully aligned and coupled with the factory-standard braking response curve. This guarantees that the vehicle speed timing deviation and brake pedal travel timing deviation extracted in subsequent step 3 are only effective characteristic deviations induced by the physical wear of the friction pads and the mechanical offset of the brake, completely eliminating irrelevant operating condition disturbances and ensuring the singularity and authenticity of the curve deviation characteristics.

[0027] It should be noted that the method used to obtain the vehicle's factory-calibrated baseline braking response curve is as follows: First, the operating parameters are calibrated and the standard initial vehicle speed is set: by controlling the chassis dynamometer to drive the wheels to rotate, the whole vehicle is kept stable at the preset standard initial vehicle speed. Then, the standard brake pedal travel is set: the brake pedal is precisely controlled by the servo drive mechanism to ensure that the maximum pedal travel, pedal rate, and pressure holding time are completely fixed, replicating the uniform standard braking input action. Under the aforementioned fixed operating conditions, perform multiple rounds of standard braking tests continuously, no less than 10 sets, preferably 10-20 sets, to eliminate random errors in a single test and fluctuations in instantaneous sensor sampling. Throughout the test, high-frequency synchronous acquisition of wheel speed sensor signals and brake pedal position sensor signals is conducted. The wheel speed sensor signals are used to calculate the real-time vehicle speed at each moment to form raw vehicle speed time-series data; the brake pedal position sensor signals are used to acquire the real-time pedal travel at each moment to form raw pedal travel time-series data. Digital filtering was performed on multiple sets of raw time-series data to remove electrical noise from sensors and glitches caused by mechanical vibrations of the test bench; and deviations caused by brief equipment malfunctions or operational errors during the test were eliminated, retaining only the most consistent and valid data sets to unify the time series. Using time as the time axis, the average values ​​of vehicle speed and pedal travel at the same time for multiple sets of grid samples are calculated to obtain the baseline vehicle speed and baseline pedal travel under each standard time node. Based on the time node data, the baseline vehicle speed response curve and the baseline pedal travel response curve are respectively fitted and generated.

[0028] Furthermore, the vehicle speed curves and brake pedal travel curves under different operating conditions are uniformly mapped to standard vehicle speed and standard brake pedal travel conditions to obtain standardized braking samples. The method used is as follows: Preset, unified braking condition parameters are retrieved, including standard initial vehicle speed and standard brake pedal travel. Based on a time-series data linear mapping normalization algorithm, full-domain condition calibration is performed on the discrete vehicle speed time-series curves and brake pedal travel time-series curves corresponding to each historical braking cycle. This eliminates data interference caused by differences in initial vehicle speed and initial pedal travel in different braking cycles. All original vehicle speed curves and original brake pedal travel curves are uniformly mapped to the same benchmark condition with standard initial vehicle speed and standard brake pedal travel. This completes the condition alignment and data reconstruction of the two types of braking time-series curves, generating standardized braking samples with unified condition dimensions.

[0029] It should be noted that the standard initial vehicle speed is calibrated and obtained using a brake test bench before the vehicle leaves the factory. First, atypical conditions such as low-speed maneuvering and extreme high-speed driving are eliminated based on the overall vehicle usage scenarios, and the daily high-frequency driving speed range is defined. Repeated braking tests are carried out with multiple gradient vehicle speeds within this range. The sample coverage ratio, data stability, and linear working characteristics of the wheel speed sensor are comprehensively considered to complete the screening. After joint working condition verification, the final value is determined and pre-stored as a fixed parameter in the EMB controller. This vehicle speed is consistent with the calibration speed of the reference braking response curve. The standard brake pedal travel is also calibrated through factory bench testing. First, the range is divided according to the mechanical travel of the pedal, and invalid ranges such as micro-touch and full-stroke emergency braking are eliminated to lock the normal braking travel range. Under the determined standard initial vehicle speed, the maximum pedal travel of multiple gradients is set, and the action logic of pedal pressing, holding pressure and returning is unified. The optimal selection is completed by combining the frequency of actual vehicle use, the linearity of sensor signals and the smoothness of the timing curve. After verification, complete operating condition parameters are formed and stored to ensure that the pedal operating condition matches the reference braking response curve.

[0030] Step 3: Compare and analyze the standardized braking sample with the reference braking response curve, extract the curve deviation characteristics of the actual braking response relative to the reference braking response, and determine the initial wear of the current friction pad based on the preset curve deviation characteristics and the correspondence between the initial wear of the friction pad.

[0031] In a specific embodiment of the present invention, a unified time series variable is adopted. A unique alignment benchmark is used to achieve point-to-point coupling and matching of standardized braking samples and factory-standard braking response curves at each time node. This abandons the traditional method of overall curve envelope comparison and coarse matching of feature intervals. The technical benefits are as follows: First, by using the time difference at the same moment as the calculation basis, pseudo-deviations caused by time misalignment and response time zone offset are eliminated, ensuring the accuracy of vehicle speed time sequence deviation. Brake pedal travel timing deviation First, the timing dimension is completely homogeneous; second, redundant curve slope deviation and excessive lag duration features are discarded, and only two core features strongly coupled with friction plate wear, namely vehicle speed timing deviation and pedal travel timing deviation, are retained. Weakly correlated interference features such as brake damping fluctuation and instantaneous current disturbance of motor are eliminated, simplifying the input dimension of the back-end model; third, a point-to-point difference basic arithmetic algorithm is adopted, with extremely simple operation logic, no matrix operation, and no nonlinear fitting iteration, which is adapted to the low computing power hardware architecture of the vehicle EMB embedded controller and ensures the timeliness of real-time vehicle operation. The initial wear value is calculated based on the offline calibration linear correlation mapping model on the vehicle factory bench. Unlike existing technologies that use physical mechanism formulas and real-time machine learning training models, the core technical functions include: First, the model is constructed based on multi-gradient real wear friction pad samples and corresponding braking deviation samples through full-domain offline calibration. Sample training and relationship fitting are completed in advance. During the vehicle operation phase, only linear lookup table matching calculations are performed. There is no real-time vehicle training or parameter adaptive iteration, which eliminates the problem of model overfitting and fitting failure caused by fluctuations in actual vehicle operating conditions. Second, the linear correlation fitting relationship is used to replace the multi-parameter braking dynamic simultaneous equations, reducing the computing power consumption of the vehicle controller and the difficulty of program burning, and making it more portable for mass production. Third, the initial wear value output by the model is the pure wear value of the friction pad body after removing the external mechanical errors of lead screw displacement and actuator return clearance. It deliberately distinguishes between two types of error sources: body wear and brake assembly mechanical errors, realizing the separation of error sources and adapting to the source error compensation logic in step 4, avoiding the inability to separate and compensate for wear errors and mechanical structure errors due to coupling and mixing.

[0032] It should be noted that this invention deliberately eliminates two auxiliary features: braking response delay deviation and curve slope deviation. Only vehicle speed timing deviation and brake pedal travel timing deviation are selected as model inputs. This is because these two types of deviations have the highest sensitivity and strongest correlation to the uniform wear of friction pads. The delay deviation is easily affected by motor control delay and wiring harness electrical delay, while the slope deviation is easily affected by road surface adhesion coefficient. Eliminating these features further improves the anti-interference ability of wear assessment, which is a key point of the differentiated design of this invention.

[0033] Furthermore, the standardized braking samples are compared and analyzed with the reference braking response curve to extract the curve deviation characteristics of the actual braking response relative to the reference braking response. The method used is as follows: Standardized braking samples and benchmark braking response curves are coupled and matched on a time-series node-by-time basis to unify time-series variables. Using the reference axis, extract the time difference between the standardized vehicle speed and standardized brake pedal travel and the reference vehicle speed and reference brake pedal travel at the same time node; Among them, the vehicle speed timing deviation value and the brake pedal travel timing deviation value are used as curve deviation characteristics; Among them, the vehicle speed timing deviation value and the brake pedal travel timing deviation value are calculated using a timing point-to-point difference algorithm, and the corresponding deviation value calculation formula is as follows: in, , They are time points The timing deviation between the standardized vehicle speed and the reference vehicle speed, and the timing deviation between the standardized brake pedal travel and the reference pedal travel. , These are the time intervals after normalization. Corresponding standardized vehicle speed and standardized brake pedal travel, , They are time points The corresponding reference vehicle speed and reference brake pedal travel.

[0034] Furthermore, based on the preset relationship between the curve deviation characteristics and the initial wear of the friction plate, the initial wear of the current friction plate is determined. The method used is as follows: Retrieve the curve deviation feature-friction pad initial wear correlation mapping model that is pre-calibrated at the factory and stored in the EMB controller. Input the extracted curve deviation features consisting of vehicle speed timing deviation and brake pedal travel timing deviation into the correlation mapping model. Based on the linear correlation fitting relationship of the pre-trained fitting, the initial wear value of the friction pad is obtained by matching and solving. After completing the working condition matching correction by combining the standardized braking sample and the benchmark braking response curve, the initial wear value corresponding to the current braking friction pad is output. The correlation mapping model is obtained offline based on multiple sets of friction pads with different wear levels and matching the corresponding braking response curve deviation samples. The model input is the curve deviation feature, and the model output is the initial wear amount of the friction pad.

[0035] It should be noted that the pre-training of this correlation mapping model was completed offline on a brake test bench before the vehicle left the factory. First, brake pad samples with multiple wear levels (new, light, moderate, and heavy) were prepared. The actual wear amount of each sample was obtained through precise measurement and used as a training label. Under uniform standard initial vehicle speed and standard brake pedal travel conditions, multiple sets of repeated braking tests were conducted on each wear sample, simultaneously collecting full-time vehicle speed and pedal travel data. After normalizing the raw data, the temporal deviation features of vehicle speed and pedal travel were extracted by combining them with the baseline braking response curve. These deviation features were then paired with the corresponding measured wear amounts to construct a training dataset. Linear regression fitting was performed on the dataset using the least squares method to obtain a fixed linear correlation between the deviation features and the wear amount of the brake pads. The model accuracy was verified using reserved test samples. After passing the verification, the linear model parameters were permanently stored in the EMB controller, completing the model pre-training.

[0036] Step 4: Combine the brake actuator return clearance and the absolute displacement of the ball screw to perform error compensation on the initial wear amount, and obtain the actual wear amount of the friction plate at present.

[0037] In a specific embodiment of the present invention, the initial wear amount obtained in step 3 is... The calculated wear amount is derived by back-calculating the total displacement of the ball screw feed. This solution process does not exclude non-wear-related additional displacements caused by the mechanical assembly and transmission mechanism of the brake, and only relies on the closed-loop brake displacement signal for calculation. Under the ideal standard brake operating condition with no assembly tolerances, no mechanism clearances, and no spring fatigue drift, this value is equivalent to the wear amount of the friction material itself. However, during the long-term service of the EMB electromechanical brake installed in actual vehicles, there are two unavoidable inherent non-wear-related mechanical additional displacements: the first is the brake actuator return clearance, which is caused by the brake caliper assembly tolerance at the factory, the long-term reciprocating fatigue deformation of the brake return spring, and the drift of the caliper body fit clearance. The first type is caused by the combined effects of two types of mechanical displacement errors. The second type is the absolute displacement reference deviation of the ball screw, which is caused by the axial assembly offset of the screw at the factory, the drift of the reference zero position caused by long-term transmission wear, and the change of the fit clearance of the motor screw transmission. Neither type of mechanical structural deviation produces physical loss of the friction plate material, but only adds an extra amount of apparent feed displacement of the ball screw. This part of the invalid displacement is coupled and collected by the braking displacement acquisition system and included in the initial wear calculation process in step 3, which causes the initial wear amount to be mixed with the mechanism clearance error and the calculated value to be falsely high, resulting in a distorted friction plate wear assessment result. Therefore, the two types of mechanical displacement errors are decoupled and compensated to eliminate the interference of non-wearing structural displacement in step 4, and the true actual wear amount of the friction plate is obtained by calibration.

[0038] Set the error compensation coefficient to The purpose of this setting is: firstly, , The values ​​are all greater than 0. Both types of mechanical deviations—the brake actuator return clearance and the absolute displacement of the ball screw—will be positively superimposed on the brake response timing deviation, causing the initial wear calculated in step 3 to be generally larger. Both types of structural pseudo-errors need to be positively compensated to offset them; therefore, both compensation coefficients are positive values. Secondly... , All values ​​are less than 1. Both types of mechanical assembly drift and transmission displacement deviation belong to minor secondary structural errors of the brake. The error amplitude is far lower than the wear loss of the friction pad material. A limiting coefficient less than 1 can avoid excessive compensation amplitude, prevent overshooting of actual wear correction, and avoid reverse distortion of evaluation results, thus conforming to the calibration criteria for vehicle brake error compensation electronic control; thirdly, it meets the requirements... Differentiated constraints based on strong and weak weights, error compensation coefficient The return clearance of the brake actuator is caused by multiple factors, including the assembly tolerance of the brake caliper, the long-term fatigue deformation of the return spring, and the play in the caliper body. This clearance fluctuates significantly and directly affects the closed-loop stroke feedback control of the brake, resulting in strong coupling interference with the brake response curve deviation and the accuracy of wear measurement. The error compensation coefficient... The absolute displacement compensation coefficient of the ball screw corresponds to the slight drift of the axial reference zero position of the screw and the slight fit clearance of the screw transmission pair. It is a slight secondary error at the end of the transmission link and does not directly participate in the closed-loop control of the braking clamping stroke. Its coupling interference with braking response characteristics and wear assessment results is extremely weak.

[0039] Furthermore, by combining the brake actuator return clearance and the absolute displacement of the ball screw, error compensation is applied to the initial wear amount to obtain the current actual wear amount of the friction plate. The formula used is as follows: in, This indicates the actual wear of the friction pads. This represents the initial wear of the friction plate. This is the return clearance of the brake actuator. For the absolute displacement of the ball screw, , These are the error compensation coefficients for the brake actuator return clearance and the absolute displacement of the ball screw, respectively. .

[0040] Step 5: Retrieve the pre-calibrated mapping relationship between the wear amount of the friction pads and the correction coefficient of the brake motor parameters, and combine it with the actual wear amount of the current friction pads to obtain the corresponding correction coefficient of the brake motor parameters.

[0041] In a specific embodiment of the present invention, the pre-calibrated offline mapping relationship between the wear amount of the friction pad and the correction coefficient of the brake motor parameters is retrieved from the non-volatile storage unit inside the EMB controller. The actual wear amount of the friction pad, which is the final output of step 4 and the result of error compensation, is used as the only input variable. Relying on the vehicle-mounted embedded segmented lookup table matching algorithm, the preset mapping relationship library is traversed and matched to accurately match the correction coefficient of the brake motor parameters under the corresponding wear condition. The mapping relationship includes two sets of independent sub-mapping relationships, which correspond to the motor drive current correction coefficient mapping and the lead screw target feed stroke correction coefficient mapping, respectively. The two sets of correction coefficients are synchronously matched and output, directly providing a reference proportional coefficient for the proportional correction of the original motor control parameters in step 6. The mapping relationship between the wear amount of the friction pad and the correction coefficient of the brake motor parameters is fitted and solidified through full-domain calibration on the brake test bench before the vehicle rolls off the production line. It is stored in the built-in Flash non-volatile storage area of ​​the EMB brake controller. The mapping data is not lost after the vehicle is powered off and restarted. No on-board real vehicle data collection and training or subsequent adaptive updates are required. It should be noted that this mapping relationship is a piecewise discrete linear mapping library, divided into three threshold intervals: light wear, moderate wear, and heavy wear. The mapping independent variable is the actual wear amount of the friction plate output in step 4. The dependent variable includes two types of independent correction coefficients: motor drive current correction coefficient and lead screw target feed stroke correction coefficient. The two types of coefficients are independent of each other, are bound and calibrated in separate areas, and have no coupling interference. The mapping relationship calibration condition is uniformly adopted using the standard target braking condition described in step 2 to complete the calibration; multiple sets of gradient wear sample friction plates are selected, and the same EMB brake actuator as the actual vehicle is matched. The reference vehicle speed and reference pedal stroke are fixed, and the optimal brake compensation motor control ratio parameters under different wear amounts are collected. The one-to-one correspondence between wear amount and dual motor correction coefficient is obtained by fitting, ensuring that the bench calibration condition and the normalized standard condition of the actual vehicle are completely the same source; The matching process adopts the embedded electronic control general fixed-point lookup table matching algorithm, which first determines the wear zone to which the current actual wear amount belongs, and then retrieves the reference correction coefficient bound in the zone; when the wear amount is in the middle range between two calibration points, the built-in linear interpolation algorithm is used to smoothly fit the correction coefficient, avoid the motor control jitter caused by the step change of the coefficient, and improve the braking smoothness.

[0042] Furthermore, the corrected brake motor control parameters were obtained using the following method: Retrieve the original factory reference control parameters of the brake motor stored in the EMB controller. The original reference control parameters include the motor drive current and the target feed stroke of the lead screw. The brake motor parameter correction coefficients obtained by matching are coupled with the original reference control parameters in a global proportional coupling operation. The original reference control parameters are adjusted upwards based on the proportional correction algorithm. Finally, the corrected brake motor control parameters are calculated and output based on the actual wear state of the friction pad. Among them, the proportional coupling operation is a direct proportional multiplication correction operation. The matching brake motor parameter correction coefficient is used as the proportional reference to perform a uniform proportional amplification operation on the motor drive current and the target feed stroke of the lead screw.

[0043] Step 6: Based on the brake motor parameter correction coefficient, match and correct the original control parameters of the brake motor to obtain the corrected brake motor control parameters. Drive the brake motor to complete the brake clamping force compensation according to the corrected brake motor control parameters.

[0044] In a specific embodiment of the invention, the original factory reference control parameters of the brake motor stored in the EMB controller are retrieved. These original reference control parameters include two independent parameters: the motor reference drive current and the lead screw reference target feed stroke. The motor drive current correction coefficient and the lead screw target feed stroke correction coefficient obtained in step 5 are coupled with the corresponding original reference control parameters in a globally proportional manner. A fixed-proportion correction algorithm is used to synchronously adjust and correct the two sets of original reference control parameters, eliminating parameter adaptation deviations caused by wear conditions and mechanical clearance deviations. The corrected brake motor control parameters, adapted to the actual wear conditions of the current friction plates, are then output. The EMB controller calls the corrected motor drive parameters in real time to issue closed-loop drive commands, based on… The corrected drive current and the corrected lead screw target feed stroke are used to synchronously drive the brake servo motor. The brake motor converts the electrical signal command into axial mechanical feed displacement through the ball screw transmission pair, and completes error cancellation and clamping force compensation in two ways: the additional axial feed displacement compensation of the lead screw compensates for the wear and loss thickness of the friction pad body material, and the feed amount matched with the actuator clearance compensates for the residual return clearance of the brake actuator. At the same time, the brake force attenuation caused by the dual disturbances of ball screw reference displacement drift and brake assembly clearance is eliminated. Finally, under the current actual vehicle braking conditions, the steady-state braking clamping force of the brake converges to the reference clamping force of the standard working condition without wear of the vehicle at the factory, and completes the adaptive closed-loop compensation of the braking clamping force under the wear conditions of the friction pad throughout its entire life cycle.

[0045] It should be noted that the two sets of correction coefficients are independently bound to the original control parameters one-to-one and are not coupled to each other. The motor drive current correction coefficient only corrects the original reference drive current, and the lead screw target feed stroke correction coefficient only corrects the original reference lead screw feed stroke, thus eliminating coefficient cross-interference. This invention uses direct proportional multiplication correction, abandons addition and subtraction offset correction, and nonlinear fitting correction. The reason is that the wear of the friction plate, the mechanical clearance deviation and the motor control requirements are linearly positively correlated. The direct proportional operation fits the factory calibration linear mapping logic. The algorithm has a very small amount of computation and no iterative convergence time, which is suitable for the real-time control requirements of the EMB embedded controller. At the same time, it fits the linear interpolation and linear mapping global unified algorithm system in step 5.

[0046] It should be noted that the dual control parameter division of labor compensation mechanism is as follows: after correction, the target feed stroke of the lead screw is specifically compensated for the wear thickness of the friction plate material and the displacement deviation of the lead screw reference zero position; after correction, the motor drive current is specifically compensated for the transmission load loss of the brake motor and the motor output torque attenuation caused by the caliper clearance. The two types of parameters work together to compensate and counteract the two types of mechanical error sources in step 4; the brake motor receives the current command and outputs the rated torque, which is converted into axial linear feed displacement through the ball screw transmission pair. The transmission displacement and the motor drive current have a factory-calibrated linear transmission relationship. The electric motor parameter coupling conversion is completed by relying on the fixed transmission ratio of the nominal lead of the EMB ball screw.

[0047] It should be noted that the factory-standard clamping force is the same as the steady-state rated clamping force calibrated from the benchmark braking response curve in step 2. After the compensation is completed, the steady-state clamping force error of the brake converges to the factory-calibrated allowable error threshold range, and the clamping force compensation is determined to be completed, meeting the vehicle braking regulatory benchmark requirements.

[0048] Furthermore, the brake motor is driven to complete the brake clamping force compensation based on the corrected brake motor control parameters. The method used is as follows: The EMB controller calls the corrected brake motor control parameters and issues drive commands, synchronously driving the brake motor based on the corrected motor drive current and the target feed stroke of the lead screw. The brake motor drives the ball screw to move axially, corresponding to the offsetting of two types of mechanical errors: the lead screw displacement compensation offsets the wear and loss thickness of the friction pads, and the clearance compensation offsets the return clearance of the brake actuator. This eliminates the brake clamping force attenuation caused by the absolute displacement of the ball screw and the return clearance of the brake actuator, and adaptively compensates for the attenuated brake clamping force. Thus, under the current braking condition, the actual brake clamping force returns to the vehicle's factory reference clamping force standard, completing the adaptive compensation of brake clamping force under the condition of friction pad wear.

[0049] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0050] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0051] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A clamping force compensation method based on brake friction pad wear condition assessment, characterized in that, The specific steps include: Step 1: Set the time interval determination conditions for the vehicle braking cycle. Based on the time interval determination conditions, obtain the braking sample data and braking mechanical data corresponding to several historical braking cycles before the current moment. The braking sample data includes the vehicle speed change curve and the brake pedal travel curve. The braking mechanical data includes the brake actuator return clearance and the absolute displacement of the ball screw. Step 2: Normalize the braking sample data corresponding to each braking cycle, and map the vehicle speed curve and brake pedal travel curve under different working conditions to the target standard vehicle speed and target standard brake pedal travel working conditions to obtain standardized braking samples and obtain the benchmark braking response curve calibrated by the vehicle factory. Step 3: Compare and analyze the standardized braking sample with the reference braking response curve, extract the curve deviation characteristics of the actual braking response relative to the reference braking response, and determine the initial wear of the current friction pad based on the preset curve deviation characteristics and the correspondence between the initial wear of the friction pad. Step 4: Combine the brake actuator return clearance and the absolute displacement of the ball screw to perform error compensation on the initial wear amount and obtain the actual wear amount of the friction plate at present; Step 5: Retrieve the pre-calibrated mapping relationship between the wear amount of the friction pad and the correction coefficient of the brake motor parameters, and combine it with the actual wear amount of the current friction pad to obtain the corresponding correction coefficient of the brake motor parameters; Step 6: Based on the brake motor parameter correction coefficient, match and correct the original control parameters of the brake motor to obtain the corrected brake motor control parameters. Drive the brake motor to complete the brake clamping force compensation according to the corrected brake motor control parameters.

2. The clamping force compensation method based on brake friction pad wear state assessment according to claim 1, characterized in that, The method used to determine the time interval for vehicle braking cycles is as follows: The time interval determination condition for the vehicle braking cycle is obtained from the calibration of the front frame before the vehicle leaves the factory and is pre-stored in the EMB controller. The time interval determination condition is jointly set based on the collected signals of the original vehicle brake pedal position sensor and wheel speed sensor. The time interval determination conditions are divided into three types of fixed thresholds: start determination threshold, end determination threshold, and invalid cycle elimination threshold. The effective braking time interval is divided based on these three types of fixed thresholds. Among them, the start determination threshold includes the minimum effective brake pedal travel threshold and the lower limit of the initial braking speed threshold, and the end determination threshold includes the brake pedal travel zero threshold and the vehicle braking deceleration zero threshold. Based on the start and end times of the braking cycle locked by three types of fixed thresholds, the standard effective braking cycle time interval satisfies the following formula: in, The starting time of the braking cycle is determined by the following conditions: the real-time brake pedal travel of the vehicle is greater than the preset minimum effective brake pedal travel threshold and the real-time vehicle speed is greater than the preset initial braking speed threshold lower limit. The braking cycle is determined to start when both conditions are met simultaneously. The braking cycle ends when the braking cycle is terminated. The triggering conditions are: the real-time travel of the brake pedal returns to zero, the vehicle speed change curve tends to be stable and the real-time vehicle speed remains constant. The braking cycle ends when both conditions are met simultaneously. The standard effective braking cycle time interval after filtering out invalid disturbances.

3. The clamping force compensation method based on brake friction pad wear state assessment according to claim 2, characterized in that, Standardized braking samples are obtained by mapping vehicle speed curves and brake pedal travel curves under different operating conditions to standard vehicle speed and standard brake pedal travel conditions. The method used is as follows: Preset, unified braking condition parameters are retrieved, including standard initial vehicle speed and standard brake pedal travel. Based on a time-series data linear mapping normalization algorithm, full-domain condition calibration is performed on the discrete vehicle speed time-series curves and brake pedal travel time-series curves corresponding to each historical braking cycle. This eliminates data interference caused by differences in initial vehicle speed and initial pedal travel in different braking cycles. All original vehicle speed curves and original brake pedal travel curves are uniformly mapped to the same benchmark condition with standard initial vehicle speed and standard brake pedal travel. This completes the condition alignment and data reconstruction of the two types of braking time-series curves, generating standardized braking samples with unified condition dimensions.

4. The clamping force compensation method based on brake friction pad wear state assessment according to claim 3, characterized in that, The standardized braking samples were compared and analyzed with the reference braking response curves to extract the curve deviation characteristics of the actual braking response relative to the reference braking response. The method used was as follows: Standardized braking samples and benchmark braking response curves are coupled and matched on a time-series node-by-time basis to unify time-series variables. Using the reference axis, extract the time difference between the standardized vehicle speed and standardized brake pedal travel and the reference vehicle speed and reference brake pedal travel at the same time node; Among them, the vehicle speed timing deviation value and the brake pedal travel timing deviation value are used as curve deviation characteristics; Among them, the vehicle speed timing deviation value and the brake pedal travel timing deviation value are calculated using a timing point-to-point difference algorithm, and the corresponding deviation value calculation formula is as follows: in, , They are time points The timing deviation between the standardized vehicle speed and the reference vehicle speed, and the timing deviation between the standardized brake pedal travel and the reference pedal travel. , These are the time intervals after normalization. Corresponding standardized vehicle speed and standardized brake pedal travel, , They are time points The corresponding reference vehicle speed and reference brake pedal travel.

5. The clamping force compensation method based on brake friction pad wear state assessment according to claim 4, characterized in that, Based on the preset relationship between curve deviation characteristics and initial wear of the friction plate, the initial wear of the current friction plate is determined. The method used is as follows: Retrieve the curve deviation feature-friction pad initial wear correlation mapping model that is pre-calibrated at the factory and stored in the EMB controller. Input the extracted curve deviation features consisting of vehicle speed timing deviation and brake pedal travel timing deviation into the correlation mapping model. Based on the linear correlation fitting relationship of the pre-trained fitting, the initial wear value of the friction pad is obtained by matching and solving. After completing the working condition matching correction by combining the standardized braking sample and the benchmark braking response curve, the initial wear value corresponding to the current braking friction pad is output. The correlation mapping model is obtained offline based on multiple sets of friction pads with different wear levels and matching the corresponding braking response curve deviation samples. The model input is the curve deviation feature, and the model output is the initial wear amount of the friction pad.

6. The clamping force compensation method based on brake friction pad wear state assessment according to claim 5, characterized in that, By combining the brake actuator return clearance and the absolute displacement of the ball screw, error compensation is applied to the initial wear amount to obtain the current actual wear amount of the friction plate. The formula used is as follows: in, This indicates the actual wear of the friction pads. This represents the initial wear of the friction plate. This is the return clearance of the brake actuator. For the absolute displacement of the ball screw, , These are the error compensation coefficients for the brake actuator return clearance and the absolute displacement of the ball screw, respectively. .

7. The clamping force compensation method based on brake friction pad wear state assessment according to claim 6, characterized in that, The corrected brake motor control parameters were obtained using the following method: Retrieve the original factory reference control parameters of the brake motor stored in the EMB controller. The original reference control parameters include the motor drive current and the target feed stroke of the lead screw. The brake motor parameter correction coefficients obtained by matching are coupled with the original reference control parameters in a global proportional coupling operation. The original reference control parameters are adjusted upwards based on the proportional correction algorithm. Finally, the corrected brake motor control parameters are calculated and output based on the actual wear state of the friction pad. Among them, the proportional coupling operation is a direct proportional multiplication correction operation. The matching brake motor parameter correction coefficient is used as the proportional reference to perform a uniform proportional amplification operation on the motor drive current and the target feed stroke of the lead screw.

8. The clamping force compensation method based on brake friction pad wear state assessment according to claim 7, characterized in that, The brake motor is driven to complete the brake clamping force compensation based on the corrected brake motor control parameters. The method used is as follows: The EMB controller calls the corrected brake motor control parameters and issues drive commands, synchronously driving the brake motor based on the corrected motor drive current and the target feed stroke of the lead screw. The brake motor drives the ball screw to move axially, corresponding to the offsetting of two types of mechanical errors: the lead screw displacement compensation offsets the wear and loss thickness of the friction pads, and the clearance compensation offsets the return clearance of the brake actuator. This eliminates the brake clamping force attenuation caused by the absolute displacement of the ball screw and the return clearance of the brake actuator, and adaptively compensates for the attenuated brake clamping force. Thus, under the current braking condition, the actual brake clamping force returns to the vehicle's factory reference clamping force standard, completing the adaptive compensation of brake clamping force under the condition of friction pad wear.

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