Dual-axis emb friction plate wear adaptive warning and control method

Abstract

The application provides a kind of dual-shaft EMB friction plate wear self-adaptive early warning and control method, it is related to automobile electronic mechanical brake technical field, the present application determines reference parameter by calibrating initial contact point rotation angle, identifies current contact point based on motor current rate of change in braking process, and combines lead screw lead coefficient to calculate rough estimate of wear;Equivalent temperature is estimated by introducing winding and ambient temperature, the thermal expansion reference coefficient is used to compensate the wear amount, and the real wear amount is obtained;Accordingly, update the comprehensive support stiffness, dynamically calculate the target stroke after compensation to realize adaptive control of clamping force;At the same time, compare the wear difference of dual-shaft to determine the eccentric wear state, adjust the torque distribution to actively balance;And according to the ratio of real wear amount and maximum allowable wear amount, divide multiple levels of early warning grade, output corresponding early warning signal.

Description

Technical Field

[0001] This invention relates to the field of automotive electromechanical braking technology, specifically a method for adaptive early warning and control of wear on dual-axis EMB friction pads. Background Technology

[0002] With the rapid development of intelligent electric vehicles and advanced autonomous driving technologies, electromechanical braking systems (EMBs) are gradually becoming the mainstream solution for next-generation vehicle braking systems due to their advantages such as fast response, high control precision, and ease of integration into drive-by-wire chassis. Among these, the dual-axis redundant drive (EMB) system, through the collaborative operation of the main drive shaft and redundant drive shafts, not only improves system reliability but also places higher demands on the ability to perceive friction pad wear, precisely control clamping force, and provide fault warnings. In existing technologies, some EMB systems have attempted to indirectly estimate friction pad wear using motor current or rotation angle signals, and adjust the target stroke accordingly to maintain stable clamping force. For example, the prior art with publication number CN120039242A proposes a dynamic wear rate identification method based on current temperature compensation and cumulative net angle, which is used to trigger active calibration and correct the caliper target angle, thereby improving braking accuracy; the prior art with publication number CN116877610A determines the piston zero point position through a pressure build-up zero point adaptive algorithm, and realizes a sensorless friction pad alarm function by combining nominal wear amount; the prior art with publication number CN120327470A further introduces a temperature and piston displacement data fusion strategy to predict clamping force and compensate for the influence of friction pad wear; and the prior art with publication number CN121515937A uses environmental compensation and key characteristic time period cross-validation to calculate the actual clearance value to output control commands.

[0003] However, the aforementioned existing technologies still have several key shortcomings that limit the reliability and safety of biaxial EMB systems under complex operating conditions. First, wear detection generally does not adequately consider the thermal expansion effect of the motor windings, lead screw mechanism, and friction pairs due to temperature rise during braking, resulting in wear calculations based on angle differences containing significant temperature drift errors and failing to reflect the true wear state. Second, the system support stiffness dynamically decreases with friction plate wear. If the clamping force-stroke mapping relationship is not updated by combining real-time wear data with the reference stiffness, uncontrollable deviations will occur between the target clamping force and the actual output force, affecting the consistency of braking performance. Third, biaxial structures are prone to wear rate differences (i.e., "uneven wear") on both sides due to manufacturing tolerances, assembly deviations, or uneven load distribution. Existing methods lack quantitative assessment and active balancing control mechanisms for biaxial wear differences, which will exacerbate braking imbalance and accelerate local failures over long-term operation. Finally, current early warning mechanisms mostly rely on a single wear threshold for judgment, failing to cover uneven wear failure modes and lacking tiered early warning and torque distribution intervention capabilities, making it difficult to support predictive maintenance and safety redundancy management. The aforementioned issues collectively make it difficult for existing dual-axis EMB systems to meet the stringent requirements of high-level autonomous vehicles in terms of high-precision control, long-life operation, and fault tolerance.

[0004] 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

[0005] The purpose of this invention is to provide an adaptive early warning and control method for wear of biaxial EMB friction plates, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A biaxial EMB friction pad wear adaptive early warning and control method, the specific steps of which include: S1: Retract the main drive shaft and redundant drive shaft to the mechanical limit and record it as the mechanical reference zero position. Drive the dual shafts synchronously forward with a preset low current. Determine the current change point as the initial contact point angle of the new friction plate of each shaft. Calculate the initial total piston stroke based on the lead screw coefficient. At the same time, calibrate the system reference stiffness and thermal expansion reference coefficient. S2: During braking, the drive motor rotation angle and motor current of each axis are collected synchronously. The current contact point rotation angle of each axis is determined by the current change rate threshold. Based on the lead screw coefficient, the current contact point rotation angle and the initial contact point rotation angle of each axis, the rough estimate of wear of each axis is calculated. S3: Collect the motor winding temperature and ambient temperature of each axis, estimate the equivalent temperature, calculate the thermal expansion compensation based on the thermal expansion reference coefficient and equivalent temperature, perform thermal expansion compensation on the rough estimate of wear for each axis, and obtain the actual wear of each axis. S4: Calculate the comprehensive support stiffness based on the actual wear of each axis and the system reference stiffness. Calculate the compensated target stroke based on the given target clamping force of each axis and the comprehensive support stiffness. The drive motors of the main drive shaft and the redundant drive shaft run synchronously to compensate the target stroke, thus completing the adaptive compensation control of the clamping force. S5: Based on the difference between the current contact point rotation angle and the corresponding initial contact point rotation angle of each axis, determine the wear difference between the two axes, judge the uneven wear state, and adjust the torque distribution of the two axes for active balancing control. S6: Based on the preset maximum allowable wear amount for each axis and the actual wear amount, classify the warning level; output the warning signal corresponding to the level of the main drive shaft and the redundant drive shaft according to the warning level.

[0007] Furthermore, in step S3, obtaining the actual wear amount of each shaft specifically includes: Collect the motor winding temperature and ambient temperature of the main drive shaft and redundant drive shaft; The equivalent temperature of each shaft is calculated based on the motor winding temperature, ambient temperature, and preset temperature rise correction coefficient. The equivalent temperature increases with the increase of the motor winding temperature and the temperature difference between the motor winding temperature and the ambient temperature. The thermal expansion compensation amount of each axis is calculated based on the difference between the equivalent temperature of each axis and the preset reference temperature, and in combination with the thermal expansion reference coefficient. The thermal expansion compensation amount increases as the difference increases. Subtract the corresponding thermal expansion compensation from the rough estimate of wear on each shaft to obtain the actual wear amount of each shaft.

[0008] Furthermore, the calculation of the initial total piston stroke specifically includes: controlling the main drive shaft and the redundant drive shaft to retract to the mechanical limit, and recording the corresponding absolute rotation angle position as the mechanical reference zero rotation angle; The main drive shaft and redundant drive shaft are driven synchronously forward with a preset low current, and the rotation angle corresponding to the detected current change point is determined as the initial contact point rotation angle of each shaft. Based on the angle difference between the initial contact point angle of each axis and the zero position angle of the mechanical reference, and in conjunction with the lead screw coefficient, calculate the initial total piston stroke corresponding to each axis.

[0009] Furthermore, the calculation of the rough estimate of wear specifically includes: During each braking process, the motor rotation angle and motor current of the main drive shaft and the redundant drive shaft are collected synchronously; The current contact point rotation angle of the main drive shaft and the redundant drive shaft is determined according to the motor current change rate threshold. Take the average value of the current contact points between the main drive shaft and the redundant drive shaft as the current effective contact point, and determine the rotation angle of the current effective contact point; Based on the angle difference between the current effective contact point angle and the initial contact point angle of the main drive shaft, and combined with the lead screw coefficient, a rough estimate of the wear of the main drive shaft is calculated. Based on the angle difference between the current effective contact point angle and the initial contact point angle of the redundant drive shaft, and combined with the lead screw coefficient, a rough estimate of the wear of the redundant drive shaft is calculated.

[0010] Furthermore, the determination of the comprehensive support stiffness specifically includes: Based on the actual wear of each shaft, the system reference stiffness, and the initial total piston stroke, the comprehensive support stiffness of each shaft at the current braking moment is calculated. The comprehensive support stiffness of each shaft is related to the system reference stiffness and the initial total piston stroke, and decreases as the actual wear increases.

[0011] Furthermore, the determination of the compensated target journey specifically includes: Based on the target clamping force, comprehensive support stiffness, actual wear amount, and thermal expansion compensation amount of each axis, calculate the target stroke of each axis after compensation at the current braking moment. The drive motors of the main drive shaft and the redundant drive shaft are controlled to run synchronously to the compensated target stroke, so that the actual clamping force of each shaft is determined by the comprehensive support stiffness and the difference between the compensated target stroke, the actual wear amount and the thermal expansion compensation amount.

[0012] Furthermore, determining the wear difference between the two shafts specifically involves: Calculate the wear amount of the main drive shaft and the wear amount of the redundant drive shaft separately. The wear amount of the main drive shaft is the difference between the current contact point angle and the initial contact point angle of the main drive shaft multiplied by the lead screw lead coefficient. The wear amount of the redundant drive shaft is the difference between the current contact point and the initial contact point of the redundant drive shaft multiplied by the lead screw lead coefficient. Calculate the wear difference between the two shafts, i.e., the uneven wear amount. The wear condition is determined, and the dual-axis torque distribution is adjusted for active balancing control. Specifically, when the wear amount exceeds the preset wear threshold, it is determined to be a wear condition; the dual-axis torque distribution coefficient is adjusted to reduce the torque of the motor on the severely worn side and increase the torque of the motor on the other side, so that the wear rate on both sides tends to be consistent.

[0013] Furthermore, the wear amount is determined based on the angle difference between the current contact point angle of the main drive shaft and its initial contact point angle, the angle difference between the current contact point angle of the redundant drive shaft and its initial contact point angle, and the lead screw coefficient. The torque distribution coefficient of the main drive shaft and the redundant drive shaft is adjusted according to the ratio of the wear amount to the preset maximum allowable wear amount. The larger the wear amount, the smaller the torque distribution coefficient on the side with more severe wear, and the larger the torque distribution coefficient on the other side.

[0014] Furthermore, the step of dividing the warning levels based on the preset maximum allowable wear amount corresponding to each axis and the actual wear amount, and outputting different levels of warning signals according to the warning levels, specifically includes: setting the maximum allowable wear amount for each axis; outputting a level one warning signal when the actual wear amount reaches a first preset proportion of the maximum allowable wear amount; outputting a level two warning signal when the actual wear amount reaches a second preset proportion of the maximum allowable wear amount; and outputting a level three warning signal when the actual wear amount reaches a third preset proportion of the maximum allowable wear amount, or when the wear deviation exceeds the maximum allowable wear deviation.

[0015] Compared with existing technologies, the advantages of this invention are as follows: It addresses the technical shortcomings of existing dual-axis EMB systems, such as large wear estimation errors, clamping force decay with wear, inability to actively correct dual-axis wear imbalances, and imperfect early warning mechanisms. Through multi-technology collaborative innovation, significant results are achieved: A triple architecture combining current-sudden-change contact point identification, dual-temperature coupled thermal compensation, and initial benchmark self-calibration is adopted, eliminating the need for additional sensors and effectively eliminating temperature thermal deformation and assembly discreteness errors, thus reducing wear estimation errors. Based on dynamic comprehensive support stiffness iteration and multi-parameter coupled stroke compensation, wear and temperature effects are corrected in real time, reducing clamping force control errors and ensuring braking consistency and driving safety. Through quantitative detection of wear imbalance and adaptive torque distribution, wear aggravation is suppressed under the premise of constant total braking torque, extending the overall service life of the friction pads. A dual-dimensional, three-level early warning system is constructed for each axis, independently determining the dual-axis status, covering normal wear and wear imbalance faults, and achieving layered alarms and proactive preventative maintenance. This solution is entirely based on existing EMB hardware architecture, with low algorithm computation and low modification costs, making it suitable for large-scale mass production applications. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall method flow of the present invention; Figure 2 This is a graph showing the actual wear and uneven wear data in an embodiment 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 The present invention provides a technical solution: A biaxial EMB friction pad wear adaptive early warning and control method, the specific steps of which include: S1: Retract the main drive shaft and redundant drive shaft to the mechanical limit and record it as the mechanical reference zero position. Drive the dual shafts synchronously forward with a preset low current. Determine the current change point as the initial contact point angle of the new friction plate of each shaft. Calculate the initial total piston stroke based on the lead screw coefficient. At the same time, calibrate the system reference stiffness and thermal expansion reference coefficient. In this embodiment, 10 sets of continuous braking conditions of the dual-axis EMB system were selected to carry out a dual-axis EMB friction pad wear simulation experiment; firstly, the calculation of the initial total piston stroke specifically includes: controlling the main drive shaft and the redundant drive shaft to retract to the mechanical limit, and recording the corresponding absolute rotation angle position as the mechanical reference zero rotation angle; The main drive shaft and redundant drive shaft are driven synchronously forward with a preset low current, and the rotation angle corresponding to the detected current change point is determined as the initial contact point rotation angle of each shaft. Based on the angle difference between the initial contact point angle and the mechanical reference zero-position angle of each axis, and in conjunction with the lead screw coefficient, the initial total piston stroke for each axis is calculated. The specific calculation formula is as follows: in, This represents the initial total piston stroke. The lead coefficient of the leadscrew. Initial contact point angle, This is the zero-position rotation angle of the mechanical reference. In this embodiment... Under the same angle difference, Increasing the initial piston stroke linearly increasing, Increased contact point feed distance: The angle difference becomes larger. Increase synchronously; Increase: The angle difference decreases. Consequently, it decreases; the design logic of this formula: the EMB system uses a motor and ball screw drive, which is a purely mechanical physical relationship of converting rotary motion into linear motion; the piston stroke is linearly proportional to the motor rotation angle, therefore, a linear modeling method using the lead coefficient multiplied by the rotation angle difference is adopted, which perfectly fits the ball screw drive mechanism. In this embodiment, the motor current is collected in real time, and the inflection point of the current change is determined as the initial contact point of the new friction plate, and the spindle is recorded. Redundant shafts Based on experimental calibration, the initial stroke of the main drive shaft is 0.64 mm and the initial stroke of the redundant drive shaft is 0.636 mm. This eliminates manual calibration errors, adapts to minor differences in dual-axis assembly, and provides an absolute benchmark for all calculations under the subsequent 10 working conditions.

[0020] This step achieves dual-axis synchronous self-calibration, eliminating the need for manual offline calibration of the mechanical zero position and the initial contact point of the friction plate; it utilizes the sudden change characteristics of motor current to adaptively identify the critical point of new friction plate contact, rather than the traditional fixed position threshold judgment; and it simultaneously calibrates the three basic reference parameters of screw drive, structural stiffness, and thermal expansion in one go.

[0021] S2: During braking, the drive motor rotation angle and motor current of each axis are collected synchronously. The current contact point rotation angle of each axis is determined by the current change rate threshold. Based on the lead screw coefficient, the current contact point rotation angle and the initial contact point rotation angle of each axis, the rough estimate of wear of each axis is calculated. In this embodiment, the calculation of the rough estimate of wear specifically includes: During each braking process, the motor rotation angle and motor current of the main drive shaft and the redundant drive shaft are collected synchronously; The current contact point rotation angle of the main drive shaft and the redundant drive shaft is determined according to the motor current change rate threshold. Take the average value of the current contact points between the main drive shaft and the redundant drive shaft as the current effective contact point, and determine the rotation angle of the current effective contact point; Based on the angle difference between the current effective contact point angle and the initial contact point angle of the main drive shaft, and combined with the lead screw coefficient, a rough estimate of the wear of the main drive shaft is calculated. Based on the angle difference between the current effective contact point angle and the initial contact point angle of the redundant drive shaft, and combined with the lead screw coefficient, a rough estimate of the wear of the redundant drive shaft is calculated; the specific formula is as follows: in, At the current braking moment, for The current contact point rotation angle of the main drive shaft at any given moment. for The current contact point rotation angle of the redundant drive shaft at all times. The initial contact point rotation angle of the main drive shaft. Initial contact point rotation angle of redundant drive shafts for Rough estimate of wear on the main drive shaft at any given time. for Rough estimate of wear on the redundant drive shaft. The lead coefficient of the lead screw. After the friction plate wears, the piston needs to feed a larger stroke to fit the brake disc, which is reflected in the motor as the contact point angle gradually increases; the wear amount is essentially the difference in stroke between the current contact point and the initial contact point. The linear model of lead screw angle and stroke is used, which is consistent with the physical mechanism of S1. The model is unified and the algorithm has strong reusability. A unified transmission ratio ensures that the physical dimension of wear is length. Wear is essentially the offset of the contact point angle; only the difference between two sets of angles can characterize the wear displacement. Separate independent formulas are used for both shafts to adapt to independent wear conditions and uneven wear scenarios; single-shaft models cannot be used as substitutes. The larger the current contact point angle, the larger the angle difference, and the larger the rough estimate of wear; conversely, an overly large initial contact point angle calibration will result in an underestimation of the calculated wear. This embodiment selects 10 sets of continuous braking conditions to conduct a dual-shaft EMB friction pad wear simulation experiment. The original experimental input data is shown in Table 1 below. Table 1: Raw Data for Rough Wear Calculation This table contains the core raw data collected for 10 braking conditions of the dual-axis EMB system, along with the rough calculation results of axle wear in step S2. The data reveals the true pattern of progressive wear of the friction pads. The contact point angle of the dual axes continuously increases with the number of braking cycles, and the rough wear estimate increases monotonically in tandem. Furthermore, the wear rate of the main shaft is slightly higher than that of the redundant shaft, naturally resulting in a slight uneven wear trend. This table provides the basic input data for the axle wear in the subsequent S3 thermal expansion compensation step.

[0022] Traditional EMB systems often use fixed contact points without real-time updates. As the friction pads wear, the contact points shift, leading to severely distorted wear estimates. They rely on external displacement sensors for wear measurement, which are costly, difficult to install, and susceptible to vibration interference. Dual-axis independent estimation lacks synchronous data acquisition, resulting in poor foundational identification of uneven wear. This step, however, uses no additional sensors, leveraging the motor's native current and rotation angle signals for wear estimation, reducing costs and increasing reliability. The contact points are dynamically refreshed with each braking action, adapting to the progressive wear characteristics of the friction pads. Dual-axis synchronous sampling provides consistent data for subsequent S5 uneven wear difference calculations.

[0023] This step synchronously collects the dual-axis rotation angle and current in real time during the braking process, and dynamically identifies the real-time contact point for each braking based on the current change rate threshold; using the difference in rotation angle between the initial and current contact points, combined with the lead screw parameters, the coarse wear value is directly calculated, without the need for additional displacement sensors, and wear is estimated purely from electrical signals.

[0024] S3: Collect the motor winding temperature and ambient temperature of each axis, estimate the equivalent temperature, calculate the thermal expansion compensation based on the thermal expansion reference coefficient and equivalent temperature, perform thermal expansion compensation on the rough estimate of wear for each axis, and obtain the actual wear of each axis. Obtaining the actual wear of each axis specifically includes: collecting the motor winding temperature and ambient temperature of the main drive shaft and redundant drive shaft; The equivalent temperature of each shaft is calculated based on the motor winding temperature, ambient temperature, and preset temperature rise correction coefficient. The equivalent temperature increases with the increase of the motor winding temperature and the temperature difference between the motor winding temperature and the ambient temperature. The thermal expansion compensation amount of each axis is calculated based on the difference between the equivalent temperature of each axis and the preset reference temperature, and in combination with the thermal expansion reference coefficient. The thermal expansion compensation amount increases as the difference increases. The actual wear of each shaft is obtained by subtracting the corresponding thermal expansion compensation from the rough estimate of wear for each shaft; the specific calculation formulas involved are as follows: in, At the current braking moment, for The equivalent temperature at any given moment. for The motor winding temperature at any given time. for The ambient temperature at any given time To preset the temperature rise correction factor, For preset reference temperature, The coefficient of thermal expansion is the reference coefficient. for Thermal expansion displacement at any given moment for Rough estimate of wear and tear over time. for The actual wear and tear at any given moment. In this embodiment... , , This formula design considers the motor windings as the main heat source and the ambient temperature as the heat dissipation boundary. The weighted coupling model more closely matches the actual thermal field distribution and is more accurate than a single temperature point model. The thermal deformation of solid materials is linearly related to the temperature difference. Using the classic linear thermal deformation formula of the coefficient of thermal expansion multiplied by the temperature difference, thermal expansion causes the piston to extend further, which may be misjudged as wear. Therefore, subtracting the thermal expansion from the rough wear amount restores the true wear. Increased winding temperature leads to an increase in the equivalent temperature, increasing the thermal expansion displacement and thus underestimating the actual wear amount. Conversely, decreased ambient temperature increases the temperature difference, increasing the thermal expansion and also underestimating the actual wear amount. This embodiment uses temperature parameters to perform thermal expansion compensation, solves for the true wear amount of the two shafts, and determines the warning level. The results are shown in Table 2 below. Table 2: Thermal Compensation and Actual Wear This table presents the core calculation results for S3 thermal compensation and S6 axle-by-axle warning, and is for reference only. Figure 2 The actual wear and uneven wear of the dual shafts are visualized. Data shows that with increasing braking frequency, the motor winding temperature gradually rises from 30℃ to 65℃, and the thermal expansion increases synchronously from 0.0081mm to 0.0545mm. The actual wear, after thermal compensation correction, is significantly lower than the coarse estimate, effectively eliminating the artificially inflated wear caused by temperature interference. The spindle wear reaches 0.0795mm in operating condition number 10, exceeding the first-level warning threshold of 0.075mm, triggering a first-level warning. The redundant shaft's wear is consistently below the warning threshold, resulting in no warning output. Data shows that with increasing braking frequency, the motor winding temperature gradually rises, and the thermal expansion increases synchronously. The actual wear, after thermal compensation correction, is significantly lower than the coarse estimate, effectively eliminating the artificially inflated wear caused by temperature interference.

[0025] This step integrates the motor winding temperature and ambient temperature to construct an equivalent temperature, considering the influence of temperature rise gradient; it introduces a thermal expansion reference coefficient to quantitatively calculate structural thermal deformation; and it subtracts thermal expansion errors from the coarse wear value to obtain the true wear amount free from temperature interference. Traditional wear estimation does not consider braking heat generation and ambient temperature changes, and the thermal expansion of the motor, lead screw, and brake caliper may be misjudged as friction plate wear, resulting in inflated estimates; it only uses simple single-point temperature compensation, without distinguishing between winding temperature rise and ambient temperature difference, resulting in low compensation accuracy. This step establishes a dual-temperature coupled equivalent temperature model that closely matches the actual temperature rise distribution of the EMB; it quantitatively offsets the false increase in wear caused by structural thermal expansion, significantly improving the accuracy of wear estimation; and it maintains estimation accuracy under all operating conditions, both high and low temperatures.

[0026] S4: Calculate the comprehensive support stiffness based on the actual wear of each axis and the system reference stiffness. Calculate the compensated target stroke based on the given target clamping force of each axis and the comprehensive support stiffness. The drive motors of the main drive shaft and the redundant drive shaft run synchronously to compensate the target stroke, thus completing the adaptive compensation control of the clamping force. The determination of the comprehensive support stiffness specifically includes: calculating the comprehensive support stiffness of each shaft at the current braking moment based on the actual wear amount of each shaft, the system reference stiffness, and the initial total piston stroke. The comprehensive support stiffness of each shaft is related to the system reference stiffness and the initial total piston stroke, and decreases as the actual wear amount increases.

[0027] In this embodiment, the formula for calculating the overall support stiffness of each shaft is as follows: in, for The overall support stiffness at any given time. For the system's reference stiffness, This represents the initial total piston stroke. for The actual wear at any given moment. The greater the wear of the friction pads, the longer the equivalent support length, and the lower the system stiffness. The attenuation model of multiplying the reference stiffness by the initial stroke / current total stroke is adopted, which conforms to the mechanical law that the stiffness of the elastic support decreases with the increase of length. Based on the target clamping force of each shaft, the comprehensive support stiffness, the actual wear, and the thermal expansion compensation, the compensated target stroke of each shaft at the current braking moment is calculated. In this embodiment, the specific formula for calculating the compensated target travel distance is as follows: in, for The target journey after time-compensation. for The target clamping force at all times, for The overall support stiffness at any given time. The thermal expansion compensation amount is used to control the drive motors of the main drive shaft and redundant drive shafts to run synchronously to the compensated target stroke, so that the actual clamping force of each shaft is determined by the comprehensive support stiffness and the difference between the compensated target stroke, the actual wear amount, and the thermal expansion compensation amount. In this embodiment, the output of each shaft... Actual clamping force at any moment The calculation formula is as follows: in, for The actual clamping force at any given moment. The design logic of this formula is: substituting Hooke's law in reverse, subtracting wear and thermal deformation displacement, to obtain the actual braking clamping force.

[0028] In this embodiment, The system retrieves the reference stiffness and initial piston stroke of the S1 system, and retrieves the actual wear amount output by the S3 system. It then substitutes these values ​​into the formula to calculate the comprehensive support stiffness at the current moment. Based on the target clamping force issued by the vehicle controller, it calculates the compensated target stroke by combining stiffness, actual wear amount, and thermal expansion amount. It controls the main and redundant drive shaft motors to feed synchronously to the target stroke. It then substitutes these values ​​into the formula to calculate the actual output clamping force in real time, forming a closed-loop monitoring system.

[0029] This step dynamically iterates the overall support stiffness based on actual wear, considering the stiffness decay law of the system after friction pad wear; it combines the target clamping force, stiffness, wear amount, and thermal deformation to jointly solve the compensation stroke; achieving adaptive closed-loop control of clamping force under the dual factors of wear and temperature. Traditional EMB uses fixed support stiffness, ignoring the softening of structural stiffness caused by friction pad wear, resulting in continuous decay of clamping force under the same stroke; it only performs simple stroke compensation, without coupling thermal deformation and stiffness changes, leading to poor consistency of braking clamping force and longer braking distance. In this step, the stiffness decays and updates in real time with wear, closely matching actual mechanical characteristics; multi-parameter coupled calculation of the target compensation stroke accurately offsets the clamping force loss caused by wear and temperature; dual-axis synchronous stroke control ensures balanced braking output of both axes.

[0030] S5: Based on the difference between the current contact point rotation angle and the corresponding initial contact point rotation angle of each axis, determine the wear difference between the two axes, judge the uneven wear state, and adjust the torque distribution of the two axes for active balancing control. In this embodiment, determining the wear difference between the two shafts specifically involves: calculating the wear amount of the main drive shaft and the wear amount of the redundant drive shaft respectively. The wear amount of the main drive shaft is the difference between the current contact point angle and the initial contact point angle of the main drive shaft multiplied by the lead screw lead coefficient. The wear amount of the redundant drive shaft is the difference between the current contact point and the initial contact point of the redundant drive shaft multiplied by the lead screw lead coefficient. The wear difference between the two shafts, i.e., the amount of uneven wear, is calculated. The uneven wear state is determined, and the torque distribution of the two shafts is adjusted for active balancing control. Specifically, when the uneven wear amount exceeds a preset uneven wear threshold, it is determined to be an uneven wear state. The torque distribution coefficient of the two shafts is adjusted to reduce the torque of the motor on the severely worn side and increase the torque of the motor on the other side, so that the wear rate on both sides tends to be consistent.

[0031] The wear amount is determined based on the angle difference between the current contact point angle of the main drive shaft and its initial contact point angle, the angle difference between the current contact point angle of the redundant drive shaft and its initial contact point angle, and the lead screw coefficient. The torque distribution coefficient of the main drive shaft and the redundant drive shaft is adjusted according to the ratio of the wear amount to the preset maximum allowable wear amount. The larger the wear amount, the smaller the torque distribution coefficient on the side with more severe wear, and the larger the torque distribution coefficient on the other side.

[0032] In this embodiment, the formula for calculating the wear amount is: in, for The amount of wear at any given moment. The lead coefficient of the leadscrew. for The current contact point rotation angle of the main drive shaft at any given moment. for The current contact point rotation angle of the redundant drive shaft at all times. The initial contact point rotation angle of the main drive shaft. The initial contact point rotation angle of the drive shaft is given; this formula takes the absolute difference in wear between the two shafts, which intuitively represents the degree of uneven wear on both sides, and has a clear physical meaning; the adjustment method of the torque distribution coefficient is as follows: in, The torque distribution coefficient of the main drive shaft. This is the torque distribution factor for the redundant drive shaft. This represents the maximum permissible amount of uneven wear. In this embodiment... It adopts a linear normalization design, where the greater the wear deviation, the lower the coefficient on the side with severe wear, and the other side automatically compensates, while also meeting the following requirements. The total braking torque remains unchanged, only internal distribution is made, and it does not affect the total braking output of the vehicle. The side with greater wear should have a distribution coefficient less than 1 to reduce its wear rate; the side with less wear should have a distribution coefficient greater than 1 to balance wear. The formula cleverly uses uneven wear as a penalty term, subtracting or adding to the mean value of 1. The closer to the mean value... The larger the adjustment range, the better. This embodiment completes the comprehensive stiffness update, clamping force adaptive control, and wear-balanced active balancing calculation. The results are shown in Table 3 below: Table 3: Control and Equilibrium Results This table covers the full-dimensional calculation results of S4 clamping force adaptive control and S5 wear-balanced active balancing. Data shows that as wear increases, the system's overall support stiffness monotonically decreases from 8474.84 N / mm to 7709.45 N / mm, while the compensated target stroke increases synchronously from 0.3640 mm to 1.1168 mm. The actual clamping force precisely follows the target clamping force, with a maximum error of only 0.28%, effectively offsetting the braking force loss caused by wear and stiffness reduction. Simultaneously, the wear-balanced amount gradually increases from 0.004 mm to 0.064 mm, the spindle torque coefficient adaptively decreases from 0.9950 to 0.9200, the redundant shaft torque coefficient increases synchronously, and the total braking torque remains unchanged, effectively suppressing the aggravation of wear-balanced factors. This table includes the overall support stiffness, compensated target stroke, actual clamping force, wear-balanced amount, and dual-axis torque distribution coefficient. The data shows that the overall stiffness decreases continuously with wear, while the compensation stroke increases synchronously. The actual clamping force accurately follows the target clamping force, with the error controlled within 0.3%. As the amount of uneven wear gradually increases, the torque distribution coefficient is adaptively adjusted, and the total braking torque remains unchanged, effectively suppressing the aggravation of uneven wear.

[0033] This step quantitatively calculates the amount of uneven wear by measuring the difference in wear between the two axles, sets a threshold to determine the uneven wear state, and designs an adaptive torque distribution coefficient to automatically reduce the torque on the severely worn side and increase the torque on the other side, achieving active wear balancing and suppressing the aggravation of uneven wear. Traditional dual-axle EMB uses fixed torque distribution, which cannot adapt to the aggravation of uneven wear; it lacks quantitative uneven wear calculation and can only passively alarm after a fault, which can easily lead to brake deviation and rapid wear and tear on one side of the friction pads; while this solution quantitatively quantifies the degree of uneven wear, realizing the measurement, judgment and control of uneven wear; the dynamic torque distribution adaptively balances the wear rate, extending the overall life of the friction pads; and it avoids uneven braking force on the left and right sides, improving the braking stability of the entire vehicle. S6: Based on the preset maximum allowable wear amount for each axis and the actual wear amount, classify the warning level; output the warning signal corresponding to the level of the main drive shaft and the redundant drive shaft according to the warning level.

[0034] In this embodiment, the step of dividing the warning level based on the preset maximum allowable wear amount corresponding to each axis and the actual wear amount, and outputting different levels of warning signals according to the warning level, specifically includes: setting the maximum allowable wear amount for each axis; outputting a level one warning signal when the actual wear amount reaches a first preset proportion of the maximum allowable wear amount; outputting a level two warning signal when the actual wear amount reaches a second preset proportion of the maximum allowable wear amount; and outputting a level three warning signal when the actual wear amount reaches a third preset proportion of the maximum allowable wear amount, or when the wear deviation exceeds the maximum allowable wear deviation.

[0035] Specifically, in this embodiment, the maximum permissible wear for both axes is... The first-level warning ratio is defined as actual wear and tear ≥ 5%. The first-level warning ratio is defined as actual wear and tear ≥ 8%. The first-level warning ratio is defined as actual wear and tear ≥ 10%. Or wear amount ≥ The system outputs warning signals according to the following rules: when the actual wear of a single axis is ≥0.075mm and <0.120mm, a first-level warning signal is output; when the actual wear of a single axis is ≥0.120mm and <0.150mm, a second-level warning signal is output; and when the actual wear of a single axis is ≥0.150mm or the wear deviation is ≥0.4mm, a third-level warning signal is output.

[0036] In this embodiment, the main shaft triggers a level 1 warning under operating condition 10, the redundant shaft has no warning throughout the process, and the wear amount does not reach the level 3 warning threshold. Therefore, the system finally outputs a "main drive shaft level 1 warning" signal to the vehicle controller.

[0037] This solution divides warning levels into three levels based on both the actual wear percentage and uneven wear amount. It outputs warning signals in layers according to wear degree and uneven wear fault, achieving progressive wear alerts and uneven wear fault alarms. Traditional solutions only set a single wear limit alarm, lacking tiered warnings and dedicated uneven wear alarms; they cannot provide early maintenance reminders, only allowing for direct shutdown after wear exceeds limits, resulting in a poor user experience and reactive maintenance. This solution achieves early warning, moderate warning, and acute fault alerts through a three-level tiered warning system; it also considers both normal wear exceeding limits and uneven wear faults, covering all failure modes; facilitating the development of tiered maintenance strategies for the entire vehicle.

[0038] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0039] 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.

[0040] 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.

[0041] 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 dual-axis EMB friction pad wear adaptive early warning and control method, applied to a dual-axis electromechanical braking system including a main drive shaft and a redundant drive shaft, characterized in that, include: S1: Retract the main drive shaft and redundant drive shaft to the mechanical limit and record it as the mechanical reference zero position. Drive the dual shafts synchronously forward with a preset low current. Determine the current change point as the initial contact point angle of the new friction plate of each shaft. Calculate the initial total piston stroke based on the lead screw coefficient. At the same time, calibrate the system reference stiffness and thermal expansion reference coefficient. S2: During braking, the drive motor rotation angle and motor current of each axis are collected synchronously. The current contact point rotation angle of each axis is determined by the current change rate threshold. Based on the lead screw coefficient, the current contact point rotation angle and the initial contact point rotation angle of each axis, the rough estimate of wear of each axis is calculated. S3: Collect the motor winding temperature and ambient temperature of each axis, estimate the equivalent temperature, calculate the thermal expansion compensation based on the thermal expansion reference coefficient and equivalent temperature, perform thermal expansion compensation on the rough estimate of wear for each axis, and obtain the actual wear of each axis. S4: Calculate the comprehensive support stiffness based on the actual wear of each axis and the system reference stiffness. Calculate the compensated target stroke based on the given target clamping force of each axis and the comprehensive support stiffness. The drive motors of the main drive shaft and the redundant drive shaft run synchronously to compensate the target stroke, thus completing the adaptive compensation control of the clamping force. S5: Based on the difference between the current contact point rotation angle and the corresponding initial contact point rotation angle of each axis, determine the wear difference between the two axes, judge the uneven wear state, and adjust the torque distribution of the two axes for active balancing control. S6: Based on the preset maximum allowable wear amount for each axis and the actual wear amount, classify the warning level; Based on the warning level, output the corresponding warning signal for the main drive shaft and redundant drive shaft.

2. The biaxial EMB friction plate wear adaptive early warning and control method according to claim 1, characterized in that: In step S3, obtaining the actual wear amount of each shaft specifically includes: Collect the motor winding temperature and ambient temperature of the main drive shaft and redundant drive shaft; The equivalent temperature of each shaft is calculated based on the motor winding temperature, ambient temperature, and preset temperature rise correction coefficient. The equivalent temperature increases with the increase of the motor winding temperature and the temperature difference between the motor winding temperature and the ambient temperature. The thermal expansion compensation amount of each axis is calculated based on the difference between the equivalent temperature of each axis and the preset reference temperature, and in combination with the thermal expansion reference coefficient. The thermal expansion compensation amount increases as the difference increases. Subtract the corresponding thermal expansion compensation from the rough estimate of wear on each shaft to obtain the actual wear amount of each shaft.

3. The biaxial EMB friction plate wear adaptive early warning and control method according to claim 2, characterized in that: The calculation of the initial total piston stroke specifically includes: controlling the main drive shaft and redundant drive shaft to retract to the mechanical limit, and recording the corresponding absolute rotation angle position as the mechanical reference zero rotation angle; The main drive shaft and redundant drive shaft are driven synchronously forward with a preset low current, and the rotation angle corresponding to the detected current change point is determined as the initial contact point rotation angle of each shaft. Based on the angle difference between the initial contact point angle of each axis and the zero position angle of the mechanical reference, and in conjunction with the lead screw coefficient, calculate the initial total piston stroke corresponding to each axis.

4. The biaxial EMB friction plate wear adaptive early warning and control method according to claim 2, characterized in that: The calculation of the rough wear estimate specifically includes: During each braking process, the motor rotation angle and motor current of the main drive shaft and the redundant drive shaft are collected synchronously; The current contact point rotation angle of the main drive shaft and the redundant drive shaft is determined according to the motor current change rate threshold. Take the average value of the current contact points between the main drive shaft and the redundant drive shaft as the current effective contact point, and determine the rotation angle of the current effective contact point; Based on the angle difference between the current effective contact point angle and the initial contact point angle of the main drive shaft, and combined with the lead screw coefficient, a rough estimate of the wear of the main drive shaft is calculated. Based on the angle difference between the current effective contact point angle and the initial contact point angle of the redundant drive shaft, and combined with the lead screw coefficient, a rough estimate of the wear of the redundant drive shaft is calculated.

5. The biaxial EMB friction plate wear adaptive early warning and control method according to claim 3 or 4, characterized in that: The determination of the overall support stiffness specifically includes: Based on the actual wear of each shaft, the system reference stiffness, and the initial total piston stroke, the comprehensive support stiffness of each shaft at the current braking moment is calculated. The comprehensive support stiffness of each shaft is related to the system reference stiffness and the initial total piston stroke, and decreases as the actual wear increases.

6. The biaxial EMB friction plate wear adaptive early warning and control method according to claim 5, characterized in that: The determination of the compensated target trip specifically includes: Based on the target clamping force, comprehensive support stiffness, actual wear amount, and thermal expansion compensation amount of each axis, calculate the target stroke of each axis after compensation at the current braking moment. The drive motors of the main drive shaft and the redundant drive shaft are controlled to run synchronously to the compensated target stroke, so that the actual clamping force of each shaft is determined by the comprehensive support stiffness and the difference between the compensated target stroke, the actual wear amount and the thermal expansion compensation amount.

7. The biaxial EMB friction plate wear adaptive early warning and control method according to claim 1, characterized in that: The determination of the wear difference between the two shafts specifically involves: Calculate the wear amount of the main drive shaft and the wear amount of the redundant drive shaft separately. The wear amount of the main drive shaft is the difference between the current contact point angle and the initial contact point angle of the main drive shaft multiplied by the lead screw lead coefficient. The wear amount of the redundant drive shaft is the difference between the current contact point and the initial contact point of the redundant drive shaft multiplied by the lead screw lead coefficient. Calculate the wear difference between the two shafts, i.e., the uneven wear amount. The wear condition is determined, and the dual-axis torque distribution is adjusted for active balancing control. Specifically, when the wear amount exceeds the preset wear threshold, it is determined to be a wear condition; the dual-axis torque distribution coefficient is adjusted to reduce the torque of the motor on the severely worn side and increase the torque of the motor on the other side, so that the wear rate on both sides tends to be consistent.

8. The biaxial EMB friction plate wear adaptive early warning and control method according to claim 7, characterized in that: The wear amount is determined based on the angle difference between the current contact point angle of the main drive shaft and its initial contact point angle, the angle difference between the current contact point angle of the redundant drive shaft and its initial contact point angle, and the lead screw coefficient. The torque distribution coefficient of the main drive shaft and the redundant drive shaft is adjusted according to the ratio of the wear amount to the preset maximum allowable wear amount. The larger the wear amount, the smaller the torque distribution coefficient on the side with more severe wear, and the larger the torque distribution coefficient on the other side.

9. The biaxial EMB friction plate wear adaptive early warning and control method according to claim 5, characterized in that: The method involves classifying warning levels based on the preset maximum allowable wear amount for each axis and the actual wear amount, and outputting different levels of warning signals according to the warning levels. Specifically, this includes: setting the maximum allowable wear amount for each axis; outputting a level one warning signal when the actual wear amount reaches a first preset proportion of the maximum allowable wear amount; outputting a level two warning signal when the actual wear amount reaches a second preset proportion of the maximum allowable wear amount; and outputting a level three warning signal when the actual wear amount reaches a third preset proportion of the maximum allowable wear amount, or when the wear deviation exceeds the maximum allowable wear deviation.

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