An EMB system active calibration method and device for improving braking accuracy

Abstract

The present application relates to the field of automotive braking technology, and more specifically to a method and device for actively calibrating an EMB system for improving braking accuracy. The method comprises: collecting the current and temperature of a brake motor winding, the temperature of a brake disc, and the vehicle's driving speed in real time; compensating the current current of the brake motor winding based on the current temperature change of the brake motor winding; determining a wear sensitivity factor for the current braking; determining the cumulative net angle of the current braking by comparing the difference between the clamping angle and the retraction angle of the current and previous braking events; obtaining a current temperature correction factor and a speed correction factor; determining the dynamic wear rate of the current braking based on the cumulative net angle; triggering active calibration of the EMB system using the wear sensitivity factor and the dynamic wear rate, determining a brake pad wear coefficient based on the wear sensitivity factor, and correcting the target angles of the left and right calipers. This improves the braking accuracy of the EMB system.

Description

Technical Field

[0001] The present application relates to the field of automobile braking technology, and in particular to an EMB system active calibration method and device for improving braking accuracy. Background Art

[0002] The Electromechanical Brake (EMB) system is a brake-by-wire technology that uses an electric motor to directly drive the brake caliper, replacing traditional hydraulic fluid with electrical energy. Its core architecture comprises a motor, transmission mechanism, sensors, and controller. By analyzing brake pedal signals and vehicle status in real time, it precisely controls the conversion of motor torque into friction pad clamping force. Unlike the mechanical lag of hydraulic brakes, the EMB system utilizes electrical signal transmission to achieve millisecond-level response and offers digital advantages such as brake energy recovery and intelligent brake energy distribution. It is a key technology for automotive and drive-by-wire chassis.

[0003] During long-term vehicle operation, brake disc wear, friction pad thermal degradation, and transmission component deformation can cause the initially calibrated brake clearance parameters to become invalid, leading to braking force deviation or response lag. Therefore, the EMB system needs to be calibrated. However, existing EMB system calibration methods suffer from calibration lag, making it impossible to automatically trigger and achieve active calibration. Furthermore, during the calibration process, only the average brake clearance is calibrated, resulting in insufficient braking force on one side of the vehicle and low calibration accuracy. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide an EMB system active calibration method and device for improving braking accuracy. The technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of the present application provides an EMB system active calibration method for improving braking accuracy, the method comprising the following steps:

[0006] respectively collecting the current and temperature of the brake motor windings in the car, and collecting the temperature of the brake disc and the driving speed of the car in real time, wherein the brake motor includes the left front wheel motor and the right front wheel motor;

[0007] Based on the current temperature change of the brake motor winding, the current current of the brake motor winding is compensated; the compensated current is converted into a frequency domain and filtered to obtain a fifth harmonic current; and the wear sensitivity factor of the current brake is determined by using the amplitude difference and phase difference of the fifth harmonic current of the left front wheel motor and the right front wheel motor;

[0008] The cumulative net braking angle is determined by the difference between the clamping angle and the retraction angle of the current and previous braking events. The temperature correction factor is obtained by combining the difference between the current brake disc temperature and the preset reference temperature with the thermal expansion coefficient of the brake disc.

[0009] Based on the difference between the current vehicle speed and the preset critical speed, and in combination with the relationship between the driving speed and the amount of brake pad wear, a current speed correction coefficient is obtained; and the current dynamic brake wear rate is determined by combining the accumulated net turning angle, the temperature correction coefficient, and the speed correction coefficient.

[0010] The EMB system is actively calibrated by triggering the wear sensitivity factor and the dynamic wear rate, and the brake pad wear coefficient is determined based on the wear sensitivity factor to correct the left and right caliper target angles.

[0011] In one embodiment, compensating the current of the brake motor winding includes:

[0012] The difference between the current temperature of the brake motor winding and the preset reference temperature is calculated. The current compensated current of the brake motor winding is negatively correlated with the difference and the physical quantity of the brake motor winding that changes with temperature, and is positively correlated with the current current of the brake motor winding.

[0013] In one embodiment, determining the wear sensitivity factor includes:

[0014] The cosine value of the phase difference is calculated, and the wear sensitivity factor is the product of the cosine value and the amplitude difference.

[0015] In one embodiment, the cumulative net turning angle is calculated as follows:

[0016] Where Δθ sum is the cumulative net turning angle of the current braking, Δθ k is the difference between the clamping angle and the retraction angle of the kth braking before the current one, μ is the preset time weighting factor, N is the preset number of braking times before the current one, and k is the sequence number of braking times.

[0017] In one embodiment, determining the temperature correction coefficient includes:

[0018] The difference between the current brake disc temperature and the preset reference temperature is recorded as a first difference, and a multiplication result of the first difference and the thermal expansion coefficient corresponding to the brake disc is calculated. The temperature correction coefficient is positively correlated with the multiplication result.

[0019] In one embodiment, determining the speed correction coefficient includes:

[0020] The difference between the preset critical speed and the current driving speed of the vehicle is recorded as the second difference. The speed weight coefficient is preset using the relationship between the driving speed and the amount of brake pad wear. The speed correction coefficient is the product of the second difference and the speed weight coefficient.

[0021] In one embodiment, the dynamic wear rate is calculated as follows:

[0022] Where ω is the dynamic wear rate of the current brake, Δθ sum is the cumulative net turning angle of the current braking, K T is the current temperature correction coefficient, K v is the current speed correction coefficient, η is the conversion coefficient between the preset turning angle and the brake clearance, and Δθ0 is the initial net turning angle when the vehicle has no wear.

[0023] In one embodiment, triggering active calibration of the EMB system using the wear sensitivity factor and the dynamic wear rate includes:

[0024] If the absolute value of the wear sensitivity factor of the current braking is greater than a preset first threshold, or the dynamic wear rate of the current braking is greater than a preset second threshold, the EMB system is triggered to perform active calibration.

[0025] In one embodiment, the correcting the target angles of the left and right calipers includes:

[0026] The brake pad wear coefficient is the absolute value of the wear sensitivity factor. When the wear sensitivity factor is greater than 0, the left caliper is determined to be worn. When the wear sensitivity factor is less than 0, the right caliper is determined to be worn. When the left or right caliper is worn, the target turning angle of the left or right caliper is increased. Where Δθ b is the increase in the target rotation angle, Δg is the brake pad wear coefficient, P is the screw lead, and π is pi.

[0027] In a second aspect, an embodiment of the present application also provides an active calibration device for an EMB system for improving braking accuracy, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of any one of the above methods when executing the computer program.

[0028] This application has at least the following beneficial effects:

[0029] The present application collects the current and temperature of the brake motor windings in the car in real time, and collects the temperature of the brake disc in the car and the driving speed of the car in real time, wherein the brake motor includes a left front wheel motor and a right front wheel motor; based on the current temperature change of the brake motor winding, the current current of the brake motor winding is compensated; the problem of the current measurement value being artificially high due to the increase in motor winding resistance with increasing temperature, which affects the accuracy of subsequent harmonic current determination, is avoided; the compensated current is converted and filtered in the frequency domain to obtain the fifth harmonic current; the wear sensitivity factor of the current brake is determined by using the amplitude difference and phase difference of the fifth harmonic current of the left front wheel motor and the right front wheel motor; the wear sensitivity factor realizes high-precision detection, direction discrimination and quantitative evaluation of unilateral wear of the vehicle brake by fusing the amplitude difference and phase difference of the harmonic current, providing a key basis for active calibration of the EMB system and improving the braking accuracy and reliability of the EMB system; the current brake is determined by the difference between the clamping angle and the retraction angle of the current and previous multiple brakes. The invention relates to a method for determining the dynamic wear rate of a vehicle by combining the accumulated net turning angle, the temperature correction coefficient and the speed correction coefficient. The method further comprises the following steps: first, determining the dynamic wear rate of the vehicle by combining the accumulated net turning angle, the temperature correction coefficient and the speed correction coefficient. The method further comprises the following steps: first, determining the dynamic wear rate of the vehicle by combining the accumulated net turning angle, the temperature correction coefficient and the speed correction coefficient. The dynamic wear rate takes into account the influence of different working conditions of temperature and vehicle speed on the wear of the brake pad, and correcting the wear rate by using the brake disc temperature and vehicle speed, thereby improving the accuracy and reliability of determining the brake wear condition of the vehicle. The active calibration of the EMB system is triggered by the wear sensitive factor and the dynamic wear rate, thereby overcoming the defect that the traditional EMB system calibration method cannot be actively calibrated. The brake pad wear coefficient is determined based on the wear sensitive factor, and the target turning angle of the left and right calipers is corrected. By calibrating the left and right calipers respectively, the calibration accuracy of the EMB system is improved, thereby improving the braking accuracy of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0031] Figure 1 A flowchart of a method for actively calibrating an EMB system to improve braking accuracy provided by one embodiment of the present application;

[0032] Figure 2 This is a flow chart of the relationship between the caliper target angle correction indicators. DETAILED DESCRIPTION

[0033] To further illustrate the technical means and effectiveness of this application's objectives, the following, in conjunction with the accompanying drawings and preferred embodiments, details the implementation, structure, features, and effectiveness of an active calibration method and device for an EMB system for improving braking accuracy, as proposed in this application. In the following description, references to "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0034] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0035] The following describes in detail a specific solution of an EMB system active calibration method and device for improving braking accuracy provided by the present application with reference to the accompanying drawings.

[0036] See also Figure 1 , which shows a flowchart of a method for active calibration of an EMB system for improving braking accuracy provided by an embodiment of the present application, the method comprising the following steps:

[0037] S1, respectively collecting the current and temperature of the brake motor winding in the car, and collecting the temperature of the brake disc in the car and the driving speed of the car in real time, wherein the brake motor includes the left front wheel motor and the right front wheel motor.

[0038] The EMB system achieves braking control through electrical signals. When the brake pedal is depressed, the travel sensor collects the pedal travel signal in real time. After analysis, the controller drives the motor to rotate, and converts the rotational motion into linear motion of the caliper through the screw-nut transmission mechanism, so that the brake pad, that is, the brake pad clamps the brake disc to generate braking force.

[0039] In this embodiment, a current sensor is installed in the conductive circuit of the brake motor winding to collect the line current of the left front wheel motor and the right front wheel motor in real time. At the same time, a temperature sensor is used to collect the temperature of the left and right motor windings in real time, the temperature of the brake disc in real time, and the vehicle speed sensor is used to collect the vehicle's driving speed in real time.

[0040] It should be noted that, in this embodiment, all data collected in real time are collected synchronously, and the collection frequency is 10 kHz. The implementer can set it according to the actual situation, and this embodiment does not impose any restrictions here.

[0041] S2, based on the current temperature change of the brake motor winding, compensates the current current of the brake motor winding; performs frequency domain conversion and filtering on the compensated current to obtain the fifth harmonic current; uses the amplitude difference and phase difference of the fifth harmonic current of the left front wheel motor and the right front wheel motor to determine the current brake wear sensitivity factor.

[0042] The resistance of the motor-driven caliper clamping during EMB braking directly reflects the contact state between the brake pad and the brake disc. As the brake pad wears and becomes thinner, the motor must rotate further to compensate for the brake clearance. At the same time, due to changes in contact area and pressure distribution, the load torque increases, leading to an increase in the effective value of the circuit current. Unilateral wear can cause an imbalance in the resistance between the left and right calipers. For example, if the left caliper is more severely worn, it requires additional torque to overcome the larger brake clearance. The peak current of the left front wheel motor circuit will be higher than that of the right front wheel motor circuit, and the current waveform will exhibit a phase difference during the clamping phase. Therefore, this embodiment extracts wear characteristics from the brake motor circuit current signal.

[0043] In actual operating conditions, the brake motor's line current is susceptible to temperature drift (i.e., changes in winding resistance with temperature), electromagnetic noise, and mechanical vibration (i.e., fluctuations in caliper friction), leading to current signal distortion. These interferences can obscure the unilateral wear characteristics inherent in the current harmonics, directly impacting the EMB system's wear detection accuracy. Therefore, this embodiment first preprocesses the current signal.

[0044] The motor winding resistance increases with temperature, resulting in an artificially high current measurement value, which directly affects the calculation of harmonic amplitudes. Therefore, this embodiment performs temperature compensation on the measured current above the reference temperature. Taking the line current collected from the left front wheel motor as an example, the current collected on this side is compensated based on the corresponding motor winding temperature. The specific calculation method is:

[0045] Where, I n is the current value of the left front wheel motor after temperature compensation at the current moment, I is the current value collected by the left front wheel motor at the current moment, α is the conductor temperature coefficient, that is, the physical quantity of the brake motor winding changing with temperature, which measures the percentage change in conductor resistance when the temperature changes by 1°C. In this embodiment, the motor winding is copper wire, and α is set to 0.00393 / °C. The implementer can set it according to the actual situation. T is the current temperature of the left front wheel motor winding, T ref It represents the reference temperature of the brake motor winding. In this embodiment, the reference temperature is set to 25°C. The implementer can set it according to the actual situation. This embodiment does not limit it here.

[0046] The current value of the right front wheel motor after temperature compensation at the current moment is obtained by using the same calculation method as the current value of the left front wheel motor after temperature compensation at the current moment.

[0047] Taking the temperature-compensated current value of the left front wheel motor at the current moment and all previous moments as an example, this embodiment uses a fast Fourier transform to convert the compensated current data into the frequency domain. This is then filtered using a Butterworth bandpass filter with a lower cutoff frequency of 250 Hz, an upper cutoff frequency of 400 Hz, and a quality factor of Q = 1.5. Harmonics 5-7 are retained. This is because the fundamental frequency contains the main component of the motor torque and is unrelated to the brake clearance, while also suppressing high-frequency noise. The purpose of retaining harmonics 5-7 is to isolate harmonic features strongly associated with unilateral wear and eliminate irrelevant signal interference.

[0048] Then, the Hilbert transform is used to perform orthogonal decomposition on the filtered current data to calculate the amplitude A5 and phase of the 5th harmonic. When the brake pad wears on one side, the gap between the brake disc and the caliper becomes unbalanced, causing spatial asymmetry in the motor load. This asymmetry is coupled to the stator current through variations in the air gap permeability. According to electromechanical principles, unilateral stiffness defects in rotating machinery can excite characteristic harmonics in the current that are related to the number of pole pairs.

[0049] It should be understood that the widening of the gap on one side caused by wear in the EMB system increases the local magnetic resistance, causing the amplitude of the fifth harmonic in the stator current to be positively correlated with the brake gap. Wear on the left and right sides can cause a characteristic phase difference in the fifth harmonic of the line current, which stems from the orthogonal response of the asymmetric load on the dq axes. Furthermore, compared to the third harmonic, which is susceptible to zero-sequence noise contamination, and the seventh harmonic, which is susceptible to bearing vibration interference, the fifth harmonic has a higher degree of separation from the multiples of the mechanical main frequency under braking conditions and is not directly affected by the PWM carrier frequency. Therefore, this embodiment analyzes the fifth harmonic of the current data.

[0050] Due to unilateral wear on the left and right sides of the vehicle, the air gap magnetic permeability is asymmetric, which causes the formation of a fifth harmonic in the current data. The amplitude of the fifth harmonic is sensitive to changes in the brake clearance and is not affected by the motor speed. Therefore, this embodiment also uses the current value of the left front wheel motor after temperature compensation at the current moment and all previous moments to obtain the fifth harmonic. The current value of the right front wheel motor after temperature compensation at the current moment and all previous moments is used to obtain the fifth harmonic corresponding to the temperature-compensated current value of the right front wheel motor. Then, the amplitude difference ΔA5 between the fifth harmonic corresponding to the temperature-compensated current value of the left front wheel motor and the fifth harmonic corresponding to the temperature-compensated current value of the right front wheel motor is calculated. The specific calculation method is:

[0051] ΔA5=|A5 left -A5 right |; Where A5 left A5 is the amplitude of the fifth harmonic corresponding to the current value of the left front wheel motor after temperature compensation. rightis the amplitude of the fifth harmonic corresponding to the temperature-compensated current value of the right front wheel motor. ΔA5 reflects the wear of the EMB system. A larger brake gap and higher local magnetic resistance increase the amplitude difference of the fifth harmonic.

[0052] In addition, the phase difference between the 5th harmonic of the current value after temperature compensation of the left front wheel motor and the 5th harmonic of the current value after temperature compensation of the right front wheel motor is obtained. The specific calculation method is:

[0053] Where, is the phase of the fifth harmonic corresponding to the current value of the left front wheel motor after temperature compensation, The phase of the fifth harmonic corresponding to the temperature-compensated current value of the right front wheel motor.

[0054] It should be understood that when the left side of the vehicle is worn, the stiffness of the left caliper decreases and the inductance of the left phase winding of the motor decreases, resulting in the phase advance of the 5th harmonic, that is, the phase difference Increase, the right side wear is opposite, that is, the phase difference when the left side wears Greater than 0, phase difference when the right side is worn Less than 0, so the phase difference Can indicate the direction of wear.

[0055] A single ΔA5 or It is susceptible to noise interference. Therefore, this embodiment projects the amplitude difference into the phase difference direction to eliminate the influence of phase angle fluctuation and avoid the ambiguity of a single feature. The wear sensitivity factor of the current brake is determined. The specific calculation method is:

[0056] Where S is the wear sensitivity factor of the current brake, and cos() is the trigonometric cosine function.

[0057] It should be understood that mechanical wear in the EMB system causes the amplitude and phase of the corresponding fifth harmonics of the left and right front wheel motors to grow in tandem, while short-term noise can cause random phase jitter. By multiplying the amplitude difference by the cosine of the phase difference, only the in-frequency and in-phase variations associated with mechanical wear are retained, while asynchronous fluctuations caused by noise are attenuated, thereby highlighting wear characteristics and suppressing interference. By integrating the amplitude and phase differences of the current signals, the wear sensitivity factor achieves high-precision detection, directional discrimination, and quantitative assessment of unilateral wear, providing a key basis for active calibration and ultimately improving the braking accuracy and reliability of the EMB system.

[0058] S3, determining the cumulative net angle of the current brake by the difference between the clamping angle and the retraction angle of the current and previous braking operations; obtaining the current temperature correction coefficient by using the difference between the current brake disc temperature and the preset reference temperature, combined with the corresponding thermal expansion coefficient of the brake disc.

[0059] At present, the existing EMB system calibration method is often through offline calibration or fixed mileage calibration, and cannot achieve active calibration. Brake pad wear is affected by different working conditions such as braking frequency, temperature and vehicle speed. The existing EMB system calibration method cannot reflect the actual loss in real time. This embodiment obtains the clamping and retraction angle difference through the motor encoder, and corrects it in combination with the brake disc temperature and vehicle speed, thereby converting the physical gap into a real-time wear rate, thereby achieving active calibration.

[0060] When the vehicle brakes, the motor drives the caliper to clamp and generate friction, and wear will cause the brake pad to become thinner and the brake clearance to increase; when retracting, the spring resets, and when it is not worn, the difference between the clamping angle and the retraction angle is close to the theoretical clearance. Therefore, the net angle Δθ of a single brake is i =θ clamp -θ release , which can reflect the effective wear consumption of a single brake. The greater the wear, the more angles the clamping needs to turn, that is, the greater the net angle. clamp ,θ release They represent the clamping angle and retraction angle respectively. It should be noted that the clamping angle and retraction angle are obtained through the motor encoder.

[0061] Under different operating conditions, for example, when a car is driving in a city, braking frequency is high and wear is rapid. Therefore, the net turning angle closer to the current single braking is more critical. On the other hand, when a car is driving on a highway, braking frequency is low and wear is slow. Therefore, wear within a certain time period is more representative of the actual situation. Therefore, this embodiment weights the net turning angle of a single braking with a certain number of braking times to obtain the cumulative net turning angle. This embodiment selects the 100 braking times before the current braking for analysis to balance real-time performance and noise. The implementer can determine the number of braking times selected, and this embodiment does not impose any restrictions.

[0062] In this embodiment, the calculation method of the current cumulative net turning angle of braking is: Where Δθ sum is the cumulative net turning angle of the current braking, Δθ k is the difference between the clamping angle and the retraction angle of the kth braking before the current one, μ is the preset time weighting factor, in this embodiment μ = 0.95, and a higher weight is given to the net angle of a single braking closer to the current one, reflecting the change in the vehicle's driving conditions, N is the preset number of braking times before the current one, in this embodiment N = 100, and k is the sequence number of braking times.

[0063] In addition, this embodiment obtains the current temperature correction coefficient based on the real-time temperature of the brake disc. The specific calculation method is: K T =1+β T ×(T-T0); where K T is the current temperature correction coefficient, T is the current brake disc temperature, T0 is the preset reference temperature, in this embodiment T0 = 25 ° C, the implementer can set it according to the actual situation, β T is the thermal expansion coefficient corresponding to the brake disc, recorded as the temperature sensitivity coefficient. In this embodiment, β T = 0.003 / °C, indicating that for every 1°C the brake disc temperature exceeds the reference temperature, the EMB system wear rate increases by 0.3%. The greater the difference between the brake disc temperature and the reference temperature, the more severe the EMB system wear, and the larger the temperature correction factor. (T - T0) is recorded as the first difference.

[0064] It should be noted that the difference indicates the degree of difference between two variables, which can be calculated by difference, absolute value of difference, ratio, etc.

[0065] S4, based on the difference between the current driving speed of the vehicle and the preset critical speed, combined with the relationship between the driving speed and the amount of brake pad wear, obtain the current speed correction coefficient; combine the cumulative net turning angle, the temperature correction coefficient and the speed correction coefficient to determine the current dynamic wear rate of the brake.

[0066] Comparing the current cumulative net rotation angle of braking with the initial net rotation angle when the vehicle is not worn can generate a real-time dynamic wear rate. However, brake pads expand at high temperatures, causing the net rotation angle measured by the encoder to include thermal deformation rather than actual wear. In addition, during low-speed sudden braking, the contact time between the brake pad and the brake disc is prolonged, the contact pressure is concentrated, and adhesive wear is the main cause. During high-speed light braking, the sliding speed of the friction pair is high, and the proportion of abrasive wear increases. At the same net rotation angle, the amount of wear at low speed is greater than that at high speed. Therefore, this embodiment performs temperature and speed corrections on the wear rate.

[0067] In this embodiment, the current dynamic brake wear rate ω is calculated as follows: Where Δθ sum K is the cumulative net turning angle of the current braking, Δθ0 is the initial net turning angle when the vehicle is not worn. In this embodiment, Δθ0 = 2°, and η is the conversion coefficient between the preset turning angle and the brake clearance. In this embodiment, η = 0.02, which converts the angle change into the brake clearance change, that is, 1° turning angle = 0.02mm brake clearance change. v The current speed correction coefficient is calculated as follows: Among them, v is the current speed of the car, v cThe critical speed is set to 50 km / h in this embodiment to distinguish between low-speed and high-speed operating conditions. When the vehicle speed is higher, the EMB system wears less than that at low speed. v is a preset speed weight coefficient, which is mapped based on the relationship between different vehicle speeds and brake pad wear. In this embodiment, when the vehicle speed is between 0 and 50 km / h, β v =1.5, indicating that the wear rate during low-speed braking is magnified by 1.5 times. When the vehicle speed is between 50 and 90 km / h, β v =1, when the vehicle speed is greater than 90km / h, β v = 0.5. When the vehicle speed is less than the critical speed, the wear contribution of the net turning angle is magnified by the speed weight coefficient. That is, in urban conditions, low speed driving and high braking frequency lead to greater brake pad wear, K T is the current temperature correction coefficient, N is the preset number of braking times before the current time, in this embodiment, N = 100. Recorded as the second difference.

[0068] S5, triggering active calibration of the EMB system through the wear sensitivity factor and the dynamic wear rate, determining the brake pad wear coefficient based on the wear sensitivity factor, and correcting the left and right caliper target angles.

[0069] The EMB system triggers active calibration based on the current braking wear sensitivity factor and dynamic wear rate. Trigger condition 1: |S| > 0.15A. The wear sensitivity factor S combines amplitude and phase differences. When |S| exceeds a preset first threshold of 0.15A, the vehicle is judged to have unilateral brake wear. In this embodiment, the first threshold is 0.15A, based on the maximum allowable brake clearance difference of 0.1mm. Trigger condition 2: ω > 0.015mm / 100 times. 0.015mm / 100 times is the preset second threshold. The dynamic wear rate ω reflects the actual wear rate by accumulating net rotation angle, temperature correction, and speed correction. For example, frequent low-speed braking in urban conditions accelerates wear, necessitating frequent calibration. In this embodiment, the second threshold range is 0.01-0.02mm / 100 times. A low second threshold will result in overly frequent calibration, while a high second threshold may miss early wear, increasing safety risks. If the current brake wear sensitivity factor and dynamic wear rate meet trigger condition 1 or trigger condition 2, the EMB system can be triggered to perform active calibration.

[0070] During active EMB calibration, the wear direction and extent are determined based on the wear sensitivity factor. If the wear sensitivity factor S > 0, the left caliper is worn; if S < 0, the right caliper is worn. The brake pad wear coefficient Δg is calculated, where Δg = |S|.

[0071] Calibrate according to the brake pad wear coefficient. In this embodiment, the motor drives the compensation. When the left caliper is worn, the motor increases the target turning angle of the left caliper. Where Δθ b is the increase in the target angle, Δg is the brake pad wear coefficient, P is the screw lead, and π is the pi. The motor's rotation angle is converted into the actual displacement of the caliper. Similarly, when the right caliper is worn, the motor increases the target angle of the right caliper. The flow chart of the relationship between the caliper target angle correction index is as follows: Figure 2 shown.

[0072] Based on the same inventive concept as the above method, an embodiment of the present application also provides an EMB system active calibration device for improving braking accuracy, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of any one of the above-mentioned methods for active calibration of the EMB system for improving braking accuracy are implemented.

[0073] It should be noted that the order in which the embodiments of the present application are presented is for illustrative purposes only and does not necessarily represent the superiority or inferiority of the embodiments. Furthermore, the foregoing descriptions of specific embodiments of this specification are provided. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the specific order or sequential sequence shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0074] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0075] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principles of the present application shall be included in the scope of protection of the present application.

Claims

1. An active calibration method for an EMB system to improve braking accuracy, characterized in that: The method comprises the following steps: respectively collecting the current and temperature of the brake motor windings in the car, and collecting the temperature of the brake disc and the driving speed of the car in real time, wherein the brake motor includes the left front wheel motor and the right front wheel motor; Based on the current temperature change of the brake motor winding, the current current of the brake motor winding is compensated; the compensated current is converted into a frequency domain and filtered to obtain a fifth harmonic current; and the wear sensitivity factor of the current brake is determined by using the amplitude difference and phase difference of the fifth harmonic current of the left front wheel motor and the right front wheel motor; The cumulative net braking angle is determined by the difference between the clamping angle and the retraction angle of the current and previous braking events. The temperature correction factor is obtained by combining the difference between the current brake disc temperature and the preset reference temperature with the thermal expansion coefficient of the brake disc. Based on the difference between the current vehicle speed and the preset critical speed, and in combination with the relationship between the driving speed and the amount of brake pad wear, a current speed correction coefficient is obtained; and the current dynamic brake wear rate is determined by combining the accumulated net turning angle, the temperature correction coefficient, and the speed correction coefficient. The EMB system is actively calibrated by triggering the wear sensitivity factor and the dynamic wear rate, and the brake pad wear coefficient is determined based on the wear sensitivity factor to correct the left and right caliper target angles.

2. The EMB system active calibration method for improving braking accuracy according to claim 1, characterized in that: The compensating the current of the brake motor winding includes: The difference between the current temperature of the brake motor winding and the preset reference temperature is calculated. The current compensated current of the brake motor winding is negatively correlated with the difference and the physical quantity of the brake motor winding that changes with temperature, and is positively correlated with the current current of the brake motor winding.

3. The EMB system active calibration method for improving braking accuracy according to claim 1, characterized in that: Determination of the wear sensitivity factor includes: The cosine value of the phase difference is calculated, and the wear sensitivity factor is the product of the cosine value and the amplitude difference.

4. The active calibration method for an EMB system for improving braking accuracy according to claim 3, characterized in that: The cumulative net turning angle is calculated as follows: Where Δθ sum is the cumulative net turning angle of the current braking, Δθ k is the difference between the clamping angle and the retraction angle of the kth braking before the current one, μ is the preset time weighting factor, N is the preset number of braking times before the current one, and k is the sequence number of braking times.

5. The EMB system active calibration method for improving braking accuracy according to claim 1, characterized in that: Determination of the temperature correction coefficient includes: The difference between the current brake disc temperature and the preset reference temperature is recorded as a first difference, and a multiplication result of the first difference and the thermal expansion coefficient corresponding to the brake disc is calculated. The temperature correction coefficient is positively correlated with the multiplication result.

6. The EMB system active calibration method for improving braking accuracy according to claim 1, characterized in that: Determination of the speed correction coefficient includes: The difference between the preset critical speed and the current driving speed of the vehicle is recorded as the second difference. The speed weight coefficient is preset using the relationship between the driving speed and the amount of brake pad wear. The speed correction coefficient is the product of the second difference and the speed weight coefficient.

7. The EMB system active calibration method for improving braking accuracy according to claim 4, characterized in that: The dynamic wear rate is calculated as follows: Where ω is the dynamic wear rate of the current brake, Δθ sum is the cumulative net turning angle of the current braking, K T is the current temperature correction coefficient, K v is the current speed correction coefficient, η is the conversion coefficient between the preset turning angle and the brake clearance, and Δθ0 is the initial net turning angle when the vehicle has no wear.

8. The EMB system active calibration method for improving braking accuracy according to claim 1, characterized in that: The triggering of active calibration of the EMB system by using the wear sensitivity factor and the dynamic wear rate includes: If the absolute value of the wear sensitivity factor of the current braking is greater than a preset first threshold, or the dynamic wear rate of the current braking is greater than a preset second threshold, the EMB system is triggered to perform active calibration.

9. The EMB system active calibration method for improving braking accuracy according to claim 1, characterized in that: The correcting of the left and right caliper target angles includes: The brake pad wear coefficient is the absolute value of the wear sensitivity factor. When the wear sensitivity factor is greater than 0, the left caliper is determined to be worn. When the wear sensitivity factor is less than 0, the right caliper is determined to be worn. When the left or right caliper is worn, the target turning angle of the left or right caliper is increased. Where Δθ b is the increase in the target rotation angle, Δg is the brake pad wear coefficient, P is the screw lead, and π is pi.

10. An EMB system active calibration device for improving braking accuracy, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 9 are implemented.

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