Clamping force correction method of electronic mechanical braking system

Abstract

The invention discloses a clamping force correction method for an electronic mechanical braking system. The clamping force correction method comprises the steps that S1, estimated clamping force on four wheels is obtained in the vehicle braking process; s2, estimated clamping force deviation detection is carried out to determine that the estimated clamping force has overall deviation or left-right deviation; and S3, the estimated clamping force of the wheel needing to be corrected in the estimated clamping force of the four wheels is recognized in a single-shaft braking mode and corrected. By means of the method, the phenomena that longitudinal deceleration and expected deviation of the whole vehicle are too large due to the large clamping force estimation error and the whole vehicle generates unexpected yawing can be eliminated, so that the influence caused by the clamping force estimation error is reduced, and the reliability of a pressure-sensor-free scheme is improved; according to the method, the estimated clamping force can be corrected in real time according to the dynamic state of the whole vehicle; dependence of an electronic mechanical braking system on a force sensor can be eliminated, possibility is provided for closed-loop control of clamping force under the condition that no force sensor exists, installation is convenient, and meanwhile cost is greatly saved.

Description

Technical Field

[0001] The present invention relates to the technical field of automobiles, and particularly to a method for correcting the clamping force of an electromechanical braking system. Background Art

[0002] The electromechanical braking system combines electronics and mechanical technologies. Due to its advantages in terms of safety, response speed, support for intelligent driving, etc., it has become the main development direction of the braking industry.

[0003] In order to achieve the control of the clamping force, the electromechanical braking system needs to use force sensors to provide feedback signals, that is, force sensors are installed on all four wheels of the vehicle. This poses problems such as difficult layout under the wheel-side integration space, severe interference, and high cost for the force sensors.

[0004] In view of this problem, in the prior art, an estimation method is adopted for the clamping force of the electromechanical braking system. However, there will be estimation errors in different clamping force estimation methods. An excessive estimation error will lead to a large deviation between the longitudinal deceleration of the whole vehicle and the expected value, as well as an unexpected yaw of the whole vehicle, thus affecting the running stability of the vehicle. Summary of the Invention

[0005] The purpose of the present invention is to provide, in view of the deficiencies in the prior art, a method for correcting the clamping force of an electromechanical braking system, by which the estimated clamping force of the electromechanical braking system can be corrected to improve the running stability of the vehicle.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for correcting the clamping force of an electromechanical braking system, comprising:

[0008] S1. During the vehicle braking process, obtain the estimated clamping forces of the electromechanical braking systems on the four wheels, namely the estimated clamping force Fcl_FL of the left front wheel, the estimated clamping force Fcl_FR of the right front wheel, the estimated clamping force Fcl_RL of the left rear wheel, and the estimated clamping force Fcl_RR of the right rear wheel;

[0009] S2. Detect the deviation of the estimated clamping force to determine whether there is an overall deviation or a left-right deviation in the estimated clamping force;

[0010] S3. Adopt the single-axis braking method to identify and correct the estimated clamping force of the wheel that needs to be corrected among the estimated clamping forces of the four wheels.

[0011] In some embodiments, in step S2, when the vehicle speed is greater than the set value and the brake is applied, the actual longitudinal deceleration of the whole vehicle is within the set range, and the ABS is not triggered. If the absolute value of the longitudinal deceleration deviation ΔAx is greater than the set value, it is determined that there is an overall deviation in the estimated clamping force.

[0012] In some embodiments, the calculation method of the longitudinal deceleration deviation ΔAx is as follows:

[0013] ΔAx = TarAx - Ax,

[0014] TarAx = (Fcl_FL + Fcl_FR + Fcl_RL + Fcl_RR) * μ * Rb * 2 / Rw;

[0015] In the formula, TarAx is the expected longitudinal deceleration; Ax is the actual longitudinal deceleration of the whole vehicle; μ is the friction coefficient of the friction plate of the electro - mechanical braking system; Rb is the effective braking radius of the electro - mechanical braking system; Rw is the rolling radius of the wheel.

[0016] In some embodiments, when there is an overall deviation in the estimated clamping force and single - axis braking is being implemented, when the ratio of TarAx / Ax exceeds the set value, the estimated clamping force is corrected.

[0017] In some embodiments, when the ratio of TarAx / Ax is less than the set value, multiply the estimated clamping force by a correction coefficient greater than 1, or add a positive clamping force deviation to the estimated clamping force until the ratio of TarAx / Ax is within the set range;

[0018] When the ratio of TarAx / Ax is greater than the set value, multiply the estimated clamping force by a correction coefficient less than 1, or add a negative clamping force deviation to the estimated clamping force until the ratio of TarAx / Ax is within the set range.

[0019] In some embodiments, when only the front - axle brakes are applied without steering and the actual longitudinal deceleration of the whole vehicle is within the set range, the expected longitudinal deceleration TarAx = (Fcl_FL + Fcl_FR) * μ * Rb * 2 / Rw. When the ratio of TarAx / Ax exceeds the set value, the estimated clamping force of the left front wheel Fcl_FL and the estimated clamping force of the right front wheel Fcl_FR are corrected simultaneously;

[0020] When only the rear - axle brakes are applied without steering and the actual longitudinal deceleration of the whole vehicle is within the set range, the expected longitudinal deceleration TarAx = (Fcl_RL + Fcl_RR) * μ * Rb * 2 / Rw. When the ratio of TarAx / Ax exceeds the set value, the estimated clamping force of the left rear wheel Fcl_RL and the estimated clamping force of the right rear wheel Fcl_RR are corrected simultaneously.

[0021] In some embodiments, in step S2, when braking is applied at a vehicle speed greater than the set value, the actual longitudinal deceleration of the whole vehicle is within the set range, the ABS is not triggered, and the driver does not turn the steering wheel, if the absolute value of the actual yaw rate of the whole vehicle or the lateral acceleration is greater than the set value, it is determined that there is a left - right deviation in the estimated clamping force.

[0022] In some embodiments, when there are left - right deviations in the estimated clamping force, the deflection direction of the vehicle is determined according to the sign of the actual yaw rate of the whole vehicle, and the estimated clamping force of the left and / or right wheels is corrected according to the deflection direction of the vehicle.

[0023] In some embodiments, when the vehicle deflects to the left, the estimated clamping force of the left wheel is multiplied by a correction coefficient greater than 1, or the estimated clamping force of the right wheel is multiplied by a correction coefficient less than 1; alternatively, a positive clamping force deviation is added to the estimated clamping force of the left wheel, or a negative clamping force deviation is added to the estimated clamping force of the right wheel;

[0024] When the vehicle deflects to the right, the estimated clamping force of the right wheel is multiplied by a correction coefficient greater than 1, or the estimated clamping force of the left wheel is multiplied by a correction coefficient less than 1; alternatively, a positive clamping force deviation is added to the estimated clamping force of the right wheel, or a negative clamping force deviation is added to the estimated clamping force of the left wheel.

[0025] In some embodiments, the correction coefficient is obtained through calibration, or the correction coefficient is set to a fixed value; the clamping force deviation is obtained through calibration, or the clamping force deviation is set to a fixed value.

[0026] Due to the application of the above - mentioned technical solutions, the clamping force correction method of the electro - mechanical braking system of the present invention has the following advantages compared with the prior art:

[0027] (1) Through this method, the phenomenon that the longitudinal deceleration of the whole vehicle and the expected deviation are too large due to large estimated clamping force errors, and the unexpected yaw of the whole vehicle can be eliminated, thereby reducing the influence brought by the estimated clamping force errors and improving the reliability of the pressure - sensor - free scheme.

[0028] (2) This method can correct the estimated clamping force in real - time according to the dynamics of the whole vehicle, improving the real - time performance of the correction.

[0029] (3) Through this method, the dependence of the electro - mechanical braking system on the force sensor can be eliminated, providing the possibility for the closed - loop control of the clamping force in the case of no mechanical sensor, facilitating the installation of the electro - mechanical braking system and greatly saving costs at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Attached Figure 1 is a flowchart of the clamping force correction method of the electro - mechanical braking system of this embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work belong to the scope of protection of the present invention.

[0032] As Figure 1 shown, the flowchart of the clamping force correction method for the electromechanical braking system of the present invention is as Figure 1 shown, and specifically includes the following steps:

[0033] S1, estimate the clamping force

[0034] During the vehicle braking process, obtain the estimated clamping forces of the electromechanical braking systems on the four wheels, namely the estimated clamping force Fcl_FL of the left front wheel, the estimated clamping force Fcl_FR of the right front wheel, the estimated clamping force Fcl_RL of the left rear wheel, and the estimated clamping force Fcl_RR of the right rear wheel.

[0035] The estimated clamping forces on each wheel can be obtained by methods in the prior art, such as CN117928795A, CN115431938A, etc.

[0036] S2, estimate the clamping force deviation detection

[0037] Through the estimated clamping force deviation detection, determine whether there is an overall deviation or a left-right deviation in the estimated clamping force, specifically including:

[0038] (1) Calculate the longitudinal deceleration deviation ΔAx.

[0039] The calculation formula for the longitudinal deceleration deviation ΔAx is as follows:

[0040] ΔAx = TarAx - Ax

[0041] TarAx = (Fcl_FL + Fcl_FR + Fcl_RL + Fcl_RR) * μ * Rb * 2 / Rw

[0042] In the formula, TarAx is the expected longitudinal deceleration; Ax is the actual longitudinal deceleration of the whole vehicle; μ is the friction coefficient of the friction plate of the electromechanical braking system; Rb is the effective braking radius of the electromechanical braking system; Rw is the wheel rolling radius.

[0043] (2) Calculate the yaw rate deviation Δγ and obtain the lateral acceleration.

[0044] The calculation formula for the yaw rate deviation Δγ is as follows:

[0045] Δγ = Tarγ - γ

[0046] Wherein, Tarγ is the expected yaw rate; γ is the actual yaw rate of the whole vehicle.

[0047] When the vehicle is running and the driver does not turn the steering wheel, Tarγ = 0, and Δγ = -γ.

[0048] The lateral acceleration can be detected by the vehicle's built-in sensors.

[0049] (3) Determine that there is an overall deviation or left-right deviation in the estimated clamping force.

[0050] When braking at a vehicle speed greater than the set value, the actual longitudinal deceleration of the whole vehicle is within the set range, and the ABS is not triggered. If the absolute value of the longitudinal deceleration deviation ΔAx is greater than the set value, it is determined that there is an overall deviation in the estimated clamping force.

[0051] When braking at a vehicle speed greater than the set value, the actual longitudinal deceleration of the whole vehicle is within the set range, the ABS is not triggered, and the driver does not turn the steering wheel. If the absolute value of the yaw rate deviation Δγ, that is, the absolute value of the actual yaw rate of the whole vehicle, is greater than the set value, or the lateral acceleration is greater than the set value, it is determined that there is a left-right deviation in the estimated clamping force.

[0052] Once it is detected that there is an overall deviation or left-right deviation in the estimated clamping force, this deviation flag will persist until the next time the deviation detection condition is met and it is detected that there is no deviation.

[0053] S3, Clamping force correction

[0054] After it is determined in step S2 that there is an overall deviation or left-right deviation in the estimated clamping force, it is still impossible to locate which axis or which wheel's estimated clamping force is abnormal.

[0055] In this step, in the subsequent braking cycles, a single-axis braking method of only front-axle braking or only rear-axle braking is alternately performed to identify the estimated clamping force of the wheel that needs to be corrected among the estimated clamping forces of the four wheels.

[0056] The conditions for single-axis braking are: the vehicle speed is greater than the set value, normal braking, and the clamping force request is less than the set value. This can prevent insufficient braking and thus cause accidents. When the clamping force request is greater than the set value, the single-axis braking method is exited.

[0057] (1) The correction method when there is an overall deviation in the estimated clamping force.

[0058] When there is an overall deviation in the estimated clamping force and single-axis braking is being implemented, when the ratio of TarAx / Ax exceeds the set value, the estimated clamping force is corrected.

[0059] When only the front axle brakes without steering and the actual longitudinal deceleration of the whole vehicle is within the set range, the expected longitudinal deceleration TarAx = (Fcl_FL + Fcl_FR) * μ * Rb * 2 / Rw. When the ratio of TarAx / Ax exceeds the set value, the estimated clamping force Fcl_FL of the left front wheel and the estimated clamping force Fcl_FR of the right front wheel are corrected simultaneously. Specifically:

[0060] When the ratio of TarAx / Ax is less than the set value, the estimated clamping force Fcl_FL of the left front wheel and the estimated clamping force Fcl_FR of the right front wheel are respectively multiplied by a correction coefficient greater than 1, or a positive clamping force deviation is respectively added to the estimated clamping force Fcl_FL of the left front wheel and the estimated clamping force Fcl_FR of the right front wheel until the ratio of TarAx / Ax is within the set range.

[0061] When the ratio of TarAx / Ax is greater than the set value, the estimated clamping force Fcl_FL of the left front wheel and the estimated clamping force Fcl_FR of the right front wheel are respectively multiplied by a correction coefficient less than 1, or a negative clamping force deviation is respectively added to the estimated clamping force Fcl_FL of the left front wheel and the estimated clamping force Fcl_FR of the right front wheel until the ratio of TarAx / Ax is within the set range.

[0062] When only the rear axle brakes without steering and the actual longitudinal deceleration of the whole vehicle is within the set range, the expected longitudinal deceleration TarAx = (Fcl_RL + Fcl_RR) * μ * Rb * 2 / Rw. When the ratio of TarAx / Ax exceeds the set value, the estimated clamping force Fcl_RL of the left rear wheel and the estimated clamping force Fcl_RR of the right rear wheel are corrected simultaneously. Specifically:

[0063] When the ratio of TarAx / Ax is less than the set value, the estimated clamping force Fcl_RL of the left rear wheel and the estimated clamping force Fcl_RR of the right rear wheel are respectively multiplied by a correction coefficient greater than 1, or a positive clamping force deviation is respectively added to the estimated clamping force Fcl_RL of the left rear wheel and the estimated clamping force Fcl_RR of the right rear wheel until the ratio of TarAx / Ax is within the set range.

[0064] When the ratio of TarAx / Ax is greater than the set value, the estimated clamping force Fcl_RL of the left rear wheel and the estimated clamping force Fcl_RR of the right rear wheel are respectively multiplied by a correction coefficient less than 1, or a negative clamping force deviation is respectively added to the estimated clamping force Fcl_RL of the left rear wheel and the estimated clamping force Fcl_RR of the right rear wheel,

[0065] The above correction coefficient can be obtained through calibration, or the correction coefficient can be set to a fixed value. The clamping force deviation can be obtained through calibration, or the clamping force deviation can be set to a fixed value. Until the ratio of TarAx / Ax is within the set range.

[0066] (2) Correction method when there are left - right deviations in the estimated clamping force.

[0067] When there are left - right deviations in the estimated clamping force, determine the deflection direction of the vehicle according to the sign of the actual yaw rate of the whole vehicle, and correct the estimated clamping force of the left or right wheels according to the deflection direction.

[0068] If when only the front axle brakes and no steering is applied, the absolute value of the yaw rate deviation Δγ, that is, the absolute value of the actual yaw rate of the whole vehicle, is greater than the set value, or the lateral acceleration is greater than the set value, it is considered that there are deviations in the estimated clamping forces of the left and right wheels on the front axle, and thus correct the estimated clamping force Fcl_FL of the left front wheel or the estimated clamping force Fcl_FR of the right front wheel. Specifically:

[0069] When the vehicle deflects to the left, it can be considered that the estimated clamping force Fcl_FL of the left front wheel is too small, or the estimated clamping force Fcl_FR of the right front wheel is too large. Therefore, the estimated clamping force Fcl_FL of the left front wheel can be multiplied by a correction coefficient greater than 1, or the estimated clamping force Fcl_FR of the right front wheel can be multiplied by a correction coefficient less than 1. Or, a positive clamping force deviation can be added to the estimated clamping force Fcl_FL of the left front wheel, or a negative clamping force deviation can be added to the estimated clamping force Fcl_FR of the right front wheel.

[0070] When the vehicle deflects to the right, it can be considered that the estimated clamping force Fcl_FL of the left front wheel is too large, or the estimated clamping force Fcl_FR of the right front wheel is too small. Therefore, the estimated clamping force Fcl_FR of the right front wheel can be multiplied by a correction coefficient greater than 1, or the estimated clamping force Fcl_FL of the left front wheel can be multiplied by a correction coefficient less than 1. Or, a positive clamping force deviation can be added to the estimated clamping force Fcl_FR of the right front wheel, or a negative clamping force deviation can be added to the estimated clamping force Fcl_FL of the left front wheel.

[0071] If when only the rear axle brakes and no steering is applied, the absolute value of the yaw rate deviation Δγ, that is, the absolute value of the actual yaw rate of the whole vehicle, is greater than the set value, or the lateral acceleration is greater than the set value, it is considered that there are deviations in the estimated clamping forces of the left and right wheels on the rear axle, and thus correct the estimated clamping force Fcl_RL of the left rear wheel or the estimated clamping force Fcl_RR of the right rear wheel. Specifically:

[0072] When the vehicle deflects to the left, it can be considered that the estimated clamping force Fcl_RL of the left rear wheel is too small, or the estimated clamping force Fcl_RR of the right rear wheel is too large. Therefore, a correction coefficient greater than 1 can be multiplied by the estimated clamping force Fcl_RL of the left rear wheel, or a correction coefficient less than 1 can be multiplied by the estimated clamping force Fcl_RR of the right rear wheel. Alternatively, a positive clamping force deviation can be added to the estimated clamping force Fcl_RL of the left rear wheel, or a negative clamping force deviation can be added to the estimated clamping force Fcl_RR of the right rear wheel.

[0073] When the vehicle deflects to the right, it can be considered that the estimated clamping force Fcl_RL of the left rear wheel is too large, or the estimated clamping force Fcl_RR of the right rear wheel is too small. Therefore, a correction coefficient greater than 1 can be multiplied by the estimated clamping force Fcl_RR of the right rear wheel, or a correction coefficient less than 1 can be multiplied by the estimated clamping force Fcl_RL of the left rear wheel. Alternatively, a positive clamping force deviation can be added to the estimated clamping force Fcl_RR of the right rear wheel, or a negative clamping force deviation can be added to the estimated clamping force Fcl_RL of the left rear wheel.

[0074] The above correction coefficient can be obtained through calibration based on the actual yaw rate or lateral acceleration of the whole vehicle, or the correction coefficient can be set to a fixed value. The clamping force deviation can be obtained through calibration based on the actual yaw rate or lateral acceleration of the whole vehicle, or the clamping force deviation can be set to a fixed value. Until the absolute value of the actual yaw rate and the lateral acceleration of the whole vehicle are both within the set range.

[0075] Through the above steps, it is possible to eliminate the phenomenon that the longitudinal deceleration of the whole vehicle and the expected deviation are too large, and the whole vehicle generates an unexpected yaw caused by a large error in the estimated clamping force, thereby improving the running stability of the vehicle.

[0076] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and their purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for correcting the clamping force of an electromechanical brake system, characterized in that: include: S1, during the vehicle braking process, obtaining the estimated clamping force of the electronic mechanical brake system on the four wheels, namely, the estimated clamping force Fcl_FL of the left front wheel, the estimated clamping force Fcl_FR of the right front wheel, the estimated clamping force Fcl_RL of the left rear wheel, and the estimated clamping force Fcl_RR of the right rear wheel; S2, estimated clamping force deviation detection to determine whether the estimated clamping force has an overall deviation or a left-right deviation; S3, using a single-axle braking method, identifying the estimated clamping force of the wheel that needs to be corrected among the estimated clamping forces of the four wheels and correcting it.

2. The clamping force correction method of an electronic mechanical brake system according to claim 1, characterized in that: In step S2, when the vehicle speed is greater than the set value and the brake is applied, the actual longitudinal deceleration of the vehicle is within the set range, and the ABS is not triggered, if the absolute value of the longitudinal deceleration deviation ΔAx is greater than the set value, it is determined that there is an overall deviation in the estimated clamping force.

3. The clamping force correction method of the electronic mechanical brake system according to claim 2, characterized in that: The calculation method of the longitudinal deceleration deviation ΔAx is: ΔAx=TarAx-Ax, TarAx=(Fcl_FL+Fcl_FR+Fcl_RL+Fcl_RR)*μ*Rb*2 / Rw; Where TarAx is the expected longitudinal deceleration; Ax is the actual longitudinal deceleration of the vehicle; μ is the friction coefficient of the friction plate of the electronic mechanical braking system; Rb is the effective braking radius of the electronic mechanical braking system; and Rw is the wheel rolling radius.

4. The clamping force correction method of an electronic mechanical brake system according to claim 3, characterized in that: When there is an overall deviation in the estimated clamping force and single-axis braking is being implemented, the estimated clamping force is corrected when the ratio of TarAx / Ax exceeds a set value.

5. The clamping force correction method of an electromechanical brake system according to claim 4, characterized in that: When the ratio of TarAx / Ax is less than the set value, the estimated clamping force is multiplied by a correction coefficient greater than 1, or a positive clamping force deviation is superimposed on the estimated clamping force until the ratio of TarAx / Ax is within the set range; When the ratio of TarAx / Ax is greater than the set value, the estimated clamping force is multiplied by a correction coefficient less than 1, or a negative clamping force deviation is superimposed on the estimated clamping force until the ratio of TarAx / Ax is within the set range.

6. The clamping force correction method of an electromechanical brake system according to claim 5, characterized in that: If only the front axle is braked without steering and the actual longitudinal deceleration of the vehicle is within the set range, the expected longitudinal deceleration TarAx = (Fcl_FL + Fcl_FR) * μ * Rb * 2 / Rw, when the ratio of TarAx / Ax exceeds the set value, the estimated clamping force Fcl_FL of the left front wheel and the estimated clamping force Fcl_FR of the right front wheel are corrected at the same time; If only the rear axle is braked without steering and the actual longitudinal deceleration of the vehicle is within the set range, the expected longitudinal deceleration TarAx = (Fcl_RL + Fcl_RR)*μ*Rb*2 / Rw. When the ratio of TarAx / Ax exceeds the set value, the estimated clamping force Fcl_RL of the left rear wheel and the estimated clamping force Fcl_RR of the right rear wheel are corrected at the same time.

7. The clamping force correction method of an electromechanical brake system according to claim 1, characterized in that: In step S2, when the vehicle speed is greater than the set value and the brake is applied, the actual longitudinal deceleration of the vehicle is within the set range, the ABS is not triggered, and the driver does not steer, if the absolute value of the actual yaw angular velocity or lateral acceleration of the vehicle is greater than the set value, it is determined that there is a left-right deviation in the estimated clamping force.

8. The clamping force correction method of an electronic mechanical brake system according to claim 7, characterized in that: When there is a left-right deviation in the estimated clamping force, the deflection direction of the vehicle is determined according to the sign of the actual yaw angular velocity of the vehicle, and the estimated clamping force of the left or right wheel is corrected according to the deflection direction of the vehicle.

9. The clamping force correction method of an electronic mechanical brake system according to claim 8, characterized in that: When the vehicle deviates to the left, the estimated clamping force of the left wheel is multiplied by a correction factor greater than 1, or the estimated clamping force of the right wheel is multiplied by a correction factor less than 1; or, a positive clamping force deviation is superimposed on the estimated clamping force of the left wheel, or a negative clamping force deviation is superimposed on the estimated clamping force of the right wheel; When the vehicle deviates to the right, the estimated clamping force of the right wheel is multiplied by a correction coefficient greater than 1, or the estimated clamping force of the left wheel is multiplied by a correction coefficient less than 1; or, a positive clamping force deviation is superimposed on the estimated clamping force of the right wheel, or a negative clamping force deviation is superimposed on the estimated clamping force of the left wheel.

10. The clamping force correction method of an electronic mechanical brake system according to claim 5 or 9, characterized in that: The correction coefficient is obtained through calibration, or the correction coefficient is set to a fixed value; the clamping force deviation is obtained through calibration, or the clamping force deviation is set to a fixed value.

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