Disc contact point correction method of electronic mechanical brake system

Abstract

The invention discloses a disc contact point correction method of an electronic mechanical braking system. The method comprises the steps that S1, system efficiency Eff is obtained through self-learning; s2, the current clamping force EffBasdClmpF is calculated according to the system efficiency Eff; s3, according to the current clamping force EffBasdClmpF, the stroke offset offs is calculated through self-learning; and S4, according to the stroke offset offs, calculating a finally used stroke sapplied, and correcting the contact point of the disc. According to the disc contact point correction method of the electronic mechanical braking system, the influence caused by system friction and gaps can be reduced, so that the precision of contact point correction can be improved, and the precision of clamping force estimation can be improved through contact point correction.

Description

Technical Field

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

[0002] The electromechanical brake belongs to a type of wire control brake, which has a rapid response and excellent performance. Compared with the traditional hydraulic braking system, it eliminates components such as hydraulic oil pipelines and brake wheel cylinders, which not only solves the environmental pollution problem of hydraulic oil but also simplifies the structure of the braking system, facilitating the optimization of the vehicle chassis structure layout.

[0003] An electromechanical braking system using a sensorless scheme usually needs to identify the disc contact point and calculate the stroke and clamping force based on the contact point. The accuracy of contact point identification has a great impact on the final estimated value of the clamping force.

[0004] There are various commonly used methods for identifying contact points in the prior art, such as the current method, that is, when the current exceeds a certain threshold, it is considered that the disc contacts. The stiffness method, when the change rate of the current divided by the change rate of the stroke is greater than a certain value, it is considered that the disc contacts. The method of taking the average value of multiple contact point identifications. In the contact point identification stage of traditional contact point identification methods, the system friction accounts for a relatively large proportion, and due to the influence of system clearance, it may lead to premature or late identification of the contact point. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for correcting the disc contact point of an electromechanical braking system in view of the deficiencies in the prior art, so as to correct the disc contact point and improve the accuracy of clamping force estimation in the sensorless electromechanical braking system.

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

[0007] A method for correcting the disc contact point of an electromechanical braking system, comprising:

[0008] S1, obtaining the system efficiency Eff through self-learning;

[0009] S2, calculating the current clamping force EffBasdClmpF according to the system efficiency Eff;

[0010] S3, calculating the stroke offset offs through self-learning according to the current clamping force EffBasdClmpF;

[0011] S4, calculating the finally used stroke s_applied according to the stroke offset offs and correcting the disc contact point.

[0012] In some embodiments, the calculation method of the system efficiency Eff is:

[0013] Eff = 1 - Tf_c / Tm_c;

[0014] Tf_c = (Tm_c - Tm_r) / (1 + k);

[0015] Wherein, Tm_c is the motor torque when the system is clamping through the stroke s; Tm_r is the motor torque when the system is releasing through the stroke s; Tf_c is the system frictional torque when the system is clamping through the stroke s; Tf_r is the system frictional torque when the system is releasing through the stroke s; k is the ratio of the system frictional torque when the system is releasing to the system frictional torque when the system is clamping, which is measured through the laboratory.

[0016] In some embodiments, by repeatedly stepping on the brake through the same stroke position multiple times, different system efficiencies are obtained through multiple learnings, and the average value of the system efficiencies obtained through multiple learnings is used as the final system efficiency Eff.

[0017] In some embodiments, by repeatedly stepping on the brake through different stroke positions one or more times, different system efficiencies are obtained through multiple learnings, and the average value of the system efficiencies obtained through multiple learnings is used as the final system efficiency Eff.

[0018] In some embodiments, the calculation method of the current clamping force EffBasdClmpF is as follows:

[0019] EffBasdClmpF = Eff * Tm_c * i_mech;

[0020] Wherein, Tm_c is the motor torque when the system is clamping through the stroke s; i_mech is the system reduction ratio.

[0021] In some embodiments, when all the learning conditions are satisfied, according to the preset stroke and clamping force curve, the corresponding stroke s_corrected at the clamping force EffBasdClmpF is obtained, and the stroke offset offs = s_corrected - s_uncorrected, wherein s_uncorrected is the uncorrected stroke at the clamping force EffBasdClmpF in the real vehicle test.

[0022] In some embodiments, the learning conditions include:

[0023] The uncorrected stroke s_uncorrected is within the set interval;

[0024] The clamping force EffBasdClmpF is not less than the set value;

[0025] The motor speed is within the set interval;

[0026] Currently, it is in the clamping state;

[0027] The brake disc temperature is within the set range.

[0028] In some embodiments, the preset stroke and clamping force curves are measured through experiments in a laboratory.

[0029] In some embodiments, step S3 further includes: as long as all the learning conditions are met each time the brake is depressed, the learning of the stroke offset offs is performed, and the latest learned stroke offset offs-new is compared with the currently used stroke offset offs; if the change amount between the two exceeds the set value, the latest learned stroke offset offs-new is updated to the currently used stroke offset offs; if the change amount between the two does not exceed the set value, the currently used stroke offset offs is retained.

[0030] In some embodiments, the finally used stroke s_applied = s_uncorrected + offs, and the disc contact point is s_applied = 0.

[0031] Due to the application of the above technical solutions, the method for correcting the disc contact point of the electro-mechanical braking system of the present invention has the following advantages compared with the prior art: this correction method can reduce the influence brought by system friction and clearance, thereby improving the accuracy of contact point correction and improving the accuracy of clamping force estimation through contact point correction. Description of the Drawings

[0032] Attached Figure 1 is a flowchart of the method for correcting the disc contact point of the electro-mechanical braking system of this embodiment;

[0033] Attached Figure 2 is the stroke and motor torque curves during the clamping and releasing processes of the electro-mechanical braking system of this embodiment;

[0034] Attached Figure 3 is the preset stroke and clamping force curves measured through experiments in a laboratory for the electro-mechanical braking system of this embodiment. Detailed Embodiments

[0035] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] As Figure 1 shown, the flowchart of the method for correcting the disc contact point of the electro-mechanical braking system of the present invention is as Figure 1 shown, and specifically includes the following steps:

[0037] S1. Obtain the system efficiency Eff through self - learning.

[0038] First, define the following parameters: the motor torque Tm_c when the system clamping process passes through the stroke s, the motor torque Tm_r when the system release process passes through the stroke s, the system friction torque Tf_c when the system clamping process passes through the stroke s, the system friction torque Tf_r when the system release process passes through the stroke s, and the ratio k of the system friction torque when the system is released to the system friction torque when the system is clamped.

[0039] The calculation method of the system efficiency Eff is as follows:

[0040] As Figure 2 shown, according to the difference in the motor torque when the system passes through the same stroke position s during the clamping and release processes, the system friction torque Tf_c during the clamping process can be obtained. Specifically:

[0041] Tf_c = (Tm_c - Tm_r) / (1 + k) (1).

[0042] In this formula, both Tm_c and Tm_r can be obtained by calculating the motor operation parameters during actual vehicle testing, and the k value is measured in advance in the laboratory.

[0043] Thus, the system efficiency Eff during the clamping process can be obtained as:

[0044] Eff = 1 - Tf_c / Tm_c (2).

[0045] In order to improve the learning accuracy of the efficiency, multiple learning times are required to consider that the efficiency learning is completed to ensure the reliability of the efficiency value.

[0046] There are the following ways of learning the efficiency:

[0047] Method 1: By repeatedly stepping on the brake through the same stroke position S multiple times, using the above formulas (1) and (2), obtain different system efficiencies Eff1, Eff2, Eff3,..., Effn through multiple learning, and take the average value of the system efficiencies Eff1, Eff2, Eff3,..., Effn obtained from multiple learning as the final system efficiency Eff, that is:

[0048] Eff = (Eff1 + Eff2 + Eff3 +... + Effn) / n (3).

[0049] Method 2: By stepping on the brake one or more times repeatedly through different stroke positions S1, S2... Sn, the system efficiencies Eff1, Eff2, Eff3,... Effn are obtained through multiple learning processes. The average value of the system efficiencies Eff1, Eff2, Eff3,... Effn obtained from multiple learning processes is used as the final system efficiency Eff. Similarly, it can be obtained that:

[0050] Eff = (Eff1 + Eff2 + Eff3 +... + Effn) / n (4).

[0051] S2. Calculate the current clamping force EffBasdClmpF according to the system efficiency Eff.

[0052] After the efficiency learning is completed, the clamping force EffBasdClmpF is calculated according to the following formula:

[0053] EffBasdClmpF = Eff * Tm_c * i_mech (5).

[0054] In the formula, i_mech is the system reduction ratio and is a fixed value.

[0055] S3. Calculate the stroke offset offs through self-learning according to the current clamping force EffBasdClmpF.

[0056] When all the learning conditions are met, look up the table inversely according to the preset stroke and clamping force curve to obtain the corresponding stroke s_corrected at the clamping force EffBasdClmpF, as Figure 3 shown, and thus the stroke offset offs can be calculated. Specifically:

[0057] offs = s_corrected - s_uncorrected (6).

[0058] Among them, s_uncorrected is the uncorrected stroke at the clamping force EffBasdClmpF in the actual vehicle test.

[0059] The above learning conditions include:

[0060] (1) The uncorrected stroke s_uncorrected is within the set range;

[0061] (2) The clamping force EffBasdClmpF is not less than the set value, such as EffBasdClmpF ≥ 10KN;

[0062] (3) The motor speed is within the set range;

[0063] (4) Currently in the clamping state;

[0064] (5) The brake disc temperature is within the set range.

[0065] Among the learning conditions, since the clamping force EffBasdClmpF is required to be relatively large, and the contact point correction is carried out under the condition of using a large clamping force, the influence brought by system friction and clearance can be reduced, thereby improving the accuracy of contact point correction.

[0066] The above Figure 3 The preset stroke and clamping force curves shown above are measured through the laboratory.

[0067] Every time the brake is depressed, as long as all the above learning conditions are met, the learning of the stroke offset offs is carried out, and the latest learned stroke offset offs-new is compared with the currently used stroke offset offs. If the change amount between the two exceeds the set value, the latest learned stroke offset offs-new is updated to the currently used stroke offset offs. If the change amount between the two does not exceed the set value, the currently used stroke offset offs is retained. In this way, the continuous learning of the stroke offset offs can be realized, so that the stroke offset offs can be dynamically updated, and the accuracy of contact point correction can be improved.

[0068] S4, correction of the disc contact point.

[0069] According to the stroke offset offs, the finally used stroke s_applied can be obtained, specifically:

[0070] s_applied = s_uncorrected + offs (7).

[0071] The above strokes are all defined with the disc contact point as the zero point. Therefore, after determining the finally used stroke s_applied, the disc contact point can be determined, and thus the existing disc contact point can be corrected. That is, the corrected disc contact point is:

[0072] s_applied = 0, that is, s_uncorrected = -offs (8).

[0073] In this way, the correction of the disc contact point is completed. By correcting the disc contact point, the accuracy of system clamping force estimation is improved.

[0074] The above embodiments are only for explaining the technical concept and characteristics of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. All 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 contact point of a disc of an electromechanical brake system, characterized in that: include: S1, obtains system efficiency Eff through self-learning; S2, calculate the current clamping force EffBasdClmpF according to the system efficiency Eff; S3, calculate the stroke offset offs through self-learning according to the current clamping force EffBasdClmpF; S4, calculating the final used stroke s_applied according to the stroke offset offs, and correcting the disc contact point.

2. The disc contact point correction method of the electronic mechanical brake system according to claim 1, characterized in that: The calculation method of system efficiency Eff is: Eff = 1 - Tf_c / Tm_c; Tf_c=(Tm_c-Tm_r) / (1+k); Wherein, Tm_c is the motor torque when the system clamps through a stroke s; Tm_r is the motor torque when the system releases through a stroke s; Tf_c is the system friction torque when the system clamps through a stroke s; Tf_r is the system friction torque when the system releases through a stroke s; k is the ratio of the system friction torque when the system is released to the system friction torque when the system is clamped, which is measured in the laboratory.

3. The disc contact point correction method of the electronic mechanical brake system according to claim 2, characterized in that: By repeatedly braking at the same travel position, different system efficiencies are learned multiple times, and the average of the system efficiencies learned multiple times is taken as the final system efficiency Eff.

4. The disc contact point correction method of the electronic mechanical brake system according to claim 2, characterized in that: By repeatedly braking once or multiple times through different travel positions, different system efficiencies are learned multiple times, and the average of the system efficiencies learned multiple times is taken as the final system efficiency Eff.

5. The disc contact point correction method of the electronic mechanical brake system according to claim 1, characterized in that: The current clamping force EffBasdClmpF is calculated as: EffBasdClmpF=Eff*Tm_c*i_mech; Where, Tm_c is the motor torque when the system clamps through a stroke of s; i_mech is the system reduction ratio.

6. The disc contact point correction method of the electronic mechanical brake system according to claim 1, characterized in that: When all learning conditions are met, the stroke s_corrected corresponding to the clamping force EffBasdClmpF is obtained according to the preset stroke and clamping force curve, and the stroke offset offs = s_corrected - s_uncorrected, wherein s_uncorrected is the uncorrected stroke at the clamping force EffBasdClmpF of the actual vehicle test.

7. The disc contact point correction method of the electronic mechanical brake system according to claim 6, characterized in that: Study conditions include: The uncorrected stroke s_uncorrected is within the set range; The clamping force EffBasdClmpF is not less than the set value; The motor speed is within the set range; Currently in clamping state; The brake disc temperature is within the set range.

8. The disc contact point correction method of the electronic mechanical brake system according to claim 6, characterized in that: The preset stroke and clamping force curves are obtained by laboratory testing.

9. The disc contact point correction method of the electronic mechanical brake system according to claim 6, characterized in that: Step S3 also includes learning the stroke offset offs each time the brake is applied as long as all the learning conditions are met, and comparing the latest learned stroke offset offs-new with the currently used stroke offset offs; if the change between the two exceeds the set value, updating the latest learned stroke offset offs-new to the currently used stroke offset offs; if the change between the two does not exceed the set value, retaining the currently used stroke offset offs.

10. The disc contact point correction method of the electronic mechanical brake system according to claim 1, characterized in that: The final stroke used is s_applied=s_uncorrected+offs, and the disk contact point is s_applied=0.

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