A method for calibrating a brake pedal travel sensor

Abstract

The application discloses a kind of brake pedal stroke sensor calibration methods, including calibration structure zero point;Configuration stroke sensor SENT signal and PWM signal parameter, using the brake pedal stroke sensor calibration method described above, zero point magnetic field reference angle is introduced in stroke sensor, corresponding relationship between stroke sensor output signal and zero point magnetic field reference angle is established, at this time although the actual magnetic field angle of structure zero point is indefinite, but by adjusting offset angle value, zero point magnetic field reference angle can be fixed, the position where zero point magnetic field reference angle abrupt point is also adjusted to relatively fixed position, so that stroke sensor obtains relatively stable displacement measurement range, to solve the problem of magnetic field angle abrupt in the process of push rod movement, simultaneously by adjusting zero point reference magnetic field angle, the size of displacement measurement range of stroke sensor can also be adjusted, so that the measurement interval of stroke sensor is more flexible.

Description

Technical Field

[0001] This invention relates to the field of sensor calibration technology, and in particular to a calibration method for a brake pedal travel sensor. Background Technology

[0002] The brake assist system is an important component of modern automotive braking systems. It is mainly used to reduce the force required by the driver when pressing the brake pedal, thereby improving the efficiency and stability of the braking system.

[0003] In the existing technology, the calibration of the stroke sensor in the automotive brake assist system mainly uses a programmer to write relevant parameters. The specific calibration method mostly adopts two-point calibration or multi-point calibration, that is, selecting two or more known position points and recording the corresponding values ​​of the sensor output. A linear or nonlinear mathematical model is established based on the input and output values ​​of the position points, thereby converting the sensor output into the corresponding position value.

[0004] However, during the movement of the push rod in a car's brake booster system, the magnetic field angle may abruptly change from 360° to 0° or vice versa. If the sensor output signal is directly correlated with the actual magnetic field angle, this abrupt change in angle will cause abrupt changes in the sensor output signal. Furthermore, due to the differences in magnets, the location of the abrupt change in magnetic field angle varies, and consequently, the signal abrupt change point also varies. A varying signal abrupt change point is undesirable, leading to uncontrollable displacement measurement range of the sensor. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a calibration method for a brake pedal travel sensor with high measurement accuracy.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions.

[0007] This application provides a calibration method for a brake pedal travel sensor, including:

[0008] A simulated mating system between the HCU and the automotive pedal assembly was built, and the structural zero point was calibrated when the pre-pressure between the HCU electric cylinder and the push rod of the automotive pedal assembly met the preset pressure range.

[0009] Configuration parameters for the SENT signal and PWM signal are written into the travel sensor of the automotive pedal assembly;

[0010] Configure the calibration points and target values ​​for the SENT signal and PWM signal in the stroke sensor respectively, and set the angle change trend of the PWM signal output value to decrease.

[0011] Perform two-point calibration of the stroke sensor and generate a correlation function between the SENT signal, the PWM signal output value and the push rod stroke;

[0012] Set the zero-point magnetic field reference angle for the SENT signal and PWM signal respectively, and calculate the offset angle value between the zero-point magnetic field reference angle and the actual zero-point magnetic field angle of the SENT signal and PWM signal output values ​​respectively.

[0013] Based on the correlation function between the SENT signal and PWM signal output values ​​and the push rod stroke in the offset angle correction stroke sensor;

[0014] The actual angle of the zero-point magnetic field is the magnetic field angle at the zero-point position of the structure.

[0015] Further defining the above-mentioned calibration method for the brake pedal travel sensor, the configuration parameters of the SENT signal and PWM signal include the frame length, data bits, verification method, decoding method, and communication rate of the SENT frame.

[0016] The configuration parameters of the PWM signal include frequency, duty cycle, upper and lower limits of pulse width, and voltage range.

[0017] Further defining the above-mentioned calibration method for the brake pedal travel sensor, the two-point calibration of the travel sensor includes:

[0018] The first calibration point of the travel sensor is triggered at the structural zero point position, and the second calibration point is triggered when the push rod of the car pedal assembly extends a predetermined distance;

[0019] Obtain the two SENT signal output values ​​and two PWM signal output values ​​of the travel sensor at the first calibration point and the second calibration point.

[0020] Further specifying the above-mentioned calibration method for the brake pedal travel sensor, the method for calculating the offset angle value is as follows:

[0021] Offset angle value = Signal output value of zero-point magnetic field reference angle - Signal output value of zero-point magnetic field actual angle;

[0022] The signal output value of the actual angle of the zero-point magnetic field is the SENT signal / PWM signal output value of the structural zero-point travel sensor.

[0023] Further specifying the above-mentioned calibration method for the brake pedal travel sensor, the method for obtaining the signal output value of the zero-point magnetic field reference angle for the SENT signal is as follows:

[0024] Y = 65535X / 360 - 32768;

[0025] Where X is the zero-point magnetic field reference angle of the SENT signal, and Y is the output value of the SENT signal at the zero-point magnetic field reference angle.

[0026] Further specifying the above-mentioned calibration method for the brake pedal travel sensor, the method for obtaining the signal output value of the zero-point magnetic field reference angle for the PWM signal is as follows:

[0027] Y = 32767 - 65535X / 360;

[0028] Where X is the zero-point magnetic field reference angle of the PWM signal, and Y is the output value of the PWM signal at the zero-point magnetic field reference angle.

[0029] Further specifying the above-mentioned calibration method for the brake pedal travel sensor, the zero-point magnetic field reference angle of the SENT signal is set to 35°, and the zero-point magnetic field reference angle of the PWM signal is set to 325°.

[0030] Further defining the above-mentioned calibration method for the brake pedal travel sensor, the method further includes, after correcting the correlation function between the SENT signal and PWM signal output values ​​of the travel sensor and the push rod travel:

[0031] With the push rod of the automotive pedal assembly in the fully released state, the SENT / PWM signal output value of the stroke sensor at the structural zero point is obtained;

[0032] A judgment result is formed by comparing the CAN signal encapsulated with the original signal corresponding to the SENT / PWM signal output value at the structural zero point with the corresponding zero point standard upper / lower limit value.

[0033] The error range between the original signal packaged CAN signal and the corresponding zero-point standard upper / lower limit value of the SENT / PWM signal output value at the structural zero point is set to be no greater than 0.5%.

[0034] Further specifying the above-mentioned calibration method for the brake pedal travel sensor, the method further includes, after forming a judgment result:

[0035] The HCU electric cylinder moves the push rod of the car pedal assembly from the structural zero position by a predetermined stroke at a predetermined speed, and obtains the SENT / PWM signal output value of the stroke sensor during the push rod movement process;

[0036] Based on the CAN signal encapsulated by the original signal corresponding to the SENT / PWM signal output value during the push rod movement, signal curves are generated respectively. The signal curves corresponding to the SENT / PWM signal output values ​​are compared with the corresponding standard upper / lower limit curves to form a judgment result.

[0037] Specifically, when the push rod of the automotive pedal assembly moves to the predetermined end point of its stroke, the thrust of the HCU electric cylinder on the push rod of the automotive pedal assembly is not greater than the rated top pressure.

[0038] Further specifying the above-mentioned calibration method for the brake pedal travel sensor, the standard upper / lower limit curve calculation function corresponding to the SENT signal output value is:

[0039] Y1=(X / 25.2*3766+320)*(1±2%);

[0040] Where Y1 is the upper or lower limit of the SENT signal standard, and X is the displacement (mm) of the HCU electric cylinder relative to the structural zero point, which is greater than zero.

[0041] The standard upper / lower limit curve calculation function corresponding to the PWM signal output value is:

[0042] Y2=(X / 25.2*73+16.1)*(1±2%);

[0043] Where Y2 is the upper or lower limit of the PWM signal standard, and X is the displacement (mm) of the HCU electric cylinder relative to the structural zero point, which is greater than zero.

[0044] This invention has at least the following beneficial effects:

[0045] 1. A zero-point magnetic field reference angle is introduced inside the stroke sensor to establish a correspondence between the stroke sensor output signal and the zero-point magnetic field reference angle. Although the actual magnetic field angle of the structural zero point is not fixed, the zero-point magnetic field reference angle can be fixed by adjusting the offset angle value. The position of the abrupt change point of the zero-point magnetic field reference angle is also adjusted to a relatively fixed position, so that the stroke sensor obtains a relatively stable displacement measurement range, thereby solving the problem of abrupt change of magnetic field angle during the movement of the push rod. At the same time, by adjusting the zero-point reference magnetic field angle, the displacement measurement range of the stroke sensor can also be adjusted, making the measurement range of the stroke sensor more flexible.

[0046] 2. By comparing the upper and lower limits of the SENT / PWM signal values ​​output by the stroke sensor at the structural zero point and during the movement of the push rod, the measurement accuracy of the stroke sensor is ensured. For unqualified stroke sensors, recalibration can be performed, thereby improving the overall calibration quality of the stroke sensor. Attached Figure Description

[0047] Figure 1 This is a flowchart illustrating the calibration method for the brake pedal travel sensor according to an embodiment of this application;

[0048] Figure 2This is a schematic diagram of the "calibration system" in the calibration method for the brake pedal travel sensor according to an embodiment of this application;

[0049] Figure 3 This is a graph showing the functional relationship between the output value of the SENT signal of the travel sensor and the magnetic field angle in the calibration method of the brake pedal travel sensor according to an embodiment of this application.

[0050] Figure 4 This is a graph showing the functional relationship between the PWM signal output value of the travel sensor and the magnetic field angle in the calibration method of the brake pedal travel sensor according to an embodiment of this application.

[0051] Figure Labels

[0052] Host computer-100, hydraulic control unit-200, automotive pedal assembly-300, burner-400. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0054] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0055] The calibration method for the brake pedal travel sensor provided in this application will be described in detail below with reference to the accompanying drawings, through specific embodiments and application scenarios.

[0056] like Figure 1 As shown in the figure, this application provides a calibration method for a brake pedal travel sensor, including:

[0057] S1. Build a simulation system for the interaction between the HCU and the automotive pedal assembly, obtain the pre-pressure between the HCU electric cylinder and the push rod of the automotive pedal assembly, and calibrate the structural zero point when the pre-pressure meets the preset pressure range.

[0058] S2. Write the configuration parameters of the SENT signal and PWM signal into the travel sensor of the automotive pedal assembly;

[0059] S3. Configure the calibration points and target values ​​of the SENT signal and PWM signal in the stroke sensor respectively, and set the angle change trend of the PWM signal output value to decrease.

[0060] S4. Trigger the first calibration point of the stroke sensor at the zero point of the structure, and trigger the second calibration point when the push rod of the car pedal assembly extends a predetermined distance. Generate the correlation function between the SENT signal, the PWM signal output value and the push rod stroke based on the first calibration point and the second calibration point.

[0061] S5. Set the zero-point magnetic field reference angle for the SENT signal and PWM signal respectively, and calculate the offset angle value between the zero-point magnetic field reference angle and the actual zero-point magnetic field angle of the SENT signal and PWM signal output values ​​respectively.

[0062] S6. Correlation function between the output values ​​of the SENT signal and PWM signal in the offset angle correction stroke sensor and the push rod stroke;

[0063] The actual angle of the zero-point magnetic field is the magnetic field angle at the zero-point position of the structure.

[0064] It is understood that HCU stands for Hydraulic Control Unit, which includes displacement sensors, electric cylinders, and pressure sensors. In the automotive brake assist system, the hydraulic control system provides push assistance to the automotive pedal assembly. In step S1, the simulated cooperation system between HCU and automotive pedal assembly is established by connecting the telescopic end of the electric cylinder of HCU to the push rod of automotive pedal assembly, thereby realizing the pre-pushing action of HCU electric cylinder on the push rod of automotive pedal assembly.

[0065] In step S1, the predetermined pre-pressure is obtained by the pressure sensor of the HCU. The reason for setting the preset pressure range is that the car pedal assembly itself has gravity, which will generate a certain pressure on the electric cylinder of the HCU under normal working conditions.

[0066] In step S1, the preset pressure range is set to 0 to 24 N. That is, when the preset pressure falls within the preset pressure range, the position is marked as the structural zero point, which is the structural mating origin between the HCU electric cylinder and the push rod of the car pedal assembly.

[0067] Understandably, during the calibration process of the travel sensor, it is also necessary to connect the HCU and the simulated coupling system of the automotive pedal assembly to the calibration system, such as... Figure 2As shown, the calibration system includes a host computer 100 connected to the hydraulic control unit 200, and a programmer 400 connected to the host computer 100 and the vehicle pedal assembly 300. The host computer 100 is used for visual interaction with the programmer 400 and to control the execution of the hydraulic control unit 200. The programmer 400 is used to configure the stroke sensor in the vehicle pedal assembly.

[0068] It is understandable that in step S1, after the simulation system of HCU and car pedal assembly is completed, the overall relative position between HCU and car pedal assembly is fixed, thereby ensuring the accuracy of the stroke information obtained by the stroke sensor.

[0069] In step S2, the configuration parameters of the SENT signal include the frame length, data bits, and verification method of the SENT frame, as well as the decoding method and communication rate; the configuration parameters of the PWM signal include the frequency, duty cycle, upper and lower limits of pulse width, and voltage range.

[0070] In a preferred embodiment, in step S3, the calibration point of the SENT signal in the stroke sensor is set to -18000, the first target value is set to 320, and the second target value is set to 4086; the calibration point of the PWM signal is set to 18000, the first target value is set to 16.1%, the second target value is set to 89.1%, and the output value angle change trend is set to decreasing.

[0071] In step S4, the first calibration point of the stroke sensor is triggered at the structural zero point position, and the second calibration point of the stroke sensor is triggered when the HCU electric cylinder pushes the push rod of the car pedal assembly to extend 25.2MM.

[0072] Based on the two SENT signal output values ​​of the travel sensor at the first and second calibration points, and the travel of the push rod of the automotive pedal assembly, a correlation function between the SENT signal output value and the push rod travel can be calculated; based on the two PWM signal output values ​​of the travel sensor at the first and second calibration points, and the travel of the push rod of the automotive pedal assembly, a correlation function between the PWM signal output value and the push rod travel can be calculated.

[0073] The stroke sensor can cross-verify its output values ​​using the SENT signal and PWM signal, thereby ensuring the accuracy of data acquisition.

[0074] In a preferred embodiment, in step S5, as follows: Figure 3 As shown, the relationship between the SNET output value of the stroke sensor and the magnetic field angle is:

[0075] Y = 65535X / 360 - 32768;

[0076] Where Y is the output value of the stroke sensor SNET, corresponding to Figure 3 The vertical axis in the diagram represents the magnetic field angle, corresponding to... Figure 3 The horizontal axis in the diagram has an X range of (0 to 360°) and a corresponding Y range of (-32768 to 32767).

[0077] For the SENT signal output chip, the magnetic field angle increases with the increase of the push rod displacement. Therefore, when the push rod moves forward relative to the structural zero point, the smaller the zero point magnetic field reference angle, the larger the range of magnetic field angle that the stroke sensor can measure, and the larger the range of displacement that can be measured. Therefore, the smaller the zero point magnetic field reference angle is, the better. However, in extreme cases, the push rod may move backward relative to the structural zero point. Therefore, the range of displacement that the stroke sensor can measure needs to include the displacement of the push rod moving backward relative to the zero point in extreme cases. Therefore, the preferred zero point magnetic field reference angle is 35°.

[0078] The SENT signal output value of the travel sensor at structural zero point is -24414, based on Y = 65535X / 360 - 32768. When the zero-point magnetic field reference angle is set to 35°, the corresponding SENT signal output value is (35 * 65535 / 360 - 32768), based on the formula:

[0079] Offset angle value = Signal output value of zero-point magnetic field reference angle - Signal output value of zero-point magnetic field actual angle;

[0080] Substituting the SENT signal output value of the actual angle of the zero-point magnetic field and the SENT signal output value of the reference angle of the zero-point magnetic field, we obtain:

[0081] Offset angle value = (35*65535 / 360-32768)-(-24414);

[0082] The above formula shows that when the zero-point magnetic field reference angle is set to 35°, the offset angle between the actual zero-point magnetic field angle and the zero-point magnetic field reference angle is -1982.

[0083] It is understood that the setting value of the zero-point magnetic field reference angle is not limited to the one mentioned above. The above only represents a preferred setting value. Based on the working stroke range and accuracy requirements of the stroke sensor, the zero-point magnetic field reference angle can also be set to other values. For example, when the zero-point magnetic field reference angle is set to 50°, the corresponding adjustment of the above formula is the offset angle value = (50*65535 / 360-32768)-(-24414).

[0084] In a preferred embodiment, in step S5, as follows: Figure 4 As shown, the relationship function between the stroke sensor PWM output value and the magnetic field angle is:

[0085] Y = 32767 - 65536X / 360;

[0086] Where Y is the PWM output value of the travel sensor, corresponding to Figure 4 The vertical axis in the diagram represents the magnetic field angle, corresponding to... Figure 4 The horizontal axis in the diagram has an X range of (0 to 360°) and a corresponding Y range of (-32768 to 32767).

[0087] For PWM signal output chips, the magnetic field angle decreases as the push rod displacement increases. Therefore, when the push rod moves forward relative to the structural zero point, the larger the zero-point reference magnetic field angle, the larger the range of magnetic field angles that the stroke sensor can measure, and the larger the range of displacement that can be measured. Thus, the larger the zero-point magnetic field reference angle is set, the better. However, in extreme cases, the push rod may move backward relative to the structural zero point. Therefore, the range of displacement that the stroke sensor can measure needs to include the displacement of the push rod moving backward relative to the zero point in extreme cases. Therefore, the preferred zero-point magnetic field reference angle is 325°.

[0088] The PWM signal output value of the travel sensor at structural zero point is 23515, based on Y = 32767 - 65536X / 360. When the zero-point magnetic field reference angle is set to 325°, the corresponding PWM signal output value is (32767 - 65536 * 325 / 360), based on the formula:

[0089] Offset angle value = Signal output value of zero-point magnetic field reference angle - Signal output value of zero-point magnetic field actual angle;

[0090] Substituting the PWM signal output value of the actual angle of the zero-point magnetic field and the PWM signal output value of the reference angle of the zero-point magnetic field, we obtain:

[0091] Offset angle value = (32767 - 65536 * 325 / 360) - (23515);

[0092] The above formula shows that when the zero-point magnetic field reference angle is set to 325°, the offset angle between the actual zero-point magnetic field angle and the zero-point magnetic field reference angle is 2880°.

[0093] It is understood that the setting value of the zero-point magnetic field reference angle is not limited to the one mentioned above. The above only represents a preferred setting value. Based on the working stroke range and accuracy requirements of the stroke sensor, the zero-point magnetic field reference angle can also be set to other values. For example, when the zero-point magnetic field reference angle is set to 310°, the corresponding adjustment of the above formula is the offset angle value = (32767-65536*310 / 360)-(23515).

[0094] It is understandable that in the relationship function between the stroke sensor SNET, the PWM output value and the magnetic field angle, the range of Y (-32768 to 32767) represents the range of 16-bit binary numbers in the two's complement case.

[0095] It is understandable that, since there should be a corresponding relationship between the SENT signal and PWM signal output by the stroke sensor and the stroke of the push rod, when the push rod moves forward a certain displacement relative to the zero point of the structure, the stroke sensor can output a set value corresponding to the displacement, and thus the movement stroke of the push rod can be determined based on the signal value output by the stroke sensor.

[0096] Throughout the entire travel range of the automotive pedal assembly, the magnetic field angle detected by the travel sensor changes as the push rod position changes. That is, there is a corresponding relationship between the magnetic field angle and the push rod displacement. Therefore, as long as a correspondence is established between the magnetic field angle and the output signal, a correspondence can be established between the push rod travel and the output signal. The purpose of travel sensor calibration is to establish a correspondence between the output signal and the magnetic field angle.

[0097] In this embodiment, the above-mentioned calibration method for the brake pedal travel sensor is adopted. In order to solve the problem of sudden changes in magnetic field angle during the movement of the push rod and obtain a relatively stable displacement measurement range, a zero-point magnetic field reference angle is introduced inside the travel sensor. A correspondence is established between the output signal of the travel sensor and the zero-point magnetic field reference angle. The signal output value of the zero-point magnetic field reference angle = the signal output value of the actual angle of the zero-point magnetic field + the offset angle value. At this time, although the actual magnetic field angle of the structural zero point is not fixed, the zero-point magnetic field reference angle can be fixed by adjusting the offset angle value. The position of the sudden change point of the zero-point magnetic field reference angle is also adjusted to a relatively fixed position. The travel sensor obtains a relatively stable displacement measurement range. At the same time, adjusting the zero-point reference magnetic field angle can also adjust the size of the displacement measurement range of the travel sensor.

[0098] In a preferred embodiment, in step S6, after obtaining the offset angle values ​​of the SENT signal and the PWM signal, the programmer 500 can correct the correlation function between the output values ​​of the SENT signal and the PWM signal and the push rod stroke and write it into the control chip of the stroke sensor.

[0099] In a preferred embodiment, it further includes:

[0100] S7. With the push rod of the automotive pedal assembly in the fully released state, acquire the SENT / PWM signal output value of the stroke sensor at the structural zero point;

[0101] S8. Compare the CAN signal encapsulated with the original signal corresponding to the SENT / PWM signal output value at the structural zero point with the corresponding zero point standard upper / lower limit value to form a judgment result.

[0102] It is understandable that, in step S8, the zero-point standard upper / lower limit values ​​corresponding to the SENT / PWM signal output values ​​at the structural zero point are shown in Table 1 below:

[0103] Table 1. Schematic diagram of upper / lower limits for structural zero-point standards.

[0104]

[0105]

[0106] In a preferred embodiment, in step S8, when comparing the CAN signal corresponding to the original signal package at the SENT / PWM signal output value at the structural zero point with the corresponding zero point standard upper / lower limit value, the expected error range is no greater than 0.5%. That is, if the error between the CAN signal corresponding to the SENT / PWM signal output value at the structural zero point and the corresponding zero point standard upper / lower limit value does not exceed 0.5%, it is judged as qualified; otherwise, it is judged as unqualified.

[0107] Understandably, non-compliant stroke sensors need to be recalibrated, and stroke sensors that fail to meet the standard after more than three calibration attempts are marked as defective parts.

[0108] In a preferred embodiment, it further includes:

[0109] S9, HCU electric cylinder moves the push rod of the car pedal assembly from the structural zero position by a predetermined stroke at a predetermined speed, and obtains the SENT / PWM signal output value of the stroke sensor during the push rod movement process;

[0110] S10. Based on the CAN signal encapsulated by the original signal corresponding to the SENT / PWM signal output value during the push rod movement, generate signal curves respectively, and compare the signal curves corresponding to the SENT / PWM signal output values ​​with the corresponding standard upper / lower limit curves to form a judgment result.

[0111] Specifically, when the push rod of the automotive pedal assembly moves to the predetermined end point of its stroke, the thrust of the HCU electric cylinder on the push rod of the automotive pedal assembly is not greater than the rated top pressure.

[0112] Understandably, stroke sensors that are deemed qualified in step S8 will then undergo signal testing in steps S9 and S10.

[0113] In a preferred embodiment, in step S9, the HCU electric cylinder pushes the push rod of the car pedal assembly at a speed of 1.2 mm / s until the push rod moves 30 mm relative to the zero point of the structure.

[0114] If the HCU electric cylinder exerts a thrust of 250N on the push rod during the process of the push rod moving 30mm relative to the zero point of the structure, then the 250N position is taken as the predetermined end point of the push rod's stroke.

[0115] In a preferred embodiment, in step S10, the standard upper limit curve calculation function for the SENT signal output value is:

[0116] Y=(X / 25.2*3766+320)*(1+2%);

[0117] Where Y is the upper limit of the SENT signal standard, and X is the displacement (mm) of the HCU electric cylinder relative to the structural zero point, which is greater than zero.

[0118] In a preferred embodiment, in step S10, the standard lower limit curve calculation function for the SENT signal output value is:

[0119] Y=(X / 25.2*3766+320)*(1-2%);

[0120] Where Y is the lower limit of the SENT signal standard, and X is the displacement (mm) of the HCU electric cylinder relative to the structural zero point, which is greater than zero.

[0121] In a preferred embodiment, in step S10, the standard upper limit curve calculation function for the PWM signal output value is:

[0122] Y=(X / 25.2*73+16.1)*(1+2%);

[0123] Where Y is the upper limit of the PWM signal standard, and X is the displacement (mm) of the HCU electric cylinder relative to the structural zero point, which is greater than zero.

[0124] In a preferred embodiment, in step S10, the standard lower limit curve calculation function for the PWM signal output value is:

[0125] Y=(X / 25.2*73+16.1)*(1-2%);

[0126] Where Y is the standard lower limit of the PWM signal, and X is the displacement (mm) of the HCU electric cylinder relative to the structural zero point, which is greater than zero.

[0127] In a preferred embodiment, in step S10, if the signal curve corresponding to the SENT / PWM signal output value does not exceed the corresponding standard upper / lower limit curve during the movement of the push rod, it is deemed qualified; otherwise, it is deemed unqualified.

[0128] Understandably, non-compliant stroke sensors need to be recalibrated, and stroke sensors that fail to meet the standard after more than three calibration attempts are marked as defective parts.

[0129] In this embodiment, the above-mentioned calibration method for the brake pedal travel sensor is adopted. The upper and lower limits of the SENT / PWM signal values ​​output by the travel sensor at the structural zero point and during the movement of the push rod are compared to ensure the measurement accuracy of the travel sensor. For unqualified travel sensors, recalibration can be performed, thereby improving the overall calibration quality of the travel sensor.

[0130] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0131] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A calibration method for a brake pedal travel sensor, characterized in that, include: A simulated mating system between the HCU and the automotive pedal assembly was built, and the structural zero point was calibrated when the pre-pressure between the HCU electric cylinder and the push rod of the automotive pedal assembly met the preset pressure range. Configuration parameters for the SENT signal and PWM signal are written into the travel sensor of the automotive pedal assembly; Configure the calibration points and target values ​​for the SENT signal and PWM signal in the stroke sensor respectively, and set the angle change trend of the PWM signal output value to decrease. Perform two-point calibration of the stroke sensor and generate a correlation function between the SENT signal, the PWM signal output value and the push rod stroke; Set the zero-point magnetic field reference angle for the SENT signal and PWM signal respectively, and calculate the offset angle value between the zero-point magnetic field reference angle and the actual zero-point magnetic field angle of the SENT signal and PWM signal output values ​​respectively. Based on the correlation function between the SENT signal and PWM signal output values ​​and the push rod stroke in the offset angle correction stroke sensor; Wherein, the actual angle of the zero-point magnetic field is the magnetic field angle at the zero-point position of the structure; The method for calculating the offset angle value is as follows: Offset angle value = Signal output value of zero-point magnetic field reference angle - Signal output value of zero-point magnetic field actual angle; The signal output value of the actual angle of the zero-point magnetic field is the SENT signal / PWM signal output value of the structural zero-point lower stroke sensor. For the SENT signal, the method for obtaining the signal output value of the zero-point magnetic field reference angle is as follows: Y = 65535X / 360 - 32768; Where X is the zero-point magnetic field reference angle of the SENT signal, and Y is the output value of the SENT signal at the zero-point magnetic field reference angle. For PWM signals, the method for obtaining the signal output value of the zero-point magnetic field reference angle is as follows: Y = 32767 - 65535X / 360; Where X is the zero-point magnetic field reference angle of the PWM signal, and Y is the output value of the PWM signal at the zero-point magnetic field reference angle; The zero-point magnetic field reference angle of the SENT signal is set to 35°, and the zero-point magnetic field reference angle of the PWM signal is set to 325°.

2. The calibration method for the brake pedal travel sensor according to claim 1, characterized in that, The configuration parameters for writing the SENT signal and PWM signal include the frame length, data bits, verification method, decoding method, and communication rate of the SENT signal. The configuration parameters of the PWM signal include frequency, duty cycle, upper and lower limits of pulse width, and voltage range.

3. The calibration method for the brake pedal travel sensor according to claim 1, characterized in that, The two-point calibration of the stroke sensor includes: The first calibration point of the travel sensor is triggered at the structural zero point position, and the second calibration point is triggered when the push rod of the car pedal assembly extends a predetermined distance; Obtain the two SENT signal output values ​​and two PWM signal output values ​​of the travel sensor at the first calibration point and the second calibration point.

4. The calibration method for the brake pedal travel sensor according to claim 1, characterized in that, The correlation function between the SENT signal and PWM signal output values ​​and the push rod stroke in the corrected stroke sensor also includes: With the push rod of the automotive pedal assembly in the fully released state, the SENT / PWM signal output value of the stroke sensor at the structural zero point is obtained; A judgment result is formed by comparing the CAN signal encapsulated with the original signal corresponding to the SENT / PWM signal output value at the structural zero point with the corresponding zero point standard upper / lower limit value. The error range between the original signal packaged CAN signal and the corresponding zero-point standard upper / lower limit value of the SENT / PWM signal output value at the zero point of the structure is set to be no greater than 0.5%.

5. The calibration method for the brake pedal travel sensor according to claim 4, characterized in that, After forming a judgment result, the following is also included: The HCU electric cylinder moves the push rod of the car pedal assembly from the structural zero position by a predetermined stroke at a predetermined speed, and obtains the SENT / PWM signal output value of the stroke sensor during the push rod movement process; Based on the CAN signal encapsulated by the original signal corresponding to the SENT / PWM signal output value during the push rod movement, signal curves are generated respectively. The signal curves corresponding to the SENT / PWM signal output values ​​are compared with the corresponding standard upper / lower limit curves to form a judgment result. Specifically, when the push rod of the automotive pedal assembly moves to the predetermined end point of its stroke, the thrust of the HCU electric cylinder on the push rod of the automotive pedal assembly is not greater than the rated top pressure.

6. The calibration method for the brake pedal travel sensor according to claim 5, characterized in that, The standard upper / lower limit curve calculation function corresponding to the SENT signal output value is: Y1=(X / 25.2*3766+320)*(1±2%); Where Y1 is the upper or lower limit of the SENT signal standard, and X is the displacement of the HCU electric cylinder relative to the structural zero point in mm, which is greater than zero. The standard upper / lower limit curve calculation function corresponding to the PWM signal output value is: Y2=(X / 25.2*73+16.1)*(1±2%); Where Y2 is the upper or lower limit of the PWM signal standard, and X is the displacement of the HCU electric cylinder relative to the structural zero point in mm, which is greater than zero.

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