Calibration method and device for brake-by-wire displacement sensor

Abstract

The invention discloses a line control brake displacement sensor calibration method and device, and belongs to the field of displacement sensor calibration after assembly, and the method comprises the following steps: S1, enabling a main cylinder push rod of a brake assembly to be coaxial with a vertical loading mechanism push rod in the vertical direction; s2, determining a calibration reference zero position; s3, collecting calibration data of the linear control dynamic displacement sensor; s4, calibration data checking; and S5, converting the calibration data acquired in the step S3 and the check data acquired in the step S4 into a calibration signal output curve and a check signal curve respectively, and judging whether the calibration precision meets a preset requirement by comparing the overlap ratio of the calibration signal output curve and the check signal curve. By the adoption of the line control brake displacement sensor calibration method and device, high-precision calibration of the displacement sensor, compatibility of multiple types of brake assemblies and rapid fault positioning are achieved, and safety and reliability of a line control brake system are guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of calibrating displacement sensors after assembly, and in particular to a linear brake displacement sensor calibration method and device. BACKGROUND

[0002] Under the development trend of automobile electrification and intelligentization, the linear brake system has become the mainstream development direction of modern automobile brake systems due to its fast response speed, high control precision, strong integration compatibility and other core advantages. The performance of the linear brake system directly determines the braking safety and handling stability of the vehicle. As a key component of the linear brake system, the displacement sensor is responsible for the important function of real-time monitoring of the displacement of the brake pedal stroke or brake actuator (such as the master cylinder push rod) - by converting the mechanical displacement signal into a standardized electrical signal, it provides the core input basis for the control system to accurately calculate the brake force demand.

[0003] At present, domestic brake system manufacturers generally use Hall-type displacement sensor components. The working principle of the Hall-type displacement sensor components in the brake assembly is as follows: the magnet assembly is fixed on the master cylinder piston that is linked with the master cylinder push rod. When the driver steps on the brake pedal, the master cylinder piston drives the magnet assembly to move linearly synchronously. With the change of the displacement of the master cylinder push rod, the relative spatial position of the magnet assembly and the sensor chip assembly changes, resulting in a regular change in the magnetic field distribution between them. The sensor chip converts the change in the magnetic field into a linear change in the output voltage through the built-in sensing unit, and finally realizes indirect measurement of the displacement. Therefore, the measurement accuracy and reliability of the displacement sensor are highly bound to the safety of the system.

[0004] The calibration of the existing displacement sensor needs to establish an accurate mapping relationship between the output electrical signal of the sensor and the actual mechanical displacement through a standardized method, and eliminate the errors introduced by the characteristic drift of the sensor itself or external environmental interference, so as to ensure the accuracy of the subsequent brake control logic. However, the existing technical solutions have the following significant defects: the Hall-type displacement sensor components used by domestic brake system manufacturers are all purchased from lower-level suppliers, and the "pre-calibration scheme" is generally used in the industry - that is, the supplier only completes the calibration once before the sensor components are shipped, and the brake system manufacturer does not perform secondary calibration or error correction on the sensor after assembling the components to the brake assembly. The core problem of this scheme is that there are inevitable factors such as position tolerance, part assembly deformation or assembly stress in the assembly process of the brake assembly, which causes the actual working state of the sensor after assembly to deviate from the reference state at the time of factory calibration, and further introduces significant output errors. Such errors not only reduce the displacement measurement accuracy, but also may cause the software algorithm of the brake assembly control system to mismatch the actual output characteristics of the sensor, affecting the accuracy of the brake force demand calculation, and even posing a potential risk to the safety performance of the brake system.

[0005] Meanwhile, the existing scheme lacks effective fault tracing capability: when the sensor signal output of the brake assembly product is abnormal after leaving the factory, since there is no calibration data and tracing information at the assembly end, the manufacturer cannot quickly distinguish whether the fault root is the performance defect of the sensor itself or the error introduced in the assembly process, resulting in low problem positioning efficiency and greatly increasing the cost and cycle of after-sales maintenance. SUMMARY

[0006] The purpose of the present application is to provide a brake-by-wire displacement sensor calibration method and device, which solves the above technical problems.

[0007] To achieve the above purpose, the present application provides a brake-by-wire displacement sensor calibration method, comprising the following steps: S1, brake assembly fixation: install the brake assembly to be calibrated on the positioning tool of the mobile station through its firewall connecting plate, and control the mobile station to move the brake assembly to be calibrated through the positioning tool until the master cylinder push rod of the brake assembly and the vertical loading mechanism push rod are coaxial in the vertical direction; S2, calibration reference zero determination: start the vertical loading mechanism, control the loading push rod of the vertical loading mechanism to move towards the master cylinder push rod, and use the resistance contact sensor to monitor whether the loading push rod and the master cylinder push rod are in contact, if not, the loading push rod continues to move down, if yes, the position of the loading push rod at this time is determined as the calibration reference zero; S3, brake-by-wire displacement sensor calibration data acquisition: input calibration parameters through the man-machine interface, the PLC controller receives the calibration parameters, and controls the vertical loading mechanism to push the master cylinder push rod to move along the calibration stroke, thereby driving the magnet assembly of the brake-by-wire displacement sensor to move with the master cylinder push rod; wherein the calibration parameters include calibration stroke range, target displacement point number, coordinates of each target displacement point, movement speed and acceleration; In the movement process, the actual displacement data of the master cylinder push rod is collected in real time by using the grating ruler and fed back to the PLC controller, the PLC controller compares the displacement error of the actual displacement and the target displacement through the PID algorithm, and then dynamically adjusts the displacement of the vertical loading mechanism according to the displacement error to eliminate the displacement error; at the same time, when the master cylinder push rod moves to any target displacement point, the PLC controller triggers the sensor chip calibrator and the data acquisition module, synchronously collects the output electrical signal of the built-in brake-by-wire displacement sensor of the brake assembly and the actual displacement value recorded by the current grating ruler, establishes the mapping relationship between the actual displacement and the sensor output signal at the target displacement point, until the signal collection of all target displacement points is completed; S4. Calibration data verification: The PLC controller controls the loading push rod of the vertical loading mechanism to move upward, and the main cylinder push rod retracts and resets along the calibration stroke under the action of the reset spring; during the retraction process, when the main cylinder push rod passes through the target displacement points set in step S3 again, the data acquisition module collects the output electrical signal of the displacement sensor and the actual displacement value of the grating ruler again to generate verification data. S5. Convert the calibration data collected in step S3 and the verification data collected in step S4 into calibration signal output curves and verification signal curves, respectively. By comparing the overlap between the calibration signal output curves and verification signal curves, determine whether the calibration accuracy meets the preset requirements. If the accuracy requirements are met, calculate the linear error and repeatability error of each target displacement point, and bind the calibration parameters, the actual displacement-sensor output signal mapping relationship of each target displacement point, the linear error, the repeatability error, and the verification curve data to the unique code of the braking assembly to be calibrated. Otherwise, determine that the calibration is abnormal.

[0008] Preferably, in step S3, the calibrated stroke range is 0-26mm, and a total of 7 target displacement points are set, which are set sequentially as 0mm, 4mm, 8mm, 12mm, 16mm, 20mm and 26mm.

[0009] Preferably, in step S3, the control strategy for the vertical loading mechanism is as follows: The target displacement point coordinates are mapped to the output pulse signal of the PLC controller. The PLC controller then sends the pulse signal to the servo driver of the vertical loading mechanism. The servo driver converts the pulse signal into the current and voltage commands required by the servo motor of the vertical loading mechanism, driving the servo motor to rotate in the preset direction. At the same time, the servo motor's built-in encoder collects the actual rotation angle data of the servo motor in real time and feeds it back to the servo driver, forming a position closed loop at the motor level to correct the servo motor's rotation error. The servo motor converts the rotational motion into linear motion through the transmission unit to drive the master cylinder push rod to move. During the movement of the master cylinder push rod, the PLC controller constructs a displacement closed loop control through a PID algorithm to ensure that the master cylinder push rod reaches the target displacement point.

[0010] Preferably, the PID algorithm expression described in step S3 is as follows: ; In the formula, This indicates the output instructions of the PLC controller; , and These represent proportion, integral, and differential, respectively. This indicates the displacement error.

[0011] Preferably, in steps S3 and S4, the PLC reads the status signal of the vertical loading mechanism in real time, and combines it with the actual displacement data of the main cylinder push rod fed back by the grating ruler to determine whether the calibration process is completed in stages.

[0012] An apparatus for performing a calibration method for a brake-by-wire displacement sensor includes a frame, a worktable mounted on the frame, a movable stage mounted on the worktable, a positioning fixture fixed on the movable stage for mounting a brake assembly, and a vertical loading mechanism. The loading push rod of the vertical loading mechanism is aligned with the master cylinder push rod of the brake assembly on the vertical axis. A resistive contact sensor is provided at the end of the loading push rod facing the master cylinder push rod to determine whether the loading push rod and the master cylinder push rod are in contact. The frame is also equipped with a grating ruler for collecting the actual displacement of the master cylinder. The grating ruler and the resistive contact sensor are both connected to the PLC controller. The PLC controller is connected to the servo driver of the vertical loading mechanism. The PLC controller is also connected to the human-machine interface and the displacement sensor built into the braking assembly.

[0013] Preferably, the servo driver of the vertical loading mechanism is connected to the drive motor, and the drive motor is fixedly connected to the top of the loading push rod via a transmission unit.

[0014] Preferably, the positioning fixture has positioning holes adapted to various specifications of brake assemblies, and the firewall of the brake assembly is detachably connected to the positioning holes via mounting screws.

[0015] Therefore, the present invention employs the above-described method and apparatus for calibrating a linear control displacement sensor, which has the following beneficial effects: 1. Eliminate assembly errors and improve displacement measurement accuracy: By performing secondary calibration after the brake assembly is assembled, the sensor output error problem caused by assembly position tolerance and component deformation in the traditional "supplier pre-calibration" is solved; at the same time, by combining the precise zero finding of the resistive contact sensor, the real-time feedback of the grating ruler and the dynamic correction of the PID algorithm, a precise mapping relationship between "actual displacement and sensor electrical signal" is established, which effectively improves the measurement accuracy of the displacement sensor and ensures the accuracy of the braking force calculation of the braking system. 2. Compatible with multiple brake assembly models, reducing equipment investment costs: The positioning fixture has holes drilled according to the screw positions of the firewall connecting plate of different brake assemblies. The moving table can drive the fixture to move, so that the master cylinder push rod and the loading push rod of different brake assemblies are coaxially aligned; there is no need to design separate fixtures for a single brake assembly model, which greatly improves equipment compatibility and reduces the investment cost of manufacturers for multiple sets of calibration equipment. 3. Achieve full traceability of calibration data and quickly locate the root cause of faults: During the calibration process, the equipment binds and stores the calibration parameters (stroke, target point, etc.), the "actual displacement-electrical signal" data of each target displacement point, linearity error, repeatability error, and calibration / verification curves of dual SENT signals with the unique code of the braking assembly; if sensor signal abnormalities occur later, the factory calibration data of the sensor can be compared with the calibration data of the assembly to quickly distinguish whether the fault is due to sensor defects or assembly errors, shorten the fault diagnosis cycle, and reduce after-sales maintenance costs; 4. Dual SENT signal redundancy design to ensure braking system safety: The sensor chip outputs two SENT signals, which are simultaneously acquired and corresponding curves are generated during calibration and verification. On the one hand, if one signal fails, the other can continue to provide displacement data, avoiding signal loss that could lead to brake control interruption. On the other hand, by comparing the consistency of the two signals, the working status of the sensor chip can be verified in real time, and potential problems such as failure of a single sensing unit of the chip can be detected in advance, which meets the redundancy design requirements of automotive safety-critical systems. 5. The calibration process is visualized and controllable, improving the convenience and reliability of operation: The human-machine interface can display the dual SENT signal output / verification curves, displacement stroke curves, PLC execution steps, and target point calibration / verification data tables in real time. Operators can intuitively monitor the calibration progress and status. At the same time, the calibration process is automatically controlled by PLC (such as motion trajectory planning and data acquisition triggering), reducing manual operation intervention, lowering the risk of human error, and improving the convenience and reliability of the calibration process.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a flowchart of a calibration method for a linear control displacement sensor according to the present invention; Figure 2 This is a schematic diagram of the overall structure of the device for performing a calibration method for a linear control displacement sensor according to the present invention; Figure 3 This is a schematic diagram illustrating the determination of the calibration reference zero point as described in this invention; Figure 4 This is a schematic diagram of the positioning fixture structure of the device for performing a calibration method for a linear control displacement sensor according to the present invention; Figure 5 This is a schematic diagram of the human-machine interface of the device for performing a calibration method for a linear control displacement sensor according to the present invention.

[0018] Figure Labels 1. Frame; 2. Moving stage; 3. Positioning fixture; 31. Positioning hole; 4. Vertical loading mechanism; 41. Loading push rod; 42. Servo motor; 5. Grating ruler; 6. Human-machine interface; 7. Braking assembly; 71. Master cylinder push rod; 8. Resistive contact sensor. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0020] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as a process, method, system, product, or server that includes a series of steps or units, not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or device.

[0021] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] like Figure 1 As shown, a calibration method for a brake-by-wire displacement sensor includes the following steps: S1. Brake assembly 7 is fixed: The brake assembly 7 to be calibrated is installed on the positioning fixture 3 of the moving table 2 through its firewall connecting plate, and the moving table 2 is operated to move the brake assembly 7 to be calibrated through the positioning fixture 3 until the main cylinder push rod 71 of the brake assembly 7 and the push rod of the vertical loading mechanism 4 are coaxial in the vertical direction. In this embodiment, the mobile stage is mounted on the workbench of the calibration equipment, and its planar position adjustment is achieved through two sets of independent servo cylinders: one servo cylinder is arranged along the X-axis and Y-axis directions respectively in the moving plane, and the two sets of cylinders work together to cover all alignment requirements in the plane; each servo cylinder integrates a high-precision displacement sensor, and is equipped with a proportional valve or servo valve, which together form a closed-loop control system for the position of the cylinder movement, providing hardware support for the displacement adjustment accuracy.

[0023] Specifically, the position adjustment of the moving platform is achieved through the collaboration of a PLC controller and a human-machine interface (HMI), adapting to the alignment requirements of various braking assemblies: First, the PLC controller pre-stores the target point coordinates of "master cylinder push rod-load push rod coaxial" for different specifications of brake assemblies (i.e., the XY axis alignment parameters required for different models of brake assemblies). Then, the operator only needs to select the brake assembly model to be calibrated in the human-machine interface, and the PLC controller will automatically call the preset target position parameters corresponding to that model. Finally, the PLC sends action commands to the XY axis servo cylinders, driving the two sets of cylinders to coordinately adjust the position of the moving stage according to the target parameters until the actual position fed back by the displacement sensor is completely matched with the preset target position. At this time, the main cylinder push rod of the braking assembly and the loading push rod of the vertical loading mechanism are vertically coaxially aligned, laying the foundation for the subsequent calibration process.

[0024] S2. Calibration reference zero position determination: Start the vertical loading mechanism 4 and control the loading push rod 41 of the vertical loading mechanism 4 to move towards the master cylinder push rod 71. Use the resistive contact sensor 8 to monitor whether the loading push rod 41 and the master cylinder push rod 71 are in contact (when the brake push rod and the loading push rod 41 are in contact and subjected to force, the pressure between the two conductive materials of the resistive contact sensor 8 changes, causing a change in contact resistance. By measuring the change in resistance value, it can be determined whether contact has occurred). If not, the loading push rod 41 continues to move downward. If so, it is determined that the position of the loading push rod 41 at this time is the calibrated reference zero position. S3. Calibration data acquisition of the brake-by-wire displacement sensor: Calibration parameters are input through the human-machine interface 6. The PLC controller receives the calibration parameters and controls the vertical loading mechanism 4 to push the main cylinder push rod 71 to move along the calibration stroke according to the calibration parameters, thereby driving the magnet assembly of the brake-by-wire displacement sensor to move with the main cylinder push rod 71. The calibration parameters include the calibration stroke range, the number of target displacement points, the coordinates of each target displacement point, the movement speed and acceleration. During the movement, the actual displacement data of the master cylinder push rod 71 is collected in real time using the grating ruler 5 and fed back to the PLC controller. The PLC controller compares the displacement error between the actual displacement and the target displacement using a PID algorithm, and then dynamically adjusts the displacement of the vertical loading mechanism 4 according to the displacement error to eliminate the displacement error. At the same time, when the master cylinder push rod 71 moves to any target displacement point, the PLC controller triggers the sensor chip calibrator and data acquisition module to synchronously collect the output electrical signals (such as the sent1 signal and sent2 signal) of the brake assembly 7 built-in brake-by-wire displacement sensor and the actual displacement value recorded by the grating ruler 5 at the current time, and establishes the mapping relationship between the actual displacement and the sensor output signal at the target displacement point until the signal acquisition of all target displacement points is completed. S4. Calibration data verification: The PLC controller controls the loading push rod 41 of the vertical loading mechanism 4 to move upward, and the main cylinder push rod 71 retracts and resets along the calibration stroke under the action of the reset spring; during the retraction process, when the main cylinder push rod 71 passes through the target displacement points set in step S3 again, the data acquisition module collects the output electrical signal of the displacement sensor and the actual displacement value of the grating ruler 5 again to generate verification data. S5. Convert the calibration data collected in step S3 and the verification data collected in step S4 into calibration signal output curves and verification signal curves, respectively. By comparing the overlap between the calibration signal output curves and verification signal curves, determine whether the calibration accuracy meets the preset requirements. If the accuracy requirements are met, calculate the linear error and repeatability error of each target displacement point, and bind the calibration parameters, the actual displacement-sensor output signal mapping relationship of each target displacement point, the linear error, the repeatability error, and the verification curve data to the unique code of the braking assembly 7 to be calibrated. Otherwise, determine that the calibration is abnormal.

[0025] In step S3, the calibrated stroke range is 0-26mm, and a total of 7 target displacement points are set, which are sequentially set to 0mm, 4mm, 8mm, 12mm, 16mm, 20mm, and 26mm. It should be noted that the number and location of the target displacement points mentioned above are merely illustrative examples. The setting of other target displacement points using the method described in this invention is still within the scope of protection of this invention, and should not be interpreted by those skilled in the art as a limitation on the specific number and location.

[0026] In step S3, the control strategy for the vertical loading mechanism 4 is as follows: The target displacement point coordinates are mapped to the output pulse signal of the PLC controller. The PLC controller then sends the pulse signal to the servo driver of the vertical loading mechanism 4. The servo driver converts the pulse signal into the current and voltage commands required by the servo motor 42 of the vertical loading mechanism 4, driving the servo motor 42 to rotate in a preset direction. At the same time, the encoder built into the servo motor 42 collects the actual rotation angle data of the servo motor 42 in real time and feeds it back to the servo driver, forming a position closed loop at the motor level to correct the rotation error of the servo motor 42. The servo motor 42 converts the rotational motion into linear motion through the transmission unit to drive the master cylinder push rod 71 to move. During the movement of the master cylinder push rod 71, the PLC controller constructs a displacement closed loop control through the PID algorithm to ensure that the master cylinder push rod 71 reaches the target displacement point.

[0027] In this embodiment, each pulse signal corresponds to the servo motor 42 of the vertical loading mechanism 4 rotating by a fixed angle. This angle is calibrated by the electronic gear ratio, and the calculation formula of the electronic gear ratio is: electronic gear ratio = encoding resolution of servo motor 42 / number of instruction pulses required per revolution. By setting the electronic gear ratio, the physical coordinates (mm) of the target displacement point can be directly mapped to the number of pulses output by the PLC, thereby achieving accurate positioning of the target displacement point.

[0028] In this embodiment, the PLC controller can also read the status signals of the vertical loading mechanism 4 in real time, including the running status of the servo motor 42 (running / stopping / fault), the validity of the grating ruler 5 signal (normal / lost), and the overtravel status of the push rod displacement (whether it exceeds the 0-26mm calibrated stroke range). If a servo motor 42 fault, grating ruler 5 signal loss, or overtravel is detected, the PLC immediately triggers an emergency stop command, cuts off the servo driver output, and displays the fault type (such as "grating ruler 5 signal interruption" or "push rod overtravel alarm") on the human-machine interface 6 (HMI). At the same time, it records the displacement data and timestamp at the time of the fault to facilitate subsequent fault troubleshooting.

[0029] The PID algorithm expression described in step S3 is as follows: ; In the formula, This indicates the output instructions of the PLC controller; , and These represent proportion, integral, and differential, respectively. This indicates the displacement error.

[0030] In steps S3 and S4, the PLC reads the status signal of the vertical loading mechanism 4 in real time, and combines it with the actual displacement data of the main cylinder push rod 71 fed back by the grating ruler 5 to determine whether the calibration process is completed in stages.

[0031] Specifically, in step S3, for all target displacement points input by the human-machine interface 6 (such as 0mm, 4mm, 8mm, 12mm, 16mm, 20mm, 26mm), the PLC controller needs to judge the acquisition progress of each target displacement point separately: first, read the motion status bit of the vertical loading mechanism 4 to confirm whether it has switched to "motion completed"; at the same time, check whether the error between the actual displacement of the main cylinder push rod 71 fed back by the grating ruler 5 and the current target displacement point is less than the preset accuracy threshold; when both are satisfied, it is determined that the calibration data acquisition of the target displacement point is completed; after all target displacement points have been acquired, the PLC further confirms that no "motion fault" status bit is triggered before it can be determined that the calibration data acquisition process of step S3 is completed as a whole. In step S4, the PLC controller tracks the motion direction status of the vertical loading mechanism 4 in real time (confirming that the loading push rod 41 is in the retraction motion mode) and motion status position: when the main cylinder push rod 71 retracts past each target displacement point, the PLC locks the point position through the actual displacement of the grating ruler 5 and determines whether the data acquisition of the point is completed; after all target displacement point data acquisition is completed, the PLC continues to monitor whether the actual displacement fed back by the grating ruler 5 returns to the reference zero position determined in step S2, and when the motion status position of the vertical loading mechanism 4 switches to "motion completed" and no abnormal status position is triggered, the calibration data verification process of step S4 is determined to be completed.

[0032] like Figures 2-5 As shown, an apparatus for performing a calibration method for a brake-by-wire displacement sensor includes a frame 1, a worktable mounted on the frame 1, a movable stage 2 movably mounted on the worktable, a positioning fixture 3 fixed on the movable stage 2 for mounting a brake assembly 7, and a vertical loading mechanism 4. The loading push rod 41 of the vertical loading mechanism 4 is aligned with the master cylinder push rod 71 of the brake assembly 7 on the vertical axis. A resistive contact sensor 8 is provided at the end of the loading push rod 41 facing the master cylinder push rod 71 to determine whether the loading push rod 41 and the master cylinder push rod 71 are in contact. The frame 1 is also equipped with a grating ruler 5 for collecting the actual displacement of the main cylinder. The grating ruler 5 and the resistive contact sensor 8 are both connected to the PLC controller. The PLC controller is connected to the servo driver of the vertical loading mechanism 4. The PLC controller is also connected to the human-machine interface 6 and the displacement sensor built into the braking assembly 7.

[0033] The servo driver of the vertical loading mechanism 4 is connected to the drive motor, and the drive motor is fixedly connected to the top of the loading push rod 41 via the transmission unit.

[0034] The positioning fixture 3 has positioning holes 31 that are adapted to various specifications of brake assemblies 7. The firewall of the brake assembly 7 is detachably connected to the positioning holes 31 by mounting screws.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A calibration method for a linear braking displacement sensor, characterized in that: Includes the following steps: S1. Brake assembly fixing: The brake assembly to be calibrated is installed on the positioning fixture of the moving table through its firewall connecting plate, and the moving table is operated to move the brake assembly to be calibrated through the positioning fixture until the main cylinder push rod of the brake assembly and the vertical loading mechanism push rod are coaxial in the vertical direction. S2. Calibration reference zero position determination: Start the vertical loading mechanism and control the loading push rod of the vertical loading mechanism to move towards the master cylinder push rod. Use a resistive contact sensor to monitor whether the loading push rod is in contact with the master cylinder push rod. If not, the loading push rod continues to move down. If so, the position of the loading push rod at this time is determined to be the calibration reference zero position. S3. Calibration data acquisition of brake-by-wire displacement sensor: Calibration parameters are input through the human-machine interface. The PLC controller receives the calibration parameters and controls the vertical loading mechanism to push the master cylinder push rod along the calibration stroke according to the calibration parameters, thereby driving the magnet assembly of the brake-by-wire displacement sensor to move with the master cylinder push rod. The calibration parameters include the calibration stroke range, the number of target displacement points, the coordinates of each target displacement point, the movement speed and acceleration. During the movement, the actual displacement data of the master cylinder push rod is collected in real time using a grating ruler and fed back to the PLC controller. The PLC controller compares the displacement error between the actual displacement and the target displacement using a PID algorithm, and then dynamically adjusts the displacement of the vertical loading mechanism according to the displacement error to eliminate the displacement error. At the same time, when the master cylinder push rod moves to any target displacement point, the PLC controller triggers the sensor chip calibrator and the data acquisition module to synchronously collect the output electrical signal of the brake assembly's built-in brake-by-wire displacement sensor and the actual displacement value recorded by the grating ruler, and establishes the mapping relationship between the actual displacement and the sensor output signal at the target displacement point until the signal acquisition of all target displacement points is completed. S4. Calibration data verification: The PLC controller controls the loading push rod of the vertical loading mechanism to move upward, and the main cylinder push rod retracts and resets along the calibration stroke under the action of the reset spring; during the retraction process, when the main cylinder push rod passes through the target displacement points set in step S3 again, the data acquisition module collects the output electrical signal of the displacement sensor and the actual displacement value of the grating ruler again to generate verification data. S5. Convert the calibration data collected in step S3 and the verification data collected in step S4 into calibration signal output curves and verification signal curves, respectively. By comparing the overlap between the calibration signal output curves and verification signal curves, determine whether the calibration accuracy meets the preset requirements. If the accuracy requirements are met, calculate the linear error and repeatability error of each target displacement point, and bind the calibration parameters, the actual displacement-sensor output signal mapping relationship of each target displacement point, the linear error, the repeatability error, and the verification curve data to the unique code of the braking assembly to be calibrated. Otherwise, determine that the calibration is abnormal.

2. The calibration method for a linear braking displacement sensor according to claim 1, characterized in that: In step S3, the calibrated stroke range is 0-26mm, and a total of 7 target displacement points are set, which are 0mm, 4mm, 8mm, 12mm, 16mm, 20mm and 26mm respectively.

3. The calibration method for a linear control displacement sensor according to claim 1, characterized in that: In step S3, the control strategy for the vertical loading mechanism is as follows: The target displacement point coordinates are mapped to the output pulse signal of the PLC controller. The PLC controller then sends the pulse signal to the servo driver of the vertical loading mechanism. The servo driver converts the pulse signal into the current and voltage commands required by the servo motor of the vertical loading mechanism, driving the servo motor to rotate in the preset direction. At the same time, the servo motor's built-in encoder collects the actual rotation angle data of the servo motor in real time and feeds it back to the servo driver, forming a position closed loop at the motor level to correct the servo motor's rotation error. The servo motor converts the rotational motion into linear motion through the transmission unit to drive the master cylinder push rod to move. During the movement of the master cylinder push rod, the PLC controller constructs a displacement closed loop control through a PID algorithm to ensure that the master cylinder push rod reaches the target displacement point.

4. The calibration method for a linear braking displacement sensor according to claim 3, characterized in that: The PID algorithm expression described in step S3 is as follows: ； In the formula, This indicates the output instructions of the PLC controller; , and These represent proportion, integral, and differential, respectively. This indicates the displacement error.

5. The calibration method for a linear braking displacement sensor according to claim 4, characterized in that: In steps S3 and S4, the PLC reads the status signal of the vertical loading mechanism in real time and, in conjunction with the actual displacement data of the main cylinder push rod fed back by the grating ruler, determines in stages whether the calibration process is complete.

6. An apparatus for performing a calibration method for a linear braking displacement sensor according to any one of claims 1-5, characterized in that: It includes a frame, a worktable mounted on the frame, a movable stage mounted on the worktable, a positioning fixture fixed on the movable stage for installing the brake assembly, and a vertical loading mechanism. The loading push rod of the vertical loading mechanism is aligned with the master cylinder push rod of the brake assembly on the vertical axis. A resistive contact sensor is provided at the end of the loading push rod facing the master cylinder push rod to determine whether the loading push rod and the master cylinder push rod are in contact. The frame is also equipped with a grating ruler for collecting the actual displacement of the master cylinder. The grating ruler and the resistive contact sensor are both connected to the PLC controller. The PLC controller is connected to the servo driver of the vertical loading mechanism. The PLC controller is also connected to the human-machine interface and the displacement sensor built into the braking assembly.

7. The apparatus for calibrating a linear control displacement sensor according to claim 6, characterized in that: The servo driver of the vertical loading mechanism is connected to the drive motor, and the drive motor is fixedly connected to the top of the loading push rod via a transmission unit.

8. The apparatus for calibrating a linear braking displacement sensor according to claim 6, characterized in that: The positioning fixture has positioning holes adapted to various sizes of brake assemblies, and the firewall of the brake assembly can be detachably connected to the positioning holes via mounting screws.

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