Sensor self-calibration method, system for vehicle braking system

Abstract

The application discloses a sensor self-calibration method and system for a vehicle braking system. In order to solve the technical problem that residual pressure is caused by oil entrapment in a blind end of a high-frequency brake adjusting pipeline, leading to zero point error calibration of a hydraulic sensor, when the vehicle is stationary and the pedal is returned to the home position, a stable pressure reading average is collected and locked as a suspected zero point reference value; then, a diagnostic control parameter that does not cause loss of liquid volume in the wheel cylinder is set, a diagnostic control pulse is sent to the liquid outlet electromagnetic valve, the valve is temporarily opened to connect the blind end pipeline; after the pressure is stable again, the current reading is extracted, and the pressure attenuation difference between the current reading and the suspected reference value is calculated; finally, whether there is trapped pressure in the pipeline is determined according to the difference, so that the true zero point is confirmed and updated. The application actively detects the pressure by slight leakage, effectively eliminates the interference of the false zero point, and improves the accuracy of calibration and the system robustness.

Description

Technical Field

[0001] This invention relates to the field of sensor self-calibration technology, specifically to a sensor self-calibration method and system for vehicle braking systems. Background Technology

[0002] With the development of automotive electronic control technology, brake-by-wire systems (such as One-Box / Two-Box systems) and Electronic Stability Program (ESP) have been widely used in modern vehicles. In these highly integrated braking systems, hydraulic sensors are the core measuring elements for achieving precise braking force distribution and closed-loop control. To eliminate signal deviations caused by mechanical aging or temperature drift of hydraulic sensors due to long-term operation, the control system typically needs to periodically perform zero-point self-calibration of the sensors when the vehicle is not braking.

[0003] Existing hydraulic sensor zero-point self-calibration strategies typically employ passive observation logic. The basic process is as follows: when the vehicle controller detects that the vehicle is stationary and the brake pedal has physically returned to its original position, it opens a fixed-duration resting observation window. If, within this window, the output signal of the hydraulic sensor shows minimal fluctuation and tends towards a stable straight line, the system assumes that the fluid in the pipeline is completely still, and thus uses the current average reading as the sensor's new zero point for calibration and writes it into storage.

[0004] However, after a vehicle has just undergone high-frequency adjustments by the Anti-lock Braking System (ABS) or Electronic Stability Program (ESP), multiple inlet and outlet solenoid valves within the system will close rapidly. Due to hydrodynamic characteristics and the physical dead zones of the valve body's internal structure, a small amount of high-pressure brake fluid can easily be trapped in the blind end of the line between the valve and the pressure sensor at the moment of high-speed closure, resulting in trapped brake fluid.

[0005] This physically trapped, minute hydraulic pressure, lacking a release channel, creates a fixed residual pressure. For traditional self-calibration algorithms, because this residual pressure is static and constant, the signal output by the hydraulic sensor will still exhibit a highly stable waveform. Existing passive observation strategies are prone to mistakenly interpreting this weak physical pressure remaining within the pipeline as electrical zero-point drift of the sensor hardware itself, leading to incorrect calibration and zeroing, thus disrupting the underlying hydraulic reference of the braking system. When the driver presses the brake pedal again, the system will calculate the pressure build-up logic and motor compensation torque based on the incorrect zero-point starting point, directly resulting in sluggish initial braking response, a longer effective brake pedal travel (i.e., a softer feel or free travel), and even causing imbalance in wheel braking force distribution during emergency braking, posing a serious threat to the vehicle's active safety.

[0006] Therefore, accurately identifying and eliminating false zero points caused by the minute pressure retention of the solenoid valve, and improving the authenticity and robustness of the hydraulic sensor's self-calibration, is a technical problem that urgently needs to be solved. Summary of the Invention

[0007] In order to address at least one of the technical defects mentioned in the background art, the present invention aims to provide a sensor self-calibration method and system for a vehicle braking system.

[0008] A first aspect of the present invention provides a sensor self-calibration method for a vehicle braking system, the method comprising: The vehicle driving status and brake pedal displacement signal are acquired. When the vehicle driving status indicates that the vehicle is stationary and the brake pedal displacement signal indicates that the pedal is at the physical zero position, the continuous pressure reading of the hydraulic sensor is collected. If the fluctuation range of the continuous pressure reading within a preset time is less than the steady-state threshold, its average value is locked as the suspected zero-point reference value. After locking the suspected zero-point reference value, set diagnostic control parameters that do not cause fluid loss in the wheel cylinder, including duty cycle and duration; send a diagnostic control pulse to the outlet solenoid valve of the braking system according to the diagnostic control parameters, so that the outlet solenoid valve is briefly opened to connect the hydraulic blind end pipeline. After sending the diagnostic control pulse, the pressure reading of the hydraulic sensor is collected again. After the pressure reading stabilizes, it is extracted as the current pressure reading, and the pressure attenuation difference between the suspected zero-point reference value and the current pressure reading is calculated. Perform a self-calibration update based on the pressure attenuation difference.

[0009] A second aspect of the present invention provides a sensor self-calibration system for a vehicle braking system, the system comprising: The reference locking module is used to acquire the vehicle driving status and brake pedal displacement signal. When the vehicle driving status indicates that the vehicle is stationary and the brake pedal displacement signal indicates that the pedal is at the physical zero position, the module acquires the continuous pressure reading of the hydraulic sensor. If the fluctuation range of the continuous pressure reading within a preset time period is less than the steady-state threshold, the average value is locked as the suspected zero-point reference value. The diagnostic micro-motion module is used to set diagnostic control parameters, including duty cycle and duration, that will not cause loss of fluid in the wheel cylinder after locking the suspected zero-point reference value; and to send a diagnostic control pulse to the outlet solenoid valve of the braking system according to the diagnostic control parameters, so that the outlet solenoid valve is briefly opened to connect the hydraulic blind end pipeline. The pressure drop extraction module is used to collect the pressure reading of the hydraulic sensor again after sending the diagnostic control pulse, extract the current pressure reading after the pressure reading stabilizes, and calculate the pressure attenuation difference between the suspected zero point reference value and the current pressure reading. The self-calibration update module is used to perform self-calibration updates based on the pressure attenuation difference.

[0010] Compared with existing technologies, this invention uses active micro-pressure relief flaw detection to verify the authenticity of suspected zero points, thus effectively solving the problem of zero-point miscalibration caused by the inability of traditional passive observation strategies to distinguish between sensor electrical zero drift and physical residual pressure in pipelines. Simultaneously, by limiting diagnostic control parameters to a safe range that does not cause fluid loss in the wheel cylinders, it also ensures that the active flaw detection process has no negative impact on braking safety. Therefore, this invention significantly improves the authenticity and robustness of hydraulic sensor zero-point self-calibration, avoiding safety hazards such as brake response delay, increased effective pedal travel, and brake force distribution imbalance caused by incorrect zero-point calibration, providing a reliable pressure reference for the precise control of the vehicle braking system. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the main flow of a sensor self-calibration method for a vehicle braking system disclosed in an embodiment of the present invention; Figure 2 This is a flowchart illustrating the specific implementation process of step S2 disclosed in an embodiment of the present invention; Figure 3 This is a schematic diagram of a sensor self-calibration system for a vehicle braking system disclosed in an embodiment of the present invention. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention.

[0013] This invention provides a sensor self-calibration method for vehicle braking systems, which can operate in the domain controller of a vehicle controller or an electro-hydraulic braking system (such as a One-Box / Two-Box system). This method actively sends diagnostic control pulses to the outlet solenoid valve, briefly connecting the blind-end pipeline to release potential trapped pressure. The true zero point is then confirmed based on the pressure attenuation difference before and after pressure release, effectively eliminating false zero-point interference caused by oil trapping at the blind end of the pipeline after high-frequency braking adjustment. The method of this invention will be described in detail below with reference to the accompanying drawings.

[0014] Reference Figure 1 As shown, the method includes the following steps: S1: Acquire vehicle driving status and brake pedal displacement signal. When the vehicle driving status indicates that the vehicle is stationary and the brake pedal displacement signal indicates that the pedal is at the physical zero position, collect continuous pressure readings of the hydraulic sensor. If the fluctuation range of the continuous pressure reading within a preset time is less than the steady-state threshold, lock its average value as the suspected zero-point reference value. In this embodiment, vehicle driving status signals and brake pedal displacement signals are acquired in real time via the vehicle's CAN bus or a dedicated signal line. The vehicle driving status signal originates from the vehicle speed information output by the wheel speed sensor or the vehicle stability control unit. When this signal indicates a zero speed for a certain period (e.g., more than 500ms), the vehicle is determined to be stationary. Simultaneously, the displacement signal output by the brake pedal displacement sensor is read. When this signal indicates the pedal is at its physical zero position (i.e., the driver has not depressed the brake pedal, and the pedal displacement is less than its physical return tolerance threshold, e.g., less than 1% of the rated full scale), the trigger condition for executing the zero-point calibration procedure is confirmed. After meeting the above trigger conditions—that is, the vehicle is stationary and the pedal is physically returned to its original position—the process of continuously acquiring pressure readings from the hydraulic sensors is initiated.

[0015] Understandably, after a vehicle has just undergone high-frequency adjustments from ABS (Anti-lock Braking System) or ESP (Electronic Stability Program), the inlet and outlet solenoid valves within the system will quickly shut off. Due to fluid dynamics and the physical dead zones of the valve body's internal structure, a small amount of high-pressure brake fluid can easily be trapped in the blind-end pipeline between the valve and the pressure sensor at the moment of high-speed closure, resulting in trapped fluid. This physically trapped small amount of hydraulic fluid, lacking a release channel, forms a fixed residual pressure. For traditional self-calibration algorithms, since this residual pressure is static and constant, the signal output by the hydraulic sensor will still exhibit a highly stable waveform, and its fluctuation amplitude often meets the conventional steady-state determination conditions. Therefore, it is easily mistaken for electrical zero-point drift of the sensor hardware itself, leading to incorrect zero-point calibration.

[0016] Therefore, after collecting continuous pressure readings, this step does not directly store the average value as the final zero point. Instead, it first determines whether the fluctuation range meets the steady-state conditions. If it does, the average value of the current reading is locked as a suspected zero-point reference value to be further verified, thus preserving the basis for judgment in the active diagnosis and verification in subsequent steps.

[0017] As an example, continuous pressure readings from a hydraulic sensor are collected; if the fluctuation range of the continuous pressure readings within a preset time period is less than a steady-state threshold, its average value is locked as a suspected zero-point reference value, specifically including: S11: Acquire multiple pressure sampling points at a fixed sampling frequency within the preset time period, and calculate the difference between the maximum and minimum values ​​among the multiple pressure sampling points; In practice, after entering the zero-point calibration procedure, a rest observation window of a preset duration is opened. The preset duration can be set based on the damping characteristics of the hydraulic lines of the braking system and the fluid stabilization time. Its value should be sufficient to attenuate high-frequency pressure fluctuations while also considering the efficiency of the calibration procedure. For example, the preset duration can be set to any value between 500 milliseconds and 2 seconds; preferably, for a conventional hydraulic braking system, this duration can be set to 1 second.

[0018] Within a preset time period, the electrical signals output by the hydraulic sensor are continuously acquired at a fixed sampling frequency and converted into corresponding pressure values ​​as pressure sampling points. To ensure complete and distortion-free acquisition of dynamic changes in pipeline pressure, the fixed sampling frequency must meet the requirements of the Nyquist sampling theorem, i.e., it must be at least twice the natural oscillation frequency of the pipeline pressure. For example, the fixed sampling frequency can be set between 100Hz and 1kHz, and preferably 200Hz.

[0019] During the sampling process, the value of each pressure sampling point is recorded in real time. When the preset time ends, the maximum and minimum values ​​are extracted from the stored multiple pressure sampling points, and the difference between the two is calculated. This difference serves as a key indicator for measuring the pressure fluctuation amplitude within the current preset time.

[0020] S12: If the difference is consistently less than the steady-state threshold, the pipeline pressure is determined to be in a seemingly stable state, and the average of multiple pressure sampling points is calculated as the suspected zero-point reference value.

[0021] In practice, the difference between the calculated maximum and minimum values ​​is compared with a preset steady-state threshold. The steady-state threshold is used to distinguish whether the fluid in the pipeline has recovered from transient disturbances and reached a stable state. Its specific value should meet the following conditions: the threshold should be greater than the noise floor of the hydraulic sensor itself and the amplitude of electrical interference that may couple onto the signal link, to ensure that normal noise fluctuations are not misjudged as an unstable state; simultaneously, the threshold should be less than the minimum residual pressure that may be generated by the solenoid valve trapping trapped oil, so that when there is indeed a trace amount of trapped pressure in the pipeline, this trapped pressure can still be effectively identified by subsequent steps. For example, the steady-state threshold can be set to any value between 0.05 MPa and 0.1 MPa, preferably 0.06 MPa.

[0022] It should be noted that the apparent stability described above only indicates that the pressure signal does not exhibit significant periodic fluctuations or abrupt changes in amplitude, and does not mean that there is absolutely no residual pressure inside the pipeline. As mentioned earlier, when residual pressure is physically trapped in the blind end of the pipeline by the valve body and there is no venting channel, this residual pressure is also static and constant. That is, the pressure signal curve at this time will also present as a stable straight line, and the difference between its maximum and minimum values ​​will also be less than the steady-state threshold. This is the fundamental reason why traditional passive observation strategies easily misjudge trapped oil residual pressure as sensor zero drift. Therefore, at this stage, this invention does not directly write the current reading as the true zero point into the non-volatile memory, but only calculates the arithmetic mean of multiple pressure sampling points collected within a preset time period when it is determined that the difference is continuously less than the steady-state threshold, and locks this mean as the suspected zero-point reference value.

[0023] It should be understood that the suspected status indicator is used to indicate that the benchmark value has not yet been truly verified and needs to be confirmed by the intercept pressure flaw detection in the subsequent active diagnostic control pulse before it can be decided whether to adopt it as the final true zero-point calibration value.

[0024] S2: After locking the suspected zero-point reference value, set diagnostic control parameters that do not cause loss of wheel cylinder fluid, including duty cycle and duration; send a diagnostic control pulse to the outlet solenoid valve of the braking system according to the diagnostic control parameters, so that the outlet solenoid valve is briefly opened to connect the hydraulic blind end pipeline. After locking the stable pressure reading to a suspected zero-point reference value, further active control is applied to the outlet solenoid valve to create a brief connection between the blind-end pipeline and the low-pressure accumulator or brake master cylinder, thereby releasing any trapped pressure that may exist in the blind end. However, during the active pressure relief process, if the outlet solenoid valve is open for too long or the valve opening is too large, the brake fluid in the wheel cylinder will leak through this pressure relief path, causing the piston in the wheel cylinder to physically retract. Once fluid loss occurs, the initial braking response will be significantly delayed when the driver presses the brake pedal again, the effective travel of the brake pedal will be longer (i.e., the pedal feel will be softer), and it may even cause brake force distribution imbalance during emergency braking. Therefore, this step achieves controllable release of trapped pressure in the blind-end pipeline while ensuring that the fluid in the wheel cylinder is absolutely not lost. To this end, this invention does not use the conventional method of sending fixed-width pulses, but first, a set of diagnostic control parameters that will not cause fluid loss in the wheel cylinder are precisely set according to the physical characteristics of the braking system, and then a corresponding diagnostic control pulse is generated based on these diagnostic control parameters and sent to the outlet solenoid valve.

[0025] As an example, such as Figure 2 As shown, the diagnostic control parameters that do not cause fluid loss in the wheel cylinder are set, including: S21: Obtain the minimum response time required for the piston inside the cylinder to overcome mechanical friction and generate physical displacement, as well as the hardware dead time of the liquid outlet solenoid valve. In practice, before sending the diagnostic pulse, the two key physical time parameters mentioned above are read from the parameter storage area of ​​the braking system. Specifically: 1) The minimum response time required for the piston inside the wheel cylinder to overcome mechanical friction and generate physical displacement. It is defined as follows: the moment when pressure begins to release at the wheel cylinder inlet is the starting moment; the moment when the pressure inside the wheel cylinder drops to a level insufficient to overcome the combined force of the piston's static friction and the return spring, and the piston begins to generate a measurable axial retraction displacement, is the ending moment. This parameter characterizes the shortest safe response time required for the piston to generate actual physical displacement after being subjected to pressure disturbance, and is the time boundary for determining whether the pressure release process will have a substantial impact on the mechanical state of the wheel cylinder.

[0026] It should be understood that this time parameter depends on the inherent physical properties of the wheel cylinder, including the compression and lubrication status of the seal between the piston and the cylinder, the preload of the return spring, and the viscosity-temperature characteristics of the current brake fluid. This parameter can be obtained through preliminary bench calibration tests. The specific method is as follows: after applying the rated working pressure to the wheel cylinder, open the pressure relief valve at different pressure relief rates, and simultaneously monitor the piston displacement using a high-precision displacement sensor. Record the shortest time from the start of pressure relief to the start of piston movement, and use this as the calibration value of this parameter, which is pre-stored in the controller's non-volatile memory.

[0027] 2) Hardware dead time of the discharge solenoid valve. It is defined as follows: the start time is the moment when the rated excitation voltage is applied to the solenoid valve coil from the controller's drive circuit; the end time is the moment when the valve core begins to detach from the valve seat due to the accumulation of electromagnetic force. The time interval between the start and end times is this parameter. This parameter characterizes the inherent response delay of the solenoid valve from receiving an electrical command to actually starting to execute mechanical action, and is the time threshold for determining whether the drive signal can effectively excite the valve core to move.

[0028] It should be understood that the above parameters are all inherent characteristic parameters of the braking system and its solenoid valve components. They are not variables that are identified and obtained in real time during vehicle operation, but are obtained in advance through previous bench calibration tests and stored in the controller's non-volatile memory in the form of a parameter table, which is directly read and called when step S21 is executed.

[0029] The minimum response time of the wheel cylinder is obtained as follows: During bench calibration, brake fluid at its rated working pressure (e.g., 8MPa to 10MPa) is injected into the wheel cylinder. After the pressure stabilizes, the pressure relief valve is opened at different pressure relief rates (e.g., through pressure relief valves of different diameters or by adjusting the PWM duty cycle to achieve different equivalent pressure relief openings). Simultaneously, the axial displacement of the wheel cylinder piston is continuously monitored using a high-precision displacement sensor. The time interval from the moment the pressure relief valve opens to the first measurable change in the piston displacement signal (i.e., the critical moment when the piston begins to overcome static friction and generate retraction displacement) is recorded. This calibration is repeated at multiple pressure relief rates (at least covering the maximum possible pressure relief rate of the system) and multiple temperature points. The minimum value among all test results is taken as the calibration value of the minimum response time of the wheel cylinder. This ensures that under any operating condition, the set diagnostic pulse duration will not reach the critical boundary at which the wheel cylinder piston begins to move, thereby ensuring the absolute safety of the wheel cylinder fluid volume.

[0030] The specific method for obtaining the hardware dead time of the solenoid valve is as follows: During the bench calibration process, the rated drive voltage is applied to the outlet solenoid valve, and the moment when the drive voltage is applied and the moment when the first change of the output signal of the valve core displacement sensor is recorded simultaneously using a high-speed data acquisition system. The valve core displacement sensor can be a laser displacement sensor or an eddy current displacement sensor installed at the end of the valve core extension rod to monitor the axial movement of the valve core in real time in a non-contact manner. The starting moment is the trigger moment of the rising edge of the drive voltage, and the ending moment is the moment when the valve core displacement signal first shows a measurable positive change (e.g., a displacement exceeding 3 standard deviations of the sensor noise floor). The time interval between the two is recorded as the hardware dead time of the solenoid valve under the current operating condition. The calibration process can be repeated at multiple voltage levels (e.g., 80%, 100%, 120% of the rated voltage) and multiple temperature points (e.g., -30℃, 0℃, 40℃, 80℃) to cover the range of electrical parameter drift and temperature changes that may be encountered in actual vehicle operation. Finally, the maximum dead time measured under the most severe conditions (e.g., low temperature and low voltage conditions) is stored in the controller as a storage value to ensure that the diagnostic pulse can reliably cross the dead zone under any operating condition, so that the valve core can indeed produce actual movement.

[0031] The two time parameters obtained through the aforementioned bench calibration are pre-stored in the controller's storage unit. It should be understood that during actual vehicle operation, the feedback value from the current brake fluid temperature sensor can be used to read the corresponding correction coefficient from a preset temperature compensation mapping table to make minor online corrections to the aforementioned time parameters, thereby further improving the control accuracy of the time safety window across the entire operating temperature range. Further details will not be elaborated upon here.

[0032] S22: The duration in the diagnostic control parameters is limited to a time safety window that is greater than the hardware dead time and less than the minimum response time, and the duty cycle in the diagnostic control parameters is configured to be a single short pulse that can only drive the valve core of the liquid discharge solenoid valve to disengage from the valve seat, but is insufficient to establish a continuous fluid unloading channel.

[0033] In practical implementation, the duration is limited by a lower limit greater than the solenoid valve's hardware dead time to ensure that the width of the sent diagnostic pulse can reliably overcome the inherent response delay of the solenoid valve, enabling the valve core to generate actual physical movement. The upper limit is limited to less than the minimum response time of the wheel cylinder to ensure that even under extreme conditions, the duration of the pressure drop inside the wheel cylinder is far insufficient for the piston to overcome resistance and generate displacement, thus eliminating the physical possibility of wheel cylinder fluid loss from a temporal perspective. Therefore, the duration is limited to a time safety window composed of the aforementioned upper and lower limits, ensuring both effective actuation of the solenoid valve and absolute safety of the wheel cylinder fluid volume. For example, when the calibrated solenoid valve dead time is 1.5ms and the minimum wheel cylinder response time is 5ms, the duration can be set to 3ms.

[0034] Meanwhile, the duty cycle of the diagnostic control pulse is specifically configured. Specifically, when applied to a single short pulse, the duty cycle determines the equivalent average driving voltage applied across the solenoid valve coil during the pulse duration, which in turn determines the magnitude of the average driving current flowing through the coil. This average driving current ultimately determines the electromagnetic driving force experienced by the solenoid valve spool.

[0035] It should be noted that a liquid outlet solenoid valve typically consists of an electromagnetic coil, a return spring, and a valve core assembly. When current flows through the coil, the resulting electromagnetic force attracts the valve core, overcoming the preload of the return spring and the static contact friction between the valve core and the valve seat, causing it to move in the opening direction. When the current is cut off, the return spring pushes the valve core back to the valve seat and maintains a seal. The displacement of the valve core depends on the dynamic balance between the electromagnetic force, the spring force, and the hydraulic pressure. The magnitude of the electromagnetic force is approximately proportional to the square of the coil current; therefore, even small changes in the duty cycle directly affect the equilibrium position that the valve core can reach.

[0036] Based on the above physical mechanism, the present invention configures the duty cycle as follows: the corresponding average driving current is only sufficient to drive the valve core to overcome the static contact friction between it and the valve seat, so that the valve core produces an extremely small axial displacement and just separates from the contact surface of the valve seat, thereby forming a micro-level gap (e.g., 10μm to 50μm) pressure relief microchannel at the valve port; however, the average driving current is absolutely insufficient to make the valve core continue to move to the fully open position; where fully open means that the valve core moves to the end of its mechanical stroke and the flow area of ​​the valve port reaches its maximum value (e.g., the flow diameter reaches more than 2mm); it is even less sufficient to establish a complete fluid unloading channel that allows the brake fluid to flow continuously and stably on the basis of this tiny gap.

[0037] For example, assuming the rated operating voltage of the solenoid valve is 12V and the DC resistance of the coil is 10Ω, the rated current is 1.2A. Bench calibration shows that the starting current (the minimum average current required for the valve core to begin separating from the valve seat) is 0.6A, and the holding current (the minimum average current required to maintain the valve core in the fully open position) is 0.9A. Therefore, the duty cycle is set to the value corresponding to an average current of 0.65A, i.e., duty cycle = 0.65A / 1.2A ≈ 54%. The average drive current (0.65A) corresponding to this duty cycle is slightly higher than the starting current (0.6A), sufficient to allow the valve core to overcome static friction and just begin to move away from the valve seat; however, this current is much lower than the holding current (0.9A). Therefore, after the valve core moves to a small displacement, the electromagnetic force is insufficient to overcome the increasing hydraulic force and further compression of the spring force as the valve opening widens, and it will automatically stop at a micro-equilibrium position only a few micrometers away from the valve seat. At this point, the equivalent flow diameter of the valve orifice is only on the order of tens of micrometers, far smaller than the flow diameter of 2 mm or more when fully open. At this flow scale, the brake fluid flow is subject to extremely high throttling resistance, resulting in a very low Reynolds number and a slow, seeping flow rather than a continuous pipe flow. The volumetric flow rate of brake fluid passing through the valve orifice per unit time can be limited to less than a few milliliters per minute, far less than one-thousandth of the fluid volume required for normal wheel cylinder operation, thus having no measurable impact on the wheel cylinder piston position. Simultaneously, this micrometer-level gap is sufficient to allow the minute amount of high-pressure brake fluid trapped in the blind-end pipeline (its volume is typically on the order of tens of cubic millimeters) to slowly leak to the low-pressure accumulator side within milliseconds to tens of milliseconds, effectively releasing the residual pressure in the blind end.

[0038] It should be further noted that the aforementioned 54% duty cycle value is only for the purpose of understanding the technical principle of this invention. In actual applications, due to differences in physical parameters such as coil inductance, magnetic circuit structure, spring stiffness, and valve port area, the specific values ​​of the starting current and holding current of different solenoid valves vary. The specific value of the duty cycle needs to be determined by bench calibration for the specific model of solenoid valve. The calibration principle is: under the premise of ensuring that the valve core can overcome static friction to generate micro-disengagement, select the lowest possible duty cycle to limit the valve port opening to the greatest extent, thereby ensuring that the fluid unloading channel can never be established.

[0039] By constraining the duty cycle as described above, the small amount of high-pressure brake fluid trapped in the blind end pipeline can only leak out to the low-pressure side through this micron-level gap in an extremely slow leakage manner. This not only achieves the effective release of the trapped pressure, but also further ensures the absolute safety of the wheel cylinder fluid volume from a fluid dynamics perspective.

[0040] It should be noted that when the ambient temperature drops below -20℃, the viscosity of the brake fluid increases significantly. Simultaneously, the clearance between the valve core and valve seat tends to decrease due to the shrinkage effect of the metal material during cooling. The static mechanical friction of the valve core can increase several times compared to normal temperature conditions. At this time, the electromagnetic force generated by the average drive current corresponding to the duty cycle calibrated at normal temperature in step S22 may be insufficient to overcome the increased static friction, causing the valve core to fail to start completely, resulting in the failure of the entire diagnostic flaw detection process. Furthermore, if a conventional hard-shutdown method is used at any temperature, i.e., instantly cutting off all drive current, the valve core will accelerate at a high speed under the drive of the return spring and impact the valve seat. This mechanical impact will cause a sudden change in the brake fluid flow rate in the blind-end pipeline, generating strong transient fluid pressure fluctuations, i.e., water hammer effect. This results in high-frequency oscillation distortion in the subsequently acquired pressure waveform, lasting for hundreds of milliseconds, severely affecting the accuracy and timeliness of extracting the current pressure reading in subsequent step S3.

[0041] To address the two interrelated technical problems of difficulty in low-temperature startup and water hammer effect caused by hard shutdown, the present invention further employs the following processing method, as detailed in steps S23-S24: S23: Obtain the current ambient temperature data, and based on the ambient temperature data, retrieve the preset pulse mapping table to reconstruct the diagnostic control pulse into a multi-level stepped pulse consisting of a pre-excitation initiation segment, a micro-motion maintenance segment, and a slow descent closing segment; In practice, the current ambient temperature or brake fluid temperature data is acquired through a temperature sensing unit already configured in the braking system. This temperature sensing unit can be a thermistor-type temperature sensor integrated into the hydraulic control unit (HCU) valve body, with its probe extending into the brake fluid flow channel to directly sense the brake fluid temperature. Alternatively, it can be a temperature sensing element built into the wheel speed sensor, whose output signal is converted from analog to digital and then read by the controller. After acquiring the temperature data, it is used as a search index to retrieve a pulse mapping table pre-stored in the controller's non-volatile memory.

[0042] The pulse mapping table is constructed as follows: During the initial bench calibration phase, the hydraulic control unit equipped with the target solenoid valve is placed in a high and low temperature environment chamber. Solenoid valve drive tests are performed at multiple preset temperature points covering the entire vehicle's operating range (e.g., -40℃, -30℃, -20℃, -10℃, 0℃, 20℃, 40℃, 60℃, 80℃). At each temperature point, pulses are sent to the solenoid valve with different current amplitudes. Simultaneously, the valve core's motion response is observed using a high-speed camera or valve core displacement sensor. The minimum initial current value that reliably overcomes static friction at that temperature to induce a micro-motion disengagement of the valve core, the minimum micro-motion current value that maintains the micro-motion position, and the optimal step-off parameters (including the number of steps, duration of each step, and current decrease per step) that do not induce pressure oscillations under slow-descent shut-off conditions are recorded.

[0043] Therefore, for each preset temperature range, the pulse mapping table stores a set of corresponding multi-level stepped pulse parameters. Based on the current temperature data, the mapping table is matched to the range, the corresponding parameters are read, and the previously determined single short pulse is reconstructed on the time axis into a multi-level stepped pulse waveform consisting of three continuous functional segments: the pre-excitation initiation segment, the micro-motion maintenance segment, and the slow descent closure segment.

[0044] S24: Send control signals to the outlet solenoid valve according to the reconstructed multi-stage stepped pulse; wherein, in the pre-excitation start-up stage, an initial current is applied to overcome the static mechanical friction of the valve core; in the micro-motion maintenance stage, a micro-motion current is applied according to the diagnostic control parameters to connect the hydraulic blind end pipeline; in the slow descent closing stage, the current is reduced stepwise to smoothly close the valve core, so as to suppress the internal hydraulic vibration caused by the transient cut-off of fluid.

[0045] In practice, based on the reconstructed multi-stage stepped pulse waveform, precise current commands are output segment by segment to the drive circuit of the outlet solenoid valve, as follows: 1) In the pre-excitation initiation phase, an initiation current with a significantly higher amplitude than the conventional holding current is applied at the pulse start moment. The amplitude of this initiation current is directly taken from the calibration value corresponding to the current temperature range in the pulse mapping table, and its amplitude setting follows the principle that: under the current temperature conditions, the electromagnetic force generated by this initiation current is sufficient to reliably overcome the static mechanical friction between the valve core and the valve seat, including the increased frictional resistance of the sealing ring due to the viscosity effect of the low-temperature brake fluid and the additional contact force generated by the reduced mating clearance due to metal contraction, so that the valve core starts from a completely static state and generates an initial tendency for axial movement. At the same time, the duration of this initiation current is also taken from the calibration value of the pulse mapping table, usually set between 0.3ms and 0.8ms. This duration is subject to the following physical constraints: its duration is only sufficient to break the static friction balance of the valve core and start moving, but not sufficient to allow the valve core to obtain excessive movement speed or excessive displacement under this high current drive, thereby avoiding the valve core from exceeding the micro-motion range and causing overshoot.

[0046] For example, under low temperature conditions of -20°C, the starting current of the pre-excitation start-up phase can be set to 150% to 200% of the rated current, with a duration of 0.5ms; while under normal temperature conditions (20°C to 40°C), the static friction force is small, and the starting current can be reduced to 120% to 150% of the rated current, with the duration shortened to 0.3ms.

[0047] With the above-mentioned pre-excited starting section configuration, the valve core can be reliably started under different temperature conditions, thus solving the problem that conventional pulses cannot start the valve core under low temperature conditions because the electromagnetic force is insufficient to overcome the increased static friction.

[0048] 2) During the micro-motion sustaining phase, the drive current is rapidly reduced from a high initial amplitude and stabilized at a lower current level, determined by the aforementioned duty cycle constraint. Specifically, the duty cycle, along with the solenoid valve coil resistance and the system supply voltage, determines the magnitude of the average drive current applied across the coil. When the duty cycle is configured to only drive the valve core to micro-motion away from the valve seat, but insufficient to establish a continuous fluid unloading channel, the corresponding average drive current is indirectly limited to a specific numerical range through the value of this duty cycle. This range is greater than the minimum current required for valve core activation (starting current) and less than the holding current required for the valve core to move to the fully open position.

[0049] In this step, the average drive current determined by the duty cycle constraint is defined and referred to as the fretting current. The electromagnetic force generated by this fretting current is able to dynamically balance the preload of the return spring and the hydraulic pressure at the valve port, keeping the valve core in the fretting position just off the valve seat. This continuously maintains the micron-level pressure relief gap open, allowing the blind end pipeline to connect to the low-pressure accumulator side, and the trapped pressure to be released smoothly under controlled conditions. The amplitude of this fretting current and its corresponding duration (i.e., the duration of the fretting maintenance segment in the entire pulse) strictly follow the diagnostic control parameters. That is, its average drive current is only sufficient to keep the valve core fretting off the valve seat but not sufficient to establish a continuous fluid unloading channel. Its duration is within a safe time window that is greater than the dead time of the solenoid valve hardware and less than the minimum response time of the wheel cylinder, ensuring that the entire pressure relief process is always within a safe boundary that does not cause fluid loss from the wheel cylinder. It should be noted that there is a current step drop process between the starting current and the fretting current. The slope of this drop edge is also controlled by the transition time parameter stored in the pulse mapping table to avoid valve core oscillation caused by current abrupt changes.

[0050] 3) During the slow-closing phase, the current is gradually reduced to shut off according to the step parameters read from the pulse mapping table. Specifically, unlike the hard shutdown method in conventional control that directly cuts off all drive current, this invention gradually reduces the drive current from the micro-current level to zero according to a preset number of steps, the current reduction amount at each step, and the duration of each step. These step shutdown parameters are stored in the pulse mapping table corresponding to the current temperature range, and their calibration target is to reduce the valve core's seating speed to below a threshold that will not trigger fluid pressure oscillations in the pipeline.

[0051] During the execution of the slow-closing closure phase, with each reduction in current, the valve core moves a tiny step towards the valve seat under the push of the return spring. Thus, the valve core's movement speed is decomposed into multiple discrete tiny displacement steps, with the kinetic energy increment of each step controlled at a low level. The average speed of the entire closing process is significantly lower than the instantaneous speed under hard-shutdown mode. For example, under normal temperature conditions, the slow-closing closure phase can be set to four steps, each lasting 0.8 ms, with each step's current reduction being 25% of the micro-current. The total duration of the slow-closing closure phase is then 3.2 ms, with the valve core gradually approaching the valve seat in four steps, ultimately settling smoothly with extremely low impact kinetic energy. Under low temperature conditions, due to the increased viscosity of the brake fluid itself damping fluid transients, the number of steps can be appropriately reduced to three, and the duration of each step shortened to 0.5 ms to improve execution efficiency.

[0052] Through the aforementioned step-by-step decrement control, the fluid channel is smoothly cut off rather than abruptly reduced to zero. This significantly suppresses internal hydraulic excitation caused by transient fluid cut-off, ensuring that the pressure in the blind-end pipeline can recover to a stable state in the shortest possible time after the diagnostic pulse ends. This provides stable and reliable pipeline pressure conditions for the rapid extraction of subsequent current pressure readings.

[0053] S3: After sending the diagnostic control pulse, the pressure reading of the hydraulic sensor is collected again. After the pressure reading stabilizes, it is extracted as the current pressure reading, and the pressure attenuation difference between the suspected zero-point reference value and the current pressure reading is calculated. After the multi-stage stepped pulse transmission is completed and the valve core smoothly settles down, the pressure value of the depressurized pipeline is reacquired to assess whether there is any released trapped pressure in the blind end pipeline. Specifically, timing begins when the final current of the slow-descent closing section reaches zero, and a preset stabilization period (e.g., 50ms to 100ms) is waited to ensure that the slight pressure fluctuations generated during valve core closure have sufficiently attenuated. Next, multiple consecutive pressure sampling points are acquired again at a fixed sampling frequency (e.g., 200Hz), and the arithmetic mean of these sampling points is calculated as the current pressure reading.

[0054] After obtaining the current pressure reading, the difference between the locked suspected zero-point reference value and the current pressure reading is calculated and recorded as the pressure attenuation difference. It should be understood that if there was residual pressure trapped in the blind-end pipeline due to the high-frequency cutoff of the solenoid valve, when the diagnostic control pulse briefly opens the outlet solenoid valve, this trapped pressure is released to the low-pressure side through a micron-level pressure relief gap. The current pressure reading measured after pressure relief will be lower than the locked suspected zero-point reference value before pressure relief; the difference between the two is the amplitude of the released trapped pressure. Conversely, if there was no trapped pressure in the blind-end pipeline, the pressure readings before and after pressure relief are basically the same, and the pressure attenuation difference will be close to zero (affected only by sensor noise). Therefore, the magnitude of this difference directly reflects whether there is residual pressure in the blind-end pipeline due to oil trapping.

[0055] S4: Perform a self-calibration update based on the pressure attenuation difference, specifically: If the pressure attenuation difference is not less than the preset pressure drop threshold, the current pressure reading is confirmed as the true zero-point calibration value and written into storage; if the pressure attenuation difference is less than the preset pressure drop threshold, the suspected zero-point reference value is confirmed as the true zero-point calibration value and written into storage.

[0056] The preset pressure drop threshold should be greater than the measurement noise of the hydraulic sensor itself and the error range introduced by temperature drift, while being less than the minimum residual pressure value that may be generated due to the trapped oil trapped by the solenoid valve. For example, it can be set to any value between 0.05MPa and 0.15MPa. The specific value needs to be bench calibrated according to the sensor characteristics and pipeline structure of the specific braking system.

[0057] If the pressure drop difference is not less than the preset pressure drop threshold, it is determined that there is indeed residual pressure in the blind end pipeline caused by the solenoid valve trapping pressure after high-frequency braking adjustment, and this residual pressure has been successfully released during the diagnostic pressure relief process in steps S2 to S3. At this time, the locked suspected zero-point reference value actually includes the trapped pressure component and is not the true zero-pressure reference; while the current pressure reading extracted after pressure relief reflects the true zero-pressure state inside the pipeline. At this time, the current pressure reading is confirmed as the true zero-point calibration value and written into the non-volatile memory to replace the original zero-point calibration value.

[0058] If the pressure attenuation difference is less than the preset pressure drop threshold, it is determined that there was originally no perceptible trapped pressure in the blind end pipeline, meaning that the locked suspected zero-point reference value is already the true zero-pressure state inside the pipeline, and the transmission of the diagnostic control pulse did not cause a substantial change in pressure. At this time, the suspected zero-point reference value is confirmed as the true zero-point calibration value and written into storage.

[0059] Through the aforementioned judgment and update mechanism, this invention can actively eliminate false zero-point interference caused by trapped oil and write the true zero-pressure value after depressurization into storage; when there is no interference, it directly adopts the initial suspected zero-point reference value, avoiding unnecessary calibration value changes. This effectively solves the problem of zero-point miscalibration caused by the inability of passive observation strategies to distinguish between sensor electrical zero drift and pipeline physical residual pressure, improving the authenticity of hydraulic sensor self-calibration and the underlying safety assurance of the braking system.

[0060] like Figure 3 As shown, this embodiment of the invention also provides a sensor self-calibration system 100 for a vehicle braking system, the system comprising: The reference locking module 101 is used to acquire the vehicle driving status and brake pedal displacement signal. When the vehicle driving status indicates that the vehicle is stationary and the brake pedal displacement signal indicates that the pedal is at the physical zero position, the continuous pressure reading of the hydraulic sensor is collected. If the fluctuation amplitude of the continuous pressure reading within a preset time is less than the steady-state threshold, its average value is locked as the suspected zero-point reference value. The diagnostic micro-motion module 102 is used to set diagnostic control parameters, including duty cycle and duration, that will not cause loss of fluid in the wheel cylinder after locking the suspected zero-point reference value; and to send a diagnostic control pulse to the outlet solenoid valve of the braking system according to the diagnostic control parameters, so that the outlet solenoid valve is briefly opened to connect the hydraulic blind end pipeline. The pressure drop extraction module 103 is used to collect the pressure reading of the hydraulic sensor again after sending the diagnostic control pulse, extract the current pressure reading after the pressure reading stabilizes, and calculate the pressure attenuation difference between the suspected zero point reference value and the current pressure reading. The self-calibration update module 104 is used to perform self-calibration update based on the pressure attenuation difference.

[0061] As an example, the reference locking module 101 is specifically used for: Multiple pressure sampling points are acquired at a fixed sampling frequency within the preset time period, and the difference between the maximum and minimum values ​​among the multiple pressure sampling points is calculated. If the difference is consistently less than the steady-state threshold, the pipeline pressure is determined to be in a seemingly stable state, and the average of multiple pressure sampling points is calculated as the suspected zero-point reference value.

[0062] As an example, the diagnostic micro-motion module 102 is specifically used for: The minimum response time required for the piston inside the brake wheel cylinder to overcome mechanical friction and generate physical displacement, as well as the hardware dead time of the discharge solenoid valve, are obtained. The duration in the diagnostic control parameters is limited to a time safety window that is greater than the hardware dead time and less than the minimum response time, and the duty cycle in the diagnostic control parameters is configured to be a single short pulse that can only drive the valve core of the liquid discharge solenoid valve to disengage from the valve seat, but is insufficient to establish a continuous fluid unloading channel.

[0063] As an example, the diagnostic micro-motion module 102 is also specifically used for: The current ambient temperature data is acquired, and a preset pulse mapping table is retrieved based on the ambient temperature data to reconstruct the diagnostic control pulse into a multi-level stepped pulse consisting of a pre-excitation initiation segment, a micro-motion maintenance segment, and a slow descent closing segment. Control signals are sent to the outlet solenoid valve according to the reconstructed multi-stage stepped pulse; wherein, in the pre-excitation start-up phase, an initial current is applied to overcome the static mechanical friction of the valve core; in the micro-motion maintenance phase, a micro-motion current is applied according to the diagnostic control parameters to connect the hydraulic blind end pipeline; in the slow descent closing phase, the current is reduced stepwise to smoothly close the valve core, so as to suppress the internal hydraulic vibration caused by the transient cut-off of fluid.

[0064] As an example, the self-calibration update module 104 is specifically used for: If the pressure attenuation difference is not less than the preset pressure drop threshold, the current pressure reading is confirmed as the true zero-point calibration value and written into storage; If the pressure attenuation difference is less than the preset pressure drop threshold, the suspected zero-point reference value is confirmed as the true zero-point calibration value and written into storage.

[0065] Those skilled in the art will understand that the principle, technical effect, and specific execution process of the system 100 for sensor self-calibration in the vehicle braking system are completely consistent with those described in the foregoing method embodiments. The specific working methods, parameter setting logic, and judgment conditions of each module have been described in detail in the foregoing method embodiments, and will not be repeated here.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A sensor self-calibration method for a vehicle braking system, characterized in that, include: The vehicle driving status and brake pedal displacement signal are acquired. When the vehicle driving status indicates that the vehicle is stationary and the brake pedal displacement signal indicates that the pedal is at the physical zero position, the continuous pressure reading of the hydraulic sensor is collected. If the fluctuation range of the continuous pressure reading within a preset time is less than the steady-state threshold, its average value is locked as the suspected zero-point reference value. After locking the suspected zero-point reference value, set diagnostic control parameters that do not cause loss of wheel cylinder fluid, including duty cycle and duration; According to the diagnostic control parameters, a diagnostic control pulse is sent to the outlet solenoid valve of the braking system to briefly open the outlet solenoid valve to connect the hydraulic blind end pipeline. After sending the diagnostic control pulse, the pressure reading of the hydraulic sensor is collected again. After the pressure reading stabilizes, it is extracted as the current pressure reading, and the pressure attenuation difference between the suspected zero-point reference value and the current pressure reading is calculated. Perform a self-calibration update based on the pressure attenuation difference.

2. The sensor self-calibration method for a vehicle braking system according to claim 1, characterized in that, Collect continuous pressure readings from the hydraulic sensor; if the fluctuation range of the continuous pressure readings within a preset time period is less than a steady-state threshold, then lock its average value as a suspected zero-point reference value, specifically including: Multiple pressure sampling points are acquired at a fixed sampling frequency within the preset time period, and the difference between the maximum and minimum values ​​among the multiple pressure sampling points is calculated. If the difference is consistently less than the steady-state threshold, the pipeline pressure is determined to be in a seemingly stable state, and the average of multiple pressure sampling points is calculated as the suspected zero-point reference value.

3. The sensor self-calibration method for a vehicle braking system according to claim 1, characterized in that, Set diagnostic control parameters that do not cause fluid loss in the wheel cylinders, including: The minimum response time required for the piston inside the cylinder to overcome mechanical friction and generate physical displacement, as well as the hardware dead time of the liquid outlet solenoid valve, are obtained. The duration in the diagnostic control parameters is limited to a time safety window that is greater than the hardware dead time and less than the minimum response time, and the duty cycle in the diagnostic control parameters is configured to be a single short pulse that can only drive the valve core of the liquid discharge solenoid valve to disengage from the valve seat, but is insufficient to establish a continuous fluid unloading channel.

4. The sensor self-calibration method for a vehicle braking system according to claim 1, characterized in that, According to the diagnostic control parameters, a diagnostic control pulse is sent to the outlet solenoid valve of the braking system to briefly open the outlet solenoid valve to connect the hydraulic blind end pipeline, including: The current ambient temperature data is acquired, and a preset pulse mapping table is retrieved based on the ambient temperature data to reconstruct the diagnostic control pulse into a multi-level stepped pulse consisting of a pre-excitation initiation segment, a micro-motion maintenance segment, and a slow descent closing segment. Control signals are sent to the outlet solenoid valve according to the reconstructed multi-stage stepped pulse; wherein, in the pre-excitation start-up stage, an initial current is applied to overcome the static mechanical friction of the valve core; in the micro-motion maintenance stage, a micro-motion current is applied according to the diagnostic control parameters to connect the hydraulic blind end pipeline; in the slow descent closing stage, the current is reduced stepwise to smoothly close the valve core, so as to suppress the internal hydraulic vibration caused by the transient cut-off of fluid.

5. The sensor self-calibration method for a vehicle braking system according to claim 1, characterized in that, The step of performing self-calibration update based on the pressure attenuation difference includes: If the pressure attenuation difference is not less than the preset pressure drop threshold, the current pressure reading is confirmed as the true zero-point calibration value and written into storage; if the pressure attenuation difference is less than the preset pressure drop threshold, the suspected zero-point reference value is confirmed as the true zero-point calibration value and written into storage.

6. A sensor self-calibration system for a vehicle braking system, characterized in that, The system includes: The reference locking module is used to acquire the vehicle driving status and brake pedal displacement signal. When the vehicle driving status indicates that the vehicle is stationary and the brake pedal displacement signal indicates that the pedal is at the physical zero position, the module acquires the continuous pressure reading of the hydraulic sensor. If the fluctuation range of the continuous pressure reading within a preset time period is less than the steady-state threshold, the average value is locked as the suspected zero-point reference value. The diagnostic micro-motion module is used to set diagnostic control parameters, including duty cycle and duration, that will not cause loss of fluid in the wheel cylinder after locking the suspected zero-point reference value; and to send a diagnostic control pulse to the outlet solenoid valve of the braking system according to the diagnostic control parameters, so that the outlet solenoid valve is briefly opened to connect the hydraulic blind end pipeline. The pressure drop extraction module is used to collect the pressure reading of the hydraulic sensor again after sending the diagnostic control pulse, extract the current pressure reading after the pressure reading stabilizes, and calculate the pressure attenuation difference between the suspected zero point reference value and the current pressure reading. The self-calibration update module is used to perform self-calibration updates based on the pressure attenuation difference.

7. The sensor self-calibration system for a vehicle braking system according to claim 6, characterized in that, The reference locking module is specifically used for: Multiple pressure sampling points are acquired at a fixed sampling frequency within the preset time period, and the difference between the maximum and minimum values ​​among the multiple pressure sampling points is calculated. If the difference is consistently less than the steady-state threshold, the pipeline pressure is determined to be in a seemingly stable state, and the average of multiple pressure sampling points is calculated as the suspected zero-point reference value.

8. The sensor self-calibration system for a vehicle braking system according to claim 6, characterized in that, The diagnostic micro-motion module is specifically used for: The minimum response time required for the piston inside the brake wheel cylinder to overcome mechanical friction and generate physical displacement, as well as the hardware dead time of the discharge solenoid valve, are obtained. The duration in the diagnostic control parameters is limited to a time safety window that is greater than the hardware dead time and less than the minimum response time, and the duty cycle in the diagnostic control parameters is configured to be a single short pulse that can only drive the valve core of the liquid discharge solenoid valve to disengage from the valve seat, but is insufficient to establish a continuous fluid unloading channel.

9. The sensor self-calibration system for a vehicle braking system according to claim 6, characterized in that, The diagnostic micro-motion module is also specifically used for: The current ambient temperature data is acquired, and a preset pulse mapping table is retrieved based on the ambient temperature data to reconstruct the diagnostic control pulse into a multi-level stepped pulse consisting of a pre-excitation initiation segment, a micro-motion maintenance segment, and a slow descent closing segment. Control signals are sent to the outlet solenoid valve according to the reconstructed multi-stage stepped pulse; wherein, in the pre-excitation start-up phase, an initial current is applied to overcome the static mechanical friction of the valve core; in the micro-motion maintenance phase, a micro-motion current is applied according to the diagnostic control parameters to connect the hydraulic blind end pipeline; in the slow descent closing phase, the current is reduced stepwise to smoothly close the valve core, so as to suppress the internal hydraulic vibration caused by the transient cut-off of fluid.

10. The sensor self-calibration system for a vehicle braking system according to claim 6, characterized in that, The self-calibration update module is specifically used for: If the pressure attenuation difference is not less than the preset pressure drop threshold, the current pressure reading is confirmed as the true zero-point calibration value and written into storage; If the pressure attenuation difference is less than the preset pressure drop threshold, the suspected zero-point reference value is confirmed as the true zero-point calibration value and written into storage.

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