Calibration method for disc temperature model of electronic parking system

Abstract

The invention relates to an electronic parking system disc temperature model calibration method, and belongs to the field of automobile electronic parking systems. Aiming at the problems of low efficiency and poor precision of the existing online calibration method, the method comprises the following steps: S1, acquiring a brake disc temperature signal through a K-type thermocouple and slip ring equipment; s2, establishing a temperature rise model and a temperature drop model, and separating calibration coefficients kf, kp and kh; s3, performing dynamic braking, static cooling and dynamic driving condition data based on the RWU; and S4, parameters are optimized through simulation iteration, so that the maximum error between the model temperature and actual measurement is smaller than + / -5 DEG C. The calibration period is shortened by more than 70%, the defect that a traditional method depends on multiple real vehicle tests is overcome, and the model universality and the high-temperature reclamping function reliability are improved.

Description

Technical Field

[0001] The present invention belongs to the field of automotive electronic parking systems, and relates to a method for calibrating a disc temperature model of an electronic parking system. Background Art

[0002] The high-temperature re-clamping function of an electronic parking system (EPB) is one of the core technologies to ensure vehicle parking safety. By monitoring the change in brake disc temperature, it performs secondary clamping after high-temperature braking to compensate for the increased gap caused by thermal expansion and contraction, thus avoiding the risk of vehicle rollback. The realization of this function highly depends on the accuracy of the disc temperature model, and the model needs to calculate the temperature rise (friction heat generation and kinetic energy conversion) and temperature drop (thermal convection heat dissipation) processes of the brake disc during vehicle operation in real time.

[0003] Currently, the calibration of the disc temperature model generally adopts an online calibration method, that is, in real vehicle tests, by repeatedly adjusting the temperature rise coefficients k f 、k p and the temperature drop coefficient k h , iterating the parameters one by one until the model output matches the measured temperature. However, this method has significant defects:

[0004] (1) Each time the parameters are adjusted, real vehicle tests need to be carried out again, involving repeated tests of various working conditions such as dynamic braking (RWU), static cooling, and driving in multiple speed ranges, resulting in a calibration cycle of up to several weeks;

[0005] (2) It frequently occupies test sites and equipment (such as CSM acquisition systems, slip ring devices), and relies on calibration personnel to monitor the whole process, with high labor and equipment costs;

[0006] (3) Due to real vehicle environment interference (such as wind speed, road conditions) and sensor noise, the calibration results are easily affected by random factors, and the maximum error of the model often exceeds ±10°C, requiring multiple rework corrections.

[0007] In the prior art, although there are studies attempting to reduce the calibration workload by simplifying the model or presetting empirical parameters, such methods are difficult to adapt to the structural differences of braking systems of different vehicle models, and ignore the non-linear coupling relationship between dynamic working conditions and heat dissipation conditions, resulting in insufficient model robustness. In addition, traditional methods lack systematic error evaluation indicators (such as absolute error threshold control), the parameter optimization process is highly subjective, and the calibration consistency is poor.

[0008] Therefore, there is an urgent need for an efficient, high-precision and reusable method for calibrating the disc temperature model, which can combine offline simulation to optimize the calibration parameters through limited real vehicle test data, thereby breaking through the limitations of online calibration and improving the development efficiency and reliability of the electronic parking system. Summary of the Invention

[0009] In view of this, the purpose of the present invention is to provide a method for calibrating the disc temperature model of an electronic parking system.

[0010] To achieve the above object, the present invention provides the following technical solutions:

[0011] A method for calibrating the disc temperature model of an electronic parking system, comprising the following steps:

[0012] S1: Collect the actual temperature signal of the brake disc of the vehicle, including burying temperature sensors in the contact area of the brake disc and converting the temperature signal into an acquirable CAN signal through a slip ring device;

[0013] S2: Establish a disc temperature calculation model including a temperature rise model and a temperature drop model. The temperature rise model calculates the temperature rise based on the frictional heat Q f and the kinetic energy conversion heat Q p The temperature drop model calculates the temperature drop based on the heat convection heat Q c wherein the calculation formulas of Q f , Q p , Q c respectively include the coefficients k f , k p , k h to be calibrated;

[0014] S3: Collect the vehicle operating condition data, including obtaining the temperature rise data by performing the dynamic caliper braking condition and obtaining the temperature drop data by performing the static cooling and dynamic driving conditions;

[0015] S4: Input the operating condition data into the disc temperature calculation model for simulation, and iteratively optimize the k f , k p , k h coefficients to make the maximum absolute error between the model output temperature and the measured temperature less than ±5°C, and write the optimized parameters back to the electronic parking system.

[0016] Further, in S1, the temperature sensor is a K-type thermocouple, and the burial positions include: drilling a hole in the center of the contact area between the brake disc and the friction block to bury the first thermocouple, and drilling a hole at the center of the brake disc edge to bury the second thermocouple. The wiring of the thermocouple is led out to the CSM signal acquisition device through the slip ring installed on the wheel hub.

[0017] Further, the CSM device is configured with a sampling frequency channel of 1 to 200 Hz, and maps the temperature signal into a CAN signal through a DBC file, and synchronously records the actual disc temperature and the model disc temperature observation in the data acquisition software.

[0018] Further, in the temperature rise model:

[0019] The frictional heat Q f (n)=kf ·ω p (n)·P c (n), where ω p (n) is the wheel speed pulse, and P c (n) is the wheel cylinder pressure;

[0020] Kinetic energy is converted into heat where m is the vehicle mass and v n is the real-time vehicle speed.

[0021] Furthermore, in the temperature drop model, the convective heat Q c (n) = h·S·ΔT, where ΔT is the temperature difference between the brake disc and the environment, and k h = h·S is the product of the convective heat transfer coefficient and the effective heat dissipation area.

[0022] Furthermore, in S3, the dynamic caliper braking condition includes repeating the RWU clamping-release operation 3 times, recording the temperature data for 0 to 1 hour in the static cooling test and repeating it 3 times, and the dynamic driving condition includes driving at a constant speed in different speed intervals and recording the temperature data.

[0023] Furthermore, in S4, during model initialization, the actual disc temperature value of the first sampling period is assigned to the model as the initial temperature value to ensure the initial synchronization of the model and the measured temperature.

[0024] Furthermore, the iterative optimization uses the gradient descent algorithm to recalculate the model temperature curve after each parameter adjustment until the maximum absolute error of 3 consecutive iterations is less than 5°C.

[0025] Furthermore, it also includes a verification step: writing the calibrated parameters into the electronic parking controller, confirming the consistency of the change trends of the model temperature curve and the measured temperature through real vehicle tests, and solidifying the calibrated parameters when the mean absolute error ≤ 3°C.

[0026] An electronic parking system uses the disc temperature model calibrated by the above method to achieve the high-temperature re-clamping function. When it detects that the temperature drop value of the brake disc exceeds the set threshold, it automatically performs the secondary clamping operation.

[0027] The beneficial effects of the present invention are as follows:

[0028] (1) By combining real vehicle data acquisition and offline simulation optimization, the dozens of real vehicle tests required for traditional online calibration are reduced to 3 repeated tests, the calibration cycle is shortened from several weeks to several days, and there is no need to occupy the test site throughout the process, greatly reducing the time and resource costs.

[0029] (2) Introducing the absolute error (maximum error ±5°C) as the core index for parameter optimization, and iteratively correcting k in combination with the gradient descent algorithm f 、kp , k h The coefficient makes the model output highly consistent with the measured temperature curve, effectively avoiding the problem of error accumulation caused by environmental interference in traditional methods.

[0030] (3) By defining standardized temperature rise (RWU dynamic braking) and temperature drop (static cooling, constant-speed driving) test procedures, adapting to the brake disc structures and heat dissipation characteristics of different vehicle models, solving the defect of insufficient robustness of traditional empirical parameter methods, the calibration results can be reused across platforms.

[0031] (4) Using CSM equipment and slip rings to achieve non-intrusive temperature signal acquisition, avoiding damage to the structural integrity of the brake disc. At the same time, through model-in-the-loop simulation, the number of on-road vehicle verifications is reduced by more than 90%, significantly reducing equipment losses and labor input.

[0032] (5) The calibrated disc temperature model can accurately predict the temperature change trend of the brake disc, ensuring that the high-temperature re-clamping function is triggered within an error range of ±5°C, effectively reducing the risk of vehicle rollback caused by model inaccuracy, and improving the reliability of the electronic parking system.

[0033] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0035] Figure 1 is the flow chart of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The following uses specific specific examples to illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present invention schematically. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0037] Among them, the attached drawings are only for illustrative purposes, showing only schematic diagrams rather than physical diagrams, and should not be construed as a limitation to the present invention; for better illustration of the embodiments of the present invention, some components in the attached drawings may be omitted, enlarged or reduced, which do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the attached drawings may be omitted.

[0038] In the attached drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the attached drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the attached drawings are only for illustrative purposes and should not be construed as a limitation to the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0039] As Figure 1 shown, it is the process schematic diagram of the present invention.

[0040] Embodiment 1

[0041] Sensor installation: Drill a hole at the center of the contact area between the rear brake disc and the friction block of the test vehicle, and embed a K-type thermocouple (model OMEGA TT-K-30), and lead the positive and negative leads along the groove on the disc surface to the center of the disc; at the same time, drill a hole at the center of the edge of the brake disc and embed a second thermocouple, and the lead passes through the center hole of the wheel hub.

[0042] Slip ring integration: Install a Mofukang MFC-12 channel slip ring on the wheel hub, connect the thermocouple leads to the slip rotor end, and connect the leads at the slip stator end to channels CH1 and CH2 of the CSM CX405 data acquisition module, and set the sampling frequency to 100Hz.

[0043] Signal conversion: Load the DBC file (EPB_Temp.dbc) of the CSM device in CANape V4.2, map CH1 to Left_RotorTemp and CH2 to Left_EdgeTemp, synchronously record the Temp_Model signal calculated by the model, and store the data in MF4 format.

[0044] Initial synchronization: When the vehicle is cold-started, read the measured value of Left_RotorTemp (such as 25.3°C) in the first frame of data, and forcefully assign the initial temperature parameter Temp_Model(0) of the model to 25.3°C to eliminate the initial deviation.

[0045] Embodiment 2

[0046] RWU Working Condition Test: The vehicle travels at 30 km / h, and the EPB dynamic clamping is triggered through a diagnostic instrument (clamping force 120 bar, released after holding for 2 seconds), and this is repeated 20 times to heat the brake disc to 200 °C ± 10 °C.

[0047] Data Acquisition: Record the wheel speed pulse ω p (n) (such as 1200 pulses per second), wheel cylinder pressure P c (n) (120 bar), vehicle speed v n (obtained from the CAN bus), and synchronously collect the thermocouple temperature (sampling interval 10 ms).

[0048] Parameter Calculation:

[0049] Calculate k f Initial Value: Given the piston diameter dc = 48 mm, friction coefficient μ = 0.38, rear wheel radius Re = 325 mm, number of pulses W = 48, coefficient K = 0.85, then k f = 0.85 * (482 * 0.38 * 325) / 48 = 2587.2 J / (bar·pulse)

[0050] Calculate k p Initial Value: The vehicle mass m = 2000 kg, select the braking process from a vehicle speed of 30 km / h to 0, kinetic energy difference ΔE = 2000 * (8.33 2 - 0) / 2 = 69,444 J, measured temperature rise ΔT = 15 °C, assuming the brake disc mass M = 8 kg, specific heat capacity c = 460 J / (kg·°C), then k p = (8 * 460 * 15) / 69,444 ≈ 0.79

[0051] Iterative Optimization: Import the measured temperature curve in MATLAB / Simulink, and adjust k f 、k p to reduce the maximum error of the model output from the initial ±12 °C to ±4.5 °C.

[0052] Example 3

[0053] Static Cooling Test: Heat the brake disc to 180 °C and then stop the vehicle, turn off the engine, record the ambient temperature (25 °C) and thermocouple data, sample every 5 seconds for 1 hour.

[0054] Dynamic Driving Test: After heating to 150 °C, drive at a constant speed of 60 km / h, 80 km / h, and 100 km / h for 30 minutes each, and record the vehicle speed, wind speed (through an on-vehicle anemometer), and temperature data.

[0055] Parameter Calculation:

[0056] Static cooling stage: fitting temperature curve T(t)=T0exp(-k h t), initial k h =0.0032(corresponding to h=12W / (m 2 K), S = 0.15m 2 ), after 3 times of experimental data optimization, k h =0.0028±0.0001.

[0057] Dynamic driving stage: k is corrected according to vehicle speed h , for example, at 80km / h, k h =0.0045 (60% increase compared to static), k is established by multi-speed point calibration h =f(v) mapping table.

[0058] Model validation: k h The parameters were written into the model to simulate the dynamic cooling process (such as deceleration from 100 km / h to parking). The maximum deviation between the model temperature and the measured data was ≤4.2°C.

[0059] Example 4

[0060] Data import: Convert the MF4 data of Examples 2 and 3 into CSV format and input it into the dSPACE ASM simulation platform. The model input signal includes ω p (n), P c (n), vehicle speed v n , output Temp_Model.

[0061] Error evaluation: Calculate the absolute error of each sampling point|Temp Model (n)-Temp Real (n), set the optimization goal: max(|ΔT|)≤5℃ and average error≤2℃.

[0062] Gradient descent optimization: with k f 、k p 、k h For variables, set the learning rate α = 0.01, and the parameters converge after 20 iterations: k f =2450→2630, k p =0.79→0.83, k h =0.0028→0.0031.

[0063] Vehicle verification: The optimized parameters were flashed to the EPB controller (model MK C1) and the RWU operating condition test was performed. The maximum error of the measured model was 4.7°C. After meeting the threshold requirements, the calibration parameters were solidified in the OTP memory.

[0064] In the above embodiments, the reference in the specification to "this embodiment" means that the specific features, structures, or characteristics described in connection with the embodiment are included in at least some embodiments, but not necessarily all embodiments. Multiple occurrences of "this embodiment" do not necessarily all refer to the same embodiment.

[0065] In the above embodiments, although the present invention has been described in connection with specific embodiments of the present invention, many alternatives, modifications, and variations of these embodiments will be apparent to those of ordinary skill in the art based on the foregoing description. For example, other storage structures (e.g., dynamic RAM (DRAM)) may be used with the embodiments discussed. Embodiments of the present invention are intended to cover all such alternatives, modifications, and variations that fall within the broad scope of the appended claims.

[0066] This embodiment also provides a computer-readable storage medium having a computer program stored thereon, and when the program is executed by a processor, it implements any one of the methods in this embodiment.

[0067] This embodiment also provides an electronic terminal, including: a processor and a memory;

[0068] The memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory so that the terminal executes any one of the methods in this embodiment.

[0069] For the computer-readable storage medium in this embodiment, those of ordinary skill in the art can understand that all or part of the steps of implementing the above method embodiments can be completed by hardware related to a computer program. The foregoing computer program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps including the above method embodiments; and the foregoing storage medium includes: various media such as ROM, RAM, magnetic disk, or optical disk that can store program code.

[0070] The electronic terminal provided in this embodiment includes a processor, a memory, a transceiver, and a communication interface. The memory and the communication interface are connected to the processor and the transceiver and complete communication therebetween. The memory is used to store a computer program, the communication interface is used for communication, and the processor and the transceiver are used to run the computer program so that the electronic terminal executes each step of the above method.

[0071] In this embodiment, the memory may include a random access memory (Random Access Memory, abbreviated as RAM), and may also include non-volatile memory, such as at least one disk memory.

[0072] The above-mentioned processor may be a general-purpose processor, including a Central Processing Unit (CPU for short), a Network Processor (NP for short), etc.; it may also be a Digital Signal Processor (DSP for short), an Application Specific Integrated Circuit (ASIC for short), a Field-Programmable Gate Array (FPGA for short), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0073] The present invention can be used in numerous general-purpose or special-purpose computing system environments or configurations. For example: personal computers, server computers, handheld or portable devices, tablet devices, multi-processor systems, microprocessor-based systems, set-top boxes, programmable consumer electronic devices, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, and so on.

[0074] The present invention can be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The present invention can also be practiced in a distributed computing environment, where tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules can be located in local and remote computer storage media including storage devices.

[0075] The disc temperature model of the electronic parking system is calibrated by combining on-vehicle testing and off-line calibration. Based on on-vehicle data, model-in-the-loop simulation testing is carried out, and ideal calibration parameters are obtained in an off-line manner and substituted back into the vehicle for testing. After verification, the current parameters are solidified. Through this method, the calibration efficiency and accuracy of the disc temperature model of the electronic parking system can be greatly improved.

[0076] 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 the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A calibration method for the disk temperature model of an electronic parking system, characterized in that: It includes the following steps: S1: Collect the actual temperature signal of the vehicle brake disc, including burying temperature sensors in the contact area of the brake disc and converting the temperature signal into a collectable CAN signal through a slip ring device; S2: Establish a disk temperature calculation model including a temperature rise model and a temperature drop model. The temperature rise model calculates the temperature rise based on the frictional heat Q f and the heat converted from kinetic energy Q p . The temperature drop model calculates the temperature drop based on the convective heat Q c . Among them, the calculation formulas of Q f , Q p , and Q c respectively contain the coefficients k f , k p , and k h to be calibrated; S3: Collect the vehicle operating condition data, including obtaining temperature rise data by performing the dynamic caliper braking condition and obtaining temperature drop data by performing the static cooling and dynamic driving conditions; S4: Input the operating condition data into the disk temperature calculation model for simulation, and iteratively optimize the k f , k p , k h coefficients to make the maximum absolute error between the temperature output by the model and the measured temperature less than ±5°C, and write the optimized parameters back to the electronic parking system.

2. The method for calibrating the disc temperature model of the electronic parking system according to claim 1, wherein: In S1, the temperature sensor is a K-type thermocouple. The burying positions include: drilling a hole in the center of the contact area between the brake disc and the friction block to bury the first thermocouple, and drilling a hole at the center of the edge of the brake disc to bury the second thermocouple. The wiring of the thermocouple is led out to the CSM signal acquisition device through the slip ring installed on the wheel hub.

3. The method for calibrating the disc temperature model of the electronic parking system according to claim 2, wherein: The CSM device is configured with a sampling frequency channel of 1 - 200Hz, and maps the temperature signal into a CAN signal through a DBC file, and synchronously records the observed values of the actual disc temperature and the model disc temperature in the data acquisition software.

4. The method for calibrating the disk temperature model of the electronic parking system according to claim 1, wherein: In the temperature rise model: Frictional heat Q f (n) = k f ·ω p (n)·P c (n), where ω p (n) is the wheel speed pulse, P c (n) is the wheel cylinder pressure; Kinetic energy is converted into heat where m is the vehicle mass and v n is the real-time vehicle speed.

5. The method for calibrating the disc temperature model of the electronic parking system according to claim 1, wherein: The heat Q of heat convection in the temperature drop model c (n) = h·S·ΔT, where ΔT is the temperature difference between the brake disc and the environment, k h = h·S is the product of the convective heat transfer coefficient and the effective heat dissipation area.

6. The method for calibrating the disc temperature model of the electronic parking system according to claim 1, wherein: In S3, the dynamic caliper braking condition includes repeating the RWU clamping - release operation 3 times. The static cooling test records the temperature data for 0 - 1 hour and repeats 3 times. The dynamic driving condition includes driving at a constant speed in different speed intervals and recording the temperature data.

7. The method for calibrating the disc temperature model of the electronic parking system according to claim 1, wherein: In S4, when the model is initialized, the actual disc temperature value of the first sampling period is assigned to the model as the initial temperature value to ensure the initial synchronization of the model and the measured temperature.

8. The method for calibrating the disk temperature model of the electronic parking system according to claim 1, characterized in that: The iterative optimization uses the gradient descent algorithm, recalculates the model temperature curve after each parameter adjustment until the maximum absolute error of 3 consecutive iterations is less than 5°C.

9. The method for calibrating the disc temperature model of the electronic parking system according to claim 1, wherein: It also includes a verification step: writing the calibrated parameters into the electronic parking controller, and confirming the consistency of the change trend between the model temperature curve and the measured temperature through vehicle tests. When the mean absolute error ≤ 3°C, the calibrated parameters are solidified.

10. An electronic parking system, characterized in that: The disc temperature model calibrated by the method according to any one of claims 1 - 9 realizes the high-temperature re-clamping function. When it is detected that the temperature drop value of the brake disc exceeds the set threshold, the secondary clamping operation is automatically executed.

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