Braking recession parameter determination method, device and equipment and readable storage medium

Abstract

The invention provides a brake recession parameter determination method, device and equipment and a readable storage medium, and is applied to the technical field of vehicle braking. The method comprises the steps that for the current time period, the brake pad temperature of the current time period is determined; determining a reference friction coefficient according to the current deceleration and hydraulic pressure of the vehicle and the brake pad temperature of the current time period; for a target time period in the future time period, the predicted brake pad temperature of the target time period is determined based on the brake pad temperature corresponding to the last time period of the target time period and the predicted heat absorption capacity of the brake pad in the target time period; determining a predicted friction coefficient of the target time period based on the preset deceleration, the preset hydraulic pressure and the predicted brake pad temperature; and according to the reference friction coefficient and the predicted friction coefficient, determining a brake recession parameter of the target time period. According to the invention, the convenience of brake recession prediction can be improved.

Description

Technical Field

[0001] Embodiments of the present application relate to the technical field of vehicle braking, and in particular, to a method, device, equipment, and readable storage medium for determining braking fade parameters. Background Art

[0002] Braking fade refers to the phenomenon that the braking performance of a vehicle braking system significantly decreases after long-term or high-intensity use. The reason is that the heat generated during braking raises the temperature of the brake friction material, resulting in a decrease in its friction coefficient, which in turn affects the transmission and exertion of the caliper clamping force. By evaluating the braking fade situation, the performance change of the braking system can be understood in a timely manner, and potential risks can be discovered in advance.

[0003] In related technologies, a temperature sensor is installed at key parts such as brake pads or brake discs, and the sensor collects temperature data in real time. Since braking fade is closely related to temperature, by monitoring the temperature change and combining with an empirical threshold, the degree of braking fade is judged.

[0004] However, the above solution requires setting the temperature sensor at a specific part, continuously collecting data based on the sensor, and evaluating braking fade according to a large amount of continuously collected temperature data, with relatively low convenience. Summary of the Invention

[0005] In view of the above problems, embodiments of the present application are proposed to provide a method, device, electronic equipment, and readable storage medium for determining braking fade parameters that overcome the above problems or at least partially solve the above problems.

[0006] In a first aspect, embodiments of the present application disclose a method for determining braking fade parameters, including: For the current time period, determine the brake pad temperature of the current time period; According to the current deceleration, hydraulic pressure of the vehicle, and the brake pad temperature of the current time period, determine the reference friction coefficient; For a target time period in a future time period, based on the brake pad temperature corresponding to the previous time period of the target time period and the predicted heat absorption of the brake pad in the target time period, determine the predicted brake pad temperature of the target time period; the predicted heat absorption is obtained based on the predicted speed of the vehicle and a preset caliper clamping force; Based on a preset deceleration, preset hydraulic pressure, and the predicted brake pad temperature, determine the predicted friction coefficient of the target time period; According to the reference friction coefficient and the predicted friction coefficient, determine the braking fade parameter of the target time period.

[0007] Optionally, the step of determining the predicted friction coefficient for the target time period based on the preset deceleration, the preset hydraulic pressure, and the predicted brake pad temperature includes: Determine the actual frictional force according to the preset deceleration and the vehicle mass, and determine the theoretical frictional force according to the preset hydraulic pressure and the preset conversion coefficient; Based on the actual frictional force and the theoretical frictional force, determine an initial friction coefficient, and determine a temperature correction parameter corresponding to the predicted brake pad temperature; different brake pad temperatures correspond to different temperature correction parameters; Adjust the initial friction coefficient based on the temperature correction parameter to obtain the predicted friction coefficient for the target time period.

[0008] Optionally, the step of determining the temperature correction parameter corresponding to the predicted brake pad temperature includes: Determine the temperature correction parameter corresponding to the predicted brake pad temperature in a first mapping relationship between the brake pad temperature and the temperature correction parameter pre-constructed; or Determine a correction function corresponding to the temperature range in which the predicted brake pad temperature is located in a second mapping relationship between the pre-constructed brake pad temperature range and the correction function, and determine the temperature correction parameter corresponding to the predicted brake pad temperature based on the correction function and the predicted brake pad temperature.

[0009] Optionally, the method further includes: When it is determined that the vehicle is in an extreme working condition, determine the target time period that is currently being iterated, and the previous time period of the target time period; the extreme working condition includes that the operating frequency of the target system in the vehicle reaches a preset threshold, and the sensors of the vehicle drift; Use the predicted friction coefficient corresponding to the previous time period of the target time period as the friction coefficient for the target time period and subsequent time periods until the vehicle exits the extreme working condition.

[0010] Optionally, the step of determining the predicted brake pad temperature for the target time period based on the brake pad temperature corresponding to the previous time period of the target time period and the predicted heat absorption of the brake pad in the target time period includes: Determine the predicted braking heat according to the predicted speed and the preset caliper clamping force; Based on the predicted braking heat and the preset heat absorption ratio, determine the braking heat absorption of the brake pad; the preset heat absorption ratio represents the proportion of the heat absorbed by the brake pad in the predicted braking heat; Determine the heat conducted into, conducted out of, and dissipated from the brake pad based on the temperature differences between the brake pad temperature and the brake disc temperature, brake caliper temperature, and ambient temperature in the previous time period of the target time period, as well as a preset pad-disc thermal conductivity, a preset pad-caliper thermal conductivity, and a preset convective heat transfer coefficient. Determine the predicted brake pad temperature for the target time period based on the brake pad temperature, the heat absorbed by braking, the heat conducted into, the heat conducted out of, and the heat dissipated in the previous time period of the target time period.

[0011] Optionally, the method further includes: Determine the deceleration difference in the case where there is a difference between the actual deceleration of the vehicle and the preset deceleration. Update the preset pad-disc thermal conductivity, the preset pad-caliper thermal conductivity, and the preset convective heat transfer coefficient according to the deceleration difference and a preset gain matrix.

[0012] Optionally, the brake fade parameter includes a brake fade ratio; the method further includes: Construct a third mapping relationship between different brake fade ratio intervals and warning methods. Based on the target ratio interval in which the brake fade ratio is located, determine the target warning method corresponding to the target ratio interval in the third mapping relationship, and give a warning to the user based on the target warning method.

[0013] In a second aspect, an embodiment of the present application discloses a brake fade parameter determination device, including: A reference parameter module, configured to determine the brake pad temperature for the current time period for the current time period. A reference friction module, configured to determine a reference friction coefficient according to the current deceleration of the vehicle, the hydraulic pressure, and the brake pad temperature for the current time period. A prediction parameter module, configured to, for a target time period in a future time period, determine the predicted brake pad temperature for the target time period based on the brake pad temperature corresponding to the previous time period of the target time period and the predicted heat absorption of the brake pad in the target time period; the predicted heat absorption is obtained based on the predicted speed of the vehicle and a preset caliper clamping force. A prediction friction module, configured to determine the predicted friction coefficient for the target time period based on a preset deceleration, a preset hydraulic pressure, and the predicted brake pad temperature. A fade determination module, configured to determine the brake fade parameter for the target time period according to the reference friction coefficient and the predicted friction coefficient.

[0014] Optionally, the prediction friction module includes: A friction calculation sub-module, configured to determine the actual friction force according to a preset deceleration and vehicle mass, and determine the theoretical friction force according to a preset hydraulic pressure and a preset conversion coefficient; An initial friction sub-module, configured to determine an initial friction coefficient based on the actual friction force and the theoretical friction force, and determine a temperature correction parameter corresponding to the predicted brake pad temperature; different brake pad temperatures correspond to different temperature correction parameters; A friction adjustment sub-module, configured to adjust the initial friction coefficient based on the temperature correction parameter to obtain the predicted friction coefficient for the target time period.

[0015] Optionally, the initial friction sub-module includes: A first mapping unit, configured to determine the temperature correction parameter corresponding to the predicted brake pad temperature in a first mapping relationship between the brake pad temperature and the temperature correction parameter pre-constructed; or A second mapping unit, configured to determine a correction function corresponding to the temperature range in which the predicted brake pad temperature is located in a second mapping relationship between the pre-constructed brake pad temperature range and the correction function, and determine the temperature correction parameter corresponding to the predicted brake pad temperature based on the correction function and the predicted brake pad temperature.

[0016] Optionally, the device further includes: A working condition judgment module, configured to determine the target time period currently being iterated and the previous time period of the target time period when it is determined that the vehicle is in an extreme working condition; the extreme working condition includes that the operating frequency of the target system in the vehicle reaches a preset threshold, and the sensors of the vehicle drift; A parameter maintenance module, configured to use the predicted friction coefficient corresponding to the previous time period of the target time period as the friction coefficient for the target time period and subsequent time periods until the vehicle exits the extreme working condition.

[0017] Optionally, the prediction parameter module includes: A braking heat sub-module, configured to determine the predicted braking heat according to the predicted speed and the preset caliper clamping force; An endothermic ratio sub-module, configured to determine the braking absorbed heat of the brake pad based on the predicted braking heat and the preset heat absorption ratio; the preset heat absorption ratio represents the proportion of the heat absorbed by the brake pad in the predicted braking heat; A heat conduction sub-module, configured to determine the imported heat, the exported heat and the dissipated heat of the brake pad according to the temperature differences between the brake pad temperature and the brake disc temperature, the brake caliper temperature, and the ambient temperature in the previous time period of the target time period, and the preset pad-disc thermal conductivity, the preset pad-caliper thermal conductivity, and the preset convective heat transfer coefficient; A temperature determination sub-module, configured to determine the predicted brake pad temperature of the target time period according to the brake pad temperature of the previous time period of the target time period, the absorbed braking heat, the imported heat, the exported heat, and the dissipated heat.

[0018] Optionally, the device further includes: A deceleration difference module, configured to determine a deceleration difference when there is a difference between the actual deceleration of the vehicle and the preset deceleration; A parameter update module, configured to update the preset disc-pad thermal conductivity, the preset caliper-pad thermal conductivity, and the preset convective heat transfer coefficient according to the deceleration difference and a preset gain matrix.

[0019] Optionally, the brake fade parameter includes a brake fade ratio; the device further includes: A third mapping module, configured to construct a third mapping relationship between different brake fade ratio intervals and warning methods; A fade warning module, configured to determine a target warning method corresponding to the target ratio interval in the third mapping relationship according to the target ratio interval where the brake fade ratio is located, and give a warning to the user based on the target warning method.

[0020] In a third aspect, an embodiment of the present application further discloses an electronic device, including a processor, a communication interface, a memory, and a communication bus; wherein, the processor, the communication interface, and the memory complete communication with each other through the communication bus; the memory is used for storing a computer program; when the processor executes the program stored on the memory, the steps of the brake fade parameter determination method as described above are implemented.

[0021] In a fourth aspect, an embodiment of the present application further discloses a readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the steps of the brake fade parameter determination method as described above are implemented.

[0022] Implementing the embodiments of the present application, for the current time period, determine the temperature of the brake pads in the current time period. According to the current deceleration of the vehicle, the hydraulic pressure, and the temperature of the brake pads in the current time period, determine the reference friction coefficient. For the target time period in the future, based on the temperature of the brake pads corresponding to the previous time period of the target time period and the predicted heat absorption of the brake pads in the target time period, determine the predicted temperature of the brake pads in the target time period. The predicted heat absorption is obtained based on the predicted speed of the vehicle and the preset caliper clamping force. Based on the preset deceleration, the preset hydraulic pressure, and the predicted temperature of the brake pads, determine the predicted friction coefficient in the target time period. According to the reference friction coefficient and the predicted friction coefficient, determine the brake fade parameter in the target time period. Furthermore, it is possible to determine the reference friction coefficient in the current time period for use as a benchmark for evaluating brake fade, and then determine the predicted friction coefficient in the target time period in the future. Based on the reference friction coefficient and the predicted friction coefficient, determine the brake fade parameter corresponding to any target time period in the future, avoiding the need to separately set a temperature sensor for the braking system and the cumbersome process of collecting data, and improving the convenience of evaluating brake fade. Description of the Drawings

[0023] Figure 1 is a step diagram of a method for determining a brake fade parameter provided by an embodiment of the present application; Figure 2 is a step diagram of another method for determining a brake fade parameter provided by an embodiment of the present application; Figure 3 is an architecture diagram of brake fade prediction provided by an embodiment of the present application; Figure 4 is a flowchart of brake fade prediction provided by an embodiment of the present application; Figure 5 is a block diagram of a device for determining a brake fade parameter provided by an embodiment of the present application; Figure 6 is a block diagram of an electronic device provided by an embodiment of the present application.

[0024] Description of the Reference Numerals: Reference parameter module 501, reference friction module 502, prediction parameter module 503, prediction friction module 504, fade determination module 505; processor 1001, communication interface 1002, memory 1003, communication bus 1004. Detailed Embodiments

[0025] Exemplary embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present application can be more thoroughly understood and the scope of the present application can be fully communicated to those skilled in the art.

[0026] Figure 1 is a step diagram of a method for determining a brake fade parameter provided by an embodiment of the present application. The method includes: Step 101, for the current time period, determine the brake pad temperature of the current time period.

[0027] In the embodiment of the present application, the execution subject of the method can be a device with data processing capabilities, which can be a device in a vehicle, such as an in-vehicle terminal, or the server processes relevant data after obtaining it. There is no specific limitation here.

[0028] The current time period can start from when the vehicle starts driving again, or can start from when data such as the current speed and caliper clamping force of the vehicle are obtained, or can start from the first brake, or can start after several brakes. There is no specific limitation here. The length of each time period can be several milliseconds, such as 500 milliseconds, or a smaller time period. There is no specific limitation here.

[0029] The braking system in the vehicle can at least include brake pads, brake discs, and brake calipers. When the driver presses the brake pedal, the hydraulic pressure of the brake is transmitted through the brake line to the brake caliper, and the brake caliper piston pushes the brake pad to tightly press it against the brake disc connected to the wheel. Friction is generated between the brake pad and the brake disc, converting the kinetic energy of the vehicle into heat energy, thereby decelerating the vehicle until it stops.

[0030] If the vehicle has been stationary for a long time and the current time period is within a short time after the vehicle has just resumed operation, for example, the current time period is within 30 seconds or 1 minute after the vehicle has just resumed operation, then the brake pad temperature of the current time period can adopt the ambient temperature, and the ambient temperature can be obtained through a temperature sensor in the vehicle; if the time since the vehicle's last stop is short, for example, the current time period is only 10 seconds or 20 seconds since the vehicle's last stop, the brake pad temperature recorded by the vehicle when it stopped can also be adopted, and this brake pad temperature can be obtained by a temperature sensor arranged beside the brake pad. There is no specific limitation here on how to determine the brake pad temperature of the current time period.

[0031] Step 102, according to the current deceleration of the vehicle, the hydraulic pressure, and the brake pad temperature of the current time period, determine the reference friction coefficient.

[0032] When the vehicle brakes, the clamping force of the caliper causes the vehicle to decelerate, and the clamping force of the caliper is provided by the frictional force between the brake pads and the brake disc. The clamping force of the caliper is also related to the friction coefficient and the normal force. For a disc brake system, the normal force is generated by the hydraulic pressure of the brake caliper, and the friction coefficient can measure the conversion relationship between the clamping force of the caliper and the hydraulic pressure. Under the same hydraulic pressure, the higher the friction coefficient, the greater the clamping force of the caliper and the better the braking effect.

[0033] The hydraulic pressure can be obtained in various ways. For example, it can be obtained through a pressure sensor. The pressure sensor can be installed in the hydraulic pipeline of the braking system, generally near the brake caliper or the master cylinder. Based on working principles such as the piezoresistive effect and the piezoelectric effect, when the hydraulic pressure acts on the sensor, the sensor will convert the pressure signal into a hydraulic signal, and the hydraulic signal can represent the magnitude of the hydraulic pressure. It can also be read through the vehicle diagnostic system (OBD, On-Board Diagnostics). For example, the vehicle diagnostic system can communicate with the vehicle's electronic control unit (ECU, Electronic Control Unit) to obtain the hydraulic pressure information of the braking system. There is no specific limitation on how to obtain the hydraulic pressure here.

[0034] Since the material properties of components such as brake pads in the braking system may change at different temperatures, and brake pads and other components are usually composed of different materials, an increase in temperature may cause changes in the physical and chemical properties of the materials. For example, the mechanical properties such as hardness and elastic modulus of the material will change at high temperatures, thereby affecting the friction coefficient. Therefore, the friction coefficient calculated from the clamping force of the caliper and the hydraulic pressure can be corrected based on the brake pad temperature corresponding to the current time period. It can be based on a preset operation formula or model. Input the friction coefficient and the brake pad temperature to obtain the processed friction coefficient. The operation process is not specifically limited here.

[0035] Step 103, for the target time period in the future time period, determine the predicted brake pad temperature of the target time period based on the brake pad temperature corresponding to the previous time period of the target time period and the predicted heat absorption of the brake pad in the target time period; the predicted heat absorption is obtained based on the predicted speed of the vehicle and the preset caliper clamping force.

[0036] It can be understood that the current time period in step 101 is the time period that actually occurs currently, and the subsequent second, third, and several other time periods are all target time periods in the future time period. For the second time period, the brake pad temperature corresponding to the previous time period is the brake pad temperature corresponding to the current time period in step 101; for the third time period, the brake pad temperature corresponding to the previous time period is the brake pad temperature corresponding to the second time period, and so on.

[0037] Since it is to predict future brake fade conditions, the subsequent time period can be a target time period in a future time period that has not occurred. Therefore, for the subsequent target time period, the data used to calculate the predicted heat absorption can be predicted data or preset data, such as predicted speed and preset caliper clamping force.

[0038] Based on the vehicle speed and deceleration, the predicted speed of the vehicle in the subsequent target time period can be determined. For example, if the speed of the vehicle at the current time period is 20 meters per second and the deceleration is 2 meters per square second, the speed in the second time period can be 18 meters per second. It is also possible to construct a speed prediction model and input relevant data such as the current speed and deceleration to obtain the predicted speed. How to predict the vehicle speed will not be elaborated here.

[0039] The preset caliper clamping force can be the maximum caliper clamping force that the braking system can provide, so as to be able to evaluate the brake fade situation under the worst conditions. It can be calculated by calculating the maximum caliper clamping force reached during the historical operation of the vehicle as the preset caliper clamping force. The caliper clamping force can be calculated in a variety of different ways. For example, it can be calculated based on kinematics. According to Newton's second law F = ma, where F is the caliper clamping force, m is the vehicle mass, and a is the acceleration of the vehicle during braking. The acceleration can be calculated from the change in vehicle speed before and after braking and the braking time, and then the caliper clamping force can be determined based on the vehicle mass and vehicle deceleration. It can also be calculated based on the conservation of energy. The work done by the caliper clamping force is equal to the change in the vehicle's kinetic energy. The change in the vehicle's kinetic energy can be calculated based on the vehicle speed at the start and end of a period of time, and the caliper clamping force can be determined based on the change in kinetic energy and the braking distance. It can also be calculated through the conversion coefficient between hydraulic pressure and caliper clamping force. Given the known hydraulic pressure and conversion coefficient, the magnitude of the caliper clamping force can be obtained. If the vehicle uses an electronic mechanical brake system (EMB, Electronic Mechanical Brake System), the magnitude of the caliper clamping force output by the EMB can be directly read. How to calculate the caliper clamping force will not be specifically limited here.

[0040] Calculate the braking power based on the predicted speed and preset caliper clamping force to predict the predicted braking heat generated by the braking system, which can be expressed by the following formula: Qin(k)=ηh×[Fbrake_total(k)×Vvehicle(k)×Δt] Among them, Qin(k) represents the predicted braking heat generated by braking in cycle k, ηh is the conversion coefficient between power and heat, ηh ∈ (0, 1), which can be set as a constant (such as 0.8) during simulation or fine-tuned according to material properties. Fbrake_total(k) represents the preset caliper clamping force corresponding to cycle k, Vvehicle(k) represents the predicted speed corresponding to cycle k, and Δt represents the duration of the time cycle.

[0041] After determining the predicted braking heat generated by the braking system, since the braking system may include components such as brake pads, brake discs, and brake calipers, the braking heat absorbed by each component may be different. Not all of the braking heat generated during braking is absorbed by the brake pads, and different components in the braking system absorb different amounts of braking heat, that is, different components have different absorption ratios of braking heat. The heat absorption ratio can be obtained through experiments or by querying existing data. Then, based on the heat absorption ratio, the magnitude of the predicted braking heat absorbed by the brake pads can be determined. To reduce the complexity of data processing, the braking heat absorbed by the brake pads can be used as the predicted heat absorption in the target time cycle.

[0042] Since the heat absorbed or released by an object is proportional to its mass, specific heat capacity, and temperature change, the temperature change of the brake pads can be calculated based on the mass, specific heat capacity, and heat absorption of the brake pads, which can be expressed by the following formula: In the above formula, ΔT represents the temperature change, Q represents the heat absorption, m represents the mass of the brake pads, and c represents the specific heat capacity of the brake pads.

[0043] According to the above formula, based on the heat absorption of the brake pads, the specific heat capacity of the brake pads, and the mass of the brake pads in the target time cycle, the temperature change of the brake pads, such as rising by a certain number of degrees Celsius, can be calculated. Since the initial temperature of the target time cycle can be the temperature of the brake pads corresponding to the previous time cycle, based on the temperature of the brake pads corresponding to the previous time cycle and the temperature change, the temperature of the brake pads in the target time cycle can be calculated.

[0044] For example, the temperature of the brake pads corresponding to the previous time cycle is 25 degrees Celsius, the heat absorption is 10000 joules (J), the mass of the brake pads is 1 kilogram (kg), and the specific heat capacity is 1000 J / kg. Then the temperature of the brake pads in the target time cycle is 35 degrees Celsius.

[0045] Among them, if the target time period to be calculated currently is the second time period, the brake pad temperature corresponding to the previous time period is the brake pad temperature corresponding to the current time period in step 101, for example, the ambient temperature. Further, if the target time period to be calculated currently is the third time period, the initial temperature of the target time period is the brake pad temperature corresponding to the second time period, and the brake pad temperature corresponding to the second time period has also been obtained based on the brake pad temperature corresponding to the current time period in step 101. By analogy, the predicted brake pad temperature of each subsequent target time period can be continuously iteratively obtained. The predicted brake pad temperature of each target time period is determined by predicting the heat absorption amount based on the brake pad temperature of the previous time period to obtain the predicted brake pad temperature.

[0046] Step 104: Based on the preset deceleration, preset hydraulic pressure, and the predicted brake pad temperature, determine the predicted friction coefficient of the target time period.

[0047] Since each predicted brake pad temperature is obtained based on the brake pad temperature of the previous time period, the brake pad temperature is continuously iterated. After iterating through multiple time periods, the predicted brake pad temperature at a specific future time point can be obtained. Similarly, the predicted friction coefficient can be calculated according to the preset deceleration, preset hydraulic pressure, and predicted brake pad temperature, and the specific calculation process will not be elaborated here.

[0048] Among them, the preset deceleration can be the maximum deceleration that the vehicle can achieve, and the maximum deceleration can be determined through vehicle testing or in the vehicle's historical deceleration data. The preset hydraulic pressure can also be the maximum hydraulic pressure that the vehicle can provide.

[0049] Step 105: According to the reference friction coefficient and the predicted friction coefficient, determine the brake fade parameter of the target time period.

[0050] The reference friction coefficient is a friction coefficient value used as a reference standard. The reference friction coefficient is the friction coefficient between the brake pad and the brake disc under ideal conditions or when the braking system is brand new and has not been used for a long time. The value of the reference friction coefficient is relatively stable and can be determined through experiments or according to the design specifications of the braking system.

[0051] The predicted friction coefficient is an estimated value of the friction coefficient between the brake pad and the brake disc during the target time period in the future. As the number of brakings increases and the brake pad temperature rises, the friction coefficient will change, and the predicted friction coefficient can reflect the friction coefficient value after future changes.

[0052] Based on the reference friction coefficient and the predicted friction coefficient, the brake fade situation can be determined. It can be to calculate the difference between the predicted friction coefficient and the reference friction coefficient. If the predicted friction coefficient is less than the reference friction coefficient, it indicates that there may be brake fade. The greater the difference, the more obvious the fade. It is also possible to calculate the ratio of the two as the brake fade parameter and observe the change trend of the brake fade parameter over the time period to determine the change of the brake fade situation.

[0053] For example, according to the current time period, the reference friction coefficient is determined to be 0.4. In the fifth time period, the predicted friction coefficient is 0.38, the difference between the two is 0.02, and the ratio is 0.95; by the tenth time period, the predicted friction coefficient becomes 0.36, the difference becomes 0.04, and the ratio becomes 0.9.

[0054] It can be understood that if only based on the predicted friction coefficient corresponding to the preset number of time periods, the brake fade situation corresponding to the future specific time point of this time period can be determined. If the predicted friction coefficients corresponding to each time period within the preset number of time periods are continuously analyzed, the change process of the brake fade can be understood.

[0055] In summary, when implementing the embodiments of the present application, for the current time period, based on the ambient temperature and the heat absorption of the brake pads in the current time period, the temperature of the brake pads in the current time period is determined. The heat absorption is obtained based on the current speed of the vehicle and the caliper clamping force. According to the current deceleration of the vehicle, the hydraulic pressure, and the temperature of the brake pads in the current time period, the reference friction coefficient is determined. For the target time period in the future time period, based on the temperature of the brake pads corresponding to the previous time period of the target time period and the predicted heat absorption of the brake pads in the target time period, the predicted temperature of the brake pads in the target time period is determined. The predicted heat absorption is obtained based on the predicted speed of the vehicle and the preset caliper clamping force. Based on the preset deceleration, the preset hydraulic pressure, and the predicted temperature of the brake pads, the predicted friction coefficient in the target time period is determined. According to the reference friction coefficient and the predicted friction coefficient, the brake fade parameter in the target time period is determined, which can determine the reference friction coefficient in the current time period for use as a reference for evaluating brake fade, and then determine the predicted friction coefficient in the target time period in the future time period, and determine the brake fade parameter corresponding to any target time period in the future time period based on the reference friction coefficient and the predicted friction coefficient, avoiding the need to separately set a temperature sensor for the brake system and the cumbersome process of collecting data, and improving the convenience of evaluating brake fade.

[0056] Reference Figure 2 , which shows a flowchart of the steps of a method for determining a brake fade parameter provided by the embodiments of the present application. The method includes: Step 201, for the current time period, determine the temperature of the brake pads in the current time period; Step 202: Determine a reference friction coefficient based on the current deceleration of the vehicle, the hydraulic pressure, and the brake pad temperature in the current time period. Step 203: For a target time period in a future time period, determine the predicted brake pad temperature for the target time period based on the brake pad temperature corresponding to the previous time period of the target time period and the predicted heat absorption of the brake pad in the target time period; the predicted heat absorption is obtained based on the predicted speed of the vehicle and a preset caliper clamping force. Step 204: Determine the predicted friction coefficient for the target time period based on a preset deceleration, a preset hydraulic pressure, and the predicted brake pad temperature. Step 205: Determine the brake fade parameter for the target time period according to the reference friction coefficient and the predicted friction coefficient.

[0057] Steps 201 - 205 above can refer to the content of the above Figure 1 embodiment and will not be elaborated here.

[0058] Optionally, step 203 of determining the predicted brake pad temperature for the target time period based on the brake pad temperature corresponding to the previous time period of the target time period and the predicted heat absorption of the brake pad in the target time period includes: Sub - step 2031: Determine the predicted braking heat according to the predicted speed and the preset caliper clamping force. Sub - step 2032: Determine the braking heat absorption of the brake pad based on the predicted braking heat and a preset heat absorption ratio; the preset heat absorption ratio represents the proportion of the heat converted by braking that is absorbed by the brake pad. Sub - step 2033: Determine the heat conducted into the brake pad, the heat conducted out of the brake pad, and the heat dissipated according to the temperature difference between the brake pad temperature in the previous time period of the target time period and the brake disc temperature, the brake caliper temperature, and the ambient temperature, as well as a preset disc - pad thermal conductivity, a preset caliper - pad thermal conductivity, and a preset convective heat transfer coefficient. Sub - step 2034: Determine the predicted brake pad temperature for the target time period according to the brake pad temperature in the previous time period of the target time period, the braking heat absorption, the heat conducted into the brake pad, the heat conducted out of the brake pad, and the heat dissipated.

[0059] In the embodiment of the present application, the predicted braking heat can be calculated according to the predicted speed of the vehicle and the preset caliper clamping force to be applied. Since the actions of the vehicle speed and the caliper clamping force will cause energy conversion, this energy is mainly generated in the form of heat.

[0060] Not all of the heat generated during the braking process is absorbed by the brake pads. Different components in the braking system absorb different amounts of braking heat, that is, the absorption ratios of braking heat by different components are different. The preset heat absorption ratio can be obtained through experiments or by querying existing data. Then, based on the preset heat absorption ratio, the predicted braking heat is calculated according to this ratio to determine the braking heat absorbed by the brake pads.

[0061] However, there is a temperature difference between the brake pads and the brake disc, brake caliper, and the environment. According to the principles of heat conduction and heat convection, heat will be transferred between different objects. Therefore, the braking heat absorbed by the brake pads is not directly equal to the heat absorption of the brake pads during the target time period.

[0062] Therefore, on the basis of taking the braking heat absorbed by the brake pads as the predicted heat absorption during the target time period, in order to further improve the accuracy of determining the predicted heat absorption, the heat conducted into the brake pads (the heat transferred from other components to the brake pads), the heat conducted out of the brake pads (the heat transferred from the brake pads to other components), and the heat dissipated (the heat dissipated by the brake pads to the environment) can be calculated respectively through relevant heat conduction, heat transfer coefficients, and temperature differences. Finally, based on the braking heat absorbed by the brake pads, the heat conducted into the brake pads, the heat conducted out of the brake pads, and the heat dissipated, the heat absorption of the brake pads during the target time period is comprehensively determined.

[0063] Among them, the preset brake-disc thermal conductivity is a parameter representing the heat transfer ability between the brake pads and the brake disc; the preset brake-caliper thermal conductivity is a parameter representing the heat transfer ability between the brake pads and the brake caliper; the preset convective heat transfer coefficient is a parameter representing the heat transfer ability between the brake pads and the surrounding environment.

[0064] Since the temperature of the brake disc can be higher than the temperature of the brake pads, based on the temperature of the brake pads and the brake disc, it can be determined that the brake disc conducts heat into the brake pads, corresponding to the heat conducted into the brake pads; since the temperature of the brake pads can be higher than the temperature of the brake caliper, based on the temperature of the brake pads and the brake caliper, it can be obtained that the brake pads conduct heat out to the brake caliper, corresponding to the heat conducted out of the brake pads; in addition, the brake pads will dissipate heat to the surrounding environment, so the heat dissipated can be obtained according to the temperature difference between the brake pads and the environment temperature.

[0065] The sum of the heat conducted into the brake pads, the heat conducted out of the brake pads, and the heat dissipated is the heat absorption during the time period. Then, based on the temperature of the brake pads, the braking heat absorbed, the heat conducted into the brake pads, the heat conducted out of the brake pads, and the heat dissipated in the previous time period, as well as the specific heat capacity of the brake pads, the temperature of the brake pads in the target time period can be determined.

[0066] For the brake pads, brake disc, and brake caliper in the braking system, the following heat balance equations can be obtained: mdisc×cdisc×[Tdisc(k + 1)-Tdisc(k)]÷Δt=a×Qin(k)-Qout_disc(k)-Qx_disc_to_pad(k) Among them, mdisc represents the mass of the brake disc, cdisc represents the specific heat capacity of the brake disc, Tdisc(k + 1) represents the temperature of the brake disc in the time period k + 1, Tdisc(k) represents the temperature of the brake disc in the time period k, Δt is the duration of the time period, α represents the heat absorption ratio of the brake disc, Qin(k) represents the braking heat generated in the time period k, Qout_disc(k) represents the heat dissipation of the brake disc, and Qx_disc_to_pad(k) represents the heat conducted from the brake disc to the brake pad; mpad×cpad×[Tpad(k + 1)-Tpad(k)]÷Δt=(1 - a)×Qin(k)+Qx_disc_to_pad(k)-Qx_pad_to_caliper(k)-Qout_pad(k) The right side of the equation in the above formula represents the predicted heat absorption of the brake pad in the target time period: the braking heat absorbed by the brake pad (1 - a)×Qin(k), plus the heat conducted from the brake disc to the brake pad (Qx_disc_to_pad(k)), minus the heat conducted from the brake pad to the brake caliper (Qx_pad_to_caliper(k)), and then minus the heat dissipation of the brake pad (Qout_pad(k)); among them, mpad represents the mass of the brake pad, cpad represents the specific heat capacity of the brake pad, Tpad(k + 1) represents the temperature of the brake pad in the time period k + 1, Tpad(k) represents the temperature of the brake pad in the time period k, Δt is the duration of the time period, (1 - α) represents the preset heat absorption ratio of the brake pad, and Qin(k) represents the braking heat generated in the time period k.

[0067] mcaliper×ccaliper×[Tcaliper(k + 1)-Tcaliper(k)]÷Δt=Qx_pad_to_caliper(k)-Qout_caliper(k) Among them, mpad represents the mass of the brake caliper, cpad represents the specific heat capacity of the brake caliper, Tpad(k + 1) represents the temperature of the brake caliper in the time period k + 1, Tpad(k) represents the temperature of the brake caliper in the time period k, Δt is the duration of the time period, and Qout_caliper(k) represents the heat dissipation of the brake caliper.

[0068] Based on the Euler forward method, the temperature of the brake disc in the time period k + 1 can be expressed as: Tdisc(k + 1)= Tdisc(k)+ Δt÷(mdisc×cdisc)×[a×Qin(k)- hdisc×Adisc×(Tdisc(k)- Tair(k))- kdp×(Tdisc(k)- Tpad(k))]; The temperature of the brake disc at time period k + 1 can be expressed as: Tpad(k + 1)= Tpad(k)+ Δt÷(mpad×cpad)×[(1 - a)×Qin(k)+ kdp×(Tdisc(k)- Tpad(k))- kpc×(Tpad(k)- Tcaliper(k))- hpad×Apad×(Tpad(k)- Tair(k))]; The temperature of the brake caliper at time period k + 1 can be expressed as: Tcaliper(k + 1)= Tcaliper(k)+ Δt÷(mcaliper×ccaliper)×[kpc×(Tpad(k)- Tcaliper(k))- hcal×Acal×(Tcaliper(k)- Tair(k))] Where hdisc, hpad, and hcal are the convective heat transfer coefficients of the brake disc, brake pad, and brake caliper respectively; Adisc, Apad, and Acal are the heat dissipation surface areas of the brake disc, brake pad, and brake caliper respectively; kdp and kpc are the thermal conductivities between the brake disc and brake pad, and between the brake pad and brake caliper respectively; Tair(k) is the ambient temperature, which can be set as a constant value in the simulation and directly used for iteration with Tair.

[0069] Among them, the unit of the convective heat transfer coefficient is W / (m²×K). The convective heat transfer coefficient represents the strength of the convective heat transfer ability between the fluid and the solid surface. W represents the power unit Watt, that is, the rate of heat transfer (Joule / second). m² represents the area unit square meter, referring to the heat transfer surface area. K represents the thermodynamic temperature unit Kelvin, which is used to measure the temperature difference. The unit of the thermal conductivity is W / (m×K), which represents the ability of the material to conduct heat. W represents the power unit Watt. m represents the length unit meter, referring to the path length of heat conduction. K represents the thermodynamic temperature unit Kelvin. Based on the above formulas, the temperatures of the brake disc, brake pad, and brake caliper can be continuously iteratively updated, and then the predicted friction coefficients corresponding to each target time period in the future time period can be continuously iteratively calculated.

[0070] In an embodiment of the present application, based on the predicted speed and the preset caliper clamping force, the predicted braking heat is determined. Based on the predicted braking heat and the preset heat absorption ratio, the braking absorption heat of the brake pads is determined. According to the temperature differences between the brake pad temperature and the brake disc temperature, the brake caliper temperature, and the ambient temperature in the previous time period, as well as the preset disc-pad thermal conductivity, the preset pad-caliper thermal conductivity, and the preset convective heat transfer coefficient, the heat input, the heat output, and the heat dissipation of the brake pads are determined. According to the brake pad temperature, the braking absorption heat, the heat input, the heat output, and the heat dissipation in the previous time period, the brake pad temperature in the target time period is determined. It is possible to establish a three-body coupled heat model (brake disc, brake pads, and brake caliper), and at the same time consider the heat coupling and dynamic heat dissipation process between the brake disc, the brake pads, and the brake caliper, and can more accurately predict the temperature change of the brake pads, improving the accuracy of determining the brake pad temperature.

[0071] Optionally, the step 204 of determining the predicted friction coefficient in the target time period based on the preset deceleration, the preset hydraulic pressure, and the predicted brake pad temperature includes: Sub-step 2041, determining the actual frictional force according to the preset deceleration and the vehicle mass, and determining the theoretical frictional force according to the preset hydraulic pressure and the preset conversion coefficient; Sub-step 2042, determining the initial friction coefficient based on the actual frictional force and the theoretical frictional force, and determining the temperature correction parameter corresponding to the predicted brake pad temperature; different brake pad temperatures correspond to different temperature correction parameters; Sub-step 2043, adjusting the initial friction coefficient based on the temperature correction parameter to obtain the predicted friction coefficient in the target time period.

[0072] In the embodiment of the present application, according to the preset deceleration and the vehicle mass, the actual frictional force that generates the actual braking effect can be obtained, and the calculation process can be expressed as: Fbrake_total(k)=m×ax_f(k) Wherein, Fbrake_total(k) is the actual frictional force, i.e., the caliper clamping force, m is the vehicle mass, and ax_f(k) is the preset deceleration.

[0073] The preset conversion coefficient is a coefficient used to measure the conversion efficiency when the hydraulic pressure is converted into frictional force. The preset conversion coefficient can represent how much frictional force can be converted per unit of the preset hydraulic pressure, and the preset conversion coefficient is related to factors such as the structure, material, and design principle of the braking system. The preset conversion coefficient can be obtained through experiments and analysis. For example, for a specific braking system, the preset conversion coefficient may be 0.6, 0.7, etc.

[0074] The theoretical frictional force, i.e., the theoretical friction, that should be generated can be determined based on the hydraulic pressure provided by the vehicle and a preset conversion coefficient. The theoretical friction is the frictional force that the braking system can generate under ideal conditions, such as during the first braking. The calculation process can be expressed as: Fbrake_total(k) = kp×Pbrake_f(k)×R Where Fbrake_total(k) represents the theoretical friction, Pbrake_f(k) is the hydraulic pressure, kp is the preset conversion coefficient, and R is the distribution coefficient. If the front and rear wheels are summarized and equivalent, the distribution coefficient can be 1, and the distribution coefficient and the preset conversion coefficient can also be integrated into the same parameter.

[0075] Based on the actual friction and the theoretical friction, the initial friction coefficient can be determined. It can be obtained by dividing the actual friction by the theoretical friction, or based on the difference between the actual friction and the theoretical friction. The initial friction coefficient reflects the magnitude relationship between the actual friction and the theoretical friction.

[0076] When the calculation process is dividing the actual friction by the theoretical friction, it can be expressed as: μest(k) = [ m×ax_f(k) ]÷[ kp×Pbrake_f(k) ] Where μest(k) represents the initial friction coefficient at the k time period, m is the vehicle mass, ax_f(k) is the deceleration, kp is the conversion coefficient between the hydraulic pressure and the caliper clamping force, and Pbrake_f(k) is the hydraulic pressure. As long as the vehicle has braking deceleration, μest(k)>0, but it is necessary to judge the situation of ax_f(k)≈0 or Pbrake_f(k)≈0 to avoid calculation errors.

[0077] In addition, for the deceleration signal and the hydraulic pressure signal, additional filtering processing can be performed, which can be expressed as: Pbrake_f(k) = LPF{Pbrake(k)} ax_f(k) = LPF{ax(k)} Where Pbrake_f(k) is the hydraulic pressure after filtering processing, LPF (Low-Pass Filter) represents low-pass filtering, Pbrake(k) is the hydraulic pressure before filtering; ax_f(k) is the deceleration after filtering processing, and ax(k) is the deceleration before filtering.

[0078] Each predicted brake pad temperature can correspond to a different temperature correction parameter. There can be a positive correlation between the predicted brake pad temperature and the temperature correction parameter. The larger the predicted brake pad temperature, the larger the temperature correction parameter.

[0079] Based on the predicted brake pad temperature, a corresponding temperature correction parameter is determined. The temperature correction parameter can be less than 1. The initial friction coefficient can be multiplied by the temperature correction parameter or other more complex operations to correct the initial friction coefficient and obtain the predicted friction coefficient. The correction of the initial friction coefficient based on the temperature correction parameter can be expressed as: μest_corr(k) =μest(k)×fμ( Tpad(k) ) where μest_corr(k) is the predicted friction coefficient after correction in the k time period, μest(k) is the initial friction coefficient in the k time period, and fμ( Tpad(k) ) represents the temperature correction parameter corresponding to the brake pad temperature Tpad(k) of the brake pad in the k time period.

[0080] Implementing the embodiments of the present application, based on the preset deceleration and vehicle mass, the actual frictional force is determined, and based on the preset hydraulic pressure and preset conversion coefficient, the theoretical frictional force is determined. Based on the actual frictional force and the theoretical frictional force, the initial friction coefficient is determined, and then based on the temperature correction parameter corresponding to the predicted brake pad temperature, the initial friction coefficient is adjusted to obtain the predicted friction coefficient in the target time period, which can accurately determine the performance of the braking system in the target time period. By considering the influence of temperature on the friction coefficient and performing parameter correction to obtain the predicted friction coefficient, the accuracy of the predicted friction coefficient can be improved.

[0081] Optionally, the sub-step 2043 of determining the temperature correction parameter corresponding to the predicted brake pad temperature includes: Sub-step 20431, in the first mapping relationship between the brake pad temperature and the temperature correction parameter pre-constructed, determine the temperature correction parameter corresponding to the predicted brake pad temperature; or Sub-step 20432, in the second mapping relationship between the pre-constructed brake pad temperature range and the correction function, determine the correction function corresponding to the temperature range in which the predicted brake pad temperature is located, and based on the correction function and the predicted brake pad temperature, determine the temperature correction parameter corresponding to the predicted brake pad temperature.

[0082] In the embodiments of the present application, based on bench tests or querying manufacturing data, the temperature correction parameters corresponding to different brake pad temperatures can be determined, and then the first mapping relationship between the brake pad temperature and the temperature correction parameter is pre-constructed. The first mapping relationship can be represented by various data structures, such as a hash table. The mapping relationship can be stored in a dictionary mapping, with the brake pad temperature as the key and the corresponding temperature correction parameter as the value. When the predicted brake pad temperature is known, the corresponding temperature correction parameter can be obtained from the dictionary.

[0083] Similarly, it can also be based on bench tests or querying manufacturing data to pre-construct a second mapping relationship between the brake pad temperature range and the correction function. In this second mapping relationship, there are different brake pad temperature ranges, each temperature range corresponding to its own correction function, and each correction function is used to calculate the corresponding temperature correction parameter according to the specific brake pad temperature.

[0084] The brake pad temperature range and the correction function can include Temperature Range 1: Tlow ≤ Tpad ≤ Topt, Correction Function 1: fμ(T) = 0.6 + 0.0025 × (Tpad - Tlow); Temperature Range 2: Topt < Tpad ≤ Thigh, Correction Function 2: fμ(T) = 1.0 - 0.001 × (Tpad - Topt); Temperature Range 3: Tpad(k) > Thigh, Correction Function 3: fμ(T) = max(fmin, 1.0 - 0.005 × (Tpad - Thigh)). Among them, Tpad represents the brake pad temperature, Tlow represents a lower temperature value, Thigh represents a higher temperature value, and Topt represents a temperature value between Tlow and Thigh. Temperature Range 1 can be the rising section of the correction parameter, indicating that within Temperature Range 1, if the brake pad temperature Tpad is higher, the temperature correction parameter fμ is larger; similarly, in Temperature Range 2, if the brake pad temperature Tpad is higher, the temperature correction parameter fμ is smaller; in Temperature Range 3, the correction function indicates that if the brake pad temperature Tpad is higher, the temperature correction parameter fμ is smaller but not less than fμ(min).

[0085] The above temperature range and correction function are only examples, and different temperature ranges divided by different specific temperature values can be set as needed, as well as different correction functions to calculate the temperature correction parameter.

[0086] Implementing the embodiments of the present application, in the first mapping relationship between the pre-constructed brake pad temperature and the temperature correction parameter, determine the temperature correction parameter, or in the second mapping relationship between the pre-constructed brake pad temperature range and the correction function, determine the correction function, and based on the correction function and the predicted brake pad temperature, determine the temperature correction parameter. In the first mapping method, fast and accurate matching can be achieved, improving the efficiency of determining the correction parameter, and it is applicable to scenarios where the correspondence between the brake pad temperature and the parameter is clear. In addition, for the mapping between the temperature range and the correction function, it has strong flexibility, and functions can be set according to the characteristics of different temperature ranges, covering complex and variable brake pad temperature conditions, effectively improving the applicability of the process of determining the correction parameter.

[0087] Optionally, the method further includes: Step A1, when it is determined that the vehicle is in an extreme working condition, determine the currently iterated target time period and the previous time period of the target time period; the extreme working condition includes that the operating frequency of the target system in the vehicle reaches a preset threshold and the sensors of the vehicle drift. Step A2, use the predicted friction coefficient corresponding to the previous time period of the target time period as the friction coefficient for the target time period and subsequent time periods until the vehicle exits the extreme working condition.

[0088] In the embodiments of the present application, various condition judgments can be used to detect whether an extreme working condition occurs. For example, detect whether the operating frequency of the target system in the vehicle reaches a preset threshold, whether the sensors of the vehicle drift, etc. A flag bit can also be set for the extreme working condition, and variables are defined in the global variable area or relevant classes and structures to represent the flag bit of the extreme working condition. When the identification bit is the first preset value, it indicates that the vehicle is in an extreme working condition; when it is the second preset value, it indicates that the vehicle is in a normal working condition.

[0089] When it is detected that these extreme working condition conditions are met, it can be determined that the vehicle is in an extreme working condition, and the flag bit is set to the first preset value (such as extremeflag(k)=1); if the conditions are not met, the flag bit remains the second preset value.

[0090] The target system can be a system inside the vehicle such as an Anti-lock Braking System (ABS) or an Electronic Stability Program (ESP). Vehicle sensor drift refers to the phenomenon that the output changes with time when the input quantity of the sensor remains unchanged. It may be caused by external environmental interference or internal factors of the sensor, resulting in interference signals being mixed in the output signal of the sensor and inaccurate measurement results.

[0091] For example, when the target system runs frequently and the operating frequency reaches a preset threshold, an extreme working condition occurs; or when the sensor is working, the measured value of the sensor fluctuates irregularly and greatly and exceeds the normal error range, it may be that the sensor drifts, that is, an extreme working condition occurs. Different extreme working conditions can be configured according to actual needs, and the types of extreme working conditions are not specifically limited here.

[0092] The working condition flag bit can be read to determine that an extreme working condition has occurred, triggering subsequent operations. Since the predicted friction coefficient can be calculated based on the brake pad temperature in the previous time period for each time period, which is an iterative process, an extreme working condition may occur during the iterative process. Therefore, in a preset number of time periods, the target time period being iterated when the extreme working condition occurs can be determined.

[0093] According to the occurrence time of the extreme working condition, the target time period currently being iterated at that time can be determined, and the previous time period of the target time period and the corresponding predicted friction coefficient can be determined.

[0094] For example, the time period of the vehicle is set to one cycle per second. When the vehicle is running, the operating frequency of the target control system suddenly reaches the preset threshold, and the vehicle enters an extreme working condition. At this time, the iteration reaches the 5th time period, then the 4th time period is the previous time period, and the predicted friction coefficient corresponding to the 4th time period is determined. Then, the predicted friction coefficient of the 4th time period is used as the predicted friction coefficient of the 5th time period and subsequent target time periods, and there is no need to iteratively calculate a new predicted friction coefficient based on relevant data. That is, the update of the predicted friction coefficient μest_corr(k) is paused, and μest_corr(k)=μest_corr(k - 1) is set to maintain the predicted friction coefficient of the previous specific time period.

[0095] Until the vehicle exits the extreme working condition, at this time the flag bit is the second preset value, and the vehicle is in a normal working condition. At this time, for subsequent time periods, a new predicted friction coefficient can be calculated based on relevant data again.

[0096] Implementing the embodiments of the present application, when it is determined that the vehicle is in an extreme working condition, the target time period currently being iterated and the previous time period of the target time period are determined. The extreme working condition includes that the operating frequency of the target system in the vehicle reaches the preset threshold and the sensors of the vehicle drift. The predicted friction coefficient corresponding to the previous time period of the target time period is used as the friction coefficient of the target time period and subsequent time periods until the vehicle exits the extreme working condition, thereby improving the adaptability of the braking system. In an extreme working condition, the update of the predicted friction coefficient can be paused to avoid the interference of the extreme working condition on the determination process of the predicted friction coefficient and improve the accuracy of the predicted friction coefficient.

[0097] Optionally, the method further includes: Step B1, determining a deceleration difference in the case where there is a difference between the actual deceleration and the predicted deceleration of the vehicle; Step B2, updating the preset disc - pad thermal conductivity, the preset caliper - pad thermal conductivity, and the preset convective heat transfer coefficient according to the deceleration difference and a preset gain matrix.

[0098] In the embodiments of the present application, since the vehicle is in continuous operation, for the predicted deceleration in a specific future target time period, when the time reaches this specific time period as the vehicle runs, the actual deceleration of the vehicle can be obtained. There may be a difference between the predicted deceleration and the actual deceleration, and the existence of the difference indicates insufficient prediction accuracy of the deceleration. Then, based on the actual deceleration and the predicted deceleration, the deceleration difference can be determined, and the deceleration difference is used for adjustment and update. The error definition can be: eacc(k) = ax_meas(k)-ax_model(k) where eacc(k) represents the deceleration difference, ax_meas(k) represents the actual deceleration, and ax_model(k) represents the predicted deceleration. Further, ax_meas(k) can represent the actual longitudinal acceleration of the vehicle, which can be collected by the vehicle's accelerometer, and ax_model(k) can be the model-predicted longitudinal acceleration output by the prediction model.

[0099] The gain matrix can be determined based on the recursive least squares method (RLS, Recursive Least Square), Kalman filter, and other algorithms. Taking the Kalman filter algorithm as an example, the state space model of the system can be established first, the state equation and the observation equation can be clarified, and then the relevant parameters can be initialized, including the state estimate value, the error covariance matrix, and the noise covariance matrix. According to the state equation, the current state and the predicted error covariance matrix can be predicted, and then according to the predicted error covariance matrix and the observation noise covariance matrix, the gain matrix can be calculated. Finally, the gain matrix is used to fuse the observed value and the predicted value to update the state estimate value and the error covariance matrix to determine the gain matrix.

[0100] The process of parameter update can be expressed as: θ(k + 1) = θ(k) + K(k)×eacc(k) where θ(k) represents the vector of convective heat transfer coefficient and thermal conductivity [hdisc, hpad, kdp, kpc,...] that has not been updated in the current k time period, θ(k + 1) represents the vector of heat transfer / thermal conductivity parameters in the updated k + 1 time period, K(k) represents the gain matrix in the k time period, and eacc(k) represents the deceleration difference.

[0101] Before each iteration at the k + 1 cycle, the new θ(k + 1), that is, the updated parameters such as the disc thermal conductivity, pad thermal conductivity, and convective heat transfer coefficient, can be passed into the three-body coupled heat model, and then more accurate temperatures of the brake disc, brake pad, and brake caliper can be obtained through iteration.

[0102] In addition, if the working condition flag extremeflag(k) = 1, that is, an extreme working condition occurs, the update of parameters such as the disc thermal conductivity, the caliper thermal conductivity, and the convective heat transfer coefficient can be suspended: let θ(k + 1) = θ(k) to avoid misinterpreting an extreme working condition such as an ABS response as a heat fade error correction. Also, upper and lower limits can be set for parameters such as the thermal conductivity and the heat transfer coefficient according to the physically feasible range to prevent these parameters from exceeding or falling below the normal parameter range.

[0103] Implementing the embodiments of the present application, in the case where there is a difference between the actual deceleration and the predicted deceleration of the vehicle, determining the deceleration difference, and updating the preset disc thermal conductivity, the preset caliper thermal conductivity, and the preset convective heat transfer coefficient according to the deceleration difference and the preset gain matrix, can adapt to the dynamic changes of the braking system based on the gain matrix; based on the acceleration error, without the need for a temperature sensor, the relevant parameters for calculating the temperature of the braking components can be updated in real time, improving the convenience and accuracy of determining the brake pad temperature.

[0104] Optionally, the brake fade parameter includes a brake fade ratio; the method further includes: Step C1, constructing a third mapping relationship between different brake fade ratio intervals and warning methods; Step C2, according to the target ratio interval where the brake fade ratio is located, determining the target warning method corresponding to the target ratio interval in the third mapping relationship, and warning the user based on the target warning method.

[0105] In the embodiments of the present application, the brake fade parameter obtained according to the reference friction coefficient and the predicted friction coefficient and including the brake fade ratio may refer to the ratio between the reference friction coefficient and the predicted friction coefficient. Calculating the brake fade ratio can be expressed as: ratiofade(k + i) = μpred(k + i)÷μest_corr(k) where ratiofade(k + i) represents the brake fade ratio in the k + i time period, μpred(k + i) represents the predicted friction coefficient in the k + i time period, and μest_corr(k) represents the reference friction coefficient in the current time period. If ratiofade(k + i) < 1, the predicted friction coefficient is lower than the current reference friction coefficient, and the smaller ratiofade(k + i) means the more serious the brake fade.

[0106] The brake fade situation can be quantified and classified for warning, helping the driver or the system to obtain warning information before the heat fade occurs. Therefore, a third mapping relationship between different brake fade ratio intervals and warning methods can be constructed in advance.

[0107] For example, the implementation process can be: if ratiofade(k+i)≥0.9, it is normal (green light); else if0.8≤ratiofade<0.9, it is slightly decayed (yellow light); else if 0.6≤ratiofade<0.8, it is severely decayed (orange light); else, it is dangerous (red light). The above process includes ratio intervals such as braking fade ratio greater than or equal to 0.9, braking fade ratio greater than or equal to 0.8 and less than 0.9, as well as text warnings such as normal and mild decay, and light warnings such as green light and yellow light.

[0108] The alarm level can be determined according to the ratio range of the brake decay ratio to trigger the dashboard or central control to display different texts, colors, icons, etc., and when it is red, the driver can be advised to stop the car to cool down or reduce heavy braking. In addition, if the sensor (such as hydraulic sensor, accelerometer) fails, for example, the deceleration ax(k)∈[-10, +10] meters per square second, the hydraulic pressure Pbrake(k)≥0 Pa and other data ranges are set, and if the range is exceeded, it means that an extreme working condition has occurred, indicating that the decay may not be estimated stably, then it will switch to conservative mode and directly warn with the worst case, such as displaying a red light warning.

[0109] By implementing the embodiments of the present application, a mapping relationship between different brake fade ratio intervals and warning methods is constructed, and a target warning method corresponding to the target ratio interval is determined according to the target ratio interval in which the brake fade ratio is located. Then, the user is warned based on the target warning method. This can provide the user with accurate warnings. By constructing a mapping relationship, the warning method can be selected in a targeted manner according to the different intervals of the brake fade ratio, so that the user can clearly understand the degree of brake system decay, thereby improving the accuracy of the brake fade warning.

[0110] Figure 3 is a schematic diagram of the brake fade prediction provided by an embodiment of the present application; S1, output acquisition and preprocessing: obtaining hydraulic pressure, deceleration, vehicle speed; signal filtering synchronization; setting working condition flag; S2, instant friction coefficient identification: theoretical relationship: caliper clamping force equals the product of preset conversion coefficient, hydraulic pressure and friction coefficient; calculate uncorrected initial friction coefficient; temperature correction parameters; extreme working conditions suspend updates; S3, three-body thermal coupling model: brake heat equals the product of caliper clamping force, vehicle speed, and preset coefficient; brake disc, brake disc, and brake caliper are thermally balanced, and the temperature is calculated separately; predict the next N time periods S4, adaptive parameter correction: deceleration error; update heat transfer parameters and thermal conductivity parameters; suspend update in extreme conditions; feed back updated parameters to the next cycle; S5, Comprehensive evaluation and output: Calculate the decay ratio; Determine the ratio interval and correspond to different alarm methods; Output alarms, such as lights and sounds; If a sensor fails, enter the degradation mode warning.

[0111] Figure 4 It is a flowchart of brake fade prediction provided by an embodiment of the present application; Step 401, Sensor input; Step 402, STEP1: Input acquisition and preprocessing (sensor data acquisition and filtering); Step 403, STEP2: Instantaneous friction coefficient identification μest(k) = [ m×ax(k) ] / [ kp×Pbrake_f(k) ]; Step 404, Friction coefficient calculation and correction μest_corr(k) =μest(k)×fμ( Tpad(k) ); Step 405, STEP3: Three-body thermal model + future fade prediction (brake disc / pad / caliper temperature calculation and prediction); Step 406, STEP4: Adaptive parameter correction (update thermal model parameters based on acceleration error); Step 407, Decay rate calculation ratiofade(k+i) = μpred(k+i) / μest_corr(k); Step 408, Comprehensive evaluation and output (decay level evaluation and warning output).

[0112] The solution of the present application corrects the friction coefficient based on the three-body coupling thermal model and introduces an adaptive temperature correction parameter, realizing accurate prediction and grading warning of brake fade under the condition of no measured temperature. By predicting and correcting the friction coefficient, it can effectively cope with the change of heat dissipation environment and material aging; It can automatically degrade to warn in the worst case under extreme working conditions, improving safety. The prediction of future fade trend and grading alarm can provide early prediction for drivers or control systems, reducing the risk brought by the sudden drop of braking efficiency. The solution of the present application not only has the advantage of low cost, but also takes into account real-time performance and accuracy, and can be widely applied to the braking safety management of vehicles.

[0113] Figure 5 It is a device for determining brake fade parameters provided by an embodiment of the present application. The device 50 includes: A reference parameter module 501, configured to determine the brake pad temperature of the current time period for the current time period; A reference friction module 502, configured to determine a reference friction coefficient according to the current deceleration of the vehicle, the hydraulic pressure, and the brake pad temperature of the current time period; A prediction parameter module 503, configured to determine a predicted brake pad temperature for a target time period in a future time period based on a brake pad temperature corresponding to a previous time period of the target time period and a predicted heat absorption amount of the brake pad in the target time period; the predicted heat absorption amount is obtained based on a predicted speed of the vehicle and a preset caliper clamping force; A predicted friction module 504, configured to determine a predicted friction coefficient for the target time period based on a preset deceleration, a preset hydraulic pressure, and the predicted brake pad temperature; A fade determination module 505, configured to determine a brake fade parameter for the target time period according to the reference friction coefficient and the predicted friction coefficient.

[0114] Optionally, the predicted friction module 504 includes: A friction calculation sub-module, configured to determine an actual frictional force according to a preset deceleration and a vehicle mass, and determine a theoretical frictional force according to a preset hydraulic pressure and a preset conversion coefficient; An initial friction sub-module, configured to determine an initial friction coefficient based on the actual frictional force and the theoretical frictional force, and determine a temperature correction parameter corresponding to the predicted brake pad temperature; different brake pad temperatures correspond to different temperature correction parameters; A friction adjustment sub-module, configured to adjust the initial friction coefficient based on the temperature correction parameter to obtain the predicted friction coefficient for the target time period.

[0115] Optionally, the initial friction sub-module includes: A first mapping unit, configured to determine a temperature correction parameter corresponding to the predicted brake pad temperature in a first mapping relationship between a brake pad temperature and a temperature correction parameter constructed in advance; or A second mapping unit, configured to determine a correction function corresponding to a temperature range in which the predicted brake pad temperature is located in a second mapping relationship between a brake pad temperature range and a correction function constructed in advance, and determine a temperature correction parameter corresponding to the predicted brake pad temperature based on the correction function and the predicted brake pad temperature.

[0116] Optionally, the device further includes: An operating condition judgment module, configured to determine a currently iterated target time period and a previous time period of the target time period when it is determined that the vehicle is in an extreme operating condition; the extreme operating condition includes that an operating frequency of a target system in the vehicle reaches a preset threshold, and a sensor of the vehicle drifts; A parameter maintenance module, configured to use the predicted friction coefficient corresponding to the previous time period of the target time period as the friction coefficient for the target time period and subsequent time periods until the vehicle exits the extreme operating condition.

[0117] Optionally, the prediction parameter module 503 includes: A braking heat quantum module, configured to determine predicted braking heat according to a predicted speed and a preset caliper clamping force; An endothermic ratio sub-module, configured to determine the braking absorption heat of the brake pad based on the predicted braking heat and a preset heat absorption ratio; the preset heat absorption ratio represents the proportion of the heat absorbed by the brake pad in the predicted braking heat; A heat conduction sub-module, configured to determine the imported heat, the exported heat, and the dissipated heat of the brake pad according to the temperature differences between the brake pad temperature and the brake disc temperature, the brake caliper temperature, and the ambient temperature in the previous time period of the target time period, as well as a preset pad-disc thermal conductivity, a preset pad-caliper thermal conductivity, and a preset convective heat transfer coefficient; A temperature determination sub-module, configured to determine the predicted brake pad temperature in the target time period according to the brake pad temperature in the previous time period of the target time period, the braking absorption heat, the imported heat, the exported heat, and the dissipated heat.

[0118] Optionally, the device further includes: A deceleration difference module, configured to determine a deceleration difference when there is a difference between the actual deceleration of the vehicle and the preset deceleration; A parameter update module, configured to update the preset pad-disc thermal conductivity, the preset pad-caliper thermal conductivity, and the preset convective heat transfer coefficient according to the deceleration difference and a preset gain matrix.

[0119] Optionally, the brake fade parameter includes a brake fade ratio; the device further includes: A third mapping module, configured to construct a third mapping relationship between different brake fade ratio intervals and warning methods; A fade warning module, configured to determine a target warning method corresponding to the target ratio interval in the third mapping relationship according to the target ratio interval where the brake fade ratio is located, and give a warning to the user based on the target warning method.

[0120] In summary, by implementing the embodiments of the present application, for the current time period, the temperature of the brake pads in the current time period is determined. Based on the current deceleration of the vehicle, the hydraulic pressure, and the temperature of the brake pads in the current time period, the reference friction coefficient is determined. For the target time period in the future time period, based on the temperature of the brake pads corresponding to the previous time period of the target time period and the predicted heat absorption of the brake pads in the target time period, the predicted temperature of the brake pads in the target time period is determined. The predicted heat absorption is obtained based on the predicted speed of the vehicle and the preset caliper clamping force. Based on the preset deceleration, the preset hydraulic pressure, and the predicted temperature of the brake pads, the predicted friction coefficient in the target time period is determined. According to the reference friction coefficient and the predicted friction coefficient, the brake fade parameter in the target time period is determined. Furthermore, the reference friction coefficient can be determined in the current time period to be used as a benchmark for evaluating brake fade, and then the predicted friction coefficient in the target time period in the future time period can be determined. Based on the reference friction coefficient and the predicted friction coefficient, the brake fade parameter corresponding to any target time period in the future time period is determined, avoiding the need to separately set a temperature sensor for the braking system and the cumbersome process of collecting data, and improving the convenience of evaluating brake fade.

[0121] The embodiments of the present application also provide an electronic device, as Figure 6 shown, including a processor 1001, a communication interface 1002, a memory 1003, and a communication bus 1004. Among them, the processor 1001, the communication interface 1002, and the memory 1003 communicate with each other through the communication bus 1004.

[0122] The memory 1003 is used to store computer programs.

[0123] When the processor 1001 is used to execute the program stored in the memory 1003, it implements the steps in the above-mentioned method for determining the brake fade parameter, which will not be elaborated here.

[0124] The communication bus mentioned in the above electronic device may be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. This communication bus can be divided into an address bus, a data bus, a control bus, etc. For the sake of simplicity, only a thick line is shown in the figure, but it does not mean that there is only one bus or one type of bus.

[0125] The communication interface is used for communication between the above electronic device and other devices.

[0126] The memory may include a Random Access Memory (RAM), or may also include a non-volatile memory, such as at least one disk memory. Optionally, the memory may also be at least one storage device located away from the aforementioned processor.

[0127] The aforementioned processor may be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), etc.; it may also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0128] In another embodiment provided by the present application, a readable storage medium is also provided, on which a computer program is stored, and when the program is executed by a processor, the braking decay parameter determination method described in the above embodiment is implemented.

[0129] In the above embodiment, it can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions described in the embodiments of the present application are generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions may be stored in a readable storage medium, or transmitted from one readable storage medium to another readable storage medium. For example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center by wire (such as coaxial cable, optical fiber, Digital Subscriber Line (DSL)) or wirelessly (such as infrared, wireless, microwave, etc.). The readable storage medium may be any available medium that can be accessed by a computer, or a data storage device such as a server, data center, etc. that includes one or more integrated available media. The available medium may be a magnetic medium (for example, a floppy disk, a hard disk, a magnetic tape), an optical medium (for example, a DVD), or a semiconductor medium (for example, a Solid State Disk (SSD)).

[0130] It should be noted that in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

[0131] Each embodiment in this specification is described in a related manner. For the same and similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. For the embodiments of the apparatus, electronic device, readable storage medium and computer program product containing instructions, since they are basically similar to the method embodiments, the description is relatively simple, and reference can be made to the relevant parts of the method embodiments for the relevant content.

[0132] The above description is only a preferred embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application is included in the protection scope of the present application.

Claims

1. A method for determining a brake fade parameter, characterized in that The method includes: For the current time period, determining the brake pad temperature of the current time period; Based on the current deceleration of the vehicle, the hydraulic pressure, and the brake pad temperature of the current time period, determining a reference friction coefficient; For a target time period in a future time period, based on the brake pad temperature corresponding to the previous time period of the target time period and the predicted heat absorption of the brake pad in the target time period, determining the predicted brake pad temperature of the target time period; the predicted heat absorption is obtained based on the predicted speed of the vehicle and a preset caliper clamping force; Based on a preset deceleration, a preset hydraulic pressure, and the predicted brake pad temperature, determining the predicted friction coefficient of the target time period; Based on the reference friction coefficient and the predicted friction coefficient, determining the brake fade parameter of the target time period.

2. The method according to claim 1, characterized in that, The step of determining the predicted friction coefficient of the target time period based on a preset deceleration, a preset hydraulic pressure, and the predicted brake pad temperature includes: Based on the preset deceleration and the vehicle mass, determining the actual frictional force, and based on the preset hydraulic pressure and a preset conversion coefficient, determining the theoretical frictional force; Based on the actual frictional force and the theoretical frictional force, determining an initial friction coefficient, and determining a temperature correction parameter corresponding to the predicted brake pad temperature; different brake pad temperatures correspond to different temperature correction parameters; Adjusting the initial friction coefficient based on the temperature correction parameter to obtain the predicted friction coefficient of the target time period.

3. The method according to claim 2, wherein The step of determining the temperature correction parameter corresponding to the predicted brake pad temperature includes: In a first mapping relationship between the brake pad temperature and the temperature correction parameter constructed in advance, determining the temperature correction parameter corresponding to the predicted brake pad temperature; or In a second mapping relationship between a brake pad temperature range and a correction function constructed in advance, determining the correction function corresponding to the temperature range in which the predicted brake pad temperature is located, and based on the correction function and the predicted brake pad temperature, determining the temperature correction parameter corresponding to the predicted brake pad temperature.

4. The method according to claim 1, characterized in that, The method further includes: When it is determined that the vehicle is in an extreme working condition, determining the target time period that is currently being iterated, and the previous time period of the target time period; the extreme working condition includes that the operating frequency of a target system in the vehicle reaches a preset threshold, and the sensors of the vehicle drift; Using the predicted friction coefficient corresponding to the previous time period of the target time period as the friction coefficient of the target time period and subsequent time periods until the vehicle exits the extreme working condition.

5. The method according to claim 1, wherein The step of determining the predicted brake pad temperature of the target time period based on the brake pad temperature corresponding to the previous time period of the target time period and the predicted heat absorption of the brake pad in the target time period includes: Based on the predicted speed and the preset caliper clamping force, determining the predicted braking heat; Based on the predicted braking heat and a preset heat absorption ratio, determining the braking heat absorption of the brake pad; the preset heat absorption ratio represents the proportion of the heat absorbed by the brake pad in the predicted braking heat; Determine the heat input, heat output, and heat dissipation of the brake pad based on the temperature differences between the brake pad temperature and the brake disc temperature, brake caliper temperature, and ambient temperature in the previous time period of the target time period, as well as the preset pad-disc thermal conductivity, preset pad-caliper thermal conductivity, and preset convective heat transfer coefficient. Determine the predicted brake pad temperature for the target time period based on the brake pad temperature, the heat absorbed by braking, the heat input, the heat output, and the heat dissipation in the previous time period of the target time period.

6. The method according to claim 5, characterized in that, The method further includes: Determine the deceleration difference when there is a difference between the actual deceleration of the vehicle and the preset deceleration. Update the preset pad-disc thermal conductivity, the preset pad-caliper thermal conductivity, and the preset convective heat transfer coefficient according to the deceleration difference and the preset gain matrix.

7. The method according to claim 1, characterized in that, The brake fade parameter includes a brake fade ratio; the method further includes: Construct a third mapping relationship between different brake fade ratio intervals and warning methods. Based on the target ratio interval in which the brake fade ratio is located, determine the target warning method corresponding to the target ratio interval in the third mapping relationship, and issue a warning to the user based on the target warning method.

8. A device for determining a brake fade parameter, characterized in that, The device includes: A reference parameter module for determining the brake pad temperature of the current time period for the current time period. A reference friction module for determining the reference friction coefficient according to the current deceleration of the vehicle, the hydraulic pressure, and the brake pad temperature of the current time period. A prediction parameter module for determining the predicted brake pad temperature for the target time period in a future time period based on the brake pad temperature corresponding to the previous time period of the target time period and the predicted heat absorption of the brake pad in the target time period; the predicted heat absorption is obtained based on the predicted speed of the vehicle and the preset caliper clamping force. A prediction friction module for determining the predicted friction coefficient for the target time period based on the preset deceleration, the preset hydraulic pressure, and the predicted brake pad temperature. A fade determination module for determining the brake fade parameter for the target time period according to the reference friction coefficient and the predicted friction coefficient.

9. An electronic device, characterized in that, Includes: A processor, a communication interface, a memory, and a communication bus; wherein, the processor, the communication interface, and the memory complete communication with each other through the communication bus. The memory is used to store a computer program. The processor, when executing the program stored on the memory, implements the steps in the brake fade parameter determination method according to any one of claims 1 to 7.

10. A readable storage medium storing a computer program thereon, characterized in that, When the program is executed by the processor, it implements the steps in the brake fade parameter determination method according to any one of claims 1 to 7.

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