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

Abstract

The present application provides a brake fade parameter determination method, apparatus, device, and readable storage medium, which are applied to the field of vehicle braking technology. The method includes: determining the brake pad temperature for the current time period; determining a baseline friction coefficient based on the vehicle's current deceleration, hydraulic pressure, and the brake pad temperature for the current time period; determining a predicted brake pad temperature 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 a predicted friction coefficient for the target time period based on a preset deceleration, a preset hydraulic pressure, and the predicted brake pad temperature; and determining a brake fade parameter for the target time period based on the baseline friction coefficient and the predicted friction coefficient. The present application can improve the convenience of brake fade prediction.

Description

Technical Field

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

[0002] Brake fade refers to a significant decrease in braking performance after prolonged or intensive use. This occurs when the heat generated during braking raises the temperature of the brake friction material, reducing its friction coefficient and, in turn, affecting the transmission and application of the caliper's clamping force. By assessing brake fade, we can promptly understand changes in brake system performance and identify potential risks in advance.

[0003] In related technologies, temperature sensors are installed in key locations, such as brake pads and discs, to collect temperature data in real time. Because brake fade is closely related to temperature, the degree of brake fade can be determined by monitoring temperature changes and combining empirical thresholds.

[0004] However, the above solution requires that the temperature sensor be placed at a specific location, and the sensor continuously collects data. Braking degradation is evaluated based on the large amount of continuously collected temperature data, which is less convenient. Summary of the Invention

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

[0006] In a first aspect, an embodiment of the present application discloses a method for determining a brake fade parameter, comprising:

[0007] For a current time period, determining a brake pad temperature for the current time period;

[0008] determining a reference friction coefficient based on a current deceleration of the vehicle, a hydraulic pressure, and a brake pad temperature during the current time period;

[0009] determining, for a target time period in a future time period, a predicted brake pad temperature for the target time period based on a brake pad temperature corresponding to a time period immediately preceding the target time period and a predicted amount of heat absorbed by the brake pad during the target time period; the predicted amount of heat absorbed being based on a predicted speed of the vehicle and a preset caliper clamping force;

[0010] determining a predicted friction coefficient for the target time period based on a predetermined deceleration, a predetermined hydraulic pressure, and the predicted brake pad temperature;

[0011] A brake fade parameter of the target time period is determined according to the reference friction coefficient and the predicted friction coefficient.

[0012] 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:

[0013] determining an actual friction force based on a preset deceleration and a vehicle mass, and determining a theoretical friction force based on a preset hydraulic pressure and a preset conversion coefficient;

[0014] determining an initial friction coefficient based on the actual friction force and the theoretical friction force, and determining a temperature correction parameter corresponding to the predicted brake pad temperature; different brake pad temperatures correspond to different temperature correction parameters;

[0015] The initial friction coefficient is adjusted based on the temperature correction parameter to obtain a predicted friction coefficient for the target time period.

[0016] Optionally, the step of determining a temperature correction parameter corresponding to the predicted brake pad temperature includes:

[0017] Determining a temperature correction parameter corresponding to the predicted brake pad temperature in a pre-established first mapping relationship between brake pad temperature and temperature correction parameter; or

[0018] In a pre-constructed second mapping relationship between brake pad temperature intervals and correction functions, a correction function corresponding to the temperature interval in which the predicted brake pad temperature is located is determined, and based on the correction function and the predicted brake pad temperature, a temperature correction parameter corresponding to the predicted brake pad temperature is determined.

[0019] Optionally, the method further includes:

[0020] If it is determined that the vehicle is in an extreme operating condition, determining a target time period currently being iterated and a time period previous to the target time period; the extreme operating condition includes an operating frequency of a target system in the vehicle reaching a preset threshold and a sensor of the vehicle drifting;

[0021] The predicted friction coefficient corresponding to the previous time period of the target time period is used as the friction coefficient for the target time period and subsequent time periods until the vehicle leaves the extreme working condition.

[0022] 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:

[0023] Determining predicted brake heat based on predicted speed and preset caliper clamping force;

[0024] determining the brake absorption heat of the brake pad based on the predicted brake heat and a preset heat absorption ratio; the preset heat absorption ratio represents the proportion of heat absorbed by the brake pad in the predicted brake heat;

[0025] Determining the heat input, heat output, and heat dissipation of the brake pad based on the temperature difference between the brake pad temperature and the brake disc temperature, the brake caliper temperature, and the ambient temperature in the time period before the target time period, as well as a preset disc thermal conductivity, a preset caliper thermal conductivity, and a preset convection heat transfer coefficient;

[0026] The predicted brake pad temperature of the target time period is determined according to the brake pad temperature of the previous time period of the target time period, the brake absorption heat, the imported heat, the exported heat and the heat dissipation.

[0027] Optionally, the method further includes:

[0028] determining a deceleration difference when there is a difference between the actual deceleration of the vehicle and the preset deceleration;

[0029] The preset disc thermal conductivity, the preset clamp thermal conductivity and the preset convection heat transfer coefficient are updated according to the deceleration difference and the preset gain matrix.

[0030] Optionally, the brake fade parameter includes a brake fade ratio; and the method further includes:

[0031] Constructing a third mapping relationship between different brake fade ratio intervals and warning modes;

[0032] According to the target ratio interval in which the brake fade ratio is located, a target warning mode corresponding to the target ratio interval is determined in the third mapping relationship, and a warning is given to the user based on the target warning mode.

[0033] In a second aspect, an embodiment of the present application discloses a device for determining a brake fade parameter, comprising:

[0034] a reference parameter module, configured to determine, for a current time period, a brake pad temperature during the current time period;

[0035] a baseline friction module, configured to determine a baseline friction coefficient based on a current deceleration of the vehicle, a hydraulic pressure, and a brake pad temperature during the current time period;

[0036] a prediction parameter module for determining, for a target time period in a future time period, a predicted brake pad temperature for the target time period based on a brake pad temperature corresponding to a time period immediately preceding the target time period and a predicted amount of heat absorbed by the brake pad during the target time period; the predicted amount of heat absorbed being based on a predicted speed of the vehicle and a preset caliper clamping force;

[0037] a predicted friction module for determining a predicted friction coefficient for the target time period based on a preset deceleration, a preset hydraulic pressure, and the predicted brake pad temperature;

[0038] The fade determination module is configured to determine a brake fade parameter of the target time period according to the baseline friction coefficient and the predicted friction coefficient.

[0039] Optional, predictive friction module, including:

[0040] a friction calculation submodule, for determining an actual friction force based on a preset deceleration and a vehicle mass, and determining a theoretical friction force based on a preset hydraulic pressure and a preset conversion coefficient;

[0041] an initial friction submodule, configured to determine an initial friction coefficient based on the actual friction force and the theoretical friction force, and to determine a temperature correction parameter corresponding to the predicted brake pad temperature; different brake pad temperatures correspond to different temperature correction parameters;

[0042] The friction adjustment submodule is configured to adjust the initial friction coefficient based on the temperature correction parameter to obtain a predicted friction coefficient for the target time period.

[0043] Optional, initial friction submodule, including:

[0044] a first mapping unit, configured to determine a temperature correction parameter corresponding to the predicted brake pad temperature in a pre-established first mapping relationship between the brake pad temperature and the temperature correction parameter; or

[0045] The second mapping unit is used to determine a correction function corresponding to the temperature interval in which the predicted brake pad temperature is located in a second mapping relationship between pre-constructed brake pad temperature intervals and correction functions, and to determine a temperature correction parameter corresponding to the predicted brake pad temperature based on the correction function and the predicted brake pad temperature.

[0046] Optionally, the device further comprises:

[0047] an operating condition determination module, configured to determine a target time period currently being iterated and a time period preceding the target time period if the vehicle is determined to be in an extreme operating condition; the extreme operating condition includes an operating frequency of a target system in the vehicle reaching a preset threshold or a sensor of the vehicle drifting;

[0048] The parameter maintaining module is used to use 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 leaves the extreme working condition.

[0049] Optional, prediction parameter module, including:

[0050] A brake heat submodule is used to determine the predicted brake heat based on the predicted speed and the preset caliper clamping force;

[0051] a heat absorption ratio submodule, configured to determine the amount of heat absorbed by the brake pad based on the predicted amount of brake heat and a preset heat absorption ratio; the preset heat absorption ratio representing a proportion of the predicted amount of brake heat absorbed by the brake pad;

[0052] a heat transfer submodule, configured to determine heat input, heat output, and heat dissipation of the brake pad based on a temperature difference between the brake pad temperature and the brake disc temperature, the brake caliper temperature, and the ambient temperature in a time period preceding the target time period, as well as a preset disc thermal conductivity, a preset caliper thermal conductivity, and a preset convection heat transfer coefficient;

[0053] The temperature determination submodule is used to determine the predicted brake pad temperature of the target time period based on the brake pad temperature of the previous time period of the target time period, the brake absorption heat, the imported heat, the exported heat and the heat dissipation.

[0054] Optionally, the device further comprises:

[0055] 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;

[0056] A parameter updating module is used to update the preset disc thermal conductivity, the preset clamp thermal conductivity and the preset convection heat transfer coefficient according to the deceleration difference and the preset gain matrix.

[0057] Optionally, the brake fade parameter includes a brake fade ratio; and the device further includes:

[0058] a third mapping module, configured to construct a third mapping relationship between different braking fade ratio intervals and warning modes;

[0059] The fade warning module is configured to determine, according to the target ratio interval in which the brake fade ratio is located, a target warning mode corresponding to the target ratio interval in the third mapping relationship, and warn a user based on the target warning mode.

[0060] On the 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 communicate with each other through the communication bus; the memory is used to store computer programs; the processor is used to implement the steps of the above-mentioned brake fade parameter determination method when executing the program stored in the memory.

[0061] In a fourth aspect, an embodiment of the present application further discloses a readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-mentioned method for determining brake fade parameters.

[0062] In an embodiment of the present application, for a current time period, a brake pad temperature is determined for the current time period. A baseline friction coefficient is determined based on the vehicle's current deceleration, hydraulic pressure, and the brake pad temperature for the current time period. For a target time period in a future time period, a predicted brake pad temperature for the target time period is determined based on the brake pad temperature corresponding to the time period immediately preceding 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 vehicle speed and a preset caliper clamping force. A predicted friction coefficient for the target time period is determined based on the preset deceleration, preset hydraulic pressure, and predicted brake pad temperature. A brake fade parameter for the target time period is determined based on the baseline friction coefficient and the predicted friction coefficient. Thus, a baseline friction coefficient can be determined for the current time period as a benchmark for evaluating brake fade. A predicted friction coefficient for a target time period in a future time period is then determined. The brake fade parameter corresponding to any target time period in the future time period is determined based on the baseline friction coefficient and the predicted friction coefficient. This avoids the need for a separate temperature sensor for the brake system and the cumbersome process of collecting data, thereby improving the convenience of evaluating brake fade. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 This is a step diagram of a method for determining brake fade parameters provided by an embodiment of the present application;

[0064] Figure 2 This is a step diagram of another method for determining brake fade parameters provided by an embodiment of the present application;

[0065] Figure 3 This is a diagram of the architecture of brake fade prediction provided by an embodiment of the present application;

[0066] Figure 4 This is a flowchart of brake fade prediction provided by an embodiment of the present application;

[0067] Figure 5 is a block diagram of a brake fade parameter determination device provided by an embodiment of the present application;

[0068] Figure 6 This is a block diagram of an electronic device provided in an embodiment of the present application.

[0069] Description of reference numerals:

[0070] Reference parameter module 501 , reference friction module 502 , prediction parameter module 503 , prediction friction module 504 , degradation determination module 505 ; processor 1001 , communication interface 1002 , memory 1003 , communication bus 1004 . DETAILED DESCRIPTION

[0071] The following describes exemplary embodiments of the present application in more detail with reference to the accompanying drawings. Although exemplary embodiments of the present application are shown in the accompanying 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. Rather, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0072] 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 comprising:

[0073] Step 101: for a current time period, determine the brake pad temperature of the current time period.

[0074] In the embodiment of the present application, the execution subject of the method can be a device with data processing capabilities, a device in a vehicle such as an on-board terminal, or a server that obtains relevant data and processes it, which is not specifically limited here.

[0075] The current time period may be calculated from when the vehicle resumes driving, from when data such as the vehicle's current speed and caliper clamping force are first acquired, from the first braking operation, or after several braking operations, without specific limitation. The length of each time period may be several milliseconds, such as 500 milliseconds, or a smaller time period, without specific limitation.

[0076] A vehicle's braking system consists of at least brake pads, brake discs, and brake calipers. When the driver depresses the brake pedal, hydraulic pressure is transmitted through the brake lines to the brake calipers. The caliper piston pushes the brake pads, pressing them tightly against the brake discs attached to the wheels. Friction between the pads and discs converts the vehicle's kinetic energy into heat, slowing the vehicle down until it stops.

[0077] If the vehicle has been stationary for an extended period and the current time period falls within a relatively short period after the vehicle has resumed operation, for example, within 30 seconds or 1 minute after the vehicle has resumed operation, the brake pad temperature for the current time period may be the ambient temperature, which can be obtained by a temperature sensor in the vehicle. If the vehicle has been stationary for a relatively short period of time, for example, only 10 or 20 seconds after the current time period, the brake pad temperature recorded by the vehicle when it was stationary may also be used, which can be obtained by a temperature sensor located near the brake pad. There is no specific limitation on how to determine the brake pad temperature for the current time period.

[0078] Step 102 : determining a reference friction coefficient based on the current deceleration of the vehicle, the hydraulic pressure, and the brake pad temperature during the current time period.

[0079] When a vehicle brakes, the caliper's clamping force, generated by the friction between the brake pad and disc, decelerates the vehicle. This force is related to the coefficient of friction and the normal pressure. For disc brake systems, the normal pressure is generated by the hydraulic pressure in the caliper. The coefficient of friction measures the conversion between the caliper's clamping force and the hydraulic pressure. At the same hydraulic pressure, the higher the coefficient of friction, the greater the caliper's clamping force and the better the braking effect.

[0080] Hydraulic pressure can be obtained in a variety of ways, such as through a pressure sensor. The pressure sensor can be installed in the hydraulic pipeline of the brake system, generally near the brake caliper or master cylinder. Based on the working principles of piezoresistive effect and piezoelectric effect, when hydraulic pressure acts on the sensor, the sensor converts the pressure signal into a hydraulic signal, which 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 obtain the hydraulic pressure information of the brake system by communicating with the vehicle's electronic control unit (ECU, Electronic Control Unit). There is no specific restriction on how to obtain the hydraulic pressure.

[0081] Because the material properties of components such as brake pads in a braking system can change at different temperatures, and brake pads and other components are typically composed of different materials, rising temperatures can cause changes in the physical and chemical properties of these materials. For example, mechanical properties such as hardness and elastic modulus of a material can change at high temperatures, which in turn affects the friction coefficient. Therefore, the friction coefficient calculated from the caliper clamping force and hydraulic pressure can be corrected based on the brake pad temperature corresponding to the current time period. This can be done by inputting the friction coefficient and brake pad temperature based on a preset calculation formula or model to obtain the processed friction coefficient, without any specific restrictions on the calculation process.

[0082] Step 103, for a target time period in the future time period, determine a predicted brake pad temperature for the target time period based on the brake pad temperature corresponding to the time period immediately preceding the target time period and the predicted heat absorption of the brake pad during the target time period; the predicted heat absorption is based on the predicted speed of the vehicle and a preset caliper clamping force.

[0083] It is understood that the current time period in step 101 is the currently occurring time period, and the subsequent second, third, and other time periods are target time periods in the future. 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.

[0084] Since the goal is to predict future brake fade, the subsequent time period can be a target time period in the future that has not yet 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.

[0085] Based on the vehicle's speed and deceleration, the predicted speed for the vehicle in the subsequent target time period can be determined. For example, if the vehicle's speed in the current time period is 20 meters per second and its deceleration is 2 meters per second squared, the speed in the second time period could be 18 meters per second. Alternatively, a speed prediction model can be constructed, inputting relevant data such as the current speed and deceleration to obtain the predicted speed. The method for predicting vehicle speed is not detailed here.

[0086] The preset caliper clamping force can be the maximum caliper clamping force the braking system can provide, allowing for worst-case brake fade assessment. The preset caliper clamping force can be calculated based on the maximum caliper clamping force achieved during the vehicle's historical operation. The caliper clamping force can be calculated using various methods, such as 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 vehicle acceleration during braking. Acceleration can be calculated based on the change in vehicle speed before and after braking and the braking time, and the caliper clamping force can be determined based on the vehicle mass and deceleration. Alternatively, the work done by the caliper clamping force is equal to the change in vehicle kinetic energy. The change in vehicle kinetic energy can be calculated based on the vehicle speed at the beginning and end of a period. The caliper clamping force can then be determined based on the change in kinetic energy and the braking distance. Alternatively, the caliper clamping force can be calculated using the conversion coefficient between hydraulic pressure and caliper clamping force. The caliper clamping force can be determined based on the known hydraulic pressure and conversion coefficient. If the vehicle uses an electronic mechanical brake system (EMB), the caliper clamping force output by the EMB can be directly read. There are no specific restrictions on how to calculate the caliper clamping force.

[0087] The brake power is calculated based on the predicted speed and the preset caliper clamping force to predict the predicted brake heat generated by the brake system, which can be expressed as the following formula:

[0088] Qin(k)=ηh×[Fbrake_total(k)×Vvehicle(k)×Δt]

[0089] Where Qin(k) represents the predicted brake heat generated by braking in cycle k, ηh is the conversion coefficient between power and heat, ηh∈(0,1), which can be set to 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.

[0090] After determining the predicted brake heat generated by the braking system, the brake system includes components such as brake pads, brake discs, and brake calipers. Each component can absorb different amounts of brake heat. Consequently, not all of the brake heat generated during braking is absorbed by the brake pads. Different components in the braking system absorb different amounts of brake heat, meaning that different components absorb different amounts of brake heat. This heat absorption ratio can be determined experimentally or by querying existing data. Based on this heat absorption ratio, the predicted amount of brake heat absorbed by the brake pads can be determined. To reduce data processing complexity, the brake heat absorbed by the brake pads can be used as the predicted amount of heat absorbed during the target time period.

[0091] 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 pad can be calculated based on the mass, specific heat capacity and heat absorption of the brake pad, which can be expressed by the following formula:

[0092]

[0093] In the above formula, ΔT represents the temperature change, Q represents the amount of heat absorbed, m represents the mass of the brake pad, and c represents the specific heat capacity of the brake pad.

[0094] The above formula can be used to calculate the brake pad temperature change, for example, a certain degree Celsius increase, based on the amount of heat absorbed by the brake pad during the target time period, its specific heat capacity, and its mass. Since the initial temperature of the target time period can be the brake pad temperature corresponding to the previous time period, the brake pad temperature for the target time period can be calculated based on the brake pad temperature and temperature change during the previous time period.

[0095] For example, if the brake pad temperature corresponding to the previous time period is 25 degrees Celsius, the heat absorption is 10,000 joules (J), the brake pad mass is 1 kilogram (kg), and the specific heat capacity is 1000 J / kg, then the brake pad temperature in the target time period is 35 degrees Celsius.

[0096] If the target time period currently to be calculated 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. Furthermore, if the target time period currently to be calculated 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. Similarly, the predicted brake pad temperature for each subsequent target time period can be obtained through continuous iteration. The predicted brake pad temperature for each target time period is determined based on the brake pad temperature of the previous time period and the predicted amount of heat absorption.

[0097] Step 104 : determining a predicted friction coefficient for the target time period based on a preset deceleration, a preset hydraulic pressure, and the predicted brake pad temperature.

[0098] Because each predicted brake pad temperature is derived based on the brake pad temperature from the previous time period, the brake pad temperature is continuously iterated. After iterating through multiple time periods, the predicted brake pad temperature for a specific point in the future can be obtained. Similarly, the predicted friction coefficient can be calculated based on the preset deceleration, preset hydraulic pressure, and predicted brake pad temperature. The detailed calculation process is not detailed here.

[0099] The preset deceleration may be the maximum deceleration that the vehicle can achieve, which may be determined through vehicle testing or from historical deceleration data of the vehicle. The preset hydraulic pressure may also be the maximum hydraulic pressure that the vehicle can provide.

[0100] Step 105 : Determine a brake fade parameter for the target time period based on the baseline friction coefficient and the predicted friction coefficient.

[0101] The baseline friction coefficient is a friction coefficient value used as a reference standard. The baseline friction coefficient is the friction coefficient between the brake pad and the brake disc under ideal conditions, or when the brake system is new and has not been used for a long time. The baseline friction coefficient value is relatively stable and can be determined through experiments or according to the design specifications of the brake system.

[0102] The predicted friction coefficient is an estimated value of the friction coefficient between the brake pad and the brake disc in a target time period in the future. As the number of braking times increases and the temperature of the brake pad rises, the friction coefficient will change. The predicted friction coefficient can reflect the friction coefficient value after the change in the future.

[0103] The braking fade situation can be determined based on the baseline friction coefficient and the predicted friction coefficient. The difference between the predicted friction coefficient and the baseline friction coefficient can be calculated. If the predicted friction coefficient is less than the baseline friction coefficient, it means that braking fade may occur. The larger the difference, the more obvious the fade. The ratio of the two can also be calculated as the braking fade parameter. The changing trend of the braking fade parameter over time can be observed to determine the changing situation of braking fade.

[0104] For example, according to the current time period, the baseline 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. In the tenth time period, the predicted friction coefficient becomes 0.36, the difference becomes 0.04, and the ratio becomes 0.9.

[0105] It is understood that, based solely on the predicted friction coefficients corresponding to a predetermined number of time periods, the brake fade at a specific future point in time corresponding to that time period can be determined. However, by continuously analyzing the predicted friction coefficients corresponding to each of the predetermined number of time periods, the evolution of brake fade can be understood.

[0106] In summary, in implementing the embodiments of the present application, for the current time period, the brake pad temperature for the current time period is determined based on the ambient temperature and the amount of heat absorbed by the brake pad during the current time period. The amount of heat absorbed is obtained based on the current speed of the vehicle and the caliper clamping force. The reference friction coefficient is determined based on the current deceleration of the vehicle, the hydraulic pressure, and the brake pad temperature for the current time period. For a target time period in a future time period, the predicted brake pad temperature for the target time period is determined based on the brake pad temperature corresponding to the previous time period of the target time period and the predicted amount of heat absorbed by the brake pad during the target time period. The predicted amount of heat absorbed is based on the predicted speed of the vehicle and a preset caliper clamping force. It is obtained that, based on the preset deceleration, the preset hydraulic pressure and the predicted brake pad temperature, the predicted friction coefficient of the target time period is determined, and the brake fade parameter of the target time period is determined according to the baseline friction coefficient and the predicted friction coefficient. The baseline friction coefficient can be determined in the current time period, which is used as a benchmark for evaluating brake fade, and then the predicted friction coefficient of the target time period in the future time period is determined. The brake fade parameter corresponding to any target time period in the future time period is determined based on the baseline friction coefficient and the predicted friction coefficient, which avoids the need to set up a separate temperature sensor for the braking system and the tedious process of collecting data, thereby improving the convenience of evaluating brake fade.

[0107] refer to Figure 2 , which shows a flowchart of the steps of a method for determining a brake fade parameter provided by an embodiment of the present application, the method comprising:

[0108] Step 201, for a current time period, determining the brake pad temperature of the current time period;

[0109] Step 202 , determining a reference friction coefficient based on the vehicle's current deceleration, hydraulic pressure, and brake pad temperature during the current time period;

[0110] Step 203 , for a target time period in the future time period, determining a predicted brake pad temperature for the target time period based on the brake pad temperature corresponding to the time period immediately preceding the target time period and a predicted amount of heat absorbed by the brake pad during the target time period; the predicted amount of heat absorbed is based on a predicted vehicle speed and a preset caliper clamping force;

[0111] Step 204 , determining a predicted friction coefficient for the target time period based on a preset deceleration, a preset hydraulic pressure, and the predicted brake pad temperature;

[0112] Step 205 : Determine a brake fade parameter for the target time period based on the baseline friction coefficient and the predicted friction coefficient.

[0113] The above steps 201 to 205 can refer to the above Figure 1 The contents of the embodiments will not be repeated here.

[0114] Optionally, the 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:

[0115] Sub-step 2031 , determining predicted brake heat based on the predicted speed and the preset caliper clamping force;

[0116] Sub-step 2032, determining the brake absorption heat of the brake pad based on the predicted brake heat and a preset heat absorption ratio; the preset heat absorption ratio represents the proportion of the brake conversion heat absorbed by the brake pad;

[0117] Sub-step 2033, determining the heat input, heat output, and heat dissipation of the brake pad based on the temperature difference between the brake pad temperature and the brake disc temperature, the brake caliper temperature, and the ambient temperature in the time period before the target time period, as well as a preset disc thermal conductivity, a preset caliper thermal conductivity, and a preset convection heat transfer coefficient;

[0118] Sub-step 2034, determining the predicted brake pad temperature of the target time period based on the brake pad temperature of the previous time period of the target time period, the brake absorption heat, the imported heat, the exported heat and the heat dissipation.

[0119] In the embodiment of the present application, the predicted brake heat can be calculated based on the predicted vehicle speed and the preset caliper clamping force to be applied. Since the interaction between vehicle speed and caliper clamping force will result in energy conversion, this energy is mainly generated in the form of heat.

[0120] Not all the heat generated during braking is absorbed by the brake pads. Different components in the braking system absorb different amounts of brake heat, meaning they absorb different amounts of brake heat at different rates. A preset heat absorption rate can be determined through experimentation or by consulting existing data. Based on this preset heat absorption rate, the predicted brake heat is calculated using this rate to determine the brake heat absorbed by the brake pads.

[0121] However, there is a temperature difference between the brake pad 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 pad is not directly equal to the heat absorbed by the brake pad in the target time period.

[0122] Therefore, to further improve the accuracy of the predicted heat absorption during the target time period, the brake pad's heat input (heat transferred from other components to the pad), heat output (heat transferred from the pad to other components), and heat dissipation (heat lost to the environment) can be calculated based on the brake heat absorbed by the brake pad as the predicted heat absorption during the target time period. Ultimately, the brake pad's heat absorption during the target time period is comprehensively determined based on the brake heat absorbed, heat input, heat output, and heat dissipation.

[0123] Among them, the preset disc thermal conductivity coefficient is a parameter that represents the heat transfer capacity between the brake pad and the brake disc; the preset caliper thermal conductivity coefficient is a parameter that represents the heat transfer capacity between the brake pad and the brake caliper; and the preset convection heat transfer coefficient is a parameter that represents the heat transfer capacity between the brake pad and the surrounding environment.

[0124] Since the brake disc temperature can be greater than the brake pad temperature, based on the brake pad temperature and the brake disc temperature, it can be determined that the brake disc imports heat into the brake pad temperature, which corresponds to the imported heat of the brake pad; since the brake pad temperature can be greater than the brake caliper temperature, based on the brake pad temperature and the brake caliper temperature, it can be concluded that the brake pad exports heat to the brake caliper, which corresponds to the exported heat of the brake pad; in addition, the brake pad will dissipate heat to the surrounding environment, so the heat dissipation can be obtained based on the temperature difference between the brake pad temperature and the ambient temperature.

[0125] The sum of the heat imported, heat exported and heat dissipated is the heat absorbed within the time period. Then, based on the brake pad temperature, brake absorption heat, heat imported, heat exported and heat dissipated in the previous time period, as well as the specific heat capacity of the brake pad, the brake pad temperature in the target time period can be determined.

[0126] For the brake pads, brake discs, and brake calipers in the brake system, the following thermal balance equation can be used:

[0127] mdisc×cdisc×[Tdisc(k+1)-Tdisc(k)]÷Δt=a×Qin(k)-Qout_disc(k)-Qx_disc_to_pad(k)

[0128] Where 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 brake 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 transferred from the brake disc to the brake pad.

[0129] 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)

[0130] The right side of the equation represents the predicted heat absorption of the brake pad during the target time period: (1-a)×Qin(k) is the brake heat absorbed by the brake pad, plus the heat transferred from the brake disc to the brake pad (Qx_disc_to_pad(k)), minus the heat transferred from the brake pad to the brake caliper (Qx_pad_to_caliper(k)), minus the heat dissipated by the brake pad (Qout_pad(k)); where mpad is the mass of the brake pad, cpad is the specific heat capacity of the brake pad, Tpad(k+1) is the temperature of the brake pad in time period k+1, Tpad(k) is the temperature of the brake pad in time period k, Δt is the duration of the time period, (1-α) is the preset heat absorption ratio of the brake pad, and Qin(k) is the brake heat generated in time period k.

[0131] mcaliper×ccaliper×[Tcaliper(k+1)-Tcaliper(k)]÷Δt=Qx_pad_to_caliper(k)-Qout_caliper(k)

[0132] Where 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.

[0133] Based on the Euler forward method, the temperature of the brake disc in the k+1 time period can be expressed as:

[0134] Tdisc(k+1)=Tdisc(k)+Δt÷(mdisc×cdisc)×[a×Qin(k)-hdisc×Adisc×(Tdisc(k)-Tair(k))-kdp×(Tdisc(k)-Tpad(k))];

[0135] The temperature of the brake pad in the k+1 time period can be expressed as:

[0136] 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))];

[0137] The temperature of the brake caliper in the k+1 time period can be expressed as:

[0138] Tcaliper(k+1)=Tcaliper(k)+Δt÷(mcaliper×ccaliper)×[kpc×(Tpad(k)-Tcaliper(k))-hcal×Acal×(Tcaliper(k)-Tair(k))]

[0139] Among them, 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 conductivity coefficients 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 to a constant in the simulation and directly used for iteration.

[0140] The unit of the convective heat transfer coefficient is W / (m²×K), which indicates the strength of the convective heat transfer between the fluid and the solid surface. W represents the power unit (Watt), which is the rate of heat transfer (Joules per second). m² represents the area unit (square meter), which refers to the surface area of ​​heat transfer. K represents the thermodynamic temperature unit (Kelvin), which is used to measure temperature differences. The unit of thermal conductivity is W / (m×K), which indicates the material's ability to conduct heat. W represents the power unit (Watt). m represents the length unit (meter), which refers to the length of the heat conduction path. K represents the thermodynamic temperature unit (Kelvin). Based on the above formula, the temperatures of the brake disc, brake pad, and brake caliper can be continuously updated, and the predicted friction coefficient corresponding to each target time period in the future can be continuously calculated.

[0141] In an embodiment of the present application, the predicted brake heat is determined based on the predicted speed and the preset caliper clamping force, and the brake absorption heat of the brake pad is determined based on the predicted brake heat and the preset heat absorption ratio. The imported heat, exported heat and heat dissipation of the brake pad are determined based on the temperature difference between the brake pad temperature in the previous time period and the brake disc temperature, the brake caliper temperature and the ambient temperature, as well as the preset disc thermal conductivity, the preset caliper thermal conductivity and the preset convection heat transfer coefficient. The brake pad temperature in the target time period is determined based on the brake pad temperature, brake absorption heat, imported heat, exported heat and heat dissipation in the previous time period. A three-body coupled thermal model (brake disc, brake pad and brake caliper) can be established, while considering the thermal coupling and dynamic heat dissipation process among the brake disc, brake pad and brake caliper. This can more accurately predict the temperature change of the brake pad, thereby improving the accuracy of determining the brake pad temperature.

[0142] Optionally, the step 204 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:

[0143] Sub-step 2041 , determining the actual friction force according to the preset deceleration and the vehicle mass, and determining the theoretical friction force according to the preset hydraulic pressure and the preset conversion coefficient;

[0144] Sub-step 2042: determining an initial friction coefficient based on the actual friction force and the theoretical friction force, and determining a temperature correction parameter corresponding to the predicted brake pad temperature; different brake pad temperatures correspond to different temperature correction parameters;

[0145] Sub-step 2043: adjusting the initial friction coefficient based on the temperature correction parameter to obtain a predicted friction coefficient for the target time period.

[0146] In the embodiment of the present application, the actual friction force that produces the actual braking effect can be obtained based on the preset deceleration and the vehicle mass. The calculation process can be expressed as:

[0147] Fbrake_total(k)=m×ax_f(k)

[0148] Among them, Fbrake_total(k) is the actual friction force, that is, the caliper clamping force, m is the vehicle mass, and ax_f(k) is the preset deceleration.

[0149] The preset conversion coefficient measures the efficiency of converting hydraulic pressure into friction. It indicates how much friction is converted per unit of preset hydraulic pressure. The preset conversion coefficient depends on factors such as the brake system's structure, materials, and design principles. The preset conversion coefficient can be determined through experimentation and analysis. For example, for a specific brake system, the preset conversion coefficient might be 0.6, 0.7, and so on.

[0150] The theoretical friction force, which should be generated theoretically, can be determined based on the hydraulic pressure provided by the vehicle and the preset conversion coefficient. The theoretical friction force is the friction force that the braking system can generate under ideal conditions, such as initial braking. The calculation process can be expressed as:

[0151] Fbrake_total(k) = kp×Pbrake_f(k)×R

[0152] Where Fbrake_total(k) represents the theoretical friction force, Pbrake_f(k) is the hydraulic pressure, kp is the preset conversion factor, and R is the distribution coefficient. If the front and rear wheels are combined and equivalent, the distribution coefficient can be 1. The distribution coefficient and preset conversion coefficient can also be combined into a single parameter.

[0153] Based on the actual friction force and the theoretical friction force, the initial friction coefficient is determined. The actual friction force can be divided by the theoretical friction force, or the initial friction coefficient is obtained based on the difference between the actual friction force and the theoretical friction force. The initial friction coefficient reflects the relationship between the actual friction force and the theoretical friction force.

[0154] When the calculation process is the actual friction force divided by the theoretical friction force, it can be expressed as:

[0155] μest(k) = [ m×ax_f(k) ]÷[ kp×Pbrake_f(k) ]

[0156] Where μest(k) represents the initial friction coefficient for time period k, m is the vehicle mass, ax_f(k) is the deceleration, kp is the conversion coefficient between hydraulic pressure and caliper clamping force, and Pbrake_f(k) is the hydraulic pressure. As long as the vehicle is braking, μest(k) > 0. However, it is necessary to determine whether ax_f(k) ≈ 0 or Pbrake_f(k) ≈ 0 to avoid calculation errors.

[0157] In addition, additional filtering can be performed on the deceleration signal and the hydraulic pressure signal, which can be expressed as:

[0158] Pbrake_f(k) = LPF{Pbrake(k)}

[0159] ax_f(k) = LPF{ax(k)}

[0160] Where Pbrake_f(k) is the hydraulic pressure after filtering, LPF (Low-Pass Filter) represents low-pass filtering, and Pbrake(k) is the hydraulic pressure before filtering. ax_f(k) is the deceleration after filtering, and ax(k) is the deceleration before filtering.

[0161] Each predicted brake pad temperature may correspond to a different temperature correction parameter. The predicted brake pad temperature and the temperature correction parameter may be positively correlated, and the greater the predicted brake pad temperature, the greater the temperature correction parameter.

[0162] Based on the predicted brake pad temperature, the corresponding temperature correction parameter is determined. The temperature correction parameter can be less than 1. The initial friction coefficient can be corrected by multiplying the initial friction coefficient and the temperature correction parameter or performing other more complex operations to obtain the predicted friction coefficient. The correction of the initial friction coefficient based on the temperature correction parameter can be expressed as:

[0163] μest_corr(k) =μest(k)×fμ( Tpad(k) )

[0164] Where μest_corr(k) is the predicted friction coefficient after correction for time period k, μest(k) is the initial friction coefficient for time period k, and fμ( Tpad(k) ) represents the temperature correction parameter corresponding to the brake pad temperature Tpad(k) for time period k.

[0165] In implementing the embodiments of the present application, the actual friction force is determined based on the preset deceleration and vehicle mass, and the theoretical friction force is determined based on the preset hydraulic pressure and the preset conversion coefficient. The initial friction coefficient is determined based on the actual friction force and the theoretical friction force. The initial friction coefficient is then adjusted based on the temperature correction parameter corresponding to the predicted brake pad temperature to obtain the predicted friction coefficient for the target time period. The performance of the braking system in the target time period can be accurately determined. 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.

[0166] Optionally, the sub-step 2043 of determining the temperature correction parameter corresponding to the predicted brake pad temperature includes:

[0167] Sub-step 20431, determining a temperature correction parameter corresponding to the predicted brake pad temperature in a pre-established first mapping relationship between brake pad temperature and temperature correction parameter; or

[0168] 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.

[0169] In the embodiments of the present application, the temperature correction parameters corresponding to different brake pad temperatures can be determined based on bench tests or querying manufacturing data, and then the first mapping relationship between the brake pad temperature and the temperature correction parameter can be 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, where the key is the brake pad temperature and the value is the corresponding temperature correction parameter. When the predicted brake pad temperature is known, the corresponding temperature correction parameter can be obtained from the dictionary.

[0170] Similarly, it is also possible to pre-construct the second mapping relationship between the brake pad temperature range and the correction function based on bench tests or querying manufacturing data. In this second mapping relationship, there are different brake pad temperature ranges, and each temperature range corresponds to its own correction function. Each correction function is used to calculate the corresponding temperature correction parameter according to the specific brake pad temperature.

[0171] 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)). Here, 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 section where the correction parameter increases, 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).

[0172] The above temperature range and correction function are only examples. Different temperature ranges divided by different specific temperature values can be set as needed, and different correction functions can be set to calculate the temperature correction parameter.

[0173] In implementing the embodiments of the present application, the temperature correction parameter is determined within a first mapping relationship between a pre-established brake pad temperature and a temperature correction parameter, or the correction function is determined within a second mapping relationship between a pre-established brake pad temperature range and a correction function. The temperature correction parameter is then determined based on the correction function and the predicted brake pad temperature. The first mapping method allows for fast and accurate matching, improving the efficiency of determining the correction parameter and is suitable for scenarios where the relationship between brake pad temperature and parameters is clearly defined. Furthermore, the mapping between temperature ranges and correction functions offers significant flexibility, enabling the configuration of functions tailored to the characteristics of different temperature ranges, covering complex and variable brake pad temperature conditions and effectively enhancing the applicability of the correction parameter determination process.

[0174] Optionally, the method further includes:

[0175] Step A1: determining a target time period currently being iterated and a time period preceding the target time period when the vehicle is determined to be in an extreme operating condition; the extreme operating condition includes an operating frequency of a target system in the vehicle reaching a preset threshold and a sensor of the vehicle drifting;

[0176] Step A2: Using 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 escapes from the extreme working condition.

[0177] In embodiments of the present application, various conditions can be used to detect whether an extreme operating condition has occurred. For example, this can include detecting whether the operating frequency of a target system within the vehicle has reached a preset threshold, or whether the vehicle's sensors are drifting. A flag can also be set for extreme operating conditions. A variable can be defined in a global variable area or in a related class or structure to indicate the flag for an extreme operating condition. A first preset value indicates that the vehicle is in an extreme operating condition, while a second preset value indicates that the vehicle is in a normal operating condition.

[0178] When it is detected that these extreme operating conditions are met, it can be determined that the vehicle is in an extreme operating condition and the flag is set to a first preset value (such as extremeflag(k)=1); if the condition is not met, the flag is kept at a second preset value.

[0179] The target system can be an internal vehicle system such as the Anti-lock Braking System (ABS) or the Electronic Stability Program (ESP). Vehicle sensor drift refers to the phenomenon where the sensor output changes over time while the input remains constant. This can be caused by external environmental interference or internal sensor factors, which can lead to interference signals being mixed into the sensor's output signal, resulting in inaccurate measurement results.

[0180] For example, an extreme operating condition occurs when the target system runs frequently, reaching a preset threshold. Alternatively, if a sensor's measured values ​​fluctuate erratically and significantly, exceeding the normal error range, sensor drift may have occurred, indicating an extreme operating condition. Different extreme operating conditions can be configured based on actual needs, and the types of extreme conditions are not specifically limited here.

[0181] The operating condition flag can be read to confirm the occurrence of an extreme operating condition, triggering subsequent actions. Since the predicted friction coefficient is calculated for each time period based on the brake pad temperature in the previous time period, an iterative process is performed. Extreme operating conditions may occur during the iteration process. Therefore, the target time period in which the extreme operating condition occurs can be determined within a preset number of time periods.

[0182] According to the time when the extreme working condition occurs, 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.

[0183] For example, a vehicle's time cycle is set to one cycle per second. While the vehicle is driving, the operating frequency of the target control system suddenly reaches a preset threshold, and the vehicle enters an extreme operating condition. At this time, it is iterating to the fifth time cycle, and the fourth time cycle is the previous time cycle, and the predicted friction coefficient corresponding to the fourth time cycle is determined. The predicted friction coefficient of the fourth time cycle is then used as the predicted friction coefficient for the fifth time cycle and subsequent target time cycles, without the need to iteratively calculate a new predicted friction coefficient based on relevant data. In other words, the predicted friction coefficient μest_corr(k) is temporarily updated, and μest_corr(k) is set to μest_corr(k-1) to maintain the predicted friction coefficient for the previous specific time cycle.

[0184] Until the vehicle leaves the extreme operating condition, the flag is at the second preset value and the vehicle is in the normal operating condition. At this time, for subsequent time periods, a new predicted friction coefficient can be calculated based on the relevant data.

[0185] In an embodiment of the present application, when it is determined that the vehicle is in an extreme operating condition, the target time period currently being iterated and the previous time period of the target time period are determined. The extreme operating conditions include the operating frequency of the target system in the vehicle reaching a preset threshold and the vehicle's sensor drifting. The predicted friction coefficient corresponding to the previous time period of the target time period is used as the friction coefficient for the target time period and subsequent time periods until the vehicle is out of the extreme operating condition, thereby improving the adaptability of the braking system. Under extreme operating conditions, the update of the predicted friction coefficient can be suspended to avoid extreme operating conditions interfering with the determination process of the predicted friction coefficient, thereby improving the accuracy of the predicted friction coefficient.

[0186] Optionally, the method further includes:

[0187] Step B1, determining a deceleration difference when there is a difference between the actual deceleration and the predicted deceleration of the vehicle;

[0188] Step B2: updating the preset disc thermal conductivity, the preset clamp thermal conductivity, and the preset convection heat transfer coefficient according to the deceleration difference and the preset gain matrix.

[0189] In the embodiment of the present application, since the vehicle is in continuous operation, the predicted deceleration for a specific target time period in the future can be used to obtain the actual deceleration of the vehicle when the time reaches the specific time period as the vehicle runs. There may be a difference between the predicted deceleration and the actual deceleration, and the existence of a difference indicates that the deceleration prediction accuracy is insufficient. Based on the actual deceleration and the predicted deceleration, a deceleration difference can be determined, and the deceleration difference is used for adjustment and updating. The error definition can be:

[0190] eacc(k) = ax_meas(k)-ax_model(k)

[0191] Where eacc(k) represents the deceleration difference, ax_meas(k) represents the actual deceleration, and ax_model(k) represents the predicted deceleration. Furthermore, ax_meas(k) can represent the vehicle's actual longitudinal acceleration, which can be acquired by the vehicle's accelerometer, while ax_model(k) can be the model-predicted longitudinal acceleration output by the prediction model.

[0192] The gain matrix can be determined based on recursive least squares (RLS), Kalman filtering, and other algorithms. Taking the Kalman filtering algorithm as an example, the system's state-space model is first established, clarifying the state equation and observation equation. Then, the relevant parameters, including the state estimate, error covariance matrix, and noise covariance matrix, are initialized. The current state and the prediction error covariance matrix are predicted based on the state equation. The gain matrix is ​​then calculated based on the prediction error covariance matrix and the observation noise covariance matrix. Finally, the gain matrix is ​​used to fuse the observed and predicted values, updating the state estimate and error covariance matrix to determine the gain matrix.

[0193] The process of parameter updating can be expressed as:

[0194] θ(k+1) = θ(k) + K(k)×eacc(k)

[0195] Where θ(k) represents the unupdated convective heat transfer coefficient and thermal conductivity coefficient vector [hdisc, hpad, kdp, kpc,…] for the current k-th time period, θ(k+1) represents the updated heat transfer / conduction parameter vector for the k+1th time period, K(k) represents the gain matrix for the kth time period, and eacc(k) represents the deceleration difference.

[0196] Before the start of each k+1 iteration, the new θ(k+1), i.e. the updated disc thermal conductivity, caliper thermal conductivity, convection heat transfer coefficient and other parameters, can be passed into the three-body coupled thermal model, and then the more accurate temperatures of the brake disc, brake pad and brake caliper can be obtained by iteration.

[0197] Furthermore, if the operating condition flag extremeflag(k) = 1, indicating an extreme operating condition, the update of parameters such as the disk thermal conductivity, clamp thermal conductivity, and convective heat transfer coefficient can be suspended: θ(k+1) = θ(k). This prevents the correction of extreme operating conditions, such as ABS response, from being mistaken for thermal decay errors. Furthermore, upper and lower limits can be set for parameters such as thermal conductivity and heat transfer coefficient based on the physically feasible range to prevent them from exceeding or falling below their normal parameter range.

[0198] In an embodiment of the present application, when there is a difference between the actual deceleration and the predicted deceleration of the vehicle, the deceleration difference is determined, and the preset disc thermal conductivity, preset clamp thermal conductivity and preset convection heat transfer coefficient are updated based on the deceleration difference and the preset gain matrix. This allows the system to adapt to dynamic changes in the braking system based on the gain matrix. Based on the acceleration error, the relevant parameters for calculating the temperature of the brake components can be updated in real time without the need for a temperature sensor, thereby improving the convenience and accuracy of determining the brake pad temperature.

[0199] Optionally, the brake fade parameter includes a brake fade ratio; and the method further includes:

[0200] Step C1, constructing a third mapping relationship between different braking fade ratio intervals and warning modes;

[0201] Step C2: determining a target warning mode corresponding to the target ratio interval in the third mapping relationship according to the target ratio interval in which the braking fade ratio is located, and alerting the user based on the target warning mode.

[0202] In the embodiment of the present application, the brake fade parameter obtained based on the baseline friction coefficient and the predicted friction coefficient includes a brake fade ratio, which can refer to the ratio between the baseline friction coefficient and the predicted friction coefficient. The calculated brake fade ratio can be expressed as:

[0203] ratiofade(k+i) = μpred(k+i)÷μest_corr(k)

[0204] Where ratiofade(k+i) represents the brake fade ratio for the k+i time period, μpred(k+i) represents the predicted friction coefficient for the k+i time period, and μest_corr(k) represents the baseline friction coefficient for the current time period. If ratiofade(k+i) < 1, the predicted friction coefficient is lower than the current baseline friction coefficient. A smaller ratiofade(k+i) indicates more severe brake fade.

[0205] Brake fade conditions can be quantified and graded to provide warnings, helping drivers and systems obtain early warning information before thermal fade occurs. Therefore, a third mapping relationship between different brake fade ratio intervals and warning methods can be pre-established.

[0206] For example, the implementation process can be: if ratiofade(k+i)≥0.9, then normal (green light); else if 0.8≤ratiofade<0.9, then slight decay (yellow light); else if 0.6≤ratiofade<0.8, then severe decay (orange light); else, then dangerous (red light). The above process includes ratio intervals such as brake fade ratio greater than or equal to 0.9, brake fade ratio greater than or equal to 0.8 and less than 0.9, as well as text warnings such as normal and slight decay, and light warnings such as green light and yellow light.

[0207] The alarm level can be determined based on the brake fade ratio's range, triggering different text, colors, and icons to be displayed on the instrument panel or central control panel. If the indicator light is red, the driver can be advised to stop the vehicle to cool down or reduce braking pressure. Furthermore, if a sensor (e.g., hydraulic sensor, accelerometer) fails, for example, if the deceleration rate ax(k)∈[-10, +10] meters per second squared, or the hydraulic pressure Pbrake(k)≥0 Pa, falls outside this range, indicating an extreme operating condition, indicating that a stable fade estimate may be unavailable. The system then switches to a conservative mode, directly issuing a worst-case warning, such as displaying a red light.

[0208] 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. The user is warned based on the target warning method, which 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.

[0209] Figure 3 This is a diagram of the architecture of brake fade prediction provided by an embodiment of the present application;

[0210] S1, output acquisition and preprocessing: obtaining hydraulic pressure, deceleration, vehicle speed; signal filtering synchronization; setting working condition flag;

[0211] S2, real-time friction coefficient identification: theoretical relationship: caliper clamping force equals the product of the preset conversion coefficient, hydraulic pressure, and friction coefficient; calculation of the uncorrected initial friction coefficient; temperature correction parameters; suspension of updates in extreme working conditions;

[0212] 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 temperatures are calculated separately; prediction for the next N time periods

[0213] S4, adaptive parameter correction: deceleration error; update heat transfer parameters and thermal conductivity parameters; suspend update in extreme working conditions; feed back updated parameters to the next cycle;

[0214] S5, comprehensive evaluation and output: calculation of the degradation ratio; determination of the ratio range, corresponding to different alarm methods; output of alarms, such as lights and sounds; if the sensor fails, it will enter the degraded mode warning.

[0215] Figure 4 This is a flowchart of brake fade prediction provided by an embodiment of the present application;

[0216] Step 401, sensor input; Step 402, STEP 1: input acquisition and preprocessing (sensor data acquisition and filtering); Step 403, STEP 2: real-time 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, STEP 3: three-body thermal model + future decay prediction (brake disc / pad / brake caliper temperature calculation and prediction); Step 406, STEP 4: 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 (decline level evaluation and warning output).

[0217] This application solution is based on a three-body coupled thermal model and introduces adaptive temperature correction parameters to correct the friction coefficient, achieving accurate prediction and graded warning of brake fade without actual temperature measurement conditions. By predicting the friction coefficient and correcting the parameters, it can effectively cope with changes in the heat dissipation environment and material aging; in extreme working conditions, it can automatically downgrade to warn of the worst case scenario and improve safety. Future decay trend predictions and graded alarms can provide early predictions for the driver or control system, reducing the risks brought about by a sudden drop in braking efficiency. This application solution has the advantages of low cost, real-time performance and accuracy, and can be widely used in vehicle braking safety management.

[0218] Figure 5 The present invention provides a braking fade parameter determination device 50, which includes:

[0219] A reference parameter module 501 is used to determine the brake pad temperature in a current time period.

[0220] a baseline friction module 502 for determining a baseline friction coefficient based on the vehicle's current deceleration, hydraulic pressure, and brake pad temperature during the current time period;

[0221] a prediction parameter module 503 for determining, for a target time period in a future time period, a predicted brake pad temperature for the target time period based on the brake pad temperature corresponding to a time period immediately preceding the target time period and a predicted amount of heat absorbed by the brake pad during the target time period; the predicted amount of heat absorbed being based on a predicted vehicle speed and a preset caliper clamping force;

[0222] a predicted friction module 504 for determining a predicted friction coefficient for the target time period based on a predetermined deceleration, a predetermined hydraulic pressure, and the predicted brake pad temperature;

[0223] The fade determination module 505 is configured to determine a brake fade parameter for the target time period based on the reference friction coefficient and the predicted friction coefficient.

[0224] Optionally, the friction prediction module 504 includes:

[0225] a friction calculation submodule, for determining an actual friction force based on a preset deceleration and a vehicle mass, and determining a theoretical friction force based on a preset hydraulic pressure and a preset conversion coefficient;

[0226] an initial friction submodule, configured to determine an initial friction coefficient based on the actual friction force and the theoretical friction force, and to determine a temperature correction parameter corresponding to the predicted brake pad temperature; different brake pad temperatures correspond to different temperature correction parameters;

[0227] The friction adjustment submodule is configured to adjust the initial friction coefficient based on the temperature correction parameter to obtain a predicted friction coefficient for the target time period.

[0228] Optional, initial friction submodule, including:

[0229] a first mapping unit, configured to determine a temperature correction parameter corresponding to the predicted brake pad temperature in a pre-established first mapping relationship between the brake pad temperature and the temperature correction parameter; or

[0230] The second mapping unit is used to determine a correction function corresponding to the temperature interval in which the predicted brake pad temperature is located in a second mapping relationship between pre-constructed brake pad temperature intervals and correction functions, and to determine a temperature correction parameter corresponding to the predicted brake pad temperature based on the correction function and the predicted brake pad temperature.

[0231] Optionally, the device further comprises:

[0232] an operating condition determination module, configured to determine a target time period currently being iterated and a time period preceding the target time period if the vehicle is determined to be in an extreme operating condition; the extreme operating condition includes an operating frequency of a target system in the vehicle reaching a preset threshold or a sensor of the vehicle drifting;

[0233] The parameter maintaining module is used to use 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 leaves the extreme working condition.

[0234] Optionally, the prediction parameter module 503 includes:

[0235] A brake heat submodule is used to determine the predicted brake heat based on the predicted speed and the preset caliper clamping force;

[0236] a heat absorption ratio submodule, configured to determine the amount of heat absorbed by the brake pad based on the predicted amount of brake heat and a preset heat absorption ratio; the preset heat absorption ratio representing a proportion of the predicted amount of brake heat absorbed by the brake pad;

[0237] a heat transfer submodule, configured to determine heat input, heat output, and heat dissipation of the brake pad based on a temperature difference between the brake pad temperature and the brake disc temperature, the brake caliper temperature, and the ambient temperature in a time period preceding the target time period, as well as a preset disc thermal conductivity, a preset caliper thermal conductivity, and a preset convection heat transfer coefficient;

[0238] The temperature determination submodule is used to determine the predicted brake pad temperature of the target time period based on the brake pad temperature of the previous time period of the target time period, the brake absorption heat, the imported heat, the exported heat and the heat dissipation.

[0239] Optionally, the device further comprises:

[0240] 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;

[0241] A parameter updating module is used to update the preset disc thermal conductivity, the preset clamp thermal conductivity and the preset convection heat transfer coefficient according to the deceleration difference and the preset gain matrix.

[0242] Optionally, the brake fade parameter includes a brake fade ratio; and the device further includes:

[0243] a third mapping module, configured to construct a third mapping relationship between different braking fade ratio intervals and warning modes;

[0244] The fade warning module is configured to determine, according to the target ratio interval in which the brake fade ratio is located, a target warning mode corresponding to the target ratio interval in the third mapping relationship, and warn a user based on the target warning mode.

[0245] In summary, according to the embodiments of the present application, for a current time period, the brake pad temperature for the current time period is determined, a baseline friction coefficient is determined based on the vehicle's current deceleration, hydraulic pressure, and the brake pad temperature for the current time period, and for a target time period in a future time period, a predicted brake pad temperature for the target time period is determined based on the brake pad temperature corresponding to the time period immediately preceding 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 vehicle speed and a preset caliper clamping force. A predicted friction coefficient for the target time period is determined based on the preset deceleration, the preset hydraulic pressure, and the predicted brake pad temperature. A brake fade parameter for the target time period is determined based on the baseline friction coefficient and the predicted friction coefficient. Consequently, a baseline friction coefficient can be determined for the current time period as a benchmark for evaluating brake fade. A predicted friction coefficient for a target time period in a future time period is then determined. The brake fade parameter corresponding to any target time period in the future time period is determined based on the baseline friction coefficient and the predicted friction coefficient. This avoids the need for a separate temperature sensor for the brake system and the cumbersome process of collecting data, thereby improving the convenience of evaluating brake fade.

[0246] The present application also provides an electronic device, such as Figure 6 As shown, it includes a processor 1001 , a communication interface 1002 , a memory 1003 and a communication bus 1004 , wherein the processor 1001 , the communication interface 1002 , and the memory 1003 communicate with each other via the communication bus 1004 .

[0247] The memory 1003 is used to store computer programs.

[0248] When the processor 1001 is used to execute the program stored in the memory 1003, the steps in the above-mentioned method for determining the brake fade parameters are implemented, which will not be repeated here.

[0249] The communication bus mentioned in the electronic device mentioned above may be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. This communication bus can be divided into address buses, data buses, control buses, etc. For ease of illustration, the figure shows only one thick line, but this does not mean that there is only one bus or only one type of bus.

[0250] The communication interface is used for communication between the above electronic device and other devices.

[0251] The memory may include random access memory (RAM) or non-volatile memory, such as at least one disk storage. Alternatively, the memory may be at least one storage device located away from the processor.

[0252] The above-mentioned processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can 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, or discrete hardware components.

[0253] In another embodiment provided in the present application, a readable storage medium is further provided, on which a computer program is stored. When the program is executed by a processor, the method for determining the brake fade parameter described in the above embodiment is implemented.

[0254] In the above embodiments, all or part of the embodiments can be implemented using software, hardware, firmware, or any combination thereof. When implemented using software, all or part of the embodiments can be implemented 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 can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a readable storage medium or transmitted from one readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The readable storage medium can be any available medium that can be accessed by a computer, or a data storage device such as a server or data center that integrates one or more available media. The available medium can be magnetic media (e.g., floppy disk, hard disk, tape), optical media (e.g., DVD), or semiconductor media (e.g., solid-state drive (SSD)).

[0255] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0256] Each embodiment in this specification is described in a related manner. Similar portions between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments. The embodiments of the apparatus, electronic device, readable storage medium, and computer program product containing instructions thereof are generally similar to the method embodiments, so their description is relatively simple. For related portions, reference can be made to the description of the method embodiments.

[0257] The above description is only a preferred embodiment of the present application and is not intended to limit the scope of protection of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the scope of protection of the present application.

Claims

1. A method for determining brake fade parameters, characterized in that: The method comprises: For a current time period, determining a brake pad temperature for the current time period; determining a reference friction coefficient based on a current deceleration of the vehicle, a hydraulic pressure, and a brake pad temperature during the current time period; determining, for a target time period in a future time period, a predicted brake pad temperature for the target time period based on a brake pad temperature corresponding to a time period immediately preceding the target time period and a predicted amount of heat absorbed by the brake pad during the target time period; the predicted amount of heat absorbed is based on a predicted speed of the vehicle and a preset caliper clamping force; the preset caliper clamping force is a maximum caliper clamping force that can be provided by the braking system; determining a predicted friction coefficient for the target time period based on a preset deceleration, a preset hydraulic pressure, and the predicted brake pad temperature; wherein the preset deceleration is a maximum deceleration of the vehicle; and the preset hydraulic pressure is a maximum hydraulic pressure of the vehicle; A brake fade parameter of the target time period is determined according to the reference friction coefficient and the predicted friction coefficient.

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

3. The method according to claim 2, characterized in that The step of determining a temperature correction parameter corresponding to the predicted brake pad temperature comprises: Determining a temperature correction parameter corresponding to the predicted brake pad temperature in a pre-established first mapping relationship between brake pad temperature and temperature correction parameter; or In a pre-constructed second mapping relationship between brake pad temperature intervals and correction functions, a correction function corresponding to the temperature interval in which the predicted brake pad temperature is located is determined, and based on the correction function and the predicted brake pad temperature, a temperature correction parameter corresponding to the predicted brake pad temperature is determined.

4. The method according to claim 1, wherein The method further comprises: If it is determined that the vehicle is in an extreme operating condition, determining a target time period currently being iterated and a time period previous to the target time period; the extreme operating condition includes an operating frequency of a target system in the vehicle reaching a preset threshold and a sensor of the vehicle drifting; The predicted friction coefficient corresponding to the previous time period of the target time period is used as the friction coefficient for the target time period and subsequent time periods until the vehicle leaves 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: Determining predicted brake heat based on predicted speed and preset caliper clamping force; determining the brake absorption heat of the brake pad based on the predicted brake heat and a preset heat absorption ratio; the preset heat absorption ratio represents the proportion of heat absorbed by the brake pad in the predicted brake heat; Determining the heat input, heat output, and heat dissipation of the brake pad based on the temperature difference between the brake pad temperature and the brake disc temperature, the brake caliper temperature, and the ambient temperature in the time period before the target time period, as well as a preset disc thermal conductivity, a preset caliper thermal conductivity, and a preset convection heat transfer coefficient; The predicted brake pad temperature of the target time period is determined according to the brake pad temperature of the previous time period of the target time period, the brake absorption heat, the imported heat, the exported heat and the heat dissipation.

6. The method according to claim 5, characterized in that The method further comprises: determining a deceleration difference when there is a difference between the actual deceleration of the vehicle and the preset deceleration; The preset disc thermal conductivity, the preset clamp thermal conductivity and the preset convection heat transfer coefficient are updated 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: Constructing a third mapping relationship between different brake fade ratio intervals and warning modes; According to the target ratio interval in which the brake fade ratio is located, a target warning mode corresponding to the target ratio interval is determined in the third mapping relationship, and a warning is given to the user based on the target warning mode.

8. A braking fade parameter determination device, characterized in that: The device comprises: a reference parameter module, configured to determine, for a current time period, a brake pad temperature during the current time period; a baseline friction module, configured to determine a baseline friction coefficient based on a current deceleration of the vehicle, a hydraulic pressure, and a brake pad temperature during the current time period; a prediction parameter module for determining, for a target time period in a future time period, a predicted brake pad temperature for the target time period based on a brake pad temperature corresponding to a time period immediately preceding the target time period and a predicted amount of heat absorbed by the brake pad during the target time period; the predicted amount of heat absorbed is based on a predicted speed of the vehicle and a preset caliper clamping force; the preset caliper clamping force is a maximum caliper clamping force that can be provided by the braking system; a predicted friction module, 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; wherein the preset deceleration is a maximum deceleration of the vehicle; and the preset hydraulic pressure is a maximum hydraulic pressure of the vehicle; The fade determination module is configured to determine a brake fade parameter of the target time period according to the baseline friction coefficient and the predicted friction coefficient.

9. An electronic device, characterized in that: include: A processor, a communication interface, a memory, and a communication bus; wherein the processor, the communication interface, and the memory communicate with each other via the communication bus; Memory for storing computer programs; The processor is configured to implement the steps of the method for determining brake fade parameters as described in any one of claims 1 to 7 when executing the program stored in the memory.

10. A readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method for determining a brake fade parameter according to any one of claims 1 to 7 are implemented.

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