Method and device for calculating characteristic vehicle speed in combination with road surface and aging factors

Abstract

This invention discloses a method and apparatus for calculating characteristic vehicle speed by combining road surface and aging factors. It belongs to the field of vehicle technology. The method includes: determining a comprehensive aging factor based on vehicle mileage, tire condition, and suspension aging condition; determining a road surface identification factor based on vehicle condition parameters; and calculating a characteristic vehicle speed based on the comprehensive aging factor, the road surface identification factor, and pre-calibrated first and second characteristic vehicle speeds. The first characteristic vehicle speed is the characteristic speed obtained by testing the vehicle on a designated circular track using winter tires and an aging suspension, and the second characteristic speed is the characteristic speed obtained by testing the vehicle on the same circular track using summer tires and a sport suspension. This invention calculates the characteristic vehicle speed based on the comprehensive aging factor and the road surface identification factor, resulting in a characteristic vehicle speed that better reflects the actual vehicle conditions and road conditions, thus improving the accuracy of the characteristic vehicle speed calculation.

Description

Technical Field

[0001] This invention belongs to the field of vehicle technology, specifically relating to a method and apparatus for calculating characteristic vehicle speed by combining road surface and aging factors. Background Technology

[0002] Currently, ESC (Electronic Stability Control) calculates the vehicle's reference yaw rate based on a two-degree-of-freedom vehicle model and the steering wheel angle controlled by the driver. This reference yaw rate is then compared with the actual yaw rate measured by an IMU (Inertial Measurement Unit) to determine the vehicle's current stability. Characteristic vehicle speeds are required in calculating the reference yaw rate based on the two-degree-of-freedom vehicle model.

[0003] In traditional methods, the characteristic speed is a fixed value, determined through actual vehicle calibration. However, a fixed characteristic speed cannot adapt to various conditions such as changes in road surface coefficients, tire wear or replacement, and load variations, affecting the accuracy of calculating the reference yaw rate. Summary of the Invention

[0004] One objective of this invention is to provide a method and apparatus for calculating characteristic vehicle speed by combining road surface and aging factors, which can solve the technical problem of low accuracy in calculating reference yaw rate due to fixed characteristic vehicle speed in the prior art.

[0005] According to a first aspect of the present invention, a method for calculating characteristic vehicle speed by combining road surface and aging factors is provided, comprising:

[0006] The comprehensive aging factor is determined based on vehicle mileage, tire condition, and suspension aging condition.

[0007] Determine the road surface recognition factor based on vehicle status parameters;

[0008] The characteristic vehicle speed is calculated based on the comprehensive aging factor, the road surface identification factor, and the pre-calibrated first and second characteristic vehicle speeds. The first characteristic vehicle speed is the characteristic vehicle speed obtained by testing the vehicle on a designated circular track when using winter tires and aging suspension, and the second characteristic vehicle speed is the characteristic vehicle speed obtained by testing the vehicle on the same circular track when using summer tires and sport suspension.

[0009] Optionally, determining the comprehensive aging factor based on vehicle mileage, tire condition, and suspension aging condition includes:

[0010] A tire wear factor is determined based on the vehicle mileage and the tire condition, and the tire wear factor is used to represent the degree of tire wear.

[0011] The suspension aging factor is determined based on the vehicle mileage and the suspension aging condition.

[0012] The four-wheel alignment offset factor is determined based on the real-time calculated steering wheel zero-point drift, the pre-calibrated maximum zero-point drift threshold, and the pre-calibrated maximum correction magnitude of the four-wheel alignment offset to the characteristic vehicle speed.

[0013] The comprehensive aging factor is determined based on the tire wear factor, the suspension aging factor, and the four-wheel alignment offset factor.

[0014] Optionally, determining the suspension aging factor based on the vehicle mileage and the suspension aging condition includes:

[0015] The suspension aging factor is calculated using the following formula:

[0016] ;

[0017] in, Suspension aging factor, This refers to the suspension aging condition coefficient, which is determined based on the influence of the vehicle suspension aging condition on the lateral stiffness. For vehicle mileage, This refers to the number of kilometers within the lifespan of the vehicle's suspension.

[0018] Optionally, determining the four-wheel alignment offset factor based on the real-time calculated steering wheel zero-point drift, the pre-calibrated maximum zero-point drift threshold, and the pre-calibrated maximum correction magnitude of the four-wheel alignment offset to the characteristic vehicle speed includes:

[0019] The four-wheel alignment offset factor is calculated according to the following formula:

[0020] ;

[0021] in, This is the four-wheel alignment offset factor. This represents the maximum correction margin for the characteristic vehicle speed based on the pre-calibrated four-wheel alignment offset. For the pre-calibrated maximum zero-point drift threshold, This is for real-time calculation of steering wheel zero-point drift.

[0022] Optionally, determining the comprehensive aging factor based on the tire wear factor, the suspension aging factor, and the four-wheel alignment misalignment factor includes:

[0023] The comprehensive aging factor is calculated using the following formula:

[0024] ;

[0025] in, To comprehensively address aging factors, For tire wear factor, Suspension aging factor, This is the four-wheel alignment offset factor.

[0026] Optionally, determining the road surface recognition factor based on vehicle state parameters includes:

[0027] The wheel speed fluctuation factor is determined based on the changes in vehicle wheel speed;

[0028] The pressure activity factor is determined based on changes in vehicle braking pressure.

[0029] The comprehensive road friction coefficient is determined based on the vehicle state parameters.

[0030] The road surface identification factor is determined based on the wheel speed fluctuation factor, the pressure activity factor, and the comprehensive road surface friction coefficient.

[0031] Optionally, determining the comprehensive road friction coefficient based on the vehicle state parameters includes:

[0032] The comprehensive road surface friction coefficient is calculated using the following formula:

[0033] ;

[0034] in, To take into account the road surface friction coefficient, For longitudinal acceleration, It is the acceleration due to gravity. The coefficient of friction for dry road surfaces. The rate of decrease of the adhesion factor, For the first The slip ratio of each wheel Number the wheels. Based on the basic slip ratio threshold, For the threshold sensitivity of wheel instability, For the first The angular deceleration of each wheel, For the moment of inertia of the wheel, The radius of the wheel's rolling motion. For the first The braking pressure of each wheel cylinder. The braking gain constant is... This is a user-defined constant.

[0035] Optionally, determining the road surface identification factor based on the wheel speed fluctuation factor, the pressure activity factor, and the comprehensive road surface friction coefficient includes:

[0036] The road surface identification factor is calculated according to the following formula:

[0037] ;

[0038] in, For road surface identification factors, To take into account the road surface friction coefficient, For wheel speed fluctuation factor, It is a stress-active factor.

[0039] Optionally, calculating the characteristic vehicle speed based on the comprehensive aging factor, the road surface identification factor, and the pre-calibrated first and second characteristic vehicle speeds includes:

[0040] The third characteristic vehicle speed is calculated based on the comprehensive aging factor, the road surface identification factor, and the second characteristic vehicle speed. The third characteristic vehicle speed is the product of the comprehensive aging factor, the road surface identification factor, and the second characteristic vehicle speed.

[0041] If the third characteristic vehicle speed is less than the first characteristic vehicle speed, the first characteristic vehicle speed is determined as the characteristic vehicle speed.

[0042] If the third characteristic vehicle speed is greater than the second characteristic vehicle speed, the second characteristic vehicle speed is determined as the characteristic vehicle speed;

[0043] When the third characteristic vehicle speed is greater than or equal to the first characteristic vehicle speed and the third characteristic vehicle speed is less than or equal to the second characteristic vehicle speed, the third characteristic vehicle speed is determined as the characteristic vehicle speed.

[0044] According to a second aspect of the present invention, a characteristic vehicle speed calculation device is provided, comprising a processor and a memory, the memory storing a program or instructions executable on the processor, the program or instructions being executed by the processor to implement the steps of a method for calculating characteristic vehicle speed by combining road surface and aging factors as described in the first aspect of the present invention.

[0045] The beneficial effects of this invention are as follows: This invention calculates the characteristic vehicle speed based on a comprehensive aging factor and a road surface recognition factor. The calculated characteristic vehicle speed is more consistent with the actual vehicle conditions and road conditions, thus improving the accuracy of the characteristic vehicle speed. Simultaneously, by pre-calibrating a first and second characteristic vehicle speed, the minimum and maximum values ​​of the characteristic vehicle speed are constrained, ensuring that the final calculated characteristic vehicle speed does not exceed the vehicle's physical limits. Even if there are errors in the calculation of the aging factor and the road surface recognition factor, the speed will still fall within the calibration range, improving safety. Attached Figure Description

[0046] Figure 1This is a flowchart of a method for calculating characteristic vehicle speed by combining road surface and aging factors in an embodiment of the present invention. Detailed Implementation

[0047] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0048] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0049] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0050] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0051] In the specification of this invention, the terms "first" and "second" may explicitly or implicitly include one or more of the same feature. In the description of this invention, unless otherwise stated, "multiple" means two or more. Furthermore, in the specification, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0052] like Figure 1 As shown in the figure, this embodiment introduces a method for calculating characteristic vehicle speed by combining road surface and aging factors, including steps 1100-1300.

[0053] Step 1100: Determine the comprehensive aging factor based on vehicle mileage, tire condition, and suspension aging condition.

[0054] The overall aging factor quantifies the impact of overall vehicle aging on driving characteristics. The higher the overall aging degree of the vehicle, the larger the overall aging factor. Tire condition indicates the degree of tire aging and wear, while suspension aging condition indicates the degree of suspension system aging. The longer the vehicle's mileage and the more severe the aging of the tires and suspension, the larger the overall aging factor.

[0055] Step 1200: Determine the road surface recognition factor based on the vehicle status parameters.

[0056] Road surface identification factors are used to reflect road surface characteristics such as road surface adhesion coefficient.

[0057] Step 1300: Calculate the characteristic vehicle speed based on the comprehensive aging factor, the road surface identification factor, and the pre-calibrated first characteristic vehicle speed and second characteristic vehicle speed, wherein the first characteristic vehicle speed is the characteristic vehicle speed obtained by testing the vehicle on a designated circular track when using winter tires and aging suspension, and the second characteristic vehicle speed is the characteristic vehicle speed obtained by testing the vehicle on the same circular track when using summer tires and sports suspension.

[0058] The first and second characteristic vehicle speeds are pre-calibrated values, and both are calibrated on the same circular track. When calibrating the first characteristic speed, the vehicle tires are winter tires, and the suspension is an aged suspension. With this configuration, the lateral stiffness of the tires and suspension is low, making the vehicle more prone to understeer and resulting in a lower characteristic speed. In this situation, the vehicle's handling response is sluggish, and the driver needs to turn the steering wheel earlier and more frequently to maintain the circular speed.

[0059] When calibrating the second characteristic speed, the vehicle uses summer tires and a sport suspension. This configuration results in higher lateral stiffness of the tires and suspension, making the vehicle closer to neutral steering and resulting in a higher characteristic speed. This configuration allows the vehicle to maintain a smaller steering wheel angle increment at higher speeds, leading to more precise steering.

[0060] The first characteristic speed represents the lower limit of the vehicle's characteristic speed, and the second characteristic speed represents the upper limit. The final calculated characteristic speed will vary depending on the overall age of the vehicle and actual road conditions.

[0061] Specifically, step 1300 includes: calculating a third characteristic vehicle speed based on the comprehensive aging factor, the road surface identification factor, and the second characteristic vehicle speed, wherein the third characteristic vehicle speed is the product of the comprehensive aging factor, the road surface identification factor, and the second characteristic vehicle speed; determining the first characteristic vehicle speed as the characteristic vehicle speed when the third characteristic vehicle speed is less than the first characteristic vehicle speed; determining the second characteristic vehicle speed as the characteristic vehicle speed when the third characteristic vehicle speed is greater than the second characteristic vehicle speed; and determining the third characteristic vehicle speed as the characteristic vehicle speed when the third characteristic vehicle speed is greater than or equal to the first characteristic vehicle speed and less than or equal to the second characteristic vehicle speed.

[0062] The formula for calculating characteristic vehicle speed is as follows:

[0063] ;

[0064] in, For characteristic vehicle speed, The second characteristic speed is the vehicle speed. The first characteristic speed is the vehicle speed. For road surface identification factors, To comprehensively address aging factors, This is a clamping function. The function is used to limit the output between a minimum and a maximum value. In the formula for calculating the characteristic vehicle speed above, the characteristic vehicle speed... The minimum value is the first characteristic speed. Characteristic vehicle speed The maximum value is the second characteristic vehicle speed .

[0065] This is the third characteristic speed. The second characteristic speed is the pre-calibrated maximum value of the characteristic speed, representing the characteristic speed of the vehicle under optimal conditions. Vehicle aging or road surface deterioration will reduce the actual characteristic speed. The combined aging factor and road surface recognition factor range from 0 to 1. These factors are used as attenuation coefficients to scale the second characteristic speed, reflecting the impact of vehicle aging and road surface conditions.

[0066] The first characteristic speed is the characteristic speed of the vehicle under the worst-case scenario. Even if the actual calculated third characteristic speed is lower, the final characteristic speed of the vehicle should not be lower than the first characteristic speed to ensure the safety bottom line of the control strategy.

[0067] This embodiment calculates the characteristic vehicle speed based on a comprehensive aging factor and a road surface recognition factor. The calculated characteristic vehicle speed is more consistent with the actual vehicle conditions and road conditions, thus improving the accuracy of the characteristic vehicle speed. Simultaneously, by pre-calibrating a first and second characteristic vehicle speed, the minimum and maximum values ​​of the characteristic vehicle speed are constrained, ensuring that the final calculated characteristic vehicle speed does not exceed the vehicle's physical limits. Even if there are errors in the calculation of the aging factor and the road surface recognition factor, the speed will still fall within the calibration range, improving safety.

[0068] In this embodiment, step 1100 includes steps 1110-1140.

[0069] Step 1110: Determine the tire wear factor based on the vehicle mileage and the tire condition, wherein the tire wear factor is used to represent the degree of tire wear.

[0070] Tire wear factor is estimated based on mileage and tire wear. For example, when the mileage is between 0-30,000 km, the tire wear factor ranges from 1.0 to 0.98. The higher the mileage, the lower the tire wear factor. The specific range is adjusted based on actual vehicle data.

[0071] Step 1120: Determine the suspension aging factor based on the vehicle mileage and the suspension aging condition.

[0072] Specifically, the suspension aging factor is calculated according to the following formula:

[0073] ;

[0074] in, Suspension aging factor, This refers to the suspension aging condition coefficient, which is determined based on the influence of the vehicle suspension aging condition on the lateral stiffness. For vehicle mileage, This refers to the number of kilometers within the lifespan of the vehicle's suspension.

[0075] The degree of impact of suspension aging on lateral stiffness determines the severity of aging; the more severe the aging, the greater the decrease in lateral stiffness. The larger. The change in lateral stiffness of the suspension before and after aging can be obtained by bench testing.

[0076] This indicates the design life mileage of the suspension system, such as 100,000 km. It can be determined by durability testing.

[0077] exist Less than In this case, The suspension aging factor decreases linearly with vehicle mileage, gradually decreasing from 1 to... A suspension aging factor of 1 indicates that the vehicle is new. The suspension aging factor decreases to... When this time is reached, it indicates that the suspension system has reached its designed reference lifespan.

[0078] exist Greater than In this case, Subsequently, as vehicle mileage increases, the suspension aging factor no longer decreases. This means that the impact of suspension aging on lateral stiffness saturates after reaching its design life and no longer worsens.

[0079] For example, the suspension aging condition coefficient can be obtained through testing. A value of 0.2 indicates a 20% decrease in lateral stiffness after the suspension has fully aged. The design life mileage of the suspension system. The current vehicle mileage is 100,000 km. The suspension aging factor can be calculated based on a distance of 60,000 km. It is 0.88.

[0080] Step 1130: Determine the four-wheel alignment offset factor based on the real-time calculated steering wheel zero-point drift, the pre-calibrated maximum zero-point drift threshold, and the pre-calibrated maximum correction magnitude of the four-wheel alignment offset to the characteristic vehicle speed.

[0081] The four-wheel alignment offset factor is calculated according to the following formula:

[0082] ;

[0083] in, This is the four-wheel alignment offset factor. This represents the maximum correction margin for the characteristic vehicle speed based on the pre-calibrated four-wheel alignment offset. For the pre-calibrated maximum zero-point drift threshold, This is for real-time calculation of steering wheel zero-point drift.

[0084] Steering wheel drift refers to the angle at which the steering wheel deviates from its center position when the vehicle is traveling in a straight line, and it is usually related to the offset of the four-wheel alignment parameters. The greater the drift, the more serious the four-wheel alignment deviation, the worse the vehicle's straight-line stability, and the characteristic speed should be reduced.

[0085] Maximum zero-point drift threshold This can be obtained through a large number of real-vehicle statistics. For example, when a normal vehicle is driving on a flat road, the steering wheel drift is usually within ±3°. When the steering wheel drifts more than 5°, the driver will clearly feel that the steering wheel is off-center, at which point it is considered that the four-wheel alignment has been seriously misaligned.

[0086] The maximum correction range for characteristic vehicle speed due to four-wheel alignment misalignment can be determined through comparative experiments. For example, characteristic vehicle speeds are measured at the test track under both normal vehicle conditions and severe deviation conditions. The maximum correction margin for the characteristic vehicle speed due to four-wheel alignment misalignment is then calculated. For example, if a vehicle's characteristic speed is 100 km / h under normal conditions, but decreases to 85 km / h during severe drift, then we get... The value is 0.15.

[0087] In one example Set to 0.12. Set to 4°, real-time calculation of steering wheel zero-point drift. The offset was set at 2.5°, and the final four-wheel alignment offset factor was calculated. It is 0.925.

[0088] Step 1140: Determine the comprehensive aging factor based on the tire wear factor, the suspension aging factor, and the four-wheel alignment offset factor.

[0089] The comprehensive aging factor is calculated using the following formula:

[0090] ;

[0091] in, To comprehensively address aging factors, For tire wear factor, Suspension aging factor, This is the four-wheel alignment offset factor.

[0092] Tire wear factor reflects the impact of tire tread depth and rubber aging on lateral stiffness and adhesion limit. Suspension aging factor reflects the impact of suspension aging on dynamic changes in wheel alignment. Four-wheel alignment offset factor reflects the impact of static alignment parameter offsets (such as steering wheel zero-point drift) on straight-line stability and steering response.

[0093] Multiplying these three factors means that the overall aging effect on the characteristic vehicle speed is the sum of the independent attenuation effects of each factor. If any one of these factors is significantly less than 1, the overall aging factor will decrease significantly, thus lowering the characteristic vehicle speed. When all aging conditions reach their most severe state, the overall aging factor becomes the product of the lower limits of the three factors. The minimum value of the overall aging factor remains greater than 0, and it will not be negative or zero, ensuring that the characteristic vehicle speed still has a reasonable lower limit.

[0094] In this embodiment, step 1200 includes steps 1210-1240.

[0095] Step 1210: Determine the wheel speed fluctuation factor based on the changes in vehicle wheel speed.

[0096] The wheel speed fluctuation factor reflects wheel speed vibration caused by uneven road surface or uneven adhesion. The greater the wheel speed vibration, the smaller the wheel speed fluctuation factor. For example, the wheel speed fluctuation factor can be set to a range of 0.8-1.0, and the actual wheel speed fluctuation factor can be further determined based on the wheel speed vibration within this range. When the road surface is bumpy or the adhesion changes abruptly, the wheel speed will vibrate violently. In this case, the road surface recognition factor should be reduced, and excessively high characteristic vehicle speeds should not be used.

[0097] Step 1220: Determine the pressure activity factor based on the changes in vehicle braking pressure.

[0098] More frequent and larger changes in brake pressure may indicate that the driver is braking frequently on low-friction surfaces, or that systems such as ABS (Anti-lock Braking System) or ESC are intervening, requiring a reduction in characteristic vehicle speed. Therefore, the pressure activity factor will decrease accordingly. Brake pressure is direct evidence of active control intervention.

[0099] Step 1230: Determine the comprehensive road friction coefficient based on the vehicle state parameters.

[0100] The comprehensive road surface friction coefficient is calculated using the following formula:

[0101] ;

[0102] in, To take into account the road surface friction coefficient, For longitudinal acceleration, It is the acceleration due to gravity. The coefficient of friction for dry road surfaces. The rate of decrease of the adhesion factor, For the first The slip ratio of each wheel Number the wheels. Based on the basic slip ratio threshold, For the threshold sensitivity of wheel instability, For the first The angular deceleration of each wheel, For the moment of inertia of the wheel, The radius of the wheel's rolling motion. For the first The braking pressure of each wheel cylinder. The braking gain constant is... This is a user-defined constant.

[0103] In calculating the comprehensive road friction coefficient When the minimum of the two parameters is reached, the first parameter is the friction coefficient estimate based on longitudinal acceleration. This represents the proportion of the currently available longitudinal adhesion coefficient relative to the dry road surface. For example, the friction coefficient of a dry road surface. The measured longitudinal acceleration is 1.0. for If the value is 0.5, it means the current road surface adhesion is only half that of a dry road surface. This parameter only applies to conditions with significant longitudinal acceleration or deceleration. During constant speed travel, the longitudinal acceleration... The value is approximately 0, causing this parameter to approach zero and leading to misjudgment. This is addressed by supplementing the value with a second parameter.

[0104] The second parameter represents the corrected adhesion estimate based on slip ratio and wheel angular deceleration. In the correction term of the inner denominator:

[0105] ;

[0106] in This represents the inertial torque generated by the angular deceleration of the wheel. Indicates hydraulic braking torque. As a small constant, it is used to avoid a denominator of zero. The ratio reflects the proportion of inertial torque to braking torque. When the wheels tend to lock up, the angular deceleration increases, and this ratio increases, thus... It decreases. This means that when braking approaches lock-up, the slip ratio threshold... When dynamically reduced, it is easier to trigger the adhesion decline judgment.

[0107] Then calculate Multiply by The attenuation amount is obtained, and finally, the adhesion factor of the wheel is obtained by subtracting 1 from it.

[0108] ;

[0109] in, Indicates the first The adhesion factor of each wheel.

[0110] Finally, the minimum adhesion factor of the four wheels is taken and compared with the first parameter to obtain the comprehensive road friction coefficient. .

[0111] longitudinal acceleration It can be measured using an IMU.

[0112] The dry road friction coefficient characterizes the maximum adhesion coefficient that a dry, clean, high-adhesion road surface can provide. Using the dry road friction coefficient as a normalized benchmark, the longitudinal acceleration measured by an IMU (Integrated Mutor Unit) is divided by the acceleration due to gravity and the dry road friction coefficient to obtain the currently available adhesion ratio. For example, if the dry road friction coefficient is set to 1.0 and the longitudinal acceleration measured by the IMU is 0.5g, then the ratio is 0.5, indicating that the current road surface adhesion is only 50% of that of a dry road surface. Dry Road Friction Coefficient It is a pre-calibrated value. For example, for ordinary tires, the coefficient of friction on dry roads is usually set in the range of 1.0-1.2.

[0113] Adhesion factor decrease rate It is typically set in the range of 0.5-0.8. The rate of decrease in adhesion factor indicates the rate at which the coefficient of adhesion provided by the road surface decreases as the slip ratio increases after the wheel slip ratio exceeds a certain threshold. It reflects the degree of softening between the tire and the road surface when approaching the adhesion limit.

[0114] No. slip ratio of each wheel According to the The wheel speed of each wheel and the reference vehicle speed are calculated.

[0115] The baseline slip ratio threshold represents the reference slip ratio value at which a wheel is considered to begin entering an unstable state under standard braking conditions. It typically corresponds to the slip ratio near the peak of the coefficient of friction-slip ratio curve. It is usually set in the range of 0.1-0.15.

[0116] Threshold sensitivity of wheel instability This characterizes the sensitivity of wheel angular deceleration to a reduction in the slip ratio threshold. Threshold sensitivity to wheel instability. When the larger the value, the greater the angular deceleration. The faster the descent, the more sensitive the system is to instability caused by wheels locking up.

[0117] Used to adjust correction items The strength of this correction term decreases when the vehicle's angular deceleration is very large (close to locking), making it... much smaller This makes it easier to trigger the adhesion descent detection. Threshold sensitivity of wheel instability. It is usually set in the range of 0.3-0.7.

[0118] exist Time of the first The braking pressure of the wheel cylinder corresponding to each wheel for:

[0119] ;

[0120] ;

[0121] in, Indicates in Time of the first The braking pressure of each wheel cylinder. Main cylinder pressure, This refers to the opening degree of the oil inlet valve. For the opening degree of the oil outlet valve, This represents the pressure change value.

[0122] After ABS intervention, the ABS switches between boost control, pressure holding control, and pressure reduction control at a relatively high frequency. During the pressure reduction phase... Rapid decline, It will suddenly increase, falsely simulating a large inertial torque, leading to... The coefficient of friction is excessively low, leading to an incorrect assessment of low road surface adhesion and resulting in a distorted overall road surface friction coefficient.

[0123] The comprehensive road surface friction coefficient calculation formula integrates information from both longitudinal acceleration and slip ratio, offering good complementarity. It also considers the influence of wheel inertial torque on braking pressure, improving accuracy. Furthermore, a minimum value strategy is employed to ensure safety.

[0124] Step 1240: Determine the road surface identification factor based on the wheel speed fluctuation factor, the pressure activity factor, and the comprehensive road surface friction coefficient.

[0125] The road surface identification factor is calculated according to the following formula:

[0126] ;

[0127] in, For road surface identification factors, To take into account the road surface friction coefficient, For wheel speed fluctuation factor, It is a stress-active factor.

[0128] The road surface identification factor is the product of the road surface friction coefficient, wheel speed fluctuation factor, and pressure activity factor. If any one of these factors is low (high wheel speed vibration, high pressure activity, or low friction coefficient), the road surface identification factor will be low, ultimately reducing the characteristic vehicle speed. The road surface identification factor reflects the current road surface adhesion conditions and driving stability, providing environmental correction for characteristic vehicle speed calculation.

[0129] This embodiment introduces a characteristic vehicle speed calculation device, including a processor and a memory. The memory stores programs or instructions that can run on the processor. When the program or instructions are executed by the processor, they implement the steps of a method for calculating characteristic vehicle speed by combining road surface and aging factors as described in any embodiment of the present invention.

[0130] While specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention.

[0131] Those skilled in the art will recognize that the modules and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0132] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the above-described apparatus and equipment can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0133] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or modules may be electrical, mechanical, or other forms.

[0134] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of the embodiments of the present invention, depending on actual needs.

[0135] In addition, the functional modules in the embodiments of the present invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0136] If the aforementioned functions are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, ROM, RAM, magnetic disks, or optical disks.

[0137] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

[0138] It should be understood that the sequence numbers of the steps in the invention's content and embodiments do not absolutely imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention. The foregoing description of embodiments of this disclosure has been provided for illustrative and descriptive purposes. The foregoing description is not exhaustive and is not intended to limit this disclosure to the exact form disclosed. Various modifications and variations may exist based on the foregoing teachings, or various modifications and variations may be derived from the practice of this disclosure. These embodiments were chosen and described to illustrate the principles of this disclosure and its practical application, so that those skilled in the art can utilize this disclosure in various implementations and modifications suitable for the specific purpose of the concept.

Claims

1. A method for calculating characteristic vehicle speed by combining road surface and aging factors, characterized in that, include: The comprehensive aging factor is determined based on vehicle mileage, tire condition, and suspension aging condition. Determine the road surface recognition factor based on vehicle status parameters; The characteristic vehicle speed is calculated based on the comprehensive aging factor, the road surface identification factor, and the pre-calibrated first characteristic vehicle speed and second characteristic vehicle speed. The first characteristic vehicle speed is the characteristic vehicle speed obtained by testing the vehicle on a designated circular track when using winter tires and aging suspension. The second characteristic vehicle speed is the characteristic vehicle speed obtained by testing the vehicle on the same circular track when using summer tires and sports suspension. The determination of the comprehensive aging factor based on vehicle mileage, tire condition, and suspension aging condition includes: A tire wear factor is determined based on the vehicle mileage and the tire condition, and the tire wear factor is used to represent the degree of tire wear. The suspension aging factor is determined based on the vehicle mileage and the suspension aging condition. The four-wheel alignment offset factor is determined based on the real-time calculated steering wheel zero-point drift, the pre-calibrated maximum zero-point drift threshold, and the pre-calibrated maximum correction magnitude of the four-wheel alignment offset to the characteristic vehicle speed. The comprehensive aging factor is determined based on the tire wear factor, the suspension aging factor, and the four-wheel alignment offset factor; The suspension aging factor is calculated using the following formula: ； in, Suspension aging factor, This refers to the suspension aging condition coefficient, which is determined based on the influence of the vehicle suspension aging condition on the lateral stiffness. For vehicle mileage, This refers to the number of kilometers within the lifespan of the vehicle's suspension. The step of calculating the characteristic vehicle speed based on the comprehensive aging factor, the road surface identification factor, and the pre-calibrated first and second characteristic vehicle speeds includes: The third characteristic vehicle speed is calculated based on the comprehensive aging factor, the road surface identification factor, and the second characteristic vehicle speed. The third characteristic vehicle speed is the product of the comprehensive aging factor, the road surface identification factor, and the second characteristic vehicle speed. If the third characteristic vehicle speed is less than the first characteristic vehicle speed, the first characteristic vehicle speed is determined as the characteristic vehicle speed. If the third characteristic vehicle speed is greater than the second characteristic vehicle speed, the second characteristic vehicle speed is determined as the characteristic vehicle speed; When the third characteristic vehicle speed is greater than or equal to the first characteristic vehicle speed and the third characteristic vehicle speed is less than or equal to the second characteristic vehicle speed, the third characteristic vehicle speed is determined as the characteristic vehicle speed.

2. The method for calculating characteristic vehicle speed by combining road surface and aging factors according to claim 1, characterized in that, The determination of the four-wheel alignment offset factor based on the real-time calculated steering wheel zero-point drift, the pre-calibrated maximum zero-point drift threshold, and the pre-calibrated maximum correction magnitude of the four-wheel alignment offset to the characteristic vehicle speed includes: The four-wheel alignment offset factor is calculated according to the following formula: ； in, This is the four-wheel alignment offset factor. This represents the maximum correction margin for the characteristic vehicle speed based on the pre-calibrated four-wheel alignment offset. For the pre-calibrated maximum zero-point drift threshold, This is for real-time calculation of steering wheel zero-point drift.

3. The method for calculating characteristic vehicle speed by combining road surface and aging factors according to claim 1, characterized in that, The determination of the comprehensive aging factor based on the tire wear factor, the suspension aging factor, and the four-wheel alignment misalignment factor includes: The comprehensive aging factor is calculated using the following formula: ； in, To comprehensively address aging factors, For tire wear factor, Suspension aging factor, This is the four-wheel alignment offset factor.

4. The method for calculating characteristic vehicle speed by combining road surface and aging factors according to claim 1, characterized in that, The process of determining the road surface recognition factor based on vehicle state parameters includes: The wheel speed fluctuation factor is determined based on the changes in vehicle wheel speed; The pressure activity factor is determined based on changes in vehicle braking pressure. The comprehensive road friction coefficient is determined based on the vehicle state parameters. The road surface identification factor is determined based on the wheel speed fluctuation factor, the pressure activity factor, and the comprehensive road surface friction coefficient.

5. The method for calculating characteristic vehicle speed by combining road surface and aging factors according to claim 4, characterized in that, The step of determining the comprehensive road friction coefficient based on the vehicle state parameters includes: The comprehensive road surface friction coefficient is calculated using the following formula: ； in, To take into account the road surface friction coefficient, For longitudinal acceleration, It is the acceleration due to gravity. The coefficient of friction for dry road surfaces. The rate of decrease of the adhesion factor, For the first The slip ratio of each wheel Number the wheels. Based on the basic slip ratio threshold, For the threshold sensitivity of wheel instability, For the first The angular deceleration of each wheel, For the moment of inertia of the wheel, The radius of the wheel's rolling motion. For the first The braking pressure of each wheel cylinder. The braking gain constant is... This is a user-defined constant.

6. The method for calculating characteristic vehicle speed by combining road surface and aging factors according to claim 4, characterized in that, The step of determining the road surface identification factor based on the wheel speed fluctuation factor, the pressure activity factor, and the comprehensive road surface friction coefficient includes: The road surface identification factor is calculated according to the following formula: ； in, For road surface identification factors, To take into account the road surface friction coefficient, For wheel speed fluctuation factor, It is a stress-active factor.

7. A characteristic vehicle speed calculation device, characterized in that, It includes a processor and a memory, the memory storing a program or instructions that can run on the processor, the program or instructions being executed by the processor to implement the steps of a method for calculating characteristic vehicle speed by combining road surface and aging factors as described in any one of claims 1 to 6.

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