Method for obtaining lateral slack length and applications

Abstract

The application provides a method for obtaining a lateral relaxation length, comprising: obtaining a curve of a side slip angle and a lateral force with time, to obtain a SA-t curve and a F y -t curve respectively; a data processing step, comprising: eliminating the influence of the taper effect of the tire and the angle effect of the cord layer on the F y -t curve; and a lateral relaxation length calculation step, comprising: linearly fitting the SA-t curve and the F y -t curve in the same time period of a cycle respectively, calculating the time t1 when the side slip angle is 0 and the time t2 when the lateral force is 0 respectively according to the fitting result, obtaining a relaxation time Δt=t2-t1; and calculating the lateral relaxation length according to a formula R ly =(V r *Δt) / 3.6.

Description

Technical Field

[0001] This application belongs to the field of tire technology, and specifically relates to a method for obtaining lateral slack length and its application. Background Technology

[0002] In current research on vehicle and tire dynamics, the mechanical properties of a tire consist of two parts: steady-state mechanical properties and transient properties. The data in the steady-state properties can describe the dynamic driving process of the tire. However, the steady-state property data cannot fully reflect the tire force and torque situation at the moment of vehicle rollover or sudden braking. At this time, the study of tire transient properties becomes extremely important.

[0003] The transient response of a tire mainly includes relaxation length, inertia, and gyroscopic effects. Among these, lateral relaxation length is one of the important parameters for evaluating tire transient characteristics, and its magnitude reflects, to some extent, how quickly the tire responds to external forces. Subjective evaluation in real-world vehicles also includes transient road tests, which typically involve rapidly turning the steering wheel left and right at a certain angular velocity to feel the responsiveness of the steering wheel to the driving direction, reflecting the tire's steering sensitivity. In indoor tests, lateral relaxation length (the distance the tire rolls) is often used to predict the steering sensitivity of the real-world vehicle. Furthermore, lateral relaxation length is an important module in the tire PAC (Personal Acoustic Control) model used for vehicle dynamics simulation; therefore, accurately calculating lateral relaxation length is a crucial means of improving the accuracy of tire handling and vehicle dynamics simulation models.

[0004] Based on existing methods for testing and calculating lateral relaxation length, there are three main types:

[0005] One approach is to approximate the lateral relaxation length by using the ratio of tire lateral stiffness to tire offset stiffness using the stiffness equivalence method. This method requires both tire offset stiffness and tire carcass lateral stiffness. However, due to the lack of equipment to test tire carcass stiffness separately, the ratio of the overall tire's lateral stiffness to offset stiffness is used as an approximation. This results in inaccurate calculations. Furthermore, tire offset stiffness and tire lateral stiffness require two separate testing devices, further increasing testing costs. Additionally, the errors caused by the two testing devices must be considered simultaneously, which significantly reduces the reliability of the data.

[0006] Secondly, using the step angle test, the tire's lateral force is slowly accelerated at a fixed sideslip angle to obtain a curve showing the change of lateral force over time. The time corresponding to 63.2% of the steady-state lateral force is calculated as the relaxation time, and the product of this time and the speed is the lateral relaxation length. This method uses the change of speed and a fixed sideslip angle to achieve the dynamic response of the tire. However, since the speed is constantly changing, it will affect the value of the tire's lateral force, thus affecting the accuracy of the value. Moreover, this method is generally used at speeds below 10 km / h, which is seriously inconsistent with the actual vehicle speed, making it difficult to establish a correlation and predict steering performance.

[0007] Thirdly, a sinusoidal sweep sideslip angle test using a six-component force test bench is employed to obtain sinusoidal transfer functions of the lateral force and sideslip angle as a function of time. Based on the transfer function, the phase difference between the two is obtained, and the time difference between the input and output signals is calculated. The product of the time difference and the test speed equals the lateral relaxation length. This method, based on the sinusoidal transfer function, obtains the phase difference between the lateral force and sideslip angle after sinusoidal fitting, calculates the time difference, and then obtains the lateral relaxation length. On the one hand, the computational cost is increased due to the need to use Matlab software for sinusoidal fitting. On the other hand, it requires first fitting all data to obtain the phase difference between the two, then obtaining the time difference, and finally calculating the lateral relaxation length. The calculation process is cumbersome and inefficient, and the unstable data in the first part of the test is not removed, affecting the data accuracy. Summary of the Invention

[0008] The purpose of this application is to provide a method and application for obtaining lateral relaxation length. The lateral relaxation length obtained by this method is relatively stable and can be used to predict tire steering sensitivity.

[0009] The first aspect of this application provides a method for obtaining lateral relaxation length, comprising the following steps:

[0010] The steps for obtaining the curves showing the changes in sideslip angle and lateral force over time yield at least one period of SA-t curve and F. y -t curve;

[0011] The data processing steps include: eliminating the conicity effect of the tire and the angular effect of the ply layer on the F y The impact of the -t curve; and

[0012] The calculation steps for the lateral relaxation length include: linearly fitting the SA-t curve and F within the same time period of the same period, respectively. y Based on the fitting results of the -t curve, calculate the time t1 when the sideslip angle is 0 and the time t2 when the lateral force is 0 in the same period, and obtain the relaxation time Δt = t2 - t1; according to the formula R ly =(V r *Δt) / 3.6 calculates the lateral relaxation length; where Rly V is the lateral relaxation length, in meters. r The test speed is measured in km / h, and Δt is the relaxation time in seconds.

[0013] In some embodiments of this application, in the step of obtaining the curves of the change of the sideslip angle and the lateral force over time, a six-component force test bench is used, and the input parameters are loaded by setting a periodic triangular sweep sideslip angle.

[0014] In some embodiments of this application, the side deviation angle is not greater than 2°, so that the positive peak value of the SA-t curve is not greater than 2° and the negative peak value is not less than -2°.

[0015] In some embodiments of this application, the data processing steps further include: acquiring the SA-t curve and F... y - Data from multiple stable periods of the -t curve. For example, deleting unstable data from the first period, or selecting data from multiple intermediate stable periods across several periods.

[0016] In some embodiments of this application, the data processing steps further include: targeting F y The -t curve eliminates the effects of tire taper and ply angle by shifting the coordinate system.

[0017] In some embodiments of this application, the data processing step further includes: calculating F y The average value of the positive peak avg1 and the average value of the negative peak avg2 of the -t curve are obtained using the formula... Calculate the displacement D; by using F y -t curve shifts by D, making F y The positive and negative peaks of the -t curve are approximately equal to eliminate the effects of tire taper and ply angle.

[0018] In some embodiments of this application, F after the data processing steps y The -t curve and the SA-t curve have at least two cycles; calculate the lateral relaxation length of each cycle according to the lateral relaxation length calculation steps described above, and then calculate the average value of these lateral relaxation lengths as the lateral relaxation length of the tire.

[0019] In some embodiments of this application, F after the data processing steps y The -t curve and the SA-t curve have at least two periods; the calculation steps for the lateral relaxation length more specifically include: linearly fitting the SA-t curve and the F curve within the same time period of the same period, respectively. yBased on the fitting results of the -t curve, calculate the time t1 when the sideslip angle is 0 and the time t2 when the lateral force is 0 in the same cycle, and obtain the relaxation time Δt = t2 - t1. Then, calculate the relaxation time for each cycle in the at least two cycles using the above steps, and calculate the average value Δt' of these relaxation times. Finally, use formula R... ly =(V r *Δt') / 3.6 calculates the lateral relaxation length, which is taken as the lateral relaxation length of the tire; where R ly V is the lateral relaxation length, in meters. r The test speed is measured in km / h, and Δt' is the average relaxation time in seconds.

[0020] In some embodiments of this application, when F is processed by the data processing steps... y When the -t curve and the SA-t curve have at least two periods, the calculation step of the lateral relaxation length further includes:

[0021] When performing linear fitting on the SA-t curve, the time periods for each period are selected from the same rising or falling segment of the SA-t curve; for F y When performing linear fitting on the -t curve, choose the same time period as the SA-t curve; or...

[0022] In the case of F y When performing linear fitting on the -t curve, the time period for each period is selected as F. y -t segment on the same rising or falling segment; when linearly fitting the SA-t curve, choose the segment with F. y -t curves for the same time period.

[0023] The second aspect of this application provides an application of lateral relaxation length in the study of tire transient characteristics, wherein the lateral relaxation length is obtained by the method for obtaining lateral relaxation length described in any of the preceding embodiments.

[0024] A third aspect of this application provides an application of lateral relaxation length in the study of tire steering sensitivity, wherein the lateral relaxation length is obtained by the method for obtaining lateral relaxation length described in any of the preceding embodiments.

[0025] Compared with the prior art, the beneficial effects of this application are as follows:

[0026] The method for obtaining the lateral relaxation length provided in at least one embodiment of this application is an efficient and accurate method for calculating the lateral relaxation length using the triangular sweep method.

[0027] Compared to current methods for testing lateral relaxation length, this method fully utilizes the physical meaning of lateral relaxation length, combining it with vehicle steering input and tire response output to obtain the time difference between the input sideslip angle and the output lateral force, thereby obtaining the lateral relaxation length.

[0028] Compared to current methods for processing lateral relaxation length test data, this method considers both the instability caused by the equipment immediately executing the loading command and the inconsistent lateral force amplitudes due to the tire's ply angle and taper effect, which result in the same slip angle. Through data preprocessing, it eliminates unstable data from the initial period and removes the influence of tire ply angle and taper effects, thereby improving data accuracy and ensuring data reliability.

[0029] Compared to current methods for processing lateral relaxation length test data, this method only uses linear fitting to obtain the lateral relaxation length, without the need for data processing tools such as Matlab, resulting in low computational cost and high efficiency.

[0030] In summary, this application makes full use of the physical meaning of lateral relaxation length, the experimental process is simple and efficient, and the data processing takes into account the influence of other factors on the data from multiple perspectives, which ensures the rationality and correctness of the calculation results to the greatest extent. Moreover, the fitting method is simple, effective and low-cost, which is conducive to long-term sustainable development. Attached Figure Description

[0031] Figure 1A This is an SA-t curve diagram of one implementation method;

[0032] Figure 1B F is one implementation method y -t curve;

[0033] Figure 2 It is the SA-t curve and F y Overlay plot of -t curves;

[0034] Figure 3 Yes Figure 2 The image after the first cycle of deletion;

[0035] Figure 4 Yes Figure 3 F in y The graph after adjusting the -t curve;

[0036] Figure 5A One embodiment of the SA-t curve;

[0037] Figure 5B F is an example of an embodiment y -t curve;

[0038] Figure 6A Yes Figure 5A The image after the first cycle of deletion;

[0039] Figure 6B Yes Figure 5B The image after the first cycle of deletion;

[0040] Figure 7 Yes Figure 6B Perform F y The graph after adjusting the -t curve;

[0041] Figure 8A Yes Figure 6A The graph after linear fitting;

[0042] Figure 8B Yes Figure 7 The graph after linear fitting;

[0043] Figure 9A This is a diagram showing the lateral relaxation length test results for a tire design.

[0044] Figure 9B This is a graph showing the lateral slack length test results for another tire design.

[0045] Figure 10 This is a comparison chart of lateral slack length tests for different tire designs. Detailed Implementation

[0046] The technical solutions of this application are described in detail below with reference to specific embodiments. However, it should be understood that, without further description, the elements, structures and features in one embodiment can also be beneficially incorporated into other embodiments.

[0047] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0048] The physical meaning of lateral relaxation length is as follows: During vehicle steering, the driver turns the steering wheel at a certain angular velocity. Since the tire is a viscoelastic object made of rubber and other skeleton materials, the lateral force generated after the steering wheel turns does not cause the tire to respond and rotate immediately. Instead, the rigid rim will first rotate a certain angle with the steering wheel according to the vehicle's gear ratio. After traveling for a period of time, the tire reaches the steering angle of the rim. This time is called relaxation time. The distance the tire travels during this relaxation time is called lateral relaxation length. Essentially, it refers to the lag between the vehicle's input slip angle and the lateral force generated by tire deformation.

[0049] The first aspect of this application provides a method for obtaining lateral relaxation length, which includes:

[0050] (1) Steps for obtaining the curves of the change of sideslip angle and lateral force over time.

[0051] A six-component force test bench can be used to simulate the changes in tire force and torque during small-angle vehicle steering. This allows for the determination of the difference between the input slip angle and the output lateral force at small angles, thus obtaining the curves of the slip angle and lateral force changing over time. In this application, "small angle" generally refers to a slip angle α ≤ 2°, such as 0.8°, 1°, 1.2°, 1.5°, 1.8°, 2°, etc.

[0052] Using a six-component force test bench to simulate tire parameter changes during vehicle steering is a common technique in this field. This application utilizes this test bench to obtain the curves of the slip angle and lateral force over time, which is also a standard procedure. Specifically, it may include a pre-break-in step and a formal testing step; wherein:

[0053] The pre-run-in step is as follows: set test parameters such as speed, load and sideslip angle on a six-component force test bench, and conduct a pre-run-in test on the tire to eliminate residual stress in the tire during assembly and prevent it from affecting the test data.

[0054] The formal testing steps are as follows: ① Set the speed to V r It can be consistent with the actual driving speed of the vehicle, for example, V. r ① Speeds of 60km / h, 80km / h, etc., are used to improve the accuracy of predicting the steering performance of the actual vehicle; ② Real-time air pressure control is adopted to ensure that the test data is not affected by changes in air pressure with temperature; ③ The load is set to the front axle load of the vehicle, consistent with the driving state, to improve the prediction accuracy; ④ Input parameters are loaded by periodically sweeping the triangular angle ±α°; for a six-component force test bench, the triangular sweep method is simpler to implement, and compared with other filtering methods for data fitting and filtering, the triangular sweep method can reduce the fitting error; ⑤ The input side slip angle α and the output lateral force F are collected. y Changes over time.

[0055] The sideslip angle α and the lateral force F can be obtained through the above operations. y Curve showing how it changes over time. Figure 1A and Figure 1B The figures show, respectively, the curves of the sideslip angle versus time (i.e., the SA-t curve) and the curves of the lateral force versus time (i.e., the F curve) obtained by the triangular sweep method in a six-component force test rig according to one embodiment. y -t curve), where the periodic triangular sweep is ±1° lateral slip angle. To better compare the differences between the two over time, in Figure 2 Lieutenant General SA-t curve and F y The -t curves were superimposed, and the lateral force F was considered. y The sign of F has been processed (i.e., F) y -t curve was horizontally inverted; Figure 2 The middle circle shows the value of F when the SA-t curve reaches 0. y The -t curve takes longer to reach 0, indicating a lag. This means that the output lateral force lags behind the input sideslip angle during the relaxation time.

[0056] (2) Data processing steps

[0057] The data processing steps include:

[0058] 2.1 Obtain data from stable periods to reduce experimental errors.

[0059] This implementation removes the unstable data from the first cycle. Because the six-force test bench experiences slight fluctuations when it first executes the command to test the tire, leading to unstable data, the unstable data from the first cycle needs to be removed during the calculation process. The curve after removal is shown in [image / description]. Figure 3 . Figure 2 Zhongyuan initially tested data from three cycles. After removing the unstable data from the first cycle, in Figure 3 Only two periods of data remain. However, it is worth noting that in actual testing, different numbers of periods can be selected based on the required accuracy, such as five periods of data, ten periods of data, etc., and then the data from the first period can be discarded; or several periods with stable data can be selected from multiple periods, for example, if a total of ten periods of data were tested, the data from periods 3 to 8 can be selected.

[0060] 2.2 Eliminate the influence of tire taper effect and ply angle effect on the data.

[0061] For F y The -t curve, by shifting the coordinate system, eliminates the effects of tire taper and ply angle on F. y The influence of the -t curve.

[0062] from Figure 2 and Figure 3 It can be seen that at a sideslip angle of ±1°, F y The positive and negative peak values ​​of the -t curve differ significantly. Theoretically, under the same sideslip angle α, F y The absolute values ​​of the positive and negative peaks of the -t curve should be similar; however, due to the influence of the tire's ply angle and taper effects, F y The positive and negative peaks of the -t curve differ significantly. Figure 3The positive peak value is approximately 1200N, and the negative peak value is approximately -1000N. The absolute difference between the two is |1200|-|-1000|=200N. This will have a certain impact on the calculation of the lateral relaxation length, increase the calculation error, and reduce the reliability of the data.

[0063] This effect can be removed through the following data processing methods. Figure 3 In the process, obtain the positive peak value of the stable period and calculate the average value as avg1; obtain the negative peak value of the same stable period and calculate the average value as avg2, and use the formula... Calculate the displacement D; by adding or subtracting D from the original lateral force data, adjust F. y - The overall upward or downward shift of the -t curve eliminates the effects of tire cord layer angle and taper effects, making F y The positive and negative peaks of the -t curve are close.

[0064] For example, in Figure 3 In the above, assuming the calculated average value of the positive peaks is avg1 = approximately 1200, and the average value of the negative peaks is avg2 = -1000, then... Will Figure 3 F in y -Shift the t curve down by 100 to obtain Figure 4 The attached diagram is shown. From Figure 4 As can be seen from the data, after removing the taper effect and the angle effect of the fabric layer, F... y The peak values ​​of the -t curves are close. During this process, the SA-t curve does not require adjustment.

[0065] (3) Calculation of lateral relaxation length

[0066] After the data processing steps, the SA-t curve and F curve within the same time period of the same cycle are linearly fitted using the formula y = a1*x + b1. y Based on the fitting results of the -t curve, calculate the time t1 when the slip angle is 0 and the time t2 when the lateral force is 0 in the same cycle. Due to the tire's hysteresis characteristics, t2 > t1 in the same cycle. The tire's hysteresis time (i.e., relaxation time Δt) is: Δt = t2 - t1; according to the formula for calculating the lateral relaxation length: R ly =(V r The lateral relaxation length for the same period can be calculated using *Δt) / 3.6; where R ly V is the lateral relaxation length, in meters. r The test speed is measured in km / h, and Δt is the relaxation time in seconds.

[0067] Calculate the lateral relaxation length for each cycle using the method described above, and then calculate the average of the lateral relaxation lengths for each cycle to obtain the tire's lateral relaxation length. Alternatively, you can first calculate the relaxation time Δt for each cycle, then calculate the average relaxation time Δt' for each cycle, and then use the formula R... ly =(V r Calculate and obtain the lateral relaxation length of the tire using *Δt') / 3.6.

[0068] As described above, within the same period, for the SA-t curve and F... y The -t curve is fitted using the same time period. However, when linearly fitting the SA-t curve between different periods, the time period for each period must be the same rising or falling segment of the SA-t curve; for F... y When performing linear fitting on the -t curve, the same time period as the SA-t curve should be selected. For example, in Figure 4 In fitting the SA-t curve, if the rising segment (A2) is selected in the second period, then the rising segment (A3) must be selected in the third period; similarly, if the falling segment is selected in a certain period, then the corresponding falling segment must be selected in other periods.

[0069] Similarly, you can also choose F first. y -t curve, and then fit the SA-t curve; at this time, when F y When performing linear fitting on the -t curve, the time intervals for each period need to be selected using F. y -t curves are selected from the same rising or falling segment; when linearly fitting the SA-t curve, the same segment as F is chosen. y -t curves operate over the same time period. These two methods are completely equivalent.

[0070] Furthermore, it is worth noting that regardless of the method used Figure 1B F in y -t curve performs data processing steps or selects Figure 2 F after horizontal flipping y The data processing steps performed on the -t curve will not affect the final relaxation time Δt. This is because, although the curves obtained by linear fitting using the formula y=a1*x+b1 after processing the two curves mentioned above will have positive and negative differences, the time t2 calculated when the lateral force is 0 will not change (i.e., the time value when the ordinate is 0 will not change). Therefore, it will not affect the final result.

[0071] The second aspect of this application provides an application of a lateral relaxation length, which can be obtained using the acquisition method described in any of the preceding embodiments and can be used for the study of tire transient characteristics.

[0072] A third aspect of this application provides an application of a lateral relaxation length, which can be obtained using the acquisition method described in any of the preceding embodiments and can be used for the study of tire steering sensitivity.

[0073] The following description, in conjunction with more specific embodiments, will further illustrate this document. Based on the foregoing, this embodiment will first utilize the stability of the lateral relaxation length over time using different methods to verify the superiority of the triangular sweep method for obtaining the lateral relaxation length provided in this embodiment, and will then detail the calculation process of the lateral relaxation length using the triangular sweep method. Secondly, it will calculate the lateral relaxation length for different tire configurations and compare it with the results of real-vehicle tests.

[0074] Comparative example:

[0075] To verify the stability of the lateral relaxation length acquisition method provided in this application, two sizes with significant differences, 215 / 65R17 and 235 / 55R18 (supplied by Qingdao Sentury Tire Co., Ltd.), were used to test different lateral relaxation length methods. First, raw data was obtained using a six-component force test bench, with a test speed of 60 km / h and a sideslip angle α = 1°. Then, the raw data was calculated using the stiffness method, angular step method, and sine method, respectively.

[0076] Stiffness method: Lateral relaxation length = Lateral stiffness / Lateral stiffness.

[0077] Angular step method: Calculate the time corresponding to 63.2% of the steady-state lateral force, and then use the product of time and velocity to obtain the lateral relaxation length.

[0078] Sine method: Using Matlab software, the raw data of the input sideslip angle and output lateral force as a function of time are processed according to the sine fitting formula f(t)=a1*sin(b1*t+c1), b1=2π*f, where f(t) is the sideslip angle and lateral force, f is the frequency (f=1Hz in this method), and the other parameters are the parameters after sine fitting. After fitting, the phases c1 and c2 of the sideslip angle and lateral force are obtained. According to the phase difference and the formula Δt=(|c1-c2|) / b1, the time difference, i.e., the relaxation time, can be obtained. Finally, the lateral relaxation length is obtained by multiplying the relaxation time by the velocity.

[0079] The calculation processes of these three testing methods have the following major problems:

[0080] The stiffness method uses the ratio of the tire's lateral stiffness to its lateral stiffness as an equivalent, which leads to inaccurate calculation results. Furthermore, it requires the use of two different testing devices, further increasing testing costs. In addition, the errors caused by the two testing devices must be taken into account, which greatly reduces the reliability of the data.

[0081] Angular step method: The speed of the angular step test method is constantly changing, which affects the value of the lateral force generated by the tire; moreover, the speed of this method is generally below 10km / h, which is seriously inconsistent with the actual vehicle speed, making it difficult to establish a correlation and predict steering performance.

[0082] Sine method: On the one hand, the computational cost increases because it requires the use of Matlab software for sine fitting; on the other hand, it requires first fitting all the data to obtain the phase difference between the two, and then obtaining the time difference, which is a complicated and inefficient calculation process. In addition, it does not remove the unstable data in the first part of the test, which affects the accuracy of the data.

[0083] The above three methods have problems such as cumbersome calculation process and inaccurate calculation results.

[0084] Example:

[0085] The process of obtaining the lateral relaxation length according to the method provided in this application is as follows:

[0086] (1) Taking the test data of specification 215 / 65R17 as an example, the calculation process for specification 235 / 55R18 is the same. After completing the tire pre-break-in and formal test, the six-component force test bench outputs the original test data, and plots the curves of the side slip angle and lateral force in the original data over time, respectively obtaining the SA-t curve and F. y -t curve (containing three periods), such as Figure 5A and Figure 5B As shown; further removing unstable data from the first period, the resulting curve is as follows. Figure 6A and Figure 6B As shown (only two cycles remain).

[0087] (2) Due to the influence of the tire's ply angle effect and taper effect, F y The positive and negative peak values ​​of the -t curve differ significantly (e.g.) Figure 6B By moving downwards. Figure 6B The coordinate system in the middle (equivalent to moving upwards by F) y -t curve), making F y The difference between the positive and negative peaks of the -t curve is reduced and becomes approximately equal, thus eliminating the effects of tire ply angle and taper effects. The processed curve is as follows: Figure 7 As shown.

[0088] (3) Using the formula y=a1*x+b1, linearly fit the two periods respectively, selecting data within the time intervals t of 3~3.5s and 5.2~5.7s (for the SA-t curve, the rising segment is selected; or for F y -t curves, all selected from the descending segment).

[0089] This example illustrates the fitting and subsequent calculation process of data within a 3-3.5s time period: Data on the changes in lateral force and sideslip angle over time are selected within this 3-3.5s time period. A linear fit is then performed using the linear equation y = a1*x + b1 to fit the sideslip angle-time and lateral force-time. Figure 8A and Figure 8B As shown in the figure, the fitting accuracy R for the sideslip angle and lateral force is greater than 99%, indicating high fitting accuracy and stable and reliable data. Based on their formulas, t1 and t2 are calculated when the sideslip angle and lateral force are both 0. Due to the hysteresis effect, the output lateral force requires more time to reach 0, i.e., t2 > t1. The relaxation time Δt = t2 - t1 is then calculated. Finally, the relaxation time Δt is used in conjunction with the velocity V... r Calculate the lateral relaxation length R by multiplying the product of the speeds by 60 km / h. ly =(V r *Δt) / 3.6.

[0090] (4) Using the same calculation method, the slip angle and lateral force data within the time period of 5.2 to 5.7s are linearly fitted to obtain the relaxation time Δt, and the lateral relaxation length is calculated; the average value of the lateral relaxation length of the two cycles is further calculated to obtain the lateral relaxation length of the tire.

[0091] (5) Repeat steps (1)-(4) to calculate the lateral relaxation length for the other test times (a total of four days) for both specifications. Figure 9A and Figure 9B The figure shows the curves of two different test methods as a function of test time. Figure 9A and Figure 9B The curve results of different testing methods show that, compared with the stiffness method, angular step method and sine method, the lateral relaxation length provided by this embodiment changes most stably with test time.

[0092] (6) Repeat steps (1)-(4) to calculate the lateral relaxation length test data for different tire schemes, and compare the results as follows: Figure 10 As shown in the figure, different tire designs have different lateral relaxation lengths. Case 1 has the lowest sensitivity, while case 4 has the highest sensitivity. On the one hand, according to theoretical knowledge, the lateral relaxation length reflects the tire's steering sensitivity, which can be used to predict the steering sensitivity of the actual vehicle and reduce the cost of actual vehicle testing. On the other hand, the differences between the designs are relatively small overall, so the stability and reliability of the data must be ensured during testing and calculation in order to apply it to the matching of steering performance with the actual vehicle.

[0093] The above embodiments detail the calculation principle and process of the lateral relaxation length of the triangular sweep method, and verify it with different test methods. The results show the effectiveness of the triangular sweep calculation method involved in this embodiment, which can be processed using a conventional Excel spreadsheet.

[0094] This embodiment firstly compares different lateral relaxation length methods, demonstrating the high stability of the lateral relaxation length acquisition method provided in this application; secondly, it examines the lateral relaxation length values ​​under different tire designs and matches them with real-vehicle subjective steering evaluation. Firstly, lateral relaxation length is a crucial tool for studying tire transient characteristics, reflecting tire steering sensitivity. By comparing the lateral relaxation lengths of different tire designs to predict real-vehicle steering sensitivity, the cost of real-vehicle testing is reduced. Secondly, accumulating lateral relaxation length test data for different tire structures provides data reserves for improving vehicle steering sensitivity. Thirdly, as a key input module of the tire PAC handling and stability model, improving the accuracy of lateral relaxation length data is beneficial for improving tire model accuracy and further enhancing the accuracy of the vehicle dynamics simulation model.

[0095] Compared with existing methods for calculating lateral relaxation length, the triangular sweep data processing method involved in this application has a simple calculation process, does not require the use of other software for fitting, is low in cost, easy to operate, has high data accuracy, and has a certain degree of stability. It can reduce testing and fitting errors, improve the accuracy of tire models, and further improve the accuracy of vehicle dynamics simulation models, which is of great significance for the study of vehicle dynamics simulation.

[0096] This application, based on the theory of lateral relaxation length, fully utilizes the physical meaning of relaxation length. Considering that the tire is a rubber elastomer and exhibits hysteresis during response, the hysteresis time is used to calculate the lateral relaxation length. In practice, an indoor test using a six-component force test bench is conducted. The sideslip angle is applied in a triangular sweep manner, and data on the change of lateral force output parameters over time are collected. This yields curves showing the change of input sideslip angle and output lateral force over time. The influence of the tire's taper effect and ply angle effect on the data is eliminated by shifting the coordinate system upwards. Furthermore, unstable test data from the first cycle is removed to reduce experimental error. The average time difference of the remaining cycles is calculated to ensure reliable results. This method fully utilizes theoretical knowledge and the actual physical meaning of parameters, eliminates unstable data and the influence of the tire itself during testing, has low testing costs, a simple and efficient calculation process, and high accuracy.

[0097] The described embodiments are merely preferred embodiments of this application and are not intended to limit the scope of this application. Any modifications and improvements made by those skilled in the art to the technical solutions of this application without departing from the spirit of this application shall fall within the protection scope defined by the claims of this application.

Claims

1. A method for obtaining lateral relaxation length, characterized in that, Includes the following steps: The steps for obtaining the curves of the change in sideslip angle and lateral force over time are to obtain at least one period of... SA-t curves and F y -t curve; The data processing steps include: eliminating the effects of tire taper and ply angle on the tire. F y -t The influence of the curve; and The steps for calculating the lateral relaxation length include: linearly fitting the same time interval of the same period. SA-t curves and F y -t Based on the fitting results, calculate the time when the lateral slip angle is 0 for the same period of the curve. t 1 and the time when the lateral force is 0 t 2. Obtain the relaxation time Δt=t 2 -t 1; According to the formula R ly =(V r *Δt) / 3.6 Calculate the lateral relaxation length; where R ly The lateral relaxation length is expressed in meters (m). V r For testing speed, the unit is km / h. Δt Relaxation time, in seconds; The data processing steps include: calculation F y -t The average of the positive peaks of the curve avg 1, and the average value of the negative peak. avg 2. Using the formula Calculate the displacement D By F y -t Curve movement D , making F y -t The positive and negative peaks of the curve are approximately equal to eliminate the effects of tire taper and ply angle.

2. The method for obtaining the lateral relaxation length according to claim 1, characterized in that, In the step of obtaining the curves of the change of sideslip angle and lateral force over time, a six-component force test bench is used, and the input parameters are loaded by setting a periodic triangular sweep sideslip angle.

3. The method for obtaining the lateral relaxation length according to claim 2, characterized in that, The side slip angle is no greater than 2°, therefore the SA-t The positive peak of the curve is no greater than 2°, and the negative peak is no less than -2°.

4. The method for obtaining the lateral relaxation length according to any one of claims 1-3, characterized in that, The data processing steps also include: acquiring SA-t curves and F y -t Data for multiple stable periods of the curve.

5. The method for obtaining the lateral relaxation length according to any one of claims 1-3, characterized in that, After the data processing steps are described above F y -t curves and SA-t The curve has at least two periods; The lateral relaxation length of each cycle is calculated according to the lateral relaxation length calculation steps described above, and then the average value of these lateral relaxation lengths is calculated as the lateral relaxation length of the tire. or, The calculation steps for the lateral relaxation length more specifically include: linearly fitting the same time period of the same period. SA-t curves and F y -t Based on the curve, the time t1 when the sideslip angle is 0 and the time t2 when the lateral force is 0 are calculated for the same period, respectively, to obtain the relaxation time. Δt=t 2 -t 1. Calculate the relaxation time for each of the at least two cycles using the steps described above, and then calculate the average of these relaxation times. Δt' Using formula R ly =(V r *Δt') / 3.6 Calculate the lateral relaxation length, which is taken as the lateral relaxation length of the tire; where R ly The lateral relaxation length is expressed in meters (m). V r For testing speed, the unit is km / h. Δt' This represents the average relaxation time, expressed in seconds.

6. The method for obtaining the lateral relaxation length according to any one of claims 1-3, characterized in that, After the data processing steps are completed F y -t curves and SA-t When the curve has at least two periods, the calculation step of the lateral relaxation length further includes: In the SA-t When performing linear fitting on the curve, the time period for each cycle is selected. SA-t The same rising segment or the same falling segment on the curve; for F y -t When performing linear fitting on a curve, choose with SA-t The same time period for the curves; or, In the F y -t When performing linear fitting on the curve, the time period for each cycle is selected. F y -t The same rising segment or the same falling segment on the curve; for SA-t When performing linear fitting on a curve, choose with F y -t The curves are the same for the same time period.

7. An application of lateral relaxation length in the study of tire transient characteristics, characterized in that, The lateral relaxation length is obtained using the method for obtaining the lateral relaxation length as described in any one of claims 1-6.

8. An application of lateral relaxation length in the study of tire steering sensitivity, characterized in that, The lateral relaxation length is obtained using the method for obtaining the lateral relaxation length as described in any one of claims 1-6.

Images