Method for testing longitudinal relaxation length of tire

Abstract

The invention provides a method for testing the longitudinal relaxation length of a tire, solves the technical problems that the loading of an existing six-component triangular wave is difficult to control, corresponding errors exist when more parameters are obtained in a formula, and the result of the longitudinal relaxation length is inaccurate, and can be widely applied to the field of tire performance testing. The method specifically comprises the following steps: carrying out zero setting calibration on a tire six-component testing machine; mounting the inflated tire on a mechanical testing machine, and preheating the tire until the tire reaches heat balance; after the tire reaches heat balance, setting a slip angle and a slip angle parameter, enabling the tire to roll at a test speed, and collecting sine sweep frequency test data in a test slip rate range; changing the scanning frequency of sine frequency sweep, and collecting sine frequency sweep test data under different scanning frequencies; de-noising all the sine frequency sweep test data to obtain pure data; the pure data is converted into frequency domain data, then spectrum analysis is carried out, and the longitudinal relaxation length of the tire is calculated.

Description

Technical Field

[0001] The invention belongs to the technical field of tire performance testing, and in particular relates to a method for testing the longitudinal relaxation length of a tire. Background Art

[0002] For a vehicle, the tire is the only part of the vehicle that contacts the ground. Therefore, the study of the braking performance of the vehicle must start from the study of the mechanical properties of the tire. The longitudinal relaxation length of the tire is the main mechanical parameter of the tire research. The tire model parameters can be obtained through the identification of the PAC2002 tire model, and the longitudinal transient simulation of the whole vehicle can be performed to evaluate the linear braking performance of the vehicle. At present, the main methods for studying the longitudinal relaxation length of the tire are the stiffness method and the triangular wave sweep frequency method. The stiffness method is the ratio of the longitudinal sliding stiffness measured by the six-component force testing machine and the longitudinal stiffness measured by the five-component stiffness testing machine. Since it is two devices, the cost is high, the test is cumbersome, the efficiency is relatively low, and the errors of the two devices are included, and the data accuracy is low. The triangular wave sweep frequency method is to measure the loading rate and loading amplitude of the tire longitudinal slip rate, so that the tire longitudinal slip rate is loaded according to the set triangular wave, and the longitudinal slip rate is loaded according to the set triangular wave loading method to collect test data, wherein the test data at least includes the tire longitudinal force Fx, longitudinal slip rate Sx, longitudinal slip rate loading rate Vr and longitudinal slip stiffness Kx, and then calculate the longitudinal relaxation length of the tire. Since the six-component triangular wave loading is difficult to control and there are corresponding errors when obtaining the parameters in the formula, the result of the longitudinal relaxation length is inaccurate. Summary of the invention

[0003] The purpose of the present invention is to solve the shortcomings of the above technology and provide a method for testing the longitudinal relaxation length of a tire.

[0004] To this end, the present invention provides a method for testing the longitudinal slack length of a tire, comprising the following steps:

[0005] S10: Zeroing and calibrating the tire six-component force testing machine;

[0006] S20: installing the inflated tire on a mechanical testing machine to preheat the tire until the tire reaches thermal equilibrium;

[0007] S30: after the tire reaches thermal equilibrium, setting the slip angle and slip angle parameters, rolling the tire at a test speed, and collecting sine sweep test data within a test slip rate range;

[0008] S40: changing the sweep frequency of the sine sweep frequency, and collecting sine sweep frequency test data at different sweep frequencies;

[0009] S50: denoising all the sine sweep test data to obtain pure data;

[0010] S60: Convert the clean data into frequency domain data, and then perform spectrum analysis to calculate the longitudinal slack length of the tire.

[0011] Furthermore, the inflated tire is mounted on a mechanical testing machine to preheat the tire until the tire reaches thermal equilibrium. The specific steps are:

[0012] The inflated tire and rim assembly is mounted on a mechanical testing machine, and the tire is rolled at a speed of 60 km / h and the maximum tire load. The tire is preheated for 3 minutes at slip rates equal to -3%, 0 degrees and +3%, 0 degrees, respectively. Subsequently, the tire is deflected at an angular velocity of 0.5 degrees / s, and the sideslip angle is controlled within the range of ±10 degrees to preheat the test tire until it reaches thermal equilibrium.

[0013] Furthermore, after the tire reaches thermal equilibrium, the slip angle and slip angle parameters are set, the tire is rolled at a test speed, and the specific steps of collecting sine sweep test data within the test slip rate range are as follows:

[0014] The tire load was applied to 100% of the reference load, the slip angle was set to 0 degrees, the roll angle was set to 0 degrees, the tire was rolled forward at a speed of 60 km / h, and then a sine sweep test was performed at a slip rate of -1% to +1% to collect test data.

[0015] Furthermore, test data of multiple cycles are collected, and the test data are filtered to eliminate the influence of high-frequency signals on the data, so as to obtain pure data.

[0016] Furthermore, the test data is filtered using an elliptical low-pass filter.

[0017] Furthermore, the clean data is converted into frequency domain data, and then spectrum analysis is performed. The specific steps for calculating the longitudinal relaxation length of the tire are as follows:

[0018] Perform Fourier transform on the slip rate in the clean data to convert the time domain data into frequency domain data;

[0019] Perform spectrum analysis on the data after Fourier transformation to determine the maximum amplitude of the slip rate SR and the longitudinal force Fx, the frequency corresponding to the maximum amplitude, and the phase corresponding to the maximum amplitude;

[0020] Calculate the phase difference between Fx and SR

[0021]

[0022] Then calculate the tire rolling time t:

[0023]

[0024] Where T is the period of the sine wave;

[0025] Finally, calculate the relaxation length L x :

[0026] L x =V t *t;

[0027] Among them, V t is the tire rolling speed.

[0028] Furthermore, when collecting sine sweep test data within the test slip rate range, the tire needs to be rotated at least once before collecting the data.

[0029] Furthermore, when the tire sweep test data is taken, the air pressure is 250 kPa.

[0030] The present invention provides a method for testing the longitudinal slack length of a tire, which has the following beneficial effects:

[0031] The present invention is tested on a six-component force testing machine, and a sine sweep frequency method is developed to obtain the longitudinal relaxation length of the tire by calculating the phase difference between the slip rate and the longitudinal force and multiplying the speed of the tire. Since the tire is a viscoelastic object, there is a certain phase difference between the input value of the tire slip rate and the actual value of the slip rate, and when the tire is braked, the tire will generate corresponding vibration, so the longitudinal force is not a complete sine wave. The present invention adopts "Fourier series" for data fitting to eliminate the influence of the data caused by the tire vibration, and the measured longitudinal relaxation length data is accurate and simple to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a graph of original test data and filtered data when the present invention performs a sine frequency sweep test;

[0033] Figure 2 This is a data diagram of the average slip rate and longitudinal force when the present invention performs a sine sweep test;

[0034] Figure 3 This is a 1 Hz frequency data diagram when the present invention performs a sine frequency sweep test;

[0035] Figure 4 This is a 2Hz frequency data diagram when the present invention performs a sine frequency sweep test;

[0036] Figure 5 This is a 3 Hz frequency data diagram when the present invention performs a sine frequency sweep test;

[0037] Figure 6 This is a data diagram of a frequency of 4 Hz when the present invention performs a sine frequency sweep test. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments to help understand the content of the present invention. The methods used in the present invention are all conventional methods unless otherwise specified; the raw materials and devices used are all conventional commercial products unless otherwise specified.

[0039] 1. Preliminary preparation

[0040] Select test tires according to the predetermined test requirements. The production year and storage conditions of the tires used for structural and material comparison tests are roughly the same. Clean the tire surface hair, mold glue, label residual glue, and dust before installation. Then install the test tires on the standard rims and inflate them with the corresponding air pressure. If the tire has a symmetrical pattern, the side with "DOT" is defined as the outer side of the tire.

[0041] 2. Tire preheating

[0042] Install the tire and rim assembly on the testing machine, readjust to the specified test air pressure, adjust the slip angle and roll angle to zero, then start the drum steel belt, and then roll the tire at a speed of 60km / h and 100% of the maximum tire load. Preheat for 3 minutes at slip rates equal to -3%, 0deg and +3%, 0deg respectively. Then the tire is deflected at an angular velocity of 0.5deg / s, and the slip angle SA is controlled within the range of ±10° to preheat the test tire until it reaches thermal equilibrium, that is, within 10 minutes, the tire lateral force changes less than 1%.

[0043] 3. Tire Test

[0044] Apply the tire load to 100% of the reference load, set the side slip angle to 0 degrees, set the roll angle to 0 degrees, set the test air pressure to "controllable", roll forward at a speed of 60 km / h, and then perform a sine sweep test at a slip rate of -1% to +1%, with sweep frequencies of 1Hz, 2Hz, 3Hz, and 4Hz. The test machine can collect data after rolling for at least 1 week, collect data for 2 weeks, and finally adjust the tire back to zero. The test conditions are as follows:

[0045]

[0046] 4. Data Processing

[0047] In this embodiment, data of two cycles are first collected, and then the processed data is filtered using an "elliptical low-pass filter" to eliminate the influence of high-frequency signals on the data. The frequency domain response H(f) of the "elliptical low-pass filter" is calculated:

[0048]

[0049] Wherein, Rp is the passband ripple, Ep is the stopband ripple, Fc is the cutoff frequency, and N is the order. The parameters of the filter set by the present invention are: Rp=0.005, Ep=3, Fc=5, and N=1. Figure 1 As shown, it is the original test data and the filtered data image of this embodiment.

[0050] The filtered data is split into the data of each cycle by sampling time, and then the data of each cycle is added and averaged to form the data of one cycle, thereby eliminating the instability of the data caused by a single cycle. Figure 2 FIG. 2 shows an averaged data image of the slip ratio and the longitudinal force of the present embodiment.

[0051] The averaged slip rate SR is subjected to Fourier transform to convert the time domain data into frequency domain data. According to Fourier series fitting, the amplitude and phase at each angular frequency can be calculated, so that the expression of the amplitude function can be written, and then the spectrum analysis of the Fourier transformed data can be performed.

[0052] The basic form of the Fourier series is:

[0053]

[0054] Among them, the peak f(t) is the periodic signal, a0 is the DC component, and a n and b n is the Fourier coefficient, n is the harmonic order, and ω is the angular frequency.

[0055] like Figure 3-6 As shown, by observing the properties of the spectrum, the maximum SR amplitude SR is found max , the frequency corresponding to the maximum amplitude f SR , the phase corresponding to the maximum amplitude ψ SR Similarly, the maximum amplitude Fx of Fx can be obtained by Fourier transforming the filtered longitudinal force Fx. max , the frequency corresponding to the maximum amplitude f Fx , the phase corresponding to the maximum amplitude ψ Fx .

[0056] Calculate the phase difference between Fx and SR

[0057]

[0058] Then calculate the tire rolling time t:

[0059]

[0060] Where T is the period of the sine wave;

[0061] Finally, calculate the relaxation length Lx :

[0062] L x =V t *t;

[0063] Among them, V t is the tire rolling speed.

[0064] 5. Calculation results

[0065] Test frequency Hz Longitudinal relaxation length m 1 0.7161 2 0.6510 3 0.5859 4 0.5208

[0066] Using "Fourier series" for data fitting can eliminate the impact of external influences on tire test data vibration. The slip rate and longitudinal force are both sinusoidal waves when output, and then the phase difference between the two is calculated to obtain the longitudinal relaxation length of the tire, making the data more accurate.

[0067] However, what is described above is only a specific embodiment of the present invention and should not be used to limit the scope of implementation of the present invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the scope of protection of the present invention should still fall within the scope covered by the claims of the present invention.

Claims

1. A method for testing the longitudinal slack length of a tire, characterized in that: The following steps are involved: S10: Zeroing and calibrating the tire six-component force testing machine; S20: installing the inflated tire on a mechanical testing machine to preheat the tire until the tire reaches thermal equilibrium; S30: after the tire reaches thermal equilibrium, setting the slip angle and slip angle parameters, rolling the tire at a test speed, and collecting sine sweep test data within a test slip rate range; S40: changing the sweep frequency of the sine sweep frequency, and collecting sine sweep frequency test data at different sweep frequencies; S50: denoising all the sine sweep test data to obtain pure data; S60: Convert the clean data into frequency domain data, and then perform spectrum analysis to calculate the longitudinal slack length of the tire.

2. The method for testing the longitudinal slack length of a tire according to claim 1, characterized in that: The specific steps of installing the inflated tire on the mechanical testing machine and preheating the tire until the tire reaches thermal equilibrium are as follows: The inflated tire and rim assembly is mounted on a mechanical testing machine, and the tire is rolled at a speed of 60 km / h and the maximum tire load. The tire is preheated for 3 minutes at slip rates equal to -3%, 0 degrees and +3%, 0 degrees, respectively. Subsequently, the tire is deflected at an angular velocity of 0.5 degrees / s, and the sideslip angle is controlled within the range of ±10 degrees to preheat the test tire until it reaches thermal equilibrium.

3. The method for testing the longitudinal slack length of a tire according to claim 1, characterized in that: After the tire reaches thermal equilibrium, set the slip angle and side slip angle parameters, roll the tire at the test speed, and collect sine sweep test data within the test slip rate range. The specific steps are: The tire load was applied to 100% of the reference load, the slip angle was set to 0 degrees, the roll angle was set to 0 degrees, the tire was rolled forward at a speed of 60 km / h, and then a sine sweep test was performed at a slip rate of -1% to +1% to collect test data.

4. The method for testing the longitudinal slack length of a tire according to claim 1, characterized in that: The specific steps to denoise all the sine sweep test data and obtain pure data are as follows: Collect test data of multiple cycles, filter the test data, eliminate the influence of high-frequency signals on the data, and obtain pure data.

5. The method for testing the longitudinal slack length of a tire according to claim 4, characterized in that: The test data is filtered using an elliptical low-pass filter.

6. The method for testing the longitudinal slack length of a tire according to claim 1, characterized in that: The specific steps of converting the pure data into frequency domain data and then performing spectrum analysis to calculate the longitudinal slack length of the tire are as follows: Perform Fourier transform on the slip rate in the clean data to convert the time domain data into frequency domain data; Perform spectrum analysis on the data after Fourier transformation to determine the maximum amplitude of the slip rate SR and the longitudinal force Fx, the frequency corresponding to the maximum amplitude, and the phase corresponding to the maximum amplitude; Calculate the phase difference between Fx and SR Then calculate the tire rolling time t: Where T is the period of the sine wave; Finally, calculate the relaxation length L x : L x =V t *t; Among them, V t is the tire rolling speed.

7. The method for testing the longitudinal slack length of a tire according to claim 1, characterized in that: When collecting sine sweep test data within the test slip rate range, the tire needs to rotate at least one circle before collecting data.

8. The method for testing the longitudinal slack length of a tire according to claim 1, characterized in that: When the tire is swept for test data, the air pressure is 250kpa.

Images