Vehicle handling stability product force test evaluation method based on actual travel conditions

Abstract

The application discloses a kind of based on actual travel working condition's whole vehicle steering stability product force test evaluation method, is by the whole vehicle steering stability test to vehicle, obtains the steady-state steering stability of vehicle, transient steering stability, center area steering characteristic, steering return performance, steering response characteristic, maneuverability corresponding data of index, obtains the final result of test: based on test result, the steering stability performance overall score for evaluating whole vehicle steering stability product force is calculated, and the whole vehicle steering stability of vehicle is evaluated according to the steering stability performance overall score.This test method of the application is systematic, reasonable and whole new based on the whole vehicle steering stability product force test and evaluation method of actual travel working condition in China, gives a kind of test and scoring method consistent with actual travel working condition in China, is objective, quantifiable, can better reflect the steering stability of whole vehicle in actual travel scene.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle handling performance test, in particular to a vehicle handling stability product force test evaluation method based on actual travel conditions. BACKGROUND

[0002] With the rise of new energy vehicles and drive-by-wire chassis, the traditional structure layout of vehicles becomes more compact, and the characteristics of vehicle handling stability are different from traditional vehicles. Handling stability not only affects the ease of handling of the vehicle cab, but also determines the key performance of safe driving of the vehicle, so the requirement for the handling stability performance of the vehicle is higher and higher.

[0003] Currently, there are two evaluation methods for vehicle handling stability performance evaluation: subjective evaluation method and objective evaluation method. The subjective evaluation is based on the feeling of the person to evaluate, which is more in line with the actual consumer vehicle situation, but it is greatly affected by the state and environmental factors of the evaluator, and the consistency and accuracy of the evaluation results are difficult to guarantee. The objective evaluation method is based on objective test, and the performance problems of handling stability are objectively reflected through the test results of the set specific conditions. The test conditions of this method are derived from the handling stability of the national standard. The conditions in the national standard include snake test, steering transient response test (steering wheel angle step input, steering wheel angle pulse input), steering return performance test, steering light test, steady-state turning test and steering wheel center zone handling stability test. These tests have great differences with the actual use of the vehicle, and the evaluation indexes are numerous and difficult to understand, and it cannot be clearly stated how each index reflects the quality characteristics of vehicle handling stability.

[0004] In view of the actual travel conditions in China, a performance verification method is provided for the host factory in the development process, and an intuitive vehicle handling stability performance selection and purchase reference is provided for consumers, and an innovative vehicle handling stability product force test and evaluation method based on the actual travel conditions in China needs to be solved urgently. SUMMARY

[0005] The purpose of the present application is to solve the technical defects in the prior art, and to provide a vehicle handling stability product force test evaluation method based on actual travel conditions, which can be used for the host factory to verify the performance in the new product development process, and then promote the technical upgrading of the product, and finally improve the travel quality of consumers.

[0006] The technical scheme adopted to achieve the purpose of the present application is:

[0007] A kind of vehicle handling stability product force test evaluation method based on actual travel condition, is by the vehicle handling stability test of vehicle, the data corresponding to the index of the steady-state handling stability, transient handling stability, center zone steering characteristic, steering return performance, steering response characteristic, maneuverability of vehicle are obtained, the final result of test is obtained: based on the test result, the overall score of handling stability performance for evaluating vehicle handling stability product force is calculated, and the overall score of handling stability performance is used to evaluate the vehicle handling stability of vehicle:

[0008] Test is carried out on dry, flat and clean test road, the slope in any direction of test road in test area should not be greater than 2%, and the slope of steering wheel center zone characteristic test should not be greater than 1%; before test, drive 10km at test speed or drive 500m left turn and right turn at a speed of 3m / s 2 of lateral acceleration along the radius of 15m circle, so as to warm up tire, after completion of tire warming, test vehicle enters test area to carry out various tests;

[0009] 1.1 Vehicle body roll test

[0010] Draw a circle with radius not less than 15m on test site with eye-catching color;Start the car, and drive the car along the drawn circle at the lowest stable speed, accelerate slowly and uniformly, and the longitudinal acceleration should not exceed 0.25m / s 2 , until the lateral acceleration of the car reaches 6.5m / s 2 or the maximum lateral acceleration that can be reached by the engine power limit, or the car appears unstable state, record the whole process;

[0011] Test is carried out in two directions of left turn and right turn, and each direction is tested three times;The arithmetic mean of the results of 3 left turn tests and 3 right turn tests of vehicle body roll is taken as the final result;

[0012] 1.2 Obstacle avoidance test

[0013] Test starts from low speed, and gradually increases the speed until the test driver feels that the vehicle cannot be controlled;Record the highest passing speed of obstacle avoidance, and obtain the initial speed of vehicle entering the stake area;The maximum value of multiple test results is taken as the final result of the highest passing speed of obstacle avoidance;

[0014] 1.3 Center zone steering characteristic test

[0015] The initial state of the test is straight-line driving at a constant speed, and the test standard speed is 100 km / h, or the speed of 100 km / h is taken as a reference, and the test speed is increased or decreased, and the speed interval is 20 km / h; the steering wheel input during the test is an oscillating angular input, and the preferred input form is a sine wave, and the reference value of the input frequency is 0.2 Hz, and the frequency deviation is not more than 10%; the steering input during the test is realized by manual or steering robot; when the steering signal is input manually, the test should last at least 40 s; when the steering signal is input by the steering robot, the test should last at least 20 s, and the steering wheel angle, the steering wheel angular velocity, the vehicle longitudinal acceleration and the vehicle lateral acceleration are recorded during the test;

[0016] The test data are processed to obtain the lateral acceleration hysteresis and the steering wheel angle hysteresis; the arithmetic mean of the test results of each index is taken as the final result;

[0017] 1.4 Low-speed steering return performance test

[0018] The test vehicle drives straight along the test section at a speed of 10±1 km / h, and the zero line of each measured variable is recorded; then the steering wheel is turned to the limit position, and after stabilization and recording, the steering wheel is quickly released, and the vehicle motion process within at least 6 s after the hand is released is recorded, and the vehicle speed remains unchanged during the recording time; the test is performed in two directions of left and right turns, and each direction is tested 3 times;

[0019] The residual steering wheel angle is calculated: the steering wheel angle at the time of 5 s after the steering wheel is released is obtained; the arithmetic mean of the test results of 3 left turns and 3 right turns of the residual steering wheel angle is taken as the final result;

[0020] 1.5 High-speed steering return performance test

[0021] The test vehicle drives straight along the test section at a speed of 100±1 km / h, and the zero line of each measured variable is recorded. Then the steering wheel is turned to make the vehicle lateral acceleration reach 2+0.2 m / s 2 , and after stabilization and recording, the steering wheel is quickly released, and the vehicle motion process within at least 4 s after the hand is released is recorded, and the accelerator pedal position remains unchanged during the recording time; the test is performed in two directions of left and right turns, and each direction is tested 3 times;

[0022] The test data are processed to obtain the yaw rate overshoot; the arithmetic mean of the test results of 3 left turns and 3 right turns of the yaw rate overshoot is taken as the final result;

[0023] 1.6 Steering wheel angle step input test

[0024] Before the test, drive at a speed of 100 km / h, and the steady-state lateral acceleration value is 4 m / s 2, preselected steering wheel angle position; the vehicle is driven straight at the test speed, the steering wheel is gently pressed in the input direction to eliminate the free play of the steering wheel and to record the zero line of the measured variables, after 0.2-0.5 s, the steering wheel is rotated at a speed of not more than 0.2 s or not less than 200° / s, so that it reaches the preselected position and is fixed for a few seconds, until the measured variables transition to a new steady state value and the recording is stopped; the vehicle speed is kept constant during the recording; the test is performed in two directions, left and right, alternately or continuously in one direction, and then in the other direction;

[0025] The test data are processed to obtain the lateral acceleration response time; the arithmetic mean of the results of three left turns and three right turns of the lateral acceleration response time is taken as the final result;

[0026] 1.7 Sweep test

[0027] The vehicle is driven straight at a test speed of 100±2 km / h, and under the condition of balance of yaw rate of 0±0.5° / s, a continuous sinusoidal input with gradually increasing frequency is applied to the steering wheel at a pre-determined steering wheel angle amplitude, the frequency gradually increases from 0.2 Hz to 3 Hz, and the time is not less than 20 s; the vehicle speed is kept constant during the test; the test vehicle is driven in a circle at the selected test speed, and the steering wheel angle at the predetermined steady-state lateral acceleration is taken as the preselected steering wheel angle; the standard steady-state lateral acceleration is 4 m / s2; three effective tests are repeated;

[0028] The test data are processed to obtain the resonance frequency; the arithmetic mean of the results of three times is taken as the final result;

[0029] 1.8 Minimum turning diameter test

[0030] According to the need, the running track display device is installed on the farthest point from the steering center, the closest point and the center of the tire tread on the vehicle body, the vehicle is driven at a low speed in the lowest forward gear, the steering wheel is turned to the limit position and kept unchanged, the track display device is started after stabilization, the vehicle is driven for one round, so that each measuring point displays a closed motion track on the ground, and then the vehicle is driven out of the measurement area; the diameters of the track circles formed by each measuring point on the ground are measured with a steel tape, which should be measured in two mutually perpendicular directions, and the maximum value is read by moving left and right; the arithmetic mean of the measured values in two directions is taken as the test result; the vehicle is measured once for left turn and once for right turn, and the test results are recorded; the test data are processed to obtain the final result of the minimum turning diameter;

[0031] 1.9 Steering wheel turn number test

[0032] The test vehicle should be parked on the test site, start the vehicle, put the transmission in neutral, release the brake, and place the steering wheel in the neutral position. Record the zero line of each measured variable. Slowly and evenly turn the force steering wheel to the maximum left angle, then turn it to the maximum right angle in the opposite direction, and finally turn it to the neutral position. Record the changes of each measured variable during the entire process. Perform at least three tests. Calculate the average value of the results of the three tests as the final result.

[0033] The evaluation indexes are divided into primary indexes and secondary indexes. The primary indexes are steady-state handling stability, transient handling stability, center zone steering characteristics, steering return performance, steering response characteristics, and vehicle maneuverability. The secondary indexes are body roll, maximum obstacle avoidance speed, lateral acceleration hysteresis, steering wheel angle hysteresis, residual steering wheel angle, yaw rate overshoot, lateral acceleration response time, resonant frequency, minimum turning diameter, and steering wheel turns.

[0034] The primary index score is calculated based on the secondary index score and the weight, with two decimal places. The calculation method is shown in the following formula.

[0035]

[0036] In the formula, j is the serial number of the secondary index within the primary index, and ni is the number of secondary indexes of the i-th primary index. ij , b ij are the score of the secondary index with serial number j within the primary index with serial number i and the weight of the corresponding secondary index, respectively.

[0037] The secondary index score is calculated based on the test results and the index limits corresponding to 60 points and 100 points through linear interpolation, with two decimal places. If the calculation result is greater than 100 points, it is calculated as 100 points.

[0038] The overall score of the steering stability performance of the product for evaluating the vehicle handling stability is calculated based on the primary index score and the weight, with one decimal place. The calculation method is shown in the following formula.

[0039]

[0040] In the formula, S is the overall score of the steering stability performance evaluation, i is the serial number of the primary index, S i and a i are the score and weight of the primary index with serial number i, respectively.

[0041] 2. The product force test evaluation method for vehicle handling stability based on actual driving conditions according to claim 1, wherein the weights of the steady-state handling stability, the transient handling stability, the center zone steering characteristic, the steering return performance, the steering response characteristic and the maneuverability are 20%, 15%, 15%, 15%, 20% and 15% respectively; the weight of the body roll degree in the steady-state handling stability is 100%, the weight of the obstacle avoidance maximum passing speed in the transient handling stability is 100%, the weights of the lateral acceleration hysteresis and the steering wheel angle hysteresis in the center zone steering characteristic are 50% and 50% respectively, the weights of the residual steering wheel angle and the yaw rate overshoot in the steering return performance are 50% and 50% respectively, the weights of the lateral acceleration response time and the resonance frequency in the steering response characteristic are 50% and 50% respectively, and the weights of the minimum turning diameter and the steering wheel number in the maneuverability are 60% and 40% respectively.

[0042] 60 points correspond to the following index limit values:

[0043] The body roll degree, the obstacle avoidance maximum passing speed, the lateral acceleration hysteresis, the steering wheel angle hysteresis, the residual steering wheel angle, the yaw rate overshoot, the lateral acceleration response time, the resonance frequency, the minimum turning diameter and the steering wheel number are 6° / g, 65km / h, 1.5m / s 2 , 9°, 10°, 60%, 0.35s, 1Hz, 12.6m, 3.4r respectively.

[0044] 100 points correspond to the following index limit values:

[0045] The body roll degree, the obstacle avoidance maximum passing speed, the lateral acceleration hysteresis, the steering wheel angle hysteresis, the residual steering wheel angle, the yaw rate overshoot, the lateral acceleration response time, the resonance frequency, the minimum turning diameter and the steering wheel number are 3° / g, 80km / h, 0.2m / s 2 , 1°, 2°, 20%, 0.2s, 1.8Hz, 9.8m, 2.1r respectively.

[0046] The test method of the application is a systematic, reasonable and brand-new product force test and evaluation method for vehicle handling stability based on actual driving conditions in China, which can be used for the content tested in the national standard for vehicle handling stability, and the problem that the actual driving conditions in China are not consistent with the content tested in the national standard for vehicle handling stability is solved, a test and scoring method consistent with the actual driving conditions in China is given, which is objective and quantifiable, and the vehicle handling stability in the actual driving scene can be better reflected. In the new vehicle development process, the test and evaluation conditions mentioned in the application can be used to calibrate and verify the vehicle handling stability strategy of the engineering prototype in the development or verification stage, so that the positioning of the vehicle development target is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 is a flow chart of the vehicle handling stability product force test evaluation method based on actual travel working conditions.

[0048] Figure 2 is a schematic diagram of an obstacle avoidance playground performance site.

[0049] Figure 3 is a relationship curve between the body roll angle and the lateral acceleration.

[0050] Figure 4 is a schematic diagram of a hysteresis loop.

[0051] Figure 5 is a yaw rate time history curve.

[0052] Figure 6 is a lateral acceleration response curve.

[0053] Figure 7 is a amplitude-frequency phase-frequency characteristic diagram of an automobile. DETAILED DESCRIPTION

[0054] The application will be further described below in conjunction with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application.

[0055] As shown in Figure 1 the vehicle handling stability product force test evaluation method based on actual travel working conditions of the embodiment of the application is to obtain the data corresponding to the indexes of the steady-state handling stability, the transient handling stability, the center zone steering characteristic, the steering return performance, the steering response characteristic, and the maneuverability of the vehicle through the vehicle handling stability test, and to obtain the final test result: based on the test result, the overall handling stability performance score for evaluating the vehicle handling stability product force is calculated, and the vehicle handling stability is evaluated according to the overall handling stability performance score. The following steps are implemented:

[0056] 1. Test site

[0057] 1.1 The test should be carried out on a dry, flat and clean road surface paved with cement concrete or asphalt, and the slope in any direction from the test road surface should not be greater than 2%, and for the steering wheel center zone characteristic test, the slope should not be greater than 1%.

[0058] 1.2 The road surface should be paved in the same period, and the road surface should be flat, uniform in structure, consistent in abrasion, and free of loose materials or foreign deposits on the surface.

[0059] 2. Environmental conditions

[0060] The average wind speed during the test shall not be greater than 5 m / s, the atmospheric temperature shall be within the range of 0°C to 40°C, and the weather condition shall be free of rain, snow and fog.

[0061] 3. Test equipment

[0062] 3.1 Test vehicle

[0063] 3.1.1 Before the test, the wheel alignment parameters shall be measured. The steering system and the suspension system shall be inspected, adjusted and fastened, and lubricated according to the provisions. Only when it is determined that the test vehicle has met the technical conditions specified by the manufacturer, the test can be carried out.

[0064] 3.1.2 New tires shall be used for the test, and the tires shall be run-in for at least 200 km before the test. If old tires are used, the remaining tread depth of the tire crown shall be not less than 1.6 mm at the end of the test. The tire pressure shall meet the technical requirements of the vehicle manufacturer.

[0065] 3.1.3 The test load state is the light load state, i.e. the total mass of the test vehicle, the test equipment and the driver and the test operator.

[0066] 3.2 Test instruments

[0067] 3.2.1 The test instruments shall be able to withstand environmental conditions such as dust, impact, vibration and 100% humidity.

[0068] 3.2.2 Test instruments required: speedometer; steering wheel torque and steering wheel angle measuring instrument; vehicle handling stability tester; stopwatch; multi-channel data acquisition system.

[0069] 3.2.3 The measurement range and maximum error of each measuring instrument meet the requirements of Table 1.

[0070] Table 1 Measurement range and maximum error of measuring instruments

[0071]

[0072] 4. Test procedure

[0073] Before the test, the test vehicle shall be driven straight at the test speed for 10 km, or driven along a circle with a radius of 15 m at a corresponding vehicle speed with a lateral acceleration of 3 m / s 2 for 500 m (once for left turn and once for right turn), so as to warm up the tires. After the tires are warmed up, the test vehicle enters the test area to perform various tests.

[0074] 4.1 Vehicle body roll test

[0075] 4.1.1 Test procedure

[0076] The test load condition is light load. On the test site, draw a circle with a radius of not less than 15 m in a conspicuous color. Start the car and steer the car to travel along the drawn circle at the lowest stable speed, slowly and uniformly accelerating (the longitudinal acceleration should not exceed 0.25 m / s 2 ), until the lateral acceleration of the car reaches 6.5 m / s 2 (or the maximum lateral acceleration that can be reached due to the engine power limitation, or the car appears unstable state), record the entire process. The test is carried out in two directions, left and right, and each direction is tested three times. At the beginning of each test, the longitudinal symmetry plane of the vehicle body should be in the center of the drawn circle.

[0077] 4.1.2 Data processing and result expression

[0078] The true value of lateral acceleration (unit, m / s2) is equal to the instantaneous yaw rate (unit, rad / s) multiplied by the instantaneous speed of the car forward (unit, m / s). Draw the relationship curve between the body roll angle and the lateral acceleration in the form of Figure 2 . Figure 2 The relationship between the body roll angle and the lateral acceleration is shown. Find the body roll K φ , that is, the average slope of the lateral acceleration at 2 m / s 2 on the body roll angle and lateral acceleration relationship curve (the longitudinal coordinate value is divided by the horizontal coordinate value). Take the arithmetic mean of the results of 3 left turn tests and 3 right turn tests of the body roll as the final result.

[0079] 4.2 Obstacle avoidance test

[0080] 4.2.1 Test process

[0081] The test load condition is light load. According to the vehicle width, determine the distance between stakes and the length of each part according to Table 1, and arrange the stakes on the site according to Figure 3 . Figure 3 The black dots in Figure 3 represent the positions of the stakes, and 6 in Figure 3 represents the offset amount.

[0082]

[0083]

[0084] The w in the table indicates the vehicle width, the w in Table 5 indicates the vehicle width, the length of the site of No. 1 is 12 m corresponding to two rows of stakes, the length of the site of No. 2 is 13.5 m without stakes, the length of the site of No. 3 is 11 m corresponding to two rows of stakes offset on one side, the site of No. 4 of the length of 12.5 m has no stakes, and the two rows of stakes of the site of No. 5 of the length of 12 m form a straight line of the vehicle with the two rows of stakes of the site of No. 1, and the two rows of stakes are used for the vehicle to pass through.

[0085] Before the test, each test instrument is turned on and preheated to the normal working temperature. The test driver should have rich driving experience, and before the formal test, multiple practices are performed according to the route shown in the figure;

[0086] During the formal test, the test vehicle with a manual transmission is positioned at the highest gear, and the test vehicle with an automatic transmission is positioned at the “D” gear. The vehicle enters the first test section at a certain speed. After entering the line for 2 m in the first section (as shown in Figure 1 ), the accelerator pedal is released, the engine is driven in the engaged state to complete the subsequent passage, and the vehicle parameters and the time for passing through the stake area during the whole process are recorded.

[0087] The test starts from a lower vehicle speed (here, the speed of entering the first section is recommended to be 50 km / h), and the vehicle speed is gradually increased until the test driver feels that the vehicle cannot be controlled.

[0088] 4.2.2 Data processing and result expression

[0089] The highest passing speed of obstacle avoidance (the initial speed of the vehicle entering the stake area) is recorded. The maximum value of multiple test results is taken as the final result of the highest passing speed of obstacle avoidance.

[0090] 4.3 Center zone steering characteristic test

[0091] 4.3.1 Test process

[0092] The test load state is a light load state. The instrument power is turned on to reach the normal working temperature. The initial state of the test is straight-line driving at a constant speed, and the standard test speed is 100 km / h. Alternatively, the test speed can be increased or decreased based on the speed of 100 km / h (the speed interval is 20 km / h).

[0093] During the test, the steering wheel input is an oscillating angular input, and the preferred input form is a sine wave. Alternatively, other inputs (such as triangular wave inputs) can be used. The reference value of the steering wheel input frequency is 0.2 Hz, and the frequency deviation should not exceed ±10%. The amplitude of the input angle should be sufficient to make the peak value of the lateral acceleration of the vehicle reach the reference value, and the allowed peak value deviation is ±10%. In order to make the peak value of the lateral acceleration 1 m / s 2Good test data is obtained and the vehicle and its subsystems are operated in a range beyond the hysteresis zone. The reference value for the lateral acceleration peak is 2 m / s 2 Smaller values or not more than 4 m / s 2 may also be used.

[0094] During the entire test, the steering wheel angle amplitude and the angular velocity through the center zone should be kept as constant as possible. The accelerator pedal position should be varied as little as possible, provided that the longitudinal speed of the vehicle is within the specified range. The longitudinal speed variation within the data segment used for data analysis should not exceed ±3% of the test speed.

[0095] All measured parameters are recorded during the entire test, including the measured variables in the initial driving state. To ensure that the test is not affected by the use of the instrument, the data recording should continue for at least 1 s after the end of the entire test.

[0096] The steering input during the test can be achieved by manual or steering robot. When manual input of the steering signal is used, the test should last at least 40 s to ensure that at least 8 input cycles of data are obtained. When the limitations of the test site do not allow for sufficiently long and consistent continuous data, a series of short data is allowed to be combined for test analysis. In this case, at least 20 cycles of data should be ensured and appropriate statistical methods should be used to process the test data, and the statistical methods should be included in the test report. When a steering robot is used to input the steering signal, the test should last at least 20 s to ensure that at least 4 input cycles of data are obtained.

[0097] 4.3.2 Data processing and result expression

[0098] Lateral acceleration (unit, m / s 2 ) True value is equal to instantaneous yaw rate (unit, rad / s) multiplied by instantaneous speed of the vehicle (unit, m / s).

[0099] The measured time history is screened, and cycles with good steering wheel angle and vehicle lateral acceleration data are selected for data analysis. The steering wheel angle and vehicle lateral acceleration data are plotted in a rectangular coordinate system, and the graph is a group of hysteresis loops formed by superimposing a plurality of hysteresis loops. The number of loops is equal to the number of cycles selected.

[0100] The loop group should be averaged in an appropriate manner. The recommended method is to use the average of the maximum and minimum values of the loop group. Figure 4The upper and lower parts of the test curve in the interval A are fitted by polynomials respectively, and the fitting order is 3. During data processing, the data abscissa interval is determined first, and then interval A is selected in the interval according to a certain proportion. When selecting, it should be ensured that interval A is large enough to cover the data region of interest, but the influence of hysteresis effect at both ends should be avoided, and the proportion of the abscissa interval occupied by interval A is recommended to be 50% to 70%.

[0101] Figure 4 Fig. 1 is a schematic diagram of hysteresis loops, Figure 4 In Fig. 1, 1 is the ordinate hysteresis region, 2 is the abscissa hysteresis region, and A is the polynomial fitting region. It is recommended to perform linear fitting on the polynomial fitted in the data region of interest to estimate the slope. The average slope should be fitted in the specified region, and the transient slope should be fitted in a small region near the point of interest. The typical region value is ±0.1 m / s 2 of the lateral acceleration change. Each hysteresis loop can be analyzed separately, and the characteristic parameters of each loop are averaged to obtain the final result. Through polynomial fitting of the hysteresis loop group, the following parameters can be obtained: ordinate hysteresis region, abscissa hysteresis region, and slope. For example, Figure 4 Draw the lateral acceleration versus steering wheel torque curve and the steering wheel angle versus steering wheel torque curve to obtain the lateral acceleration hysteresis and the steering wheel angle hysteresis. Take the arithmetic mean of the results of 3 tests of each index as the final result.

[0102] 4.4 Low-speed steering return performance test

[0103] 4.4.1 Test process

[0104] The test load state is light load. The test vehicle drives straight along the test section at a speed of 10±1 km / h, and the zero line of each measured variable is recorded. Then turn the steering wheel to the limit position, wait for stability and start recording, and then quickly release the steering wheel. The vehicle motion process within 6s after releasing the hand is recorded, and the vehicle speed remains unchanged during the recording time. The test is performed in two directions of left and right, and each direction is performed 3 times.

[0105] 4.4.2 Data processing and result expression

[0106] Calculate the residual steering wheel angle: the steering wheel angle at 5s when the steering wheel is released. Take the arithmetic mean of the results of 3 left-turn tests and 3 right-turn tests of the residual steering wheel angle as the final result.

[0107] 4.5 High-speed steering return performance test

[0108] 4.5.1 Test process

[0109] The test vehicle drives straight along the test section at a constant speed of 100 ± 1 km / h, and the zero lines of the measured variables are recorded. Then the steering wheel is turned to make the lateral acceleration of the vehicle reach (2 + 0.2) m / s 2 After the vehicle stabilizes and starts to record, the steering wheel is quickly released, and the vehicle motion is recorded for at least 4 s after the release. The position of the accelerator pedal is kept unchanged during the recording time. The test is performed in two directions, left and right, and each direction is tested 3 times.

[0110] 4.5.2 Data processing and result expression

[0111] The time history curve of the yaw rate is plotted. On the curve, the ratio of the response of the yaw rate to the first peak value to the new steady-state value (see Fig. 2) is determined, and the yaw rate overshoot is determined according to formula (1): Figure 5

[0112]

[0113] In the formula: — the average value of the yaw rate overshoot, %; σ i — the yaw rate overshoot of the i-th test, %.

[0114] Figure 5 The response of the yaw rate

[0115] The arithmetic mean of the results of the 3 left-turn tests and the 3 right-turn tests of the yaw rate overshoot is taken as the final result.

[0116] 4.6 Steering wheel angle step input test

[0117] 4.6.1 Test process

[0118] The test load state is the light load state. Before the test, the vehicle drives at a speed of 100 km / h, and the position of the steering wheel angle is preselected according to the steady-state lateral acceleration value of 4 m / s 2 The vehicle drives straight at the test speed, and the steering wheel is gently turned in the input direction to eliminate the free travel of the steering wheel and start recording the zero lines of the measured variables. After (0.2-0.5) s, the steering wheel is turned at the fastest speed (the rise time is not greater than 0.2 s or the rise speed is not less than 200° / s) to reach the preselected position and be fixed for a few seconds (until the measured variables transition to the new steady-state value) to stop recording. The vehicle speed is kept unchanged during the recording process.

[0119] The test is performed in two directions, left and right. The two directions can be alternately performed, or a test in one direction is continuously performed, and then a test in the other direction is performed.

[0120] 4.6.2 Data processing and result expression

[0121] For example,​Figure 6 The lateral acceleration response time is plotted. Figure 6 The lateral acceleration response curve is plotted. The arithmetic mean of the results of 3 left turns and 3 right turns of the lateral acceleration response time is taken as the final result.

[0122] 4.7 Sweep test

[0123] 4.7.1 Test procedure

[0124] The test load state is light load. The vehicle is driven straight at a test speed of 100 ± 2 km / h, and starts under the balance condition of a yaw rate of 0 ± 0.5° / s, and a continuous sinusoidal input with gradually increasing frequency is applied to the steering wheel at a predetermined steering wheel angle amplitude, and the frequency gradually increases from 0.2 Hz to 3 Hz, and the time is not less than 20 s. The vehicle speed is kept unchanged during the test. The vehicle is driven around a circle at the selected test speed, and the steering wheel angle when the predetermined steady-state lateral acceleration is reached is taken as the preselected steering wheel angle. The standard steady-state lateral acceleration level is 4 m / s 2 . The effective test is repeated for 3 times.

[0125] The vehicle speed and steering wheel angle time history (v-t and θ-t curves) recorded during the test should be displayed on the computer, and the actual vehicle speed change should not exceed ± 5% of the specified speed. The zero line of the steering wheel angle should be consistent before and after the pulse input of the rotating steering wheel. When the difference is not more than ± 10% of the maximum steering wheel angle, the line connecting the starting point and the ending point of the steering wheel pulse input should be taken as the reference zero line; if the vehicle speed change exceeds 10%, the test record is invalid.

[0126] 4.7.2 Data processing and result expression

[0127] The amplitude-frequency characteristic and phase-frequency characteristic of the steering wheel angle pulse input and the yaw rate response are calculated and analyzed on a special signal processing device or on a general-purpose computer according to formula (2).

[0128]

[0129] In the formula: r(t) - yaw rate time history; δ sw (t) - steering wheel angle time history; ω0 - the minimum circular frequency selected for calculation, generally 0.2π. k = 1, 2, 3, … n

[0130] According to the average value of the test data processing results, the amplitude-frequency and phase-frequency characteristic diagrams of the vehicle are plotted respectively by rotating the steering wheel to the left and to the right, as shown in Figure 7 Figure 7 ​The abscissa is logarithmic and represents the frequency. Linear coordinates can also be used. The abscissa should be 0 Hz - 3 Hz and the ordinate is the phase lag angle, the amplitude ratio. Figure 6 Automobile phase-frequency characteristic and amplitude-frequency characteristic. Resonance frequency f p is the frequency corresponding to the amplitude-frequency characteristic resonance peak. When there is no obvious resonance peak, the passband divided by 70% yaw rate gain is used as f The value of f p is calculated. The arithmetic mean of three test results at the resonance frequency is taken as the final result.

[0131] 4.8 Minimum turning diameter test

[0132] 4.8.1 Test procedure

[0133] The automobile is in an empty state, with only one driver on board, and all wheels are on the ground. If necessary, install the running track display device on the highest point, the lowest point, and the center of the tire tread above the steering center on the vehicle body. The automobile is in the lowest forward gear and travels at a low speed. The steering wheel is turned to the limit position and remains unchanged. After stabilizing, start the track display device, and the vehicle travels one lap, so that each measurement point displays a closed motion track on the ground, and then the vehicle is driven out of the measurement area. The diameter of the track circle formed by each measurement point on the ground is measured with a steel tape measure. The measurement should be taken in two mutually perpendicular directions, moving left and right, and the maximum value should be read. The arithmetic mean of the measurement values in the two directions is taken as the test result. The automobile is measured once for left and right turns, and the test results are recorded.

[0134] 4.8.2 Data processing and result expression

[0135] If the difference between the test results measured in the left and right turning directions is within 0.1 m, the average of the left and right turning test results is taken as the final result of the vehicle, otherwise the larger value of the experimental results measured in the left and right turning directions is taken as the final result.

[0136] 4.9 Steering wheel revolution test

[0137] 4.9.1 Test procedure

[0138] The test automobile should be parked on the test site. Start the vehicle, put the transmission in neutral, release the brake, and the steering wheel is in the middle position. Record the zero line of each measured variable. Slowly and evenly turn the force measuring steering wheel to the maximum turning angle to the left, then turn the force measuring steering wheel in the opposite direction (to the right) to the maximum turning angle, and finally turn the force measuring steering wheel to the middle position (to the left). Record the changes of each measured variable during the entire process. At least three tests should be performed.

[0139] 4.9.2 Data processing and result expression

[0140] The calculation method of the number of turns of the steering wheel is shown in formula (3).

[0141]

[0142] In the formula, n is the number of turns of the steering wheel; δ Lmax —left limit position steering wheel rotation angle (°);

[0143] δ Rmax —right limit position steering wheel rotation angle (°).

[0144] The average value calculated from the results of 3 tests is taken as the final result.

[0145] 4.10 Calculation method of steering stability evaluation score

[0146] The score of the secondary index is calculated according to the objective test results, the index results measured in the test, the index limit values corresponding to 60 points and 100 points in Table 3, and the linear interpolation method, and is rounded to two decimal places. If the calculation result is greater than 100 points, it is calculated as 100 points.

[0147] The score of the primary index is calculated according to the score of the secondary index and the weight, and is rounded to two decimal places. The calculation method is shown in formula 4.

[0148]

[0149] In the formula, j is the serial number of the secondary index in the primary index, and ni is the number of secondary indexes of the i th primary index. ij , b ij are the score of the secondary index with serial number j in the primary index with serial number i and the weight of the corresponding secondary index, respectively. The weights of the primary index and the secondary index are shown in Table 3.

[0150] Table 3 Weights of primary index and secondary index

[0151]

[0152] The score of the secondary index needs to be tested objectively, and is calculated according to the index results measured in the test, the index limit values corresponding to 60 points and 100 points in Table 4, and the linear interpolation method, and is rounded to two decimal places. If the calculation result is greater than 100 points, it is calculated as 100 points. See Table 4.

[0153] Table 4 Score limit values of secondary index

[0154]

[0155] The overall score of the steering stability performance is calculated according to the score of the primary index and the weight, and is rounded to one decimal place. The calculation method is shown in formula 4.

[0156]

[0157] In the formula, S is the total score of the evaluation of the steering stability performance, i is the serial number of the primary index, S i and a i are the score and weight of the primary index with serial number i, respectively.

[0158] The basic principles and main features of the present application and the advantages thereof have been shown and described above, it is apparent to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application;

[0159] Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed within the present application.

[0160] Furthermore, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the present specification is described in this manner only for the sake of clarity, those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A product force test evaluation method for vehicle handling stability based on actual travel conditions, characterized by, The vehicle is tested for overall handling stability, and the steady-state handling stability, transient handling stability, centering behavior, steering returnability, steering response characteristics, and maneuverability of the vehicle are obtained. The overall handling stability of the vehicle is evaluated based on the test results. The test is carried out on a dry, flat and clean test road, and the slope in any direction of the test road in the test area should not be greater than 2%, and the slope in the center area of the steering wheel should not be greater than 1%; before the experiment, drive straight at the test speed for 10km or along a radius of 15m circle, with lateral acceleration of 3m / s 2 Carry out left and right turns each once to warm up the tire, and after the tire is warmed up, the test vehicle enters the test area to carry out various tests; 1.1 Vehicle body roll test On the test site, draw a circle with a radius of not less than 15 m in a conspicuous colour; start the car and drive it along the drawn circle at the lowest steady speed, accelerating slowly and uniformly, the longitudinal acceleration not exceeding 0.25 m / s 2 , until the lateral acceleration of the car reaches 6.5 m / s 2 or the maximum lateral acceleration that can be achieved due to the engine power, or the car becomes unstable, and record the entire process; The test is performed in two directions, left and right, and each direction is tested three times. The arithmetic mean of the three left and right test results is taken as the final result. 1.2 Obstacle avoidance test The test starts at a low speed and gradually increases the speed until the test driver feels that the vehicle is uncontrollable. The maximum passing speed is recorded, and the initial speed of the vehicle entering the stake area is obtained. The maximum value of multiple test results is taken as the final result of the maximum passing speed. 1.3 Centering behavior test The initial state of the test is straight-line driving at a constant speed, and the test standard speed is 100 km / h. Alternatively, the test speed is increased or decreased based on 100 km / h, with an interval of 20 km / h. The steering wheel input is an oscillating angular input, with a sine wave as the preferred input form, and the frequency reference value is 0.2 Hz, with a frequency deviation of no more than 10%. The steering input during the experiment is achieved by manual or steering robot. When manually inputting the steering signal, the test should last at least 40 s. When using a steering robot to input the steering signal, the test should last at least 20 s. The steering wheel angle, steering wheel angular velocity, vehicle longitudinal acceleration, and vehicle lateral acceleration are recorded during the test. The test data is processed to obtain the lateral acceleration hysteresis and steering wheel angle hysteresis. The arithmetic mean of the three test results of each index is taken as the final result. 1.4 Low-speed steering returnability test The test vehicle drives straight at a speed of 10 ± 1 km / h along the test section, and the zero line of each measured variable is recorded. Then, the steering wheel is turned to the limit position, and after stabilizing and starting to record, the steering wheel is quickly released. The vehicle motion process within 6 s after releasing the steering wheel is recorded, and the vehicle speed remains unchanged during the recording time. The test is performed in two directions, left and right, with three tests in each direction. The residual steering wheel angle is calculated: the steering wheel angle at 5 s after releasing the steering wheel is obtained. The arithmetic mean of the three left and right test results of the residual steering wheel angle is taken as the final result. 1.5 High-speed steering returnability test The test vehicle drives along the test section at a constant speed of 100 ± 1 km / h, and the zero line of each measured variable is recorded; then the steering wheel is turned to make the lateral acceleration of the vehicle reach 2 ± 0.2 m / s 2 After being stable and starting to be recorded, the steering wheel is quickly released, and the vehicle movement process within at least 4s after the hand is released is recorded, and the position of the accelerator pedal remains unchanged during the recording time; the test is performed in two directions of left turn and right turn, and each direction is performed 3 times; The test data is processed to obtain the yaw rate overshoot; the arithmetic mean of the three left and right test results of the yaw rate overshoot is taken as the final result. 1.6 Steering wheel angle step input test Before the test, the vehicle is driven at a speed of 100 km / h, and the steady-state lateral acceleration value is 4 m / s 2 , the position of the pre-selected steering wheel angle; the vehicle is driven straight at the test speed, the steering wheel is gently pressed in the input direction to eliminate the free travel of the steering wheel and start recording the zero line of each measured variable, and after 0.2-0.5 s, the steering wheel is turned at a speed of not more than 0.2 s or not less than 200° / s, so that it reaches the pre-selected position and is fixed for a few seconds, until the measured variable transitions to a new steady-state value and the recording is stopped; the vehicle speed remains unchanged during the recording; the test is performed in two directions, left and right, which can be alternated or continuous in one direction, and then the other direction is tested; The test data is processed to obtain the lateral acceleration response time; the arithmetic mean of the three left and right test results of the lateral acceleration response time is taken as the final result. 1.7 Sweep test The vehicle travels straight at a test speed of 100 ± 2 km / h, and starts under the condition that the yaw rate is 0 ± 0.5° / s, and then a continuous sinusoidal input with gradually increasing frequency is applied to the steering wheel at a predetermined steering wheel angle amplitude, the frequency gradually increases from 0.2 Hz to 3 Hz, and the time is not less than 20 s; the vehicle speed is kept constant during the test; the vehicle travels around a circle at the selected test speed, and the steering wheel angle when the predetermined steady-state lateral acceleration is reached is taken as the preselected steering wheel angle; The standard steady-state lateral acceleration level is 4 m / s2; the effective test is repeated for 3 times; The test data is processed to obtain the resonance frequency; the arithmetic mean of the results of 3 times is taken as the final result; 1.8 Minimum turning diameter test According to the needs, the running track display device is installed on the farthest point, the nearest point and the center of the wheel tire surface of the vehicle body from the steering center, the automobile is in the lowest forward gear and travels at a low speed, the steering wheel is turned to the limit position and kept unchanged, after stabilization, the track display device is started, the vehicle travels around a circle, so that each measuring point respectively displays a closed motion track on the ground, and then the vehicle is driven out of the measurement area; the diameters of the track circles formed by each measuring point on the ground are measured by using a steel tape, which should be measured in two mutually perpendicular directions, and the maximum value should be read by moving left and right during the measurement; the arithmetic mean of the measured values in the two directions is taken as the test result; the automobile is measured once for left turn and once for right turn, and the test results are recorded; The test data is processed to obtain the final result of the minimum turning diameter; 1.9 Steering wheel circle number test The test automobile is parked on the test site, the vehicle is started, the transmission is placed in the neutral position, the brake is released, and the steering wheel is in the middle position, and the zero line of each measured variable is recorded; the force steering wheel is slowly and uniformly turned to the maximum steering angle to the left, then the force steering wheel is reversely turned to the maximum steering angle to the right, and finally the force steering wheel is turned to the middle position to the left; the changes of each measured variable during the whole process are recorded; at least three tests are performed; the average value of the test results of 3 times is taken as the final result; The evaluation indexes are divided into primary indexes and secondary indexes; the primary indexes are steady-state handling stability, transient handling stability, center zone steering characteristics, steering return performance, steering response characteristics and vehicle maneuverability; the secondary indexes are vehicle body roll, obstacle avoidance maximum passing speed, lateral acceleration hysteresis, steering wheel angle hysteresis, residual steering wheel angle, yaw rate overshoot, lateral acceleration response time, resonance frequency, minimum turning diameter and steering wheel circle number; The primary index score is calculated according to the secondary index score and the weight, and the last two digits after the decimal point are retained, and the calculation method is as shown in the following formula: In the formula, j is the serial number of the secondary index within the primary index, n i is the number of secondary indexes of the i th primary index, S ij , b ij are the score of the secondary index with serial number j within the primary index with serial number i and the weight of the corresponding secondary index, respectively. The secondary index score is calculated according to the objective test, the index results measured by the test, the index limits corresponding to 60 points and 100 points, and the linear interpolation method, and the last two digits after the decimal point are retained, and the calculation result is greater than 100 points, which is calculated as 100 points; The overall score of the handling stability performance of the product for evaluating the handling stability of the whole vehicle is calculated according to the primary index score and the weight, and the last digit after the decimal point is retained, and the calculation method is as shown in the following formula: In the formula, S is the total score of the evaluation of the handling stability performance, i is the serial number of the primary index, S i and a i are the score and weight of the primary index with serial number i, respectively.

2. The product force test evaluation method for vehicle handling stability based on actual travel conditions according to claim 1, characterized in that, The weights of the steady-state handling stability, the transient handling stability, the center zone steering characteristic, the steering return performance, the steering response characteristic and the maneuverability are 20%, 15%, 15%, 15%, 20% and 15% respectively; the weight of the body roll degree of the steady-state handling stability is 100%, the weight of the maximum passing speed of the obstacle avoidance under the transient handling stability is 100%, the weights of the lateral acceleration hysteresis and the steering wheel angle hysteresis under the center zone steering characteristic are 50% and 50% respectively, the weights of the residual steering wheel angle and the yaw rate overshoot under the steering return performance are 50% and 50% respectively, the weights of the lateral acceleration response time and the resonance frequency under the steering response characteristic are 50% and 50% respectively, and the weights of the minimum turning diameter and the steering wheel angle under the maneuverability are 60% and 40% respectively; The index limit values corresponding to 60 points are as follows: The body roll, the maximum obstacle avoidance passing speed, the lateral acceleration hysteresis, the steering wheel angle hysteresis, the residual steering wheel angle, the yaw rate overshoot, the lateral acceleration response time, the resonance frequency, the minimum turning diameter, the steering wheel turns are respectively 6° / g, 65km / h, 1.5m / s 2 , 9°, 10°, 60%, 0.35s, 1Hz, 12.6m, 3.4r; The index limit values corresponding to 100 points are as follows: The body roll, the highest passing speed of obstacle avoidance, the lateral acceleration hysteresis, the steering wheel angle hysteresis, the residual steering wheel angle, the yaw rate overshoot, the lateral acceleration response time, the resonance frequency, the minimum turning diameter, the steering wheel turns are respectively 3° / g, 80km / h, 0.2m / s 2 , 1°, 2°, 20%, 0.2s, 1.8Hz, 9.8m, 2.1r.

3. The product force test evaluation method for vehicle handling stability based on actual driving conditions according to claim 1, characterized in that, During the obstacle avoidance test, the lower vehicle speed is 50km / h.

4. The product force test evaluation method for vehicle handling stability based on actual travel conditions according to claim 1, characterized by, During the test, the average wind speed should be less than 5m / s, the atmospheric temperature is within the range of 0℃ to 40℃, and the weather condition is no rain, no snow and no fog.

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