Vehicle braking performance 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 braking product force test evaluation method, by dry ground braking test, wet ground braking test, braking stability test, brake pedal linearity test, slight braking test, obtain corresponding index data;According to index data, the braking performance overall score for evaluating whole vehicle braking product force is calculated and obtained, and the evaluation of whole vehicle braking product force is realized.The present application is a kind of test and scoring method consistent with Chinese actual travel working condition, is objective, quantifiable, can better reflect the whole vehicle braking performance in the actual travel scene of Chinese consumer.

Description

TECHNICAL FIELD

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

[0002] In the process of gradual development of the automobile industry, traffic and traffic safety have always been the primary problem. The automobile braking performance is the core index of automobile safety performance detection, and it is necessary to have an objective, efficient and advanced automobile braking performance evaluation method.

[0003] At present, the evaluation conditions of the vehicle braking performance are mostly based on national standards. The conditions in the national standards include 0 type test, I type test (degradation and recovery test), full load failure test, response test, ABS test (empty load, full load), wheel lock sequence test and torque wheel test. The conditions of these tests are extreme conditions, which do not conform to the typical travel conditions. These condition tests are the minimum standard for vehicle access, and cannot completely and accurately reflect the braking performance of the vehicle under actual travel conditions.

[0004] In view of the actual travel conditions in China, it is necessary to provide a performance verification method for the host factory in the research and development process, and to provide an intuitive reference for consumers to select and purchase the braking performance of the vehicle. It is necessary to urgently solve the problem of the vehicle braking performance product force test and evaluation method based on the actual travel conditions in China. SUMMARY

[0005] The purpose of the present application is to provide a vehicle braking performance product force test and evaluation method based on actual travel conditions, which can be used as a reference for performance verification by the host factory in the new product development process, and can be used for technical upgrading of the braking performance of the vehicle to ensure the safety of the consumers.

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

[0007] A vehicle braking performance product force test and evaluation method based on actual travel conditions, which obtains corresponding index data through dry ground braking test, wet ground braking test, braking stability test, braking pedal linearity test and slight braking test; according to the index data, the braking performance overall score for evaluating the vehicle braking performance product force is calculated, so as to realize the evaluation of the vehicle braking performance product force.

[0008] 1.1 Wet ground braking test

[0009] In full load state, confirm the average temperature of service brake on the hottest axle of vehicle is 65-100℃, accelerate the test vehicle to above 105km / h, release the accelerator pedal, shift the manual transmission to neutral, keep the automatic transmission in D, when the vehicle speed drops to 100±2km / h, step on the brake pedal until the ABS system starts to work or the pedal force reaches 500N, until the vehicle stops; record the vehicle speed, braking distance, brake pedal force, deceleration, vehicle body pitch angle, braking stability and abnormal conditions during braking; repeat the braking test for 5 times;

[0010] 1.2 Wet braking test

[0011] Accelerate the test vehicle to 85±2km / h on the starting section, enter the test road, release the accelerator pedal, shift the manual transmission to neutral, keep the automatic transmission in D, and perform emergency braking at the same time, activate the ABS system on each wheel, and maintain braking until the vehicle stops; record the distance traveled by the test vehicle from 80km / h to 20km / h; the first two test data of each test are discarded, and the test vehicle completes at least 6 valid tests;

[0012] 1.3 Braking stability test

[0013] At the beginning of the test, the left and right wheels of the vehicle are on two road surfaces with different adhesion coefficients, and the longitudinal center plane of the vehicle passes through the junction line of the high and low adhesion coefficient road surfaces; emergency braking at full power at an initial speed of 80km / h, any part of the tire cannot cross the junction line until the vehicle stops, steering wheel correction is allowed during the test; record the longitudinal speed and yaw rate signals during the test; the left and right sides of the test vehicle complete 3 valid tests respectively;

[0014] 1.4, Brake pedal linearity test

[0015] In light load state, confirm the average temperature of service brake on the hottest axle of vehicle is 65-100℃, the brake booster is at normal level; accelerate the test vehicle to above 105km / h, release the accelerator pedal, shift the manual transmission to neutral, keep the automatic transmission in D, when the vehicle speed drops to 100±2km / h, step on the brake pedal slowly until the ABS works, the process requires linear change of deceleration, and the pedal process is as long as possible, record the vehicle speed, deceleration, pedal force, pedal stroke, ABS working condition; if the brake pedal action is too fast to trigger the ABS working when the vehicle speed is above 50km / h, this test is invalid; the test vehicle completes at least 3 valid tests.

[0016] 1.5 Light braking test

[0017] Under light load, the test vehicle is accelerated to over 65km / h, the accelerator pedal is released, the manual transmission model is switched to neutral gear, and the automatic transmission model is kept in D gear. When the vehicle speed drops to 60±2km / h, the brake pedal is quickly stepped on and the pedal stroke is kept unchanged. The brake pedal jump time does not exceed 0.2s until the vehicle stops. The brake pedal stroke should be selected to ensure that during the test, the average deceleration is within the range of 1.8-2.2m / s within the vehicle speed range of 50-30km / h. 2 Within the range; record vehicle speed, deceleration, and pedal travel; the test vehicle must complete at least three valid tests;

[0018] The index data obtained from the test are divided into primary indicators and secondary indicators. The primary indicators are braking distance, braking stability, brake pedal linearity, brake response sensitivity and braking comfort; the secondary indicators are dry braking distance from 100 to 0 km / h, wet braking distance from 80 to 20 km / h, yaw rate peak, initial brake pedal force linearity, final brake pedal force linearity, initial brake pedal travel linearity, light braking response time, emergency braking response time, braking pitch angle and deceleration change rate;

[0019] The first-level indicator score is calculated based on the second-level indicator score and weight, with two decimal places retained. The calculation method is as follows:

[0020]

[0021] In the formula, j is the serial number of the secondary indicator within the first-level indicator, and ni is the number of secondary indicators of the i-th first-level indicator. ij 、b ij are the score of the second-level indicator with serial number j within the first-level indicator with serial number i and the weight of the corresponding second-level indicator;

[0022] The secondary indicator score is based on objective testing. The test results are combined with the indicator limits corresponding to 60 points and 100 points, and are calculated by linear interpolation. Two decimal places are retained. If the calculated result is greater than 100 points, it is calculated as 100 points.

[0023] The overall braking performance score is calculated based on the first-level indicator score and weight, with one decimal place retained. The calculation method is shown in the following formula.

[0024]

[0025] Where, S is the total evaluation score of braking performance, i is the first-level index number, S i and a i are the scores and weights of the first-level indicators with serial number i.

[0026] The weights of the braking distance, braking stability, braking pedal linearity, braking response sensitivity and braking comfort are 30%, 10%, 20%, 20% and 20% respectively; the weights of the dry braking 100-0km / h braking distance and wet braking 80-20km / h braking distance are 70% and 30% respectively, the weight of the yaw rate peak value under the braking stability is 100%, the weights of the initial braking pedal force linearity, final braking pedal force linearity and initial braking pedal stroke linearity under the braking pedal linearity are 40%, 20% and 40% respectively, the weights of the slight braking response time and emergency braking response time under the braking response sensitivity are 50% and 50% respectively, and the weights of the braking pitch angle and deceleration rate under the braking comfort are 60% and 40% respectively;

[0027] The index limit values corresponding to 60 points are as follows:

[0028] The dry braking 100-0km / h braking distance, wet braking 80-20km / h braking distance, yaw rate peak value, initial braking pedal force linearity, final braking pedal force linearity, initial braking pedal stroke linearity, slight braking response time, emergency braking response time, braking pitch angle and deceleration rate correspond to 45m, 35m, 10° / s, 0.89, 0.9, 0.8, 0.3s, 0.25s, 2.5° and 30% respectively.

[0029] The index limit values corresponding to 100 points are as follows:

[0030] The dry braking 100-0km / h braking distance, wet braking 80-20km / h braking distance, yaw rate peak value, initial braking pedal force linearity, final braking pedal force linearity, initial braking pedal stroke linearity, slight braking response time, emergency braking response time, braking pitch angle and deceleration rate correspond to 38m, 24m, 2° / s, 1, 1, 1, 0.12s, 0.12s, 0.8° and 2% respectively.

[0031] The test method of the application is a systematic and reasonable whole vehicle braking performance product force test and evaluation method based on the actual driving conditions in China, which can effectively solve the problem that the test conditions in the national standard of whole vehicle braking performance are not consistent with the actual driving conditions in China. The method of the application is a test and scoring method consistent with the actual driving conditions in China, which is objective and quantifiable, and can better reflect the whole vehicle braking performance in the actual driving scene of Chinese consumers. In the development process of new vehicle models, the engineering prototype in the development or verification stage can be subjected to whole vehicle braking performance strategy calibration and verification evaluation by using the test and evaluation conditions mentioned in the application, so as to achieve the positioning of the whole vehicle development target. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a flowchart of the vehicle braking performance product force test evaluation method based on actual travel conditions of the present application. DETAILED DESCRIPTION

[0033] The application will be further described below in conjunction with the drawings and specific examples. It should be understood that the specific examples described herein are merely intended to explain the application and are not intended to limit the application.

[0034] As shown in Figure 1 , the vehicle braking performance product force test evaluation method based on actual travel conditions of the present application embodiment,

[0035] 1. Dry road braking test method

[0036] 1.1 Test conditions

[0037] 1.1.1 The mass state of the vehicle should meet the corresponding provisions of various tests.

[0038] 1.1.2 Various tests should be carried out at the corresponding specified speed; if the maximum design speed of the vehicle is lower than the specified test speed, the test should be carried out at the maximum design speed.

[0039] 1.1.3 During the test, the force applied to the brake control device to achieve the specified braking performance should not exceed the specified maximum value.

[0040] 1.1.4 The test road surface should have good adhesion performance, and the test road should be a high adhesion coefficient road with an adhesion coefficient of about 0.8.

[0041] 1.1.5 The test should be carried out under conditions where wind does not affect the test results.

[0042] 1.1.6 At the beginning of the test, the tires should be cold and at the specified pressure corresponding to the actual load of the vehicle wheels when the vehicle is stationary.

[0043] 1.1.7 The specified performance should be achieved without wheel lock, vehicle deviation from the 3.5m wide test lane, lateral angle less than or equal to 15°, and no abnormal vibration when the vehicle speed is greater than 15km / h.

[0044] 1.2 Instruments and equipment

[0045] The measurement range and maximum error of the instruments and equipment meet the requirements in Table 1.

[0046] Table 1 Measurement range and maximum error of instruments and equipment

[0047] Measurement parameter Measurement range Test instrument and recording system error Pedal force 0 N ~ 1500 N 2％ Pedal travel 0 mm ~ 350 mm 0.25％ Longitudinal deceleration -2 g ~ 2 g ±0.01g Longitudinal speed 0 km / h ~ 200 km / h 0.2 km / h Vehicle body pitch angle -15°～15° 0.15°

[0048] 1.3 Vehicle load

[0049] The vehicle test load is full load, i.e. loaded to the maximum design gross mass of the vehicle.

[0050] 1.4 Test method

[0051] 1.4.1 Test procedure

[0052] Under full load condition, the average temperature of service brake on the hottest axle of the vehicle is confirmed to be within 65-100℃, the test vehicle is accelerated to above 105km / h, the accelerator pedal is released, the manual transmission vehicle is shifted to neutral, the automatic transmission vehicle is kept in D, when the vehicle speed drops to 100±2km / h, the brake pedal is quickly depressed until the ABS system starts to work or the pedal force reaches 500N, until the vehicle stops. The vehicle speed, braking distance, brake pedal force, deceleration, vehicle body pitch angle, braking stability and abnormal conditions during braking are recorded. The braking test is repeated for 5 times.

[0053] 1.4.2 Test state judgment

[0054] During each test, the brake control force shall not exceed the maximum allowable value (≤500N), and the vehicle body shall not deviate from the specified passage. If the test state does not meet the above requirements, the test result is invalid and needs to be repeated.

[0055] 1.5 Data processing and result expression

[0056] 1.5.1 Dry ground braking 100-0km / h braking distance

[0057] The actual braking distance (S2) shall be corrected to the dry ground braking 100-0km / h braking distance (S1) according to the following formula:

[0058]

[0059] In the formula: V 规定 is the specified initial speed, i.e. 100km / h; V 实际 is the actual initial speed.

[0060] The shortest braking distance in 5 test results is taken as the final result of the dry ground braking 100-0km / h braking distance.

[0061] 1.5.2 Emergency braking response time

[0062] The time required from the start of depressing the brake pedal to the longitudinal deceleration reaching 6m / s 2 . The arithmetic mean of the emergency braking response time in 5 test results is taken as the final result of the emergency braking response time.

[0063] 1.5.3 Braking pitch angle

[0064] During braking, the average value of the body pitch angle in the speed range of 80 km / h to 20 km / h. The arithmetic mean of the braking pitch angle in 5 test results is taken as the final result of the braking pitch angle.

[0065] 2. Wet braking test method

[0066] 2.1 Test conditions

[0067] 2.1.1 The slope of the test road surface should not be greater than 2% and uniform, the slope of the test road surface in the length or width direction should not be greater than 6mm when measured with a 3m long ruler.

[0068] 2.1.2 The material used for the road surface, the laying period, and the corrosion should be consistent, and there should be no loose materials and foreign objects on the road surface.

[0069] 2.1.3 The road surface should use dense asphalt mixture material, and the maximum nominal size of the stone should be 8mm to 13mm.

[0070] 2.1.4 The sand layer of the road surface should be tested according to ASTM E965-96 and should be 0.7mm ± 0.3mm.

[0071] 2.1.5 The wet friction characteristics of the test road surface should meet one of the following two:

[0072] a) British Pendulum Number (BPN) method

[0073] When tested with a pendulum tester, the average BPN value corrected by the temperature correction formula as follows formula (2), formula (3) should be between 42 to 60, the test road is 10m long as a point, test BPN according to ASTM E303-93, each point is repeated 5 times, the coefficient of variation of the average BPN value is not more than 10%.

[0074] Temperature correction value = (-0.0018t 2 )+0.34t-6.1 (2)

[0075] BPN = BPN (measured value) + temperature correction value (3)

[0076] In the formula: t - the temperature of the test road surface, unit: Celsius (℃).

[0077] The BPN of the test road surface should not change with the entire braking distance to reduce the dispersion of test results. The composition and physical properties of the pendulum tester friction block rubber formula should meet the relevant provisions. According to the requirements of ASTM E303-93, when the degree of wear of the sliding block hitting the edge reaches 3.2mm in the plane or 1.6mm in the vertical distance, the maximum wear degree has been reached, and the sliding block pad should be replaced.

[0078] b) Standard Tire Test (SRTT) Procedure

[0079] The average peak braking coefficient measured by the trailer method at a test speed of 65 km / h and corrected by the temperature correction factors of equations (4) and (5) is 0.7 ± 0.1. The test surface is selected to be within 10 m of the braking position and the deviation of the braking position on the test surface is required to be within 2 m.

[0080] Temperature correction = -0.0035 (t-20) (4)

[0081] Average peak braking coefficient (μ peak ave ) = peak braking coefficient (measured) + temperature correction (5)

[0082] Where: t = temperature of the test surface under wet conditions in degrees Celsius (°C).

[0083] 2.1.6 The water spray device is located on the side of the test surface or on the special tire test vehicle (trailer). If the water spray is located on the side of the test surface, the water spray should be on for at least 0.5 h before the test to allow the test surface to reach a temperature equilibrium with the water.

[0084] 2.1.7 The water spray should be maintained throughout the test and the water film thickness should be controlled to be within 1.0 mm ± 0.5 mm as measured from the center of the test surface. The water film thickness should be uniform throughout the test cycle.

[0085] 2.1.8 The wind speed should be controlled to avoid interference with the wet test surface. If necessary, a barrier device can be used.

[0086] 2.1.9 The temperature of the wet test surface and the ambient temperature should be within the range of 2 °C to 20 °C for snow tire testing and 5 °C to 35 °C for normal tire testing. The temperature of the wet test surface should not vary by more than 10 °C during the test. The ambient temperature should be similar to the temperature of the wet test surface and the temperature difference should not exceed 10 °C.

[0087] 2.1.10 The tire inflation pressure of the vehicle should be checked at ambient temperature and adjusted to the specified pressure for the vehicle under full load conditions.

[0088] 2.2 Equipment

[0089] 2.2.1 The test equipment should be able to withstand the environmental conditions of dust, impact, vibration, and 100% humidity.

[0090] 2.2.2 The test vehicle shall be equipped with speed and distance sensors capable of meeting the test requirements. The speed of the test vehicle shall be measured using a five-wheel instrument or other non-contact speed measurement instrument (including Vbox, radar, GPS, etc. measurement system).

[0091] The allowable errors are as follows:

[0092] Vehicle speed: ±1% of the vehicle speed or 0.5 km / h, whichever is greater;

[0093] Distance: ±0.1 m

[0094] 2.2.3 During the test, the test vehicle should display the difference between the time speed and the standard speed, so that the driver can adjust the speed.

[0095] 2.3 Vehicle load

[0096] The vehicle test load is full load, i.e. loaded to the maximum design total mass of the vehicle.

[0097] 2.4 Test method

[0098] The test vehicle is accelerated to 85±2 km / h on the starting section, the vehicle enters the test road, the accelerator pedal is released, the manual transmission model is switched to neutral, the automatic transmission model is kept in D, the emergency brake is applied, the ABS system is activated to act on each wheel, and the brake is maintained until the vehicle stops. Each test is strictly controlled in the same test area, and the actual driving distance of each test is not more than 5 m in longitudinal direction and not more than 0.5 m in transverse direction. The distance traveled by the test vehicle from 80 km / h to 20 km / h is recorded. The first two test data of each test are discarded, and the test vehicle completes at least 6 valid tests.

[0099] 2.5 Data processing and result expression

[0100] For any two consecutive groups of three times of standard test tires and test data of test tires, if the coefficient of variation of the average braking distance is greater than 3%, the test data of the standard test tires and the test tires are discarded, and the test is retested. The coefficient of variation of the average braking distance is calculated according to formula (6):

[0101]

[0102] In the formula: C.V. - coefficient of variation, %; S - standard deviation; A - average value of the average braking distance.

[0103] The arithmetic mean of the wet braking distance of 80-20 km / h in the 6 test results is taken as the final result.

[0104] 3. Braking stability test method

[0105] 3.1 Test conditions

[0106] 3.1.1 The quality status of the vehicle should comply with the relevant regulations of various tests.

[0107] 3.1.2 All types of tests should be conducted at the corresponding specified speeds. If the vehicle's maximum design speed is lower than the specified test speed, the test should be conducted at the maximum design speed.

[0108] 3.1.3 During the test, the force applied to the brake control device to achieve the specified braking performance should not exceed the specified maximum value.

[0109] 3.1.4 The test road is a split road with a high adhesion coefficient. H ≥0.5, the adhesion coefficient of low adhesion coefficient road surface and high adhesion coefficient road surface should meet k H / k L ≥2 requirement.

[0110] 3.1.5 The test should be carried out under conditions where the wind will not affect the test results.

[0111] 3.1.6 At the start of the test, the tires should be cold and at the specified pressure corresponding to the actual load on the wheels when the vehicle is stationary.

[0112] 3.1.7 The specified performance shall be achieved when the vehicle speed is greater than 15 km / h, no wheel locking occurs, the vehicle does not deviate from the 3.5 m wide test channel, the yaw angle is less than or equal to 15°, and there is no abnormal vibration.

[0113] 3.2 Instruments and Equipment

[0114] The measurement range and maximum error of the instrument meet the requirements in Table 2.

[0115] Table 2 Measurement range and maximum error of instruments

[0116] Measurement parameter Measurement range Test instrument and recording system error Longitudinal speed 0 km / h ~ 200 km / h 0.2 km / h Yaw rate -50 ° / s ~ 50 ° / s 0.5° / s

[0117] 3.3 Vehicle load

[0118] The test load state is a light load state, that is, the total mass of the test vehicle's curb weight plus the test equipment, driver and tester.

[0119] 3.4 Test methods

[0120] At the beginning of the test, the left and right wheels of the vehicle are located at different adhesion coefficients (k H 、k LThe longitudinal center plane of the vehicle passes the boundary between the high and low μ road. With an initial speed of 80 km / h, the vehicle is braked to a standstill with full braking force. Steering corrections are allowed during the test. The longitudinal vehicle speed and yaw rate signals are recorded. The test is repeated three times on each side of the vehicle.

[0121] 3.5 Data processing and result expression

[0122] The peak yaw rate is the maximum absolute value of the yaw rate within 2 s after the brake pedal is depressed. The arithmetic mean of the results of six tests is taken as the final result.

[0123] 4. Test method for brake pedal linearity

[0124] 4.1 Test conditions

[0125] Same as 1.1.

[0126] 4.2 Instruments and equipment

[0127] Same as 1.2.

[0128] 4.3 Vehicle load

[0129] The test load state is the light load state, i.e. the total mass of the test vehicle, test equipment and the driver and test operator.

[0130] 4.4 Test method

[0131] Under the light load state, the average temperature of the service brake on the hottest axle of the vehicle is confirmed to be 65-100°C, and the brake booster is at a normal level. The test vehicle is accelerated to above 105 km / h, the accelerator pedal is released, the manual transmission vehicle is switched to neutral, and the automatic transmission vehicle is kept in D. When the vehicle speed drops to 100 ± 2 km / h, the brake pedal is slowly depressed at a constant speed until the ABS is triggered. The process requires the deceleration to change linearly and the pedal depression process to be as long as possible. The vehicle speed, deceleration, pedal force, pedal stroke, and ABS working condition are recorded. If the brake pedal is depressed too quickly, resulting in a vehicle speed of above 50 km / h when the ABS is triggered, the test is invalid. The test vehicle completes at least three valid tests.

[0132] 4.5 Data processing and result expression

[0133] 4.5.1 Initial brake pedal force linearity

[0134] The brake pedal force and deceleration signals collected during the test are intercepted, and the pedal stroke is selected to be greater than 5 mm to the deceleration of 4 m / s 2Brake pedal force and deceleration in the range of 5-8 m / s

[0135]

[0136] Where: R 2 - linearity; F - brake pedal force (N-m); A - deceleration (m / s 2 ).

[0137] 4.5.2 Final stage brake pedal force linearity

[0138] The brake pedal force and deceleration signals collected during the test were intercepted, and the deceleration in the range of 5-8 m / s 2 and the brake pedal force and deceleration were calculated for linearity, the calculation method being shown in formula 9.

[0139] 4.5.3 Initial stage brake pedal stroke linearity

[0140] The brake pedal stroke and deceleration signals collected during the test were intercepted, and the deceleration in the range of 5-8 m / s 2 and the brake pedal stroke and deceleration were calculated for linearity, the calculation method being shown in formula 8.

[0141]

[0142] Where: R 2 - linearity; S - brake pedal stroke (mm); A - deceleration (m / s 2 ).

[0143] The arithmetic mean of the results of each effective index was taken as the final result of the index.

[0144] 5. Light braking test method

[0145] 5.1 Test conditions

[0146] The same as 1.1.

[0147] 5.2 Instruments and equipment

[0148] The same as 1.2.

[0149] 5.3 Vehicle load

[0150] The test load state was a light load state, i.e. the total mass of the test vehicle, test equipment and driver and test personnel after preparation.

[0151] 5.4 Test method

[0152] Under light load condition, the test vehicle accelerates to more than 65 km / h, the accelerator pedal is released, the manual transmission vehicle is switched to neutral gear, and the automatic transmission vehicle is kept in D gear. When the vehicle speed drops to 60±2 km / h, the brake pedal is quickly stepped on and the pedal stroke is kept unchanged (the brake pedal jump time is not more than 0.2 s) until the vehicle stops. The brake pedal stroke is selected to meet the average deceleration in the range of 50-30 km / h in the test process, which is in the range of 1.8-2.2 m / s 2 The vehicle speed, deceleration and pedal stroke are recorded. The test vehicle completes at least 3 valid tests.

[0153] 5.5 Data processing and result expression

[0154] 5.5.1 Light braking response time

[0155] The average deceleration Ax in the range of 50-30 km / h is calculated 50-30 , and the light braking response time is the time required from stepping on the brake pedal to reaching 90% of the deceleration Ax 50-30 .

[0156] 5.5.2 Deceleration change rate

[0157] The calculation method of deceleration change rate is shown in formula 9.

[0158]

[0159] In the formula: K-deceleration change rate; Ax 50-30 -average deceleration in the range of 50-30 km / h (m / s 2 ) Ax 10-5 -average deceleration in the range of 10-5 km / h (m / s 2 ).

[0160] The arithmetic mean of the results of each valid index is taken as the final result of the index.

[0161] 6. Calculation method of braking performance evaluation score

[0162] The score of the secondary index is calculated according to the objective test results, the index results measured by the test, the index limits corresponding to 60 and 100 points in Table 3, and the linear interpolation method, with two decimal places. If the calculation result is greater than 100 points, it is calculated as 100 points.

[0163] The score of the primary index is calculated according to the score of the secondary index and the weight, with two decimal places. The calculation method is shown in formula 10.

[0164]

[0165] 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 ith 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. The score limit of the secondary index is shown in Table 3.

[0166] Table 3 Score limit of secondary index

[0167]

[0168] The overall score of the braking performance is calculated according to the score and weight of the primary index, and is rounded to one decimal place. The calculation method is shown in formula 11.

[0169]

[0170] In the formula, S is the overall score of the evaluation of the braking 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. The weight of the primary index and the secondary index is shown in Table 4.

[0171] Table 4 Weight of primary index and secondary index

[0172]

[0173]

[0174] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. It is obvious for 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 realized in other specific forms without departing from the spirit or essential characteristics of the present application.

[0175] Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, and 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 included in the present application.

[0176] In addition, it should be understood that although the present specification is described in terms of embodiments, each embodiment does not contain only one independent technical solution, and the description manner of the specification is only for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be properly combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for evaluating the braking performance of a vehicle based on actual driving conditions, characterized in that the method comprises the following steps: 1.1 dry braking test; 1.2 wet braking test; 1.3 braking stability test; 1.4 braking pedal linearity test; and 1.5 slight braking test, to obtain corresponding index data; and 1.6 calculating the overall braking performance score based on the index data to evaluate the braking performance of the vehicle. 1.1 Dry braking test Under full load conditions, the average temperature of the service brake on the hottest axle is confirmed to be between 65°C and 100°C, the test vehicle is accelerated to a speed of more than 105 km / h, the accelerator pedal is released, the manual transmission vehicle is shifted to neutral, the automatic transmission vehicle is kept in D, when the vehicle speed drops to 100±2 km / h, the brake pedal is depressed until the ABS system starts to work or the pedal force reaches 500N, and the vehicle stops; the vehicle speed, braking distance, brake pedal force, deceleration, vehicle body pitch angle, braking stability, and abnormal conditions during braking are recorded; the braking test is repeated 5 times. 1.2 Wet braking test The test vehicle is accelerated to a speed of 85±2 km / h on the starting section, the vehicle enters the test road, the accelerator pedal is released, the manual transmission vehicle is shifted to neutral, the automatic transmission vehicle is kept in D, and emergency braking is performed at the same time, the ABS system is activated to act on each wheel, and braking is maintained until the vehicle stops; the distance traveled by the vehicle from 80 km / h to 20 km / h is recorded; the first two test data of each test are discarded, and the test vehicle completes at least 6 valid tests. 1.3 Braking stability test At the beginning of the test, the left and right wheels of the vehicle are located on two road surfaces with different adhesion coefficients, and the longitudinal center plane of the vehicle passes through the junction line of the high and low adhesion coefficient road surfaces; with an initial speed of 80 km / h, emergency full braking is performed, and any part of the tire cannot cross the junction line until the vehicle stops, and steering wheel correction is allowed during the test; record the longitudinal vehicle speed and yaw rate signals during the test; the left and right sides of the test vehicle complete 3 effective tests respectively; 1.4, brake pedal linearity test Under light load conditions, the average temperature of the service brake on the hottest axle of the vehicle is confirmed to be 65-100°C, and the brake booster is at a normal level; the test vehicle accelerates to more than 105 km / h, releases the accelerator pedal, the manual transmission vehicle switches to neutral, and the automatic transmission vehicle remains in D range; when the vehicle speed drops to 100±2 km / h, slowly press the brake pedal until the ABS works, the process requires the deceleration to change linearly, and the pedal pressing process is as long as possible, record the vehicle speed, deceleration, pedal force, pedal stroke, AB working condition; if the brake pedal action is too fast to trigger the ABS working when the vehicle speed is above 50 km / h, the test is invalid; the test vehicle completes at least 3 effective tests; 1.5 Light braking test In the light load state, the test vehicle accelerates to more than 65 km / h, the accelerator pedal is released, the manual transmission model is switched to neutral, and the automatic transmission model remains in D. When the vehicle speed drops to 60 ± 2 km / h, the brake pedal is quickly depressed and the pedal stroke is kept constant. The brake pedal jump time does not exceed 0.2 s until the vehicle stops. The brake pedal stroke is selected to meet the average deceleration in the range of 1.8-2.2 m / s 2 in the range of 50-30 km / h during the test; record the vehicle speed, deceleration, and pedal stroke; and the test vehicle completes at least 3 valid tests. The index data obtained by the test are first-level indicators and second-level indicators, the first-level indicators are braking distance, braking stability, brake pedal linearity, braking response sensitivity and braking comfort; the second-level indicators are dry braking 100-0 km / h braking distance, wet braking 80-20 km / h braking distance, yaw rate peak value, initial braking pedal force linearity, final braking pedal force linearity, initial braking pedal stroke linearity, light braking response time, emergency braking response time, braking pitch angle and deceleration rate; The first-level indicator score is calculated according to the second-level indicator score and weight, and is rounded to two decimal places, and the calculation method is as follows: 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 second-level indicator score is based on objective testing, and the index limit value corresponding to 60 points and 100 points is combined with the test measured index result to calculate the score by 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; The overall braking performance score is calculated according to the first-level indicator score and weight, and is rounded to one decimal place, and the calculation method is as follows: In the formula, S is the total score of the evaluation of braking 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 braking performance based on actual driving conditions according to claim 1, characterized in that, In the wet braking test, each braking test is in the same test area, and the longitudinal error of the actual road surface for each test is not more than 5 m, and the lateral error is not more than 0.5 m.

3. The product force test evaluation method for vehicle braking performance based on actual driving conditions according to claim 2, characterized in that, The weights of the braking distance, braking stability, braking pedal linearity, braking response sensitivity and braking comfort are 30%, 10%, 20%, 20% and 20% respectively; the weights of the dry braking 100-0km / h braking distance and the wet braking 80-20km / h braking distance are 70% and 30% respectively, the weight of the yaw rate peak value in the braking stability is 100%, the weights of the initial braking pedal force linearity, the final braking pedal force linearity and the initial braking pedal stroke linearity in the braking pedal linearity are 40%, 20% and 40% respectively, the weights of the slight braking response time and the emergency braking response time in the braking response sensitivity are 50% and 50% respectively, and the weights of the braking pitch angle and the deceleration change rate in the braking comfort are 60% and 40% respectively; The index limit values corresponding to 60 points are as follows: The dry braking 100-0km / h braking distance, the wet braking 80-20km / h braking distance, the yaw rate peak value, the initial braking pedal force linearity, the final braking pedal force linearity, the initial braking pedal stroke linearity, the slight braking response time, the emergency braking response time, the braking pitch angle and the deceleration change rate correspond to 45m, 35m, 10° / s, 0.89, 0.9, 0.8, 0.3s, 0.25s, 2.5° and 30% respectively; The index limit values corresponding to 100 points are as follows: The dry braking 100-0km / h braking distance, the wet braking 80-20km / h braking distance, the yaw rate peak value, the initial braking pedal force linearity, the final braking pedal force linearity, the initial braking pedal stroke linearity, the slight braking response time, the emergency braking response time, the braking pitch angle and the deceleration change rate correspond to 38m, 24m, 2° / s, 1, 1, 1, 0.12s, 0.12s, 0.8° and 2% respectively.

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