CN106918459B - Truck overload judgment method - Google Patents
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Abstract
A truck overload judgment method. A truck overload judging method selects trucks with different axle numbers, different loading conditions of the trucks and different initial speeds; selecting a test site; measuring a braking deceleration a by using a braking deceleration meter; solving a true value L of the braking distance at a certain speed by utilizing a kinetic energy theorem; actually measuring the road surface display braking distance L under various conditions on an accident test site; determining the actual road adhesion coefficient of the vehicle using the functional relationship between the braking deceleration and the road adhesion coefficientφ(ii) a Obtaining data by using tests, determining the relation between the actual braking distance of the vehicle and the actual road surface distance by using a statistical method, and finally obtaining a correction coefficient of the actual road surface distanceK(ii) a And (4) processing the data by using a regression analysis method, and analyzing the data to obtain a result. The method and the device are used for judging the overload of the truck.
Description
The technical field is as follows:
the invention relates to a truck overload judgment method.
Background art:
since China enters twenty-first century, great progress and development are made in road truck transportation, but the overload problem in the truck transportation process is more and more serious, the road surface structure and the service life of a road are influenced, road traffic safety in China is seriously damaged, and traffic accidents are easily caused.
The overload phenomenon of the truck running on the road is serious, the safe braking distance of the truck in an overload state in the road running process is increased, the braking deceleration is reduced, and the truck becomes the great hidden trouble for inducing traffic accidents. In the traffic accident identification, the speed identification of the accident vehicle is not only to confirm the reason of the accident and analyze important evidence of the accident property, but also to be used as an important basis for making responsibility identification for the accident. Vehicle speed identification of an accident vehicle is most difficult in many identifications of traffic accidents. Through continuous experiments and a series of researches, the fact that the size of the adhesion coefficient directly influences the length of the braking distance when a vehicle brakes is found, and the adhesion coefficient is greatly changed in the process from the beginning of braking to the final complete stop of the vehicle, however, how to accurately determine the adhesion coefficient under the overload state of a large truck and correct the road surface actual measurement distance becomes an unsolvable problem at present when the problems are researched.
When the speed of the vehicle is identified after a traffic accident occurs, parameters such as the selection of the adhesion coefficient, the actual measurement distance of the road surface and the like become more uncertain due to the overload of the vehicle, and the correction of the parameters is a problem which is difficult to solve all the time. In dealing with such problems, the braking deceleration varies due to vehicle overload resulting in a significant uncertainty in the adhesion coefficient under different loading conditions. The current methods of adhesion coefficient selection and actual ground distance measurement have not been adequate for determining speed determinations for overloaded truck travel, resulting in distorted adhesion coefficient selection. And the deviation between the actual braking distance and the test distance at the accident site causes no drag mark print or a print shorter than the actual distance to be formed between the tire and the ground, so that the uncertainty of the identification result is increased. The calculation conclusion is inaccurate, and an objective vehicle running speed identification conclusion is difficult to define and give, so that the identification work is difficult.
The invention content is as follows:
the invention aims to provide a truck overload judgment method with accurate truck overload judgment.
The above purpose is realized by the following technical scheme:
a truck overload judging method comprises the steps of selecting trucks with different axle numbers, different loading conditions and different initial speeds of the trucks in the first step, selecting a test site in the second step, and measuring braking deceleration a by using a braking deceleration instrument in the third step; solving a true value L of the braking distance at a certain speed by utilizing a kinetic energy theorem; actually measuring the road surface display braking distance L under various conditions on an accident test site; the fourth step uses the functional relationship between the braking deceleration and the road adhesion coefficient (a = g)
) Determining the actual road adhesion coefficient of the vehicle(ii) a Obtaining data by using a test, determining the relation between the actual braking distance of the vehicle and the actual road surface distance by using a statistical method, and finally obtaining a correction coefficient K of the actual road surface distance; and fifthly, processing data by using a regression analysis method, and analyzing the data to obtain a result.
According to the truck overload judgment method, trucks with different axle numbers are selected in the first step, namely a three-axle truck, a four-axle truck and a five-axle truck; the different loading conditions of the truck are that the truck is braked at different initial speeds of 40km/h, 50km/h and 60km/h when the truck is unloaded, full, 50% overloaded, 100% overloaded, 150% overloaded and 200% overloaded respectively.
In the truck overload judging method, in the second step, the test site is selected to be an asphalt pavement with good drying, leveling and adhesion conditions, and five trucks, namely a three-axle truck, a four-axle truck and a five-axle truck with a braking deceleration instrument are subjected to braking tests at speeds of 40, 50 and 60km/h under the conditions of no load, full load, 50% overload, 100% overload, 150% overload and 200% overload.
In the truck overload judging method, the third step is that the braking deceleration a is the time required from the start of the operation to the time when the vehicle deceleration reaches 75% of the average deceleration fully sent by the specified vehicle by using a braking deceleration meter, and the braking distance is in direct proportion to the square of the initial braking speed.
The truck overload judging method comprises the fourth step of adhesion coefficient
Equal to the maximum value of the tangential stress of the road surface to the vehicle tyre
Divided by the normal stress of the road surfaceI.e. by
。
The truck overload judging method comprises the fourth step of correcting the coefficientKIs composed of
(ii) a Wherein the content of the first and second substances,
；
。
the fifth step of carrying out data processing by using a regression analysis method, wherein the result obtained by analyzing data is that firstly, unitary regression analysis is carried out on the adhesion coefficient by speed, the adhesion coefficient by shaft number and the adhesion coefficient by load weight, a regression equation is obtained according to the scattering points of the adhesion coefficients under different conditions, correlation coefficient detection is carried out, and the influence of the three factors on the adhesion coefficients is judged; the value of the corresponding adhesion coefficient does not change along with the change of the speed under the condition that the trucks with the same number of axles have the same loading capacity, and the value of the adhesion coefficient has no correlation and is irrelevant to the initial speed of the trucks.
Has the advantages that:
1. the invention carries out dynamic road test on the vehicle, truly reflects the whole process of vehicle braking, obtains the braking deceleration, the coordination time, the actual braking distance and the road surface actual measurement distance of trucks with different axles under different states from the early preparation of the test to the field actual measurement, saves the original data and marks the data, screens the data strictly according to the national standard and provides reliable basis for the subsequent calculation work.
2. When the MFDD is measured, the influence of the deviation of the initial braking speed on the test result of the truck is small, so that the braking test on a test site is difficult, and the success rate of the test and the accuracy rate of the result are high.
3. The invention carries out dynamic road test on the vehicle, truly reflects the whole process of vehicle braking, obtains the braking deceleration, the coordination time, the actual braking distance and the road surface actual measurement distance of trucks with different axles under different states from the early preparation of the test to the field actual measurement, saves the original data and marks the data, screens the data strictly according to the national standard and provides reliable basis for the subsequent calculation work. The field test needs to pay attention to the brake marks of the field and the brake performance of the truck, and strong evidence is provided for the speed identification work of the road traffic accident.
Description of the drawings:
FIG. 1 is a flow chart of the product.
The specific implementation mode is as follows:
example 1:
a truck overload judging method includes such steps as choosing trucks with different axles number and loading conditions and different initial speeds, choosing test field, using braking speed reducer,measuring the braking deceleration a; solving a true value L of the braking distance at a certain speed by utilizing a kinetic energy theorem; actually measuring the road surface display braking distance L under various conditions on an accident test site; the fourth step uses the functional relationship between the braking deceleration and the road adhesion coefficient (a = g)
) Determining the actual road adhesion coefficient of the vehicle(ii) a Obtaining data by using a test, determining the relation between the actual braking distance of the vehicle and the actual road surface distance by using a statistical method, and finally obtaining a correction coefficient K of the actual road surface distance; and fifthly, processing data by using a regression analysis method, and analyzing the data to obtain a result.
Example 2:
in the method for determining the overload of the truck in the embodiment 1, trucks with different axle numbers are selected in the first step, namely a three-axle truck, a four-axle truck and a five-axle truck; the different loading conditions of the truck are that the truck is braked at different initial speeds of 40km/h, 50km/h and 60km/h when the truck is unloaded, full, 50% overloaded, 100% overloaded, 150% overloaded and 200% overloaded respectively.
Example 3:
in the truck overload determination method described in embodiment 1, in the second step, a test site is selected to be an asphalt pavement with good drying, leveling and adhesion conditions, and five trucks, namely a three-axle truck, a four-axle truck and a five-axle truck, equipped with a braking deceleration meter are subjected to braking tests at speeds of 40, 50 and 60km/h under the conditions of no load, full load, 50% overload, 100% overload, 150% overload and 200% overload in sequence.
Example 4:
in the truck overload determination method according to embodiment 1, in the third step, the measured braking deceleration a is a time required from the start of the operation until the vehicle deceleration reaches 75% of the average deceleration that is sufficiently generated by the predetermined vehicle, and the braking distance is proportional to the square of the initial braking speed.
Example 5:
the truck overload determination method according to embodiment 1, fourth step adhesion coefficient
Equal to the maximum value of the tangential stress of the road surface to the vehicle tyreDivided by the normal stress of the road surface
I.e. by
。
The truck overload judging method comprises the fourth step of correcting the coefficientKIs composed of(ii) a Wherein the content of the first and second substances,
；。
example 6:
the truck overload determination method in embodiment 1, in the fifth step, data processing is performed by using a regression analysis method, and the analysis data results are that first, unitary regression analysis is performed on the adhesion coefficient by speed, the adhesion coefficient by axis, and the adhesion coefficient by load, a regression equation is obtained according to scattering points of the adhesion coefficient under different conditions, correlation coefficient inspection is performed, and the influence of three factors on the adhesion coefficient is determined; the value of the corresponding adhesion coefficient does not change along with the change of the speed under the condition that the trucks with the same number of axles have the same loading capacity, and the value of the adhesion coefficient has no correlation and is irrelevant to the initial speed of the trucks.
Example 7:
the truck overload judgment method in the embodiment 1 firstly ensures the accuracy of experimental data in the test process to have the following points: (1) the accuracy of the braking distance and the braking mark is influenced, and the test needs to be carried out on the same clean, smooth and dry asphalt pavement. (2) The braking performance of a large truck has many factors, and the data measured in the test has errors, for example, the truck is braked for a long time, the generated heat fading can rapidly reduce the speed of the truck until the truck stops, and whether the performance of the brake is good or not is checked. (3) The vehicle load state is as follows (no load, full load, overload 50%, overload 100%, overload 150%, overload 200%). The truck load capacity is weighed, the abrasion degree of the tested vehicle tire conforms to the national specified standard, and the measurement for improving the braking distance is more accurate by using the laser range finder.
And secondly, for the scientificity of data processing, selecting a proper data processing method according to the data characteristics.
(1) On the basis of collecting a large amount of test data, a regression relation function expression between the adhesion coefficient and the large truck under different loading capacities is established by a mathematical statistics method.
(2) Because the test times of each vehicle are more, and the braking performance of the truck is reduced in different degrees, the obtained data part does not meet the test requirements, and the data should be screened according to the industry standard established by the state.
The test principle is as follows: because no corresponding test environment exists in the current road traffic accident site, the appraiser cannot test the vehicle in the accident site, and the method is obviously not preferable. The field test is to obtain the variation trend of different braking deceleration rates of different loading quantities for the reproduction of the truck braking performance under different loading conditions, and the tester accurately and completely records and saves the obtained test result by using a scientific method and a modern technical means. The functional function of the portable brake performance tester of the MBK-01 (III) model is fully exerted in the test, and the principle is that the acceleration sensor is used as the detection element, the brake start signal is provided by the brake pedal contact switch (or the pedal force sensor (B model)), the brake deceleration and the time are actually measured, the high-speed operation is carried out in the microprocessor, and the results of the average deceleration (MFDD), the brake initial speed, the brake coordination time, the actual brake distance and the like can be output.
The portable braking performance tester adopted in the test is reliable in measured data due to the high precision of the tester, adopts the advanced acceleration sensors at home and abroad, can well integrate data processing and expert experience together, and provides convenience. The design is very simple and reasonable, the test results of the braking performance and the acceleration performance of the test truck can be stored in the instrument together and directly printed out on site by the micro printer, the test data can be further analyzed after the test data is connected with a computer through RS232 serial communication (or a USB interface), and the test condition can be converged into a curve graph to visually see the change of the test data.
With the increasing popularity of automobiles with ABS (anti-lock brake system) in recent years, the automobiles with the ABS usually cannot generate obvious brake marks under the condition of emergency braking, so that a manual detection method is definitely not advisable, so that an instrument is used for testing in the test, and compared with the result of a manual road test, the MBK-01 type portable brake performance tester has more scientific and accurate results. And carrying out further analysis according to the measured data. In the test, whether the final result can be influenced by the detection of an instrument is suspected, the possibility that the road test is carried out by using the braking performance tester in the test is greatly reduced, and the influence of the initial braking speed on the detection result is found to be small. The high-sensitivity acceleration sensor applied to the instrument can meet the microprocessor technology of rapid acquisition and calculation requirements, effectively solves the problems of measurement precision and parameter calculation of the braking performance of the motor vehicle, and conforms to the regulation in the road test brake performance of GB7258-2004 technical conditions for motor vehicle operation safety.
The apparatus required for the test: the braking performance tester, the speed tester, the laser range finder and the like are all qualified by annual inspection of national technical quality supervision departments and run normally after testing.
The working principle of the brake instrument is as follows: the measurement in the test is mainly completed by matching the host machine, the acceleration sensor, the pedal contact switch and the like. Firstly, after the instrument is installed in a vehicle and the related information license plate and the vehicle type of the large truck to be tested are set, the test preparation state can be entered in two minutes. At this time, the instrument eliminates installation deviation to carry out zero point calibration, and the braking test of the large truck is started according to a road test inspection method specified in motor vehicle operation safety technical conditions and a test requirement set for the test: when a driver begins to brake and tread a brake pedal, a brake pedal contact switch which is installed on the automobile brake pedal in advance quickly transmits a brake starting signal to a host, the host carries out high-speed sampling at this time, test data are processed and all data are stored, then the fully-sent average deceleration (MFDD) and brake coordination time are calculated according to the instantaneous deceleration and brake time measured by an instrument, the result and the brake initial speed, and the brake distance is displayed on a screen through high-speed operation. When the measurement is finished, the vehicle braking performance is judged to be qualified or not according to a judgment standard in a road test requirement of motor vehicle operation safety technical conditions set in a host, the step can be immediately reversed, a portable printer can be connected to print a final test result, and then the final test result is stored by being connected with a computer, so that a related result can be conveniently looked up after the test is finished.
Sensor principle: silicon micro-capacitive solid-state acceleration sensors at an advanced level are embodied in portable brake deceleration meters under test. Based on the most basic principle of mechanics
The acceleration sensor is made by finding a mass block with sensitive acceleration inside, which is fixed on the sensor shell by elastic cantilever, and an electrode plate is set on the top and bottom of the mass block, which has a narrow equal gap with the mass block and can form an equal capacitance with the mass block. When the acceleration of the inner part occurs in the vertical direction of the shell, the inertia force can be appliedSo that the mass is displaced, the gap is changed, and consequently the capacitance is subsequently changed. The difference between the two capacitances is found to be proportional to the acceleration, thus producing a capacitive acceleration sensor. Therefore, silicon is used as a base material in consideration of this characteristic, and the silicon is produced by using the technologies of microlithography and vapor deposition, and is characterized by small drift. When the sensor works, the relation between capacitance and displacement can be realized, the inertia element and the two fixed electrodes form a variable capacitor, and the inertia element is converted into acceleration measurement output through the capacitance measurement circuit during vibration.
The installation of the DXT laser range finder of the laika requires as follows:
(1) and (3) loading the 9V battery into the battery mounting position according to the correct polarity, checking whether the instrument is damaged or not, and checking whether the instrument normally operates or not after the instrument is started. (2) After each test is finished, the instrument is placed in a horizontal state on the asphalt pavement, and the truck brake mark needing to be measured is selected. (3) Lightly pressing the "launch key" button and then turning on the rangefinder internal power! The rangefinder is in a ready-to-measure state as seen through the eyepiece, and measurement is started, and the instrument will automatically save each set of measurement results.
Example 8:
the truck overload determination method according to embodiment 7,
the test is carried out on the spot, the test frequency is multiple, the test data is wide, and three-axis, four-axis and five-axis trucks are respectively tested at different initial speeds when in no-load, full-load, 50% overload, 100% overload, 150% overload and 200% overload: braking is carried out at 40km/h, 50km/h and 60 km/h.
Firstly, part of vehicles are selected, 15 vehicles are selected according to different shaft numbers to participate in the test, driver training is organized in the early stage aiming at the test, all the tested vehicles are checked from the aspects of vehicle brakes, tires and the like, and the problem is found and solved in time. Because driver's operation custom's difference in the experiment, do not step on the brake pedal to the end when braking, and experimental difference lies in must stepping on the brake pedal to the end when braking at every turn, does not surely appear "some phenomenon of stopping", hardly surveys comparatively complete braking seal on the road surface, has lost experimental purpose, tests through readjustment, and the total experimental effect is satisfied.
The test is based on the tests of large trucks under different loading capacities, so the test is divided into no-load, full-load and overload of 50 percent, overload of 100 percent, overload of 150 percent and overload of 200 percent according to different loading capacities, particularly, sand grains are selected as loading weights to facilitate the research and the smooth test during overload, the loading is convenient, the tests under different loading capacities are met through a loader in the test, and the test purpose is achieved. The road transport truck adopts the diagonal tires, and the tire wear degree used by the test vehicle is relatively low, thereby meeting the test requirements.
When the sand and stone particles are loaded according to different carrying capacities, the loader bucket is used as a standard, so that the weight of the sand and stone particles is closer to the test requirement when the carrying capacity is different, and the real reliability of data when the brake test is carried out under different carrying capacities is met.
On dry, flat, good and good-adhesion asphalt pavement, five trucks (three-shaft, four-shaft and five-shaft) provided with braking deceleration meters are respectively subjected to braking tests at the speeds of 40, 50 and 60km/h under the conditions of no load, full load, 50% overload, 100% overload, 150% overload and 200% overload, the speed of the trucks after overload is less than 70km/h, so that the test at the initial speed of 70km/h is not measured in the test, data are stored in the braking deceleration meters after the test is finished each time, the sequentially measured data results can be printed out by a micro printer on site and stored, and the data are filled in a test vehicle test data information registration table shown in the following table 2.1 after the test of all trucks is finished.
TABLE 2.1
(by analogy: three-axis, four-axis, five-axis trucks were tested at 40, 50, 60km/h and maximum speed with no load, full load, 50% overload, 100% overload, 150% overload, 200% overload; test for brake parking at maximum speed.)
Through test measurement, the vehicle state is selected in two parts, the first part is the change reason of the vehicle state, at least five trucks are guaranteed in each group according to different axle numbers in the test process, more than five groups of data of each truck in the test meet the standard, the braking performance of the trucks can be reduced due to the increase of times in the braking process, heat fading is generated, screening and eliminating are carried out on all measured data, and unqualified data screened for the first time can account for 10% -15% of the total data. The second part is referred to as "brake coordination time" defined in 7.13.1.2 of "technical conditions for safety of operation of motor vehicles" (GB 7258-2004), the so-called coordination time being the time required from the start of action until the vehicle deceleration reaches 75% of the prescribed average deceleration at which the vehicle adequately issues when braking is taken in the event of an emergency. The time for the truck to be hydraulically braked is not more than 0.35s, the brake coordination time of the automobile train and the articulated bus is not more than 0.8s, and the time for the truck to be pneumatically braked is not more than 0.6.
In addition, the braking distance is proportional to the square of the initial braking speed, so when the braking distance is used for testing the service braking performance, the initial braking speed is required to be accurate, but the operation is difficult to realize in a braking test, and the braking distance when the specified initial speed is corrected through reasonable calculation is needed. When the standard requirement cannot be met, the braking coordination time is too long, or the braking distance is too long due to insufficient braking deceleration, further analysis is needed, namely the braking coordination time and the average deceleration which is fully sent out are measured. Table 2.2 is an assessment of the road test brake performance test in GB 7258-2004. Table 2.3 is an assessment of the road test braking performance test in 3GB 7258-2004.
TABLE 2.2
TABLE 2.3
The standards in the table are used for judging whether the braking deceleration of different types of vehicles is qualified when braking measures are taken, if the braking deceleration is not qualified, unqualified data is deleted, and the unqualified data screened out integrally has 25% -35% of the total amount. The type of the brakes of the trucks adopted in the test is air pressure braking, so that relevant parameters can be searched and compared with field test data, and the validity and the accuracy of the data are ensured.
Example 9:
truck overload determination method and truck braking process described in embodiment 1
When a truck driver meets an emergency situation during running of the truck, the time which is elapsed until the driver presses a brake pedal to start acting is called reaction time, and the reaction distance is short. The reaction time is directly related to the reaction degree and the technical proficiency degree of the drivers participating in the test. The braking distance is the distance the vehicle travels during the period from the time the driver receives the emergency braking signal to the time the vehicle is completely stopped. The test shows that the driver reacts to the action of the brake and then the truck continuously brakes the three aspects that the automobile runs by the distances respectively
、
And
to show that we see the wagon with a coefficient of adhesion of
At an initial speed on the road surface
The whole process when the emergency braking is carried out,
(1) testingThe distance the truck travels during the reaction time is
:
(3.1)
(2) The distance covered by the truck during the brake actuation of the truck is
：
(3.2)
(3) During the continuous braking phase, the truck is driven
Making uniform deceleration movement and braking distance
Comprises the following steps:
(3.3)
so that the total stopping distance of the truck
Comprises the following steps:
(3.4)
driver reaction time in generalIs 0.3 to 1.0 s, the brake has the action time
Generally 0.3 to 0.95 s. So approximate selection
The value of (d) was 1.5 s.
Therefore, the whole braking process comprises four stages of reaction of the driver, brake application, continuous braking and brake release. The correction coefficient of the braking distance is the measured road surface distance under the condition that the truck is unloaded and fully loaded in the braking process.
There are many factors that affect the adhesion coefficient of a truck, and the theoretical value of the adhesion coefficient is often a range, but is affected by many factors due to its variation. Therefore, in practice, the calculation and selection should be performed according to the variation trend and in combination with the specific road traffic accident identification case.
Influence of (a) road conditions on the adhesion coefficient
(1) The adhesion coefficient varies with the properties of the road surface to different degrees depending on the roughness of the road, the material of the road surface, and the wetness of the road surface. The adhesion coefficient is large on dry road surfaces, whereas the adhesion coefficient is small on wet road surfaces, and the adhesion coefficient becomes smaller on ice and snow road surfaces in winter.
(2) And the relationship with the unevenness of the road surface. When the vehicle is on uneven road surface, the instantaneous value of the brake adhesion coefficient can be
Changes along with the change of road shape; on a road with an uneven road surface, the average value of the adhesion coefficient becomes smaller as the speed of the wheels increases.
(II) influence of tire on adhesion coefficient
(1) Due to the variety of tires. The vehicle can obtain a higher adhesion coefficient with a radial tire than with a bias tire by about 10%, however, after further research it was found that the results were just opposite on wet road surfaces with a high adhesion coefficient and on slippery ice roads with a low adhesion coefficient. As shown in table 3.1 below for the adhesion coefficient test values for different tires under different road conditions.
TABLE 3.1
(2) Air pressure and external wear of vehicle tires. The low-air-pressure and wide-section tire and meridian tire adhesion coefficient on a hard road surface are higher than those of other common tires; on soft and muddy road surfaces, the high-pressure and large-pattern oblique tire is more suitable for the environment; the greater the wear, the smaller the coefficient of adhesion.
(III) Effect of slip Rate on adhesion coefficient
The slip ratio, which is the degree to which the vehicle tire and the hard road surface slip relative to each other when they are in contact with the ground, is also affected to a greater or lesser extent. In general we express the degree of slippage by the following expression:
the adhesion coefficient is different at different stages when the vehicle is braked. The slip ratio is greater than zero because the rolling radius of the vehicle tire is becoming larger during this process. The tire does not really slide relative to the ground, but only has a certain sliding rate at the beginning. Then local relative sliding occurs in the footprint of the tyre and the adhesion coefficient is seen to deserve an increase in speed. The coefficient of adhesion value is in a descending trend after reaching the highest point, and the reason of gradual reduction is caused by that the static friction factor is greater than the dynamic friction factor between the friction pairs.
When the brake wheel is locked and slides along the road surface (
) Or the driving wheel is slipped in situ (
) In the limit, not only the longitudinal adhesion coefficient is significantly reduced but also the lateral adhesion coefficient is sharply reduced to approach zero. The variation curves of the adhesion coefficient and the slip rate are different under different road surface conditions, and the maximum adhesion coefficientThe corresponding slip rates are different, the maximum adhesion coefficients under different road surface conditions are also different, and the magnitude of the slip rate has great influence on the adhesion coefficients between the wheels and the ground.
(1) For coefficient of adhesion
Expressed as the maximum value of the tangential stress of the road surface to the vehicle tyre
Normal stress of road surface
(3.6); common formulas in dealing with such problems are exponential model magic formulas, and neural network models.
An adjustment formula of the adhesion coefficient is designed, and the adjustment is carried out by adopting the following product model:
The correction factor given by the above equation is divided into five levels:
、
、
、
、
the corresponding weights are 1, 0.8, 0.6, 0.4 and 0.2, respectively.
Taking a two-axle truck as an example, the wheelbase of the truck is
Height of center of gravity of
Total weight of
The distance of the center of gravity from the front axle is
The center of gravity is at a distance from the rear axle of
. At rest the front axle reaction force is
The reaction force of the rear axle is
. Then
，. If order
Then, then
，
。
Inertia force in braking and decelerating process of automobile
Acting at the centre of gravity
When braking, the front axle and the rear axle are not synchronous, the front axle adhesion coefficient is 1, the corresponding rear axle adhesion coefficient is 2, and the braking adhesion forces of the road surface to the front axle and the rear axle are respectively
And. The pressure of the front axle of the automobile is increased and the pressure of the rear axle is reduced due to braking, and the load transfer amount of the axle is. The system of equations is thus established as follows:
TABLE 3.2
| Braking situation | Description of the preferred embodiment | Calculation formula |
| Synchronous braking | All wheels are braked simultaneously, and the adhesion coefficients of the wheels and the road surface are all |
 |
| Only braking of front and rear axles | Two wheels of the front axle are braked, two wheels of the rear axle roll freely, and the adhesion coefficients of the front wheels and the road surface are all |
 |
| With rear-axle braking only | Two wheels of the rear axle are braked, two wheels of the front axle roll freely, and the adhesion coefficients of the rear wheels and the road surface are all |
 |
| With only one front wheel and one rear wheel braking | Only one front wheel and one rear wheel are braked, the other front wheel and the other rear wheel roll freely, and the adhesion coefficients of the front wheel and the rear wheel and the road surface are all  |
 |
Braking deceleration generated by truck during braking
The ratio of (a) to (b) is used as a basic formula for obtaining the road adhesion coefficient, that is, the magnitude of the braking deceleration determines the magnitude of the adhesion coefficient, and the adhesion coefficient calculation expression:
（3.13）
in the formula:
-truck cling coefficients under different loading conditions;
-instrumented truck brake plus (minus) speed, m/s 2;
-standard gravitational acceleration, taking 9.8m/s 2; and respectively calculating the adhesion coefficient of each axle number truck when the truck is subjected to brake test detection at different initial speeds under different loading amounts according to the qualified data of the primary screening test through the relational expression.
All tested vehicles have corresponding adhesion coefficients, whether the solved adhesion coefficients have certain relations with the number of vehicle axles, the initial speed and different cargo loads or not needs to be discussed, and the regression analysis method is used for determining which influence factors exist on the basis of considering that the adhesion coefficients under different conditions are in normal distribution.
Influence of overload on braking distance
The braking distance becomes longer with the increase of the load capacity; the larger the initial braking speed is, the larger the influence of the change in the load capacity on the braking distance is, and the relationship between the initial traveling speed of the truck and the square of the braking distance is in direct proportion.
Influence of the reaction time of the braking system on the braking distance
When the vehicle speed is
When the driver steps on the brake pedal, the brake system has clearance and is influenced by the idle stroke of the pedal, the corresponding time is needed for the energy to be transmitted in the pipeline, and the influence of the reaction time of the driver and other factors is also influenced, so the vehicle is continued in the period of timeVelocity of continuous flow
Go forward until the distance of forward travel
Thereafter, the brake starts to act, which is the reaction time and the corresponding reaction distance. When the truck starts braking, the speed of the vehicle decreases rapidly until it reaches 0, but actually until it reaches a point
The braking deceleration of the vehicle is started only after the vehicle is started, and the braking distance is defined according to the technical condition of safe operation of the vehicle
ToSince the vehicle speed is relatively fast before the braking deceleration occurs, the reaction time of the vehicle brake system has a great influence on the braking distance.
In an emergency situation, the driver takes braking measures from the start of braking of the vehicle to the maximum braking force of the truck, and during this process, the tires and the road rub to leave a brake mark, which is the brake mark. As the braking force increases, the tire footprint remaining on the road surface will change accordingly. The truck brake footprint can be clearly distinguished when initially formed, then the slow patterns are gradually unclear until the thick black footprint appears finally, and the tire patterns are gradually deepened until the thick black footprint appears at the front of the brake footprint, which is called brake impression. From this moment on, the wheels of the truck have rolled from pure (
) State entry slip (
) Status.
The wheel is in a complete slipping state, and the brake mark is completely changed into a black strip after the tire is rubbed with the road surface, which is called brake drag mark. In an emergency situation the driver instinctively and rapidly depresses the brake pedal, the vehicle then leaving a brake mark on the ground.
The length of the brake dragging mark is mainly determined by the speed of a vehicle before braking and the adhesion coefficient of a road surface, the dragging distance is found to be in a direct proportion relation with the square of the running speed of the vehicle, and the length of the brake dragging mark also depends on factors such as road surface materials, road surface conditions (dry, wet and the like) and slip speed, and the factors can cause influence.
When a truck is braked, the actual braking distance deviates from the actual distance measured at an accident site by a certain distance, and the slip rate between the tire and the ground is influenced by different conditions such as loading, brake type, initial braking speed and the like in the process of increasing the braking force of a truck brake, so that no drag mark is formed between the tire and the ground or the formed mark is shorter than the actual distance, so that the uncertainty of the identification result is increased.
The invention is based on a large number of actual measurement tests to measure the actual road surface distance under different speeds, and utilizes the test or the obtained data, and utilizes a statistical method to determine the relationship between the actual vehicle braking distance and the actual road surface distance, and finally obtains the correction coefficient of the actual road surface distance under various conditions. The invention only researches the correction coefficients of trucks with different axle numbers (three-axle, four-axle and five-axle) under the conditions of no load and full load respectively
. The following formula can be used to obtain the adhesion coefficient of the truck at different initial speeds and different adhesion coefficients
Lower part
The corresponding value is more than the number of tests measured hereThe adhesion coefficient selected typically is the mean value in each case, as follows:
TABLE 3.5
Example 10:
the truck overload judgment method of embodiment 1, wherein the data processing method is regression analysis
The change of the adhesion coefficient of the dependent variable truck is often influenced by several important factors, namely the initial speed, the number of shafts and different loading weights, and at the moment, the three influencing factors are required to be used as independent variables to explain the change of the adhesion coefficient of the dependent variable, so that multiple regression, namely multiple regression, is required to be carried out. When the independent variable (initial speed, number of shafts and different loading capacity) and the dependent variable attachment coefficient are in a linear relation, judging whether the independent variable has influence on the dependent variable. Is provided withIn order to be a dependent variable of the coefficient of adhesion,
，，
when the independent variable is the axial number, the initial speed and the different weights, and the independent variable and the dependent variable are in linear relation, the multiple linear regression model is as follows:
（3.17）
wherein the content of the first and second substances,
is a constant term and is a constant number,
，
in order to be the regression coefficient, the method,
is composed of
，
When the fixing is carried out, the fixing device,
each increased unit pair
The effect of (A) isTo pair
Partial regression coefficients of; in the same wayIs composed of
，
When the fixing is carried out, the fixing device,
each increased unit pairThe effect of (a) of (b), i.e.,to pair
Partial regression coefficients, etc. If two independent variables
，
，
Same dependent variableWhen the linear correlation is presented, the three-element linear regression model can be described as:
（3.18）
adhesion coefficient treatment process
For the experimental study of 3 factors 3 × 6 levels, each level is tested 25 times, and 54 test conditions are totally provided, at least five three-axis, four-axis and five-axis vehicles are respectively tested, 2000 groups of data are obtained, for the convenience of test data processing, each vehicle respectively takes 5 effective data, the change conditions of the adhesion coefficient and the braking deceleration under each test condition are listed below, as shown by the test experimental data of the three-axis truck in table 4.1, the three-axis truck respectively carries out the braking test at the speed of 40, 50 and 60km/h under the conditions of no load, full load, 50% overload, 100% overload, 150% overload and 200% overload, and the data of the rest vehicles are shown in the appendix.
TABLE 4.1
Excluding data with large discreteness
The data with large discreteness are screened out, so that influence on the next analysis is avoided, and the conclusion is misled. The box type is made according to the change of the adhesion coefficient when different shaft numbers, different initial speeds and different loading amounts are adopted.
The relation values of the three-axis, four-axis and five-axis attachment coefficients meet the requirement of normal distribution, and the data result is stable and reliable in display and has no abnormal phenomenon.
According to the adhesion coefficients at different initial speeds, all data are contained in a normal distribution graph, and the result is stable and reliable.
From the view of the adhesion coefficient at different overload numbers, the adhesion coefficient is smaller as the overload number is the largest. When data with large discreteness is seen, the row number marked with singular values is deleted and removed, and other data are all around the normal distribution and can be accepted.
(1) When the same axle number of trucks has the same overload, the independent variable
Is an initial velocity, dependent variableThe adhesion coefficient is 40, 50,At an initial speed of 60km/h
，
On the same scatter diagram, it is found that, as shown in the following table 4.2, the three-axle truck is overloaded 100% and the adhesion coefficients at different initial speeds are respectively shown, and the three-axle truck is overloaded 100% and the change of the adhesion coefficients at the initial speeds of 40, 50 and 60km/h is taken as an example, the scatter diagram between the initial speed and the adhesion coefficient is drawn, so as to obtain a unitary regression equation and the first-order regression equationChange and then pass through
And comparing with the correlation coefficient checking table to determine whether the two are correlated or not.
TABLE 4.2
| Triaxial 40km/h overload 100% | Coefficient of adhesion | Triaxial 50km/h overload 100% | Coefficient of adhesion | Three-axis 60km/h overload 100% | Coefficient of adhesion |
| 39.90 | 0.36 | 50.20 | 0.33 | 54.20 | 0.27 |
| 40.80 | 0.37 | 49.20 | 0.32 | 58.00 | 0.34 |
| 40.40 | 0.34 | 49.80 | 0.29 | 59.80 | 0.29 |
| 41.70 | 0.38 | 50.00 | 0.35 | 58.00 | 0.35 |
| 39.30 | 0.29 | 49.70 | 0.33 | 59.80 | 0.31 |
| 39.20 | 0.25 | 50.20 | 0.24 | 60.90 | 0.28 |
| 42.90 | 0.27 | 49.80 | 0.23 | 62.20 | 0.27 |
| 41.00 | 0.24 | 54.30 | 0.28 | 56.90 | 0.35 |
| 41.90 | 0.32 | 53.10 | 0.23 | 60.90 | 0.28 |
| 40.60 | 0.31 | 51.30 | 0.36 | 61.50 | 0.33 |
| 42.40 | 0.29 | 49.60 | 0.24 | 61.00 | 0.31 |
| 39.70 | 0.28 | 51.30 | 0.36 | 62.10 | 0.27 |
| 43.10 | 0.32 | 49.20 | 0.32 | 61.50 | 0.35 |
| 39.30 | 0.29 | 53.10 | 0.23 | 59.80 | 0.28 |
| 42.90 | 0.27 | 50.00 | 0.35 | 56.90 | 0.36 |
| 42.10 | 0.29 | 50.60 | 0.24 | 61.10 | 0.28 |
| 40.10 | 0.28 | 48.90 | 0.28 | 60.90 | 0.30 |
| 39.70 | 0.25 | 49.70 | 0.32 | 62.10 | 0.30 |
| 38.50 | 0.32 | 50.20 | 0.35 | 56.90 | 0.35 |
| 41.70 | 0.31 | 51.30 | 0.36 | 58.10 | 0.34 |
| 40.80 | 0.36 | 49.20 | 0.32 | 60.00 | 0.36 |
| 43.00 | 0.32 | 49.70 | 0.34 | 61.00 | 0.27 |
| 39.30 | 0.29 | 50.40 | 0.33 | 59.80 | 0.28 |
| 41.70 | 0.38 | 49.70 | 0.33 | 59.80 | 0.34 |
| 41.50 | 0.38 | 48.30 | 0.32 | 61.10 | 0.31 |
(1) The axial number and the load capacity are constant, and the initial speeds and the adhesion coefficients are respectively 40km/h, 50km/h and 60km/h
In the context of (a) or (b),
=0.026, according to
，Checking the correlation coefficient to obtainCritical value
=0.026<0.39, therefore
And
the linear correlation relationship between the two is not significant, namely the initial velocity and the adhesion coefficient are not correlated. By analogy, no matter three-axis, four-axis, five-axis trucks are irrelevant to the change of the speed and the adhesion coefficient under the condition.
And (4) conclusion: the corresponding values of the adhesion coefficients of the trucks with the same axle number do not change along with the change of the speed under the same loading capacity, and have no correlation, so that the magnitude of the adhesion coefficients is proved to be irrelevant to the initial speed of the trucks.
(2) When a certain speed (50 km/h) and a certain overload (150 percent overload) are taken for a certain time, the independent variable
Is the number of axes, dependent variableFor the adhesion coefficient, the adhesion coefficients of three shafts, four shafts and five shafts under the condition are compared, and the change of the dependent variable adhesion coefficient along with the difference of the independent variable shaft number can be seen through a scatter diagram, and the adhesion coefficient changes when the three types of trucks in the table 4.3 overload by 150 percent at 50 km/h.
TABLE 4.3
| Overload of 150% at 50km/h of three-axle truck | Coefficient of adhesion | Overload of 150% for four-axle truck 50km/h | Coefficient of adhesion | Overload of 150% at 50km/h of five-axis truck | Coefficient of adhesion |
| 3 | 0.30 | 4 | 0.37 | 5 | 0.25 |
| 3 | 0.27 | 4 | 0.28 | 5 | 0.26 |
| 3 | 0.29 | 4 | 0.23 | 5 | 0.24 |
| 3 | 0.31 | 4 | 0.23 | 5 | 0.26 |
| 3 | 0.29 | 4 | 0.25 | 5 | 0.25 |
| 3 | 0.23 | 4 | 0.33 | 5 | 0.33 |
| 3 | 0.26 | 4 | 0.36 | 5 | 0.31 |
| 3 | 0.24 | 4 | 0.33 | 5 | 0.30 |
| 3 | 0.27 | 4 | 0.31 | 5 | 0.23 |
| 3 | 0.24 | 4 | 0.29 | 5 | 0.31 |
| 3 | 0.24 | 4 | 0.37 | 5 | 0.24 |
| 3 | 0.42 | 4 | 0.25 | 5 | 0.24 |
| 3 | 0.26 | 4 | 0.23 | 5 | 0.24 |
| 3 | 0.27 | 4 | 0.24 | 5 | 0.23 |
| 3 | 0.24 | 4 | 0.24 | 5 | 0.34 |
| 3 | 0.25 | 4 | 0.38 | 5 | 0.33 |
| 3 | 0.23 | 4 | 0.32 | 5 | 0.25 |
| 3 | 0.24 | 4 | 0.28 | 5 | 0.31 |
| 3 | 0.24 | 4 | 0.33 | 5 | 0.28 |
| 3 | 0.25 | 4 | 0.38 | 5 | 0.35 |
| 3 | 0.35 | 4 | 0.37 | 5 | 0.25 |
| 3 | 0.32 | 4 | 0.24 | 5 | 0.24 |
| 3 | 0.29 | 4 | 0.28 | 5 | 0.23 |
| 3 | 0.30 | 4 | 0.23 | 5 | 0.23 |
| 3 | 0.31 | 4 | 0.23 | 5 | 0.21 |
When the overload amount is constant, the speed is constant and only the number of axes is different, the attachment coefficients of the three-axis, the four-axis or the five-axis have great similarity, and the values are shown in
In the context of (a) or (b),
=0.06, according to
=0.05，
=23, checking correlation coefficient table to obtain critical value
=0.06<0.39, therefore
And
the linear correlation relationship between the two is not significant, namely the number of axes is not correlated with the adhesion coefficient. By analogy, the number of axes and the change in the coefficient of adhesion were not relevant under this type of test.
And (4) conclusion: under the conditions of certain overload and certain initial speed, the adhesion coefficients of three-axis, four-axis and five-axis trucks are not different due to the change of the number of the axles, and are distributed similarly, and tests under the same test conditions prove that no correlation exists between the independent variable number of the axles and the dependent variable adhesion coefficients, and the truck number is proved to be irrelevant to the adhesion coefficients.
(3) Independent variable under the condition of constant speed and number of shafts
For different loads of the truck, dependent variableFor truck coefficient of adhesion, by observationAnd
in between, as the weight of the truck increasesThe value of the adhesion coefficient is reduced, which shows that the load capacity and the adhesion coefficient have a functional relationship and the correlation degree is very close. As shown in table 4.4 the adhesion coefficient of the truck for different loading conditions of a four-axle truck at an initial speed of 40 km/h.
TABLE 4.4
| No load | Coefficient of adhesion phi | Full load | Coefficient of adhesion phi | Overload by 50% | Coefficient of adhesion phi | Overload 100% | Coefficient of adhesion phi | Overload 150% | Coefficient of adhesion phi | Overload 200% | Coefficient of adhesion phi |
| No load | 0.61 | Full load | 0.69 | Overload by 50% | 0.53 | Overload 100% | 0.42 | Overload 150% | 0.29 | Overload 200% | 0.25 |
| No load | 0.60 | Full load | 0.63 | Overload by 50% | 0.50 | Overload 100% | 0.47 | Overload 150% | 0.26 | Overload 200% | 0.26 |
| No load | 0.63 | Full load | 0.62 | Overload by 50% | 0.49 | Overload 100% | 0.48 | Overload 150% | 0.24 | Overload 200% | 0.24 |
| No load | 0.61 | Full load | 0.67 | Overload by 50% | 0.62 | Overload 100% | 0.45 | Overload 150% | 0.23 | Overload 200% | 0.27 |
| No load | 0.69 | Full load | 0.62 | Overload by 50% | 0.53 | Overload 100% | 0.47 | Overload 150% | 0.27 | Overload 200% | 0.25 |
| No load | 0.66 | Full load | 0.59 | Overload by 50% | 0.49 | Overload 100% | 0.43 | Overload 150% | 0.32 | Overload 200% | 0.37 |
| No load | 0.68 | Full load | 0.54 | Overload by 50% | 0.49 | Overload 100% | 0.40 | Overload 150% | 0.32 | Overload 200% | 0.32 |
| No load | 0.67 | Full load | 0.52 | Overload by 50% | 0.49 | Overload 100% | 0.43 | Overload 150% | 0.34 | Overload 200% | 0.32 |
| No load | 0.67 | Full load | 0.58 | Overload by 50% | 0.54 | Overload 100% | 0.42 | Overload 150% | 0.36 | Overload 200% | 0.23 |
| No load | 0.64 | Full load | 0.57 | Overload by 50% | 0.51 | Overload 100% | 0.44 | Overload 150% | 0.31 | Overload 200% | 0.31 |
| No load | 0.61 | Full load | 0.62 | Overload by 50% | 0.54 | Overload 100% | 0.41 | Overload 150% | 0.23 | Overload 200% | 0.24 |
| No load | 0.60 | Full load | 0.63 | Overload by 50% | 0.56 | Overload 100% | 0.46 | Overload 150% | 0.23 | Overload 200% | 0.26 |
| No load | 0.65 | Full load | 0.63 | Overload by 50% | 0.55 | Overload 100% | 0.48 | Overload 150% | 0.28 | Overload 200% | 0.25 |
| No load | 0.64 | Full load | 0.68 | Overload by 50% | 0.56 | Overload 100% | 0.45 | Overload 150% | 0.26 | Overload 200% | 0.23 |
| No load | 0.73 | Full load | 0.62 | Overload by 50% | 0.62 | Overload 100% | 0.47 | Overload 150% | 0.24 | Overload 200% | 0.26 |
| No load | 0.58 | Full load | 0.53 | Overload by 50% | 0.51 | Overload 100% | 0.40 | Overload 150% | 0.44 | Overload 200% | 0.39 |
| No load | 0.53 | Full load | 0.54 | Overload by 50% | 0.44 | Overload 100% | 0.37 | Overload 150% | 0.36 | Overload 200% | 0.31 |
| No load | 0.61 | Full load | 0.55 | Overload by 50% | 0.43 | Overload 100% | 0.39 | Overload 150% | 0.37 | Overload 200% | 0.31 |
| No load | 0.62 | Full load | 0.53 | Overload by 50% | 0.42 | Overload 100% | 0.41 | Overload 150% | 0.41 | Overload 200% | 0.31 |
| No load | 0.61 | Full load | 0.55 | Overload by 50% | 0.42 | Overload 100% | 0.39 | Overload 150% | 0.42 | Overload 200% | 0.38 |
| No load | 0.67 | Full load | 0.42 | Overload by 50% | 0.36 | Overload 100% | 0.28 | Overload 150% | 0.28 | Overload 200% | 0.27 |
| No load | 0.58 | Full load | 0.43 | Overload by 50% | 0.37 | Overload 100% | 0.27 | Overload 150% | 0.26 | Overload 200% | 0.25 |
| No load | 0.63 | Full load | 0.37 | Overload by 50% | 0.36 | Overload 100% | 0.23 | Overload 150% | 0.23 | Overload 200% | 0.23 |
| No load | 0.63 | Full load | 0.41 | Overload by 50% | 0.31 | Overload 100% | 0.26 | Overload 150% | 0.27 | Overload 200% | 0.24 |
| No load | 0.62 | Full load | 0.38 | Overload by 50% | 0.33 | Overload 100% | 0.32 | Overload 150% | 0.23 | Overload 200% | 0.23 |
The independent variable load capacity is continuously increased, the value of the dependent variable adhesion coefficient is gradually reduced, and scattered points all fall on a straight lineOn both sides of the first and second side walls,
=0.9, according to significance level=0.05，
=73, checking correlation coefficient table to obtain critical value
=0.9>0.22, belonging to height correlation, so that the linear correlation between the load capacity and the adhesion coefficient is quite remarkable, and the regression equation is valid. By analogy, different load capacities are closely and highly related to the adhesion coefficient under this type of test.
And (4) conclusion: the adhesion coefficient of the truck with the same axle number is gradually reduced along with the increase of the load capacity at the same initial speed, and the high correlation proves that the magnitude of the adhesion coefficient is closely related to the load capacity.
Through a unary linear regression method and a correlation coefficient test method, whether the speed, the number of axes and the load capacity influence the adhesion coefficient or not is found, and only the load capacity has a close relation with the adhesion coefficient, so that the correlation degree is high. The invention is a study of 3 factors 3 x 6 levels, each level is tested 25 times, and the total number of 54 test cases is shown below, and the change of the adhesion coefficient and the brake deceleration in each test case is shown in the table 4.5, the average value of the adhesion coefficient and the brake deceleration of trucks with different axle numbers at different speeds under different loading capacity.
TABLE 4.5
| Load capacity | Braking deceleration | Coefficient of adhesion | Load capacity | Braking deceleration | Coefficient of adhesion |
| Overload of 200 percent for five-axis 60km/h | 2.29 | 0.23 | Overload of 50% at five-axis 60km/h | 3.66 | 0.37 |
| Three shafts 50km/h200% | 2.31 | 0.24 | Overload of 50% at five-axis 50km/h | 3.71 | 0.38 |
| Overload of 200% at five-axis 50km/h | 2.33 | 0.24 | Four-axis 50km/h overload 100% | 3.92 | 0.40 |
| Three-axis overload of 200% at 60km/h | 2.37 | 0.24 | Four-axis 40km/h overload 100% | 3.92 | 0.40 |
| Five-axis 40km/h overload 200 | 2.49 | 0.25 | Four-axis overload of 100% at 60km/h | 3.93 | 0.40 |
| Triaxial 40km/h overload 200% | 2.50 | 0.26 | Overload of 50% at five-axis 40km/h | 4.01 | 0.41 |
| Overload of 150% at 60km/h on three axes | 2.63 | 0.27 | Three-shaft 50km/h full load | 4.52 | 0.46 |
| Four-axis overload of 50km/h of 200% | 2.63 | 0.27 | Three-shaft 40km/h full load | 4.54 | 0.46 |
| Overload of 150% at five-axis 50km/h | 2.64 | 0.27 | Four-axis overload of 40km/h 50% | 4.69 | 0.48 |
| Overload of 150% at five-axis 60km/h | 2.71 | 0.28 | Triaxial 60km/h full load | 4.69 | 0.48 |
| Three shafts 50km/h150% | 2.72 | 0.28 | Four-axis overload of 50% at 60km/h | 4.71 | 0.48 |
| Overload of 150 percent at five-axis 40km/h | 2.73 | 0.28 | Four-axis 50km/h overload 50% | 4.81 | 0.49 |
| Triaxial 40km/h overload 150% | 2.75 | 0.28 | Five-axis 50km/h no-load | 5.16 | 0.53 |
| Four-axis 40km/h overload 200% | 2.75 | 0.28 | Five-axis 60km/h no-load | 5.21 | 0.53 |
| Four-axis overload of 200% at 60km/h | 2.79 | 0.28 | Five-axis 60km/h full load | 5.30 | 0.54 |
| Four-axis overload of 150% at 60km/h | 2.88 | 0.29 | Four-axis 50km/h full load | 5.32 | 0.54 |
| Four-axis overload of 150% at 50km/h | 2.89 | 0.29 | Four-shaft 60km/h full load | 5.38 | 0.55 |
| Four-axis 40km/h overload 150% | 2.91 | 0.30 | Four-axis 40km/h full load | 5.45 | 0.56 |
| Three-axis overload of 50% at 60km/h | 2.93 | 0.30 | Five-axis 40km/h no-load | 5.48 | 0.56 |
| Overload of 100% at five-axis 60km/h | 2.99 | 0.31 | Five-axis 50km/h full load | 5.49 | 0.56 |
| Triaxial 50km/h overload 100% | 3.01 | 0.31 | Five-axis 40km/h full load | 5.59 | 0.57 |
| Three-axis 60km/h overload 100% | 3.03 | 0.31 | Three-shaft no-load of 60km/h | 5.79 | 0.59 |
| Triaxial 40km/h overload 100% | 3.07 | 0.31 | Three-axis 40km/h no-load | 5.90 | 0.60 |
| Overload of 100% at 50km/h in five shafts | 3.32 | 0.34 | Three-axis 50km/h no-load | 5.95 | 0.61 |
| Triaxial 50km/h overload 50% | 3.44 | 0.35 | Four-shaft no-load of 60km/h | 6.13 | 0.63 |
| Overload of 100% at five-axis 40km/h | 3.55 | 0.36 | Four-axis no-load of 50km/h | 6.15 | 0.63 |
| Triaxial 40km/h overload 50% | 3.66 | 0.37 | Four-axis 40km/h no-load | 6.18 | 0.63 |
The correlation degree between the speed and the adhesion coefficient and the correlation degree between the number of shafts and the adhesion coefficient are weak gradually through the unitary linear regression, the correlation of the braking deceleration to the adhesion coefficient is very obvious, and the change of the adhesion coefficient and the braking deceleration at each test levelRelationship according to level of significance
=0.05，
=52, checking correlation coefficient table to obtain critical value
=0.98>0.268, is highly correlated.
After preliminary analysis, it is found that, of the three influencing factors of speed, number of shafts and load capacity, only the load capacity is highly correlated with the adhesion coefficient, the correlation between the speed and number of shafts and the adhesion coefficient is weak, and the influence on the adhesion coefficient is small. In the following multivariate regression analysis, the number of axes, speed, load capacity, and adhesion coefficient are independent variables, and the spss analysis shows which of the three variables has the most significant influence factor. Table 4.8 shows the hypothesis test of the regression equation model, Table 4.9 shows the regression equation of the three factors for the adhesion coefficient
TABLE 4.8
F of the whole regression equation model is 15386849.829, P is less than 0.0, meaning that the regression equation is meaningful and exists.
TABLE 4.9
From the sps output results, it was found that the significance (Sig.) between the initial velocity and the number of axles, respectively, for the comparative braking deceleration is: 0.000, 0.001 and 0.022, and when the significance value is less than 0.05, the significance is obvious; when in useSignificance of (Sig.) =0.022>0.05, shows that
Has no effect on y; when in useSignificance of (Sig.) =0.001<0.05 relative toTo be less significant for y; when in useSignificance of (Sig.) =0.000<0.05, significance for y is evident.
The number of axes is seen from the figureSpeed of braking
，
The regression equation for brake deceleration with respect to adhesion coefficient is:
it can be seen from the regression equation that the number of axles and the initial speed have no influence on the magnitude of the adhesion coefficient, that is, the brake deceleration has the greatest influence on the adhesion coefficient, and the brake deceleration is directly influenced by the load weight, so that the different load weights of the trucks have great influence on the adhesion coefficient.
The data analysis can show that the magnitude of the adhesion coefficient is only related to the load capacity, and is unrelated to the number of shafts and the initial speed, only the influence of different load capacities on the adhesion coefficient is researched, then 95% confidence intervals of the adhesion coefficients under different load capacities are required, the data are integrated according to no load, full load, 50% overload, 100% overload, 150% overload and 200% overload, the confidence level is 95%, 95% confidence intervals of the mean value of the adhesion coefficients of trucks under different load capacities are calculated, and the obtained confidence intervals can be used as reference values for selecting the magnitude of the adhesion coefficients in truck traffic accidents. The following table 4.6 shows the adhesion coefficient reference values of the trucks under different loading weights.
TABLE 4.6
| Load capacity | Minimum value | Maximum value | Mean number | Standard deviation of | Lower limit of confidence interval | Upper limit of confidence interval | Lower limit of standard | Upper limit of standard |
| No load | .41 | .79 | .5893 | 0.004166872 | 0.58112182 | 0.597455958 | 0.58 | 0.60 |
| Full load | .28 | .69 | .5245 | 0.006108747 | 0.512515745 | 0.536462033 | 0.51 | 0.54 |
| Overload by 50% | .26 | .63 | .4041 | 0.006034356 | 0.39226155 | 0.415916227 | 0.39 | 0.42 |
| Overload 100% | .23 | .55 | .3487 | 0.004695912 | 0.33946268 | 0.357870654 | 0.34 | 0.36 |
| Overload 150% | .20 | .44 | .2815 | 0.003249195 | 0.275142689 | 0.287879533 | 0.27 | 0.29 |
| Overload 200% | .18 | .51 | .2547 | 0.002882624 | 0.249016723 | 0.260316611 | 0.25 | 0.26 |
The correction coefficient of the braking distance is the measured road surface distance in the test, and the ratio of the actual braking distance to the measured road surface distance is the correction coefficient.
Through the measurement of the road surface actual measurement distance after the automobile is braked in the test, the road surface actual measurement distance is obtained under each test, the data volume is relatively large, the road surface actual measurement distance of the unloaded and fully loaded vehicles is tested, and the correction coefficient of the brake distance of each axle truck under the condition of no load and full load is shown in a table 4.7.
TABLE 4.7
The correction coefficients of the braking distance of three-axis trucks, four-axis trucks and five-axis trucks under the conditions of no load and full load at initial speeds of 40km/h, 50km/h and 60km/h respectively.
Firstly, making a box-type graph according to the change of the adhesion coefficient when the number of shafts, the initial speed and the loading capacity are different;
from the boxplot of the braking distance correction coefficient under different shaft numbers, three shafts, four shafts and five shafts have data with large discreteness, the data are obviously higher than the data in the normal distribution diagram and should be removed, and other data are all around the normal distribution diagram and can be accepted.
After the correction coefficient of the braking distance is obtained, whether the number of shafts, the speed and the load capacity have an influence on the correction coefficient or whether the influence of the three factors is larger is analyzed, the processing method is the same as the processing method of the adhesion coefficient, the correction coefficient, the speed and the correction coefficient and the load capacity and the correction coefficient are subjected to unitary regression respectively by the number of shafts, the speed and the correction coefficient and the load capacity and the correction coefficient, and the obtained equation judges the influence by checking the correlation coefficient.
Independent variable when the same axle number of trucks has the same load capacity
Is an initial velocity, dependent variable
For braking distance correction coefficient, at initial speed of 40, 50, 60km/h
，On the same scatter diagram, it is found that, as shown in the following table 4.8, the attachment coefficients of the three-axle truck at different initial speeds during no-load condition are shown, and the scatter diagram between the initial speeds and the correction coefficients is drawn by taking the change of the correction coefficients of the three-axle truck at the initial speeds of 40, 50 and 60km/h under the no-load condition as an example, so as to obtain a unitary regression equation and a sum
Change and then pass through
And comparing with the correlation coefficient checking table to determine whether the two are correlated or not.
TABLE 4.8
| Four-axis 40km/h no-load | Correction factor | Four-axis no-load of 50km/h | Correction factor | Four-shaft no-load of 60km/h | Correction factor |
| 38.1 | 1.27 | 54.3 | 1.48 | 54.2 | 1.04 |
| 39.7 | 1.42 | 48.5 | 1.24 | 56.8 | 1.01 |
| 40.5 | 1.21 | 50.1 | 1.34 | 62.81 | 1.32 |
| 40.3 | 1.26 | 47.1 | 1.17 | 60.1 | 1.04 |
| 45.1 | 1.22 | 53.6 | 1.82 | 58.4 | 1.14 |
| 40.3 | 1.45 | 49.6 | 1.47 | 57.6 | 1.73 |
| 39.4 | 1.32 | 50 | 1.46 | 58.2 | 1.76 |
| 39.7 | 1.34 | 49.4 | 1.55 | 58.9 | 1.77 |
| 40.7 | 1.51 | 49.5 | 1.51 | 60 | 1.69 |
| 40.7 | 1.46 | 48 | 1.55 | 58.4 | 1.45 |
| 40.3 | 1.26 | 51.9 | 1.24 | 60.4 | 1.30 |
| 39.7 | 1.42 | 47 | 1.00 | 59.9 | 1.31 |
| 41.5 | 1.10 | 53.1 | 1.14 | 61.4 | 1.35 |
| 40.1 | 1.24 | 49.1 | 1.15 | 62.7 | 1.40 |
| 40.6 | 1.20 | 49.7 | 1.19 | 61.1 | 1.09 |
| 42.1 | 1.06 | 53 | 1.30 | 59.7 | 1.07 |
| 42.3 | 1.20 | 53.3 | 1.25 | 62.6 | 1.21 |
| 45.2 | 1.26 | 49.7 | 1.20 | 60.5 | 1.24 |
| 41.5 | 1.07 | 50.9 | 1.18 | 62.2 | 1.18 |
| 40.2 | 1.05 | 51 | 1.34 | 63.8 | 1.27 |
| 42.8 | 1.30 | 48.5 | 1.26 | 58.4 | 1.17 |
| 39 | 1.13 | 53.6 | 1.82 | 63.3 | 1.19 |
| 43.3 | 1.44 | 47.1 | 0.96 | 62.8 | 1.36 |
| 40.5 | 1.26 | 49 | 1.03 | 60.1 | 1.05 |
| 39.6 | 0.97 | 49.5 | 1.31 | 58.1 | 1.26 |
The axial number and the load capacity are constant, and the values are between the initial speeds of 40km/h, 50km/h and the correction coefficients
In the context of (a) or (b),=0.0141, according to
，
Checking the correlation coefficient table to obtain a critical value
0.026<=0.39, therefore
And
the linear correlation relationship between the initial velocity and the correction coefficient is not obvious, namely the initial velocity and the correction coefficient are not correlated. By analogy, no matter three-axis, four-axis and five-axis trucks, the speed and the change of the correction coefficient are irrelevant in the condition, and the change is not listed.
When a certain speed (50 km/h) and a certain load capacity (no load) are taken for a certain time, the independent variable
Is the number of axes, dependent variable
For correcting the coefficient, three axes, four axes, and five axes in this case can be compared, and the change of the dependent variable correction coefficient along with the difference of the independent variable axes can be seen through the scatter diagram. As shown in table 4.9, the change in the adhesion coefficient at 50km/h when three types of trucks are unloaded.
TABLE 4.9
| When the three-axle truck is in 50km/h no-load state | Correction factor | When the four-axle truck is in no-load condition of 50km/h | Correction factor | At 50 km/no-load time of five-axis truck | Correction factor |
| 3 | 1.19 | 4 | 1.48 | 5 | 1.22 |
| 3 | 1.33 | 4 | 1.24 | 5 | 1.39 |
| 3 | 1.17 | 4 | 1.34 | 5 | 1.17 |
| 3 | 1.15 | 4 | 1.17 | 5 | 1.47 |
| 3 | 1.39 | 4 | 1.82 | 5 | 1.19 |
| 3 | 1.49 | 4 | 1.47 | 5 | 1.20 |
| 3 | 1.64 | 4 | 1.46 | 5 | 1.39 |
| 3 | 1.73 | 4 | 1.55 | 5 | 1.15 |
| 3 | 1.36 | 4 | 1.51 | 5 | 1.23 |
| 3 | 1.57 | 4 | 1.55 | 5 | 1.14 |
| 3 | 1.13 | 4 | 1.24 | 5 | 1.15 |
| 3 | 1.19 | 4 | 1.00 | 5 | 1.17 |
| 3 | 1.29 | 4 | 1.14 | 5 | 1.20 |
| 3 | 1.23 | 4 | 1.15 | 5 | 1.13 |
| 3 | 1.36 | 4 | 1.19 | 5 | 1.26 |
| 3 | 1.20 | 4 | 1.30 | 5 | 1.39 |
| 3 | 1.21 | 4 | 1.25 | 5 | 1.34 |
| 3 | 1.22 | 4 | 1.20 | 5 | 1.16 |
| 3 | 1.15 | 4 | 1.18 | 5 | 1.31 |
| 3 | 1.30 | 4 | 1.34 | 5 | 1.33 |
| 3 | 1.24 | 4 | 1.26 | 5 | 1.06 |
| 3 | 1.27 | 4 | 1.82 | 5 | 1.08 |
| 3 | 1.30 | 4 | 0.96 | 5 | 0.97 |
| 3 | 1.31 | 4 | 1.03 | 5 | 0.92 |
| 3 | 1.13 | 4 | 1.31 | 5 | 0.91 |
When the load capacity is constant, the speed is constant and only the number of shafts is different, the attachment coefficients of the three shafts, the four shafts or the five shafts have great similarity, and the weight is expressed asIn the context of (a) or (b),
=0.23, according to
=0.05，
=23, checking correlation coefficient table to obtain critical value
0.23<=0.39, thereforeAnd
the linear correlation relationship between the two is not significant, namely the number of axes is not correlated with the adhesion coefficient. By analogy, the number of axes and the change in the correction factor are not relevant under this type of test.
TABLE 4.10
Table 4.10 correction factors for trucks with different loading conditions for a four-axle truck at an initial speed of 40km/h are shown. The independent variable under the condition of constant speed and number of axes
For different loads of the truck, dependent variable
For truck braking distance correction factor, by observation
And
the scatter diagram shows that the value of the correction coefficient is reduced along with the increase of the loading capacity of the truck, which shows that the loading capacity and the correction coefficient have a functional relationship and the correlation degree is very close.
The values of the independent variable adhesion coefficients fall on straight lines at the gradually-decreasing scattering points when the independent variable carrying capacity is continuously increased
On both sides of the first and second side walls,=0.47, according to significance level
=0.05，
=23, checking correlation coefficient table to obtain critical value
0.47<
=0.39, and is a significant correlation, so the linear correlation between the load capacity and the braking distance correction coefficient is significantly correlated, and the regression equation is valid. By analogy, under the type of test, the different load capacities are closely related to the correction coefficient, and the relationship is obvious.
Through a unary linear regression method and a correlation coefficient test method, whether the speed, the number of axes and the load capacity influence the correction coefficient or not is found, and only the load capacity has close relation with the correction coefficient and is obviously related. The study is a test study of 3 factors 3 × 6 levels, each level is tested 25 times, and the total number of the test cases is 54, but only the correction coefficient of the load weight at the time of no load and full load is studied here, and the change of the correction coefficient and the braking deceleration at each test case is listed below, as shown in table 4.11, and the correlation existing between the two is verified again by a double-coordinate graph, as shown in the average of the correction coefficients at the time of no load and full load at each test case of table 4.14.
TABLE 4.11
In the previous preliminary analysis, it was found that the load capacity and the braking distance correction coefficient are significantly correlated, and the number of shafts and the initial speed have no influence on the correction coefficient. The three factor pairs were verified by multiple regression analysis
The magnitude of the effect of the correction factor, as shown in the hypothetical test of the regression equation in Table 4.12 and the three factor-to-factor system in Table 4.13
The regression equation of the dynamic distance correction coefficient is shown.
TABLE 4.12
It is meaningful to state that the entire equation is present. F of the whole regression equation model is 10.115, and P is less than 0.0, so that the meaning of the regression equation can be explained, and the regression equation exists.
TABLE 4.13
From the sps output results, it was found that the significance (Sig.) between the initial velocity and the number of axles, respectively, for the comparative braking deceleration is: 0.907, 0.056 and 0.000, and when the significance value is less than 0.05, the significance is obvious; when in use
Significance of (Sig.) =0.907>0.05, shows that
Has no effect on y; when in use
Significance of (Sig.) =0.056<0.05 relative to
To be less significant for y; when in use
Significance of (Sig.) =0.000<0.05, significance for y is evident. The regression equation for the adhesion coefficient is:
the regression equation shows that the number of axles and the braking deceleration have little influence on the braking distance correction coefficient, which shows that the braking deceleration and the correction coefficient have an inverse relationship and have correlation.
Through the analysis, the influence of the speed and the number of shafts on the braking distance correction coefficient is very small, so that the influence of the two variables on the adhesion coefficient is eliminated, only the influence of the no-load and full-load on the correction coefficient is researched, the data are integrated according to the no-load and full-load, the confidence level is 95%, and the confidence interval of 95% of the mean value of the correction coefficient of the truck under the no-load and full-load conditions is calculated, which is the conclusion to be obtained by researching the problem, as shown in the table 4.14 below of the adhesion coefficient reference value table of the truck under different load weights.
TABLE 4.14
| Load capacity | Minimum value | Maximum value | Mean number | Standard deviation of | Lower limit of confidence interval | Upper limit of confidence interval | Lower limit of standard | Upper limit of standard |
| No load | .91 | 1.55 | 1.2353 | 0.13128 | 1.2155 | 1.2552 | 1.21 | 1.25 |
| Full load | .28 | 1.80 | 1.3433 | 0.18152 | 1.3159 | 1.3707 | 1.31 | 1.37 |
According to the obtained braking distance correction coefficient, the value within the range of 1.21-1.25 is taken under the condition of no load, and the value within the range of 1.31-1.37 is taken under the condition of full load, so that the method can be widely applied to data reference when the braking distance is calculated in the truck accident.
The method is characterized in that data processing is respectively carried out on the truck attachment coefficient and the braking distance correction coefficient by using a mathematical statistics method, firstly, data with large discreteness are eliminated, misleading conclusion caused by existence of abnormal values is avoided, then, only the influence of the load on the attachment coefficient is the largest through primary unitary regression analysis and correlation test, the correction coefficient of the braking distance is directly influenced by different loads, confidence intervals of the attachment coefficient under different loads and confidence intervals of the braking distance correction coefficient under no-load and full-load conditions are respectively obtained after the influence factors are determined, and the method can be widely applied to the aspect of traffic accident identification and used as value reference of the attachment coefficient and the correction coefficient.
Example 1 the truck overload determination method, confidence intervals of adhesion coefficients at different loading capacities
Through the analysis and summary, of three influence factors of the number of shafts (three shafts, four shafts and five shafts), initial speeds (40 km/h, 50km/h and 60 km/h) and load capacities (no load, full load, overload 50%, overload 100%, overload 150% and overload 200%), only the load capacity directly influences the adhesion coefficient and shows a negative correlation trend, and a table 5.1 shows a reference value table of longitudinal adhesion coefficients of trucks under different load capacities, which is summarized according to the analysis result.
(1) Under the conditions of no load and full load, when the large truck brakes on a dry asphalt pavement, the values of the coefficient of adhesion with the pavement are both greater than 0.5, the braking performance is good, and the national braking requirements on the large truck are met.
(2) In the case of an overload (50% overload, 100% overload, 150% overload, 200% overload), the braking deceleration decreases with increasing load capacity, and the corresponding adhesion coefficient decreases gradually. The method can be used for selecting the adhesion coefficient when the large truck is subjected to traffic accident calculation initial speed, can remind a driver that the more the truck is overloaded, the lower the road adhesion coefficient is, and the more serious the traffic accident is once generated.
(3) Tests show that the adhesion coefficient of a large truck is irrelevant to the initial running speed and has no obvious influence.
(4) In the test, three-axis, four-axis and five-axis vehicles are used for braking test, and test data and analysis show that the relationship between the adhesion coefficient of a large truck and the number of truck axles is not large, namely the adhesion coefficient does not change along with the increase of the number of truck axles.
(5) The analysis result of the test proves that the adhesion coefficient between the road surface and the large truck during braking is only related to the load capacity of the truck, namely, the braking deceleration of the truck is gradually reduced along with the increase of the load capacity, and the adhesion coefficient is reduced. In a traffic accident, an appraiser can judge whether the truck is overloaded and the overload degree according to the magnitude of the attachment coefficient.
(6) As the adhesion coefficient between the large truck and the road surface is only proved to be related to the load capacity, and is unrelated to the number of axles, trucks (three axles, four axles and five axles) in the test can all meet the conclusion, and trucks which are not used for two axles or more than five axles are also suitable for the conclusion due to condition limitation, so that the truck is real and reliable.
Through analysis and verification, the change of the braking distance correction coefficient under the conditions of no load and full load is found, wherein the influence of the number of shafts and the initial speed on the correction coefficient is not obvious, the change of the loading capacity influences the change of the braking distance correction coefficient, and the following table 5.2 shows that the reference value table of the braking distance correction coefficient under the conditions of no load and full load of the freight car under the dry asphalt pavement is the confidence interval of the braking distance correction coefficient under the conditions of no load and full load when the freight car performs braking detection.
In the embodiment, data analysis shows that the correlation degree of the correction coefficient of the braking distance and the truck-mounted weight is obvious, the correlation degree of the braking distance and the truck-mounted weight is low, the larger the load is, the higher the correction coefficient of the braking distance is, and the vehicle is less prone to stop, so that traffic accidents are induced. When the vehicle is braked at an initial speed of 40km/h, the dragging print is clear when the vehicle is fully loaded, the dragging print formed by the road surface is shorter and shorter along with the increase of the overload amount, no clear dragging print exists after the overload amount exceeds 100%, and only the impression exists. Whether the truck is overloaded or not can be judged according to the brake marks on the spot in the traffic accident. The variation curves of the adhesion coefficients of three-axis, four-axis and five-axis trucks with the initial speeds of 40km/h, 50km/h and 60km/h when braking are respectively no-load, full-load, 50% overload, 100% overload, 150% overload and 200% overload, as shown in the following table 5.3 of the mean adhesion coefficient values of trucks with different axle numbers under different load weights.
TABLE 5.3
| Three-axis 40km/h | No load | Full load | Overload by 50% | Overload 100% | Overload 150% | Overload 200% |
| Coefficient of adhesion | 0.60 | 0.46 | 0.37 | 0.31 | 0.28 | 0.25 |
| Three-axis 50km/h | No load | Full load | Overload by 50% | Overload 100% | Overload 150% | Overload 200% |
| Coefficient of adhesion | 0.61 | 0.46 | 0.35 | 0.31 | 0.28 | 0.24 |
| Three-axis 60km/h | No load | Full load | Overload by 50% | Overload 100% | Overload 150% | Overload 200% |
| Coefficient of adhesion | 0.59 | 0.48 | 0.36 | 0.31 | 0.27 | 0.24 |
| Four-axis 40km/h | No load | Full load | Overload by 50% | Overload 100% | Overload 150% | Overload 200% |
| Coefficient of adhesion | 0.63 | 0.56 | 0.48 | 0.40 | 0.30 | 0.28 |
| Four-axis 50km/h | No load | Full load | Overload by 50% | Overload 100% | Overload 150% | Overload 200% |
| Coefficient of adhesion | 0.63 | 0.54 | 0.49 | 0.40 | 0.29 | 0.27 |
| Four-axis 60km/h | No load | Full load | Overload by 50% | Overload 100% | Overload 150% | Overload 200% |
| Coefficient of adhesion | 0.63 | 0.55 | 0.48 | 0.40 | 0.29 | 0.29 |
| Five-axis 40km/h | No load | Full load | Overload by 50% | Overload 100% | Overload 150% | Overload 200% |
| Coefficient of adhesion | 0.56 | 0.57 | 0.41 | 0.36 | 0.28 | 0.25 |
| Five-axis 50km/h | No load | Full load | Overload by 50% | Overload 100% | Overload 150% | Overload 200% |
| Coefficient of adhesion | 0.52 | 0.56 | 0.38 | 0.34 | 0.27 | 0.24 |
| Five-axis 60km/h | No load | Full load | Overload by 50% | Overload 100% | Overload 150% | Overload 200% |
| Coefficient of adhesion | 0.53 | 0.54 | 0.37 | 0.31 | 0.28 | 0.23 |
The data are expressed in the form of a curve.
The change of the adhesion coefficient under different conditions can be seen, the adhesion coefficient of a three-axis and four-axis truck is reduced along with the increase of the load capacity, the reduction trend is obvious, the adhesion coefficient of a five-axis truck is found to be larger when the five-axis truck is in an empty load condition and a full load condition than when the five-axis truck is in the empty load condition, the change can be clearly seen through the attached drawing, and the five-axis truck is found by looking up related data, and the brake jump phenomenon occurs when the five-axis truck is in the empty load braking condition, because the tire and the ground do not completely generate sliding friction during the braking, only part of wheels are clung to the ground, so the adhesion coefficient of the five-axis truck.
The confidence intervals of the adhesion coefficients under different loading capacities and the braking distance correction coefficients under the conditions of no load and full load when trucks with different axle numbers brake at different initial speeds are obtained on the basis of the analysis of the embodiment. It has been found that the unloaded sticking coefficient of five-axis trucks is lower than that of full-load trucks, both three-axis and four-axis trucks.
Claims (4)
1. A truck overload judgment method is characterized in that trucks with different axle numbers, different loading conditions and different initial speeds of the trucks are selected in the first step, a test site is selected in the second step, and a braking deceleration instrument is used for measuring braking deceleration a of the trucks with different axle numbers, which are selected in the first step, under different loading conditions and different initial speed combinations; solving a true value L of the braking distance at a certain speed by utilizing a kinetic energy theorem; actually measuring the road surface actual measurement distance L' under various conditions on an accident test site; fourthly, determining the actual road adhesion coefficient phi of the vehicle by using the functional relation a between the braking deceleration and the road adhesion coefficient as g phi; obtaining data by tests, determining the relation between a true value L of the braking distance of the vehicle at a certain speed and the actual road surface distance L' by a statistical method, finally obtaining a correction coefficient K of the actual road surface distance,
in the formula (I), the compound is shown in the specification,
wherein v is the initial speed of the vehicle, g is the standard gravity acceleration, and 9.8m/s is taken2(ii) a Fifthly, processing data by using a regression analysis method, and analyzing the data to obtain a result;
wherein the content of the first and second substances,
selecting a test site, namely, performing a braking test at speeds of 40, 50 and 60km/h respectively under the conditions of no load, full load, 50 percent overload, 100 percent overload, 150 percent overload and 200 percent overload on a dry, flat and well-adhered asphalt pavement by using five three-axis trucks or four-axis trucks and five-axis trucks which are provided with braking deceleration meters;
fifthly, processing data by using a regression analysis method, wherein the result of analyzing the data is that unitary regression analysis is performed on the adhesion coefficient by speed, the adhesion coefficient by axis and the adhesion coefficient by load gradually, a regression equation is obtained according to scatter points of the adhesion coefficients under different conditions, correlation coefficient detection is performed, and the influence of the three factors on the adhesion coefficient is judged; the value of the corresponding adhesion coefficient does not change along with the change of the speed under the condition that the trucks with the same number of axles have the same loading capacity, and has no correlation, and the magnitude of the adhesion coefficient is irrelevant to the initial speed of the trucks;
the braking distance becomes longer with the increase of the load capacity; whether the truck is overloaded or not can be judged according to the brake marks on the spot in the traffic accident; and judging whether the truck is overloaded or not and the overload degree according to the magnitude of the adhesion coefficient.
2. The method for determining overload of truck as claimed in claim 1, wherein in the first step, trucks with different axle numbers are selected from three-axle trucks, four-axle trucks and five-axle trucks; the different loading conditions of the truck are that the truck is braked at different initial speeds of 40km/h, 50km/h and 60km/h when the truck is unloaded, full, 50% overloaded, 100% overloaded, 150% overloaded and 200% overloaded respectively.
3. A method for determining a truck overload according to claim 1, wherein said third step of measuring a braking deceleration a is to measure the braking deceleration a using a braking deceleration meter from the start of the deceleration of the vehicle until the deceleration of the vehicle reaches 75% of the predetermined average deceleration of the vehicle and the time required for the deceleration.
4. A method for determining overload of truck as defined in claim 1, wherein said road adhesion coefficient phi in said fourth step is the maximum value tau of tangential stress of vehicle tyre on road surfacemaxDivided by the normal stress P of the road surfaceGThe value of (c).
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