CN117890128A - Method for testing running resistance of heavy vehicle under any load - Google Patents
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Abstract
The application discloses a method for testing running resistance of a heavy vehicle under any load, and relates to the technical field of running resistance testing. The method comprises the following steps: and controlling the heavy vehicle with the load m to carry out a sliding test to obtain speed-time data of the heavy vehicle in a plurality of speed intervals, determining a relation between a momentum variation and resistance in each speed interval based on a momentum theorem, solving unknowns according to at least 4 relation, and calculating the running resistance F of the heavy vehicle under the conditions of the load and the air density at each speed V. The running resistance of the heavy vehicle under any load can be calculated through one-time sliding test, the test cost is reduced, and the method has certain accuracy.
Description
Technical Field
The application relates to the technical field of running resistance testing, in particular to a method for testing running resistance of a heavy vehicle under any load.
Background
The chassis dynamometer is used for testing and evaluating the dynamic performance, oil consumption, emission and the like of a vehicle, and is a common method in the design development and performance evaluation test of modern automobile products. When the chassis dynamometer test is carried out, the actual running resistance of the automobile can be accurately simulated by controlling the test conditions, and the test is carried out on the basis. Before these tests are carried out, it is necessary to first determine the road resistance curve of the vehicle in order to configure the parameters of the chassis dynamometer. Because of the large difference between the commonly recommended empirical values and the actual conditions, it is more preferable to use a test method to obtain the relationship between the actual resistance of the vehicle and the vehicle speed. Specifically, the vehicle resistance value may be obtained by recording the vehicle speed and looking up a table according to the coasting resistance curve. The method can accurately reflect the resistance conditions of the vehicle at different speeds.
Currently, the standard method for determining the running resistance of a vehicle mainly adopts the coasting method. The sliding method is that under good weather conditions (in a certain humidity and temperature range, the small wind speed can not affect the test), the vehicle can accelerate to a specified speed on a specially designed straight road test runway, and then the transmission is adjusted to a neutral position, so that the vehicle can slide freely to a low speed. In this process, data of the entire taxiing procedure is recorded synchronously using a data acquisition system equipped with GPS positioning. By a standard prescribed method, a quadratic function relationship between the vehicle resistance and the vehicle speed during coasting can be obtained, expressed as f=a+b·v+c·v 2, where F is the coasting resistance, V is the vehicle speed, and A, B, C is the resistance coefficient, respectively. The relation can accurately reflect the resistance condition in the vehicle sliding process.
The drag curve of the vehicle can be accurately obtained by using a sliding method, and the method is suitable for standard laboratory regulation standard detection, but has the defects. The sliding method is a test performed under a fixed load, the test result only represents the resistance under the current condition, when the external condition is changed, particularly when the load is changed, the resistance curve is changed greatly, and at the moment, in order to obtain a more accurate resistance curve, the sliding test needs to be performed again, so that the test times are increased and the test cost is increased.
In view of this, the present application has been made.
Disclosure of Invention
In order to solve the problems, the application provides a method for testing the running resistance of the heavy vehicle under any load, which can calculate the running resistance of the heavy vehicle under any load through one-time sliding test, reduces the test cost and has certain accuracy.
The application provides a method for testing running resistance of a heavy vehicle under any load, which specifically comprises the following steps:
S10, controlling a heavy vehicle with a load m to perform a sliding test to obtain speed-time data of the heavy vehicle in a plurality of speed intervals;
S20, determining a relation between the momentum change quantity and the resistance in each speed interval based on a momentum theorem:
Wherein, V 1 and V 2 are the starting and ending speeds of a speed interval, t 1 is the time consumption of the speed interval, A represents the windward area of the vehicle, represents the air density in the test, V 3=（V1+V2)/2, g is the gravity acceleration, and C d、/>、/>、/> is defined as the air resistance coefficient, the first rolling resistance coefficient, the second rolling resistance coefficient and the other resistance coefficient related to the load respectively;
S30, solving C d、、/> and/> according to at least 4 relational expressions;
s40, introducing the solution value into the following formula:
And calculating the running resistance F of the heavy vehicle at each speed V under the conditions of a load and an air density/> .
Optionally, the S30 includes:
S31, selecting different numbers and different combinations of relational expressions from all relational expressions to solve C d、、/> and/> ;
s32, calculating the running resistance of the heavy vehicle at each speed according to the solved C d、、/> and/> ;
s33, comparing the running resistance obtained in the S32 with an actual load sliding test value to obtain a deviation value;
S34, selecting a relation combination with the smallest deviation value, and solving to C d、、/> and/> .
Optionally, the different numbers and different combinations of the relational expressions are uniformly distributed in each speed interval.
Optionally, the S32 includes:
the solved C d、、/> and/> are taken to the following equation, resulting in a running resistance/> at speed V 1.
Optionally, the S33 includes:
Subtracting the running resistance obtained in S32 at each speed from the actual load sliding test value, and dividing the running resistance by the actual load sliding test value at the corresponding speed to obtain relative deviation;
And averaging the relative deviation of each speed to obtain a deviation value.
Optionally, S40 includes:
Calculating the discrete running resistance F of the heavy vehicle at each speed V under the conditions of a load and an air density/> ;
fitting the speed-running resistance scattered points to obtain a resistance curve of the heavy truck under different loads, and determining the coefficients of a secondary term, a primary term and a constant term of a resistance function.
The embodiment of the application has the following technical effects:
1) Only one sliding test is needed to be carried out on the target vehicle, when the load of the vehicle is changed, the resistance curve after the change of the test quality can be accurately calculated by only changing the test quality of the vehicle in a calculation formula, the test times are reduced, and the test cost is saved;
2) The method is flexible and simple, the object-oriented can aim at all heavy vehicles, and test verification shows that the calculation result can meet the test requirement well.
3) Based on the existing sliding test data record table, other parameters in the sliding process are not required to be additionally added, and the method can be applied only through the historical sliding test data record table.
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In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present application, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for testing running resistance of a heavy vehicle under any load, provided by the application;
FIG. 2a is a graph comparing 80% load resistance curve calculated from a full load coast V-T curve with test values provided by the present application;
FIG. 2b is a graph comparing a 60% load resistance curve calculated from a full load coast V-T curve with test values provided by the present application;
FIG. 2c is a graph comparing 40% load resistance curve calculated from a full load coast V-T curve provided by the present application with test values;
FIG. 2d is a graph comparing a 20% load resistance curve calculated from a full load coast V-T curve with test values provided by the present application;
FIG. 2e is a graph of the calculated 0% load resistance curve from the full load coast V-T curve versus the test value provided by the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be clearly and completely described below. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the application, are within the scope of the application.
Example 1
Fig. 1 is a flowchart of a method for testing running resistance of a heavy vehicle under any load, which is provided by the application, and is used for testing the running resistance of the heavy vehicle under any load. The application comprises the following steps:
S10, controlling the heavy vehicle with the load m to conduct a sliding test, and obtaining speed-time data of the heavy vehicle in a plurality of speed intervals.
One of various loads m such as full load/no load/half load is carried out on the heavy vehicle for a sliding test, and the environmental conditions are as follows: the length of the clean, dry and straight asphalt mixed collar soil or the mixed collar soil pavement and the test pavement should meet the test requirement, the longitudinal gradient is within +/-0.1 percent, the asphalt mixed collar soil or the mixed collar soil pavement has no rain, no fog, the relative humidity is less than 95 percent, the air temperature is 0-40 ℃, the average air speed measured at the position 1.6m higher than the pavement is less than or equal to 3m/s, and the air gust is less than or equal to 5m/s. In the coasting test, a change law of the vehicle speed (km/h) with time(s) is recorded, and the vehicle speed unit is converted into an international standard unit (m/s). Recording the time T required by the vehicle when the speed is reduced by 10km/h, and obtaining a regular scatter diagram of the change of the vehicle speed along with time, namely obtaining speed-time (V-T) data with a plurality of speed interval sections of 10 km/h.
Referring to table 1, the change rule of the speed of a heavy vehicle with time is recorded when the heavy vehicle is in full-load sliding test. The information available in the table is: the speed of the vehicle is 21.605625s in the process of sliding from 75km/h to 65km/h, 24.8425s in the process of sliding from 65km/h to 55km/h, 29.111875s in the process of sliding from 55km/h to 45km/h, 32.885s in the process of sliding from 45km/h to 35km/h, 37.26625s in the process of sliding from 35km/h to 25km/h, and 41.283125s in the process of sliding from 25km/h to 15 km/h; the time spent by 70km/h to 60km/h is 22.896875s, 60km/h to 50km/h is 26.989375s, 50km/h to 40km/h is 30.509375s, 40km/h to 30km/h is 35.39375s, and 30km/h to 20km/h is 39.145s. A total of 11 speed intervals, each speed interval having a speed difference of fatv=10 km/h.
TABLE 1 speed time (V-T) data table for multiple speed intervals in a vehicle coast test
And S20, determining a relation between the momentum change amount and the resistance in each speed interval based on a momentum theorem.
During the sliding process of the vehicle, the vehicle speed gradually decreases from high due to the blocking effect of various forces. In the sliding process, the resistance mainly comprises air resistance, rolling resistance and other resistances. Other resistances include many, such as the front axle rear axle friction resistance, the vehicle internal resistance, etc., which are actually present, but just like a black box, it is difficult to know and grasp the law of change inside, which is collectively referred to as other resistances in the present application. According to a vehicle sliding calculation formula, the air resistance calculation method comprises the following steps:
；（1）
Wherein: c d represents the air resistance coefficient of the vehicle, A represents the windward area of the vehicle (m 2）, represents the air density in the test (kg/m 3), and V represents the vehicle running speed (m/s).
The rolling resistance calculating method comprises the following steps:
；（2）
Wherein is a first rolling resistance coefficient,/> is a second rolling resistance coefficient, m is a vehicle test mass (kg), and g is a gravitational acceleration (m/s 2).
Other resistances can also have an obstructing effect on the sliding of the vehicle, the law of the resistance is difficult to fumbly, and the law of the resistance is related to a plurality of factors, such as the vehicle speed, the vehicle weight and the like, other resistances have a great relation with the weight of the vehicle than the friction resistance of the front shaft and the rear shaft, the internal resistance of the vehicle and the like, and the heavier the vehicle is, the greater the resistance is, the lighter the vehicle is, and the smaller the resistance is. The application mainly explores a calculation method of the sliding resistance of the heavy vehicle under different loads, which has great relevance with the test quality of the vehicle, and the influence factors of the weight change are extracted independently. Assuming that the resistance is a linear function of weight, other resistance calculation methods are defined in the present application as:
；（3）
Wherein and b are constants, and are called other resistance coefficients.
According to the momentum theorem, the momentum change of the vehicle is equal to the time of each resistance multiplied by each resistance action, and the calculation method is as follows:
mΔV=F Air-conditioner .t1+F Scrolling .t1+F Other resistance forces .t1（4）
Since the vehicle speed is continuously reduced during the sliding process, the air resistance and the rolling resistance are not constant, and the corresponding resistance at the intermediate vehicle speed of the vehicle speed interval is taken as the average value of the calculated air resistance and the rolling resistance in the speed change interval, namely the air resistance and the rolling resistance value at the intermediate vehicle speed of the speed interval are used for replacing the instantaneous change value in the speed interval.
=/>（5）
Wherein V 1 and V 2 are the starting and ending speeds of one speed interval, t 1 is the time of use of the speed interval, A represents the windward area of the vehicle, ρ represents the air density in the test, and V 3=（V1+V2)/2. Looking at equation (5), it is readily found that the other drag coefficient b can be combined with the first rolling drag coefficient to/> , derived as:
（6）
Note is the first rolling resistance coefficient after combination, and equation (6) is defined as a novel sliding resistance calculation equation provided by the present application. C d、/>、/> and/> in equation (6) are defined as the air resistance coefficient, the first rolling resistance coefficient, the second rolling resistance coefficient, and the other resistance coefficients related to the load, respectively, of the present application design.
S30, solving C d、、/>、/> according to at least 4 relational expressions.
Since there are a total of 4 unknowns in equation (6), at least 4 relationships are needed to solve.
S40, introducing the solution value into a formula (7), and calculating the running resistance F of the heavy vehicle at each speed V under the conditions of a load and an air density/> ;
When the vehicle is under other arbitrary loads, the test vehicle weight and the air density/> are required to be obtained, and then the resistance value of the vehicle under other arbitrary loads at each speed V under the conditions of the vehicle weight/> and the air density/> can be calculated according to the formula (7):
（7）
The only speed-resistance scatter obtained by the formula (7) is that the running resistance F is discrete. The method is characterized in that the speed-running resistance scattered points are required to be fitted, the method is not limited to a least square method, the resistance curves of the heavy truck under different loads are obtained, and the coefficients of the quadratic term, the primary term and the constant term of the resistance function F=A+B.V+C.V 2 are determined, so that other load resistance curves are calculated through the full-load sliding V-T curve.
Example two
In this embodiment, S30 in the above embodiment is further refined, and since the test has a deviation, the influence of the abnormal relational expression on the calculation accuracy needs to be removed.
Specifically, S31 selects different numbers and different combinations of relational expressions from all relational expressions to solve C d、、/> and ; s32, calculating the running resistance of the heavy vehicle at each speed according to the solved C d、/>、/> and/> ; s33, comparing the running resistance obtained in the S32 with an actual load sliding test value to obtain a deviation value; s34, selecting a relation combination with the smallest deviation value, and solving to C d、/>、/> and/> .
Assuming that there are n relational expressions in total, m (4.ltoreq.m.ltoreq.n) relational expressions are extracted therefrom, and all possible cases are exemplified, and C d、、/> and/> in each possible case are found, respectively. And then substituting the calculated C d、/>、/> and/> into the formula (8) and the formula (9) so that the deviation between the calculated value of the formula (8) and the calculated value of the formula (9) and the actual load sliding test value at each corresponding speed is the smallest divided by the actual load sliding test value at the corresponding speed. There must be at least one set of combinations that will minimize the deviation when the solved C d、/>、/> and/> back-substitute for the load, outputting the minimum deviation at this time and the corresponding C d、/>、/> and/> values.
N, n-1, n-2, n-3, , 5,4 momentum equations are extracted from the n relational expressions, all possible cases are listed, the values of C d、/>、/> and/> in each possible case are respectively calculated, and the values of C d、/>、/> and/> corresponding to the combination with the smallest deviation are output after being substituted into the relational expressions and compared with the actual load sliding test value at the corresponding speed. Thus, when n, n-1, n-2, n-3,/> , 5,4 equations are extracted from the n momentum equations, respectively, each combination has a corresponding minimum deviation value, the number of extraction equations corresponding to the minimum value in the minimum deviations is found, and finally the number of extraction equations, the corresponding minimum deviation value and the values of C d、/>、/> and/> solved in this case are confirmed.
The method of calculating the bias after each solution of the unknowns is described as follows: when unknowns C d、、/> and/> are solved, they can be substituted into the load-sliding resistance calculation formula to calculate the sliding resistance values at each speed during V 1 (m/s) to V 2 (m/s).
When the vehicle speed is equal to V 1 (m/s), the corresponding load sliding resistance value is:
（8）
When the vehicle speed is equal to V 2 (m/s), the corresponding load sliding resistance value is:
（9）
Similar to equations (8) and (9), the corresponding load sliding resistance values at the respective speeds can be obtained. And then, comparing the calculated value with the actual load sliding resistance value (as a true value) obtained by the sliding test. The actual load coast test is: under the environmental conditions meeting national standards, a coasting test is started, the vehicle speed is driven to a high speed, such as 90km/h, then the vehicle is in neutral gear, coasting is started, the vehicle speed is gradually reduced, the time used for the vehicle speed to slip from 90km/h to 80km/h is recorded, the time used for the vehicle speed to slip from 80km/h to 70km/h is recorded, and the like. Taking the 90km/h sliding to 80km/h process as an example, the section resistance . The resistance of each speed segment is calculated in this way.
The calculated values of the formula (8) and the formula (9) are subtracted from the actual load sliding test values at the corresponding speeds respectively and divided by the actual load sliding test values at the corresponding speeds to obtain the relative deviation. And averaging the relative deviation of each speed to obtain a deviation value. There must be at least one set of combinations that can be made to take the solution of C d、、/> and/> back to equations (8) and (9), where the deviation value is minimal, outputting the minimal deviation value at that time and the corresponding C d、/>、/> and/> .
In a preferred embodiment, each time a certain number of equations is extracted, a corresponding minimum deviation is calculated. The calculation method of the deviation is as follows: the calculated 4 unknowns C d、、/> and/> are calculated by the formula (8) and the formula (9), respectively, and the difference between the calculated value and the actual load coast test value at the vehicle speeds 4.1667, 5.5556, 6.9444, 8.3333, 9.7222, 11.1111, 12.5, 13.8889, 15.2778, 16.6667, 18.0556, 19.4444m/s is divided by the actual load coast test value at the corresponding vehicle speed, and the absolute values are all calculated and then averaged. The minimum deviation is the minimum average value.
And selecting a certain relation number from n momentum equations to solve. The number of the selected relational expressions is not more and better, nor is the number of the selected relational expressions less and better. The reason for this is: when the number of the selected relation is larger, the number of the speed interval sections in the sliding process is larger, the speed time (V-T) data are obtained through test measurement, the test is biased, the main bias of the test is the time required for the vehicle speed to slide from the initial speed to the final speed of a certain speed interval, and the purpose of adopting an algorithm is to eliminate the influence of some abnormal points on the speed-time (V-T) scatter diagram on the calculation precision. When the number of the selected relational expressions is smaller, the number of the speed interval sections in the sliding process is smaller, the rolling resistance is the main part when the vehicle speed is lower, the air resistance is the secondary part when the vehicle speed is higher, the air resistance is the main part, the rolling resistance is the secondary part, and the selected speed interval sections need to be covered to the low-speed and high-speed intervals as much as possible, so that the phenomenon of fitting the whole part by part is most likely to be caused when the number of the selected points is smaller, and the prediction accuracy is reduced. Preferably, the relationships of different numbers and different combinations are evenly distributed over the respective speed intervals.
According to the number of the selected relational expressions from most to least, the rule presented on the calculated minimum deviation is that the minimum deviation gradually decreases, and finally, the minimum deviation almost tends to be stable and fluctuates only in a tiny range. And selecting a stable section with relatively moderate equality number as the C d、、/> and/> values when the vehicle slides finally.
Example III
This example provides a specific embodiment to describe in detail the method provided by the present application.
Referring to table 1, there are 11 total speed intervals, each of which is fatv=10 km/h. On this basis, for the first speed interval (75 km/h (20.8333 m/s) to 65km/h (18.0556 m/s), the momentum theorem is used with equation (6).
Test mass at full load of vehicle in formula (6): m= 24480kg, windward area: a= 7.46194m 2, air density in test: ρ= 1.28694444kg/m 3, gravitational acceleration: g=9.8m/s 2, the initial velocity V 1 = 20.8333m/s, the final velocity V 2 = 18.0556m/s, the intermediate velocity V 3=（V1+V2)/2= 19.4445m/s, the momentum equation for the first velocity segment (75 km/h to 65 km/h) can be obtained.
Similarly, the momentum equations for the vehicle in the other 10 speed intervals can be obtained, together forming 11 momentum equations with 4 unknowns C d、、/> and/> , and then solving and optimizing the 4 unknowns using an algorithm.
Of the 11 momentum equations, 11 equations are extracted, obviously there is only one combination in this case, and the calculation of C d、、/> and/> under this combination, i.e. the solution of C d、/>、/> and/> , can satisfy the 11 equations simultaneously so that the full load deviation is minimal, essentially finding the optimal solution for the 11 equations. The calculation method of the full load deviation is as follows: the calculated 4 unknowns C d、/>、/> and/> are calculated by the formula (8) and the formula (9), respectively, and the difference between the calculated value and the actual full coast test value at the vehicle speeds 4.1667, 5.5556, 6.9444, 8.3333, 9.7222, 11.1111, 12.5, 13.8889, 15.2778, 16.6667, 18.0556, 19.4444m/s is divided by the actual full coast test value at the corresponding vehicle speed, and the absolute value is calculated and then averaged. And finally outputting the C d、/>、/> and/> solved under the combination of the cases.
Of the 11 momentum equations, 10 equations are extracted, and obviously there are 11 combinations in this case, and C d、、/>、/> under the 11 combinations are calculated respectively, that is, the solved C d、/>、/>、/> can simultaneously satisfy the 10 equations under the current situation so that the error is minimum, which is essentially to find the optimal solution for the 10 equations. And finally outputting the C d、/>、/>、/> solved by the set of equations with the smallest deviation under all combinations.
By analogy, among the 11 momentum equations, 9, 8, 7, 6, 5 and 4 equations are extracted, and obviously, in this case, there are very many combinations, and C d、、/>、/> under each combination is calculated respectively, that is, the solved C d、/>、/>、/> can simultaneously satisfy several equations under the current situation combination so that the error is minimum, and essentially, find the optimal solution for the multiple equations. And finally outputting the C d、/>、/>、/> solved by the set of equations with the smallest deviation under all combinations.
After solving the C d、、/>、/> values under all possible conditions, substituting the values into other loads through a formula (7), and solving the resistance value of each speed of the vehicle under any load.
The accuracy of calculating other load resistances by the method is required to be judged, and the vehicle is subjected to the sliding tests under the loads of 80%, 60%, 40%, 20% and 0% to obtain the actual load sliding test value. The practical effect of this method is shown in table 2. The calculation methods of 80%, 60%, 40%, 20%, and 0% load deviations in table 2 are the same as the calculation method of the full load deviation.
Table 2 calculation results
In table 2, it can be seen that the error is larger by more than 10% when the 11 equations are extracted and larger by more than 10% when the 0% load is calculated, and the error is also larger by more than 10% when the 0% load is calculated by extracting the 4 equations from the 11 equations, thereby proving that the more and the less the number of the extracted equations is, the better the case full load error is finally stabilized in the range of 0.58% -0.54%, and the moderate number of the equations, such as 6-9, is suitable. And (3) obtaining calculated C d、、/> and/> values, respectively calculating and bringing the calculated values into a formula (7), obtaining resistance values of the vehicle at various speeds under other loads, and finally carrying out least square fitting on the speed-resistance (V-F) scattered points to obtain a resistance curve of the vehicle under different loads, thereby determining the coefficients of a quadratic term, a primary term and a constant term of the resistance function. Other load resistance curves were calculated from the full-load coast V-T curve. Fig. 2a to 2e are dot graphs showing the calculation results of 8 equations extracted from 11 equations, and show the actual sliding test values under different loads and the calculation values according to the method provided by the present patent, so that the method provided by the present application has a good matching degree with the test values.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present application. As used in this specification, the terms "a," "an," "the," and/or "the" are not intended to be limiting, but rather are to be construed as covering the singular and the plural, unless the context clearly dictates otherwise. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method or apparatus that includes the element.
It should also be noted that the positional or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the positional or positional relationship shown in the drawings, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the apparatus or element in question must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present application. Unless specifically stated or limited otherwise, the terms "mounted," "connected," and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present application.
Claims (6)
1. The method for testing the running resistance of the heavy vehicle under any load is characterized by comprising the following steps of:
S10, controlling a heavy vehicle with a load m to perform a sliding test to obtain speed-time data of the heavy vehicle in a plurality of speed intervals;
S20, determining a relation between the momentum change quantity and the resistance in each speed interval based on a momentum theorem:
Wherein, V 1 and V 2 are the starting and ending speeds of a speed interval, t 1 is the time consumption of the speed interval, A represents the windward area of the vehicle, represents the air density in the test, V 3=（V1+V2)/2, g is the gravity acceleration, and C d、/>、/>、/> is defined as the air resistance coefficient, the first rolling resistance coefficient, the second rolling resistance coefficient and the other resistance coefficient related to the load respectively;
S30, solving C d、、/> and/> according to at least 4 relational expressions;
s40, introducing the solution value into the following formula:
And calculating the running resistance F of the heavy vehicle at each speed V under the conditions of a load and an air density/> .
2. The method according to claim 1, wherein S30 comprises:
s31, selecting different numbers and different combinations of relational expressions from all relational expressions to solve C d、、/> and/> ;
s32, calculating the running resistance of the heavy vehicle at each speed according to the solved C d、、/> and/> ;
s33, comparing the running resistance obtained in the S32 with an actual load sliding test value to obtain a deviation value;
s34, selecting a relation combination with the smallest deviation value, and solving to C d、、/> and/> .
3. The method of claim 2, wherein the different numbers of relationships, different combinations, are evenly distributed across each speed interval.
4. The method according to claim 2, wherein S32 comprises:
Substituting the solved C d、、/> and/> into the following formula to obtain the running resistance/> at the speed V 1;
。
5. The method according to claim 2, wherein S33 comprises:
Subtracting the running resistance obtained in S32 at each speed from the actual load sliding test value, and dividing the running resistance by the actual load sliding test value at the corresponding speed to obtain relative deviation;
And averaging the relative deviation of each speed to obtain a deviation value.
6. The method of claim 1, wherein S40 comprises:
Calculating the discrete running resistance F of the heavy vehicle at each speed V under the conditions of a load and an air density/> ;
fitting the speed-running resistance scattered points to obtain a resistance curve of the heavy truck under different loads, and determining the coefficients of a secondary term, a primary term and a constant term of a resistance function.
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