1. A light vehicle RDE test method based on a chassis dynamometer is characterized by comprising the following steps:

step one, confirming a vehicle state;

step two, adjusting the vehicle load to 90% of the maximum load of the vehicle;

step three, moving the vehicle to a chassis dynamometer and fixing the vehicle, and setting the load of the chassis dynamometer;

step four, carrying out pretreatment driving according to WLTC circulation;

step five, after the pretreatment of running, the vehicle is kept still in the environmental chamber for vehicle dipping;

step six, randomly adjusting test circulation according to the requirement of development and calibration of RDE;

step seven, starting the vehicle, driving the vehicle according to the test cycle requirement, and sampling gas;

step eight, starting an air conditioner when the test is carried out for 5 min;

step nine, immediately shutting down the engine after the test is finished, and then stopping data measurement; the equipment connection is disconnected, and the vehicle is removed from the chassis dynamometer.

2. The chassis dynamometer-based light vehicle RDE test method of claim 1, wherein the specific method of the first step is as follows:

a) confirming that the tire pressure meets the requirements of vehicle technical conditions, wherein the tire pattern depth is more than 80% of the initial pattern depth;

b) confirming that an air inlet system and an air exhaust system of the engine are complete and air-tight;

c) confirming that vehicle lighting, signaling devices and other electrical equipment are working normally;

d) confirming that the brake system works normally;

e) and confirming that the four-wheel positioning parameters of the vehicle meet the technical condition requirements.

3. The chassis dynamometer-based light vehicle RDE test method of claim 1, wherein the road load of the vehicle in the third step is calculated as follows:

wherein F is the automobile road load and the unit is Newton (N);

C_Dair resistance coefficient (dimensionless value);

a-area of the vehicle facing the wind, in square meters (m)²)；

Rho-air density in kilograms per cubic meter (kg/m)³) Taking 1.293kg/m³；

V is the running speed of the automobile, and the unit is kilometer per hour (km/h);

f is the coefficient of friction resistance (dimensionless value), 0.012;

m-test mass in kilograms (kg);

g-gravitational acceleration in meters per second of square (m/s)²) Taking 9.8066m/s²。

4. The chassis dynamometer-based light vehicle RDE test method of claim 1, wherein the concrete method of the fourth step is as follows:

the environmental temperature is set between-5 ℃ and 30 ℃ during the pretreatment driving, and the environmental temperature is kept stable; the allowable tolerance between the actual vehicle speed while driving and the speed specified in the test cycle is as follows:

-an upper tolerance limit, +2.0km/h, time within ± 1.0 s;

-a lower tolerance limit of-2.0 km/h, time within ± 1.0 s;

allowing the speed tolerance to be larger than the specified requirement, but the out-of-tolerance time cannot exceed 1 s; during the test, the above speed over-difference can not occur more than 20 times;

steering wheel rotation is strictly prohibited during vehicle operation on the chassis dynamometer.

5. The chassis dynamometer-based light vehicle RDE test method of claim 1, wherein the concrete method of the fifth step is as follows:

the ambient temperature was set to 0 ℃; after the temperature in the environment cabin reaches the set temperature, the vehicle is still for 6-36 h; during immersion, the engine hood can be opened or closed; if a forced cooling mode is adopted, the transmission system, the engine and the exhaust aftertreatment system can be uniformly cooled.

6. The chassis dynamometer-based light vehicle RDE test method of claim 1, wherein the concrete method of the seventh step is as follows:

the temperature of the engine oil and the temperature of the cooling liquid measured before the test should be within the range of 0 +/-2 ℃, and the temperature of a test room should be controlled during the test0 +/-5 ℃; connecting an exhaust equipment connecting pipe to a vehicle exhaust pipe; closing the engine cover, the vehicle door and the trunk lid; starting the vehicle and driving the vehicle according to the test cycle requirement; starting the vehicle and simultaneously starting gas sampling, wherein parameters measured during the test comprise vehicle speed, engine rotating speed, engine coolant temperature, accelerator pedal opening, environment temperature, environment humidity, atmospheric pressure and CO₂Concentration, NO_XConcentration, CO concentration, PN concentration, and exhaust flow rate.

7. The chassis dynamometer-based light vehicle RDE test method of claim 1, wherein the concrete method of the step eight is as follows:

for a vehicle with a middle-exhaust air outlet and a rear-exhaust air outlet, opening the middle-exhaust air outlet and the rear-exhaust air outlet; the opening degree of all air outlets is set to be maximum, and the air outlet direction regulator is regulated to the middle position; for the manual control type air conditioner, an air circulation switch is arranged at an external circulation position, a foot blowing mode is selected, a temperature control switch is adjusted to be at the position of the maximum heating mode, an air volume adjusting switch is arranged at the middle position when the air conditioner is just started, and the air volume adjusting switch is adjusted to be at the position of the minimum air volume when the test is carried out for 30min and is continued until the test is finished; for an automatic control type air conditioner, an 'automatic' mode is set, and the temperature is set to a 'comfortable temperature'; if the automatic mode can not be used normally, the manual control type air conditioner is used for adjustment; and if the vehicle window is fogged, selecting a demisting mode.

Background

Along with the increasing severity of global environmental pollution and energy crisis problems, the energy conservation and emission reduction of vehicles are more and more emphasized by people. The living standard of Chinese people is continuously improved, the reserved quantity of private cars is continuously increased, the vehicle exhaust emission is more and more serious, and the RDE is one part of the national six-emission standard which is set for reducing the vehicle exhaust emission. The RDE requires that the vehicle be driven on a real road and that exhaust pollutants be measured by means of PEMS (portable emission testing system).

When the RDE test is carried out on an actual road, the influence factors are very many. For example, traffic conditions are very random, the same path may be very clear in this test and very congested in the next test, which results in a great difference between the two tests. Moreover, the test is very seriously influenced by weather, the test cannot be carried out when the temperature is higher than 35 ℃ and lower than minus 7 ℃, and the test cannot be carried out in rainy and snowy days. Some emergencies, such as temporary road repair, traffic accidents, etc., may also result in failure of the test. The development and calibration test of the RDE needs to research the influence of different calibration strategies on the RDE test result, and if the test result is poor in consistency, the calibration work is greatly disturbed. In a word, the RDE test of the actual road has many influencing factors, poor result consistency and low success rate, and is not beneficial to development and calibration of RDE.

A chassis dynamometer is a device used to simulate road loads. The chassis dynamometer generally comprises a roller, a motor, a control system, a safety protection system and the like. The test device can complete the power economy performance test and the emission test of the whole vehicle by combining an environmental chamber and an emission analyzer. The chassis dynamometer simulates an actual road surface through a roller, and simulates the resistance of a vehicle on the actual road through a loading device and rotational inertia, so that the aim of simulating the vehicle to run on the actual road is fulfilled.

The existing method for testing the RDE of the light automobile generally performs the RDE test on an actual road. The RDE is able to more realistically reflect the level of emissions from the vehicle when actually used by the user, as compared to emissions testing in a laboratory. However, when the RDE test is performed, uncontrollable factors such as weather, road conditions, traffic flow and the like are too much, so that the difference between the test results of multiple times is large, and the RDE calibration work in the vehicle development process is not facilitated. The RDE test is carried out by simulating an actual road on the chassis dynamometer, so that uncontrollable factors can be greatly reduced, the consistency of test results is improved, and the RDE calibration work is facilitated.

Disclosure of Invention

The invention provides a light vehicle RDE test method based on a chassis dynamometer, which can simulate the RDE test of an actual road on the chassis dynamometer in a test room, has no influence of traffic conditions and weather conditions on the test, can improve the test efficiency of RDE development calibration, shortens the RDE development period, and solves the problems of poor consistency and low success rate of the actual road test.

The technical scheme of the invention is described as follows by combining the attached drawings:

the invention has the beneficial effects that:

a light vehicle RDE test method based on a chassis dynamometer comprises the following steps:

step one, confirming a vehicle state;

step two, adjusting the vehicle load to 90% of the maximum load of the vehicle;

step three, moving the vehicle to a chassis dynamometer and fixing the vehicle, and setting the load of the chassis dynamometer;

step four, carrying out pretreatment driving according to WLTC circulation;

step five, after the pretreatment of running, the vehicle is kept still in the environmental chamber for vehicle dipping;

step six, randomly adjusting test circulation according to the requirement of development and calibration of RDE;

step seven, starting the vehicle, driving the vehicle according to the test cycle requirement, and sampling gas;

step eight, starting an air conditioner when the test is carried out for 5 min;

step nine, immediately shutting down the engine after the test is finished, and then stopping data measurement; the equipment connection is disconnected, and the vehicle is removed from the chassis dynamometer.

The specific method of the first step is as follows:

a) confirming that the tire pressure meets the requirements of vehicle technical conditions, wherein the tire pattern depth is more than 80% of the initial pattern depth;

b) confirming that an air inlet system and an air exhaust system of the engine are complete and air-tight;

c) confirming that vehicle lighting, signaling devices and other electrical equipment are working normally;

d) confirming that the brake system works normally;

e) and confirming that the four-wheel positioning parameters of the vehicle meet the technical condition requirements.

The calculation method of the automobile road load in the third step is as follows:

wherein F is the automobile road load and the unit is Newton (N);

C_Dair resistance coefficient (dimensionless value);

a-area of the vehicle facing the wind, in square meters (m)²)；

Rho-air density in kilograms per cubic meter (kg/m)³) Taking 1.293kg/m³；

V is the running speed of the automobile, and the unit is kilometer per hour (km/h);

f is the coefficient of friction resistance (dimensionless value), 0.012;

m-test mass in kilograms (kg);

g-gravitational acceleration in meters per second of square (m/s)²) Taking 9.8066m/s²。

The concrete method of the fourth step is as follows:

the environmental temperature is set between-5 ℃ and 30 ℃ during the pretreatment driving, and the environmental temperature is kept stable; the allowable tolerance between the actual vehicle speed while driving and the speed specified in the test cycle is as follows:

-an upper tolerance limit, +2.0km/h, time within ± 1.0 s;

-a lower tolerance limit of-2.0 km/h, time within ± 1.0 s;

allowing the speed tolerance to be larger than the specified requirement, but the out-of-tolerance time cannot exceed 1 s; during the test, the above speed over-difference can not occur more than 20 times;

steering wheel rotation is strictly prohibited during vehicle operation on the chassis dynamometer.

The concrete method of the step five is as follows:

the ambient temperature was set to 0 ℃; after the temperature in the environment cabin reaches the set temperature, the vehicle is still for 6-36 h; during immersion, the engine hood can be opened or closed; if a forced cooling mode is adopted, the transmission system, the engine and the exhaust aftertreatment system can be uniformly cooled.

The concrete method of the seventh step is as follows:

before the test, the temperature of the engine oil and the temperature of the cooling liquid of the engine are measured to be within the range of 0 +/-2 ℃, and the temperature of a test room is controlled to be 0 +/-5 ℃ during the test; connecting an exhaust equipment connecting pipe to a vehicle exhaust pipe; closing the engine cover, the vehicle door and the trunk lid; starting the vehicle and driving the vehicle according to the test cycle requirement; starting the vehicle and simultaneously starting gas sampling, wherein parameters measured during the test comprise vehicle speed, engine rotating speed, engine coolant temperature, accelerator pedal opening, environment temperature, environment humidity, atmospheric pressure and CO₂Concentration, NO_XConcentration, CO concentration, PN concentration, and exhaust flow rate.

The concrete method of the step eight is as follows:

for a vehicle with a middle-exhaust air outlet and a rear-exhaust air outlet, opening the middle-exhaust air outlet and the rear-exhaust air outlet; the opening degree of all air outlets is set to be maximum, and the air outlet direction regulator is regulated to the middle position; for the manual control type air conditioner, an air circulation switch is arranged at an external circulation position, a foot blowing mode is selected, a temperature control switch is adjusted to be at the position of the maximum heating mode, an air volume adjusting switch is arranged at the middle position when the air conditioner is just started, and the air volume adjusting switch is adjusted to be at the position of the minimum air volume when the test is carried out for 30min and is continued until the test is finished; for an automatic control type air conditioner, an 'automatic' mode is set, and the temperature is set to a 'comfortable temperature'; if the automatic mode can not be used normally, the manual control type air conditioner is used for adjustment; and if the vehicle window is fogged, selecting a demisting mode.

The invention can simulate the RDE test of an actual road on the chassis dynamometer in a test room, has no influence of traffic conditions and weather conditions on the test, can improve the test efficiency of RDE development calibration, and shortens the RDE development period.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the contents of the embodiments of the present invention and the drawings without creative efforts.

Fig. 1 is a speed tolerance graph.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

A light vehicle RDE test method based on a chassis dynamometer comprises the following steps:

step one, confirming a vehicle state;

a) confirming that the tire pressure meets the requirements of vehicle technical conditions, wherein the tire pattern depth is more than 80% of the initial pattern depth;

b) confirming that an air inlet system and an air exhaust system of the engine are complete and air-tight;

c) confirming that vehicle lighting, signaling devices and other electrical equipment are working normally;

d) confirming that the brake system works normally;

e) and confirming that the four-wheel positioning parameters of the vehicle meet the technical condition requirements.

Step two, adjusting the vehicle load to 90% of the maximum load of the vehicle;

step three, moving the vehicle to a chassis dynamometer and fixing the vehicle, and setting the load of the chassis dynamometer;

the calculation of the road load of the car is as follows:

wherein F is the automobile road load and the unit is Newton (N);

C_Dair resistance coefficient (dimensionless value);

a-area of the vehicle facing the wind, in square meters (m)²)；

Rho-air density in kilograms per cubic meter (kg/m)³) Taking 1.293kg/m³；

V is the running speed of the automobile, and the unit is kilometer per hour (km/h);

f is the coefficient of friction resistance (dimensionless value), 0.012;

m-test mass in kilograms (kg);

g-gravitational acceleration in meters per second of square (m/s)²) Taking 9.8066m/s²。

Step four, carrying out pretreatment driving according to WLTC circulation;

referring to fig. 1, the environment temperature is set between-5 ℃ and 30 ℃ and kept stable during the pretreatment driving; the allowable tolerance between the actual vehicle speed while driving and the speed specified in the test cycle is as follows:

-an upper tolerance limit, +2.0km/h, time within ± 1.0 s;

-a lower tolerance limit of-2.0 km/h, time within ± 1.0 s;

allowing the speed tolerance to be larger than the specified requirement, but the out-of-tolerance time cannot exceed 1 s; during the test, the above speed over-difference can not occur more than 20 times;

steering wheel rotation is strictly prohibited during vehicle operation on the chassis dynamometer.

Step five, after the pretreatment of running, the vehicle is kept still in the environmental chamber for vehicle dipping;

the ambient temperature was set to 0 ℃; after the temperature in the environment cabin reaches the set temperature, the vehicle is still for 6-36 h; during immersion, the engine hood can be opened or closed; if a forced cooling mode is adopted, the transmission system, the engine and the exhaust aftertreatment system can be uniformly cooled.

Step six, randomly adjusting test circulation according to the requirement of development and calibration of RDE;

step seven, starting the vehicle, driving the vehicle according to the test cycle requirement, and sampling gas; before the test, the temperature of the engine oil and the temperature of the cooling liquid of the engine are measured to be within the range of 0 +/-2 ℃, and the temperature of a test room is controlled to be 0 +/-5 ℃ during the test; connecting an exhaust equipment connecting pipe to a vehicle exhaust pipe; closing the engine cover, the vehicle door and the trunk lid; starting the vehicle and driving the vehicle according to the test cycle requirement; the parameters measured at the start of the gas sampling service test while the vehicle was started are shown in table 1.

TABLE 1 measurement parameters

Parameter(s)	Mode of acquisition
		Vehicle speed	ECU
Rotational speed of engine	ECU
		Engine coolant temperature	ECU
Opening degree of accelerator pedal	ECU
		Ambient temperature	Environmental chamber
Humidity of the environment	Environmental chamber
		Atmospheric pressure	Environmental chamber
CO2Concentration of	Emission analyzer
		NOXConcentration of	Emission analyzer
CO concentration	Emission analyzer
		Concentration of PN	Emission analyzer
Exhaust flow rate	Emission analyzer

Step eight, starting an air conditioner when the test is carried out for 5 min;

for a vehicle with a middle-exhaust air outlet and a rear-exhaust air outlet, opening the middle-exhaust air outlet and the rear-exhaust air outlet; the opening degree of all air outlets is set to be maximum, and the air outlet direction regulator is regulated to the middle position; for the manual control type air conditioner, an air circulation switch is arranged at an external circulation position, a foot blowing mode is selected, a temperature control switch is adjusted to be at the position of the maximum heating mode, an air volume adjusting switch is arranged at the middle position when the air conditioner is just started, and the air volume adjusting switch is adjusted to be at the position of the minimum air volume when the test is carried out for 30min and is continued until the test is finished; for an automatic control type air conditioner, an 'automatic' mode is set, and the temperature is set to a 'comfortable temperature'; if the automatic mode can not be used normally, the manual control type air conditioner is used for adjustment; and if the vehicle window is fogged, selecting a demisting mode.

Step nine, immediately shutting down the engine after the test is finished, and then stopping data measurement; the equipment connection is disconnected, and the vehicle is removed from the chassis dynamometer.

The invention can simulate the RDE test of an actual road on the chassis dynamometer in a test room, has no influence of traffic conditions and weather conditions on the test, can improve the test efficiency of RDE development calibration, and shortens the RDE development period.