A method for evaluating the actual road CO2 emissions of light vehicles based on VSP

Abstract

The present invention discloses a method for evaluating the actual road CO2 emissions of light vehicles based on VSP, including: obtaining relevant data of multiple test vehicles during laboratory cycles and actual road driving, and calculating the vehicle specific power VSP of the corresponding test cycle; dividing the VSP of each test vehicle into multiple intervals Bin, and calculating the distance-based CO2 emission factor for each interval Bin; obtaining the slope of the fitting line segment by linearly fitting the emission factor of the WLTC or CLTC-P test cycle with the emission factor under RDE test; using the slope as the WR factor or CR factor, formulating emission limits, and judging whether the actual road carbon emissions of the light vehicles to be evaluated are compliant. The present invention provides a quantitative method for formulating actual road CO2 emission limits, which is beneficial to reducing road transport carbon emissions. At the same time, this method effectively alleviates the influence of driving behavior and traffic conditions on actual road CO2 emissions; the evaluation of actual road CO2 emissions based on VSP has high reliability and is convenient for judging whether the vehicle is compliant.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle exhaust monitoring, and more specifically, to a method for evaluating the actual road CO2 emissions of light-duty vehicles based on VSP. Background Art

[0002] As a basic greenhouse gas, CO2 plays an important role in global warming. Road transportation, as the largest source of pollution in transportation, accounts for 84.1% of the total greenhouse gas emissions, among which light-duty vehicle emissions rank first, accounting for 50.9% of road transportation emissions. These data emphasize the importance of researching and effectively reducing road transportation emissions.

[0003] Currently, the Worldwide Light-duty Driving Test Cycle (WLTC) is widely used when light-duty vehicles conduct chassis dynamometer tests. Research shows that using local driving cycles for emission estimation can significantly improve carbon emission reduction effects. Therefore, the China Light-duty Vehicle Test Cycle - Passenger (CLTC-P) has been developed in China. As laboratory tests, WLTC and CLTC-P have controllable environmental and traffic conditions, and the deviation during repeated tests is usually acceptable. In addition to laboratory tests, light-duty vehicles also need to conduct real driving emission (RDE) tests. The environmental, traffic, and road conditions during this test process are uncontrollable, resulting in extremely poor repeatability, which poses a great challenge to formulating the carbon dioxide emission limit for RDE tests. Summary of the Invention

[0004] In view of this, the present invention provides a method for evaluating the actual road CO2 emissions of light-duty vehicles based on VSP. By combining the specific power and emission characteristics of vehicles in different driving states, it can more accurately evaluate the CO2 emissions of light-duty vehicles under actual road conditions.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for evaluating the actual road CO2 emissions of light-duty vehicles based on VSP, including the following steps:

[0007] S10. Obtain the motion parameters, road parameters, and emission data of multiple test vehicles during laboratory cycles and actual road driving, and calculate the vehicle specific power VSP of the corresponding test cycles;

[0008] S20. Divide the VSP of each test vehicle into multiple intervals Bin at a preset interval, and calculate the instantaneous carbon dioxide emission factor based on distance for each interval Bin;

[0009] S30. Obtain the slope of the fitted line segment by linearly fitting the carbon dioxide emission factor of each VSP interval Bin in the WLTC or CLTC-P test cycle with the carbon dioxide emission factor of each VSP interval Bin under the RDE test; the slope is the WLTC-RDE factor or the CLTC-RDE factor;

[0010] S40. Set the emission limit according to the WLTC-RDE factor or the CLTC-RDE factor of multiple test vehicles obtained by fitting; based on the emission limit, judge whether the actual road carbon emissions of the light vehicles to be evaluated are compliant.

[0011] Furthermore, the step S10 includes:

[0012] Obtain the instantaneous speed v, instantaneous acceleration a, road slope θ and emission data of multiple test vehicles during the laboratory cycle and actual road driving, and calculate the VSP using the following formula:

[0013] VSP = v{1.1a + 9.81[arctan(sinθ)] + 0.132} + 0.000302v 3 (1)

[0014] For the laboratory test cycle, the road slope θ is uniformly taken as 0; finally, we get:

[0015] VSP = v(1.1a + 0.132) + 0.000302v 3 (2)

[0016] In the formula: v is the instantaneous vehicle speed, m / s; a is the instantaneous vehicle acceleration, m / s 2 .

[0017] Furthermore, in the step S20, dividing the VSP of each test vehicle into multiple intervals Bin at a preset interval includes: making the following divisions for the VSP of each test vehicle: where:

[0018] (-∞, -20) is used as the 1st interval Bin;

[0019] (-20, 24) is used as the 2nd to 12th interval Bins; the division of VSP is made with every 4 units as an interval, that is, divided into multiple intervals with an increment of 4;

[0020] (24, +∞) is used as the 13th interval Bin.

[0021] Further, in the step S20, calculating the distance-based instantaneous carbon dioxide emission factor for each interval Bin includes the following:

[0022] For the laboratory test cycle, the formula is as follows:

[0023]

[0024] where EF lab is the distance-based instantaneous carbon dioxide emission factor, g / km; n is the current time, s; i and j are the start and end times, s; C e is the concentration of carbon dioxide in the diluted exhaust gas, %; C d is the concentration of carbon dioxide in the dilution air, %; DF is the dilution factor; Q is the dilution flow rate, L / s; ρ is the density of carbon dioxide under standard temperature and pressure, g / L; D n is the driving mileage, km; C CO and C HC are the concentrations of carbon dioxide, CO, and HC in the diluted exhaust gas, %;

[0025] For the RDE test, the formula is as follows:

[0026]

[0027] where, ER RDE is the instantaneous carbon dioxide emission, g / s; ρ RDE is the density of carbon dioxide, kg / m 3 ; ρ RDE,exhaust is the density of the exhaust gas, kg / m 3 ; c RDE is the volume concentration of carbon dioxide, ppm; q is the exhaust gas volume flow rate, m 3 / s; is the distance-based carbon dioxide emission factor, g / km; D n is the driving mileage, km.

[0028] Further, the step S30 includes:

[0029] S301. When the first condition is satisfied, linearly fitting the curve by taking the carbon dioxide emission factor of each VSP interval Bin of WLTC or CLTC-P as the x-axis and the RDE carbon dioxide emission factor of each VSP interval Bin as the y-axis;

[0030] S302. Select the carbon dioxide emission factors of some or all of the VSP interval bins for fitting, and obtain a straight line after fitting; when the second condition is met, use the slope of the straight line as the WLTC-RDE factor or the CLTC-RDE factor.

[0031] Further, in the step S302, selecting the carbon dioxide emission factors of some or all of the VSP interval bins for fitting includes three methods:

[0032] A: Use the carbon dioxide emission factors of all VSP interval bins to fit the curve;

[0033] B: Use the carbon dioxide emission factors of the VSP interval bins 3 - 12 to fit the curve;

[0034] C: Use the carbon dioxide emission factors of the VSP interval bins 3 - 11 to fit the curve.

[0035] Further, in the step S301, when the first condition is met, it includes:

[0036] 1) Calculate the correlation factor between the VSP of the entire test cycle and the corresponding instantaneous carbon dioxide emissions, and calculate the average correlation factor, then execute step 2);

[0037] 2) When the average correlation factor is greater than 0.7, check the emission characteristics of multiple VSP interval bins, and execute step 3);

[0038] 3) When the instantaneous carbon dioxide emission rate of the interval bins 1 - 6 is about 1 g / s and the deviation is less than 30%.

[0039] Further, in the step S302, when the second condition is met, it includes:

[0040] After fitting to obtain a straight line, ensure that the standard variance R 2 exceeds 0.9, and the WLTC-RDE factor and / or CLTC-RDE factor obtained by following method A ≥ the WLTC-RDE factor and / or CLTC-RDE factor obtained by following method B ≥ the WLTC-RDE factor and / or CLTC-RDE factor obtained by following method C.

[0041] Further, in the step S40, according to the WLTC-RDE factor or the CLTC-RDE factor of multiple test vehicles obtained by fitting, formulate an emission limit; it includes:

[0042] According to the WLTC-RDE factor or the CLTC-RDE factor of multiple test vehicles obtained by fitting,

[0043] Take its median as the emission limit value, or take the average value within the concentrated area as the emission limit value.

[0044] As can be seen from the above technical solutions, compared with the prior art, the present invention has the following advantages:

[0045] (1) It provides a quantitative method for formulating the actual road CO2 emission limit value, which is beneficial to reducing carbon emissions from road transportation;

[0046] (2) Taking the CLTC-P cycle as the evaluation basis is more in line with the actual road conditions in China;

[0047] (3) Based on VSP, the reliability of evaluating the actual road CO2 emission is high, and it is convenient to judge whether the vehicle complies with the regulations.

[0048] (4) This evaluation method effectively alleviates the influence of driving behavior and traffic conditions on the actual road CO2 emission. Description of the Drawings

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0050] Figure 1 It is a flowchart of the method for evaluating the actual road CO2 emission of light-duty vehicles based on VSP.

[0051] Figure 2a It is a diagram of the instantaneous CO2 emission amount and frequency of each VSP interval of the N0.1 pure fuel vehicle.

[0052] Figure 2b It is a diagram of the instantaneous CO2 emission amount and frequency of each VSP interval of the N0.2 pure fuel vehicle.

[0053] Figure 2c It is a diagram of the instantaneous CO2 emission amount and frequency of each VSP interval of the N0.3 pure fuel vehicle.

[0054] Figure 2d It is a diagram of the instantaneous CO2 emission amount and frequency of each VSP interval of the N0.4 pure fuel vehicle.

[0055] Figure 2e It is a diagram of the instantaneous CO2 emission amount and frequency of each VSP interval of the N0.5 hybrid vehicle.

[0056] Figure 3a It is a WR factor diagram of the N0.1 pure fuel vehicle under three modes of A, B, and C.

[0057] Figure 3b CR factor diagrams for N0.1 pure fuel vehicles under three modes of A, B, and C.

[0058] Figure 4a WR factor diagrams for N0.2 pure fuel vehicles under three modes of A, B, and C.

[0059] Figure 4b CR factor diagrams for N0.2 pure fuel vehicles under three modes of A, B, and C.

[0060] Figure 5a WR factor diagrams for N0.3 pure fuel vehicles under three modes of A, B, and C.

[0061] Figure 5b CR factor diagrams for N0.3 pure fuel vehicles under three modes of A, B, and C.

[0062] Figure 6a WR factor diagrams for N0.4 pure fuel vehicles under three modes of A, B, and C.

[0063] Figure 6b CR factor diagrams for N0.4 pure fuel vehicles under three modes of A, B, and C.

[0064] Figure 7a WR factor diagrams for N0.5 hybrid vehicles under three modes of A, B, and C and normal driving mode.

[0065] Figure 7b WR factor diagrams for N0.5 hybrid vehicles under three modes of A, B, and C and aggressive driving mode.

[0066] Figure 7c WR factor diagrams for N0.5 hybrid vehicles under three modes of A, B, and C and traffic congestion mode.

[0067] Figure 8a CR factor diagrams for N0.5 hybrid vehicles under three modes of A, B, and C and normal driving mode.

[0068] Figure 8b CR factor diagrams for N0.5 hybrid vehicles under three modes of A, B, and C and aggressive driving mode.

[0069] Figure 8c CR factor diagrams for N0.5 hybrid vehicles under three modes of A, B, and C and traffic congestion mode.

[0070] Figure 9 Schematic diagram for formulating the carbon dioxide emission limit on actual roads provided by the present invention.

[0071] Figure 10This is the schematic diagram for judging the carbon dioxide emissions of a vehicle to be evaluated provided by the present invention. Detailed implementation manners

[0072] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0073] The environment, traffic, and road conditions for the actual road emission test of light-duty vehicles are uncontrollable, resulting in extremely poor repeatability, which poses a great challenge to formulating the actual road CO2 emission limit.

[0074] Therefore, the present invention provides a method for evaluating the actual road CO2 emissions of light-duty vehicles based on VSP, which quantitatively evaluates the RDE CO2 emissions based on WLTC or CLTC-P in combination with VSP. The specific steps are as follows Figure 1 shown, including:

[0075] S10. Obtain the motion parameters, road parameters, and emission data of multiple test vehicles during the laboratory cycle and actual road driving, and calculate the vehicle specific power VSP of the corresponding test cycle;

[0076] S20. Divide the VSP of each test vehicle into multiple intervals Bin at a preset interval, and calculate the distance-based instantaneous carbon dioxide emission factor for each interval Bin;

[0077] S30. Obtain the slope of the fitting line segment by linearly fitting the carbon dioxide emission factors of each VSP interval Bin in the WLTC or CLTC-P test cycle with the carbon dioxide emission factors of each VSP interval Bin under the RDE test; the slope is the WLTC-RDE factor or the CLTC-RDE factor;

[0078] S40. Formulate an emission limit according to the obtained WLTC-RDE factor or CLTC-RDE factor of multiple test vehicles; based on the emission limit, judge whether the actual road carbon emissions of the light-duty vehicle to be evaluated are compliant.

[0079] This method can first improve the accuracy of actual road carbon dioxide emissions assessment. By making a fine division based on vehicle specific power (VSP), the instantaneous carbon dioxide emissions are processed in zones, and combined with the fitting method of WLTC or CLTC-P and real driving emissions (RDE) tests, the emissions of vehicles under complex actual road conditions can be more accurately evaluated. This method improves the repeatability and reliability of RDE tests.

[0080] Secondly, it can effectively cope with different driving modes and environmental impacts. By using different VSP bins, the emissions under various working conditions from low speed, idling to high-speed acceleration can be covered, comprehensively reflecting the operating state of the vehicle on the actual road. This method is especially suitable for dealing with the impact of different driving styles (such as aggressive driving, traffic congestion, etc.) on carbon dioxide emissions, which helps to improve the overall evaluation of the vehicle's true emissions.

[0081] In addition, this method provides data support for the formulation of regulations. The WLTC-RDE factor or CLTC-RDE factor obtained by linear fitting can be used to formulate the regulatory limits for vehicle actual road emissions. These factors reflect the differences between laboratory tests and actual road emissions, providing a quantitative basis to ensure that the limits are scientific and enforceable.

[0082] Finally, it is convenient to judge vehicle compliance; based on the established emission limits, using the WLTC-RDE factor or CLTC-RDE factor, it can quickly judge whether the vehicle meets the actual road emission regulations. This process simplifies the compliance assessment, reduces the need for repeated tests, and provides convenience for the implementation of light vehicle emission standards.

[0083] The present invention is applicable not only to traditional fuel vehicles but also to vehicle types such as plug-in hybrid electric vehicles (PHEVs). It can provide accurate emission assessments according to the carbon dioxide emission factors in different VSP bins. This adaptability expands the application scope of this method.

[0084] Next, taking 5 test vehicles as an example, where No.1 - 4 are pure fuel vehicles and No.5 is a plug-in hybrid electric vehicle, the technical solution of the present invention will be described in detail:

[0085] Step S10: The RDE tests of pure fuel vehicles (No.1 - 4) are carried out in the normal mode. The plug-in hybrid electric vehicle (No.5) conducts RDE tests on the same route, including three different modes, namely the normal mode, the aggressive driving mode, and the traffic congestion mode, to judge that this method can effectively reduce the impact of the test environment on RDE carbon dioxide emissions.

[0086] Obtain the instantaneous speed and instantaneous acceleration of the above 5 test vehicles during actual driving, and calculate the corresponding vehicle specific power VSP.

[0087] Among them, the vehicle specific power (VSP, Vehicle Specific Power), as a road load model, can evaluate the actual road emissions second by second by allocating the driving data per second to specific modes. Based on the GPS acquisition data under different road types and traffic states, the calculation formula of VSP is as follows:

[0088] VSP = v{1.1a + 9.81[arctan(sinθ)] + 0.132} + 0.000302v 3 (1)

[0089] In the formula: v is the instantaneous speed of the vehicle, m / s; a is the instantaneous acceleration of the vehicle, m / s 2 ; θ is the road slope. Since the road slope of the chassis dynamometer test is constantly 0 and the road slope of the actual road test fluctuates extremely little, its influence on the test results can be ignored. Therefore, θ is uniformly taken as 0 here. The final calculation formula of VSP is:

[0090] VSP = v(1.1a + 0.132) + 0.000302v 3 (2)

[0091] Step S20:

[0092] Divide VSP at intervals of 4, divide it into multiple intervals Bin, and calculate the instantaneous carbon dioxide emissions of each Bin. By dividing VSP into multiple intervals (Bin), the CO2 emissions of the vehicle under different driving states can be accurately evaluated. Each interval corresponds to a different driving state, from low-speed state to high-speed state, and different power modes of hybrid vehicles. By analyzing the CO2 emissions of these intervals, the emission characteristics of the vehicle can be understood more comprehensively.

[0093] Figures 2a to 2e Shows the instantaneous CO2 emissions and frequencies of each VSP interval under different test cycles. The carbon dioxide emission rate corresponds to the rectangular column, and the frequency corresponds to the line segment; the frequency refers to the number of VSPs falling into the interval Bin. Figure 2e In, RDE-NW represents the normal mode, RDE-AD represents the aggressive driving mode, and RDE-TC represents the traffic congestion mode. The VSP of each test vehicle is divided as follows: Among them:

[0094] (-∞, -20) is used as the first interval Bin;

[0095] (-20, 24) is used as the 2nd to 12th interval Bin; the division of VSP is every 4 units as an interval, that is, divided into multiple intervals with an increment of 4.

[0096] (24, +∞) is used as the 13th interval Bin.

[0097] For pure fuel vehicles, when VSP is in the range of (-∞, 4), since the vehicle is mainly in a low-speed, decelerating or idling state, the instantaneous CO2 emissions are relatively low (about 1 g / s). As VSP increases in the range of [4, 24], the instantaneous CO2 emissions gradually increase. At this time, the vehicle is mainly in a high-speed or accelerating state, and the power demand increases significantly, resulting in increased fuel consumption. In terms of frequency, a VSP peak is observed in the range of [0, 4). The VSP distributions of WLTC and CLTC-P are mainly in the range of [-8, 12] (accounting for more than 80%), while the VSP distribution of RDE test is mainly in the range of [-12, 20] (accounting for more than 90%). Compared with WLTC, CLTC-P has a higher VSP peak and a more concentrated VSP distribution. The larger the VSP, the more aggressive the driving, resulting in higher instantaneous carbon dioxide emissions. However, under WLTC, CLTC-P and RDE tests, the VSP frequency in the range of [20, +∞) is significantly lower, especially in WLTC and CLTC-P.

[0098] For plug-in hybrid vehicles, when VSP is in the range of (-∞, 4), the instantaneous CO2 emissions are lower than those of traditional vehicles, which can be attributed to the lower power demand. PHEV can be powered by an electric motor. As VSP increases, the CO2 emission trend is similar to that of pure fuel vehicles, and the frequency distribution in various driving modes is also similar to that of pure fuel vehicles. The higher peak in the traffic congestion mode is attributed to the longer driving duration.

[0099] In step S20, calculate the distance-based instantaneous carbon dioxide emission factor for each interval Bin, including the following:

[0100] For laboratory test cycles, the formula is as follows:

[0101]

[0102] where EF lab is the distance-based instantaneous carbon dioxide emission factor, g / km; n is the current time, s; i and j are the start and end times, s; C e is the concentration of carbon dioxide in the diluted exhaust gas, %; C d is the concentration of carbon dioxide in the diluted air, %; DF is the dilution factor; Q is the dilution flow rate, L / s; ρ is the density of carbon dioxide under standard temperature and pressure, g / L; D n is the driving mileage, km; C CO and C HC is the concentration of carbon dioxide, CO and HC in the diluted exhaust gas, %;

[0103] For the RDE test, the formula is as follows:

[0104]

[0105] where ER RDE is the instantaneous emission of carbon dioxide, g / s; ρ RDE is the density of carbon dioxide, kg / m 3 ; ρ RDE,exhaust is the density of the exhaust gas, kg / m 3 ; c RDE is the volume concentration of carbon dioxide, ppm; q is the exhaust gas volume flow rate, m 3 / s; is the carbon dioxide emission factor based on distance, g / km; D n is the driving mileage, km.

[0106] Step S30:

[0107] By taking the CO2 emission factor of each VSP interval Bin of WLTC or CLTC-P as the x-axis and the RDE CO2 emission factor of each interval Bin as the y-axis, a linear fit is performed on the curve. This means that the uncontrollable RDE CO2 emissions can be evaluated through the controllable WLTC and CLTC-P.

[0108] Specifically, it includes:

[0109] S301. When the first condition is met, by taking the carbon dioxide emission factor of each VSP interval Bin of WLTC or CLTC-P as the x-axis and the RDE carbon dioxide emission factor of each VSP interval Bin as the y-axis, a linear fit is performed on the curve;

[0110] S302. Select the carbon dioxide emission factors of some or all of the VSP interval Bins for fitting, and obtain a straight line after fitting; when the second condition is met, take the slope of the straight line as the WLTC-RDE factor or the CLTC-RDE factor. Among them, selecting the carbon dioxide emission factors of some or all of the VSP interval Bins for fitting includes three methods:

[0111] A: Fit the curve with the CO2 emission factors of all VSP interval Bins.

[0112] B: Fit the curve using the CO2 emission factors in VSP bins 3 - 12. Since the frequencies of WLTC and CLTC-P are low, bins 1 - 2 are excluded because the reliability of the reference CO2 emission factors is low. Omitting bin 13 is mainly to exclude emissions from aggressive driving in RDE tests.

[0113] C: Fit the curve using the CO2 emission factors in VSP bins 3 - 11 to further eliminate emissions corresponding to high VSP. However, it should be ensured that the utilization rate of RDE data is above 90%.

[0114] Based on the three proposed methods, three straight lines with different slopes can be obtained, where the slope is the desired WLTC - RDE (WR) factor and CLTC - RDE (CR) factor. Figures 3a to 3b Shows the WR and CR factors for the three methods A, B, and C of the N0.1 pure fuel vehicle. Figures 4a to 4b Shows the WR and CR factors for the three methods A, B, and C of the N0.2 pure fuel vehicle. Figures 5a to 5b Shows the WR and CR factors for the three methods A, B, and C of the N0.3 pure fuel vehicle. Figures 6a to 6b Shows the WR and CR factors for the three methods A, B, and C of the N0.4 pure fuel vehicle. Figures 7a to 7c Shows the WR factors for different driving modes of the three methods A, B, and C of the N0.5 hybrid vehicle. Figures 8a to 8c Shows the CR factors for different driving modes of the three methods A, B, and C of the N0.5 hybrid vehicle.

[0115] Generally speaking, the WR and / or CR factors obtained by method A ≥ the WR and / or CR factors obtained by method B ≥ the WR and / or CR factors obtained by method C. To strengthen carbon emission reduction, the smaller WR and / or CR factors obtained by method C can be selected for application.

[0116] Step S40:

[0117] According to the above process of steps S10 - S30, the WR factors and CR factors of 5 vehicles can be obtained. In actual implementation, it is not limited to 5 vehicles, and there can be multiple test vehicles. The multiple WR factors and CR factors obtained can be used as data support for formulating regulatory limits. For example, selecting the median or mode of a set composed of multiple WR factors and CR factors, or using the mean value within the concentrated area as the emission limit is acceptable.

[0118] Then, after determining the regulatory limit, the WR factor or CR factor of the light vehicle to be evaluated can be compared with the emission limit. If the limit is higher than any of the factors obtained by the three methods A, B, and C, the vehicle emissions are considered compliant; otherwise, it is determined that the vehicle's CO2 emissions do not meet the regulations.

[0119] In addition, the data needs to be carefully reviewed before applying the proposed evaluation method, following the steps below:

[0120] (1) Use the CORREL formula in Excel to calculate the correlation factor between VSP and instantaneous carbon dioxide emissions, ensuring that the average correlation factor is at least greater than 0.7;

[0121] (2) Examine the emission characteristics of VSP Bins, especially those of Bin 1 - 6, ensuring that the instantaneous CO2 emission rate under different tests is approximately 1 g / s and the deviation is less than 30%;

[0122] The above (1) and (2) are the first conditions.

[0123] (3) The second condition is: Fit the curve to ensure that the standard variance R 2 exceeds 0.9, and the WR and / or CR factors obtained following Method A ≥ the WR and / or CR factors obtained following Method B ≥ the WR and / or CR factors obtained following Method C.

[0124] The method for evaluating the actual road CO2 emissions of light vehicles based on VSP provided by the embodiments of the present invention, as shown in Figure 9 After obtaining the vehicle specific power VSP of multiple test vehicles and the instantaneous carbon dioxide emissions of each interval Bin, for example:

[0125] First, use the CORREL formula in Excel to calculate the correlation factor between VSP and instantaneous carbon dioxide emissions, and calculate the average correlation factor, ensuring that it is at least greater than 0.7; Second, examine the emission characteristics of VSP Bins, especially those of Bin 1 - 6, ensuring that the instantaneous CO2 emission rate under different tests is approximately 1 g / s and the deviation is less than 30%; Then, use the CO2 emission factor of each VSP Bin of WLTC or CLTC - P as the x - axis and the CO2 emission factor of each VSP Bin of RDE as the y - axis to perform a linear fit of the curve, ensuring that the standard variance R 2 exceeds 0.9; Finally, obtain the slope of the fitted curve for different plans, that is, the WR factor and the CR factor, ensuring that the WR and / or CR factors obtained following Method A ≥ the WR and / or CR factors obtained following Method B ≥ the WR and / or CR factors obtained following Method C.

[0126] These WR factors and CR factors can help formulate the actual road CO2 emission limits. As shown in Figure 10 After obtaining the WR factor or CR factor of the test vehicle, it is possible to determine whether its CO2 emissions are compliant, that is, compare it with the emission limit. If the limit is higher than any of the planned factors, the vehicle emissions are considered compliant; otherwise, it is determined that the vehicle's CO2 emissions do not meet the regulations.

[0127] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method section.

[0128] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for evaluating the actual road CO2 emissions of light vehicles based on VSP, characterized in that, It includes the following steps: S10. Obtain the motion parameters, road parameters, and emission data of multiple test vehicles during laboratory cycles and actual road driving, and calculate the vehicle specific power (VSP) for the corresponding test cycles; S20. Divide the VSP of each test vehicle into multiple intervals (Bins) at a preset interval, and calculate the distance-based instantaneous carbon dioxide emission factor for each interval (Bin); S30. Obtain the slope of the fitted line segment by linearly fitting the carbon dioxide emission factors of each VSP interval (Bin) in the WLTC or CLTC-P test cycle with the carbon dioxide emission factors of each VSP interval (Bin) under RDE test; the slope is the WLTC-RDE factor or the CLTC-RDE factor; S40. Set the emission limit according to the WLTC-RDE factor or the CLTC-RDE factor of multiple test vehicles obtained by fitting; Based on the emission limit, determine whether the actual road carbon emissions of the light vehicles to be evaluated are compliant; Among them, the step S10 includes: Obtain the instantaneous speed v, instantaneous acceleration a, road slope θ, and emission data of multiple test vehicles during laboratory cycles and actual road driving. The calculation formula for VSP is as follows: VSP = v{1.1a + 9.81[arctan(sinθ)] + 0.132} + 0.000302v 3 (1) For laboratory test cycles, the road slope θ is uniformly taken as 0; and finally: VSP = v(1.1a + 0.132) + 0.000302v 3 (2) Where: v is the instantaneous vehicle speed, in m / s; a is the instantaneous vehicle acceleration, in m / s 2 ; In the step S20, dividing the VSP of each test vehicle into multiple intervals (Bins) at a preset interval includes: performing the following division on the VSP of each test vehicle: where: (-∞, -20) is used as the 1st interval (Bin); (-20, 24) is used as the 2nd to 12th intervals (Bins); the division of VSP is in intervals of every 4 units, that is, divided into multiple intervals with an increment of 4; (24, +∞) is used as the 13th interval (Bin); In the step S20, calculating the distance-based instantaneous carbon dioxide emission factor for each interval (Bin) includes the following: For laboratory test cycles, the formula is as follows: Among them, EF lab is the instantaneous carbon dioxide emission factor based on distance, g / km; n is the current time, s; i and j are the start and end times, s; C e is the concentration of carbon dioxide in the diluted exhaust gas, %; C d is the concentration of carbon dioxide in the dilution air, %; DF is the dilution factor; Q is the dilution flow rate, L / s; ρ is the density of carbon dioxide under standard temperature and pressure, g / L; D n is the driving mileage, km; C CO and C HC are the concentrations of carbon dioxide, CO, and HC in the diluted exhaust gas, %. For RDE tests, the formula is as follows: Among them, ER RDE is the instantaneous carbon dioxide emission rate, g / s; ρ RDE is the density of carbon dioxide, kg / m 3 ; ρ RDE,exhaust is the density of the exhaust gas, kg / m 3 ; c RDE is the volume concentration of carbon dioxide, ppm; q is the exhaust gas volume flow rate, m 3 / s; is the distance-based carbon dioxide emission factor, g / km; D n is the driving mileage, km; The step S30 includes: S301. When the first condition is met, linearly fit the curve by taking the carbon dioxide emission factors of each VSP interval (Bin) in WLTC or CLTC-P as the x-axis and the RDE carbon dioxide emission factors of each VSP interval (Bin) as the y-axis; S302. Select the carbon dioxide emission factors of some or all VSP intervals (Bins) for fitting, and obtain a straight line after fitting; when the second condition is met, take the slope of the straight line as the WLTC-RDE factor or the CLTC-RDE factor.

2. The method for evaluating the actual road CO2 emissions of light vehicles based on VSP according to claim 1, wherein In the step S302, selecting the carbon dioxide emission factors of some or all VSP intervals (Bins) for fitting includes three methods: Method A: Fit the curve with the carbon dioxide emission factors of all VSP intervals (Bins); Method B: Fit the curve with the carbon dioxide emission factors of VSP intervals (Bins) 3 - 12; Method C: Fit the curve with the carbon dioxide emission factors of VSP intervals (Bins) 3 - 11.

3. The method for evaluating the actual road CO2 emissions of light vehicles based on VSP according to claim 2, wherein, In the step S301, when the first condition is satisfied, it includes: 1) Calculate the correlation factor between the VSP of the entire test cycle and the corresponding instantaneous carbon dioxide emissions, and calculate the average correlation factor, and execute step 2); 2) When the average correlation factor is greater than 0.7, check the emission characteristics of multiple intervals Bin of VSP, and execute step 3); 3) When the instantaneous carbon dioxide emission rate of intervals Bin 1-6 is about 1 g / s and the deviation is less than 30%.

4. The method for evaluating the actual road CO2 emissions of light vehicles based on VSP according to claim 3, characterized in that In the step S302, when the second condition is satisfied, it includes: A straight line is obtained after fitting to ensure that the standard variance R 2 exceeds 0.9, and the WLTC-RDE factor and / or CLTC-RDE factor obtained by following Method A ≥ the WLTC-RDE factor and / or CLTC-RDE factor obtained by following Method B ≥ the WLTC-RDE factor and / or CLTC-RDE factor obtained by following Method C.

5. The method for evaluating the actual road CO2 emissions of light vehicles based on VSP according to claim 4, wherein In the step S40, according to the WLTC-RDE factor or CLTC-RDE factor of multiple test vehicles obtained by fitting, formulate emission limits; it includes: According to the WLTC-RDE factor or CLTC-RDE factor of multiple test vehicles obtained by fitting, use the median as the emission limit, or use the mean value in the concentrated area as the emission limit.

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