Emission calibration method, device, equipment and medium based on powertrain test bench

Abstract

The present invention discloses an emission calibration method, device, equipment and medium based on a powertrain bench, which is applied to automobile engine technology. The method comprises: adjusting the engine operating conditions to multiple steady-state operating points on the powertrain bench; collecting the first emission data of the exhaust system at each steady-state operating point; taking each steady-state operating point as a target steady-state operating point, and calibrating the feedforward parameter and feedback parameter of the target steady-state operating point according to the first emission data of the exhaust system at the target steady-state operating point. The present invention solves the technical problem of low emission calibration efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of automobile engines, and in particular relates to an emission calibration method, device, equipment and medium based on a powertrain bench. Background Art

[0002] Affected by the energy crisis and environmental issues, the research and development of energy-saving and emission-reduction technologies for engines is becoming increasingly important. However, the current emission calibration of engines is developed based on vehicle resources, resulting in low emission calibration efficiency and a long emission development test cycle for the vehicle. Summary of the invention

[0003] In view of the above-mentioned technical problems in the prior art, an embodiment of the present invention provides an emission calibration method, device, equipment and medium based on a powertrain test bench.

[0004] In a first aspect, an embodiment of the present invention provides an emission calibration method based on a powertrain test bench, wherein the powertrain test bench includes an engine and an exhaust system connected to an exhaust side of the engine, the method including: adjusting the operating condition of the engine to a plurality of steady-state operating points on the powertrain test bench; collecting first emission data of the exhaust system at each of the steady-state operating points; taking each of the steady-state operating points as a target steady-state operating point, and calibrating feedforward parameters and feedback parameters of the target steady-state operating point according to the first emission data of the exhaust system at the target steady-state operating point.

[0005] Optionally, the exhaust system comprises an exhaust pipe connected to the exhaust side of the engine, and a front oxygen sensor for detecting an excess air coefficient of the engine is mounted on the exhaust pipe. The method further comprises: taking each of the steady-state operating points as a target steady-state operating point;

[0006] When the actual measured value of the excess air coefficient reaches the target excess air coefficient at the target steady-state operating point, the number of combustion cycles required by the engine is determined, wherein the actual measured value of the excess air coefficient is detected by the front oxygen sensor; and based on the number of combustion cycles, the detection delay of the front oxygen sensor in detecting the excess air coefficient at the target steady-state operating point is calibrated.

[0007] Optionally, the exhaust system also includes a first-stage catalyst connected to the exhaust side of the engine through the exhaust pipe, and a post-oxygen sensor connected after the first-stage catalyst, and the collecting of the first emission data of the exhaust system at each steady-state operating point includes: at the target steady-state operating point, the excess air coefficient of the combustion in the engine cylinder is reduced multiple times with a preset step size so that the post-oxygen voltage detected by the post-oxygen sensor gradually increases within a preset voltage range; after each reduction of the excess air coefficient, the first emission data of the exhaust system is collected.

[0008] Optionally, the feedforward parameter and feedback parameter of the target steady-state operating point are calibrated according to the first emission data of the exhaust system at the target steady-state operating point, including: detecting the rear oxygen voltage by the rear oxygen sensor after the excess air coefficient is reduced each time at the target steady-state operating point; comparing the first emission data collected each time at the target steady-state operating point, and determining the target emission data according to the comparison result; calibrating the excess air coefficient of the engine as the feedforward parameter of the target steady-state operating point when the target emission data is collected; and calibrating the rear oxygen voltage detected by the rear oxygen sensor as the feedback parameter of the target steady-state operating point when the target emission data is collected.

[0009] Optionally, when the measured value of the excess air coefficient reaches a target excess air coefficient, the number of combustion cycles required for the engine is determined, including: on the powertrain test bench, adjusting the injection pulse width of the engine to a preset injection pulse width, the preset injection pulse width corresponding to the target excess air coefficient; when the injection pulse width of the engine reaches the preset injection pulse width, starting to count the combustion cycles of the engine, and detecting the excess air coefficient through the front oxygen sensor; when the measured value of the excess air coefficient detected by the front oxygen sensor reaches the target excess air coefficient, obtaining the number of combustion cycles passed by the engine.

[0010] Optionally, the method also includes: on the powertrain test bench, adjusting the operating conditions of the engine to a plurality of preset ignition operating points; adjusting the VVT ​​angle combination multiple times at each of the ignition operating points, and obtaining combustion fluctuation data of the engine and second emission data of the exhaust system after each adjustment of the VVT ​​angle combination; taking each ignition operating point as a target ignition operating point, comparing the combustion fluctuation data and the second emission data obtained each time at the target ignition operating point, and selecting a target VVT angle combination based on the comparison results; and performing VVT intake calibration and VVT exhaust calibration on the target ignition operating point based on the target VVT angle combination.

[0011] Optionally, the second emission data of the exhaust system includes the amount of particulate matter emitted, and the method further includes: on the powertrain test bench, adjusting the operating condition of the engine to at least one preset transient operating condition; in each of the transient operating conditions, respectively adjusting at least one control parameter of the engine using a plurality of different parameter adjustment methods, and obtaining the change in the amount of particulate matter emitted by the exhaust system under each parameter adjustment method; respectively taking each transient operating condition as a target transient operating condition, comparing the change in the amount of particulate matter corresponding to different parameter adjustment methods under the target transient operating condition, and determining the target parameter adjustment method based on the comparison result; and calibrating the target parameter adjustment method as the parameter adjustment method for the target transient operating condition.

[0012] In a second aspect, an embodiment of the present invention provides an emission calibration device based on a powertrain test bench, wherein the powertrain test bench includes an engine and an exhaust system connected to the exhaust side of the engine, and the device includes: an operating condition adjustment unit, used to adjust the operating condition of the engine to multiple steady-state operating points on the powertrain test bench; a data acquisition unit, used to collect first emission data of the exhaust system at each of the steady-state operating points; a first calibration unit, used to take each of the steady-state operating points as a target steady-state operating point, and calibrate feedforward parameters and feedback parameters of the target steady-state operating point according to the first emission data of the exhaust system at the target steady-state operating point.

[0013] In a third aspect, an embodiment of the present invention provides an emission calibration device based on a powertrain test bench, wherein the powertrain test bench includes an engine and an exhaust system connected to the exhaust side of the engine, and the emission calibration device also includes: a processor and a memory, wherein the memory is coupled to the processor, and the memory stores instructions, and when the instructions are executed by the processor, the method described in any embodiment of the first aspect is implemented.

[0014] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described in any embodiment of the first aspect.

[0015] One or more technical solutions provided by the embodiments of the present invention achieve at least the following technical effects or advantages:

[0016] By adjusting the operating conditions of the engine on a powertrain test bench to multiple steady-state operating points; collecting the first emission data of the exhaust system at each steady-state operating point; taking each steady-state operating point as a target steady-state operating point, and calibrating the feedforward parameters and feedback parameters of the target steady-state operating point according to the first emission data of the exhaust system at the target steady-state operating point, it is achieved that, without the availability of complete vehicle resources, only the emission system on the powertrain test bench can effectively replace the emission results of the Type I test of the complete vehicle, thereby completing the emission calibration on the powertrain test bench, thereby improving the calibration efficiency, and without being limited by the resources of the complete vehicle. When only engine resources are available in the vehicle development process, the emission development of the complete vehicle can be carried out in advance, thereby shortening the development cycle of the complete vehicle.

[0017] Moreover, compared with the hub resources of the entire vehicle, the test bench resources are cheaper, easier to operate, have lower labor costs, and use fewer consumables. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0019] Figure 1 A schematic diagram of the structure of an exhaust system in an embodiment of the present invention;

[0020] Figure 2 It is a flow chart of a method for performing emission calibration at a steady-state operating point based on a powertrain test bench in an embodiment of the present invention;

[0021] Figure 3 This is a flow chart of emission calibration based on a powertrain test bench for a light-off condition in an embodiment of the present invention;

[0022] Figure 4 It is a schematic diagram of emission data and combustion fluctuation under different VVT angle combinations in transient conditions;

[0023] Figure 5 This is a flow chart of emission calibration for transient conditions based on a powertrain test bench in an embodiment of the present invention;

[0024] Figure 6 Schematic diagram of the speed and cylinder density based on the transient working condition of the powertrain test bench in an embodiment of the present invention;

[0025] Figure 7 It is a functional module diagram of an emission calibration device based on a powertrain bench in the implementation of the present invention;

[0026] Figure 8It is a schematic diagram of the structure of an emission calibration device based on a powertrain test bench in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In a first aspect, an embodiment of the present invention provides an emission calibration method based on a powertrain test bench, which is used to calibrate the emission of an engine based on the powertrain test bench without relying on vehicle resources.

[0029] refer to Figure 1 As shown, the hardware part of the powertrain test bench in the embodiment of the present invention includes an engine and an exhaust system connected to the exhaust side of the engine, and the exhaust system includes an exhaust pipe connected to the exhaust side of the engine, a front oxygen sensor for detecting the excess air coefficient of the engine is installed on the exhaust pipe, and the other end of the exhaust pipe is connected to a first-stage catalyst or a multi-stage catalyst connected in series (for example: a first-stage catalyst and a second-stage catalyst connected in series). Among them, the first-stage catalyst is connected to the exhaust side of the engine through the exhaust pipe, and a muffler can also be connected after the last-stage catalyst.

[0030] Among them, the front oxygen sensor is arranged before the first-stage catalyst. The front oxygen sensor adopts a linear oxygen sensor, which is used to monitor the excess air coefficient of the engine cylinder in real time. The excess air coefficient is the ratio of the actual amount of air supplied to the engine for fuel combustion to the theoretical amount of air, and the excess air coefficient is represented by Lambda (λ).

[0031] Among them, the rear oxygen sensor is arranged after the first-stage catalyst. The rear oxygen sensor adopts a switch oxygen sensor to monitor the concentration of the mixed gas after passing through the first-stage catalyst in real time. The voltage measured by the rear oxygen sensor (ie: rear oxygen voltage) represents the concentration of the mixed gas after passing through the first-stage catalyst.

[0032] In the specific implementation process, each stage of the catalyst can adopt a three-way catalyst, which is an important external purification device in the exhaust system. It can remove CO and HC ( 碳氢化合物 ) and NO x (Nitrogen oxides) are oxidized and reduced into harmless CO2, water and nitrogen. The three-way catalytic converter can purify CO, HC, NO xThe λ window for three pollutants reaching more than 90% is very small and is not symmetrical relative to λ=1.00, but rather biased towards the slightly richer side. In order to match the three-way catalytic converter, fine control of λ can greatly improve the conversion efficiency of the catalytic converter. Therefore, the calibration of λ is very important.

[0033] Based on the embodiments of the present invention and Figure 1 The powertrain test bench shown can implement an emission calibration method based on the powertrain test bench. Figure 2 As shown, the emission calibration method based on the powertrain bench includes the following steps:

[0034] S101. On a powertrain test bench, adjust the operating condition of the engine to a plurality of steady-state operating points.

[0035] It should be noted that the engine operating point is defined by the engine speed and cylinder density. For example, the engine operating condition is adjusted to a steady-state operating point where the engine speed is 1200 rpm and the cylinder density is 250 mg / l. In the specific implementation process, each preset steady-state operating point can be run in sequence from small to large until all steady-state operating points are run.

[0036] S102: Collect first emission data of the exhaust system at each steady-state operating point.

[0037] Each steady-state operating point is used as a target steady-state operating point. When the engine runs to the target steady-state operating point, the excess air coefficient of combustion in the engine cylinder is reduced multiple times with a preset step size, so that the post-oxygen voltage detected by the post-oxygen sensor gradually increases within a preset voltage range; after each reduction in the excess air coefficient, the first emission data of the exhaust system is collected.

[0038] It is understandable that the first emission data collected each time includes: CO, HC, NO x The concentrations of each of these three air pollutants.

[0039] When the post-oxygen voltage is within the voltage range of 0.5V to 0.8V, the exhaust system emits CO, HC, and NO. x The concentrations of these three air pollutants are relatively low, so the preset voltage range can be set to 0.5V to 0.8V.

[0040] The following is an example of the process of collecting the first emission data of the exhaust system at a certain steady-state operating point (for example, a speed of 1050 rpm and a cylinder density of 250 mg / l):

[0041] Step 1: On the powertrain test bench, adjust the injection pulse width of the engine, and monitor the rear oxygen voltage detected by the rear oxygen sensor during the adjustment of the injection pulse width until the rear oxygen voltage reaches around 0.5V.

[0042] Step 2: After the post-oxygen voltage reaches 0.5V, wait for the working condition to stabilize. After the working condition stabilizes for a preset period of time, collect and record the exhaust system emissions of CO, HC, and NO. x concentration.

[0043] Next, execute step 3: continue to adjust the injection pulse width of the engine, reduce λ by 0.0005 by adjusting the injection pulse width, and collect and record the exhaust system emissions of CO, HC, and NO again after the working condition stabilizes for 5 minutes. x concentration.

[0044] Repeat step 3 to adjust the injection pulse width multiple times and record the exhaust system emissions of CO, HC, and NO at each lambda. x When the post-oxygen voltage rises to around 0.8V, the concentrations of CO, THC (total hydrocarbons, the total amount of hydrocarbons in the exhaust gas), and NOx emitted by the exhaust system are finally collected and recorded.

[0045] For example, as shown in Table 1, when λ=0.9965, the post-oxygen voltage is 0.51V, which is the first collected CO, HC, and NO x Concentration; the voltage rises to 0.82V, which is the last collected CO, HC, NO x concentration.

[0046] Through the above steps 1 to 3, the first emission data can be collected multiple times for the same steady-state operating point.

[0047] S103, taking each steady-state operating point as a target steady-state operating point, and calibrating a feedforward parameter and a feedback parameter for the target steady-state operating point according to first emission data of the exhaust system at the target steady-state operating point.

[0048] When the engine runs to the target steady-state operating point, the rear oxygen voltage is detected by the rear oxygen sensor each time the excess air coefficient is reduced by a preset step size; the first emission data collected each time at the target steady-state operating point is compared, and the target emission data is determined based on the comparison result; when the target emission data is collected, the excess air coefficient of the engine is calibrated as a feedforward parameter of the target steady-state operating point; when the target emission data is collected, the rear oxygen voltage detected by the rear oxygen sensor is calibrated as a feedback parameter of the target steady-state operating point.

[0049] Specifically, according to the comparison result, a group of emission data with the lowest emission concentration among all the groups of first emission data collected at the target steady-state operating point can be used as the target emission data.

[0050] Below, an example is given as shown in Table 1: At a steady-state operating point: engine speed 1050rpm, cylinder density 250mg / l, when λ=0.9955, the emission concentration of the three pollutants emitted by the exhaust system is relatively the lowest in general, and the post-oxygen is stable at around 0.75V. Therefore, λ=0.9955 is calibrated as the feedforward parameter of the steady-state operating point of engine speed 1050rpm and cylinder density 250mg / l, and 0.75V is calibrated as the feedback parameter of the 1050rpm, 250mg / l operating point.

[0051] Table 1. First emission data and post-oxygen voltage corresponding to different λ at 200rpm and 250mg / l operating point

[0052] λ Post oxygen voltage (V) CO(ppm) THC(ppm) NOx(ppm) 0.9965 0.51 -4.634 58.714 5.486 0.996 0.54 -4.703 2.611 -1.961 0.9955 0.75 -4.686 1.385 -2.315 0.995 0.78 -4.723 -0.241 0.576 0.9945 0.82 -4.663 231.488 32.21

[0053] For each steady-state operating point, the calibration of the feedforward parameters and feedback parameters can be completed through the above step S103, which will not be repeated here. After completing the calibration of the feedforward parameters and feedback parameters of all steady-state operating points, fill in the corresponding calibration table. Specifically, the feedforward parameter is λ, and the feedback parameter is the post-oxygen voltage. The corresponding feedforward parameter and feedback parameter calibration table is shown in Table 2 below:

[0054] Table 2. Feedforward parameter and feedback parameter calibration table

[0055]

[0056]

[0057] Because there is a certain delay between the true value of the λ in the cylinder combustion of the engine and the actual value of the λ detected by the front oxygen sensor, the delay depends on the exhaust pipe and the installation position of the front oxygen sensor. Therefore, at each steady-state operating point, the detection delay of λ can also be calibrated.

[0058] Specifically, the detection delay of λ is calibrated, including the following step S104: each steady-state operating point is used as a target steady-state operating point; at the target steady-state operating point, when the actual value of the excess air coefficient detected by the front oxygen sensor reaches the target excess air coefficient, the number of combustion cycles required by the engine is determined, wherein the actual value of the excess air coefficient is detected by the front oxygen sensor; and the detection delay of the front oxygen sensor in detecting the excess air coefficient at the target steady-state operating point is calibrated according to the number of combustion cycles.

[0059] It should be noted that there is no sequence between step S104 and the aforementioned steps S102 to S103, and the engine operating condition can be readjusted to each target steady-state operating condition.

[0060] In step S104, at a certain steady-state operating point, on a powertrain test bench, the fuel injection pulse width of the engine is adjusted to a preset fuel injection pulse width, which corresponds to a target excess air coefficient, so that the true value of the λ in the cylinder combustion is equal to the target excess air coefficient; when the fuel injection pulse width of the engine reaches the preset fuel injection pulse width, the combustion cycle of the engine is counted, and the excess air coefficient is detected by the front oxygen sensor; when the measured value of the excess air coefficient detected by the front oxygen sensor reaches the target excess air coefficient, the number of combustion cycles passed by the engine is obtained. The number of combustion cycles passed by the engine is calibrated as the detection delay.

[0061] Specifically, when the engine is currently running at the target operating point, by adjusting the engine's injection pulse width to the preset injection pulse width, the actual value of the excess air coefficient burning in the engine cylinder can be made equal to the target excess air coefficient. However, due to the detection delay of the front oxygen sensor, the engine needs to go through a certain combustion cycle from the actual value of the excess air coefficient burning in the engine cylinder being equal to the target excess air coefficient to the actual measured value of the excess air coefficient detected by the front oxygen sensor being equal to the target excess air coefficient.

[0062] Specifically, the target excess air coefficient can be set to 1.1. By adjusting the engine's injection pulse width to the preset injection pulse width, the actual value of the excess air coefficient burning in the engine cylinder = 1.1. From this moment on, after the engine has gone through a certain number of combustion cycles, the actual value of the excess air coefficient detected by the front oxygen sensor = 1.1. The number of combustion cycles the engine has gone through at this time is recorded.

[0063] Taking the adjustment of the engine operating condition to the steady-state operating point of 1200rpm and 250mg / l as an example, the process of calibrating the detection delay of λ is given as an example:

[0064] Step A: On the powertrain test bench, adjust the engine operating condition to a steady-state operating point of 1200 rpm and 250 mg / l;

[0065] Step B, adjusting the fuel injection pulse width of the engine so that λ=1.1 during combustion in the engine cylinder;

[0066] Step C, starting from the moment when the real value of λ during combustion in the engine cylinder is 1.1, after a certain number of combustion cycles of the engine, the measured value of λ obtained by the front oxygen sensor is 1.1, and the record starts from the moment when λ during combustion in the engine cylinder is 1.1 and ends at the moment when the oxygen sensor measures λ=1.1. The number of combustion cycles of the engine during this process is 30;

[0067] Step D: Calibrate the recorded combustion cycle number 30 as the detection delay of the steady-state operating point of 1200 rpm and 250 mg / l.

[0068] For each steady-state operating point, the above steps A to D are repeated to complete the detection delay calibration at all steady-state operating points and fill in the corresponding calibration table. The detection delay calibration table of λ is obtained, as shown in Table 3 below.

[0069] Table 3. λ detection delay calibration table

[0070]

[0071]

[0072] After completing the emission calibration of all steady-state operating points through the above S101 to S104, the obtained feedforward parameter and feedback parameter calibration table, as well as the λ detection delay calibration table are written into the ECU (Electronic Control Unit) so that the ECU controls the engine to continue to perform emission calibration for ignition conditions and transient conditions.

[0073] Among them, the emission calibration of the ignition condition is specifically the process of calibrating the intake VVT ​​angle and exhaust VVT angle of the VVT ​​(Variable Valve Timing) under different ignition conditions based on the powertrain test bench. Figure 3 As shown, the process of calibrating the intake VVT ​​angle and exhaust VVT angle of the engine under different ignition conditions includes the following steps S301-S304:

[0074] S301. On a powertrain test bench, adjust the operating conditions of the engine to a plurality of preset ignition operating points.

[0075] For example, a preset ignition operating condition is defined as: the engine ignition speed is 1200rpm, the air density of the cylinder is 250gm / l, the ignition efficiency is set to 0.6, and the engine water temperature is controlled to 30°C according to the circulating water system of the powertrain test bench to better simulate the cold engine state of the whole vehicle.

[0076] S302, adjusting the VVT ​​angle combination of the engine multiple times at each ignition operating point, and obtaining the combustion fluctuation data of the engine and the second emission data of the exhaust system after each adjustment of the VVT ​​angle combination.

[0077] Each VVT angle combination includes: the angle of intake VVT ​​(iVVT) and the angle of exhaust VVT (EVVT). The combustion fluctuation data can be expressed by the combustion fluctuation amount (Coefficient of Variation, COV): the size of the result can intuitively reflect the stability of the performance during the cycle. The second emission data includes THC and CO, NO xThe concentrations and particulate matter numbers (PN) of these three gas emissions.

[0078] Specifically, the engine can be adjusted according to the VVT ​​angle combinations shown in Table 4. As shown in Table 4, a unique number is set for each VVT angle combination, and the unique number is used for each VVT angle combination identified in a one-to-one correspondence.

[0079] Table 4 VVT angle combination corresponding number table

[0080]

[0081] The emission data of the emission system and the combustion fluctuation of the engine under the 49 VVT angle combinations in Table 4 are collected respectively. The emission data and combustion fluctuation are referenced to Figure 4 As shown, the unique number corresponding to each intake and exhaust combination in Table 4 is Figure 4 Middle horizontal axis, Figure 4 The vertical axis is the corresponding gas pollutant emission concentration or combustion fluctuation.

[0082] For example, at a certain combustion condition, the VVT ​​angle combination adjusted to is: intake VVT ​​(iVVT) angle is 23°, exhaust VVT (EVVT) angle is -10°. After adjusting to the preset time of the VVT ​​angle combination (for example, after 5 minutes), the combustion fluctuation of the engine, as well as THC, CO, NO x The concentrations of these three gas emissions and the number of particulate matter (PN).

[0083] S303, taking each ignition operating point as a target ignition operating point, comparing the combustion fluctuation data and the second emission data obtained each time at the target ignition operating point, and selecting a target VVT angle combination according to the comparison result.

[0084] Specifically, as the intake VVT ​​increases, the THC concentration, CO concentration, and the number of particulate matter deteriorate to a certain extent, while NO x The concentration is optimized to a certain extent; if the intake VVT ​​is fixed, if the exhaust VVT is opened too wide, the THC concentration, CO concentration and the number of particulate matter will also deteriorate. At the same time, the excessive intake and exhaust overlap angle will lead to a large COV and unstable engine speed. Based on the balance considerations of gas emissions and speed fluctuations, multiple candidate VVT ​​angle combinations can be selected according to the comparison results, thereby narrowing the range of VVT angle combinations. Reference Figure 4As shown, the intake VVT ​​angle ranges from 0 to 5 degrees, and the exhaust VVT angle ranges from 0 to 10 degrees, which can take into account both gas emissions and combustion fluctuations (CoV below 50 can meet the requirements). The number of particulate matter is also optimal within this VVT angle range, and the same VVT ​​area range can be selected.

[0085] Since the most suitable VVT ​​angle combination cannot be determined through the above-mentioned steady-state working condition scanning method. Therefore, it is necessary to conduct a cyclic dynamic working condition scanning of the VVT ​​angle combination on the powertrain test bench based on the P1 stage of the WLTC (Worldwide Light-duty Test Cycle), and monitor the changes in the number of emitted particulate matter during the cyclic dynamic working condition scanning process. According to the changes in the number of particulate matter, a set of VVT angle combinations with the best particulate matter emissions are obtained from each candidate VVT ​​angle combination as the target VVT angle combination. For example, in order to take into account both emissions and CoV, the intake VVT ​​angle can be selected as 0° and the exhaust VVT angle as 3°.

[0086] S304: Perform VVT intake calibration and VVT exhaust calibration on the target ignition operating point based on the target VVT angle combination.

[0087] The selected target VVT angle combination is used as the VVT ​​control parameter of the target ignition operating point. According to the definition, a decrease in the intake VVT ​​angle is characterized by an increase in the physical angle; an increase in the exhaust VVT angle is characterized by an increase in the physical angle.

[0088] Through the above process, it is possible to control the water temperature of the engine in a cold state based on the powertrain test bench, select the range of VVT angles according to emissions and engine combustion stability, and use dynamic operating conditions to select the best VVT combination based on particulate matter emissions.

[0089] Based on the same method, the VVT ​​angle combination of other ignition operating points can be calibrated (the engine water temperature and ignition efficiency remain unchanged), as shown in Table 5 below:

[0090] Table 5.

[0091]

[0092]

[0093] Due to the large load change, air-fuel ratio fluctuation and combustion deterioration in transient conditions, particulate matter emissions are correspondingly high. Therefore, the embodiment of the present invention designs transient conditions on the powertrain bench for WLTC transient conditions, and uses bench repetitive point scanning optimization to obtain a control parameter combination that is optimal for transient conditions.

[0094] Among them, the second emission data of the exhaust system includes the number of particulate matter, refer to Figure 5 As shown, the emission calibration for transient conditions includes the following steps:

[0095] S401, on a powertrain test bench, adjusting the engine operating condition to at least one preset transient operating condition. In the embodiment of the present invention, the preset transient operating condition is each operating condition point where the amount of emitted particulate matter is relatively high.

[0096] For example, based on the WLTC transient operating conditions (WLTC P4 stage) in areas with high particulate matter emissions, the transient operating conditions are directly programmed on the powertrain bench for calibration optimization. Figure 6 As shown, the programmed transient operating conditions can be: the speed increases from 1930 rpm to 2300 rpm, which takes 3 seconds, and the cylinder density increases from 1090 mg / l to 2075 mg / l, which takes 3 seconds.

[0097] S402: In each transient operating condition, a plurality of different parameter adjustment methods are used to adjust at least one control parameter of the engine, and a change in the amount of particulate matter emitted from the exhaust system under each parameter adjustment method is obtained.

[0098] Specifically, the control parameters of the engine include injection angle, injection number, rail pressure and transient fuel control. There are four ways to adjust the parameters:

[0099] Method 1: Only adjust the number of injections of the engine: from 2 injections to 3 injections, and the injection ratio is adjusted to 2:1:1. The effect of improving particulate matter emissions is limited.

[0100] Method 2: Synchronously adjust the number of injections and the injection angle of the engine, the number of injections is adjusted from 2 to 3, and the injection ratio is adjusted to 2:1:1. The SOI (start of injection) angle is 270°, and the EOI (end of injection) angle is 40° close to the compression top dead center position to ensure that the fuel is ignited just before it is transferred to the spark plug, and particulate matter emissions are on a downward trend.

[0101] Method 3: On the basis of synchronously adjusting the number of injections and the injection angle of the engine, the rail pressure is also increased from 25Mpa to 35Mpa to increase atomization. At this time, the number of particulate matter is the least.

[0102] Method 4: On the basis of synchronously adjusting the number of injections and the injection angle of the engine, the rail pressure is increased to 35 MPa and the transient fuel is adjusted, but the amount of particulate matter increases.

[0103] S403, taking each transient operating condition as a target transient operating condition, comparing the change in the number of particulate matter corresponding to different parameter adjustment methods under the target transient operating condition, and determining the target parameter adjustment method according to the comparison result.

[0104] S404: Calibrate the target parameter adjustment method as the parameter adjustment method of the target transient working condition.

[0105] Specifically, by comparing the changes in the number of particulate matter under the above four parameter adjustment methods, it is determined that the number of particulate matter corresponding to parameter adjustment method three is the least. Therefore, parameter adjustment method three can be determined as the target parameter adjustment method and calibrated as the parameter adjustment method for the target transient operating condition.

[0106] Ignition conditions and transient conditions are areas where vehicle emissions are difficult to optimize, and emissions account for more than 90% of the entire WLTC cycle. Relying on the high repeatability of the powertrain test bench, the efficiency of emissions calibration can be improved.

[0107] Based on the above emission calibration processes, these calibrations are input into the ECU software and the WLTC cycle test is carried out on the powertrain bench. As can be seen from Table 6, the emission results of the powertrain bench test are far lower than the requirements of the National VI regulations, and the emission results meet the requirements.

[0108] Table 6.

[0109]

[0110] After each emission calibration based on the powertrain test bench, the engine is quickly cooled by the cooling water of the powertrain test bench. Therefore, the number of tests per day is greatly increased, far exceeding the limit of one test per day for the whole vehicle hub.

[0111] The catalyst selection test based on the powertrain bench has more stable test boundary conditions and engine control strategies, making the catalyst selection test emissions more consistent. At the same time, after the engine is tested on the bench, the bench can control the cooling water system to quickly cool the engine, shortening the time to enter the next test, thereby greatly improving the efficiency of the catalyst selection test.

[0112] Establish a powertrain test bench emission calibration method to guide test bench emission development, and establish evaluation indicators to improve the working efficiency of the emission forward test bench.

[0113] Based on the same inventive concept, the present invention provides an emission calibration device based on a powertrain bench, referring to Figure 1 As shown, the powertrain rig includes an engine and an exhaust system connected to the exhaust side of the engine, referring to Figure 7 As shown, the emission calibration device includes:

[0114] A working condition adjustment unit 701, used for adjusting the working condition of the engine to a plurality of steady-state working condition points on the powertrain test bench;

[0115] A data collection unit 702 is used to collect first emission data of the exhaust system at each steady-state operating point;

[0116] The first calibration unit 703 is used to take each of the steady-state operating points as a target steady-state operating point, and calibrate a feedforward parameter and a feedback parameter of the target steady-state operating point according to the first emission data of the exhaust system at the target steady-state operating point.

[0117] In some embodiments, the exhaust system includes an exhaust pipe connected to the exhaust side of the engine, and a front oxygen sensor for detecting the excess air coefficient of the engine is installed on the exhaust pipe. The emission calibration device also includes: a second calibration unit 704, used to: take each of the steady-state operating points as a target steady-state operating point; at the target steady-state operating point, when the actual measured value of the excess air coefficient reaches the target excess air coefficient, the number of combustion cycles required by the engine is determined, wherein the actual measured value of the excess air coefficient is detected by the front oxygen sensor; and according to the number of combustion cycles, the detection delay of the front oxygen sensor in detecting the excess air coefficient at the target steady-state operating point is calibrated.

[0118] In some embodiments, the exhaust system also includes a first-stage catalyst connected to the exhaust side of the engine through the exhaust pipe, and a post-oxygen sensor connected after the first-stage catalyst. The data acquisition unit 702 is specifically used to: at the target steady-state operating point, multiple reductions in the excess air coefficient of the combustion in the engine cylinder are made with a preset step size so that the post-oxygen voltage detected by the post-oxygen sensor gradually increases within a preset voltage range; and after each reduction in the excess air coefficient, the first emission data of the exhaust system is collected.

[0119] In some embodiments, the first calibration unit 703 is specifically used to: detect the rear oxygen voltage through the rear oxygen sensor after the excess air coefficient is reduced each time at the target steady-state operating point; compare the first emission data collected each time at the target steady-state operating point, and determine the target emission data based on the comparison result; calibrate the excess air coefficient of the engine as the feedforward parameter of the target steady-state operating point when the target emission data is collected; calibrate the rear oxygen voltage detected by the rear oxygen sensor as the feedback parameter of the target steady-state operating point when the target emission data is collected.

[0120] In some embodiments, the second calibration unit 704 is specifically used to: on the powertrain test bench, adjust the injection pulse width of the engine to a preset injection pulse width, wherein the preset injection pulse width corresponds to a target excess air coefficient; when the injection pulse width of the engine reaches the preset injection pulse width, start counting the combustion cycles of the engine, and detect the excess air coefficient through the front oxygen sensor; when the actual measured value of the excess air coefficient detected by the front oxygen sensor reaches the target excess air coefficient, obtain the number of combustion cycles passed by the engine.

[0121] In some embodiments, a third calibration unit is also included, which is used to: adjust the operating conditions of the engine to multiple preset ignition operating points on the powertrain test bench; adjust the VVT ​​angle combination multiple times at each ignition operating point, and obtain the combustion fluctuation data of the engine and the second emission data of the exhaust system after each adjustment of the VVT ​​angle combination; take each ignition operating point as a target ignition operating point, compare the combustion fluctuation data and the second emission data obtained each time at the target ignition operating point, and select a target VVT angle combination based on the comparison result; and perform VVT intake calibration and VVT exhaust calibration on the target ignition operating point based on the target VVT angle combination.

[0122] In some embodiments, the second emission data of the exhaust system includes the amount of particulate matter emitted, and also includes a fourth calibration unit, which is used to: on the powertrain test bench, adjust the operating condition of the engine to at least one preset transient operating condition; in each of the transient operating conditions, respectively adjust at least one control parameter of the engine using a plurality of different parameter adjustment methods, and obtain the change in the amount of particulate matter emitted by the exhaust system under each parameter adjustment method; respectively take each transient operating condition as a target transient operating condition, compare the change in the amount of particulate matter corresponding to different parameter adjustment methods under the target transient operating condition, and determine the target parameter adjustment method based on the comparison result; and calibrate the target parameter adjustment method as the parameter adjustment method of the target transient operating condition.

[0123] Based on the same inventive concept, an embodiment of the present invention provides an emission calibration device based on a powertrain test bench, referring to Figure 1 As shown, the powertrain bench includes an engine and an exhaust system connected to the exhaust side of the engine, referring to Figure 8 As shown, the emission calibration device also includes: a processor 802 and a memory 804, the memory 804 is coupled to the processor 802, a computer program stored in the memory 804 and executable on the processor 802, and when the processor 802 executes the program, the emission calibration method based on the powertrain test bench described in any of the above method embodiments is implemented, which will not be repeated here for the sake of brevity of the specification.

[0124] Among them, Figure 8 In the embodiment of the present invention, a bus architecture (represented by bus 800) is provided, and bus 800 may include any number of interconnected buses and bridges, and bus 800 links various circuits including one or more processors represented by processor 802 and memory represented by memory 304. Bus 800 may also link various other circuits such as peripherals, voltage regulators, and power management circuits, which are well known in the art and are therefore not further described herein. Bus interface 805 provides an interface between bus 800 and receiver 801 and transmitter 803. Receiver 801 and transmitter 803 may be the same element, namely a transceiver, providing a unit for communicating with various other devices over a transmission medium. Processor 802 is responsible for managing bus 800 and general processing, while memory 804 may be used to store data used by processor 802 when performing operations.

[0125] Based on the same inventive concept, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the powertrain bench-based emission calibration method described in any of the foregoing method embodiments.

[0126] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0127] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An emission calibration method based on a powertrain test bench, characterized in that: The powertrain rig includes an engine and an exhaust system connected to an exhaust side of the engine, and the method includes: On the powertrain test bench, adjusting the operating condition of the engine to a plurality of steady-state operating points; Collecting first emission data of the exhaust system at each steady-state operating point; Each of the steady-state operating points is used as a target steady-state operating point, and the feedforward parameter and feedback parameter of the target steady-state operating point are calibrated according to the first emission data of the exhaust system at the target steady-state operating point, including: when the target emission data is collected, the excess air coefficient of the engine is calibrated as the feedforward parameter of the target steady-state operating point; when the target emission data is collected, the rear oxygen voltage detected by the rear oxygen sensor is calibrated as the feedback parameter of the target steady-state operating point.

2. The method according to claim 1, characterized in that The exhaust system includes an exhaust pipe connected to the exhaust side of the engine, and a front oxygen sensor for detecting an excess air coefficient of the engine is installed on the exhaust pipe. The method further includes: Taking each of the steady-state operating points as a target steady-state operating point; At the target steady-state operating point, when the measured value of the excess air coefficient reaches the target excess air coefficient, the number of combustion cycles required by the engine is determined, wherein the measured value of the excess air coefficient is detected by the front oxygen sensor; According to the number of combustion cycles, a detection delay of the front oxygen sensor in detecting the excess air coefficient at the target steady-state operating point is calibrated.

3. The method according to claim 2, characterized in that The exhaust system further includes a primary catalyst connected to the exhaust side of the engine through the exhaust pipe, and a post oxygen sensor connected after the primary catalyst, and the collecting of the first emission data of the exhaust system at each steady-state operating point includes: At the target steady-state operating point, the excess air coefficient of combustion in the engine cylinder is repeatedly reduced with a preset step length, so that the rear oxygen voltage detected by the rear oxygen sensor gradually increases within a preset voltage range; After each reduction of the excess air ratio, first emission data of the exhaust system is collected.

4. The method according to claim 3, characterized in that The step of calibrating the feedforward parameter and the feedback parameter of the target steady-state operating point according to the first emission data of the exhaust system at the target steady-state operating point also includes: After the excess air coefficient is reduced each time at the target steady-state operating point, detecting the rear oxygen voltage by the rear oxygen sensor; The first emission data collected each time at the target steady-state operating point are compared, and the target emission data is determined according to the comparison result.

5. The method according to claim 2, characterized in that The step of determining the number of combustion cycles required by the engine when the measured value of the excess air coefficient reaches the target excess air coefficient comprises: On the powertrain bench, adjusting the fuel injection pulse width of the engine to a preset fuel injection pulse width, wherein the preset fuel injection pulse width corresponds to a target excess air coefficient; When the fuel injection pulse width of the engine reaches the preset fuel injection pulse width, starting to count the combustion cycles of the engine, and detecting the excess air coefficient through the front oxygen sensor; When the actual value of the excess air coefficient detected by the front oxygen sensor reaches the target excess air coefficient, the number of combustion cycles passed by the engine is obtained.

6. The method according to claim 1, characterized in that Also includes: On the powertrain test bench, adjusting the operating condition of the engine to a plurality of preset ignition operating condition points; Adjusting the VVT ​​angle combination multiple times at each of the ignition operating points, and acquiring combustion fluctuation data of the engine and second emission data of the exhaust system after each adjustment of the VVT ​​angle combination; Taking each ignition operating point as a target ignition operating point, comparing the combustion fluctuation data and the second emission data obtained each time at the target ignition operating point, and selecting a target VVT angle combination according to the comparison result; Based on the target VVT angle combination, VVT intake calibration and VVT exhaust calibration are performed on the target ignition operating point.

7. The method according to claim 1, characterized in that The second emission data of the exhaust system includes the amount of particulate matter emitted, and the method further includes: On the powertrain test bench, adjusting the operating condition of the engine to at least one preset transient operating condition; In each of the transient operating conditions, at least one control parameter of the engine is adjusted using a plurality of different parameter adjustment methods, and a change in the amount of particulate matter emitted by the exhaust system under each parameter adjustment method is obtained; Taking each transient operating condition as a target transient operating condition, comparing the change in the number of particulate matter corresponding to different parameter adjustment methods under the target transient operating condition, and determining the target parameter adjustment method according to the comparison result; The target parameter adjustment method is calibrated as the parameter adjustment method of the target transient operating condition.

8. An emission calibration device based on a powertrain test bench, characterized in that: The powertrain bench comprises an engine and an exhaust system connected to the exhaust side of the engine, and the device comprises: A working condition adjustment unit, used for adjusting the working condition of the engine to a plurality of steady-state working condition points on the powertrain test bench; A data collection unit, used for collecting first emission data of the exhaust system at each steady-state operating point; The first calibration unit is used to take each of the steady-state operating points as a target steady-state operating point, and calibrate the feedforward parameters and feedback parameters of the target steady-state operating point according to the first emission data of the exhaust system at the target steady-state operating point, including: when the target emission data is collected, the excess air coefficient of the engine is calibrated as the feedforward parameter of the target steady-state operating point; when the target emission data is collected, the rear oxygen voltage detected by the rear oxygen sensor is calibrated as the feedback parameter of the target steady-state operating point.

9. An emission calibration device based on a powertrain test bench, characterized in that: The powertrain bench includes an engine and an exhaust system connected to the exhaust side of the engine, and the emission calibration device also includes: a processor and a memory, the memory is coupled to the processor, the memory stores instructions, and when the instructions are executed by the processor, the method described in any one of claims 1-7 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method described in any one of claims 1 to 7 is implemented.

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