CN113530695B - Closed-loop control method and system for engine EGR - Google Patents

Closed-loop control method and system for engine EGR Download PDF

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CN113530695B
CN113530695B CN202110926835.XA CN202110926835A CN113530695B CN 113530695 B CN113530695 B CN 113530695B CN 202110926835 A CN202110926835 A CN 202110926835A CN 113530695 B CN113530695 B CN 113530695B
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engine
residual oxygen
oxygen amount
target value
egr
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CN113530695A (en
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耿元会
冯玮玮
解亮
朱凌龙
林园园
许可森
崔文军
陈召强
刘迎生
张娟
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Anhui Jianghuai Automobile Group Corp
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Anhui Jianghuai Automobile Group Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/0047—Controlling exhaust gas recirculation [EGR]
    • F02D41/0065—Specific aspects of external EGR control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/0047—Controlling exhaust gas recirculation [EGR]
    • F02D41/005—Controlling exhaust gas recirculation [EGR] according to engine operating conditions
    • F02D41/0052—Feedback control of engine parameters, e.g. for control of air/fuel ratio or intake air amount
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/0047—Controlling exhaust gas recirculation [EGR]
    • F02D41/0077—Control of the EGR valve or actuator, e.g. duty cycle, closed loop control of position
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
    • F02D2041/1409—Introducing closed-loop corrections characterised by the control or regulation method using at least a proportional, integral or derivative controller
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)
  • Exhaust-Gas Circulating Devices (AREA)

Abstract

The invention provides a closed-loop control method and a closed-loop control system for engine EGR, wherein the method comprises the following steps: obtaining engine in-line NO X map and according to said NO X map for determining primary NO corresponding to each working condition of engine X A target value; obtaining the original NO of the engine under various working conditions X A required residual oxygen amount target value corresponding to the target value; and detecting the actual residual oxygen amount of the engine exhaust in real time, and performing PID control on the opening degree of the EGR valve by taking the actual residual oxygen amount and the required residual oxygen amount target value as input parameters for PID control regulation. The invention can solve the problem of inaccurate EGR control of the existing engine, can ensure that the EGR rate in the whole life cycle of the engine always meets the target value of the original NOx emission, and improves the gasoline combustion performance of the engine.

Description

Closed-loop control method and system for engine EGR
Technical Field
The invention relates to the technical field of engine exhaust gas recycling, in particular to a closed-loop control method and a closed-loop control system for engine EGR.
Background
Exhaust Gas Recirculation (EGR) is a main means for reducing NOx emission of an engine, and as shown in fig. 1, a part of Exhaust Gas in an Exhaust pipe is introduced into an intake manifold, so that the oxygen concentration entering a cylinder of the engine is reduced by introducing Exhaust Gas with extremely low oxygen content, the combustion temperature is reduced, a low-temperature and low-oxygen combustion environment is achieved, and further, the generation of NOx is reduced. The EGR rate is generally defined as the ratio of EGR flow to total intake air amount (fresh air flow + EGR flow). Theoretically, higher EGR rates result in lower engine-out NOx, which is more beneficial for tail-out NOx control, but too high EGR rates are detrimental to engine combustion. Therefore, in the calibration process of the engine bench test, the opening degree of the EGR valve is adjusted, namely the EGR rate is adjusted, so that the actual primary NOx is slightly smaller than the NOx target emission value (generally controlled to be less than 10%), and the optimal EGR rate (calibration required value) of the operating point is found. Theoretically, although each operating point can reach the required EGR rate by presetting the EGR valve opening, actually, an EGR valve position sensor is not accurate, the EGR flow corresponding to the EGR valve opening under different air flow conditions cannot be in a linear relation, simultaneously, after the engine is used for a long time, a large amount of impurities are deposited on the hole wall of the EGR valve, the accumulation of the impurities inevitably leads to the reduction of the hole diameter, so that the actually-passing exhaust gas quantity of the engine on the whole vehicle is smaller than the exhaust gas throughput when in an ideal state, namely, the actual EGR rate is smaller than the ideal EGR rate, the gasoline combustion performance is reduced, and the performance of the whole vehicle is seriously influenced. Therefore, how to provide accurate control of EGR in the whole life cycle of the engine and enable the EGR rate to always meet the target value has important research significance.
Disclosure of Invention
The invention provides a closed-loop control method and a closed-loop control system for engine EGR, which solve the problem of inaccuracy in the existing engine EGR control, can ensure that the EGR rate in the full life cycle of an engine always meets the target value of original NOx emission, and improve the gasoline combustion performance of the engine.
In order to achieve the above purpose, the invention provides the following technical scheme:
a closed-loop control method of engine EGR, comprising:
obtaining engine raw NO X map, and according to said NO X map image for determining original NO corresponding to each working condition of engine X A target value;
obtaining the original NO of the engine under various working conditions X A required residual oxygen amount target value corresponding to the target value;
and detecting the actual residual oxygen amount of the engine exhaust in real time, and performing PID control on the opening degree of the EGR valve by taking the actual residual oxygen amount and the required residual oxygen amount target value as input parameters of PID control regulation.
Preferably, the method further comprises the following steps:
taking the difference value between the actual residual oxygen amount and the required residual oxygen amount target value as a feedback value of PID control, and calculating to obtain the fluctuation amount output by the PID according to the feedback value;
and adjusting the opening degree of the EGR valve according to the fluctuation amount so as to gradually reduce the difference until the actual residual oxygen amount is equal to the required residual oxygen amount target value.
Preferably, the acquisition of the engine operating conditions reaches the primary NO X The target value corresponds to a required residual oxygen amount target value, and comprises the following steps:
reaching the original NO according to various working conditions of the calibrated engine X Obtaining the corresponding residual oxygen amount by the target value, and forming a residual oxygen amount demand map;
and determining the required residual oxygen amount target value of each working condition of the engine according to the residual oxygen amount demand map.
Preferably, the calibration of each working condition of the engine to reach the primary NO X The target value obtains the corresponding residual oxygen amount, including:
and manually adjusting the opening degree of the EGR valve for each working condition point on the engine bench, and recording the corresponding residual oxygen amount when each working condition point reaches the original NOx emission target value.
Preferably, the method further comprises the following steps:
acquiring a corresponding relation between the opening of an EGR valve and the residual oxygen amount of engine exhaust to form a corresponding table of the opening and the residual oxygen amount;
proportional coefficient K for PID control P Integral coefficient K I And a differential coefficient K D And calibrating and pre-controlling the opening of the EGR valve according to the corresponding table.
Preferably, the method further comprises the following steps:
acquiring the opening degree of an EGR valve and an EGR rate target value, and calculating according to the opening degree of the EGR valve to obtain an actual EGR rate;
and taking the difference value between the actual EGR rate and the EGR rate target value as an input parameter for PID control adjustment, and carrying out PID control on the opening degree of the EGR valve.
The present invention also provides a closed loop control system for engine EGR, comprising:
a first obtaining unit for obtaining the original NO of the engine X map, and according to said NO X map for determining primary NO corresponding to each working condition of engine X A target value;
a second acquisition unit for acquiring the original NO of the engine under various working conditions X A required residual oxygen amount target value corresponding to the target value;
an oxygen sensor for detecting an actual amount of remaining oxygen of the engine exhaust gas in real time;
and the first PID controller is used for taking the actual residual oxygen amount and the required residual oxygen amount target value as input parameters of PID control adjustment and carrying out PID control on the opening degree of the EGR valve.
Preferably, the method further comprises the following steps: an EGR valve opening degree adjusting unit;
the first PID controller is also used for taking the difference value between the actual residual oxygen amount and the required residual oxygen amount target value as a feedback value of PID control, and calculating to obtain the PID output fluctuation amount according to the feedback value;
and the EGR valve opening adjusting unit is used for adjusting the opening of the EGR valve according to the variation to gradually reduce the difference until the actual residual oxygen amount is equal to the required residual oxygen amount target value.
Preferably, the method further comprises the following steps:
a third acquisition unit, configured to acquire a correspondence between an opening degree of the EGR valve and a remaining oxygen amount of the engine exhaust gas to form a correspondence table of the opening degree and the remaining oxygen amount;
a pre-control unit for controlling the proportional coefficient K of PID P Integral coefficient K I And a differential coefficient K D And calibrating and pre-controlling the opening of the EGR valve according to the corresponding table.
Preferably, the method further comprises the following steps:
the fourth acquisition unit is used for acquiring the EGR valve opening and the EGR rate target value and calculating the actual EGR rate according to the EGR valve opening;
and the second PID controller is used for performing PID control on the opening degree of the EGR valve by taking the difference value between the actual EGR rate and the EGR rate target value as an input parameter for PID control adjustment.
The invention provides a closed-loop control method and a closed-loop control system for engine EGR (exhaust gas recirculation), which can solve the problem of inaccuracy in the existing engine EGR control by detecting the actual residual oxygen amount of engine exhaust in real time and taking the target value of the actual residual oxygen amount and the required residual oxygen amount as input parameters for PID control adjustment to perform PID control on the opening degree of an EGR valve, can ensure that the EGR rate in the whole life cycle of an engine always meets the target value of NOx emission, and can improve the gasoline combustion performance of the engine.
Drawings
In order to more clearly describe the specific embodiments of the present invention, the drawings to be used in the embodiments will be briefly described below.
FIG. 1 is a schematic diagram of engine EGR operation.
FIG. 2 is a schematic diagram of a closed-loop engine EGR control method provided by the present invention.
FIG. 3 is a schematic diagram of a closed loop control system for engine EGR provided by the present invention.
Detailed Description
In order to make the technical field of the invention better understand the scheme of the embodiment of the invention, the embodiment of the invention is further described in detail with reference to the drawings and the implementation mode.
Aiming at the problem of inaccurate control of the EGR of the engine at present, the invention provides a closed-loop control method and a closed-loop control system for the EGR of the engine, which are used for carrying out PID control on the opening degree of an EGR valve by detecting the actual residual oxygen amount of the exhaust gas of the engine in real time and taking the target value of the actual residual oxygen amount and the required residual oxygen amount as input parameters for PID control regulation, thereby solving the problem of inaccuracy of the existing EGR control of the engine, ensuring that the EGR rate of the engine in the whole life cycle always meets the target value of NOx emission, and improving the gasoline combustion performance of the engine.
As shown in FIG. 2, a closed-loop control method for engine EGR includes:
s1: obtaining engine raw NO X map, and according to said NO X map for determining primary NO corresponding to each working condition of engine X A target value.
S2: obtaining the original NO of the engine under various working conditions X The target value corresponds to a target value of the required residual oxygen amount.
S3: and detecting the actual residual oxygen amount of the engine exhaust in real time, and performing PID control on the opening degree of the EGR valve by taking the actual residual oxygen amount and the required residual oxygen amount target value as input parameters for PID control regulation.
Specifically, according to the combustion principle of the engine, fuel enters a cylinder to be mixed with fresh air, and combustion reaction is carried out at high temperature and high pressure to generate H 2 O、CO 2 While also generating a portion of the exhaust pollutants, such as CO, NO, HC, etc.
For oxygen rich (excess oxygen, excess air factor generally above 1.2) combustion mode, O in fresh air 2 There are 3 basic paths into the cylinder:
combustion reaction of diesel oil:
CxHy+l 0 O 2 →CO 2 +H 2 O；
the reaction is only related to the physicochemical property of the fuel, and the stoichiometric ratio l is determined by the fuel property 0 Determined (e.g. for diesel fuel, the stoichiometric ratio is equal to about 3), the fraction O 2 The consumption m' is l 0 *m 2 。
②N 2 High-temperature oxygen-rich reaction occurs to generate NOx:
N 2 +O 2 →NOx；
n in the air under the oxygen-enriched high-temperature environment in the cylinder 2 Will react with O 2 Take place inverselyNOx should be generated. For diesel engines, the main component of NOx can be considered to be NO, i.e. the above formula can be simplified.
N 2 +O 2 →2NO；
This part O 2 The relation between the consumption m 'and the exhaust gas NO is m' -2 m NO 。
③ O not participating in the reaction due to rich O2 2 The rest is m O2 For example, the residual O2 remaining unreacted in diesel exhaust is about 15% of the total exhaust.
The basic principle of oxygen conservation shows that under a certain working condition, O participating in fuel combustion 2 To determine known l 0 *m 2 And is with N 2 This part of the reaction O 2 As the temperature environment, EGR rate, etc. vary, and are uncertain. If an oxygen sensor is added to the exhaust to measure residual O 2 Through the principle of conservation: and N 2 Reacted O 2 Amount-oxygen content in fresh intake air (generally considered to be about 21% oxygen content in air) -amount of oxygen consumed by fuel-amount of residual oxygen participating in the reaction, i.e., m ═ m ″ 1 *21％-m'-m O2 。
The method comprises the steps of obtaining a map of the NOx of the original exhaust, determining a NOx target value of each working condition, adjusting the opening degree of an EGR valve to enable the actual measured value of the NOx of the original exhaust to reach the NOx target value, and recording the residual oxygen amount m of the exhaust at the moment O2 That is, the measured value of the exhaust oxygen sensor is obtained, and the residual oxygen m of the whole working condition is collected O2 To obtain the residual oxygen amount m O2 A map is required. During actual engine operation, PID regulation is adopted, so that the actual residual oxygen mO2 reaches the required value. For the closed-loop control of the EGR valve, namely the pre-control of the opening degree of the EGR valve and the amount m of the residual oxygen can be adopted O2 And carrying out closed-loop control in a PID regulation control combination mode. The EGR rate in the whole life cycle of the engine can be ensured to always meet the target value of the original NOx emission, and the gasoline combustion performance of the engine is improved.
The method further comprises the following steps:
s4: taking the difference value between the actual residual oxygen amount and the required residual oxygen amount target value as a feedback value of PID control, and calculating to obtain the fluctuation amount output by the PID according to the feedback value;
s5: and adjusting the opening degree of the EGR valve according to the fluctuation amount so as to gradually reduce the difference until the actual residual oxygen amount is equal to the required residual oxygen amount target value.
In practical application, for a certain operating point, for the (i + 1) th calculation, the EGR valve opening EGR ACT (i+1)＝EGR ACT (i)+u(i)。
The PID calculation output value u (i) in the above equation can be obtained according to the following calculation formula:
Figure BDA0003209563030000061
wherein e (i) is the difference between the residual oxygen demand value and the actual residual oxygen amount during the ith calculation; e (n) calculating the integral value of all the difference values for the previous n times; k P For the scaling factor, the actual engineering example may be constant, or may be a function of e (i), and the term P (K) P E (i)) to approach a stable value; k I For the integral coefficient, the actual engineering example may be constant, or may be a function of e (I), I term
Figure BDA0003209563030000062
Eliminating dynamic error between the stable value and the target value; k is D For the differential coefficient, the actual engineering example can be constant, or can be a function of e (i), and the D term (K) D *[e(i)-e(i-1)]) The overshoot effect caused when the dynamic error is eliminated by introducing the integral term is eliminated to the maximum extent.
Through multiple iterative calculations, stable u (i) and EGR valve opening EGRACT are finally calculated, namely stable actual residual oxygen amount is obtained, and therefore the aim that the actual value reaches the required value is achieved.
Further, the obtained working conditions of the engine reach the original NO X The target value of the required residual oxygen amount corresponding to the target value comprises the following steps:
reaching the original NO according to various working conditions of the calibrated engine X The target value obtains the corresponding residual oxygen amount and forms a residual oxygen amount demand mapFigure (a).
And determining the required residual oxygen amount target value of each working condition of the engine according to the residual oxygen amount demand map.
Furthermore, the calibration of the engine to reach the original NO exhaust condition X The target value obtains the corresponding residual oxygen amount, including:
and manually adjusting the opening degree of the EGR valve at each working point on the engine pedestal, and recording the corresponding residual oxygen amount when each working point reaches the original NOx emission target value.
The method further comprises the following steps:
s6: acquiring a corresponding relation between the opening of an EGR valve and the residual oxygen amount of engine exhaust to form a corresponding table of the opening and the residual oxygen amount;
s7: proportional coefficient K for PID control P Integral coefficient K I And a differential coefficient K D And calibrating and pre-controlling the opening of the EGR valve according to the corresponding table.
The PID control coefficients (P term, I term and D term) are properly calibrated, so that the opening of the EGR valve can quickly and accurately reach a stable value by utilizing a PID controller in the actual engine running process, and the actual residual oxygen amount reaches a residual oxygen amount required value.
The method further comprises the following steps:
s8: acquiring an EGR valve opening and an EGR rate target value, and calculating according to the EGR valve opening to obtain an actual EGR rate;
s9: and taking the difference value between the actual EGR rate and the EGR rate target value as an input parameter of PID control adjustment, and performing PID control on the opening degree of the EGR valve.
Therefore, the invention provides a closed-loop control method for engine EGR, which can solve the problem of inaccuracy in the existing engine EGR control, ensure that the EGR rate in the full life cycle of the engine can always meet the target value of the original NOx emission and improve the gasoline combustion performance of the engine by detecting the actual residual oxygen amount of the engine exhaust in real time and taking the actual residual oxygen amount and the target value of the required residual oxygen amount as input parameters for PID control regulation to perform PID control on the opening degree of an EGR valve.
Accordingly, as shown in FIG. 3, the present invention also provides a closed loop control system for engine EGR, comprising: a first obtaining unit for obtaining the original NO of the engine X map, and according to said NO X map for determining primary NO corresponding to each working condition of engine X A target value. A second acquisition unit for acquiring the original NO of the engine under various working conditions X The target value corresponds to a target value of the required residual oxygen amount. And the oxygen sensor is used for detecting the actual residual oxygen amount of the engine exhaust in real time. And the first PID controller is used for taking the actual residual oxygen amount and the required residual oxygen amount target value as input parameters of PID control adjustment and carrying out PID control on the opening degree of the EGR valve.
The system further comprises: EGR valve opening degree adjusting unit. And the first PID controller is also used for taking the difference value between the actual residual oxygen amount and the required residual oxygen amount target value as a feedback value of PID control, and calculating to obtain the PID output fluctuation amount according to the feedback value. And the EGR valve opening degree adjusting unit is used for adjusting the opening degree of the EGR valve according to the fluctuation amount so as to gradually reduce the difference until the actual residual oxygen amount is equal to the required residual oxygen amount target value.
The system further comprises: and the third acquisition unit is used for acquiring the corresponding relation between the opening of the EGR valve and the residual oxygen amount of the engine exhaust so as to form a corresponding table of the opening and the residual oxygen amount. A pre-control unit for controlling the proportional coefficient K of PID P Integral coefficient K I And a differential coefficient K D And calibrating and pre-controlling the opening of the EGR valve according to the corresponding table.
The system further comprises: and the fourth acquisition unit is used for acquiring the EGR valve opening and the EGR rate target value and calculating the actual EGR rate according to the EGR valve opening. And the second PID controller is used for performing PID control on the opening degree of the EGR valve by taking the difference value between the actual EGR rate and the EGR rate target value as an input parameter for PID control adjustment.
Therefore, the invention provides a closed-loop control system for engine EGR, which can solve the problem of inaccuracy of the existing engine EGR control by detecting the actual residual oxygen amount of the engine exhaust in real time and taking the target value of the actual residual oxygen amount and the required residual oxygen amount as the input parameters of PID control adjustment to perform PID control on the opening degree of an EGR valve, can ensure that the EGR rate in the whole life cycle of the engine always meets the target value of the original NOx emission, and can improve the gasoline combustion performance of the engine.
The construction, features and functions of the present invention have been described in detail with reference to the embodiments shown in the drawings, but the present invention is not limited to the embodiments shown in the drawings, and all equivalent embodiments modified or modified by the spirit and scope of the present invention should be protected without departing from the spirit of the present invention.

Claims (6)

1. A method of closed-loop control of engine EGR comprising:
obtaining engine raw NO X map and according to said NO X map for determining primary NO corresponding to each working condition of engine X A target value;
obtaining the original NO of the engine under various working conditions X A required residual oxygen amount target value corresponding to the target value;
detecting the actual residual oxygen amount of the engine exhaust in real time, and performing PID control on the opening degree of the EGR valve by taking the actual residual oxygen amount and the required residual oxygen amount target value as input parameters for PID control regulation;
taking the difference value between the actual residual oxygen amount and the required residual oxygen amount target value as a feedback value of PID control, and calculating to obtain the fluctuation amount output by the PID according to the feedback value;
adjusting the opening of the EGR valve according to the fluctuation amount to gradually reduce the difference until the actual residual oxygen amount is equal to the required residual oxygen amount target value;
acquiring a corresponding relation between the opening of an EGR valve and the residual oxygen amount of engine exhaust to form a corresponding table of the opening and the residual oxygen amount;
proportional coefficient K for PID control P Integral coefficient K I And a differential coefficient K D And calibrating and pre-controlling the opening of the EGR valve according to the corresponding table.
2. The closed-loop control method for engine EGR of claim 1 wherein said deriving engine individual operating conditions to said in-line NO X The target value of the required residual oxygen amount corresponding to the target value comprises the following steps:
reaching the original NO according to various working conditions of the calibrated engine X Obtaining the corresponding residual oxygen amount by the target value, and forming a residual oxygen amount demand map;
and determining the required residual oxygen amount target value of each working condition of the engine according to the residual oxygen amount demand map.
3. Closed loop control method for engine EGR according to claim 2, characterized in that said calibration of engine individual operating conditions up to said in-line NO X The target value obtains the corresponding residual oxygen amount, including:
and manually adjusting the opening degree of the EGR valve for each working condition point on the engine bench, and recording the corresponding residual oxygen amount when each working condition point reaches the original NOx emission target value.
4. The closed-loop control method for engine EGR according to claim 3, further comprising:
acquiring the opening degree of an EGR valve and an EGR rate target value, and calculating according to the opening degree of the EGR valve to obtain an actual EGR rate;
and taking the difference value between the actual EGR rate and the EGR rate target value as an input parameter of PID control adjustment, and performing PID control on the opening degree of the EGR valve.
5. A closed-loop control system for engine EGR comprising:
a first obtaining unit for obtaining the original NO of the engine X map according to said NO X map for determining primary NO corresponding to each working condition of engine X A target value;
a second acquisition unit for acquiring the original NO of the engine under various working conditions X A required residual oxygen amount target value corresponding to the target value;
an oxygen sensor for detecting an actual amount of residual oxygen of the engine exhaust in real time;
the first PID controller is used for taking the actual residual oxygen amount and the required residual oxygen amount target value as input parameters for PID control adjustment and carrying out PID control on the opening degree of the EGR valve;
an EGR valve opening degree adjusting unit;
the first PID controller is also used for taking the difference value between the actual residual oxygen amount and the required residual oxygen amount target value as a feedback value of PID control, and calculating to obtain the fluctuation amount output by the PID according to the feedback value;
the EGR valve opening degree adjusting unit is used for adjusting the opening degree of the EGR valve according to the fluctuation amount so as to gradually reduce the difference until the actual residual oxygen amount is equal to the required residual oxygen amount target value;
a third acquisition unit, configured to acquire a correspondence between an opening degree of the EGR valve and a remaining oxygen amount of the engine exhaust gas to form a correspondence table between the opening degree and the remaining oxygen amount;
and the pre-control unit is used for calibrating a proportional coefficient KP, an integral coefficient KI and a differential coefficient KD controlled by the PID and pre-controlling the opening of the EGR valve according to the corresponding table.
6. The closed-loop control system for engine EGR of claim 5, further comprising:
the fourth acquisition unit is used for acquiring the opening degree of the EGR valve and the target value of the EGR rate and calculating the actual EGR rate according to the opening degree of the EGR valve;
and the second PID controller is used for performing PID control on the opening degree of the EGR valve by taking the difference value between the actual EGR rate and the EGR rate target value as an input parameter of PID control adjustment.
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