CN112343725B - Control system and control method - Google Patents
Control system and control method Download PDFInfo
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- CN112343725B CN112343725B CN201910724330.8A CN201910724330A CN112343725B CN 112343725 B CN112343725 B CN 112343725B CN 201910724330 A CN201910724330 A CN 201910724330A CN 112343725 B CN112343725 B CN 112343725B
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- 238000000034 method Methods 0.000 title claims abstract description 36
- 239000001301 oxygen Substances 0.000 claims abstract description 226
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 226
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 225
- 239000000446 fuel Substances 0.000 claims abstract description 114
- 238000010438 heat treatment Methods 0.000 claims abstract description 17
- 239000007789 gas Substances 0.000 claims description 17
- 238000005259 measurement Methods 0.000 claims description 15
- 230000007704 transition Effects 0.000 description 8
- 238000010586 diagram Methods 0.000 description 5
- 238000002347 injection Methods 0.000 description 5
- 239000007924 injection Substances 0.000 description 5
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 1
- ODUCDPQEXGNKDN-UHFFFAOYSA-N Nitrogen oxide(NO) Natural products O=N ODUCDPQEXGNKDN-UHFFFAOYSA-N 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000011217 control strategy Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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Classifications
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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
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
- F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
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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
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1473—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation method
- F02D41/1475—Regulating the air fuel ratio at a value other than stoichiometry
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- 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)
- Measuring Oxygen Concentration In Cells (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
Abstract
The invention provides a control system and a control method, which are used for closed-loop control of an engine, and the control method comprises the following steps: measuring the resistance of the non-heated oxygen sensor; obtaining the working temperature of the oxygen sensor through the resistance of the oxygen sensor, obtaining the theoretical air-fuel ratio according to the voltage signal of the oxygen sensor, and correcting the theoretical air-fuel ratio by combining the working temperature of the oxygen sensor to obtain the actual air-fuel ratio; and carrying out closed-loop control on the engine according to the actual air-fuel ratio. By the actual air-fuel ratio, closed-loop control of the engine can be realized, the engine can reliably and stably run, emission consistency is kept, and meanwhile, accurate closed-loop control of the non-heating type oxygen sensor can be realized under the condition of lower exhaust temperature.
Description
Technical Field
The invention relates to the technical field of closed-loop control of engines, in particular to a control system and a control method.
Background
With the enhancement of environmental awareness, emission control of engines is becoming more and more strict. The existing engine adopts an electronic fuel injection system, and an automobile of the electronic fuel injection system reduces carbon monoxide (CO) and hydrocarbon (CH) in exhaust gas for obtaining high exhaust gas purification rate x ) And Nitrogen Oxide (NO) x ) The components must be used in a catalyst. However, in order to use the catalyst effectively, it is necessary to accurately control the air-fuel ratio by the oxygen sensor so that it is always close to the stoichiometric air-fuel ratio (14.7. The closed-loop control of the engine electronic fuel injection system is a closed triangular relation among a real-time oxygen sensor, an electronic control unit and a fuel quantity control device. The oxygen sensor transmits the air-fuel ratio condition signal of the exhaust gas to the electronic control unit, and the electronic control unit sends a command to the fuel quantity control device to adjust the actual air-fuel ratio to the direction of the theoretical air-fuel ratio. This adjustment will often slightly exceed the theoretical value, which the oxygen sensor detects and reports to the electronic control unit, which in turn issues a command to adjust back to 14.7. Since each cycle of adjustment is fast, the actual air-fuel ratio does not deviate too much from 14.7. The electronic fuel injection engine adopting closed-loop control can ensure that the engine always runs under an ideal working condition, namely the actual air-fuel ratio does not deviate too much from a theoretical value, thereby ensuring that the automobile not only has better dynamic performance, but also can save fuel and energy and reduce emission.
In order to reduce the cost of the engine system or reduce the electric power consumption of the oxygen heater, a non-heating oxygen sensor can be adopted when the electronic injection engine is subjected to closed-loop control. When a non-heating type oxygen sensor is used, the oxygen sensor is heated by the heat of the engine exhaust gas. When the oxygen sensor is heated to a certain temperature, the oxygen sensor can be normally activated to work, and then the concentration of oxygen in the oxygen sensor is identified through the signal voltage of the oxygen sensor, so that the closed-loop control is carried out on the oxygen sensor. However, even after the oxygen sensor starts operating, the actual temperature of the oxygen sensor varies and the characteristics thereof vary due to a difference in the degree to which the oxygen sensor is heated by the engine exhaust heat, which is caused by a large variation in the engine operating condition. This tends to cause differences in the air-fuel ratio and the stoichiometric value after actual closed-loop control, presents challenges to the precise control of the oxygen sensor closed-loop, and negatively affects engine operating stability and emissions consistency. When the exhaust temperature is low, a difference exists between the characteristics of the oxygen sensor under the condition of low exhaust temperature and the characteristics of the oxygen sensor under the condition of high exhaust temperature, and the difference causes the operation of the closed-loop control oxygen sensor to deviate, delays the time for entering the closed-loop control and influences the actual emission and the running stability of the engine.
Therefore, in view of the above technical problems, it is necessary to provide a control system and a control method that can achieve accurate closed-loop control of an engine when the exhaust temperature of the engine is low.
Disclosure of Invention
The invention aims to provide a control system and a control method, which are used for solving the problem that the characteristic of a non-heating type oxygen sensor is different when the exhaust temperature of an engine is low and the characteristic of the non-heating type oxygen sensor is high.
In order to solve the above technical problem, the present invention provides a control system for closed-loop control of an engine, the control system comprising: the engine comprises an oxygen sensor connected with the engine, a resistance measuring circuit connected with the oxygen sensor and an electronic control unit connected with the oxygen sensor and the resistance measuring circuit;
wherein the oxygen sensor is a non-heating type oxygen sensor;
the resistance measuring circuit is used for measuring the resistance of the oxygen sensor and supplying the resistance to the electronic control unit;
the electronic control unit is used for obtaining the working temperature of the oxygen sensor according to the resistance of the oxygen sensor, obtaining the theoretical air-fuel ratio of engine exhaust according to the voltage signal of the oxygen sensor, and correcting the theoretical air-fuel ratio by combining the working temperature of the oxygen sensor to obtain the actual air-fuel ratio of the engine exhaust.
Optionally, in the control system, the electronic control unit includes a processor, a correlation model, and an analog-to-digital converter; the correlation model represents a relationship between the resistance of the oxygen sensor and the temperature of the oxygen sensor and a relationship between the temperature of the oxygen sensor and a behavior law of the oxygen sensor; the processor is used for obtaining the theoretical air-fuel ratio according to the correlation model and the resistance and voltage signals of the oxygen sensor; the analog-to-digital converter is used for converting the voltage signal of the oxygen sensor into a digital voltage signal.
Optionally, in the control system, the operating characteristic rule of the oxygen sensor includes: the relationship between the digital voltage signal and the engine exhaust air-fuel ratio, the law of the engine exhaust air-fuel ratio rich-lean transition delay characteristic, and the law of the engine exhaust air-fuel ratio lean-rich transition delay characteristic.
Optionally, in the control system, the electronic control unit further includes an engine temperature model that represents a relationship between an operating temperature of the oxygen sensor and a temperature of the engine exhaust gas, and the processor is further configured to correct the operating temperature of the oxygen sensor output by the correlation model according to the engine temperature model.
Optionally, in the control system, the resistance measurement circuit includes a switch, a first resistor, and a second resistor, the switch is connected to the first resistor and the oxygen sensor, one end of the second resistor is connected to the oxygen sensor, the oxygen sensor is grounded to the second resistor, a first voltage is input to an end of the first resistor not connected to the switch, and an output voltage of an end of the second resistor not grounded is measured to obtain the resistance of the oxygen sensor.
Optionally, in the control system, the control system further includes fuel amount control means, the actual air-fuel ratio being provided to the fuel amount control means, and the fuel amount control means is configured to control an output of fuel of the engine according to the actual air-fuel ratio.
The invention also provides a control method for closed-loop control of an engine, which comprises the following steps:
measuring the resistance of the non-heating type oxygen sensor;
obtaining the working temperature of the oxygen sensor through the resistance of the oxygen sensor, obtaining the theoretical air-fuel ratio according to the voltage signal of the oxygen sensor, and correcting the theoretical air-fuel ratio by combining the working temperature of the oxygen sensor to obtain the actual air-fuel ratio;
and carrying out closed-loop control on the engine according to the actual air-fuel ratio.
Optionally, in the control method, a resistance measurement circuit is used to measure the resistance of the oxygen sensor.
Optionally, in the control method, the operating temperature of the oxygen sensor is derived from the resistance of the oxygen sensor according to a relationship between the resistance of the oxygen sensor and the temperature of the oxygen sensor.
Optionally, in the control method, the operating temperature of the oxygen sensor derived from the resistance of the oxygen sensor is corrected according to the engine temperature model.
Optionally, in the control method, the theoretical air-fuel ratio is obtained from a voltage signal and an operating temperature of the oxygen sensor according to an operating characteristic rule of the oxygen sensor and an operating characteristic rule of the oxygen sensor.
In one aspect of the present invention, there is provided a control system for closed loop control of an engine, the control system comprising: the engine comprises an oxygen sensor connected with the engine, a resistance measuring circuit connected with the oxygen sensor and an electronic control unit connected with the oxygen sensor and the resistance measuring circuit; wherein the oxygen sensor is a non-heating type oxygen sensor; the resistance measuring circuit is used for measuring the resistance of the oxygen sensor and supplying the resistance to the electronic control unit; the electronic control unit is used for obtaining the working temperature of the oxygen sensor according to the resistance of the oxygen sensor, obtaining the theoretical air-fuel ratio of engine exhaust according to the voltage signal of the oxygen sensor, and correcting the theoretical air-fuel ratio by combining the working temperature of the oxygen sensor to obtain the actual air-fuel ratio of the engine exhaust. Through the actual air-fuel ratio, accurate closed-loop control of the engine can be achieved, influences on closed-loop control of the engine due to factors such as different temperatures are eliminated, and the problem that the characteristic of the non-heating type oxygen sensor is different when the exhaust temperature of the engine is low and the characteristic of the non-heating type oxygen sensor is different when the exhaust temperature of the engine is high is solved.
In a control method provided by the present invention, the control method includes: measuring the resistance of the non-heated oxygen sensor; obtaining the working temperature of the oxygen sensor through the resistance of the oxygen sensor, obtaining the theoretical air-fuel ratio according to the voltage signal of the oxygen sensor, and correcting the theoretical air-fuel ratio by combining the working temperature of the oxygen sensor to obtain the actual air-fuel ratio; and carrying out closed-loop control on the engine according to the actual air-fuel ratio. The engine can reliably and stably run, the consistency of emission is kept, and meanwhile, the accurate closed-loop control of the non-heating type oxygen sensor can be realized under the condition of lower exhaust temperature.
Drawings
FIG. 1 is a schematic flow diagram of a prior art closed-loop control method for an oxygen sensor;
FIG. 2 is a schematic structural diagram of a control system of an embodiment of the present invention;
FIG. 3 is a flow chart diagram of a control method of an embodiment of the invention;
FIG. 4 is a schematic diagram of a resistance measurement circuit in the control method according to the embodiment of the present invention;
wherein,
100-a control system; 110-an oxygen sensor; 120-resistance measurement circuit; 130-an electronic control unit; 200-engine.
Detailed Description
The core idea of the invention is to provide a control system and a control method for closed-loop control of an engine, wherein the comparison between the actual air-fuel ratio of engine exhaust obtained by the control system and the control method and the reference electromotive force is positive/negative according to the difference value between the actual air-fuel ratio and a standard theoretical air-fuel ratio (14.7.
To achieve the above idea, the present invention provides a control system for closed-loop control of an engine, the control system comprising: the engine comprises an oxygen sensor connected with the engine, a resistance measuring circuit connected with the oxygen sensor and an electronic control unit connected with the oxygen sensor and the resistance measuring circuit; wherein the oxygen sensor is a non-heating type oxygen sensor; the resistance measuring circuit is used for measuring the resistance of the oxygen sensor and supplying the resistance to the electronic control unit; the electronic control unit is used for obtaining the working temperature of the oxygen sensor according to the resistance of the oxygen sensor, obtaining the theoretical air-fuel ratio of engine exhaust according to the voltage signal of the oxygen sensor, and correcting the theoretical air-fuel ratio by combining the working temperature of the oxygen sensor to obtain the actual air-fuel ratio of the engine exhaust.
To make the objects, advantages and features of the present invention more apparent, the control system and the control method according to the present invention will be described in detail with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention. Further, the structures illustrated in the drawings are often part of actual structures. In particular, the drawings may have different emphasis points and may sometimes be scaled differently.
First, referring to fig. 2, fig. 2 is a schematic structural diagram of a control system according to an embodiment of the present invention. In a control system 100 provided in the present embodiment, for closed-loop control of an engine 200, the control system 100 includes: an oxygen sensor 110 connected to the engine 200, a resistance measurement circuit 120 connected to the oxygen sensor 110, and an electronic control unit 130 connected to both the oxygen sensor 110 and the resistance measurement circuit 120; wherein the oxygen sensor 110 is a non-heating type oxygen sensor; the input end of the resistance measuring circuit 120 is connected to the oxygen sensor 110, and the resistance measuring circuit 120 is used for measuring the resistance of the oxygen sensor 110 and providing the resistance to the electronic control unit 130; the input end of the electronic control unit 130 is connected to the output end of the oxygen sensor 110 and the output end of the resistance measurement circuit 120, and the electronic control unit 130 is configured to obtain the operating temperature of the oxygen sensor 110 according to the resistance of the oxygen sensor 110, obtain the theoretical air-fuel ratio of the exhaust gas of the engine 200 according to the voltage signal of the oxygen sensor 110, and correct the theoretical air-fuel ratio in combination with the operating temperature of the oxygen sensor 110 to obtain the actual air-fuel ratio of the exhaust gas of the engine 200. The comparison between the actual air-fuel ratio obtained by the electronic control unit 130 and the reference electromotive force is positive or negative, and the difference between the actual air-fuel ratio and the standard stoichiometric air-fuel ratio (14.7.
Preferably, the electronic control unit 130 includes a processor, a correlation model and an analog-to-digital converter; the correlation model represents the relationship between the resistance of the oxygen sensor 110 and the temperature of the oxygen sensor 110 and the relationship between the temperature of the oxygen sensor 110 and the operating characteristic law of the oxygen sensor 110, so that the temperature of the oxygen sensor 110 can be obtained from the resistance of the oxygen sensor 110 according to the correlation model, and the operating characteristic of the oxygen sensor 110 can be obtained from the temperature of the oxygen sensor 110, the correlation model can represent data which cannot be directly measured through data which can be directly measured, and particularly, the feasibility and the accuracy of measuring the actual air-fuel ratio are greatly increased through the characteristic law curve of the correlation model obtained by measuring the oxygen sensor 110; the processor is configured to derive the theoretical air-fuel ratio according to the correlation model and the resistance and voltage signals of the oxygen sensor 110, and thus, the processor obtains the theoretical air-fuel ratio of the engine 200 through processing the resistance of the oxygen sensor 110 measured by the resistance measurement circuit 120 in combination with the correlation model, and the theoretical air-fuel ratio is used as basic data of the actual air-fuel ratio required by a subsequent program. The analog-to-digital converter is used for converting the voltage signal of the oxygen sensor 110 into a digital voltage signal.
Preferably, the operating characteristic rule of the oxygen sensor 110 includes: the relationship between the digital voltage signal and the exhaust air-fuel ratio of the engine 200, the law of the rich-lean transition delay characteristic of the exhaust air-fuel ratio of the engine 200, and the law of the lean-rich transition delay characteristic of the exhaust air-fuel ratio of the engine 200. The exhaust air-fuel ratio of the engine 200 includes the theoretical air-fuel ratio and the actual air-fuel ratio, and both the theoretical air-fuel ratio and the actual air-fuel ratio may exhibit a certain regularity with the digital voltage signal, the rich-lean transition delay characteristic, and the lean-rich transition delay characteristic. These regularity are measured by experimental tests and derived to the universality by theoretical analysis.
Preferably, the electronic control unit 130 further includes an engine temperature model representing a relationship between the operating temperature of the oxygen sensor 110 and the temperature of the exhaust gas of the engine 200, and the processor is further configured to correct the operating temperature of the oxygen sensor 110 output by the correlation model according to the engine temperature model. Therefore, the processor converts the voltage signal of the oxygen sensor 110 into a digital voltage signal according to the analog-to-digital converter, and corrects the working temperature of the oxygen sensor 110 output by the correlation model in combination with the engine temperature model, and since a certain rule relation is presented between the working temperature of the oxygen sensor 110 and the temperature of the exhaust gas of the engine 200, the accuracy of finally obtaining the actual air-fuel ratio of the exhaust gas of the engine 200 is ensured, the situation that the working temperature of the oxygen sensor 110 is different from the temperature of the exhaust gas of the engine 200 and the temperature value applied by a subsequent program is wrong is eliminated, and the influence of the working temperature of the oxygen sensor 110 having specificity on the closed-loop control is avoided.
Referring to fig. 4, in the present embodiment, the resistance measurement circuit 120 includes a switch K, a first resistor R1 and a second resistor R2, the switch K connects the first resistor R1 and the oxygen sensor 110, one end of the second resistor R2 is connected to the oxygen sensor 110, the oxygen sensor 110 and the second resistor R2 are grounded, a first voltage U1 is input to one end of the first resistor R1 not connected to the switch K, and an output voltage Uout at one end of the second resistor R2 not connected to the ground is measured to obtain the resistance of the oxygen sensor 110. Therefore, the resistance Rsensor and the voltage Usensor of the oxygen sensor 110 can be calculated by applying two different states to the resistance measuring circuit 120 and combining the electrical principle by equivalently using the oxygen sensor 110 as a battery with a resistor. Specifically, when the switch K is turned on, the value of the output voltage Uout of the oxygen sensor 110 at this time is collected as Uout1, and the value is obtained by combining an electrical equation: uout1/R2= Usensor/(Rsensor + R2); when the switch K is closed, the first voltage U1 applies a bias current to the oxygen sensor 110 through the first resistor R1, and at this time, the value of the output voltage Uout of the oxygen sensor 110 is Uout2, which, in combination with an electrical equation, is:
(U1-Uout 2)/R1 = (Uout 2/R2) + (Uout 2-Usensor)/Rsensor, wherein the first voltage U1, the first resistor R1, the second resistor R2, uout1 and Uout2 are available, and the values of the resistor Rsensor and the voltage Usensor of the oxygen sensor 110 can be calculated according to the above two equations. It is understood that fig. 4 is only one form of the resistance measurement circuit 120, and the resistance measurement circuit 120 may be other forms of circuits as long as two circuit states are generated, which do not affect the resistance measurement circuit 120 to derive the resistance of the oxygen sensor 110.
Preferably, the control system 100 further includes fuel amount control means to which the actual air-fuel ratio is supplied, the fuel amount control means being configured to control the output of fuel from the engine in accordance with the actual air-fuel ratio. Thus, closed-loop control of the engine 200 is achieved by adjusting the amount of fuel injected to change the air-fuel ratio to approach the standard stoichiometric air-fuel ratio by the actual air-fuel ratio, i.e., by detecting a rich state of oxygen in the exhaust gas of the engine 200. Specifically, the engine 200 is precisely closed-loop controlled by using different control parameters according to different characteristics of the oxygen sensor 110 at different temperatures in combination with the voltage signal, where the control parameters specifically refer to actual control strategies, such as: when PID (proportional, integral, derivative) control is employed, it is expressed as a parameter of PID, and the remaining parameters are: the closed-loop control process of the engine 200 can be completed more accurately and rapidly by parameters such as the filtering parameter of the signal, the delay time parameter of the control, the identification parameter of whether the oxygen sensor is activated, the judgment standard of the signal concentration of the oxygen sensor and the like.
Referring to fig. 1 and 3, fig. 1 is a schematic flow chart of a closed-loop control method for an oxygen sensor in the prior art; fig. 3 is a flowchart illustrating a control method according to an embodiment of the present invention. The control method is used for closed-loop control of the engine 200, and comprises the following steps:
step S20: measuring the resistance of the non-heated oxygen sensor;
step S21: obtaining the working temperature of the oxygen sensor according to the resistance of the oxygen sensor;
step S23: then obtaining the theoretical air-fuel ratio according to the voltage signal of the oxygen sensor;
step S24: correcting the theoretical air-fuel ratio by combining the working temperature of the oxygen sensor to obtain the actual air-fuel ratio;
step S25: and carrying out closed-loop control on the engine according to the actual air-fuel ratio.
Through the steps of the control method, the engine can reliably and stably run, the consistency of emission is kept, and meanwhile, the accurate closed-loop control of the non-heating type oxygen sensor can be realized under the condition of lower exhaust temperature.
Preferably, the resistance of the oxygen sensor is measured using a resistance measurement circuit. Therefore, the resistance data of the non-heating type oxygen sensor can be obtained and applied to a subsequent procedure, and the data which can be directly measured is used as a basis, so that the data which cannot be directly measured can be obtained quickly. The resistance measuring circuit has multiple forms, and the resistance measuring circuit with different forms can be designed according to the use environment of an actual product, so that the efficiency and the accuracy of the resistance measuring circuit are improved.
Preferably, the operating temperature of the oxygen sensor is derived from the resistance of the oxygen sensor based on a relationship between the resistance of the oxygen sensor and the temperature of the oxygen sensor. Therefore, the working temperature of the oxygen sensor is obtained from the resistance data of the oxygen sensor obtained by the resistance measuring circuit in the previous step, wherein the regular relation between the resistance of the oxygen sensor and the temperature of the oxygen sensor is a characteristic curve model summarized by combining data measured by a laboratory and theoretical knowledge, the working temperature of the oxygen sensor can be rapidly and accurately judged, and the method has universality.
Preferably, the operating temperature of the oxygen sensor derived from the resistance of the oxygen sensor is corrected according to the engine temperature model. Therefore, the working temperature of the oxygen sensor is more accurate, the problem that different initial parameters are caused by the problems of special working environment or difference and change of parts of the oxygen sensor is solved, specifically, the temperature sensor is installed on the engine and used for detecting the actual engine temperature, meanwhile, the electronic control unit can simulate the temperature of engine exhaust according to the temperature of the engine and other operation information, the oxygen sensor is installed in the exhaust pipe, and the correlation between the temperature inside the oxygen sensor and the engine exhaust temperature is the engine temperature model.
In the present embodiment, step S22: and obtaining the theoretical air-fuel ratio according to the working characteristic rule of the oxygen sensor and the voltage signal and the working temperature of the oxygen sensor. Therefore, the theoretical air-fuel ratio is obtained from the corrected voltage signal of the oxygen sensor, and the theoretical air-fuel ratio is an important basic parameter of the actual air-fuel ratio and helps to complete accurate closed-loop control of the engine. Specifically, the operating characteristic law of the oxygen sensor includes a relationship between the digital voltage signal and the engine exhaust gas air-fuel ratio, a law of the engine exhaust gas air-fuel ratio rich-lean transition delay characteristic, and a law of the engine exhaust gas air-fuel ratio lean-rich transition delay characteristic. The engine exhaust air-fuel ratio comprises the theoretical air-fuel ratio and the actual air-fuel ratio, and the theoretical air-fuel ratio and the actual air-fuel ratio and the digital voltage signal, the rich-lean jump delay characteristic and the lean-rich jump delay characteristic show certain regularity.
In summary, the control system and the control method provided by the invention have the following advantages:
in the control system provided by the invention, the temperature parameter of the non-heating oxygen type oxygen sensor is obtained by measuring the resistance of the oxygen sensor and utilizing the characteristic that the resistance of the oxygen sensor changes greatly at different temperatures, and then the engine is accurately controlled in a closed loop manner by adopting different control parameters according to different characteristics of the sensor at different temperatures and combining voltage signals of the oxygen sensor, so that the engine can reliably and stably run, the consistency of emission is kept, and meanwhile, the accurate closed loop control of the oxygen sensor can be realized under the condition of lower exhaust temperature.
Further, the control system provided by the invention measures the resistance of the oxygen sensor through a resistance measuring circuit arranged in the controller; utilizing the temperature-resistance characteristic of the oxygen sensor, preferably, the characteristic can be further corrected through an engine temperature model to compensate for differences and changes of parts to obtain the actual working temperature of the oxygen sensor; the method comprises the steps that the actual characteristics of an oxygen sensor at different temperatures, including but not limited to the voltage-oxygen sensor characteristic of the sensor, the rich-lean jump delay characteristic, the lean-rich jump delay characteristic and the like, are utilized, and the voltage signal of the oxygen sensor is combined for correction, so that the actual rich-lean state of the oxygen sensor in the current exhaust gas is accurately obtained; performing closed-loop control of the engine by using the actual state of the oxygen sensor; the oxygen sensor is accurately controlled, and the consistency of emission control and the stability of engine operation are guaranteed; and the closed-loop control can be started in advance at a lower temperature, so that the emission of the engine is further reduced.
Furthermore, the oxygen sensor is accurately controlled in a closed loop mode through the method, so that the engine can reliably and stably run, the consistency of emission is kept, and meanwhile, the oxygen sensor can be accurately controlled in a closed loop mode under the condition of lower exhaust temperature, so that the exhaust pollutants of the engine can be reduced, and the method is more environment-friendly and energy-saving.
The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.
Claims (9)
1. A control system for closed loop control of an engine, the control system comprising: the engine control system comprises an oxygen sensor connected with the engine, a resistance measuring circuit connected with the oxygen sensor and an electronic control unit connected with the oxygen sensor and the resistance measuring circuit;
wherein the oxygen sensor is a non-heating type oxygen sensor;
the resistance measuring circuit is used for measuring the resistance of the oxygen sensor and supplying the resistance to the electronic control unit;
the electronic control unit is used for obtaining the working temperature of the oxygen sensor according to the resistance of the oxygen sensor, obtaining the theoretical air-fuel ratio of engine exhaust according to the voltage signal of the oxygen sensor, and correcting the theoretical air-fuel ratio by combining the working temperature of the oxygen sensor to obtain the actual air-fuel ratio of the engine exhaust;
the electronic control unit includes a processor and an engine temperature model, the engine temperature model representing a relationship between an operating temperature of the oxygen sensor and a temperature of the engine exhaust, the processor being configured to correct the operating temperature of the oxygen sensor based on the engine temperature model.
2. The control system of claim 1, wherein said electronic control unit further comprises a correlation model and an analog-to-digital converter; the correlation model represents a relationship between the resistance of the oxygen sensor and the temperature of the oxygen sensor and a relationship between the temperature of the oxygen sensor and a behavior law of the oxygen sensor; the processor is further used for obtaining the theoretical air-fuel ratio according to the correlation model and the resistance and voltage signals of the oxygen sensor; the analog-to-digital converter is used for converting the voltage signal of the oxygen sensor into a digital voltage signal.
3. The control system of claim 2, wherein the operating characteristic law of the oxygen sensor comprises: the relation between the digital voltage signal and the engine exhaust air-fuel ratio, the law of the delay characteristic of the rich-lean jump of the engine exhaust air-fuel ratio and the law of the delay characteristic of the lean-rich jump of the engine exhaust air-fuel ratio.
4. The control system of claim 1, wherein the resistance measurement circuit comprises a switch, a first resistor, and a second resistor, the switch connects the first resistor and the oxygen sensor, one end of the second resistor connects the oxygen sensor, the oxygen sensor and the second resistor are grounded, one end of the first resistor not connected to the switch inputs a first voltage, and an output voltage of one end of the second resistor not connected to the ground is measured to obtain the resistance of the oxygen sensor.
5. The control system according to any one of claims 1 to 4, characterized by further comprising fuel amount control means to which the actual air-fuel ratio is supplied, the fuel amount control means being configured to control an output of fuel from the engine in accordance with the actual air-fuel ratio.
6. A control method for closed loop control of an engine, the control method comprising:
measuring the resistance of the non-heated oxygen sensor;
obtaining the working temperature of the oxygen sensor through the resistance of the oxygen sensor, correcting the working temperature of the oxygen sensor according to an engine temperature model, obtaining the theoretical air-fuel ratio of engine exhaust according to a voltage signal of the oxygen sensor, and correcting the theoretical air-fuel ratio by combining the corrected working temperature of the oxygen sensor to obtain the actual air-fuel ratio of the engine exhaust; the engine temperature model represents a relationship between an operating temperature of the oxygen sensor and a temperature of the engine exhaust gas;
and carrying out closed-loop control on the engine according to the actual air-fuel ratio.
7. The control method according to claim 6, wherein the resistance of the oxygen sensor is measured using a resistance measurement circuit.
8. The control method according to claim 7, characterized in that the operating temperature of the oxygen sensor is derived from the resistance of the oxygen sensor based on a relationship between the resistance of the oxygen sensor and the temperature of the oxygen sensor.
9. The control method according to claim 6, characterized in that the theoretical air-fuel ratio is derived from a voltage signal and an operating temperature of the oxygen sensor in accordance with an operating characteristic law of the oxygen sensor.
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