CN107387249B - Method for controlling transient air-fuel ratio of high-power gas engine - Google Patents
Method for controlling transient air-fuel ratio of high-power gas engine Download PDFInfo
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- CN107387249B CN107387249B CN201710468406.6A CN201710468406A CN107387249B CN 107387249 B CN107387249 B CN 107387249B CN 201710468406 A CN201710468406 A CN 201710468406A CN 107387249 B CN107387249 B CN 107387249B
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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
- F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
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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
- F02D41/0027—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures the fuel being gaseous
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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
- F02D41/1401—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
-
- 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
- F02D2041/141—Introducing closed-loop corrections characterised by the control or regulation method using a feed-forward control element
Abstract
The invention relates to a method for controlling transient air-fuel ratio of a high-power gas engine, which comprises the following steps: 1) constructing a transient air-fuel ratio control system of the high-power gas engine; 2) the feedforward compensation controller outputs gas compensation quantity; 3) the basic gas quantity acquisition module takes a target air-fuel ratio and air per cycle of each cylinder as input and outputs basic gas quantity; 4) the self-adaptive PID feedback controller based on the wide-area oxygen sensor calculates and outputs the corrected gas quantity of the PID controller by setting proportional gain, integral gain and differential gain and taking the actual air-fuel ratio and the target air-fuel ratio as input; 5) the output of the feedforward compensation controller, the basic gas quantity acquisition module and the adaptive PID feedback controller based on the wide-area oxygen sensor is accumulated and then output to the actual gas quantity output module through the amplitude limiter, and finally the actual gas quantity is output. Compared with the prior art, the invention has the advantages of quick response, good practicability, high efficiency and the like.
Description
Technical Field
The invention relates to the field of engine closed-loop air-fuel ratio control, in particular to a method for controlling transient air-fuel ratio of a high-power gas engine.
Background
In recent years, environmental pollution is aggravated, the emission of automobile exhaust is one of the main causes of environmental pollution, natural gas is accepted and used as a clean energy source, and a gas engine is widely popularized and developed. With the strictness of the engine efficiency and emission control regulations, the reduction of harmful gas emission is one of the main research directions of natural gas engine development on the premise of ensuring the dynamic property and the economical efficiency of the natural gas engine. The emission performance of the engine is reflected by the real-time air-fuel ratio of the engine; therefore, it is important to accurately control the air-fuel ratio in real time.
During the operation of the engine, it takes a certain time for the natural gas to be mixed with the air, the exhaust gas to be discharged, the sensor signal to be fed back, and the like. The engine air-fuel ratio control system is therefore a process with a time delay. When the engine is in a transient working condition, if the controller cannot obtain the rich and lean state of the current mixed gas as soon as possible, the engine cannot normally run. The existing gas engine is mainly used for low-power automobiles adopting single-point injection or high-power generators, and the main reason is that the closed-loop control strategy of the air-fuel ratio of the gas engine is imperfect under the transient working condition, so that the rich and lean conditions of mixed gas are unstable, and the engine cannot work stably.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for controlling the transient air-fuel ratio of a high-power gas engine, which has quick response, good practicability and high efficiency.
The purpose of the invention can be realized by the following technical scheme:
a method for transient air-fuel ratio control of a high power gas engine, comprising the steps of:
1) constructing a transient air-fuel ratio control system of a high-power gas engine, wherein the system comprises a feedforward compensation controller, a basic gas quantity acquisition module, a wide-range oxygen sensor-based adaptive PID feedback controller and an actual gas quantity output module;
2) the feedforward compensation controller takes the throttle opening variation delta TPS and the variation delta rpm of the rotating speed as input to carry out defuzzification weighted average and output gas compensation;
3) the basic gas quantity acquisition module takes a target air-fuel ratio and air per cycle of each cylinder as input and outputs basic gas quantity;
4) the self-adaptive PID feedback controller based on the wide-area oxygen sensor calculates and outputs the corrected gas quantity of the PID controller by setting proportional gain, integral gain and differential gain and taking the actual air-fuel ratio and the target air-fuel ratio as input;
5) the output of the feedforward compensation controller, the basic gas quantity acquisition module and the adaptive PID feedback controller based on the wide-area oxygen sensor is accumulated and then output to the actual gas quantity output module through the amplitude limiter, and finally the actual gas quantity is output.
In the feedforward compensation controller, the calculation formula of the defuzzification weighted average is as follows:
wherein u (Z)k) Transient gas compensation quantity Z obtained by taking input quantity delta TPS and delta rpm as conditionskIs the median value in the k-th gas Compensation quantity Fuel _ Compensation domain.
The calculation formula of the gas quantity gain algorithm of the self-adaptive PID feedback controller based on the wide-area oxygen sensor is as follows:
wherein PID _ fuel is the corrected gas quantity of the output, Kp、Ki、KdProportional, integral and differential gains, T, respectivelysSample time of incremental module, TiIntegration time, T, for incremental modulesdThe sampling times of the integrator and the differentiator, η is the rich-lean condition factor of the mixture, and Δ AFR is the difference of the air-fuel ratio dynamics.
In the adaptive PID feedback controller based on the wide-area oxygen sensor, the differential gain KdThe value is 0.
In the step 1), a transient air-fuel ratio control system of the high-power gas engine is constructed in a modularized mode through MATLAB/Simulink software.
Compared with the prior art, the invention has the following advantages:
firstly, quick response: regarding the feedback delay of the mixture concentration, the present invention proposes a feedforward controller capable of ensuring a quick response to the engine operating conditions according to the throttle opening change Δ TPS and the change amount Δ rpm of the rotation speed, thereby accurately increasing or decreasing the amount of compensation gas, so that the actual air-fuel ratio can smoothly fluctuate near the target air-fuel ratio, and thus, the engine operation is more stable.
Secondly, the practicability is good: the invention adds the self-adaptive learning PID feedback controller based on the wide-range oxygen sensor in the air-fuel ratio closed-loop control process, can more quickly and accurately regulate the air quantity by regulating the gain coefficient of the proportional-integral-derivative, can be well suitable for the control process of various high-power gas engines, and has good practicability.
Thirdly, the efficiency is high: the invention adopts Model-Based Design (Model-Based Design) to develop the air-fuel ratio closed-loop control strategy, MATLAB/Simulink software is used for constructing the modularized control strategy, the readability is strong, the modification is convenient and easy, c codes, a2l files and the like can be directly generated by using the MATLAB/Simulink software, the time of process development is reduced, and the working efficiency is improved.
Drawings
FIG. 1 is a flow chart illustrating closed-loop control of air-fuel ratio of a gas engine according to the present invention.
FIG. 2 is a model diagram of the air-fuel ratio closed-loop control strategy of the present invention.
FIG. 3 is a diagram of a feedforward controller model according to the present invention.
FIG. 4 is a diagram of an adaptive learning PID feedback controller model according to the invention.
FIG. 5 is a graph showing the dynamic variation of the air-fuel ratio in the rich/lean condition of the reaction mixture according to the present invention.
The notation in the figure is:
1. the fuel gas control system comprises a feed-forward compensation controller, 2, an adaptive PID feedback controller based on a wide-area oxygen sensor, 3, a basic fuel gas quantity acquisition module, 4, an actual fuel gas quantity, 5, an engine speed rpm, 6, a throttle opening TPS, 7, an actual air-fuel ratio AFR, 8, a target air-fuel ratio AFR _ sp, 9, an air quantity per cylinder cycle MAF _ cyl, 10, a proportional gain, 11, an integral gain, 12, a differential gain, 13, a feed-forward control compensation fuel gas quantity, 14, a difference value between the target air-fuel ratio and the actual air-fuel ratio, 15, rich and lean state factors η, 16, integral and differential sampling time of a mixed gas, 17, the basic fuel gas quantity, 18, a proportional gain algorithm module, 19, an integral module, 20, a differential module, 21, a PID controller correction fuel gas quantity, 22 and a limiter.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments.
Examples
As shown in a closed-loop control flow chart of an air-fuel ratio in FIG. 1 and a closed-loop control strategy model of an air-fuel ratio in FIG. 2, the invention provides a method for controlling a transient air-fuel ratio of a high-power gas engine, and a control system corresponding to the method consists of three gas quantity calculation controllers:
constructing a feedforward compensation controller 1;
a wide-area oxygen sensor-based adaptive learning PID feedback controller 2;
a basic gas amount acquisition module 3;
the construction of the feedforward compensation controller 1 is specifically described below,
1. constructing the feedforward compensation controller 1 enables ensuring a quick response to the engine operating conditions according to the amount of change Δ TPS in the throttle opening degree 6 and the amount of change Δ rpm in the rotation speed 5, thereby accurately increasing or decreasing the feedforward control compensation gas amount 13 so that the actual air-fuel ratio 7 can smoothly fluctuate around the target air-fuel ratio 8.
2. In the engine closed-loop control strategy, as shown in fig. 3, a feedforward control strategy constructed by using Simulink software is shown to correct and compensate the fuel gas.
Δ TPS and Δ rpm are input variables of the feedforward controller 1, and are described in table 1, Δ TPS ═ TPS (t) -TPS (t-1), Δ rpm ═ rpm (t) -rpm (t-1);
TABLE 1 controller Fuel Compensation
The input variable Δ TPS of the controller is classified into 5 categories, which are expressed as follows: NL for Negative and Large Negative Small, NS for Negative and Small Negative Small, Z for Zero, PS for Positive and Small Positive Small, and PL for Large Positive Large.
The input variable Δ rpm is expressed as follows: z, Small, S, M, Large, L.
The output variables Fuel _ Compensation of the controller fall into seven categories, which are represented as follows: NL for Negative and Large Negative Positive Large Medium, NS for Negative and Small Negative Small, Z for Zero, PS for Positive and Small Positive Small, PM for Positive and Medium Positive Medium, and PL for Positive and Large Positive Large.
And performing defuzzification weighted average calculation on the actual values of the delta TPS and the delta rpm to obtain a more accurate output gas compensation variable 13. The formula of which is shown below,
wherein u (Z)k) Obtained on condition of input quantities Δ TPS and Δ rpm, ZkIs the median value in each domain of the gas Compensation quantity 13(Fuel _ Compensation) obtained.
The wide-area oxygen sensor based adaptive learning PID feedback controller 2 is specifically described as follows,
1. the difference between the actual air-fuel ratio 7(AFR) and the target air-fuel ratio 8(AFR _ sp), which is transmitted in real time by the wide-area oxygen sensor, is used as an input variable of the PID controller.
2. As shown in FIG. 4, the part of the rich-lean condition factor η 15(Integral _ factor) of the mixture in the air-fuel ratio closed-loop control strategy constructed by using Simulink software is shown as a dynamic reaction to the rich-lean condition of the mixture.
3. As shown in fig. 5, the dynamic curve acquisition of AFR clearly observes that as | AFR | increases, the actual air-fuel ratio 7(AFR) is changing the direction of deviation, so the deviation needs to be controlled by PID feedback controller 2, the actual air-fuel ratio 7 is represented as AFR, the difference of its dynamic change is represented as Δ AFR, and the dynamic curve of AFR is divided into four different changes of AB, BC, CD and DE. The dynamic change states of the four processes can be respectively obtained as follows:
4. the incremental algorithm of the PID controller gas correction amount in the invention is as follows:
wherein, PID _ fuel: corrected gas quantity 21 of the PID controller;
Kp，Ki，Kd: proportional gain 10, integral gain 11, derivative gain 12;
rich-lean state factor of mixed gas
Ts: the sampling time of the increment module 18;
Ti: the integration time of the increment module 18;
Td: sample time 16 of integrator 19, differentiator 20.
5. The addition of the differential module 20 in the increment algorithm of the PID controller causes the gas quantity to change too quickly, so the differential control module 20 part in the PID controller, namely the command K, is not used normallyd0; the sampling time T of the differentiator can also be varieddTo adjust the rate of change of the differentiator.
The basic gas amount acquisition module 3 directly calculates and obtains a basic gas amount 17 from the air amount 9 calculated by the speed density method and the target air-fuel ratio 8 as input amounts.
The actual gas quantity 4 is obtained by accumulating the gas compensation quantity 13 of the feedforward controller 1, the gas correction quantity 21 of the PID feedback controller 2 and the basic gas quantity 17.
The invention adopts Model-Based Design (Model-Based Design) to develop an air-fuel ratio closed-loop control strategy, the air-fuel ratio closed-loop control strategy adopts MATLAB/Simulink software to carry out modular construction, the Simulink software can directly generate a c code, an a2l file and the like for the modular control strategy in the compiling process, and then the code is downloaded into an engine ECU through special software.
Claims (1)
1. A method for transient air-fuel ratio control of a high power gas engine, comprising the steps of:
1) a high-power gas engine transient air-fuel ratio control system is constructed in a modularization mode through MATLAB/Simulink software, and comprises a feedforward compensation controller (1), a basic gas quantity acquisition module (3), a wide-range oxygen sensor-based self-adaptive PID feedback controller (2) and an actual gas quantity output module (4);
2) the feedforward compensation controller (1) takes the throttle opening variation delta TPS and the rotational speed variation delta rpm as input to carry out defuzzification weighted average and output the gas compensation amount, and in the feedforward compensation controller (1), the calculating formula of the defuzzification weighted average is as follows:
wherein u (Z)k) Transient gas compensation quantity Z obtained by taking input quantity delta TPS and delta rpm as conditionskIs the median value in the k-th gas Compensation quantity Fuel _ Compensation domain;
3) the basic gas quantity acquisition module (3) takes a target air-fuel ratio and air per cylinder per cycle as input and outputs the basic gas quantity;
4) the adaptive PID feedback controller (2) based on the wide-area oxygen sensor calculates and outputs the corrected gas quantity of the PID controller by setting proportional gain, integral gain and differential gain and taking an actual air-fuel ratio and a target air-fuel ratio as input, and the calculation formula of the gas quantity gain algorithm of the adaptive PID feedback controller (2) based on the wide-area oxygen sensor is as follows:
wherein PID _ fuel is the corrected gas quantity of the output, Kp、Ki、KdProportional, integral and differential gains, T, respectivelysSample time of incremental module, TiIntegration time, T, for incremental modulesdThe sampling time of the integrator and the differentiator, η is the rich-lean state factor of the mixture, Δ AFR is the difference of the dynamic change of the air-fuel ratio, and the value isFractional gain KdThe value is 0;
5) the output of the feedforward compensation controller (1), the basic gas quantity acquisition module (3) and the adaptive PID feedback controller (2) based on the wide-area oxygen sensor is accumulated and then output to the actual gas quantity output module (4) through the amplitude limiter (22), and finally the actual gas quantity is output.
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| CN109268159B (en) * | 2018-09-18 | 2020-08-18 | 吉林大学 | Control method of fuel-air ratio system of lean-burn gasoline engine |
| CN109896026B (en) * | 2019-03-21 | 2020-08-07 | 南京航空航天大学 | Helicopter-turboshaft engine comprehensive control method and device with variable rotor rotation speed |
| CN110748425B (en) * | 2019-09-30 | 2021-03-26 | 同济大学 | Natural gas engine transient air-fuel ratio control method |
| CN112761803A (en) * | 2021-01-04 | 2021-05-07 | 潍柴动力股份有限公司 | Gas injection transient compensation method and device, vehicle and storage medium |
| CN115030829B (en) * | 2022-06-16 | 2023-03-21 | 东风汽车集团股份有限公司 | Short-term fuel correction control method for engine |
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