A method and system for controlling the air-fuel ratio in a cylinder of a marine methanol dual-fuel engine

Abstract

The present invention discloses a method and system for controlling the in-cylinder air-fuel ratio of a marine methanol dual-fuel engine. The method includes collecting oxygen concentration data from the exhaust pipe of the methanol dual-fuel engine, calculating the real-time excess air coefficient in the engine exhaust based on the oxygen concentration data, and collecting the intake manifold pressure and temperature. Then, based on the pressure and temperature before and after the intake manifold, the air mass flow entering the intake manifold is estimated in real time. A real-time air-fuel ratio transmission delay model is established based on the engine's operating mechanism and structural characteristics, and a delay prediction estimator is designed to estimate the in-cylinder air-fuel ratio in real time. Based on the real-time air-fuel ratio transmission delay model, a predetermined performance air-fuel ratio control algorithm based on ideal internal dynamics is designed. The present invention is suitable for precise air-fuel ratio control of marine methanol dual-fuel engines and has excellent air-fuel ratio control effects.

Description

Technical Field

[0001] The present invention belongs to the technical field of automatic control of methanol dual-fuel engines, and in particular relates to a method and system for controlling the air-fuel ratio in a cylinder of a marine methanol dual-fuel engine. Background Art

[0002] Methanol fuel has become an increasingly important fuel choice for marine power systems due to its low emissions, economical fuel economy, and easy storage and transportation. However, methanol-diesel dual-fuel engines face significant control challenges during in-cylinder combustion due to fuel property differences, combustion nonlinearity, and complex operating conditions. This leads to high air-fuel ratio control accuracy requirements. The air-fuel ratio is a key parameter affecting engine combustion efficiency, emissions, and power output. In terms of air-fuel ratio control, leading engine manufacturers and research institutions at home and abroad are focusing on combustion stability, fuel injection strategies, emissions control, and real-time air-fuel ratio optimization for methanol dual-fuel engines to ensure stable in-cylinder combustion and address combustion lag and incomplete combustion. In practical applications, in-cylinder air-fuel ratio data is often not available in real time due to sensor response time, data transmission delays, and complex environmental influences. This results in traditional control methods being unable to respond promptly, impacting engine combustion efficiency and stability. Therefore, an adaptive control method is needed that can adaptively adjust control parameters according to different operating conditions to achieve stable and efficient control. Based on this background, a method and system for in-cylinder air-fuel ratio control in marine methanol dual-fuel engines is proposed to address data delay issues and improve control accuracy and stability. Summary of the Invention

[0003] In order to solve the problem of delayed acquisition and estimation of the air-fuel ratio in the cylinder of a methanol dual-fuel engine, this study provides a method and system for controlling the air-fuel ratio in the cylinder of a marine methanol dual-fuel engine.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for controlling the air-fuel ratio in a cylinder of a marine methanol dual-fuel engine, comprising the following steps:

[0005] S1. Collecting oxygen concentration data in the exhaust pipe of a methanol dual-fuel engine, and calculating a real-time excess air coefficient in the engine exhaust according to the oxygen concentration data;

[0006] S2. collecting temperature and pressure data of the intake manifold;

[0007] S3, based on the pressure and temperature data before and after the intake manifold, using the throttle flow equation physical model, calculate and estimate the air mass flow in the intake manifold in real time;

[0008] S4. Establish an air-fuel ratio transmission delay model based on the engine operating mechanism and structural characteristics;

[0009] S5. Inputting the real-time excess air coefficient and air mass flow obtained in S1 and S3 into a transmission delay model to obtain a real-time transmission delay model of the air-fuel ratio of the methanol dual-fuel engine. Based on the real-time transmission delay model of the air-fuel ratio of the methanol dual-fuel engine, a delay prediction estimator is designed to perform real-time estimation of the air-fuel ratio in the cylinder of the methanol dual-fuel engine and obtain a real-time estimated value of the air-fuel ratio in the cylinder.

[0010] S6. Constructing a dynamic predetermined performance air-fuel ratio control algorithm based on the air-fuel ratio real-time transmission delay model in S5;

[0011] S7. Combined with the predetermined performance air-fuel ratio control algorithm of S6, with the real-time estimated value of the methanol dual-fuel engine cylinder air-fuel ratio by the prediction estimator as the target, the design engineering predetermined performance convergence is carried out to achieve adaptive control of the methanol dual-fuel engine cylinder air-fuel ratio.

[0012] Preferably, establishing the air-fuel ratio transmission delay model in S4 includes:

[0013] Combined with the standard gas state equation, the dynamic expression of the air-fuel ratio at the intake manifold is established based on the relationship between gas inflow and outflow, namely the air-fuel ratio transmission delay model:

[0014]

[0015]

[0016] The air-fuel ratio at the exhaust manifold and the air-fuel ratio at the intake manifold are related as follows:

[0017]

[0018] Preferably, in S5, the delay estimator includes a prediction item for the in-cylinder air-fuel ratio and an estimation item for the in-cylinder air-fuel ratio, and the in-cylinder air-fuel ratio parameter estimation function is as follows:

[0019] Step 1: Gain after delayed input of the in-cylinder air-fuel ratio , the gain of the predicted state of the air-fuel ratio in the cylinder , correction term for the predicted state of the in-cylinder air-fuel ratio ,in is the observation gain matrix, which is adjusted by To make the error dynamic is the Hurwitz matrix, and the predicted state of the air-fuel ratio in the cylinder is as follows:

[0020]

[0021] Step 2: Estimate the time-delay state. This can be done using the input history values and known system dynamics. The in-cylinder air-fuel ratio parameter estimation function is as follows:

[0022]

[0023]

[0024] in is the air gas constant of the intake manifold, is the gas pressure in the intake manifold, is the volume of the intake manifold, is the gas temperature in the intake manifold, is the air mass flow rate in the intake manifold, is the integral of the change in the methanol mass flow rate of the intake manifold, is the air-fuel ratio in the exhaust manifold, is the delay from the intake manifold to the exhaust manifold, is the estimated air-fuel ratio at the intake manifold, is the estimated in-cylinder air-fuel ratio, x is the integral variable, and tx is the time interval from time point x to the current t;

[0025] The delay from the air-fuel ratio in the intake manifold to the air-fuel ratio in the cylinder is , the air-fuel ratio in the cylinder can be known as:

[0026]

[0027] This delayed prediction estimator algorithm can estimate the current state of the system and further predict the future state through this estimate. The air-fuel ratio in the cylinder is the Time series of real-time air-fuel ratio.

[0028] Preferably, in S6, according to the real-time transmission delay model of the air-fuel ratio, a predetermined performance air-fuel ratio control algorithm based on ideal internal dynamics is designed as follows:

[0029] Step 1: For the in-cylinder air-fuel ratio system:

[0030]

[0031] Where s is the differential operator;

[0032] Introducing new variables For internal dynamics, is the change of internal dynamics, where Then we can deduce:

[0033]

[0034] The control model and internal dynamics can be derived as:

[0035]

[0036]

[0037] in , , ;because , the internal dynamics are unstable, is the external disturbance to the system, is the designed air-fuel ratio control input;

[0038] Defining system state error , The error dynamic model of the air-fuel ratio is obtained as follows:

[0039]

[0040]

[0041] in, is the error of the actual value of the air-fuel ratio in the cylinder, is the internal dynamic error, is the target in-cylinder air-fuel ratio, is a bounded ideal internal dynamic, To design robust control to force the internal dynamics and output Track separately and .

[0042] Step 2: To solve the bounded ideal internal dynamics, the bounded reference trajectory (i.e., bounded reference trajectory) is estimated using the center of the stable system The central idea is to combine the traditional stable system center with the high-order sliding mode parameter observer, assuming that the reference signal Can be linear The outer system is modeled piecewise, so the bounded estimate of the ideal inner dynamics is satisfied. It can be solved by the following differential equation:

[0043]

[0044] Where, , ,…, is the design parameter, represents the order of the hypothetical external system; , ,… , which can be calculated by the following formula:

[0045]

[0046] in , ,…, are the coefficients of the system characteristic polynomial, which can be estimated in real time by a high-order sliding mode estimator;

[0047] Step 3: To ensure and The fast convergence of , the nonlinear sliding surface based on can be designed as:

[0048]

[0049] In the formula are design parameters, is the design parameter, For predefined time, is a nonlinear sliding surface. Once the sliding surface is established, , the internal dynamics and output dynamics will converge;

[0050] Step 4: To ensure that the error dynamic model of the in-cylinder air-fuel ratio converges to the predefined time sliding manifold within the predefined time, the adaptive predefined time air-fuel ratio control law is designed as follows:

[0051]

[0052] The design parameters >0 and , is the design parameter, For predefined time, Is used to compensate for estimation errors The adaptive parameter, sgn(•) is the sign function, is the wave function.

[0053] Preferably, in S7, an adaptive mechanism for designing the predetermined performance convergence is designed to realize the adaptive control of the air-fuel ratio in the cylinder, which is specifically as follows:

[0054] The adaptive strategy is designed as follows:

[0055]

[0056] In the formula is the design parameter; and are all positive numbers, which are consistent with the design parameters 、 Related, that is and , is the change of the adaptive parameter.

[0057] In order to solve the above problems, the present invention also provides a system using a method for controlling the air-fuel ratio in a cylinder of a marine methanol dual-fuel engine, which specifically includes:

[0058] Oxygen concentration collection and excess air coefficient calculation module, used to collect oxygen concentration data in the exhaust pipe of the methanol dual-fuel engine and calculate the real-time excess air coefficient in the engine exhaust based on the oxygen concentration data;

[0059] Intake manifold temperature and pressure acquisition module, used to collect intake manifold temperature and pressure data;

[0060] The air mass flow estimation module is used to calculate and estimate the air mass flow in the intake manifold in real time based on the pressure and temperature data before and after the intake manifold through the throttle flow equation physical model;

[0061] An air-fuel ratio transmission delay model building module is used to build an air-fuel ratio transmission delay model based on the engine operating mechanism and structural characteristics;

[0062] The air-fuel ratio real-time transmission delay model and prediction estimator module is used to input the real-time excess air coefficient and air mass flow obtained by S1 and S3 into the transmission delay model to obtain the real-time transmission delay model of the air-fuel ratio of the methanol dual-fuel engine, and design a delay prediction estimator to perform real-time estimation of the air-fuel ratio in the cylinder of the methanol dual-fuel engine;

[0063] A predetermined performance air-fuel ratio control algorithm module is used to construct a dynamic predetermined performance air-fuel ratio control algorithm based on the air-fuel ratio real-time transmission delay model in S5;

[0064] The in-cylinder air-fuel ratio adaptive control module is used to combine the S6's predetermined performance air-fuel ratio control algorithm, with the prediction estimator's real-time estimated value of the methanol dual-fuel engine's in-cylinder air-fuel ratio as the target, and design engineering predetermined performance convergence to achieve adaptive control of the methanol dual-fuel engine's in-cylinder air-fuel ratio.

[0065] The beneficial effect of the present application is that through the adaptive control method of the present application, the control parameters can be adaptively adjusted according to different working conditions to achieve stable and efficient control, solve the data delay problem and improve control accuracy and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 This is a flow chart of the steps of the method for controlling the air-fuel ratio in the cylinder of a marine methanol dual-fuel engine according to the present invention;

[0067] Figure 2 This is a flowchart of the steps of the method for controlling the air-fuel ratio in the cylinder of a marine methanol dual-fuel engine according to embodiment 1 of the present invention. DETAILED DESCRIPTION

[0068] The technical solution of the present invention is further described below with reference to the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0069] Example 1

[0070] The present invention provides a technical method, combined with Figures 1 to 2 As shown, a method for controlling the air-fuel ratio in a cylinder of a marine methanol dual-fuel engine includes the following steps:

[0071] S1. Using a wide-band oxygen sensor installed in the exhaust manifold to collect an oxygen concentration signal in the exhaust pipe, and calculating a real-time excess air coefficient in the engine exhaust based on the oxygen concentration signal;

[0072] S2. collecting intake manifold pressure and temperature through pressure and temperature sensors;

[0073] S3, based on the collected pressure and temperature before and after the intake manifold, the intake manifold air mass flow can be estimated in real time through calculation using the throttle flow equation physical model;

[0074] S4. Methanol injection into the intake manifold has a first-order inertia delay due to the wet wall effect as follows:

[0075]

[0076] A transmission delay model is established based on the engine's operating mechanism and structural characteristics. According to the principle of mass conservation, the change in mass of the working fluid within the system is equal to the sum of the masses exchanged across the system's boundaries. The law of mass conservation states that in an open system (such as the intake manifold), the change in mass within the system is equal to the mass flow entering the system minus the mass flow leaving the system. In other words, the change in mass of the working fluid within the intake manifold is equal to the total inflow of fuel and air minus the outflow of the mixture. Combined with the standard gas equation of state, a dynamic expression for the air-fuel ratio at the intake manifold is established based on the relationship between gas inflow and outflow. The air-fuel ratio transmission delay model is as follows:

[0077]

[0078]

[0079] The air-fuel ratio at the exhaust manifold and the air-fuel ratio at the intake manifold are related as follows:

[0080]

[0081] S5. Input the excess air coefficient and intake manifold air mass flow obtained by S1 and S3 into S4 to obtain a transmission delay model, thereby obtaining an air-fuel ratio real-time transmission delay model. Then, based on the air-fuel ratio real-time transmission delay model of the methanol dual-fuel engine, a delay prediction estimator is designed to estimate the in-cylinder air-fuel ratio in real time. The delay estimator is divided into two parts: one is the in-cylinder air-fuel prediction item, and the other is the in-cylinder air-fuel ratio estimation item. The specific description is as follows:

[0082] Step 1: Gain after delayed input of the in-cylinder air-fuel ratio , the gain of the predicted state of the air-fuel ratio in the cylinder , correction term for the predicted state of the in-cylinder air-fuel ratio ,in is the observation gain matrix, which is adjusted by To make the error dynamic is the Hurwitz matrix, and the predicted state of the air-fuel ratio in the cylinder is as follows:

[0083]

[0084] Step 2: Estimate the time-delay state. This can be done using the input history values and known system dynamics. The in-cylinder air-fuel ratio parameter estimation function is as follows:

[0085]

[0086]

[0087] The delay from the air-fuel ratio in the intake manifold to the air-fuel ratio in the cylinder is , the air-fuel ratio in the cylinder can be known as:

[0088]

[0089] This delayed prediction estimator algorithm can estimate the current state of the system and further predict the future state through this estimate. The air-fuel ratio in the cylinder is the Time series of real-time air-fuel ratio.

[0090] S6. Based on the real-time transmission delay model of the air-fuel ratio, design a predetermined performance air-fuel ratio control algorithm based on ideal internal dynamics:

[0091] Step 1: For the in-cylinder air-fuel ratio system:

[0092]

[0093] Introducing new variables The derivation is:

[0094]

[0095] The control model and internal dynamics can be derived as:

[0096]

[0097]

[0098] in , , ;because , the internal dynamics are unstable.

[0099] Defining system state error , The error dynamic model of the air-fuel ratio is obtained as follows:

[0100]

[0101]

[0102] in , is the target in-cylinder air-fuel ratio, is a bounded ideal internal dynamic, To design robust control to force the internal dynamics and output Track separately and .

[0103] Step 2: To solve the bounded ideal internal dynamics, the bounded reference profile is estimated using the center of the stable system The central idea is to combine the traditional stable system center with the high-order sliding mode parameter observer, assuming that the reference signal Can be linear The outer system is modeled piecewise, so the bounded estimate of the ideal inner dynamics is satisfied. It can be solved by the following differential equation:

[0104]

[0105] Where, , ,…, is the design parameter, represents the order of the hypothetical external system; , ,… , which can be calculated by the following formula:

[0106]

[0107] in , ,…, are the coefficients of the system characteristic polynomial, which can be estimated in real time by a high-order sliding mode estimator.

[0108] Step 3: To ensure and The fast convergence of , the nonlinear sliding surface based on can be designed as:

[0109]

[0110] In the formula are design parameters, is the design parameter, is a predefined time. Once the sliding surface is established, , the internal dynamics and output dynamics will converge.

[0111] The internal dynamic tracking error can be derived as:

[0112]

[0113] Select a Lyapunov function and calculate its derivative, and we get:

[0114]

[0115] Tracking Error At a predefined time After it converges to zero, due to the equation , making converges to zero, so and At a predefined time Converges to zero.

[0116] Step 4: To ensure that the error dynamic model of the in-cylinder air-fuel ratio converges to the predefined time sliding manifold within the predefined time, the adaptive predefined time air-fuel ratio control law is designed as follows:

[0117]

[0118] The design parameters >0 and .

[0119] S7, design an adaptive mechanism for engineering scheduled performance convergence to achieve adaptive control of the air-fuel ratio in the cylinder. Combined with the scheduled performance air-fuel ratio control algorithm of S6, the target is to predict the real-time estimation value of the air-fuel ratio in the cylinder of the methanol dual-fuel engine by the estimator. The engineering scheduled performance convergence is to ensure that the system state reaches a given error range within a preset time and strictly follow the convergence trajectory. By adjusting The system state converges within a predefined time. The adaptive mechanism is used to adjust the control parameters online to cope with system uncertainties or external disturbances. When the two are combined, the adaptive mechanism can adjust the control gain or compensation term in real time so that the system always meets the convergence performance requirements of the project, that is, the error converges according to the predetermined trajectory, and the S6 It is used to compensate for the external disturbance of the estimation error system Adaptive parameters of

[0120] The adaptive strategy is designed as follows:

[0121]

[0122] In the formula is the design parameter; and are all positive numbers, which are consistent with the design parameters 、 Related, that is and , is the change of the adaptive parameter.

[0123] Example 2

[0124] A marine methanol dual-fuel engine cylinder air-fuel ratio estimation and control system, specifically comprising:

[0125] Oxygen concentration collection and excess air coefficient calculation module, used to collect oxygen concentration data in the exhaust pipe of the methanol dual-fuel engine and calculate the real-time excess air coefficient in the engine exhaust based on the oxygen concentration data;

[0126] Intake manifold temperature and pressure acquisition module, used to collect intake manifold temperature and pressure data;

[0127] The air mass flow estimation module is used to calculate and estimate the air mass flow in the intake manifold in real time based on the pressure and temperature data before and after the intake manifold through the throttle flow equation physical model;

[0128] An air-fuel ratio transmission delay model building module is used to build an air-fuel ratio transmission delay model based on the engine operating mechanism and structural characteristics;

[0129] The air-fuel ratio real-time transmission delay model and prediction estimator module is used to input the real-time excess air coefficient and air mass flow obtained by S1 and S3 into the transmission delay model to obtain the real-time transmission delay model of the air-fuel ratio of the methanol dual-fuel engine, and design a delay prediction estimator to perform real-time estimation of the air-fuel ratio in the cylinder of the methanol dual-fuel engine;

[0130] A predetermined performance air-fuel ratio control algorithm module is used to construct a dynamic predetermined performance air-fuel ratio control algorithm based on the air-fuel ratio real-time transmission delay model in S5;

[0131] The in-cylinder air-fuel ratio adaptive control module is used to combine the S6's predetermined performance air-fuel ratio control algorithm and design engineering predetermined performance convergence to achieve in-cylinder air-fuel ratio adaptive control of the methanol dual-fuel engine.

[0132] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Under the guidance of the present invention, ordinary technicians in this field can make various similar expressions without violating the purpose and claims of the present invention. Such changes fall within the scope of protection of the present invention.

Claims

1. A method for controlling the air-fuel ratio in a cylinder of a marine methanol dual-fuel engine, characterized in that: The specific steps include: S1. Collecting oxygen concentration data in the exhaust pipe of a methanol dual-fuel engine, and calculating a real-time excess air coefficient in the engine exhaust according to the oxygen concentration data; S2. collecting temperature and pressure data of the intake manifold; S3, based on the pressure and temperature data before and after the intake manifold, using the throttle flow equation physical model, calculate and estimate the air mass flow in the intake manifold in real time; S4. Establish an air-fuel ratio transmission delay model based on the engine operating mechanism and structural characteristics; S5. Inputting the real-time excess air coefficient obtained in S1 and the air mass flow obtained in S3 into an air-fuel ratio transmission delay model to obtain a real-time air-fuel ratio transmission delay model of the methanol dual-fuel engine, and designing a delay prediction estimator based on the real-time air-fuel ratio transmission delay model. The delay prediction estimator is used to perform real-time estimation of the air-fuel ratio in the cylinder of the methanol dual-fuel engine; S6. Constructing a dynamic predetermined performance air-fuel ratio control algorithm based on the air-fuel ratio real-time transmission delay model in S5; S7. Combined with the predetermined performance air-fuel ratio control algorithm of S6, with the real-time estimated value of the in-cylinder air-fuel ratio as the target, the engineering predetermined performance convergence is designed to achieve adaptive control of the in-cylinder air-fuel ratio of the methanol dual-fuel engine.

2. The method for controlling the air-fuel ratio in a cylinder of a marine methanol dual-fuel engine according to claim 1, characterized in that: Establish an air-fuel ratio transmission delay model, including: Combined with the standard gas state equation, the dynamic expression of the air-fuel ratio at the intake manifold is established based on the relationship between gas inflow and outflow, namely the air-fuel ratio transmission delay model: ； ； Where, is the air gas constant of the intake manifold, is the gas temperature in the intake manifold, is the gas pressure in the intake manifold, is the volume of the intake manifold, is the change in methanol mass flow rate in the intake manifold, is the change in the air mass flow rate of the intake manifold, is the air-fuel ratio at the mixer, is the air-fuel ratio at the intake manifold, is the mass flow rate of diesel; The air-fuel ratio at the exhaust manifold and the air-fuel ratio at the intake manifold are related as follows: ； is the air-fuel ratio at the exhaust manifold, is the air-fuel ratio at the intake manifold after the delay is eliminated, is a time series, is the delay from the intake manifold to the exhaust manifold.

3. The method for controlling the air-fuel ratio in a cylinder of a marine methanol dual-fuel engine according to claim 1, characterized in that: In step S5, the delay prediction estimator includes a prediction item for the air-fuel ratio at the intake manifold and an estimation item for the air-fuel ratio at the intake manifold, and the specific steps are: The prediction function of the air-fuel ratio at the intake manifold is as follows: Gain after delayed input of air-fuel ratio at intake manifold , the gain of the air-fuel ratio prediction state at the intake manifold , the correction term for the predicted state of the air-fuel ratio at the intake manifold ,in is the observation gain matrix, which is adjusted by To make the error dynamics a Hurwitz matrix, the change in the predicted air-fuel ratio at the intake manifold is for: ； Where, is the predicted value of the air-fuel ratio at the intake manifold, is the correction factor; is the air-fuel ratio at the exhaust manifold; The estimation function of the air-fuel ratio at the intake manifold is as follows: To estimate the time lag state, the estimation function at the intake manifold is as follows: ； ； Where, is the integral of the change in the methanol mass flow rate of the intake manifold, is the air-fuel ratio estimation function of the mixer, is the air-fuel ratio estimation function at the intake manifold, x is the integral variable, and tx is the time interval from time point x to the current t; The delay from the air-fuel ratio in the intake manifold to the air-fuel ratio in the cylinder is , estimated value of the air-fuel ratio in the cylinder for: ； The delayed prediction estimator can estimate the current state of the system and further predict the future state through the prediction function of the air-fuel ratio at the intake manifold and the estimation function of the air-fuel ratio at the intake manifold. The estimated value of the air-fuel ratio in the cylinder is the air-fuel ratio at the intake manifold. Time series of real-time air-fuel ratio.

4. The method for controlling the air-fuel ratio in a cylinder of a marine methanol dual-fuel engine according to claim 1, characterized in that: In step S6, a dynamic predetermined performance air-fuel ratio control algorithm is constructed based on the air-fuel ratio real-time transmission delay model, as follows: Step 1: The actual value of the air-fuel ratio in the cylinder is: ； Where s is the differential operator; Introducing new variables For internal dynamics, is the change of internal dynamics, where , then we can deduce: ； The control model and internal dynamics can be derived as: ； ； in , , ;because , It is unstable. is the external disturbance to the system, is the designed air-fuel ratio control input; Defining system state error , , the error dynamic model of the air-fuel ratio is obtained as: ； ； in, is the error of the actual value of the air-fuel ratio in the cylinder, is the internal dynamic error, is the target in-cylinder air-fuel ratio, is a bounded standard internal dynamic function, that is The target value, is the designed air-fuel ratio control input, which forces the internal dynamic and the actual value of the air-fuel ratio in the cylinder Track separately and ; Step 2: In order to solve the bounded standard internal dynamics, the bounded standard internal dynamic function is estimated based on the extended stable system center method. is the estimated value of the bounded standard internal dynamic function, the stable system center method is combined with the high-order sliding mode parameter observer, and the target cylinder air-fuel ratio is assumed to be Can be linear The external system (i.e., the external reference signal generating system) is modeled piecewise, and the estimated value of the bounded standard internal dynamic function is satisfied. It can be solved by the following differential equation: ； Where, , ,…, is the design parameter, represents the order of the hypothetical external system; , ,… , which can be calculated by the following formula: ； in, , ,…, is the coefficient of the system characteristic polynomial, which can be estimated in real time by a high-order sliding mode estimator; Step 3: In order to ensure and The fast convergence of , the nonlinear sliding surface based on can be designed as: ； Where, is the design parameter, is the design parameter, For predefined time, is a nonlinear sliding surface. Once the sliding surface is established, , the internal dynamics and output dynamics will converge; Step 4: To ensure that the error dynamic model of the in-cylinder air-fuel ratio converges to the predefined time sliding manifold within the predefined time, the air-fuel ratio control input is designed as follows: ； Among them, the design parameters >0 and , is the design parameter, For predefined time, Is used to compensate for estimation errors The adaptive parameter, sgn(•) is the sign function, is the wave function.

5. The method for controlling the air-fuel ratio in a cylinder of a marine methanol dual-fuel engine according to claim 1, characterized in that: In step S7, the predetermined performance air-fuel ratio control algorithm of S6 is combined to design and engineer the predetermined performance convergence to achieve adaptive control of the in-cylinder air-fuel ratio of the methanol dual-fuel engine, wherein: The adaptive strategy is: ； In the formula is the design parameter; and are all positive numbers, which are consistent with the design parameters 、 Related, that is and , is the change of the adaptive parameter.

6. A system using the method for controlling the in-cylinder air-fuel ratio of a marine methanol dual-fuel engine according to any one of claims 1 to 5, characterized in that: Specifically include: Oxygen concentration collection and excess air coefficient calculation module, used to collect oxygen concentration data in the exhaust pipe of the methanol dual-fuel engine and calculate the real-time excess air coefficient in the engine exhaust based on the oxygen concentration data; Intake manifold temperature and pressure acquisition module, used to collect intake manifold temperature and pressure data; The air mass flow estimation module is used to calculate and estimate the air mass flow in the intake manifold in real time based on the pressure and temperature data before and after the intake manifold through the throttle flow equation physical model; An air-fuel ratio transmission delay model building module is used to build an air-fuel ratio transmission delay model based on the engine operating mechanism and structural characteristics; The air-fuel ratio real-time transmission delay model and prediction estimator module is used to input the real-time excess air coefficient and air mass flow obtained by S1 and S3 into the transmission delay model to obtain the air-fuel ratio real-time transmission delay model of the methanol dual-fuel engine. A delay prediction estimator is designed based on the air-fuel ratio real-time transmission delay model, and the prediction estimator is used to perform real-time estimation of the air-fuel ratio in the cylinder of the methanol dual-fuel engine; A predetermined performance air-fuel ratio control algorithm module is used to construct a dynamic predetermined performance air-fuel ratio control algorithm based on the air-fuel ratio real-time transmission delay model in S5; The in-cylinder air-fuel ratio adaptive control module is used to combine the S6's predetermined performance air-fuel ratio control algorithm, with the prediction estimator's real-time estimated value of the methanol dual-fuel engine's in-cylinder air-fuel ratio as the target, and design engineering predetermined performance convergence to achieve adaptive control of the methanol dual-fuel engine's in-cylinder air-fuel ratio.

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