CN114893315A - High-pressure common rail fuel injector fuel injection quantity control system based on online sensing and MPC closed loop thereof - Google Patents
High-pressure common rail fuel injector fuel injection quantity control system based on online sensing and MPC closed loop thereof Download PDFInfo
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- CN114893315A CN114893315A CN202210374392.2A CN202210374392A CN114893315A CN 114893315 A CN114893315 A CN 114893315A CN 202210374392 A CN202210374392 A CN 202210374392A CN 114893315 A CN114893315 A CN 114893315A
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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
- F02D41/30—Controlling fuel injection
- F02D41/38—Controlling fuel injection of the high pressure type
- F02D41/3809—Common rail control systems
- F02D41/3827—Common rail control systems for diesel engines
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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
- F02D41/30—Controlling fuel injection
- F02D41/38—Controlling fuel injection of the high pressure type
- F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
- F02M63/02—Fuel-injection apparatus having several injectors fed by a common pumping element, or having several pumping elements feeding a common injector; Fuel-injection apparatus having provisions for cutting-out pumps, pumping elements, or injectors; Fuel-injection apparatus having provisions for variably interconnecting pumping elements and injectors alternatively
- F02M63/0225—Fuel-injection apparatus having a common rail feeding several injectors ; Means for varying pressure in common rails; Pumps feeding common rails
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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
- F02D2041/1433—Introducing closed-loop corrections characterised by the control or regulation method using a model or simulation of the system
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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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- Combustion & Propulsion (AREA)
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- General Engineering & Computer Science (AREA)
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- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
Abstract
The invention discloses a fuel injection quantity control system of a high-pressure common rail fuel injector and a control method thereof. Step 1: installing a pressure sensor (2-1) at the oil injector end of a high-pressure oil pipe (1-6) of an oil injector (1-4), amplifying a signal through a pressure sensor charge amplifier (4-1), and collecting inlet pressure by using a data acquisition card; step 2: based on the pressure collected in the step 1, obtaining the relation between the mass flow rate of change dG and the pressure rate of change dP according to the Riemann invariant theory; and 3, step 3: calculating the fuel injection quantity according to the relation between the mass flow rate of change dG and the pressure rate of change dP in the step 2; and 4, step 4: and (3) performing optimal control on the fuel injection quantity of the step 3 by predicting the performance of the system in a certain future time period through an MPC model. The invention is used for solving the problem that the fuel injection quantity can not be accurately measured and controlled on line.
Description
Technical Field
The invention belongs to the field of power energy, and particularly relates to a high-pressure common rail fuel injector fuel injection quantity control system based on online sensing and an MPC closed-loop control method thereof.
Background
The marine high-power diesel engine is used as a main engine or an auxiliary engine of a ship and always occupies an important position in national economy. With the depletion of fossil fuels and the deterioration of global environment, ships have made higher demands on the dynamic property, economic property, environmental protection index and the like of diesel engines. The marine diesel engine is required to have high power, high thermal efficiency and low pollutant discharge, so that an electronic control high-pressure common rail fuel injection technology, an exhaust emission treatment technology, a combustion control technology, an exhaust waste heat recovery technology and the like which are suitable for the development of the high-power marine diesel engine become important directions for the development of the marine diesel engine. Among them, the electrically controlled high-pressure common rail fuel injection technology has become a hot spot of world countries competing in the marine diesel engine technology as the third diesel engine technology following the high-pressure injection technology and the supercharging technology is leap forward.
Along with the gradual rise of the fuel injection pressure of the high-pressure common rail technology and the great increase of the movement speed of the needle valve by the piezoelectric crystal fuel injector, the fuel injection strategy of the high-pressure common rail fuel injection system is more and more flexible. The increasing operating pressures and switching speeds of fuel injectors have created new challenges for fuel injection control technologies.
Disclosure of Invention
The invention provides a high-pressure common rail fuel injector fuel injection quantity control system based on-line sensing and an MPC closed-loop control method thereof, which are used for solving the problem that the fuel injection quantity cannot be accurately measured and controlled on line.
The invention is realized by the following technical scheme:
a fuel injection quantity control system of a high-pressure common rail fuel injector based on-line sensing comprises a data acquisition unit, a signal amplification unit, a fuel injector driving unit, a fuel system unit, a PXI real-time processor, an MPC control unit, a power supply unit and an upper computer;
the data acquisition unit is used for acquiring signals of the pressure sensor and the needle valve lift sensor;
the signal amplifying unit is used for amplifying original signals of the pressure sensor and the needle valve lift sensor;
the oil sprayer driving unit is used for converting the 5V square wave into a driving current waveform of the oil sprayer and driving the oil sprayer to act;
the fuel system unit is used for supplying fuel for the fuel injection quantity closed-loop control system;
the PXI processor is used for calculating the oil injection quantity through the inlet pressure signal and calculating an MPC control algorithm of the oil injection quantity;
the MPC control unit is used for controlling the fuel injection quantity of the fuel system;
the power supply unit is used for providing corresponding voltage for all the devices;
and the upper computer is used for loading an algorithm for converting the inlet pressure into the fuel injection quantity and an MPC control algorithm to the PXI processor, starting and closing the acquisition system and the injection system, and monitoring the PXI processor in real time.
The control system is characterized in that the fuel system unit 1 comprises an oil pump 1-1, a motor 1-2, a high-pressure oil rail 1-3 and an oil injector 1-4, the motor 1-2 is connected with the oil pump 1-1, the oil pump 1-1 is respectively connected with an oil source 1-5 and the high-pressure oil rail 1-3, and the high-pressure oil rail 1-3 is connected with the oil injector 1-4 through a high-pressure oil pipe;
the data acquisition unit 2 comprises a pressure sensor 2-1 and a needle valve lift sensor 2-2;
the MPC control unit 3 comprises a PXI controller 3-1, a collection board card and a driving unit ipod 3-3;
the signal amplification unit 4 comprises a pressure sensor charge amplifier 4-1 and a needle valve lift sensor charge amplifier;
the PXI controller 3-1 is connected with a pressure sensor 2-1 and a needle valve lift sensor 2-2 of the fuel injector 1-4 through a charge amplifier 3-3.
An MPC closed-loop control method of a high-pressure common rail fuel injector fuel injection quantity control system based on-line sensing comprises the following steps:
step 1: installing a pressure sensor 2-1 at the oil injector end of a high-pressure oil pipe 1-6 of an oil injector 1-4, amplifying a signal through a pressure sensor charge amplifier 4-1, and collecting inlet pressure by using a data acquisition card;
step 2: based on the pressure collected in the step 1, obtaining the relation between the mass flow rate of change dG and the pressure rate of change dP according to the Riemann invariant theory;
and step 3: calculating the fuel injection quantity according to the relation between the mass flow rate of change dG and the pressure rate of change dP in the step 2;
and 4, step 4: and (3) performing optimal control on the fuel injection quantity of the step 3 by predicting the performance of the system in a certain future time period through an MPC model.
In the control method, the step 2 is specifically that the high-pressure common rail end is regarded as an isobaric reflection end, inlet pressure signal pressure fluctuation in the fuel system is regarded as one-dimensional unsteady pipe flow, the influences of friction force and fluid viscosity are ignored, and according to a sound velocity equation and a conservation equation, the direct relation between the mass flow rate change rate dG and the pressure change rate dP can be obtained as follows:
wherein A is the cross-sectional area of the high-pressure oil pipe, a is the sound velocity of the fuel oil, and G is the mass flow rate.
In the control method, the step 3 is specifically,
when the injection pulse width is short, the injection end timing is earlier than the timing at which the reflected wave W3 returns to the measurement point, and the fuel injection amount is calculated by the following equation:
wherein W1 is left-going expansion wave generated by controlling cavity pressure relief, P test For the tested fuel system inlet pressure;
when the reflected wave W3 returns to the measurement point during injection, but the needle valve does not move to the maximum limit during injection, the fuel injection amount is calculated by the following equation:
when the needle valve reaches the maximum limit position in the injection process, the fuel injection quantity is calculated by the following formula;
wherein A is the inner diameter of the oil pipe, a is the current speed of sound of the fuel oil, and P is test For measuring pressure, P, for the sensor W1 Expansion wave, P, generated for opening of ball valves W3 Is a reflected wave at the oil rail, t 0 Starting time of exciting current for the oil injector; Δ t is t 2 -t 1 ，t s For delay time, t c And t 3 At the closing time of the needle valve, t 1 At the moment when the needle valve just reaches the maximum lift, t 2 The time when the needle valve just departs from the maximum lift.
In the control method, the step 4 is specifically,
step 4.1: measuring and reading the current system state, and setting the future state X of the time k Carrying out prediction;
step 4.2: based on u k ，u k+1 ，……u k+N To perform a rolling optimization control amount u (k);
step 4.3: and (4) applying the control quantity u (k) optimized in the step 4.2 to the system, and predicting the state variable and the state input variable of the system again when the next optimization is carried out, so as to carry out rolling optimization.
In the control method, the step 4.1 is specifically,
firstly, collecting the fuel injection quantity and the fuel injection pulse width of an actual fuel injection system, establishing a relation between the fuel injection quantity and the fuel injection pulse width by using system identification, and expressing a transfer function as follows:
wherein, a, b, T 1 、T 2 、T 3 Is the coefficient of the fuel injection quantity transfer function model, a, b are the coefficients of the second-order integral element, T 1 、T 2 、T 3 Is the coefficient of the third-order differential link;
and converting the transfer function to obtain a state space equation of the system:
x(k+1)＝Ax(k)+Bu(k)
k is a non-negative integer, x () is a state variable of a system, and the fuel injection quantity of an injector is in the system;
calculating A and B from the transfer function; reading the current system state X (k | k), predicting the state of the future system by using MPC, and recording the predicted system state variable X in the future N control cycles k Comprises the following steps:
n is called the prediction horizon, (k + i | k) represents the state of the system at the time when k + i is predicted at the current time. In addition, when predicting the future state of the dynamic system, the control output variable U in the prediction time domain needs to be acquired k :
The system transition states of the future N control periods are predicted in sequence through a discretization state equation, and the system transition states are integrated into a matrix in the form that:
X(k)＝Mx(k)+Cu(k) (11)
wherein:
in the control method, the step 4.2 is specifically to introduce a loss function, which is defined as:
wherein, the first term is an error weighted sum, the second term is an input weighted sum, the third term is a terminal matrix, Q is an error loss function, R is an input loss matrix, F is a terminal error loss matrix, and a future state variable in the loss function is eliminated, so that the loss function only contains a control quantity u (k) predicted at the time k and a current system state variable x (k):
J＝x(k) T Gx(k)+U(k) T HU(k)+2x(k) T EU(k) (15)
let the loss function go to the minimum and find u (k), u (k +1), u (k +2),. u (k + N) under this condition.
In the control method, the step 4.3 is specifically to apply the control output variable u (k) to the system only, and when the next optimization is performed, predict the state variable and the state input variable of the system again, so as to perform the rolling optimization.
An electronic device comprises a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory are communicated with each other through the communication bus;
a memory for storing a computer program;
and the processor is used for realizing the steps of the method when executing the program stored in the memory.
The invention has the beneficial effects that:
compared with the traditional PID algorithm, the MPC algorithm has the advantages of high response speed, short time for reaching a steady state, small overshoot and higher robustness.
The method not only considers the influence of the structural parameters of the oil sprayer on the oil spraying rule, but also can predict the fuel oil spraying amount of the oil sprayer according to the real-time inlet pressure.
The invention does not need to destroy the integral structure of the engine fuel injector and the combustion chamber, only needs to install a rail pressure sensor on the high-pressure fuel pipe, has simple equipment and can realize out-cylinder measurement.
The source of the feedback signal of the invention is the inlet pressure sensor, the working environment is more relaxed, the service life of the sensor is long, and the cost is low.
Drawings
FIG. 1 is a signal diagram of fuel pressure fluctuation at the inlet of an injector under different injection conditions of the present invention, wherein (a) the signal diagram of fuel pressure fluctuation at the inlet of the injector under the injection conditions of-10 MPa to 10MPa, and (b) the signal diagram of fuel pressure fluctuation at the inlet of the injector under the injection conditions of-20 MPa to 20 MPa.
FIG. 2 is a control block diagram of the MPC of the present invention.
Fig. 3 is a flow chart of the method of the present invention.
FIG. 4 is a diagram of an experimental apparatus of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The oil pressure closed loop-based oil injection quantity control technology adopts the inlet pressure of an oil injector as a sensing signal, and the installation position of a sensor is positioned at a high-pressure oil pipe. For installing the cylinder pressure sensor on engine cylinder wall, the operating environment of the pressure sensor of high pressure fuel pipe department is comparatively mild, and for the measuring method of other fuel injection volume like momentum method, displacement method, the oil pressure closed loop mode is very little to the structural damage of fuel system, does not receive the environmental limitation of laboratory bench, can carry out on-line monitoring when the engine normal operating specifically to be:
a high-pressure common rail fuel injector fuel injection quantity control system based on-line sensing comprises a data acquisition unit, a signal amplification unit, an injector driving unit, a fuel system unit, a PXI real-time processor, an MPC control unit, a power supply unit and an upper computer;
the data acquisition unit is used for acquiring signals of the pressure sensor and the needle valve lift sensor;
the signal amplification unit is used for amplifying original signals of the pressure sensor and the needle valve lift sensor;
the oil sprayer driving unit is used for converting the 5V square wave into a driving current waveform of the oil sprayer and driving the oil sprayer to act;
the fuel system unit is used for supplying fuel for the fuel injection quantity closed-loop control system;
the PXI processor is used for calculating the oil injection quantity through the inlet pressure signal and calculating an MPC control algorithm of the oil injection quantity;
the MPC control unit is used for controlling the fuel injection quantity of the fuel system;
the power supply unit is used for providing corresponding voltage for all the devices;
and the upper computer is used for loading an algorithm for converting the inlet pressure into the fuel injection quantity and an MPC control algorithm to the PXI processor, starting and closing the acquisition system and the injection system, and monitoring the PXI processor in real time.
The control system is characterized in that the fuel system unit 1 comprises an oil pump 1-1, a motor 1-2, a high-pressure oil rail 1-3 and an oil injector 1-4, the motor 1-2 is connected with the oil pump 1-1, the oil pump 1-1 is respectively connected with an oil source 1-5 and the high-pressure oil rail 1-3, and the high-pressure oil rail 1-3 is connected with the oil injector 1-4 through a high-pressure oil pipe;
the data acquisition unit 2 comprises a pressure sensor 2-1 and a needle valve lift sensor 2-2;
the MPC control unit 3 comprises a PXI controller 3-1, a collection board card and a driving unit ipod 3-3;
the signal amplification unit 4 comprises a pressure sensor charge amplifier 4-1 and a needle valve lift sensor charge amplifier;
the PXI controller 3-1 is connected with a pressure sensor 2-1 and a needle valve lift sensor 2-2 of the fuel injector 1-4 through a charge amplifier 3-3.
An MPC closed-loop control method of a high-pressure common rail fuel injector fuel injection quantity control system based on-line sensing comprises the following steps:
step 1: installing a pressure sensor 2-1 at the oil injector end of a high-pressure oil pipe 1-6 of an oil injector 1-4, amplifying a signal through a pressure sensor charge amplifier 4-1, and collecting inlet pressure by using a data acquisition card;
step 2: based on the pressure collected in the step 1, obtaining the relation between the mass flow rate of change dG and the pressure rate of change dP according to the Riemann invariant theory;
and step 3: calculating the fuel injection quantity according to the relation between the mass flow rate of change dG and the pressure rate of change dP in the step 2;
and 4, step 4: and (3) performing optimal control on the fuel injection quantity of the step 3 by predicting the performance of the system in a certain future time period through an MPC model.
In the control method, the step 2 is specifically that the high-pressure common rail end is regarded as an isobaric reflection end, inlet pressure signal pressure fluctuation in the fuel system is regarded as one-dimensional unsteady pipe flow, the influences of friction force and fluid viscosity are ignored, and according to a sound velocity equation and a conservation equation, the direct relation between the mass flow rate change rate dG and the pressure change rate dP can be obtained as follows:
wherein A is the cross-sectional area (unit: mm) of the high-pressure oil pipe 2 ) And a is the fuel sound velocity (unit: m/s), G is the mass flow rate (mg/ms).
In the control method, the step 3 is specifically,
when the fuel injection pulse width is short as shown in fig. 1(a), the fuel injection amount is calculated by the following equation, with the injection end timing earlier than the timing at which the reflected wave W3 returns to the measurement point:
wherein W1 is left-going expansion wave generated by controlling cavity pressure relief, P test For the tested fuel system inlet pressure;
when the reflected wave W3 returns to the measurement point during injection as shown in fig. 1(b), but the needle valve does not move to the maximum limit during injection, the fuel injection amount is calculated by the following equation:
when the needle valve reaches the maximum limit position in the injection process, the fuel injection quantity is calculated by the following formula;
wherein A is the inner diameter of the oil pipe, a is the current speed of sound of the fuel oil, and P is test For measuring pressure, P, for the sensor W1 Expansion wave, P, generated for opening of ball valves W3 Is a reflected wave at the oil rail, t 0 Starting time of exciting current for the oil injector; Δ t is t 2 -t 1 ，t s For delay time, t c And t 3 At the closing time of the needle valve, t 1 At the moment when the needle valve just reaches the maximum lift, t 2 The time when the needle valve just departs from the maximum lift.
In the control method, the step 4 is specifically,
step 4.1: measuring and reading the current system state, and setting the future state X of the time k Carrying out prediction;
step 4.2: based on u k ，u k+1 ，……u k+N To perform a rolling optimization control amount u (k);
step 4.3: and (4) applying the control quantity u (k) optimized in the step 4.2 to the system, and predicting the state variable and the state input variable of the system again when the next optimization is carried out, so as to carry out rolling optimization.
In the control method, the step 4.1 is specifically,
firstly, collecting the fuel injection quantity (obtained by calculating inlet pressure) and fuel injection pulse width of an actual fuel injection system, and establishing a relation between the fuel injection quantity and the fuel injection pulse width by using system identification, wherein a transfer function of the relation is expressed as:
wherein, a, b, T 1 、T 2 、T 3 Is the coefficient of the fuel injection quantity transfer function model, a, b are the coefficients of the second-order integral element, T 1 、T 2 、T 3 Is the coefficient of the third-order differential link;
and converting the transfer function to obtain a state space equation of the system:
x(k+1)＝Ax(k)+Bu(k)
k is a non-negative integer, x () is a state variable of a system, and the fuel injection quantity of an injector is in the system;
calculating A and B from the transfer function; reading the current system state X (k | k), predicting the state of the future system by using MPC, and recording the predicted system state variable X in the future N control cycles k Comprises the following steps:
n is called the prediction horizon, (k + i | k) represents the state of the system at the time when k + i is predicted at the current time. In addition, when predicting the future state of the dynamic system, the control output variable U in the prediction time domain needs to be acquired k :
The system transition states of the future N control periods are predicted in sequence through a discretization state equation, and the system transition states are integrated into a matrix in the form that:
X(k)＝Mx(k)+Cu(k) (11)
wherein:
in the control method, the step 4.2 is specifically to introduce a loss function, which is defined as:
wherein, the first term is an error weighted sum, the second term is an input weighted sum, the third term is a terminal matrix, Q is an error loss function, R is an input loss matrix, F is a terminal error loss matrix, and a future state variable in the loss function is eliminated, so that the loss function only contains a control quantity u (k) predicted at the time k and a current system state variable x (k):
J＝x(k) T Gx(k)+U(k) T HU(k)+2x(k) T EU(k) (15)
let the loss function go to the minimum and find u (k), u (k +1), u (k +2),. u (k + N) under this condition.
In the control method, the step 4.3 is specifically to apply the control output variable u (k) to the system only, and when the next optimization is performed, predict the state variable and the state input variable of the system again, so as to perform the rolling optimization.
An electronic device comprises a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory are communicated with each other through the communication bus;
a memory for storing a computer program;
and the processor is used for realizing the steps of the method when executing the program stored in the memory.
Claims (10)
1. A high-pressure common rail fuel injector fuel injection quantity control system based on-line sensing is characterized in that the control system comprises a data acquisition unit, a signal amplification unit, a fuel injector driving unit, a fuel system unit, a PXI real-time processor, an MPC control unit, a power supply unit and an upper computer;
the data acquisition unit is used for acquiring signals of the pressure sensor and the needle valve lift sensor;
the signal amplification unit is used for amplifying original signals of the pressure sensor and the needle valve lift sensor;
the oil sprayer driving unit is used for converting the 5V square wave into a driving current waveform of the oil sprayer and driving the oil sprayer to act;
the fuel system unit is used for supplying fuel for the fuel injection quantity closed-loop control system;
the PXI processor is used for calculating the oil injection quantity through the inlet pressure signal and calculating an MPC control algorithm of the oil injection quantity;
the MPC control unit is used for controlling the fuel injection quantity of the fuel system;
the power supply unit is used for providing corresponding voltage for all the devices;
and the upper computer (7) is used for loading an algorithm for converting the inlet pressure into the fuel injection quantity and an MPC control algorithm to the PXI processor, starting and closing the acquisition system and the injection system, and monitoring the PXI processor in real time.
2. The control system according to claim 1, characterized in that the fuel system unit (1) comprises an oil pump (1-1), a motor (1-2), a high-pressure oil rail (1-3) and an oil injector (1-4), the motor (1-2) is connected with the oil pump (1-1), the oil pump (1-1) is respectively connected with an oil source (1-5) and the high-pressure oil rail (1-3), and the high-pressure oil rail (1-3) is connected with the oil injector (1-4) through a high-pressure oil pipe;
the data acquisition unit (2) comprises a pressure sensor (2-1) and a needle valve lift sensor (2-2);
the MPC control unit (3) comprises a PXI controller (3-1), a collection board card and a driving unit ipod (3-3);
the signal amplification unit (4) comprises a pressure sensor charge amplifier (4-1) and a needle valve lift sensor charge amplifier;
the PXI controller (3-1) is connected with a pressure sensor (2-1) and a needle valve lift sensor (2-2) of the fuel injector (1-4) through a charge amplifier (3-3).
3. The MPC closed-loop control method based on the on-line sensing-based fuel injection quantity control system of the high-pressure common rail fuel injector as claimed in any one of claims 1-2, wherein the control method comprises the following steps:
step 1: installing a pressure sensor (2-1) at the oil injector end of a high-pressure oil pipe (1-6) of an oil injector (1-4), amplifying a signal through a pressure sensor charge amplifier (4-1), and collecting inlet pressure by using a data acquisition card;
step 2: based on the pressure collected in the step 1, obtaining the relation between the mass flow rate of change dG and the pressure rate of change dP according to the Riemann invariant theory;
and step 3: calculating the fuel injection quantity according to the relation between the mass flow rate of change dG and the pressure rate of change dP in the step 2;
and 4, step 4: and (3) performing optimal control on the fuel injection quantity of the step 3 by predicting the performance of the system in a certain future time period through an MPC model.
4. The control method according to claim 3, wherein the step 2 is specifically that the high-pressure common rail end is regarded as an isobaric reflection end, the inlet pressure signal pressure fluctuation in the fuel system is regarded as one-dimensional unsteady pipe flow, the influence of friction force and viscosity of fluid is ignored, and according to a sound velocity equation and a conservation equation, the direct relation between the mass flow rate change rate dG and the pressure change rate dP is obtained as follows:
wherein A is the cross-sectional area of the high-pressure oil pipe, a is the speed of sound of the fuel oil, and G is the mass flow rate.
5. The control method according to claim 3, wherein the step 3 is specifically,
when the injection pulse width is short, the injection end timing is earlier than the timing at which the reflected wave W3 returns to the measurement point, and the fuel injection amount is calculated by the following equation:
wherein W1 is left-going expansion wave generated by controlling cavity pressure relief, P test For the tested fuel system inlet pressure;
when the reflected wave W3 returns to the measurement point during injection, but the needle valve does not move to the maximum limit during injection, the fuel injection amount is calculated by the following equation:
when the needle valve reaches the maximum limit position in the injection process, the fuel injection quantity is calculated by the following formula;
wherein A is the inner diameter of the oil pipe, a is the current speed of sound of the fuel oil, and P is test For measuring pressure, P, for the sensor W1 Expansion wave, P, generated for opening of ball valves W3 Is a reflected wave at the oil rail, t 0 Starting time of exciting current for the oil injector; Δ t is t 2 -t 1 ，t s For delay time, t c And t 3 At the closing time of the needle valve, t 1 At the moment when the needle valve just reaches the maximum lift, t 2 The time when the needle valve just departs from the maximum lift.
6. The control method according to claim 3, wherein the step 4 is specifically,
step 4.1: measuring and reading the current system state, and setting the future state X of the time k Carrying out prediction;
step 4.2: based on u k ，u k+1 ，……u k+N To perform a rolling optimization control amount u (k);
step 4.3: and (4) applying the control quantity u (k) optimized in the step 4.2 to the system, and predicting the state variable and the state input variable of the system again when the next optimization is carried out, so as to carry out rolling optimization.
7. The control method according to claim 6, characterized in that said step 4.1 is, in particular,
firstly, collecting the fuel injection quantity and the fuel injection pulse width of an actual fuel injection system, establishing a relation between the fuel injection quantity and the fuel injection pulse width by using system identification, and expressing a transfer function as follows:
wherein, a, b, T 1 、T 2 、T 3 Is the coefficient of the fuel injection quantity transfer function model, a, b are the coefficients of the second-order integral element, T 1 、T 2 、T 3 Is the coefficient of the third-order differential link;
and converting the transfer function to obtain a state space equation of the system:
x(k+1)＝Ax(k)+Bu(k)
k is a non-negative integer, x () is a state variable of a system, and the fuel injection quantity of an injector is in the system;
calculating A and B from the transfer function; reading the current system state X (k | k), predicting the state of the future system by using MPC, and recording the predicted system state variable X in the future N control cycles k Comprises the following steps:
n is called the prediction horizon, (k + i | k) represents the state of the system at the time when k + i is predicted at the current time. In addition, when predicting the future state of the dynamic system, the control output variable U in the prediction time domain needs to be acquired k :
The system transition states of the future N control periods are predicted in sequence through a discretization state equation, and the system transition states are integrated into a matrix in the form that:
X(k)＝Mx(k)+Cu(k) (11)
wherein:
8. control method according to claim 6, characterized in that said step 4.2 consists in introducing a loss function defined as:
wherein, the first term is an error weighted sum, the second term is an input weighted sum, the third term is a terminal matrix, Q is an error loss function, R is an input loss matrix, F is a terminal error loss matrix, and a future state variable in the loss function is eliminated, so that the loss function only contains a control quantity u (k) predicted at the time k and a current system state variable x (k):
J＝x(k) T Gx(k)+U(k) T HU(k)+2x(k) T EU(k) (15)
let the loss function go to the minimum value and get u (k), u (k +1), u (k +2),. u (k + N) under this condition.
9. The control method according to claim 7, wherein the step 4.3 is specifically to apply the control output variables u (k) only to the system, and when next optimization is performed, predict the state variables and the state input variables of the system again, so as to perform rolling optimization.
10. An electronic device is characterized by comprising a processor, a communication interface, a memory and a communication bus, wherein the processor and the communication interface are used for realizing mutual communication by the memory through the communication bus;
a memory for storing a computer program;
a processor for implementing the method steps of any of claims 1-9 when executing a program stored in the memory.
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