CN114893315B - Injection quantity control system of high-pressure common rail fuel injector and MPC control method thereof - Google Patents

Injection quantity control system of high-pressure common rail fuel injector and MPC control method thereof Download PDF

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CN114893315B
CN114893315B CN202210374392.2A CN202210374392A CN114893315B CN 114893315 B CN114893315 B CN 114893315B CN 202210374392 A CN202210374392 A CN 202210374392A CN 114893315 B CN114893315 B CN 114893315B
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pressure
oil
fuel injection
fuel
injection quantity
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CN114893315A (en
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董全
周谈庆
王迪
杨晰宇
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Harbin Engineering University
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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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—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
    • 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
    • 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
    • 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

Abstract

The invention discloses a fuel injection quantity control system and a control method of a high-pressure common rail fuel injector. 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 (4) performing optimal control on the fuel injection quantity in the step 3 by predicting the performance of the system in a certain future time period through an MPC (MPC) model. The fuel injection quantity online measurement and control device is used for solving the problem that the fuel injection quantity cannot be accurately measured and controlled online.

Description

Injection quantity control system of high-pressure common rail fuel injector and MPC control method thereof
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 marine main engine or an auxiliary engine and always occupies an important position in national economy. With the increasing exhaustion of fossil fuels and the increasing deterioration of global environment, ships put higher demands on the dynamic, economic and environmental indexes 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 online 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 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 processor, an MPC control unit, a power supply unit and an upper computer;
the data acquisition unit is used for acquiring pressure sensor signals and needle valve lift sensor signals;
the signal amplification unit is used for amplifying the 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 data acquisition unit and the fuel system unit, 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 ipod3-3;
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 4-1.
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 (4) performing optimal control on the fuel injection quantity in the step 3 by predicting the performance of the system in a certain future time period through an MPC (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:
Figure GDA0003978417210000031
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.
In the control method, the step 3 is specifically,
when the fuel injection pulse width is short, the fuel 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:
Figure GDA0003978417210000032
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 the injection,the needle valve, however, does not move to its maximum during the injection process Limit position, fuel injection amountThe calculation is made by the following formula:
Figure GDA0003978417210000033
when the needle valve reaches the maximum limit position in the injection process, the fuel injection quantity is calculated according to the following formula;
Figure GDA0003978417210000034
/>
Figure GDA0003978417210000035
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 of the oil injector; Δ t is t 2 -t 1 ，t s As delay time, t c And t 3 At the closing time of the needle valve, t 1 The moment at which the needle valve just reaches maximum lift, t 2 The moment 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;
and 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 (3) 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:
Figure GDA0003978417210000041
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 the injector is in the system;
calculating A and B from the transfer function; reading the current system state x (k | k), and predicting the state of the future system by MPCMeasuring and recording the predicted system state variable X in the next N control periods k Comprises the following steps:
Figure GDA0003978417210000042
n is called the prediction horizon, (k + i | k) represents the system state at the current k time instant at which k + i is predicted. 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 :
Figure GDA0003978417210000051
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 form as follows:
X(k)＝Mx(k)+Cu(k)(11)
wherein:
Figure GDA0003978417210000052
in the control method, the step 4.2 is specifically to introduce a loss function, which is defined as:
Figure GDA0003978417210000053
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 k moment and a current system state variable x (k):
Figure GDA0003978417210000054
J＝x(k) T Gx(k)+U(k) T HU(k)+2x(k) T EU(k)(15)
Figure GDA0003978417210000055
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, in the step 4.3, specifically, the control output variable u (k) is only applied to the system, and when next optimization is performed, the state variables and the state input variables of the system are predicted again, so that rolling optimization is performed.
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 the measurement outside the cylinder.
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 block diagram of MPC control 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 below 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 processor, an MPC control unit, a power supply unit and an upper computer;
the data acquisition unit is used for acquiring pressure sensor signals and needle valve lift sensor signals;
the signal amplifying unit is used for amplifying the 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 data acquisition unit and the fuel system unit, 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 ipod3-3;
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 4-1.
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 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.
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:
Figure GDA0003978417210000081
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 injection pulse width is short as shown in fig. 1 (a), 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:
Figure GDA0003978417210000082
wherein W1 is left-going expansion wave generated by controlling cavity pressure relief, P test Is 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:
Figure GDA0003978417210000091
when the needle valve reaches the maximum limit position in the injection process, the fuel injection quantity is calculated according to the following formula;
Figure GDA0003978417210000092
Figure GDA0003978417210000093
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 of 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 (3) 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 follows:
Figure GDA0003978417210000094
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 MPC, recording the predicted system state variable X in the future N control cycles k Comprises the following steps:
Figure GDA0003978417210000101
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 :
Figure GDA0003978417210000102
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:
Figure GDA0003978417210000103
in the control method, the step 4.2 is specifically to introduce a loss function, which is defined as:
Figure GDA0003978417210000104
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 k moment and a current system state variable x (k):
Figure GDA0003978417210000111
J＝x(k) T Gx(k)+U(k) T HU(k)+2x(k) T EU(k)(15)
Figure GDA0003978417210000112
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 (9)

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 processor, an MPC control unit, a power supply unit and an upper computer;
the data acquisition unit is used for acquiring pressure sensor signals and needle valve lift sensor signals;
the signal amplification unit is used for amplifying the 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;
the upper computer (7) is used for loading an algorithm for converting inlet pressure into fuel injection quantity and an MPC control algorithm to the PXI processor, starting and closing the data acquisition unit and the fuel system unit, and monitoring the PXI processor in real time;
the fuel system unit comprises an oil pump (1-1), a motor (1-2), a high-pressure oil rail (1-3) and an oil injector (1-4), wherein 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 comprises a pressure sensor (2-1) and a needle valve lift sensor (2-2);
the MPC control unit 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 oil injector (1-4) through a charge amplifier (4-1).
2. The MPC control method of the on-line sensing-based high-pressure common rail fuel injector fuel injection quantity control system as recited in claim 1, wherein the control method comprises the steps of:
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;
and 2, step: 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.
3. The control method according to claim 2, wherein the step 2 is specifically that the direct relationship between the mass flow rate of change dG and the pressure rate of change dP is obtained by regarding the high-pressure common rail end as an isobaric reflection end, regarding the inlet pressure signal pressure fluctuation in the fuel system as a one-dimensional unsteady pipe flow, ignoring the friction force and the viscous influence of the fluid, according to the sound velocity equation and the conservation equation as follows:
Figure FDA0003978417200000021
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.
4. The control method according to claim 2, 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:
Figure FDA0003978417200000022
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:
Figure FDA0003978417200000023
when the needle valve reaches the maximum limit position in the injection process, the fuel injection quantity is calculated by the following formula;
Figure FDA0003978417200000031
Figure FDA0003978417200000032
wherein A is the inner diameter of the oil pipe, a is the current sound velocity of the fuel oil, and P 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 For the needle just leaving maximum liftThe time of the trip.
5. The control method according to claim 2, 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 (3) 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.
6. The control method according to claim 5, 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:
Figure FDA0003978417200000033
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 The coefficient of a 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:
Figure FDA0003978417200000041
n is called a prediction time domain, (k + i | k) represents the system state at the moment when k + i is predicted at the current moment k; 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 ；
Figure FDA0003978417200000042
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:
Figure FDA0003978417200000043
7. control method according to claim 5, characterized in that said step 4.2 consists in introducing a loss function defined as:
Figure FDA0003978417200000044
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 k moment and a current system state variable x (k):
Figure FDA0003978417200000051
J＝x(k) T Gx(k)+U(k) T HU(k)+2x(k) T EU(k)(15)
Figure FDA0003978417200000052
let the loss function go to the minimum and find u (k), u (k + 1), u (k + 2),. U (k + N) under this condition.
8. The control method according to claim 6, characterized in that 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.
9. The electronic equipment 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 the communication between the processor and the memory through the communication bus;
a memory for storing a computer program;
a processor for implementing the method steps of any of claims 2 to 8 when executing a program stored in the memory.
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