CN102562336B - Rail pressure control method for gasoline direct injection engine common rail fuel system - Google Patents

Abstract

The invention discloses a rail pressure control method for a gasoline direct injection engine common rail fuel system, which includes: the first step, building a mathematical model of the gasoline direct injection engine common rail fuel system, namely building a mathematical model of a high-pressure pump, then building a common rail mathematical model and finally building a mathematical model of a fuel injector; the second step, simplifying the mathematical model of the common rail fuel system; the third step, designing the control algorithm and regulating the form of the control algorithm on the basis of the mathematical model of the common rail fuel system; the fourth step, filtering by a rail pressure sensor and delaying signal transmission, namely acquiring rail pressure signals by an AD (analog-digital) passage of a single-chip microcomputer and removing individual error points and signal interference by the filter algorithm, and then designing signal tests for the rail pressure sensor (7); the fifth step, testing characteristics of a pressure control valve, converting the output of the control algorithm into action time of the pressure control valve, namely testing the characteristics of the pressure control valve (5) to acquire relation between the switching delay of the pressure control valve (5) and voltage of a vehicular storage battery and then building the relation between the opening angle of the pressure control valve (5) and the flow of the high-pressure pump (3).

Description

The rail pressure control method of directly jetting gasoline engine common rail fuel combustion system

Technical field

The present invention relates to a kind of controlling method that belongs to the engine electronic control system technical field, more particularly, the present invention relates to a kind of rail pressure control method of directly jetting gasoline engine common rail fuel combustion system.

Background technique

Car engine electronic control unit ECU (Electronic Control Unit) is one of motor core component that can work, the introducing of current various energy-conserving and emission-cutting technologies, make the function of ECU (Electrical Control Unit) more powerful, thereby greatly increased the ECU development difficulty, mainly contained following problem:

1. the introducing of various complicated electric control elements, increased the degree of coupling of each parts in the system, foundation calibration method in the past makes the development amount of ECU greatly increase, technology such as EGR EGR (Exhaust Gas Recirculation), Variable Valve Time VVT (Variable Valve Timing), gasoline in-cylinder direct injection GDI (Gasoline Direct Injection);

2.ECU conventional development process needs a large amount of experience and rating test, workload is large, and the artificial subjective factor impact is larger, and system development cycle is longer;

3. the interference rejection ability that demarcation control algorithm out shows for factors such as parameter uncertainties is difference to some extent.

The present invention is mainly for the development process of taking as the leading factor with rating test and experience in routine, the electrical control unit of petrol engine development process of take based on model is thinking, on the basis of setting up in-cylinder direct fuel-injection engine common rail fuel combustion system nonlinear mathematical model, the application controls Theoretical Design has been developed corresponding non-linear rail pressure control algorithm, thereby can reduce calibration process too much in the ECU development process, and according to the theoretical property analysis, can strengthen the robustness of rail pressure control algorithm, for the system external disturbance, inhibitory action preferably be arranged.

Be similarly and solved the difficulty run in the Engine ECU development process, had now some to be directed to the development plan of motor rail pressure control problem moulding:

China Patent Publication No. CN102062007, open day is on May 18th, 2011, and number of patent application is 201010601766.7, and patent name is " the rail pressure control method of motor and rail pressure pre-control method and system ".A kind of controlling method of common rail for diesel engine pressure has been described in patent application.At first the target rail pressure is divided into to some grades in the method, and determine corresponding current reference value by the upper and lower of each rate range, can determine current current reference value according to the scope at target rail pressure place thus, and with this electric current, common rail pressure is carried out to pre-control, then with rotating speed and fuel injection quantity, the pressure control of common rail system signal is revised.The method can be improved controlling effect preferably, but the prerequisite of exploitation needs a large amount of Experimental Calibration data too.

China Patent Publication No. CN101968018A, open day is on February 9th, 2011, and number of patent application is 201010252161.1, and name of patent application is " controlling method of rail pressure in diesel injector monitor station common rail system and system thereof ".Adopted (Proportional-Integral-Derivative in patent application, being proportion integration differentiation) PID is as feedback control algorithm, and the differential term in algorithm is carried out to Fuzzy processing, make related algorithm can adapt to the adjusting requirement of different phase.Although the method is introduced Fuzzy Thought on the basis of original pid control algorithm, improved to a certain extent the robustness of system, but the method is not considered structure and the characteristics of common rail fuel combustion system in more detail, increased like this adjusting difficulty of control algorithm parameter.

Traditional control algorithm majority is not based on model, the development process of electronic control unit ECU depends on a large amount of experiences and experiment more, and for common rail fuel combustion system such high non-linearity system, comparatively suitable nonlinear control algorithm can overcome non-linear brought fluctuation better.

In the research and practice process to the method, the present inventor finds: through directly jetting gasoline engine common rail fuel combustion system structural feature is analyzed, take fluid mechanics equation as basis, build the common rail fuel combustion system nonlinear model, its model feature comparatively is applicable to, by the feedback linearization method control algorithm of deriving, providing thus second nonlinear feedback rail pressure control method.

Summary of the invention

Technical problem to be solved by this invention is to have overcome the problem that prior art exists, and a kind of rail pressure control method of directly jetting gasoline engine common rail fuel combustion system is provided.

For solving the problems of the technologies described above, the present invention adopts following technological scheme to realize: the step of the rail pressure control method of described directly jetting gasoline engine common rail fuel combustion system is as follows:

1. set up the mathematical model of directly jetting gasoline engine common rail fuel combustion system:

(1) set up the high-pressure service pump mathematical model:

${\stackrel{\·}{p}}_p=\frac{K_f}{v_p\left(\mathrm{\θ}\right)}(A_p\·{\mathrm{\ω}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\θ}}-\mathrm{sgn})(P_t-p_p)\·c_{\mathrm{tp}}\·(U\·A_{\mathrm{tp}})\·\sqrt{\frac{2|P_t-p_p|}{\mathrm{\ρ}}}$ (11)

$-\mathrm{sgn}(p_p-p_r)\·c_{\mathrm{pr}}\·A_{\mathrm{pr}}\·\sqrt{\frac{2|p_p-p_r|}{\mathrm{\ρ}}}-q_0)$

Wherein: p _p. pressure in the high pressure pump chamber, unit, Pa; K _f. the volumetric modulus of elasticity of fuel oil, unit, Pa; θ. cam angle, unit, rad; v _p(θ). high-pressure service pump volume, unit, m ³; A _p. high-pressure service pump plunger sectional area, unit, m ²; ω _rpm. cam rotating speed, unit, r/min; h _p. ram lift, unit, m; P _t. low-pressure electric fuel pump outlet oil pressure, unit, Pa; A _tp. high-pressure service pump oiler sectional area, unit, m ²; c _tp. flow coefficient; The switch controlled quentity controlled variable of U pressure controlled valve, be 0 or 1, and the expression pressure controlled valve is opened and closed condition; Sgn (). mean the sign function that fuel oil flows to; ρ. the density of fuel oil, unit, kg/m ³; p _r. be total to fuel pressure in rail, unit, Pa; A _pr. be total to rail end oiler sectional area, unit, m ²; c _pr. flow coefficient; q ₀. gap oil leakage amount between plunger and plunger cavity, unit, m ³/ s.

(2) set up rail mathematical model altogether:

${\stackrel{\·}{p}}_r=\frac{K_f}{V_r}(\mathrm{sgn}(p_p-p_r)\·c_{\mathrm{pr}}\·A_{\mathrm{pr}}\·\sqrt{\frac{2|p_p-p_r|}{\mathrm{\ρ}}}-\mathrm{sgn}(p_r-p_i)\·c_{\mathrm{ri}}\·A_{\mathrm{ri}}\·\sqrt{\frac{2|p_r-p_i|}{\mathrm{\ρ}}})---\left(14\right)$

Wherein: V _r. be total to the rail volume, unit, m ³; p _i. fuel pressure in oil sprayer, unit, Pa; A _ri. oil sprayer oiler sectional area, unit, m ²; c _ri. oil sprayer entry end flow coefficient.

(3) set up the oil sprayer mathematical model:

${\stackrel{\·}{p}}_{\mathrm{ik}}=\frac{K_f}{V_{\mathrm{ik}}}(\mathrm{sgn}(p_r-p_{\mathrm{ik}})\·c_{\mathrm{rik}}\·A_{\mathrm{rik}}\·\sqrt{\frac{2|p_r-p_{\mathrm{ik}}|}{\mathrm{\ρ}}}-\mathrm{sgn}(p_{\mathrm{ik}}-p_{\mathrm{cylk}})\·E_{\mathrm{Tk}}\·c_{\mathrm{ik}}\·A_{\mathrm{ik}}\·\sqrt{\frac{2|p_{\mathrm{ik}}-p_{\mathrm{cylk}}|}{\mathrm{\ρ}}})---\left(18\right)$

Wherein: the k in lower footnote means the sequence number of oil sprayer, and k gets 1,2,3 or 4; p _ik. fuel pressure in k oil sprayer, unit, Pa; A _rik. k oil sprayer oiler sectional area, unit, m ²; c _rik. k oil sprayer entry end flow coefficient; p _cylk. k inner pressure of air cylinder, unit, Pa; V _ik. k oil sprayer cavity volume, unit, m ³; A _ik. k oil sprayer spray orifice sectional area, unit, m ²; c _ik. k oil sprayer spray orifice flow coefficient; E _tk. k fuel injection pulsewidth, when the oil sprayer oil spout, its value is 1, other situation is 0.

2. simplify the mathematical model of common rail fuel combustion system:

$\left\{\begin{array}{c}{\stackrel{\·}{x}}_1=\frac{K_f}{v_p\left(\mathrm{\θ}\right)}(A_p\·{\mathrm{\ω}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\θ}}+u-a_2\·\sqrt{x_1-x_2}-q_0)\\ {\stackrel{\·}{x}}_2=\frac{K_f}{V_f}(a_2\·\sqrt{x_1-x_2}-q_{\mathrm{ri}})\end{array}\right.---\left(25\right)$

Wherein: choose respectively fuel pressure p in high-pressure service pump _preach the interior fuel pressure p of rail altogether _rstate variable x for common rail fuel combustion system ₁and x ₂; k _f. the volumetric modulus of elasticity of fuel oil, unit, Pa; θ. cam angle, unit, rad; v _p(θ). high-pressure service pump volume, unit, m ³; A _p. high-pressure service pump plunger sectional area, unit, m ²; ω _rpm. cam rotating speed, unit, r/min; h _p. ram lift, unit, m; U is controlled quentity controlled variable, i.e. the fuel flow of high-pressure service pump ingress, unit, m ³/ s,

u means the switch controlled quentity controlled variable of pressure controlled valve, and it is 0 or 1, and the expression valve body is opened and closed condition; P _t. low-pressure electric fuel pump outlet oil pressure, unit, Pa; Variable a ₁be expressed as

a _tp. high-pressure service pump oiler sectional area, unit, m ², c _tp. flow coefficient, variable a ₂be expressed as

a _pr. be total to rail end oiler sectional area, unit, m ², c _prfor flow coefficient, ρ. the density of fuel oil, unit, kg/m ³; q ₀. gap oil leakage amount between plunger and plunger cavity, unit, m ³/ s; q _ri. common rail fuel combustion system fuel injection quantity, unit, m ³/ s.

3. based on common rail fuel combustion system model design control algorithm and arrange the control algorithm form:

$u=\left\{\begin{array}{cc}A\left(z\right)+B(x_2-x_{2d})+C({\stackrel{\·}{x}}_2-{\stackrel{\·}{x}}_{2d})& x_1\≠x_2\\ q_0-A_p\·{\mathrm{\ω}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\θ}}& x_1=x_2\end{array}\right.---\left(57\right)$

In formula:

$A\left(z\right)=-A_p{\mathrm{\&omega;}}_{\mathrm{rpm}}\&CenterDot;\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}\&CenterDot;+(\frac{v_p\left(\mathrm{\&theta;}\right)}{V_r}+1)\&CenterDot;a_2\&CenterDot;z+q_0-\frac{v_p\left(\mathrm{\&theta;}\right)}{V_r}\&CenterDot;q_{\mathrm{ri}}+\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{{{\mathrm{<figure-callout\; id="2"\; label="K\; f"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">K</figure-callout>}}_f}^2\&CenterDot;a_2}\&CenterDot;{\stackrel{\&CenterDot;\&CenterDot;}{x}}_{2d}---\left(49\right)$

$B=-\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{{{\mathrm{<figure-callout\; id="2"\; label="k\; f"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">k</figure-callout>}}_f}^2\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="a"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">a</figure-callout>}}_2}\&CenterDot;k_1---\left(50\right)$

$C=-\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{K_f\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="a"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">a</figure-callout>}}_2}\&CenterDot;k_2---\left(51\right)$

Wherein: the u. controlled quentity controlled variable is the fuel flow of high-pressure service pump ingress, unit, m ³/ s; A _p. high-pressure service pump plunger sectional area, unit; ω _rpm. cam rotating speed, unit, r/min; h _p. ram lift, unit, m; θ. cam angle, unit, rad; v _p(θ). high-pressure service pump volume, unit, m ³; V _r. be total to the rail volume, unit, m ³; Variable a ₂be expressed as

a _pr. be total to rail end oiler sectional area, unit, m ², c _pr. flow coefficient; q ₀. gap oil leakage amount between plunger and plunger cavity, unit, m ³/ s; q _ri. common rail fuel combustion system fuel injection quantity, unit, m ³/ s; K _f. the volumetric modulus of elasticity of fuel oil, unit, Pa; k ₁and k ₂. control law parameter, x ₁. the state variable of fuel pressure in high-pressure service pump, unit, Pa; x ₂. be total to the state variable of fuel pressure in rail, unit, Pa; x _2d. expectation rail pressure, unit, Pa; State variable

4. rail pressure sensor filtering and signal transmission delay are processed:

A. 10 rail pressure signals of AD passage collection by single-chip microcomputer do on average, adopt filtering algorithm to remove discrete error point and signal interference.

B. design rail pressure sensor (7) signal and measure test, and carry out data and measure and process, signal transmission and response time delay are thought of as to the delay τ of first order inertial loop, build hardware cell and overcome rail pressure sensor (7) time delay.

5. measure the pressure controlled valve characteristic output of control algorithm be converted to the pressure controlled valve action constantly:

A. experiment measures pressure controlled valve (5) characteristic, obtains the relation of pressure controlled valve (5) switch motion time delay and vehicular power-bottle voltage.

B. the relation of build-up pressure control valve (5) opening angle and high-pressure service pump (3) influent stream amount by experiment, be formula by designed control law $u=\left\{\begin{array}{cc}A\left(z\right)+B(x_2-x_{2d})+C({\stackrel{\&CenterDot;}{x}}_2-{\stackrel{\&CenterDot;}{x}}_{2d})& x_1\&NotEqual;x_2\\ q_0-A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}& x_1=x_2\end{array}\right.$ Change the action of actual pressure controlled valve (5) into, realize the real-time control of rail (8) internal pressure altogether;

In formula:

$A\left(z\right)=-A_p{\mathrm{\&omega;}}_{\mathrm{rpm}}\&CenterDot;\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+(\frac{v_p\left(\mathrm{\&theta;}\right)}{V_r}+1)\&CenterDot;a_2\&CenterDot;z+q_0-\frac{v_p\left(\mathrm{\&theta;}\right)}{V_r}\&CenterDot;q_{\mathrm{ri}}+\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{{{\mathrm{<figure-callout\; id="2"\; label="K\; f"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">K</figure-callout>}}_f}^2\&CenterDot;a_2}\&CenterDot;{\stackrel{\&CenterDot;\&CenterDot;}{x}}_{2d}---\left(49\right)$

$B=-\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{{{\mathrm{<figure-callout\; id="2"\; label="k\; f"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">k</figure-callout>}}_f}^2\&CenterDot;a_2}\&CenterDot;k_1---\left(50\right)$

$C=-\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{K_f\&CenterDot;a_2}\&CenterDot;k_2---\left(51\right)$

Wherein: the u. controlled quentity controlled variable is the fuel flow of high-pressure service pump ingress, unit, m ³/ s; A _p. high-pressure service pump plunger sectional area, unit; ω _rpm. cam rotating speed, unit, r/min; h _p. ram lift, unit, m; θ. cam angle, unit, rad; v _p(θ). high-pressure service pump volume, unit, m ³; V _r. be total to the rail volume, unit, m ³; Variable a ₂be expressed as

a _prbe total to rail end oiler sectional area, unit, m ², c _pr. flow coefficient; q ₀. gap oil leakage amount between plunger and plunger cavity, unit, m ³/ s; q _ri. common rail fuel combustion system fuel injection quantity, unit, m ³/ s; K _f. the volumetric modulus of elasticity of fuel oil, unit, Pa; k ₁and k ₂. control law parameter, x ₁. the state variable of fuel pressure in high-pressure service pump, unit, Pa; x ₂. be total to the state variable of fuel pressure in rail, unit, Pa; x _2d. expectation rail pressure, unit, Pa; State variable

Compared with prior art the invention has the beneficial effects as follows:

1. the directly jetting gasoline engine common rail fuel combustion system has larger wave properties and parameter uncertainty (for example, fuel leakage when the plunger pump in high-pressure service pump is oily has stronger uncertainty), non-linear rail pressure algorithm in the present invention has been considered the uncertainty of common rail fuel combustion system in derivation, promoted well the robustness of common rail fuel combustion system when having guaranteed well common rail fuel combustion system stability, had and control preferably effect.

2. be established to concrete scheme from model and realize, the rail pressure control method of directly jetting gasoline engine common rail fuel combustion system of the present invention has been described the non-linear rail pressure control method of directly jetting gasoline engine and implementation method in kind more all sidedly, has practicability.

3. will to take modeling and parameter matching be working contents to the rail pressure control method of directly jetting gasoline engine common rail fuel combustion system of the present invention, when parameter measures, through data, processes, and by making, the parameter usability of acquisition is stronger.

3. the rail pressure control method of directly jetting gasoline engine common rail fuel combustion system of the present invention is compared the control unit of engine development plan of tradition based on Experimental Calibration and has been reduced the workload that the lot of experiments process is brought, thereby has reduced the cost in real engine control unit development process.

The accompanying drawing explanation

Below in conjunction with accompanying drawing, the present invention is further illustrated:

Fig. 1 is the FB(flow block) of the rail pressure control method of directly jetting gasoline engine common rail fuel combustion system of the present invention;

Fig. 2 is that the directly jetting gasoline engine common rail fuel combustion system structure of implementing the rail pressure control method of directly jetting gasoline engine common rail fuel combustion system of the present invention forms and the schematic block diagram of principle;

Fig. 3 is the rail pressure control theory diagram based on feedback linearization in the rail pressure control method of directly jetting gasoline engine common rail fuel combustion system of the present invention;

Fig. 4 is the schematic diagram of implementing the directly jetting gasoline engine common rail fuel combustion system mesohigh pump work principle that the rail pressure control method of directly jetting gasoline engine common rail fuel combustion system of the present invention adopts;

Fig. 5 is that the rail pressure control method of implementing directly jetting gasoline engine common rail fuel combustion system of the present invention realizes block diagram under the simulink simulated environment;

Fig. 6 is that the feedback linearization rail pressure control algorithm simulink simulation result I of the rail pressure control method of employing directly jetting gasoline engine common rail fuel combustion system of the present invention is the figure as a result of steady track;

Fig. 7 is that the feedback linearization rail pressure control algorithm simulink simulation result I shown in Fig. 6 is steady track 0.1 second partial enlarged drawing to 0.15 second time period in figure as a result;

Fig. 8 is that the feedback linearization rail pressure control algorithm simulink simulation result II of the rail pressure control method of employing directly jetting gasoline engine common rail fuel combustion system of the present invention is the figure as a result of sinusoidal tracking;

Fig. 9 is that the feedback linearization rail pressure control algorithm simulink simulation result II shown in Fig. 8 is sinusoidal tracking 1.4 seconds partial enlarged drawings to 1.6 second time period in figure as a result;

In figure: 1. fuel tank, 2. cam, 3. high-pressure service pump, 4. one-way valve, 5. pressure controlled valve, 6. oil sprayer, 7. rail pressure sensor, 8. rail, 9. pressure-limit valve, 10. low-pressure electric fuel pump altogether.

Embodiment

Below in conjunction with accompanying drawing, the present invention is explained in detail:

Consult Fig. 2, the invention provides a kind of rail pressure control method of directly jetting gasoline engine common rail fuel combustion system, can reach rail pressure control effect preferably.Common rail fuel combustion system is as the of paramount importance constituent element of directly jetting gasoline engine fuel oil supply system, its mechanism and characteristics make the directly jetting gasoline engine injection pressure can reach 150～200bar, and injection pressure can be independent of the directly jetting gasoline engine rotating speed, also can obtain oil spout effect preferably when directly jetting gasoline engine under the slow-speed of revolution.Directly jetting gasoline engine common rail fuel combustion system basic structure includes fuel tank 1, cam 2, high-pressure service pump 3, one-way valve 4, pressure controlled valve 5, oil sprayer 6, rail pressure sensor 7, is total to rail 8, pressure-limit valve 9, low-pressure electric fuel pump 10 and electronic control unit ECU.

The directly jetting gasoline engine common rail fuel combustion system has larger difference for the motor of traditional intake port injection, and its specific works principle is as follows: at first low-pressure electric fuel pump 10 produces about 3～5kg/cm ²fuel oil, flow to high-pressure service pump 3 through pressure controlled valve 5, produce 50～120kg/cm through high-pressure service pump 3 ²high pressure fuel flow into rail 8 altogether.Rail 8 is in order to absorb the pulsation of high pressure fuel, usually certain volume will to be arranged altogether, and is made by aluminum alloy.Rail 8 connects oil sprayer 6 altogether, and rail 8 provides high pressure fuel for oil sprayer 6 altogether.Rail pressure sensor 7 Real-Time Monitorings are the interior oil pressure of rail 8 altogether, and feeds back to control unit ECU, sends control command by control unit ECU and acts on pressure controlled valve 5, the final adjusting that realizes being total to rail 8 interior oil pressure.Another effect of control unit ECU is to send the oil spout that oil sprayer 6 is controlled in the fuel injection pulsewidth instruction.High-pressure service pump 3 is arranged near common rail 8, and rail pressure sensor 7 and oil sprayer 6 are arranged on common rail 8, on rail 8, pressure-limit valve 9 also is installed altogether, for the protection of common rail 8, is unlikely to be damaged by too high pressure.High-pressure service pump 3 is to realize lubricated sneaking in fuel oil when preventing additional oil lubrication with fuel oil itself.For the normal operation of assurance system, high-pressure service pump 3 outlet end need to add one-way valve 4, to prevent fuel oil, flow backwards.

The step of the rail pressure control method of directly jetting gasoline engine common rail fuel combustion system of the present invention is as follows:

1. set up the mathematical model of directly jetting gasoline engine common rail fuel combustion system

Form structure and performance characteristic in conjunction with the directly jetting gasoline engine common rail fuel combustion system, according to the fluid mechanics relevant knowledge, set up the common rail fuel combustion system mathematical model, mainly consider high-pressure service pump 3 in the common rail fuel combustion system mathematical model, be total to rail 8 and oil sprayer 6.Common rail fuel combustion system modeling basic principle is as follows:

For a compressible liquid, its volumetric modulus of elasticity K _f(Pa) definition can be written as following form:

$K_f=-\frac{\mathrm{dp}}{\mathrm{d\&rho;}/\mathrm{\&rho;}}---\left(1\right)$

This physical quantity has been described the variable density situation of liquid correspondence under the different pressures state, in the directly jetting gasoline engine common rail fuel combustion system, means the state of fuel density under different pressures.Wherein: the pressure that p is liquid (Pa), the density (kg/m that ρ is liquid ³).From definition, if in selected container, the fuel oil of a constant volume is as research object, according to mass conservation law, in its chamber, the fuel flow of the pressure change rate of fuel oil and inflow and outflow has definite relation,

$K_f=-\frac{\mathrm{dp}}{\mathrm{dv}/v}---\left(2\right)$

Wherein: v is fuel oil volume (m ³), (2) formula is out of shape to conversion, obtain formula (3), can be expressed as formula (4) thereby can obtain fuel pressure variance ratio in chamber, wherein dv/dt is fuel oil flow change rate in cavity, thus the formula of obtaining (5):

$K_f=-\frac{\mathrm{dp}}{\mathrm{dt}}\&CenterDot;\frac{\mathrm{dt}}{\mathrm{dv}}\&CenterDot;v---\left(3\right)$

$\frac{\mathrm{dp}}{\mathrm{dt}}=-\frac{K_f}{v}\&CenterDot;\frac{\mathrm{dv}}{\mathrm{dt}}---\left(4\right)$

$\frac{\mathrm{dp}}{\mathrm{dt}}=-\frac{K_f}{v}\&CenterDot;(\frac{\mathrm{dm}}{\mathrm{dt}}-q_{\mathrm{in}}+q_{\mathrm{out}})---\left(5\right)$

Wherein: dm/dt is that due to Volume Changes, caused fluid flow changes (m to fuel chamber ³/ s), q _in, q _outbe respectively volume chamber ingress fuel flow (m ³/ s) and outlet port fuel flow (m ³/ s).For common rail fuel combustion system, the fuel flow that flows through a cross section is relevant with the pressure difference at sectional area and two ends, and concrete form can be expressed as formula (6):

$q=\mathrm{sgn}\left(\mathrm{\&delta;p}\right)\&CenterDot;c_d\&CenterDot;A_0\&CenterDot;\sqrt{\frac{2\left|\mathrm{\&delta;p}\right|}{\mathrm{\&rho;}}}---\left(6\right)$

Wherein: δ p is cross section pressure at two ends poor (Pa), A ₀for sectional area (m ²), c _dfor flow coefficient, the hole shape that its size is passed through with fuel oil is relevant, the sign function of sgn (δ p) for meaning that fuel oil flows to.Choose successively high-pressure service pump 3, common rail 8 and oil sprayer 6 as main study subject according to above-mentioned principle thus, set up the fuel pressure equation, modeling procedure is as follows:

(1) set up the high-pressure service pump mathematical model

Consult Fig. 4, common rail fuel combustion system mesohigh pump 3 is the cammingly structure.During work, driven by engine cam 2 rotates (velocity ratio is 2: 1), concrete working principle is as follows: when the cam of high-pressure service pump 3 turns to lower dead center by top dead center, plunger moves downward, due to pressure difference, fuel oil flows into high-pressure service pumps 3 by high-pressure service pump 3 entrances, because there is one-way valve 4 at filler opening and oil outlet place, so now the oil outlet place does not have fuel oil and flows backwards; On the contrary, when cam 2 turns to top dead center by lower dead center, fuel oil only can be by the outside fuel feeding of high-pressure service pump 3.Consider fuel flow pressure equation (5), high-pressure service pump internal pressure concrete form is suc as formula (7):

${\stackrel{\&CenterDot;}{p}}_p=\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}(\frac{\mathrm{dm}}{\mathrm{dt}}+q_u-q_{\mathrm{pr}}-q_0)---\left(7\right)$

Wherein: p _pfor pressure (Pa) in the high pressure pump chamber, θ is cam angle (rad), q _ufor high-pressure service pump inlet flow rate (m ³/ s), q _proil pump capacity (m for pump ³/ s), q ₀for gap oil leakage amount (m between plunger and plunger cavity ³/ s), the inflow flow (m that dm/dd is fuel oil ³/ s).V _p(θ) be high-pressure service pump volume (m ³), it is the function of cam angle θ, concrete form is v _p(θ)=V _p ⁰-A _ph _p(θ), A _pfor high-pressure service pump plunger sectional area (m ²), h _pfor ram lift (m), V _p ⁰for high-pressure service pump cavity total volume (m ³).Can arrange dm/dt, q according to formula (6) _uand q _prconcrete form suc as formula (8), (9) and (10):

$\frac{\mathrm{dm}}{\mathrm{dt}}=A_p\&CenterDot;\frac{{\mathrm{dh}}_p}{\mathrm{dt}}=A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\&CenterDot;\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}---\left(8\right)$

$q_u=\mathrm{sgn}(P_t-p_p)\&CenterDot;c_{\mathrm{tp}}\&CenterDot;(U\&CenterDot;A_{\mathrm{tp}})\&CenterDot;\sqrt{\frac{2|P_t-p_p|}{\mathrm{\&rho;}}}---\left(9\right)$

$q_{\mathrm{pr}}=\mathrm{sgn}(p_p-p_r)\&CenterDot;c_{\mathrm{pr}}\&CenterDot;A_{\mathrm{pr}}\&CenterDot;\sqrt{\frac{2|p_p-p_r|}{\mathrm{\&rho;}}}---\left(10\right)$

Wherein: ω _rpmfor cam rotating speed (r/min), P _tfor low-pressure electric fuel pump outlet oil pressure (Pa), A _tpfor high-pressure service pump oiler sectional area (m ²), c _tpfor high-pressure service pump 3 entry end flow coefficients, U means the controlled quentity controlled variable of pressure controlled valve, and it is 0 or 1, and the expression valve body is opened and closed condition, p _rfor fuel pressure (Pa) in common rail, A _prfor common rail end oiler sectional area (m ²), c _prfor flow coefficient.Formula (8), (9) and (10) are brought into to formula (7) and can be obtained high-pressure service pump 3 mathematical models suc as formula (11).

${\stackrel{\&CenterDot;}{p}}_p=\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}(A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}-\mathrm{sgn}(P_t-p_p)\&CenterDot;c_{\mathrm{tp}}(U\&CenterDot;A_{\mathrm{tp}})\&CenterDot;\sqrt{\frac{2|P_t-p_p|}{\mathrm{\&rho;}}})---\left(11\right)$

$-\mathrm{sgn}(p_p-p_r)\&CenterDot;c_{\mathrm{pr}}\&CenterDot;A_{\mathrm{pr}}\&CenterDot;\sqrt{\frac{2|p_p-p_r|}{\mathrm{\&rho;}}}-q_0)$

(2) set up rail mathematical model altogether

Rail 8 is as an oil storage element altogether, and its Main Function is so that the oil pressure of oil circuit part is stable, to reduce pressure fluctuation.Briefly, rail 8 is exactly a pressurized container with a constant volume altogether.The left side of rail 8 is equipped with rail pressure sensor 7 altogether, and the bottom of rail 8 is equipped with pressure-limit valve 9 altogether, and pressure-limit valve 9 is opened pressure release when the interior oil pressure of common rail 8 is excessive, to protect common rail 8.When common rail 8 enters oil mass, be that high-pressure service pump 3 is supplied with the oil mass of rail 8 altogether, when oil pump capacity is supplied with the oil mass of oil sprayers 6 for being total to rail 8, according to fuel flow pressure equation (5), the model of rail 8 correspondences can be established as formula (12) altogether, now rail 8 does not have Volume Changes altogether, so do not consider because the caused fuel flow of common rail 8 Volume Changes changes:

${\stackrel{\&CenterDot;}{p}}_r=\frac{K_f}{V_r}(q_{\mathrm{pr}}-q_{\mathrm{ri}})---\left(12\right)$

Wherein: p _rfor common rail fuel pressure (Pa), V _rfor common rail volume (m ³), q _rifor the fuel flow (m of common rail to oil sprayer ³/ s), for common rail 8, the fuel flow that high-pressure service pump 3 flows out is and flows into the fuel flow q of rail 8 altogether _pr, cotype (10), and, according to formula (6), flow into the fuel flow form of oil sprayer 6 suc as formula shown in (13):

$q_{\mathrm{ri}}=\mathrm{sgn}(p_r-p_i)\&CenterDot;c_{\mathrm{ri}}\&CenterDot;A_{\mathrm{ri}}\&CenterDot;\sqrt{\frac{2|p_r-p_i|}{\mathrm{\&rho;}}}---\left(13\right)$

Wherein: p _ifor fuel pressure in oil sprayer (Pa), A _rifor oil sprayer end oiler sectional area (m ²), c _rifor oil sprayer entry end flow coefficient, bring formula (10) and (13) into formula (12) and can be total to rail 8 fuel pressure equations suc as formula (14).

${\stackrel{\&CenterDot;}{p}}_r=\frac{K_f}{V_r}(\mathrm{sgn}(p_p-p_r)\&CenterDot;c_{\mathrm{pr}}\&CenterDot;A_{\mathrm{pr}}\&CenterDot;\sqrt{\frac{2|p_p-p_r|}{\mathrm{\&rho;}}}-\mathrm{sgn}(p_r-p_i)\&CenterDot;c_{\mathrm{ri}}\&CenterDot;A_{\mathrm{ri}}\&CenterDot;\sqrt{\frac{2|p_r-p_i|}{\mathrm{\&rho;}}})---\left(14\right)$

(3) set up the oil sprayer mathematical model

Oil sprayer 6 is that oil burning jet enters the device of cylinder the most at last, is the final final controlling element of common rail fuel combustion system.In oil sprayer 6 chambeies, fuel oil is as controlled device, first consider single oil spout dynamic characteristic, when entering oil mass, oil sprayer 8 supplies with the oil mass of oil sprayers 8 for being total to rail 8, oil pump capacity is that oil sprayer 8 is while being ejected into the oil mass in cylinder, according to fuel flow pressure equation (5), the model of oil sprayer 8 correspondences can be established as formula (15), and now oil sprayer 6 does not have Volume Changes, so do not consider because the caused fuel flow of oil sprayer 6 Volume Changes changes:

${\stackrel{\&CenterDot;}{p}}_i=\frac{K_f}{V_i}(q_{\mathrm{ri}}-q_{\mathrm{inj}})---\left(15\right)$

Wherein: V _ifor oil sprayer cavity volume (m ³), q _injfuel injection quantity (m for oil sprayer ³/ s).For oil sprayer, the fuel flow that rail 8 flows out altogether is the fuel flow q that flows into oil sprayer 6 _ri, cotype (13), and, according to formula (6), the fuel injection quantity of oil sprayer 6 is suc as formula shown in (16):

$q_{\mathrm{inj}}=\mathrm{sgn}(p_i-p_{\mathrm{cyl}})\&CenterDot;E_T\&CenterDot;c_i\&CenterDot;A_i\&CenterDot;\sqrt{\frac{2|p_i-p_{\mathrm{cyl}}|}{\mathrm{\&rho;}}}---\left(16\right)$

Wherein: p _cylfor inner pressure of air cylinder (Pa), A _ifor oil sprayer spray orifice sectional area (m ²), c _ifor oil sprayer spray orifice flow coefficient, E _tfor fuel injection pulsewidth, when the oil sprayer oil spout, its value is 1, and other situation is 0.

The above result for only considering that single oil sprayer 6 obtains.If consider four cylinder direct injection petrol engine, the q in formula (12) _injbe four oil sprayer fuel injection quantity sums, shown in (17):

$q_{\mathrm{ri}}=q_{\mathrm{ril}}+{\mathrm{<figure-callout\; id="2"\; label="q\; ri"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">q</figure-callout>}}_{\mathrm{ri}}+q_{\mathrm{ri}3}+{\mathrm{<figure-callout\; id="4"\; label="q\; ri"\; filenames="HDA0000133556400000062.png"\; state="\{\{state\}\}">q</figure-callout>}}_{\mathrm{ri}}=\underset{k=1}{\overset{4}{\mathrm{\&Sigma;}}}\mathrm{sgn}(p_r-p_{\mathrm{ik}})\&CenterDot;c_{\mathrm{rik}}\&CenterDot;A_{\mathrm{rik}}\&CenterDot;\sqrt{\frac{2|p_{\mathrm{rk}}-p_{\mathrm{ik}}|}{\mathrm{\&rho;}}}---\left(17\right)$

Wherein: the k in lower footnote means the sequence number of oil sprayer, and k gets 1,2,3 or 4.

And for pressure and fuel injection quantity in the chamber of each oil sprayer, corresponding form is arranged, take k oil sprayer for example, as example (,, when k=1, being expressed as first oil sprayer), bring formula (13) and (16) into formula (15), formula (18), (19) are arranged.

${\stackrel{\&CenterDot;}{p}}_{\mathrm{ik}}=\frac{K_f}{V_{\mathrm{ik}}}(\mathrm{sgn}(p_r-p_{\mathrm{ik}})\&CenterDot;c_{\mathrm{rik}}\&CenterDot;A_{\mathrm{rik}}\&CenterDot;\sqrt{\frac{2|p_r-p_{\mathrm{ik}}|}{\mathrm{\&rho;}}}-\mathrm{sgn}(p_{\mathrm{ik}}-p_{\mathrm{cylk}})\&CenterDot;E_{\mathrm{Tk}}\&CenterDot;c_{\mathrm{ik}}\&CenterDot;A_{\mathrm{ik}}\&CenterDot;\sqrt{\frac{2|p_{\mathrm{ik}}-p_{\mathrm{cylk}}|}{\mathrm{\&rho;}}})---\left(18\right)$

$q_{\mathrm{injk}}=\mathrm{sgn}(p_{\mathrm{ik}}-p_{\mathrm{cylk}})\&CenterDot;c_{\mathrm{ik}}\&CenterDot;A_{\mathrm{ik}}\&CenterDot;\sqrt{\frac{2|p_{\mathrm{ik}}-p_{\mathrm{cylk}}|}{\mathrm{\&rho;}}}---\left(19\right)$

Wherein: the k in lower footnote means the sequence number of oil sprayer, and k gets 1,2,3 or 4; p _cylkbe k inner pressure of air cylinder (Pa), V _ikbe k oil sprayer cavity volume (m ³), A _ikbe k oil sprayer spray orifice sectional area (m ²), c _ikbe k oil sprayer spray orifice flow coefficient, E _tkbe k fuel injection pulsewidth, when the oil sprayer oil spout, its value is 1, and other situation is 0, q _injkbe the fuel injection quantity (m of k oil sprayer ³/ s), p _ikit is fuel pressure (Pa) in k oil sprayer.

2. simplify the mathematical model of common rail fuel combustion system

For the application controls theory realizes the design of control algorithm, for the directly jetting gasoline engine common rail fuel combustion system mathematical model of setting up, simplified, wherein need to consider the depression of order of model and the adjustment of state variable.Detailed process is as follows:

Consider whole directly jetting gasoline engine common rail fuel combustion system pressure state (high-pressure service pump 3, common rail 8 and four oil sprayers 6), convolution (11), (14) and (18), the mathematical model of setting up in the 1st step can be written as:

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{p}}_p=\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}(A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+\mathrm{sgn}(P_t-p_p)\&CenterDot;c_{\mathrm{tp}}\&CenterDot;(U\&CenterDot;A_{\mathrm{tp}})\&CenterDot;\sqrt{\frac{2|P_t-p_p|}{\mathrm{\&rho;}}}\\ -\mathrm{sgn}(p_p-p_r)\&CenterDot;c_{\mathrm{pr}}\&CenterDot;A_{\mathrm{pr}}\&CenterDot;\sqrt{\frac{2|p_p-p_r|}{\mathrm{\&rho;}}}-q_0)\\ {\stackrel{\&CenterDot;}{p}}_r=\frac{K_f}{V_r}(\mathrm{sgn}(p_p-p_r)\&CenterDot;c_{\mathrm{pr}}\&CenterDot;A_{\mathrm{pr}}\&CenterDot;\sqrt{\frac{2|p_p-p_r|}{\mathrm{\&rho;}}}-\underset{k=1}{\overset{4}{\mathrm{\&Sigma;}}}\mathrm{sgn}(p_r-p_{\mathrm{ik}})\&CenterDot;c_{\mathrm{rik}}\&CenterDot;A_{\mathrm{rik}}\&CenterDot;\sqrt{\frac{2|p_{\mathrm{rk}}-p_{\mathrm{ik}}|}{\mathrm{\&rho;}}})\\ {\stackrel{\&CenterDot;}{p}}_{i1}=\frac{K_f}{V_{i1}}(\mathrm{sgn}(p_r-p_{i1})\&CenterDot;c_{\mathrm{ri}1}\&CenterDot;A_{\mathrm{ri}1}\&CenterDot;\sqrt{\frac{2|p_r-p_{i1}|}{\mathrm{\&rho;}}}-\mathrm{sgn}(p_{i1}-p_{\mathrm{cyl}1})\&CenterDot;E_{T1}\&CenterDot;c_{i1}\&CenterDot;A_{i1}\&CenterDot;\sqrt{\frac{2|p_{i1}-p_{\mathrm{cyl}1}|}{\mathrm{\&rho;}}})\\ {\stackrel{\&CenterDot;}{p}}_{i2}=\frac{K_f}{V_{i2}}(\mathrm{sgn}(p_r-p_{i2})\&CenterDot;c_{\mathrm{ri}2}\&CenterDot;A_{\mathrm{ri}2}\&CenterDot;\sqrt{\frac{2|p_r-p_{i2}|}{\mathrm{\&rho;}}}-\mathrm{sgn}(p_{i2}-p_{\mathrm{cyl}2})\&CenterDot;E_{T2}\&CenterDot;c_{i2}\&CenterDot;A_{i2}\&CenterDot;\sqrt{\frac{2|p_{i2}-p_{\mathrm{cyl}2}|}{\mathrm{\&rho;}}})\\ {\stackrel{\&CenterDot;}{p}}_{i3}=\frac{K_f}{V_{i3}}(\mathrm{sgn}(p_r-p_{i3})\&CenterDot;c_{\mathrm{ri}3}\&CenterDot;A_{\mathrm{ri}3}\&CenterDot;\sqrt{\frac{2|p_r-p_{i3}|}{\mathrm{\&rho;}}}-\mathrm{sgn}(p_{i3}-p_{\mathrm{cyl}3})\&CenterDot;E_{T3}\&CenterDot;c_{i3}\&CenterDot;A_{i3}\&CenterDot;\sqrt{\frac{2|p_{i3}-p_{\mathrm{cyl}3}|}{\mathrm{\&rho;}}})\\ {\stackrel{\&CenterDot;}{p}}_{i4}=\frac{K_f}{V_{i4}}(\mathrm{sgn}(p_r-p_{i4})\&CenterDot;c_{\mathrm{ri}4}\&CenterDot;A_{\mathrm{ri}4}\&CenterDot;\sqrt{\frac{2|p_r-p_{i4}|}{\mathrm{\&rho;}}}-\mathrm{sgn}(p_{i4}-p_{\mathrm{cyl}4})\&CenterDot;E_{T4}\&CenterDot;c_{i4}\&CenterDot;A_{i4}\&CenterDot;\sqrt{\frac{2|p_{i4}-p_{\mathrm{cyl}4}|}{\mathrm{\&rho;}}})\end{array}\right.---\left(20\right)$

Now, common rail fuel combustion system has six states, in order to carry out the rail pressure control algorithm design based on model, choosing respectively high-pressure service pump 3 pressure and being total to rail 8 fuel pressures is two system modes, ignoring fuel pressure in oil sprayer 6 chambeies fluctuates dynamically, with fuel leakage in high-pressure service pump 3 chambeies, together in the mode of disturbance, consider in the common rail fuel combustion system model, the second-order model that obtains thus the directly jetting gasoline engine common rail fuel combustion system is suc as formula (21):

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{p}}_p=\frac{K_f\left(p_p\right)}{v_p\left(\mathrm{\&theta;}\right)}(A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+\mathrm{sgn}(P_t-p_p)\&CenterDot;c_{\mathrm{tp}}\&CenterDot;(U\&CenterDot;A_{\mathrm{tp}})\&CenterDot;\sqrt{\frac{2|P_t-p_p|}{\mathrm{\&rho;}}}\\ -\mathrm{sgn}(p_p-p_r)\&CenterDot;c_{\mathrm{pr}}\&CenterDot;A_{\mathrm{pt}}\&CenterDot;\sqrt{\frac{2|p_p-p_r|}{\mathrm{\&rho;}}}-q_0)\\ {\stackrel{\&CenterDot;}{p}}_r=\frac{K_f\left(p_r\right)}{V_r}(\mathrm{sgn}(p_p-p_r)\&CenterDot;c_{\mathrm{pr}}\&CenterDot;A_{\mathrm{pt}}\&CenterDot;\sqrt{\frac{2|p_p-p_r|}{\mathrm{\&rho;}}}-q_{\mathrm{ri}})\end{array}\right.---\left(21\right)$

Selecting All Parameters a ₁, a ₂, by system simplification, be formula (22):

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{p}}_p=\frac{K_f\left(p_p\right)}{v_p\left(\mathrm{\&theta;}\right)}(A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+U\&CenterDot;a_1\&CenterDot;\sqrt{P_t-p_p}-a_2\&CenterDot;\sqrt{p_p-p_r}-q_0)\\ {\stackrel{\&CenterDot;}{p}}_r=\frac{K_f\left(p_r\right)}{V_r}(a_2\&CenterDot;\sqrt{p_p-p_r}-q_{\mathrm{ri}})\end{array}\right.---\left(22\right)$

Wherein: q _rifor common rail fuel combustion system fuel injection quantity (m ³/ s), parameter a ₁, a ₂suc as formula (23):

$a_1=c_{\mathrm{tp}}\&CenterDot;A_{\mathrm{tp}}\&CenterDot;\sqrt{\frac{2}{\mathrm{\&rho;}}},a_2=c_{\mathrm{pr}}\&CenterDot;A_{\mathrm{pr}}\&CenterDot;\sqrt{\frac{2}{\mathrm{\&rho;}}}---\left(23\right)$

Respectively by the high-pressure service pump pressure p _pand common rail pressure p _ras state variable x ₁and x ₂, formula (22) can be rewritten as the state space formula, suc as formula (24):

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{x}}_1=\frac{K_f\left(x_1\right)}{v_p\left(\mathrm{\&theta;}\right)}(A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+U\&CenterDot;a_1\sqrt{x_1-P_t}-a_2\&CenterDot;\sqrt{x_1-x_2}{-q}_0)\\ {\stackrel{\&CenterDot;}{x}}_2=\frac{K_f\left(x_2\right)}{V_r}(a_2\&CenterDot;\sqrt{x_1-x_2}-q_{\mathrm{ri}})\end{array}\right.---\left(24\right)$

Using high-pressure service pump 3 inlet flow rates as controlled quentity controlled variable in order to carry out control algorithm design,

formula (24) becomes formula (25)

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{x}}_1=\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}(A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+u-a_2\&CenterDot;\sqrt{x_1-x_2}{-q}_0)\\ {\stackrel{\&CenterDot;}{x}}_2=\frac{K_f}{V_r}(a_2\&CenterDot;\sqrt{x_1-x_2}-q_{\mathrm{ri}})\end{array}\right.---\left(25\right)$

3. based on common rail fuel combustion system model design control algorithm and arrange the control algorithm form

According to the feedback linearization theory, the rail pressure control algorithm of the second order common rail fuel combustion system of the simplification of deriving.

Feedback linearization is turned to a kind of maturation, effectively processes the method for nonlinear system, be widely used in the fields such as space flight, hydraulic pressure, motor and robot control, be characterized in making closed-loop system become linear system to the state feedback, and design corresponding virtual controlling input according to the Theory of Stability of linear system, finally obtain the controlled quentity controlled variable of whole nonlinear system.

Consult Fig. 3, according to the common rail fuel combustion system model form of final simplification, select feedback linearization method to carry out the derivation of control algorithm.Be directed to model feature, consider in model and there is stronger coupling terms so choose coupling terms, it is new state variable

work as x ₁≠ x ₂shi Ze has formula (26) and (27)

$\stackrel{\&CenterDot;}{z}={\left(\sqrt{x_1-x_2}\right)}^{\&prime;}=\frac{{\stackrel{\&CenterDot;}{x}}_1-{\stackrel{\&CenterDot;}{x}}_2}{2\sqrt{x_1-x_2}}=\frac{{\stackrel{\&CenterDot;}{x}}_1-{\stackrel{\&CenterDot;}{x}}_2}{2z}---\left(26\right)$

$\stackrel{\&CenterDot;}{z}=\frac{1}{2z}[\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}\&CenterDot;A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}\&CenterDot;u-(\frac{K_f}{V_r}+\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)})\&CenterDot;a_{12}\&CenterDot;z]---\left(27\right)$

By first equation of state in formula (27) substitution type (25), formula (28) is arranged

$\left\{\begin{array}{c}\stackrel{\&CenterDot;}{z}=\frac{1}{2z}[\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}\&CenterDot;A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}\&CenterDot;u-(\frac{K_f}{V_r}+\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)})\&CenterDot;a_2\&CenterDot;z-\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="q"\; filenames="HDA0000133556400000032.png,HDA0000133556400000051.png"\; state="\{\{state\}\}">q</figure-callout>}}_0+\frac{K_f}{V_r}\&CenterDot;q_{\mathrm{ri}}]\\ {\stackrel{\&CenterDot;}{x}}_2=\frac{K_f}{V_r}\&CenterDot;(a_2\&CenterDot;z-q_{\mathrm{ri}})\end{array}\right.---\left(28\right)$

And then the common rail fuel combustion system model is formula (29)

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{x}}_2=\frac{K_f}{V_r}\&CenterDot;(a_2\&CenterDot;z-q_{\mathrm{ri}})\\ \stackrel{\&CenterDot;}{z}=f\left(z\right)+a\left(z\right)\&CenterDot;u\end{array}\right.---\left(29\right)$

Wherein: f (z) and a (z) are the non-linear relation about common rail fuel combustion system state z, and its form is formula (30), (31).

$f\left(z\right)=\frac{1}{2z}\&CenterDot;[\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}\&CenterDot;A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\&CenterDot;\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}-(\frac{K_f}{V_r}+\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)})\&CenterDot;a_2\&CenterDot;z-\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="q"\; filenames="HDA0000133556400000032.png,HDA0000133556400000051.png"\; state="\{\{state\}\}">q</figure-callout>}}_0+\frac{K_f}{V_r}\&CenterDot;q_{\mathrm{ri}}]---\left(30\right)$

$a\left(z\right)=\frac{1}{2z}\&CenterDot;\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}---\left(31\right)$

X now ₁≠ x ₂so it is meaningful for a (z) ≠ 0.

Can use the method for feedback linearization for the assurance system and carry out control algorithm design, need to calculate the relative rank of common rail fuel combustion system, to system mode x ₂ask second dervative, shown in (32):

${\stackrel{\&CenterDot;\&CenterDot;}{x}}_2={[\frac{K_f}{V_r}\&CenterDot;(a_2\&CenterDot;z-q_{\mathrm{ri}})]}^{\&prime;}=\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;\stackrel{\&CenterDot;}{z}---\left(32\right)$

$=\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;f\left(z\right)+\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;a\left(z\right)\&CenterDot;u$

Due to

in aobvious containing control law u, so the relative rank of common rail fuel combustion system are 2, can apply feedback linearization method and carry out control algorithm design.

Order

by x ₂, x ₃the new state variable as common rail fuel combustion system, common rail fuel combustion system is shown in formula (33):

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{x}}_2=x_3\\ {\stackrel{\&CenterDot;}{x}}_3=\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;f\left(z\right)+\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;a\left(z\right)\&CenterDot;u\end{array}\right.---\left(33\right)$

If virtual controlling input u ₁for formula (34), system linear turns to formula (35).

${\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="HDA0000133556400000061.png"\; state="\{\{state\}\}">u</figure-callout>}}_1=\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;f\left(z\right)+\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;a\left(z\right)\&CenterDot;u---\left(34\right)$

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{x}}_2=x_3\\ {\stackrel{\&CenterDot;}{x}}_3=u_1\end{array}\right.---\left(35\right)$

Now control law u is formula (36).

$u=\frac{1}{\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;a\left(z\right)}[-\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;f\left(z\right)+u_1]---\left(36\right)$

The system after linearization is formula (37).

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{x}}_2=x_3\\ {\stackrel{\&CenterDot;}{x}}_3=u_1\end{array}\right.---\left(37\right)$

Allow the expectation rail pressure of common rail fuel combustion system rail pressure tracing preset because control target and be, establishing the expectation rail pressure is x _2d(Pa), error variance is defined as to e ₂, e ₃, suc as formula (38), (39),

e ₂＝x ₂-x _2d (38)

${\stackrel{\&CenterDot;}{e}}_2=e_3---\left(39\right)$

corresponding derivative has formula (40), (41),

${\stackrel{\&CenterDot;}{e}}_2={\stackrel{\&CenterDot;}{x}}_2-{\stackrel{\&CenterDot;}{x}}_{2d}---\left(40\right)$

${\stackrel{\&CenterDot;}{e}}_3={\stackrel{\&CenterDot;\&CenterDot;}{x}}_2-{\stackrel{\&CenterDot;\&CenterDot;}{x}}_{2d}---\left(41\right)$

The common rail fuel combustion system model is rewritten as with e ₂, e ₃for the model of state, suc as formula (42).

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{e}}_2=e_3\\ {\stackrel{\&CenterDot;}{e}}_3=u_1-{\stackrel{\&CenterDot;\&CenterDot;}{x}}_{2d}\end{array}\right.---\left(42\right)$

Order

wherein: k ₁and k ₂for the control law parameter, common rail fuel combustion system is reduced to formula (43):

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{e}}_2=e_3\\ {\stackrel{\&CenterDot;}{e}}_3=-k_1{e}_2-k_2{e}_3\end{array}\right.---\left(43\right)$

Now there are formula (44), (45) to set up,

${\stackrel{\&CenterDot;\&CenterDot;}{e}}_2=-k_1{e}_2-k_2{e}_3---\left(44\right)$

${\stackrel{\&CenterDot;\&CenterDot;}{e}}_2+k_2{\stackrel{\&CenterDot;}{e}}_2+k_1{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">e</figure-callout>}}_2=0---\left(45\right)$

Known according to the linear system routh stability criterion, the condition that second-order system is stable is that each item system is greater than zero.Thereby can obtain the stable condition of common rail fuel combustion system is k ₁>0, k ₂>0, final common rail fuel combustion system control law is formula (46):

$u=\frac{1}{\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;a\left(z\right)}[-\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;f\left(z\right)+u_1]$ (46)

$=\frac{1}{\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;a\left(z\right)}[-\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;f\left(z\right)-k_1{e}_2-k_2{e}_3+{\stackrel{\&CenterDot;\&CenterDot;}{x}}_{2d}]$

By nonlinear function (30) and (31) substitution formula (46), obtain formula (47):

$u=\frac{1}{\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;\frac{1}{2z}\&CenterDot;\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}}\{-k_1{e}_2-k_2{e}_3+{\stackrel{\&CenterDot;\&CenterDot;}{x}}_{2d}$

$-\frac{K_f}{V_r}\&CenterDot;a_2\&CenterDot;\frac{1}{2z}\&CenterDot;[\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}\&CenterDot;A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\&CenterDot;\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}-(\frac{K_f}{V_r}+\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)})\&CenterDot;a_2\&CenterDot;z-\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="q"\; filenames="HDA0000133556400000032.png,HDA0000133556400000051.png"\; state="\{\{state\}\}">q</figure-callout>}}_0+\frac{K_f}{V_r}\&CenterDot;q_{\mathrm{ri}}]\}---\left(47\right)$

$=-A_p{\mathrm{\&omega;}}_{\mathrm{rpm}}\&CenterDot;\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+(\frac{v_p\left(\mathrm{\&theta;}\right)}{V_r}+1)\&CenterDot;a_2\&CenterDot;z+q_0-\frac{v_p\left(\mathrm{\&theta;}\right)}{V_r}\&CenterDot;q_{\mathrm{ri}}$

$-\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{{{\mathrm{<figure-callout\; id="2"\; label="K\; f"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">K</figure-callout>}}_f}^2\&CenterDot;a_2}\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="HDA0000133556400000061.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\&CenterDot;e_2-\frac{2z\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{K_f\&CenterDot;a_2}\&CenterDot;k_2{e}_3+\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{{{\mathrm{<figure-callout\; id="2"\; label="K\; f"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">K</figure-callout>}}_f}^2\&CenterDot;a_2}\&CenterDot;{\stackrel{\&CenterDot;\&CenterDot;}{x}}_{2d}$

Final control law is arranged, and the form of being write as error is suc as formula (48):

$u=A\left(z\right)+{\mathrm{Be}}_2+{\mathrm{Ce}}_3$ (48)

$=A\left(z\right)+{\mathrm{Be}}_2+C{\stackrel{\&CenterDot;}{e}}_2$

Wherein: A (z), B, C are formula (49), (50), (51)

$A\left(z\right)=-A_p{\mathrm{\&omega;}}_{\mathrm{rpm}}\&CenterDot;\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+(\frac{v_p\left(\mathrm{\&theta;}\right)}{V_r}+1)\&CenterDot;a_2\&CenterDot;z+q_0-\frac{v_p\left(\mathrm{\&theta;}\right)}{V_r}\&CenterDot;q_{\mathrm{ri}}+\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{{{\mathrm{<figure-callout\; id="2"\; label="K\; f"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">K</figure-callout>}}_f}^2\&CenterDot;a_2}\&CenterDot;{\stackrel{\&CenterDot;\&CenterDot;}{x}}_{2d}---\left(49\right)$

$B=-\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{{{\mathrm{<figure-callout\; id="2"\; label="K\; f"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">K</figure-callout>}}_f}^2\&CenterDot;a_2}\&CenterDot;k_1---\left(50\right)$

$C=-\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{K_f\&CenterDot;a_2}\&CenterDot;k_2---\left(51\right)$

The pressure of the high-pressure service pump 3 before considering reaches the pressure equation form (25) of rail 8 altogether, and A (z) formula (49) that will feedover is arranged, Selection of Function f ₁and f ₂be respectively formula (52), (53).

${\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="HDA0000133556400000061.png"\; state="\{\{state\}\}">f</figure-callout>}}_1=-A_p{\mathrm{\&omega;}}_{\mathrm{rpm}}\&CenterDot;\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+a_2\&CenterDot;z+q_0---\left(52\right)$

${\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">f</figure-callout>}}_2=\frac{v_p\left(\mathrm{\&theta;}\right)}{V_r}\&CenterDot;(a_2\&CenterDot;z-q_{\mathrm{ri}})---\left(53\right)$

$A\left(z\right)={\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="HDA0000133556400000061.png"\; state="\{\{state\}\}">f</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">f</figure-callout>}}_2+\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{{{\mathrm{<figure-callout\; id="2"\; label="K\; f"\; filenames="HDA0000133556400000021.png,HDA0000133556400000061.png"\; state="\{\{state\}\}">K</figure-callout>}}_f}^2\&CenterDot;a_2}\&CenterDot;{\stackrel{\&CenterDot;\&CenterDot;}{x}}_{2d}---\left(54\right)$

Wherein: f ₁for high-pressure service pump pump oil characteristic, it means the pumping ability of high-pressure service pump, its form cotype (11), f ₂mean the interior Fuel dynamic characteristic of rail altogether, its form cotype (14).The control algorithm designed thus feedforward part has been considered high-pressure service pump 3 pumps oil characteristics, rail 8 fuel characteristics and with reference to the rail pressure variation characteristic altogether altogether.

Work as x ₁=x ₂the time, the common rail fuel combustion system model is

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{x}}_1=\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}(A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+u-q_0)\\ {\stackrel{\&CenterDot;}{x}}_2=\frac{K_f}{V_r}(-q_{\mathrm{ri}})\end{array}\right.---\left(55\right)$

Be now an instantaneous state of common rail fuel combustion system, because controlled quentity controlled variable u can't affect the system rail pressure, so now need to meet

controlled quentity controlled variable is chosen a lot, and for the sake of simplicity, choosing now controlled quentity controlled variable u is formula (56).

$u=q_0-A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}---\left(56\right)$

Consider x ₁≠ x ₂and x ₁=x ₂two kinds of situations, according to formula (47), (54), (50), (51) and (56), the final control law of system is:

$u=\left\{\begin{array}{cc}A\left(z\right)+B\&CenterDot;(x_2-x_{2d})+C\&CenterDot;({\stackrel{\&CenterDot;}{x}}_2-{\stackrel{\&CenterDot;}{x}}_{2d})& x_1\&NotEqual;x_2\\ q_0-A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}& x_1=x_2\end{array}\right.---\left(57\right)$

Due to the control law complicated structure normally obtained, so the form with error is rewritten it, finally can arrange as the common rail fuel combustion system state feedovers and add proportion differential Error Feedback control algorithm, shown in (57), the high-pressure service pump 3 pumps oil characteristics that wherein comprise in the feedforward and altogether rail 8 fuel characteristics can replace by the empirical equation simplified or the characteristic map of a small amount of test determination, the writing and the Project Realization of algorithm of final so that C code.

4. rail pressure sensor filtering and signal transmission delay are processed

Because precision and the transmission speed of rail pressure sensor 7 in the actual common rail oil-fired system are limited, in order to improve the validity of control algorithm, the signal that need to gather rail pressure sensor 7 carries out filtering, and considers the processing of control algorithm to the signal transmission delay.

Control preferably effect in order to make designed control algorithm to have, need to consider sampling error and the response time delay of rail pressure sensor 7 in model.

1) design software filtering link at first, 10 the rail pressure signals of AD passage collection by single-chip microcomputer are also done on average, and write filtering algorithm in program, can remove discrete error point and signal interference;

2) time delay of rail pressure sensor 7 is usually very little, is generally the 1ms left and right.Design as required rail pressure sensor 7 signals and measure test, and carry out data and measure and process, signal transmission and response time delay are thought of as to the delay τ of first order inertial loop, now can build hardware cell and overcome rail pressure sensor 7 time delays.

5. measure the pressure controlled valve characteristic output of control algorithm is converted to the pressure controlled valve action constantly

Because 5 actions of actual pressure controlled valve have certain time delay with control signal, for the rail pressure control algorithm based on the common rail fuel combustion system model design is realized, need contrived experiment to measure pressure controlled valve 5 characteristics, finally obtain the relation of pressure controlled valve 5 switch motion time delays and current vehicular power-bottle voltage.Be input as high-pressure service pump 3 inlet flow rates due to the rail pressure control algorithm based on the common rail fuel combustion system model design, and the actual common rail oil-fired system be input as closed electromagnetic valve constantly, so need to be tested the relation of electromagnetic valve switch action and high-pressure service pump 3 fuel deliveries in build-up pressure control valve 5.

Consult Fig. 4, the rail pressure control final controlling element of actual directly jetting gasoline engine common rail fuel combustion system is pressure controlled valve 5, and pressure controlled valve 5 can be realized the real-time adjusting of fuel pressure in conjunction with the action of high-pressure service pump 3.The pump oil content of high-pressure service pump 3 is three processes: at first at plunger from top dead center between lower dead center, pressure controlled valve 5 often leaves, because high-pressure service pump 3 oil outlet ends have one-way valve, fuel oil flow in high-pressure service pump 3 from low pressure oil way; Secondly before lower dead center to pressure controlled valve 5 cuts out, fuel oil is back to low pressure oil way from high-pressure service pump 3; Finally at pressure controlled valve 5, close between the plunger top dead center, pressure controlled valve 5 cuts out, and fuel oil pumps in common rail 8 from high-pressure service pump 3.Actual pressure controlled valve 5 is current drives, and its action has certain time delay with the control signal of drive circuit.The current characteristics that drive circuit produces is relevant with actual given voltage, be actual vehicular power-bottle voltage, so according to actual conditions, measure the characteristic curve of pressure controlled valve 5 drive circuit voltages and electric current, through processing the relation that can obtain given voltage and control valve action delay.

For the common rail fuel combustion system control law that actual design is good is applied on actual rail pressure control, needing build-up pressure control valve 5 opening angles and designed rail pressure control rule formula (57) is the relation that high-pressure service pump flows into flow

now need contrived experiment, test accordingly, obtain by measuring laboratory data and carrying out suitable data processing.As shown in Figure 4,5 shut-in times of pressure controlled valve are determining the time length in oil return stage and pump oil stage, and then the pump oil mass of high-pressure service pump 3 reality in final decision.Can be the action U that formula (57) changes actual pressure controlled valve 5 into thus by designed control law, to realize the real-time control of common rail pressure.

Consult Fig. 5, for verifying the validity of designed control algorithm, the rail pressure control algorithm in simulink simulation software environmental structure based on feedback linearization and directly jetting gasoline engine oil-way system model, and carry out off-line simulation, and analyze simulation result;

The mathematical model of association schemes mesohigh pump 3, common rail 8 and oil sprayer 6, carry out corresponding comprehensive, control effect for the preliminary identification control algorithm, at first carry out simulating, verifying under the simulink environment, simulink is as the simulated environment of the upper extensive use of engineering application, there is copying preferably, and with a lot of RTS real time system (as dSAPCE or xPC Target), interface is arranged, can realize well the HWIL simulation of system, so encircling simulated environment as main software early stage in system development.Wherein parameter is respectively V _r=65.824 * 10 ^-6(m ³), a ₂=12.566 * 10 ^-6* 0.65 (m ²), a ₁=8.553 * 10 ^-6* 0.75 (m ²), A _p=78.5398 * 10 ^-6(m ²), V _p0=0.27 * 10 ^-6(m ³), q ₀=0.0005 (m ³), P _l=5.7 (bar), rail pressure sensor transmission delay τ=0.2 (ms), k _l=3.1, k ₂=2.03.Simulink emulate system architecture figure as shown in Figure 5, does respectively following two groups of tests:

1) the normal value that the target rail pressure is 150bar, and add high-pressure service pump fuel leakage instantaneous perturbation (5 * 10 in emulation simultaneously ^-4m ³/ s), simulation time is 0.5s.Simulation result is as Fig. 6 and Fig. 7, and its result shows, final rail pressure fluctuation maximum is at ± 0.7bar, and the rail pressure control error is 0.47%, controls effect better.

2) the target rail pressure is the sinusoidal curve that amplitude is 130～150, and frequency is 4.5Hz, and simulation time is 2s, and simulation result is as Fig. 8 and Fig. 9, and its result shows, final rail pressure fluctuation maximum is at ± 2bar, and the rail pressure control error is 1.4%.

Through off-line simulation, can find out that the rail pressure control method work of directly jetting gasoline engine common rail fuel combustion system of the present invention is good, there is the ability of controlling rail pressure, stablizing rail pressure fluctuation.

It should be noted that, in order further to verify real-time and the reliability of designed common rail fuel pressure control algorithm, one of ordinary skill in the art will appreciate that the part steps in the rail pressure control method of directly jetting gasoline engine common rail fuel combustion system of the present invention is to complete by hardware, now need to choose the actual hardware circuit, designed common rail fuel pressure control algorithm is downloaded in single-chip microcomputer and tests in real time.

Claims (1)

1. the rail pressure control method of a directly jetting gasoline engine common rail fuel combustion system, is characterized in that, the step of the rail pressure control method of described directly jetting gasoline engine common rail fuel combustion system is as follows:

1) set up the mathematical model of directly jetting gasoline engine common rail fuel combustion system:

(1) set up the high-pressure service pump mathematical model:

${\stackrel{\&CenterDot;}{p}}_p=\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}(A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}-\mathrm{sgn}(P_t-p_p)\&CenterDot;c_{\mathrm{tp}}\&CenterDot;(U\&CenterDot;A_{\mathrm{tp}})\&CenterDot;\sqrt{\frac{2|P_t-p_p|}{\mathrm{\&rho;}}}$

(11)

$-\mathrm{sgn}(p_p-p_r)\&CenterDot;c_{\mathrm{pr}}\&CenterDot;A_{\mathrm{pr}}\&CenterDot;\sqrt{\frac{2|p_p-p_r|}{\mathrm{\&rho;}}}-q_0)$

Wherein: p _p. pressure in the high pressure pump chamber, unit, Pa; K _f. the volumetric modulus of elasticity of fuel oil, unit, Pa; θ. cam angle, unit, rad; v _p(θ). high-pressure service pump volume, unit, m ³; A _p. high-pressure service pump plunger sectional area, unit, m ²; ω _rpm. cam rotating speed, unit, r/min; h _p. ram lift, unit, m; P _t. low-pressure electric fuel pump outlet oil pressure, unit, Pa; A _tp. high-pressure service pump oiler sectional area, unit, m ²; c _tp. flow coefficient; The switch controlled quentity controlled variable of U pressure controlled valve, be 0 or 1, and the expression pressure controlled valve is opened and closed condition; Sgn (). mean the sign function that fuel oil flows to; ρ. the density of fuel oil, unit, kg/m ³; p _r. be total to fuel pressure in rail, unit, Pa; A _pr. be total to rail end oiler sectional area, unit, m ²; c _pr. flow coefficient; q ₀. gap oil leakage amount between plunger and plunger cavity, unit, m ³/ s;

(2) set up rail mathematical model altogether:

${\stackrel{\&CenterDot;}{p}}_r=\frac{K_f}{V_r}(\mathrm{sgn}(p_p-p_r)\&CenterDot;c_{\mathrm{pr}}\&CenterDot;A_{\mathrm{pr}}\&CenterDot;\sqrt{\frac{2|p_p-p_r|}{\mathrm{\&rho;}}}-\mathrm{sgn}(p_r-p_i)\&CenterDot;c_{\mathrm{ri}}\&CenterDot;A_{\mathrm{ri}}\&CenterDot;\sqrt{\frac{2|p_r-p_i|}{\mathrm{\&rho;}}})---\left(14\right)$

Wherein: V _r. be total to the rail volume, unit, m ³; p _i. fuel pressure in oil sprayer, unit, Pa; A _ri. oil sprayer oiler sectional area, unit, m ²; c _ri. oil sprayer entry end flow coefficient;

(3) set up the oil sprayer mathematical model:

${\stackrel{\&CenterDot;}{p}}_{\mathrm{ik}}=\frac{K_f}{V_{\mathrm{ik}}}(\mathrm{sgn}(p_r-p_{\mathrm{ik}})\&CenterDot;c_{\mathrm{rik}}\&CenterDot;A_{\mathrm{rik}}\&CenterDot;\sqrt{\frac{2|p_r-p_{\mathrm{ik}}|}{\mathrm{\&rho;}}}-\mathrm{sgn}(p_{\mathrm{ik}}-p_{\mathrm{cylk}})\&CenterDot;E_{\mathrm{Tk}}\&CenterDot;c_{\mathrm{ik}}\&CenterDot;A_{\mathrm{ik}}\&CenterDot;\sqrt{\frac{2|p_{\mathrm{ik}}-p_{\mathrm{cylk}}|}{\mathrm{\&rho;}}})---\left(18\right)$

Wherein: the k in lower footnote means the sequence number of oil sprayer, and k gets 1,2,3 or 4; p _ik. fuel pressure in k oil sprayer, unit, Pa; A _rik. k oil sprayer oiler sectional area, unit, m ²; c _rik. k oil sprayer entry end flow coefficient; p _cyik. k inner pressure of air cylinder, unit, Pa; V _ik. k oil sprayer cavity volume, unit, m ³; A _ik. k oil sprayer spray orifice sectional area, unit, m ²; c _ik. k oil sprayer spray orifice flow coefficient; E _tk. k fuel injection pulsewidth, when the oil sprayer oil spout, its value is 1, other situation is 0;

2) simplify the mathematical model of common rail fuel combustion system:

$\left\{\begin{array}{c}{\stackrel{\&CenterDot;}{x}}_1=\frac{K_f}{v_p\left(\mathrm{\&theta;}\right)}(A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+u-a_2\&CenterDot;\sqrt{x_1-x_2}-q_0)\\ {\stackrel{\&CenterDot;}{x}}_2=\frac{K_f}{V_r}(a_2\&CenterDot;\sqrt{x_1-x_2}-q_{\mathrm{ri}})\end{array}\right.---\left(25\right)$

Wherein: choose respectively fuel pressure p in high-pressure service pump _preach the interior fuel pressure P of rail altogether _rstate variable x for common rail fuel combustion system ₁and x ₂; K _f. the volumetric modulus of elasticity of fuel oil, unit, Pa; θ. cam angle, unit, rad; v _p(θ). high-pressure service pump volume, unit, m ³; A _p. high-pressure service pump plunger sectional area, unit, m ²; ω _rpm. cam rotating speed, unit, r/min; h _p. ram lift, unit, m; U is controlled quentity controlled variable, i.e. the fuel flow of high-pressure service pump ingress, and unit,

u means the switch controlled quentity controlled variable of pressure controlled valve, and it is 0 or 1, and the expression valve body is opened and closed condition; P _t. low-pressure electric fuel pump outlet oil pressure, unit, Pa; Variable a ₁be expressed as

a _tp. high-pressure service pump oiler sectional area, unit, m ², c _tp. flow coefficient, variable a ₂be expressed as

a _pr. be total to rail end oiler sectional area, unit, m ², c _prfor flow coefficient, ρ. the density of fuel oil, unit, kg/m ³; q ₀. gap oil leakage amount between plunger and plunger cavity, unit, m ³/ s; q _ri. common rail fuel combustion system fuel injection quantity, unit, m ³/ s;

3) based on common rail fuel combustion system model design control algorithm and arrange the control algorithm form:

$u=\left\{\begin{array}{cc}A\left(z\right)+B(x_2-x_{2d})+C({\stackrel{\&CenterDot;}{x}}_2-{\stackrel{\&CenterDot;}{x}}_{2d})& x_1\&NotEqual;x_2\\ q_0-A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}& x_1=x_2\end{array}\right.---\left(57\right)$

In formula:

$A\left(z\right)=-A_p{\mathrm{\&omega;}}_{\mathrm{rpm}}\&CenterDot;\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+(\frac{v_p\left(\mathrm{\&theta;}\right)}{V_r}+1)\&CenterDot;a_2\&CenterDot;z+q_0-\frac{v_p\left(\mathrm{\&theta;}\right)}{V_r}\&CenterDot;q_{\mathrm{ri}}+\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{{K_f}^2\&CenterDot;a_2}{\&CenterDot;\stackrel{\&CenterDot;\&CenterDot;}{x}}_{2d}---\left(49\right)$

$B=-\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{{K_f}^2\&CenterDot;a_2}\&CenterDot;k_1---\left(50\right)$

$C=-\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{K_f\&CenterDot;\&CenterDot;a_2}\&CenterDot;k_2---\left(51\right)$

Wherein: the u. controlled quentity controlled variable is the fuel flow of high-pressure service pump ingress, unit, m ³/ s; A _p. high-pressure service pump plunger sectional area, unit; ω _rpm. cam rotating speed, unit, r/min; h _p. ram lift, unit, m; θ. cam angle, unit, rad; v _p(θ). high-pressure service pump volume, unit, m ³; V _r. be total to the rail volume, unit, m ³; Variable a ₂be expressed as

a _prbe total to rail end oiler sectional area, unit, m ², c _pr. flow coefficient; q ₀. gap oil leakage amount between plunger and plunger cavity, unit, m ³/ s; q _ri. common rail fuel combustion system fuel injection quantity, unit, m ³/ s; K _f. the volumetric modulus of elasticity of fuel oil, unit, Pa; k ₁and k ₂. control law parameter, x ₁. the state variable of fuel pressure in high-pressure service pump, unit, Pa; x ₂. be total to the state variable of fuel pressure in rail, unit, Pa; x _2d. expectation rail pressure, unit, Pa; State variable

4) rail pressure sensor filtering and signal transmission delay are processed:

A. 10 rail pressure signals of AD passage collection by single-chip microcomputer do on average, adopt filtering algorithm to remove discrete error point and signal interference;

B. design rail pressure sensor (7) signal and measure test, and carry out data and measure and process, signal transmission and response time delay are thought of as to the delay τ of first order inertial loop, build hardware cell and overcome rail pressure sensor (7) time delay;

5) measure the pressure controlled valve characteristic output of control algorithm be converted to the pressure controlled valve action constantly:

A. experiment measures pressure controlled valve (5) characteristic, obtains the relation of pressure controlled valve (5) switch motion time delay and vehicular power-bottle voltage;

B. the relation of build-up pressure control valve (5) opening angle and high-pressure service pump (3) influent stream amount by experiment, be formula by designed control law $u=\left\{\begin{array}{cc}A\left(z\right)+B(x_2-x_{2d})+C({\stackrel{\&CenterDot;}{x}}_2-{\stackrel{\&CenterDot;}{x}}_{2d})& x_1\&NotEqual;x_2\\ q_0-A_p\&CenterDot;{\mathrm{\&omega;}}_{\mathrm{rpm}}\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}& x_1=x_2\end{array}\right.$ Change the action of actual pressure controlled valve (5) into, realize the real-time control of rail (8) internal pressure altogether;

In formula:

$A\left(z\right)=-A_p{\mathrm{\&omega;}}_{\mathrm{rpm}}\&CenterDot;\frac{{\mathrm{dh}}_p}{\mathrm{d\&theta;}}+(\frac{v_p\left(\mathrm{\&theta;}\right)}{V_r}+1)\&CenterDot;a_2\&CenterDot;z+q_0-\frac{v_p\left(\mathrm{\&theta;}\right)}{V_r}\&CenterDot;q_{\mathrm{ri}}+\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{{K_f}^2\&CenterDot;a_2}\&CenterDot;{\stackrel{\&CenterDot;\&CenterDot;}{x}}_{2d}---\left(49\right)$

$B=-\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{{K_f}^2\&CenterDot;a_2}\&CenterDot;k_1---\left(50\right)$

$C=-\frac{2z\&CenterDot;V_r\&CenterDot;v_p\left(\mathrm{\&theta;}\right)}{K_f\&CenterDot;\&CenterDot;a_2}\&CenterDot;k_2---\left(51\right)$

Wherein: the u. controlled quentity controlled variable is the fuel flow of high-pressure service pump ingress, unit, m ³/ s; A _p. high-pressure service pump plunger sectional area, unit; ω _rpm. cam rotating speed, unit, r/min; h _p. ram lift, unit, m; θ. cam angle, unit, rad; v _p(θ). high-pressure service pump volume, unit, m ³; V _r. be total to the rail volume, unit, m ³; Variable a ₂be expressed as

a _prbe total to rail end oiler sectional area, unit, m ², c _pr. flow coefficient; q ₀. gap oil leakage amount between plunger and plunger cavity, unit, m ³/ s; q _ki. common rail fuel combustion system fuel injection quantity, unit, m ³/ s; K _f. the volumetric modulus of elasticity of fuel oil, unit, Pa; k ₁and k ₂. control law parameter, x ₁. the state variable of fuel pressure in high-pressure service pump, unit, Pa; x ₂. be total to the state variable of fuel pressure in rail, unit, Pa; x _2d. expectation rail pressure, unit, Pa; State variable

Images