Method for setting a throttle valve, engine control unit, and a vehicle

Abstract

A method for setting a throttle valve that includes feedback control of a throttle position of the throttle valve in the entire operating range of an internal combustion engine, wherein the feedback control is based on an internal model control principle.

Claims

1. A method for setting a throttle valve, the method comprising: feedback controlling a throttle position of the throttle valve in an entire operating range of an internal combustion engine; and basing the feedback control on an internal model control (IMC) principle, wherein the feedback control comprises: receiving a desired intake manifold pressure as input variable; and calculating a desired position of the throttle valve based on the desired intake manifold pressure, and wherein the feedback control additionally filters the desired intake manifold pressure via a filter.

2. The method according to claim 1, wherein the entire operating range of the internal combustion engine comprises an intake range, an overtravel range (pressure equalization), and a supercharged operating range of the internal combustion engine.

3. The method according to claim 1, wherein the desired position of the throttle valve is provided to a process and a process model simultaneously in accordance with the IMC principle.

4. The method according to claim 3, wherein the calculated desired position is a desired position limited by physical actuator limits.

5. The method according to claim 1, wherein the process determines the position of the throttle valve based on the calculated desired position and measures the intake manifold pressure thus created, and wherein the process model determines a modeled intake manifold pressure based on the calculated desired area position.

6. The method according to claim 5, wherein the feedback control additionally comprises: identifying a difference between the measured intake manifold pressure and the modeled intake manifold pressure; and identifying a corrected desired intake manifold pressure based on the identified difference.

7. The method according to claim 6, wherein the feedback control additionally filters the identified difference via a filter.

8. The method according to claim 1, wherein the feedback control additionally filters the desired position of the throttle valve via a filter.

9. The method according to claim 1, wherein the feedback control of the throttle position of the throttle valve is assisted by a variable turbine geometry in the supercharged operating range of the internal combustion engine.

10. An engine control unit configured to perform the method according to claim 1.

11. A vehicle comprising an engine control unit according to claim 10.

12. A method for setting a throttle valve, the method comprising: feedback controlling a throttle position of the throttle valve in an entire operating range of an internal combustion engine: and basing the feedback control on an internal model control (IMC) principle, wherein the feedback control comprises: receiving a desired intake manifold pressure as input variable; and calculating a desired position of the throttle valve based on the desired intake manifold pressure, and wherein the desired position of the throttle valve is calculated as follows: $A_{\mathrm{DK},\mathrm{soll}}=\frac{\frac{V}{{\mathrm{KRT}}_2}{\stackrel{.}{p}}_{\mathrm{SPcor}.f}+W_{\mathrm{viv}}\left(p\right)-W_{\mathrm{TEV}}}{p_1\sqrt{\frac{2}{{\mathrm{RT}}_1}}\Psi \left(p\right)}-A_{\mathrm{DK},\mathrm{leak}}$ where: V is the volume of the intake manifold, R is the specific gas constant of air, K is the isentropic exponent , p is the air pressure in the intake manifold, T.sub.2 is the temperature of the air in the intake manifold, w.sub.vlv(p) is the outgoing air mass flow as a function of the air pressure p that flows out of the intake manifold through the intake valves, w.sub.TEV is the incoming air mass flow that flows into the intake manifold through the fuel-tank ventilation valve, p.sub.1 is the air pressure that is present upstream of the throttle valve, T.sub.1 is the temperature of the air that flows into the intake manifold through the throttle valve, Ψ(p) is the flow function as a function of the air pressure p and A.sub.DK,leak is the effective leakage position of the throttle valve.

13. A method for setting a throttle valve, the method comprising, feedback controlling a throttle position of the throttle valve in an entire operating range of an internal combustion engine; and basing the feedback control on an internal model control (IMC) principle, wherein the feedback control comprises: receiving a desired intake manifold pressure as input variable; and calculating a desired position of the throttle valve based on the desired intake manifold pressure, wherein the process determines the position of the throttle valve based on the calculated desired position and measures the intake manifold pressure thus created, and wherein the process model determines a modeled intake manifold pressure based on the calculated desired position, and wherein the modeled intake manifold pressure is calculated as follows: $\hat{p}=\int \left(\stackrel{.}{\hat{p}}\right)\mathrm{dt}$ $\mathrm{where}$ $\frac{V}{{\mathrm{KRT}}_2}\left(\stackrel{.}{\hat{p}}\right)=.Math.W_G=W_{\mathrm{thr}}-W_{\mathrm{viv}}+W_{\mathrm{TEV}}=p_1\sqrt{\frac{2}{{\mathrm{RT}}_1}}(A_{\mathrm{DK},\lim }+A_{\mathrm{DK},\mathrm{leak})}\Psi \left(p\right)-w_{\mathrm{viv}}\left(p\right)+w_{\mathrm{TEV}}$ and where: W.sub.G is the air mass flow in the intake manifold, W.sub.thr is the incoming air mass flow that flows into the intake manifold through the throttle valve, p.sub.1 is the air pressure upstream of the throttle valve (boost pressure), V is the volume of the intake manifold, R is the specific gas constant of air, K is the isentropic exponent, p is the air pressure in the intake manifold, T.sub.2 is the temperature of the air in the intake manifold, w.sub.vlv(p) is the outgoing air mass flow as a function of the air pressure p that flows out of the intake manifold through the intake valves, w.sub.TEV is the incoming air mass flow that flows into the intake manifold through the fuel-tank ventilation valve, T.sub.1 is the temperature of the air that flows into the intake manifold through the throttle valve, Ψ(p) is the flow function as a function of the air pressure p, and A.sub.DK,leak is the effective leakage position of the throttle valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 shows a block diagram that schematically represents the configuration of a vehicle according to an exemplary embodiment of the present invention;

(3) FIG. 2 shows a block diagram that schematically represents the configuration of a 4-cylinder internal combustion engine of a vehicle according to an exemplary embodiment of the present invention;

(4) FIG. 3 shows, as an exemplary embodiment, a closed-loop control system for the closed-loop control of the throttle position in the intake, overtravel, and boost ranges of the internal combustion engine;

(5) FIG. 4 shows, as an exemplary embodiment, an approach to a method for model-based precontrol of the closed-loop control system; and

(6) FIG. 5 shows, as an exemplary embodiment, an approach to a method for the process model of the closed-loop control system.

DETAILED DESCRIPTION

(7) FIG. 1 shows a block diagram that schematically represents the configuration of a vehicle according to an exemplary embodiment of the present invention.

(8) The vehicle 100 includes multiple components that communicate with one another over a data bus 20, namely an engine control unit 10, a throttle control unit 30, an exhaust turbocharger control unit 40, a transmission control unit 50, and a clutch control unit 60. The vehicle 100 can be driven by an internal combustion engine, wherein the internal combustion engine is a multicylinder spark ignition engine.

(9) An engine control unit (ECU) 10 is an electronic control unit that controls a number of actuators of the internal combustion engine in order to ensure optimal engine performance. For example, the engine control unit (ECU) 10 can control the position of a throttle valve and/or the operation of an exhaust turbocharger. The control of the throttle valve and/or of the exhaust turbocharger can be based on a continuous closed-loop control (intake manifold pressure control, boost-pressure control) over the entire operating range (intake range, overtravel range (pressure equalization), supercharged operating range) of the internal combustion engine 4. A more detailed explanation of the closed-loop control can be found under FIG. 3 below.

(10) The data bus 20 can be implemented according to communications technologies such as CAN (controller area network), LIN (local interconnect network), FlexRay, LAN/Ethernet or MOST, for example. Multiple different bus types can also be used in combination in the vehicle.

(11) The throttle control unit 30 controls the throttle position of a throttle valve, wherein the control of the throttle control unit 30 is based on the continuous closed-loop control of the engine control unit (ECU) 10. A throttle valve is arranged in the intake tract of the internal combustion engine. The throttle valve regulates the delivery of air or mixture to the internal combustion engine.

(12) The exhaust turbocharger control unit 40 controls the operation of an exhaust turbocharger, wherein the control of the exhaust turbocharger is based on the boost-pressure control of the engine control unit (ECU) 10. An exhaust turbocharger compresses the combustion air delivered to the internal combustion engine. An exhaust turbocharger includes a turbine and a compressor. A portion of the energy of the exhaust gas of the internal combustion engine is used to drive the turbine. The compressor is mounted on a turbocharger shaft opposite the turbine. The compressor draws in the combustion air and delivers it in compressed form to the internal combustion engine.

(13) The transmission control unit 50 analyzes relevant sensor signals and, with the aid of the engine control unit, converts them into control commands for the transmission actuators. The transmission control unit 20 can be a dual-clutch transmission, which permits fully automatic gear shifting with no interruption of traction by means of two subtransmissions. The transmission control unit 50 selects the gears on the basis of control signals from the engine control unit 10 or by driver command (shift paddles/selector levers).

(14) The clutch control unit 60 is a clutch system for vehicle transmissions in which the opening (disengagement) and closing (engagement) of the separating clutches is triggered by signals from the engine control unit (ECU) 10.

(15) FIG. 2 shows a block diagram that schematically represents the configuration of a 4-cylinder internal combustion engine of a vehicle according to an exemplary embodiment of the present invention.

(16) The internal combustion engine 200 is coupled to an exhaust turbocharger 210, which includes a turbine 211 and a compressor 212, wherein the turbine 211 and the compressor 212 are located on a common shaft 213, the so-called turbocharger shaft.

(17) The turbine 211 is connected to the internal combustion engine 200 by an exhaust manifold 220. The turbine 211 receives the exhaust gas of the internal combustion engine 200 through the exhaust manifold 220, and uses the energy contained in the exhaust gas of the internal combustion engine 200 to drive the compressor 212. The compressor 212 is coupled to an air filter through an intake runner 214. The compressor 212 draws in the fresh air that is filtered through the air filter, and forces precompressed air into the individual cylinders of the internal combustion engine 200. In addition, the turbine 211 is connected to an exhaust emission system by an exhaust pipe 230 in the direction of exhaust gas flow. The exhaust emission system breaks down the pollutants in the exhaust gases produced during operation of the internal combustion engine 200 and discharges the remaining exhaust gases. The turbocharger shaft 213 of the exhaust turbocharger 210 rotates ever faster with increasing motor speed and power on account of the increasing quantities of exhaust gas that drive it. At a certain speed, the compressor 212 reaches its delivery limit, and the danger also exists that the mechanical and thermal limits of the exhaust turbocharger 210 or of the internal combustion engine 200 will be exceeded. The supercharging of the internal combustion engine 200 that is desired at low speeds can become problematic at higher speeds. In order to avoid this, the exhaust turbocharger 210 is equipped with boost-pressure control, which makes it possible for the supercharger to deliver high output even at low exhaust gas flows and to not exceed the load limit at high speeds. A pressure sensor provides the current actual boost pressure to the engine control unit (10 in FIG. 1). Based on the current actual boost pressure, the engine control unit (10 in FIG. 1) controls the boost pressure. The boost-pressure control has the task of leveling out the difference between desired and actual boost pressures as quickly as possible. To this end, the boost-pressure control moves the actuator that is present (wastegate or adjustable guide vanes (variable turbine geometry, VTG)) as the actuating variable. The air that is drawn in and precompressed by the compressor is delivered to the throttle valve 240. The throttle valve 240 controls the passage of air that is precompressed to a greater or lesser degree into the individual cylinders of the internal combustion engine 200 as a function of the opening angle. The flow of precompressed air controlled by the throttle valve 240 is delivered to the individual cylinders of the internal combustion engine 200 through an intake manifold 250. The intake manifold 250 includes a pressure sensor that measures the current actual boost pressure of the intake manifold pressure. The throttle position of the throttle valve 240 is controlled through continuous closed-loop control of the throttle position in the entire operating range of the internal combustion engine 200. The area of application extends from the intake range through the overtravel range (pressure equalization at the throttle valve) to the supercharged operating range of the internal combustion engine. Due to the continuous closed-loop control of the throttle position in the entire operating range of the internal combustion engine 200, it is possible to set the intake manifold pressure accurately in a steady state in the entire operating range, as well. Because of the steady-state accuracy of the intake manifold pressure, it is additionally ensured that the requisite desired fresh air charge in the cylinder is set. Moreover, the continuous closed-loop control of the throttle position can also assist intake manifold pressure control in supercharged internal combustion engines with variable turbine geometry (VTG), as well. During phases of load reduction, the position of the throttle valve can have an assistive effect as a result of the continuous closed-loop control of the throttle position and consequently prevent pushing. Detailed closed-loop control of the throttle position is represented in FIG. 3.

(18) FIG. 3 shows, as an exemplary embodiment, a closed-loop control system for the closed-loop control of the throttle position in the intake, overtravel, and boost ranges of the internal combustion engine.

(19) The closed-loop control system 300 shows a closed internal model control (IMC) control loop. An IMC control loop is a process that simulates the response of the system in order to estimate the result of a system disturbance. The closed-loop control system 300 includes three filters 310, 330, and 370, a model-based precontrol 320, a limiting element 340, a process 350, and a process model 360.

(20) The filters 310, 330, and 370 can be low-pass filters, for example. A low-pass filter (LPF) is a filter that allows signals with a frequency below a selected limit frequency to pass and that attenuates signals with frequencies above the limit frequency. The precise frequency response of the filter depends on the filter design. In one embodiment, the filters 310, 330, and 370 can be PT.sub.1 elements or PT.sub.2 elements. A PT.sub.1 element is a linear time-invariant system (LTI) transfer element that has proportional transfer behavior with first order lag (low-pass). A PT.sub.2 element is an LTI transfer element in control engineering that has proportional transfer behavior with second order lag. Because of its complex conjugate poles, the PT.sub.2 element responds to an input signal change with a damped oscillatory output signal.

(21) The desired intake manifold pressure p.sub.SP constitutes the input in the closed-loop control system. This desired intake manifold pressure p.sub.SP is filtered with the PT.sub.1 element 310 to form the time derivative and stabilize the desired value. First, the time-filtered difference Δp.sub.f between the process 350 and the process model 360 is subtracted from this time-filtered desired value p.sub.SP,f, resulting in the corrected desired value p.sub.SPcor,f. Next, the model-based precontrol 320 calculates a desired area of the throttle valve A.sub.DK,coll from the corrected desired value p.sub.SPcor,f. This desired value A.sub.DK,soll is stabilized and steadied by the PT.sub.1 element 330. The dynamics of the controller can also be set with the PT.sub.1 element 330. Then the time-filtered desired area of the throttle valve A.sub.DK,soll,f is limited by a limiting element 340 of the physical actuator limits A.sub.DK,lim and provided to the process 350 and the process model 360 simultaneously in accordance with the IMC principle. The throttle valve is adjusted on the basis of the limited desired area of the throttle valve A.sub.DK,lim. The intake manifold pressure p resulting from the throttle position is measured by a pressure sensor. The measured intake manifold pressure p and the modeled intake manifold pressure {circumflex over (p)} may deviate from one another on account of noise that is introduced into the system either through internal sources (e.g., sensor noise—body sensors are not perfect) or external sources (e.g., unforeseeable forces from outside the body). The difference Δp between the measured intake manifold pressure p and the modeled intake manifold pressure {circumflex over (p)} is filtered with the PT.sub.1 element 370 and fed back in order to shape the dynamics and suppress measurement noise. Consequently the control loop is closed. A detailed method approach for the model-based precontrol 320 is shown in FIG. 4, and a detailed method approach for the process model 360 is shown in FIG. 5.

(22) FIG. 4 shows, as an exemplary embodiment, an approach to a method for model-based precontrol of the closed-loop control system.

(23) In step 400, the model-based precontrol receives the corrected desired value p.sub.SPcor,f and the time derivative of the desired value {dot over (p)}.sub.SPcor,f.

(24) In step 410, the desired area of the throttle valve (effective cross-sectional area of the throttle valve A.sub.DK,soll is calculated on the basis of the received desired values p.sub.SPcor,f and {dot over (p)}.sub.SPcor,f. The desired area of the throttle valve A.sub.DK,coll is calculated as follows:

(25) $\begin{array}{cc}{A}_{\mathrm{DK},\mathrm{soll}}=\frac{\frac{V}{{\mathrm{KRT}}_2}{\stackrel{.}{p}}_{\mathrm{SPcor}.f}+W_{\mathrm{viv}}\left(p\right)-W_{\mathrm{TEV}}}{p_1\sqrt{\frac{2}{{\mathrm{RT}}_1}}\Psi \left(p\right)}-A_{\mathrm{DK},\mathrm{leak}},& \left(\mathrm{Eq}.1\right)\end{array}$

(26) where: V is the volume of the intake manifold, R is the specific gas constant of air, K is the isentropic exponent, p is the air pressure in the intake manifold, T.sub.2 is the temperature of the air in the intake manifold, w.sub.vlv(p) is the outgoing air mass flow as a function of the air pressure p that flows out of the intake manifold through the intake valves, w.sub.TEV is the incoming air mass flow that flows into the intake manifold through the fuel-tank ventilation valve, p.sub.1 is the air pressure that is present upstream of the throttle valve, T.sub.1 is the temperature of the air that flows into the intake manifold through the throttle valve, Ψ(p) is the flow function as a function of the air pressure p, and A.sub.DK,leak is the effective leakage area of the throttle valve. The effective leakage area of the throttle valve A.sub.DK,leak can arise as a result of an incomplete closure of the throttle valve.

(27) The effective leakage area of the throttle valve A.sub.DK,leak, the temperature T.sub.1 of the air that flows into the intake manifold through the throttle valve, and the temperature T.sub.2 of the air in the intake manifold can be identified by means of a reference characteristic map. The reference characteristic map can be identified in a normal operating mode on the test stand by means of mass flow and boost pressure variations. Alternatively, the temperatures T.sub.1 and T.sub.2 can be measured by sensors.

(28) In step 420, the calculated desired area of the throttle valve A.sub.DK,soll is transmitted to the PT.sub.1 element (330 in FIG. 3).

(29) FIG. 5 shows, as an exemplary embodiment, an approach to a method for the process model of the closed-loop control system.

(30) In step 500, the process model receives the limited desired area of the throttle valve A.sub.DK,lim.

(31) In step 510, the modeled intake manifold pressure {circumflex over (p)} is calculated on the basis of the received limited desired area of the throttle valve A.sub.DK,lim. The modeled intake manifold pressure {circumflex over (p)} is calculated as follows:

(32) $\begin{array}{cc}\hat{p}=\int \left(\stackrel{.}{\hat{p}}\right)\mathrm{dt},\mathrm{where}& \left(\mathrm{Eq}.2\right)\\ \frac{V}{{\mathrm{KRT}}_2}\left(\stackrel{.}{\hat{p}}\right)=.Math.W_G=W_{\mathrm{thr}}-W_{\mathrm{viv}}+W_{\mathrm{TEV}}=p_1\sqrt{\frac{2}{{\mathrm{RT}}_1}}(A_{\mathrm{DK},\lim }+A_{\mathrm{DK},\mathrm{leak})}\Psi \left(p\right)-w_{\mathrm{viv}}\left(p\right)+w_{\mathrm{TEV}}\mathrm{is}.& \left(\mathrm{Eq}.3\right)\end{array}$

(33) Here: W.sub.G is the air mass flow in the intake manifold, W.sub.thr is the incoming air mass flow that flows into the intake manifold through the throttle valve, p.sub.1 is the air pressure upstream of the throttle valve (boost pressure), V is the volume of the intake manifold, R is the specific gas constant of air, K is the isentropic exponent, p is the air pressure in the intake manifold, T.sub.2 is the temperature of the air in the intake manifold, w.sub.vlv(p) is the outgoing air mass flow as a function of the air pressure p that flows out of the intake manifold through the intake valves, w.sub.TEV is the incoming air mass flow that flows into the intake manifold through the fuel-tank ventilation valve, T.sub.1 is the temperature of the air that flows into the intake manifold through the throttle valve, Ψ(p) is the flow function as a function of the air pressure p, and A.sub.DK,leak is the effective leakage area of the throttle valve.

(34) The effective leakage area of the throttle valve A.sub.DK,leak, the temperature T.sub.1 of the air that flows into the intake manifold through the throttle valve, and the temperature T.sub.2 of the air in the intake manifold can be identified by means of a reference characteristic map. The reference characteristic map can be identified in a normal operating mode on the test stand by means of mass flow and boost pressure variations. Alternatively, the temperatures T.sub.1 and T.sub.2 can be measured by sensors.

(35) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.