JP2002070621A - Method and apparatus for compensating for nonlinear characteristics of an air system of an internal combustion engine - Google Patents

Abstract

An object of the present invention is to compensate for an influence amount which occurs during operation of an engine and affects a nonlinear characteristic of a closed loop control section (air system). A regulator changes an adjustment amount for an actuator of an air system, which is derived from a deviation between a target amount and an actual amount of the air system. A method for compensating for a non-linear characteristic of an air system of an internal combustion engine, such that a linear relationship is established, wherein a new control variable is determined from at least one state variable of the air system and a control variable supplied by the regulator. And the dependence of the new adjustment on the adjustment from the regulator is the inverse of the non-linear dependence of the actual on the new adjustment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and a device for compensating for non-linear characteristics of an air system of an internal combustion engine. In the present invention, the adjustment amount for the actuator of the air system, which is derived by the regulator from the deviation between the target amount and the actual amount of the air system, is changed such that a linear relationship holds between the adjustment amount and the actual amount. You.

[0002]

2. Description of the Related Art The air system of an internal combustion engine refers to all devices that affect the amount of air to be taken. These devices include, for example, throttle valves, turbochargers or exhaust gas recirculation devices, in which case only one of these devices may be provided,
A plurality may be provided. Usually, each of the devices constituting the air system of the internal combustion engine has one actuator and one regulator (for example, a P regulator, a PI regulator, or a PID regulator). From the deviation from the quantity, an adjustment quantity for the actuator of the air system device is derived. The closed-loop control section consisting of the air system device and the actuators belonging thereto exhibits a non-linear characteristic, ie the dependence of the actual quantity formed by the air system on the adjustment quantity is non-linear. This non-linearity requires a special design for the regulator, which can be very time consuming in some situations.

[0003] In DE 198 12 843 A1, the problem of non-linearities in the air system is described using closed-loop control of the boost pressure as an example. Devices for changing the turbine geometry or bypass valves are used as actuators for turbochargers. In all these actuators, there is a non-linear relationship between the boost pressure formed by the turbocharger and the amount of adjustment to the actuator. This non-linear relationship will be negligible as long as the operating point of the boost pressure control is shifted only within very narrow boundaries. However, if the operating range of the boost pressure control device is not limited to a very narrow operating range but a further operating range, that is, a changing range of the adjustment amount, is required, the movement of the operating point in the control process is relatively small. On the one hand, this leads, on the one hand, to excessive delays in the closed-loop control process and, on the other hand, to excessive fluctuations in the closed-loop control. Said DE 1
According to 9812 843 A1, in order to solve the above-mentioned problem, an adjustment amount for the actuator of the turbocharger, or one or more other characteristic amounts forming the adjustment amount, is adjusted in the characteristic map by the adjustment amount and the control amount. The conversion between the quantity (charging pressure) and the quantity (charging pressure) results in a value that at least establishes a substantially linear relationship. As a result of this measure, a linear closed-loop control characteristic is formed, which enables a fast and stable closed-loop control of the supercharging pressure without depending on the position of the operating point. The conversion value for the adjustment amount filed in the characteristic map for linearization is
Since the characteristic amount is fixedly set only once, in some cases, the amount of influence on the closed loop control section that may occur in the current event cannot be compensated by this value.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and a device which are able to compensate for the amount of influence on the non-linear characteristics of the closed loop control section (air system) which occurs during operation of the engine. It is.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide, according to the present invention, a method of changing an adjustment amount for an actuator of an air system, which is derived from a deviation between a target amount and an actual amount of the air system by a regulator. A method for compensating for a non-linear characteristic of an air system of an internal combustion engine, wherein a linear relationship is established between the adjustment quantity and the actual quantity, provided by at least one state quantity of the air system and the regulator. From the adjustment amount, a new adjustment amount is derived, and the non-linear dependency of the new adjustment amount on the adjustment amount from the regulator is:
This is solved by making the inverse of the non-linear dependence of the actual quantity on the new adjustment quantity.

According to the present invention, there is also provided an object of the present invention is to change an adjustment amount for an actuator of an air system, which is derived from a deviation between a target amount and an actual amount of the air system by a regulator. Apparatus for compensating for a non-linear characteristic of an air system of an internal combustion engine, wherein the means is provided with means for establishing a linear relationship with the actual quantity, the means comprising at least one state quantity of the air system and the A new adjustment amount is derived from the adjustment amount supplied by the regulator, and a non-linear dependence of the new adjustment amount on the adjustment amount from the regulator is a non-linear dependence of the actual amount on the new adjustment amount. It is solved by configuring to be the reverse of.

The advantage of this method or device is that compensation for the non-linearity of the control section takes place in real time, taking into account the current state of the control section. This takes into account the dynamics of the air system and possibly the influence of other systems.

[0008] Advantageous modifications of the invention result from the dependent claims.

[0009]

The at least one state variable which derives a new adjustment value for the air system is advantageously determined by means of a model calculation. Therefore, measurement of various state quantities can be omitted by constructing a model.

The state variables include, for example, supercharging pressure, turbocharger rotation speed, exhaust gas recirculation rate, mass of air accumulated in the intake pipe, gas temperature in the intake pipe, throttle valve position, exhaust recirculation valve position, The position of the bypass valve or the state of the variable turbine geometry of the turbocharger, or one or more parameters derived therefrom, are taken into account in the linearization of the closed-loop control section.

For the purpose of linearization, one new control variable can be derived for the variable turbine geometry or for the turbocharger bypass valve or exhaust recirculation valve or throttle valve actuator.

In order to achieve a relatively high accuracy in the modeling of the state variables, it is advantageous to generate the difference between the state variables determined by the model calculation and the corresponding state variables determined by measurement. From this difference, a correction coefficient for the state quantity by modeling is obtained.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in more detail in the following description using an embodiment shown in the drawings.

FIG. 1 shows an internal combustion engine 1 having an intake passage 2 and an exhaust passage 3. In the exhaust path 3, a turbine 4
Are arranged, and a compressor 5 of an exhaust turbine supercharger is arranged in the intake passage 2. Further, the internal combustion engine may include an exhaust recirculation path 6 connecting the exhaust path 3 and the intake pipe 2. Within the exhaust gas recirculation path 6 is a controllable exhaust gas recirculation valve 7. In the intake pipe 2, the supercharging pressure p
pressure sensor 8 for measuring ld and the air mass l to be taken
An air mass sensor 9 for measuring m is arranged. In addition, there is a throttle valve 10 in the intake pipe. Thus, in the illustrated embodiment of the internal combustion engine, there are three air system devices that affect the intake air mass: turbochargers 4,5, exhaust recirculation devices 6,7 and throttle valve 10. ing.

In FIG. 1, there are two possible actuators for the turbocharger. The first actuator 11 is a valve in a bypass 12 that bypasses the turbine 4. Alternatively, another actuator 13 is provided, which acts on the turbine geometry, ie adjusts the blades of the turbine. The actuator 11 which is a bypass valve has an adjustment amount b
pv, and the variable turbine geometry actuator 13 receives the adjustment amount vtg. An adjustment amount arf is supplied to the exhaust gas recirculation valve 7, and an adjustment amount dk is supplied to the throttle valve 10. All of the adjustment amounts bpv, vtg, arf and dk are:
Provided from the control device 14. The control unit 14 is supplied with a series of state variables of the internal combustion engine. FIG. 1 shows, for example, the supercharging pressure pld measured by the supercharging pressure sensor 8 and the intake air amount lm measured by the air amount sensor 9 in FIG. As additional state variables, the control device 14 further includes a supercharger speed, an exhaust gas recirculation rate, an air mass accumulated in the intake pipe, a gas temperature in the intake pipe, a throttle valve position, a position of the exhaust recirculation valve, The position of the bypass valve or the state of the variable turbo geometry of the turbocharger, or one derived therefrom
One or more characteristic quantities are supplied.

Already at the introduction, individual air system units,
That is, the turbochargers 4, 5, the exhaust recirculation devices 6, 7,
The problem of the non-linear characteristics of the throttle valve 10 has been described. According to the control device 14, the adjustment amounts bpv, vtg,
arf and dk are determined, and these adjustment amounts are:
Calculations are made such that the relationship between these and the actual quantities supplied to the respective air system devices is linear. How this linearization is performed will be described with reference to the block diagram shown in FIG.

FIG. 2 shows a closed loop control system in which the air system L of the internal combustion engine is used.
There is a closed loop control section consisting of S and the actuator ST belonging to S. As already explained above, the air system LS can consist of one or more devices, for example a turbocharger 5, 6 or an exhaust recirculation device 6, 7, or a throttle valve 10. The blocks labeled LS in FIG. 2 thus represent one or more of these air system devices.

At the output of the air system LS, an actual quantity y appears, which represents the actual state of the air system. This actual state is, for example, in the case of a turbocharger, the supercharging pressure pld measurable by the sensor 8
It is. The actual quantity y is compared with the target quantity w at the node VK to form a deviation e between the target quantity w and the actual quantity y. The target amount w is, for example, a target boost pressure, which is derived from the engine speed, the throttle valve position and the driver's demands, and possibly also from other operating quantities of the engine. is there. The deviation e of the closed loop control amount is, for example, a P regulator or PI
It is supplied to a regulator RG which is a regulator or a PID regulator. An adjustment amount v appears on the output side of the regulator RG.

Due to the non-linear characteristics of the closed-loop control section consisting of the air system LS and the actuators ST belonging to it, the relationship between the actual quantity y and the adjustment quantity v is not linear. The goal of the present invention is to extend the closed loop control system such that a linear relationship holds between the actual amount y and the adjustment amount v of the air system LS. For this purpose, a circuit block LI is inserted between the regulator RG and the actuator ST.
Derives a new adjustment amount u from the adjustment amount v for linearization. In the linearization circuit block LI, a dependency on the adjustment amount v from the regulator RG is formed for the new adjustment amount u. This dependency is the inverse of the non-linear dependency of the actual quantity y of the air system LS on the new adjustment quantity u. Therefore, the closed loop control section ST,
The nonlinear characteristic of LS is compensated by the nonlinear dependence of the new adjustment amount u on the adjustment amount v of the regulator RG. In other words, the adjustment amount for the actuator ST is distorted in advance so that the nonlinear characteristic of the closed loop control section including the air system LS and the actuator ST belonging thereto is compensated. And finally, the series circuit consisting of the linearization circuit block LI, the actuator ST and the air system LS has the same characteristics as a chain of integrators.

Hereinafter, how the new adjustment amount u is obtained from the adjustment amount v of the regulator RG and the state amount x of the air system in the linearization circuit block LI will be described. The state quantity x is, for example, the supercharging pressure pld, the supercharger speed, the exhaust gas recirculation rate, the air mass accumulated in the intake pipe, the gas temperature in the intake pipe, the position of the throttle valve 10, the position of the bypass valve 11, or It can be the state of the variable turbine geometry 13 of the supercharger 4, or one quantity derived therefrom. For simplicity, the following focuses on the state quantity x only. However, more than one of the above quantities may be used. In very simplicity, the air system is described by equation (1).

[0021]

(Equation 1)

This equation (1) represents a temporal change of the state quantity x. This illustrates the simple PT1 characteristics of the air system. The non-linear characteristic of the air system is given by equation (2)
Described by

[0023]

(Equation 2)

Equation (2) shows the relationship between the actual quantity y and the state quantity x in the form of a parabola. Time-dependent parameters a ₀ (t) and a ₁ (t) and constants c ₁ and c
₂ defines the time-dependent position and shape of the parabola.

The at least one state quantity x is measured by a sensor or in a circuit block MD:
It is calculated from other operating quantities of the internal combustion engine. Such model calculations are known per se and therefore will not be described here in detail. In order to approximate the state quantity x by modeling to the actual state quantity as accurately as possible, it is advantageous in some cases to consider the correction coefficient Δx in the model calculation. This correction coefficient Δx is formed by the observer BB. This observer BB represents the deviation between the modeled state quantity x and the measured state quantity, and forms a correction factor Δx which influences the state quantity x in the model calculation according to this deviation.

In the following equation (3), the time derivative of the actual quantity y is expressed according to equation (2).

[0027]

(Equation 3)

As required, when a linear relationship according to the integrator is established between the actual amount y and the adjustment amount v of the regulator RG,

[0029]

(Equation 4)

The following relationship must be satisfied. From equations (3) and (4), finally, for a new adjustment amount u,

[0031]

(Equation 5)

Is obtained. This equation (5) represents a new adjustment amount u for the state amount x and the adjustment amount v of the regulator RG.
Represents a dependency. The dependence of the new adjustment u on the adjustment v is therefore exactly the opposite of the non-linear dependence of the actual quantity y on the new adjustment u. Therefore, a linear relationship holds between the actual amount y and the adjustment amount v of the regulator RG.

The regulator should be a robust regulator, for example a switching regulator that always accepts only one of the two extremes. Such a robust regulator is insensitive to parameter variations in a closed loop control system.

[Brief description of the drawings]

FIG. 1 schematically shows an internal combustion engine having a plurality of air system devices.

FIG. 2 shows a block circuit diagram of a closed loop control system with a linearization function for an air system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake path 3 Exhaust path 4 Turbine 5 Compressor 6 Exhaust recirculation path 7 Exhaust recirculation valve 8 Pressure sensor 9 Air flow sensor 10 Throttle valve 11 Bypass valve 12 Bypass 13 Actuator 14 Control device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 11/10 F02D 41/20 310A 41/14 310 F02M 25/07 550C 41/20 310 550F F02M 25/07 550 550R F02B 37/12 301Q 301A (72) Inventor Manfred Birg Germany Oberleighingen Gartenstraße 1 (72) Inventor Frank Maier Germany Federal Republic Kornwestheim Neufenstrasse 5 (72) Inventor Thomas Bryle Germany Stuttgart Bohlenstrasse 29 (72) Inventor Peter Rupp Germany Germany Remsek Sternbergweg 9 (72) Invention Wolfgang Kraemer Germany Ingolstadt Bömerwaldstrasse 22 F-term (reference) 3G005 EA15 FA06 GA04 GB17 GB24 GB28 GE01 HA04 HA05 HA12 HA19 JA02 JA06 JA12 JA36 JA39 JA45 3G062 AA05 BA04 BA06 CA06 FA08 GA01 GA04 GA05 GA06 GA08 AA03 AA04 CA22 CA23 CA26 DA04 FA11 GA01 GA04 GA05 GA06 GA10 GA14 GA41 GA46 KA31 KA33 KA35 KA36 3G301 HA01 HA11 HA13 JA18 JA20 KA21 LA01 LA03 LC10 MA01 NA09 NB20 ND06 ND18 PA01Z PA07Z PA11Z PA15Z PA16Z PD15Z

Claims (8)

[Claims] 1. A method for compensating for non-linear characteristics of an air system of an internal combustion engine, the method comprising compensating the air system (L) by a regulator (RG).
Deviation (e) between the target quantity (w) and the actual quantity (y) of S)
By changing the adjustment amount (v) of the air system (LS) with respect to the actuator (ST), the linear relationship holds between the adjustment amount (v) and the actual amount (y). Deriving a new adjustment quantity (u) from at least one state quantity (x) of the air system and an adjustment quantity (v) supplied by the regulator (RG), The nonlinear dependence of the new adjustment amount (u) on the adjustment amount (v) from (RG) is the inverse of the nonlinear dependence of the actual amount (y) on the new adjustment amount (u). A method for compensating for non-linear characteristics of an air system of an internal combustion engine. 2. A bypass valve (1) for a variable turbine geometry (13) or for a turbocharger (4, 5).
2. The method according to claim 1, wherein a new adjustment amount (vtg, bpv) for 1) is derived. 3. The method according to claim 1, further comprising deriving a new control variable (arf) for the exhaust gas recirculation valve (7). 4. A throttle valve actuator (1)
Method according to claim 1, wherein a new adjustment value (dk) for 0) is derived. 5. The method according to claim 1, wherein at least one state quantity (x) of the air system (LS) is determined by a model calculation (MD). 6. The state quantity (x) may be one or more of the following quantities: a supercharging pressure, a supercharger rotation speed, an exhaust gas recirculation rate, an air amount accumulated in an intake pipe, The gas temperature, the position of a throttle valve, the position of an exhaust gas recirculation valve, the position of a variable turbine geometry of a bypass valve or a turbocharger, or one or more characteristic quantities derived therefrom, according to claim 1 or 5. The method according to 5. 7. A difference between a state quantity (x) determined by the model calculation (MD) and a corresponding state quantity determined by measurement, and the modeled state is calculated from the difference. 6. The method according to claim 5, comprising forming a correction factor ([Delta] x) for the quantity (x). 8. An apparatus for compensating for non-linear characteristics of an air system of an internal combustion engine, wherein the air system (L) is controlled by a regulator (RG).
Deviation (e) between the target quantity (w) and the actual quantity (y) of S)
By changing the adjustment amount (v) of the air system (LS) with respect to the actuator (ST), the linear relationship holds between the adjustment amount (v) and the actual amount (y). An apparatus of the type provided with means (LI) for providing at least one of the air systems.
From the two state quantities (x) and the adjustment quantity (v) supplied by the regulator (RG), a new adjustment quantity (u)
The nonlinear dependence of the new adjustment amount (u) on the adjustment amount (v) from the regulator (RG) is the nonlinear dependence of the actual amount (y) on the new adjustment amount (u). Device for compensating for non-linear characteristics of an air system of an internal combustion engine, characterized in that the relationship is reversed.