DE102004035317B4 - Method and device for controlling an internal combustion engine - Google Patents

Abstract

A method for controlling an internal combustion engine with an actuator (104) for influencing the fresh air mass flow and an actuator (118) for influencing the exhaust gas recirculation mass flow supplied to the internal combustion engine, based on a comparison between a setpoint and an actual value for the fresh air mass flow and the exhaust gas recirculation mass flow by means of a controller (220, 320) the manipulated variables for the actuators (104, 118) can be specified, the manipulated variables each being superimposed with a model-based pre-control value that can be specified by means of a model, the model at least one first partial model (230) for a mixing point of fresh air mass flow and exhaust gas recirculation mass flow and second partial models (235, 335) for the actuators (104, 118).

Description

The invention relates to a method and a device for controlling an internal combustion engine.

A method and a device for controlling an internal combustion engine is, for example, from DE 196 20 039 known. In the system described there, a first actuator is used to influence the fresh air mass flow supplied to the internal combustion engine and a second actuator is used to influence the exhaust gas recirculation mass flow. A control flap which is arranged in the suction line after the compressor is preferably used as the first actuator. An exhaust gas recirculation valve which is arranged in the exhaust gas recirculation line is preferably used as the second actuator.

In certain operating states, precise setting of both the fresh air mass flow and the proportion of the recirculated exhaust gas is necessary. For this purpose, both the exhaust gas recirculation valve and the control flap must be operated in a controlled manner. Such an operating state occurs, for example, during the regeneration of an exhaust gas aftertreatment system, for example during the regeneration of a NOx storage catalytic converter.

The DE 102 56 241 A1 describes a method for controlling exhaust gas recirculation. The amount of recirculated exhaust gas is regulated as a function of the raw exhaust gas emissions recorded upstream and / or downstream of an exhaust gas recirculation device and / or other exhaust gas components.

The DE 199 20 498 A1 describes a method for controlling an amount of recirculated exhaust gas from an internal combustion engine. Based on the difference between an actual variable and a target variable, which characterizes the amount of recirculated exhaust gas, a controller specifies a manipulated variable for controlling an actuator.

The WO 01/48 363 A1 describes a method for controlling an internal combustion engine with an air system. A model is used to determine at least one variable that characterizes the air system on the basis of at least one manipulated variable and at least one measured variable. The model comprises several sub-models. The sub-models use output quantities of other sub-models as input quantities.

The DE 102 43 268 A1 describes a method for regulating the charging of an internal combustion engine. In this case, a manipulated variable is generated from the control deviation between a setpoint value of an operating parameter and an actual value of this operating parameter, which has at least one component supplied by an integral rule. A limit value is specified for this, which is determined from several operating parameters. This limit value is adapted.

The intake manifold pressure, that is to say the pressure upstream of the intake into the internal combustion engine, is usually regulated. The regulation of the intake manifold pressure via the exhaust gas recirculation valve is based on the assumption that the intake manifold pressure always increases, regardless of the position of the control flap, if the exhaust gas recirculation valve is opened further. However, this only applies if the control flap is set so far that there is a significant pressure drop across the control flap. However, this effect can be reversed from a certain opening angle of the control valve. If the exhaust gas recirculation valve is opened in this case, more exhaust gas flows through the exhaust gas recirculation line and thus less mass flow through the turbine. For this reason, the compressor delivers less and the pressure downstream of the compressor is lower. This in turn causes the intake manifold pressure to drop. In summary, this means that the control direction of the intake manifold pressure control by means of the exhaust gas recirculation valve can change depending on the opening angle of the control flap. The controller cannot compensate for this behavior and thus cannot adjust the setpoint either.

The task is to achieve the most precise possible regulation of the intake manifold pressure, the application and / or adaptation of which is as simple as possible.

With conventional controller structures, a balance must always be found between good control behavior and good disruptive behavior. In that a first actuator is provided for influencing the fresh air mass flow supplied to the internal combustion engine and / or the exhaust gas recirculation mass flow, based on a comparison between a setpoint and an actual value for the fresh air mass flow and / or the exhaust gas recirculation mass flow using a controller at least one manipulated variable for the at least one Actuator can be specified, and that a model-based precontrol value is superimposed on the at least one manipulated variable, the controller only needs to regulate minor deviations. I.e. the controller can be applied to good disturbance behavior.

It is particularly advantageous if a first actuator, which influences the fresh air mass flow supplied to the internal combustion engine, and a second actuator, which influences the exhaust gas recirculation mass flow, are provided, based on a comparison between a first setpoint and a first actual value for the fresh air mass flow the first steeper and that based on a comparison between one second setpoint value and a second actual value for the fresh air mass flow, a second manipulated variable for the second actuator can be specified, and that a model-based precontrol value is superimposed on at least one manipulated variable. This means that a controller for the fresh air mass flow and a controller for the exhaust gas recirculation mass flow are provided and at least one of the controllers is additionally assigned a pilot control.

Because the pre-control value can be specified by means of a model, the pre-control value can be specified very precisely.

It is particularly advantageous if the model contains at least a first partial model for a mixing point and / or a second partial model for the actuator. The space between the inlet of the internal combustion engine and the two actuators is referred to as the mixing point. The actuators are preferably the control flap and the exhaust gas recirculation valve. The adaptation of the model is significantly simplified by dividing the model.

It is particularly advantageous if the first partial model for the mixer controls processes the temperature T3 after the exhaust of the internal combustion engine, the temperature T21 before the actuator, the speed N, the setpoint values for the fresh air mass flow and the exhaust gas recirculation mass flow. These variables have a significant effect on the pre-control values. Additional parameters can be taken into account to increase the accuracy.

It is advantageous if the second partial model for specifying the manipulated variable for the fresh air mass flow processes at least one pressure P22 in the intake manifold and the setpoint value for the fresh air mass flow as input variables. These variables have a significant effect on the pre-control value. Additional parameters can be taken into account to increase the accuracy.

It is particularly advantageous if the second partial model (235) processes at least temperature T21 and / or a pressure P21 upstream of the actuator and downstream of the compressor and / or a setpoint air mass flow MA as input variables to specify the manipulated variable for the fresh air mass flow. These variables have a significant effect on the pre-control value. Additional parameters can be taken into account to increase the accuracy.

It is particularly advantageous if the second sub-model 335 processes at least a temperature T3 and / or a pressure P3 of the exhaust gas downstream of the outlet of the internal combustion engine and upstream of the turbine and / or a target exhaust gas mass flow MR to specify the manipulated variable for the exhaust gas recirculation mass flow. These variables have a significant effect on the pre-control value. Additional parameters can be taken into account to increase the accuracy.

By adapting the setpoint to the behavior of the control loop over time, the behavior of the controller and the precontrol can be significantly improved.

Because the actual value can be specified using a second model, cost-intensive sensors for determining the actual value can be saved.

The fact that the controller can be switched off in certain operating states improves the behavior of the system significantly.

drawing

• 1 ein Blockdiagramm einer Brennkraftmaschine und
• 2 ein Blockdiagramm der erfindungsgemäßen Vorgehensweise.

The invention is explained below with reference to the embodiments shown in the drawing. It shows

• 1 a block diagram of an internal combustion engine and
• 2 a block diagram of the procedure according to the invention.

The procedure according to the invention is described below using the example of a control flap and an exhaust gas recirculation valve. In principle, the procedure according to the invention can be applied to all actuators with which the fresh air mass flow or the exhaust gas recirculation mass flow can be influenced. Instead of the fresh air mass flow or the exhaust gas recirculation mass flow, other variables that correspond to these variables can also be regulated and / or controlled. I.e. The setpoint values or the actual values are variables that characterize the fresh air mass flow or the exhaust gas recirculation mass flow. The manipulated variables are suitable variables for controlling the corresponding actuator.

The procedure according to the invention is described below using the example of a diesel internal combustion engine. However, the invention is not restricted to use in diesel internal combustion engines; it can also be used in other internal combustion engines, in particular in direct-injection gasoline internal combustion engines.

An internal combustion engine 100 is supplied with a certain amount of gas ML22, which contains a certain oxygen content MO22, via a high pressure fresh air line 102. The size MO22 is also known as the percentage of oxygen before combustion. The high pressure fresh air line 102 consists of two Divide. A first part is designated 102a, a second is designated 102b. The first part corresponds to the line up to the exhaust gas admixture. The second part 102b corresponds to the line after the exhaust gas admixture. A regulating flap 104 is arranged in the first part 102a. The air in the first part of the high pressure fresh air line 102a has a temperature T2 and a pressure P2. The fresh air mass flow MA flows through this part of the high pressure fresh air line or through the regulating flap.

The ambient air reaches a compressor 106 via a low-pressure fresh air line 108 and then flows through the control flap 104 into the high-pressure fresh air line 102. Via the compressor, the amount of air ML21 with the oxygen content MO21 flows into the high-pressure fresh air line 102. The air amount ML21 with the oxygen content MO21, which is passed through the Low-pressure fresh air line 108 flows, corresponds in the static state to the amount of air with the corresponding proportion of oxygen that flows through the compressor 106 or through the control flap 104. The pressure P21 and the temperature T21 prevail between the compressor 106 and the control flap.

The temperature T1 and the pressure P1 prevailing in the low-pressure fresh air line 108 correspond to the ambient conditions, i.e. the ambient pressure and the ambient temperature.

The amount of air ML31 with the oxygen component MO31 flows from the internal combustion engine 100 into a high-pressure exhaust gas line 110. The variable MO31 is also referred to as the oxygen component after combustion. The temperature T3 and the pressure P3 prevail in the high-pressure exhaust gas line 110. These values are also referred to as exhaust gas pressure P3 and exhaust gas temperature T3.

A quantity of air ML32 reaches a turbine 112 from the high-pressure exhaust gas line 110; this is also referred to as the quantity of air via the turbine. The exhaust gas passes from the turbine 112 into a low-pressure exhaust gas line 114, which is also referred to as the exhaust line 114. The temperature in the low-pressure exhaust line is T4 and the pressure is P4.

The turbine 112 drives the compressor 106 via a shaft 111. The speed NL of the shaft is referred to as the supercharger speed. The characteristics of the turbine and thus of the entire charger can be influenced by means of a charge generator 113. To control the charger, a control signal LTV is applied to the charger, which results in an adjustment of the charger by a stroke LH. The size LH is also referred to as the charger stroke and the size LTV as the charger duty cycle.

A connection, which is referred to as exhaust gas recirculation line 116, exists between the high pressure exhaust gas line 110 and the high pressure fresh air line 102. The amount of air MR, which contains the oxygen component MOA, flows through this exhaust gas recirculation line 116. The cross section of the exhaust gas recirculation line 116 can preferably be controlled by means of an exhaust gas recirculation valve 118. To control the exhaust gas recirculation actuator 119, a control signal ATV is applied, which results in an adjustment of the exhaust gas recirculation valve 118 by a stroke AH. The variable AH is also referred to as the exhaust gas recirculation stroke and the variable ATV as the exhaust gas recirculation duty cycle.

The speed N at the crankshaft and / or the camshaft of the internal combustion engine is preferably detected by means of a speed sensor 101. Furthermore, quantity adjusting elements 103 are provided which determine the fuel quantity ME to be injected, which is supplied to the internal combustion engine. For this purpose, the actuators 103 are acted upon by a quantity signal ME.

In 2 the procedure according to the invention is shown using a block diagram. An actual value determination 200 determines an actual value for the fresh air mass flow on the basis of various input variables (not shown). In a simple embodiment, it is provided that the actual value determination 200 is designed as a sensor that directly detects the fresh air mass flow. In an improved embodiment it is provided that a model calculation is used to determine the actual value, for example in the DE 199 63 358 is described. There the fresh air mass flow corresponds to the size ML21.

The output signal of the actual value determination 200 reaches a controller 220 via a node 205. The output signal of the controller 220 is applied to a node 225, which in turn applies a manipulated variable to the control valve 104. At the second input of the node 205, the output signal of a setpoint filter 210 is present with a negative sign, to which the output signal of a setpoint specification 215 is fed as an input. The target value specification 215 specifies the desired target value for the fresh air mass flow MA as a function of various operating parameters and various operating states. The output signal of the setpoint filter 210 also reaches a model 230 of the mixing point. The model 230 also processes the output signal of various sensors 232 which detect signals relating to the temperature T3 between the outlet of the internal combustion engine and the inlet of the turbine, the temperature T21 between the outlet of the compressor and the control valve and the speed N. Besides these sensors Further sensor signals can be recorded and evaluated by the model 230.

The output signal of the model 230 is applied to an inverse model 235 of the control flap. The model 230 supplies signals relating to the fresh air mass flow MA and the pressure P22, which corresponds to the pressure in front of the inlet of the internal combustion engine, to the inverse model 235. Furthermore, the inverse model 235 receives the signals from various sensors 240, the pressure P21 and the temperature T21 characterize between the outlet of the compressor and the control valve 104, supplied. Instead of the sensors 240, a model can also be provided which determines these variables on the basis of other variables. The output signal of the inverse model 235 reaches the node 225 via a characteristic curve 245. The model 230, in conjunction with the inverse model 235 and the characteristic curve 245 act as a pilot control for the manipulated variable of the regulating flap 104.

A parallel branch for regulating the exhaust gas recirculation mass flow MR is denoted by corresponding reference symbols. The exhaust gas recirculation valve 118 is supplied with the output signal of a node 325, at one input of which the output signal of a controller 320 is present. The output signal from node 305 is fed to controller 320, which in turn is fed the output signal of an actual value determination 300 as an input variable. The actual value determination 300 is designed similarly to the actual value determination 200; H. it can be designed as a sensor or as a model. Setpoint specification 315 specifies a setpoint for the exhaust gas recirculation mass flow, which also reaches node 305 or model 230 via a setpoint filter 310. Instead of the exhaust gas recirculation mass flow, the exhaust gas recirculation rate can also be specified as a setpoint. The model 230 applies a signal to a second inverse model 335 which characterizes the exhaust gas recirculation mass flow MR and the pressure P22 upstream of the intake of the internal combustion engine. Furthermore, the inverse model 335 processes signals from sensors 340, in particular the pressure P3 and the temperature T3 between the outlet of the internal combustion engine and the inlet of the turbine. Instead of the sensors 340, a model can also be provided which determines these variables on the basis of other variables. The output signal of the second inverse model 335 arrives at node 325 via a second characteristic curve 345.

The controller 220 regulates the fresh air mass flow MA to the setpoint specified by the setpoint specification 215. For this purpose, the actual value that is provided by actual value determination 200 is compared with the filtered setpoint. Based on the deviation of the setpoint value from the actual value, the manipulated variable for acting on the regulating flap 104 is specified by the controller 220. The actual value determination 200 can be used as a sensor that determines the fresh air mass flow directly, or as a model, as it is, for example, from the DE 199 63 358 is known to be trained.

A precontrol is superimposed on this regulation. The pilot control essentially contains a model which, based on the setpoint value for the fresh air mass, specifies a manipulated variable for the regulating flap 104. The model includes at least two sub-models. A partial model 230 simulates the mixing point, i. H. the area between the exhaust gas recirculation valve, the control flap 104 and the inlet of the internal combustion engine. A further partial model 235 contains an inverse model of the regulating flap 104. Using the characteristic curve 245, this output signal of the model, which corresponds to the desired effective flow area of the regulating flap, is converted into a manipulated variable for the regulating flap 104.

This means that the precontrol calculates, on the basis of the target value for the fresh air mass MA and various operating parameters, in particular temperature and pressure variables, a desired effectively flowed through area of the regulating flap and thus a precontrol value. Based on the deviation of the setpoint from the actual value of the fresh air mass, the control also calculates a manipulated variable for the control flap. These two variables are preferably superimposed additively at the point of connection to form the manipulated variable.

A corresponding control loop with a pilot control is also provided for the exhaust gas recirculation mass flow MR. Here, target value specification 315 specifies a corresponding target value that is filtered in filter 310 and compared with the actual value of actual value determination 300 at node 305. A sensor that directly detects the exhaust gas recirculation mass flow is preferably also used as the actual value determination 300. Since such sensors are usually very expensive and complex and are not available inexpensively, a model is also used here in a preferred embodiment which corresponds to the model of the actual value determination, which determines these variables on the basis of further operating parameters. The controller 320 calculates the manipulated variable for controlling the exhaust gas recirculation valve 118 as a function of the deviation between the setpoint value and the actual value.

Furthermore, a precontrol is provided which, based on the setpoint value, also specifies a precontrol value using a model. The model contains the first partial model that models the mixing point and an inverse model of the exhaust gas recirculation valve. A characteristic curve is attached to the model.

This means that, based on a comparison between a first setpoint value, which characterizes the fresh air mass flow, and a first actual value, a manipulated variable is specified for the first actuator, which is preferably designed as a control flap. Furthermore, based on the comparison between a second setpoint, which characterizes the exhaust gas recirculation mass flow, and a second actual value, a manipulated variable for the second actuator, which is preferably designed as an exhaust gas recirculation valve, is specified.

I.e. a parallel structure is provided in which a setpoint value for the fresh air mass flow or a setpoint value for the exhaust gas recirculation mass flow is adjusted to the specified setpoint. In a preferred embodiment, it is provided that the manipulated variable, which is determined by the regulation, is superimposed with a pre-control value. It is preferably provided here that the setpoint value that is also fed to the control loop is used to form the pilot control value. To form the pilot control values, a model is used which contains at least a first or a second partial model that model the mixing point or represent an inverse model of the actuator. Accordingly, in a particularly advantageous embodiment, it is provided that the actual value determination is also designed as a model that determines the actual value on the basis of various operating parameters.

The exhaust gas recirculation mass flow, d. H. the mass flow that flows through the exhaust gas recirculation valve is specified as the setpoint and the actual value is adjusted to this specified setpoint. Alternatively, the exhaust gas recirculation rate can also be specified as the setpoint and adjusted to the setpoint.

It is advantageous that a control loop is provided for the fresh air mass flow and for the exhaust gas recirculation mass flow, this control loop containing a controller on the one hand and a pilot control on the other. I.e. the two variables are each adjusted to a setpoint independently of one another.

According to the invention, the pre-control is designed in such a way that it specifies the temporal progressions of the manipulated variable for the control flap and the exhaust gas recirculation valve in such a way that the system is able to follow the setpoint changes solely through this pre-control. I.e. In extreme cases, the controller 220 and 320 can be dispensed with entirely or it can be switched off in certain operating states. The model with which the setpoint is converted into the manipulated variable contributes significantly to the success of the precontrol. The model includes a model for the mixing point of fresh air and exhaust gas recirculation, which is regarded as a container with the volume V22 and the pressure P22. Furthermore, partial models are provided that depict the exhaust gas recirculation valve and the control valve as throttles. The main input variables for these models are the pressure P3 downstream of the exhaust of the internal combustion engine and upstream of the turbine, the pressure P21 upstream of the control valve and downstream of the compressor the pressure P22 in the intake manifold, i.e. H. between the inlet of the internal combustion engine and the exhaust gas recirculation valve or the control flap, the temperature T3 after the outlet of the internal combustion engine, the setpoint for the exhaust gas recirculation rate or the exhaust gas recirculation mass flow and the setpoint for the air mass flow.

The variables P3, P21, P22, T21 and T3 can be measured directly with sensors or calculated using a model based on other operating parameters. A suitable model is preferably one in the DE 199 63 358 described model. The setpoint values MR and MA for the exhaust gas recirculation rate and for the air mass flow that are used by the model are preferably the same setpoint values that are also fed to the control system. On the basis of these input variables, the model provides temporal progressions for surfaces of the control flaps and / or the exhaust gas recirculation valve that are effectively flowed through. These are mapped using characteristic curves 245 or 345 or more complex dynamic models in manipulated variables for the control flap and / or the exhaust gas recirculation valve.

The target value specification 215 or 315 specifies the target value for the corresponding manipulated variable depending on various operating parameters and operating states. When an operating variable changes or when switching to another operating state, the setpoint value is generally discontinuous. As a rule, the corresponding variable cannot follow such a discontinuous or abrupt course of the setpoint value. This leads to a control deviation occurring which the controller tries to correct. Overall, this leads to an undesirable behavior of the controller. It is therefore provided according to the invention that the setpoint filters 210 and 310 filter the setpoint specification in such a way that the setpoint value is continuous and that the overall system can follow these specifications at any time. I.e. the time behavior of the setpoint is adapted by the setpoint filter to the time behavior of the overall system or to the time behavior of the manipulated variable. I.e. the setpoint filter 210 or 310 generates a dynamically smoothed course of the setpoint. The filter also provides the time derivative of this variable.

The model 230 uses various input variables to calculate the required fresh air mass flow and the pressure P22 in the intake manifold. The model 230 uses the temperature T3, the temperature T21 in front of the control flap, the dynamically smoothed target air mass flow, the time derivative of the dynamically smoothed target air mass flow, the dynamically smoothed exhaust gas recirculation rate, the temporal derivative of the dynamically smoothed exhaust gas recirculation rate and the engine speed as input variables. On the basis of these variables, the model 230 calculates the target air mass flow ML via the control flap 104, the target exhaust gas mass flow via the exhaust gas recirculation valve and the target pressure P22 in the mixing container.

The inverse models 235 and 335 calculate the effective flow area of the respective throttle from the desired target mass flow that is to flow through the throttle. For this purpose, the pressure and / or the temperature upstream of the throttle and the pressure and / or the temperature after the throttle are used. The input variables for the model 245 of the regulating flap are the pressure P21 before the regulating flap and after the compressor, the pressure P22 in the suction pipe and the temperature T21 before the regulating flap. The input variables of the model 335 of the exhaust gas recirculation valve 118 are the pressure P3 after the exhaust of the internal combustion engine and upstream of the turbine, the pressure P22 in the intake manifold, the temperature T3 after the exhaust of the internal combustion engine and the target exhaust gas mass flow MR, which should flow through the exhaust gas recirculation valve 118.

The setpoint values for the areas effectively flowed through for the control flap and the exhaust gas recirculation valve are converted into manipulated variables for the control flap and the exhaust gas recirculation valve using the characteristic curves 245 and 345. Instead of the characteristic curve, more complex dynamic models can also be used for this.

The pre-control has the advantage that it is possible to react very quickly to changes in the setpoint, i.e. H. there is a very quick leadership behavior. The system dynamics are already taken into account here. This means that both the exhaust gas recirculation rate or exhaust gas recirculation mass flow and the air mass flow can be adapted very quickly to changing conditions through the pilot control. This is particularly advantageous when switching between different operating states such as, for example, into the regeneration mode or from the regeneration mode. Since the two control loops are independent of one another and there is no feedback at all in a system without control, there are no stability problems with this structure. If a controller is also used, it only has to compensate for interference and model inaccuracies, since the control behavior is guaranteed by the feedforward control. The coupling of the two actuators is mapped using the model of the mixing point 230. I.e. the controllers are decoupled, which significantly simplifies the application.

It is particularly advantageous if, in certain operating states, only the pilot control is active and the regulation is dispensed with; H. that the control is switched off. This takes place, for example, in that when certain operating states are present, the connection between controller 220 and node 225 or between controller 320 and node 325 is interrupted by means of a switching means. Such an operating state exists, for example, when a small control deviation results in a large change in the manipulated variable. In such operating states there is a low sensitivity between the manipulated variable and the variable to be regulated. In these operating states, the regulation is dispensed with and only the pilot control values are used to control the actuator. This protects the actuator and prevents interference. This can also be advantageous with regard to tolerances.

Using the example of regulating the air mass by means of a control flap in regeneration mode, this means the following: The influence of the control flap position on the air mass in the wide-open area of the control flap is practically invisible. If an attempt were made to regulate a setpoint value in this non-sensitive area with the help of a control system, the controller would cause large fluctuations in the manipulated variable due to the measurement noise, which could unnecessarily load the control valve. When using a model-based pilot control, the control is switched off in such non-sensitive areas. In the area of low sensitivity, the feedforward control delivers a significantly smoother control value curve than a controller. This protects the controller's mechanics and prevents interference in the air system.

Usually, a regulator is used as regulator 220 or 320, which in particular has PI behavior. The I component builds up essentially proportionally to the signed area between the setpoint and actual value. If an abrupt course is specified for the manipulated variable, the process and actuator dynamics result in a time-delayed change in the actual value to be regulated. For this reason, sudden setpoint values lead to a build-up of the I component that is not physically caused. In order to reduce this again, the controller must undershoot or overshoot in the corresponding other direction with respect to the setpoint. This behavior leads to poor control behavior and can only be mitigated by appropriate values for the control parameters. If the control parameters are appropriate, however, poor management behavior will again result.

According to the invention it is provided that this effect can be significantly reduced by the setpoint filters 210 and 310. This is achieved in that the setpoint filter 210 or 310 is used to adapt the course of the setpoint to the dynamics of the controlled system and / or actuator. This is achieved in that the setpoint is filtered in such a way that it has the same or at least a similar behavior over time as the actuator and / or the entire controlled system. For example, if the controller has PT1 behavior, a filter with PT1 behavior is used. This significantly reduces the area that is relevant for the construction of the I component. The controller can now be designed with a larger KI, since the undesired build-up of the I component is avoided.

According to the invention, the setpoint filters 210 and 310 are designed in such a way that the setpoints are dynamically adapted to the route behavior. A target area effectively flowed through is calculated from this adapted course of the target values. This variable is used both for calculating the pre-control values by the model 230 and the models 235 and 335 and as a setpoint for the control 210 or 320. The calculation of the control deviation is based on the non-modeled residual dynamics, e.g. B. The actuator dynamics of this manipulated variable are mapped using a dead time and a PT1 element. As a result of this measure, the controller 220 or 320 only needs to correct model inaccuracies and interfering influences and can thus be designed for speed accordingly.

If large control deviations occur in a controller that has at least one integral behavior, this leads to large values of the integral component for control parameters that are necessary for good dynamic behavior. These large values cause overshoots or undershoots. This behavior is not desired. If corresponding values are selected for the control parameters in which no overshoots or undershoots occur, this leads to poor dynamic behavior, that is, the actual value only slowly reaches the corresponding setpoint.

To avoid this, a particularly advantageous embodiment provides that the amount of the control deviation, that is, the signal pending at node 205 and / or at node 305, is limited to a maximum permissible value using a limiter.

Claims (9)

Method for controlling an internal combustion engine with an actuator (104) for influencing the fresh air mass flow and an actuator (118) for influencing the exhaust gas recirculation mass flow supplied to the internal combustion engine, based on a comparison between a setpoint and an actual value for the fresh air mass flow and the exhaust gas recirculation mass flow by means of a controller (220, 320) the manipulated variables for the actuators (104, 118) can be specified, the manipulated variables each being superimposed with a model-based precontrol value that can be specified by means of a model, the model at least one first sub-model (230) for a mixing point of fresh air mass flow and contains exhaust gas recirculation mass flow and second partial models (235, 335) for the actuators (104, 118). Procedure according to Claim 1 , characterized in that the first partial model (230) for the mixer processes the temperature T3 after the exhaust of the internal combustion engine, the temperature T21 before the actuator, the speed N, the setpoints for the fresh air mass flow and the exhaust gas recirculation mass flow. Procedure according to Claim 2 , characterized in that the second partial model (235) processes at least one pressure (P22) in the intake manifold and the setpoint value for the fresh air mass flow as input variables for specifying the manipulated variable for the fresh air mass flow. Procedure according to Claim 1 , characterized in that the second partial model (235) for specifying the manipulated variable for the fresh air mass flow as input variables at least temperature (T21) and / or a pressure (P21) before the actuator (104) and after the compressor (106) and / or a Target air mass flow MA processed. Procedure according to Claim 1 , characterized in that the second partial model (335) for specifying the manipulated variable for the exhaust gas recirculation mass flow as input variables at least a temperature (T3) and / or a pressure (P3) of the exhaust gas after the outlet of the internal combustion engine and upstream of the turbine and / or a target exhaust gas mass flow ( MR) processed. Procedure according to Claim 1 , characterized in that the setpoint is adapted to the behavior of the control loop over time. Procedure according to Claim 1 , characterized in that the actual value can be specified by means of a second model. Procedure according to Claim 1 , characterized in that the controller can be switched off in certain operating states. Device for controlling an internal combustion engine with an actuator (104) for influencing that supplied to the internal combustion engine Fresh air mass flow and an actuator (118) for influencing the exhaust gas recirculation mass flow supplied to the internal combustion engine, each with a controller which, based on a comparison between a setpoint and an actual value for the fresh air mass flow and the exhaust gas recirculation mass flow, specifies manipulated variables for the actuators (104, 118), and means, each of which superimposes a model-based pre-control value on the manipulated variables, which can be specified by means of a model, the model containing at least a first partial model for a mixing point of fresh air mass flow and exhaust gas recirculation mass flow and second partial models (235, 335) for the actuators (104, 118).

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