JP2013050045A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine control device which does not generate discontinuous estimation values outputted from a plant model even in the change of operating conditions regarding an internal combustion engine including the plant model for outputting the estimation value of control amount of an internal combustion engine by defining the control amount of an actuator for controlling the internal combustion engine as an input parameter.SOLUTION: The internal combustion engine control device includes: the plant model which outputs the estimation value of the control amount of the internal combustion engine (supercharging pressure, EGR ratio) by defining the control amount of the actuator for controlling the internal combustion engine (EGR valve opening degree, variable nozzle opening degree of variable nozzle type turbo supercharger, opening degree of exhaust throttle) as the input parameter; and a coefficient output model which outputs a coefficient used for calculating the plant model. The coefficient output model linearly outputs the coefficient for continuously changing the estimation value outputted from the plant model according to the change of the operating conditions by having an engine speed of the internal combustion engine and a fuel injection amount as the input parameter.

Description

  The present invention relates to a control device for an internal combustion engine.

  Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-132357, a plurality of control inputs (for example, target throttle opening, target valve lift) and a plurality of control amounts (for example, intake pipe internal pressure, intake air amount) There is known a plant control apparatus in which mutual interference exists between the two. In this apparatus, a target throttle opening as a control input and a predetermined algorithm by combining a predetermined response designating control algorithm based on a plant model obtained by modeling a plant as a discrete time system model and a predetermined non-interference control algorithm, and The target valve lift is calculated as two non-interacting inputs that cancel the mutual interference for causing the intake pipe internal pressure and the intake air amount to follow the target intake pipe internal pressure and the target intake air amount, respectively.

JP 2006-132357 A

  By the way, when applying model predictive control to an internal combustion engine, it is necessary to identify a plant model. At this time, in the conventional technique, in order to avoid deterioration of the accuracy of the plant model due to the difference in the time constant or the like in the operating conditions of the internal combustion engine, the plant model is changed according to the operating conditions (for example, the engine speed and the injection amount) of the internal combustion engine. The area is divided into a plurality of parts. Thus, by identifying the plant model for each divided area, the model accuracy in each area is effectively increased.

  However, if the plant model area is divided according to the operating conditions as in the conventional technique described above, discontinuity occurs in the model predicted value output when the operating conditions of the internal combustion engine cross the area, and the actuator control Sexuality will deteriorate.

  The present invention has been made in order to solve the above-described problems, and an internal combustion engine having a plant model that outputs a predicted value of a control amount of an internal combustion engine, with the control amount of an actuator that controls the internal combustion engine as an input parameter. It is an object of the present invention to provide a control device for an internal combustion engine in which discontinuity does not occur in a predicted value output from a plant model even when operating conditions change in the engine.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A plant model that outputs a predicted value of the control amount of the internal combustion engine, with the control amount of an actuator that controls the internal combustion engine as an input parameter;
A coefficient output model for outputting a coefficient used for the calculation of the plant model,
In the coefficient output model, the coefficient for continuously changing the predicted value output from the plant model in accordance with the change in the operating condition of the internal combustion engine, the engine speed and the fuel injection amount of the internal combustion engine are set. It is a model that outputs linearly as an input parameter.

According to a second invention, in the first invention,
The internal combustion engine is configured as a diesel engine including an EGR valve, a variable nozzle turbocharger, and an exhaust throttle valve as the actuator.
The plant model has at least one of a supercharging pressure and an EGR rate with the opening of the EGR valve, the variable nozzle of the variable nozzle turbocharger, and the opening of the exhaust throttle valve as input parameters. It is a model that outputs a predicted value.

  According to the first invention, in the plant model, the predicted value of the control amount of the internal combustion engine is output with the control amount of the actuator as an input parameter. In the coefficient output model, a coefficient used for calculation in the plant model is output. At this time, in the coefficient output model, the coefficient for continuously changing the predicted value of the control amount calculated in the plant model according to the operating condition of the internal combustion engine is the input parameter of the engine speed and the fuel injection amount. Is output linearly. For this reason, according to the present invention, the predicted value of the control amount of the internal combustion engine can be continuously output using the plant model, so that the situation in which the controllability of the actuator using the predicted value deteriorates is effectively suppressed. can do.

  According to the second aspect of the invention, the plant model uses the opening of the EGR valve, the variable nozzle of the variable nozzle turbocharger, and the opening of the exhaust throttle valve as input parameters. The model is configured to output at least one predicted value. For this reason, according to the present invention, the predicted value of the supercharging pressure and / or the EGR rate changes continuously, and therefore, the EGR valve opening degree, the variable nozzle, and the control amount are determined according to these values. The controllability of the opening and the opening of the exhaust throttle valve can be improved effectively.

It is a figure for demonstrating schematic structure of the internal combustion engine system as embodiment of this invention. It is a figure for demonstrating the outline | summary of the conventional model base control. It is a figure for demonstrating an example of the area | region divided | segmented according to the driving | running condition. It is a figure for demonstrating the discontinuity of the predicted value of a plant model. It is a figure for demonstrating the model structure of Embodiment 1 of this invention. It is a figure for demonstrating the continuity of the predicted value of a plant model.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a schematic configuration of an internal combustion engine system as an embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes a four-cycle diesel engine 10 having a plurality of cylinders (four cylinders in FIG. 1). It is assumed that the diesel engine 10 is mounted on a vehicle and used as a power source.

  Hereinafter, although this embodiment demonstrates the case where this invention is applied to control of a diesel engine (compression ignition internal combustion engine), this invention is not limited to a diesel engine, A gasoline engine (spark ignition internal combustion engine) It can be applied to control of various other internal combustion engines.

  Each cylinder of the diesel engine 10 is provided with an injector 12 for directly injecting fuel into the cylinder. The injectors 12 of each cylinder are connected to a common common rail 14. Fuel in a fuel tank (not shown) is pressurized to a predetermined fuel pressure by a supply pump 16, stored in the common rail 14, and supplied from the common rail 14 to each injector 12. Further, the exhaust passage 18 of the diesel engine 10 is branched by an exhaust manifold 20 and connected to an exhaust port (not shown) of each cylinder.

  The diesel engine 10 includes a variable nozzle type turbocharger 24. The turbocharger 24 includes a turbine 24a that is operated by the exhaust energy of the exhaust gas, and a compressor 24b that is integrally connected to the turbine 24a and is rotationally driven by the exhaust energy of the exhaust gas that is input to the turbine 24a. ing. Further, the turbocharger 24 has a variable nozzle (VN) 24c for adjusting the flow rate of the exhaust gas supplied to the turbine 24a.

  The variable nozzle 24c can be opened and closed by an actuator (for example, an electric motor) not shown. When the opening of the variable nozzle 24c (hereinafter referred to as “VN opening”) is reduced, the inlet area of the turbine 24a is reduced, and the flow rate of the exhaust gas blown to the turbine 24a can be increased. As a result, the rotational speeds of the compressor 24b and the turbine 24a (hereinafter referred to as “turbo rotational speed”) are increased, so that the supercharging pressure can be increased. Conversely, when the VN opening is increased, the inlet area of the turbine 24a is increased, and the flow rate of the exhaust gas blown to the turbine 24a is decreased. As a result, the turbo rotation speed decreases, so that the supercharging pressure can be reduced.

  The turbine 24 a of the turbocharger 24 is disposed in the middle of the exhaust passage 18. A post-treatment device 26 for purifying exhaust gas is provided in the exhaust passage 18 on the downstream side of the turbine 24a. As the post-processing device 26, for example, an oxidation catalyst, a NOx catalyst, a DPF (Diesel Particulate Filter), a DPNR (Diesel Particulate-NOx-Reduction system), or the like can be used.

An air cleaner 30 is provided near the inlet of the intake passage 28 of the diesel engine 10. The air sucked through the air cleaner 30 is supplied to the compressor 24 of the turbocharger 24.
After being compressed by b, it is cooled by the intercooler 32. The intake air that has passed through the intercooler 32 is distributed by an intake manifold 34 to intake ports (not shown) of each cylinder.

  An intake throttle valve 36 is installed between the intercooler 32 and the intake manifold 34 in the intake passage 28. The intake throttle valve 36 is configured to be electrically opened and closed by an actuator (not shown). An air flow meter 52 for detecting the amount of intake air is installed in the intake passage 28 near the downstream of the air cleaner 30.

  One end of an EGR (Exhaust Gas Recirculation) passage 40 is connected to the vicinity of the intake manifold 34 in the intake passage 28. The other end of the EGR passage 40 is connected to the vicinity of the exhaust manifold 20 in the exhaust passage 18. In the present system, a part of the exhaust gas (burned gas) can be recirculated to the intake passage 28 through the EGR passage 40, that is, external EGR can be performed.

  An EGR cooler 42 for cooling the EGR gas is provided in the middle of the EGR passage 40. An EGR valve 44 is provided downstream of the EGR cooler 42 in the EGR passage 40. By changing the opening of the EGR valve 44 (hereinafter referred to as “EGR valve opening”), the amount of exhaust gas passing through the EGR passage 40, that is, the EGR amount can be adjusted.

  The system according to the present embodiment includes an ECU (Electronic Control Unit) 50 as shown in FIG. In addition to the air flow meter 52 described above, the input portion of the ECU 50 includes an accelerator position sensor 60 for detecting the amount of depression of the accelerator pedal (accelerator opening), and a crank angle sensor 62 for detecting the crank angle of the diesel engine 10. Various sensors for controlling the diesel engine 10 are connected. In addition to the injector 12, the intake throttle valve 36, the EGR valve 44, and the turbocharger 24, various actuators for controlling the diesel engine 10 are connected to the output unit of the ECU 50. The ECU 50 drives each device in accordance with a predetermined program based on various types of input information.

[One Operation of Embodiment]
Next, the operation of the first embodiment will be described. As described above, the internal combustion engine 10 according to the present embodiment controls the internal combustion engine 10 in addition to the injector 12, the intake throttle valve 36, the EGR valve 44, and the turbocharger 24 as actuators for controlling the operation thereof. Various actuators are provided for this purpose. The control device according to the present embodiment controls the internal combustion engine by so-called model-based control. The control state is estimated using a lot of prediction by a plant model, and the control amounts of the various actuators described above are determined.

  First, an example in which conventional model-based control is applied to the system of the first embodiment shown in FIG. 1 will be described. FIG. 2 is a diagram for explaining an overview of conventional model-based control. As shown in this figure, in the plant model 501, as the control amounts of various actuators, the opening degree of the EGR valve 44 (EGR valve opening degree), the opening degree of the variable nozzle 24c (VN opening degree), and the intake throttle valve 36 open. Degree (hereinafter referred to as “throttle opening”) is input, and predicted values such as a supercharging pressure and an EGR rate are output.

  Here, in order to apply the model base control shown in FIG. 2 to the internal combustion engine, it is necessary to identify the plant model. Therefore, in the conventional technique, in order to avoid deterioration in accuracy due to a difference in time constant or the like in the operating conditions, the area is divided into a plurality of areas according to the operating conditions, and the model is identified for each area. FIG. 3 is a diagram for explaining an example of a region divided according to the operating conditions. In the example shown in this figure, the region is divided into six according to the engine speed and the fuel injection amount. As an example, the polynomial of the plant model identified in regions 1 and 2 is shown below.

The above equation (1) represents the plant model in region 1, and the above equation (2) represents the plant model in region 2. Θ _1-8 is a model coefficient (fixed value) in region 1, θ _9-16 is a model coefficient (fixed value) in region 2, u is a model input parameter such as EGR valve opening, VN opening, and the like. , Y respectively indicate model outputs (predicted values) such as EGR rate and supercharging pressure.

  As shown in the above formulas (1) and (2), when a model is identified for each divided area, the polynomial of the model is different for each area. For this reason, it is assumed that when the operating condition is across a plurality of regions, discontinuity occurs in the predicted value output from the plant model, and the controllability of the actuator using the predicted value is deteriorated. Is done. This will be described in detail with reference to FIG.

  FIG. 4 is a diagram for explaining discontinuity of predicted values of the plant model. In this figure, (a), (b), (c) and (d) are vehicle speed, plant model area, model output value (predicted boost pressure value), and time of VN opening as a controlled variable. Each change is shown. When the vehicle speed increases as shown in FIG. 4A, the engine speed and the fuel injection amount change, so that the area of the plant model shifts from areas 1 to 2 and 3 with time (in FIG. 4). (See (b)). In this case, the boost pressure predicted value that is the output value of the plant model becomes discontinuous at the timing when the region shifts to another region, as shown in (c) of FIG. The control amount of the VN opening is set based on the predicted supercharging pressure output from the plant model. For this reason, when the supercharging pressure prediction value becomes discontinuous, as shown in FIG. 4D, a sharp change occurs in the VN opening, and there is a problem that the controllability deteriorates.

Therefore, in the system according to the first embodiment, the plant model shown in FIG. 5 is used. FIG. 5 is a diagram for explaining a model configuration according to the first embodiment of the present invention. As shown in this figure, in the model configuration of the first embodiment of the present invention, a plant model 502 common to all operating conditions is configured instead of identifying a plant model for each region. Then, a coefficient output model 504 that outputs the coefficients θ 1 to _n (n is the number of terms of the plant model 502) of each term of the plant model 502 with the operation condition as an input is configured. Specifically, the plant model 502 can be expressed by a polynomial as shown in the following equation (3), for example.

In the above equation (3), θ is a model coefficient of each term of the plant model 502, u is a model input parameter such as EGR valve opening, throttle opening, VN opening, etc., y is an EGR rate, supercharging The model output such as pressure is shown respectively. The model coefficient θ used in the above equation (3) is output by the coefficient output model 504. Specifically, the engine output detected by the crank angle sensor 62 and the fuel injection amount injected from the injector 12 are input to the coefficient output model 504. The coefficient output model 504 is a model coefficient θ 1 to _n (n is a plant constant ₎ for continuously changing the model output y in the above equation (3) by performing, for example, polynomial calculation using the input operating conditions. Output the number of terms in the model).

  FIG. 6 is a diagram for explaining the continuity of predicted values of the plant model. In addition, (a), (b), and (c) in this figure have each shown the time change of the vehicle speed, the model output value (supercharging pressure predicted value), and the VN opening degree as a controlled variable. When the vehicle speed increases as shown in FIG. 6A, the engine speed and the fuel injection amount change according to the increase in the vehicle speed. In this case, in the coefficient output model 504, a model coefficient θ for continuously changing the model output is output and input to the plant model 502. For this reason, as shown in (b) in FIG. 6, the predicted value of the supercharging pressure, which is the output value of the plant model, continuously changes according to changes in the operating conditions. As described above, the control amount of the VN opening is set based on the predicted boost pressure output from the plant model. For this reason, the VN opening degree changes continuously without causing a steep change, as shown in FIG.

  As described above, according to the system of the present embodiment, the plant model 502 common to all operating conditions is configured, and the model coefficient θ for obtaining a continuous model output (predicted value) is the coefficient output model 504. Is output linearly. Thereby, since the predicted value of the controlled variable of the diesel engine 10 can be continuously output using the plant model 502, the situation where the controllability of the actuator using the predicted value is deteriorated can be effectively suppressed. .

  In the first embodiment described above, the EGR valve opening, the throttle opening, and the VN opening are used as the input parameters to the plant model 502. However, usable values are not limited to these. The input parameters may be used. Further, the model structure of the plant model 502 is not limited to the polynomial shown in the above equation (3), and may be constructed by other polynomials, RBF functions, or the like.

  In the first embodiment described above, the ECU 50 corresponds to the “control unit” in the first aspect of the invention, and the ECU 50 executes the processing of steps 100 and 102 described above, thereby The “acquisition means” in the second invention realizes the “selection means” in the first invention by executing the steps 104 to 108 described above.

10 Diesel engine (engine)
12 Injector 18 Exhaust passage 24 Variable nozzle turbocharger 24c Variable nozzle 28 Intake passage 36 Intake throttle valve 40 EGR passage 44 EGR valve 50 ECU (Electronic Control Unit)
502 Plant model 504 Coefficient output model 62 Crank angle sensor

Claims (2)

A plant model that outputs a predicted value of the control amount of the internal combustion engine, with the control amount of an actuator that controls the internal combustion engine as an input parameter;
A coefficient output model for outputting a coefficient used for the calculation of the plant model,
In the coefficient output model, the coefficient for continuously changing the predicted value output from the plant model in accordance with the change in the operating condition of the internal combustion engine, the engine speed and the fuel injection amount of the internal combustion engine are set. A control apparatus for an internal combustion engine, characterized by being a model that outputs linearly as an input parameter. The internal combustion engine is configured as a diesel engine including an EGR valve, a variable nozzle turbocharger, and an exhaust throttle valve as the actuator.
The plant model has at least one of a supercharging pressure and an EGR rate with the opening of the EGR valve, the variable nozzle of the variable nozzle turbocharger, and the opening of the exhaust throttle valve as input parameters. 2. The control apparatus for an internal combustion engine according to claim 1, wherein the control apparatus is a model that outputs a predicted value.

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