JP2008248859A - Control method and control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce or avoid adverse influence when a given target value cannot be achieved or hard to be achieved by the reason such as saturation of control input. <P>SOLUTION: In controlling a plurality of controlled variables to target values by operating parts 34, 41 and 45, when it is impossible or hard to control all of the controlled variables to the target values, a correction value of the controlled variable required to make the controlled variable having high priority reach the target value is calculated based on a mathematical model prescribing the relationship between the controlled variable and the manipulated variable, and the operating parts 34, 41 and 45 are operated with the usage of the calculated correction value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention particularly relates to control of an internal combustion engine such as an automobile.

It is known that exhaust gas recirculation and air-fuel ratio feedback control are combined to suppress the amount of harmful substances generated during combustion and improve exhaust gas purification performance. In the EGR control disclosed in the following patent document, the total gas amount (total amount of gas introduced into the cylinder) obtained by adding the intake air amount and the EGR amount is calculated, and air-fuel ratio feedback is performed based on the total gas amount. Correction is performed. More specifically, target values are set for intake air amount, turbocharger pre-pressure and scavenging air pressure, and control inputs for achieving these target values, ie, throttle valve opening, external EGR valve opening, variable capacity turbo, The required EGR amount is realized by determining the turbine output (or the waste gate valve opening).
JP 2007-032462 A JP 2006-274842 A

  In a control system, even if a given target value can be theoretically achieved, it may not be actually controlled. For example, in the above-mentioned EGR control, when the intake air amount requirement is raised in a situation where the valve has already been opened to the full, the valve opening degree that achieves the requirement will not exceed the mechanical limit of the actual valve. It will exceed the value, and it cannot be realized after all.

  An object of the present invention is to reduce or avoid an adverse effect when a given target value cannot be achieved or is difficult to achieve due to reasons such as saturation of a control input.

  In order to solve the above-described problems, in the control method according to the present invention, it is not possible to control all the control amounts to the respective target values when operating the operation unit to control the plurality of control amounts to the respective target values. Based on a mathematical model that defines the relationship between the controlled variable and the manipulated variable when possible or difficult, calculate the manipulated variable correction value necessary to reach the target value for the controlled variable with the highest priority. Therefore, it was decided to operate the operation unit using the calculated correction value. In other words, the control state is kept good by positively reaching the target value with a control amount having a high priority for comparison. A control amount with a high priority means that the control amount has a great influence on other control amounts, and other control amounts are difficult to approach the target value unless they are brought close to the target value. Conversely, a control amount with a low priority is one that has a small influence on other control amounts or can be replaced by another control amount. The intake air amount in the EGR control in the above example is a source of the supercharger pre-pressure and scavenging air pressure, and is a control amount with high priority. Further, since the scavenging pressure can be controlled almost only by increasing / decreasing the turbine output of the variable capacity turbo, it is a low priority control amount.

  If the parameters of the feedforward controller in the two-degree-of-freedom control system are used in the mathematical model, it is easy to reversely calculate the operation amount that achieves the target value having a high priority. This is because the feedforward controller is in principle a reverse system of the plant.

  According to the present invention, even when the target value given for reasons such as saturation of the control input cannot be achieved or is difficult to achieve, the adverse effect can be reduced or avoided.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an EGR control apparatus to which a control method according to the present invention is applied. The control device includes measuring devices 11, 12, and 13 that measure a plurality of flow rate or fluid pressure parameters in the intake and exhaust systems 3 and 4, and a target value setting that sets a target value of the plurality of parameters based on at least the engine speed. Unit 14, an operation amount calculation unit 15 that calculates an operation amount given to the plurality of operation units 34, 41, and 45 so as to direct a plurality of parameters to a target value, a correction unit 16 that calculates a correction value of the operation amount, And a control unit 17 that operates the operation units 34, 41, and 45 using the calculated operation amount and correction value.

  An outline of the hardware configuration is shown in FIG. In the present embodiment, the internal combustion engine 2 is a two-cycle diesel engine. The intake system 3 of the internal combustion engine 2 is provided with a supercharger 31 as a scavenging blower and a compressor 32 of a variable capacity turbo system, and an intercooler 33 for cooling the scavenging is provided downstream thereof. A D throttle valve 34 for adjusting the intake air (fresh air) amount is provided upstream of the supercharger. In addition, a flow meter 11 for detecting the intake air amount, a pressure gauge 12 for detecting the precharger pre-pressure, and a pressure gauge 13 for detecting the scavenging air pressure are installed.

  On the other hand, the exhaust system 4 is provided with a variable nozzle turn (VNT) 41 that drives the compressor 32, and the amount of exhaust gas flowing into the VNT 41 can be adjusted via a variable vane (not shown) and a waste gate valve 42. I am doing so. In addition, an exhaust gas recirculation passage 43 that recirculates part of the exhaust gas discharged from the combustion chamber of the internal combustion engine 2 to the intake system 3 is provided. The exhaust gas recirculation passage 43 is connected to an intermediate portion between the throttle valve 34 and the superchargers 31 and 32 in the intake system 3. The exhaust gas recirculation passage 43 is provided with an EGR cooler 44 for cooling the exhaust gas and an external EGR valve 45 for adjusting the amount of exhaust gas passing therethrough.

  The EGR includes an external EGR that recirculates the exhaust gas to the intake system 3 via the exhaust gas recirculation passage 43 and an internal EGR that causes the burned gas to remain in the combustion chamber. In the two-cycle engine with a supercharger as shown in the drawing, the external EGR can be controlled by controlling the intake air amount and the supercharger pre-pressure, and the internal EGR can be controlled by controlling the scavenging pressure. Therefore, in this embodiment, a target value is set for each of a plurality of parameters for determining the EGR amount (or EGR rate), that is, the intake air amount, the turbocharger pre-pressure and the scavenging pressure, and these parameters are collectively set as the target. The control of the EGR amount is realized by controlling a plurality of operation units, that is, the variable vanes (or the waste gate valve 42) of the VNT 41 so as to make the value go to the value.

  The operation units such as the throttle valve 34, the external EGR valve 45, and the VNT 41 are controlled by the electronic control unit 5 to change the opening thereof linearly. Valves 34, 45, 42 are electrical valves that change the opening by increasing or decreasing the duty ratio of the drive signal, or a machine that changes the opening by controlling the lift amount of the valve body in combination with a vacuum control valve or the like. A valve of the formula is used.

  The electronic control unit 5 is a microcomputer including a processor, RAM, ROM or flash memory, an A / D converter, an I / O interface, and the like. In addition to the measuring devices 11, 12, 13 for detecting the intake air amount, the precharger pressure and the scavenging air pressure, the electronic control unit 5 is also used for engine speed, accelerator pedal depression amount, cooling water temperature, intake air temperature, and external air temperature. Each parameter can be obtained by electrically connecting to various measuring instruments (not shown) for detecting atmospheric pressure and the like, and receiving signals output from these measuring instruments. In addition, the electronic control unit 5 is electrically connected to the throttle valve 34, the external EGR valve 45, the VNT 41, the waste gate valve 42, the fuel injection pump 21, and the like, and can input signals for driving them. it can.

  A program to be executed by the electronic control unit 5 is stored in advance in a ROM or a flash memory, and is read into the RAM at the time of execution and is decoded by the processor. The electronic control unit 5 executes control of the internal combustion engine 2 according to a program. For example, a required fuel injection amount (in other words, an engine load) is determined based on various conditions such as the engine speed, the accelerator pedal depression amount, the cooling water temperature, and the like, and a drive signal corresponding to the required injection amount is sent to the fuel injection pump 21. To control the fuel injection. In addition, the electronic control device 5 exhibits functions as a target value setting unit 14, an operation amount calculation unit 15, a correction unit 16, and a control unit 17 that are elements of the control device according to a program.

  A procedure of processing executed by the electronic control unit 5 to realize EGR control is shown in the flowchart of FIG. The electronic control unit 5 receives signals output from various measuring instruments (not shown), and knows the engine speed, the accelerator depression amount, the cooling water temperature, the intake air temperature, the outside air temperature, the atmospheric pressure, and the like (step S1). A required injection amount is determined (step S2).

  Next, target values are set for the intake air amount, the supercharger pre-pressure, and the scavenging pressure, respectively. In the present embodiment, the target intake air amount, the target supercharger pre-pressure, and the target scavenging pressure are set based on at least the engine speed and the required injection amount. In the ROM or flash memory of the electronic control unit 5, map data indicating each target value to be set corresponding to the engine speed and the required injection amount is stored in advance. Each target value described in this map is a value that realizes an appropriate EGR amount according to the engine speed, the required injection amount, etc., and is adapted by a bench test. The electronic control unit 5 searches the map using the engine speed and the required injection amount as keys (step S3), and obtains target values for the intake air amount, the supercharger pre-pressure, and the scavenging pressure. Further, a target value obtained by referring to the map is set as a basic value, which is corrected according to the cooling water temperature, the intake air temperature, the outside air temperature, the atmospheric pressure, and the like (step S4) to obtain a final target value.

  Then, feedback control is performed to operate the throttle valve 34, the external EGR valve 45, and the VNT 41 so that the intake air amount, the supercharger pre-pressure, and the scavenging air pressure are directed to the respective target values. The electronic control unit 5 receives signals output from the measuring instruments 11, 12, and 13 to obtain the intake air amount, the supercharger pre-pressure, and the scavenging pressure (step S5). The opening of the throttle valve 34 to be operated, the opening of the external EGR valve 45, and the opening of the variable vane of the VNT 41 are calculated from the deviation (step S6), and drive signals corresponding to the respective operation amounts are output to the valves 34. , 45 and VNT 41 for input (step S7).

  However, when it is impossible or difficult to control all of the intake air amount, the turbocharger pre-pressure and the scavenging air pressure to each target value (step S8), the control amount having a higher priority is set to the target value. A correction value for the operation amount necessary for reaching is calculated (step S9), and the operation amount obtained in step S6 is corrected. In step S8, for example, it is determined whether or not the operation amount calculated in step S6 exceeds the saturation value (threshold value, constraint condition) of the operation amount that can be input to the actual operation units 35, 45, and 41. If not, the process proceeds to step S7, and if it exceeds, the process proceeds to step S9. The highest priority control amount is the intake air amount, and the next highest control amount is the turbocharger pre-pressure.

  Therefore, the electronic control unit 5 repeatedly executes the processing procedure shown in FIG. 3 and continues the EGR control.

  The calculation of the correction value in step S9 will be described in detail. A mathematical model of the control system of the input u and the output y is expressed in the form of a state equation and an output equation (Equation 1).

上記の数学モデルは、同定によって求める。同定実験は、様々な周波数成分を含む２値信号（Ｍ系列）からなるデューティ信号を入力して操作したときの出力を観測し、両者の関係から行列Ａ、Ｂ、Ｃを得るものである。

The above mathematical model is obtained by identification. In the identification experiment, an output when a duty signal composed of a binary signal (M series) including various frequency components is inputted and operated is observed, and matrices A, B, and C are obtained from the relationship between the two.

The control system is, for example, a target value feedforward two-degree-of-freedom control system. A block diagram of the two-degree-of-freedom LQ control system is shown in FIG. The observer estimates state quantities with reference to input / output signals, and estimates identification modeling errors, plant parameter fluctuations, etc. as part of the control system, and offsets and absorbs these in a controlled manner. The stabilization term F ₀ is a feedback gain (Equation 2) that minimizes the evaluation function J.

Ｑ、Ｒはそれぞれ重み、Ｐはリカッチ型代数方程式（数３）の解である。

Q and R are weights, respectively, and P is a solution of the Riccati-type algebraic equation (Equation 3).

追従遅れ項Ｆ₁は（数４）、フィードバックゲインＧは（数５）のようになる。

The follow-up delay term F ₁ is (Equation 4) and the feedback gain G is (Equation 5).

Ｗは重みである。また、フィードフォワード項Ｈ₀は、状態方程式をラプラス変換して得られる伝達関数（数６）の周波数が０であるときにゲインが１となるように設定するものであって、（数７）のようになる。

W is a weight. The feedforward term H ₀ is set so that the gain becomes 1 when the frequency of the transfer function (Equation 6) obtained by Laplace transform of the state equation is 0, (Equation 7) become that way.

行列Ｈ₀は、制御量と操作量との関係を規定する。外部ＥＧＲバルブ４５の開度をｕ₁、ＶＮＴ４１の可変ベーンの開度をｕ₂、スロットルバルブ３４の開度をｕ₃とおき、過給機前圧をｙ₁、掃気圧をｙ₂、吸入空気量をｙ₃とおくと、（数８）が成立する。

The matrix H ₀ defines the relationship between the control amount and the operation amount. The opening of the external EGR valve 45 is u ₁ , the opening of the variable vane of the VNT 41 is u ₂ , the opening of the throttle valve 34 is u ₃ , the supercharger pre-pressure is y ₁ , the scavenging air pressure is y ₂ , and suction If the amount of air is y ₃ , (Equation 8) is established.

上式（数８）より、所要の目標値を達成する操作量の補正値の算定が可能である。例えば、スロットルバルブ３４をこれ以上開くことが難しく、ステップＳ６で算定した操作量をそのまま入力できないことから目標を達成できない場合、最も優先順位の高い吸入空気量の不足分または超過分ΔＧａから、
外部ＥＧＲバルブ４５の開度の補正値Δｕ₁＝ΔＧａ×Ｈ₁₃、
過給機前圧の補正値Δｙ₁＝Δｕ₁／Ｈ₁₁、
・・・・・・
というように、吸入空気量の目標値を達成するために必要なスロットルバルブ３４以外の操作量の補正値、並びに吸入空気量以外の制御量の補正値を順次算出することができる。さらに、可能であれば、次に優先順位の高い過給機前圧を達成するために必要な補正値を算出しても構わない。

From the above equation (Equation 8), it is possible to calculate the correction value of the manipulated variable that achieves the required target value. For example, when it is difficult to open the throttle valve 34 any more and the target cannot be achieved because the operation amount calculated in step S6 cannot be input as it is, from the shortage or excess ΔGa of the intake air amount with the highest priority,
Correction value Δu ₁ = ΔGa × H _{13 for} the opening degree of the external EGR valve 45,
Correction value Δy ₁ = Δu ₁ / H _{11 for} supercharger pre-pressure,
・ ・ ・ ・ ・ ・
As described above, the correction value for the operation amount other than the throttle valve 34 and the correction value for the control amount other than the intake air amount necessary to achieve the target value of the intake air amount can be sequentially calculated. Further, if possible, a correction value necessary to achieve the next highest priority turbocharger pressure may be calculated.

According to the present embodiment, when it is impossible or difficult to control all control amounts to each target value, a mathematical model that defines the relationship between the control amount and the manipulated variable, particularly in a two-degree-of-freedom control system. Based on the parameter H ₀ of the feedforward controller, a correction value for the operation amount necessary for the control amount having a high priority to reach the target value is calculated, and the operation units 35 and 41 are calculated using the calculated correction value. , 45 can be operated, the control amount having a high priority for the comparison house can be positively reached the target value, and the control state can be maintained well. In the case of a method that refers to a map that determines the correction value of the manipulated variable from the engine speed, the injection amount, etc., consider the creation of the map (what is the index axis, etc.), the conformance of the map, and the verification of the conformance However, the above-described method eliminates the need for map creation and adaptation.

  The present invention is not limited to the embodiment described in detail above. For example, when a passage that bypasses the superchargers 31 and 32 exists in the intake system 3, a valve provided on the passage may be an operation target. At this time, a 4-input 4-output control system including the gas flow rate of the bypass passage in the output and the operation of the valve on the bypass passage in the input is provided.

  The internal combustion engine 2 to which the present invention is applied is not limited to a diesel engine, and is not limited to a two-cycle engine.

  In addition, the specific configuration of each unit, the processing procedure, and the like can be variously modified without departing from the spirit of the present invention.

The structure explanatory view of the present invention. Schematic which shows the plant in one Embodiment of this invention. The flowchart which shows the process sequence of control. The block diagram of a 2-degree-of-freedom control system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 12, 13 ... Measuring instrument 14 ... Target value setting part 15 ... Operation amount calculation part 16 ... Correction | amendment part 17 ... Control part 2 ... Internal combustion engine 3, 4 ... Intake / exhaust system 34, 41, 45 ... Operation part (D throttle) Valve, external EGR valve, VNT)

Claims (4)

In operating the operation unit to control multiple control amounts to their target values,
When it is impossible or difficult to control all the controlled variables to each target value, the controlled variable with the highest priority reaches the target value based on the mathematical model that defines the relationship between the controlled variable and the manipulated variable. Calculate the correction value of the operation amount required to
A control method comprising operating an operation unit using a calculated correction value. The control method according to claim 1, wherein a parameter of a feedforward controller in a two-degree-of-freedom control system is used for the mathematical model. Applied to a two-cycle internal combustion engine with a supercharger,
When the intake air amount or air pressure, the supercharger pre-pressure, and the scavenging air pressure exist as the plurality of control amounts, and it is impossible or difficult to control all these control amounts to each target value, the intake air The control method according to claim 1 or 2, wherein a correction value of an operation amount required to make the amount or air pressure reach the target value is calculated. It is used for carrying out the control method according to claim 1, 2, or 3,
When it is impossible or difficult to control all the controlled variables to each target value, the controlled variable with the highest priority reaches the target value based on the mathematical model that defines the relationship between the controlled variable and the manipulated variable. A correction unit that calculates a correction value of the operation amount required to
And a control unit that operates the operation unit using the calculated correction value.

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