JP2008248863A - Control method and control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain a good control state by avoiding saturation of a control input. <P>SOLUTION: When an operation amount u required to make controlled variables reach a target value exceeds a saturation value as a limit of the operation amount which can be given to an operation part, the operation amount u actually given to the operation part is set within the saturation value, by negatively feeding back an exceed amount Δu with respect to the saturation value of the operation amount at a portion after an integral element integrating deviation e between the target value r and the controlled variables y. <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 avoid the saturation of the control input and maintain a good control state.

  In order to solve the above-described problems, in the control method according to the present invention, the operation amount required for the control amount to reach the target value is controlled by operating the operation unit to control the control amount to the target value. When the saturation value, which is the limit of the manipulated variable that can be given to the part, is exceeded, the amount that exceeds the saturated value of the manipulated variable is negatively fed back to the part after the integral element that integrates the deviation between the target value and the controlled variable By doing so, the amount of operation actually given to the operation unit was kept within the saturation value. If it is such, a control state can be maintained favorable. In addition, control overshoot (according to hunting) can be suppressed by not performing the integration of the transcendental amount.

  According to the present invention, it is possible to satisfactorily maintain the control state by avoiding saturation of the control input.

  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, operation amount calculation unit 15 that calculates the operation amount to be given to the plurality of operation units 34, 41, 45 in order to direct the plurality of parameters to the target value, and the calculated operation amount is the actual operation unit 34, 41, When the operation amount saturation value (threshold value, constraint condition) that can be input to 45 is exceeded, the correction unit 16 corrects the operation amount, and the operation units 34, 41, and 45 are operated using the operation amount. And a control unit 17.

  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 the operation amount calculated in step S6 exceeds the saturation value of the operation amount that can be input to the actual operation units 35, 45, and 41 (step S8), the operation amount is kept within the saturation value. A correction amount necessary for the calculation is calculated (step S9) and the operation amount is corrected.

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

  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 an LQI control system. FIG. 4 shows a block diagram of the control device of this embodiment including the LQI control system. 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. If the deviation between the controlled variable and its target value is e, the deviation integrated through the integration element is w, and the estimated state quantity in the observer is x, the operation unit 34, 41, 45 when correction is not performed The control input u is expressed by (Expression 2).

If the integral value at which the manipulated variable is exactly the saturation value u _max when correction is not performed is set as w ′, (Equation 3) is established.

Subtracting (Equation 3) from (Equation 2) yields (Equation 4).

When (Equation 4) is arranged, (Equation 5) is obtained.

If the manipulated variable is saturated, the integral value w may be changed to w ′ so that the manipulated variable u becomes u _max . In other words, Δu may be fed back so that the integral value w becomes w ′.

In step S9, when the operation amount u which is calculated in step S6 exceeds the saturation value u _max, calculates a correction amount of w from the difference i.e. transcendental quantity Δu with that calculated operation amount u and saturation value u _max . As shown in FIG. 4, if the correction amount based on the transcendent amount Δu is negatively fed back immediately after the integration element, the correction amount is the second term Δu / F _{2 on} the right side of the above equation (Equation 5). . That is, the gain J of the anti-windup control part is 1 / F ₂ .

According to the present embodiment, when the operation amount necessary for the control amount to reach the target value exceeds the saturation value that is the limit of the operation amount that can be given to the operation units 34, 41, 45, The amount of operation actually given to the operation units 34, 41, and 45 is within the saturation value by negatively feeding back the amount exceeding the saturation value of the operation amount to the portion after the integration element that integrates the deviation between the target value and the control amount. Therefore, the control state can be maintained satisfactorily. This embodiment, the components resulting from the non-deviation input via the integrating element, for example, the operation amount of the result of adding the components of F ₁ wherein passing through the observer is also adequately address situations exceeds the saturation value it can. Further, the control overshoot can be suppressed by not performing the integration of the transcendental amount.

  The present invention is not limited to the embodiment described in detail above. In particular, the control method is not limited to LQI control.

  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 LQI 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, 45, 41 ... Operation part (D throttle) Valve, external EGR valve, VNT)

Claims (2)

In what controls the control amount to the target value by operating the operation unit,
When the manipulated variable required to reach the control value reaches the target value exceeds the saturation value, which is the limit of the manipulated variable that can be given to the control unit, the transcendent value for the saturated value of the manipulated variable is set to the target value. A control method characterized in that an operation amount that is actually given to the operation unit is kept within a saturation value by negatively feeding back to a portion after an integration element that integrates a deviation between the control amount and the control amount. It is used for carrying out the control method according to claim 1,
When the manipulated variable required to reach the control value reaches the target value exceeds the saturation value that is the limit of the manipulated variable that can be given to the operating unit, based on the transcendental amount of the manipulated variable with respect to the saturated value A correction unit for calculating the correction amount;
A control device comprising: a control unit that operates an operation unit using an operation amount obtained by negatively feeding back the calculated correction amount to a portion after an integration element that integrates a deviation between a target value and a control amount.

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