JP5276552B2 - Control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a sliding mode control device capable of maintaining high control performance for a plant with input and output characteristics changing each moment. <P>SOLUTION: The control device 5 includes a sliding mode controller 51 for repetitively calculating linear input and non-linear input with reference to state variables, and a correction control part 52 for changing according to predetermined conditions either one of or both a switching gain and a smoothing coefficient defining the non-linear input for rewriting the state variables by calculating backward a state variable to provide a non-linear input after the change of the same value as the non-linear input before the change. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a control device for controlling an internal combustion engine or a device attached thereto.

  An exhaust gas recirculation system disclosed in Patent Document 1 below controls an EGR rate (or EGR amount) of an internal combustion engine equipped with a supercharger. There is a mutual interference between the EGR rate and the supercharging pressure, and it is difficult to simultaneously control both the EGR rate and the intake pipe pressure (or intake air amount) with a one-input one-output controller. In addition, the responsiveness varies depending on the operation region of the internal combustion engine, and the turbocharger has a turbo lag (dead time). Under such circumstances, the system described in Patent Document 1 employs sliding mode control, which is an effective control method for a non-linear control target, and designs a multi-input multi-output controller that takes into account the interaction. I have control.

  When designing a controller, it is considered to derive one switching hyperplane from a specific state space model called a nominal model and to keep the state in this hyperplane. The nominal model is obtained, for example, by identifying input / output characteristics of an engine operating under a specific rotation speed and fuel injection amount. However, in an actual automobile, the driving range, that is, the engine speed and the fuel injection amount change every moment. The input / output characteristics of the engine also vary depending on the operating region.

  Sliding mode control is a highly robust control method, and can properly absorb errors (perturbations) between the input / output characteristic model assumed during controller design and the actual input / output characteristics of the plant. However, perturbations become large in low-rotation and low-load areas such as idle and high-rotation and high-load areas such as high-speed cruise, and it is not always best to apply a single controller designed offline to the entire operation area. It wasn't.

JP 2007-032462 A

  The present invention, which has been made by paying attention to the above-mentioned problems, aims to realize a sliding mode control device capable of maintaining high control performance for a plant whose input / output characteristics change every moment.

  In the present invention, an internal combustion engine or a device attached thereto is controlled in a sliding mode, and a sliding mode controller that repeatedly calculates a linear input and a nonlinear input with reference to a state variable, and the above-mentioned according to a predetermined condition Change one or both of the switching gain and smoothing coefficient that define the nonlinear input, and back-calculate the state variables so that the nonlinear input after the change is equivalent to the nonlinear input before the change. A control device is provided that includes a correction control unit that rewrites a state variable.

  In other words, by changing the switching gain and / or the smoothing coefficient, which are the elements of the nonlinear input term of the sliding mode controller, by following the changes in the input / output characteristics of the plant and preventing excessive perturbation. is there. With such a configuration, the control performance is not deteriorated even in a low rotation / low load region, a high rotation / high load region, and the like, and temporary exhaust gas deterioration and output torque decrease can be suppressed or avoided.

  However, when the switching gain and / or the smoothing coefficient are simply changed, the nonlinear input calculated by the sliding mode controller fluctuates in a stepwise manner before and after the change. As a result, the opening degree of each valve as the operation unit changes so as to jump, which may cause hunting of control input / output. Therefore, in the present invention, when changing the switching gain and / or the smoothing coefficient, the state variable referred to by the sliding mode controller is rewritten, so that the divergence between the non-linear input before the change and the non-linear input after the change is suppressed. Plan.

  The correction control unit stores in advance a map that defines a relationship between an index value related to the current status of the internal combustion engine or the device attached thereto, and the switching gain or the smoothing coefficient, and the index value is used as a key If the change gain or smoothing coefficient after change is known through searching the map, an extra calculation load is not applied to the ECU (Electronic Control Unit) when changing the change gain and / or smoothing coefficient. It will end.

  ADVANTAGE OF THE INVENTION According to this invention, the sliding mode control apparatus which can maintain high control performance with respect to the plant in which an input-output characteristic changes every moment can be implement | achieved.

The hardware resource block diagram of the EGR system in one Embodiment of this invention. Configuration explanatory drawing of the control apparatus of the embodiment. The block diagram of the adaptive sliding mode controller of the embodiment. The figure which illustrates the map which prescribes | regulates the relationship between engine speed and fuel injection quantity, switching gain k, and smoothing coefficient (eta). The graph which illustrates the relationship between switching function (sigma) and factor JΣ. The graph which illustrates the relationship between switching function (sigma) and factor JΣ. The flowchart which shows the procedure of the process which the control apparatus of the embodiment performs. The graph which illustrates the relationship between switching function (sigma) and factor JΣ. The graph which illustrates the relationship between switching function (sigma) and factor JΣ.

  An embodiment of the present invention will be described with reference to the drawings. What is shown in FIG. 1 is an EGR system that is one of the objects to which the present invention is applied. The EGR system incidental to the internal combustion engine 2 includes measuring devices 11 and 12 for detecting values related to a plurality of fluid pressures or flow rates in the intake and exhaust systems 3 and 4, and setting target values to these values. ECU5 which is a control apparatus which operates several operation part 45,42,33 so that it may follow target value.

  The internal combustion engine 2 is a diesel engine equipped with a supercharger, for example. The intake system 3 of the internal combustion engine 2 is provided with a variable turbo compressor 31 and an intercooler 32 for intake air cooling and a D throttle valve 33 for adjusting the amount of fresh air downstream thereof. In addition, a flow meter 11 that measures the amount of fresh air and a pressure meter 12 that measures the pressure in the intake pipe are installed.

  The exhaust system 4 of the internal combustion engine 2 is provided with a turbine 41 for driving the compressor 31, and a nozzle vane 42 for increasing or decreasing the A / R ratio of the supercharger is provided at the inlet of the turbine 41. A DPF (Diesel Particulate Filter) (not shown) is installed downstream of the turbine 41. Then, an EGR passage 43 for recirculating a part of the exhaust gas discharged from the combustion chamber of the internal combustion engine 2 to the intake system 3 is formed. The EGR passage 43 is connected downstream of the throttle valve 33 in the intake system 3. The EGR passage 43 is provided with an EGR cooler 44 for cooling the exhaust, and an external EGR valve 45 that adjusts the amount of exhaust gas (EGR gas) that passes therethrough.

  In the present embodiment, a target value is set for each of the EGR rate (or EGR amount) and the intake pipe pressure (or intake air amount), and a plurality of operation units are set so that both control amounts are directed toward the target value. That is, control for operating the EGR valve 45, the variable turbo nozzle 42 and the throttle valve 33 is performed.

  The EGR valve 45, the nozzle vane 42, and the throttle valve 33 are controlled by the ECU 5 to change their opening degrees linearly. Each operation unit 45, 42, 33 is combined with an electric valve that changes the opening by increasing or decreasing the duty ratio of the drive signal, or a vacuum control valve, etc. It uses mechanical valves that change.

  The ECU 5 is a microcomputer including a processor, a RAM (Random Access Memory), a ROM (Read Only Memory) or a flash memory, an A / D conversion circuit, a D / A conversion circuit, and the like. In addition to the measuring instruments 11 and 12 for detecting the EGR rate and the intake pipe pressure, the ECU 5 includes the engine speed, the accelerator pedal depression amount, the cooling water temperature, the intake air temperature, the external air temperature, the atmospheric pressure, and the differential pressure across the DPF. It is electrically connected to various measuring instruments (not shown) that detect (difference between upstream and downstream exhaust pressures of DPF), etc., and receives signals output from these measuring instruments to know each value. Can be obtained.

Incidentally, in this embodiment, the EGR rate is not directly measured. The amount of air entering the cylinder of the internal combustion engine 2 can be predicted based on the nozzle opening of the variable turbo. The predicted value of the air amount g _cyl Distant, if the fresh air amount measured by the flow meter 11 is denoted by g _a, the estimated EGR rate _{e egr, e egr = 1-} g a / g cyl the relationship is established To do. The ROM or flash memory of the ECU 5 stores in advance map data that defines the relationship between the variable turbo nozzle opening and the amount of air entering the cylinder. The ECU 5 searches the map using the nozzle opening of the variable turbo as a key, obtains a predicted value of the amount of air entering the cylinder, and substitutes this and the new amount of air into the above formula to calculate the EGR rate.

  In addition, the ECU 5 is electrically connected to the EGR valve 45, the variable turbo nozzle 42, the throttle valve 33, an injector for controlling fuel injection, a fuel pump, and the like (not shown), and signals for driving them. Can be entered.

  A program to be executed by the ECU 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 ECU 5 controls the internal combustion engine 2 according to a program. For example, a required fuel injection amount (so-called required engine load) is determined based on various conditions such as engine speed, accelerator pedal depression amount, cooling water temperature, etc., and a drive signal corresponding to the required injection amount is injected into the injector. To control the fuel injection. In addition, the ECU 5 exhibits functions as the servo controller 51 and the correction control unit 52 shown in FIGS. 2 and 3 according to the program.

  The servo controller 51 is a sliding mode controller and is responsible for the sliding mode control of the EGR rate and the intake pipe pressure. During feedback control, the ECU 5 receives signals output from various measuring instruments (not shown), and knows the engine speed, accelerator depression amount, cooling water temperature, intake air temperature, external temperature and pressure, etc., and the required injection amount To decide. Subsequently, the target EGR rate and the target intake pipe pressure are set based on at least the engine speed and the required injection amount. The ROM or flash memory of the ECU 5 stores in advance map data indicating each target value to be set according to the engine speed and the required injection amount. The ECU 5 searches the map using the engine speed and the required injection amount as keys, and obtains target values for the EGR rate and the intake pipe pressure. Further, the target value obtained by referring to the map is set as a basic value, and this is corrected according to the cooling water temperature, the intake air temperature, the outside air temperature, the atmospheric pressure, and the like to obtain the final target value.

  Then, the ECU 5 receives signals output from the measuring instruments 11 and 12 to obtain the current values of the EGR rate and the intake pipe pressure, and the opening of the EGR valve 45 from the deviation between the current value of each control variable and the target value. Then, the opening degree of the variable turbo nozzle 42 and the opening degree of the throttle valve 33 are calculated, and a drive signal corresponding to each operation amount is input to the operation units 45, 42, 33 to operate the opening degree.

  A supplementary explanation will be given regarding adaptive sliding mode control of the EGR rate. The state equation and the output equation are as shown in the following equation (Equation 1).

  In this embodiment, the state quantity vector X has a structure that can be directly obtained from the output vector Y. In other words, a value that can be detected via the measuring instruments 11 and 12 is directly controlled, so that the state estimation observer. This prevents the deterioration of the control performance due to the estimation error. The output matrix C is known, and is a unit matrix in this embodiment.

  In plant modeling, that is, identification of the coefficient matrix A and the input matrix B in the state equation (Equation 1), the opening degree is manipulated by inputting M-sequence signals having various frequencies to the operation units 45, 42, and 33. Then, the values of the EGR rate and the intake pipe pressure are observed, and the matrices A and B are identified from the input / output data. It is assumed that the M-sequence signals input to the operation units 45, 42, and 33 are uncorrelated with each other. This makes it possible to create a model that takes into account the mutual interference between the values.

FIG. 3 shows a block diagram of the adaptive sliding mode control system of the present embodiment. The design procedure of the sliding mode controller 51 includes the design of the switching hyperplane and the design of a nonlinear switching input for constraining the state quantity to the switching hyperplane. If a new state quantity vector _Xe is defined by adding an integral value vector Z of the deviation between the target value vector R and the output vector Y to the original state quantity vector X in order to constitute a type 1 servo system, The equation of state of the expanded system shown in (Expression 2) is obtained.

  In consideration of the stability margin, the design method using the zero of the system is used to design the switching hyperplane. That is, the hyperplane is designed so that the equivalent control system is stable when the expansion system of the above equation (Equation 2) is generating the sliding mode. When the switching function σ is defined by Expression (Expression 3), σ = 0 and Expression (Expression 4) holds when the state is constrained to the hyperplane.

  Therefore, the linear input (equivalent control input) when the sliding mode occurs is expressed by the following equation (Equation 5).

  Substituting the linear input of the above equation (Equation 5) into the state equation (Equation 2) of the expanded system results in an equivalent control system of the following equation (Equation 6).

  Since designing a hyperplane so that this equivalent control system is stable is equivalent to designing a system ignoring the target value R, the following equation (Equation 7) holds.

  Taking the stability ε into consideration for the system of the above equation (Equation 7), obtaining the feedback gain using the optimal control theory, and making it a hyperplane, the following equation (Equation 8) is obtained.

The matrix P _s is a positive definite solution of the Riccati equation (Equation 9).

Q _s in the Riccati equation (Equation 9) is a weight matrix for control purposes, and is a non-negative definite symmetric matrix. q ₁ and q ₂ are weights for the integral Z of the deviation, and are determined by the difference in the speed of the frequency response of the control system. q ₃ and q ₄ are weights for the output Y, and are determined by the difference in the magnitude of the gain. Further, R _s in the Riccati equation (Equation 9) is a weight matrix of the control input and is a positive definite symmetric matrix. ε is a stability margin coefficient and is specified so that ε ≧ 0.

  Instead of the above equations (Equation 8) and (Equation 9), the following discrete hyperplane construction equation (Equation 10) and algebraic Riccati equation (Equation 11) may be used.

The final sliding mode method is used to design the input for constraining to the hyperplane. Here, the control input U is expressed by the following expression (Equation 12) as the sum of the linear input U _eq and a new input, that is, a nonlinear input (nonlinear control input) U _nl .

  Since it is desired to stabilize the switching function σ, the Lyapunov function for σ is selected as shown in the following equation (Equation 13) and differentiated to obtain the equation (Equation 14).

  Substituting the equation (Equation 12) into the equation (Equation 14) yields the following equation (Equation 15).

When the nonlinear input U _nl to the following expression (Expression 16), the derivative of the Lyapunov function becomes equation (17).

  Therefore, if the switching gain k is positive, the differential value of the Lyapunov function can be negative, and the stability of the sliding mode is guaranteed. The control input U at this time is expressed by the following equation (Equation 18).

  η is a smoothing coefficient introduced to reduce chattering, and η> 0.

  In the sliding mode control, it is necessary to increase the nonlinear gain in order to constrain the state quantity to the hyperplane. However, if the nonlinear gain is increased, chattering occurs in the control input. Therefore, the uncertainty of the model is divided into a definite part whose structure is unknown and whose parameter is unknown, and an uncertain part whose structure is unknown but whose upper bound is known. Uncertainty (f + Δf) is added to the state equation (Equation 1), and is expressed by the following equation (Equation 19).

  The uncertainty determination part f is compensated by identifying the unknown parameter θ. In this case, the switching gain is applied only to the uncertain part Δf of the uncertainty, and the chattering of the control input can be greatly reduced as compared with the case where the switching gain is applied to the entire uncertain component (f + Δf).

The control input U is represented by the following equation (Equation 20) obtained by adding the adaptive term U _ad to the equation (Equation 18).

Γ _{1 at the} control input (Equation 20) is an adaptive gain matrix. The function h is generally a function of the state quantity x and / or the unknown parameter θ. However, in the present embodiment, by making h a simple expression and a constant unrelated to x and θ, x is quickly converged, and θ To increase the adaptation speed. In particular, when h = 1, the estimated parameter can be identified according to the following equation (Equation 21).

In the present embodiment, the EGR ratio y ₁ and the intake pipe pressure y ₂ as a control output variable, the opening degree u ₁ of the EGR valve 45, the opening degree u ₃ of opening u ₂ and the throttle valve 33 of the variable turbo nozzle 42 Performs 3-input 2-output feedback control using control input variables. The number of state variables (system order) is 2 in the initial system (Equation 1), and 4 in the expanded system (Equation 2). By specifying the control output and the state quantity in this way, there is no need to install a measuring instrument such as a flow meter at a location where it directly contacts the exhaust gas.

However, in a three-input two-output system as in this embodiment, det (SB _e ) = 0 holds, and the matrix (SB _e ) is not regular. Therefore, the inverse matrix (SB _e ) ⁻¹ is calculated as a generalized inverse matrix. As the generalized inverse matrix, for example, a Moore-Penrose-type inverse matrix (SB _e ) ^† is used.

  Thus, the correction control unit 52 controls switching of the control according to the current state of the internal combustion engine 2. In the present embodiment, at least the following four types are assumed as the operation region classification of the internal combustion engine 2.

  (I) NA region (negative pressure region, no supercharging region); a low load region such as idle operation, that is, a region where the engine speed and torque are low. In the NA region, the pressure in the intake pipe is approximately close to atmospheric pressure. At this time, the exhaust turbocharger does not work even if the opening degree of the nozzle vane 42 is changed. If the target value of the intake pipe pressure is slightly higher than the actually measured value of the intake pipe pressure, the nozzle opening is throttled, eventually saturated (minimized), and the nozzle opening no longer changes. If this is the case, the control of the EGR rate, which is important for maintaining the exhaust gas purification efficiency, may be hindered.

  (Ii) EGR cut region: This is a region where the recirculation of EGR gas via the EGR passage 43 is stopped. When high-speed high-load areas where high output torque is required, high-altitude areas where the combustion is unstable or misfires (atmospheric pressure is low), when a load operation exceeding a certain level is required, or when a warm-up operation is required This corresponds to the EGR cut area.

  (Iii) EGR cut NA area: This is also an area where the recirculation of the EGR gas via the EGR passage 43 is stopped. The difference from the EGR cut area is that the pressure in the intake pipe can be increased or decreased through the opening / closing operation of the nozzle vane 42 in the EGR cut area, but not in the EGR cut NA area. For example, when the DPF is regenerated or when a low-load low-rotation operation is performed at a high altitude, the EGR cut NA region corresponds. In the former, the temperature of the DPF must be increased by sending high-temperature exhaust gas to the DPF more and more with post injection (for the purpose of oxidizing and removing PM (Particulate Matter) collected in the DPF). For the purpose of controlling the pressure in the intake pipe, the opening of the nozzle vane 42 is not desired to be throttled. In the latter case, EGR is cut to prevent combustion instability or misfire, but the exhaust gas turbocharger works like the NA area because the exhaust gas volume is low and the exhaust pressure is low. There is no circumstance.

  (Iv) Normal region: This is a region that does not fall under any of the above, and may completely entrust the control of the internal combustion engine 2 to the sliding mode controller 51.

  The correction control unit 52 determines the current operation region classification of the internal combustion engine 2 based on the engine speed, the required fuel injection amount (required load), the coolant temperature, the atmospheric pressure, the differential pressure across the DPF, and the like.

FIG. 4 shows the relationship between the engine speed and the fuel injection amount and the operation region. In principle, the low rotation and low load areas where the engine speed and the fuel injection amount are each lower than the threshold value L ₁ are NA areas, and the high rotation and high load areas where the engine speed and the fuel injection quantity are each higher than the threshold value L _2. The EGR cut area is set, and the other area is set as the normal area.

  However, in situations where the atmospheric pressure is lower than the threshold value and the automobile is considered to be located at high altitude, the low-rotation and low-load area is set as the EGR cut NA area, and the medium-rotation or higher area and Eload-cut area are EGR cut. A zone.

  Further, when the cooling water temperature is lower than a predetermined value (typically 40 ° C.), the EGR cut region is set for warm-up operation. When the differential pressure across the DPF exceeds a predetermined value, the EGR cut NA region is set for DPF regeneration.

Next, the correction control unit 52 changes the switching gain k and / or the smoothing coefficient η that defines the nonlinear input term _Unl according to the determined operation region segment.

  As already described, when designing the sliding mode controller 51, a nominal model (matrix A, B) of the internal combustion engine 2 under a specific operating region, that is, a certain engine speed and a required fuel injection amount is identified. The switching hyperplane S is derived by obtaining the state equation (Equation 2). The modeling error (perturbation) between the nominal model and the actual plant is relatively small in the normal region, but is enlarged in other regions. Therefore, in the present embodiment, the perturbation is suppressed by setting different switching gains k and / or smoothing coefficients η for each of the region sections of the NA region, the EGR cut region, the EGR cut NA region, and the normal region. I am trying.

  The ROM or flash memory of the ECU 5 stores in advance a map that defines the relationship between each area segment and the switching gain k and / or the smoothing coefficient η as shown in FIG. The correction control unit 52 determines k and / or η with reference to this map data. That is, the map is searched using the index values (engine speed and combustion injection amount, cooling water temperature, atmospheric pressure, differential pressure before and after the DPF, etc.) relating to the current state of the internal combustion engine 2 or its accompanying devices as keys. And / or know η.

Further, the auxiliary control unit 52 determines that the non-linear input _Unl calculated by the sliding mode controller 51 is stepwise when the transition of the region division occurs between the NA region, the EGR cut region, the EGR cut NA region, and the normal region. so as not to abruptly change, back to find k and / or η nonlinear input after changing U _nl state variable X _e such that the front of the non-linear input U _nl becomes equivalent to the changes, the state variable X _e rewrite.

Placing the factor Jshiguma the following expression (Expression 22), the nonlinear input U _nl generalized inverse matrix - a ((SB _e) ^†) in multiplied by the factor Jshiguma.

  FIG. 5 schematically illustrates the relationship between the switching function σ and the factor JΣ. In this embodiment, since σ and JΣ are both three-dimensional vectors, FIG. 5 is not mathematically accurate. However, if it is described with reference to FIG. 5 (or σ and JΣ are both considered as scalar values), JΣ gradually approaches the switching gain k as σ increases. Further, the change in which JΣ approaches the asymptotic line k becomes more rapid as the smoothing coefficient η is smaller, and becomes slower as η is smaller.

For k and / or non-linear input U _nl between before and after the change of η is prevented from variation, Jshiguma in as before and after the change must not to be become equivalent. Therefore, the following equation (Equation 23) needs to be established.

JΣ _n−1 , σ _n−1 , k _n−1 , and η _n−1 are a factor, a switching function, a switching gain, and a smoothing coefficient at a point just before the transition of the operation region. Similarly, JΣ _n , σ _n , k _n , and η _n are a factor, a switching function, a switching gain, and a smoothing coefficient at the time immediately after the operation region section is changed. FIG. 6 shows an example of transition from the NA area to the normal area.

  When formula (Formula 23) is transformed, Formula (Formula 24) is obtained.

If the factor vector JΣ _n−1 = [jσ ₁ jσ ₂ jσ ₃ ] ^T and the switching function vector σ _n = [σ _n1 σ _n2 σ _n3 ] ^T , each component jσ _i (i = 1) of the factor vector JΣ _n− 1 , 2, 3), the equation (Equation 25) holds if jσ _i > 0, and the equation (Equation 26) holds if jσ _i ≦ 0.

  If Formula (Formula 25) is modified, Formula (Formula 27) is obtained, and if Formula (Formula 26) is modified, Formula (Formula 28) is obtained.

Expressions (Equation 27) to (Equation 28) reveal the switching function σ _n that does not cause the variation of the factor JΣ and hence the nonlinear input U _nl . An attempt is made to back-calculate the state quantity X _e from this switching function σ _n .

The state quantity vector X _e = [x _e1 x _e2 x _e3 x _e4 ] ^T has, as its components, time integrals x _e1 and x _e2 of deviation between the control output Y and its target value R, and other x _e3 , X _e4 . x _e1 and x _e3 relate to the EGR rate y ₁ as the first control output, x _e2 and x _e4 relate to the intake pipe pressure y ₂ as the second control output, and these state variables x _e1 and x _e3 , x _e2 And x _e4 are individual for each control output y ₁ , y ₂ . Further, x _e3 and x _e4 are respectively connected to the control outputs y ₁ and y ₂ via the output equation (Equation 1).

From the equation (Equation 3), the relationship of the following equation (Equation 29) is established between the switching function σ _n and the state quantity x _e .

S _j (j = 1, 2, 3, 4) is a column vector to be multiplied by the state variable x _ej among the components of the matrix S constituting the switching hyperplane.

From the above equation (Equation 29), the state variables x _e1 , x _e2 , x _e3 , x _e4 that realize the switching function σ _n can be calculated backward. However, in this embodiment, x _e3 is the EGR rate itself, and x _e4 is the intake pipe pressure itself. The state variables x _e1 and x _e2 affect the nonlinear input U _nl , but do not affect the linear input U _eq (note the definition of the matrix A _e ). Therefore, the state variables x _e3 and x _e4 are not rewritten, and the switching functions σ _n shown in the equations (Equation 27) to (Equation 28) are realized by rewriting the state variables x _e1 and x _e2. Prevent fluctuations in the input _Unl . The x _e1 and x _e2 required for this are given by the following equation (Equation 30).

However, the matrix [S ₁ S ₂ ] is not a square matrix. Therefore, the inverse matrix [S ₁ S ₂ ] ⁻¹ is calculated as a generalized inverse matrix. As the generalized inverse matrix, for example, a Moore-Penrose-type inverse matrix [S ₁ S ₂ ] ^† is used.

  In addition, when it is determined that the current operation region is in the NA region, the EGR cut region, or the EGR cut NA region, the correction control unit 52 performs a necessary correction for each region.

In the NA region, the opening degree of the nozzle vane 42 is fixed to a predetermined value that does not depend on the control input value u ₂ calculated by the sliding mode controller 51. At the same time, the target value r ₂ of the intake pipe pressure is given to the sliding mode controller 51 as the actually measured values y ₂ and x _e4 of the intake pipe pressure. In the sliding mode controller 51, it is considered that the deviation of the intake pipe pressure is zero.

In the EGR cut region, the control input value u ₁ calculated by the sliding mode controller 51 for calculating the opening degree of the EGR valve 45 is ignored, and the control is performed by the sliding mode controller 51 for calculating the opening degree of the D throttle valve. ignoring the input value u ₃ is fully opened. At the same time, the target value r ₁ of the EGR rate is given to the sliding mode controller 51 as the actually measured values y ₁ and x _e3 of the EGR rate. In the sliding mode controller 51, it is considered that the deviation of the EGR rate is zero.

In the EGR cut NA region, the control input value u ₁ calculated by the sliding mode controller 51 for the opening degree of the EGR valve 45 is ignored and the valve is fully closed. At the same time, the target value r ₁ of the EGR rate is given to the sliding mode controller 51 as the actually measured values y ₁ and x _e3 of the EGR rate. In the sliding mode controller 51, it is considered that the deviation of the EGR rate is zero. The nozzle vane 42 may be operated by giving the control input value u ₂ calculated by the sliding mode controller 51 as it is, or its opening degree may be fixed to a predetermined value that does not depend on the control input value u _2. .

  These corrections are not performed in the normal range.

In FIG. 7, the example of a procedure of the process which ECU5 performs is shown. The ECU 5 refers to the engine speed, the required fuel injection amount, the cooling water temperature, the atmospheric pressure, the differential pressure before and after the DPF, and the transition of the region between the NA region / EGR cut region / EGR cut NA region / normal region is performed. It is determined whether or not it has occurred (step S1). If it is determined that the region transition has occurred, the switching gain k and / or the smoothing coefficient η to be set based on the engine speed, the required fuel injection amount, and the like are obtained (step S2). _{Alternatively} , the state variables x _e1 and x _e2 are calculated so that the switching function σ _n after the setting change of η becomes equal to σ _n−1 immediately before the setting change (step S3). Then, k and / or η, x _e1 , x _e2 stored in the memory of the ECU 5 are rewritten (step S4). It goes without saying that steps S2 to S4 are not performed if there is no region transition.

  Then, the control input U is calculated in accordance with the sliding mode control method (step S5). Thereafter, the calculated control input U is given to the operation units 45, 42 and 33 to operate them (step S6). However, when the current operation region is in the NA region, the EGR cut region or the EGR cut NA region, a value different from the original EGR rate or the intake pipe pressure is given to the sliding mode controller 51 in step S5, and the step In S6, the calculation result of the sliding mode controller 51 is ignored and the EGR valve 45, the nozzle vane 42 or the D throttle valve 33 is operated.

  The ECU 5 repeatedly performs the above steps S1 to S6.

According to this embodiment, the internal combustion engine 2 or a device attached thereto is controlled in a sliding mode, and sliding is performed by repeatedly calculating the linear input U _eq and the nonlinear input U _nl with reference to the state variable X _e. The mode controller 51 changes one or both of the switching gain k and the smoothing coefficient η that define the nonlinear input _Unl according to a predetermined condition, and the nonlinear input _Unl after the change changes the change. back calculated for configuring the control device 5 comprising a correction control unit 52 to rewrite the state variable X _e, the switching gain k and / or smoothing the state variable X _e such that before the non-linear input U _nl and equivalent to By appropriately changing the coefficient η, it is possible to follow changes in the input / output characteristics of the plant and to prevent excessive perturbation. Therefore, control performance does not deteriorate even in a low rotation / low load region, a high rotation / high load region, and the like, and it is possible to suppress or avoid a temporary deterioration of exhaust gas and a decrease in output torque.

  The correction control unit 52 stores in advance a map that defines a relationship between an index value relating to the current state of the internal combustion engine 2 or an apparatus attached thereto, and the switching gain k or the smoothing coefficient η. Since the change gain k or the smoothing coefficient η is obtained by searching the map using the key as a key, an extra calculation load is imposed on the ECU 5 when the change gain k and / or the smoothing coefficient η is changed. No need to spend

  The present invention is not limited to the embodiment described in detail above. In particular, when transitioning from one region to another region, there may occur a case where JΣ cannot be kept constant. For example, when the magnitude of the switching gain k is different for each region, there may be no matching JΣ when transitioning from a region where k is relatively large to a region where k is relatively small. There are two possible ways to deal with such problems.

  (I) Unify k for each region; as shown in FIG. 8, if all regions have the same value k, the same JΣ always exists in any region. When the region transition occurs, only the smoothing coefficient η is changed.

(II) The upper and lower limits of the switching function σ are set; as shown in FIG. 9, the upper limit σ _max and the lower limit σ _{min of} σ such that JΣ exists in all regions are determined. When σ exceeds these thresholds σ _max or σ _min , σ is clipped to σ _max or σ _min .

  Further, the control input variables in the EGR control are not limited to the EGR valve opening, the variable nozzle turbo opening, and the throttle valve opening. The control output variable is not limited to the EGR rate (or EGR amount) and the intake pipe pressure (or intake amount). It is also possible to construct a tertiary system with four inputs and three outputs by adding new input variables and output variables. For example, when a passage that bypasses the supercharger (compressor) is present in the intake system, a valve provided on the passage may be operated. At this time, the pressure or flow rate in the bypass passage can be included in the control output variable, and the opening of the valve on the bypass passage can be included in the control input variable.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be used, for example, as a control controller for controlling the EGR rate of an internal combustion engine attached with a supercharger and an EGR device.

5 ... ECU (control device)
51 ... Adaptive sliding mode controller 52 ... Correction control unit

Claims (2)

A sliding mode control of an internal combustion engine or a device attached thereto,
A sliding mode controller that iteratively computes linear and nonlinear inputs with reference to state variables;
According to a predetermined condition, one or both of the switching gain and the smoothing coefficient that define the nonlinear input are changed, and the nonlinear input after the change becomes the same value as the nonlinear input before the change. A control device comprising: a correction control unit that reversely calculates the state variable and rewrites the state variable. The correction control unit stores in advance a map that defines a relationship between an index value relating to the current state of the internal combustion engine or an apparatus attached thereto, and the switching gain or the smoothing coefficient, and the index value is used as a key 2. The control device according to claim 1, wherein the switching gain or the smoothing coefficient after change is obtained through searching the map.

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