JP2010112306A - Control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve control convergence in a point separate from a nominal point, in sliding mode control of an internal combustion engine or a device attached to the same. <P>SOLUTION: A sliding mode control device 5 is constituted for controlling the internal combustion engine or the device attached to the same in a sliding mode, and providing control input by using its matrix by determining a switching hyperplane matrix S corresponding to an operation condition by referring to this map, by prestoring the map of determining the operation condition (an engine speed and a fuel injection quantity) of the internal combustion engine and the relationship between a weight matrix Q of a control object and a weight matrix R of the control input for regulating a Riccati equation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for controlling a sliding mode of 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 mutual interference between the supercharging pressure and the EGR rate, and it is difficult to simultaneously control both the supercharging pressure and the EGR rate 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 adopts sliding mode control, which is an effective control method for a non-linear control target, and designs an EGR controller by designing a multi-input multi-output controller in consideration of interaction. I have control.
JP 2007-032462 A

  In the sliding mode control, a slight delay occurs in the control convergence when the current state of the plant to be controlled, specifically, the operating region of the internal combustion engine is away from the nominal point. When designing a sliding mode 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. In conventional sliding mode control, a single switching hyperplane constructed off-line is applied to all operating regions. However, even if it is the optimal switching hyperplane at the nominal point, it is not necessarily optimal at other points, and the control performance will be deteriorated depending on the operating region.

  An object of the present invention made in view of the above is to improve control convergence at a point away from a nominal point in sliding mode control of an internal combustion engine or an apparatus attached thereto.

  In the present invention, the internal combustion engine or the device attached thereto is controlled in the sliding mode, and the operating condition of the internal combustion engine, the switching hyperplane matrix S, the solution P of the Riccati equation for designing the switching hyperplane matrix S or the Riccati equation A map defining the relationship between the control-purpose weight matrix Q and the control input weight matrix R is stored in advance, and the switching hyperplane matrix S corresponding to the operating conditions is determined with reference to this map, A control device characterized by obtaining a control input using the same was constructed.

  In other words, the switching hyperplane is changed in accordance with the operating conditions, in other words, the switching hyperplane that is optimal for the operating area at that time is constructed in real time. If the control device of the present invention is used, it is possible to improve the control accuracy and convergence at a point away from the nominal point, contributing to the improvement of exhaust gas and the like. Further, in the present invention, since the plant model itself, that is, it does not involve on-line updating of parameters such as a coefficient matrix and an input matrix in the state equation, the man-hour for model identification or adaptation is not increased, and the electronic control device The calculation load of (Electronic Control Unit) can be relatively light.

  More specifically, the engine speed and the fuel injection amount, the switching hyperplane matrix S, the solution P of the Riccati equation for designing the switching hyperplane matrix S, or the control-purpose weight matrix Q and the control input weight matrix It is preferable that a map defining the relationship with R is stored in advance, and the switching hyperplane matrix S corresponding to the operating conditions is determined with reference to this map.

  ADVANTAGE OF THE INVENTION According to this invention, in the sliding mode control of an internal combustion engine or an apparatus incidental to it, the improvement of control convergence in the point away from the nominal point can be aimed at.

  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. This EGR system attached to the internal combustion engine 2 includes measuring devices (or sensors) 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 target values for these values. ECU5 which is a control apparatus which operates the some operation part 45,42,33 in order to set and to make each value follow a 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 intake air (fresh air) amount downstream thereof. Further, a flow meter 11 for measuring the intake air amount and a pressure meter 12 for measuring the intake pipe pressure 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. 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, and a plurality of operation units, that is, an EGR valve 45, Control is performed to operate the variable turbo nozzle 42 and the throttle valve 33.

  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 pressure in the intake pipe, the ECU 5 detects various measuring instruments for detecting the engine speed, the accelerator pedal depression amount, the cooling water temperature, the intake air temperature, the outside air temperature, the atmospheric pressure, and the like. Each value can be known by receiving signals output from these measuring instruments.

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. When the predicted value of the air amount is set as g _cyl and the intake air amount measured by the flow meter 11 is set as g _a , the relationship of e _egr = 1−g _a / g _cyl is established for the estimated EGR rate e _egr. 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 air amount entering the cylinder, and substitutes this and the intake air amount 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, the required fuel injection amount (in other words, engine load) is determined based on various conditions such as engine speed, accelerator pedal depression amount, and coolant temperature, and a drive signal corresponding to the required injection amount is input to an injector or the like. And control the fuel injection. In addition, the ECU 5 exhibits functions as the sliding mode controller 51 and the switching hyperplane determination unit 52 shown in FIGS. 2 and 3 according to the program.

  The sliding mode controller 51 is responsible for 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 2).

  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.

  When modeling the plant, that is, identifying the coefficient matrix A and the input matrix B in the equation of state (Equation 2), M series signals having various frequencies are input to the operation units 45, 42, and 33 to control the opening degree. 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. 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 3) 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 3) is generating the sliding mode. When the switching function σ is defined by the equation (Equation 4), σ = 0 and the equation (Equation 5) 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 6).

  Substituting the linear input of the above equation (Equation 6) into the state equation (Equation 3) of the expanded system results in an equivalent control system of the following equation (Equation 7).

  Designing the hyperplane so that this equivalent control system is stable is equivalent to designing the system in which the target value R is ignored, so the following equation (Equation 8) holds.

  Taking the stability ε into consideration for the system of the above equation (Equation 8), obtaining the feedback gain using the optimal control theory and making it a hyperplane, the following equation (Equation 9) is obtained.

The matrix P _s is a positive definite solution of the Riccati equation (Equation 10).

Q _s in the Riccati equation (Equation 10) 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 10) 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 9) and (Equation 10), the following discrete hyperplane construction equation (Equation 11) and algebraic Riccati equation (Equation 12) 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 equation (Equation 13) 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 14) and differentiated to obtain the equation (Equation 15).

  Substituting equation (Equation 13) into equation (Equation 15) yields the following equation (Equation 16).

When the following expression nonlinear input U _nl and (Expression 17), the derivative of the Lyapunov function becomes equation (18).

  Therefore, if the switching gain k is positive, the differential value of the Lyapunov function can be negative, and the sliding mode is guaranteed. The control input U at this time is expressed by the following equation (Equation 19).

  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 2), and is expressed by the following equation (Equation 20).

  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 expression (Expression 21) obtained by adding the adaptive term U _ad to the expression (Expression 19).

Γ _{1 at the} control input (Equation 21) 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 22).

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 2), and 4 in the expanded system (Equation 3). By specifying the control output and the state quantity in this way, it is not necessary 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.

Therefore, the switching hyperplane determination unit 52 updates the switching hyperplane matrix S that defines linear input and nonlinear input online. In the present embodiment, by changing the control input weight matrix R _s and / or the control purpose weight matrix Q _s in the Riccati equation (Equation 10) or (Equation 12) according to the operating conditions of the internal combustion engine 2, The switching hyperplane matrix S is constructed in a timely manner.

In the ROM or flash memory of the ECU 5, map data indicating weights to be set according to the engine speed and the fuel injection amount as illustrated in FIG. 4 is stored in advance. A map is individually provided for each of the weights r ₁ , r ₂ , r ₃ , q ₁ , q ₂ , q ₃ , and q ₄ , and there are seven convenient maps. The switching hyperplane determining unit 52 refers to these maps to determine the weight matrices R _s and Q _s . That is, the map is searched using the engine speed and the fuel injection amount as keys to obtain r ₁ , r ₂ , r ₃ and q ₁ , q ₂ , q ₃ , q ₄ .

However, the control input weight matrix R _s may be constant regardless of the operating conditions of the internal combustion engine 2. Furthermore, the weight matrix R _s may be a unit matrix.

  According to the present embodiment, the internal combustion engine 2 or a device attached thereto is controlled in the sliding mode, and the operating condition of the internal combustion engine 2, the weight matrix Q for the control purpose that defines the Riccati equation, and the weight matrix of the control input A control device that stores in advance a map that defines a relationship with R, determines a switching hyperplane matrix S corresponding to the operation region with reference to this map, and obtains a control input using the switching hyperplane matrix S Therefore, it is possible to construct a switching hyperplane S that is optimal for the operating region at that time in real time, and it is possible to improve control accuracy and convergence at a point away from the nominal point. As a result, it contributes to the improvement of exhaust gas. In addition, since the plant model itself, that is, it does not involve on-line updating of parameters such as coefficient matrix A and input matrix B in the state equation, the number of man-hours for model identification or adaptation is not increased, and the calculation load of ECU 5 is compared. It only needs to be small.

  The control device according to the present embodiment stores in advance a map that defines the relationship between the engine speed and the fuel injection amount, the weight matrix Q for control purposes, and the weight matrix R for control input. Since the switching hyperplane matrix S corresponding to the operating conditions is determined, it is easy to change the switching hyperplane S according to the operating range of the internal combustion engine 2 in a timely manner.

  The present invention is not limited to the embodiment described in detail above. In the above embodiment, the weight matrix Q, R in the Riccati equation is changed with reference to the map data, thereby changing the solution P of the Riccati equation and thus constructing the switching hyperplane S. The map of the solution P of the Riccati equation corresponding to the operation condition 2 or the map of the switching hyperplane S is stored and stored, and the switching hyperplane S is directly referred to (without solving the Riccati equation) with reference to this map. You can also build The map data in this case indicates the solution P or the switching hyperplane S of the Riccati equation to be set according to the engine speed and the fuel injection amount.

Furthermore, in the above-described embodiment, the engine speed and the fuel injection amount are employed as the operating condition indices for constructing the switching hyperplane S in a timely manner, but other indices may be used as a basis. For example, as shown in FIG. 5, the same control input U as the actual control output Y obtained as a result of inputting the control input U calculated by the sliding mode controller 51 to the plant (the operation units 45, 42, 33) The control hyperplane determining unit 52 calculates a weight matrix Q (and weight matrix R) corresponding to the difference ΔY, as needed. It can be considered that the solution P of the Riccati equation or the switching hyperplane S is determined. The vector ΔY is the difference Δy ₁ between the actual EGR rate obtained from the plant and the virtual EGR rate obtained from the nominal model, the actual intake pipe pressure obtained from the plant and the virtual intake air obtained from the nominal model. The element has a difference Δy ₂ from the in-pipe pressure. The map data in this case indicates the weight Q to be set according to the differences Δy ₁ and Δy ₂ , the solution P of the Riccati equation, or the switching hyperplane S, as illustrated in FIG.

  In addition, the control target of the control device of the present invention is not limited to the EGR system. The control input is not limited to the EGR valve opening, the variable nozzle turbo opening, and the throttle valve opening, and the control output is not limited to the EGR rate (or EGR amount) and the intake pipe pressure.

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

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 an adaptive sliding mode controller. The figure which illustrates the map data which the control apparatus of the same embodiment memorizes and holds. The structure explanatory view of one modification of the present invention. The figure which illustrates the map data which the control apparatus of the modification has memorize | stored.

Explanation of symbols

5 ... ECU (control device)
51 ... Adaptive sliding mode controller 52 ... Switching hyperplane determining unit

Claims (2)

A sliding mode control of an internal combustion engine or a device attached thereto,
A map defining the relationship between the operating conditions of the internal combustion engine and the switching hyperplane matrix S, the solution P of the Riccati equation defining the switching hyperplane matrix S or the weight matrix Q for control purposes defining the Riccati equation is stored in advance. And
A control device characterized by determining a switching hyperplane matrix S according to operating conditions with reference to this map and using it to obtain a control input. However,

A map defining the relationship between the engine speed and the fuel injection amount and the switching hyperplane matrix S, the solution P of the Riccati equation defining the switching hyperplane matrix S or the weight matrix Q for control purposes defining the Riccati equation is stored in advance. And
The control device according to claim 1, wherein a switching hyperplane matrix S corresponding to operating conditions is determined with reference to this map.

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