JP5460267B2 - Control device - Google Patents

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 sliding mode control, which is an effective control method for the non-linear control target, is adopted, and a multi-input multi-output controller is designed in consideration of the interaction to perform EGR control (for example, (See Patent Document 1).

The nonlinear input term _Unl , which is an element of the control input U calculated by the controller in the sliding mode control system, takes the form of the following equation (Equation 1) in principle.

S is a matrix constituting the switching hyperplane, B is an input matrix in the state equation, k is a non-linear switching gain multiplied in the calculation of the nonlinear input U _nl, sigma is the switching function.

Nonlinear input U _nl attracts the state of the plant on the switching hyperplane, which serves to restrain on the hyperplane. However, when the state of the plant approaches the hyperplane, the nonlinear input _{Unl switches} at high speed, and there is a risk of causing chattering that oscillates in the vicinity of the hyperplane instead of sliding on the hyperplane. Therefore, in general, the smoothing coefficient η is introduced to smooth the fluctuation of the nonlinear input and to suppress chattering (see, for example, Patent Document 2 below). The non-linear input _Unl when the smoothing coefficient η is introduced is expressed by the following equation (Equation 2).

  EGR and intake pipe pressure control of an internal combustion engine by a sliding mode controller is very promising. However, the control input / output sometimes hunted and diverged in a specific operation region (more specifically, a high rotation / high load region).

JP 2007-032462 A JP 2006-283826 A

  An object of the present invention is to effectively solve the problem that control input / output rarely hunts in a sliding mode control system.

In the present invention, the internal combustion engine or the device attached thereto is controlled in the sliding mode, and the nonlinear input term _Unl of the control input U to be given to the operation unit, which is calculated by the sliding mode controller, is _expressed by the following equation The control device is characterized by being expressed in the form of 3).

Here, S is the matrix that constitutes the switching hyperplane, B is an input matrix in the state equation, J gain multiplied in the calculation of the nonlinear input U _nl, sigma is the switching function. The gain J is switched according to the operating region of the internal combustion engine. At this time, the switching function σ immediately after the switching is calculated so that the nonlinear input term _Unl does not change stepwise before and after the switching of the gain J.

The nonlinear input U _nl ( _Equation 2) into which the conventional smoothing coefficient η is introduced will be examined again. FIG. 5 schematically shows the relationship between the switching function σ and the factor Σ (Equation 4) that defines the nonlinear input _Unl .

σ and Σ are vectors of the same dimensionality as the control input U, and FIG. 5 is not mathematically accurate. However, according to FIG. 5, the graph has the steepest slope at σ = 0. As the absolute value (or norm) of σ increases, the slope of the graph becomes gentler and gradually approaches Σ → ± 1. Also, the slope of the graph around σ = 0 becomes steeper as the smoothing coefficient η decreases. From FIG. 5, it can be seen that when the absolute value of σ is close to 0, that is, the state of the plant is in the vicinity of the hyperplane, Σ and therefore U _nl fluctuate greatly even if σ slightly increases or decreases.

  The value of the control output Y measured through various sensors usually goes up and down frequently (even if the fluctuation width itself is very small). There is an output equation relationship of Y = CX between the control output Y and the state quantity X, and the control output Y frequently going up and down means that the state quantity X goes up and down frequently. Therefore, the switching function σ = SX can also rise and fall frequently.

When σ frequently rises and falls in a value range close to 0, the nonlinear input _Unl increases and decreases rapidly, which affects the control output Y and vibrates Y. Furthermore, the vibration of the control output Y causes the vibration of σ, spurs the sudden increase / decrease of U _nl , and so on, so that the vibration of Y returns, and the control inputs / outputs U and Y hunt. It was reached.

The present invention has been made by paying attention to the above phenomenon for the first time. By changing the nonlinear input U _nl to the form of ( _Equation 3), while avoiding chattering of U _nl , σ is in a range close to 0. Even if it goes up and down, U _nl does not increase or decrease suddenly.

Along with the non-linear input U _nl from smoothing coefficient eta is lost, there is also a side benefit of reducing the number of steps for performing adaptation of the smoothing coefficient eta. Since η is a vector having the same number of dimensions as the control input U, the significance of reducing the design man-hour is not small in a multi-input system.

However, the nonlinear input U _nl of equation (3), there is a risk of huge indefinitely with an increase in the absolute value of sigma. Therefore, when the nonlinear input term U _nl calculated in accordance with Equation (3) exceeds a predetermined threshold value, it is desirable to calculate the control input U after clipping the nonlinear input term U _nl to the threshold value. An adaptive term set for each operating region of the internal combustion engine may be added to the linear input term U _eq and the nonlinear input term U _nl calculated by the sliding mode controller .

  According to the present invention, in the sliding mode control system, it is possible to effectively solve the problem that the control input / output rarely hunts.

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 flowchart which shows the procedure of the process which the control apparatus of the embodiment performs. The figure which illustrates notionally the relationship between switching function (sigma) and factor (SIGMA) which introduced smoothing coefficient (eta).

  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. ECU (Electronic Control Unit) 5 which is a control device for operating a plurality of operation units 45, 42, 33 in order to follow the 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 5).

  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, in identifying the coefficient matrix A and the input matrix B in the equation of state (Equation 5), 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, An expanded system equation of state shown in (Expression 6) is obtained.

Sliding mode controller 51, the EGR rate 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 vanes 42 Performs 3-input 2-output feedback control using as a control input variable. The number of state variables (system order) is 2 in the initial system (Formula 5), and 4 in the expanded system (Formula 6). 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.

  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 6) is generating the sliding mode. When the switching function σ is defined by Expression (Expression 7), σ = 0 and Expression (Expression 8) 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 9).

  Substituting the linear input of the above equation (Equation 9) into the state equation (Equation 6) of the expanded system results in an equivalent control system of the following equation (Equation 10).

  Designing a hyperplane so that this equivalent control system is stable is equivalent to designing a system in which the target value R is ignored, so the following equation (Equation 11) holds.

  Taking the stability ε into consideration for the system of the above equation (Equation 11), obtaining the feedback gain using the optimal control theory, and making it a hyperplane, the following equation (Equation 12) is obtained.

The matrix P _s is a positive definite solution of the Riccati equation (Equation 13).

Q _s in the Riccati equation (Equation 13) 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 13) 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 12) and (Equation 13), the following discrete hyperplane construction equation (Equation 14) and algebraic Riccati equation (Equation 15) 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 16) as the sum of the linear input U _eq and a new input, that is, a non-linear input (non-linear 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 17) and differentiated to obtain the equation (Equation 18).

  Substituting equation (Equation 16) into equation (Equation 18) yields the following equation (Equation 19).

When the following expression nonlinear input U _nl (number 20), the derivative of the Lyapunov function becomes equation (21).

  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.

When the switching gain k in the equation (Equation 20) is replaced with the equation (Equation 22), the nonlinear input _Unl becomes the equation (Equation 23).

The nonlinear gain J is obtained by multiplying the vector factor J _k by the scalar factor k as shown in the following equation (Equation 24).

The vector J _k = [j _k1 , j _k2 , j _k3 ] ^T in the equation (Equation 24) is similar to the switching gain vector k in the conventional nonlinear input U _nl (Equation 2), the opening degree u _{1 of} the EGR valve 45, This is determined based on input / output characteristics between the opening degree u ₂ of the variable vane nozzle vane 42 and the opening degree u ₃ of the throttle valve 33, and the EGR rate y ₁ and the intake pipe pressure y ₂ .

If the step responses of the control outputs y ₁ , y ₂ with respect to the control inputs u ₁ , u ₂ , u ₃ are observed, the openings u ₁ , u ₂ , u _{3 of} the valves 45, 42, 33 are unit quantities (typical) Specifically, it is possible to know the amount of change in the EGR rate y ₁ and the intake pipe pressure y ₂ when the opening degree is changed by 1%. J _k is preferably determined so that contributions to the control outputs y ₁ and y ₂ of the valves 45, 42 and 33 in the step response are equalized. That is, the sensitivity of the control outputs y ₁ and y ₂ with respect to changes in the opening degree of the EGR valve 45 is relatively low (the control outputs y ₁ and y ₂ do not change much even when the EGR valve 45 is operated). The gain j _k1 to be multiplied in order to calculate the nonlinear input value _unl1 is a relatively large value. On the contrary, the sensitivity of the control outputs y ₁ and y ₂ with respect to the change in the opening degree of the nozzle vane 42 is relatively high (the control outputs y ₁ and y ₂ change not a little by operating the nozzle vane 42). The gain j _k2 to be multiplied to calculate the nonlinear input value _unl2 is a relatively small value.

The vector J _k is determined as, for example, J _k = [2.18, 0.68, 1] ^T. This example value J _k indicates the amount of change in the control inputs y ₁ and y ₂ generated when the opening u ₁ of the EGR valve 45 is changed 2.18% in the step response, and the opening u _{2 of the} nozzle vane 42. and the amount of change in the control input y _1, y ₂ generated when varying 0.68%, and the amount of change in the control input y _1, y ₂ which occurs when the opening degree u ₃ of the throttle valve 33 is changed 1% Is considered to be roughly equal.

  Further, the scalar k in the equation (Equation 24) is a fitness coefficient, and is appropriately determined through adaptation at the time of designing the controller 51.

  In general, the control input U calculated by the sliding mode controller 51 is expressed by the following equation (Equation 25).

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.

  Accordingly, the correction control unit 52 corrects the control input U to be given to the operation units 45, 42, 33 in accordance with the current operation region of the internal combustion engine 2.

First, the correction control unit 52, when the nonlinear input U _nl of the sliding mode controller 51 calculates pursuant to equation (23) exceeds a predetermined threshold value, clips the nonlinear input term U _nl to the threshold value. That is, when the components u _nl1 , u _nl2 or u _{nl3 of} the nonlinear input U _nl = [u _nl1 , u _nl2 , u _nl3 ] ^T calculated by the controller 51 exceed the respective threshold values, the component values u _nl1 , u _{n1 Rewrite nl2} or _unl3 as a threshold value. In the present embodiment, the threshold value for each component value u _nl1 , u _nl2 or u _nl3 is defined as ± 50% in terms of the opening value of the valves 45, ₄₂ , ₃₃ , and the value of u _nl1 , u _nl2 or _unl3 If the value _exceeds 50%, the value of _unil1 , _unl2, or _unl3 is clipped to 50%, and if it is less than -50%, the value of _unl1 , _unl2, or _unl3 is set to -50%. Clip.

In addition, the correction control unit 52 further adds a correction term U _map to the control input U (Equation 25) which is the sum of the linear input U _eq and the nonlinear input U _nl . In the design of the sliding mode controller 51, a nominal model (matrixes A and B) of the internal combustion engine 2 under a specific operating region, that is, a specific engine speed and a required fuel injection amount is identified, and a state equation (Equation 6 ) To derive the switching hyperplane S. The modeling error (perturbation) between the nominal model and the actual plant is increased in a region away from the nominal point, such as a low rotation / low load region or a high rotation / high load region. The correction term U _map is an adaptive term (map term) for reducing this modeling error and causing the nonlinear input Unl to quickly converge to zero.

The U _map map defines a target EGR rate and a target intake pipe pressure that are suitable (or representative) for each operating region [engine speed, fuel injection amount] and sets this target as an internal combustion engine of the actual machine. While measuring the opening degree U _base of each operation part 45, 42, 33 in the steady state achieved by the engine 2, the same target is given to the sliding mode controller 51 to calculate the linear input U _eq in the steady state with no deviation. Create by. If the calculated value U _eq of the linear input by the sliding mode controller 51 is subtracted from the actual measured values U _base of the operating units 45, 42, and 33 in the actual machine, individual operation regions [engine speed, intake pipe pressure] A map term U _map = U _base −U _eq corresponding to is obtained.

In the ROM or flash memory of the ECU 5, map data indicating U _map to be set according to the engine speed and the required injection amount is stored in advance. The ECU 5 searches the map using the engine speed and the required injection amount as keys, obtains the correction term U _map , and adds the U _map to the control input U calculated by the sliding mode controller 51. Finally, the control input U given to the operation units 45, 42 and 33 is expressed by the following equation (Equation 26).

In the actual control of the internal combustion engine 2, even if the operation region [engine speed, fuel injection amount] is the same, there are cases where the target EGR rate and / or the target intake pipe pressure to be achieved are different. Can do. When the target in actual control is different from the target set when the map is created, the optimal map term U _map also changes. Therefore, it is more preferable to add an environmental correction to the map term U _{map obtained} by referring to the _map . The environmental correction is to correct the map term U _map according to the cooling water temperature, the intake air temperature, the outside air temperature, the atmospheric pressure, etc., which are parameters for correcting the basic value of the target EGR rate and / or the target intake pipe pressure.

Further, the correction control unit 52 can switch the gain J (vector J _k and / or scalar k) used by the sliding mode controller 51 for calculating the nonlinear input _Unl according to the operating region of the internal combustion engine 2. There is a high possibility that hunting of control input / output due to a sudden increase / decrease in the non-linear input _Unl will occur in a high rotation / high load operation region. Therefore, it is conceivable to set the gain J in the high load high rotation region to a value smaller than the gain J in the other operation regions.

In the ROM or flash memory of the ECU 5, map data indicating J that should be set according to the engine speed and the required injection amount is stored in advance. The ECU 5 searches the map using the engine speed and the required injection amount as keys, and obtains the gain J. In the subsequent calculation cycle, the ECU 5 calculates the nonlinear input _Unl using the J.

Of course, if the gain J is simply switched, the nonlinear input _Unl calculated by the sliding mode controller 51 varies stepwise before and after the switching. As a result, the opening degree of each of the valves 45, 42, and 33 as the operation unit changes so as to jump, which may cause hunting of control input / output. Therefore, when switching the gain J is rewritten state variables X _e where the sliding mode controller 51 refers to suppressing the divergence of the non-linear input U _nl gain before switching of the non-linear input U _nl and after the switching.

Gain and the J _n-1 non-linear input is calculated just before switching to J _n from U _{nl (n-1),} to the nonlinear input U _{nl (n)} calculated immediately after switching are equal, the lower Formula (Equation 27) needs to be satisfied.

σ _n-1 is a switching function immediately before gain switching, and σ _n is a switching function immediately after gain switching. If σ _n satisfying equation (Equation 27) is calculated, and X _e that realizes σ _n is calculated back based on equation (Equation 7), U _{nl (n−1)} and U _{nl (n)} are obtained. Can be equal.

The state quantity X _e = [x _e1 x _e2 x _e3 x _e4 ] ^T includes, as its components, time integrals x _e1 and x _e2 of deviation between the control output Y and the target value R, and the control output Y itself x _e3 and x _e . _{Includes e4} . The state variable x _e3 is the EGR rate y ₁ itself, and the state variable x _e4 is the intake pipe pressure y ₂ itself. On the other hand, the state variables x _e1 and x _e2 affect the nonlinear input U _nl but not the linear input U _eq (note the definition of the matrix A _e ). Therefore, the state variables x _e1 and / or x _e2 satisfying the equation (Equation 27) are calculated backward and rewritten. The state variables x _e3 and x _e4 are not rewritten.

  In FIG. 4, 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, and the like to determine whether or not the operating region has changed greatly between the past calculation cycle and the current calculation cycle and the gain J needs to be switched. (Step S1).

If it is determined that it is not necessary to switch the gain J, the linear input U _eq is calculated (step S2), and the nonlinear input _Unl is calculated using the previous gain J as it is (step S3). If any component U _nl1 , U _nl2 , U _{nl3 of the} calculated nonlinear input U _nl exceeds a predetermined threshold (step S4), the components U _nl1 , U _nl2 , U _nl3 exceeding the threshold are _set as the threshold To obtain the final nonlinear input _Unl (step S5). In addition, a correction term U _map is determined based on the engine speed, the required fuel injection amount, and the like (step S6).

Conversely, when it is determined that the gain J needs to be switched, the gain J is determined based on the engine speed, the required fuel injection amount, and the like (step S7). Furthermore, calculated back state quantity X _e that satisfies the conditions of equation (27), rewrites the state quantity X _e are stored and held in the memory of the ECU 5 (step S8). After that, the linear input U _eq and the nonlinear input U _nl are calculated (steps S2 to S5), and the correction term U _map is determined (step S6).

Thereafter, a control input U that is the sum of the linear input U _eq , the nonlinear input U _nl, and the correction term U _map is given to the operation units 45, 42, 33, and these operation units 45, 42, 33 are operated (step S 9). . The ECU 5 repeats the above steps S1 to S9.

According to this embodiment, the internal combustion engine 2 or a device attached thereto is controlled in the sliding mode, and the control mode U of the control inputs U to be given to the operation units 45, 42, 33 calculated by the sliding mode controller 51 is Since the control device 5 is characterized in that the nonlinear input term U _nl is expressed in the form of the equation (Equation 23), the switching function σ is close to 0, that is, the plant state X _e is close to the switching hyperplane S. Even if the value fluctuates up and down, the nonlinear input _Unl does not increase or decrease rapidly and does not trigger hunting. Further, along with the disappearance of the smoothing coefficient η from the nonlinear input _{Unl, the} man-hour for performing the smoothing coefficient η is reduced.

In addition, when the nonlinear input term U _nl calculated according to the equation (Equation 23) exceeds a predetermined threshold, the nonlinear input term U _nl is clipped to the threshold and the control input U is calculated. input U _nl is nor does it endlessly huge.

  The present invention is not limited to the embodiment described in detail above. For example, in the above-described embodiment, the gain J is switched according to the operating region of the internal combustion engine. However, a mode in which the gain J is constant regardless of the operating region can be taken.

The method for determining the correction term U _map added to the control input U is not uniquely limited.

  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,
The nonlinear input term _Unl of the control inputs U to be given to the operation unit, which is calculated by the sliding mode controller, is expressed in the form of the following equation (Equation 28) (where S is a matrix constituting the switching hyperplane, and B is input matrix in the state equation, J gain multiplied in the calculation of the nonlinear input U _nl, sigma is switching function),
When the nonlinear input term U _nl calculated according to the equation (Equation 28) exceeds a predetermined threshold, the nonlinear input term U _nl is clipped to the threshold and the control input U is calculated.
Gain J is multiplied in the calculation of the nonlinear input U _nl and switching in accordance with the operating range of the internal combustion engine,
When switching the gain from J _n-1 to J _n is the relation of the following equation (Equation 29) between the switching function sigma _n at the time immediately after the switching between the switching function sigma _n-1 at the time of the immediately before switching A control device that calculates a switching function σ _n so as to hold .

2. The control apparatus according to claim 1 , wherein the control input U is calculated by adding an adaptive term set for each operating region of the internal combustion engine to the linear input term U _eq and the nonlinear input term U _nl calculated by the sliding mode controller. .

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