JP5250826B2 - 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 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.

  During normal operation, the operation units such as the EGR valve, the variable vane nozzle vane, and the D throttle valve are operated according to the control input (opening) value calculated by the sliding mode controller. However, sometimes there is a case where it is desired to operate the operation unit regardless of the calculation result by the sliding mode controller. For example, during fuel cut due to deceleration, there is no combustion of fuel, which frees you from the need to control the EGR rate. Meanwhile, there is a demand to freely operate the operation unit for the purpose of suppressing vibration and noise or for the purpose of diagnosis.

  In order to satisfy such a requirement, it is conceivable to adopt a switching control mechanism in which the sliding mode controller is disconnected from the plant during a period such as during fuel cut and the plant is controlled by another open controller instead. However, even during this period, the sliding mode controller continues to calculate the control input, and there is a difference between the control input values calculated by both controllers when switching from the control by the open controller to the control by the sliding mode controller. The return to the sliding mode control may cause hunting to the control input or control output.

JP 2007-032462 A

  The present invention, which has been made paying attention to the above problems, is intended to maintain control continuity when shifting from control other than sliding mode control to sliding mode control, and to suppress hunting of control inputs and control outputs. The purpose.

In the present invention, the control input to be given to the operation unit, which is the sum of the linear input term U _eq , the nonlinear input term U _nl, and the adaptive term U _ad which is other term, is recursively according to the equation (Equation 20). A predetermined period in which the sliding mode controller to be calculated and the control input to be given to the operation unit is set to an input U _op irrelevant to the original control input calculated by the sliding mode controller is a parameter Z calculated by the sliding mode controller and A control device is provided that includes a correction control unit that replaces U _ad with a value represented by Equation (22).

If this is the case, the switching function σ = 0 and the nonlinear input term U _nl = 0 in a predetermined period, and the sliding mode controller itself can output an arbitrary input U _op as the control input U. It becomes. Then, the control continuity can be maintained even when the control returns to the sliding mode control thereafter, and hunting of the control input and control output can be prevented.

If the adaptive term U _ad calculated by the sliding mode controller in a period other than the predetermined period is a function of time integration of the parameter Z, the adaptive term U _ad together with the deviation integral Z after returning to the sliding mode control. The control output follows the target value while gradually changing. Therefore, switching of control becomes smoother.

  According to the present invention, continuity of control when shifting from control other than sliding mode control to sliding mode control can be maintained, and hunting of control inputs and control outputs can be suppressed.

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.

  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. An electronic control unit (Electronic Control Unit) 5 serving as a control device that operates the plurality of operation units 45, 42, and 33 to set and make each value follow the target value is provided.

  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 intake pipe pressure, the ECU 5 performs various measurements 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 obtained by electrically connecting to a measuring instrument (not shown) and 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 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 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 sets the control input U given to the operation units 45, 42, and 33 to an arbitrary input U _op that does not depend on the control output Y and the target value R, for example, EGR during fuel cut In an implementation period such as diagnosis (with forced opening of the EGR valve 45), the integral Z of the deviation and the adaptive term U _ad calculated by the sliding mode controller 51 are replaced with values shown in the following equation (Equation 22).

S ₁ and S ₂ are sub-matrices of the matrix S constituting the switching hyperplane. Using these S ₁ and S ₂ , the switching function σ can be expressed as the following equation (Equation 23).

z ₁ is the time integration (or integration) of the deviation of the EGR rate, and z ₂ is the time integration of the intake pipe pressure. x ₁ is a plant related to the EGR ratio state, x ₂ is the state of the plant associated with the intake pipe pressure, found y _1, respectively in the present embodiment the EGR rate, the measured value y ₂ of the intake pipe pressure equal.

The correction control unit 52 sets the nonlinear input term _Unl to 0 in order to output an arbitrary control input U _op from the sliding mode controller 51. In order to satisfy the nonlinear input term U _nl = 0, the switching function σ = 0 needs to be satisfied. In Formula (Equation 23), forcibly changing state X is synonymous with forcibly changing control output Y, and causes output hunting when returning to normal sliding mode control. There is a risk of becoming. Therefore, the correction control unit 52 sets the nonlinear input term _Unl to 0 by replacing the deviation Z with a value represented by the following equation (Equation 24).

This substitution of deviation Z does not affect the linear input term U _eq (note the definition of X _e and A _e in equation (Equation 2)).

However, in the three-input two-output system as in this embodiment, S ₁ is a non-square matrix, and the inverse matrix S ₁ ⁻¹ that satisfies S ₁ ⁻¹ S ₁ = I is not uniquely determined. Therefore, the inverse matrix S ₁ ⁻¹ is calculated as a generalized inverse matrix. As the generalized inverse matrix, for example, the Moore-Penrose-type inverse matrix S ₁ ^† is used.

If the nonlinear input term U _nl = 0 and the adaptive term U _ad = U _op −U _eq , the control input U = U _op regardless of the control output Y and the target value R.

When the period for setting the control input U to be given to the operation units 45, 42, and 33 to an arbitrary input U _op is over and the control of the plant is again left to the sliding mode controller 51, the correction control unit 52 performs the sliding control at the time immediately before that. The calculation of the control input U according to the control output Y and the target value R may be started after Z and U _{ad (} forcibly given to the mode controller 51) are taken over as Z and U _ad as they are. Thereafter, the control output Y follows the target value R while the integral Z of the deviation, the nonlinear input term U _nl , and the adaptive term U _ad change gradually. As already described, even during the open control in which the operation units 45, 42, and 33 are set to the arbitrary opening degree U _op , the state X _e is continuously restrained on the switching hyperplane with σ = 0. The operation units 45, 42, and 33 are quickly operated by the shift to the control, and the control input Y can reach the original target R.

According to the present embodiment, the internal combustion engine 2 or a device attached thereto is controlled by operating the operation units 45, 42, and 33, and the linear input term U _eq , the nonlinear input term U _nl, and other terms A sliding mode controller 51 that repetitively calculates a control input U to be given to the operation units 45, 42, 33, which is a sum of the adaptive terms U _ad , according to the equation (Equation 20), and the operation units 45, 42, In a predetermined period in which the sliding mode controller 51 sets the control input U to be given to a value U _op that is unrelated to the original value calculated by the sliding mode controller 51 based on the control output Y and the target value R, the sliding mode controller 51 Since the control device including the correction control unit 52 that replaces the parameters Z and U _ad to be calculated with the values shown in the formula (Equation 22) is configured, It is possible to output an arbitrary control input U _op from the wing mode controller 51 itself. Then, the continuity of control can be maintained even after returning to the sliding mode control, and hunting of the control input U and the control output Y can be prevented.

In a period other than the predetermined period, the adaptive term U _ad calculated by the sliding mode controller 51 is a function of the time integration of the parameter Z as shown in Expression (21). After returning to the control, the control output Y can follow the target value R while gradually changing the adaptive term U _ad together with the integral Z of the deviation. Therefore, switching of control becomes smoother.

  The present invention is not limited to the embodiment described in detail above. In particular, the application target of the present invention is not limited to an internal combustion engine provided with a variable turbocharger and an EGR device.

  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 controller for controlling the EGR rate of an EGR device attached to an internal combustion engine equipped with a supercharger.

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

Claims (2)

An internal combustion engine or a device attached thereto is controlled by operating an operation unit,
A sliding mode in which a control input to be given to the operation unit, which is a sum of a linear input term U _eq , a nonlinear input term U _nl, and an adaptive term U _ad as other terms, is iteratively calculated according to the equation (Equation 25). A controller,
For a predetermined period in which the control input given to the operation unit is set to the input U _op irrelevant to the original control input calculated by the sliding mode controller, the parameters Z and U _ad calculated by the sliding mode controller are expressed by the following equation (26). And a correction control unit that replaces the value shown in FIG.

The control device according to claim 1, wherein the adaptive term U _ad calculated by the sliding mode controller in a period other than the predetermined period is a function of time integration of the parameter Z.

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