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A control system for an internal combustion engine having a compressor wheel and a turbine wheel connected with the compressor wheel and rotationally driven by kinetic energy of exhaust gases from the engine, an exhaust gas flow rate changing device for changing a flow rate of exhaust gases injected

A control system for an internal combustion engine having a compressor wheel and a turbine wheel connected with the compressor wheel and rotationally driven by kinetic energy of exhaust gases from the engine, an exhaust gas flow rate changing device for changing a flow rate of exhaust gases injected to the turbine wheel, an exhaust gas recirculation passage for recirculating the exhaust gases to an intake pipe of the engine, and an exhaust gas recirculation control valve disposed in the exhaust gas recirculation passage. An exhaust pressure is detected, and a value of an intake gas parameter is obtained. A target value of the exhaust pressure and a target value of the intake pipe gas parameter are calculated. A control amount of the exhaust gas flow rate changing device and an opening control amount of the exhaust gas recirculation control valve are calculated using a model predictive control.

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What is claimed is: 1. A control system for an internal combustion engine provided with a turbocharger having a compressor wheel for pressurizing intake air of the engine and a turbine wheel connected with the compressor wheel and rotationally driven by kinetic energy of exhaust gases discharged fr

What is claimed is: 1. A control system for an internal combustion engine provided with a turbocharger having a compressor wheel for pressurizing intake air of the engine and a turbine wheel connected with the compressor wheel and rotationally driven by kinetic energy of exhaust gases discharged from the engine, exhaust gas flow rate changing means for changing a flow rate of exhaust gases injected to the turbine wheel, an exhaust gas recirculation passage for recirculating the exhaust gases to an intake pipe of the engine, and an exhaust gas recirculation control valve disposed in the exhaust gas recirculation passage, the control system comprising: exhaust pressure detecting means for detecting an exhaust pressure in an exhaust pipe of the engine; intake pipe gas parameter obtaining means for obtaining a value of an intake pipe gas parameter indicating a state of gases in the intake pipe; first target value calculating means for calculating a target value of the exhaust pressure; second target value calculating means for calculating a target value of the intake pipe gas parameter; and gas control means for calculating a control amount of the exhaust gas flow rate changing means and an opening control amount of the exhaust gas recirculation control valve using a model predictive control, so that values of the detected exhaust pressure and the intake pipe gas parameter, respectively, coincide with the target values of the exhaust pressure and the intake pipe gas parameter. 2. The control system according to claim 1, wherein the exhaust pressure is a pressure on an upstream side of the turbine wheel in the exhaust pipe, and the intake pipe gas parameter is a partial pressure of one of fresh air and recirculated exhaust gases on a downstream side of the compressor wheel in the intake pipe, or a flow rate of one of fresh air and the recirculated exhaust gases flowing in the intake pipe. 3. The control system according to claim 1, wherein the exhaust pressure is a pressure on an upstream side of the turbine wheel in the exhaust pipe, and the intake pipe gas parameter is a partial pressure of one of oxygen and inert gases on a downstream side of the compressor wheel in the intake pipe, or a flow rate of one of oxygen and inert gases flowing in the intake pipe. 4. The control system according to claim 1, further including boost pressure detecting means for detecting a boost pressure in the intake pipe, wherein the second target value calculating means includes steady state target value calculating means for calculating a steady state target value corresponding to a steady state of the engine according to an operating condition of the engine, and modifying means for modifying the steady state target value according to the detected boost pressure to calculate the target value of the intake pipe gas parameter. 5. The control system according to claim 1, further including boost pressure detecting means for detecting a boost pressure in the intake pipe and intake air flow rate detecting means for detecting a flow rate of fresh air flowing in the intake pipe, wherein the first target value calculating means includes target power value calculating means for calculating a target power value of the compressor wheel according to a target boost pressure and a target fresh air flow rate calculated according to an operating condition of the engine, estimated power value calculating means for calculating an estimated power value of the compressor wheel according to the detected boost pressure and the detected fresh air flow rate, and feedback calculating means for calculating the target value of the exhaust pressure, so that the estimated power value coincides with the target power value. 6. The control system according to claim 1, wherein a controlled object model used in the model predictive control is defined using, as control inputs, a mass flow rate of gases passing through the exhaust gas flow rate changing means, and a mass flow rate of gases passing through the exhaust gas recirculation control valve. 7. A control system for an internal combustion engine provided with a turbocharger having a compressor wheel for pressurizing intake air of the engine and a turbine wheel connected with the compressor wheel and rotationally driven by kinetic energy of exhaust gases discharged from the engine, exhaust gas flow rate changing means for changing a flow rate of exhaust gases injected to the turbine wheel, an exhaust gas recirculation passage for recirculating the exhaust gases to an intake pipe of the engine, an exhaust gas recirculation control valve disposed in the exhaust gas recirculation passage, and a throttle valve disposed in the intake pipe, the control system comprising: exhaust pressure detecting means for detecting an exhaust pressure in an exhaust pipe of the engine; intake pipe gas parameter obtaining means for obtaining values of intake pipe gas parameters indicating a state of gases in the intake pipe; first target value calculating means for calculating a target value of the exhaust pressure; second target value calculating means for calculating target values of the intake pipe gas parameters; and gas control means for calculating a control amount of the exhaust gas flow rate changing means, an opening control amount of the exhaust gas recirculation control valve, and an opening control amount of the throttle valve using a model predictive control, so that values of the detected exhaust pressure and the intake pipe gas parameters, respectively, coincide with the target values of the exhaust pressure and the intake pipe gas parameters. 8. The control system according to claim 7, wherein the exhaust pressure is a pressure on an upstream side of the turbine wheel in the exhaust pipe, and the intake pipe gas parameters are any two of a partial pressure of fresh air on a downstream side of the throttle valve in the intake pipe, a partial pressure of the recirculated exhaust gases on the downstream side of the throttle valve in the intake pipe, and a sum of the partial pressures of the fresh air and the recirculated exhaust gases, or any two of a flow rate of fresh air flowing in the intake pipe, a flow rate of recirculated exhaust gases flowing in the intake pipe, and a sum of flow rates of fresh air and recirculated exhaust gases. 9. The control system according to claim 7, wherein the exhaust pressure is a pressure on an upstream side of the turbine wheel in the exhaust pipe, and the intake pipe gas parameters are any two of a partial pressure of oxygen on a downstream side of the throttle valve in the intake pipe, a partial pressure of inert gases on the downstream side of the throttle valve in the intake pipe, and a sum of partial pressures of oxygen and inert gases, or any two of a flow rate of the oxygen flowing in the intake pipe, a flow rate of the inert gases flowing in the intake pipe, and a sum of the flow rates of the oxygen and the inert gases. 10. The control system according to claim 7, further including boost pressure detecting means for detecting a boost pressure in the intake pipe, wherein the second target value calculating means includes a steady state target value calculating means for calculating a steady state target value corresponding to a steady state of the engine according to an operating condition of the engine, and modifying means for modifying the steady state target value according to the detected boost pressure to calculate the target values of the intake pipe gas parameters. 11. The control system according to claim 7, wherein a controlled object model used in the model predictive control is defined using, as control inputs, a mass flow rate of gases passing through the exhaust gas flow rate changing means, a mass flow rate of gases passing through the exhaust gas recirculation control valve, and a mass flow rate of fresh air passing through the throttle valve. 12. A control method for an internal combustion engine provided with a turbocharger having a compressor wheel for pressurizing intake air of the engine and a turbine wheel connected with the compressor wheel and rotationally driven by kinetic energy of exhaust gases from the engine, an exhaust gas flow rate changing device for changing a flow rate of exhaust gases injected to the turbine wheel, an exhaust gas recirculation passage for recirculating the exhaust gases to an intake pipe of the engine, and an exhaust gas recirculation control valve disposed in the exhaust gas recirculation passage, the control method comprising the steps of: a) detecting an exhaust pressure in an exhaust pipe of the engine; b) obtaining a value of an intake pipe gas parameter indicating a state of gases in the intake pipe; c) calculating a target value of the exhaust pressure; d) calculating a target value of the intake pipe gas parameter; and e) calculating a control amount of the exhaust gas flow rate changing device and an opening control amount of the exhaust gas recirculation control valve using a model predictive control, so that values of the detected exhaust pressure and the intake pipe gas parameter, respectively, coincide with the target values of the exhaust pressure and the intake pipe gas parameter. 13. The control method according to claim 12, wherein the exhaust pressure is a pressure on an upstream side of the turbine wheel in the exhaust pipe, and the intake pipe gas parameter is a partial pressure of one of fresh air and recirculated exhaust gases on a downstream side of the compressor wheel in the intake pipe, or a flow rate of one of fresh air and the recirculated exhaust gases flowing in the intake pipe. 14. The control method according to claim 12, wherein the exhaust pressure is a pressure on an upstream side of the turbine wheel in the exhaust pipe, and the intake pipe gas parameter is a partial pressure of oxygen and inert gases on a downstream side of the compressor wheel in the intake pipe, or a flow rate of one of oxygen and the inert gases flowing in the intake pipe. 15. The control method according to claim 12, further including the step of detecting a boost pressure in the intake pipe, wherein the step d) includes the steps of: i) calculating a steady state target value corresponding to a steady state of the engine according to an operating condition of the engine; and ii) modifying the steady state target value according to the detected boost pressure to calculate the target value of the intake pipe gas parameter. 16. The control method according to claim 12, further including the steps of detecting a boost pressure in the intake pipe and detecting a flow rate of fresh air flowing in the intake pipe, wherein the step c) includes the steps of: i) calculating a target power value of the compressor wheel according to a target boost pressure and a target fresh air flow rate, which are calculated according to an operating condition of the engine; ii) calculating an estimated power value of the compressor wheel according to the detected boost pressure and the detected fresh air flow rate; and iii) calculating the target value of the exhaust pressure, so that the estimated power value coincides with the target power value. 17. The control method according to claim 12, wherein a controlled object model used in the model predictive control is defined using, as control inputs, a mass flow rate of gases passing through the exhaust gas flow rate changing means, and a mass flow rate of gases passing through the exhaust gas recirculation control valve. 18. A control method for an internal combustion engine provided with a turbocharger having a compressor wheel for pressurizing intake air of the engine and a turbine wheel connected with the compressor wheel and rotationally driven by kinetic energy of exhaust gases from the engine, an exhaust gas flow rate changing device for changing a flow rate of exhaust gases injected to the turbine wheel, an exhaust gas recirculation passage for recirculating the exhaust gases to an intake pipe of the engine, an exhaust gas recirculation control valve disposed in the exhaust gas recirculation passage, and a throttle valve disposed in the intake pipe, the control method comprising the steps of: a) detecting an exhaust pressure in an exhaust pipe of the engine; b) obtaining values of intake pipe gas parameters indicating a state of gases in the intake pipe; c) calculating a target value of the exhaust pressure; d) calculating target values of the intake pipe gas parameters; and e) calculating a control amount of the exhaust gas flow rate changing device, an opening control amount of the exhaust gas recirculation control valve, and an opening control amount of the throttle valve using a model predictive control, so that values of the detected exhaust pressure and the intake pipe gas parameters, respectively, coincide with the target values of the exhaust pressure and the intake pipe gas parameters. 19. The control method according to claim 18, wherein the exhaust pressure is a pressure on an upstream side of the turbine wheel in the exhaust pipe, and the intake pipe gas parameters are any two of a partial pressure of fresh air on a downstream side of the throttle valve in the intake pipe, a partial pressure of recirculated exhaust gases on the downstream side of the throttle valve in the intake pipe, and a sum of the partial pressures of fresh air and the recirculated exhaust gases, or any two of a flow rate of the fresh air flowing in the intake pipe, a flow rate of the recirculated exhaust gases flowing in the intake pipe, and a sum of the flow rates of the fresh air and the recirculated exhaust gases. 20. The control method according to claim 18, wherein the exhaust pressure is a pressure on an upstream side of the turbine wheel in the exhaust pipe, and the intake pipe gas parameters are any two of a partial pressure of oxygen on a downstream side of the throttle valve in the intake pipe, a partial pressure of inert gases on the downstream side of the throttle valve in the intake pipe, and a sum of the partial pressures of the oxygen and the inert gases, or any two of a flow rate of the oxygen flowing in the intake pipe, a flow rate of the inert gases flowing in the intake pipe, and a sum of the flow rates of the oxygen and the inert gases. 21. The control method according to claim 18, further including the step of detecting a boost pressure in the intake pipe, wherein the step d) includes the steps of: i) calculating a steady state target value corresponding to a steady state of the engine according to an operating condition of the engine; and ii) modifying the steady state target value according to the detected boost pressure to calculate the target values of the intake pipe gas parameters. 22. The control method according to claim 18, wherein a controlled object model used in the model predictive control is defined using, as control inputs, a mass flow rate of gases passing through the exhaust gas flow rate changing means, a mass flow rate of gases passing through the exhaust gas recirculation control valve, and a mass flow rate of fresh air passing through the throttle valve. 23. A computer program embodied on a computer-readable medium, for causing a computer to implement a control method for an internal combustion engine provided with a turbocharger having a compressor wheel for pressurizing intake air of the engine and a turbine wheel connected with the compressor wheel and rotationally driven by kinetic energy of exhaust gases from the engine, exhaust gas flow rate changing device for changing a flow rate of exhaust gases injected to the turbine wheel, an exhaust gas recirculation passage for recirculating the exhaust gases to an intake pipe of the engine, an exhaust gas recirculation control valve disposed in the exhaust gas recirculation passage, and a throttle valve disposed in the intake pipe, the control method comprising the steps of: a) detecting an exhaust pressure in an exhaust pipe of the engine; b) obtaining values of intake pipe gas parameters indicating a state of gases in the intake pipe; c) calculating a target value of the exhaust pressure; d) calculating target values of the intake pipe gas parameters; and e) calculating a control amount of the exhaust gas flow rate changing device, an opening control amount of the exhaust gas recirculation control valve, and an opening control amount of the throttle valve using a model predictive control, so that values of the detected exhaust pressure and the intake pipe gas parameters, respectively, coincide with the target values of the exhaust pressure and the intake pipe gas parameters. 24. The computer program according to claim 23, wherein the exhaust pressure is a pressure on an upstream side of the turbine wheel in the exhaust pipe, and the intake pipe gas parameters are any two of a partial pressure of fresh air on a downstream side of the throttle valve in the intake pipe, a partial pressure of the recirculated exhaust gases on the downstream side of the throttle valve in the intake pipe, and a sum of the partial pressures of the fresh air and the recirculated exhaust gases, or any two of a flow rate of the fresh air flowing in the intake pipe, a flow rate of the recirculated exhaust gases flowing in the intake pipe, and a sum of the flow rates of the fresh air and the recirculated exhaust gases. 25. The computer program according to claim 23, wherein the exhaust pressure is a pressure on an upstream side of the turbine wheel in the exhaust pipe, and the intake pipe gas parameters are any two of a partial pressure of oxygen on a downstream side of the throttle valve in the intake pipe, a partial pressure of inert gases on the downstream side of the throttle valve in the intake pipe, and a sum of the partial pressures of the oxygen and the inert gases, or any two of a flow rate of the oxygen flowing in the intake pipe, a flow rate of the inert gases flowing in the intake pipe, and a sum of the flow rates of the oxygen and the inert gases. 26. The computer program according to claim 23, wherein the control method further includes the step of detecting a boost pressure in the intake pipe, wherein the step d) includes the steps of: i) calculating a steady state target value corresponding to a steady state of the engine according to an operating condition of the engine; and ii) modifying the steady state target value according to the detected boost pressure to calculate the target values of the intake pipe gas parameters. 27. A computer program embodied on a computer-readable medium, for causing a computer to implement a control method for an internal combustion engine provided with a turbocharger having a compressor wheel for pressurizing intake air of the engine and a turbine wheel connected with the compressor wheel and rotationally driven by kinetic energy of exhaust gases from the engine, an exhaust gas flow rate changing device for changing a flow rate of exhaust gases injected to the turbine wheel, an exhaust gas recirculation passage for recirculating the exhaust gases to an intake pipe of the engine, and an exhaust gas recirculation control valve disposed in the exhaust gas recirculation passage, the control method comprising the steps of: a) detecting an exhaust pressure in an exhaust pipe of the engine; b) obtaining a value of an intake pipe gas parameter indicating a state of gases in the intake pipe; c) calculating a target value of the exhaust pressure; d) calculating a target value of the intake pipe gas parameter; and e) calculating a control amount of the exhaust gas flow rate changing device and an opening control amount of the exhaust gas recirculation control valve using a model predictive control, so that values of the detected exhaust pressure and the intake pipe gas parameter, respectively, coincide with the target values of the exhaust pressure and the intake pipe gas parameter. 28. The computer program according to claim 27, wherein the exhaust pressure is a pressure on an upstream side of the turbine wheel in the exhaust pipe, and the intake pipe gas parameter is a partial pressure of one of oxygen and inert gases on a downstream side of the compressor wheel in the intake pipe, or a flow rate of one of oxygen and the inert gases flowing in the intake pipe. 29. The computer program according to claim 27, wherein the control method further includes the step of detecting a boost pressure in the intake pipe, wherein the step d) includes the steps of: i) calculating a steady state target value corresponding to a steady state of the engine according to an operating condition of the engine; and ii) modifying the steady state target value according to the detected boost pressure to calculate the target value of the intake pipe gas parameter. 30. The computer program according to claim 27, wherein the control method further includes the steps of detecting a boost pressure in the intake pipe and detecting a flow rate of fresh air flowing in the intake pipe, wherein the step c) includes the steps of: i) calculating a target power value of the compressor wheel according to a target boost pressure and a target fresh air flow rate calculated according to an operating condition of the engine; ii) calculating an estimated power value of the compressor wheel according to the detected boost pressure and the detected fresh air flow rate; and iii) calculating the target value of the exhaust pressure, so that the estimated power value coincides with the target power value. 31. The computer program according to claim 27, wherein the exhaust pressure is a pressure on an upstream side of the turbine wheel in the exhaust pipe, and the intake pipe gas parameter is a partial pressure of one of fresh air and the recirculated exhaust gases on a downstream side of the compressor wheel in the intake pipe, or a flow rate of one of fresh air and the recirculated exhaust gases flowing in the intake pipe. 32. The computer program according to claim 31, wherein a controlled object model used in the model predictive control is defined using, as control inputs, a mass flow rate of gases passing through the exhaust gas flow rate changing means, and a mass flow rate of gases passing through the exhaust gas recirculation control valve. 33. The computer program according to claim 31, wherein a controlled object model used in the model predictive control is defined using, as control inputs, a mass flow rate of gases passing through the exhaust gas flow rate changing means, a mass flow rate of gases passing through the exhaust gas recirculation control valve, and a mass flow rate of fresh air passing through the throttle valve.