Turbocharger boost control using exhaust pressure estimated from engine cylinder pressure

1. A method comprising:

sensing pressure within an engine cylinder;

estimating exhaust pressure based on the sensed pressure within the engine cylinder; and

controlling turbocharger boost pressure based on the estimated exhaust pressure;

wherein the exhaust pressure is formulaically estimated using the following equation:

P exhaust =f ( P cyl _ max , P cyl (θ), ν)

where:

P exhaust =exhaust manifold pressure;

P cyl =cylinder pressure before combustion, after compression;

P cyl _ max =maximum cylinder pressure over the current combustion cycle;

θ=exhaust valve opening angle;

P cyl (θ)=cylinder pressure when the engine is in the position where the exhaust valves are open; and

ν=engine revolutions per minute.

2. The method of claim 1 , wherein the estimated exhaust pressure is exhaust pressure at a turbocharger turbine inlet.

3. A method as set forth in claim 1 further comprising using a computer program to implement the method.

4. A product, comprising:

at least one engine cylinder pressure sensor to measure engine cylinder pressure;

at least one turbocharger boost pressure sensor to measure turbocharger boost pressure;

at least one memory device storing program instructions and data;

at least one control system coupled to the sensors and memory and responsive to the program instructions for causing the computer-controlled system to perform a method according to claim 1 .

5. The product of claim 4 , wherein the at least one control system includes a boost pressure closed-loop controller, and an exhaust pressure closed-loop controller.

6. The product of claim 5 , wherein the at least one control system is a dual control system also including a boost pressure open-loop controller, and an exhaust pressure open-loop controller.

7. A method comprising:

determining a boost pressure deviation between a boost pressure setpoint and an actual boost pressure;

producing an exhaust pressure setpoint in response to the boost pressure deviation;

determining an exhaust pressure deviation between the exhaust pressure setpoint and an exhaust pressure estimate that is estimated from actual cylinder pressure; and

producing a turbocharger command in response to the exhaust pressure deviation;

wherein the exhaust pressure is formulaically estimated using the following equation:

P exhaust =f ( P cyl _ max , P cyl (θ), ν)

where:

P exhaust =exhaust manifold pressure;

P cyl =cylinder pressure before combustion, after compression;

P cyl _ max =maximum cylinder pressure over the current combustion cycle;

θ=exhaust valve opening angle;

P cyl (θ)=cylinder pressure when the engine is in the position where the exhaust valves are open; and

ν=engine revolutions per minute.

8. A method as set forth in claim 7 , further comprising:

sensing cylinder pressure in an engine combustion chamber to provide the actual cylinder pressure; and

sensing turbocharger boost pressure to provide the actual boost pressure.

9. A method as set forth in claim 8 , wherein the step of producing an exhaust pressure setpoint includes using an exhaust pressure closed-loop controller, and the step of producing a turbocharger command includes using a boost pressure closed-loop controller.

10. A method comprising:

determining a boost pressure deviation between a boost pressure setpoint and an actual boost pressure;

producing a closed-loop exhaust pressure setpoint adjustment in response to the boost pressure deviation;

producing an open-loop exhaust pressure setpoint from inputs of the boost pressure setpoint and an exhaust gas recirculation parameter;

combining the closed-loop exhaust pressure setpoint adjustment with the open-loop exhaust pressure setpoint to produce an exhaust pressure setpoint;

detrmining an exhaust pressure deviation between the exhaust pressure setpoint and an exhaust pressure estimate that is estimated from actual cylinder pressure;

producing a closed-loop turbocharger command adjustment in response to the exhaust pressure deviation;

producing an open-loop turbocharger command from an input of the exhaust pressure setpoint; and

combining the closed-loop turbocharger adjustment with the open-loop turbocharger command to produce a turbocharger command.

11. A method as set forth in claim 10 , further comprising:

sensing cylinder pressure in an engine combustion chamber to provide the actual cylinder pressure; and

sensing turbocharger boost pressure to provide the actual boost pressure.