Engine control system

1. An engine control system, comprising:

an engine that outputs a rotation of a crankshaft through a torsional damper;

a calculation portion that calculates a value of engine torque based on an angular acceleration of the crankshaft and an moment of inertia of the crankshaft; and

a correction portion that calculates a correction value based on a torsional angle of the torsional damper, and corrects the calculated value of the engine torque using the correction value.

2. The engine control system according to claim 1 , wherein the correction value is calculated as a product of the torsional angle and a spring coefficient of the torsional damper.

3. The engine control system according to claim 1 , wherein the correction value is calculated as a sum of a product of the torsional angle and a spring coefficient of the torsional damper, and a product of a damping coefficient of the torsional damper and a difference between an angular velocity on one side of the torsional damper and an angular velocity on the other side of the torsional damper.

4. The engine control system according to claim 1 , further comprising an extraction portion that extracts a specific frequency component of the engine torque based on an average of the calculated value of the engine torque, which has been corrected by the correction portion, wherein the average is taken over a predetermined time period.

5. The engine control system according to claim 4 , wherein the extraction portion calculates the average over each of two different predetermined time periods, and extracts the specific frequency component of the engine torque based on a difference between the averages over the two different predetermined time periods.

6. The engine control system according to claim 1 , further comprising an extraction portion that extracts a specific frequency component of the engine torque based on an average of the calculated value of the engine torque, which has been corrected by the correction portion, wherein the average is taken over a predetermined number of combustion events at a predetermined engine speed.

7. The engine control system according to claim 6 , wherein the extraction portion calculates the average over each of two different numbers of the combustion events, and extracts the specific frequency component of the engine torque based on a difference between the averages over the two different numbers of the combustion events.

8. The engine control system according to claim 1 , further comprising an extraction portion that extracts a specific frequency component of the engine torque by applying a digital filter processing to the calculated value of the engine torque, which has been corrected by the correction portion.

9. The engine control system according to claim 4 , further comprising a determination portion that determines whether a combustion state in the engine is good based on a value of the specific frequency component of the engine torque extracted by the extraction portion.

10. The engine control system according to claim 4 , further comprising a determination portion that determines whether a combustion state in the engine is good based on a distribution of a value of the specific frequency component of the engine torque extracted by the extraction portion.

11. The engine control system according to claim 4 , further comprising a determination portion that determines whether a combustion state in the engine is good based on an average of a value of the specific frequency component of the engine torque extracted by the extraction portion.

12. The engine control system according to claim 9 , further comprising a feedback control portion that controls an engine control variable through feedback based on a determination result obtained by the determination portion so that a good combustion state is maintained in the engine.

13. The engine control system according to claim 4 , wherein the extraction portion extracts the specific frequency component of the engine torque for each of cylinders of the engine.

14. The engine control system according to claim 13 , further comprising a determination portion that separately determines whether the combustion state in each of the cylinders of the engine is good based on a value of the specific frequency component of the engine torque extracted for the cylinder by the extraction portion.

15. The engine control system according to claim 13 , further comprising a determination portion that separately determines whether the combustion state in each of the cylinders of the engine is good based on a distribution of a value of the specific frequency component of the engine torque extracted for the cylinder by the extraction portion.

16. The engine control system according to claim 13 , further comprising a determination portion that separately determines whether the combustion state in each of the cylinders of the engine is good based on an average of a value of the specific frequency component of the engine torque extracted for the cylinder by the extraction portion.

17. The engine control system according to claim 14 , further comprising a feedback control portion that separately controls an engine control variable through feedback for each of the cylinders based on a determination result obtained by the determination portion so that a good combustion state is maintained in each of the cylinders.

18. The engine control system according to claim 1 , wherein the crankshaft is connected to a rotor of an electric motor through the torsional damper.

19. The engine control system according to claim 18 , wherein the torsional damper has rigidity low enough to suppress transmission of rotational fluctuation of the crankshaft, which is caused by intermittent combustion in the engine, to the electric motor.

20. The engine control system according to claim 1 , wherein the engine control system is provided in a hybrid vehicle.