System and method for controlling a firing sequence of an engine to reduce vibration when cylinders of the engine are deactivated

1. A system comprising:

a vibration prediction module that predicts a modal response of a vehicle based on a firing sequence of an engine when a cylinder of the engine is deactivated, wherein the firing sequence indicates a firing order of the engine and indicates which cylinders of the engine are active; and

a firing sequence module that adjusts the firing sequence of the engine based on the predicted modal response of the vehicle.

2. The system of claim 1 wherein the vibration prediction module predicts the modal response based on torque pulses of firing cylinders and non-firing cylinders in the firing sequence.

3. The system of claim 2 wherein the vibration prediction module:

predicts the modal response for each torque pulse;

determines the timing of the modal response for each torque pulse; and

sums portions of the modal responses that overlap in time to yield the modal response of the firing sequence.

4. The system of claim 3 further comprising a torque pulse module that estimates the torque pulses based on a pressure within an intake manifold of the engine and engine speed.

5. The system of claim 2 wherein the vibration prediction module predicts the modal response of each torque pulse based on a predetermined relationship between crankshaft torque and modal response.

6. The system of claim 2 wherein, for each of the torque pulses, the vibration prediction module predicts the modal response for multiple vibration modes based on a modal characteristic of the vehicle.

7. The system of claim 6 wherein, for each of the vibration modes, the vibration prediction module predicts an amplitude of vibration in multiple directions based on the modal response and a multiplier.

8. The system of claim 7 wherein the vibration prediction module determines a total vibration in each direction by summing the corresponding vibration amplitudes of all of the vibration modes.

9. The system of claim 1 wherein:

the vibration prediction module predicts the modal response of the vehicle corresponding to multiple firing sequence options; and

the firing sequence module selects one of the firing sequence options based on the predicted modal response of the vehicle.

10. The system of claim 9 wherein the vibration prediction module:

determines a first modal response for a previous firing sequence;

predicts a second modal response for each of the firing sequence options;

determines a total modal response for each of the firing sequence options based on the first modal response and the corresponding second modal response; and

selects one of the firing sequence options based on the total modal response.

11. A method comprising:

predicting a modal response of a vehicle based on a firing sequence of an engine when a cylinder of the engine is deactivated, wherein the firing sequence indicates a firing order of the engine and indicates which cylinders of the engine are active; and

adjusting the firing sequence of the engine based on the predicted modal response of the vehicle.

12. The method of claim 11 further comprising predicting the modal response based on torque pulses of firing cylinders and non-firing cylinders in the firing sequence.

13. The method of claim 12 further comprising:

predicting the modal response for each torque pulse;

determining the timing of the modal response for each torque pulse; and

summing portions of the modal responses that overlap in time to yield the modal response of the firing sequence.

14. The method of claim 13 further comprising estimating the torque pulses based on a pressure within an intake manifold of the engine and engine speed.

15. The method of claim 12 further comprising predicting the modal response of each torque pulse based on a predetermined relationship between crankshaft torque and modal response.

16. The method of claim 12 further comprising, for each of the torque pulses, predicting the modal response for multiple vibration modes based on a modal characteristic of the vehicle.

17. The method of claim 16 further comprising, for each of the vibration modes, predicting an amplitude of vibration in multiple directions based on the modal response and a multiplier.

18. The method of claim 17 further comprising determining a total vibration in each direction by summing the corresponding vibration amplitudes of all of the vibration modes.

19. The method of claim 11 further comprising:

predicting the modal response of the vehicle corresponding to multiple firing sequence options; and

selecting one of the firing sequence options based on the predicted modal response of the vehicle.

20. The method of claim 19 further comprising:

determining a first modal response for a previous firing sequence;

predicting a second modal response for each of the firing sequence options;

determining a total modal response for each of the firing sequence options based on the first modal response and the corresponding second modal response; and

selecting one of the firing sequence options based on the total modal response.

21. The system of claim 1 wherein:

the vibration prediction module predicts an amplitude of vibration for multiple vibration modes based on the firing sequence and a modal characteristic of the vehicle; and

each vibration mode is characterized by a modal frequency and a modal direction.

22. The method of claim 11 further comprising predicting an amplitude of vibration for multiple vibration modes based on the firing sequence and a modal characteristic of the vehicle, wherein each vibration mode is characterized by a modal frequency and a modal direction.

23. The system of claim 1 wherein the modal response includes an amplitude of a vibration mode and a phase of the vibration mode.

24. The method of claim 11 wherein the modal response includes an amplitude of a vibration mode and a phase of the vibration mode.