Apparatus and method for estimating stopped engine crank angle

1. An engine control system for estimating a stopped engine crank angle of an internal combustion engine, said system comprising:

a crank sensor configured to output a crank signal indicative of a crank angle and a crank speed; and

a controller configured to determine the crank speed based on the crank signal, determine that the engine is coasting, determine a coast-down characteristic based on the crank signal when the crank speed is greater than a threshold speed, and estimate the stopped engine crank angle based on the coast-down characteristic, wherein the coast-down characteristic includes a pumping torque characteristic and a frictional torque characteristic, wherein the coast-down characteristic is used to adjust a coast-down model to correspond to an engine operating condition.

2. The system in accordance with claim 1 , wherein the crank sensor comprises a variable reluctance sensor.

3. The system in accordance with claim 1 , wherein the crank signal comprises a plurality of crank pulses.

4. The system in accordance with claim 3 , wherein the crank speed is based on one or more time interval between crank pulses.

5. The system in accordance with claim 3 , wherein the coast-down characteristic is based on a plurality of time intervals between crank pulses.

6. The system in accordance with claim 1 , wherein the stopped engine crank angle is also based on an estimate of a bounce-back angle.

7. An engine controller for estimating a stopped engine crank angle of an internal combustion engine, said controller configured to receive a crank signal indicative of a crank angle and a crank speed, said controller further configured to determine the crank speed based on the crank signal, determine that the engine is coasting, determine a coast-down characteristic based on the crank signal when the crank speed is greater than a threshold speed, and estimate the stopped engine crank angle based on the coast-down characteristic, wherein the coast-down characteristic includes a pumping torque characteristic and a frictional torque characteristic, wherein the coast-down characteristic is used to adjust a coast-down model to correspond to an engine operating condition.

8. The controller in accordance with claim 7 , wherein the controller further comprises a zero-crossing detector that inputs the crank signal and outputs a processed crank signal having constant amplitude.

9. A method for estimating a stopped engine crank angle of an internal combustion engine, said method comprising:

providing a crank sensor configured to output a crank signal indicative of a crank angle and a crank speed;

determining that the engine is coasting;

determining a coast-down characteristic based on the crank signal when the crank speed is greater than a threshold speed, wherein the step of determining the coast-down characteristic includes determining a pumping torque characteristic and a frictional torque characteristic;

estimating the stopped engine crank angle based on the coast-down characteristic; and

adjusting a coast-down model to correspond to an engine operating condition based on the coast-down characteristic.

10. The method in accordance with claim 9 , wherein the step of estimating the stopped crank angle includes estimating a bounce-back angle based on the coast-down characteristic.

11. The method in accordance with claim 9 , wherein the crank signal comprises a plurality of crank pulses.

12. The method in accordance with claim 11 , wherein the crank speed is based on one or more time intervals between crank pulses.

13. The method in accordance with claim 11 , wherein the coast-down characteristic is based on a plurality of time intervals between crank pulses.