Method and apparatus for controlling a multi-cylinder internal combustion engine

A method for controlling a multi-cylinder spark-ignition internal combustion engine that includes a monitored cylinder and a plurality of non-monitored cylinders, wherein a pressure sensor is disposed to monitor in-cylinder pressure in the monitored cylinder, the method comprising:

• monitoring, via the pressure sensor, in-cylinder pressure for the monitored cylinder during a combustion event for the monitored cylinder;
• determining a first spark timing for the monitored cylinder based upon a desired spark timing and the in-cylinder pressure;
• controlling spark timing for the monitored cylinder based upon the first spark timing;
• monitoring, via a rotational position sensor, engine rotational speed and crankshaft speed pulsations associated with the monitored cylinder and the non-monitored cylinders;
• determining modal coefficients for the non-monitored cylinders based upon the engine rotational speed and the crankshaft speed pulsations;
• determining coefficient errors for the non-monitored cylinders based upon the modal coefficients;
• executing a balance control to determine a spark timing adjustment for each of the non-monitored cylinders based upon the respective coefficient error;
• determining a final spark timing for each of the non-monitored cylinders based upon the desired spark timing and the respective spark timing adjustment;
• and
• controlling spark timing for each of the non-monitored cylinders based upon the respective final spark timing.

A multi-cylinder spark-ignition internal combustion engine, comprising

• a monitored cylinder and a plurality of non-monitored cylinders;
• a plurality of pistons disposed in the monitored cylinder and the non-monitored cylinders, the pistons coupled to a crankshaft;
• a pressure sensor disposed to monitor in-cylinder pressure in the monitored cylinder;
• a rotational position sensor disposed to monitor rotational position of the crankshaft;
• a spark ignition system including a spark controller in communication with a plurality of spark igniters that are disposed in the monitored cylinder and the plurality of non-monitored cylinders;
• a controller, in communication with the pressure sensor, the rotational position sensor and the spark controller, the controller including an instruction set executable to:
• monitor, via the pressure sensor, in-cylinder pressure for the monitored cylinder during a combustion event for the monitored cylinder;
• determine a first spark timing for the monitored cylinder based upon a desired spark timing and the in-cylinder pressure;
• control, via the spark controller, spark timing for the monitored cylinder based upon the first spark timing;
• monitor, via the rotational position sensor, engine rotational speed and crankshaft speed pulsations associated with the monitored cylinder and the non-monitored cylinders;
• determine a modal coefficient for the non-monitored cylinders based upon the engine rotational speed and the crankshaft speed pulsations;
• determine coefficient errors for the non-monitored cylinders based upon the modal coefficients;
• execute a balance control to determine a spark timing adjustment for each of the non-monitored cylinders based upon the coefficient error;
• determine final spark timings for the non-monitored cylinders based upon the desired spark timing and the respective spark timing adjustment;
• and
• control, via the spark controller, spark timing for each of the non-monitored cylinders based upon the respective final spark timing.