Method and processing system of sensed ionization current data for real time estimation of combustion chamber pressure in a spark ignition engine

A method comprising:

• refining a mathematical model of a spark plug ignition system, the mathematical model comprising a set of time-invariant coefficients, wherein refining the mathematical model comprises:
• monitoring an ionization current of a test engine,
• monitoring a pressure of a combustion chamber of the test engine by measuring a pressure sensor,
• generating the set of time-invariant coefficients based on the monitored ionization current of the test engine and the monitored pressure of the combustion chamber of the test engine,
• estimating a pressure of the combustion chamber of the test engine based on the generated set of time-invariant coefficients,
• comparing the estimated pressure of the combustion chamber of the test engine with the measured pressure of the combustion chamber of the test engine,
• regenerating the set of time-invariant coefficients when a residual mismatch between the estimated pressure of the combustion chamber of the test engine and the measured pressure of the combustion chamber of the test engine is higher than a predetermined threshold, and
• storing the set of time-invariant coefficients when the residual mismatch between the estimated pressure of the combustion chamber of the test engine and the measured pressure of the combustion chamber of the test engine is lower than the predetermined threshold;
• and
• applying the mathematical model to a running engine to obtain real-time estimated values of pressure of a combustion chamber of the running engine, wherein the applying the mathematical model comprises
• monitoring an ionization current of the running engine, and
• estimating a pressure of the combustion chamber of the running engine based on the monitored ionization current of the running engine and the mathematical model.

A spark plug ignition system comprising:

• an ignition coil;
• a spark plug coupled in series with the ignition coil;
• a sense resistor coupled in series with the spark plug;
• a sensing circuit coupled to the sense resistor;
• a combustion chamber comprising a first sensor;
• and
• a controller configured to:
• monitor an ionization current via the sensing circuit,
• estimate a pressure of the combustion chamber based on the monitored ionization current, a first sensor, and a mathematical model, the mathematical model comprising a set of time-invariant coefficients.