State estimator based exhaust gas chemistry measurement system and method

A system for measuring a chemical concentration of a gas exhausted during exhaust cycles from a plurality of exhaust ports of a multi-cylinder internal combustion engine, said system comprising:

• gas chemistry sensory means, responsively coupled to the plurality of exhaust ports, for measuring the gas exhausted from each of the plurality of exhaust ports and for providing a linear sensory output signal responsive thereto;
• means for determining an output sampling delay time associated with each of the plurality of exhaust cycles;
• signal reconstruction means, responsively coupled to the linear sensory output signal, for providing a constituent gas signal coincident with an expiration of the output sampling delay time, wherein the constituent gas signal has an amplitude indicative of the gas exhausted during each of the exhaust cycles.

A method for measuring a chemical concentration of a gas exhausted during exhaust cycles from a plurality of exhaust ports of a multi-cylinder internal combustion engine, wherein the gas exhausted is present at a collection point in a stable chemical concentration during intervals of engine angular rotation corresponding to the exhaust cycles, said method comprising the steps of:

• measuring the gas exhausted from each of the plurality of exhaust ports present at the collection point, and for providing a sensory output signal that, during the intervals of engine angular rotation, approaches a value representative of the stable chemical concentration of the gas exhausted;
• and
• reconstructing the stable chemical concentration of the gas exhausted from the sensory output signal provided in said step of measuring by predicting an exhaust gas oxygen concentration and providing a predicted exhaust gas oxygen concentration as an a priori input to the reconstructing step, wherein responsive to the predicted exhaust gas oxygen concentration, and the sensory output signal provided in said step of measuring, the step of reconstructing provides a constituent gas signal that has an amplitude indicative of the stable chemical concentration of the gas exhausted during the intervals of engine angular rotation corresponding to the exhaust cycles.