Early-Stage Control of Oxygen Sensors for ICE Engines Using Digital Adaptive Filtering

For Internal Combustion Engines (ICE), the control of Air-to-Fuel Ratio (AFR) is done according to the voltage delivered by the oxygen (Lambda) sensor. After starting of engine, the Lambda sensor is cold and cannot generate a useful signal for the injection computer, so it works in open-loop, with an increased fuel consumption and higher levels of toxic exhaust gases. This paper proposes two ways to control AFR during cold starting, an analog circuit and a digital adaptive filtering circuit. In both methods, during the heating period of the Lambda sensor, a periodic signal adapted to the ICE operating regime can be generated to substitute the original Lambda sensor signal, thus the injection computer can be used in closed-loop more quickly, resulting a reduction of fuel consumption and pollution.