Closed-Loop Control of EGR using Ion Currents

S. Byttner and U. Holmberg (Sweden)


Ion currents; Virtual sensing; Electronic engine control; Exhaust Gas Recirculation; Ignition timing; Combustion variability.


Two virtual sensors are proposed that use the spark-plug based ion current sensor for combustion engine control. The first sensor estimates combustion variability for the purpose of controlling exhaust gas recirculation (EGR) and the second sensor estimates the pressure peak position for control of ignition timing. Use of EGR in engines is im portant because the technique can reduce fuel consumption and NOx emissions, but recirculating too much can have the adverse effect with e.g. increased fuel consumption and poor driveability of the vehicle. Since EGR also affects the phasing of the combustion (because of the diluted gas mix ture with slower combustion) it is also necessary to control ignition timing otherwise efficiency will be lost. The com bustion variability sensor is demonstrated in a closed-loop control experiment of EGR on the highway and the pres sure peak sensor is shown to handle both normal and an EGR condition.

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