Study on Combustion Information Feedback Based on the Combination of Virtual Model and Actual Angular Velocity Measurement

Combustion closed-loop control is now being studied intensively for engineering applications to improve fuel economy. Currently, combustion closed-loop feedback control is usually based on the cylinder pressure signal, which is the most direct and exact signal that reflects engine working process. Although there were some relatively cheap types of in-cylinder pressure sensors, cylinder pressure sensors have not been widely applied because of their high price now. Moreover, the combustion analysis based on cylinder pressure imposes high requirements on the information acquisition capability of the current ECU, such as high acquisition and analog-digital conversion frequency and so on. For developing a low price and feasible technology, a new engine information feedback method based on model calculation and crank angular velocity measurement was proposed. A simplified combustion model was operated in ECU for the real-time calculation of cylinder pressure and combustion parameters. At the same time, the angular velocity of the crankshaft was measured by the crankshaft flywheel end sensor for the indication of real-time cylinder pressure. The first derivative can indicate the peak phase of cylinder pressure. The result from crankshaft sensor was fed back to ECU and used to modify the combustion model for more accurate cylinder pressure curve and peak phase. The combustion parameter from the model was used to enhance the transient control according to the variation of combustion phase. The application of this method has the potential to increase the thermal efficiency compared to the traditional MAP control strategy, and also keeps costs low because of the replacement of combustion pressure sensors.