ESTIMATION OF THE CYLINDER PRESSURE OFFSET AND POLYTROPIC EXPONENT USING EXTENDED KALMAN FILTER

The cylinder pressure information offers an increasing potential for the control of internal combustion engines. The pressure sensors measure a relative cylinder pressure signal only. For the determination of the absolute cylinder pressure, the measured cylinder pressure data, during the pre-combustion compression, is fitted to a polytropic curve. The polytropic exponent, which defines the polytropic curve, is not known and varies during the compression stroke. Therefore, a potential improvement to using predetermined polytropic exponent could be accomplished by using an estimated value. The estimation of the cylinder pressure offset and the polytropic exponent may be obtained by a nonlinear optimization. For the solution of this optimization problem an Extended Kalman Filter with a Markov-2 Process is proposed.