Real-time estimation of the volumetric efficiency in spark ignition engines using an adaptive sliding-mode observer

Abstract

Proper operation of an engine requires accurate measurement or estimation of the engine’s air charge provided to the control unit which reduces both the engine’s fuel consumption and the emissions. The volumetric efficiency of the engine is a key variable in computations using the engine control unit to estimate the air charge using the speed–density equation. This paper presents a new approach for real-time estimation of the volumetric efficiency using the sliding-mode methodology. An adaptive sliding-mode observer is proposed which relies on measurements from the engine’s conventional sensors. The observer is shown to estimate asymptotically the volumetric efficiency of the engine for different operating conditions. A method for eliminating the chattering effects caused by the sign function in the estimation of the volumetric efficiency, which improves the performance of the sliding-mode observer in terms of the accuracy and the response time, is also given. The experimental results from a modern spark ignition engine show a good performance of the sliding-mode observer for estimating the engine air charge compared with the measured data.