Engine load and equivalence ratio estimation for control and diagnostics via nonlinear sliding observer

Nonlinear engine observers can be used as part of the engine powertrain control system in order to provide information that is not measurable or that is costly to measure. In this paper, the engine load and fuel-air equivalence ratio are estimated by using a mean torque production dynamic engine model and sliding observer theory. The sliding observer is a good tool to improve transient estimation accuracy and robustness. Sliding mode theory is used to design the observer gains in order to guarantee global stability, attractiveness, and robustness. Modern engine powertrain control and diagnostics will benefit by using this nonlinear model based observer approach.