Adaptive Harmonic and Disturbance Estimators for Rotary Machines With Applications to Engines

In this article, we present a new method for estimation of the nonperiodic (mean) value and harmonics of unknown disturbance inputs with parametrically varying harmonic frequencies. The proposed methods shall be studied for mean value and harmonic estimation of internal combustion torque of an engine. The internal torque refers to the oscillatory torque resulting from the combustion process. Its estimation uses an unknown input observer approach with a proportional structure, modeling the combustion torque as disturbance. An adaptive harmonic estimator is developed to filter the nonperiodic mean value and the harmonic components using linear parameter-varying techniques. The developed estimation methods feature phase-free estimation, minimal model assumption, tunable noise attenuation, and efficient time-triggered implementation. Misfire event detection using harmonic filtering of generated torque is demonstrated using simulations. Experimental validation is performed on a dynamical engine test bench with a series-production four-cylinder diesel engine estimating the combustion torque and its mean value during engine start and transient operation. The generic nature of the proposed technique is demonstrated by applying it to estimate nonperiodic speed values of an electric machine operated in tandem with a two-cylinder gasoline engine.