DFT-based controller for fuel injection unevenness correction in turbocharged diesel engines

Although combustion failure diagnosis techniques have been widely developed over the last few years, real-time correction of fuel injection failures, such as drift, are still deficient. In this paper, a controller for the correction of fuel injection failures is presented; the aim of the algorithm is to ensure that the same quantity of fuel is injected in each one of the cylinders. The controller is based on a linear model that relates the low-frequency region of the Fourier transform of a dynamic engine signal and fuel injection unevenness. Model inversion is used as an injection failure observer, and discrepancies in the injected fuel mass in each cylinder can be estimated, even in the case of multiple and simultaneous failures. This observer is used for closing the loop and performing the control action via an integral controller. Theoretical bases are given for the controller, and the stability and settling error are related to the error of the linear engine model assumed. This technique can be used for different engine signals, like crankshaft speed, exhaust manifold pulsation, and turbocharger instantaneous speed. Experimental results obtained on a diesel turbocharged engine, where the turbocharger instantaneous speed was used as input information of the controller, are presented proving the performance of the fuel quantity control algorithm.