Model-based unified framework for detection and mitigation of cyclic torque imbalance in a gasoline engine

Torque produced by the internal combustion (IC) engine is desired to be of similar value for consecutive combustion cycles; nevertheless, difference occurs in the cyclic torque due to uncertainties in its generation. Variations between output work of successive combustion cycles are considered as the main cause of imbalance in the cyclic torque. Such variations are displayed in engine output torque and affect the engine performance. In this paper, a novel model-based unified framework is proposed for the detection and mitigation of cyclic torque imbalance in a gasoline engine by employing the first principlebased engine model (FPEM). Engine speed dynamics in the model are transformed to develop the direct relationship between engine speed dynamics and fuel input. Fault in fuel injection subsystem is induced to generate imbalance in the cyclic torque. FPEMbased uniform second-order sliding mode (USOSM) observer is applied for estimation of the unknown input, i.e., net piston force (fn) from engine speed dynamics to detect imbalance in the cyclic torque. Estimated net piston force (fn) is utilized to design the control law for certainty equivalence super twisting algorithm (CESTA) based fault tolerant control (FTC) technique to mitigate the torque imbalance. The results of numerical simulation demonstrated that the desired objective is achieved by the proposed unified framework.