Cyclic Torque Imbalance Detection in Gasoline Engines Using Second Order Sliding Mode

Engine torque imbalance is a wide-ranging problem, caused due to the variance of combustion mixture in the engine cylinder. It is desired to generate uniform output torque by the engine cylinder in successive combustion cycles. Any impediment in it causes cyclic torque imbalance which generates non-smooth output power and excessive stress in the engine components. Torque imbalance affects engine performance as it increases engine exhaust emissions and reduces fuel efficiency. In this research work, detection of cyclic torque imbalance is carried out by employing a second order sliding mode observer, based on the First Principle based Engine Model. Net piston force is treated as unknown input to torque production subsystem of the model and it is estimated using the proposed observer. Torque imbalance is simulated by varying the mass of fuel injected per cycle. Simulation results illustrated the efficacy of the proposed method to detect cyclic torque imbalance.