The time domain mean-value engine model, introduced in the next section, assumes that exhaust gas recirculation
(EGR) depends internally on variable valve timing (VVT) and spark advance (SA) remains constant in certain operating conditions. Air fuel ratio (AFR) is also well maintained at stoichiometric.Therefore, this engine model is broken down
into four subsystems: electronically controlled throttle body, intake manifold, combustion, and crank shaft Dynamics
neglecting fuel dynamics [1].