Analysis and control of transient torque response in engines with internal exhaust gas recirculation

We analyze the nonlinear dynamic behavior of an internal exhaust gas recirculation system based on a mean-value model of an experimental automotive engine equipped with a camshaft phaser. We develop a control scheme that adjusts camshaft timing to reduce feed-gas emissions while maintaining transient engine torque response similar to that of a conventional engine with zero exhaust gas recirculation. The control scheme consists of a feedforward map that specifies desired camshaft timing as a function of throttle position and engine speed in steady state, and a first-order lag that governs the transition of the camshaft timing to the desired value. The time constant of the first-order lag is adjusted based on engine speed and throttle position