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

In this paper 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 feedgas 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.