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

In this paper we analyze the nonlinear dynamic behavior of an internal exha ust gas recirculation system based on a mean-value model of an experimental automotive engine equipped with a camshaft phaser, We develop a control sc heme that adjusts camshaft timing to reduce feedgas emissions while maintai ning transient engine torque response similar to that of a conventional eng ine with zero exhaust gas recirculation. The control scheme consists of a f eedforward map that specifies desired camshaft timing as a function of thro ttle 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 tim e constant of the first-order lag is adjusted based on engine speed and thr ottle position.