Development of a transient air fuel controller for an internal combustion engine

This paper presents the use of a feedforward control strategy as applied to engine fuel control. A dynamic 3 state model of a spark ignition engine is described, and simulated on a computer. The nonlinear model was linearized and studied using classical control theory. A feedforward compensator was designed which canceled out the dynamics of the fuel film. A simulation was performed by applying a step-up step-down series of pulses to the throttle valve and air fuel ratio excursions were observed. An electronic fuel controller was designed and a discretized version of the compensator was implemented. A DC servo-motor was connected to the throttle of an engine mounted on a dynamometer, and a series of throttle pulses was applied. A wide range air fuel ratio sensor was used for measurement in the exhaust stream. The corresponding values of predicted and measured air fuel ratio are compared and discussed. Results indicate that enleanment during throttle step up can be eliminated, but at the expense of added noise in steady state