Air/fuel ratio controller design using the describing function approach

In this paper, a nonlinear fuel-injection controller is designed using the describing function method. The controller is designed to achieve a commanded air-to-fuel ratio within 14.5 to 14.9, which guarantees optimum operational characteristics. The controller is robust to changing throttle maneuvers, modeling errors and time delay. Using the describing function method, simple analog and digital controllers are designed to meet the control objectives. The simplicity of the controllers makes them particularly suitable for practical implementation using hardware or firmware.