Model Based Calibration of a Multi Cylinder Spark Ignition Engine for Idle Speed Control Using PID Control Strategy

An idle speed controller allows the engine to idle at the lowest possible RPM without stalling to support various power-consuming accessories. In this study, an idle speed control system is designed using a PID control strategy based on an engine model. The engine model was developed considering engine dynamics and various cylinder airflow calculation methodologies, such as Speed-density, Alpha-N, and Throttle-flow. The engine model was created in MATLAB Simulink. The model utilizes several calibrated lookup tables that were obtained using the model-based calibration (MBC) technique. A multi-cylinder spark ignition (SI) engine was calibrated using the MATLAB MBC Toolbox to generate real-time maps for idle speed control. This paper aims to investigate the performance of the developed idle speed controller for different cylinder airflow calculation methodologies. The idle speed control system was simulated for various load-torque disturbances to evaluate the controller's performance. The controller responses, such as the settling time and peak speed variation, were analyzed to select a suitable airflow calculation methodology for idle speed control application. The simulated results of the designed controller are compared to the experimental results of the original controller for validation. The simulated results show that the Speed-density method has a higher peak speed variation and a longer settling time than the other two methods for all loading conditions because it considers the intake manifold dynamics. Alpha-N and Throttle-flow methods display similar performance for all tested conditions. Hence, both Alpha-N and Throttle-flow techniques can be considered for idle speed control applications.