Design of Gain-Scheduled Fuzzy PID Controller for AFR Control System of SI-Based Motorcycle Engine Model

Optimum engine performance along with efficient fuel usage can be achieved by tuning Air-Fuel Ratio (AFR) at its stoichiometric level that already done by the default Electrical Control Unit (ECU). The stoichiometric AFR is not always needed and can be set into a leaner value, especially when the engine is under little or no-load condition. However, modifying and implementing the AFR control to reduce the fuel usage by using default ECU module could be quite a challenging task because the module itself is a black-box device along with nonlinear and uncertain characteristic of the motorcycle engine. The main objective of this research is to design a closed-loop controller based on Gain-Scheduled Fuzzy PID algorithm that would be able to control the AFR value on the small Spark Ignition (SI)-based motorcycle engine model at leaner level. The control system is designed based on the AFR value response obtained from open loop test data and tested using adapted single cylinder SI engine dynamic model. The controlling process is done by varying the injector pulse duration in order to manage the amount of injected fuel at no-load condition by considering the throttle opening as the main control. Variation of the throttle opening is mapped with Fuzzy logic algorithm to determine optimum value for each PID gain at various condition. The results are the controller is able to control AFR at the leaner value and reduced 5.5% and 9.4% of fuel usage for the setpoint at 17.6 and 20.54 respectively.