Design of Air-Fuel Ratio Control Using Gain- Scheduled Fuzzy-PID for Small Scooter Engine

Recently applied attempt for controlling the Air- Fuel Ratio (AFR) on a small scooter engine is by setting its value at the stoichiometric level. It is already done by the default Electrical Control Unit (ECU) module. At some points when the engine has little torque demand or no-load condition, the stoichiometric level is not always needed and continuous operation on that level may leads into less-efficient fuel usage. Thus, the AFR should be set into a leaner value, but it could be very difficult as the ECU module itself is an unmodifiable device along with nonlinear characteristic of the motorcycle engine. The main goal of this research is to design an AFR controller based on Gain-Scheduled Fuzzy PID algorithm for small gasoline-fueled scooter engine. It is aimed to control the AFR value at the leaner level. The control system is consisted of fuzzy logic to map the throttle opening and engine speed for tuning each PID gain properly. The PID controller output is injector pulse duration that used for determining the proper amount of injected fuel. The engine is tested under zero-load condition with up to one third throttle opening. The results are the controller is able to control AFR at the leaner value and reduce 5.59% the amount of gasoline fuel used.