A Fuzzy Control System for a Small Gasoline Engine

Abstract

Small spark-ignition gasoline-fuelled internal-combustion engines can be found all over the world performing in a variety of roles including power generation, agricultural applications and motive power for small boats. To attain low cost, these engines are typically air-cooled, use simple carburettors to regulate the fuel supply and employ magneto ignition systems. Electronic control, of the sort found in automotive engines, has seldom proved cost-effective for use with small engines. The future trend towards engines that have low levels of polluting exhaust emissions will make electronic control necessary, even for small engines where previously this has not been economic. This paper describes a fuzzy control system applied to a small engine to achieve regulation of the fuel injection system. The system determines the amount of fuel required from a fuzzy algorithm that uses the engine speed and manifold air pressure as input values. A major advantage of the fuzzy control technique is that it is relatively simple to set up and optimise compared to the labour-intensive process necessary when the conventional ”mapped” engine control method is used. Experimental results are presented to show that a considerable improvement in fuel regulation was achieved compared to the original carburettor-based engine configuration, with associated improvements in emissions. It is also demonstrated that the system produces improved output power and torque curves compared to those achieved when the original mechanical fuel regulation system was used.