Design of an optimal idle speed controller for a turbocharged diesel engine using fuzzy logic method

Abstract

Idle Control of Internal Combustion Engines (ICEs) is one of the most important modules of Engine Management Systems (EMS) due to its effects on fuel consumption (FC) and pollutions produced in urban traffics. PID controllers are usually used for idle speed regulation. In this paper a PID like fuzzy controller is used to control the idle speed. The aim of this research is to introduce the selection method of membership functions for nonlinear processes which have unsymmetrical behaviors around working point. Also a simple yet useful graphical base approach to optimize fuzzy like PID controller is introduced. In order to design the controller a mean value model of a 1.6 turbocharged diesel engine is applied. In this model the effects of injection timing, injected fuel mass, ambient conditions and cycle by cycle torque generation variations are taken into account. The model also predicts the engine behavior in warm-up period. Two main manipulated variables of injection timing and injected fuel mass per cycle are handled to control the engine speed under different sources of engine speed variation such as external loads made by A/C, steering hydraulic pump or alternator and also the internal loads e.g. variable internal friction. The designed controller shows high robustness in response to change in ambient conditions.