Common rail systems are conventionally employed in diesel and gasoline engines. Pressure, precision and velocity are key factors for correct engine power management. Current systems are based on digital computers and PID control systems. When anomalies occur, recovery strategies are used and engine performance is significantly reduced. Then technical assistance is required to restore normal condition. For safety reasons this approach cannot be used in aeronautical, naval and energy-supply applications. In some cases it is necessary to utilize all the possible energy from the power unit causing significant life-reduction of the engine. In this case a progressive reduction strategy should be used and injection law should be reduced accordingly. For this purpose injection control based on fuzzy logic is more effective . In this case, traditional PID control systems are substituted by fuzzy logic control. A reference map is introduced in the Full Authority Digital Electronic Control, this map is interpreted by the fuzzy logic control system that adapts the injection law to the current engine situation. For example, if fuel temperature tends to increase over the normal level, injection pressure is reduced by the fuzzy control system and injection time is increased to obtain the maximum possible power output. This approach can be easily implemented with very simple and effective fuzzy logic controllers. This method has been experimented on a common-rail test bed and results are compared with traditional “binary recovery strategy” FADEC. Maximum power output is slightly reduced since fuzzy controllers are less effective than PID in “near reference” conditions. However, when anomalies take place or are simply beginning to appear the fuzzy FADEC behaviour is more effective and preserves engine performance more effectively. Aim of this paper it to define rules and fuzzy controllers to optimize the performance of a diesel engine in various operating conditions with particular attention to the power output.
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