In marine transportation, one of the most important factors is the energy saving. In order to reduce the fuel oil consumption, ship's propulsion efficiency must be increased as much as possible. The Propulsion efficiency depends upon a combination of an engine and a propeller. This situation led the engine manufacturers to design the engine that has lower speed, longer stroke and a small number of cylinders. Consequently, the variations of rotational torque became larger than before because of the longer time delay in fuel oil injection process and increased output per cylinder. As these new trends the conventional mechanical hydraulic governors for engine speed control have been replaced by digital governors which adopt the PID control or the optimal control algorithm. And the conventional PID controller has been extensively used to speed control of marine diesel engines. However, one of drawbacks is that its control performance can be degraded if the parameters are fixed on whole operating points.
In this paper, a scheme for integrating PID control and the fuzzy technique is presented to control speed of a marine diesel engine on overall operating points. At first, the local PID controller is designed at each speed mode, whose parameters are optimally adjusted using a genetic algorithm. Then, fuzzy "if-then" rules combine the local controllers as a consequence part. To demonstrate the effectiveness of the proposed fuzzy PID controller, a set of simulation works on a marine diesel engine are carried out.