Robustness has been an important issue in control-systems design ever since 1769 when James Watt developed his flyball governor. A successfully designed control system should be always able to maintain stability and performance level in spite of uncertainties in system dynamics and/or in the working environment to a certain degree.
And the energy saving is one of the most important factors for profit in marine transportation. In order to reduce the fuel oil consumption the ship's propulsion efficiency must be increased as much as possible. This situation led the conventional mechanical-hydraulic governors for engine speed control to replace digital speed controllers which adopted the PID control or the optimal control algorithm. But these control algorithms have not enough robustness to suppress the engine's variation of the time delay and the parameter perturbation.
In this study the author compares robust stability and performance of the designed controllers with sub-optimal , loop-shaping, -synthesis and - iteration algorithm. And the validity of these three controllers is investigated through the response of computer simulation with Matlab.
Finally, the author designs the digital governor for engine speed control through the fore-mentioned robust control theory and applies it to the closed system via computer program. The result of the engine speed control shows the good disturbance rejection and reference signal tracking. In particular, controller is the most excellent in the nominal performance, robust stability and performance. But it has great difficulty in using in the industry because of controller's high order. In order to apply it to the industry, it needs to reduce its order.