Proposed optimal controller for the Canadian Patrol Frigate diesel propulsion system

The Canadian Patrol Frigates (CPF) were designed for mobility, long patrol range, and silent running to detect submarines. The propulsion configuration is combined diesel or gas turbine (CODOG), consisting of two General Electric LM 2500 gas turbines and one S.E.M.T Pielstick V20 turbo charged diesel engine. All engines drive one or both shafts through a single gearbox. Controllable reversible pitch propellers are fitted on the unidirectional shafts to provide forward and astern thrust. The diesel engine is designated both as the cruise engine and the patrol engine, and therefore has been made silent through shock mounting and sound insulation arrangements. The diesel engine is controlled by a PI governor receiving its desired set speed from the Integrated Machinery Control System (IMCS). The sea states can cause the fuel rack to cycle and at times overcompensate, leading to premature wear of the fuel rack. The engine load limiter in turn, causes the propeller pitch to cycle and the propeller blades are often off the design angle of attack. Both the pitch angle cycling and the shaft speed fluctuations cause a significant and undesirable bandwidth of underwater acoustic noise emission. An optimal controller design is proposed to reduce these effects.