Anti-Spin Thruster Control in Extreme Seas

Abstract

A hybrid control scheme for thruster control in moderate and extreme seas is proposed. Two operational regimes are defined: 1) Normal thruster control for handling of low and moderate thrust losses. 2) Anti-spin thruster control for handling of high thrust losses. Alternative thruster control schemes are possible: Conventional speed control, torque control, power control or combinations of these. When high thrust losses are detected, a switch to an anti-spin controller which counteracts the engine racing is proposed. The control system is shown to give increased performance in extreme seas in terms of reduced power system transients, increased station-keeping capability and reduced mechanical wear and tear on the propulsion system