Full speed ahead

Dynamic positioning (DP) systems are used extensively in the offshore industry and have allowed operators to drill ocean wells at depths of over 3,000m. Holding a vessel in position demands the highest level of seamanship, particularly in hostile waters. So the design of automatic positioning systems has taxed the ingenuity of the control industry. To work effectively they have to take account of the erratic nature of position signals, as well as being able to distinguish cyclic rolling, heaving and pitching motions from the steady forces exerted by wind and tide.The automated positioning system will receive signals from an anemometer, gyrocompass and a range of radio and acoustic position-location systems. While the wind speed and direction will generally be used in a feed-forward control loop, a computerised system is needed to process all this data and determine the power setting of the thrusters to maintain the desired position.