Improved Dynamic Positioning Using Wave Feed Forward Available to Purchase

Jo Pinkster made the first attempt to estimate 2nd order wave drift forces. In his PhD thesis from 1980, the first practical application of wave feed forward in DP was demonstrated both theoretically and in model tests. Knowledge of the local wave field was used to estimate the 2nd order wave drift forces. The local wave field was converted in wave forces and fed back in the DP system. The use of this knowledge in a DP system should lead to a better position keeping. Since Pinksters’ thesis 30 years ago, this technique has been tried several times with varying success. However, in 2009, the ‘nut was cracked’ and a good success was undoubtedly demonstrated. In 2008–2009, this method has been developed and applied in DP model tests on a ship equipped with azimuthing thrusters. The use of Wave Feed Forward resulted in a reduction of the watch circle by a factor of two. Important for the success of wave feed forward was the filtering of the measured wave signals to predict the wave forces with a limited delay. The performance is demonstrated during model tests in MARIN’s Seakeeping and Manoeuvring Basin at two speeds of 0 knots and 4 knots, uni-directional and multidirectional seas. Besides the application of wave feed forward for a single ship, wave feed forward is used in a side-by-side condition at zero speed and ahead speed. For both speeds, wave feed forward did not provide a significant improvement in DP accuracy. The objective was to make wave feed forward applicable to: zero and forward speed; on a ship alone and on ships sailing side-by-side; in unidirectional and multi-directional waves, with a realistic amount of sensors and as target wave heights, sea state 3 and 4 were envisaged. To measure the local wave height, wave height measurement sensors as well as pressure sensors were used. The pressure sensors can be mounted below the waterline and deliver an accurate estimation for the wave drift forces as well.