Propulsion shaft alignment measurements on warships afloat and alignment solution using multi-objective optimisation

This paper defines a generalised and simplified procedure which has been devised so that the alignment checks of a warship propulsion shaft line can be undertaken while the ship is afloat, against more traditional methods which often require dry docking of the ship. Strain gauge measurements on the shaftline are fed into the developed software titled 'MARSHAL' which uses finite element calculations to enable the entire alignment measurement process to be carried out with the ship afloat. The procedure also makes the difficult task of assessing hull deflections, required by traditional methods, unnecessary. The alignment solution is obtained by the way of a two stage 'Multi-objective Optimisation' procedure. The validation of the developed software and procedure has been carried out by comparisons of the software solutions with real propulsion shaft data and by way of simulations and experimental work.