Performance improvement of angular rate matching shipboard transfer alignment

The object of transfer alignment from a reference master navigation system to a slave navigation system onboard a moving vehicle is to estimate the angular misalignment between the two. For a large sized ship moving in the sea, the total misalignment between two points would comprise of a static constant angle and a dynamic bending angle. Use of angular rate difference as measurement of the Kalman filter has been proved to be effective for transfer alignment under such conditions. In this paper, using simulation results, we study the effect of some factors and filter parameters that influence the estimation accuracy and convergence speed of the state estimates of Kalman filter when used in the angular rate matching method for transfer alignment on moving base. It has been shown that the observability of process and the estimation accuracy have dependence on mutual correlation between angular motion of the ship and its dynamic deformation. Stronger correlation increases the estimation errors, whereas larger amplitude of angular motion reduces them. Further, the filter parameters have been modified to reduce the effect of process noise, on the outset and then gradually returned to the nominal filter values. This can increase the convergence speed of estimation. Finally on the basis of conclusions drawn recommendations are made which can improve the accuracy and speed of angular rate matching shipboard transfer alignment.