CONTROL OF THE PIVOT POINT POSITION OF A CONVENTIONAL SINGLE-SCREW VESSEL

Abstract

The issues of using the pivot point concept for the control of a conventional single-screw vessel are considered. The relevance of the task lies in the need for a more accurate assessment of the vessel's trajectory and the necessary area for maneuvering, since conventional single-screw vessels have low maneuverability, and their share in the total number of vessels exceeds 85%. For manual maneuvering of the vessel, using the pivot point, it is important to know the position of the pivot point relative to a fixed point of the vessel’s hull. Traditionally, this point was the gravity center/middle frame of the vessel. The disadvantage of the existing approaches to the calculation of the pivot point position was the use of a simplified calculation scheme ”gravity center – pivot point”, which did not take into account the dependence of the pivot point position on the rotation center position. In previous works, the authors of this article proposed the “gravity center – rotation center – pivot point” calculation scheme, which made it possible to more accurately estimate the pivot point position, taking into account the position of the rotation center. In the refined scheme proposed by the author, the pivot point position was determined relative to the moving rotation center, which is not convenient for manual control. In this article, for a single-screw conventional vessel, a formula and graphs of pivot point position relative to a fixed point on the vessel’s hull (gravity center/middle frame) are obtained, for the refined calculation scheme “gravity center – rotation center – pivot point”. The obtained formulas and graphs of the pivot point position relative to a fix point (gravity center/middle frame) allow us to use them both for automatic and manual control of the vessel’s movement. Mathematical modeling of a single-screw conventional vessel movement in the closed circuit “Control object – Control system” was carried out for the two considered calculation schemes. The simulation results showed that the use of the refined calculation schem allows for a 23% more accurate assessment of the vessel’s trajectory and the required maneuvering area.