The Motion Characteristics of Crawler Driven ROV Moving Over Bumps

Abstract

Seafloor exploration and seabed resources development are important missions for solving international energy issues. The crawler driven ROV which is capable to do heavy works is considered as one of the probable systems for those missions and some have been developed already [1][2][3][4][5][6][7]. It is well known that the movability of actual ROVs on the sea floor is worse compared with the terrestrial crawlers [8][9][10][11][12]. Therefore it is important to make clear what conditions have to be satisfied for the stable running of a ROV on the sea bottom. The experimental investigation on the crawler based ROV’s movability suggests that light weight ROVs are easy to run in bow up condition and sometimes turn over. The authors have shown the condition for the normal running of the ROV which moves on the horizontal and inclined flat water bottom by means of a simple dynamic model [13][14][15]. This normal running condition is represented by the relation between the locations of gravity and buoyancy centers to be satisfied, in case of the weight, displacement, geometry and speed of the ROV are fixed. The model experiments have shown the validity of this normal running condition. However, the sea bottom is not flat and it is very important to know the moving performance of ROV over the bumps for the practical design point of view. In this paper, a method to estimate the ROVs’ ability to climb up the bumps is shown and it is validated by model experiments. The ROV model has two sets of crawlers; the rear crawlers are set horizontally and fore ones are inclined to climb up the bumps. The requirements to climb up the bumps for the design parameters of ROV such as crawler length, weight and displacement of ROV, location of gravity and buoyancy center, derived from present method agreed with the experimental results qualitatively.