ABSTRACT:

A kinematic investigation is done for a hybrid pick-up device, whose design concept has been adopted for- an environmentally favorable separation of manganese nodules out of deep-seabed sediment layer. In order to investigate motion controllability or the pick-up device, kinematic analysis is conducted. An inverse dynamic analysis provides driving forces of hydraulic cylinders and ruction forces at each joint between structure elements in the pick-up device. A design sensitivity analysis is performed in order to examine change effects of design variables on the maximum strokes or the hydraulic cylinders. The direct differentiation method is used to obtain some design sensitivity coefficients of the pick-up device.

INTRODUCTION

Performance and efficiency of a manganese nodule collector on seabed are of basic importance for a commercial mining system. A nodule collector on deep seabed consists of nodule pick-up device and carrier vehicle. The nodule pick-up device is mounted in front of tile vehicle which carries auxiliary parts including an electro-hydraulic power supply and some control units as well. Mining efficiency of the nodule collector depends on mobility of the vehicle and performance of the pick-up device. In development of the nodule pick-up device operating on the deep seabed. whose upper layer is highly saturated with water. so called a semi-liquid layer, it is required to take into account environmental effects as well as nodule pick-up efficiency (Amann et aI., 1991; Amann and Beiersdorf, 1993). Deep sea manganese nodule pick-up devices are classified into three types, i.e. hydraulic, mechanical and hybrid ones. A mechanical type device and a purely hydraulic device were employed for the Pilot Mining Test of OMI (Ocean Management Inc.) in 1978/79 (Middelhaufe, 1979; Bath, 1989; Ocbius, 1993). Hydraulic type pick-up device collects nodules by providing pressure difference to ambient fluid without any mechanical contact to the nodules and sediments.

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