The deep seabed mining system is generally composed of surface vessel, lifting system, buffer, flexible pipe and miner. The mining system is regarded as a large-scale system in which each subsystem is interconnected to other ones. In order to control a large-scale system, decentralized control approaches have been proposed recently. In this paper, as a basic study on application of decentralized control, firstly, the mining system is modeled in a simplified way. Lifting system and buffer are regarded as a spherical pendulum and the flexible pipe is taken as a two-dimensional linear spring connection. Based on the derived model, the mining system can be decentralized two subsystems, the one consisting of surface vessel, lifting system and buffer, and the other, the miner. Next, this paper proposes the design of controller for each decentralized subsystem by regarding the interacting terms as disturbances. The controllers keep the distance between two subsystems constant even if the miner is moving freely.
The deep seabed mining system is generally composed of surface vessel, lifting system, buffer, flexible pipe and miner. From the ocean floor, manganese nodules collected by the miner are transferred to the buffer, a temporary storage. The nodules are lifted up to the surface vessel through the lifting system in turn. In this process, the miner connected with the flexible pipe must be properly controlled to collect and transfer the nodules. Particularly, when the distance between miner and buffer is kept by position control of buffer, the desired traveling performance of the miner has to be achieved.
In general, the mining system may be regarded as a large-scale system composed of subsystems. One of the earlier attempts in dealing with large-scale systems was to decompose a given system into a number of subsystems for computational efficiency and design simplification.