ASSIGNMENT 2:

Assignment 2:

Assignment 2:

Introduction

Marine control systems or Marine cybernetics is defined to be the science about techniques and methods for analysis, monitoring and control of marine systems. The main application fields for marine control systems are the three big marine industries: Sea transportation (shipping), offshore oil and gas exploration and exploitation and fisheries and aquaculture. It is suggested to divide the control structure into two main areas: real-time control and monitoring and operational and business enterprise management, see Fig. 1. The integration of real-time systems with operational management and business transactional systems is by the automation industry denoted as Industrial IT. As seen in Fig. 2 the complexity level may vary both with respect to the automation and the logistics for the various shipping segments. The complexity of the management systems will increase with the number of ships in the fleet and the corresponding logistics and transport services. This paper is an extension of the work presented by Sørensen (2004b).

Fig. 1. Control structure.

Fig. 2. Low-end and high-end market segments within automation and ship management.

The real-time control structure is as shown in Fig. 1 divided into low level actuator control , high level plant control and local optimization. We will in the paper use demonstrating examples from the offshore oil and gas industry. In particular, examples with a dynamically positioned (DP) drilling rig will be used. A DP vessel maintains its position (fixed location or pre-determined track) exclusively by means of active thrusters. Position keeping means maintaining a desired position in the horizontal-plane within the normal excursions from the desired position and heading. The advantages of DP operated vessels are the ability to operate in deep water, the flexibility to quickly establish position and leave location, and to start up in higher sea states than if a mooring system should be connected. For deep water exploration and exploitation of hydrocarbons DP operated vessels may be the only feasibly solution.(Whitcomb,1999,481) However, DP drilling operations at water depths less than 500 m may be more demanding as there are limitations on the riser angle offsets. Ideally, the angle should be within ±2°. Riser angles larger than 5- 8° at the sea bottom may be fatal. In case of a drive-off the available time window to decide and execute a controlled disconnect becomes more limited at shallow water compared to deep water.(Bachmayer,2000,146)

Operational Management

One of the main focus areas in the automation industry has been on connectivity ensuring physical integration of the various control systems. Today several vendors are in position to offer integrated automation systems. A few vendors are also in position to integrate the automation system with the electrical power generation and distribution systems. So far the integrated automation systems are proprietary. Communications with external devices, equipment and systems on control and operational management levels are provided by dedicated hard wiring, field buses and/or so-called gateways. However, some attempts to establish open communication standards between the various vendor supplied systems have been made. The driving forces on hardware and software platform development are the commodity market ...