The trend towards deepwater development requires a new approach of underwater installation of offshore structures. The present method using crane vessels has some drawbacks in the operations more than 2000m because the natural period of the coupled system of the rigged structure and crane vessel becomes longer so that the manipulation of the crane to achieve the desired positioning accuracy becomes more difficult. This paper examines application of active control technique to underwater installation as a challenging solution to the present problems. The active control technique also has the advantage that it can deal with the structural flexibility which allows the structure to be large and light weight. The structural flexibility imposes problems of suppressing elastic responses and securing stability of control system. In this paper, H(infinity) controller combined with feedforward and LAC/HAC (Low Authority Control / High Authority Control) feedback controler to improve transient response of controlled modes is designed to improve steady-state response and to achieve robustness specifications. In order to confirm the control algorithm and verify the possibility of automatic installation method, basin tests are executed using two types of neutrally buoyant flexible models with ultrasound ranging system and thrusters.
Automatic installation of flexible underwater structures using active control
Automatische Installation flexibler Unterwasserstrukturen mit Einsatz aktiver Regelung
1997
8 Seiten, 12 Bilder, 9 Quellen
Aufsatz (Konferenz)
Englisch
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