Abstract

Subsea umbilical properties are complex due to the different material layers that make up the umbilical product. Industrial practitioners often rely on a single variable, i.e., the umbilical bend radius, to ensure that the integrity of the umbilical is maintained during installation. In the installation campaign, the offshore personnel are only provided with static and dynamic results of the umbilical bend radius values, given fixed water depths and vessel laybacks for a given project. The vessel is then left without an adaptive real-time strategy to maintain bend radius in-spite of varying water depths and other environmental factors such as wave and current. Motivated by these circumstances, a black-box model is developed by using the classical system identification approach for the purposes of formulating real-time model-based control strategies for deep-water installation of subsea umbilicals. The model identification method is applied to a set of synthetic data generated by the offshore installation industry-standard finite-element commercial software Orcaflex™. The synthetic data sets consist of input-output pairs such as laybacks vs. vessel positions. Subsequently the vessel layback is correlated to the umbilical bend radius to establish a relationship between the vessel position and the umbilical bend radius. This study presents the first attempt to develop black box models based on finiteelement generated synthetic data for deep-water subsea umbilical installation applications. An example of how the black-box model can be used as basis for a Luenberger observer design is also presented.

INTRODUCTION

Subsea umbilical properties are complex due to the different material layers that make up the umbilical product. Industrial practitioners often rely on a single variable, i.e., the umbilical bend radius, to ensure that the integrity of the umbilical is maintained during installation. In the installation campaign, the offshore personnel are only provided with static and dynamic results of the umbilical bend radius value, given a set of fixed water depths and vessel laybacks for a particular project. The vessel is then left without an adaptive real-time strategy to maintain bend radius given varying water depth and other environmental factors such as current and wave.

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