Time Domain Modeling of ROV Umbilical using Beam Equations

Abstract

This paper presents a finite element model for representing the cable dynamics of a typical ROV(Remotely Operated Vehicle) umbilical. The goal is to produce a model able to capture the most important dynamic effects of the umbilical affecting the ROV by solving the Euler-Bernoulli beam equations using finite element method. The model is general and is applicable to a wide variety of deep-sea ROV systems. The presented model is demonstrated by numerical examples for umbilical and ROV systems, both for steady state and dynamic response. The model is further validated by comparison with published results.

Finite element cable-model for Remotely Operated Vehicles (ROVs) by application of beam theory

“…This paper extends the work presented in Eidsvik and Schjølberg (2016) to mathematically model and simulate the dynamic response of ROV-systems. The Euler-Bernoulli beam theory grants good results for cases when the cable has limited curvature and should retain stability also when the tension is small.…”

“…It is assumed that deep sea umbilical cables usually have a significant length to width ratio with a limited curvature due to the large vertical distance. The Euler-Bernoulli beam equations therefore represents the dynamics of the cable with satisfactory accuracy, as shown in Eidsvik and Schjølberg (2016). The governing equations in the local frame can be written:…”

“…The tether imposes additional forces on the ROV. Cable drag, inertia and stiffness forces are transferred to the ROV and can in some cases dominate the overall response of the ROV (Eidsvik and Schjølberg, 2016).For deep and ultra deep waters a Tether Management System (TMS) is applied to reduce these loads, but the cable will still have a large impact on the ROV response (Quan et al, 2015). Today these forces are mostly counteracted by human operators and the skills of the operator is therefore crucial for the mission success rate.…”

“…As the model was not tested on a ROV system without a TMS it is difficult to determine the accuracy for low tension cables. Eidsvik and Schjølberg (2016) proposed a finite element model using Euler-Bernoulli beam theory for deepwater ROV systems. The model was applied to a real ROV system showing the importance of including cable effects and the relative importance of incoming current velocities when modeling ROV-systems.…”

Cable Selection Considerations for Subsea Vehicles

“…To calculate the tension forces for different scenarios the cables are modeled as beams represented by the Euler-Bernoulli beam equations [20]. The beam equations are solved using the linear finite element approach.…”