Experimental Validation of Wave Induced Disturbances for Predictive Station Keeping of a Remotely Operated Vehicle

Abstract

Predictive control methods can substantially improve the performance of Unmanned Underwater Vehicles (UUVs), particularly in shallow water environments or near the free surface where wave induced disturbance are of magnitude comparable to the vehicle characteristic inertia. To facilitate the adoption of these methods, a fast estimation of the time evolution of hydrodynamic forces acting on a vehicle is required. To this end, we perform experiments in a wave tank with an ROV to validate the use of Linear Wave Theory (LWT) to capture the time history of surge, heave and pitch wave induced forces and moments. Validation is performed for various sea states, reconstructed with a mean correlation of 0.9138 in comparison to experimental measurements, displaying a maximum normalised mean error deviation between simulation and experimental data of 0.16 and 0.27 respectively for surge and heave forces, and 0.34 for pitch moment. The effectiveness of employing real-time wave disturbance forecasting for the purpose of anticipatory control is then assessed by incorporating the predicted loads within a Model Predictive Controller. Results display a mean RMS positional error reduction of 47.32% in comparison to a standard PD controller. This presents evidence that accurate, near real-time predictions of the wave-generated forces and moments on an ROV can be produced, laying the foundation for developing modelbased predictive control strategies that better suit operation in harsh environments.

Optimality of Safe Game and Non-Game Control of Marine Objects

“…However, for rough seas from 6 to 12 • B, corresponding to restricted visibility at sea, a safe passing distance D s of 1 to 3 nm should be assumed. In future works, the components of the disturbance vector from waves, wind and the sea current should be taken into account directly in the mathematical model of the process [22,23].…”

Station-keeping of a ROV under wave disturbance: Modeling and control design

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A semi-analytical study on fluid-induced nonlinear dynamic behavior of the flexible robotic arms

“…They assume that the elastic material to be neo-Hookean, and behave like an artificial 'muscle' which, when stimulated, generates a principal stretch of contraction. To validate the use of linear wave theory to capture the hydrodynamic forces, time history of surge, heave, pitch waves induced forces and moments acting on a vehicle, Walker et al [32] conducted experiments in a wave tank with an underwater vehicles. An experimental study by Gabl et al [33] examined the hydrodynamic loads on a restrained underwater vehicle under the influence of wave motion and fluid flow.…”