Heave Motion Estimation of a Vessel Using Acceleration Measurements

Abstract

AbstractOcean waves continuously disturb every vessel resulting in horizontal and vertical motions. Especially the vertical motion has a significant effect on certain marine applications like subsea lifting operations. Subsea lifts are required for underwater installations on the seabed. Since such operations are normally performed from vessels using offshore cranes, the vertical vessel motion results in excessive dynamic loads acting on the crane structure. Furthermore, an accurate positioning of the load on the seabed is nearly impossible during harsh sea conditions. To avoid these problems active heave compensation systems can be used. These systems actively compensate for the vessel's vertical motion and therefore reduce the dynamic loads acting on the crane structure and enable precise positioning of the load. However, active heave compensation systems always require the knowledge about a vessel's heave motion. This article presents an observer based method to estimate the heave motion of a vessel from accelerometer signals without requiring any vessel specific parameters. The observer model is formulated by a sum of periodic components that approximate the heave motion of a vessel. The parameters of these components are identified online. The identified model is used with an extended Kalman filter to estimate the heave motion with high accuracy. The proposed method is evaluated with simulation and measurement results from an experimental setup.