Using Fiducial Markers for Pose Estimation of an OSWEC in a Wave Tank

In this study, we consider a novel method of sensing the motion of a wave energy converter in a wave tank under the
influence of incoming waves. The wave energy converter considered in our research is an oscillating surge wave
energy converter, which is a hinged paddle that responds to incoming waves. Motion sensing is normally done with
inertial sensors, which can hinder motion due to suspended cables that carry power and transmit signals. Our proposed
method is contactless and can be implemented economically. A camera is used to record different marker patterns
affixed to the moving paddle and the motion deduced by pose estimation algorithms.
Fiducial markers are commonly used for robot localization and in augmented reality. There are many types of
fiducial markers, including ArUco-type markers which are accurate, fast and robust. The system consists of markers
attached to the paddle element and recorded using a machine vision camera. A pose estimation algorithm is then
applied to the detected markers to estimate the tilt of the paddle. In this work, we examine the challenges of image
acquisition and calibration for underwater targets, compare the motion obtained by this new system with a calibrated
tilt sensor and identify areas where the new system may be superior.