Page 13: of Marine Technology Magazine (January 2018)

used in conditions outside their design The vertical acceleration sensor inside range, in very long or short waves. The the buoy was compensated for rotations, hexapod tests proved very useful to gain while the compass and horizontal accel- more insight into the limits and proper- eration sensors, hexapod motions and ties of buoy measurements, by compar- MARIN acceleration sensors were not. ing them to the hexapod motions and a Alignment of the buoy and determin- set of independent MARIN acceleration ing the zero positions were not as easy sensors. as they would be for a dedicated setup,

A ? rst challenge during the project therefore comparing the measured sig- was the need to synchronize measure- nals required a careful setup and exten- ments from three different sources: the sive analysis work.

MARIN Measurement System (hexa- Although the measurement setup is not pod motions, MARIN accelerations), a perfect representation of the buoy re- the direct buoy acceleration and rotation sponse in a real-life wave environment, measurements and the derived motions we were able to make a good assessment in the buoy log ? les (which are stored of the accuracy of the wave buoy for dif-

The Author

Sanne van Essen is Project Man- every half hour). Each of these ? les was ferent motion periods, amplitudes and ager at the Business Unit Ships sampled at a different frequency. Syn- degrees of freedom. Additionally, we at MARIN, the Maritime Research chronisation was done based on a trigger have learned a lot about the buoy prop-

Institute Netherlands.

signal that was recorded by all systems. erties and limits, and gained valuable ex-

E: [email protected]

In this way the synchronisation was lim- perience in the measurement procedures ited only by the lowest sample rate. with the hexapod.

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Marine Technology Reporter 13

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