Design of an electrohydraulic wave follower system.
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An electrohydraulic wave follower capable of positioning a 25.0 LB instrumentation package at a constant height above the instantaneous sea surface was designed. A derrick to move the system from the deck of the R/V Acania to the water and retrieve it was also designed. The motivation behind the project was to provide an instrumentation platform which would enable the gathering of environmental data within the first three feet of the sea surface. The system is a valve controlled piston arrangement. The instruments are affixed to the piston. The frequency spectrum of interest for this design was from 1.0 to 10.0 HZ. The required amplitude response was derived from linear wave theory using a maximum wave steepness of one seventh. Position feedback was used exclusively in the controls scheme. System modeling showed that the wave follower provided more than sufficient cylinder amplitude response for the design payload in the frequency design range. The phase response became degraded at higher frequencies. However, this could be corrected by incorporating a lead/lag section in the controls portion of the system.
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