Due to the constantly varying sea-states with which any wave energy conversion device must contend in order to efficiently extract energy the ability to control the device" s position relative to the incident waves is critical in achieving the creation of a truly functional and economical wave energy device. In this paper, the authors will propose methodology based on a variable structure system theory to utilize a three dimensional source distribution as a model to estimate anticipated surge, sway and yaw of a wave energy conversion device relative to varying angles and characteristics of incident waves and there from derive a feedback to a sliding mode controller which would reposition the device so as to maximize its ability to extract energy from waves in constantly varying ocean conditions.
Previous attempt to efficiently extract energy from ocean waves did not achieve the desired results due to the high degree of structural complexity which must be incorporated into any wave energy conversion device attempting to extract energy from the non-linear hydrodynamic phenomena that characterize ocean waves. Ocean waves may come from any direction of incidence and have different characteristics of wave height length etc. The combination of these two sources of complexity make it extremely difficult to estimate or promote extracted wave power. as previously demonstrated both theoretically and experimentally(Kim and Park.1989) (Kudo. 1984). Therefore. a three dimensional source distribution method is used to estimate the hydrodynamic forces on a wave energy conversion device and to calculate the hydrodynamic forces according to the variations in length and direction of incident waves (Xim and Park.1989).(Kim and Park and Xim,1988). And the authors believe is possible to control the position of a wave energy conversion device by using a "water column" model" s three dimensional source distribution.