The pendulum type is one of the most effective devices to extract wave energy from ocean and we are developing new power generation system called 'Wave Rudder'. Although the pendulum type system has been designed based on the two dimensional potential theory, the three dimensional analysis is required in order to consider the directional wave field in practical use. In this study, a depth integrated model was developed to calculate pendulum (Wave Rudder) motion by multi-directional irregular waves. The accuracy of this model was verified by comparing with the conventional theory in cross-sectional cases. Since computational complexity is much less than the three dimensional model, it is useful for the design of Wave Rudder and an electrical generator.
