A new multibody modelling methodology for wind turbine structures using a cardanic joint beam element

This paper presents a new multibody modelling methodology for wind turbine structures. The methodology is based on the hybrid multibody system being composed of rigid, flexible bodies, force elements and joints. With a cardanic joint beam element based on the Timoshenko beam theory, the flexible bodies, e.g. rotor blades and tower, shafts, are modelled by a set of rigid bodies connected by cardanic joints geometrically and constrained by spring forces elastically, thus a whole wind turbine structure can be represented by a discrete system of rigid bodies, springs, and dampers. Using some concepts of the differential geometry, the Lagrange's motion equations of the multibody system are represented in explicit form. With this model, the global natural vibrations of a wind turbine structure of 600 kW are analysed.