Alternative linearisation methodology for aero-elastic Floating Offshore Wind Turbine non-linear models

Software capability for generating linear models from non-linear systems is a very powerful resource for floating offshore wind turbine (FOWT) systems. In particular, this linear models allow the application of the model design approach for system control design to improve and optimise the wind generator performance. However, systems with high non-linearities can difficult the linearisation process, where a good accuracy of the linear model is essential for the achievement of the desired control performance. So that, an alternative linearisation procedure based on the application of a chirp signal to the FOWT full non-linear model to provide high accuracy SISO linear models is presented in this work. Furthermore, this and FAST provided two linear models are analysed and compared, where frequency domain discrepancies are discussed. Time domain simulations with the FOWT full non-linear model are carried out for the linear model validation.