  Fatigue is a critical factor in structures as wind turbines exposed to harsh
operating conditions, both in the design stage and control during their
operation. In the present paper the most recognized approaches to estimate the
damage caused by fatigue are discussed and compared, with special focus on
their applicability for wind turbine control. The aim of this paper is to serve
as a guide among the vast literature on fatigue and shed some light on the
underlying relationships between these methods.
