PREVENTING BLADE TOWER STRIKE OF A WIND TURBINE

A method of estimating a position of at least a part of a rotor blade of a rotor of a wind turbine during operation of the wind turbine is provided. The part of the rotor blade is a first part. The rotor blade (103) is deflected due to a deflection motion of the rotor blade towards a tower (104) of the wind turbine (101) and the position is indicative of said deflection. The method (400) comprises measuring a first parameter by a first measuring unit (107), wherein the measured first parameter is indicative of an absolute and/or a relative position of at least a second part of the rotor blade (103) or of a further rotor blade (102) of the rotor. The method (400) further comprises measuring one or more second parameters by one or more second measuring units (108), wherein at least one of the one or more measured second parameters is indicative of an absolute and/or a relative position of at least a third part of the rotor blade (103) or of the further rotor blade (102) of the rotor. The method (400) further comprises estimating the position of the at least first part of the rotor blade (103), wherein the estimating comprises employing a state estimator (210) that estimates a state of the rotor blade (103) based on at least the measured first parameter and the one or more measured second parameters and deriving the position from the estimated state of the rotor blade (103).