US Patent 9556850 Method of controlling a wind turbine

A method of controlling a wind turbine rotor blade, the blade comprising a pitch axis about which the blade can be pitched, and a flap movable to alter the aerodynamic profile of the blade, the method comprising the steps of: providing a pitch angle request (θ) to a pitch actuator; determining an initial flap angle request (β_flap); providing a decoupled flap angle request (β) to a flap actuator; herein the decoupled flap angle request (β) is calculated from the pitch angle request (θ) and the initial flap angle request (β_flap) such that the decoupled flap angle (β) provided to the flap actuator does not counteract the pitch angle request (θ); and pitching the blade according to the pitch angle request (θ) and moving the flap according to the decoupled flap angle request (β).