Structural motion monitoring of wind turbine towers requires very accurate roll & pitch measurements during oscillatory horizontal accelerations. One can obtain the deflection, and modes of deflection, of the tower structure by measuring the roll and pitch at both the nacelle location and at the center of the tower. This information can be used together with e.g. load cells to monitor the structural integrity of the tower. The measurements may be used as input into a digital twin of the wind turbine tower structure.
For floating offshore wind turbines, it is also necessary to measure the roll and pitch motion caused by the waves as this induces in a big change in the apparent wind speed at the nacelle. These motion measurements can be used by the generator control system to optimize the pitch of the blades in real-time.
The NORSUB MRU is ideal for this application due to its very accurate roll and pitch measurements during horizontal accelerations. This is achieved because the motion constraints of the tower structure are included in the sensor fusion algorithms when the wind turbine structural mode is selected.