Vibration measurement of wind turbine blades through image analysis of moiré pattern

Wind turbine blades are becoming harder to maintain due to their growth in size in the last decade. Although the vibration of wind turbine blades can currently be monitored using sensors such as accelerometers or Fibre Bragg Grating sensors which are embedded on the blades, the maintenance work on the sensors themselves is also difficult. In this paper, a new and non-contact measurement method based on image analysis of moiré pattern is proposed to measure the out-of-plane vibration frequency of wind turbine blades. Experiments were conducted at different vibration frequencies and blade angles to verify the feasibility of the proposed method. Results show that in most conditions, the relative error of the measured frequency is within ±5 %. The proposed method is feasible on measuring vibration frequency of wind turbine blades resting at different angles.