Measurement of Flapping Wing Deformation Using Piezoelectric Modal Sensors

An experimental investigation was conducted to measure the deformation of flapping wings with distributed piezoelectric modal sensors. The sensors are bonded to the surface of a wing and shaped to extract a specific modal co-ordinate. The experimental setup consisted of a carbon fiber beam with shaped sensors designed to extract the 1^st and 2^nd modal co-ordinates. The beam was mounted to two different excitation devices (shaker or servomotor) that allowed the beam to be excited at a desired frequency and motion. The resulting electrical signals from the strained modal sensors are calibrated to modal co-ordinate measurements. In order to validate modal sensor measurements, the Digital Image Correlation (DIC) technique is used to obtain full field deformation measurements of the beam. The measured deformation from DIC is then used in conjunction with operational modal analysis to extract modal co-ordinates. Comparison of the modal co-ordinates obtained via modal sensors against DIC measurements show good agreement. Furthermore, a sensitivity analysis was performed to gauge the robustness of modal sensors against construction errors. The results obtained show that modal sensors are a simple and accurate method of obtaining the deformation of a flapping wing.