MD
M.H.A. Doornink
info
Please Note
<p>This page displays the records of the person named above and is not linked to a unique person identifier. This record may need to be merged to a profile.</p>
1 records found
1
Experimental Investigation of Resonant Dynamics in the Atalanta
Response Modification through Local Stiffness Variations in a Compliant Flapping-Wing Micro Air Vehicle Prototype
This thesis explores the dynamic behaviour of a flapping-wing micro air vehicle (FWMAV) prototype, when actuated at resonance to increase flight efficiency. The prototype is based on a four wing vehicle design called the Atalanta FWMAV. The current research adopted a Straight Linkage Concept, which was hypothesized to be more sensitive to control inputs used for steering. The used control inputs are local structural property modifications, which alter the dynamic response of the prototype when operating at resonance. The Straight Linkage Concept entails a two degree of freedom compliant mechanism capable of transferring linear actuator motion into rotational wing flapping motion. The prototype was designed and physically realized to be a representation of the fully integrated Atalanta, without lift-off capable wings. In the prototype, stiffness was passively varied to induce response modifications, giving an indication on the performance of the Straight Linkage Concept. Three experimental methods were developed to investigate the functioning of the FWMAV prototype. The first method was used to measure the individual stiffness of specific flexures in the compliant mechanism. The second method measured the amplitude response as a function of frequency in two distinct stiffness configurations. By taking photographs of the wings at different frequencies, the influence of the variations in stiffness on the amplitudes of the wings are characterized. The third method measured the phase relation between the wings in two distinct stiffness configurations. By taking stroboscopic videos of the wings at different frequencies, the influence of variations in stiffness on the phase delay of each wing were characterized. Together, the methods provided insights into the dynamic behaviour of the prototype. It was found that locally changing the sweeping hinge stiffness affected the resonant dynamics of the four wing drone as a whole, as well as the response of individual wings. In fact, the frequency response functions indicated that the applied stiffness modification increased the amplitude of one wing, while it decreased the amplitude of the other wings. The dynamic response of both amplitude and phase were modified due to the local stiffness variations, indicating an asymmetric lift distribution can be realized over the four wings, which is necessary for steering. Furthermore, it was found two eigenmodes dominate the dynamics of the physical prototype. Under a symmetric stiffness distribution, an out-of-phase mode shape was observed, wherein two wings in the Straight Linkage Concept move in opposite directions. The applied stiffness increase caused the oscillations to include an in-phase mode shape, wherein two wings move in equal directions. The in-phase mode shape is thought to have less equivalent stiffness, which allows for increased flapping amplitudes in a stiffer configuration. The capability of the Straight Linkage Concept to shift from one mode to the other is thought to allow for more elaborate and highly sensitive dynamic response modifications under limited local stiffness increase, allowing for high controllability with low control effort.
...
This thesis explores the dynamic behaviour of a flapping-wing micro air vehicle (FWMAV) prototype, when actuated at resonance to increase flight efficiency. The prototype is based on a four wing vehicle design called the Atalanta FWMAV. The current research adopted a Straight Linkage Concept, which was hypothesized to be more sensitive to control inputs used for steering. The used control inputs are local structural property modifications, which alter the dynamic response of the prototype when operating at resonance. The Straight Linkage Concept entails a two degree of freedom compliant mechanism capable of transferring linear actuator motion into rotational wing flapping motion. The prototype was designed and physically realized to be a representation of the fully integrated Atalanta, without lift-off capable wings. In the prototype, stiffness was passively varied to induce response modifications, giving an indication on the performance of the Straight Linkage Concept. Three experimental methods were developed to investigate the functioning of the FWMAV prototype. The first method was used to measure the individual stiffness of specific flexures in the compliant mechanism. The second method measured the amplitude response as a function of frequency in two distinct stiffness configurations. By taking photographs of the wings at different frequencies, the influence of the variations in stiffness on the amplitudes of the wings are characterized. The third method measured the phase relation between the wings in two distinct stiffness configurations. By taking stroboscopic videos of the wings at different frequencies, the influence of variations in stiffness on the phase delay of each wing were characterized. Together, the methods provided insights into the dynamic behaviour of the prototype. It was found that locally changing the sweeping hinge stiffness affected the resonant dynamics of the four wing drone as a whole, as well as the response of individual wings. In fact, the frequency response functions indicated that the applied stiffness modification increased the amplitude of one wing, while it decreased the amplitude of the other wings. The dynamic response of both amplitude and phase were modified due to the local stiffness variations, indicating an asymmetric lift distribution can be realized over the four wings, which is necessary for steering. Furthermore, it was found two eigenmodes dominate the dynamics of the physical prototype. Under a symmetric stiffness distribution, an out-of-phase mode shape was observed, wherein two wings in the Straight Linkage Concept move in opposite directions. The applied stiffness increase caused the oscillations to include an in-phase mode shape, wherein two wings move in equal directions. The in-phase mode shape is thought to have less equivalent stiffness, which allows for increased flapping amplitudes in a stiffer configuration. The capability of the Straight Linkage Concept to shift from one mode to the other is thought to allow for more elaborate and highly sensitive dynamic response modifications under limited local stiffness increase, allowing for high controllability with low control effort.