  Whenever a flapping robot moves along a trajectory it experiences some
vibration about its mean path. Even for a hovering case, a flier experiences
such vibration due to the oscillatory nature of the aerodynamic forces. In this
paper we have studied the effect of such vibration on hovering. We used two
setups to measure thrust force generated by flapping robots. One involving
loadcell, which does not allow any kind of vibration. The other one involves a
pendulum which allows vibration at a particular direction. We used two
different flapping robots; one is a traditional flapping robot with two wings
and the other one is a four wings robot which exploits clap and peel mechanism
to generate thrust. We observed that the loadcell setup measures more thrust
for the two wings model than the pendulum setup. The opposite trend was
observed for the four wings model. We measured the vibration induced velocity
using motion capture system. We used well known aerodynamic models to observe
the effect of the vibration during the flapping cycle. To gain physical insight
into the vibration affected flow field, we used smoke flow visualization at
different instances during the flapping cycle. It revealed that the
perturbation ebbs a jet effect in case of the two wings which leads to its
adverse effect for thrust generation. On the contrary the perturbation enhances
the clapping effect for the four wings robot, resulting favorable for thrust
generation.
