Understanding flight control at small scales
Flying insects can perform a wide range or aerial maneuvers better than any man-made flying device. Some insects can land upside down, change direction in a split of a second and engage prey or mates in mid-air. To achieve such impressive capabilities, insects have evolved unique flight mechanisms, including a control system that exhibits the fastest reflexes in the animal kingdom.
Our goal is to understand these flight control mechanisms experimentally and eventually implement them in robotic systems. This challenge involves cutting-edge topics in control theory, fluid dynamics, physiology, neuroscience and robotics.
Mid-Air Perturbations Reveals Roll Control
To study insect flight control we use the common fruit fly Drosophila melanogaster and a set of fast cameras that film the flies during free flight. We glue a tiny magnet to the back of each fly and use magnetic pulses to exert perturbation torques that rotate the flies in mid-air. By extracting the motion of the body and wings we aim to reverse-engineer the control-laws of the fly.
This movie shows a fruit fly recovers from a left-roll perturbation of 60 degrees. The magnetic perturbation pulse was one wing-beat long (5 ms, red line), and the fly started to respond within 5 ms from the pulse onset. The entire correction maneuver ended after 8 wing-beats.
Body Pitch Conrol
Changing the orientation of the magnet on the fly's back allows us to exert perturbation torques along different axes. This movie shows a fly recovering from a pitch-up perturbation.
Our method allows us to exert a wide range of perturbations and probe the flight envelope of the fly. This movie shows a perturbation where the fly was rolled over 8 times. During the perturbation the fly could not withstand the magnetic torque. but once the perturbation had ended, the fly went back in control within 4 wing beats. We haven't yet managed to make a fly dizzy.
Mimicry through motion:
ant-mimicry by a jumping spider
We discovered how the motion of an ant-mimicking spider makes it look like an ant to protect it from potential predators. Protective mimicry is a widespread phenomenon, in which a palatable species avoids predation by being mistaken for another, unpalatable species, called ‘model’. As such, protective mimicry is a striking example of adaptive evolution. Most studies on protective mimicry have focused on static traits, such as color and shape, rather than on dynamic traits like motion. Within terrestrial mimicry, mimicry of ants is among the most common, with spiders representing a large fraction of ant-mimicking species.
We used high-speed cameras and behavioral experiments to investigate the role of locomotor behavior in mimicry by the ant-mimicking jumping spider Myrmarachne formicaria. Contrary to previous suggestions, we found that mimics walk using all eight legs, raising their forelegs like ant antennae only for short stationary bouts. Strikingly, mimics exhibit winding trajectories that resemble the winding patterns of ants specifically engaged in pheromone-trail following, although mimics walked on chemically inert surfaces. Finally, we used behavioral experiments to show that a potential predator is, indeed, 'fooled' by the ant-like motion of the mimics.