Meeting Abstract
Motor control of animals has been shown to be quite robust to mechanical and environmental variation. In studying motor control, tracking behaviors have revealed important insights into sensory processing and motor performance due to their well defined tasks. However, much of the work studying these behaviors has focused on manipulating the sensory side of the animal’s sensorimotor feedback loop and less on examining the robustness of animals to behaviorally relevant changes in their mechanics. The hawkmoth, Manduca sexta, forages nectar from flowers while hovering and will feed enough to increase their body mass by more than 70%. Using a robotic flower following a prescribed 2D sum-of-sines trajectory, we measured the dynamic response of continually feeding, freely flying moths for a 60 second period leading to a mean increase in mass of 26% (5% SD). We used a control theoretic feedback model assuming simple inertial mechanics to compare the observed change in response to a predicted, uncompensated response given the measured increase in body mass. If the moths did not compensate for increasing mass, the phase difference between the flower and moths would increase. However, the observed response shows a decrease in the phase lag of the moths as they feed. This suggests compensatory neural control that helps maintain the neuromechanical performance of the system. A possible method of compensation is the moth phase shifting its response forward while simultaneously reducing the gain. This model and method supports the idea of a high pass sensory controller leading to an overall low pass locomotor response as has been found in other locomoting animals. Furthermore, the method suggests how the moth may be adjusting to provide robust maneuverability in the face of an ecologically relevant change in inertia.
