Dr. Tyson Hedrick will study how animals achieve a variety of stable locomotor behaviors with a limited set of actuators of uncertain performance and a sensory system with inherent and variable delays. Specifically, the flight control of the hawkmoth Manduca sexta will be examined in a closed loop, free flight context using a combination of computational and experimental methods to analyze the system using engineering control theory. Feeding hawkmoths hover in front of the flower from which they draw nectar, and therefore must track the position and orientation of the flower. The flowers from which the hawkmoth feeds also tend to oscillate under the perturbation of a slight breeze or even the downward airflow generated by the moth''s own wings as it hovers near the flower. Thus, the hawkmoth has had to develop an effective tracking behavior, which can be elicited under laboratory conditions where the moth tracks the movements of a mechanically actuated artificial flower. This allows direct experimental manipulation and measurement of both the system input (flower position) and output (moth position) in a biologically relevant whole organism behavior. Furthermore, flower tracking is known to have an optical rather than tactile basis, and optic pathways are subject to large delays of 50 to 150 milliseconds, or 2 to 6 wingbeats. Orientation in flight is also partially sensed via optical pathways and is subject to these same delays. These delays may dominate the function of the controller to the extent that limitations in the neural and sensory systems require damping beyond what would be necessary for the biomechanical system considered separately. The influence of these different factors will be evaluated via extension of a dynamic simulation of the flight of Manduca sexta previously developed; this computational model will be used to evaluate the inferred flight control transfer functions in light of what is physically possible given the moth''s aerodynamics and maximum muscle power output. These results will establish a new system for examining closed loop control in freely behaving animals and will be of interest to researchers seeking to apply control theory to biological systems at a variety of scales. The broader impacts resulting from this proposed research include the exposure of high school and undergraduate students to hands-on, experimental approaches in organismal biology by way of laboratory assistanceships. Results from this research will be made available on the PI''s laboratory web site, presented at national and international conferences, and published in scientific journals. Finally, the results of this research will have applications to the flight and control of micro-air vehicles and other bio-mimentic engineering efforts.
