Hawkmoths, Manduca sexta, feed mainly during early morning and late evening in low light conditions by hovering and tracking moving flowers. The variable lighting conditions in which the hawkmoths feed in nature allow for the perfect setting to examine how visual signal acquisition can affect the performance of motor controlled tasks. By varying the luminance levels, it could result in a change in the amount of time it takes for hawkmoths to react to visual stimuli. In other words, motion-sensing tasks, like tracking a moving flower while feeding, may vary with the background sensory environment. We tested our hypothesis with freely flying moths feeding from a robotically actuated artificial flower at a low luminance level of .3 lux and a high luminance level of 300 lux. Because the flower motion was composed of the superposition of multiple sine waves (0.2-20 Hz), we were able to examine how moths responded at different frequency levels, making it possible to reconstruct a performance pattern. The flower's movement was done in both the vertical and horizontal axes. By calculating the coherence at each frequency, gain, and phase delay, we discovered that moths reliably track at frequencies exceeding 5 Hz. As predicted, we perceived much larger processing delays from the moth's response to the flower's movement at lower luminance levels than higher. This processing delay corresponds to moths being able to perceive and react to visual stimuli 16ms faster at high luminance levels than low luminance levels. At low luminance levels, moths actually overcorrected by overshooting the flower's position at peak tracking frequencies (1-2Hz), possibly due to longer integration delays. Future experiments involve integrating two degrees of freedom by combining multiple axes. Background sensory environment significantly alters the performance of an ecologically-relevant tracking behavior as predicted from sensory neurophysiological mechanisms.

 Flying organisms achieve flight stability by employing a multitude of control surfaces, most notably the wings. However, airframe deformations, such as abdominal motions in the hawk moth Manduca sexta, have recently been shown to play a significant role in stabilizing flight. In my research I have studied the control potential of abdominal deflections using a closed-loop flight arena. Tethered moths controlled the velocity of a projected black bar with their abdominal angle. Image velocity varied according to the difference between the abdominal angle and the set point (relative to the average abdominal angle), scaled by a gain factor. Experimental trials were performed for a ten-fold range of gains at three different set points and consisted of 60s periods during which the moths attempted to stabilize the drifting bar. The moths were capable of stabilizing the image for all experimental conditions, with the highest average performance (50%) occurring at the medium gain and the set point corresponding to the average abdominal angle. Poor performance (<50%) during low gain trials was characterized by steady state error, likely the result of the relatively low image velocities. For high gain trials, the decreased performance (<35%) was characterized by large abdominal oscillations. These results support an active and plastic role for the abdomen in flight control, but also tested the limits of the abdominal control circuit. To continue exploring the role of the abdominal motion I have been working on performing EMG recordings from the abdominal muscles during free flight. For this research the virtual arena serves as a controlled environment to collect preliminary data and to refine the experimental procedure and animal preparation. Finally, I will present my work developing a biometric controller for the Parrot AR.Drone quadrotor. This project utilized a Kinect and custom software to control the quadrotor with body postures.

Every aspect of nature is governed by the laws of physics. These laws include the basic principle of the center of gravity which is defined as a point in an object’s body at which the total net torque due to gravity equals zero. Understanding and applying this basic principle is crucial for dancers if they are to be successful movers. Yet the popular form of dance known as breaking seems to defy the laws of physics, particularly static equilibrium – a state where an object will not rotate unless an external force is applied because the center of gravity is located above an object’s base of support. Many breakers are able to perform gravity defying movements as they invert their bodies and hold various poses known as “freezes.” Using a series of cameras and a three-dimensional (3D) modeling program, I am able to locate the center of gravity in individual breakers and reveal that their movements do not violate the laws of physics. Using the information collected from this research, I can then propose and create new possibilities for freezes based on the concepts of static equilibrium. This research will be a stepping stone for further biomechanical researches in breaking and other forms of dance. Similar experimental techniques can be used to analyze more complex principles such as dynamic equilibrium – balance while in motion.

The field of Brain Computer Interface (BCI) systems is concerned with the study of how thoughts alone can be used to interface with and control the actions of external systems. Such BCI systems have been actively studied since 1969 when the seminal work of Fitz, et. al. at the University of Washington showed that monkeys could voluntarily control the deflection of an external meter with their thoughts alone. To date, there has been extensive research in this area as concerns thought-control of external devices in focused-activity environments, such as video gaming, but research into the effectiveness of BCI methods in more-realistic, distracted-environments is somewhat sparse, with notable exceptions including the work of Lalor, et. al., who performed a non-controlled and non-randomized study of the effects of Steady-State Visual Evoked Potentials (SSVEP) on real-time video-gaming control and Friedricha, et. al. who performed a study on the effects of auditory distractions on the accuracy of BCIs. Our present study represents a refinement of the Lalor approach in a broader scope than video-game control through the addition of more carefully defined controls, and we further extend this research through the study of the effects of simultaneous auditory and visual environmental conditioning. Based on the study of Friedricha, et. al. involving auditory distractions, we expect a constant auditory tone to have no impact on BCI performance.

Acoustic levitation is a method of levitating matter against the influence of gravity using sound waves.  Small droplets of fluid can, for example, be suspended in standing wave fields produced by high-power ultrasonic transducers at locations where the gradients of the sound field potentials counterbalance the gravitational forces acting on the droplets, creating a simulated microgravity environment.  These environments could be useful in simulating and studying how chemical and biochemical reactions might take place in space.  Our research builds on earlier work by J.Santa Cruz and J. Griffith who successfully achieved acoustic levitation at EdCC in 2011.  Santa Cruz and Griffith were able to experimentally demonstrate rough preliminary agreement with Bjerknes theory for levitation stability points in a planar field approximation, but they also observed stable particle orbits completely beyond explanation by the planar theory.  Here, we compare our experimental findings to the more general Gor’kov theory of levitation to explain both one- and two-dimensional levitation stability subspaces.