Pixels operate locally. Superpixels have some potential to collect information across many pixels; supervoxels have more potential by implicitly operating across time.   In this work, we explore this well established notion thoroughly analyzing how supervoxels can be used in place of and in conjunction with other means of aggregating information across space-time.  Focusing on the problem of strictly unsupervised video object segmentation, we devise a method called supervoxel gerrymandering that links masks of foregroundness and backgroundness via local and non-local consensus measures.  We pose and answer a series of critical questions about the ability of supervoxels to adequately sway local voting; the questions regard type and scale of supervoxels as well as local versus non-local consensus, and the questions are posed in a general way so as to impact the broader knowledge of the use of supervoxels in video understanding. We work with the DAVIS dataset and find that our analysis yields an unsupervised method that outperforms all other known unsupervised methods and even many supervised ones. This research is performed in collaboration with Professor Jason Corso.

Robust robot walking control

Bipedal locomotion is well suited for mobile robotics because it promises to allow robots to traverse difficult terrain and work effectively in man-made environments. Despite this inherent advantage, however, no existing bipedal robot achieves human-level performance in multiple environments. A key challenge in robotic bipedal locomotion is the design of feedback controllers that function well in the presence of uncertainty, in both the robot and its environment. To achieve such walking, we design feedback controllers and periodic gaits that function well in the presence of modest terrain variation, without reliance on perception or a priori knowledge of the environment. Model-based design methods are introduced and subsequently validated in simulation and experiment on MARLO, an underactuated three-dimensional bipedal robot that is roughly human size and has six actuators and thirteen degrees of freedom. Innovations include virtual nonholonomic constraints that enable continuous velocity-based posture regulation and an optimization method that accounts for multiple types of disturbances and more heavily penalizes deviations that persist during critical stages of walking. Using a single continuously-defined controller taken directly from optimization, MARLO traverses sloped sidewalks and parking lots, terrain covered with randomly thrown boards, and grass fields, all while maintaining average walking speeds between 0.9-0.98 m/s and setting a new precedent for walking efficiency in realistic environments. This research is performed in collaboration with Professor Jessy Grizzle.

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Wireless Power Transfer to Ground Sensors from a UAV

Wireless magnetic resonant power transfer is an emerging technology that has many advantages over other wireless power transfer methods due to its safety, lack of interference, and efficiency at medium ranges.  We develop a wireless magnetic resonant power transfer system that enables unmanned aerial vehicles (UAVs) to provide power to, and recharge batteries of, wireless sensors and other electronics far removed from the electric grid. We address the difficulties of implementing and outfitting this system on a UAV with limited payload capabilities and develop a controller that maximizes the received power as the UAV moves into and out of range. We experimentally demonstrate the prototype wireless power transfer system by using a UAV to transfer nearly 5W of power to a ground sensor. Motivated by limitations of manual piloting, steps are taken toward autonomous navigation to locate receivers and maintain more stable power transfer. Novel sensors are created to measure high frequency alternating magnetic fields, and data from experiments with these sensors illustrate how they can be used for locating nodes receiving power and optimizing power transfer. This research is performed in collaboration with Professor Carrick Detweiler.

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