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Kessens C.C.,U.S. Army | Kessens C.C.,University of Maryland University College | Smith D.C.,U.S. Army | Smith D.C.,West Virginia University | And 2 more authors.
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2012

Increasingly, robots are being applied to challenges in dynamic, unstructured environments including urban search and rescue (USAR), planetary exploration, and military missions. During the execution of these missions, the robot may unintentionally tip over, rendering it unable to move normally. The ability to self-right and recover in such situations is crucial to mission completion and safe robot recovery. However, to date, nearly all self-righting solutions have been point solutions, each designed for a specific platform. As a first step toward a generic solution, this paper presents a framework for analyzing the self-righting capabilities of any generic robot on sloped planar surfaces. Based on the planar assumption, interactions with the ground can be defined entirely in terms of the robot's convex hull. Motion of arms, legs, or other appendages may change the convex hull shape and/or center of mass position, affecting the robot's orientation. Our framework for solving this problem can be summarized as follows: first, for each stable conformation, we analyze the position of the center of mass relative to the vertical projection of the convex hull face in contact with the ground. From this, we develop a conformation space map, defining stable state sets as nodes and the conformations where discontinuous state changes occur as transitions. Finally, we convert this map into a directed graph, and assign costs to the transitions according to changes in potential energy between states. Based upon the ability to traverse this directed graph to the goal state, one can analyze a robot's ability to self-right. To illustrate each step in our framework, we use a simple two-dimensional robot with a one degree of freedom arm, and then show a case study of iRobot's 510 Packbot®. Ultimately, we project that this framework will be useful both for designing robots with the ability to self-right and for planning joint movements to achieve efficient, autonomous self-righting behaviors. © 2012 IEEE. Source

Fullerton R.J.,Texas Tech University | Cole D.P.,Motile Robotics Inc. | Behler K.D.,U.S. Army | Das S.,Texas Tech University | And 5 more authors.
Carbon | Year: 2014

We describe a novel approach for coupling pristine graphene with superparamagnetic iron oxide nanoparticles to create dispersed, magnetically responsive hybrids. The magnetic iron oxide (Fe3O4) nanoparticles are synthesized by a co-precipitation method using ferric (Fe 3+) and ferrous (Fe2+) salts and then grafted with polyvinylpyrrolidone (PVP). These PVP-grafted Fe3O4 nanoparticles are then used to stabilize colloidal graphene in water. The PVP branches non-covalently attach to the surface of the pristine graphene sheets without functionalization or defect creation. These Fe3O 4-graphene hybrids are stable against aggregation and are highly responsive to external magnetic fields. These hybrids can be freeze-dried to a powder or magnetically separated from solution and still easily redisperse while retaining magnetic functionality. At all stages of synthesis, the Fe 3O4-graphene hybrids display no coercivity after being brought to magnetic saturation, confirming superparamagnetic properties. Microscopy and light scattering data confirm the presence of pristine graphene sheets decorated with Fe3O4 nanoparticles. These materials show promise for multifunctional polymer composites as well as biomedical applications and environmental remediation. © 2014 Elsevier Ltd. All rights reserved. Source

Rivera M.,Motile Robotics Inc.
SAE International Journal of Materials and Manufacturing | Year: 2012

The range and duration of micro vehicles, and in particular, micro aerial vehicles, is significantly restricted due to the limitations of available on-board energy storage devices. The number and type of energy storage units that can be housed in the vehicle structures is significantly limited by the demanding voltage and power requirements and stringent size and weight constraints of the vehicle. While most commercial and developmental vehicle platforms currently utilize commercial-off-the-shelf lithium polymer batteries for their energy storage needs, endurance times are limited to minutes and high discharge rates and dynamic electrical loads limit battery life. Recently, researchers have demonstrated the ability to produce lightweight, flexible energy storage devices based on nanomaterials such as carbon nanotubes and graphene. Due to their low mass, small size, and high energy storage potential, carbon nanomaterial-based energy storage devices are excellent candidates for use in micro vehicle applications. Because the performance of these prototypical devices is still limited, a significant amount of research must first be conducted before these energy storage devices can be incorporated into a micro vehicle platform. This work will examine existing energy storage devices in the context of micro vehicle applications, review recent advances in energy storage technologies, and discuss how these technologies may affect future micro vehicle design and performance. Source

Cole D.P.,Motile Robotics Inc. | Reddy A.L.M.,Rice University | Hahm M.G.,Rice University | McCotter R.,Rice University | And 5 more authors.
Advanced Energy Materials | Year: 2014

Aligned carbon nanotube (CNT) forests filled with a dehydrated polymer electrolyte are used to fabricate flexible solid state supercapacitors (SSCs) for multifunctional structural-electronic applications. Local stiffness measurements on the composite electrodes determined through nanoindentation showed an 80% increase over the neat solid polymer electrolyte matrix. Electrochemical properties are monitored as a function of average tensile strain in the SSCs. Galvanostatic charge-discharge tests with in situ microtensile testing on SSCs are used to show a 10% increase in the specific capacitance through the elastic region of the composite. The increase in capacitance is partly attributed to the enhanced double layer interaction that results from the partial alignment of the polymer electrolyte chains at the electrode- electrolyte interface. When soaked in 1 m sulfuric acid, the specific capacitance of the CNT-polymer electrolyte reached approximately 72 F g -1 at 60 °C. The electromechanical behavior of a flexible, solid state supercapacitor is examined. The structural-electronic material is characterized with galvanostatic charge-discharge with in situ microtensile testing. The capacitance increases by ≈10% as the supercapacitor is mechanically loaded, which is attributed to enhanced electrode-electrolyte interaction. Nanoindentation is used to show improved local mechanical behavior of the composite electrode with respect to the neat polymer electrolyte. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Garcia R.D.,Motile Robotics Inc. | Brown A.,U.S. Army
Journal of Intelligent and Robotic Systems: Theory and Applications | Year: 2011

According to Federal Aviation Administration (FAA) statistics on mechanical failures, tail rotor failure is the third highest cause of fatal accidents in helicopters. Tail rotor failure represents a serious hazard to personnel and mission objectives and can create high fiscal loss. This is especially true for unmanned helicopters, which cannot be equipped with the fail-safes standard on manned counterparts. This work provides an overview of how a helicopter can be controlled after a tail rotor failure and its applicability to both manned and unmanned vehicles. This work specifically details some of the limitations of this type of software failure control. © 2010 Springer Science+Business Media B.V. (outside the USA). Source

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