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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.


Hahm M.G.,Rice University | Hahm M.G.,Shinshu University | Leela Mohana Reddy A.,Rice University | Cole D.P.,Motile Robotics Inc. | And 13 more authors.
Nano Letters | Year: 2012

Here, we design and develop high-power electric double-layer capacitors (EDLCs) using carbon-based three dimensional (3-D) hybrid nanostructured electrodes. 3-D hybrid nanostructured electrodes consisting of vertically aligned carbon nanotubes (CNTs) on highly porous carbon nanocups (CNCs) were synthesized by a combination of anodization and chemical vapor deposition techniques. A 3-D electrode-based supercapacitor showed enhanced areal capacitance by accommodating more charges in a given footprint area than that of a conventional CNC-based device. © 2012 American Chemical Society.


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.


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).


Riddick J.C.,U.S. Army | Hall A.,Motile Robotics Inc.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

Army combat operations have placed a high premium on reconnaissance missions for micro air vehicles (MAVs). An analysis of insect flight indicates that in addition to the bending excitation (flapping), simultaneous excitation of the twisting degree-of-freedom is required to manipulate the control surface adequately. By adding a layer of angled piezoelectric segments to a Pb(Zr,Ti)O 3 (PZT) bimorph actuator, a bend-twist coupling may be introduced to the flexural response of the layered PZT, thereby creating a biaxial actuator capable of driving wing oscillation in flapping wing MAVs. The present study presents numerical solutions to governing equations for quasi-static three-dimensional bending of functionally-modified bimorph designs intended for active bend-twist actuation of cm-scale flapping wing devices. The results indicate a strong dependence of bimorph deflection on overall length. Further, the width and angle of orientation of the angled piezoelectric segments may be manipulated in order to increase or decrease the length effects on bimorph deflection. The relationships of geometry and orientation of the angled segments with bimorph flexural response are presented. © 2011 SPIE.


Kessens C.C.,University of Maryland University College | Kessens C.C.,Motile Robotics Inc. | Kessens C.C.,U.S. Army | Desai J.P.,University of Maryland University College
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2010

Suction cups have long been used as a means to grasp and manipulate objects. They enable active control of grasp, enhance grasp stability, and handle some objects such as large flat plates more easily than standard graspers. However, the application of suction cups to object manipulation has been confined to a relatively small, well-defined problem set. Their potential for grasping a large range of unknown objects remains relatively unexplored. This seems in part due to the complexity involved with the design and fabrication of various materials comprising the grasper as well as actuators used to enable grasping. This paper introduces the design of a suction cup that is "self-selecting." In other words, the suction cups comprising the grasper do not exert any suction force when the cup(s) are not in contact with the object, but instead exert a suction force only when they are in physical contact with the object. Since grasping is achieved purely by passive means, the cost and weight associated with individual sensors, valves, and/or actuators are essentially eliminated. Furthermore, the design permits the use of a central vacuum pump, thereby maximizing the suction force on an object and enabling some suction on surfaces that may prohibit tight seals. This paper presents the design, analysis, fabrication, and experimental results of such a "self-selecting" suction cup array. ©2010 IEEE.


Orsag M.,University of Zagreb | Korpela C.,Drexel University | Pekala M.,Motile Robotics Inc. | Oh P.,Drexel University
Proceedings of the American Control Conference | Year: 2013

Aerial manipulation, grasping, and perching in small unmanned aerial vehicles (UAVs) require specific control systems to compensate for changing inertial properties. Grasped objects, external forces from terrain objects, or manipulator movements themselves may destabilize or otherwise alter the flight characteristics of small UAVs during operation resulting in undesirable outcomes. Traditional control methods that assume static mass and inertial properties must be modified to produce stable control of a quadrotor system. This paper presents work towards a control scheme to achieve dynamic stability of an aerial vehicle while under the influence of manipulators and grasped objects. A quadrotor with attached multi-degree of freedom manipulators is implemented in simulation and constructed for testing. Compensation of the inertial changes due to in-flight manipulator movements is investigated. A control scheme is developed and results are presented. © 2013 AACC American Automatic Control Council.


Korpela C.,Drexel University | Orsag M.,University of Zagreb | Pekala M.,Motile Robotics Inc. | Oh P.,Drexel University
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2013

This paper presents a control scheme to achieve dynamic stability in an aerial vehicle with dual multi-degree of freedom manipulators. Arm movements assist with stability and recovery for ground robots, in particular humanoids and dynamically balancing vehicles. However, there is little work in aerial robotics where the manipulators themselves facilitate flight stability or the load mass is repositioned in flight for added control. We present recent results in arm motions that achieve increased flight stability without and with different load masses attached to the end-effectors. Our test flight results indicate that we can accurately model and control our aerial vehicle when both moving the manipulators and interacting with target objects. © 2013 IEEE.


Patent
University of Maryland College Park and Motile Robotics Inc. | Date: 2010-10-08

A suction gripper includes a cup member, a suction port, and a valve. The cup member has inner and outer surfaces defining an opening such that the inner surface defines an inner cavity. The suction port provides suction. The valve in is fluid communication with the suction port and the inner cavity of the cup member to modify the suction therebetween. The valve is operatively coupled to the cup member and is adapted to passively actuate in response to an applied force to the cup member.


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.

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