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College Park, MD, United States

Mathai P.P.,U.S. National Institute of Standards and Technology | Mathai P.P.,University of Maryland University College | Carmichael P.T.,U.S. National Institute of Standards and Technology | Shapiro B.A.,U.S. National Institute of Standards and Technology | And 3 more authors.
RSC Advances | Year: 2013

We present a material-property independent method for manipulating both the position and orientation of nanowires (NWs), by feedback control of flows. For example, the NWs need not be electromagnetically polarizable. Control of NWs in a microfluidic device is demonstrated across a 170 μm × 170 μm region with on-demand trapping, translation, and simultaneous rotation of dielectric, semiconducting, and metallic NWs. An average trapping precision of 0.6 μm in position and 5.4° in orientation is achieved for the NWs considered, making it attractive for sensing and directed assembly applications. This journal is © 2013 The Royal Society of Chemistry.

Gerdes J.W.,University of Maryland University College | Gupta S.K.,Institute for Systems Research | Wilkerson S.A.,U.S. Army
Proceedings of the ASME Design Engineering Technical Conference | Year: 2010

Physical and aerodynamic characteristics of the bird in flight may offer benefits over typical propeller or rotor driven miniature air vehicle (MAV) locomotion designs in certain types of scenarios. A number of research groups and companies have developed flapping wing vehicles that attempt to harness these benefits. The purpose of this paper is to report different types of flapping wing designs and compare their salient characteristics. For each category, advantages and disadvantages will be discussed. The discussion presented will be limited to miniature-sized flapping wing air vehicles, defined as 10-100 grams total weight. The discussion will be focused primarily on ornithopters which have performed at least one successful test flight. Additionally, this paper is intended to provide a representation of the field of current technology, rather than providing a comprehensive listing of all possible designs. This paper will familiarize a newcomer to the field with existing designs and their distinguishing features. By studying existing designs, future designers will be able to adopt features from other successful designs. This paper also summarizes the design challenges associated with the further advancement of the field and deploying flapping wing vehicles in practice. © 2010 by ASME.

Mallik A.,College Park | Mallik A.,Institute for Systems Research | Faulkner B.,Virginia Polytechnic Institute and State University | Khaligh A.,College Park | Khaligh A.,Institute for Systems Research
Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC | Year: 2016

Advances in power electronics are enabling More Electric Aircrafts (MEAs) to replace pneumatic systems with electrical systems. Active power factor correction (PFC) rectifiers are used in MEAs to rectify the output voltage of the three-phase AC-DC boost converter, while maintaining a unity input power factor. Many existing control strategies implement PI compensators, with slow response times, in their voltage and current loops. Alternatively, computationally expensive nonlinear controllers can be chosen to generate input currents with high power factor and low total harmonic distortion (THD), but they may need to be operated at high switching frequencies due to relatively slower execution of control loop. In this work, a novel control strategy is proposed for a three-phase, single-stage boost-type rectifier that is capable of tight and fast regulation of the output voltage, while simultaneously achieving unity input power factor, without constraining the operating switching frequency. The proposed control strategy is implemented, using one voltage-loop PI controller and a linearized transfer function of duty-ratio to input current, for inner loop current control. A 1.5 kW three-phase boost PFC prototype is designed and developed to validate the proposed control algorithm. The experimental results show that an input power factor of 0.992 and a tightly regulated DC link voltage with 3% ripple can be achieved. © 2016 IEEE.

Galloway K.S.,U.S. Naval Academy | Justh E.W.,U.S. Navy | Krishnaprasad P.S.,Institute for Systems Research | Krishnaprasad P.S.,University of Maryland University College
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2013

We specify and analyse models that capture the geometry of purposeful motion of a collective of mobile agents, with a focus on planar motion, dyadic strategies and attention graphs which are static, directed and cyclic. Strategies are formulated as constraints on joint shape space and are implemented through feedback laws for the actions of individual agents, here modelled as self-steering particles. By reduction to a labelled shape space (using a redundant parametrization to account for cycle closure constraints) and a further reduction through time rescaling, we characterize various special solutions (relative equilibria and pure shape equilibria) for cyclic pursuit with a constant bearing (CB) strategy. This is accomplished by first proving convergence of the (nonlinear) dynamics to an invariantmanifold (the CB pursuit manifold), and then analysing the closedloop dynamics restricted to the invariant manifold. For illustration, we sketch some low-dimensional examples. This formulation-involving strategies, attention graphs and sensor-driven steering laws- and the resulting templates of collective motion, are part of a broader programme to interpret the mechanisms underlying biological collective motion. © 2013 The Author(s).

Strunz R.,Airbus | Strunz R.,University of Maryland University College | Herrmann J.W.,University of Maryland University College | Herrmann J.W.,Institute for Systems Research
Journal of Propulsion and Power | Year: 2011

Manufacturers lack an adequate method to balance performance, reliability, and affordability. The reliability-asan-independent-variable methodology is the solution proposed by expressing quantitatively the reliability trade space as ranges of a number of hardware sets and a number of hot-fire tests necessary to develop and qualify/certify a liquid rocket engine against a stated reliability requirement. Therefore, reliability-as-an-independent-variable becomes one of the key decision parameters in early tradeoff studies for liquid rocket engines because the reliability trade space directly influences the performance requirements and, as a result, the affordability. The overall solution strategy of reliability-as-an-independent-variable is based on the Bayesian statistical framework using either the planned or actual number of hot-fire tests. The planned hot-fire test results may include test failures to simulate the typical design-fail-fix-test cycles present in liquid rocket engine development programs in order to provide the schedule and cost risk impacts for early tradeoff studies. The reliability-as-an-independent-variable methodology is exemplarily applied to the actual hot-fire test history of the F-1, the space shuttle main engine, and the RS-68 liquid rocket engine, showing adequate agreement between computed results and actual flight engine reliability. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc.

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