3,356 research outputs found
Formation of Multiple Groups of Mobile Robots Using Sliding Mode Control
Formation control of multiple groups of agents finds application in large
area navigation by generating different geometric patterns and shapes, and also
in carrying large objects. In this paper, Centroid Based Transformation (CBT)
\cite{c39}, has been applied to decompose the combined dynamics of wheeled
mobile robots (WMRs) into three subsystems: intra and inter group shape
dynamics, and the dynamics of the centroid. Separate controllers have been
designed for each subsystem. The gains of the controllers are such chosen that
the overall system becomes singularly perturbed system. Then sliding mode
controllers are designed on the singularly perturbed system to drive the
subsystems on sliding surfaces in finite time. Negative gradient of a potential
based function has been added to the sliding surface to ensure collision
avoidance among the robots in finite time. The efficacy of the proposed
controller is established through simulation results.Comment: 8 pages, 5 figure
A scalable nanogenerator based on self-poled piezoelectric polymer nanowires with high energy conversion efficiency
Nanogenerators based on piezoelectric materials convert ever-present
mechanical vibrations into electrical power for energetically autonomous
wireless and electronic devices. Nanowires of piezoelectric polymers are
particularly attractive for harvesting mechanical energy in this way, as they
are flexible, lightweight and sensitive to small vibrations. Previous studies
have focused exclusively on nanowires grown by electrospinning, but this
involves complex equipment, and high voltages of 10 kV that
electrically pole the nanowires and thus render them piezoelectric. Here we
demonstrate that nanowires of poly(vinylidene fluoride-trifluoroethylene)
(P(VDF-TrFE)) grown using a simple and cost-effective template-wetting
technique, can be successfully exploited in nanogenerators without poling. A
typical nanogenerator comprising 10 highly crystalline,
self-poled, aligned nanowires spanning 2 cm is shown to produce a
peak output voltage of 3 V at 5.5 nA in response to low-level vibrations. The
mechanical-to-electrical conversion efficiency of 11% exhibited by our
template-grown nanowires is comparable with the best previously reported
values. Our work therefore offers a scalable means of achieving
high-performance nanogenerators for the next generation of self-powered
electronics.SKN is grateful for support from the Royal Society through a Dorothy Hodgkin Fellowship. VN acknowledges the Herchel Smith Fund, University of Cambridge for a Fellowship. This work was supported by the EPSRC Cambridge NanoDTC, EP/G037221/1.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/aenm.20140051
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