5,962 research outputs found
Development of Navigation Control Algorithm for AGV Using D* Search Algorithm
In this paper, we present a navigation control algorithm for Automatic Guided Vehicles (AGV) that move in industrial environments including static and moving obstacles using D* algorithm. This algorithm has ability to get paths planning in unknown, partially known and changing environments efficiently. To apply the D* search algorithm, the grid map represent the known environment is generated. By using the laser scanner LMS-151 and laser navigation sensor NAV-200, the grid map is updated according to the changing of environment and obstacles. When the AGV finds some new map information such as new unknown obstacles, it adds the information to its map and re-plans a new shortest path from its current coordinates to the given goal coordinates. It repeats the process until it reaches the goal coordinates. This algorithm is verified through simulation and experiment. The simulation and experimental results show that the algorithm can be used to move the AGV successfully to reach the goal position while it avoids unknown moving and static obstacles. [Keywords— navigation control algorithm; Automatic Guided Vehicles (AGV); D* search algorithm
Path Tracking Controller of Quadruped Robot for Obstacle Avoidance Using Potential Functions Method
This paper proposes a tracking controller for obstacle avoidance of a quadruped robot using potential functions method. The followings are done for this task. At first, a ceiling-mounted camera system is installed for image processing. The goal point and obstacles are separated and recognized by a color recognition method. Second, a path planning algorithm using potential functions method is proposed to generate the path to avoid obstacles and to plan a path for the quadruped robot to reach from start point to goal point. Third, a quadruped robot is chosen as the mobile platform for this study and the kinematic model for the robot is presented. Fourth, a tracking controller is designed for the quadruped robot to track the trajectory based on the backstepping method using Lyapunov function. Finally, the simulation results are presented to show the effectiveness of the proposed trajectory planning algorithm and the tracking controller. [Keywords— Path tracking; back stepping; obstacles avoidance; potential functions; quadruped robot]
Understanding eigenfrequency shifts observed in vortex gyrotropic motions in a magnetic nanodot driven by spin-polarized out-of-plane dccurrent
We observed sizable eigenfrequency shifts in spin-polarized dc-current-driven vortex gyrotropic motions in a soft magnetic nanodot, and clarified the underlying physics through micromagnetic numerical calculations. It was found that the vortex eigenfrequency is changed to higher (lower) values with increasing Oersted field (OH) strength associated with the out-of-plane dc current for the vortex chirality parallel (antiparallel) to the rotation sense of the OH circumferential in-plane orientation. The eigenfrequency shift was found to be linearly proportional to the current density j0 in the linear regime as in ?? D ≃?? j0 / G, where G is the gyrovector constant and is a positive constant, e.g., 1.9?? 10-8 erg/A for a model Permalloy dot of 300 nm diameter and 20 nm thickness. This behavior originates from the sizable contribution of the OH to the effective potential energy of a displaced vortex core in the gyrotropic motion. The present results reveal that D, an intrinsic dynamic characteristic of a given nanodot vortex state, is controllable by changes in both the density and direction of spin-polarized out-of-plane dc currents.open191
Printing of wirelessly rechargeable solid-state supercapacitors for soft, smart contact lenses with continuous operations
Recent advances in smart contact lenses are essential to the realization of medical applications and vision imaging for augmented reality through wireless communication systems. However, previous research on smart contact lenses has been driven by a wired system or wireless power transfer with temporal and spatial restrictions, which can limit their continuous use and require energy storage devices. Also, the rigidity, heat, and large sizes of conventional batteries are not suitable for the soft, smart contact lens. Here, we describe a human pilot trial of a soft, smart contact lens with a wirelessly rechargeable, solid-state supercapacitor for continuous operation. After printing the supercapacitor, all device components (antenna, rectifier, and light-emitting diode) are fully integrated with stretchable structures for this soft lens without obstructing vision. The good reliability against thermal and electromagnetic radiations and the results of the in vivo tests provide the substantial promise of future smart contact lenses
Enhancing 2D Growth of Organic Semiconductor Thin Films with Macroporous Structures via a Small-Molecule Heterointerface
The physical structure of an organic solid is strongly affected by the surface of the underlying substrate. Controlling this interface is an important issue to improve device performance in the organic electronics community. Here we report an approach that utilizes an organic heterointerface to improve the crystallinity and control the morphology of an organic thin film. Pentacene is used as an active layer above, and m-bis(triphenylsilyl) benzene is used as the bottom layer. Sequential evaporations of these materials result in extraordinary morphology with far fewer grain boundaries and myriad nanometre-sized pores. These peculiar structures are formed by difference in molecular interactions between the organic layers and the substrate surface. The pentacene film exhibits high mobility up to 6.3 cm(2)V(-1)s(-1), and the pore-rich structure improves the sensitivity of organic-transistor-based chemical sensors. Our approach opens a new way for the fabrication of nanostructured semiconducting layers towards high-performance organic electronics.X116049Nsciescopu
Soft X-ray Circular Reflectivity from Ferromagnetic Transition-Metal Films Near the Brewster's Angle: Theoretical and Numerical X-ray Resonant Magnetic Scattering Study
We first report a novel phenomenon that manifests itself in a colossal
difference in soft x-ray reflectivity from ferromagnetic transition-metal films
between the left- and right-handed circular polarization (LCP and RCP) modes at
a resonance near normal Brewster's angle. Theoretical and numerical studies of
sft x-ray resonant magnetic scattering using the circular-polarization-mode
basis reveal that this effect arises from a totally destructive interference of
photons scattered individually from chargem orbital, and spin degrees of
freedom in magnetized thin films that selectively occurs only for one helicity
of the opposite circular modes when the required criteria are fulfilled. Across
the normal Brewster's angle. the polarization state of scattered soft x-ray is
continuously variable from the RCP to the LCP mode (or vice versa) through the
linear s polarization mode by changing the incidence angle of linear
p-polarized x rays at the resonance.Comment: 16 pages, 3 figures, 1 tabl
Solid-state metathesis reactions under pressure: A rapid route to crystalline gallium nitride
High pressure chemistry has traditionally involved applying pressure and increasing temperature until conditions become thermodynamically favorable for phase transitions or reactions to occur. Here, high pressure alone is used as a starting point for carrying out rapid, self-propagating metathesis reactions. By initiating chemical reactions under pressure, crystalline phases, such as gallium nitride, can be synthesized which are inaccessible when initiated from ambient conditions. The single-phase gallium nitride made by metathesis reactions under pressure displays significant photoluminescence intensity in the blue/ultraviolet region. The absence of size or surface-state effects in the photoluminescence spectra show that the crystallites are of micron dimensions. The narrow lines of the x-ray diffraction patterns and scanning electron microscopy confirm this conclusion. Brightly luminescent thin films can be readily grown using pulsed laser deposition
Electron orbital valves made of multiply connected armchair carbon nanotubes with mirror-reflection symmetry: tight-binding study
Using the tight-binding method and the Landauer-B\"{u}ttiker conductance
formalism, we demonstrate that a multiply connected armchair carbon nanotube
with a mirror-reflection symmetry can sustain an electron current of the
-bonding orbital while suppress that of the -antibonding orbital over
a certain energy range. Accordingly, the system behaves like an electron
orbital valve and may be used as a scanning tunneling microscope to probe
pairing symmetry in d-wave superconductors or even orbital ordering in solids
which is believed to occur in some transition-metal oxides.Comment: 4 figures, 12 page
Schwinger Pair Production at Finite Temperature in Scalar QED
In scalar QED we study the Schwinger pair production from an initial ensemble
of charged bosons when an electric field is turned on for a finite period
together with or without a constant magnetic field. The scalar QED Hamiltonian
depends on time through the electric field, which causes the initial ensemble
of bosons to evolve out of equilibrium. Using the Liouville-von Neumann method
for the density operator and quantum states for each momentum mode, we
calculate the Schwinger pair-production rate at finite temperature, which is
the pair-production rate from the vacuum times a thermal factor of the
Bose-Einstein distribution.Comment: RevTex 10 pages, no figure; replaced by the version accepted in Phys.
Rev. D; references correcte
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