92,048 research outputs found
Low-cost embedded system for relative localization in robotic swarms
In this paper, we present a small, light-weight, low-cost, fast and reliable system designed to satisfy requirements of relative localization within a swarm of micro aerial vehicles. The core of the proposed solution is based on off-the-shelf components consisting of the Caspa camera module and Gumstix Overo board accompanied by a developed efficient image processing method for detecting black and white circular patterns. Although the idea of the roundel recognition is simple, the developed system exhibits reliable and fast estimation of the relative position of the pattern up to 30 fps using the full resolution of the Caspa camera. Thus, the system is suited to meet requirements for a vision based stabilization of the robotic swarm. The intent of this paper is to present the developed system as an enabling technology for various robotic tasks
High-speed imaging and wavefront sensing with an infrared avalanche photodiode array
Infrared avalanche photodiode arrays represent a panacea for many branches of
astronomy by enabling extremely low-noise, high-speed and even photon-counting
measurements at near-infrared wavelengths. We recently demonstrated the use of
an early engineering-grade infrared avalanche photodiode array that achieves a
correlated double sampling read noise of 0.73 e- in the lab, and a total noise
of 2.52 e- on sky, and supports simultaneous high-speed imaging and tip-tilt
wavefront sensing with the Robo-AO visible-light laser adaptive optics system
at the Palomar Observatory 1.5-m telescope. We report here on the improved
image quality achieved simultaneously at visible and infrared wavelengths by
using the array as part of an image stabilization control-loop with
adaptive-optics sharpened guide stars. We also discuss a newly enabled survey
of nearby late M-dwarf multiplicity as well as future uses of this technology
in other adaptive optics and high-contrast imaging applications.Comment: Accepted to Astrophysical Journal. 8 pages, 3 figures and 1 tabl
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Enhanced aging properties of HKUST-1 in hydrophobic mixed-matrix membranes for ammonia adsorption.
Metal-organic frameworks (MOFs) in their free powder form have exhibited superior capacities for many gases when compared to other materials, due to their tailorable functionality and high surface areas. Specifically, the MOF HKUST-1 binds small Lewis bases, such as ammonia, with its coordinatively unsaturated copper sites. We describe here the use of HKUST-1 in mixed-matrix membranes (MMMs) prepared from polyvinylidene difluoride (PVDF) for the removal of ammonia gas. These MMMs exhibit ammonia capacities similar to their hypothetical capacities based on the weight percent of HKUST-1 in each MMM. HKUST-1 in its powder form is unstable toward humid conditions; however, upon exposure to humid environments for prolonged periods of time, the HKUST-1 MMMs exhibit outstanding structural stability, and maintain their ammonia capacity. Overall, this study has achieved all of the critical and combined elements for real-world applications of MOFs: high MOF loadings, fully accessible MOF surfaces, enhanced MOF stabilization, recyclability, mechanical stability, and processability. This study is a critical step in advancing MOFs to a stable, usable, and enabling technology
Design and Autonomous Stabilization of a Ballistically Launched Multirotor
Aircraft that can launch ballistically and convert to autonomous, free flying
drones have applications in many areas such as emergency response, defense, and
space exploration, where they can gather critical situational data using
onboard sensors. This paper presents a ballistically launched, autonomously
stabilizing multirotor prototype (SQUID, Streamlined Quick Unfolding
Investigation Drone) with an onboard sensor suite, autonomy pipeline, and
passive aerodynamic stability. We demonstrate autonomous transition from
passive to vision based, active stabilization, confirming the ability of the
multirotor to autonomously stabilize after a ballistic launch in a GPS denied
environment.Comment: Accepted to 2020 International Conference on Robotics and Automatio
Versatile silicon-waveguide supercontinuum for coherent mid-infrared spectroscopy
Infrared spectroscopy is a powerful tool for basic and applied science. The
molecular spectral fingerprints in the 3 um to 20 um region provide a means to
uniquely identify molecular structure for fundamental spectroscopy, atmospheric
chemistry, trace and hazardous gas detection, and biological microscopy. Driven
by such applications, the development of low-noise, coherent laser sources with
broad, tunable coverage is a topic of great interest. Laser frequency combs
possess a unique combination of precisely defined spectral lines and broad
bandwidth that can enable the above-mentioned applications. Here, we leverage
robust fabrication and geometrical dispersion engineering of silicon
nanophotonic waveguides for coherent frequency comb generation spanning 70 THz
in the mid-infrared (2.5 um to 6.2 um). Precise waveguide fabrication provides
significant spectral broadening and engineered spectra targeted at specific
mid-infrared bands. We use this coherent light source for dual-comb
spectroscopy at 5 um.Comment: 26 pages, 5 figure
Dual terahertz comb spectroscopy with a single free-running fibre laser
Dual THz comb spectroscopy has the potential to be used as universal THz
spectroscopy with high spectral resolution, high spectral accuracy, and broad
spectral coverage; however, the requirement for dual stabilized femtosecond
lasers hampers its versatility due to the bulky size, high complexity, and high
cost. We here report the first demonstration of dual THz comb spectroscopy
using a single free-running fibre laser. By tuning the cavity-loss-dependent
gain profile with an intracavity Lyot filter together with precise management
of the cavity length and dispersion, dual-wavelength pulsed light beams with
slightly detuned repetition frequencies are generated in a single laser cavity.
Due to sharing of the same cavity, such pulsed light beams suffer from
common-mode fluctuation of the repetition frequency, and hence the
corresponding frequency difference between them is passively stable around a
few hundred hertz within millihertz fluctuation. This considerably stable
frequency difference enables dual THz comb spectroscopy with a single
free-running fibre laser. While greatly reducing the size, complexity, and cost
of the laser source by use of a single free-running fibre laser, the dual THz
comb spectroscopy system maintains a spectral bandwidth and dynamic range of
spectral power comparable to a system equipped with dual stabilized fibre
lasers, and can be effectively applied to high-precision spectroscopy of
acetonitrile gas at atmospheric pressure. The demonstrated results indicate
that this system is an attractive solution for practical applications of not
only THz spectroscopy but also THz-pulse-based measurements.Comment: 29 pages, 7 figure
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