17 research outputs found
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Systems for pervasive electronics and interfaces
Energy Harvesting Active Networked Tags (EnHANTs) are a new type of wireless device in the domain between RFIDs and sensor networks. Future EnHANTs will be small, flexible, and self-powered devices that can be attached to everyday objects that are traditionally not networked to enable "Internet of Things" applications. This work describes the design and development of the EnHANT prototypes and testbed. The current prototypes use thin-film photovoltaics optimized for indoor light harvesting, form multihop networks using ultra-low-power Ultra-Wideband Impulse Radio (UWB-IR) transceivers, and implement energy harvesting adaptive networking protocols. The current testbed enables the evaluation of different algorithms by exposing individual prototypes to repeatable light conditions based on real-world irradiance data. New approaches to characterizing the energy available to energy harvesting devices were explored. A mobile data-logger was used to record the intensity of ambient light, determine the light source, and record the acceleration from motion during different real world activities. These traces were used to model the behavior of photovoltaic and inertial energy harvesters in real world deployments and can be replayed in the EnHANTs testbed. In addition, new techniques to evaluate the efficiency of different photovoltaic technologies under indoor illumination were developed. A proof-of-concept system was built to characterize photovoltaics under a standardized set of conditions in which the radiant intensity and spectral composition of the light source were systematically varied. Techniques to structure student research projects within the EnHANTs project were developed. Project-based learning approaches were implemented to engage students using real-world system development constraints. A survey of the students showed that this approach is an effective method for developing technical, professional, and soft skills. Open source hardware was also applied to EnHANTs project and extended into other domains. A laboratory-based class in flat panel display technology was developed. The course introduces fundamental concepts of display systems and reinforces these concepts through the fabrication of three display devices. A lab kit platform was developed to enable remote students to use low-cost, course specific hardware to complete the lab exercises remotely. This platform was also applied to external projects targeted at non-university students. A workshop was developed to teach artists, designers, and hobbyists how to design and build custom user interfaces using thin-film electronics and rapid prototyping tools. Surveys of the students and workshop participants showed that this platform is an effective teaching tool and can be easily adapted and expanded
Movers and Shakers: Kinetic Energy Harvesting for the Internet of Things
Numerous energy harvesting wireless devices that will serve as building
blocks for the Internet of Things (IoT) are currently under development.
However, there is still only limited understanding of the properties of various
energy sources and their impact on energy harvesting adaptive algorithms.
Hence, we focus on characterizing the kinetic (motion) energy that can be
harvested by a wireless node with an IoT form factor and on developing energy
allocation algorithms for such nodes. In this paper, we describe methods for
estimating harvested energy from acceleration traces. To characterize the
energy availability associated with specific human activities (e.g., relaxing,
walking, cycling), we analyze a motion dataset with over 40 participants. Based
on acceleration measurements that we collected for over 200 hours, we study
energy generation processes associated with day-long human routines. We also
briefly summarize our experiments with moving objects. We develop energy
allocation algorithms that take into account practical IoT node design
considerations, and evaluate the algorithms using the collected measurements.
Our observations provide insights into the design of motion energy harvesters,
IoT nodes, and energy harvesting adaptive algorithms.Comment: 15 pages, 11 figure
Project-based Learning within a Large-Scale Interdisciplinary Research Effort
The modern engineering landscape increasingly requires a range of skills to
successfully integrate complex systems. Project-based learning is used to help
students build professional skills. However, it is typically applied to small
teams and small efforts. This paper describes an experience in engaging a large
number of students in research projects within a multi-year interdisciplinary
research effort. The projects expose the students to various disciplines in
Computer Science (embedded systems, algorithm design, networking), Electrical
Engineering (circuit design, wireless communications, hardware prototyping),
and Applied Physics (thin-film battery design, solar cell fabrication). While a
student project is usually focused on one discipline area, it requires
interaction with at least two other areas. Over 5 years, 180 semester-long
projects have been completed. The students were a diverse group of high school,
undergraduate, and M.S. Computer Science, Computer Engineering, and Electrical
Engineering students. Some of the approaches that were taken to facilitate
student learning are real-world system development constraints, regular
cross-group meetings, and extensive involvement of Ph.D. students in student
mentorship and knowledge transfer. To assess the approaches, a survey was
conducted among the participating students. The results demonstrate the
effectiveness of the approaches. For example, 70% of the students surveyed
indicated that working on their research project improved their ability to
function on multidisciplinary teams more than coursework, internships, or any
other activity
Astro2020 White Paper: A Direct Measure of Cosmic Acceleration
Nearly a century after the discovery that we live in an expanding Universe,
and two decades after the discovery of accelerating cosmic expansion, there
remains no direct detection of this acceleration via redshift drift - a change
in the cosmological expansion velocity versus time. Because cosmological
redshift drift directly determines the Hubble parameter H(z), it is arguably
the cleanest possible measurement of the expansion history, and has the
potential to constrain dark energy models (e.g. Kim et al. 2015). The challenge
is that the signal is small - the best observational constraint presently has
an uncertainty several orders of magnitude larger than the expected signal
(Darling 2012). Nonetheless, direct detection of redshift drift is becoming
feasible, with upcoming facilities such as the ESO-ELT and SKA projecting
possible detection within two to three decades. This timescale is uncomfortably
long given the potential of this cosmological test. With dedicated experiments
it should be possible to rapidly accelerate progress and detect redshift drift
with only a five-year observational baseline. Such a facility would also be
ideal for precision radial velocity measurements of exoplanets, which could be
obtained as a byproduct of the ongoing calibration measurements for the
experiment.Comment: White paper submitted to the Astro2020 Decadal Survey. 6 page
Astro2020 Project White Paper: The Cosmic Accelerometer
We propose an experiment, the Cosmic Accelerometer, designed to yield
velocity precision of cm/s with measurement stability over years to
decades. The first-phase Cosmic Accelerometer, which is at the scale of the
Astro2020 Small programs, will be ideal for precision radial velocity
measurements of terrestrial exoplanets in the Habitable Zone of Sun-like stars.
At the same time, this experiment will serve as the technical pathfinder and
facility core for a second-phase larger facility at the Medium scale, which can
provide a significant detection of cosmological redshift drift on a 6-year
timescale. This larger facility will naturally provide further detection/study
of Earth twin planet systems as part of its external calibration process. This
experiment is fundamentally enabled by a novel low-cost telescope technology
called PolyOculus, which harnesses recent advances in commercial off the shelf
equipment (telescopes, CCD cameras, and control computers) combined with a
novel optical architecture to produce telescope collecting areas equivalent to
standard telescopes with large mirror diameters. Combining a PolyOculus array
with an actively-stabilized high-precision radial velocity spectrograph
provides a unique facility with novel calibration features to achieve the
performance requirements for the Cosmic Accelerometer
Movers and shakers: Kinetic energy harvesting for the internet of things
Abstract-Numerous energy harvesting mobile and wireless devices that will serve as building blocks for the Internet of Things (IoT) are currently under development. However, there is still only limited understanding of the energy availability from various sources and its impact on energy harvesting-adaptive algorithms. Hence, we focus on characterizing the kinetic (motion) energy that can be harvested by a mobile device with an IoT form factor. We first discuss methods for estimating harvested energy from acceleration traces. We then briefly describe experiments with moving objects and provide insights into the suitability of different scenarios for harvesting. To characterize the energy availability associated with specific human activities (e.g., relaxing, walking, and cycling), we analyze a motion dataset with over 40 participants. Based on acceleration measurements that we collected for over 200 hours, we also study energy generation processes associated with day-long human routines. Finally, we use our measurement traces to evaluate the performance of energy harvesting-adaptive algorithms. Overall, the observations will provide insights into the design of networking algorithms and motion energy harvesters, which will be embedded in mobile devices
A low-power, low-cost soil-moisture sensor using dual-probe heat-pulse technique
This paper presents the development and testing of an integrated low-power and low-cost dual-probe heat-pulse (DPHP) soil-moisture sensor in view of the electrical power consumed and affordability in developing countries. A DPHP sensor has two probes: a heater and a temperature sensor probe spaced 3 mm apart from the heater probe. Supply voltage of 3.3V is given to the heater-coil having resistance of 33 Omega power consumption of 330 mW, which is among the lowest in this category of sensors. The heater probe is 40 mm long with 2 mm diameter and hence is stiff enough to be inserted into the soil. The parametric finite element simulation study was performed to ensure that the maximum temperature rise is between 1 degrees C and 5 degrees C for wet and dry soils, respectively. The discrepancy between the simulation and experiment is less than 3.2%. The sensor was validated with white clay and tested with red soil samples to detect volumetric water-content ranging from 0% to 30%. The sensor element is integrated with low-power electronics for amplifying the output from thermocouple sensor and TelosB mote for wireless communication. A 3.7V lithium ion battery with capacity of 1150 mAh is used to power the system. The battery is charged by a 6V and 300 mA solar cell array. Readings were taken in 30 min intervals. The life-time of DPHP sensor node is around 3.6 days. The sensor, encased in 30 mm x 20 mm x 10 mm sized box, and integrated with electronics was tested independently in two separate laboratories for validating as well as investigating the dependence of the measurement of soil-moisture on the density of the soil. The difference in the readings while repeating the experiments was found out to be less than 0.01%. Furthermore, the effect of ambient temperature on the measurement of soil-moisture is studied experimentally and computationally. (C) 2015 Elsevier B.V. All rights reserved