Wireless sensor networks for flight applications

Die Prognosen der Marktentwicklung im Luftfahrtbereich sehen sehr positiv aus. In den kommenden 20 Jahren soll sich die Anzahl der Passagierflugzeuge verdoppeln, was sicherlich die Geschäfte im Luftfahrtbereich anregen wird. Jedoch bildet sich neue Konkurrenz in Asien, welche den Wettbewerb erhöhen wird. Um in dieser neuen Marktsituation weiterhin bestehen zu können, müssen Flugzeughersteller vermehrt innovative Flugzeugkonzepte entwickeln, mit welchen sie sich von ihren Konkurrenten absetzen können. Die meisten Innovationen zielen auf eine Reduzierung des Gewichts und auf höhere Energieeffizienz von Flugzeugen ab. Ebenso steht eine Reduzierung der Inbetriebnahme- und Betriebskosten im Fokus. Ein vielversprechender Ansatz diese Ziele zu erreichen, ist der Einsatz von drahtlosen Sensornetzen, um Luftfahrtanwendungen anzubinden. Der Einsatz so eines drahtlosen Sensornetzes kann in vielerlei Hinsicht Nutzen bringen. Verkabelung kann eingespart werden was große Gewichtsreduktionen mit sich bringt. Arbeitsabläufe können verbessert werden, wodurch Inbetriebnahme- und Betriebskosten reduziert werden können. Zusätzlich kann der Einsatz von drahtlosen Sendernetzen dazu beitragen, bisher nicht sinnvoll realisierbare Anwendungen einzuführen, beziehungsweise diese erst zu ermöglichen. In dieser Arbeit werden typische Flugzeuganwendungen identifiziert, welche von dem Einsatz eines drahtlosen Sendernetzes profitieren können. Die Herausforderungen, die der Einsatz so eines drahtlosen Sensornetzes hervorruft, werden beleuchtet, als auch entsprechende Technologien und Protokolle vorgestellt, welche darauf abzielen, diesen Herausforderungen zu begegnen.The market forecast for aircraft manufacturers is very promising; the fleet of passenger aircraft will double. This will clearly generate a strong business for aircraft manufactures. But new competitors arise and, hence, rivalry is increasing. To succeed in this market situation, aircraft manufacturers have to build innovative aircraft to set themselves apart from competitors. Most of the research effort is concentrated on developing lighter, more energy-efficient aircraft which reduce operational costs for airline operators. A very promising approach to accomplish this goal is to introduce wireless sensor networks for flight applications. Such wireless sensor networks can be very beneficial: they can help to reduce weight by saving cabling, they can improve workflows and, hence, reduce commissioning and operational costs, and they can enable new applications which were not feasible or even possible before.In this work, flight applications are investigated to identify the challenges which arise when introducing such a wireless sensor network. Technologies and protocols are presented which aim to tackle these challenges. In particular, the most demanding prerequisites are energy efficiency, transmission reliability, scalability, synchronization, and localization. Four of these demands will be addressed by three different protocols. First, a clock synchronization protocol is presented which uses a special hardware devicea wake-up receiverto achieve synchronization in a very energy-efficient, reliable, and scalable way. Second, using this same technology a clustering protocol is presented which can reduce redundant transmissions. In doing so, it becomes possible to lower the mean energy consumption for hundreds of sensor nodes. Last, a custom-tailored medium access protocol is presented which utilizes spatial diversity to increase transmission reliability while keeping a very low power demand.Tag der Verteidigung: 25.08.2015Paderborn, Univ., Diss., 201

Energy-Detecting Receivers for Wake-Up Radio Applications

In the energy-limited wireless sensor node applications, wake-up radios are required to reduce the average power consumption of the node. Energy-detecting receivers are the best fit for such low power operations. This thesis presents the energy-detecting receiver design; challenges; techniques to enhance sensitivity, selectivity; and multi-access operation. Self-mixers instead of the conventional envelope detectors are proposed and proved to be optimal for signal detection. A fully integrated wake-up receiver uses the self-mixer and time-encoded baseband signal processing to provide a sensitivity of -79.1dBm at 434MHz with 420pW of power, providing an 8dB better sensitivity at 10dB lower power consumption compared to the SoA. A novel approach using narrowband interferers as local oscillators will be presented to further enhance sensitivity and selectivity, effectively operating the energy-detector receiver as a direct down-conversion receiver. Additionally, a clockless continuous-time analog correlator will be introduced to enhance the selectivity to wide-band AM interferers. The architecture uses pulse-position-encoded analog signal processing with VCOs as integrators and pulse-controlled relaxation delays; it operates as a code-domain matched filter to de-spread asynchronous wake-up codes. This code-domain matched filtering also provides code-division multiple access (CDMA) for simultaneous wakeups. Additional enhancement in the link can be achieved using directional antennas, providing spatial gain and selectivity. Certain applications can leverage a nearby reflector similar to a Yagi antenna to enhance the directivity. A low power directional backscatter tag is proposed, it uses multiple antennas acting as a reflectarray by configuring constant phase gradients depending on the direction of arrival (DoA) of the signal. Thus, instead of harvesting energy, the same energy and the surrounding environment can be leveraged to enhance functionality (e.g. interferer as LO, using a backscatter tag on a wall) for low power operation. Innovations spanning both system and circuit architectures that leverage the ambient energy and environment to enable power-efficient solutions for next-generation wake-up radios are presented in this work

Aeronautical engineering: A continuing bibliography with indexes, supplement 103, December 1978

This bibliography lists 457 reports, articles, and other documents introduced into the NASA scientific and technical information system in November 1978

Voyager design studies. volume v- lander design, part ii

Engineering and design data for Voyager Mars and Venus lander system

Aeronautical Engineering: A continuing bibliography with indexes, supplement 107

Reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1979 are listed in this bibliography

Wireless Monitoring Systems for Long-Term Reliability Assessment of Bridge Structures based on Compressed Sensing and Data-Driven Interrogation Methods.

The state of the nation’s highway bridges has garnered significant public attention due to large inventories of aging assets and insufficient funds for repair. Current management methods are based on visual inspections that have many known limitations including reliance on surface evidence of deterioration and subjectivity introduced by trained inspectors. To address the limitations of current inspection practice, structural health monitoring (SHM) systems can be used to provide quantitative measures of structural behavior and an objective basis for condition assessment. SHM systems are intended to be a cost effective monitoring technology that also automates the processing of data to characterize damage and provide decision information to asset managers. Unfortunately, this realization of SHM systems does not currently exist. In order for SHM to be realized as a decision support tool for bridge owners engaged in performance- and risk-based asset management, technological hurdles must still be overcome. This thesis focuses on advancing wireless SHM systems. An innovative wireless monitoring system was designed for permanent deployment on bridges in cold northern climates which pose an added challenge as the potential for solar harvesting is reduced and battery charging is slowed. First, efforts advancing energy efficient usage strategies for WSNs were made. With WSN energy consumption proportional to the amount of data transmitted, data reduction strategies are prioritized. A novel data compression paradigm termed compressed sensing is advanced for embedment in a wireless sensor microcontroller. In addition, fatigue monitoring algorithms are embedded for local data processing leading to dramatic data reductions. In the second part of the thesis, a radical top-down design strategy (in contrast to global vibration strategies) for a monitoring system is explored to target specific damage concerns of bridge owners. Data-driven algorithmic approaches are created for statistical performance characterization of long-term bridge response. Statistical process control and reliability index monitoring are advanced as a scalable and autonomous means of transforming data into information relevant to bridge risk management. Validation of the wireless monitoring system architecture is made using the Telegraph Road Bridge (Monroe, Michigan), a multi-girder short-span highway bridge that represents a major fraction of the U.S. national inventory.PhDCivil EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/116749/1/ocosean_1.pd

Communication and energy delivery architectures for personal medical devices

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 219-232).Advances in sensor technologies and integrated electronics are revolutionizing how humans access and receive healthcare. However, many envisioned wearable or implantable systems are not deployable in practice due to high energy consumption and anatomically-limited size constraints, necessitating large form-factors for external devices, or eventual surgical re-implantation procedures for in-vivo applications. Since communication and energy-management sub-systems often dominate the power budgets of personal biomedical devices, this thesis explores alternative usecases, system architectures, and circuit solutions to reduce their energy burden. For wearable applications, a system-on-chip is designed that both communicates and delivers power over an eTextiles network. The transmitter and receiver front-ends are at least an order of magnitude more efficient than conventional body-area networks. For implantable applications, two separate systems are proposed that avoid reimplantation requirements. The first system extracts energy from the endocochlear potential, an electrochemical gradient found naturally within the inner-ear of mammals, in order to power a wireless sensor. Since extractable energy levels are limited, novel sensing, communication, and energy management solutions are proposed that leverage duty-cycling to achieve enabling power consumptions that are at least an order of magnitude lower than previous work. Clinical measurements show the first system demonstrated to sustain itself with a mammalian-generated electrochemical potential operating as the only source of energy into the system. The second system leverages the essentially unlimited number of re-charge cycles offered by ultracapacitors. To ease patient usability, a rapid wireless capacitor charging architecture is proposed that employs a multi-tapped secondary inductive coil to provide charging times that are significantly faster than conventional approaches.by Patrick Philip Mercier.Ph.D

Ultra low power wearable sleep diagnostic systems

Sleep disorders are studied using sleep study systems called Polysomnography that records several biophysical parameters during sleep. However, these are bulky and are typically located in a medical facility where patient monitoring is costly and quite inefficient. Home-based portable systems solve these problems to an extent but they record only a minimal number of channels due to limited battery life. To surmount this, wearable sleep system are desired which need to be unobtrusive and have long battery life. In this thesis, a novel sleep system architecture is presented that enables the design of an ultra low power sleep diagnostic system. This architecture is capable of extending the recording time to 120 hours in a wearable system which is an order of magnitude improvement over commercial wearable systems that record for about 12 hours. This architecture has in effect reduced the average power consumption of 5-6 mW per channel to less than 500 uW per channel. This has been achieved by eliminating sampled data architecture, reducing the wireless transmission rate and by moving the sleep scoring to the sensors. Further, ultra low power instrumentation amplifiers have been designed to operate in weak inversion region to support this architecture. A 40 dB chopper-stabilised low power instrumentation amplifiers to process EEG were designed and tested to operate from 1.0 V consuming just 3.1 uW for peak mode operation with DC servo loop. A 50 dB non-EEG amplifier continuous-time bandpass amplifier with a consumption of 400 nW was also fabricated and tested. Both the amplifiers achieved a high CMRR and impedance that are critical for wearable systems. Combining these amplifiers with the novel architecture enables the design of an ultra low power sleep recording system. This reduces the size of the battery required and hence enables a truly wearable system.Open Acces