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Wearable Systems in Harsh Environments: Realizing New Architectural Concepts
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Wearable systems continue to gain new markets by addressing improved performance and lower size, weight and cost. Both civilian and military markets have incorporated wearable technologies to enhance and facilitate user's tasks and activities. A wearable system is a heterogeneous system composed of diverse electronic modules: data processing, input and output modules. The system is constructed to be body-borne and therefore, several constraints are put on wearable systems regarding wearability (size, weight, placement, etc.) and robustness rendering the task of designing wearable systems challenging. In this thesis, an overview of wearable systems was given by discussing definition, technology challenges, market analysis and design methodologies. Main research targeted at network architectures and robustness to environmental stresses and electromagnetic interference (EMI). The network architecture designated the data communication on the intermodule level - topology and infrastructure. A deeper analysis of wearable requirements on the network architecture was made and a new architecture is proposed based on DC power line communication network (DC-PLC). In addition, wired data communication was compared to wireless data communication by introducing statistical communication model and looking at multiple design attributes: power efficiency, scalability, and wearability.

The included papers focused on wearable systems related issues including analysis of present situation, environmental and electrical robustness studies, theoretical and computer aided modelling, and experimental testing to demonstrate new wearable architectural concepts. A roadmap was given by examining the past and predicting the future of wearable systems in terms of technology, market, and architecture. However, the roadmap was updated within this thesis to include new market growth figures that proved to be far less than was predicted in 2004. User and application environmental requirements to be applied on future wearable systems were identified. A procedure is presented to address EMI and evaluated solutions in wearable application through modelling and simulation. Environmental robustness and wearability of wearable systems in general, and washability and conductive textile in particular are investigated. A measurement-based methodology to model electrical properties of conductive textile when subjected to washing was given.

Employing a wired data communication network was found to be more appropriate for wearable systems than wireless networks when prioritizing power efficiency. The wearability and scalability of the wired networks was enhanced through conductive textile and DC-PLC, respectively. A basic wearable application was built to demonstrate the suitability of DC-PLC communication with conductive textile as infrastructure. The conductive textile based on metal filament showed better mechanical robustness than metal plated conductive textile. A more advanced wearable demonstrator, where DC-PLC network was implemented using transceivers, further strengthened the proposed wearable architecture. Based on the overview, the theoretical, modelling and experimental work, a possible approach of designing wearable systems that met several contradicting requirements was given.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 2010. , 85 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1304
Keyword [en]
Wearable System, Wearable Network, DC Power Line Communication, Conductive Textile, Electromagnetic Coupling, Washability, Energy Efficiency, Triboelectric Noise
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-54461ISBN: 978-91-7393-423-7 (print)OAI: oai:DiVA.org:liu-54461DiVA: diva2:304088
Public defence
2010-05-11, TP51, Täppanhuset,, Campus Norrköping, Linköpings universitet, Norrköping, 10:15 (English)
Opponent
Supervisors
Available from: 2010-03-22 Created: 2010-03-17 Last updated: 2010-03-22Bibliographically approved
List of papers
1. Roadmap: Wearable Computers
Open this publication in new window or tab >>Roadmap: Wearable Computers
2005 (English)In: Proceedings of IMAPS Nordic Annaul Conference, 2005, 146-154 p.Conference paper, Published paper (Refereed)
Abstract [en]

 

The diversity of portable products on the market has increased due to the evolution of electronic components and batteries. A migration of the portable products into wearable has started by applying non-conventional user interfaces such as voice and gesture recognition, to enable hand-free use. However, major issues remain to be solved in order to make the transition complete. Key technological domains that affect the development of wearable systems are described and discussed. A review of different existing portable/wearable applications and domain of use is presented. User and environmental requirements to be applied on future wearable systems are identified. One of the major user concerns is the robustness of the system, which should withstand the stresses implied by the human body. Therefore, research is made to exploit the advantages of conductive textiles in order to build robust wearable architecture.

 

Keyword
Wearable computer, conductive textile, robustness, reliability
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-54448 (URN)951-98002-7-1 (ISBN)951-98002-8-X (ISBN)
Conference
The IMAPS Nordic Annual Conference 2005, Sep. 11-14, Tønsberg, Norway
Available from: 2010-03-16 Created: 2010-03-16 Last updated: 2010-03-22
2. Electromagnetic Coupling To a Wearable Application Based On Coaxial Cable Architecture
Open this publication in new window or tab >>Electromagnetic Coupling To a Wearable Application Based On Coaxial Cable Architecture
2006 (English)In: Progress In Electromagnetics Research, PIER, ISSN 1070-4698, Vol. 56, 109-128 p.Article in journal (Refereed) Published
Abstract [en]

A radiated susceptibility problem has been identified and solved by means of simulations for a wearable computer system in the frequency range 30 MHz – 1 GHz. Simulation strategy is presented for analyzing the effects induced by an electromagnetic plane wave within the system comprising infra-red sensors connected by coaxial cables. A procedure of creating a TLM model of the coaxial cable with controlled electromagnetic coupling characteristics on a coarse grid is proposed. Results are verified by means of theoretical calculations. Different sensor enclosures and filtering circuits are analyzed and implemented to meet the hard electromagnetic compatibility requirements while not interfering with the functionality of the wearable application.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-54451 (URN)10.2528/PIER05070101 (DOI)
Available from: 2010-03-16 Created: 2010-03-16 Last updated: 2010-06-14
3. Experimental Analysis and Modelling of Textile Transmission Line for Wearable Applications
Open this publication in new window or tab >>Experimental Analysis and Modelling of Textile Transmission Line for Wearable Applications
2007 (English)In: International Journal of Clothing Science and Technology, ISSN 0955-6222, E-ISSN 1758-5953, Vol. 19, no 1, 59-71 p.Article in journal (Refereed) Published
Abstract [en]

Purpose – By means of measurement and modelling, evaluate frequency dependent per-unit-length parameters of conductive textile transmission line (CTTL) for wearable applications and study deterioration of these parameters when CTTL is subjected to washing.

Design/methodology/approach – The studied transmission line is made of Nickel/Copper (Ni/Cu) plated polyester ripstop fabric and is subjected to standard 60oC cycle in a commercial off-the-shelf washing machine. The per-unit-length parameters (resistance and inductance) and characteristic impedance of the line are extracted from measurements before and after washing. Using the measurement data an equivalent circuit is created to model the degradation of the line. The circuit is then integrated in a three-dimensional Transmission Line Matrix (TLM) model of the transmission line.

Findings – Both an electrical equivalent circuit and a TLM model are developed describing the degradation of the conductive textile when washed. A severe deterioration of the electrical parameters of the line is noticed. Experimental and modelling results are in good agreement in the addressed frequency band.

Research limitations/implications – Analysis is performed for frequencies up to 10 MHz. The developed TLM model can be used to conduct parametric studies of the CTTL. To counteract the degradation of the line, protective coating is to be considered in further studies.

Originality/value – Experimental and simulation based characterization of the conductive textile transmission line when subjected to washing cycles.

Place, publisher, year, edition, pages
Emerald Group Publishing Limited, 2007
Keyword
Electronics industry, Impedance voltage, Modelling, Textiles
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-54460 (URN)10.1108/09556220710717053 (DOI)
Available from: 2010-03-17 Created: 2010-03-17 Last updated: 2017-12-12
4. Evaluation of Conductive Textile for Wearable Computer Applications
Open this publication in new window or tab >>Evaluation of Conductive Textile for Wearable Computer Applications
2006 (English)In: The IMAPS Nordic Annual Conference, 2006, 220-227 p.Conference paper, Published paper (Refereed)
Abstract [en]

Wearable systems put high demands on wearability and robustness. Conductive fabrics are very likely to be used in wearable systems due to their textile-like characteristics. However conductive fabrics must be able to resist environmental stresses (wearing, laundering, etc.) in the same way as clothing in order to fully comply with the requirements.

A demonstrator, TxWear, was constructed to exploit conductive fabrics in building a conductive textile transmission line for intermodular communication and power transmission (DC power line communication bus), thus eliminating the need for cables between the modules. The hardware modules are connected to the conductive line through connectors from textile industry, i.e., snap fasteners. Different types of conductive fabrics (Ni/Cu plated polyester fabrics and stainless-steel based elastic ribbon) were evaluated and compared according to their conductivity, flexibility and robustness characteristics. The effect of washing on the electrical properties (per-unit-length parameters) of the textile transmission line was studied. Different coating processes, i.e., parylene and silicone coating, were studied and evaluated in order to isolate and enhance the robustness of the conductive textile. Ni/Cu plated polyester ripstop fabric was found to be not appropriate for wearable applications, while conductive elastic ribbon showed good robustness to laundry induced stresses.

Keyword
Wearable computer, conductive textile, robustness, washing, power line communication
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-54459 (URN)951-98002-9-8 (ISBN)951-9800-0-4 (ISBN)
Conference
The IMAPS Nordic Annual Conference 2006, Gothenburg, Sweden, Sep. 17-19
Available from: 2010-03-17 Created: 2010-03-17 Last updated: 2010-03-22
5. Modelling and Characterization of Electrostatic Current Noise Induced Mechanically in Wired Wearable Applications
Open this publication in new window or tab >>Modelling and Characterization of Electrostatic Current Noise Induced Mechanically in Wired Wearable Applications
2010 (English)In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 68, no 1, 21-26 p.Article in journal (Refereed) Published
Abstract [en]

By means of statistical modelling and measurement, the triboelectric current noise spectral density is evaluated for shielded cables in body-borne wired network subjected to mechanical stresses. Assuming a shot noise model, an expression for the current spectral density of the noise is derived. The efficiency of the methodology is demonstrated by measuring the triboelectric current noise in two shielded cables subjected to bending. Thereafter the parameters of the noise pulses’ waiting time and amplitude probability density functions are extracted from measurement, thus enabling the computation of the current spectral density of the noise induced mechanically in body-borne wired networks.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-54456 (URN)10.1016/j.elstat.2009.08.004 (DOI)
Available from: 2010-03-17 Created: 2010-03-17 Last updated: 2017-12-12
6. Realization of an active inductance for a low power high bandwidth DC power line communication network transceiver
Open this publication in new window or tab >>Realization of an active inductance for a low power high bandwidth DC power line communication network transceiver
2010 (English)In: AEU - International Journal of Electronics and Communications, ISSN 1434-8411, E-ISSN 1618-0399, Vol. 64, no 10, 947-952 p.Article in journal (Refereed) Published
Abstract [en]

An active inductor based on an improved gyrator circuit is proposed. The active inductor is developed to be implemented in a high impedance transceiver for a wearable DC power line communication network where requirements such as low power consumption, high bandwidth and numerous nodes support are prioritized. A load isolation step is introduced to ensure the stability of the active inductance's size on different load currents. The proposed gyrator circuit is analyzed and optimized by means of theoretical calculations. The theoretical results are then verified by simulations and experiments in the frequency range up to 10MHz.

Place, publisher, year, edition, pages
Elsevier, 2010
Keyword
Active inductor, Gyrator, DC power line communication, High impedance transceiver, Wearable applications
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-54457 (URN)10.1016/j.aeue.2009.07.010 (DOI)
Available from: 2010-03-17 Created: 2010-03-17 Last updated: 2017-12-12Bibliographically approved
7. Low Power High Bandwidth Power-Line Communication Network for Wearable Applications
Open this publication in new window or tab >>Low Power High Bandwidth Power-Line Communication Network for Wearable Applications
2010 (English)Conference paper, Published paper (Other academic)
Abstract [en]

A DC power-line communication (PLC) network for wearable applications is proposed and studied. The DC-PLC network enhances wearability compared to other types of wired networks by requiring minimum amount of wiring. The DC-PLC transceiver is designed based on a low power high bandwidth active inductance circuit, thus not jeopardizing the low power property of the wired solution. The DC-PLC network is implemented in a wearable application and compared to a wireless wearable network by studying and comparing the bit-energy of these networks. The bitenergy study is based on a statistical model of the communication where message size and rate, preamble time and power measurements are included. The DC-PLC network showed shorter latency and lower bit-energy compared to the wireless alternatives when preamble time is kept at reasonable level.

Keyword
DC Power-Line, Wearable Network, Energy-Efficiency
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-54450 (URN)
Conference
BodyNets 2010 - Fifth International Conference on Body Area Networks, Greece, Sep. 10-12
Note
SubmittedAvailable from: 2010-03-16 Created: 2010-03-16 Last updated: 2010-03-22

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