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Sitting Posture Recognition using Screen Printed Large Area Pressure Sensors
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. (SMART)ORCID iD: 0000-0001-7395-3687
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.ORCID iD: 0000-0003-2965-0288
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
2017 (English)In: Proceedings of IEEE Sensors, IEEE, 2017, p. 232-234Conference paper, Published paper (Refereed)
Abstract [en]

In the biomedical sector, pressure sensors exhibit an important role towards monitoring and recognition of sitting posture for wheelchair users, which is helpful for pressure ulcer prevention and cure.  In this paper, a flexible and inexpensive screen printed large area pressure sensing system is presented. The large area sensor comprise three layers, is able to cancel-out false pressure detection, and achieves a sitting classification accuracy over 80 percent. The sensor matrix contains 16 sensors distributed over an area of 23.5 cm × 21.5 cm and the pressure points are monitored at a scanning rate of 77 Hz. The sensor system provides wireless communication and a Windows based GUI is developed that allows real-time presentation of pressure data by means of a pressure map. The presented sensor design targets smart wheelchairs but is suitable for any low cost and high throughput pressure distribution monitoring systems. 

Place, publisher, year, edition, pages
IEEE, 2017. p. 232-234
Series
IEEE Sensors, ISSN 1930-0395
Keywords [en]
Wheelchair, pressure sensors, conductive inks, pressure mapping, sitting posture recognition
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-32324DOI: 10.1109/ICSENS.2017.8233944ISI: 000427677500077Scopus ID: 2-s2.0-85044326019ISBN: 978-1-5090-1012-7 (print)OAI: oai:DiVA.org:miun-32324DiVA, id: diva2:1163603
Conference
16th IEEE SENSORS Conference, ICSENS 2017; Scottish Event Campus (SEC) Glasgow; United Kingdom; 30 October 2017 through 1 November 2017
Projects
SMART (Smarta system och tjänster för ett effektivt och innovativt samhälle)Available from: 2017-12-07 Created: 2017-12-07 Last updated: 2022-03-31Bibliographically approved
In thesis
1. Screen Printed Large Area Sensors for Pressure Distribution Monitoring in Wheelchairs
Open this publication in new window or tab >>Screen Printed Large Area Sensors for Pressure Distribution Monitoring in Wheelchairs
2019 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

A sedentary lifestyle can induce health related problems including pressure ulcers. Pro­longed sitting inadequacies constitute a risk for pressure ulcer to many individuals, in particular people with disabilities and re­duced mobility. The measurement of distributed pressure and detection of irregular sitting postures are essential in prevention of the risk of developing pres­sure ulcers.

In this thesis, a screen-printed pressure sensor for a large area is presented, with the objective of measuring the distributed pressure of a seated per­son in a wheelchair. The conductors and interdigital patterns are printed with silver-based ink. A blend of a non-conductive and a low resis­tive ink is used for customized resistance for an optimal sensing range of the pressure sensor. The effect of moisture and temper­ature are realized in an environment chamber. For characterization, other key performance tests such as repeatability, drift and flexibility are carried out. The surface morphology is carried out for structural analysis of printed samples. The sensor data is acquired and processed using an 8-bit ATmega-2560 micro­controller and wirelessly transmitted to a PC for post-processing, storage and analysis. For real-time data presentation of dis­tributed pressure points, a GUI has been developed to display the values ob­tained from the large area sensor. The detection of four sit­ting pos­tures; forward leaning, backward leaning, left leaning and right leaning along with a normal sitting posture is attained. An analysis for stretchable printed tracks has been conducted to investigate the changes in electrical resistance using elon­ga­tion tests, surface morphology and EDS. The optimal curing time and tem­per­ature were investigated to manufacture stretchable conductive tracks.

In summary, the contributions in this thesis provides an effective approach regarding pressure distribution measurement and recognizing irregular sitting postures for wheelchair users.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2019. p. 38
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 159
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-36139 (URN)978-91-88947-05-5 (ISBN)
Presentation
2019-06-04, M 108, Holmgatan 10, 85170, Sundsvall, 09:30 (English)
Opponent
Supervisors
Note

Vid tidpunkten för framläggningen av avhandlingen var följande delarbete opublicerat: delarbete 3 (accepterat).

At the time of the defence the following paper was unpublished: paper 3 (accepted).

Available from: 2019-05-15 Created: 2019-05-15 Last updated: 2019-05-15Bibliographically approved
2. Development and Characterization of Large Area Pressure Sensors and Sitting Posture Monitoring Systems
Open this publication in new window or tab >>Development and Characterization of Large Area Pressure Sensors and Sitting Posture Monitoring Systems
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

With the emergence of the Internet and rapid development of science and technology over the past few decades, many individuals worldwide now rely on the Internet to conduct daily activities ranging from education, business and creativity to communication and shopping. As we tend to spend more and more time on the Internet and engage less in physical activities, this persistent behaviour could result in some health-related issues within a relatively short period of time. This behaviour, known as sedentary lifestyle, may be related to a higher risk of cardiovascular disease, osteoporosis, obesity, anxiety, pressure ulcers and many other illnesses. As a consequence, there has been great interest in developing non-invasive and unobtrusive measurement techniques for a variety of health care-monitoring applications, such as for blood oxygen saturation, stress levels, electrocardiograms and glucose monitoring. In such systems, wearable and flexible electronics technologies may enable monitoring of vital signs, offering significant potential for early screening as well as long-term behaviour modelling.

In this thesis, large area pressure sensors based on non-conventional materials are proposed and realised by screen printing technique for monitoring sitting postures. The developed pressure sensing system measures distributed pressure when an individual sits on a chair equipped with a pressure sensor array. This technology could provide grounding for the advancement of health-related monitoring systems for both able-bodied and disabled individuals and inform them of their sitting time and sitting posture, and this could be used to establish a sitting pattern. To accomplish this, pressure sensors have been designed using non-conventional flexible electronics. A blend of non-conductive and low-resistance ink is used as pressure-sensitive material to enable the realization of screen-printed sensors. To characterise the performance of the suggested pressure sensor, several tests, such as repeatability, drift and flexibility, are conducted. The sensor has also been exposed to different humidity and temperature conditions in a climate chamber to examine its functionalities.

A graphical user interface was developed for real-time demonstration of data from distributed pressure points in the form of a pressure map to display the pressure values. Four sitting postures are identified: forward, backward, left, and right leaning. Furthermore, a stretchable pressure sensor is proposed that could follow slight stretching with regard to changes in the shape of the human skin. Machine learning algorithms have been employed to further enhance the sitting posture identification, and accuracy of 99.03% is attained. A standalone embedded system capable of illustrating real-time pressure data has been developed with the potential to be used in portable health monitoring systems. In summary, this work provides a promising framework for measuring pressure distribution and identifying irregular sitting postures that may help to reduce the potential risks of developing health-related issues associated with prolonged sitting time.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2021. p. 50
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 355
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-43754 (URN)978-91-89341-33-3 (ISBN)
Public defence
2021-11-30, C310, Mittuniversitetet, Sundsvall, 13:00 (English)
Opponent
Supervisors
Available from: 2021-11-18 Created: 2021-11-17 Last updated: 2021-11-18Bibliographically approved

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Ahmad, JawadAndersson, HenrikSidén, Johan

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