Development And Testing Of A Wireless Strain Sensor Based On Electro-textile UHF RFID Tags
Chen, Xiaochen (2016)
Chen, Xiaochen
2016
Master's Degree Programme in Electrical Engineering
Tieto- ja sähkötekniikan tiedekunta - Faculty of Computing and Electrical Engineering
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Hyväksymispäivämäärä
2016-06-08
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201605254115
https://urn.fi/URN:NBN:fi:tty-201605254115
Tiivistelmä
Ultra-High Frequency (UHF) passive RFID tags can be utilized as sensing platforms in the Internet of Things, such as the wireless strain sensor tag. The strain sensor can be used for monitor the human bodily functions and movements.
In my thesis work, the performance and development of a RFID strain sensor was studied to achieve practical usage. This strain sensor is made of a stretchable silver-coated material sewing with no-stretchable coper-coated material, which can stretch 200% of its original length. During the measurement, the elongation of the strain sensor was indicated by the backscattered power of the tag. Thus, the elongation of the sensor can be monitored remotely. However, in the practical environment, the wireless channel is changeable, so the variation of the backscattered power caused by the elongation is the exclusive valuable parameter regardless of the influence of the channel. In this case, the reference tag was introduced to remove the impact of the channel. When two antennas are located closely, it can be considered that they use the same channel to transmit the signal. Thus, a reference tag, which is close to the strain sensor tag, can be applied to characterize the channel features. However, the coupling will affect the performance of the tags unpredictability when two tags are located nearly. My challenge is trying to minimize the coupling effect between the sensor tag and the reference tag.
In this thesis, three different tag configuration models were applied to achieve this goal : the linear configuration, the orthogonal configuration and the parallel configuration. The parallel configuration model performed badly in the chamber test. The backscattered power of reference tag changed a lot with the higher transmitted power at different elongation. As for linear configuration model, the difference of backscattered power between the reference tag and sensor tag (ΔP) was proportional to the sensor elongation, which meant the elongation of the sensor could be read at the reader end approximately. The orthogonal configuration model performed better in both simulation and practical test. Furthermore, the linearity of the elongation and the power difference ΔP is better in this case.
In my thesis work, the performance and development of a RFID strain sensor was studied to achieve practical usage. This strain sensor is made of a stretchable silver-coated material sewing with no-stretchable coper-coated material, which can stretch 200% of its original length. During the measurement, the elongation of the strain sensor was indicated by the backscattered power of the tag. Thus, the elongation of the sensor can be monitored remotely. However, in the practical environment, the wireless channel is changeable, so the variation of the backscattered power caused by the elongation is the exclusive valuable parameter regardless of the influence of the channel. In this case, the reference tag was introduced to remove the impact of the channel. When two antennas are located closely, it can be considered that they use the same channel to transmit the signal. Thus, a reference tag, which is close to the strain sensor tag, can be applied to characterize the channel features. However, the coupling will affect the performance of the tags unpredictability when two tags are located nearly. My challenge is trying to minimize the coupling effect between the sensor tag and the reference tag.
In this thesis, three different tag configuration models were applied to achieve this goal : the linear configuration, the orthogonal configuration and the parallel configuration. The parallel configuration model performed badly in the chamber test. The backscattered power of reference tag changed a lot with the higher transmitted power at different elongation. As for linear configuration model, the difference of backscattered power between the reference tag and sensor tag (ΔP) was proportional to the sensor elongation, which meant the elongation of the sensor could be read at the reader end approximately. The orthogonal configuration model performed better in both simulation and practical test. Furthermore, the linearity of the elongation and the power difference ΔP is better in this case.