| 1. |
- Ahmad, Jawad, 1985-, et al.
(författare)
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Screen Printed Piezoresistive Sensors for Monitoring Pressure Distribution in Wheelchair
- 2019
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Ingår i: IEEE Sensors Journal. - : IEEE. - 1530-437X .- 1558-1748. ; 19:6, s. 2055-2063
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Tidskriftsartikel (refereegranskat)abstract
- Prolonged sitting inadequacies cause pressure ulcer to many individuals, especially to disadvantaged with reduced mobility. The measurement of distributed pressure and detection of irregular sitting postures is essential for preventing the risk of developing pressure ulcer. In this paper, a pressure sensing system capable of recognizing sitting postures by means of measuring interface pressure through printed pressure sensors is presented. A thin and flexible large area sensor is screen-printed using silver flake and carbon particle inks and comprises 16 sensing elements. For the evaluation of practical usability, the sensor characterization is carried out by conducting stability, repeatability, drift and bending tests. The performance of the sensor is checked under varying environmental conditions. Sitting posture detection accuracy above 80 % is achieved using a classification algorithm for four different sitting postures. Pressure distribution is monitored at a scanning rate of 10 Hz. A low power and small form factor of read-out electronics enables a compact packaging inside the seat cushion. The presented sensor design targets smart wheelchairs, but it is extendable to much larger areas, for example to be used in beds. The proposed sensing system would be of a great assistance for caregivers and health professionals.
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| 2. |
- Ashraf, Shakeel, 1984-, et al.
(författare)
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Fabrication and characterization of a SU8-epoxy membrane based thermopile detector with an integrated multilayered absorber structure for the mid-IR region
- 2019
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 19:11, s. 4000-4007
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on the fabrication and characterization of a thermopile detector with an integrated mid-infrared absorber structure. The fabricated absorber structure has shown an absorption of more than 95% in the wavelength range of 3.2 – 5.47 μm. The detector was fabricated with standard cleanroom process techniques and equipment. The serial resistance was measured at about 315 kΩ at room temperature. The photosensitivity of the detector was characterized for a signle wavelength (4.26 µm) and a band of wavelength ranging from 2.5 –5.5 µm through two different measurement setups. In the first measurement setup, the photosensitivity was estimated at 57.5 V·mm2·W-1 through a MEMS-based infrared radiation source and with an optical band-pass filter of wavelength 4.26µm. The following characterization was performed to characterise the photosensitivity of the detector in a broader wavelength range. This measurement was taken using a monochromator setup utilizing a reference photodetector for calculations of the optical power of the infrared source. The photosensitivity and the specific detectivity (D*) of the fabricated detector were measured to values of 30-92 V·W-1 and 8.0×107-2.4×108 cm·Hz1/2·W-1, respectively, in the wavelength range of 2.8 – 5 µm. The time constant was estimated to around 21 ms
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| 3. |
- Cheng, Peng, et al.
(författare)
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Torque Sensor Based on Differential Air Pressure Using Volumetric Strain
- 2017
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 17:11, s. 3269-3277
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a torque sensor based on the differential air pressure measurement method using the volumetric strain of a mechanical sensing structure. A model of the measurement system based on the differential air pressure from the volumetric strain of the mechanical sensing structure is proposed and theoretically discussed. The error sources are identified and an error propagation model is presented for the proposed torque measurement method. Considering these error sources, a prototype torque sensor is presented as a case study for the method verification. Both the mechanical and readout electronics designs are discussed and analyzed. The mechanical sensitivity, resolution, and maximum stresses are analyzed using finite-element modeling. Based on the results from the simulation, a prototype torque sensor is manufactured and experimentally verified using a readout electronics design. For verification, the sensor prototype is measured under static torque to have a sensitivity of 0.04272V/N. m and a range of +/- 117N . m. Compared with the nominal mechanical sensitivity result from the FEM simulation, this measured sensitivity has a difference less than 6%. The noise analysis of the designed readout electronics shows that the resolution of 0.006% can be achieved with this design. Furthermore, hysteresis analysis shows an error of 0.012% of full scale. From these results, it is also shown that the actual performance of the sensor is mainly limited by the differential pressure sensor and the readout electronics design and is not by the mechanical design of the sensor.
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| 4. |
- Farag, Hossam, et al.
(författare)
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A Delay-Bounded MAC Protocol for Mission- and Time-Critical Applications in Industrial Wireless Sensor Networks
- 2018
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 18:6, s. 2607-2616
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Tidskriftsartikel (refereegranskat)abstract
- Industrial Wireless Sensor Networks (IWSNs) designedfor mission- and time-critical applications require timelyand deterministic data delivery within stringent deadline bounds.Exceeding delay limits for such applications can lead to system malfunction or ultimately dangerous situations that can threaten human safety. In this paper, we propose SS-MAC, an efficient slot stealing MAC protocol to guarantee predictable and timely channel access for time-critical data in IWSNs. In the proposed SS-MAC, aperiodic time-critical traffic opportunistically steals time slots assigned to periodic non-critical traffic. Additionally, a dynamic deadline-based scheduling is introduced to provide guaranteed channel access in emergency and event-based situations where multiple sensor nodes are triggered simultaneously to transmit time-critical data to the controller. The proposed protocol is evaluated mathematically to provide the worst-case delay bound for the time-critical traffic. Performance comparisons are carried out between the proposed SS-MAC and WirelessHARTstandard and they show that, for the time-critical traffic, theproposed SS-MAC can achieve, at least, a reduction of almost 30% in the worst-case delay with a significant channel utilization efficiency.
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| 5. |
- Farag, Hossam, et al.
(författare)
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Priority-Aware Wireless Fieldbus Protocol for Mixed-Criticality Industrial Wireless Sensor Networks
- 2019
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 19:7, s. 2767-2780
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Tidskriftsartikel (refereegranskat)abstract
- Industrial wireless sensor networks are becoming popular for critical monitoring and control applications in industrial automation systems. For such type of applications, providing reliable real-time performance regarding data delivery is considered as a fundamental challenge. The problem becomes more prominent with mixed-criticality systems, where different data flow with different levels of criticality (importance) coexist and characterized by different requirements regarding delay and reliability. In this paper, we propose a wireless fieldbus protocol to enable real-time communication and service differentiation for cluster-based mixed-criticality networks. A process monitoring scenario of plastic extrusion is used to define the protocol requirements and elaborate the working principle of the proposed work. In our proposed protocol, each data flow is scheduled for channel access based on its criticality level using a distributed prioritized medium access mechanism that ensures a guaranteed channel access for the most critical traffic over other traffic types. The performance of the proposed protocol is analyzed analytically using a discrete-time Markov chain model to evaluate the performance in terms of delay and throughput. Moreover, the extensive simulations are conducted to prove the analytical claims and different performance assessments are provided, which also demonstrate the effectiveness of the proposed approach compared with the related existing work.
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| 6. |
- Guntupalli, Lakshmikanth, et al.
(författare)
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Energy Efficient Consecutive Packet Transmissions in Receiver-initiated Wake-up Radio Enabled WSNs
- 2018
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 18:11, s. 4733-4745
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Tidskriftsartikel (refereegranskat)abstract
- In wake-up radio (WuR)-enabled wireless sensor networks, data communication among nodes is triggered in an on-demand manner, by either a sender or a receiver. For receiver-initiated WuR (RI-WuR), a~receiving node wakes up sending nodes through a wake-up call. Correspondingly sending nodes transmit packets in a traditional way by competing with one another multiple times in a single operational cycle. In~this paper, we propose a receiver-initiated consecutive packet transmission WuR (RI-CPT-WuR) medium access control (MAC) protocol, which eliminates multiple competitions to achieve higher energy efficiency. Furthermore, we develop two associated discrete time Markov chains (DTMCs) for evaluating the performance of RI-CPT-WuR and an existing RI-WuR MAC protocol. Using the solutions from the DTMC models, closed-form expressions for network throughput, average delay, packet reliability ratio, energy consumption and lifetime, and energy efficiency for both protocols are obtained. Numerical results demonstrate the superiority of the RI-CPT-WuR protocol.
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| 7. |
- Jonsson, Patrik, 1968-, et al.
(författare)
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Road surface status classification using spectral analysis of NIR camera images
- 2015
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 15:3, s. 1641-1656
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Tidskriftsartikel (refereegranskat)abstract
- There is a need for an automated road status classification system considering the vast number of weather-related accidents that occur every winter. Previous research has shown that it is possible to detect hazardous road conditions, including, for example, icy pavements, using single point infrared illumination and infrared detectors. In this paper, we extend this research into camera surveillance of a road section allowing for classification of area segments of weather-related road surface conditions such as wet, snow covered, or icy. Infrared images have been obtained using an infrared camera equipped with a set of optical wavelength filters. The images have primarily been used to develop multivariate data models and also for the classification of road conditions in each pixel. This system is a vast improvement on existing single spot road status classification systems. The resulting imaging system can reliably distinguish between dry, wet, icy, or snow covered sections on road surfaces.
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| 8. |
- Ma, Xinyu, et al.
(författare)
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Characterization of Indoor Light Conditions by Light Source Classification
- 2017
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 17:12, s. 3884-3891
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Tidskriftsartikel (refereegranskat)abstract
- The characterization of light conditions plays an important role in the estimation of available energy levels to ambient light energy harvesting systems. Indoor light conditions are commonly described by illuminance levels. The same illuminance levels, however, can be generated by different light source types, which radiate different spectral components. This means that based on their spectral response, solar panels can produce different output powers even though identical illuminance levels are observed. We propose a method to distinguish these conditions based on limited spectral information. Using low-cost sensors, spectral characteristics of the light condition can be acquired and used to classify the underlying light source type, which allows for a more accurate estimation of the solar panel response. The method was evaluated experimentally for a number of common indoor light sources and under different conditions. Evaluation results have shown that the method can be used to distinguish the light sources under test with very high classification accuracy. Moreover, the method can be used accurately in situations with limited interference. This makes it a low-cost alternative to the characterization of light conditions using spectrometers, the use of which is infeasible in spatially distributed characterization applications.
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| 9. |
- Rydblom, Staffan, 1975-, et al.
(författare)
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Liquid Water Content and Droplet Sizing Shadowgraph Measuring System for Wind Turbine Icing Detection
- 2016
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Ingår i: IEEE Sensors Journal. - : IEEE Sensors Council. - 1530-437X .- 1558-1748. ; 16:8, s. 2714-2725
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Tidskriftsartikel (refereegranskat)abstract
- This study shows that the liquid water content (LWC) and the median volume diameter (MVD) can be derived from images of water droplets using a shadowgraph imaging system with incoherent LED illumination.Icing on structures such as a wind turbine is the result of a combination of LWC and MVD and other parameters like temperature, humidity and wind speed. Today, LWC and MVD are not commonly measured for wind turbines. Systems for measuring these properties are often expensive or impractical in terms of location or remote reading. The aim of this study is to gain knowledge about how to design a single instrument based on imaging that has the ability to measure these properties with enough precision and accuracy to detect icing conditions for wind turbines.A method to calculate both the LWC and the MVD from the same images is described in this paper. The size of one droplet is determined by measuring the shadow created by the droplet in background illumination. The concentration is calculated by counting the measured droplets and estimating the volumes in which these droplets can be observed.In the described study, the observation volume is shown to be dependent on the particle size and the signal to noise ratio (SNR) for each measured particle. An expected coefficient of variation of the LWC depending on the droplet size is shown to be 2.4 percent for droplets 10 µm in diameter and 1.6 percent for 25 µm droplets. This is based on an error estimation of the laboratory measurements calibrated using a micrometer dot scale.
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| 10. |
- Xu, Ye, et al.
(författare)
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A Survey on Variable Reluctance Energy Harvesters in Low-Speed Rotating Applications
- 2018
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 18:8, s. 3426-3435
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Tidskriftsartikel (refereegranskat)abstract
- Energy harvesting converts ambient energy to electrical energy that can be used to power, for example, sensors and sensor systems. Variable reluctance energy harvesting is a suitable candidate for the conversion of rotary kinetic motion, an energy form commonly found in industrial applications. The implementation of a variable reluctance energy harvester, however, has a significant effect on its performance and is not well studied. In this paper, we therefore conduct a survey on different structures of variable reluctance energy harvesters. Six existing structures, previously used in variable reluctance sensors, are presented and analyzed according to their approaches for magnetic flux change improvement. Together with a newly proposed structure, these structures are evaluated based on a finite element analysis, and their results are compared. It is demonstrated that the choice of structure considerably affects the power output of the harvester and is dependent on the improvement approaches the structure utilizes. The newly proposed structure outperforms all existing structures with respect to power output and power density, which comes at a cost of higher parasitic torque generation. A 53-fold power improvement over the reference and an 1.2-fold power improvement over the next best structure is observed. As a result, applications of variable reluctance energy harvesting become viable even at low angular velocities.
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