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Laufer B, Docherty PD, Murray R, Krueger-Ziolek S, Jalal NA, Hoeflinger F, Rupitsch SJ, Reindl L, Moeller K. Sensor Selection for Tidal Volume Determination via Linear Regression-Impact of Lasso versus Ridge Regression. Sensors (Basel) 2023; 23:7407. [PMID: 37687863 PMCID: PMC10490437 DOI: 10.3390/s23177407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 08/18/2023] [Accepted: 08/23/2023] [Indexed: 09/10/2023]
Abstract
The measurement of respiratory volume based on upper body movements by means of a smart shirt is increasingly requested in medical applications. This research used upper body surface motions obtained by a motion capture system, and two regression methods to determine the optimal selection and placement of sensors on a smart shirt to recover respiratory parameters from benchmark spirometry values. The results of the two regression methods (Ridge regression and the least absolute shrinkage and selection operator (Lasso)) were compared. This work shows that the Lasso method offers advantages compared to the Ridge regression, as it provides sparse solutions and is more robust to outliers. However, both methods can be used in this application since they lead to a similar sensor subset with lower computational demand (from exponential effort for full exhaustive search down to the order of O (n2)). A smart shirt for respiratory volume estimation could replace spirometry in some cases and would allow for a more convenient measurement of respiratory parameters in home care or hospital settings.
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Affiliation(s)
- Bernhard Laufer
- Institute of Technical Medicine (ITeM), Furtwangen University, 78054 Villingen-Schwenningen, Germany
| | - Paul D. Docherty
- Institute of Technical Medicine (ITeM), Furtwangen University, 78054 Villingen-Schwenningen, Germany
- Department of Mechanical Engineering, University of Canterbury, Christchurch 8041, New Zealand
| | - Rua Murray
- School of Mathematics and Statistics, University of Canterbury, Christchurch 8041, New Zealand
| | - Sabine Krueger-Ziolek
- Institute of Technical Medicine (ITeM), Furtwangen University, 78054 Villingen-Schwenningen, Germany
| | - Nour Aldeen Jalal
- Institute of Technical Medicine (ITeM), Furtwangen University, 78054 Villingen-Schwenningen, Germany
- Innovation Center Computer Assisted Surgery (ICCAS), University of Leipzig, 04109 Leipzig, Germany
| | - Fabian Hoeflinger
- Department of Microsystems Engineering, University of Freiburg, 79085 Freiburg, Germany
| | - Stefan J. Rupitsch
- Department of Microsystems Engineering, University of Freiburg, 79085 Freiburg, Germany
| | - Leonhard Reindl
- Department of Microsystems Engineering, University of Freiburg, 79085 Freiburg, Germany
| | - Knut Moeller
- Institute of Technical Medicine (ITeM), Furtwangen University, 78054 Villingen-Schwenningen, Germany
- Department of Mechanical Engineering, University of Canterbury, Christchurch 8041, New Zealand
- Department of Microsystems Engineering, University of Freiburg, 79085 Freiburg, Germany
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Laufer B, Jalal NA, Krueger-Ziolek S, Docherty PD, Murray R, Hoeflinger F, Reindl L, Moeller K. Optimal Positioning of Inertial Measurement Units in a Smart Shirt for Determining Respiratory Volume. Annu Int Conf IEEE Eng Med Biol Soc 2023; 2023:1-4. [PMID: 38082618 DOI: 10.1109/embc40787.2023.10340473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Tidal volume can be estimated using the surface motions of the upper body induced by respiration. However, the precision and instrumentation of such estimation must be improved to allow widespread application. In this study, respiration induced changes in parameters that can be recorded with inertial measurement units are examined to determine tidal volumes. Based on the data of an optical motion capture system, the optimal positions of inertial measurement units (IMU) in a smart shirt for sets of 4, 5 or 6 sensors were determined. The errors observed indicate the potential to determine tidal volumes using IMUs in a smart shirt.Clinical Relevance- The measurement of respiratory volumes via a low-cost and unobtrusive smart shirt would be a major advance in clinical diagnostics. In particular, conventional methods are expensive, and uncomfortable for conscious patients if measurement is desired over an extended period. A smart-shirt based on inertial sensors would allow a comfortable measurement and could be used in many clinical scenarios - from sleep apnoea monitoring to homecare and respiratory monitoring of comatose patients.
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Laufer B, Hoeflinger F, Docherty PD, Jalal NA, Krueger-Ziolek S, Rupitsch SJ, Reindl L, Moeller K. Characterisation and Quantification of Upper Body Surface Motions for Tidal Volume Determination in Lung-Healthy Individuals. Sensors (Basel) 2023; 23:1278. [PMID: 36772318 PMCID: PMC9920533 DOI: 10.3390/s23031278] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/12/2023] [Accepted: 01/18/2023] [Indexed: 06/18/2023]
Abstract
Measurement of accurate tidal volumes based on respiration-induced surface movements of the upper body would be valuable in clinical and sports monitoring applications, but most current methods lack the precision, ease of use, or cost effectiveness required for wide-scale uptake. In this paper, the theoretical ability of different sensors, such as inertial measurement units, strain gauges, or circumference measurement devices to determine tidal volumes were investigated, scrutinised and evaluated. Sixteen subjects performed different breathing patterns of different tidal volumes, while using a motion capture system to record surface motions and a spirometer as a reference to obtain tidal volumes. Subsequently, the motion-capture data were used to determine upper-body circumferences, tilt angles, distance changes, movements and accelerations-such data could potentially be measured using optical encoders, inertial measurement units, or strain gauges. From these parameters, the measurement range and correlation with the volume signal of the spirometer were determined. The highest correlations were found between the spirometer volume and upper body circumferences; surface deflection was also well correlated, while accelerations carried minor respiratory information. The ranges of thorax motion parameters measurable with common sensors and the values and correlations to respiratory volume are presented. This article thus provides a novel tool for sensor selection for a smart shirt analysis of respiration.
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Affiliation(s)
- Bernhard Laufer
- Institute of Technical Medicine (ITeM), Furtwangen University, 78054 Villingen-Schwenningen, Germany
| | - Fabian Hoeflinger
- Department of Microsystems Engineering, University of Freiburg, 79085 Freiburg, Germany
| | - Paul D. Docherty
- Institute of Technical Medicine (ITeM), Furtwangen University, 78054 Villingen-Schwenningen, Germany
- Department of Mechanical Engineering, University of Canterbury, Christchurch 8041, New Zealand
| | - Nour Aldeen Jalal
- Institute of Technical Medicine (ITeM), Furtwangen University, 78054 Villingen-Schwenningen, Germany
- Innovation Center Computer Assisted Surgery (ICCAS), University of Leipzig, 04109 Leipzig, Germany
| | - Sabine Krueger-Ziolek
- Institute of Technical Medicine (ITeM), Furtwangen University, 78054 Villingen-Schwenningen, Germany
| | - Stefan J. Rupitsch
- Department of Microsystems Engineering, University of Freiburg, 79085 Freiburg, Germany
| | - Leonhard Reindl
- Department of Microsystems Engineering, University of Freiburg, 79085 Freiburg, Germany
| | - Knut Moeller
- Institute of Technical Medicine (ITeM), Furtwangen University, 78054 Villingen-Schwenningen, Germany
- Department of Microsystems Engineering, University of Freiburg, 79085 Freiburg, Germany
- Department of Mechanical Engineering, University of Canterbury, Christchurch 8041, New Zealand
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4
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Laufer B, Docherty PD, Jalal NA, Krueger-Ziolek S, Hoeflinger F, Reindl L, Moeller K. Tiffeneau-Testing by means of a Smart-Shirt. Current Directions in Biomedical Engineering 2022. [DOI: 10.1515/cdbme-2022-1157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Abstract
Tiffeneau manoeuvres are an important method in pulmonary function testing of the human lungs and can help to diagnose respiratory obstructions. Data from a motion capture system and a spirometer was used to evaluate Tiffeneau indexes which can theoretically be derived via a Smart-Shirt that incorporates three circumference measurements of the upper body. The mean error was 4.5% regarding the Tiffeneau indexes gained by the spirometer, indicating that clinical diagnosis of obstruction is potentially possible using a Smart-Shirt.
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Affiliation(s)
- Bernhard Laufer
- Institute of Technical Medicine (ITeM), Furtwangen University, Villingen- Schwenningen , Germany
| | | | | | | | | | | | - Knut Moeller
- ITeM, Furtwangen University, Villingen-Schwenningen , Germany
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Laufer B, Docherty PD, Murray R, Jalal NA, Hoeflinger F, Reindl L, Moeller K. Optimal Sensor Location in a Smart-Shirt to Measure Accurate Tidal Volumes During Abdominal and Thoracic Respiration. Current Directions in Biomedical Engineering 2021. [DOI: 10.1515/cdbme-2021-2146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Abstract
The determination of respiratory parameters via respiration induced surface movements of the upper body has been the subject of research for many years. The displacements of 102 motion capture markers were evaluated in this study in terms of their information content with respect to the tidal volume recorded in parallel using a spirometer. Independent of the breathing types (spontaneous breathing, abdominal breathing, or chest breathing), the number and the location of sensors in a smart shirt to obtain tidal volume information was determined. Only 9 of 102 sensors were sufficient to obtain breathing volume information.
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Affiliation(s)
- Bernhard Laufer
- Institute of Technical Medicine (ITeM), Furtwangen University, Villingen- Schwenningen , Germany
| | | | - Rua Murray
- University of Canterbury, Christchurch , New Zealand
| | | | | | | | - Knut Moeller
- ITeM, Furtwangen University, Villingen-Schwenningen , Germany
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Laufer B, Krueger-Ziolek S, Docherty PD, Hoeflinger F, Reindl L, Moeller K. An alternative way to measure respiration induced changes of circumferences: a pilot study. Annu Int Conf IEEE Eng Med Biol Soc 2020; 2020:4632-4635. [PMID: 33019026 DOI: 10.1109/embc44109.2020.9175578] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Various measurement systems can be used to obtain dynamic circumferences of the human upper body, but each of these systems has disadvantages. In this feasibility study we introduce a non-invasive and wearable thoracic belt to measure dynamic changes of circumferences of thorax or abdomen. To evaluate this approach, five subjects undertook various breaths of disparate tidal volumes, which were measured by the belt and simultaneously by a motion capture system which provided a reference metric.The results of the belt concurred with the reference system. A coefficient of determination (adjusted R2) of 0.99 and a mean squared error of less than 0.87 mm2 showed that the belt is capable of measuring changes accurately and a couple of respiratory parameters, such as the respiratory rate, can be obtained.Clinical Relevance-The introduced system links surface motions of the upper body with the underlying respiratory mechanics. Thus it provides some respiratory parameters without the disadvantages of a facemask or a mouthpiece. The system could allow the analysis of breathing status in some clinical applications and could be used for low-cost monitoring in homecare or to analyse respiratory parameters during sports.
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Bordoy J, Schott DJ, Xie J, Bannoura A, Klein P, Striet L, Hoeflinger F, Haering I, Reindl L, Schindelhauer C. Acoustic Indoor Localization Augmentation by Self-Calibration and Machine Learning. Sensors (Basel) 2020; 20:s20041177. [PMID: 32093398 PMCID: PMC7070902 DOI: 10.3390/s20041177] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 01/31/2020] [Accepted: 02/14/2020] [Indexed: 11/21/2022]
Abstract
An acoustic transmitter can be located by having multiple static microphones. These microphones are synchronized and measure the time differences of arrival (TDoA). Usually, the positions of the microphones are assumed to be known in advance. However, in practice, this means they have to be manually measured, which is a cumbersome job and is prone to errors. In this paper, we present two novel approaches which do not require manual measurement of the receiver positions. The first method uses an inertial measurement unit (IMU), in addition to the acoustic transmitter, to estimate the positions of the receivers. By using an IMU as an additional source of information, the non-convex optimizers are less likely to fall into local minima. Consequently, the success rate is increased and measurements with large errors have less influence on the final estimation. The second method we present in this paper consists of using machine learning to learn the TDoA signatures of certain regions of the localization area. By doing this, the target can be located without knowing where the microphones are and whether the received signals are in line-of-sight or not. We use an artificial neural network and random forest classification for this purpose.
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Affiliation(s)
- Joan Bordoy
- Department of Computer Science (IIF), University of Freiburg, 79110 Freiburg, Germany; (J.X.); (P.K.); (L.S.); (C.S.)
- Correspondence: ; Tel.: +49-761-203-7070
| | - Dominik Jan Schott
- Department of Microsystems Engineering (IMTEK), University of Freiburg, 79110 Freiburg, Germany; (D.J.S.); (L.R.)
| | - Jizhou Xie
- Department of Computer Science (IIF), University of Freiburg, 79110 Freiburg, Germany; (J.X.); (P.K.); (L.S.); (C.S.)
| | - Amir Bannoura
- Department of Software Engineering, Bethlehem University, P.O. Box 11407, Bethlehem, 92248 Jerusalem, Palestine;
| | - Philip Klein
- Department of Computer Science (IIF), University of Freiburg, 79110 Freiburg, Germany; (J.X.); (P.K.); (L.S.); (C.S.)
| | - Ludwig Striet
- Department of Computer Science (IIF), University of Freiburg, 79110 Freiburg, Germany; (J.X.); (P.K.); (L.S.); (C.S.)
| | - Fabian Hoeflinger
- Fraunhofer Institute for Highspeed Dynamics, Ernst-Mach-Institute (EMI), 79104 Freiburg, Germany; (F.H.); (I.H.)
| | - Ivo Haering
- Fraunhofer Institute for Highspeed Dynamics, Ernst-Mach-Institute (EMI), 79104 Freiburg, Germany; (F.H.); (I.H.)
| | - Leonhard Reindl
- Department of Microsystems Engineering (IMTEK), University of Freiburg, 79110 Freiburg, Germany; (D.J.S.); (L.R.)
| | - Christian Schindelhauer
- Department of Computer Science (IIF), University of Freiburg, 79110 Freiburg, Germany; (J.X.); (P.K.); (L.S.); (C.S.)
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Laufer B, Krueger-Ziolek S, Docherty PD, Hoeflinger F, Reindl L, Moeller K. Tidal volume via circumferences of the upper body: a pilot study. Annu Int Conf IEEE Eng Med Biol Soc 2020; 2019:3559-3562. [PMID: 31946647 DOI: 10.1109/embc.2019.8857688] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The gold standard for tidal volume measurement is spirometry. Based on retrospective data, this study evaluates different geometric lung models in their ability to deliver accurate tidal volumes from changes in thoracic and abdominal circumference. The geometric lung models showed good coefficients of determination (adjusted R2 >0.97) compared to the tidal volumes measured by a body plethysmograph. Tidal volumes obtained by circumference changes might be used in surveillance systems to analyze respiration without a face mask.
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Gruenwald W, Bhattacharrya M, Jansen D, Reindl L. Electromagnetic Analysis, Characterization and Discussion of Inductive Transmission Parameters for Titanium Based Housing Materials in Active Medical Implantable Devices. Materials (Basel) 2018; 11:ma11112089. [PMID: 30366401 PMCID: PMC6266279 DOI: 10.3390/ma11112089] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 10/18/2018] [Accepted: 10/19/2018] [Indexed: 11/16/2022]
Abstract
The growing demand for active medical implantable devices requires data and or power links between the implant and the outside world. Every implant has to be encapsulated from the body by a specific housing and one of the most common materials used is titanium or titanium alloy. Titanium thas the necessary properties in terms of mechanical and chemical stability and biocompatibility. However, its electrical conductivity presents a challenge for the electromagnetic transmission of data and power. The proposed paper presents a fast and practical method to determine the necessary transmission parameters for titanium encapsulated implants. Therefore, the basic transformer-transmission-model is used with measured or calculated key values for the inductances. Those are then expanded with correction factors to determine the behavior with the encapsulation. The correction factors are extracted from finite element method simulations. These also enable the analysis of the magnetic field distribution inside of the housing. The simulated transmission properties are very close to the measured values. Additionally, based on lumped elements and magnetic field distribution, the influential parameters are discussed in the paper. The parameter discussion describes how to enhance the transmitted power, data-rate or distance, or to reduce the size of the necessary coils. Finally, an example application demonstrates the usage of the methods.
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Affiliation(s)
- Waldemar Gruenwald
- Institute for Applied Research, Offenburg University, 77652 Offenburg, Germany.
| | | | - Dirk Jansen
- Institute for Applied Research, Offenburg University, 77652 Offenburg, Germany.
| | - Leonhard Reindl
- Department of Microsystems Engineering, Institute of Albert-Ludwigs University, 79098 Freiburg, Germany.
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Laufer B, Krueger-Ziolek S, Moeller K, Docherty PD, Hoeflinger F, Reindl L. Hierarchical Analysis of Thorax Models to Measure Tidal Volume. Current Directions in Biomedical Engineering 2018. [DOI: 10.1515/cdbme-2018-0102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
AbstractMotion tracking of thorax kinematics can be used to determine respiration. However, determining a minimal sensor configuration from 64 candidate sensor locations is associated with high computational costs. Hence, a hierarchical optimization method was proposed to determine the optimal combination of sensors. The hierarchical method was assessed by its ability to quickly determine the sensor combination that will yield optimal modelled tidal volume compared to body plethysmograph measurements. This method was able to find the optimal sensor combinations, in approximately 2% of the estimated time required by an exhaustive search.
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Affiliation(s)
- Bernhard Laufer
- 1Institute of Technical Medicine (ITeM), Furtwangen University,Villingen-Schwenningen, Germany
| | - Sabine Krueger-Ziolek
- 2Institute of Technical Medicine, Furtwangen University,Villingen-Schwenningen, Germany
| | - Knut Moeller
- 2Institute of Technical Medicine, Furtwangen University,Villingen-Schwenningen, Germany
| | - Paul David Docherty
- 3Department of Mechanical Engineering, University of Canterbury,Christchurch, New Zealand
| | - Fabian Hoeflinger
- 4Department of Microsystems Engineering, University of Freiburg,Freiburg, Germany
| | - Leonhard Reindl
- 4Department of Microsystems Engineering, University of Freiburg,Freiburg, Germany
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Bhattacharyya M, Gruenwald W, Jansen D, Reindl L, Aghassi-Hagmann J. An Ultra-Low-Power RFID/NFC Frontend IC Using 0.18 μm CMOS Technology for Passive Tag Applications. Sensors (Basel) 2018; 18:s18051452. [PMID: 29735939 PMCID: PMC5982218 DOI: 10.3390/s18051452] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 04/10/2018] [Accepted: 04/18/2018] [Indexed: 11/16/2022]
Abstract
Battery-less passive sensor tags based on RFID or NFC technology have achieved much popularity in recent times. Passive tags are widely used for various applications like inventory control or in biotelemetry. In this paper, we present a new RFID/NFC frontend IC (integrated circuit) for 13.56 MHz passive tag applications. The design of the frontend IC is compatible with the standard ISO 15693/NFC 5. The paper discusses the analog design part in details with a brief overview of the digital interface and some of the critical measured parameters. A novel approach is adopted for the demodulator design, to demodulate the 10% ASK (amplitude shift keying) signal. The demodulator circuit consists of a comparator designed with a preset offset voltage. The comparator circuit design is discussed in detail. The power consumption of the bandgap reference circuit is used as the load for the envelope detection of the ASK modulated signal. The sub-threshold operation and low-supply-voltage are used extensively in the analog design—to keep the power consumption low. The IC was fabricated using 0.18 μ m CMOS technology in a die area of 1.5 mm × 1.5 mm and an effective area of 0.7 m m 2 . The minimum supply voltage desired is 1.2 V, for which the total power consumption is 107 μ W. The analog part of the design consumes only 36 μ W, which is low in comparison to other contemporary passive tags ICs. Eventually, a passive tag is developed using the frontend IC, a microcontroller, a temperature and a pressure sensor. A smart NFC device is used to readout the sensor data from the tag employing an Android-based application software. The measurement results demonstrate the full passive operational capability. The IC is suitable for low-power and low-cost industrial or biomedical battery-less sensor applications. A figure-of-merit (FOM) is proposed in this paper which is taken as a reference for comparison with other related state-of-the-art researches.
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Affiliation(s)
- Mayukh Bhattacharyya
- Institute for Applied Research, University of Applied Sciences Offenburg, 77652 Offenburg, Germany.
| | - Waldemar Gruenwald
- Institute for Applied Research, University of Applied Sciences Offenburg, 77652 Offenburg, Germany.
| | - Dirk Jansen
- Institute for Applied Research, University of Applied Sciences Offenburg, 77652 Offenburg, Germany.
| | - Leonhard Reindl
- Department of Microsystems Engineering, University of Freiburg, 79098 Freiburg, Germany.
| | - Jasmin Aghassi-Hagmann
- Institute for Applied Research, University of Applied Sciences Offenburg, 77652 Offenburg, Germany.
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-vom-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
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12
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Kumberg T, Schindelhauer C, Reindl L. Exploiting Concurrent Wake-Up Transmissions Using Beat Frequencies. Sensors (Basel) 2017; 17:E1717. [PMID: 28933749 PMCID: PMC5579554 DOI: 10.3390/s17081717] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 07/12/2017] [Accepted: 07/18/2017] [Indexed: 11/30/2022]
Abstract
Wake-up receivers are the natural choice for wireless sensor networks because of their ultra-low power consumption and their ability to provide communications on demand. A downside of ultra-low power wake-up receivers is their low sensitivity caused by the passive demodulation of the carrier signal. In this article, we present a novel communication scheme by exploiting purposefully-interfering out-of-tune signals of two or more wireless sensor nodes, which produce the wake-up signal as the beat frequency of superposed carriers. Additionally, we introduce a communication algorithm and a flooding protocol based on this approach. Our experiments show that our approach increases the received signal strength up to 3 dB, improving communication robustness and reliability. Furthermore, we demonstrate the feasibility of our newly-developed protocols by means of an outdoor experiment and an indoor setup consisting of several nodes. The flooding algorithm achieves almost a 100% wake-up rate in less than 20 ms.
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Affiliation(s)
- Timo Kumberg
- Department of Microsystems Engineering - IMTEK, Laboratory for Electrical Instrumentation, University of Freiburg, Georges-Koehler-Allee 106, 79110 Freiburg, Germany.
| | - Christian Schindelhauer
- Department of Computer Science - IIF, Computer Networks and Telematics, University of Freiburg, Georges-Koehler-Allee 51, 79110 Freiburg, Germany.
| | - Leonhard Reindl
- Department of Microsystems Engineering - IMTEK, Laboratory for Electrical Instrumentation, University of Freiburg, Georges-Koehler-Allee 106, 79110 Freiburg, Germany.
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13
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Stoecklin S, Volk T, Yousaf A, Reindl L. A programmable and self-adjusting class E amplifier for efficient wireless powering of biomedical implants. Annu Int Conf IEEE Eng Med Biol Soc 2016; 2015:3193-6. [PMID: 26736971 DOI: 10.1109/embc.2015.7319071] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
In this paper, an enhanced approach of a class E amplifier being insensitive to coil impedance variations is presented. While state of the art class E amplifiers widely being used to supply implanted systems show a strong degradation of efficiency when powering distance, coil orientation or the implant current consumption deviate from the nominal design, the presented concept is able to detect these deviations on-line and to reconfigure the amplifier automatically. The concept is facilitated by a new approach of sensing the load impedance without interruption of the power supply to the implant, while the main components of the class E amplifier are programmable by software. Therefore, the device is able to perform dynamic impedance matching. Besides presenting the operational principle and the design equations, we show an adaptive prototype reader system which achieves a drain efficiency of up to 92% for a wide range of reflected coil impedances from 1 to 40 Ω. The integrated communication concept allows downlink data rates of up to 500 kBit/s, while the load modulation based uplink from implant to reader was verified of providing up to 1.35 MBit/s.
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14
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Hamp Q, Reindl L, Güthlin D. Decision-making behaviour during urban search and rescue: a case study of Germany. Disasters 2014; 38:84-107. [PMID: 24325240 DOI: 10.1111/disa.12035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The objective of assisting with tasks and decisions during incident response is to reduce the risks to victims and rescue personnel while increasing the efficiency of the rescue operation. Handling uncertain information during urban search and rescue (USAR) missions represents additional stress to the decision-maker. The aim of this study is to identify the decision-making behaviour of rescuers during USAR missions to pinpoint trapped or buried victims in debris in order to design assistance technologies and decision-support systems that meet their needs. In 2010, a survey was conducted among 10-15 per cent of all German rescue personnel specialised in search tasks. One of the major results of this survey is that a subjective assessment of the reliability of information available from heterogeneous sources influences the rescuers' actions and that there is no methodology for decision-making involving uncertain information. In addition, the study found that compliance with procedures does not require assistance.
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Affiliation(s)
- Quirin Hamp
- Scientist, Laboratory for Electrical Instrumentation, Department of Microsystems Engineering (IMTEK), University of Freiburg, Germany
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Oller J, Demirkol I, Casademont J, Paradells J, Gamm GU, Reindl L. Performance evaluation and comparative analysis of SubCarrier Modulation Wake-up Radio systems for energy-efficient wireless sensor networks. Sensors (Basel) 2013; 14:22-51. [PMID: 24451452 PMCID: PMC3926545 DOI: 10.3390/s140100022] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 12/10/2013] [Accepted: 12/12/2013] [Indexed: 11/16/2022]
Abstract
Energy-efficient communication is one of the main concerns of wireless sensor networks nowadays. A commonly employed approach for achieving energy efficiency has been the use of duty-cycled operation of the radio, where the node's transceiver is turned off and on regularly, listening to the radio channel for possible incoming communication during its on-state. Nonetheless, such a paradigm performs poorly for scenarios of low or bursty traffic because of unnecessary activations of the radio transceiver. As an alternative technology, Wake-up Radio (WuR) systems present a promising energy-efficient network operation, where target devices are only activated in an on-demand fashion by means of a special radio signal and a WuR receiver. In this paper, we analyze a novel wake-up radio approach that integrates both data communication and wake-up functionalities into one platform, providing a reconfigurable radio operation. Through physical experiments, we characterize the delay, current consumption and overall operational range performance of this approach under different transmit power levels. We also present an actual single-hop WuR application scenario, as well as demonstrate the first true multi-hop capabilities of a WuR platform and simulate its performance in a multi-hop scenario. Finally, by thorough qualitative comparisons to the most relevant WuR proposals in the literature, we state that the proposed WuR system stands out as a strong candidate for any application requiring energy-efficient wireless sensor node communications.
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Affiliation(s)
- Joaquim Oller
- Department of Telematics Engineering, Universitat Politècnica de Catalunya, C/Jordi Girona 1-3, Barcelona 08034, Spain.
| | - Ilker Demirkol
- Department of Telematics Engineering, Universitat Politècnica de Catalunya, C/Jordi Girona 1-3, Barcelona 08034, Spain.
| | - Jordi Casademont
- Department of Telematics Engineering, Universitat Politècnica de Catalunya, C/Jordi Girona 1-3, Barcelona 08034, Spain.
| | - Josep Paradells
- Department of Telematics Engineering, Universitat Politècnica de Catalunya, C/Jordi Girona 1-3, Barcelona 08034, Spain.
| | - Gerd Ulrich Gamm
- Institut für Mikrosystemtechnik-IMTEK, Albert-Ludwigs-Universität Freiburg, Georges-Köhler-Allee 103, Freiburg 79110, Germany.
| | - Leonhard Reindl
- Institut für Mikrosystemtechnik-IMTEK, Albert-Ludwigs-Universität Freiburg, Georges-Köhler-Allee 103, Freiburg 79110, Germany.
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Richter D, Sakharov S, Forsén E, Mayer E, Reindl L, Fritze H. Thin Film Electrodes for High Temperature Surface Acoustic Wave Devices. ACTA ACUST UNITED AC 2011. [DOI: 10.1016/j.proeng.2011.12.042] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Weis F, Kilger E, Beiras-Fernandez A, Nassau K, Reuter D, Goetz A, Lamm P, Reindl L, Briegel J. Association between vasopressor dependence and early outcome in patients after cardiac surgery. Anaesthesia 2006; 61:938-42. [PMID: 16978306 DOI: 10.1111/j.1365-2044.2006.04779.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Arterial hypotension with vasopressor dependence is a major problem after cardiac surgery. We evaluated the early postoperative course of 1558 consecutive patients scheduled for cardiac surgery, and compared the outcome of patients with and without vasopressor dependence (defined as the need for > 0.1 microg x kg(-1) x h(-1) noradrenaline for > 3 h in the face of normovolaemia). Vasopressor dependence was diagnosed in 424 patients (27%) and was associated with a higher incidence of postoperative renal failure (67 (15.7%) vs 7 (0.6%), respectively; p < 0.0001), a longer duration of ventilation (median IQR [range]) 14 (8-26 [6-39]) h vs 8 (5-11 [4-32]) h; p < 0.0001), a greater need for red cell transfusion (3 (1-5 [0-10]) units vs 1 (0-2 [0-4]) units; p < 0.001) and a longer length of stay in the ICU (4 (2-6 [2-9] days) vs 2 (1-3 [1-6] days; p < 0.001). Vasopressor dependence could be predicted from a combination of factors, including pre-operative ejection fraction < 37%, cardiopulmonary bypass lasting > 94 min, and postoperative interleukin-6 > 837 pg x ml(-1).
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Affiliation(s)
- F Weis
- Department of Anaesthesiology, University of Munich, Klinikum Grosshadern, Munich, Germany.
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18
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Schuster S, Scheiblhofer S, Reindl L, Stelzer A. Performance evaluation of algorithms for SAW-based temperature measurement. IEEE Trans Ultrason Ferroelectr Freq Control 2006; 53:1177-85. [PMID: 16846150 DOI: 10.1109/tuffc.2006.1642516] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Whenever harsh environmental conditions such as high temperatures, accelerations, radiation, etc., prohibit usage of standard temperature sensors, surface acoustic wave-based temperature sensors are the first choice for highly reliable wireless temperature measurement. Interrogation of these sensors is often based on frequency modulated or frequency stepped continuous wave-based radars (FMCW/FSCW). We investigate known algorithms regarding their achievable temperature accuracy and their applicability in practice. Furthermore, some general rules of thumb for FMCW/FSCW radar-based range estimation by means of the Cramer-Rao lower bound (CRLB) for frequency and phase estimation are provided. The theoretical results are verified on both simulated and measured data.
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Affiliation(s)
- Stefan Schuster
- Institute for Communications and Information Engineering, Johannes Kepler University, AT-4040 Linz, Austria.
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Fachberger R, Bruckner G, Knoll G, Hauser R, Biniasch J, Reindl L. Applicability of LiNbO3, langasite and GaPO4 in high temperature SAW sensors operating at radio frequencies. IEEE Trans Ultrason Ferroelectr Freq Control 2004; 51:1427-1431. [PMID: 15600086 DOI: 10.1109/tuffc.2004.1367482] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The applicability of LiNbO3, langasite and GaPO4 for use as crystal substrates in high temperature surface acoustic wave (SAW) sensors operating at radio frequencies was investigated. Material properties were determined by the use of SAW test devices processed with conventional lithography. On GaPO4, predominantly surface defects limit the accessible frequencies to values of 1 GHz. Langasite SAW devices could be operated up to 3 GHz; however, high acoustic losses of 20 dB/micros were observed. On LiNbO3, the acoustic losses measured up to 3.5 GHz are one order of magnitude less. Hence, SAW sensors capable of wireless interrogation were designed and processed on YZ-cut LiNbO3. The devices could be successfully operated in the industrial-scientific-medical (ISM) band from 2.40 to 2.4835 GHz up to 400 degrees C.
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Affiliation(s)
- René Fachberger
- Carinthian Tech Research, Europastrasse 4/1, A-9524 Villach, Austria.
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20
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Vollmers HP, Zimmermann U, Krenn V, Timmermann W, Illert B, Hensel F, Hermann R, Thiede A, Wilhelm M, Rückle-Lanz H, Reindl L, Müller-Hermelink HK. Adjuvant therapy for gastric adenocarcinoma with the apoptosis-inducing human monoclonal antibody SC-1: first clinical and histopathological results. Oncol Rep 1998; 5:549-52. [PMID: 9538151 DOI: 10.3892/or.5.3.549] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In a first clinical trial with the apoptosis-inducing human antibody SC-1 eight patients with poorly differentiated stomach adenocarcinoma of diffuse-type received 20 or 30 mg of purified SC-1 antibody intravenously, followed 24 or 48 h later by gastrectomy and lymphadenectomy. In seven cases a significant induction of apoptotic activity was measured in primary tumors as compared with earlier biopsy material and in five patients a significant regression of tumor mass could be determined histopathologically. No toxic crossreactivity was observed with normal tissue or organs of patients.
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Affiliation(s)
- H P Vollmers
- Institut für Pathologie, Josef-Schneider-Str. 2, Würzburg, 97080, Germany
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Reindl L, Scholl G, Ostertag T, Scherr H, Wolff U, Schmidt F. Theory and application of passive SAW radio transponders as sensors. IEEE Trans Ultrason Ferroelectr Freq Control 1998; 45:1281-1292. [PMID: 18244291 DOI: 10.1109/58.726455] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Surface acoustic wave (SAW) radio transponders make it possible to read identification codes or measurement values from a remote location. The decisive advantage of these SAW transponders lies in their passive operation (i.e., no power-supply), and in the possibility of wireless installation at particularly inaccessible locations. The passive SAW transponders are maintenance free. Identification marks respond to an interrogation signal with their nonchanging identification pattern. In wireless SAW sensors the physical or chemical properties to be detected change the propagation characteristics of the SAW. SAW radio transponders are advantageously placed on moving or rotating parts and in hazardous environments such as contaminated or high voltage areas. They also can be used for contactless measurements in high vacuum process chambers, under concrete, extreme heat, or strong radioactive radiation, where the use of conventional sensors is complicated, dangerous, or expensive. In this paper we discuss the principles of wireless passive SAW transponders and present a radio frequency interrogation unit and several passive radio SAW sensors developed for noncontact measurements of temperatures, pressures, torques, and currents.
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Affiliation(s)
- L Reindl
- Corporate Technology, D-81739 Munich, Germany.
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Ruppel CW, Dill R, Fischerauer A, Fischerauer G, Gawlik A, Machui J, Muller F, Reindl L, Ruile W, Scholl G, Schropp I, Wagner KC. SAW devices for consumer communication applications. IEEE Trans Ultrason Ferroelectr Freq Control 1993; 40:438-452. [PMID: 18263205 DOI: 10.1109/58.238094] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
An overview of surface acoustic wave (SAW) filter techniques available for different applications is given. Techniques for TV IF applications are outlined, and typical structures are presented. This is followed by a discussion of applications for SAW resonators. Low-loss devices for mobile communication systems and pager applications are examined. Tapped delay lines (matched filters) and convolvers for code-division multiaccess (CDMA) systems are also covered. Although simulation procedures are not considered, for many devices the theoretical frequency response is presented along with the measurement curve.
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