Position Of Tag Research Articles

Robot-Based Indoor Positioning of UHF-RFID Tags: The SAR Method With Multiple Trajectories

This article presents the application of the synthetic aperture radar (SAR) localization method for indoor positioning of ultrahigh-frequency (UHF)-radio frequency identification (RFID) tags when the robot-mounted reader antenna moves along multiple trajectories. By properly combining the phase data associated with a set of multiple paths, the whole length of the combined synthetic apertures enlarges, and then, the localization accuracy may improve. Besides, during consecutive inventory rounds, several tag position estimates are available, and they can be profitably combined to minimize the localization uncertainty. Different combination approaches are investigated to determine the best choice to improve the localization performance. The method capabilities are discussed through numerical analysis by considering different configurations of the multiple apertures and different measurement uncertainty sources. Finally, the proposed localization method is validated through an experimental analysis carried out with commercial RFID hardware and a robotic wheeled walker, in an indoor scenario, by employing different types of tags. The knowledge of the reader/robot trajectory required by the SAR method is here achieved with an optical system.

UWB-Based Self-Localization Strategies: A Novel ICP-Based Method and a Comparative Assessment for Noisy-Ranges-Prone Environments.

Ultra-Wide-Band (UWB) positioning systems are now a real option to estimate the position of generic agents (e.g., robots) within indoor/GPS-denied environments. However, these environments can comprise metallic structures or other elements which can negatively affect the signal transmission and hence the accuracy of UWB-based position estimations. Regarding this fact, this paper proposes a novel method based on point-to-sphere ICP (Iterative Closest Point) to determine the 3D position of a UWB tag. In order to improve the results in noise-prone environments, our method first selects the anchors’ subset which provides the position estimate with least uncertainty (i.e., largest agreement) in our approach. Furthermore, we propose a previous stage to filter the anchor-tag distances used as input of the ICP stage. We also consider the addition of a final step based on non-linear Kalman Filtering to improve the position estimates. Performance results for several configurations of our approach are reported in the experimental results section, including a comparison with the performance of other position-estimation algorithms based on trilateration. The experimental evaluation under laboratory conditions and inside the cargo hold of a vessel (i.e., a noise-prone scenario) proves the good performance of the ICP-based algorithm, as well as the effects induced by the prior and posterior filtering stages.

Pose Sensing With a Single RFID Tag

Determining an object’s spatial pose (including orientation and position) plays a fundamental role in a variety of applications, such as automatic assembly, indoor navigation, and robot driving. In this paper, we design a fine-grained pose sensing system called Tag-Compass that attaches a single tag to an object (whose size may be small) and identifies the tagged object’s pose by determining the spatial orientation and position of the tag. We exploit the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">polarization</i> properties of the RF waves used in the communications between an RFID reader and the tag on the object. Polarization mismatch between the tag and the reader’s antenna affects the received signal strength at the reader. From the measured signal strength values, we are able to deduce the tag’s pose through a series of transformations and deviation minimization. We propose a system design for Tag-Compass and implement a prototype. We evaluate the performance of Tag-Compass through extensive experiments using the prototype. The experimental results show that Tag-Compass provides accurate estimate of object orientation with a median error of just 2.5° when the tag’s position is known and a median error of 3.8° when the tag’s position is unknown. In the latter case, Tag-Compass will provide an estimate of tag position as a byproduct of orientation sensing, with an accuracy comparable to the state of the art. It is practically appealing to find both the orientation and the position of an object using a single method, instead of having to deploy two different methods.

Assessing the Feasibility of Augmenting Fall Detection Systems by Relying on UWB-Based Position Tracking and a Home Robot.

Falls in the home environment are a primary cause of injury in older adults. According to the U.S. Centers for Disease Control and Prevention, every year, one in four adults 65 years of age and older reports experiencing a fall. A variety of different technologies have been proposed to detect fall events. However, the need to detect all fall instances (i.e., to avoid false negatives) has led to the development of systems marked by high sensitivity and hence a significant number of false alarms. The occurrence of false alarms causes frequent and unnecessary calls to emergency response centers, which are critical resources that should be utilized only when necessary. Besides, false alarms decrease the level of confidence of end-users in the fall detection system with a negative impact on their compliance with using the system (e.g., wearing the sensor enabling the detection of fall events). Herein, we present a novel approach aimed to augment traditional fall detection systems that rely on wearable sensors and fall detection algorithms. The proposed approach utilizes a UWB-based tracking system and a home robot. When the fall detection system generates an alarm, the alarm is relayed to a base station that utilizes a UWB-based tracking system to identify where the older adult and the robot are so as to enable navigating the environment using the robot and reaching the older adult to check if he/she experienced a fall. This approach prevents unnecessary calls to emergency response centers while enabling a tele-presence using the robot when appropriate. In this paper, we report the results of a novel fall detection algorithm, the characteristics of the alarm notification system, and the accuracy of the UWB-based tracking system that we implemented. The fall detection algorithm displayed a sensitivity of 99.0% and a specificity of 97.8%. The alarm notification system relayed all simulated alarm notification instances with a maximum delay of 106 ms. The UWB-based tracking system was found to be suitable to locate radio tags both in line-of-sight and in no-line-of-sight conditions. This result was obtained by using a machine learning-based algorithm that we developed to detect and compensate for the multipath effect in no-line-of-sight conditions. When using this algorithm, the error affecting the estimated position of the radio tags was smaller than 0.2 m, which is satisfactory for the application at hand.

Radio Frequency IDentification for Meat Supply-Chain Digitalisation.

Digitalised supply-chain traceability systems can offer wide prospects both for improving safety as well as enhancing perceived quality. However, the coupling between physical goods and information is often difficult for agri-food items. A solution could be the use of RFID (Radio Frequency IDentification) systems. Due to its wide reading range, Ultra-High Frequency (UHF) technology is already widely used in logistics and warehousing, mostly for the identification of batches of items. A growing interest is also emerging in Near Field Communication (NFC), as several smartphones embed an integrated NFC antenna. This paper deals with the automatic identification of meat products at item level, proposing and evaluating the adoption of different RFID technologies. Different UHF and NFC solutions are proposed, which benchmark tag performances in different configurations, including four meat types (fatty beef, lean beef, chicken and pork), by using a specifically designed test bench. As avoiding the application of two different tags could be advantageous, dual frequency devices (UHF and NFC) are also considered. Significant differences in tag performances, which also depend on meat type and packaging, are highlighted. The paper highlights that tag positioning should consider the geometry of the packaging and the relative positioning of tag, meat and reader antenna.

Range and Bearing Estimation of an UHF-RFID Tag Using the Phase of the Backscattered Signal

The narrow bandwidth of UHF RFID signals does not allow the direct measurement of the range between the reader and the tag. A Multi-Hypothesis Extended Kalman Filter is proposed in this paper to solve this issue, by fusing the phase measurements with the odometry readings of a mobile robot. While estimating the tag-reader distance, the proposed approach provides also an on-line estimation of the bearing of the tag. The knowledge of range and bearing is beneficial in positioning-based applications as in robotics, to develop algorithms for reaching and grasping a tagged object or to localize a robot using tags as anchors, or for solving a Simultaneous Localization and Mapping (SLAM) problem if positions of both tags and robot are unknown. A few steps are usually enough to obtain a univocal effective estimate of these quantities, as long as the robot is moving over a non-straight path. A comprehensive numerical analysis supports and assesses the theory.

An Ultra-Low Power Ultra-Wide Bandwidth Positioning System

An ultra-wide bandwidth (UWB) remote-powered positioning system for potential use in tracking floating objects inside space stations is presented. It makes use of battery-less tags that are powered-up and addressed through wireless power transfer in the UHF band and embeds an energy efficient pulse generator in the 3-5 GHz UWB band. The system has been mounted on the ESA Mars Rover prototype to demonstrate its functionality and performance. Experimental results show the feasibility of centimeter-level localization accuracy at distances larger than 10 meters, with the capability of determining the position of multiple tags using a 2W-ERP (Effective Radiated Power) power source in the UHF RFID frequency band.

The impact of tag position and mass on motor behavior in pigeons

Tags, such as GPS tags and satellite tags, are widely used in wildlife research as a useful tool for observing behavioral ecology. Here, we investigated the impact of tag position and mass on the motor behavior of pigeons (Columba livia domestica). We used sandbags sized 4 × 4 cm2 to simulate load and assess load capacity. The results showed that the tag had the least impact on the pigeons when attached to the middle of the synsacrum: the change rate of height (CRH) was − 4.48%, the change rate of tail angle (TA) was 14.61%, the change rate of tarsometatarsal angle (TMA) was 17.90%, and the change rate of activity level (AL) was 85.96%. The tag mass ≤ 30 g (6.0% of body mass) had relatively little impact on pigeons: CRH was ≤ 7.0%, TA was ≤ 22.51%, TMA was ≤ 5.28%, and AL was ≥ 82.95%. We then tested the impact of the tag mass at its optimum location on the motor behavior of the birds. With increase in the tag mass, the step length became longer and the time of passing through the labyrinth decreased. With the tag mass of 30 g, the pigeons could easily fly out of the arena during initial flight. In conclusion, the optimal position of the tag was in the middle of the synsacrum, and the tag mass of ≤ 6.0% of the body mass had the least impact on pigeons. Thus, tag mass should be much less than 6.0% of the body mass in application for pigeons.

Library inventory using a RFID wand: contribution of tag and book specific factors on the read rate

PurposeLow read rates are a general problem in library inventories. The purpose of this study is to examine the factors that contribute to the success of library inventory by means of a radio-frequency identification (RFID) inventory taker. The factors investigated were tag position, tag orientation, book thickness, tag density (related to thickness of a sequence of books) and position on the shelf.Design/methodology/approachA total of 210 books were placed in eight random permutations on three fixed book shelves. For each configuration, the RFID tags were read forty times. The resulting data were analysed by means of a generalized linear model, relating the combined contribution of tag position, tag orientation, book thickness and position on the bookshelf to the read rate.FindingsThe tags positioned directly next to the spine were always read, but those near the opening of the book (far from the spine and inventory reader) were not always read. Considering only books with tags near the opening, tag orientation and position on the shelf appeared not to be related to the read rate, while book thickness, thickness over three books and spine tag density appeared to have a small positive contribution to the read rate.Practical implicationsLow read rates during a library inventory can be prevented by placing the tags near the book spine – the other book specific factors (listed in the previous paragraph) are of little influence. When not scanned during a first sweep, repeated scanning can increase the read rate with 0.15.Originality/valueThis paper is one of the first to analyse the influence of tag location and book specific factors on the read rate of RFID tags in library books. The experimental approach sets an example for future work.

Assessment of Anchors Constellation Features in RSSI-Based Indoor Positioning Systems for Smart Environments

In this paper, we assess the features of a rectangular constellation of four anchors on the position estimation accuracy of a mobile tag, operating under the IEEE 802.15.4 specifications. Each anchor implements a smart antenna with eight switched beams, which is capable to collect Received Signal Strength Indicator (RSSI) data, exploited to estimate the mobile tag position within a room. We also aim at suggesting a deployment criterion, providing the discussion of the best trade-off between system complexity and positioning accuracy. The assessment validation was conducted experimentally by implementing anchor constellations with different mesh sizes in the same room. Mean accuracies spanning from 0.32 m to 0.7 m on a whole 7.5 m × 6 m room were found by varying the mesh area from 1.19 m2 to 17 m2, respectively.

Improvement of the Angle of Arrival Measurement Accuracy for Indoor UWB Localization

This paper shows that the accuracy of azimuth angle measurement for an interferometric localization system used to locate tags in its Line-of-Sight (LoS) can be improved by exploiting Impulse Radio-Ultra WideBand (IR-UWB) signals and without increasing the frequency bandwidth. This solution uses a Phase Correlation (PC) method, initially applied for Continuous Wave (CW) signals, adapted for Ultra WideBand (UWB) pulse signals. The obtained results are compared to those computed by a classical Energy Detection (ED) method where it becomes impossible to estimate azimuth angles for tag positions close to the orthogonal centered axis of the localization system baseline.

UAV-RFID Integration for Construction Resource Localization

Location data of construction resources are important in understanding on the context of a construction site, yet most sites still rely on people's observations to localize their resources. Among then various localization technologies, radio frequency identification (RFID) is considered as a good solution. However, RFID either provides limited location data when fixed receivers are used, or it requires considerable manpower for scanning the tagged resources when hand-held receivers are used. These requirements result in inefficiency and impractical demands on time and cost, particularly in the case of complex or large-scale sites. This study attempted to overcome the limitations by proposing an integrated unmanned aerial vehicle-RFID (UAV-RFID) platform to replace the considerable manpower with the UAV and to enable identifying tags on a site. It applies deep learning algorithms to localize an RFID tag position within an acceptable range of accuracy, thereby demonstrating the feasibility of the integrated platform for construction resource localization.

ACD: An Adaptable Approach for RFID Cloning Attack Detection.

With the rapid development of the internet of things, radio frequency identification (RFID) technology plays an important role in various fields. However, RFID systems are vulnerable to cloning attacks. This is the fabrication of one or more replicas of a genuine tag, which behave exactly as a genuine tag and fool the reader to gain legal authorization, leading to potential financial loss or reputation damage. Many advanced solutions have been proposed to combat cloning attacks, but they require extra hardware resources, or they cannot detect a clone tag in time. In this article, we make a fresh attempt to counterattack tag cloning based on spatiotemporal collisions. We propose adaptable clone detection (ACD), which can intuitively and accurately display the positions of abnormal tags in real time. It uses commercial off-the-shelf (COTS) RFID devices without extra hardware resources. We evaluate its performance in practice, and the results confirm its success at detecting cloning attacks. The average accuracy can reach 98.7%, and the recall rate can reach 96%. Extensive experiments show that it can adapt to a variety of RFID application scenarios.

A Novel Asynchronous UWB Positioning System for Autonomous Trucks in an Automated Container Terminal

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;As a critical technology for autonomous vehicles, high precise positioning is essential for automated container terminals to implement intelligent dispatching and to improve container transport efficiency. Because of the unstable performance of global positioning system (GPS) in some circumstances, an ultra wide band (UWB) positioning system is developed for autonomous trucks in an automated container terminal. In this paper, an asynchronous structure is adopted in the system, and a three-dimensional (3D) localization method is proposed. Other than a traditional UWB positioning system with a server, in this asynchronous system, positions are calculated in the vehicle. Therefore, propagation delays from the server to vehicles are eliminated, and the real-time performance can be significantly improved. Traditional 3D localization methods based on time difference of arrival (TDOA) are mostly invalid with anchors in the same plane. However, in order to guarantee anchors and tags in line of sight (LOS), anchors have to be installed in a vertical plane under the tire cranes. Given this problem, an improved method is presented, which overcomes the matrix singularity. Three hyperboloids can be drawn according to three TDOAs. Either two of them intersect to a plane curve, summing up to three planes in all. Two of them intersect in one line. The line and the hyperboloids intersect at two symmetrical points about the anchor-plane. Then positions of tags can be quickly confirmed as positional relations between trucks and the anchor-plane have been determined when anchors installed. Extensive experiments have been conducted to evaluate the performance in comparison to existing TDOA methods. As shown by experimental results, the proposed method performs better than traditional methods in location accuracy and stability.&lt;/div&gt;&lt;/div&gt;

Precise localization of RFID tags using hyperbolic and hologram composite localization algorithm

Thousands of items are stored in libraries, archives and supermarkets, it usually takes a long time to find what we want in thousands of items. How to achieve precise localization is particularly important. We present a fine-grained Radio Frequency Identification (RFID) positioning method to help us find the items we want. In order to achieve high-precision positioning of RFID tags, we propose Hyperbolic and Hologram Composite (HHC) localization algorithm, which determines the positioning candidate set by hyperbolic intersection, thereby reducing the positioning delay, and then use the holographic positioning to filter the candidate set. We use multi-frequency holography positioning technology to reduce the influence of the reader’s own inaccurate positioning, and use multipath suppression technology to reduce the interference of multipath in the environment, finally achieves higher precision positioning. The experimental results show that the average calculation time of one positioning of our HHC positioning system is 10.3 ms, and 90% of the positioning error margin is below 4.8 cm, which realizes high-precision and low-delay positioning.

Factors Affecting the Retention of Visible Implant Elastomer (VIE) Tags in Smooth Newts (Lissotriton vulgaris) During the Breeding Period

Population parameters can be estimated on the basis of capture-mark-recapture (CMR) studies, which require accurate and continuous identification of studied individuals. Amphibians that cannot be identified by unique color patterns represent a problem for these types of studies due to variable interspecies suitability of different marking methods. One alternative to the traditional but questionable toe-clipping method is visible implant elastomer (VIE) tagging. VIE has been used successfully, mainly for tagging different species of terrestrial salamanders, but it has not been evaluated systematically for biphasic newts. In this study, the efficiency of VIE tagging was tested on smooth newts (Lissotriton vulgaris), with controls for body length, sex, position of tag, color of tag, and personal experience with tagging. Two tags, originally injected into each individual, were visible only in 39.5% of the newts after 49 days. Most of the tags that failed (72.4%) were lost completely. Retention rates for the VIE tags were lowest for younger tags but improved over time. Tags were lost more from the front than from the hind legs (42.1% vs. 34.2%), the person more experienced in marking had fewer tag losses (22.8% vs. 51.2%), and males lost more tags from their hind legs than females (52.8% vs. 17.5%). This study shows that VIE marking is not a conclusively reliable method for CMR studies of small salamanders during the breeding (water) period. The future of individual recognition, for the purpose of CMR studies, lies probably in non-invasive, computer-assisted photo identification methods.

Susceptibility of agricultural pests of regional importance in South America to a Bacillus thuringiensis Cry1Ia protein

Bacillus thuringiensis toxins of the Cry1I class have dual specificity for insects in the orders Coleoptera and Lepidoptera. We assessed the toxicity of a Cry1Ia protein from an Argentinian B. thuringiensis strain against agricultural pests in the families Tenebrionidae, Curculionidae, Noctuidae and Tortricidae. Three recombinant protein variants were produced that differed in length and fusion tag position to rule out artifactual results. The protein was toxic to Cydia pomonella and Rachiplusia nu. In contrast, Alphitobius diaperinus, Anthonomus grandis and Spodoptera frugiperda were not susceptible. The results are discussed with respect to previous studies and the prospective use of Cry1Ia in strategies to control major cotton pests in the region.

Construction of E. coli-Mycobacterium shuttle vectors with a variety of expression systems and polypeptide tags for gene expression in mycobacteria.

Cloning and expression of a desired gene is indispensable in molecular biology studies. Expression vectors, in this regard, should offer much needed flexibility and choice of cloning strategies for both in vivo and in vitro protein expression experiments. Furthermore, availability of option to choose from various reporter tags allows one to be flexible during designing of an experiment in a more relevant manner. Thus, the need of a versatile expression system cannot be ignored. Although several different expression vectors are available for gene expression in mycobacteria, they lack the required versatility of expression and the inclusion of reporter tags. We here present the construction of a set of nine E. coli-Mycobacterium shuttle plasmids, which offer a combination of three mycobacterial promoter systems (heat shock inducible-hsp60, tetracycline-, and acetamide-inducible) along with three polypeptide tags (Green Fluorescent Protein (GFP), Glutathione S-transferase (GST) and hexa-histidine tag). These vectors offer the cloning of a target gene in all the nine given vectors in parallel, thus allowing the generation of recombinant plasmids that will express the target gene from different promoters with different tags. Here, while the hexa-histidine and GST tags can be used for protein purification and pull-down experiments, the GFP-tag can be used for protein localization within the cell. Additionally, the vectors also offer the choice of positioning of the reporter tag either at the N-terminus or at the C-terminus of the expressed protein, which is achieved by cloning of the gene at any of the two blunt-end restriction enzyme sites available in the vector. We believe that these plasmids will be extremely useful in the gene expression studies in mycobacteria by offering the choices of promoters and reporters. Our work also paves the way to developing more such plasmids with other tags and promoters that may find use in mycobacterial biology.

Negative feedback concept in tagging: Ghost tags imperil the long-term monitoring of fishes.

Wildlife monitoring using passive telemetry has become a robust method for investigating animal migration. With increased use, this method progressively pollutes the environment with technological waste represented by so called ghost tags (PIT tags ending in the environment due to reproductive expulsions, shedding or animal mortality). However, their presence in the environment may lead to failed detections of living individuals. We used tagging data from studies of the asp Leuciscus aspius and the bleak Alburnus alburnus collected from 2014 to 2018 and located ghost tag positions on the monitored spawning site using portable backpack reader for their detection. We modelled virtual river-wide flat-bed antennas (widths 0.2, 0.4, 0.6 and 0.8 m) representing monitoring effort and estimated the probability of the presence of ghost tags within the antenna field. Of 3724 PIT tags used in the study, we detected on the spawning ground 173 ghost tags originating from long-term monitoring. The ghost tags accumulated in the environment in time, suggesting insufficient degradation rate or shift downstream from the research site. Number of ghost tags present on the spawning ground led to high probability of disabled readings of tagged fish passing through the antenna electro-magnetic field. We demonstrate how accumulated ghost tags may cause detection failures for focal species and incomplete data acquisition. We infer that intensive long-term monitoring using PIT tag technology may encumber future data acquisition or entail additional costs for clean-up.

Relative Tag Locations Based on Time-Differences in Read Events for Practical Applications

Over the course of recent years, Radio Frequency Identification (RFID) technology has been applied in many different business domains to solve, for example, the problem of monitoring stock. However, keeping track of the exact (geo-) locations of items in stock is still an open problem. This is particularly problematic for logistics, retail as well as warehouses, where information about relative locations of items can drastically increase staff efficiency and business process efficacy. In this paper we set out to tackle the problem of determining relative distances between RFID tags based on time-differences in read events, without the introduction of additional hardware. To that end, we first present a novel approach, which leverages time-based distances for inferring relative RFID tag distances. We then qualitatively and quantitatively evaluate our proposed approach by inferring tag locations for different experimental setups, and comparing our results to ground truth data. Finally, we present and discuss the results of a case study, which emulates real-world conditions of retailers using RFID technology for stock taking. Our results show that time-differences in read events are suitable for calculating and approximating the relative position of RFID tags in several setups. We strongly believe that the results presented in this paper represent a novel and important step towards new approaches, which leverage time-differences in read events for inferring relative tag distances.