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Dynamic object following is an essential ability for mobile robots in various application scenarios such as auxiliary cargo transportation, disabled assistant caring, and multirobot formation. A dynamic object following method for a mobile robot based on ultrahigh-frequency (UHF) radio frequency identification (RFID), which uses a phase difference information-based dynamic following model, is presented in this article. Through this method, a mobile robot equipped with an RFID reader can follow a dynamic target object attached with a passive RFID tag. A cost function is constructed to indicate the changes in relative distance and bearing between the target object and the following robot, allowing the real-time calculation of the translational and rotational velocities of the following robot using an algorithm base on proportional integral differential (PID)-based controllers. Compared with the existing RFID-based following methods, the proposed method can achieve a satisfactory distance and bearing following accuracy by using RFID phase difference information without any tedious and time-consuming phase drift or antenna installation calibration. Real experiments were conducted using commercial off-the-shelf (COTS) UHF RFID, and results show that the proposed method is effective and robust, the respective average distance and bearing following errors were approximately 1.65 cm and 4.94° during the robot-following tests and 4.45 cm and 6.03° during the human-following tests. The proposed method has promising applications in mobile robot following of dynamic object to provide service or assistance in large storage and manufacturing industries. [ABSTRACT FROM AUTHOR]

Radio frequency identification (RFID) technology attracts extensive attention for industrial applications, especially supply chain businesses and inventory management. In this article, a passive RFID localization scheme based on unmanned aerial vehicles (UAVs) or drones is established for inventory management in warehouses. In case of the major challenge of the on-board antenna tracking errors in practical scenarios, the state-of-the-art (SOTA) numerical methods rely on accurate antenna positions, such as synthetic aperture radar (SAR)-based algorithms, which will introduce large positioning errors and become unreliable. To this end, we propose a new relative RFID localization method based on phase, received signal strength indicator (RSSI), and readability, which is little affected by antenna tracking errors. In the proposed method, the tagged items on the racks are located laterally through pinpointing the minimum of the unwrapped phases, which have been unwrapped based on the hybrid random forest (RF) model. RSSI differences and the read count of each patch antenna’s beam are utilized to distinguish the rack level of tagged assets via a boosting tree classifier. The experimental results in a real warehouse show that the proposed method achieves 27.1-cm mean lateral positioning accuracy and orders the tagged items horizontally and vertically with more than 96.7% and 98.0% accuracy, respectively. [ABSTRACT FROM AUTHOR]

Indoor device-free object detection has many applications, such as assisted living, home security, and occupant-centered building utility control. To accommodate 3-D room layout variations and improve accuracy, multiple observation units with spatial diversity are often required, which will unavoidably cause a significant increase in the component and deployment cost if each unit needs wired power or battery. In this article, we present an indoor device-free object detection system implemented by a commercial radio frequency identification reader and many passive tags around the room. The passive tag as a dispersed observation point offers a cost-effective solution for the necessary spatial diversity. The tag backscattering phase is assembled to generate the reflectivity image inside the capture volume using Fourier-based reconstruction. A new calibration technique is proposed to compensate for multiplicative path losses and subtract the effect of background clutters, such as furniture. Noisy channels and channels with their line-of-sight blocked by the target are also filtered out during postprocessing to improve locating accuracy and mitigate ambiguity. A 1:6 room model was first used to study the effects of the indoor materials and room layout, where occupant recognition and centimeter-level locating were successfully demonstrated. Real-scale rooms were then tested, where decimeter-level 3-D location error was achieved for a single occupant, and useful information for occupant posture can also be evaluated. [ABSTRACT FROM AUTHOR]

Radio frequency identification (RFID) technology brings tremendous advancements in the Industrial Internet of Things (IIoT), especially for smart inventory management, as it provides a fast and low-cost way of counting or positioning items in the warehouse. In the last decade, many novel solutions, including absolute and relative positioning methods, have been proposed for this application. However, the available methods are quite sensitive to the minor changes in the deployment scenario, including the orientation of the tag and antenna, the materials contained inside the carton, tag distortion, and multipath propagation. To this end, we propose a hybrid relative passive RFID localization method (ReLoc) based on both the received signal strength indicator (RSSI) and measured phases, which orders the RFID tags horizontally and vertically. In this article, the phase-based variant maximum likelihood estimation is proposed for lateral positioning, and the RSSI profiles of two tilted antennas are compared with each other for level distinguishing. We implement the proposed positioning system ReLoc with commercial off-the-shelf RFID devices. The experiment in a warehouse shows that ReLoc is a powerful solution for practical item-level inventory management. The experimental results show that ReLoc achieves an average lateral and level ordering accuracy of 94.6% and 94.3%, respectively. Notably, when considering liquid or metal materials inside the carton or tag distortion, ReLoc still performs excellently with more than 93% ordering accuracy both horizontally and vertically, indicating the robustness of the proposed method. [ABSTRACT FROM AUTHOR]

A waveguide with central frequency 868 MHz is used in the transmission/reflection operation regime to accurately measure the behavior of the complex permittivity of high complex permittivity granular materials, and it has been frequency-extended up to 3 GHz using the Debye fit relaxation model. It is shown that for highly granular high permittivity materials, a waveguide-based transmission/reflection technique is necessary to reduce the uncertainty of the extracted permittivity values. The technique is first described and validated with isopropyl alcohol and then applied to the characterization of cement-based materials. This article provides accurate data on the evolution of the complex permittivity of concrete and mortar from the moment of pouring until air-dried condition is achieved. [ABSTRACT FROM AUTHOR]

Passive indoor localization has gained much attention recently. Numerous applications including storage management and somatosensory systems would benefit from accurate passive indoor localization. As a potential technology for the internet of things, radio frequency identification (RFID) has many advantages for indoor localization, such as low cost, parallel processing, and low complexity. In this paper, a passive indoor localization system, named Lobain, was proposed based on interference of ultrahigh frequency RFID tags. Using commercial off-the-shelf reader, antenna, and tags, this system, functions for tagged and tag-free item localization in 2-D and 3-D indoor environments. Small numbers of reference tags were used as sensors to improve performance and reduce cost. Unlike traditional methods, an improved propagation model and an innovative method were presented to extract a target’s channel information from a complicated received signal. A relative phase wrapping integer method was presented to solve the phase wrapping problem of reference tags, and the least-squares method was used to optimize the tradeoff between number of reference tags and accuracy. A tag and tag-free items including shrimp chips, cola, and instant noodles were localized as single target in the evaluation experiments. The prototype achieved mean 2-D median localization errors of 5.9 (x-axis) and 8.2 cm (y-axis), and achieved mean 3-D median errors of 9 (x-axis), 6.7 (y-axis), and 13.3 cm (z-axis). [ABSTRACT FROM AUTHOR]

This paper explores the ability of the received signal strength indicator (RSSI) versus frequency pattern (the RSSI signature) to reliably quantify the effect of environmental multipath on RSSI-derived distance measurements for passive ultrahigh frequency systems. Radar technology has demonstrated the use of frequency information for range measurements, given an extremely large bandwidth. In this paper, we show the applicability of these concepts to the ultrahigh frequency radio frequency identification spectrum and its narrow bandwidth. First, we present a theoretical model which illustrates the need for the frequency information to separate multipath error from RSSI measurements. Practically, a closed-form method to extract the multipath component using data from a complex environment is not feasible; therefore, a neural network is used to emulate theoretical variable separation to extract measurement error due to multipath via information from the RSSI frequency signature. The subsequent-predicted distance error relationship not only reduces the error magnitude but also informs the direction of the error, thus making it possible to significantly improve the original distance prediction, even in a completely new environment. [ABSTRACT FROM AUTHOR]

A novel image analysis method for improving the reading performance of the radio frequency identification (RFID) system is proposed by arranging the geometric distribution of multiple tags reasonably based on flood fill and direct linear transformation (DLT) in this paper. An image collecting system is projected to collect the image of RFID tags, and an online detection system is designed to measure the reading distance. The proposed system has good performance of instantaneity and robustness, in which tags could be identified rapidly with the tray turning. The 2-D distribution images of tags are processed using the flood-fill technique. Furthermore, the 3-D distribution images of tags are analyzed based on DLT. Subsequently, a tag network is established, in which a tag is described as a node. Finally, support vector machine is introduced to predict the reading distance and corresponding distribution for a given number of tags after training the measured reading distance of RFID tags under various geometric distributions. The results show that the optimal geometric distribution of tags could be obtained by analyzing the images of tags and the predicted reading distance of tags. This method can improve the dynamic performance of multiple tags in the RFID system effectively. [ABSTRACT FROM PUBLISHER]

This paper presents a radio frequency (RF) measurement method that allows to determine electrical characteristics such as scattering parameters or impedance of contactless passive chips, using common measurement devices such as oscilloscope, personal computer, and directional coupler. The measurements obtained using this method are as accurate as those obtained with vector network analyzer (VNA) measurements, while providing several improvements. First, the method makes it possible to measure a chip’s impedance in activation state, which requires large input power, not compatible with VNA measurements. Second, this method realizes a real-time measurement, which consists in impedance measurement as a function of time. Therefore, this real-time measurement makes it possible to detect and measure the impedance changes of an actual contactless smart card’s integrated circuit during a load modulation communication at different powers. Finally, this real-time impedance measurement gives important information on chips’ electrical characteristics that can be used to optimize near-field communication devices design in order to reduce the power losses within an RF identification tag. [ABSTRACT FROM AUTHOR]

This paper introduces a 2-D position measurement system for passive ultra-high frequency (UHF) radio frequency identification (RFID) tags based on evaluation of backscattered transponder signals. The main application of the system is the localization of stationary objects tagged with RFID transponders. By combining phase and amplitude evaluation, the accuracy and the robustness of the position estimates are significantly improved compared with either approach alone. A multiple input multiple output system in which, sequentially, each frontend is configured to work as a transmitter while the remaining frontends serve as receivers is used to enable position estimation. For proof of concept, a local position measurement system demonstrator was built comprising conventional passive EPCglobal Class-1 Gen-2 UHF RFID tags, a commercial off-the-shelf RFID reader, eight transceiver frontends, baseband hardware, and signal processing. Measurements were carried out in an indoor office environment where the 3.5~\mathrm m \times 2.5 m measurement zone was surrounded by drywalls and concrete floor and ceiling. The experimental results showed accurate localization with a root-mean-square error of 0.020 m and a median error of 0.011 m. To determine the limits of the system, accuracy simulations were performed, which confirm the experimental results. [ABSTRACT FROM PUBLISHER]

This paper proposes Kalman-filter drift removal (DR) and Heron-bilateration location estimation (LE) to significantly reduce the received signal strength index (RSSI) drift, localization error, computational complexity, and deployment cost of conventional radio frequency identification (RFID) indoor positioning systems without any sacrifice of localization granularity and accuracy. By means of only one portable RFID reader as the targeted device and only one pair of active RFID tags as the border-deployed landmarks, this paper develops a real-time portable RFID indoor positioning device and cost-effective scalable RFID indoor positioning infrastructure, based on Kalman-filter DR, Heron-bilateration LE, and four novel preprocessing/postprocessing techniques. Experimental results reveal that the proposed Kalman-filter DR method is faster and better to converge the distance measurement (DM) error than conventional probability/statistics in terms of various relative distances under certain RSSI drift effect condition, and the proposed Heron-bilateration LE method is also faster and better to converge the LE error than conventional proximity pattern matching and trilateration in terms of three or more landmarks under certain DM error condition. On the other hand, a portable RFID indoor positioning device is smoothly implemented on an Android smartphone platform attached with a portable Bluetooth-based RFID reader. [ABSTRACT FROM PUBLISHER]

Passive ultrahigh frequency (UHF) radio frequency identification (RFID) is a powerful automatic contactless identification technique that has numerous applications. The performance of passive UHF RFID system is affected seriously by the application environments. In this paper, we propose a metrical method of application environment impact for passive UHF RFID system based on fuzzy comprehensive evaluation. The metric of application environment impact is graded by the degradation of reading distance, reading rate, and reading speed of passive UHF RFID system. Analytic hierarchy process is used to calculate the weight of factors, which reduces the subjectivity of evaluation results. For avoiding the loss of valid information, weighted average operator is employed to replace traditional max min operator. The end user can know the real performance of product selected by the grade of application environment impact visually and easily use the method proposed. Experimental results indicate that the proposed method is simple, valid, fast, accurate, and practical. [ABSTRACT FROM PUBLISHER]

This paper presents a complete radio frequency identification (RFID) test platform to characterize the nonlinear effects produced by passive ultra-high frequency (UHF) RFID chips. In full operation mode, automated measurements of activation power, harmonic response level, and impedances are performed in a wide frequency range up to the fourth harmonic. The characterization method, platform composition, and operation are explained through real measurements on UHF Class-1 Generation-2 chips. A harmonic treatment is presented thanks to the joint use of an RFID tester and impedance tuners, and the effect of the antenna-chip impedance matching on the harmonic responses is compared before and after treatment. To the best of our knowledge, no similar platform has been presented in the literature. [ABSTRACT FROM PUBLISHER]

This paper presents a radio frequency identification (RFID) augmented module for smart environmental sensing (RAMSES), which is a fully passive device with sensing and computation capabilities conceived to explore novel and unconventional RFID applications. RAMSES implements an RF energy-harvesting circuit enhanced by a dc-dc voltage booster in silicon-on-insulator technology, an ultralow-power microcontroller, temperature, light, and acceleration sensors, and a new-generation I^2C -RFID chip to wirelessly deliver sensor data to standard RFID EPCglobal Class-1 Generation-2 readers. A preliminary RAMSES prototype, fabricated on a printed circuit board using low-cost off-the-shelf discrete components, has been extensively tested through experiments conducted both in lab and real-world application scenarios. The achieved results have demonstrated the ability of RAMSES to harvest the RF energy emitted by an interrogator placed up to 10 m of distance and autonomously perform sensing, computation, and data communication. To our knowledge, this is the longest range ever reported for fully passive RFID sensors. Furthermore, for applications requiring larger operating distances, RAMSES provides also a battery-assisted passive mode yielding up to 22-m communication range. [ABSTRACT FROM PUBLISHER]

This paper presents the guidelines for the development and optimization of wireless sensors based on the modulated scattering technique (MST). In particular, this paper is focused on the design and optimization of different MST tag prototypes with different modulation techniques. In addition, it is shown how to obtain the best performance of such sensors in terms of communication range and load efficiency. The preliminary measurements obtained with different experimental tag prototypes demonstrate that these MST sensors are able to measure and to correctly send data without an expensive radio frequency (RF) transmitter or a bulky wired connection. The results obtained show that such sensors could be an interesting alternative to standard RF identifier and wireless sensors. [ABSTRACT FROM PUBLISHER]

This paper presents the development of passive high frequency (HF) and ultrahigh frequency (UHF) radio frequency identification (RFID) sensor transponders for humidity and temperature monitoring. The transponders use RFID integrated circuits with a digital interface for communicating with a ultralow-power microprocessor. The microprocessor handles the measurement, either by charging sensor and reference capacitors, or by commanding a digital sensor. The read ranges of the sensor nodes are 5 cm and up to 40 cm at HF and UHF, respectively. The sensor nodes are demonstrated in concrete casts, where the HF node provides better than 5%RH-repeatability of the moisture measurements from sensor node to another. At UHF the repeatability is about 15%RH. [ABSTRACT FROM AUTHOR]

Modulated scatterer technique (MST) probes have been commonly used for near-field mapping application in antenna measurements as well as in imaging applications. Although they can be used as a general sensor, they present limitations in the amount of information that can be obtained. The paper proposes a new configuration for MST probes that can be used for sensing applications, which consists in using a set of impedances (at least three different impedances) instead of the conventional two impedance loads. Additional sensitive loads, such as thermistors, can be added to the multi-load MST sensor, in order to remotely sense their variation and perform further sensing of parameters which could not always be sensed by conventional MST. The paper presents the formulation and approaches that can be used to exploit the sensing capabilities of such multi-loaded MST sensor, as well as experimental validations through the measurement of the temperature in the neighborhood of the sensor. [ABSTRACT FROM PUBLISHER]

Ambient intelligence (AmI) considers responsive environments in which applications and services adapt their behavior according to the user's needs and changing context. One of the most challenging aspects for many applications in AmI environments is location and orientation of the surrounding objects. This is especially important for effective cooperation among mobile physical objects in such smart environments. In this paper, we propose a robust indoor positioning system that provides 2-D positioning and orientation information for mobile objects. The system utilizes low-range passive radio frequency identification (RFID) technology. The proposed system, which consists of RFID carpets and several peripherals for sensor data interpretation, is implemented and tested through extensive experiments. Our results show that the proposed system outperforms similar existing systems in minimizing the average positioning error. [ABSTRACT FROM AUTHOR]

In this paper, a passive multiprobe sensor using conventional UHF radio frequency identification (RFID) tags is presented. The RFID link between the reader and the tag is analyzed from a general point of view by means of reciprocity principle, to obtain a compact and explicit expression of the response of RFID tags that can be exploited in sensing measurements. A calibration scheme to remove nonlinearities in the response of RFID tags, which are due to the scavenging powering mechanism of passive tags, is also presented along with measurements. Finally, experimental results and discussion of a complete multiprobe sensing scenario are used to show the different challenges involved and how to overcome them. [ABSTRACT FROM PUBLISHER]

In radio frequency identification (RFID) tag design, many measurement methods are available for individually characterizing either the RFID chip or the antenna; however, to the best of the knowledge of the authors, no direct method has been developed for the assembled RFID tag. In this paper, a measurement method for verifying the match condition of the assembled RFID tag is proposed. The proposed method can not only verify the final impedance match condition of the assembled RFID tags but also be used to identify the resistance and reactance mismatch condition between the RFID chip and the antenna. Furthermore, the measurement data obtained from the verification method can be used to estimate the assembly error introduced by different mounting methods. The use of the corrected circuit model of the RFID chip impedance, which includes the assembly error, helps improve the accuracy of the RFID tag design. Five RFID tag antennas, each with a different complex impedance, are used to verify the proposed method. This paper compares the simulated and measured results to illustrate the application of the proposed verification method to the aforementioned RFID tag antennas. It is shown that the experimental tests for the maximum read range agree well with the measured data generated by using the proposed verification method. [ABSTRACT FROM AUTHOR]

Radio frequency identification (RFID) strap attachment modality is more reliable, low cost, and easy to assemble, and therefore, it becomes increasingly more popular in RFID tag designs. This paper presents a single-ended probe method with power transmission coefficient compensation for the characterization of RFID straps. Approximate identification of the Read/Write threshold power and impedance is based on the charge status of voltage multipliers and charge pumps instead of on the Read/Write-modulated commands. For comparison purposes, the conventional source-pull system is also briefly reviewed and applied to verify the measurement results of absorbing power and impedance of RFID straps using the presented method. An enhanced source-pull system, named RFID source-pull system, for an RFID strap that can accurately measure the threshold power and impedance for Read/Write-modulated commands is also constructed for verifying the presented method. Alien and Texas Instruments (TI) straps are used for measurement examples in this paper. It is found that the measurement results of both RFID straps obtained by the presented method agree well with those by the conventional source-pull system and the RFID source-pull system. The single-ended probe method can measure the approximate Read/Write threshold power and impedance of the RFID strap with minimum operating procedures; furthermore, the complicated radio frequency (RF) facilities are not required. Obtaining the Read/Write threshold power and impedance of RFID straps allows designers to estimate the maximum read range of the designed RFID tag in advance. Therefore, the implemented cost and design cycle times can substantially be reduced. [ABSTRACT FROM AUTHOR]

This work analyzes a new method for object recognition in complex scenes combining vision-based techniques applied to the 3-D data obtained using range sensors and object identification coming from radio frequency tags (radio frequency identification (RFID) technology). Three-dimensional vision-based algorithms for object recognition have many restrictions in practical applications, i.e., uncertainty, incapability for real-time tasks, etc., but they work well for pose determination once the object is recognized. On the other hand, RFID technology allows us to detect the presence of specific objects in a scene, but it cannot provide their localization, at least not with the accuracy required in applications such as ours. In this paper, we present a new and powerful recognition method obtained by fusing both techniques. The phases of the method are described, and abundant experimentation results are included. An in-depth performance analysis has been carried out to demonstrate the recognition improvements achieved by the algorithm when RFID assistance is considered. It helps to confirm the robustness of this fusion approach and prove its effectiveness. A final discussion is included, concerning what should be the most adequate size of the object database for optimal algorithm exploitation. [ABSTRACT FROM AUTHOR]

This paper proposes an economic evaluation model for international standardization to support the decision-making process of technology development and standardization. We make use of a cost of ownership (COO) model for analyzing both expected-benefit and cost-of-technology development and standardization. Then, we apply the proposed model to a case of radio frequency identification (RFID) technology by establishing four potential scenarios. From the scenario analysis, the expected profit of the international standardization is evaluated for each scenario. We also perform sensitivity analysis to consider the effect of various parameter settings. This paper is expected to lead companies in the choice of the best strategy of technology development and standardization that would bring maximum profit. [ABSTRACT FROM AUTHOR]

This paper presents an innovative mobile robot navigation technique using Radio Frequency IDentification (RFID) technology. Navigation based on processing some analog features of an RFID signal is a promising alternative to different types of navigation methods in the state of the art. The main idea is to exploit the ability of a mobile robot to navigate a priori unknown environments without a vision system and without building an approximate map of the robot workspace, as is the case in most other navigation algorithms. This paper discusses how this is achieved by placing RFID tags in the 3-D space so that the lines linking their projections on the ground define the "free ways" along which the robot can (or is desired to) move. The suggested algorithm is capable of reaching a target point in its a priori unknown workspace, as well as tracking a desired trajectory with a high precision. The proposed solution offers a modular, computationally efficient, and cost-effective alternative to other navigation techniques for a large number of mobile robot applications, particularly for service robots, such as, for instance, in large offices and assembly lines. The effectiveness of the proposed approach is illustrated through a number of computer simulations considering testbeds of various complexities. [ABSTRACT FROM AUTHOR]