Localization of RFID-equipped assets during the operation phase of facilities

https://doi.org/10.1016/j.aei.2013.07.001Get rights and content

Abstract

Indoor localization has gained importance as it has the potential to improve various processes related to the lifecycle management of facilities and to deliver personalized and location-based services (LBSs). Radio Frequency Identification (RFID) based systems, on the other hand, have been widely used in different applications in construction and maintenance. This paper investigates the usage of RFID technology for indoor localization of RFID equipped assets during the operation phase of facilities. The location-related data on RFID tags attached to assets are extracted from a Building Information Model (BIM) and can provide context-aware information inside the building which can improve Facilities Management (FM) processes. First, using the current location of the assets saved on the tags attached to fixed assets, an FM personnel is able to read tags from a distance and locate them on a floor plan. Fixed tags with known positions act as reference tags for RFID reader localization techniques. In this scenario, the user can also estimate his/her location by scanning the surrounding reference tags. Furthermore, the paper investigates an approach to locate moveable assets using received signals from available reference tags in the building based on pattern matching and clustering algorithms. As a result, a user equipped with an RFID reader is able to estimate his/her location, as well as the location of target assets, without having access to any Real-Time Location System (RTLS) infrastructure. Several case studies are used to demonstrate the feasibility of the proposed methods.

Introduction

The localization problem has received considerable attention in the areas of pervasive computing as many applications need to know where objects are located. Location information can be used by occupants unfamiliar with a building to navigate and find their destinations. Additionally, Facilities Management (FM) personnel can be provided with locations of assets in order to decrease their search time for assets. Hence, indoor location information is especially valuable as it has the potential to improve the utilization and maintenance of facilities. Furthermore, location information is central to personalized applications in different areas and it is the basis for the delivery of personalized and location-based services (LBSs). It is the basis for context awareness within the building, which involves an automatic recognition of the user’s location and activity [36], [31].

Radio Frequency Identification (RFID) is a type of automatic identification technology in which radio frequencies are used to capture and transmit data. Similar to barcodes, RFID is a technology for identifying and tracking objects. However, it introduces several advantages over barcoding in that its operation does not require line-of-sight and clean environments, and the stored data are modifiable. A basic RFID system consists of three components: an antenna, a transceiver with a decoder (RF reader) and a transponder (RF tag) electronically programmed with information. An RFID tag is a memory storage device for storing a certain amount of data (e.g., the product ID, price and manufacturing date) that can be read wirelessly providing the ability to access large volumes of multiple data sets from multiple tags simultaneously [4]. The main types of RFID systems are passive and active, and they have different characteristics, such as communication frequency and range, and energy source. The reader can be configured either as a handheld or a fixed-mount device. It can be part of other mobile computing and communication devices such as cell phones or Personal Digital Assistants (PDAs) [7], [1]. RFID-based systems have been used in different applications in construction and maintenance, such as component tracking, inventory management, equipment monitoring, progress management, facilities and maintenance management, tool tracking, material management, and quality control (e.g., [13], [33], [8], [17].

On the other hand, Building Information Modeling (BIM) has been developed in order to tackle the problems related to interoperability and information integration by providing effective management, sharing and exchange of a building information through its entire lifecycle [12]. The BIM database contains data related to all aspects of the facility (e.g. geometry, mechanical systems, construction scheduling) that are accumulated throughout the lifecycle. Currently, BIM standards are evolving and various BIM-compatible applications are introduced in the market.

The framework developed in our previous research has proposed adding structured information taken from the BIM database to RFID tags attached to building assets [23], [24]. The stored information on tags is beneficial for several lifecycle processes and is used by various stakeholders. In this framework, every asset is a potential target for tagging. Having tags attached to assets results in a massive tag cloud in the building. The target assets are tagged during, or just after, manufacturing and are scanned at several points in time during the lifecycle. The scan events are for reading the stored data or modifying the data based on system requirements and the stage at which the scan is happening. The scanned data are transferred to different software applications and processed to manage the activities related to the assets (e.g., inspection). Considering the limited memory of the tags, the subset of BIM data has to be chosen and stored on tags based on the requirements of the tasks. This data are used by different software applications based on designated access levels [25].

The current paper builds on the above-mentioned framework for achieving the following objectives: (1) to explore the possibility of using RFID tags attached to assets for localization purpose and (2) to investigate new methods for localizing various types of RFID-equipped assets during the operation and maintenance phase without having a wired Real-Time Location System (RTLS) infrastructure. Moreover, several case studies are designed and implemented to investigate the applicability of the proposed methods.

First, a method is proposed to save current location data (e.g., coordinates) on tags attached to fixed assets. Consequently, an FM personnel is able to read a tag from a distance and locate the fixed assets on a floor plan. Fixed tags with known locations act as reference tags for RFID reader localization techniques (e.g. trilateration, scene analysis and neighborhood). In this scenario, the user can also estimate his/her location by scanning the surrounding tags. Additionally, information such as floor plans and navigational aids can be stored on these tags. Furthermore, the paper investigates a new method to locate moveable assets (e.g., tools). In this method, radio signals received from fixed tags attached to fixed assets help the user estimate the location of the target tag attached to a movable asset based on received Signal Strength Indicator (RSSI) pattern matching. This method introduces several improvements to available techniques as it incorporates the dynamics of the environments since the target tag and surrounding reference tags are affected by the same environment. Furthermore, this method does not require calibration since it uses Radio Frequency (RF) signal data without converting them into distance information. As a result, a user equipped with an RFID reader is able to estimate his/her location, as well as to obtain the location information of target assets, without having access to any RTLS infrastructure. The current paper is an extension of earlier preliminary presentations of the research [26], [27].

Section snippets

Localization and RTLS

Location data are essential for many processes related to supply chain management, facilities management (FM) and product lifecycle management (PLM) as many applications need to know where objects are located [16]. Moreover, indoor location data provide the basis for context aware information delivery in the built environment, which relies on automatic recognition of both the user’s location and activity [2]. Context-aware information can automate the delivery of information to on-site mobile

Overview of method

As explained in Section 1, in our previous research, a framework is proposed where RFID tags are attached to components at an early stage of their lifecycle and the memory on tags is used to store various types of data. The present paper aims to utilize the available mass of RFID tags in the building for localization purposes. In our approach, the user who is searching for assets is equipped with a handheld RFID reader and is able to read the content of the tags from a distance to locate fixed

Development of a simulation environment

A simulation environment is developed in Matlab [21] in order to evaluate the proposed methods for various distributions of reference and target tags, data collection points, RSSI behaviors, and the number of readings in each data collection point. Furthermore, new mathematical and procedural techniques (e.g., data filtering, pattern matching techniques, clustering and localization modules) are developed and tested. The simulation platform provides a flexible environment to define and place

Testing RFID characteristics

In order to realize the proposed method for locating moveable assets (i.e., CMTL), the characteristics of an available RFID system are analyzed. Active RFID tags from Identec Solutions [11] with relatively long nominal range (100 m), operating frequency of 915 MHz, and 32 KB of storage are used together with a handheld reader. Available tag’s antenna are omnidirectional (1/4-wave monopole with 2/3 vertical element and 1/3 horizontal element).

In order to perform the tests, an application is

Summary, conclusions and future work

This paper investigated several methods to localize various types of RFID-equipped assets in a building using handheld RFID readers. It discussed different scenarios to assist users (e.g. FM personnel or occupants) estimate their locations as well as the location of fixed and movable assets they are looking for. The main advantages of the proposed system are that it can adapt to the changes in the environment, it utilizes available RFID tags in the building, and does not require a fixed RTLS

Acknowledgement

The authors would like to acknowledge the contributions of Mr. Kehinde Adetiloye for his collaboration in developing one of the applications used in the case studies. Data collection and the execution of case studies could not be done without the information provided by Concordia University Facilities Management Office. The support and cooperation of Mr. Barry Allen from Identec Solutions is also appreciated.

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