WO2005071597A1

WO2005071597A1 - Location determination and navigation using arrays of passive rfid tags

Info

Publication number: WO2005071597A1
Application number: PCT/US2005/002131
Authority: WO
Inventors: Homer Floyd Willis
Original assignee: University Of Florida Research Foundation, Inc.
Priority date: 2004-01-22
Filing date: 2005-01-24
Publication date: 2005-08-04

Abstract

A radio frequency identification (RFID) tag array-based “smart floor” system for navigation and location determination for guiding individuals includes a plurality of spaced apart RFID tags. Each RFID tag has memory having information stored therein including positional information and attributes of objects or structures disposed in proximity to the tags. The tags convey radio frequency signals including the positional information and the attributes in response to received electromagnetic excitation fields, such as electromagnetic excitation fields triggered by blind people. The RFID tags are embedded within or rigidly attached to a walking surface, such as carpet pad, tile and wood flooring.

Description

LOCATION DETERMINATION AND NAVIGATION USING ARRAYS OF PASSIVE RFID TAGS

FIELD OF THE INNBNTION [0001] This invention relates generally to systems for navigation and location determination for guiding individuals based on RFID tag arrays.

BACKGROUND [0002] Location detection is critical to the movement of moving vehicles as well as people. In the case of blind people, special challenges arise. The blind user generally relies on familiarity with the environment and the aid of a seeing-eye-dog or assistant. The walking cane is the extension to the blind user's ability to navigate familiar and unfamiliar surroundings. These limitations make is difficult to explore or adapt to new surroundings. Improved systems navigation systems suitable for the blind are needed.

[0003] RFID tags have been used by the retail industry to solve the problem of inventory management and to act as a theft deterrent. A RFID system generally comprises three components comprising a tag having an antenna, a tag reader and an antenna for the reader. The tag is paper thin, and flexible and can be less than 1 inch by 1 inch in size. It consists of an etched antenna and a tiny chip which includes memory which stores data. RFID readers and antennas are available in various shapes and sizes to suit respective applications. The reader powers the antenna to generate an RF field. When a tag passes through this RF field, the information stored on the chip is decoded by the reader.

[0004] The passive RF tag provides low cost and fast operation. Up to 500 individual tags can be read in one second. Tags provide an extended range, so that tags can be read or . written to from up to 10 meters away with an appropriate antenna configuration. RFID tags can also be completely passive, thus requiring no batteries.

[0005] Published U.S. Application No. 20020121986 Krukowski et al. disclose the use of a code, including RFID tags to aid the blind. The method includes the steps of attaching a code or a label with code— written or printed code such as barcode, color-code, RFID tag or any other code— on any object intended to be identified, or alternatively, using an existing code or label on the object, each object has its particular code; storing a voice-message, with accordance to each code, in a memory; and using a reader or a sensor to read or sense the attached code from the object. The match voice-message according to the code is obtained from the memory, and the voice-message is announced to the user.

[0006] Krukowski is also limited to identification of objects of interest to the blind user.

This is a practical need when the user is engaged in shopping at a retail outlet or working at a warehouse and the user wants to learn more about an object they are holding. However, Krukowski does not disclose or suggest finding the location of nearby object(s) nor the current location of the blind user needed for navigational guidance.

SUMMARY [0007] A radio frequency identification (RFID) tag array-based "smart floor" system for navigation and location determination for guiding individuals includes a plurality of spaced apart RFID tags. Each RFID tag has memory having information stored therein including positional information and attributes of objects or structures disposed in proximity to the tags. As defined herein, the term "proximity" represents the full volume of a room in the case of a closed environment, or up to several hundred meters in the case of an open (outdoor) environment. The tags convey radio frequency signals including the positional information and the attributes in response to received electromagnetic excitation fields. The RFID tags are embedded within or rigidly attached to a surface, such as, but not limited to, carpet pad, tile or wood flooring. The use of RFID tags for location, orientation and storage of room inventory according to the invention provides the infrastructure to allow integration of a sight limited (e.g. blind) individuals to gain unparallel freedom to navigate in society. No external system dependencies are required for this invention as all information to determine location and perform navigation can be stored by the RFID tags and read by the user when needed. Although the invention is described with reference to blind individuals and is particularly well adapted for use by blind individuals, the invention is in no way limited to application to the blind. [0008] The surface can comprise flooring, such as carpet pad, tile and wood flooring, where the RFID tags are embedded in the flooring. The surface can also be a roadway surface, such as concrete or asphalt roadway surface, as well as non-paved surfaces and other navigatable surfaces. The system preferably includes a RFID tag reader including an electromagnetic field generator and antenna. The tag reader is movable by a user and is for generating and transmitting said electromagnetic excitation fields to or more of the RFID tags to obtain said radio frequency signals to read the data that is stored by the tags including the positional information and object attributes. The RFID tag reader can be integrated with a walking cane, an attachment to a shoe, or a hand held device, such as a cell phone (smart phone) or PDA. In the hand held embodiment, The RFID tag reader can communicate with the hand held device using serial, Bluetooth or other forms of wireless communication.

[0009] A method for guiding a blind person comprises the steps of providing at least one area having a plurality of spaced apart RFID tags, each RFID tag having information stored therein including positional information and attributes of objects or structures disposed in proximity to the tags. The tags convey radio frequency signals including the positional information and attributes in response to received electromagnetic excitation fields. The tags are embedded within or rigidly attached to a surface. Electromagnetic excitation fields are transmitted by the user to or more of RFID tags to obtain said radio frequency signals including the positional information and the attributes. The user utilizes the positional information and the attributes for location determination. In the case the tags are disposed in a room, the method can further comprise initialization steps comprising surveying the room to determine position information and feature descriptions in the room, and programming each RFID tag with the position information and feature descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS [00010] A fuller understanding of the present invention and the features and benefits thereof will be accomplished upon review of the following detailed description together with the accompanying drawings, in which: [000H] FIG. 1 shows a RFID tag grid disposed in the flooring of a typical room, according to an embodiment of the invention.

[00012] FIG. 2 shows a user having a walking cane including an RFID tag reader and antenna inside a room having a RFID tag array comprising RFID tags in the flooring of the room, according to an embodiment of the invention.

[00013] FIG. 3 shows a keypad according to an embodiment of the invention which can be used to query objects in a particular direction and includes buttons for focusing the range of interest from the user.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [00014] A radio frequency identification (RFID) tag array-based "smart floor" system for navigation and location determination for guiding individuals includes a plurality of spaced apart RFID tags. Each RFID tag has memory having information stored therein including positional information and attributes of objects or structures disposed in proximity to the tags. As defined herein, the term "proximity" represents the full volume of a room in the case of a closed environment, or up to several hundred meters in the case of an open (outdoor) environment. The tags convey radio frequency signals including the positional information and the attributes in response to received electromagnetic excitation fields. The RFID tags are embedded within or rigidly attached to a surface, such as carpet pad, tile or wood flooring. [0001 S] System according to the invention do not require external connections to databases or prior knowledge about the space. The RFID tag array provides information regarding the space sufficient to describe the room, building or other environment of interest. [00016] Figure 1 shows a RFID tag grid 100 comprising 96 passive RFID tags 110 embedded in the flooring 115 of a typical room having the dimensions 10 feet by 12 feet. Flooring 115 can be carpet padding, tile or other material. Although tags 110 are shown in FIG. 1 spaced equidistantly, the invention is in no way limited to such an arrangement. As noted below, tags 110 are preferably embedding in the flooring 115 during manufacture. [00017] As described below, location based systems according to the invention inform the user of their location in the room within the context of the room through interrogating of the RFID tag grid therein, such as shown in FIG. 1. The user is also provided feedback as to the current user orientation in the room. The system can also report the location, distance and direction of the various items in the room such as office equipment, furniture, doors and even other users present in the room relative to the position of the user.

[00018] As noted above, for indoor applications, RFID tags are preferably embedded in the flooring. A single passive RFID tag represents a single grid point in the system. Using the dimensions of the exemplary room described relative to FIG. 1, if an accuracy of one foot is used this would add a material cost of about 10 x 12 x $1.00 or $120.00 to the 10 x 12 foot room shown. For example, carpet manufactures could integrate the RFID tags as part of the weaving process or the RFID tags could be integrated into a thin layer material that is applied under the carpet (e.g. padding) or hard surface flooring. For rooms that have existing carpeting the floor could be easily upgraded by rolling up the carpet applying the RFID flooring material and then reinstalling the existing carpet. For tile floors that represent a larger cost to replace it may be possible to insert RFID tags by removing the grout at tile intersection points and then reapplying the grout. Pre-existing hardwood floors represent a larger installation and cost challenge because of the challenges in installation without impacting the visible surface. [00019] For areas that provide travel from one location to a next location, such as sidewalks, hallways, and stairs, RFID tags can be located on the edge of the path. This allows for lower implementation costs because a grid is not required to indicate position. The path is narrow and defined so only a line of RFID tags are required. The tags can indicate position, and describe major locations such as building name, room number, bathroom location, type of door and stairs. [00020] Systems according to the invention can also be used in metropolitan areas to indicate road names and addresses. This would require RFID tags to be mounted in a weather proof object that could be mounted, such as to concrete or a road surface. The object could be raised and a groove or slot in the shape of a triangle located on the top surface could indicate the direction of a reference, such as 0 degrees or North. The user could touch the object with a cane or foot feeling for the direction of the slot. The user would then be able to determine location from the RFID tag embedded in the object and orientation. It would also be possible to allow the user to broadcast a specific RF signal to a neighboring object and the response would be an audible tone. The user would use the audible to locate the object. This embodiment would generally require the object to include a power source powered. The object could be located at the base of street lights, telephone booths or pedestrian traffic signals. A system to detect the location of an automobile could also read the RFID tags located on the roads using an RFID reader attached to the automobile to determine precise location information. This is an alternative to using GPS for location determination in areas, such as large cities where the view of the satellites required for GPS navigation can be blocked by tall buildings or cause multi-path related errors in the GPS signal.

[00021] Once the grid of passive RFID tags is installed, such as in the flooring, a survey of the room is generally performed to determine the precise location of one point in reference to a global coordinate in the building or floor. The features of the room are preferably located based on this single fixed reference point which allows for relative position information to be stored on the remaining RFID tags in that room thus reducing the amount of storage space required for an absolute coordinate system. With a layout and description of the room each RFID tag in the array can then be programmed with position information and the feature description of the room. The storage capacity of conventional RFID tags is generally limited so a method to describe room attributes as it relates to the location of the RFID tag is preferably implemented. For example, those RFID tags that fall in a traffic pattern that lead to a door could provide information related to the door location and direction. This allows for a flexible system with absolute positioning relative to the fixed point and at the same time protects the privacy and location of the user from external sources.

[00022] The end user can interact with the RFID tag array-based system using a RFID tag reader including an antenna integrated into a variety of structures. Such structures can include a wal ng cane, an attachment to a shoe, or a hand held device. Figure 2 shows a user 215 having a walking cane 220 including an RFID tag reader 225 and antenna 230 inside a room 260 having a RFID tag array comprising RFID tags 270 in the flooring of the room according to the invention. RFID tags 285 are also provided in a wall 290 of the room 260. [00023] The user 215 can quickly determine his/her location by passing over any of the

RFID tags 270. To determine orientation, the user 215 can extend their foot or cane 220 forward to a neighboring cell which provides relative directional information to the neighboring cells. This information can then be integrated with an application running on a PDA, smart phone, or embedded computing device 280 which interprets the location information and provides feedback to the user 215 via voice response or some other form of usable user interface as to the user location, orientation and description of the surroundings. This system design thus allows for a completely independent navigation system with no external dependencies. The RFID grid stores all information required for navigation which eliminates the need for prior knowledge about the space and the need to query details from an external database. If detailed information about the room 260 is available in a central system, the PDA, smart phone, or embedded computing device 280 can send a location query for a room based on current location or a potential location in the future. This information can then be used by location based software on the PDA, smart phone, or embedded computing device 280 to provide additional value added services to the blind.

[00024] Systems according to the invention are expected to have an immediate impact in the home and offices of individuals who are blind and does not require major infrastructure before the system is practical to the average user. Such a practical and low cost solution can become part of future building codes and part of compliance with Americans with Disabilities Act (ADA) rules and regulations.

EXAMPLES [00025] The present invention is further illustrated by the following specific exemplary implementation, which should not be construed as limiting the scope or content of the invention in any way.

[00026] Suitable RFID tags for use with the invention are manufactured by Texas mstruments Corporation and support storage of 2000 bits or 256 bytes of data. The data is organized in blocks of 4 for 64 addressable blocks. The reader/writer supports multiple block read from 1-64 blocks but writing data is one block at a time. The primary use of the system is read only and writing of information is primarily performed only during initial setup and installation.

[00027] MIDP 2.0 was selected for the software implementation to maximize the number of cell phone devices that can be used and support for playing of audio for voice prompts to describe the room. CLDC 1.1 is required as it supports floating point calculations which are required for calculating distance and direction.

[00028] The application interfaces with the Texas mstruments S6350 RFID reader/writer or some other suitable RFID reader through a serial port or other communication interface. The protocol is described by the ISO/IEC 15693-3 transmission protocol or other suitable communication protocol. The adoption of an ISO communication protocol provides for greater flexibility in available reader/writers as the industry matures and RFID technology reaches commodity level pricing.

[00029] Antenna design is an important element of the system. To maintain accuracy the antenna should be in close proximity to the RFID tag so that absolute positioning is a result. The antenna can be integrated into the end of the cane with minimum gain. It is also desirable to have an antenna that allows maximum tags to be read for information gathering when entering a room.

It may be possible to have two antennas integrated in the cane and switching electronically between the two depending on the application.

[00030] Standard RFID tags provide 2000 bits of information for storage per ID tag which allows for a variety of data formats and data elements. At a minimum, each tag needs its X,Y or

Z location, preferably relative to a reference point. It is recommended that latitude and longitude are used for maximum information for long term data services and global positioning. This creates an accuracy and survey problem and potential added expense when laying out tag locations. This problem also exists for a coordinate system that is accurate within a building. Using latitude and longitude still provides for accurate relative or local positioning with some measure of absolute positioning error.

[00031] The room or other area needs to have its inventory stored at tags concentrated near entrances to the room. This allows the software to learn about the position of major elements in the room. The position of objects can be stored as relative to the absolute position of the tag that contains the information. This provides for conservation of storage bits by reducing the length of data that needs to be saved but still maintains resolution. [00032] The design of the system allows for complete independent and anonymous use.

This eliminates the need for a central server to provide translation or missing information. It is also important to recognize that the future uses and objects to describe are unlimited which makes data formats and codes very important. This provides a clear indication that an XML based format allows for maximum data flexibility but at the expense of very verbose and overly descriptive. With a limited storage of 256 bytes an XML format would not allow for maximum data storage. A hybrid XML data format that uses dictionary tags to represent the data grammar of the system allows for good compression in a hierarchal parent-child format. This format will be referred to as Compact Markup language (CML).

[00033] The following is an exemplary simple inventory used to describe common elements found in rooms that aid navigation. An exhaustive sampling can be performed to establish a dictionary of objects and then based on object population can have an integer or id value assigned to it. For objects that are infrequent or not included in the initial inventory the text description of the object can be used without compression.

[00034] This list is fairly descriptive having 51 elements. Allowing for a dictionary of 250 and occupying one byte can provide a high degree of compression. If the dictionary exceeds 255 elements then the primary dictionary can be reduced to 0-127 and a two byte allocation could be used for dictionary values greater than 128 at the expense of an extra byte for dictionary values greater than 128. [00035] The exemplary XML shown below represents a typical data set stored on a RFID tag and the non- white space length is 251 bytes. The CML version compresses down to a length of 117 bytes. Further forms of data compression algorithms such as Huffman encoding can also be used. This will allow for approximately six room objects to be stored per tag with maximum flexibility in the type of data that can be stored.

[00036] Knowing the location of objects in a room via absolute coordinates is part of the preferred design criteria. It is important to determine user orientation so navigation to the object can occur. To determine orientation or angle relative to the axis the user can touch two points with a frame of reference of the user body. If the user sweeps left to right touching two points the coordinates of the two tags can be used to determine the midpoint of the two points. The perpendicular to the midpoint would indicate direction and orientation. Based on orientation the system can calculate direction and distance to objects in the room.

[00037] The user interface presents some challenges when the primary user is blind. This eliminates the ability to have sophisticated controls or even the use of simple menus. This places the emphasis of using voice prompts or other forms of user interface to describe the room. It would also be possible to use text-speech translation to minimize the need for audio files that described each object. [00038] The software collects information about the room and as the user navigates the system can provide voice or other user prompts warning of objects in the path or objects of interest. As voice recognition technology improves this will likely become an option allowing the user to use voice queries to navigate and find objects. It would also be possible to use remote voice recognition with the phone connected to a voice recognition server that translates the audio and sends the data query back to the phone. These features can enhance the user interface but because of reliability concerns regarding Internet connections, should not generally be the primary user interface.

[00039] Figure 3 shows a phone 300 having a keypad that can be used to query objects in a particular direction. The lower three buttons, 311-313, are used to focus on the range of interest from the user between short range, medium range, and long range, respectively. Other keys, or combination of keys are used to query objects in a particular direction, such as 30 degrees front left (316), 60 degrees front left (317), 45 degrees front-right (318), and 90 degrees right (319). An obtain information button 320 can be used to initiate a query, which cause tags (not shown) which are interrogated to transmit radio frequency signals including positional information and its proximate attributes. Phone 300 receives the radio frequency signals from the tags via the RFID reader and converts the information received to an audio or other user interface format that can be used for navigational guidance by blind users.

[00040] While the preferred embodiments of the invention have been illustrated and described, it will be clear that the invention is not so limited. For example, For example, through use of encrypted RF signal transmissions from RF tags in a tag array, positional information and attributes of objects or structures can be accessible only to a pre-selected group of individuals who are provided appropriate decoding tools, rendering the invention potentially valuable for military applications. Numerous modifications, changes, variations, substitutions and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as described in the claims.

[00041] The system can also be used for emergency services that require the evacuation or search and rescue in a building. For example, in the case where a building is on fire, fire rescue personnel can be equipped with an RFID reader device to indicate position and information about a room during the search and rescue. If the hallway or room of a building is filled with smoke the ability to find occupants in bedrooms or to find a room number based on a 911 call can be accomplished with systems according to the invention.

[00042] In addition, if the rescue personnel are lost or need to be tracked in real time the

RFID reader used for navigation can transmit positional information via wireless link to a central service. This would allow for efficient search and rescue operations where the location of each rescue personnel can be tracked and recorded during the operation.

[00043] The FCC has required the implementation of E911 services for cell phone users to report location information in the event of an emergency during a 911 call from the cell phone. Current systems lack the accuracy to determine precise location inside of buildings. If the cell phone contained an RFID reader that read positional information from the RFID grid then that precise location from the most recent positional update could be sent as part of the 911 call. [00044] The system would also allow for precise navigation and location determination for robotics. The practical use of service robots is limited by their inability to accurately navigate a space and to have awareness about the space and the objects that are in it. The simple task of finding an electrical outlet to recharge batteries is difficult. By using the RFID grid to precisely determine the location of the robot and for the nearest electrical outlet, the robot can navigate to the plug to its recharge batteries. This is only one example of how robotics can benefit from the invention.

Claims

CLAIMSWe claim:

1. A radio frequency identification (RFJD) tag array-based navigation system for guiding individuals, comprising: a plurality of spaced apart RFJD tags, each of said RFID tag having information stored therein including positional information and attributes of objects or structures disposed in proximity to said tags, said tags conveying radio frequency signals including said positional information and said attributes in response to received electromagnetic excitation fields, and a surface upon which said plurality of radio frequency tags are embedded within or rigidly attached thereto.

2. The system of claim 1, wherein said surface comprises flooring.

3. The system of claim 2, wherein said flooring comprises at least one selected from the group consisting of carpet pad, tile and wood flooring.

4. The system of claim 2, wherein said RFID tags are embedded in said flooring.

5. The system of claim 1 , further comprising a RFID tag reader including an electromagnetic field generator and antenna, said tag reader movable by a user for generating and ttansmitting said electromagnetic excitation fields to or more of said RFID tags to obtain said radio frequency signals mcluding said positional information and said attributes.

6. The system of claim 1, wherein said RFID tag reader is integrated with at least one selected from the group consisting of a walking cane, an attachment to a shoe, and a hand held device.

7. The system of claim 6, wherein said hand held device comprises a cell phone, PDA or embedded computing device.

8. The system of claim 7, wherein said RFTD tag reader communicates with said hand held device using a communication protocol over serial Bluetooth.

9. A method for guiding a blind person, comprising the steps of: providing at least one area having a plurality of spaced apart RFID tags, each of said RFID tags having information stored therein mcluding positional information and attributes of objects or structures disposed in proximity to said tags, said tags conveying radio frequency signals including said positional information and said attributes in response to received electromagnetic excitation fields, and a surface upon which said plurality of radio frequency tags are embedded within or rigidly attached thereto, and u-ansmitting said electromagnetic excitation fields to or more of said RFID tags to obtain said radio frequency signals including said positional information and said attributes, and utilizing said positional information and said attributes for location determination by said blind person.

10. The method of claim 9, wherein said tags are disposed in a room, further comprising the steps of: surveying said room to determine position information and feature descriptions in said room, and progranining each of said plurality of RFID tags with said position information and said feature descriptions.

11. The method of claim 9, wherein said surface comprises flooring, said flooring selected from the group consisting of carpet pad, tile and wood flooring.

12. The method of claim 9, wherein said utilizing said comprises directing a RFID tag reader including an electromagnetic field generator and antenna toward at least one of said RFID tags, and interrogating tag.

13. The method of claim 12, wherein said RFID tag reader is integrated with a walking cane, an attachment to a shoe, or a hand held device.

14. Flooring, comprising: a substrate material, and at least one RFID tag having associated memory embedded in said substrate material.

15. The flooring of claim 14, wherein said flooring comprises at least one selected from the group consisting of carpet pad, tile and wood flooring.