Intelligent Mobile ROBOT Navigation Technique Using RFID Technique (1)

7/28/2019 Intelligent Mobile ROBOT Navigation Technique Using RFID Technique (1)

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2012

Intelligent Mobile ROBOTNavigation Technique UsingRFID Technique

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* I N D E X *

Abstract..3Introduction..4RFID technology..5Using RFID for Accurate Positioning .7

RFID BackgroundRFID Positining

Microprocessors..Driving relaysEncoder HT 12 EDecoder HT 12 DRF TransmitterRF ReceiverAtmel 89C2051 MicroController

System ArchitectureRFID communication ModuleFLC Navigation Module


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# A B S T R A C T #

The mobile robot is controlled using mobile and wireless RF

communication. In this method controlling is done depending on thefeedbackprovided by the sensor. This contains different modules

such as

Wireless unit module

Sensing and controlling module

When no prior knowledge of the environment is available, the problem

becomes even more challenging, since the robot has to build aMap of

Its Surroundingsas it moves. These three tasks ought to be solvedin conjunction due to their interdependency.

In the sensing module when thePIC micro controller is powered upby the high-speed dc motors. The sensor is mounted on the robot.

The encoder mounted on the robot transmitting the data continuously

And a number of standard RFID tags attached in robots environment

to define its path. Here the robot consists of Transmitter and

receiver. Here thefrequency used is 433 kHz.

Here we show that using RF signals from the RFID tags as an analog

feedback signals can be promising strategy to navigate a mobile robotwithin an unknown or uncertain environment.


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# INTRODUCTION #

This method is computationally simpler and more cost effective than

many of its counterparts in the state-of-the-art. It is also modular

and easy to implement since it isindependent of the robots

architectureand its work space. The main idea is toexploit the

ability of a mobile robotto 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. The

suggested algorithm iscapable of reaching a target point in its a

priori unknown workspace, as well as tracking a desired trajectory

with a high precision.

The proposed algorithm takes advantage of the emerging Radio

Frequency Identification (RFID) technology and a Fuzzy Logic

Controller (FLC) to guide the robot to navigate in its working volume.

This navigation method is based on continuous encoder readings that

provide the position, orientations and linear and angular velocities of

robot.

Several modules are involved in operating mobile platforms, such as,for example, the localization, navigation, obstacle avoidance, and path

planning modules.

The most common and popular navigation methods proposed in the

literature to date rely on dead-reckoning based, landmark-based,

vision-based, and behavior-based techniques.

(dia : fig 1 of 65 pdf)


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# RFID TECHNOLOGY #

RFID is an automatic identification method that relies on storing and

remotely retrieving data.

A basic RFID system consists of three components:

An antenna or coil

A transceiver (with decoder)

A transponder (RF tag) electronically programmed with unique

information

TheAntennaemits radio signals to activate the tag and to read and

write to it.Thereaderemits radio waves in ranges of anywhere from one inch to

100 feet or more, depending upon its power output and the Radio

Frequency used. When an RFID tag passes through the

electromagnetic zone,it detects the readers activation signal.

The reader decodes the data encoded in the tags integrated circuit(silicon chip) and the data is passed to thehost computerfor

processing

The purpose of an RFID system is to enable data to be transmitted by

a portable device, called a tag, which is read by an RFID reader and

processed according to the needs of a particular application. The data

transmitted by the tag may provide identification or location

information, or specifics about the product tagged, such as price,

color, date of purchase, etc. RFID quickly gained attention because of

its ability to track moving objects.


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Using RFID for Accurate Positioning

The RFID positioning can be divided into four steps: in the first step, install RFID

tags on roads in a certain way, store very accurate location information along with

other necessary information to the tags, add an RFID reader module to thenavigation system, and use this new location information. Apart from the RFID

system, we also propose to use a tag database. Due to the memory constraint on

the tag and the data size that needs be written in a tag, the use of a database for

tags is a necessary condition. In addition, the speed of the RFID communication

also makes the use of the tag database indispensable.

RFID BACKGROUND:

In this section a brief overview of RFID technology in general is given. An RFID

system consists of tags, a reader with an antenna, and software such as a driver

and middleware. The main function of the RFID system is to retrieve information

(ID) from a tag (also known as a transponder). Tags are usually affixed to objects

such as goods or animals so that it becomes possible to locate where the goods and

animals are without line-of-sight. A tag can include additional information other

than the ID, which opens up opportunities to new application areas.

An RFID reader together with an antenna reads (or interrogates) the tags. An

antenna is sometimes treated as a separate part of an RFID system. It is,

however, more appropriate to consider it as an integral feature in both readers

and tags since it is essential for communication between them. There are two

methods to communicate between readers and tags; inductive coupling and

electromagnetic waves. In the former case, the antenna coil of the reader induces

a magnetic field in the antenna coil of the tag. The tag then uses the induced field

energy to communicate data back to the reader. Due to this reason inductive

coupling only applies in a few tens of centimeter communication. In the latter case,the reader radiates the energy in the form of electromagnetic waves. Some

portion of the energy is absorbed by the tag to turn on the tags circuit. After the

tag wake up, some of the energy is reflected back to the reader. The reflected

energy can be modulated to transfer the data contained in the tag.

Three frequency ranges are generally used for RFID systems: low (100~500 kHz),

intermediate (10~15 MHz), and high (850~950 MHz, 2.4~5.8 GHz). The

communication range in an RFID system is mainly determined by the output power

of the reader to communicate with the tags. The field from an antenna extendsinto the space and its strength diminishes with respect to the distance to tags.

The antenna desi n determines the shape f the field s that the ran e is als


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More data decreases the communication speed and requires more memory,

which leads to high cost.

In summary, there are issues to be addressed before full-fledged deployment of

RFID tags nationwide.

Making RFID tags that can withstand a harsh environment.

Fast communication speed between readers and tags. The data size

Figure 1. RFID Tags on a Road

Tag Database

While there would be location information in a tag, it would be almost impossible to

embed all the necessary information in a tag due to memory constraints and the

dynamic nature of some information. Information such as absolute coordinates of

the location will not be changed. On the contrary, relative coordinates and the

property of the road on which the tag is could change some time (unlikely, though).

Moreover, we can embed more useful information such as nearest museums,

restraints, and gas stations.

However, the contents of the information vary all the time. Thedata size as well

as the dynamic nature of it prevents from writing all the information at theinstallation time. To address this issue, wedevise a tag database which stores

information corresponding to the tagsavailable on the roads in a region (country

for instance). The information stored in the tag database is whatever information

on real tags and more such as point

of interests.

Another reason for the necessity of the tag database comes from the speed of

the RFID communication. It may not be fast enough to get all the information

from a tag while driving at, for instance, 150km/h. However, getting only

identification (ID) is very feasible even at such a high velocity. Once the ID isretrieved, it can be efficiently searched the tag database and extracted whatever

inf m ti n n c ss


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The tag database is a collection of tags and a part of the digital map that a

navigation system may carry. Generally, a digital map consists of cells each of

which contains network information for route guidance. The network information is

a graph with nodes and links.

Figure 2 shows a class diagram of the digital map. In the diagram, TagDB is an

aggregation of Tag objects which represent tags in a real world. Each cell has linksto the collections of nodes, links, and tags. For simplicity, we only show the

attributes of the Tag object. As in the diagram, a Tag object includes ID, absolute

coordinates X and Y, relative coordinates RX and RY, link ID where the tag is, and

the property field. This last field is for the number of lanes of the link, type of

the road (highway, local, etc), and so on. In Java language and most of other

programming languages, type long is 8 bytes, type float and int are 4 bytes, and

type short is 2 bytes.

F igure 2. Tag Database Class Diagram

The data size of a tag is 30 bytes. Therefore even with a million tags on the roads,thereby in the database, the size of the tag database is approximately 30MB.


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# MICROPROCESSORS #

Driving Relays:Using the outputs of the HT-12D or HT-648L decoder ICs to drive relays is quitesimple. Here are schematics showing how to drive relays directly from the data-

output pins of the decoder.

ENCODER HT12E :HT12Eis anencoder integrated circuitof 2

12

series of encoders. They are paired with212series of decoders for use in remote control system applications. It is mainly used in

interfacing RF and infrared circuits. The chosen pair of encoder/decoder should have

same number of addresses and data format.

Simply put, HT12E converts the parallel inputs into serial output. It encodes the 12 bit

parallel data into serial for transmission through an RF transmitter. These 12 bits are

divided into 8 address bits and 4 data bits.

HT12E has a transmission enable pin which is active low. When a trigger signal is received

TE i th d dd /d t t itt d t th ith th h d bit


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upon receipt of a transmission enable. This cycle is repeated as long as TE is kept low. As

soon as TE returns to high, the encoder output completes its final cycle and then stops.

FEATURESOperating voltage 2.4V~12V for the HT12E

Low power and high noise immunity CMOS technology

Low standby current: 0.1_A (typ.) at VDD=5V

HT12A with a 38kHz carrier for infrared transmission mediumMinimum transmission word Four words for the HT12E

Built-in oscillator needs only 5% resistor

Data code has positive polarity

Minimal external components

HT12A/E: 18-pin DIP SOP package

Pin Diagram:


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FLOW CHART

TIMING DIAGRAM


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HT12Dis adecoder integrated circuitthat belongs to 212series of decoders. This series

of decoders are mainly used for remote control system applications, like burglar alarm,

car door controller, security system etc. It is mainly provided to interface RF and

infrared circuits. They are paired with 212series of encoders. The chosen pair of

encoder/decoder should have same number of addresses and data format.

In simple terms, HT12D converts the serial input into parallel outputs. It decodes theserial addresses and data received by, say, an RF receiver, into parallel data and sends

them to output data pins. The serial input data is compared with the local addresses three

times continuously. The input data code is decoded when no error or unmatched codes are

found. A valid transmission in indicated by a high signal at VT pin.

HT12D is capable of decoding 12 bits, of which 8 are address bits and 4 are data bits. The

data on 4 bit latch type output pins remain unchanged until new is received.

FEATURESOperating voltage 2.4V~12V

Low power and high noise immunity CMOS Technology

Low standby current

Capable of decoding 12 bits of information Pair with Holteks 2 Series of encoders

Received codes are checked 3 times

Address/Data number combination

HT12D: 8 address bits and 4 data bits

HT12F: 12 address bits only

Built-in oscillator needs only 5% resistor

Easy interface with an RF or an infrared transmission medium


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Or Pdf (dia)

PIN DESCRIPTIONPORT 1

The Port 1 is an 8-bit bi-directional I/O port.

Port pins P1.2 to P1.7 provide internal pull-ups.

P1.0 and P1.1 require external pull-ups. P1.0 and P1.1 also serve as the positive input (AIN0)

and the negative input (AIN1), respectively, of the on-chip precision analog comparator.

The Port 1 out-put buffers can sink 20 mA and can drive LED displays directly.

When 1s are written to Port 1 pins, they can be used as inputs.

When pins P1.2 to P1.7 are used as inputs and are externally pulled low, they will source

current (IIL) because of the internal pull-ups.

Port 1 also receives code data during Flash programming and verification.

PORT 3 Port 3 pins P3.0 to P3.5, P3.7 are seven bi-directional I/O pins with internal pull-ups.

P3.6 is hard-wired as an input to the output of the on-chip comparator and is not

accessible as a general-purpose I/O pin.

The Port 3 output buffers can sink 20 mA.

When 1s are written to Port 3 pins they are pulled high by the internal pull-ups and can be

used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL)

because of the pull-ups.

Port 3 also serves the functions of various special features of the AT89C2051 as listedbelow: Port 3 also receives some control signals for Flash programming and verification.

RSTReset input. All I/O pins are reset to 1s as soon as RST goes high. Holding the RST pin

high for two machine cycles while the oscillator is running resets the device. Each machine

cycle takes 12 oscillator or clock cycles.XTAL1

Input t th in tin scill t mplifi nd input t th int n l cl ck p tin ci cuit


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OSCILLATOR CHARACTERISTICSThe XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier

which can be configured for use as an on-chip oscillator, as shown in Figure. Either a

quartz crystal or ceramic resonator may be used.

To drive the device from an external clock source, XTAL2 should be left unconnected

while XTAL1 is driven as shown in Figure.(dia)

Or

Pin

No

Function Name

1

8 bit Address pins for input

A0

2

A1

3 A2

4 A3

5 A4

6 A5

7 A6

8 A7

9 Ground (0V) Ground

10

4 bit Data/Address pins for output

D0

11 D1

12 D2

13 D3

14 Serial data input Input

15 Oscillator output Osc2

16 Oscillator input Osc1

17 Valid transmission; active high VT

18 Supply voltage; 5V (2.4V-12V) Vcc

Block Diagram of HT 12D


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19

FLOW CHART


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TIMING DIAGRAM

Applications of HT 12E & HT 12D:

Burglar Alarm, Smoke Alarm, Fire Alarm, Car Alarm, Security System

Garage Door and Car Door Controllers Cordless telephone

Other Remote Control System

RF TRANSMITTER:The RF Transmitter used is TLP434A.It has frequency range of 315 MHz to

433MHz.It operates at a voltage range of 2-12VDC.

(dia)

RF RECEIVER:The RF Receiver used is RLP434A. It has frequency range of 315MHZ to

433MHZ.it operates at a voltage range of 3.3-6 VDC

(dia)


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ATMEL 89C2051 MICROCONTROLLER:The AT89C2051 is a low-voltage, high-performance CMOS 8-bit microcomputer

with 2K bytes of Flash programmable and erasable read-only memory (PEROM).

The device ismanufactured using Atmels high-density nonvolatile memorytechnology and is compatible with the industry-standard MCS-51 instruction

set.

The AT89C2051 provides the following standard features:

2K bytes of Flash

128 bytes of RAM

15 I/O lines

two 16-bit timer/counters

a five vector two-level interrupt architecture

a full duplex serial port

a precision analog comparatoron-chip oscillator and clock circuitry

In addition, the AT89C2051 is designed with static logic for operation down to

zero frequency and supports two software selectable power saving modes.

The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial

port and interrupt system to continue functioning. The power-down mode saves

the RAM contents but freezes the oscillator disabling all other chip functions

until the next hardware reset.

PIC16F877 MICROCONTROLLER:


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# SYSTEM ARCHITECTURE #

The proposed navigation system consists of two fundamental modules:an RFID communication module and

a Fuzzy Logic Controller (FLC) navigation module.

TheRFID communication moduleis responsible for communicating with the

tags (or transponders) through an RFID reader with two receiving antennas

mounted on the robot. A high level system configuration setup of the current

navigation technique is depicted in Fig. 2, where two RFID tags, T1 and T2, are

attached on the ceiling. The robots desired trajectory is the straight-line

segment connecting the orthogonal projection points, A and B, of tags T1 and

T2, respectively.Therobot employs the FLC modulein order to provide the necessary control

action to its actuators, which is required to move the robot from one point to

another in its workspace.

Consider a scenario where the robot is presented with a desired trajectory

defined by an ordered sequence of tag IDs, like (00, 01), for instance, then it

first navigates to the orthogonal projection point of the tag with ID 00, then it

moves along the virtual straight line linking the orthogonal projection points of

tag IDs 00 and 01, where it will stop. The

Novelty in this navigation scheme is that it is independent of the tag positions,

odometry information, and structure of the working environment.


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A. RFID Communication ModuleBefore starting the mission, the robot sendstime multiplexed single-tone

sinusoidal signalswith different frequencies, and then listens to thebackscattered signals from the RFID tags. The high level architecture of the

custom-designed RFID communication module is depicted in Fig 3. Preliminary

studies were conducted to confirm the fact that using a custom-built RFID

reader with two receiving antennas can determine the relative position of the

tag (left or right) with respect to the reader mounted on the robot.

Let1 and2 be the phase angles of the signal received by the readers

receiving antennas 1 and 2, respectively.

The phase difference, , is then defined by

=12. ....(1)

This phase difference is then passed to the FLC in order to decide on the

robots direction


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B. Fuzzy Logic Controller

The purpose of FLC is to provide intelligent actions to be taken by the robot.In the current work, we use asingle-input single-outputMamdani-type FLC as

shown in Fig. 4. The aim of the FLC is to decide on the amount of tune-up

that the robot has to apply to its current directionto converge to its targetposition. The FLCs input isthe phase differenceprovided by the two

directional antennas mounted to the RFID reader on the robot. The robot then

uses this information to update its direction following the update rule (2).

(new) =(old)+ (2)

The fuzzification and defuzzification membership functions are taken as linear

triangular and trapezoidal membership functions for their higher computationalefficiency [19], as depicted in Fig. 5. An empirical analysis was performed to

optimize these membership functionparameters to improve the FLCs

performance. The minand max operators are adopted as the t-norm and s-

norm operators, while the defuzzification method is set to be the center of

area.


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Three fuzzy rules are defined to reflect the fact that the phase difference of

the signal is positive when the transmitting transponder is on the left side of

the receiving


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antenna and vice versa. These rules are:If is NegThen is CCWIf is Zero Then is ZeroIf is Pos Then is CW

The rationale behind these rules is that the robot is supposed to turn

left/right (CCW/CW, for counter-clock wise and clock-wise, respectively) ifthe RFID tag is on the left/right of the receiving antenna, whereis

negative and positive, respectively.


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# PROPOSED NAVIGATION

ALGORITHM #This section explains how the modules described above fit into the overallnavigation framework. The efficient coordination among the RFID

communication module, FLC, and different actuators of the robot allows it to

hav less computational overhead while being executed on therobots processor.

The following is a description of the different steps of the algorithm.

Step 1:The robot is pre-programmed with an ordered list of tag ID numbers

defining its desired path.

Step 2:The target tag of the current navigation phase is determined from the

ordered list of tags defining thecomplete robots desired path.

Step 3:Once the target tag is known, the robot scans through the signalsbackscattered from all the tags within its communication range and records the

phase angles1 and2 of the signal coming from the tag representing the

target tag at that time instant.

Step 4:The phase difference, , of the destination tagssignal is calculated

as defined in (1). is then passed to the FLC to quantize the tuneup the robot

has to apply to its direction to better direct itself towards its destination. The

robot updates its heading as in (2) and dispatches the required control action

to its relevant actuators.

Step 6:Once the robot reaches the destination tag, it checks for more

available destination tag IDs in the desired path. If the current destination tagis the last tag, then the robot simply stops. If not, the algorithm restarts

fromStep 2.

A thorough evaluation ofthis algorithms performanceis provided in the

following section.


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CONCLUSIONA novel RFID-based robot navigation system is proposed

in this paper. The robot is first presented with a

sequence of tag IDs defining its desired trajectory. This

sequence is then broken into a sequence of ordered

pairs of IDs each of which represents a line segment of

the overall trajectory. The mobile robot tracks each

segment by continuously assessing the phase

difference of the RF signals at the readers two

receiving antennas coming from the current segments

target tag. An FLC is adopted to compute the control

effort necessary for the robot actuators to tune its

orientation appropriately. Computer simulations were

run to demonstrate the algorithms efficiency in

tracking various paths of different complexities despite

the noise in the RF feedback signal. The proposed

algorithm is very modular as it can be easily

implemented on virtually any type of robotic systemsand working environments. It is computationally

inexpensive as it is free of any visual data processing.

With the help of sensor feedback mechanism with RF

communication the mobile robot can be controlled from

a far distance, which is desirable fact when the robot is

working in hazardous environment.


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http://www.studentsaarthi.com/www.ojs.academypublisher.com/index.php/jcm/article/.../59

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Intelligent Mobile ROBOT Navigation Technique Using RFID Technique (1)

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