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XBEE IMPLEMENTATION ON MINI MULTI-ROBOT SYSTEM

Andi Adriansyah Yuliza

Department of Electrical Engineering, Faculty of Engineering, Universitas Mercu Buana

Jl. Meruya Selatan, Kembangan, Jakarta 11650

andi@mercubuana.ac.id yuliza.baes@gmail.com

ABSTRACT Wireless communications are now

growing very rapidly because it is very efficient to use. Wireless technology that is widely used at

close range is a device that can interface to the

other devices. Communication between robots is

the process of delivering informations to do

something useful task. Communication between

robots is an important component in the interaction

of the multiple robots. In multiple robot systems,

robot leader delivering orders to the follower robot

to complete a task that occurs coordination

between the robot forms of communication between

the robot wirelessly using XBee signals. This form of communication is in the form of a command to

the robot follower robot to follow the movement of

the robot leader. Advantages of communication

between the robots are efficient in completing the

task. With time quickly orders can be delivered in a

broadcast to the follower so that the job can be

completed simultaneously.

Key Word: Robot, Leader, follower,

communication, XBee, Microcontroller

1 INTRODUCTION

Wireless technology has been developing

very rapidly due to highly efficient wireless

communications. One of the wireless

communication technologies in great demand is

Wireless Local Area Network (WLAN). WLANs

are based on IEEE 802.11 standards that use has some advantageous, such as high capacity, wide

coverage and able to broadcast directly [1],[2],[3].

If the area used in wireless is not too

widely, a kind of wireless technology applied are

Wireless Personal Area Network known as WPAN.

WPAN is a network communication among devices

over wireless technologies. The reach of a WPAN

varies from a few centimeters to a few meters.

WPANs are widely used for communication

between sensors and electronic devices. There are

some technologies used in WPAN such as IrDA, Wireless USB, Bluetooth, Z-Wave and ZigBee.

Nowadays, ZigBee is applied in many

applications. ZigBee has a defined rate of 250 kbit/s, best suited for periodic or intermittent data

or a single signal transmission from a sensor or

input device. Applications include wireless light

switches, electrical meters with in-home-displays,

traffic management systems, and other consumer

and industrial equipment that requires short-range

wireless transfer of data at relatively low rates. The

technology defined by the ZigBee specification is

intended to be simpler and less expensive than

other WPANs, such as Bluetooth or Wi-Fi.

In another side, technology and application of robotic grow rapidly, in terms of reliability,

coverage ability and field applications. There are

several research themes were also developing, such

as sensor technology, motor technology, power

supply technology, telecommunications technology,

control technology and artificial intelligence

technology. The development of these technologies

support each other’s to robotic technology.

Therefore, investigations of robotic become

interesting area for researchers.

In this decade, there has been an important

variation in robotic research focus. Researchers are beginning to modify the direction of robotic

research, from investigation of a single robot

system to exploration of coordination of multi-

robot systems. Multi-robot system is a system of a

robot entities that work together to complete a

specific task [4],[5]. There are several advantageous

of the application of multi-robot systems.

Generally, the application of multi-robot system is

to produce a better system in order to solve the

problems of the system. With the multi-robot

system, the existing complex and difficult system can be performed using the robot with a cheap and

simple [6].

Therefore, this paper seeks to address

multiple robot communication system design. A

communication system design attempted as

possible compared to the existing ones. The focus

of the design is intended for communication

between the leader and the follower so that the

follower can follow the movement leaders. The

transmission medium used among the robots is a

wireless system using the XBee, Arduino

microcontroller where the mobile robot is able to

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perform bi-directional communication and

recognize the controller ID.

2 DESIGN AND IMPLEMENTATION

2.1. ZigBee and XBee

ZigBee is a specification of the

communication protocol low-power digital radios

based on the IEEE 802.15.4 specification in 2003

and Zigbee alliance with a maximum range of 100

meters. IEEE 802.15.4 specification is the basis for

the lower layers of the ZigBee MAC and PHY and

determine the standard 2.4 GHz radio that is used

in the world.

XBee is a brand that supports a variety of communication protocols including ZigBee

802.15.4 and WiFi. Figure Xbee module is shown

in Figure 1.

Figure 1. XBee Module

The ZigBee protocol is using same

standard with the Bluetooth standard. Any

manufacturer’s device that fully supports the

ZigBee standard can communicate with any other company’s ZigBee device. So just as your Motorola

Bluetooth headset can communicate with your

Apple iPhone, a CentralLite ZigBee light switch

can communicate with a Black & Decker door

lock. Architecture ZigBee protocol shown in Figure

2.

ZigBee is widely used in the market for

ZigBee has many advantages, such as [7]:

• Reach 1 meter - 100 meter.

• ISM (Industrial, Scientific and Medical) radio bands: 2.4 GHz, 868 MHz and 915

MHz.

• Low power consumption.

• CSMA-CA channel access.

• Large networks (65,000 nodes)

• Highly secure (AES encryption)

• Network topology star, mesh and mutual support various applications.

• Interoperability across the world with other products

• Co-existence with other wireless media (eg, WLAN, Bluetooth, cellular).

Figure 2. ZigBee Architecture

The process of sending and receiving data on

ZigBee. Using standard ZigBee network to transmit

data specified by IEEE 802.15.4:

• Request data means the data transmission

• Data Confirm means the knowledge of the data request

• Data Indication means receiving data

2.2. System Design

The system is designed as shown in Figure 3.

Figure 3. Block Diagram System Designed

The leader robot consists of an Arduino [8]

microcontroller as the center of all the systems, and

manages all activities of the input/output system. Sensor system which uses ultrasonic sensors

functions as sensors obstacle in order that the robot

can move well. Motion system using a DC motor

driven with L298 Shield with maximum current

2A. Communication systems use Xbee Module

with DFduino as connections between Xbee Shield

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and the Arduino microcontroller. This

communication function for communication

between leader robot and follower robots. As for

the follower robots not have a sensor system. The

movement of the follower robot just follows the leader robot by receiving commands via Xbee

modules.

2.3. Forms of Robot Communication

Leader robot sends request signal to the

robot and follower robot and the follower robot

transmit acknowledgment signals and handshaking

occurs, and then the leader robot send command,

so that follower robot follow orders. So the

follower robots will follow all movements of the

leader robot. Form of communication robot leader

and follower robots is shown in Figure 4.

Figure 4. Form of

Figure 4. Form of communication between leader and follower

robots

3 RESULTS

Overall system is made with a pair of shields

according to function. Arduino is located at the

very bottom and the motor shield L 298 is on

arduino after the XBee shield and XBee module

are on the top right on the XBee Shield. The

compilers of a series or robot are obtained. Its shown in Figure 5 as a series when it is released

from the composition of robot and Figure 6-7 is the

overall picture of the system.

Figure 5. The series of robots that have not been installed

Figure 6. The series Robot

Figure 7. The entire system

At this signal measurement spectrum

analyzer are set according to the specifications of the XBee signal with a frequency range of 2.4 GHz

marker around 2419.25 GHz and a frequency range

between 2400 and 2440 MHz spectrum and level of

-100 dBm. Transmitter signal form the leader is

shown in Figure 8.

Figure 8. Transmitter signal form the leader

From the results of measurements of the spectrum

analyzer are shown in transmitter signal power

level leader, it is Maximum -81 dBM and -97.4

dBM. The interaction between the leader and the

follower is shown in the Figure 9.

Communication system

XBee Module

Leader

Robot Folllower

Robot

Communication system

XBee Module

Request

Acknowledment

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Figure 9. Forms signaling interactions between

Table 1 are the results of measurements of transmit

power (power level) signal transmitter XBee leader

based on the distance traveled.

Table 1 The results of measurements of the signal power level

Xbee

Distance (meter) Power Level (dBm)

1 -80

2 -80

3 -82

4 -90,4

5 -86,9

6 -91,9

7 -91,4

8 -86,8

9 -90,3

10 -89,5

12 -99,1

Average -88,02

From Table 2 it can be explained that the farther the

distance, the smaller the signal power level. From

the results of measuring the power level can be

displayed in graphical form as shown in Figure 10.

This measurement is performed in the space in the

Lab.Tehnik Electro VII.

Figure 10. Graphics power level XBee transmitter signal

Based on the graph it can be concluded that the

further the distance, the smaller the power level. It

means that the distance also affects the

communication between the robot so it will affect

system performance.

Based on some experiments it can be said

that the leader and the follower robots can communicate with a maximum distance of 11

meters. Robots are not the connected at a distance

of 12 meters because of the low power level that is

-99.1 dBm. Based on the specifications XBee is

shows the minimum receiver sensitivity -92 dBm

so that if the price is less than -92 dBm, the signal

can not be captured by the XBee receiver on the

follower.

Another experiments measuring time

required to make communication between the

leader and the follower so that everything started to move. It aims to determine the speed of the robot

performance in receiving orders and execute it.

Table 2. Results of measuring the communication

time leader and follower

Experiment Duration process the

communication

between the follower

and leader

1 11

2 10

3 11

4 11

5 12

6 13

7 15

8 13

9 15

10 15

average 12,5

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From the measurement results in Table 2 that the

communication between the leader and the follower

robots takes 12.5 seconds. These measurements do

not take up the position between the leader and

follower robots. The experiments were conducted to

determine the performance of signal XBee outdoor

and environmental influences on the robot XBee

signal. The experiments were done at the of

Electrical Technical of Mercu Buana University.

These test results are shown outdoors on a Table 3.

Table 3. Test results XBee communication outdoors.

From the results of Table 3 it can be said that the

ability to capture the signal from the transmitter

transceiver is only up to 5 meters and more than worth the transceiver is not able to capture the

signal.

4 CONCLUSIONS

Robot communication system designed

able to work well in indoor and outdoor as well. Based on experiments results it can be concluded

that the experimental signal indoors can be

connected properly to a distance of 12 meters. The

average power level of the signal up to a distance of

12 meters is -88.02 dBm. The average time need to

make communications between leader and follower

robot is 12.5 seconds. Unfortunately, in outdoor

experiments transmitter receiver can catch the

signal well only up to 5 meters.

REFERENCES

[1] Labiod, H, Afifi, H. And De Santis, C. (2007).

WiFiTM, BluetoothTM, ZigBeeTM, And WimaxTM,

Netherlands, Springer.

[2] Stalling, W. (2005). Wireless Communications

And Network, 2nd Ed., USA: Pearson

Education, Inc.

[3] Garg, Vijay K. (2007), Wireless

Communications And Networking, USA: Elsevier Inc.

[4] Parker, Lynee E. (2002). Current Research in

Multi Robot System. Paper presented at The

Seventh International Symposium on Artificial

Life and Robotics, Oita, Japan.

[5] Parker, Lynne E.(2008), Distributed

Intelligence: Overview of the Field and its

Application in Multi-Robot Systems, Journal Of

Physical Agents, Vol. 2, No. 1, March 2008.

[6] Mataric Gerkey, And Brian P. (2001).

Principled Communication fo Dynamic Multi-

Robot Task Allocation, In Experimental Robotics VII, LNCIS 271D. Rus and S. Singh,

editors, pages 353-362. Springer-Verlag Berlin

Heidelberg.

[7] Gislason, Drew ( 2008 ). Zigbee Wireless

Networking, USA: Elsevier Inc

[8] Simon, Monk (2010). 30 Arduino Projects for

the Evil Genius. United States of America: Mc

Graw-Hill.

experiments distance between

leader and

follower robot

(meter)

Status

1 1 connected

2 2 connected

3 3 connected

4 4 connected

5 5 connected

6 6 no

7 7 no

8 8 no

9 9 no

10 10 no

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