Hardware Implementation of an Explorer

Bot Using XBEE & GSM Technology M. V. Sai Srinivas, K. Yeswanth, E. Vijay, B. Bhanu prakash, Gayathri Narayanan

Dept. of Electronics and Communications Engineering,

Amrita Vishwa Vidyapeetham, Amritapuri, India

venkatasaisrinivas1@gmail.com, gayathrin@am.amrita.edu

Abstract

In this work, we implement a robot for

exploration purposes using Xbee and GSM

Technology. The robot is operated by Arduino

microcontroller and the motion of the robot is

controlled by XBee Modules. We use Ultra Sonic

Sensor (obstacle detection sensor) which is based on

electro-mechanical energy transformation to

measure the distance from the sensor to the target.

The metal detector sensor, which works on the

principle of mutual inductance helps to detect

explosives, which increases the efficiency of the

Robot. All the opponent positions will be captured by

a night vision wireless camera, equipped with built-in

Audio and Video feature. At the transmitting end by

using a laptop, commands are sent to the receiver’s

end to control the motion of the robot. At the

receiver end, four motors are interfaced for

movement. In case of the failure of XBee modules,

we control the motion of the robot by using GSM

Module with a bit delay. We also receive the

messages of the sensors readings of obstacles to the

transmitter end.

Keywords Explorer Bot, Arduino microcontroller, GSM, Xbee.

1 - Introduction

Life of human beings is very precious but lots

of people are losing their lives every minute in the

world, especially in war attacks as well as due to

natural disasters. In several of these mishaps, saving

human lives is a highly challenging task due to the

difficulty in accessing the mishap prone areas. This

problem can be solved in a smart way by introducing

robots. Robots are intelligently developed such that

it can perform tasks that human beings can. In this

work, we have designed and developed the

hardware prototype of an explorer robot which can

suitably substitute for human beings where physical

human intervention is a challenging task. The

following sections outline the System Model and

gives a glimpse into the results. 2 – System Design Arduino

Arduino microcontroller is a highly

integrated chip that contains all the components

comprising a controller. It includes CPU, RAM, some

form of ROM, I/O Ports and timers [2]. Every

component in the robot like the Xbee module,

Sensors, GSM module etc., are interconnected with

the Arduino. It works with the input voltage of 7 to

12 V. The whole program to control the bot is

written in Arduino IDE(Integrated Development

Environment). XBee Module

The motion of the robot is

controlled by XBee module. It works with a supply

voltage of 2.8-3.4 V. Xbee uses IEEE 802.15.4

protocol at a frequency of ISM (Industrial Scientific

and Medical) band of 2.4 GHz which is the new

standard for low cost, highly efficient and low power

transmission and is better than IEEE 802.11 protocol

[3] .It is a reliable protocol and gives timely packet

International Journal of Pure and Applied MathematicsVolume 118 No. 20 2018, 4337-4342ISSN: 1314-3395 (on-line version)url: http://www.ijpam.euSpecial Issue ijpam.eu

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transmission while maintaining its stability [4] [5].We

use two Xbee Modules of series2 - one as the

transmitter and other as the receiver.

Fig 1: Flowchart of the Motion of the Bot

Fig 2: Camera and Xbee transmitter Interface

Here the wireless communication occurs

between two XBee devices. For communication

between two Xbee modules, we need to pair the two

modules by giving PAN ID and 16-bit address in XCTU

software. So the transmitter will able to

communicate with the receiver i.e., if we send a

message from the transmitter as shown in Fig 2 the

same will be received by the receiver placed in the

robot as shown in Fig 3. Xbee is one of the ZigBee

devices which are used as the latest technology in

wireless communication instead of Bluetooth

modules because XBee covers a range of 300 feet.

Fig 3: Transmission – Reception between Xbee

modules Sensors

(a) – UltraSonic Sensor

Ultra Sonic Sensor is popular, cheap and

reliable technique of sensing distances of objects for

localization [1] .It is a technique that uses sound

propagation to navigate, communicate or detect

objects [1]. The object range is calculated by

Range, R = cT/2

where c is the speed of sound and T is the time taken

by the beam.

Our robot consists of four ultrasonic sensors

which covers all the four sides of the bot. If any

obstacle comes in between the path it gives

information about the obstacle and gives the

distance between the path and obstacle in

centimeters as shown in Fig 4. The information is

sent to the mobile.

Fig 4: Alert received in the mobile

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X: Real time

Y: Duration to receive signal

Fig 5 : Graph between real time and duration

Fig 5 gives the duration undergone with respect to

the real time. If the object is placed in between 2cm

and 40cm the time taken will be around 2500ms. If

no object is placed then the duration is around

15000ms.

Fig 6: Duration vs. Distance graph

Fig 6 shows the relationship between the distance

and the duration of ultrasonic sensor and the object.

From the graph we deduce that if the distance

increases time increases. (b) – Metal Detector

The other sensor used in this robot is a

metal detector. It is placed in the robot to detect

explosive items like landmines etc., which works on

the principle of electromagnetism. If any metal is

detected a small beep sound is given as an alarm for

the user.

GSM-Module

In this prototype, we use GSM 900A module,

which plays a vital role in the working of the robot.

This module should be equipped with a SIM card, so

that it can transmit and receive data wirelessly. The

receiver and transmitter pins of the GSM are

connected in the inverse manner to the pins of

Arduino receiver and transmitter respectively, by

which process, data communication is established

with the Arduino Board. It can communicate by AT

commands (AT + CMGF=1; to convert module to text

sending-mode) Operations performed by GSM Module: If Xbee

connection is lost i.e., the robot has gone beyond the

exceeded range then the GSM-wireless technology

comes into play as shown in Fig 1. We can operate

robot by assigning directions with the mobile phone

by sending messages to the GSM Module. This would

imply that the range of the robot is extended to

maximum limit, where the mobile network persists.

In addition to receiving the messages from the

controller of the robot, the GSM module itself is

capable of sending messages to the controller of the

robot(i.e., the sensor values from the ultra sonic

sensors like the distance and the direction of the

obstacle from the robot)

Fig 7: Snapshot of live streaming data from the bot.

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Wireless Camera

A wireless night vision camera is placed on

the top of the robot and the receiver is attached to

the laptop as shown in Fig 2 so that we can get live

streaming in the laptop as shown in Fig 7. It

consumes low power and has built-in microphone

and transmits audio along with the video. Servo motors

Servo motor is a servo mechanism. It is

closed loop servo mechanism that uses position

feedback to control its motion and final position [6].

We have used servo motors for rotating wireless

camera and ultrasonic sensors to cover 180 degrees. DC motors and Motor drivers

In this robot, we have used DC motors of 60 RPM

which is connected to 12 V motor driver and it is

controlled by the Arduino. We used two blades

connected to DC Motors as defending feature for

cutting small bushes, plants etc., coming in the

middle of the path.

Fig 8.Circuit Diagram of bot.

Hardware Implementation-Overview

All the Individual Components are connected to

Arduino as per the circuit diagram.Primarily the data

is sent from the Xbee transmitter (Fig 2),the

transmitted data is received by the Xbee

receiver.The Arduino is pre-programmed and works

accordingly ,when the specified data is received by

the Arduino(For example ,when character `w` is

transmitted from the transmitter ,robot is setup to

move in forward motion).If else the connection

between the Xbee’s are terminated or lost,GSM-

Controlling the motion of the robot comes into

existence.Now the specified characters of the motion

are sent over the mobile to GSM.Latter Arduino is

directed by the GSM module.The Ultrasonic Sensors

attached to the robot has the ability to emit sound

waves which then travel through air and reflects

through the object which is then received by the

receiver.The total travelling time is then recorded ,by

using simple math formula we can find the actual

distance between the sensor and the object .Both

direction and the distance of the obstacle are sent to

the assigned mobile number through GSM

module.The Audio and the Video of the surroundings

of the robot are broadcasted simultaneously with

the help of night vision camera. A metal detector

contains a coil of wire known as the transmitter

coil.When electricity flows through the coil, a

magnetic field is created all around it.The metal

detector has a second coil called receiver coil which

gets active, when a metal is detected and notifies the

controller of the bot by a beep sound.Thus the

controller of the robot becomes alert and deviates

from that direction.Primary disturbances in the path

of the robot are cleared with the help of the blades

attached at the front of the robot.

The complete hardware prototype was built

and tested by assembling all the components as

shown below in Fig 9. .

Fig 9: Hardware Prototype of the Explorer Bot

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Conclusion

The project is a robotic vehicle using Xbee modules

with XCTU application for wireless operation. The

robot has a metal detector, ultrasonic sensor along

with a camera which can transmit real-time video

with night vision capabilities. GSM module is

responsible for continuous alerts through SMS. GSM

also helps in remote operation for robotic

movement. The robot will become autonomous

when the signal is lost from Xbee and GSM900A. Two

blades are placed in front of the robot which is used

for clearing the path. This prototype can be used for

exploration purposes in order to substitute for

human intervention.

References

[1] Rechie Ranaisa Dam ,”Determining 2D shape of

object using Ultrasonic Sensor”.Published in

Electrical Engineering and Information

CommunicatioTechnology (ICEEICT),2016, at Dhaka. [2] J.E Piercy, ”American National Standard: Method for

calculation of the absorption of sound by the

atmosphere,”.ANSISI-26-1978(Acoust. Soc.Am.,1978).

[3] Mohammed Umer Shahzad,” Wireless Control

Robot Using Xbee Module With Multiple Sensors

Acknowledgement on HMI”.Published in Recent

Advances in Electrical Engineering (RAEE),2017

International Symposium on 24-26 Oct.2017. [4] Pangun Park, Di Marco, ”Modeling and

Optimization of the IEEE 802.15.4 Protocol for

Reliable and Timely communications”.IEEE

Transactions on Parallel and Distributed Systems,Vol.

24,pp. 550-564,May 2009. [5] Bo Wu , Hai Lin “Stability analysis for wireless

networked control system in unslotted IEEE 802.15.4

protocol” 11th

IEEE International Conference on

Control & Automation (ICCA),June 2014,pp. 1084-

1089

[6] H.P. Moravec, A. Elfes, “ High resolution maps

from wide anle sonar”, presented at the IEEE

conference Robotics and Automation,1985.

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