coal mine robot (project report)

BACHELOR OF ELECTRICAL AND ELECTRONIC ENGINEERING UNIVERSITY OF BRADFORD

1 COAL MINING ROBOT, 2013

MUHSIN ABDUL MOHAMMED

UNIVERSITY OF BRADFORD PROGRAMME

INTI International University

Faculty of Engineering and Information Technology

COAL MINE ROBOT

Muhsin Abdul Mohammed

Bachelor of Engineering (Hons) in ELECTRICAL &

ELECTRONICS ENGINEERING

Project Supervisor: Mr. Jeya Gopi

Stage 3 BEng Project

2013




Abstract

This project tackles the problem of coal mine accidents which results in the death of several

people per year. It is found out that the rate of fatality in the coal mine industry is nearly six

times the rate for all private industry. And most of these accidents are due to toxic gasses,

fires and lack of rescue system.

By implementing a Coal Mine Surveillance robot, which can move around unmanned in the

mine and detect the level of different toxic gases and temperature level and report them live

to the control room, this level of fatality can be considerable reduced. The objective of this

project is to accomplish this task.

From a technical aspect this project is software and hardware oriented project. It requires

very specific types of sensors, and innovative methods in transmitting and receiving data.

Because a conventional approach will not do much good from an industrial aspect

The project can be considered valid if it can detect different sorts of gases, the temperature

and give a warning to the miners inside the mine in case of a danger, at the same time

transmitting all the data to the control panel. The data send to the control panel can make a lot

of difference, setting up and giving strategies to a rescue team for rescue will make the rescue

very efficient.

i




ACKNOWLEDGEMENT

I would like to take this opportunity to express my gratitude to all the people who assisted me

during the development of this project. I would like to express my appreciation to my

supervisor, Mr.Jeya Gopi, who guided me through this project and provided me with tasks

and challenges for further understanding of the project.

I would also like to express my thankfulness to my family who gave the moral and financial

support for realizing this project. I am also grateful to my friends, who provide their support

and resources in solving this project. At last, I would like to thank my lectures, the lab and

the faculty staff for giving their time and support to achieve this task.

ii




Declaration

I submit my University of Bradford, Bachelor in Electrical and Electronic Engineering, Final

Year Project, under the supervision of Mr.Jaya Gopi. I hereby certify that no part of this

Project has been copied, except where due acknowledgement is made.

Yours truly,

.

Muhsin Abdul Mohammed

INTI-UC ID: I10005723

UOB ID: 10040883

iii




List of Acronyms

PWM – Pulse Width Modulation

PCB – Printed circuit board

MCU – Microcontroller unit

IDE - Integrated Development Environment

IC – Integrated Circuit

iv




Table of Contents

Abstract – i

Acknowledgement –ii

Declaration –iii

List of Acronym – iv

Table of contents - v

Chapter 1: Introduction -------------------------------------------------------------------------------1

1.1 Background ----------------------------------------------------------------------------------1

1.1.1 History of Tools in Mining Safety-------------------------------------------1

1.2 Nature and Purpose of Study --------------------------------------------------------------2

1.3 Significance of this project ----------------------------------------------------------------3

1.4 Objectives ------------------------------------------------------------------------------------3

1.5 System Overview ---------------------------------------------------------------------------3

1.6 Project Overview ---------------------------------------------------------------------------4

Chapter 2: Literature Reviews -----------------------------------------------------------------------6

2.1 Introduction ----------------------------------------------------------------------------------6

2.2 Research in the, Field Mining Robots ----------------------------------------------------7

2.3 Autonomous Robot -------------------------------------------------------------------------8

2.4 Need for this study --------------------------------------------------------------------------9

2.5 Gas Sensors ----------------------------------------------------------------------------------9

2.5.1 Gas Detector Technologies ---------------------------------------------------10

2.5.1.1 Measurement of Toxic Gases -------------------------------------10

2.5.1.2 Measurement of Combustible Gases -----------------------------10

2.5.2 Recent development -----------------------------------------------------------11

2.5.3 Semiconductor Type Gas Sensors -------------------------------------------12

2.6 Temperature Sensor -----------------------------------------------------------------------13

2.7 Communication ----------------------------------------------------------------------------13




Chapter 3: Methodology -----------------------------------------------------------------------------15

3.1 Robot Locomotion ------------------------------------------------------------------------15

3.1.1 Differential Drive --------------------------------------------------------------18

3.1.2 Motor ----------------------------------------------------------------------------19

3.1.3 Drivers ---------------------------------------------------------------------------21

3.2 Atmel Atmega328P -----------------------------------------------------------------------25

3.3 Arduino UNO ------------------------------------------------------------------------------26

3.3.1 Arduino IDE --------------------------------------------------------------------27

3.4 Sensors --------------------------------------------------------------------------------------28

3.4.1 Toxic Gas Sensors -------------------------------------------------------------29

3.4.1.1 MQ Gas sensor Series ----------------------------------------------29

3.4.1.2 Calibration and Coding for Gas sensors -------------------------30

3.4.2 Temperature Sensor ------------------------------------------------------------32

3.4.3 Ultrasonic Ranging Module HC- SR04 -------------------------------------33

3.5 Communication ----------------------------------------------------------------------------37

3.5.1 BlueBee--------------------------------------------------------------------------38

3.6 Software Overview ------------------------------------------------------------------------40

3.7 Graphical User Interface -----------------------------------------------------------------42

Chapter 4: Test and Results -------------------------------------------------------------------------43

4.1 Mechanical Design ------------------------------------------------------------------------43

4.2 Independence of the Robot ---------------------------------------------------------------43

4.3 Working of the sensor --------------------------------------------------------------------44

4.4 Reception of Wireless Data --------------------------------------------------------------45

4.5 Graphical User Interface (GUI) ---------------------------------------------------------49

Chapter 5: Discussion -------------------------------------------------------------------------------50

5.1 Investigation -------------------------------------------------------------------------------50

5.2 Validity of the prototype -----------------------------------------------------------------50

Chapter 6: Conclusion -------------------------------------------------------------------------------51




Chapter 7: Further improvement ------------------------------------------------------------------53

References -----------------------------------------------------------------------------------------------54

Appendix A: Coding for the Microcontroller -------------------------------------------------------55

Appendix B: Processing Sketch for GUI Graph ----------------------------------------------------60

Appendix C: PCB and Schematics -------------------------------------------------------------------63

Appendix D: Pictures taken during the progress of project ---------------------------------------66

PROJECT GANTT CHART -----------------------------------------------------------------------68

LIST OF FIGURE

Figure 1.1 Safety Lamp Principle Features -----------------------------------------------------------2

Figure 1.2 System Overview Block Diagrams -------------------------------------------------------4

Figure 2.1 Total World Electricity Generations by Fuel (2009) -----------------------------------6

Figure 2.2 Modern Automated Coal Mining Processes ---------------------------------------------8

Figure 2.3 an Autonomous Komatsu Truck ----------------------------------------------------------8

Figure 2.4: M40.M precision Gas sensor for coal mines ------------------------------------------11

Figure 2.5: Basic gas sensor structure ----------------------------------------------------------------12

Figure3.1: Simplified Robot locomotion ------------------------------------------------------------16

Figure 3.2: Different types of wheel based robot Chassis -----------------------------------------16

Figure 3.3: Initial stage robot design -----------------------------------------------------------------17

Figure 3.4: Differential Drive System ----------------------------------------------------------------18

Figure 3.5: DC motor working principle ------------------------------------------------------------20

Figure 3.6: Dimension of the DC motor used -------------------------------------------------------21

Figure 3.7: Basic H-Bridge Schematics --------------------------------------------------------------21

Figure 3.8: Block Diagram of L293D IC ------------------------------------------------------------22




Figure 3.9: In-project Implementation of L293D IC -----------------------------------------------23

Figure 3.10: ATmega328P pin mapping -------------------------------------------------------------25

Figure 3.11: Serial communication between MCU and Computer -------------------------------26

Figure 3.12: An official Arduino Uno with descriptions of the I/O locations ------------------27

Figure 3.13: Arduino code editor ---------------------------------------------------------------------28

Figure 3.14: Building Block and recommended circuit connection. -----------------------------30

Figure 3.15: LM35 Pin Values ------------------------------------------------------------------------32

Figure 3.16: HC-SRO4 module Schematic and its range of sight --------------------------------34

Figure 3.17: Timing diagram --------------------------------------------------------------------------34

Figure 3.18: BlueBee Module -------------------------------------------------------------------------38

Figure 3.19: PuTTY window --------------------------------------------------------------------------39

Figure 4.1: Set up for the Obstacle Test -------------------------------------------------------------43

Figure 4.2: Result obtained using UART-USB cable ----------------------------------------------46

Figure 4.3: Results obtained from the sensors using BlueBee. -----------------------------------47

Figure 4.4: Screenshot of the reading received on an Android Mobile --------------------------48

Figure 4.5: Screenshot from Processing -------------------------------------------------------------49




LIST OF TABLES

Table 1.1: Objectives ------------------------------------------------------------------------------------3

Table 2.1 Rules for a Robot to be Autonomous -----------------------------------------------------9

Table 3.1: Design and Implementation Stages ------------------------------------------------------15

Table 3.2: MQ gas sensors -----------------------------------------------------------------------------29

Table 3.3: Most common wireless communication antennas -------------------------------------37

Table 4.1: Results from sensor and real measurement ---------------------------------------------44

Table 6.1: Objectives and status of accomplishment -----------------------------------------------52




CHAPTER 1: INTRODUCTION

1.1 Background

Most coal contents are too deep underground for opencast mining and require

underground mining, a method that currently accounts for about 60% of world coal

production. But Thousands of miners die from mining accidents each year. A Coal

Mine Surveillance Robot is an autonomous mechanical agent which can travel

through an underground mine in conditions that might be unsafe for miners to pass

through. It can collect important data from the mine like the percentage of

combustible gases, temperature in the mine and it can transmit all this data wirelessly

in real time. It can also give the miners a warning when the conditions of the mine are

unsafe.

1.1.1 History of Tools in Mining Safety

Most of the coal mine accidents are caused due to the eruption of toxic and

combustible gas. Before the advancement in the technology and invention of modern

toxic gas detectors, the miners used to relay on devices like Safety lamp and Pellistor.

A safety lamp was a device used in underground coal mines for the purpose of

lighting and to detect the presence of firedamp or methane. The invention of this

device was in the late 18th century, a demand arose in England for a miner’s lamp

that would not ignite the gas methane, a common hazard of English coal mines.

An Irish physician W. Reid Clanny, invented a lamp in 1813, in which using a layer

of water seal was use to separate the oil-fuelled flame from the atmosphere. It

required constant pumping for operation. In 1815 the English engineer George

Stephenson invented a lamp that kept explosive gases out by pressure of the flame’s

exhaust and held the flame in by drawing in air at high speed. In 1815 Sir Humphry

Davy invented the lamp that bears his name. Sir Davy used double layer metal gauze

chimney in order to surround and restrain the flame also to conduct the heat of the

flame away. This device was used for a very long period of time because of its

efficiency (Britannica, 2013).

Miners could detect if there is a presence of methane in the mine by looking in the

safety lamp, the flame of the safety lamp elongates to show this (Britannica, 2013).




But this meant that there should be someone constantly looking after the lamp, and as

the lamp had internal fuel supply it was sometimes not very accurate. But modern gas

detectors can sense the toxic and combustible gases in PPM (Parts per Million), also a

warning can be issued for the miners and the rescue team.

Figure 1.1 Safety Lamp Principle Features

1.2 Nature and Purpose of Study

As mentioned in the beginning of this chapter, the call for mine safety has been in

demand for a very long time; there has been a lot of development in the field of

surveillance robots and safety equipment. Yet the accidents are still occurring and lot of

lives are lost every year. In this project the emphasis is on developing a robot that will be

low cost in terms of mass production and also compatible with the existing technologies.

To succeed in this attempt, the project is designed using an Atmega328p microcontroller

which is a low power, long lasting, and fast in terms of processing. For communication

purposes Bluetooth is used, which is designed in such a way that any computer or

smartphone which has a Bluetooth receptor can receive the data transmitted from the

robot. The gas sensors and temperature sensors used are also efficient in terms of value

and performance, the features of the hardware and software will be discussed in detail in

the third chapter (Methodology).




1.3 Significance of this project

The central idea of this project is to build a surveillance robot which is economically,

technically and operationally feasible. I.e. the robot requires minimal maintenance and as

the robot is autonomous it does not require any operator. It can also send data to any

computer and smartphone because Bluetooth is used for communication. The robot uses

two motors to drive a caterpillar track which by design is focused on torque rather than

rpm, so it can cover more harsh terrain.

1.4 Objectives

Table-1 exhibits the objectives to be met by this project.

Number Objectives

1 Detect the toxic gases emitted from the coal mine.

2 Detect the level of heat inside the coal mine.

3 Indicate the name and the value of the gases and the temperature inside the coal mine regularly to the control room.

4 If level of the gases or temperature is too high a voice warning signal must be activated inside the coal mine.

Table 1.1: Objectives

1.5 System Overview

The active components involved in the project are illustrated in the block diagram Figure 1.

From it we can see that the core of this project is the Atmega328p microcontroller, the

Bluetooth transmitter and the Gas temperature sensors. The reasons why it is said that these

components are core because it serves the active purposes of this project. The circuit design

of the whole project was done fragmentally, namely the Inputs, the autonomous locomotive

and the wireless transmitter. This means that the failing of any one of these tasks will not

directly affect the other tasks; more on this feature will be discussed in the chapter 5

discussion.




Figure 1.2 System Overview Block Diagram

1.6 Project Overview

The duration allowed by the University of Bradford to complete the project was 27 weeks.

During which period the essence and objectives of the project title had to be recognized, the

tactics, tools and methods of doing the project had to be gathered, the project had to be build

and finally it should be made presentable. During the first semester different ways of tackling

the problems where researched, together with the current developments in the field of

surveillance robots. Later different programming environments where studied, namely C,

C++, Arduino programming environment, Processing (based on java) and VB. The second

INPUTS Sensors: mq9 gas sensor, mq4 gas

sensor, temperature

sensor (LM35)

16MHz Crystal Oscillator

9-12V DC Power

Supply

7805 voltage regulator

Bluetooth 2.4 ~

2.48GHz

Computer/

Smartphone*

*Bluetooth

capable

OUTPUT/actuators: 2 DC motors.

H-Bridge IC

OUTPUT: Buzzer, LED.




semester was more focused on implementation of circuits, testing sensors and designing

PCBs. The whole project report is broken down into 7 chapters. They are as follow:

Chapter 1: Introduction

In this section the overview of the whole project is included with the purpose of this

project. The aims and objectives of the project are mentioned. This section also gives the

reader a structure of the project report.

Chapter 2: Literature Reviews

The literature review has covered some of the recent works and researches in the field of

surveillance robots, Gas sensors, Temperature sensors, and proximity sensors.

Chapter 3: Methodology

In this chapter the physical design of the project is explained. It includes a discussion of

the hardware and software parts of the project. In the hardware section the reason of

selection, design, cost-effectiveness and other merits will be discussed. The software

section will include the algorithms (pseudo-code), flow charts and interface design.

Chapter 4: Test and Results

This section includes the final outcome from various aspects of this project, namely how

autonomous the robot is, accuracy of the sensors and data presentation. It also includes

some troubleshooting.

Chapter 5: Discussion

This chapter includes the discussion on the stability and validity of the project, and its

limitations.

Chapter 6: Conclusion

In this chapter all the key points of this project report will be reviewed. It will also

include an account of the final accomplishments from this project.

Chapter 7: Further improvement




This chapter includes some perception on the enhancement of the coal mining

surveillance robot from a prototype to a producible machine. This chapter takes heed

from the limitations discussed in chapter 5 to produce some ideas for future

improvements.

CHAPTER 2: Literature Reviews

2.1 Introduction

Coal is a combustible, sedimentary, organic rock, which is composed mainly of carbon,

hydrogen and oxygen. It is formed from vegetation, which has been fused between other rock

layers and altered by the combined effects of heat and pressure over millions of years to form

coal beds. Coal is a fossil fuel and is far more abundant than oil or gas, with around 112 years

of coal remaining worldwide (Anon, 2011).

Coal has many important uses worldwide. The most significant uses of coal are in electricity

generation, steel production, cement manufacturing and as a liquid fuel.

Since 2000, global coal consumption has grown faster than any other fuel. The five largest

coal users - China, USA, India, Russia and Japan - account for 76% of total global coal use

(Anon, 2011).




Figure 2.1 Total World Electricity Generations by Fuel (2009)

Surveys conducted on energy consumption (Anon, 2012) have shown that more than 40% of

the electricity worldwide is generated from coal.

Most coal contents are too deep underground for opencast mining and require underground

mining, a method that currently accounts for about 60% of world coal production. But

Thousands of miners die from mining accidents each year. This calls for the development of

an autonomous system (robot) which can survey the mines ahead of time and make sure that

the environment is safe for the miners to enter And also during the mining the robot can stay

in the mine and give live feedback to the control room in case of an accident (gas leak or fire)

so that the rescue team can be immediately organised.

Flammable gases are produced in the coal mines due to the oxidation of coal in the sealed off

areas. Monitoring of these toxic and flammable gases are the main tools for the determination

of fire status. On that basis, different levels of caution can be determined for examining the

extent of fire, toxic level, temperature and for planning well-organized combat methods.

(Ashok K. Singha,R.V.K. Singhb, Mahendra P. Singhc, Hem Chandraa, N.K. Shuklaa, 2007).

Robots have replaced humans in the assistance of performing those repetitive and dangerous

tasks which humans prefer not to do, or are unable to do due to size limitations, or even those

such as in outer space or at the bottom of the sea where humans could not survive the extreme

environments.

2.2 Research in the, Field Mining Robots

Mining robots are majorly aimed to help counteract a number of challenges currently facing

the mining industry, including skills shortages, improving productivity from declining ore

grades, and achieving environmental targets. Due to the hazardous nature of mining, in

particular underground mining, the prevalence of autonomous, semi-autonomous, and tele-

operated robots has greatly increased in recent times. A number of vehicle manufacturers

provide autonomous trains, trucks and loaders that will load material, transport it on the mine

site to its destination, and unload without requiring human intervention. One of the world’s

largest mining corporations, Rio Tinto, has recently expanded its autonomous vehicle fleet to




the world’s largest, consisting of 150 autonomous Komatsu trucks, operating in Western

Australia (Rio Tinto: Press Release, 2008).

Figure 2.2 Modern Automated Coal Mining Process

Figure 2.3 an Autonomous Komatsu Truck

2.3 Autonomous Robot

In the field of surveillance robot we can see a great boom in the last 5 years; it is the

processing power and rigidity of the structure that makes it possible.




The rules that define an autonomous robot are given in the Table 2.1

Number Rules

Rule #1 Gain information about the environment.

Rule #2 Work for an extended period without human intervention.

Rule #3 Move either all or part of itself throughout its operating environment without

human assistance.

Rule #4 Avoid situations that are harmful to people, property, or itself unless those are part

of its design specifications.

Table 2.1 Rules for a Robot to be Autonomous

From the table 2.1 it is understood that the movement of the robot without a human operator

alone is not sufficient for the Robot to be autonomous. In the chapter 7 Future improvements

a modification is discussed which could enable the coal mine robot to map the coal mines

which could be used further for many benefits. By achieving this the robot satisfies Rule #1

and further by including more cognitive coding Rule #4 can also be achieved.

2.4 Need for this study

A lot of effort has gone into the coal mine rescue robots and post disaster rescue bots whereas

there is not much work done in developing a robot that can do the surveillance in advance to

mining and stay in the mine during the process of mining. Such a robot can reduce the death

toll considerably, because the necessary statistics (i.e. the toxic gas level, temperature) will be

transmitted in the real time to the control room set up outside the coal mine, so when there is

a small increase in the temperature or toxic gas level the rescue team can be set up

immediately, and warning can be issued to the miners via the robot to evacuate immediately.

2.5 Gas sensors

Gas detection sensors measure the concentration of different gases in the atmosphere. There

are different technologies by which these sensors operate. These sensors are used in

households, industries, mines, laboratories, and places with chance of toxic gas exposures in

order to prevent toxic exposure and fire. These detectors are often battery operated devices

used for safety resolutions. They are made as portable or stationary units and work by

indicating high levels of gases through audible or visible indicators, such as alarms, lights or

even some time connected to operate actuators attached to a vent or exhaust system. While




many of the older, standard gas detector units were originally fabricated to detect one gas,

modern multifunctional or multi-gas devices are capable of detecting several gases at once.

As the sensor measure a specified gas concentration, usually in PPM (parts per million), the

sensor response serves as the reference point or scale. When the sensor detects a higher ppm

of gas in comparison to its reference, an alarm will actuate to warn the user.

2.5.1 Gas Detector Technologies

Gas detection sensors are categorized by the category of gas they detect: combustible or

toxic. Within this broad categorization, they are further defined by the technology they use:

catalytic and infrared sensors detect combustible gases and electrochemical and metal oxide

semiconductor technologies generally detect toxic gases (Anon,).

2.5.1.1 Measurement of Toxic Gases

Electrochemical detectors or cells are most frequently used in detecting toxic gases like

chlorine, carbon monoxide, methane and nitrogen oxides. They function by means of

electrodes signals when a gas is detected. These types of detectors are usually highly

sensitive and give off warning signals using electrical currents.

Metal Oxide Semiconductors, or MOS, are similarly used for detecting toxic gases through a

gas sensitive film made of tin or tungsten oxides. The sensitive film reacts with gases,

causing the device when toxic levels are present. Normally, metal oxide sensors are

considered efficient because of their ability to function in lower humidity ranges. On top of

that they are also efficient in detecting a variety of gases including combustible (Anon,).

2.5.1.2 Measurement of Combustible Gases

Catalytic sensors are the most widely used gas detector devices in the industry. This

equipment is used to sense combustible gases like methane, propane, butane, natural gases

hydrocarbon, and so on. The working principle of this technology is catalytic oxidation. The

sensors of this type of detector are usually built using a platinum treated coil of wire. When

the catalytic surface is brought in contact with a combustible gas, the catalytic surface starts

to oxidise and the resistance in the wiring is changed according to heat that is released. A

bridge circuit is often used to specify the change in resistance.




Infrared sensors or IR detectors have a transmitter and receiver which are positioned in

parallel to each other, to detect combustible gases, specifically hydrocarbon vapours. The

transmitters are light sources and receivers are light detectors. If a gas is present in the optical

path, it will interfere with the power of the light transmission between the transmitter and

receiver. The changed intensity of light can determine what type of gas is present in the

atmosphere and its density. The other types of gas sensors are base on semiconductors,

oxidation and so on. The gas sensors for the purpose of this project are based on

Electrochemical (oxidizing). The conditions in which the sensors operate are very crucial it

must be calibrated according to the temperature and humidity of the operating area.

2.5.2 Recent Development

The M40•M multi-sensor monitor is designed for use in mines and other work environments

to assure optimum personal protection against hazardous levels of oxygen (O2) and methane

gas (CH4), as well as toxic levels of carbon monoxide (CO) and hydrogen sulfide (H2S). The

M40•M is available in a 1, 2, 3, or 4-gas configuration including oxygen, hydrogen sulfide,

carbon monoxide and methane (Anon,).

Figure 2.4: M40.M precision Gas sensor for coal mines




2.5.3 Semiconductor Type Gas Sensors

The gas sensor used in this project is based on semiconductors; the specific sensor and the

reason for using it are discussed in Chapter 3: methodology.

Figure 2.5: Basic gas sensor structure

The gas sensor is built from a sensing element, sensor base and sensor cap. The sensing

element contains sensing material and heater to heat up sensing element. Depending upon the

gas to be detected the sensing element will employ different chemicals such as Tin dioxide

(SnO2), Tungsten oxide (WO3), and so on (Figaro,).

When a metal oxide crystal such as Tin dioxide (SnO2) is heated at a certain high

temperature in air, oxygen is adsorbed on the crystal surface with a negative charge. Then

donor electrons in the crystal surface are transferred to the adsorbed oxygen, resulting in

leaving positive charges in a space charge layer. Thus, surface potential is formed to serve as

a potential barrier against electron flow (Figaro,).

Inside the sensor, electric current flows through the junction of SnO2 micro crystals. At grain

boundaries, adsorbed oxygen forms a potential barrier which stops carriers from moving

without restrictions. The electrical resistance of the sensor is due to this potential-barrier. In

the presence of a deoxidizing gas, the surface density of the negatively charged oxygen drops,

as a result the barrier height in the grain boundary is also reduced. The reduced barrier height

decreases sensor resistance (Figaro,).

The relationship between sensor resistance and the concentration of deoxidizing gas can be

expressed by the following equation over a certain range of gas concentration:




[ ]

Where: Rs = electrical resistance of the sensor

A = constant

[C] = gas concentration

α = Slope of Rs curve

Due to the logarithmic relationship between sensor resistance and gas concentration, this

type of gas sensors have an advantage of high sensitivity to gas, even at low gas

concentration (Figaro,). This is crucial because in a coal mine the moment the initial outbreak

of a gas happens, it has to be taken in consideration for rescue operations.

2.6 Temperature Sensor

Another essential component of this project is a temperature sensor. Just like all other

technologies or components, the basic temperature sensor has also undergone many changes

as part of the growth in technology. In outwards it has become much more compact, durable

and most importantly precise. Today most temperature sensors use a solid-state mechanism to

determine temperature. Previously there were temperature sensors which used elements like

mercury to determine temperature. Then there were sensors using bimetallic strips like the

once used in the stoves and furnace. There was also temperature sensors based on heat

sensitive resistors. But modern temperature sensors use a very different approach; they

determine the temperature by analysing the increase in voltage across a diode. This increase

in voltage across the diode shows the increase in temperature. Theoretically this is the voltage

drop between the base and emitter, the VBE of a transistor. Amplifying the voltage change

between this base and emitter an analogue signal can be obtained which is proportional to the

temperature. The exact sensor used for this project, the reason for using it and its

specifications are discussed in Chapter 3: Methodology.

2.7 Communication

The last topic to be discussed in this chapter is regarding communication, than is the project

objectives it is required for the MCU to communicate with the control unit situated outside

the coal mine. To send all the data from the sensors, and give them a Mayday warning in case

of any eruption of gas or fire. The specification of the control panel system was not




mentioned In the project objective, although presumably it should have some sort of display

to show the reading and distress signal. Therefore there were many ideas one of them was to

use another MCU and display but it required additional hardware and resources, it would

make the project less practical. One solution that seemed appropriate was to use the existing

resources I.e. computers, smartphones, tablets and so on, this would make the project

extremely resourceful. Now the question was how to communicate with them. Using cables

seemed unrealistic solution. Communicating wirelessly brought up many choices as well.

Among them where gsm modem, Wi-Fi, simple Radio, Bluetooth, Zigbee and so on.




Chapter 3: Methodology

The Design and Methodology of this project was done in different stages. Initially the

Locomotive was designed, which included finding appropriate motors, constructing chassis,

mode of locomotion, materials to build and so on. Next the microcontroller or processing unit

was decided, there was a handful of Microcontrollers to choose from, the most common

being the PIC series of Microcontrollers. But for this project Atmel’s ATmega328p

Microcontroller IC was used, because of its consistency in data flow, low power

consumption, and compact size. Subsequently the sensors where picked, as the objectives

were specific, finding the sensors were a difficult task. For gas detection MQ-series gas

sensors are used, for temperature sensing the well-known LM-35 Temperature sensor is used

and for enabling the robot to be Autonomous Ultrasonic sensor is used. Next the

communication portion was designed. The objective required the robot to transmit data to a

control panel outside the mine. Therefore there was a number of choices both wireless and

wired communications. After studying the merits and demerits of everything, Bluetooth

transmitters where decided to use for communication. The software part of the project was

going hand in hand with all the above stages. For MCU programming interface Arduino

UNO which is an open source prototyping platform was used and the compiler used for

coding is Arduino IDE, which is based on C. For wireless data delivery in computer any

terminal emulator software can be used like PUTTY, Hyperteminal, or TeraTerm and to

receive data in smartphone any third party Bluetooth terminal App can be used. For

displaying the data graphically, JAVA based open source programming language Processing

is used.

Table 3.1: Design and Implementation Stages

3.1 Robot Locomotion

In designing a robot the mechanical part is just as important as the software and electronics.

Robot locomotion is one of the major obstacles faced by many engineers. A great deal of




research is going on, in designing locomotion for various robotic tasks. Today there are

robots which are walking, running, rolling, hopping, slithering, swimming, flying and

brachiating.

Figure3.1 : Simplified Robot locomotion

The terrain in which the robot operates is the major concern when it comes to deciding the

proper chassis and other mechanical parts for a robot. In this case the terrain is that of a coal

mine. Wheeled robots are the most energy efficient in locomotion and they are simple to

control as well. But the major drawback to this kind of locomotion is that when it comes to

extreme uneven terrain like a stair case or a cliff it becomes very inflexible in operation. A

solution to this problem is to design a wheeled robot with continuous tracks (commonly

known as Caterpillar tracks). I.e. A structure of vehicle propulsion in which a continuous

band of treads usually made of steel or rubber (according to usage; steel for heavy duty,

rubber or similar synthetics for smaller surface robots), is driven by two or more wheels.

Figure 3.2: Different types of wheel based robot Chassis




Tracked vehicles have better freedom of movement than air-filled tyres on rough terrains.

Caterpillar tracks can smooth out the bumps, glide over small rocks or damps and are capable

of crossing small ditches. They are also much less likely to get stuck in wet ground, mud, or

snow since they distribute the weight of the vehicle over a larger contact area, decreasing its

ground pressure. Tracks can also give higher manoeuvrability; they can turn in a place with

minimum turning radius. However designing these tracks and manufacturing them are

complex mechanical tasks. Another disadvantage of using tracks is comparatively lower

speed, but if well designed they can yield higher torque, which in the case of coal mine

navigation is more important. The dimension of the robot is 17cmX11cmX7cm. The picture

below was one of the early sketches in the first stage of design.

Figure 3.3: Initial stage robot design




3.1.1 Differential Drive

The steering of an unmanned robot is a very important aspect. In this robot the instrument

which drives the robot is two DC motors (discussed in detail under title 3.1.2 Motors). And

the sensor involved in learning the environment is a pair of ultrasonic transceivers.

Differential drive is technique of controlling a robot with simply two motorized wheels. It

does not require an axle to turn the pair of wheels, which means it can get the maximum

turning radius, which is a distinct quality in a constrained space of a coal mine. It is perhaps

the simplest mode of steering a robot as it only requires a pair of motors.

The working principle of the differential robot is assumed in the term ‘Differential’ i.e. by the

difference in the turning speed of one of the two or both the motors, the robot can be turned.

For example by keeping the left wheel still and rotating the right wheel forward the robot will

turn Left. By rotating both the wheels in opposite directions the robot can be moved

clockwise or counter clockwise. By applying same rotation speed in both the wheels the robot

can be moved forward or backward.

Figure 3.4: Differential Drive System

From the figure above the algorithm for driving the coal mine robot can be developed.




Pseudo code:

Get INPUT Reading From Ultrasonic Sensor

IF Sufficient Distance in Front

Move FORWARD

Turn both wheels forward at same speed

ELSE

Move BACKWARD OR Turn SIDEWAYS

Turn both wheels backward at same speed

Turn both wheels in opposite directions, Accordingly

3.1.2 Motor

As discussed under the title locomotion, there are several engines which can be used to drive

the robot. Given the terrain, wheel based chassis were finalised to use. To drive a wheeled

robot a Motor is required. There are several types of motors available for this purpose,

classified based on the mechanism there are simple DC motors, Servo motors, Stepper

motors, linear motor and so on. For this project the motor is controlled based on the values

from a proximity sensor, and it has to run for long period of time without any interruption.

Therefore the motor requires a combination of good rpm and torque. RPM is required

because it has to cover wider area of a coal mine in minimum time and torque is required as

the surface of a coal mine can be rocky and uneven. It does not require an accurate angular

movement therefore a fitting choice for this function is a Geared DC motor.

DC motor is an electric motor that runs on direct current (DC) electricity. Two types of DC

motors are Brush and Brushless DC motor. Brushed DC electric motor generates torque

directly from DC power supplied to the motor by using internal commutation, stationary

magnets (permanent or electromagnets), and rotating electrical magnets. Brushless DC

motors use a rotating permanent magnet or soft magnetic core in the rotor, and stationary

electrical magnets on the motor housing.




DC motor has a two wire connection. All drive power is supplied over these two wires. When

a DC motor is turned on, it just starts spinning round and round. Most DC motors are pretty

fast, about 5000 RPM, depending on its characteristics.

With the DC motor, its speed (or more accurately, its power level) is controlled using a

technique named pulse width modulation, or simply PWM. This is idea of controlling the

motor’s power level by strobing the power on and off. If the power is switched on and off fast

enough, then it just seems like the motor is running weaker—there’s no stuttering. This is

what PWM means when referring to DC motors. The key concept here is duty cycle—the

percentage of “on time” versus “off time.” If the power is ON only half of the time, the motor

runs with half the power of its full-on operation. This leads to one of the disadvantages of dc

motor; it is that to change its direction the polarity of the DC supply has to be changed. The

figure below shows how a change in electric supply can change the resulting magnetic force.

Figure 3.5: DC motor working principle

The Exact DC motor used on this robot is a pair of 150:1 Micro Metal Gear motor. It is light

weight (10g each); the gears produce a Stall torque of 1.1kg/cm, which is good enough to

hike a rough coal mine as the whole robot is built with low weight materials. It runs at full

RPM of 85 at DC 6v supply. It has a free run current of 40mA and stall current of 360mA.




Figure 3.6: Dimension of the DC motor used

3.1.3 Drivers

As discussed in the earlier title one of the disadvantage of using a DC motor is that to switch

the direction of the rotation of a DC motor the connection has to be switched, in other words

the polarity has to be changed. Doing so is a physical act and it is impossible to do it using

any binary programming. To do this task we can use a Motor Driver circuit. One of the most

common driver circuits to drive a motor in forward and reverse is an H-bridge. . The H-

Bridge is the link between digital circuitry and mechanical action. The H-bridge gets its

name from the structure of the basic circuit by which it operates.

Figure 3.7: Basic H-Bridge Schematics

From the figure it can be observed that there are four switches critical to the H-Bridge design.

By opening and closing them accordingly we can run the motors forward or backward. If S1




and S4 are to closed the motor will run clockwise. If S3 and S2 is to be closed the motor will

run counter clockwise. However closing all the switches together should be avoided, because

it will cause a short circuit. Using physical switch will be unrealistic the control unit is a

microcontroller. Therefore transistors can be used; as they are sold state switches applying a

small current on the base can close the circuit.

Note that the configuration shown above can only be used to operate one Motor at a time, and

in this project there are two DC motors and they operate in full potential at 9V, which is

higher than the voltage in which the rest of the circuit operates (including MCU, Sensors, &

Bluetooth). This means that in order for fully functioning H-Bridge matching the criterions of

the project, it requires several Transistors, voltage Regulators, Op Amps and other passive

components. There is also chance of noise, which means an additional filter circuit has to be

designed.

L293D IC

But instead of designing a complex yet unstable H-Bridge using transistors and other

components from scratch a readymade IC can be used, which meets the project requirements.

L293D is a Quadruple high-current half-H driver. It is designed to provide bidirectional drive

currents of up to 600-mA at voltages from 4.5 V to 36 V (Anon, 2004). The L293D can also

operate two DC motors at a time.

Figure 3.8: Block Diagram of L293D IC




Figure 3.9: In-project Implementation of L293D IC

Between the L293D H-Bridge IC and the Atmega328p Microcontroller there will be four

connections, as shown in the implementation figure above. By giving a High or Low signal

the two motors can be driven forward and backward accordingly. As the outputs from MCU

has only to be High or Low, the digital pins in the MCU can be used for this purpose. So first

four digital pins has to be declared:

Pins PD7, PB1, PB2, and PB3 (pin number 13, 15, 16, and 17 of the MCU respectively) are

Digital pins in Atmega328p, using the Arduino IDE(explained in detail under title 3.3

Arduino IDE) these pins are declared as 7, 9, 10 & 11. The variable names used are

Motor1Pin1, Motor1Pin2, Motor2Pin1 and Motor2Pin2, which are respectively connected to

the pins 2, 7, 10 & 15 of the L293D IC. As in the fragment of code given above it can be

observed that for declaring the variable the keyword “const” is used. The const keyword

stands for constant. It is a variable qualifier that amends the behaviour of the variable,

making a variable "read-only". This means that the variable can be used just as any other

variable of its type, but its value cannot be changed. This is required as the pins assigned are

not to be changed under any circumstance. The conventional C programming equivalent is

#Define, which can also be used instead of const.




Syntax

#define constantName value //value of pin number

Once the variables are declared, the state (HIGH or LOW) of the pins has to be defined in

view of that. There are five primary movements of the motor to be defined they are Forward,

Backward, Right, Left and Stop. The easiest and efficient way of doing this is by creating

functions for each task, this way the conditions are appropriate the program can just call these

functions. The functions are defined as follows:

Now when the ultrasonic sensors return the distance, it can be used to determine the

direction in which the robot has to go. Once the direction is determined the above functions

can be called.




3.2 Atmel Atmega328P

The ATmega328P chip is used in this project as the microcontroller. The significance of the

first two digits is to stipulate that the AVR core consists of variety of instruction set with 32

general purpose working registers which are connected directly to the Arithmetic Logical

Unit (ALU), tolerating two independent registers to be retrieved in one single instruction

executed in one clock cycle. The subsequent architecture is more programmable efficient

while attaining data transfer rates up to ten times quicker than other CISC microcontrollers.

The last digit is to indicate the 8 bit bi-directional port. It is certainly the head of the system

which is controlling the various modules. The AVR is a modified Harvard architecture 8-bit

RISC single chip microcontroller which was developed by Atmel in 1996. The AVR was one

of the first microcontroller families to use on-chip flash memory for program storage, as

opposed to one-time programmable ROM, EPROM, or EEPROM used by other

microcontrollers at the time.

Figure 3.10: ATmega328P pin mapping

The high-performance Atmel pico Power 8-bit AVR RISC-based microcontroller combines

32KB ISP flash memory with read-while-write capabilities, 1024B EEPROM, 2KB SRAM,

23 general purpose I/O lines, 32 general purpose working registers, three flexible




timer/counters with compare modes, internal and external interrupts, serial programmable

USART, a byte-oriented 2-wire serial interface, SPI serial port, a 6-channel 10-bit A/D

converter (8-channels in TQFP and QFN/MLF packages), programmable watchdog timer

with internal oscillator, and five software selectable power saving modes. The device

operates between 1.8-5.5 volts. By executing powerful instructions in a single clock cycle,

the device achieves throughputs approaching 1 MIPS per MHz, balancing power

consumption and processing speed (Atmel Corporation,).

3.3 Arduino UNO

To program the ATmega328P Microcontroller a Serial communicator is required. Serial

communication is most widespread interface between microcontroller and computer. UART

is one of the serial interfaces which are widely used. A Universal Asynchronous

Receiver/Transmitter (UART) is a piece of computer hardware that translates data between

parallel and serial forms. Classically, most serial interface from microcontroller to computer

is done through serial port (DB9). However, since computer serial port used RS232 protocol

and microcontroller used TTL UART, a level shifter is needed between these interfaces.

There are several level shifters available in the market, some of which supports USB plug and

play.

Figure 3.11: Serial communication between MCU and Computer




But in most of the times the level shifter are unstable to use due to its design and more than

one software is required to convert the programming on C to hex or machine language and

maybe another software to interface between the Microcontroller and computer.

Arduino UNO is an alternative to this solution, the internal board of Arduino consists of all

the necessary ICs for communication. It is also build compact into a PCB which has

connectors for fast and easy prototyping.

Figure 3.12: An official Arduino Uno with descriptions of the I/O locations

3.3.1 Arduino IDE

The Arduino integrated development environment (IDE) is a cross-platform application

written in Java, and is derived from the IDE for the Processing programming language and

the Wiring projects. It includes a code editor which is capable of compiling and uploading

programs to the board with a single click. A program or code written for Arduino is called a

"sketch”.




Figure 3.13: Arduino code editor

Arduino programs are written in C or C++. The Arduino IDE comes with a software library

called "Wiring" from the original Wiring project, which makes many common input/output

operations much efficient. Users only need define two functions to make a runnable cyclic

executive program:

setup(): a function run once at the start of a program that can initialize settings

loop(): a function called repeatedly until the board powers off

The Arduino IDE uses the GNU tool chain and AVR Libc to compile programs, and uses

avrdude to upload programs to the board.

3.4 Sensors

The project objectives require the robot to detect gases, temperature and to move

autonomously. As mentioned in the literature review, there has been massive change in the

technology and equipment used in detecting the gases under different circumstances, there it

is also mentioned the common and toxic gases present in the coal mine. The major ones are




monoxides of carbon, methane, butane and other natural gases. The temperature rise in a coal

mine can be a result of fire or pressure. In this title the hardware sensors used for detecting

different surroundings will be discussed, together with the software development.

3.4.1 Toxic Gas Sensors

There are several atmosphere and gas sensors available in the market today. Some of them

are for specific industries, and some for common safety measures. The different technologies

of gas sensors where also discussed in chapter 1. The gas sensors used in this project is from

the MQ series of gas sensors.

3.4.1.1 MQ Gas sensor Series

The MQ series of gas sensors use a small heater inside with an electro-chemical sensor. They

are sensitive for a range of gasses and are most commonly used indoors at room temperature,

due to the small size of the sensor filaments. The list of detectors and their sensitivity of

gases:

Sensor

Name

Sensitivity for:

MQ-2 Methane, Butane, LPG, smoke

MQ-3 Alcohol, Ethanol, smoke

MQ-4 Methane, CNG Gas

MQ-5 Natural gas, LPG

MQ-6 LPG, butane gas

MQ-7 Carbon Monoxide

MQ-8 Hydrogen Gas

MQ-9 Carbon Monoxide, flammable

gasses

MQ-131 Ozone

MQ-135 Benzene, Alcohol, smoke

Table 3.2: MQ gas sensors

The specific sensors used for this project are MQ-2, MQ-4, & MQ-9. These sensors

combined can detect the presence of Methane, Butane, smoke, LPG, CNG, Carbon

Monoxide, and flammable gasses. These are the most abundant, toxic and flammable gasses




found in the coal mines. The working principle of these sensors is similar and they are

discussed under the title 2.5.3 Semiconductor type gas sensors in Chapter 2: literature riview.

Figure 3.14: Building Block and recommended circuit connection.

3.4.1.2 Calibration and Coding for Gas sensors

As mentioned before in the theory part these sensors have a built in heater which is crucial in

sensing the gas level around it. This heater operates in 5-6V range. For a stable reading the

manufacturer recommends a Burn-in time for the MQ gas sensors, which around 24 hours.

This has to be only done once; from then on the Gas sensor becomes stable by heating around

3 minutes at 5V, before usage. This is pre-heat of 3 minutes is not included in the coding,

since even during this period of waiting the sensor can produce approximate results. This

conclusion was derived by conducting trial and errors.

A better calibration for the sensor is by connecting a load resistor, of the value from 2kOhm

to 47kOhm. The lower the load-resistance the lesser the sensitivity and the higher the load-

resistance the less accurate the result for higher concentrations of gas. But one problem with

this method is that it requires a known concentration of gas in the atmosphere, which was

unable to come up with because of the limitation in the lab equipment. Therefore the load-

resistor was tuned to a medium range.




The sensors where connected to the analogue pins of the MCU. As the input voltage to the

sensor was ~5V, the sensor returns a value from 0 to 1023. This is because the ATmega32bp

controllers used for the Arduino contain an on-board 6 channel analogue-to-digital converter

(ADC). The converter has 10 bit resolution thus returning integers from 0 to 1023. The first

part of the coding is to declare two variables for reading the values from the gas sensors:

The returning values are from a range of 0-1023, therefore the data-type used is “int”. “int”

can store up to 16-bit(2-byte) of data, which is more than sufficient in this case. Now the

value has to be read from the sensors. Defining the variables:

The function analogRead() is a pre written code in the Arduino IDE. It reads the value from

the specified analogue pins. In this case the pins are A0 and A1.

Syntax

Variable = analogRead(pin);

As mentioned above the sensor is supplied with 5v and the arduino board has 10-bit ADC

resolution. The analogRead() function therefore reads the voltage in the respective pin (which

will be between 0 and 5Volt), and will convert into an integer between 0-1023. I.e.

This reading is not converted to the standard PPM (parts per million) gas unit, because to do

so requires a known reading from a known amount of gas. Nevertheless the integer reading

(0-1023) was put into trial and error tests to find out a hazardous level for creating an alert.

For the MQ4 sensor a value higher than 500 is considered to be hazardous and for the MQ9

sensor a value higher than 100 is considered hazardous (the reason for choosing these values

are further discussed in chapter discussion.). The coding for creating the alert and displaying

in the control panel is discussed under the title software overview.




3.4.2 Temperature Sensor

The LM35 series are precision IC temperature sensors, which gives an output voltage linearly

proportional to the Centigrade temperature. The LM35 does not require any external

calibration or trimming to provide typical accuracies of ±¼°C at room temperature and ±¾°C

over a full −55°C to +150°C temperature range. The LM35 sensor is low cost and durable.

The device operates with a DC power supply of the range 4V to 30v. The current drawn by

the sensor is only 60 μA making it appropriate for a low power profile robot. The heat

generated by the sensor itself is very low, which is less than 0.1°C in still air, making it even

more accurate. The LM35 sensor is sealed air tight thus moisture or other gases in the

atmosphere cannot affect it. The sensor increments at +10mV/°C scale factor.

Figure 3.15: LM35 Pin Values

The output from the sensor is analogue therefore an analogue pin from the MCU has to be

used for LM53. In coding first a variable for storing the value of the temperature is declared:

The reason why the variable is declared in “int” is because for this project precise

temperature (i.e. in float) is not required, because the temperature we are dealing in a coal

mine is more than 35°C. Now the variable needs to get the reading from the sensor:




As mentioned earlier increment in every 10mv is an increment in 1 degree Celsius. But the

MCU is not getting the reading in 10mv. It is getting the value from an on-board 10-bit ADC,

an integer value between 0-1023 for the corresponding change in 0-5v. Hence the integer

value has to be converted back to value in terms of milli-volt. For this purpose we divide the

received value with 1024 (2^10 (10-bit ADC)), and then multiply it with 5 (because the

supply voltage is 5v). Then again obtained value is in voltage, so to convert to milli-voltage

we can multiply with 1000. Now we have the value of increment in terms of 1mv. But the

LM35 increments in term of 10mv, therefore with the last gotten value a 10 has to be divided.

Pseudo code:

Coding:

3.4.3 Ultrasonic Ranging Module HC- SR04

The coal mine robot is an unmanned robot. For it to roam around autonomously it needs to

have an eye to see its surrounding. There are many sensors to do make this task starting from

LDR sensors to Laser and satellite guided navigation. In this project it seemed fit to use an

ultrasonic sensor, because it does the intended job. That is the coal mine is a dark place and to

navigate there using a camera is very difficult and even with a lighting system there can be

smoke and dust particle which would turn out to be a problem. Ultrasonic sensors are pretty

neat solution because it works by propagating pulses of ultrasound and waiting for them to

come back.




In this project the ultrasonic sensor used is the HC-SR04 Ultrasonic Ranging Module.

Figure 3.16: HC-SRO4 module Schematic and its range of sight

In this module there is a transmitter and receiver, the transmitter sends pulses of ultrasound

frequency upon triggering and the receiver waits for it to return. The Timing diagram is

shown in the figure below.

Figure 3.17: Timing diagram

By supplying a short 10uS pulse to the trigger input, the module will send out an 8 cycle

burst of ultrasound at 40 kHz from the transmitter. After that the receiver will be expected to

receive an echo. The Echo is from a distant object. The pulse width and the range are in ratio.

Now the range of the time interval between sending trigger signal and receiving echo signal

is to be calculated. In the figure above the graph shows a practical visibility of 30 degree,

which is sufficient for the size of the robot in this project, but for a bigger robot or for more




accuracy multiple sensors are to be used or a turning motor has to be used. The manufacturer

suggest on using a constant to be divided from the time obtained to convert it to distance. I.e.

for getting the distance in centimetre divide time by 58. This constant can be more accurately

calculated. My calculation is as follows:

The calculation is very close to the manufacture recommendation, therefore for 58 was used

in the coding process. The algorithm developed from the theory:

Algorithm:

Step 1: Supply Pulse (for 10microseconds)

Step 2: Receive Echo

Step 3: Duration = Triggering time – Echo Receive time. (In microseconds)

Step 4: Distance = Duration / 58

Step 5: IF (Distance>4)

Move (Forward)

Else

Move (Reverse)

Move (Right/Left)

Step 6: Repeat from Step 1

In the algorithm and coding a distance greater than 4cm is found to be a safe distance for the

robot to move forward, thus it was used. The coding developed from the algorithm:




In the arduino the trigger pins where connected to the digital pins. The digital pins defined

are:

#define trigPin 13

#define echoPin 12

digitalWrite() is the function used to write HIGH or a LOW value to a digital pin.

Syntax

digitalWrite(pin, value)

delayMicroseconds() is a function used to pause the program for the amount of time in

microseconds specified as parameter.

pulseIn() is probably the most important function in this code. What is does is, it Reads a

pulse (either HIGH or LOW) on a pin. For example, if value is HIGH, pulseIn() waits for the

pin to go HIGH, starts timing, then waits for the pin to go LOW and stops timing then returns

the length of the pulse in microseconds.




Syntax

pulseIn(pin, value)

pulseIn(pin, value, timeout)

3.5 Communication

For this project Bluetooth was used because most devices like personal computers and almost

all the smartphone has Bluetooth module embedded in them, which gives it the advantage of

economic and technical feasibility.

Following are the most commonly used market products for wireless communication:

BlueBee Xbee Xbee-Wifi RF Transciever

Technology Bluetooth Zigbee Wifi RF

IEEE standard 802.15.1 802.15.4 802.11

Rate of transfer 2.1Mbps /

160Kbps

250Kbps 3.5Mbps /

1Mbps

>2Mbps

Frequency 2.4GHz ISM

2.4GHz

ISM

2.4GHz

2.4GHz

Voltage of

operation

3.3DC/ 50mA 2.8DC/

40mA

3.3DC/

50mA

3.6DC

Range (Meter) 20~30m 30m++ 30m+

Price (MYR) 68.00 147.00 200.00 30.00

Number of Units

Required for

Communication

One* Two One^ Two

Table 3.3: most common wireless communication antennas

*Assuming the receiving unit is a computer or smartphone and already has a Bluetooth

implanted.

^ Assuming the receiving unit is a computer or smartphone and already has a Wifi implanted.




3.5.1 BlueBee

The last topic to be accomplished in the project is to get the MCU communicate with control

unit. For this in this project Bluetooth is used and the specific module used is BlueBee which

is a Bluetooth wireless module manufactured and sold by Cytron Technologies Sdn.Bhd,

Malaysia. It is designed to adapt the form factor of the famous XBee Modules. BlueBee

module has an on-board antenna which can provide better signal quality. It is like a

transparent serial port, it can be operated with a variety of Bluetooth adapters and devices

which support Bluetooth.

Figure 3.18: BlueBee Module

There are 2 modes on BlueBee which is Transparent mode and AT mode. The baudrate of

module may be set using AT mode. To communicate with BlueBee any terminal emulator

programs can be used like PuTTY, Hyperterminal or Terea Term. For the purpose of this

project PuTTY was used.




Figure 3.19: PuTTY window

The Bluetooth module is just like a serial port, all that matters is the number of COM Port

(for Windows OS) where the data is received and the Baud rate in which it is received. By

feeding this information the emulator can receive the data from the Microcontroller send via

Bluetooth. Or other programs can be written using VB, C#, Java or any other GUI

Developing programs, to receive the data. By developing custom software the data can be

represented more graphically. In this project a code was developed using “Processing”

(JAVA based Development tool) which will be discussed in the Software overview.

BlueBee operates at 3.3vDC; thus it is very power efficient. But a small fluctuation can

damage the module, therefore a separate module for power regulation was used.

Between the ATmega328p Microcontroller and the Bluetooth there are only two connections

because the interface is serial. The connections are TX*(transmit in Bluetooth) to

RX(Receiver in MCU) and RX*(Receiver in Bluetooth) and TX(transmit in MCU). In this

project the data is only sent from the MCU to the Bluetooth therefore only one connection is

required. TX*RX.




3.6 Software Overview

Below is the flowchart by which the Microcontroller will execute the tasks:

Flowchart

POWER UP

Activate Ultrasonic sensor – By applying 10µs of HIGH pulse

on trigger

Convert Duration to Distance.

[Dist = Dur/58 ]

Receive Echo Duration

Move Forward

Move Backward

Move Forward

Move Right/Left

If

Distance

>= 4cm

YES

NO

Initialize Survey

mode: Start

Temperature and

GAS sensors.




If temperature <= 45

If GAS1 <= 500

If GAS2 <= 100

NO

NO

NO Beep Alarm &

print

“Temperature

warning”

Beep Alarm &

print ”Coal

Fumes notice”

Beep Alarm &

print “Butane or

Methane Leak”

print “Safe

temperature

level”

print “Safe

Butane and

Methane level”

print “Safe Coal

Fumes level”

YES

YES

YES

Print value of

Temperature

in , Gas levels.




The coding regarding each part has been discussed under appropriate titles in this chapter

(Methodology). The entire programming is included in Appendix A.

3.7 Graphical User Interface

The graphical interface for reading the temperature sensor was designed in processing the

coding for this is included in Appendix B. The interface and its results are discussed under

the Chapter 4: Test and Results.




Chapter 4: Test and Results

In this chapter the outcomes of the project is discussed namely the mechanical model,

Independence of the robot, working of the sensors, reception of data using Bluetooth and

GUI.

4.1 Mechanical Design

The robot is build rigid enough for a prototype; it is made from plastic and reinforced with

carbon fibre sticker. All the circuits fit in and are screwed properly to the body, so it is shock

proof. To reduce the complexity most of the components are prototyped into PCBs. The

power supply is an array of rechargeable 9V Batteries. The pictures of the robot, Schematics

and PCB designs are included in the Appendix.

4.2 Independence of the Robot

The robot has one Ultrasonic sensor fixed in the front, which can detect anything in front of

it. An obstacle was placed in front of the ultrasonic sensor at different distances and the

distance was measured using a ruler and the Sensor itself.

Figure 4.1: Set up for the Obstacle Test

The comparison in data is shown in the Table 4.1.




Distance (cm) –

Measured using ruler

Distance (cm) –

Measured using

sensor

5 5.15

10 10.25

20 20.31

30 30.50

50 47.40

70 50.73

80 50.97

Table 4.1: Results from sensor and real measurement

The precision is very close to ±7mm for distances less than 30cm, although further distances

where measured with less accuracy. It doesn’t really matter because the sensors task is to find

any obstacles in a range of 4cm and avoid them by changing the direction.

4.3 Working of the sensor

The detections sensors used are temperature sensor, MQ4 and MQ9 gas sensor. The

temperature sensor is producing very accurate results, as it was compared with other sensors

to make sure about the result. Testing the accurate results of MQ4 and MQ9 sensors are very

difficult, because the availability of the natural gases is restricted. Therefore alternates had to

be used for demonstration purposes and testing. Instead of Methane in MQ4 sensor, butane

from a cigarette lamp sensor had to be used, this showed the rise in the value, but the

percentage of the gas in comparison to the atmosphere where not able to deduce. For this a

proper chemical lab and equipment are required. Similarly instead of using pure carbon

monoxide (which is highly toxic) in MQ9 sensor, for safety purposes a burned out candle

smoke was used, this is also CO, because of the absence of oxygen. Again not an accurate

mode of testing, but the lack of resources it was required.

Nevertheless the datasheet was used to determine the properties of the MQ series sensors, and

even without proper testing a value was cooked up, using some simple set ups. A gas leak

from the cigarette lamp within seconds hiked the MQ4 sensor ADC integer output from 300




to 500. From this analysis this value was used to give a warning. Similar test conducted in

MQ9 sensor the hike observed was from 40 to 100.

4.4 Reception of Wireless Data

As mentioned in the Chapter 3 Methodology the serial data from the Bluetooth module was

received using a terminal emulator called PuTTY. The range of the Bluetooth module

specified by the manufacturer was about 30meters. But from the test conducted it was found

that in indoor the range for perfect reception at 9600Baud rate is 10meters. After this point

the data is transmitting at a lower rate and even the data starts to scramble.

One problem faced with the Bluetooth reception was that the data was fluctuating, for

example if the data from the temperature sensor was 28 , the data received could be 0, 43,

12, 56, 60, 4, 9, 67, 14, 15. This created huge confusion, but with close observation it was

found that somehow the data transmitted is scrambled. But taking the average of data over a

period of time could get the accurate results. For example in the case above:

Average = 27.6 .

Therefore this method of sampling was used in all the transmitted data.

The coding for sampling was written as follows:

for (int x=0; x<500;x++) { pot = analogRead(A0); tempC = (5.0 * pot * 100.0) / 1024; i[x]=tempC; sum=i[x]+sum; } tempC=sum/500; 500 samples of Temperature was taken to get an average, the result was accurate by doing

this.




The results obtained from the sensors using UART to USB serial cable:

Figure 4.2: Result obtained using UART-USB cable

Notice the COM4 in the top of the serial window; COM4 in the respective computer used

was only for connecting ATmega328p via Arduino,




The results obtained from the sensors using BlueBee Bluetooth module in PC:

Figure 4.3: Results obtained from the sensors using BlueBee.

Notice the software used for obtaining this result is PuTTY and the COM port is COM5

which is used by Bluetooth receiver only.




The Results obtained in an Android Smartphone:

1.

Figure 4.4: Screenshot of the reading received on an Android Mobile




4.5 Graphical User Interface (GUI)

The GUI for better understanding of data for this project was written in Processing, a Java

based programming environment. The coding for this program is included in the Appendix B.

The coding runs smoothly and gives a visual impact. Due to the limitation of understanding

in the particular programming language, it was not successful to transmit the data via

Bluetooth module, but the data could be read properly by using a UART cable from the MCU

to the PC. The screenshot of the temperature reading in the form of a graph where a safe level

of temperature is displayed in green, a precautionary level is displayed is yellow and a

hazardous level is displayed in red, with the real time reading on the right corner, is displayed

below:

Figure 4.5: Screenshot from Processing




Chapter 5: Discussion

5.1 Investigation

The project from its beginning was examined in an industrial point of view. The necessary of

such a research was highly relevant due to the continuous accidents happening in the coal

mines around the world. The literature review proved that there are technologies which can

give solution to this problem, but still the initiative to support such project was lacking from

an industrial prospective. Mainly due to the fact that most Coal mines in the world are in

developing countries and their priority of Safety are sometimes misplaced with the priority of

wages and revenues. From this conclusion a project which can be viable for these consumer

where to be developed, a new market possibly, based on the principles of valuing time, and

money. That is if the robot is feasible with the current technologies used by them and if they

are made not from the top quality products, but a resultant of Quality and value materials, and

then there is a potential market for this project.

5.2 Validity of the prototype

The prototype was designed and realized on the principle of demonstrating the possibility and

further study for such a robot. The element of mass production was less of a concern. The

prototype could demonstrate that with modifications it can be enabled for mass production.

The reason why this is mentioned here because some elements in the project might not be the

exact fit rather it is glimpse of what could be. For example using Bluetooth in the mines is

not very practical because of the range, but using a real life solution can be extremely costly

and complex to design. Likewise the Body is made out of plastic, which won’t be suitable in

higher temperature.




Chapter 6: Conclusion

The experience of doing this project was extremely rewarding, the years spent in learning the

theory was put to use. This felt fulfilling and self-reliant. , From a personal outlook the

project can be classified success for this reason. It could also be said successful in a

professional point of view because of achieving most of the objectives required by the

University.

Some limitations and lack of validity in some areas have been discussed in previous chapters.

This leaves a lot of room for improvement. The Robot itself is capable of getting the data,

transmitting it and moving around unmanned.

The project was done in Fragments; this has an impact in every aspect of this project.

Looking at the hardware it can be deduced that instead of creating 1 PCB to accommodate

everything, different layers of circuits where used. This means that the failure of one of these

circuits will not affect the other sensors. This could also be said in the case of programming,

every action was built into separate class or function for ease of access and troubleshooting.

The objectives or requirements expected from the project and its status and explanation in the

end.

Number Objective Status

1 Detect the toxic gases emitted from the

coal mine.

Achieved. For demonstration purposes

the robot can detect CH4, CO, coal

fumes, butane, and so on.

2 Detect the level of heat inside the coal

mine.

Achieved. The level of heat can be

detected with precision.

3 Indicate the name and the value of the

gases and the temperature inside the

coal mine regularly to the control

room.

Achieved. Using Bluetooth the data will

be transferred to the control room.

4 If level of the gases or temperature is

too high a voice warning signal must

be activated inside the coal mine.

Achieved. Not a voice warning but a

buzzer will be alarmed letting the

miners ready for rescue mission.

5 Graphical Interface in control room Partially achieved. With some tweaks in




the programming this can be send to the

control room.

6 Autonomous movement Partially achieved. With additional cliff

sensors and 360 degree control the robot

can surf through any surroundings.

Table 6.1: Objectives and status of accomplishment.




Chapter 7: Further improvement

With this pace of growth in the field of Robotics and Artificial Intelligence the scope for

further improvement are endless. Even though some of the further improvements from

current scopes can be:

1. An upgrade from the plastic body chassis to Carbon Reinforced Fibre Chassis which

are more light weight, and durable than most other materials like stainless steel and

iron frames.

2. Instead of the MQ series of gas detectors and industrial solution like the M40.M

sensors (discussed briefly in the literature review). They are easy to calibrate. Can

display O2, H2S, CO and CH4 all with extreme precision.

3. A compartment to store food or rescue gear. This is an easy improvement but an

extremely useful one. Because most of the time when an accident happens it will be

hard for a human to move around without proper precautions.

4. A camera and GPS integration, which can map the coal mine into the robots memory.

And further used for storing weak points inside the mine, in terms of gas Break outs

or surface tension. This could also be used by the rescue team to locate and

communicate in two ways with the miners.




References

1. Anon. (2011). COAL INFORMATION. Available: http://www.worldcoal.org/coal/.

Last accessed 4th October 2013.

2. Anon. (2011). USES OF COAL. Available: http://www.worldcoal.org/coal/. Last

accessed 4th October 2013.

3. Britannica. (2013). Safety lamp. Available:

http://www.britannica.com/EBchecked/topic/516095/safety-lamp. Last accessed 18th

Aug 2013.

4. Anon. (2012). Coal & Electricity. Available: http://www.worldcoal.org/coal/. Last

accessed 4th October 2013.

5. Ashok K. Singha,R.V.K. Singhb, Mahendra P. Singhc, Hem Chandraa, N.K. Shuklaa.

(2007). Abstract. Mine fire gas indices and their application to Indian underground

coal mine fires. 69 (3), 192–204. [online]Available at :

<http://www.sciencedirect.com/science/article/pii/S0166516206000826 > [Accessed

13 October 2013].

6. Rio Tinto: Press Release. (2008). Rio Tinto and Komatsu to develop autonomous

haulage system for Pilbara iron ore operations. Available:

http://www.riotinto.com/media/media-releases-237_1885.aspx. Last accessed 18th

November 2013.

7. Anon. (). Gas Detector Technologies. Available:

http://www.thomasnet.com/articles/instruments-controls/How-Gas-Detectors-Work.

Last accessed 18th Aug 2013.

8. Anon. (). Measurement of Toxic Gases. Available:

http://www.thomasnet.com/articles/instruments-controls/How-Gas-Detectors-Work.

Last accessed 18th Aug 2013.

9. Anon. (). M40.M. Available: http://www.indsci.com/products/multi-gas-

detectors/m40m/#overview. Last accessed 1st September 2013.

10. Figaro. (). Operating principle of semiconductor type gas sensors. Available:

http://www.figaro.co.jp/en/item2.html. Last accessed 11th September 2013.

11. Anon. (2004). L293, L293D QUADRUPLE HALF-H DRIVERS. Available:

http://www.ti.com/lit/ds/symlink/l293d.pdf. Last accessed 18th October 2013.

12. Atmel Corporation. (). ATmega328P. Available:

http://www.atmel.com/devices/atmega328p.aspx. Last accessed 18th October 2013.




APPENDICES

Appendix A: Coding for the Microcontroller

int MQ4 = 0; // first analog sensor

int MQ9 = 0; // second analog sensor

int LM35 = 0; // digital sensor

int inByte = 0; // incoming serial byte

const int Motor1Pin1 = 8;




#define trigPin 13

#define echoPin 12

void setup() //run once

{

Serial.begin(9600); //begin serial transmission at 9600 bauds

pinMode(Motor1Pin1, OUTPUT);




pinMode(trigPin, OUTPUT);

pinMode(echoPin, INPUT);

}

void loop() //keep on looping

{

long duration, distance;

digitalWrite(trigPin, LOW);




delayMicroseconds(2);

digitalWrite(trigPin, HIGH);

delayMicroseconds(10);

digitalWrite(trigPin, LOW);

duration = pulseIn(echoPin, HIGH);

distance = (duration/2) / 29.1;

if (distance>4)

{

GoForward();

survOn();

}

else

{

GoBackward();

delay(300);

GoLeft();

delay(700);

}

}

void GoRight()

{

digitalWrite(Motor1Pin2, LOW);

digitalWrite(Motor1Pin1, HIGH);



}

void GoLeft()

{








}

void GoForward()

{





}

void GoBackward()

{





}

void Stop()

{





}

void survOn()

{

// get incoming byte:

inByte = Serial.read();

// read first analog input:

MQ4 = analogRead(A0);




// read second analog input:

MQ9 = analogRead(A1);

// read switch, map it to 0 or 255L

LM35 = analogRead(A2);

// send sensor values:

LM35 = (5.0 * LM35 * 100.0) / 1024;

if (MQ4<500 && MQ9<100 && LM35<40)

{

allsafe();

delay(1000);

}

else

{

sensor1();

sensor2();

sensor3();

delay(1000);

}

}

void allsafe()

{

Serial.print(MQ4);

Serial.print(" - Methane, CNG Gas||||");

Serial.print(MQ9);

Serial.print(" - Carbon Monoxide, Flammable gas||||");

Serial.print(LM35);

Serial.println("°C||||");

Serial.println(" All Safe All Safe All Safe All Safe All Safe All Safe All

Safe ");

}




void sensor1()

{

Serial.print(MQ4);

Serial.print(" - Methane, CNG Gas ");

if(MQ4>500)

{

Serial.println(" MAYDAY!!!!!!! Methane, CNG Gas level ALARMING");

}

}

void sensor2()

{

Serial.print(MQ9);

Serial.print(" - Carbon Monoxide, Flammable gasses ");

if(MQ9>100)

{

Serial.println(" MAYDAY!!!!!!! Carbon Monoxide, Flammable gasses level

ALARMING");

}

}

void sensor3()

{

Serial.print(LM35);

Serial.print(" °C ");

if(LM35>40)

{

Serial.println(" MAYDAY!!!!!!! Temperature level ALARMING");

}

}




Appendix B: Processing Sketch for GUI Graph

import processing.serial.*;

Serial myPort;

int xPos = 1;

float y;

float inByte,check;

PFont f;

boolean onoff = false;

void setup ()

{

size(400, 300);

myPort = new Serial(this, "COM4", 9600);

myPort.bufferUntil('\n');

f = loadFont( "ArialMT-48.vlw" );

textSize(14);

background(0);

}

void draw ()

{

}

void serialEvent (Serial myPort)

{

sketchgraph();

}




void sketchgraph()

{

fill(0, 102, 153);

text ("Temperature" ,width-100,height-285);

text ("Degree C", width-85,height-272);

String inString = myPort.readStringUntil('\n');

if (inString != null)

{

inString = trim(inString);

float inByte1 = float(inString);

inByte = map(inByte1, 20, 110, 0, height);

if (inByte1>=40 && inByte1<=45)

{

stroke(245,245,10);

y=inByte*2;

point(xPos,height-y);

line(xPos, height, xPos, height - y);

}

if (inByte1>45)

{

stroke(245,10,10);

y=inByte*2;



}

if (inByte1<40)




{

stroke(6,158,11);

y=inByte*2;



}

if (xPos >= width)

{

xPos = 0;

background(0);

}

else

{

xPos++;

}

text (inByte1, width-85,height-259);

noStroke();

fill(204,204,204);

rect(width-85,height-259-10,textWidth("88.8888"),14);

stroke(0);

fill(0);

noStroke();

fill(204,204,204);

rect(width-85,height-259-10,textWidth("88.8888"),14);

stroke(0);

fill(0);

text (inByte1, width-85,height-259);

}

}




Appendix C: PCB and Schematics

PCB Designed to replace the Arduino UNO Board using Fritzing PCB Design Tool

Figure: MCU circuit with voltage regular, crystal, capacitor and other passive

components

PCB Design for L293D-IC with Motor Connectors

Figure: H-bridge circuit shield design to fit arduino Board.




Schematics of the L293D, Arduino and Temperature sensor connection.

Figure: Schematic connection of partial circuit




Copper bottom circuit ready to Etch:

Figure: Circuit to place the Atmega328p board




Figure: circuit for L293D IC and connectors to Atmega328p MCU

Appendix D: Pictures taken during the progress of project




PROJECT GANTT CHART

coal mine robot (project report)

Education

beng project

coal mining robot

final year project

hardware oriented project

muhsin abdul mohammedabstract

problem of coal

iibachelor of electrical

surveillance robot