line tracker robot

8/10/2019 Line Tracker robot

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MECHATRONICS SYSTEM

DESIGN

CASE STUDY

LINE TRACKING ROBOT

GROUP MEMBERS:

FALAK ZAHRA 120499

MUHAMMAD BIN SALEEM 120547

UMAIR KHAN 120589

SUNAN RAZA KHAN 120535

SUBMITTED TO:

SIR USMAN RAFIQUE

SIR AHMED ABDULLAH


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OBJECTIVE:

The line following is a classic introductory robot design and requires minimal

amount of resources. This robot uses Arduino (UNO) Microcontroller. This robot isintended to showcase basic sensor design and robot control system in the form of a

small autonomous robot which can follow a black line oer a white surface.

A !ro"ect design for a line following robot is !resented and discussed. The

!ro"ect descri!tion is gien# as well as the !ro"ect a!!roach. The ehicle has si$ %&

(%nfrared) sensors and two motor drier circuits ('ridges) for controlling two

se!arately controlled *+ motors. The control requirement# howeer# is s!ecified so

as to kee! the ehicle as close as !ossible to the center of the line and find its !ath

in a !u,,le of black lines oer white surface consisting of - degree turns. A

multi!le sensor# closed loo! based control algorithm is inestigated for straight#

cured and - degree !aths.

The ob"ectie of this !ro"ect is as follows/

0) To deelo! a robot that moes through a dark line on light background.

1) To make the deice automatically track the !ath and find its way to the end !oint

in the !u,,le.

MECHANICAL DESIGN:

The base of this robot is designed in such a way that it remains highly stable during

its o!eration and gies accurate and swift moements. %t has symmetric design

with two wheels located at the ends of its a$is of symmetry and a caster wheel at

the back to balance it. The robot remains at a height of about fie centimeters from

the ground.

The mechanical design of the base is illustrated below/

.

.

(%mages)


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Motor Driving:

Two# brushed *+ motors are em!loyed to run the robot. 2ach motor draws a stall

current of about .3 Am!s. Two hbridges are used for driing these motors one

for each tyre.

An 'bridge is an electronic circuit that enables a oltage to be a!!lied across a

load (*+ motor) in either direction. This allows the motor to run both forward and

backwards.

The following image demonstrates how an 'bridge works using sim!le switches.

'oweer switches are neer actually used because they can only be controlled

manually. %n order to control the direction and s!eed of the motor# these switches

are re!laced by either i!olar "unction transistors (4Ts)# 5ield effect transistors

(52Ts) or relays because they can be controlled electrically and are thus widely

used in the robotic society. 2ach one of them hae their own adantages and

disadantages and which one of the 4T6s# 52T6s and relays is used de!ends u!on

the motor to be controlled and the !arameters of the controlling deice.

7e used two single !ole double throw (89*T) relays# two 4Ts# and a MO852T in

our 'bridge design.7e had to use a 4T which acts as a switch when configured

in saturation mode. A fairly small amount of current on the base terminal causes a

high amount of current to !ass through the collector and emitter of the 4T. %n

sim!le terms when a signal is !roided on the base terminal of the 4T it acts as a


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closed switch and when there is no signal on the base terminal it acts as an o!en

switch. 7e used the 4T to control the relay to which the motor is connected. A

relay is sim!ly a magnetic switch which switches the terminal when the coil inside

is e$cited. This e$citation of the coil is actually controlled by the 4T used.

The Motor is connected to the relay as it is used to switch the terminals of the

motor hence changing the direction of flow of current through it.

As far as the s!eed of the motor is concerned# we added a MO852T to the relay in

between the ground terminal. This allows us to ary the deliered !ower to the

motor by connecting and disconnecting the ground using the MO852T. This

connecting and disconnecting is done by a!!lying a signal to the gate terminal of

MO852T using the 9ulse width modulation (!wm) feature of the microcontroller.

:ien below is the com!lete schematic of the circuit we used to make our '

bridge.


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The com!onents used are as follows/

0) 89*T relay (4;+


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et 0 and 1 be the elocities of the two tires the angular elocity will be B0 and

B1 and these can be related to each other by a mathematical e$!ression.

CrB

According to the elocities of the tires there can be two ty!es of motions of the

robot

Translation

&otation


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Translation

7hen 0 is equal to 1 the robot will moe in a straight line

Rotation

0. 7hen 0 is equal to 1 but the directions are o!!osite# the robot rotates

about its centre while not translating in any direction.

1. The rotation about other angles can be administered by controlling the

relatie elocities of the tires.

These two ty!es of motions can be controlled by controlling the rotation and

direction of rotation of the motors through a drie circuit and a microcontroller.

SENSORS:


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ADC:

5or analog to digital conersion of the oltage in!ut from the sensors# the robot is

mounted with a com!arator %+ M

line tracker robot

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