Landline Technology Of Bsnl

8/9/2019 Landline Technology Of Bsnl

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What Is Robotics ?

The word robotics is used to collectively

define a field in engineering that covers themimicking of various human characteristics

Sound concepts in many engineering

disciplines is needed for working in this

particular field It finds its uses in all aspects of our life


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What A Robot Can Mean ?

An automatic industrial machine replacing

the human in hazardous work environment An automatic mobile sweeper machine at a

modern home

An automatic toy car for a child to play with

A machine removing mines in a war field all

by itself and many more


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What Do We Mean Here ?

Here we are aiming at design and prototyping of

mobile robots capable of controlled locomotion

It may be human controlled or automatic

It must be able to perform certain tasks we set for it

The task must be achieved within some given

limitations


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Basic Parts Of Our Mobile Robot

Locomotion system

Power supply system Actuators

Sensory devices for feedback

Sensor Data processing unitControl system


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Locomotion System

As the name suggests a mobile robot must have a system to make it move

This system gives our machine the ability to move forward, backward and taketurns

It may also provide for climbing up and down The concept of locomotion invariably needs rotational motion e.g. a wheel driven by

some power source

This involves conversion of electrical energy into mechanical energy, which we caneasily achieve using electrical motors

The issue is to control these motors to give the required speed and torque


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Power Supply System

Suitable power source is needed to run the

robotsMobile robots are most suitably powered by

batteries

The weight and energy capacity of the batteriesmay become the determinative factor of its

performance


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End Actuators

They convert the electrical energy into

meaningful mechanical workMechanical output can be rotational or linear

(straight line)

Motors provide rotational motion Electromagnets provide linear motion


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Power, Torque and Speed

A simple equation: Power is the product of Torque andAngular velocity

P = X This implies that if we want more torque (pulling capacity)

from the same motor we may have to sacrifice speed andvice versa

The dc motors (tape motors) available have very high

speed of rotation which is generally not needed. But whatthey lack is torque output For reduction in speed and increase in pulling capacity we

use pulley or gear systems These are governed by: 1 X r1 = 2 X r2


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Wheeled Locomotion Systems

Differential drive

Car type drive Skid steer drive

Articulated drive

Synchronous drive Pivot drive


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Differential Drive

This is the most commonly used form of locomotionsystem used in mobile robots as its the simplest and

easiest to implement It has a free moving wheel in the front accompanied with

a left and right wheel.The two wheels are separatelypowered

When the wheels move in the same direction the

machine moves in that direction. Turning is achieved bymaking the wheels oppose each others motion, thusgenerating a couple


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Differential Drive Cont

Black arrows denote the direction of wheel. The green ones

show robot movement


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Differential Drive Cont

In-place (zero turning radius) rotation is done by

turning the drive wheels at the same rate in the

opposite direction

Arbitrary motion paths can be implemented by

dynamically modifying the angular velocity and/or

direction of the drive wheels

Total of two motors are required, both of them are

responsible for translation and rotational motion


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Car Type Drive

This is the car type drive and the most common in

real world but not in robot world

It is characterized by a pair of driving wheels and a

separate pair of steering wheels

The translation and rotation are independent of each

other. But translation and rotation are interlinked

hence this system faces severe path planning

problem


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Car Type Drive Cont


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Skid Steer Drive

A close relative of the differential drive system

It is mostly used in tracked machines e.g. tanks. Also

finds application in some four / six wheeled robots

The left and right wheels are driven independently

Steering is accomplished by actuating each side at a

different rate or in a different direction, causing the

wheels or tracks to slip, or skid, on the ground


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Skid Steer Drive


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Articulated Drive

In this mechanism the machine chassis (body)

is deformed to achieve rotation in contrast to

the steering wheels in car type drive


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Synchronous Drive

The direction of motion is given by black arrow. The alignment of themachine is shown by green arrow

As the name suggests, it uses synchronous rotation of its wheels to achievemotion & turns

It is made up of a system of motors. One set of which drive the wheels and theother set turns the wheels in a synchronous fashion

The two sets can be directly mechanically coupled as they always move in thesame direction with same speed


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Pivot Drive

The most unique type of Locomotion system It is composed of a four wheeled chassis and a platform that can be

raised or lowered


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Pivot Drive Cont

The wheels are driven by a motor for translation

motion in a straight line For rotation one motor is needed to lower/raise

the platform & another to rotate the chassis

around the platform

This system can guarantee perfect straight line

motion as well as accurate in place turns to a

desired heading


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Motors are of various kinds

AC Motors : Not used much in robotics

Stepper Motors : For controlled rotationDC Motors : Finds extensive general use

Servo Motors : DC motor with in built

feedback & error compensation


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Stepper Motors

Used for measured

rotation

Can be held at aparticular position of the

shaft

Ideal for many

autonomous robotsrequiring higher precision


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Stepper Motor Working

Stepping Sequences for Single Coil Excitation

Only one coil is active at a given instant of time


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Stepper Motor Working Cont

Stepping Sequences for Double Coil Excitation

Two coils active at any given instant of time


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Interleaved Stepping (Half Step)


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Problems with Stepper Motors

Very low torque to weight ratio

Torque decreases with increase in thestepping frequency

For sufficiently high stepping speed the

stepper motor may skip steps due to

overshoot


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DC Motors

As the name suggests,

a motor which uses a

DC (Direct Current)power

Can run in both

directions

Speed Controllable


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DC Motor Working

Direction of rotation controlled by polarity of current /

voltage Speed of rotation controlled by average energy

(power) fed to the motor

A

-

+

D C M O T O R1

2

A

-

+

D C M O T O R1

2

V D C

V D C


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DC Motor Characteristics

Free running torque & current are ideally zero

Increased load implies, increased torque, current

drawn & power consumption

Power supplied by a motor is the product of output

shafts rotational velocity & torque

DC Motors are highspeed, low-torque devices

Using gears, the high speed of the motor is traded

off into torque


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DC Motor Characteristics Cont

Zero speed at

maximum load (stall

torque) Highest speed while

free running (zero load)

Highest power at half

speed & half load

5 0 %

50%

2 0 %

1 0 %

4 0 %

1 0 0 %

8 0 %

60%

90%

S P E E D - - - - - - >

P O W E R

6 0 %

9 0 %

40%

70%

7 0 %

30%

L O A D

20%

3 0 %

100%

80%

10%


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DIFFERENT TYPE OF SENSORS

LDR - Light Dependent Resistor Made of cadmium sulphide

Resistance between two terminals vary depending on the intensity oflight Can be used to differentiate contrast colours Thermistor Manufactured from the oxides of the transition metals - manganese,

cobalt, copper and nickel

Resistor depends on temperature IR Photo Diode Detects presence of Infra Red radiations Used for obstacle proximity sensing IR Data Communication


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Landline Technology Of Bsnl