landline technology of bsnl
TRANSCRIPT
-
8/9/2019 Landline Technology Of Bsnl
1/33
-
8/9/2019 Landline Technology Of Bsnl
2/33
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
-
8/9/2019 Landline Technology Of Bsnl
3/33
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
-
8/9/2019 Landline Technology Of Bsnl
4/33
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
-
8/9/2019 Landline Technology Of Bsnl
5/33
Basic Parts Of Our Mobile Robot
Locomotion system
Power supply system Actuators
Sensory devices for feedback
Sensor Data processing unitControl system
-
8/9/2019 Landline Technology Of Bsnl
6/33
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
-
8/9/2019 Landline Technology Of Bsnl
7/33
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
-
8/9/2019 Landline Technology Of Bsnl
8/33
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
-
8/9/2019 Landline Technology Of Bsnl
9/33
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
-
8/9/2019 Landline Technology Of Bsnl
10/33
Wheeled Locomotion Systems
Differential drive
Car type drive Skid steer drive
Articulated drive
Synchronous drive Pivot drive
-
8/9/2019 Landline Technology Of Bsnl
11/33
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
-
8/9/2019 Landline Technology Of Bsnl
12/33
Differential Drive Cont
Black arrows denote the direction of wheel. The green ones
show robot movement
-
8/9/2019 Landline Technology Of Bsnl
13/33
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
-
8/9/2019 Landline Technology Of Bsnl
14/33
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
-
8/9/2019 Landline Technology Of Bsnl
15/33
Car Type Drive Cont
-
8/9/2019 Landline Technology Of Bsnl
16/33
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
-
8/9/2019 Landline Technology Of Bsnl
17/33
Skid Steer Drive
-
8/9/2019 Landline Technology Of Bsnl
18/33
Articulated Drive
In this mechanism the machine chassis (body)
is deformed to achieve rotation in contrast to
the steering wheels in car type drive
-
8/9/2019 Landline Technology Of Bsnl
19/33
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
-
8/9/2019 Landline Technology Of Bsnl
20/33
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
-
8/9/2019 Landline Technology Of Bsnl
21/33
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
-
8/9/2019 Landline Technology Of Bsnl
22/33
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
-
8/9/2019 Landline Technology Of Bsnl
23/33
Stepper Motors
Used for measured
rotation
Can be held at aparticular position of the
shaft
Ideal for many
autonomous robotsrequiring higher precision
-
8/9/2019 Landline Technology Of Bsnl
24/33
Stepper Motor Working
Stepping Sequences for Single Coil Excitation
Only one coil is active at a given instant of time
-
8/9/2019 Landline Technology Of Bsnl
25/33
Stepper Motor Working Cont
Stepping Sequences for Double Coil Excitation
Two coils active at any given instant of time
-
8/9/2019 Landline Technology Of Bsnl
26/33
Interleaved Stepping (Half Step)
-
8/9/2019 Landline Technology Of Bsnl
27/33
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
-
8/9/2019 Landline Technology Of Bsnl
28/33
DC Motors
As the name suggests,
a motor which uses a
DC (Direct Current)power
Can run in both
directions
Speed Controllable
-
8/9/2019 Landline Technology Of Bsnl
29/33
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
-
8/9/2019 Landline Technology Of Bsnl
30/33
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
-
8/9/2019 Landline Technology Of Bsnl
31/33
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%
-
8/9/2019 Landline Technology Of Bsnl
32/33
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
-
8/9/2019 Landline Technology Of Bsnl
33/33
THANK YOU