There are
certain basic components or modules, which together make a robot.
There are many of them. Some are:
1)
Sensor (Transducer)
2)
Processor
3)
Actuator (Motors and the like)
Well, these are the most basic modules of a robot. Before going into
each one, let me make it clear that,
1)
Every robot need not have all of these modules.
2)
But every robot will have at least one or some of these modules.
Moving
on to the basic definitions.
Sensor:
A
sensor is the thing which senses and provides information about the
environment. We can make some decisions based on the information it
gives. You would have come across the term Transducer. A sensor is
also an electrical transducer.
Technically,
a sensor is anything which converts some quantity to be
measured into electricity. For example, there are pressure sensors and
temperature sensors. As you can infer, they convert change in pressure
and temperature into a voltage or current. Using that voltage or current,
we may take some action, may be move a motor or something.
Actuator:
An
actuator is anything used to respond to the information from the
sensor. The most widely used actuator is the motor. You can think of the
actuator as the thing used to move the robot, or move some parts in the
robot. (Simply, it’s used to actuate the bot. Know the meaning of
‘Actuate’).
Processor:
A
processor is the interface between the sensor and actuator.
It
gets the signal from the sensor, does some processing and commands
to allow the actuator to do something. So, the inputs for the processor are
signals
from the sensor. Outputs are the signals for the actuators.
A
processor can be a micro controller, a micro processor, a DSP
processor or even a computer. And in some special cases, it can also be a human
being.
SENSOR ------> PROCESSOR ------> ACTUATOR
So,
now that you’re familiar with the frame work of a robot, we’ll see
where these modules are used.
Let’s
say you make an autonomous line follower robot (A line follower is a
robot which follows a line in the ground. The line should be a dark line
against light background or vice versa) How do you
go about making one? What modules do you need?
To
answer that; think how you can sense on which direction the line is going. You
can
sense the color, because, there’s a color contrast between the line and
background. So, you need a sensor which differentiates the light and dark
colors. One solution is to use LDR (Light Dependent Resistor). It’s
simply a resistor whose value changes based on the light falling on it. So,
when the resistance value changes, the voltage also changes. So, you
sense that the line is changing track.
A more
easy and accurate approach is to use Infra Red sensors. It’s
useful to know that dark colors (say black) absorb IR rays, and light
colors (Say white) reflect it. So, if you place an IR sensor on white color, it
gives a high voltage. On black color, it gives something near zero. This
can be used to identify which color the line is currently.
Next,
you need a processor, say a micro controller to decide what to do
with the sensor signal. The controller may, for example, move the motor
right if white color occurs, and move them left if black occurs. This is a
very crude algorithm, to give you an example.
-
So, you need a processor to process the sensor info.
Finally,
you need actuators to carry out the commands given by the
processors. You need some two or four motors to move the robot over the
line.
So,
for a line follower, you need all three modules.
Next
case, take a hand operated robot which you’ll use to pick objects from the
floor to be able place them somewhere in the shelf. You obviously do not need a
sensor to find where the object is. Also, you do not need a processor to
process the sensor information. You just need a remote control module to
give commands to the robot, and some motors to actually lift the objects
and place them in the shelf.
Here, the
human controls the operation so he is the processor.
So, you
need only actuators for such a robot.
PS
(Well, you may need a sensor after all. If you build
a bot to be used by a blind person or for automatic tasks, for example. Then
you
need at least a sensor to find where the object is).
The
point of the above discussion is simply that, which modules are
required for a robot can not be determined a priori. You need to think and
decide for yourself what components the robot is gonna need.
So, now that you know what are the basics to build a robot. We'll go into the
details of each one.
Sensor is anything that measures a
physical quantity then takes an input and gives an output which is in a form
readable via a proper instrument. There are different kinds of sensors.
Some Types of Sensors:
1 Acoustic microphone: seismometer, etc
2 Chemical: the breath analyzer that the police uses to test whether you are
drunk, etc.
3 Electric Current Sensor: ohmmeter, voltmeter etc
4 Sensors that sense change in the Environment: Gas Detector, Smoke sensors,
Rain Gauge, etc.
5 Navigation and Direction Control instruments: Gyroscope, altimeter, flux gate
indicator, etc.
6 Optical Sensors.
7 Temperature Sensors.
8 Pressure sensors.
9 Radiation Sensor.
10 Sensors used in Aotomotive application.
11 Flow sensor.
12 etc.
Gripping
Different types of grips can be used. The simplest being like forceps to
more complicated ones.
These are usually controlled using Servo motors which in turn are programmed by
a mC or mP.
The whole design depends upon the type of job the robot is being designed for.
Different types of arms are used accordingly.
For more information click those
links:
Actuator Processor A Robotic Primer
(Jacqueline Masloff/htgp.org)
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