robotics_exp1x

thunderclingΤεχνίτη Νοημοσύνη και Ρομποτική

13 Νοε 2013 (πριν από 3 χρόνια και 5 μήνες)

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Aim:
To study classification of Robots

Theory:

Robots are devices that are programmed to move parts, or to do work with a tool. Robotics is a
multidisciplinary engineering field dedicated to the development of autonomous devices,
including manipulators
and mobile vehicles.

Robots can be classified as follows:

Classification Based on drive
technology:

1.

Hydraulic drive: gives a robot great speed and strength. These systems can be designed to
actuate linear or rotational joints.
Advantages of hydraulic drive

are, they consume less
amount of power, good physical strength and provides good accuracy.
The main
disadvantage of a hydraulic system is that it occupies floor space in addition to that
required by the robot.

Apart from that they are expensive and regula
r maintenance is
required.

2.

Electric drive: compared with a hydraulic system, an electric system provides a robot
with less speed and strength. Accordingly, electric drive systems are adopted for smaller
robots. However, robots supported by electric drive s
ystems are more accurate, exhibit
better repeatability, and are cleaner to use.

3.

Pneumatic drive: are generally used for smaller robots. These robots, with fewer degrees
of freedom, carry out simple pick
-
and
-
place material handling operations.

Disadvantages

of pneumatic drive robots include

difficult speed control and use of air accessories.


Classification based on m
otion system
:

1.

Point
-
to
-
point (PTP) control robot: is capable of moving from one point to another point.
The locations are recorded in the control memory. PTP robots do not control the path to
get from one point to the next point. Common applications include component in
sertion,
spot welding, hole drilling, machine loading and unloading, and crude assembly
operations.

2.

Continuous
-
path (CP) control robot: with CP control, the robot can stop at any specified
point along the controlled path. All the points along the path mus
t be stored explicitly in
the robot’s control memory. Typical applications include spray painting, finishing,
gluing, and arc welding operations.

3.

Controlled
-
path robot: the control equipment can generate paths of different geometry
such as straight lines,

circles, and interpolated curves with a high degree of accuracy. All
controlled
-
path robots have a servo capability to correct their path.

These types of robots
are

commonly used for loading and unloading the objects.


Classification based on Physical con
figurations
/ Workspace Envelop

Four basic configurations are identified with most of the commercially available industrial robots

1.

Cartesian configuration: A robot which is constructed around this configuration consists
of three orthogonal slides, as shown

in fig. the three slides are parallel to the x, y, and z
axes of the Cartesian coordinate system. By appropriate movements of these slides, the
robot is capable of moving its arm at any point within its three dimensional
rectangular

spaced work space.
They have high resolution and greater accuracy and are easy to
control. Bu
t the disadvantages of them are

requirement of complex mechanical design for
performing linear displacement.



2.

Cylindrical configuration: in this configuration, the robot body is a
vertical column that
swivels about a vertical axis. The arm consists of several orthogonal slides which allow
the arm to be moved up or down and in and out with respect to the body.
The
advantage
includes

less complex design than
Cartesian

robot but they h
ave restrictions on
compatibility with other manipulators in workspace.
This

robot

is illustrated
schematically in figure.



3.

Polar/Spherical
configuration: this configuration also goes by the name “spherical
coordinate” because the workspace within which

it can move its arm is a partial sphere as
shown in figure. The robot has a rotary base and a pivot that can be used to raise and
lower a telescoping arm.

They have good resolution but with spherical coordinates the
spatial relationship are more difficult

compared to
Cartesian

robot and cylindrical robot.



4.

Articulated Configuration: An

articulated robot

is a robot with

rotary joints

(e.g. a

legged
robot

or an

industrial robot
). Articulated robots can range from simple two
-
jointed
structu
res to systems with 10 or more interacting joints. They are powered by a variety of
means, including

electric motors
.

These types of robots do

have high
flexibility and
accurac
y
. They have ability to avoid
obstacles

in 3
-
D workspace. But the disadvantages
are poor resolution and difficult to controls due to three
rotary

joins.



5.

SCARA
:
The

SCARA

acronym stands for

Selective Compliance Assembly Robot
Arm

or

Selective Compliance
Articulated Robot Arm. By virtue of the SCARA's parallel
-
axis joint layout, the arm is slightly compliant in the X
-
Y direction but rigid in the ‘Z’
direction, hence the term: Selective Compliant. This is advantageous for many types of
assembly operations,
i.e., inserting a round pin in a round hole without binding.

The second attribute of the SCARA is the jointed two
-
link arm layout similar to our
human arms, hence the often
-
used term, Articulated. This feature allows the arm to
extend into confined areas a
nd then retract or “fold up” out of the way. This is
advantageous for transferring parts from one cell to another or for loading/ unloading
process stations that are enclosed.



Classification based on intelligence

1.

First generation robots are
characterized by fixed control programs, they are capable to
only repeat in a strict fashion operations previously programmed into them, they cannot
adapt to the environment so no external perturbations must exist. The program can be
changed to some extent
, but these robots are best suited in industrial environments
performing repetitive operations.

They have limited memory and
offer

less flexibility.
Robot arm is not much smooth.

2.

Second generation robots are adaptive, they can operate in variable or partia
lly unknown
environments. The ability to adapt under the effect of external perturbations is enabled by
using sensors that measure various parameters of the environment. These robots execute
a series of predefined operations but can also take into account
changes in the
environment and alter their routine in order to accomplish their tasks.

They have good
amount of memory and offers a good flexibility. They are advance version of 1
st

generation robots. Second generation robots also offers
smooth

movement of

robot arm.

3.

Third generations robots are intelligent, they have certain artificial intelligence abilities,
their degree of intelligence varies according to needs identified in the design phase. These
robots are capable of defining their instantaneous actio
ns taking into account information
gathered by tactile, visual or noise sensors, resolve particular issues and modify their
routine accordingly.

Industrial robots belong

to
this generation.

4.

Fourth generation robots have walking capability. Robots like android, humanoids,
biobots, macrobots falls under this category. They are very intelligent one have good
accuracy
.


Robot classification based on their function and performance

Based on the fun
ction
s

performed by the robot
s
, they can be classified as follows:

1.

Manual manipulator: They are operated manually by the human beings.

2.

Fixed sequence robots
-

They generally have a fixed sequence which cannot be changed
or altered.

3.

Variable sequence robots
-

Sequence of operations to do particular task can be varied.

4.

Playback robots
-

In playback robot, first task is taught to the robot. During the teaching
period the
robot

memorizes the task, stores the taught instructions in memory and then
plays back the
op
erations

taught by the user. Hence the name playback robot.

5.

Numerically Controlled

(NC)

robots


they operates on numbers.

6.

Teleoperational robots
-

Robots operated by remote control, extra terrestrial robot

(like the
MARS path finder), uses

telecommunication links.

Conclusion:
Hence we studied classification of robots.