2. A robot is a mechanical agent resembling a human
being guided by a computer program with electronic
circuitry and capable of performing all sorts of
industrial actions in an automated way. A robot may
convey a sense of intelligence or thought of its own. The
branch of technology that deals with robots is called
robotics.
3. Robot anatomy usually has 3 physical configurations:-
Body
Arm
Wrist
In many industries the robots are usually stationary mounted on
a base. The body is attached to the base, arm is attached to the
body and wrist is attached to the arm. Relative motion is
achieved by movements of body, arm and wrist.
The wrist is the important component bearing the tool or work. It
is usually called as end effectors. The relative movements can be
rotating or sliding or the combination of both according to the
need.
4. The robots used in the industry have various sizes,
shapes and configurations. The common co-ordinate
systems in robots are:-
Polar co-ordinate system
Cylindrical co-ordinate system
Cartesian co-ordinate system
Jointed arm co-ordinate system
5.
6. The features of polar co-ordinate robots are:-
It uses a telescopic arm which can be raised or lowered
about a horizontal pivot.
The pivoted arm is mounted on a rotating base.
The above pivot mounted rotating configuration
allows the robot to move the arm in a spherical space.
Hence it is also called as spherical co-ordinate system.
Unimate 2000 series and MAKER 110 are the robots
working on polar co-ordinate system.
7.
8. It has a vertical column that can slide up and down
along the column.
The robot arm is attached to the vertical column.
The robotic arm can rotate radially with respect to the
column.
The robot work space resembles a cylinder and hence
called as cylindrically co-ordinate robot.
GMF model robots are cylindrical co-ordinate type.
9.
10. This uses the mutually perpendicular axes (x, y and z
respectively).
The arm is mounted in a vertical column such that it
can make any kind of motion with the permissible
limits of x, y, and z axes.
Hence this robot is also called as xyz robot or
rectilinear robot.
By moving the arm it can surround a work area which
resembles a rectangular envelope.
IBM RS-1 robots are this type.
11.
12. The configurations are:-
This kind of robot resembles a human arm.
It has two components corresponding to human forearm
and upper arm.
The fore arm is connected to upper arm by an elbow joint.
The upper arm is connected to the body by a shoulder joint.
A wrist is connected to the forearm to perform operations.
SCARA model type of robots is jointed arm type.
13.
14. It is the space within which the robot can manipulate its
wrist end. The work volume is defined by the following
characteristics:
Robots physical configuration
Sizes of arm, body and wrist components
Limits of the joints
The polar configured robot has the work envelope of
sphere, the cylindrical type has cylinder envelope,
Cartesian co-ordinate has a rectangular and the jointed
arm has spherical envelope. The dimensions of the work
envelope are defined by dimensions of the links and type of
joints.
15. The broad classifications of robots are based on the
following methods:
Configuration (same as above)
Shape of workspace (same as above)
Type of power-drive (electric, pneumatic and
hydraulic)
Type of technology( low-level, medium level and high
level)
Type of motion (linear, rotational, extensional,
twisting)
16. The movements of the body, arm and the wrist of the
robots are determined by the power drive system. It
also determines the speed, strength and performance of
robots. Even drive system varies according the
applications. The drive systems are:-
Hydraulic
Electric
Pneumatic
17. The robots working on hydraulic power have some
common features:
They are usually large type (unimate series).
The essential advantage is greater speed and strength.
The disadvantage is the requirement of more floor
space, leakage etc.
They usually actuate rotary and linear movements.
Rotary vane pump is employed for rotary motion and
hydraulic pistons for linear movement.
18. Common specifications of electrical drive robots are:-
Do not provide as much speed and power compared to
hydraulic system.
Accuracy and repeatability are far better.
Requires less floor space and suitable for precise
applications.
MAKER 110 is of this type.
They employ stepper and servo motors for rotary
movements and telescopic arms for linear movements.
The cost of the electric robot is very much proportional too
its size.
19. The pneumatic robots have the following features:
Smaller robots with fewer degrees of freedom (2-4).
Often has application in pick and place operations.
More suitable for linear and sliding motions.
It can also be used in rotary applications.
20. From the time of discovery of robotic technology
various advancements have been made till now and the
developments in technology is going on. Based on
technology, the robots are classified as
Low level
Medium level
High level
21. Mostly used for material handling.
Could carry out loading-unloading and simple
assembly operations.
Fewer degrees of freedom with movements at (2-4
axes).
Have a payload of 25 pounds.
22. Mostly used for pick and place applications.
Carry out loading-unloading and common assembly
operations.
Degrees of freedom is limited from (4-6) axes.
Has the payload up to 300 pounds.
23. Finds application in industrial manufacturing tasks.
Degrees of freedom is limited from (6-9) axes.
Has the payload from 300 pounds.
24. Robots are specified by the following terms:
Pitch
Yaw
Roll
Joint notation
Speed of motion
Payload.
25. Roll:
The wrist of the robotic arm is capable of rotating
about its arm axis. It is called roll or swivel.
Pitch:
With the wrist rotating about an axis, the up and down
motion of the wrist is called pitch.
Yaw:
With the wrist rotating about an axis, the left and
right rotation of the wrist is called yaw.
26.
27. The configuration of the robot can be represented by
notations or symbols. (L, R, T, V)
L- Linear
R- Rotation
T- Twisting
V- Revolving
A polar configured robot is of type TRL while a
cylindrical robot can be of type TLL, LTL, LVL.
28. The speed of the robot is essentially measured by a
robot extending its arm to a maximum distance from
the vertical axis and the speed is measure at the end of
the wrist.
The maximum speed of the industrial robots is about
1.7m/s.
It determines how quickly a job can be accomplished.
It minimizes the cycle time for a given task.
29. Speed depends upon 3 factors;
Accuracy
Accuracy has inverse relationship with speed. At higher
speeds, the robot could not locate the position accurately.
Weight of the object
Weight of an object also has inverse relation on speed.
When heavy objects are moved due to inertia, it lacks its
stability.
Distance to be moved
Distance is directly proportional to speed. When the robot
has to travel a greater distance, it can reach its maximum
possible speed.
31. The weight carrying capacity of the robot determined
by its weakest position is called payload. It depends
upon size, configuration, drive system etc. if the rated
load capacity of the robot is 5 kg and the end effectors
load is 2kg then the pay load is 3kg.
