Ppt

1. Week 8
Robotics
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2. Industrial Robot
• An industrial robot is a programmable mechanical
manipulator with an arm to perform works in an industrial
environment.
•According to the Robot Institute of America, an industrial
robot is defined as “a reprogrammable multi-functional
manipulator designed to move material, parts, tools or other
specialized devices through variable programmed motions for
the performance of a variety of tasks.”
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3. Importance of Robots
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Isaac Asimov's "Three Laws of Robotics"
• A robot may not injure a human being or, through inaction,
allow a human being to come to harm.
• A robot must obey orders given it by human beings except
where such orders would conflict with the First Law.
• A robot must protect its own existence as long as such
protection does not conflict with the First or Second Law.

4. Elements of a robotic system
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1. Mechanical Components
2. Control System
3. Computer System

5. 1. Mechanical Components
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Mechanical components: They provide the physical robot
motions. They consist of
1. A manipulator (the base and arm assembly)
2. End-of arm tooling, such as a gripper or end effector.
3. Actuators such as motors.
4. Transmission elements such as, belts. pulleys gearing etc.

6. 2. Control System
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Control System: It is used to generate the necessary signals to
co-ordinate the movements along the three axis.
1. Mechanical, pneumatic, hydraulic, electrical or electronic
controls.
2. Sensors such as cameras, amplifiers etc.
3. Equipment interfaces.

7. 3. Computer System
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Computer system: It provides the necessary data processing
capability to interpolate the intermediate positions and control
the movement of the links or arms of the robot. They include
1. Microprocessor or a PLC or a personal computer.
2. User interfaces such as keyboard, display etc.
3. Control software to manipulate the robot for different
applications.

8. Need for using Robotics in CIM
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1. Robots can be developed with performance capabilities superior to the human
beings in terms of strength, speed, size, repeatability and accuracy.
2. Robots are much better than humans to perform simple and repetitive works.
3. Robots can replace humans in performing tasks which are difficult and hazardous in
factories such as heat, dust, chemicals, vapors, nuclear radiations.
4. Robots can reduce the production cost through reduction in usage of materials and
their efficiency and consistency.
5. These are more economical when the labour cost are high.
6. Robots are more flexible as compared to hard automation – can be reprogrammed
7. They do not become obsolete as they can programmed for other operations.

9. WORK VOLUME
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The work volume or work envelope is the three-dimensional space in which the robot can manipulate the end
of its wrist. Work envelope (volume) is determined by the number and types of joints in the manipulator, the
ranges of various joints, and the physical size of the links
It is the shape created when a manipulator reaches forward, backward, up and down. These distances are
determined by the length of a robot's arm and the design of its axes.

10. Types of Robots
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Classification of robots based on mechanical configuration (i.e.,
Type of motion provided):
1. Rectangular or Cartesian co-ordinate (configuration) robot.
2. Cylindrical co-ordinate (configuration) robot.
1. SCARA (Selective Compliance Assembly Robot Arm)
3. 6 AXIS robot
4. DELTA ROBOT

11. 1. Rectangular or Cartesian coordinate robot
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A robot with this geometry has three linear axis using sliding joints, the motion traces a box
like shape.
The linear movements of the Cartesian elements give the robot a cube-shaped workspace that
fits best with pick-and place applications and can range from 100 millimeters to tens of
meters.

12. 2. Cylindrical configuration robots
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2. Cylindrical Configuration:
Cylindrical robots are very simple and similar to Cartesian in their
axis of motion. Most cylindrical robots are made of two moving
elements: rotary and linear actuators. Because they have a
cylindrical work envelope, machine designers might select them
for their economy of space. The robot can be placed in the middle
of a workspace and, because of its rotation element, it can work
anywhere around it. Simple applications where materials are
picked up, rotated and then placed work best for Cylindrical
robots.
• The arm assembly is moved up or down. The arm can be moved
in and out relative to the axis of the column. T joint is used to
rotate the column about its axis

13. 3. SCARA Robots
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SCARA robots offer a more complete solution than the Cartesian or Cylindrical. They are all-in-
one robots, meaning a SCARA robot is equipped with x, y, z and rotary motion in one package
that comes ready-to-go, apart from the end-of-arm tooling. The work envelope is similar to
Cylindrical robots but it has more degrees of motion in a radius or arch-shaped space.
applications are also similar to Cylindrical and Cartesian robots, but SCARA robots can move
quicker than the other two. They are seen often in bio-med applications due to their small work
area. Because SCARAs have the easiest integration, they seem like the best solution for the
majority of applications, but Cartesians are more common because of their level of
customization.

14. 4. 6 AXIS robot
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Another all-in-one robot type is the 6-Axis. Though sometimes 6-Axis robots can be almost toy-sized, they are
typically very large and used for large assembly jobs such as putting seats into a car on an assembly line. These
robots operate like a human arm and can pick up materials and move them from one plane to another. An
example of this would be picking a part up from a table top and putting it into a cupboard — something the other
robot types cannot do easily. 6-Axis robots can move quickly and come in complete solutions like SCARAs,
however, their programming is more complicated. The robots can get so large and move so quickly that, if roller
coaster seats were attached to them, they could simulate an amusement park ride. Because they are one of the
largest of the five robot types, most designers choose them for their ability to make movements that others cannot
to compensate for the loss of space

15. 5. DELTA robot
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• As the fifth and final type, Delta robots are the fastest
and most expensive. They have a unique, dome-shaped
work envelope in which they can achieve very high
speeds. Delta robots are best for fast pick-and-place or
product transfer applications, like moving parts from a
conveyor belt and placing them in boxes or onto another
conveyor belt. They also come as complete solutions for
machine designers, but are more complicated in use than
the 6-Axis or SCARA robots. The main advantage of Delta
robots is their speed and precision with which they
operate. Learn more about Omron's Hornet 565 Parallel
Robot and Quattro Parallel Robot

16. Degrees of freedom
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The robot movements are
defined in terms of the
degrees of freedom (d.o.f.)
which are supported by the
robot.
The degree of freedom
refers to the possibility of
motion along a particular
axis, either rotary or linear.

17. ROBOT CONTROL SYSTEM
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Point to Point Control Robot (PTP):
The PTP 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 insertion
Spot welding
hole drilling
Machine loading and unloading
Assembly operations

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Contouring motion system: In contouring, the robot's have the capabilities to follow a closely spaced locus of
points which describe a smooth curve.The CP robot is capable of performing movements along the controlled path.
With CP from one control, the robot can stop at any specified point along the controlled path.
All the points along the path must be stored explicitly in the robot's control memory. Applications Straight-line
motion is the simplest example for this type of robot.
Some continuous-path controlled robots also have the capability to follow a smooth curve path that has been defined
by the programmer. In such cases the programmer manually moves the robot arm through the desired path and the
controller unit stores a large number of individual point locations along the path in memory (teach-in).
Typical applications include:
• spray painting
• finishing
• gluing
• Arc welding operations
CONTINUES PATH CONTROL (CP)

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In controlled-path robots, the control equipment can generate paths of different geometry such as straight lines,
circles, and interpolated curves with a high degree of accuracy.
Good accuracy can be obtained at any point along the specified path.
Only the start and finish points and the path definition function must be stored in the robot's control memory.
It is important to mention that all controlled-path robots have a servo capability to correct their path.
CONTROLLED PATH ROBOT

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Intelligent control describes the discipline in which the control methods developed attempt to MATCH important
characteristics of human intelligence. These characteristics include adaptation and learning, planning under large
uncertainty, and coping with large amounts of data.
INTELLIGENT CONTROL ROBOT

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Co-ordinate System
A coordinate system defines a plane or space by axes from a fixed point
called the origin. Robot targets and positions are located by measurements
along the axes of coordinate systems
A robot uses several coordinate systems, each suitable for specific
types of jogging or programming.
• Joint co-ordinate system
• Rectangular co-ordinate system
• User or object coordinate system
• Tool coordinate system.

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JOINT Co-ordinate System
Joint coordinate system is the representation of the robot position in the space
using the values of its joints. We use degree as the unit of each joint value.
A rectangular coordinate system is defined, originating at the center point between
the plates with z in the direction of plate separation, x in the width direction, and y
in the length direction.
The User Coordinate System is referred to as the coordinate system set up by the
user to ease the modeling task
Object Coordinate System - When each object is created in a modelling program,
the modeller must pick some point to be the origin of that particular object, and
the orientation of the object to a set of model axes

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TOOL Co-ordinate System
The tool mounted on the mounting flange of the robot often requires its own
coordinate system to enable the definition of its TCP, which is the origin of the
tool coordinate system

24. Motion Systems in a robot
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Corresponding to arm and body:
1.Rotational traverse: Rotation of the BASE arm about the vertical
axis.
2.Vertical traverse: Vertical movement of the arm along a slide or
movement in a vertical plane by pivoting about a horizontal axis.
1. Radial traverse: VERTICAL movement of the SECOND arm
with respect to the 1ST ARM.

25. Motion Systems in a robot
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Corresponding to the wrist:
4. Wrist swivel: Rotation of the wrist about its ARM axis.
5. Wrist bend: It involves up and down rotation of wrist.
6. Wrist yaw: Rotation of the wrist to the left or right.

26. End Effectors
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• End effector is a device that is attached to the robot’s wrist to perform a
specific task.
• The task may be work piece handling, spot welding, spray painting or any
other function.
• So end effector is a special type of tooling which enables the robot to do
a specific type of job.
• End effectors are of two categories, grippers and tools.
• Grippers are used to hold work pieces for pick and place applications.
• Tools as end effectors refer to the applications where grippers are used
only for the purpose of holding the tools.

27. Grippers
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Grippers are used to hold either work-pieces or tools. Following are the common types of grippers
1. Suction cups (Vacuum cups) : Here low pressure or vacuum is used to hold parts
2. Magnetic grippers: Used to hold ferrous parts
3. Scoops or ladles: Used to hold fluids, powders, pellets and granules.
4. Adhesive devices: These devices use an adhesive substance to hold a flexible material (fabric)
5. Hooks and scoops.
6. Dual grippers: It consists of two gripper devices in one end effector for machine loading and
unloading
7. Interchangeable fingers which can be used on one gripper mechanism. To accommodate
different parts, different fingers are attached to the gripper.
8. Sensory feed back in the fingers to provide the gripper with capabilities such as (1) sensing the
present of the work part or (2) applying a specified limited force during gripping.
9. Multiple fingered grippers: This possess the general anatomy of a human hand.

28. FACTORS TO BE CONSIDERD WHILE SELECTING GRIPPERS
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• The following considerations will help you in choosing and sizing the right gripper for your application.
• Part Shape – If the product or part has two opposing flats, a 2-jaw gripper is normally used. If the part is
cylindrical, a 3-jaw gripper could be used. Tooling can be designed to accommodate cylindrical parts with a 2-
jaw gripper.
• Accessibility & Part Consistency – Angular grippers are usually low in cost, but the arcing motion of the jaws
may require additional tooling clearance and will grip at varying points as part width varies. A parallel gripper is
easier to tool in order to compensate for part size.
• Part Weight – Grip force must be adequate to safely transport the part.
• Orientation & Dimensions – Part orientation and distance from the gripper face affects the gripper selection.
• Size – Nominal gripping dimension indicates approximate gripper size.
• Variation – Variation in gripping location or encapsulation determines minimum gripper jaw travel.
• Air Pressure – The air pressure at the gripper affects gripper sizing and must be taken into account.
• Grip On Open or Close – Grip force varies in each direction due to the effective area of the piston rod on some
gripper types. Verify that the gripping direction is taken into account when sizing.
• Velocity – Higher speeds and acceleration/deceleration affects gripper selection.
• Tooling Length – Longer tooling inducts bending moments into the gripper and affects sizing.

29. Types of joints used in robots
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The Robot Joints is the important element in a robot which helps the links to travel in different
kind of movements.
There are five major types of joints such as:
Rotational Joint:
Rotational joint can also be represented as R –Joint. This type will allow the joints to move in a
rotary motion along the axis, which is vertical to the arm axes.
Linear Joint:
Linear joint can be indicated by the letter L –Joint. This type of joints can perform both
translational and sliding movements. These motions will be attained by several ways such as
telescoping mechanism and piston. The two links should be in parallel axes for achieving the
linear movement.

30. Types of joints used in robots
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Twisting Joint:
Twisting joint will be referred as V –Joint. This joint makes twisting motion among the output and input link. During this process, the output link axis will be
vertical to the rotational axis. The output link rotates in relation to the input link.
Orthogonal Joint:
The O –joint is a symbol that is denoted for the orthogonal joint. This joint is somewhat similar to the linear joint. The only difference is that the output and input
links will be moving at the right angles.
Revolving Joint:
Revolving joint is generally known as V –Joint. Here, the output link axis is perpendicular to the rotational axis, and the input link is parallel to the rotational axes.
As like twisting joint, the output link spins about the input link.

31. Tools as End Effectors
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• There are applications where grippers are used to grasp a tool and use it during
work cycle.
• In cases where robot is used to hold tools, tool is fastened directly to the robot
wrist and becomes the end effector.
• A few examples of robot using tools as end effectors are
1. Sport welding gun
2. Arc welding tool
3. Spray painting gun
4. Drilling spindle
5. Heating torches

32. Drive system used in Robots
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• The mechanical linkages and joints of manipulator are driven by
actuators, which may be either motors or valves.
• The energy for these actuators is provided by some power source
called drive systems.
• There are three major drive systems for industrial robots:
1) Hydraulic actuator system.
2) Pneumatic actuator system
3) Electric actuator system.

33. Hydraulic actuator sysem
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These systems are driven by a fluid that is pumped through motors, cylinders, or other hydraulic
actuator mechanisms.
Hydraulically driven robots can be
• relatively compact,
• they provide high levels of force, power, and speed
• with accurate control.
• They can also be made very large for heavy payloads and large working
envelopes.
• Hydraulic robots are safe and reliable in wet, dusty, and potentially explosive
environments.
• These types of robots are suitable for operations in foundries.

34. Pneumatic actuator system
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• These systems are driven by compressed air.
• Pneumatic-drive robots are usually small and have limited
flexibility, but they are relatively inexpensive to build and use.
• The weight of the payload they can carry is limited by the
compressibility and low operating pressure of air.
• These are also particularly suitable in certain application like
nuclear reactors and places were fire hazards are likely to occur.

35. Electric actuator system
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•These systems are driven by rotational electric motors.
• Electrically driven robots are best suited for applications
involving light payloads, which require high accuracy and
fast response.
•They do not have some of the maintenance and reliability
problems associated with pneumatic or hydraulic systems.
• AC Servo drives are preferred now because of their
ruggedness.

36. Control Systems used in Robots
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• In robots motion of an individual joints are controlled by a
combination of software and hardware which is programmed by the
user.
• Microprocessors-based controllers are commonly used today in
robotics as the control system hardware.
Types of robot control systems: There are two basic types of robot
control systems
1. Servo controlled system
2. Non-servo controlled system.

37. Servo-controlled system
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• This system is capable of controlling the velocity acceleration, and path of
motion, from the beginning to the end of the path.
• It uses complex control programs. Servo-controlled systems use electronic
controllers (PLC' s) or computers and sensors to control the motions of
robots.
• They are more flexible than non-servo systems, and they can control
complicated motions smoothly.
• Sensors are used in servo-control systems to trace the position of each of the
axes of motion of the manipulator.
• These sensors may be located internally, in the robot joints or externally, in
the workspace. Many different types of sensors can be used depending on
the nature of the task and performance requirements involved.

38. Non-Servo-controlled system
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• This is the simplest and least expensive type of control system, but it is also
very limited in its flexibility and performance.
• It can be a purely mechanical system of stops and limit switches, which are
pre-programmed or positioned for specific repetitive movements.
• This can provide accurate control for simple motions at low cost.
• Such a system can also use some type of electro-mechanical logic, such as
pneumatic valves or electrical relays, to control fixed sequences of
movements.
• The motions of non-servo controlled robots are controlled only at
their end points, not throughout their paths.

39. Functions of control system in robots
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1. Generating the path of motion for the manipulator: with acceleration and deceleration. For
making any movement, link starts from zero angular velocity and accelerates until it reaches a
maximum velocity. It then continues at that velocity until it begins to approach the position for
which it is programmed to reach. It then decelerates until it stops at that position. The control
system should provide the commands for this motion.
2. Getting the feedback from the sensor: The servo control receives feedback from the sensors
which track the movements of the manipulator  to make any adjustments required
3. Safety Controls: This is to ensure that the failures or errors are detected before any damage or
harm is done.
4. Interfaces:
1. Controller ↔ Programmer terminals, keyboards, switches, control pendants, etc.
2. Controller ↔ feedback devides - sensors and actuators that control the motion of
the robot.

40. Control system of a robots
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41. Key performance specifications/features of a robot
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1. Quality: Generally, one can expect higher accuracy and reliability from robots
2. Serviceability: Many features are added to the design of the robot to reduce
the frequency of failure and time for repair.
3. Safety: A wide variety of features are added to prevent the damage or injury
during robot operation including sensors, limit switches and end stops.
4. Modularity: Adoption of modular design techniques enables for the
manipulator to be reconfigured for different applications.
5. Dexterity: It is an ability of the manipulator to perform delicate, precise or
complex tasks, which depends upon the number of axis and the design of the
gripper.
6. Interfaces: to the sensors and actuators that control the motion of the robot
as shown in fig.

42. Robot programming methods
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1. Manual Teaching
2. Walkthrough Method
3. Lead-through Method
4. Offline Programming

43. 1. Manual Teaching
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• Here, the robot movement along particular
axis are controlled by setting mechanical
stops, cams, switches or relays.
• It is ideal for pick and place applications.

44. 2. Walk through method
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• Each axis of the robot is moved manually till the desired
point is reached.
• These co-ordinates are stored in memory by pressing push
buttons in a control box.
• This information can be played back later.
• The speed control is done separately.
• It is ideal for spray painting and welding applications.

45. 3. Lead through method
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• A teach pendant is used to guide the manipulator arm through the specified
motion sequence.
• The pendant consists of feather-touch keys and dials to regulate movements
of the arm.
• All the motion sequences are recorded into memory for later playback.
• In another method of lead through programming, a simulator is used, which
simulates the movements of a robot.
• The simulator is grasped manually and guided through the desired path at
the required speed.
• The position of each axis is sampled at a constant frequency and is stored in
the computer.

46. 4. Off-line Programming
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• This method involves preparation of the robot program
offline, in a manner similar to NC part programming.
• Offline robot programming is typically accomplished on a
computer terminal.
• After the program has been prepared, it is entered into the
robot memory for use during the work cycle
• This program is downloaded into the memory of the robot
controller during operation.
• The robot can be interfaced with the manufacturing
database of a CAD/CAM system.

47. Advantages of Off-line Programming
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1. Production time of the robot is not lost due to
delays in teaching the robot new task.
2. Offline programming can be done when the robot is
still on production of the previous job.
3. It is flexible, easy and convenient
4. The productivity of robots is high as time spent on
programming is minimized.

48. Applications of robots: 1. Material Transfer
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•Simple pick-and-place operations
•Transfer of work part from one conveyor to another
•Palletizing operations
•Loading into boxes etc.

49. Applications of robots: 2. Machine Loading
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• Load parts onto machines or unload the finished parts from the machine.
• To hold the part in position during processing over the machine.
• Other machine loading and unloading operations are
• Die casting
• Injection molding
• Hot forging
• Stamping press operations
• Turning, milling etc.
• Controlling several machines simultaneously for loading and unloading
operation

50. Applications of robots:
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3 Welding operations : Includes
• Spot welding
• Arc welding like TIG and MIG welding
4. Spray coating: Spray paintings are used on automobile bodies
and domestic products. But the operation poses health hazards due to
exposure to its chemical constituents.
A robot used for spray painting should have smooth motion and be able
to generate paint spray of uniform thickness.

51. Applications of robots: 2. Machine Loading
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5. Processing operations such as drilling, riveting, grinding,
polishing, debarring, wire brushing and water jet cutting.
6. Assembly operations with the use of adaptable programmable
assembly system and robot type arms. These are used in
• Automobile industries
• Toy industries
• Pump industries etc.
7. Inspection application by the use of probes, optical sensors,
measuring devices etc.