2. Introduction to Robots
■ An industrial robot is a reprogrammable, multifunctional
mechanical device designed to manipulate and transport parts,
tools, or specialized devices through variable programmed
motions to perform variety of tasks.
3. Definitions of robot
■ “Robot is a device that performs functions ordinarily ascribed to
human beings, or operates with what appears to be almost human
intelligence”.
■ “An industrial robot is a reprogrammable multifunctional
manipulator designed to move material, parts, tools or specialized
devices through various programmed motions for the performance
of a variety of tasks”.
4. Robot Components
■ The four basic components of an industrial robot are:
– Manipulator
– End-effector
– Power supply
– Control system
5.
6. Manipulator
■ Manipulator is called arm and wrist, is a mechanical unit that
provides motions similar to those of a human arm and hand.
■ The end of the wrist can reach a point in space having a specific
set of coordinates, in a specific orientation.
■ Most robots have six rotational joints.
■ The manipulator is powered by hydraulic or pneumatic cylinders or
rotary actuators and electric or hydraulic motors are used to power
the various axes of motions.
7. End effector
■ The end of the wrist in a robot is equipped with an end-effector,
also called end-of-arm tooling.
■ Depending on the type of operation, conventional end-effector are
equipped with any of the following:
– Grippers, hooks, scoops, electromagnets, vacuum cups and
adhesive fingers for material handling
– Spray guns for painting
– Attachment for spot welding and arc welding and arc cutting
– Power tools such as drills, nut drivers and burrs
– Measuring instruments such as dial indicators
8. Power supply
■ The power supply is the source of energy used to move and
regulate the robot’s drive mechanisms.
■ The energy usually comes from three sources: electric, hydraulic
and pneumatic.
9. Control system
■ Control system also known as controller is the communications
and information-processing system that gives commands for the
movements of the robot.
■ The controller is the brain of the robot, as it stores data to initiate
and terminate movements of the manipulator.
■ It is also the nerves of the robot, as it interfaces with computers
and other equipment such as manufacturing cells or assembly
systems.
■ Feed back devices such as transducers, are an important part of
the control system.
10. Basic robot motions
■ There are six basic motions.
■ Wrist motions
– Yaw: It refers to rotation in a horizontal plane through the arm.
– Pitch: It refers to rotation in a vertical plane through the arm.
– Roll: It refers to rotation in a plane perpendicular to end of the
arm.
■ Arm and Body Motions
– Vertical traverse: It refers to up and down motions of the arm
– Radial traverse: It refers to the extensions and retraction of the
arm.
– Rotational traverse: It refers to rotation about the vertical axis.
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12.
13. Classifications of robots based
on the type of control
■ Point-to-point control robot
■ Continuous path control robot
■ Controlled path (computed trajectory) control robot
14. Point-to-point control robot
■ A point to point control robot also known as PTP robot, is able to
move from one specified point to another. But it cannot stop at
arbitrary points not previously designated.
■ It is the simplest and least expensive type of control.
■ This type of robot is fast, accurate and inexpensive.
15. Continuous path control robot
■ A robot with continuous path control is able to stop at any specified
number of points along a path.
■ If no stop is specified, the robotic arm may not stay on a straight
line or constant curved path between specified points.
16. Controlled path (computed
trajectory) control robot
■ Control equipment on controlled path robots can generate straight
lines, circles, interpolated curves, and other paths with high
accuracy.
■ Path can be specified in geometric or algebraic terms in some of
these robots.
■ Good accuracy can be obtained at any point along the path.
17. Classification of robot based on
level of control involved
■ Sequence robots
■ Playback robots
■ Intelligent robots
18. Sequence robots
■ In sequence robot, the manipulator progresses successively
through the various stages of an operation according to the
predetermined sequence.
■ The sequence robots represent the lowest level of control.
19. Playback robots
■ Playback robots use a more sophisticated control unit in which a
series of positions or motions are ‘taught’ to the robot, recorded
into memory and then repeated by the robot under its own control.
20. Intelligent robots
■ In an intelligent robot, the robot can determine its own
behaviour/conduct through its functions of sense and recognition.
■ The intelligent robots represents the most sophisticated level of
control.
21. Work volume
■ The maximum volume of the space that a robot can reach
mechanically is called the work volume or work envelope or robot
reach or the workspace of a robot.
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23.
24. Joint drive system
■ Hydraulic drive system
■ Pneumatic drive system
■ Electrical drive system
25. ■ Its sophisticated for robots
■ Associated in large robots
■ This drive is only for rotational drive or linear drive
HYDRAULIC DRIVE
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27. ■ It do not provide as much speed & power
■ Associated in small robots
■ Accuracy & repeatability is better
■ Actuated by dc motor or stepper motor
■ This drive is only for rotational drive, by drive train & gear systems
■ Perform linear systems by pulley systems
ELECTRIC DRIVE
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29. ■ For smaller systems with less DOF
■ Performs pick & place operations only with fast cycles
■ This system having compliance or ability to absorb some shock
■ This is only for rotary operations.
PNEUMATIC DRIVE
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31. ■ The controller act as a brain of the robot
■ This is a information processing device.
■ The inputs are both desired and measured positions.
■ Velocity (or) other variables in a process whose o/p systems are
drive signals to control the motors or actuators.
■ Types of robot control systems:
– Non-servo (open loop) control
– Servo (closed loop) control
Robot control
32. Non-servo (open loop) control
■ Non servo robots do not have a feedback capability and their axes
are controlled through a system of mechanical stops and limit
switches.
33.
34. Servo (closed loop) control
■ The servo controlled robots are controlled through the sensors that
automatically monitor the robots axes and associated components
for position and velocity.
■ This feed back is compared to pre-taught information which has
been programmed and stored in the robot’s memory.
37. TYPES OF ROBOT CONTROL
■ Limited sequence control
■ Playback with point to point control
■ Playback with continuous path control
■ Intelligent control
38. Limited sequence control
■ Limited sequence robot do not use servo control to indicate
relative positions of the joints. Instead, they are controlled by
setting limit switches and/or mechanical stops together with a
sequencer to coordinate and time the actuation of the joints.
■ Thus the limited sequence robots use pick and place motion.
■ These type of robots are normally pneumatically actuated.
39. Playback with point to point
control
■ Point to point robots are the most common of the four
classifications and can move from one specified point to another
but cannot stop at arbitrary points not designated previously.
40. Playback with continuous path
control
■ Continuous path motion is an extension of the point to point
method. The difference is that continuous path involves the
utilization of more points. Its path can be an arc, a circle, or a
straight line.
■ Greater storage capacity
■ Interpolation calculations
41. Intelligent control
■ The intelligent control robot is capable of performing some of the
functions and tasks carried out by human beings. It can detect
changes in the work environment by means of sensory perception.
42. Robot End Effectors
■ End effector is attached to the end of the wrist arm to make
intentional contact with an object or to produce the robot’s final
effect on its surroundings by performing a particular task.
■ Depending on the type of operation, conventional end-effector are
equipped with any of the following:
– Grippers, hooks, scoops, electromagnets, vacuum cups and
adhesive fingers for material handling
– Spray guns for painting
– Attachment for spot welding and arc welding and arc cutting
– Power tools such as drills, nut drivers and burrs
– Measuring instruments such as dial indicators
44. Grippers
■ A gripper is like the arm of an operator that establishes the
connection between the work piece and robot.
■ The functions of the gripper mechanism is to translate some form
of power input into the grasping action of the fingers against the
part.
■ The mechanism must be able to open and close the fingers and to
exert sufficient force against the part to hold it securely.
45. Types of Grippers
■ Mechanical grippers
■ Magnetic grippers
■ Vacuum grippers
■ Other types
– Adhesive grippers
– Piercing grippers
– Hooks, scoops and other miscellaneous devices
46. Mechanical grippers
■ A mechanical gripper is an end effector that uses mechanical
finger or clamp actuated by mechanism to grasp an object that
actually make contact with the object.
■ Two groups
– Internal gripper
– External gripper
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48.
49. Types of Mechanical grippers
■ Single grippers
■ Dual grippers
■ Interchangeable grippers
■ Multiple fingered grippers
■ Standard grippers
■ Sensory grippers
52. Interchangeable grippers
■ The interchangeable grippers consist of interchangeable fingers
that can be used on single gripper mechanism.
53. Vacuum Grippers
■ In vacuum grippers, the suction cups are used to create negative
pressure and thus the vacuum to parts so that they adhere to the
grippers.
56. Other Type of Grippers
■ Adhesive Grippers
– Adhesive substance (sticky tape) performs the grasping action.
■ Piercing grippers
– The component to be handled are pierced
– This method is only used where slight damage to the
component is acceptable.
■ Hooks, Scoops & Ladles and other devices
– Hooks can be used as end effector to handle containers of
parts and to load and unload parts from overhead conveyors
– Scoops and ladles can be used to handle certain materials in
liquid (chemicals and molten metals) or powder form (food
materials)
– Inflatable bladder or diaphragm is expanded to grasp the
object.
57. End-of-Arm-Tooling
■ In many applications, the robot is required to manipulate a tool
rather than a work part. In such applications, the tool is used as
the end-effector, which is attached directly to the robot wrist.
■ Examples
– Spot welding guns
– Arc welding torch
– Spray painting nozzle
– Rotating spindles
– Heating torch
– Water jet cutting tool
58. Sensors in Robotics
■ Sensors are the sensory system of a robot (must like the five
senses that human system have – touch, sight, sound, smell and
taste) and the sensors measure environmental data (such as
touch, distance, light, sound, strain, rotation, magnetism, smell,
temperature, inclination, pressure, altitude, etc.).
■ A robot sensor is a device or transducer that detects information
about the robot and its surrounding, and transmits it to the robot’s
controller.
59. Type of robotic sensors
■ Classification of sensors on the basic of their location.
– Internal sensors
– External sensors
■ Classification of sensors on the basic of their physical activation
– Contact sensors
– Non-contact sensors
60. ■ Internal Sensors
■ Internal sensors use feedback information internally to ascertain
their present condition.
■ Examples:
– Potentiometers and optical encoders
– Tachometers
■ External Sensors
■ External sensors are physically mounted on the robot or on
process equipment in the robot cell so that they can be usually
seen.
■ Examples:
– Micro switches
– Touch or tactile sensors
– Photoelectric devices
– Proximity sensors
61. ■ Contact sensors
■ Contact sensors are devices used in robotics to obtain information
associated with the physical contact between a manipulator hand
and objects in work space.
■ Types of contact sensors
– Touch sensors
– Force sensors
■ Non contact sensors
■ Non contact sensors measure the condition of an object without
physically touching the part.
■ Examples
– Range sensors
– Proximity sensors
– Acoustic sensors
– Vision sensors
62. Industrial Robot Applications
■ Hazardous or uncomfortable work environment for human beings.
■ Repetitive tasks.
■ Difficult handling for humans.
■ Multi shift operation.
■ Infrequent changeovers
■ Part position and orientation are established in the work cell
63. Categories of industrial robot
applications
■ Material handling applications
– Pick and place operations
– Palletizing and/or depalletizing
– Machine loading and/or unloading
– Stacking and insertion operations
■ Processing operations
■ Assembly operations
■ Inspection operations
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70.
71. Robot Programming
■ A robot program can be defined as a path of movements of its
manipulator, combined with peripheral equipment action to support
the work cycle.
■ The process of robot programming involves ‘teaching’ it the task to
be performed, storing the program, executing the program, and
debugging it.
72. Methods of robot programming
■ Manual programming
■ Teach pendent programming
■ Walk through programming
■ Computer terminal programming
– Online programming
– Off-line programming
73. Manual Programming
■ In this manual programming, the operators set-up program by
fixing limit switches, stop, cams etc.
■ The manual programming method is adequate for limited
sequence pick and place robots.
74. Teach pendant programming
■ Teach pendent programming, also known as lead through
programming, uses a teach pendent to instruct a robot to move in
working space.
■ Teach pendent is a small hand held device with toggle switches
and dials to control the robots physical movements.
75.
76. Walk through programming
■ In this method, the programmer or the operator physically grasps
the end effector and manually moves it through the motion
sequence, recording the path into the memory.
77. Computer terminal
programming
■ The computer terminal programming, uses an English-like
language to establish the logical sequence of a work cycle.
■ Online programming
■ The online programming method requires the availability of a
robot. It gives the programmer the ability to see the motions of the
robot actually executing the program as it is being developed.
■ Offline programming
■ Off-line robot programming is typically accomplished on a remote
computer terminal. After the program has been prepared, it is
entered into the robot memory for use during the work cycle.
78. Robot programming Languages
■ All robots are programmed with some kind of programming
language. These programming languages command the robots to
more to certain locations, to signal outputs, and to read inputs.
■ Three basic categories
■ Specialized robot language
■ Robot libraries for a new general purpose language
■ Robot libraries for an existing computer language
79. Some commonly uses robot
programming languages and their
sources
■ AML-IBM
■ HELP- General Electric
■ VAL & VAL II – Unimation, Adept
■ RAIL – Automatrix
■ MCL – McDonnel Douglas
■ AL – Standford University
80. Robot Accuracy and
Repeatability
■ Three measures of precision of the robot’s movement are
– Control resolution
– Accuracy
– Repeatability
81. Control resolution
■ Control resolution is defined as the capability of the robot’s
positioning system to divide the range of the joint into closely
spaced points, called addressable points, to which the joint can be
moved by the controller.
82.
83. Accuracy
■ Accuracy is defined as the robot’s ability to position and orient the
end of its wrist at a defined target point within the work volume.
