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					                            MFGE 404

    Computer Integrated Manufacturing

          ATILIM               UNIVERSITY
               Manufacturing Engineering Department

                       Lecture 8– Industrial Robots

                              Fall 2005/2006
What is an Industrial Robot
• An industrial robot is a
  programmable,       multi-
  functional    manipulator
  designed      to     move
  materials, parts, tools, or
  special devices through
  variable     programmed
  motions       for      the
  performance of a variety
  of tasks.

• The robot, therefore,
  represents        flexible
  automation and so it fits
  well in the frame of CIM
Robot Construction
• The manipulator of an industrial robot consists of a number of
  rigid links connected by joints of different types, controlled
  and monitored by a computer.
• The link assembly is connected to the body, which is usually
  mounted on a base.
• To a large extend, the physical construction of a robot
  resembles a human arm.
• A wrist is attached to the arm.
• To facilitate gripping or handling, a hand is attached at the
  end of the wrist, this hand is called an end-effector.
• The complete motion of the end-effector is accomplished
  through a series of motions and positions of the links, joints,
  and wrist.
• Robot construction is concerned with the types and sizes of
  joints, links and other aspects of the manipulator.
Joints and Links or Robots
• A joint of an industrial robot is similar to a joint in the human
  body: It provides relative motion between two parts of the body.

• Each joint, or axis as it is sometimes called, provides the robot
  with a so-called degree-of-freedom (D.O.F) of motion.

• In nearly all cases, only one degree-of-freedom is associated
  with a joint.

• Connected to each joint are two
  links, an input link and output
• Links are the rigid components of
  the robot manipulator.
• The purpose of the joint is to
  provide    controlled  relative
  movement between the input link
  and the output link.
Joints and Links or Robots
•   Most of robots are mounted on a stationary base on the floor.
•   The base and its connection to the first joint is Link 0.
•   Link 0 is the input link of joint 1, the first joint of a series of joints used
    in the construction of the robot.
•   The output link of joint 1 is the link 1.
•   Link 1 is the input lint to joint 2, whose output link is link 2, and so forth.
Classification of Robot Joints
•   Nearly all industrial robots have mechanical joints that can be classified
    into one of the five types:
          Two types that provide translational motion.
          Three types that provide rotary motion

1. Linear Joint (type L joint)
    The relative movement between the input link and the output link
    is a translational sliding motion, with the axes of the two links
    being parallel.
Classification of Robot Joints

2. Orthogonal joint (type O joint)
  This is also a translational sliding motion, but the input link and
  output links are perpendicular to each other during the move.
Classification of Robot Joints

3. Rotational Joint (type R joint)
  This type provides rotational relative motion, with the axis of
  rotation perpendicular to the axes of the input and output links.
Classification of Robot Joints

4. Twisting Joint (type T joint)
  This joint also involves rotary motion, but the axis of rotation is
  parallel to the axes of the two links.
Classification of Robot Joints

5. Revolving Joint (type V joint, V from the “v” in revolving)
  In this joint type, the axis of the input link is parallel to the axis
  of rotation of the joint, and the axis of the output link is
  perpendicular to the axis of rotation
Common Robot Configurations
•   A robot manipulator can be divided into two sections:
          A Body-and-arm assembly.
          Wrist assembly.

•   There are usually three degree-of-freedom associated with the body-
    and-arm , and either two or three degrees-of-freedom with the wrist.

•   At the end of the manipulator’s wrist is a device related to the task that
    must be accomplished by the robot. The device, called an end effector, is
    usually either:
         1. A gripper for holding a workpart, or
         2. A tool for performing some process.

•   The body-and-arm of the robot is used to position the end effector, and
    the robot’s wrist is used to orient the end effector.
Body-and-Arm Configurations
•   There are five basic configurations commonly available in commercial
    industrial robots:

1. Spherical (Polar) Configuration
    This configuration consists of a sliding arm (L joint) actuated relative to
       the body, that can rotate about a vertical axis (T joint) and a
       horizontal axis (R joint)
Body-and-Arm Configurations
2. Cylindrical Configuration
   •   This robot configuration consists of a vertical column, relative to
       which an arm assembly is moved up and down. The arm can be
       moved in and out relative to the axis of the column.
   •   A T joint to rotate the column about its axis. An L joint is used to
       move the arm assembly vertically along the column. An O joint is
       used to achieve radial movement of the arm.
Body-and-Arm Configurations
3. Cartesian (Rectangular) Configuration
   •   It is composed of three sliding joints, two of which are orthogonal.
Body-and-Arm Configurations
4. Jointed-arm robot (articulated) Configuration
   •   This robot manipulator has the general configuration of a human
       arm. The joined arm consists of a vertical column that swivels about
       the base using a T joint.
   •   At the top of the column is a shoulder joint (R joint), whose about
       link connects to an elbow joint (R joint)
Body-and-Arm Configurations
5. SCARA (Selective Complains Assembly Robot Arm)
   •   This configuration is similar to the jointed robot except that the
       shoulder and elbow rotational axes are vertical, which means that
       the arm is very rigid in the vertical direction, but complaint in the
       horizontal direction.
Wrist Configurations
 •   The robot’s wrist is used to establish the orientation of the end
     effector. Robot wrists usually consists of two or three degrees-of-
     freedom. The three joints are defined as:
      1. Roll, using a T joint to accomplish rotation about the robot’s arm axis.
      2. Pitch, which involves up-and-down rotation, typically a R joint.
      3. Yaw, which involves right-and-left rotation, also accomplished by
         means of an R-Joint.

 •   A two D-O-F wrist typically includes only roll and pitch joints (T and
     R joints)
Joint Notation System

•   The letter symbols for the five joint types (L, O, R, T, and V) can be used
    to define a joint notation system for the robot manipulator.
•   In this notation system, the manipulator is described by the joints that
    make up the body-and-arm assembly, followed by the joint symbols that
    make up the wrist.
•   For example, the notation TLR:TR represents a five degree-of-freedom
    manipulator whose body-and-arm is made up of :
         1. A twisting joint (Joint 1 = T)
         2. A linear joint (joint 2 = L)
         3. A rotational joint (joint 3 = R)
•   The wrist consists of two joints:
         4. A twisting joint (joint 4 = T)
         5. A rotational joint (joint 5 = R)

•   A colon separates the bod-and-arm notation from the wrist notation.
Joint Notation System - Example
•   Designate the robot configurations shown below, using the joint
    notation scheme.

•   Solution
1. This configuration has two linear joints, Hence, it is designated LL.

2. This configuration has three rotational joints, Hence, it is designated RRR.
3. This configuration has one twsiting joint and one linear joint. This is
   indicated by TL
Joint Notation System - Example
•   The robots shown below are equipped with a wrist that has twisting, rotary,
    and twisting joints in sequence from the arm to the end-effector. Give the
    designation for the complete configuration of each robot

•   For the robots shown above, the complete designation is as follows:
(a) LRL:TRT      (b) RRL:TRT              (c) TRL:TRT              (d) LVL:TRT
Work Volume

•   The work volume (work envelope) of the manipulator is defined as the
    envelope or space within which the robot can manipulate the end of its

•   Work volume is determined by:
    1. the number and types of joints in the manipulator (body-and-arm
       and wrist),
    2. the ranges of the various joints, and
    3. the physical sizes of the links

•   The shape of the work volume depends largely on the robot’s
Work Volume
• A Cartesian robot has a rectangular work volume
Work Volume
• A cylindrical robot has a cylindrical work volume
Work Volume
• A spherical robot tends to have a sphere as its work volume
Joint Drive System
• A robot joints are actuated using any of three possible types of
  drive systems:
        1. Electric drive.
        2. Hydraulic drive.
        3. Pneumatic drive

• Electric drive systems use electric motors as joint actuators.
• Hydraulic and pneumatic drive systems use devices such as linear
  pistons and rotary vane actuators to accomplish the motion of
  the joint.

•   Pneumatic drive is typically limited to smaller robots used in simple
    material transfer applications.

•   Electric drive and hydraulic drive are used on more-sophisticated
    industrial robots.

•   Electric drive robots are relatively accurate compared with hydraulically
    powered robots. By contrast, the advantages of hydraulic drive include
    greater speed and strength.
Robot Control Systems
• The actuations of the individual joints must be controlled in a
  coordinated fashion for the manipulator to perform a desired
  motion cycle.
• Robot controllers can be classified into four categories:
       1. Limited sequence control.
       2. Point-to-point control.
       3. Continuous path control.
       4. Intelligent control.

• Limited sequence control uses mechanical stops to provide the
  extreme ranges of motion and when motion command is used,
  the joint is driven until the mechanical stop is reached. This
  technique is no longer used.
Robot Control Systems

• Point-to-point involves the specification of the starting point and
  end point (and often intermediate points) of the robot motion
  requiring a control system which renders some feedback at those
• This technique is used       for   spot   welding,   pick-and-place
  operations and so on.

• Continuous Path Control requires the robot end effector to follow
  a stated path from the starting point to the end point.
• This technique is required in many applications that require the
  actual tracing of a contour, for instance, in arc welding or spray
• The continuous path robots usually follow a series of closely
  spaced points on a path and these points are defined by the
  control unit rather than the programmer. In many cases, the
  paths between points are straight lines
Robot Control Systems

• Intelligent Control An intelligent robot is one that exhibits
  behavior that makes it seem intelligent. Some of the
  characteristics that make a robot appear intelligent include the
  capacity to :
   1. Interact with its environment.
   2. Make decisions when things go wrong during the work cycle.
   3. Make computations during the motion cycle.
   4. Respond to advanced sensor inputs such as machine vision.
End Effectors

• The end effector enables the robot to accomplish a specific task.
  Because of the wide variety of tasks performed by industrial
  robots, the end effector must usually be custom-engineered and
  fabricated for each different application.
• Two categories of end effectors are
        1. Grippers.
        2. Tools.

•   Tools are used in applications where the robot must perform some
    processing operation on the part. Examples of the tools are:
    1. Spot welding gun.
    2. Arc welding tool.
    3. Spray painting gun.
    4. Rotating spindle for drilling, grinding, and so forth.
    5. Assembly tool (e.g. automatic screw driver)
    6. Heating torch.
End Effectors

• Grippers are end effectors used to grasp and manipulate objects
  during the work cycle
Industrial Robot Applications

• The general characteristics of industrial work situations that tend
  to promote the substitution of robots for human labor are the
   1. Hazardous work environment for human.
   2. Repetitive work cycle.
   3. Difficult handling for human.
   4. Multishift operation.
   5. Infrequent changeover
   6. Part position and orientation are established in the work cell
Industrial Robot Applications

• Robots are being used in a wide field of applications in industry.
  Most of the current applications of industrial robots are in
• The applications can usually classified into one of the following
   1. Material handling applications
       1. Material transfer.
       2. Machine loading and/or unloading.
   2. Processing operations
       1. Spot welding
       2. Continuous arc welding
       3. Spray coating
       4. Other processing applications
   3. Assembly

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