Introduction to robotics

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INTRODUCTION TO
ROBOTICS
Shalet K S
Asst. Prof.

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DEFINITION:
A reprogrammable and multifunction machine designed to move materials,
tools or specialized instruments, by programmed movements to carry out a
variety of tasks.
Characteristics:
• Versatile
• Flexibility
• Environment adaptable

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Isaac Asimov coined the term robotic and he published three famous
robotic laws :
• A robot can't damage a human being, nor allow this to be damaged.
• A robot must obey a human order, except when these orders clash
with the first law.
• A robot must always protect themselves as long as this protection
doesn’t clash with the first and second laws.
HISTORIC VIEW

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DEGREES OF FREEDOM
The degrees of freedom (dof) of a rigid body is defined
as the number of independent movements it has.
Higher number dof indicates an increased flexibility in
positioning a tool.
For each degree of freedom a joint is required.
The degrees of freedom located in the arm define the configuration.
Three degrees of freedom located in the wrist give the end effector all the flexibility.
A total of six degrees of freedom is needed to locate a robot’s hand at any point in its
work space.

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ROBOT ARM
 The three degrees of freedom located in the arm of a robotic system
are:
 The rotational traverse: is the movement of the arm assembly about
a rotary axis, such as left-and-right swivel of the robot’s arm about
a base.
 The radial traverse: is the extension and retraction of the arm or the
in-and-out motion relative to the base.
 The vertical traverse: provides the up-and-down motion of the arm
of the robotic system.

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ROBOT WRIST
• Wrist assembly is attached to end-of-arm
• End effector is attached to wrist assembly
• Function of wrist assembly is to orient end effector
– Body-and-arm determines global position of end effector
• Two or three degrees of freedom:
– Roll
– Pitch
– Yaw

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 The three degrees of freedom located in the wrist, which
bear the names of aeronautical terms, are
 Pitch or bend: is the up-and-down movement of the
wrist.
 Yaw: is the right-and-left movement of the wrist.
 Roll or swivel: is the rotation of the hand.
CONT…….

ROBOT ANATOMY
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Joints and Links
The manipulator of an industrial robot consists of a series of joints and links. Robot
anatomy deals with the study of different joints and links and other aspects of the
manipulator's physical construction. A robotic joint provides relative motion
between two links of the robot. Each joint, or axis, provides a certain degree-of-
freedom (dof) of motion. In most of the cases, only one degree-of-freedom is
associated with each joint. Therefore the robot's complexity can be classified
according to the total number of degrees-of-freedom they possess.

ARM GEOMETRY
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Each joint is connected to two links, an input link and an output link. Joint provides
controlled relative movement between the input link and output link. A robotic link is
the rigid component of the robot manipulator. Most of the robots are mounted upon a
stationary base, such as the floor. From this base, a joint-link numbering scheme may
be recognized as shown in Figure 7.5.1. The robotic base and its connection to the
first joint are termed as link-0. The first joint in the sequence is joint-1. Link-0 is the
input link for joint-1, while the output link from joint-1 is link-1—which leads to
joint-2. Thus link 1 is, simultaneously, the output link for joint-1 and the input link for
joint-2. This joint-link-numbering scheme is further followed for all joints and links
in the robotic systems.

CLASSIFICATION OF JOINTS
12https://www.youtube.com/watch?v=SMcqUjQ2Swo

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a) 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.
b) Orthogonal joint (type U joint)
This is also a translational sliding motion, but the input and output links are
perpendicular to each other during the move.
c) 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.
CONT…….

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d) Twisting joint (type T joint)
This joint also involves rotary motion, but the axis or rotation is parallel
to the axes of the two links.
e) Revolving joint (type V-joint, V from the “v” in revolving)
In this type, axis of input link is parallel to the axis of rotation of the
joint. However the axis of the output link is perpendicular to the axis of
rotation.
CONT…….

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EXAMPLE
• Sketch following manipulator configurations
• (a) TRT:R, (b) TVR:TR, (c) RR:T.
Solution: ???

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EXAMPLE
• Sketch following manipulator configurations
• (a) TRT:R, (b) TVR:TR, (c) RR:T.
Solution:
T
R
T
V
(a) TRT:R
R
T
R
T R
TR
R
(c) RR:T(b) TVR:TR

ROBOT CONFIGURATION
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Basically the robot manipulator has two parts viz. a body-and-arm
assembly with three degrees-of-freedom; and a wrist assembly with
two or three degrees-of-freedom.
For body-and-arm configurations, different combinations of joint types
are possible for a three-degree-of-freedom robot manipulator. Five
common body-and-arm configurations are outlined in figure

RECTANGULAR OR CARTESIAN - COORDINATED
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https://www.youtube.com/watch?v=ci_mpRERMog

BODY AND ARM ASSEMBLY…….
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• Notation LOO:
• Consists of three sliding joints, two of
which are orthogonal.
• Other names include rectilinear robot and
x-y-z robot.

 HAS THREE LINEAR AXES OF MOTION.
 X REPRESENTSD LEFT AND RIGHT MOTION
 Y DESCRIBES FORWARD AND BACKWARD MOTION.
 Z IS USED TO DEPICT UP-AND-DOWN MOTION.
 THE WORK ENVELOPE OF A RECTANGULAR ROBOT IS A CUBE
OR RECTANGLE, SO THAT ANY WORK PERFORMED BY ROBOT
MUST ONLY INVOLVE MOTIONS INSIDE THE SPACE.
CONT…….
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ADVANTAGES:
 They can obtain large work envelope because travelling along
the x-axis, the volume region can be increased easily.
 Their linear movement allows for simpler controls.
 They have high degree of mechanical rigidity, accuracy, and
repeatability due to their structure.
 They can carry heavy loads because the weight-lifting capacity
does not vary at different locations with in the work envelope.
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DISADVANTAGES:
 They makes maintenance more difficult for some models
with overhead drive mechanisms and control equipment.
 Their movement is limited to one direction at a time.
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 Pick-and-place operations.
 Adhesive applications(mostly long and straight).
 Advanced munition(military weapons) handling.
 Assembly and subassembly(mostly straight).
 Automated loading CNC lathe and milling operations.
 Nuclear material handling.
 Welding.
APPLICATIONS:
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CYLINDRICAL-COORDINATED
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https://www.youtube.com/watch?v=Hj7PxjeH5y0

BODY AND ARM ASSEMBLY
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• Notation TLO:
• Consists of a vertical column, relative
to which an arm assembly is moved
up or down
• The arm can be moved in or out
relative to the column

 Has two linear motions and one rotary motion.
 Robots can achieve variable motion.
 Movements : Z – up and down movement
Z – Rotation
Y – forward and backward
 Rotational ability gives the advantage of moving rapidly to the point in z
plane of rotation.
 Results in a larger work envelope than a rectangular robot manipulator.
 Suited for pick-and-place operations.
CONT…….
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Their vertical structure conserves floor space.
Their deep horizontal reach is useful for far-reaching operations.
Their capacity is capable of carrying large payloads.
ADVANTAGES:
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DISADVANTAGES:
Their overall mechanical rigidity is lower than that of the
rectilinear robots because their rotary axis must overcome inertia.
Their repeatability and accuracy are also lower in the direction of
rotary motion.
Their configuration requires a more sophisticated control system
than the rectangular robots.
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ASSEMBLY
COATING APPLICATIONS.
CONVEYOR PALLET TRANSFER.
DIE CASTING.
FOUNDARY AND FORGING APPLICATIONS.
INSPECTION MOULDING.
INVESTMENT CASTING.
MACHINE LOADING AND UNLOADING.
APPLICATIONS:
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SPHERICAL OR POLAR COORDINATED
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ARM AND BODY ASSEMBLY
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Consists of a sliding arm (L joint) actuated
relative to the body, which can rotate about
both a vertical axis (T joint) and horizontal
axis (R joint)

 Has one linear motion and two rotary motions.
 The work volume is like a section of sphere.
 The first motion corresponds to a base rotation about a vertical axis.
 The second motion corresponds to an elbow rotation.
 The third motion corresponds to in-out, translation.
 Larger work envelope than the rectilinear or cylindirical robot.
 Design gives weight lifting capabilities.
 Advantages and disadvantages same as cylindirical-coordinated design.
CONT…….
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DIE CASTING
DIP COATING
FORGING
GLASS HANDLING
HEAT TREATING
INJECTION MOLDING
MACHINE TOOL HANDLING
MATERIAL TRANSFER
PARTS CLEANING
PRESS LOADING
STACKING AND UNSTICKING.
APPLICATIONS:
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JOINTED ARM OR REVOLUTE COORDINATED
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It is similar to the configuration of a human arm. It consists of a vertical column
that swivels about the base using a T-joint. Shoulder joint (R-joint) is located at the
top of the column. The output link is an elbow joint (another R joint).

CONT…….
 Resembles human arm
 Consist of series of links connected by rotary
joints, referred from the base it is shoulder,
arm and wrist joints.
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SCARA ROBOT
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 SCARA (Selective Compliance Assembly
Robot Arm) is a subclass used for rapid and
smooth motions.
 It is similar in construction to the jointer-
arm robot, except the shoulder and elbow
rotational axes are vertical. It means that
the arm is very rigid in the vertical
direction, but compliant in the horizontal
direction.
https://www.youtube.com/watch?v=97KX-j8Onu0

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SPECIFICATION
Axis movement
Axis
Robot motion range
Robot motion speed
Repeatability
Weight
Payload
Robot mass
Work envelope
V - Reach
H – Reach
Structure

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Axes - The individual segments of each robot manipulator are
connected with mechanical joints - each serves as an axis of movement.
The most common industrial robots have six axes of movement. The
number and placement of axes determines the flexibility of each model.
Robot Motion Range - Much like the joints between bones, robot
axes have limits to each movement. Every axis has a specific scope of
motion.
AXIS MOVEMENT

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Robot Motion Speed - Each axis moves at a different speed.
They are listed as degrees traveled per second.
Repeatability - Industrial robots are known for their accuracy. But
this ability to return to an exact location again and again, known as a
robot's repeatability, can vary with each model. More precision-driven
applications will require tighter repeatability figures. Repeatability is
listed as a millimeter of alteration plus or minus from the point.
CONT…….

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Payload - The weight capacity of each robot manipulator is its
payload. This is a critical specification and includes the tooling
weight as well.
Robot Mass - Every robot has a specific weight or mass. This
number indicates how much the robot manipulator weighs. It does not
include the weight of the robot's controller.
CONT…….

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V-Reach - How high can the robot go? A robot's vertical reach
specification refers to the height of the robot when it extends upwards from
the base.
H-Reach - How far can a robot reach? The horizontal reach measures the
distance of the fully extended arm - from the base to the wrist.
CONT…….

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Structure - Robots are engineered with different structures. The most
common by far is the vertical articulated type, sometimes called a
vertical jointed-arm robot. Other structure types include SCARA,
Cartesian and parallel kinematic robots.
CONT…….

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ROBOT SAFETY
• Robot safety depends on the size of the robot’s work envelope, its
speed, and its proximity to humans.
• Safety sensors and monitoring provide the capability of the work
cell controller and its sensors to monitor the operation during
unsafe conditions in the cell.
• Safety is an important component in
industrial automation.

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• Safeguarding is the prevention of injury or accident in the
workplace.
• Training is a major factor in the successful implementation of any
advanced technology in a company or operation.
• Safety guidelines have been developed by researchers pertaining
to safety issues in robots to reduce or eliminate accidents in a
production environment.
CONT…….

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ROBOT COMPONENTS
• The basic components of an industrial robot are the
– manipulator
– the end effector (which is the part of the manipulator).
– the power supply
– and the controller.
• The manipulator, which is the robot’s arm, consists of segments
jointed together with axes capable of motion in various directions
allowing the robot to perform work.

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ROBOT COMPONENTS
• The end effector which is a gripper tool, a special device, or
fixture attached to the robot’s arm, actually performs the work.
• Power supply provides and regulates the energy that is converted
to motion by the robot actuator, and it may be either electric,
pneumatic, or hydraulic.
• The controller initiates, terminates, and coordinates the motion of
sequences of a robot. also it accepts the necessary inputs to the
robot and provides the outputs to interface with the outside world.

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ROBOT CONTROL SYSTEMS
To perform as per the program instructions, the joint movements an
industrial robot must accurately be controlled. Micro-processor-based
controllers are used to control the robots. Different types of control that
are being used in robotics are given as follows.
a. Limited Sequence Control
It is an elementary control type. It is used for simple motion cycles, such as
pick-and-place operations. It is implemented by fixing limits or mechanical
stops for each joint and sequencing the movement of joints to accomplish
operation. Feedback loops may be used to inform the controller that the
action has been performed, so that the program can move to the next
step. Precision of such control system is less. It is generally used in
pneumatically driven robots.

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b. Playback with Point-to-Point Control
Playback control uses a controller with memory to record motion sequences in a work
cycle, as well as associated locations and other parameters, and then plays back the
work cycle during program execution. Point-to-point control means individual robot
positions are recorded in the memory. These positions include both mechanical stops
for each joint, and the set of values that represent locations in the range of each joint.
Feedback control is used to confirm that the individual joints achieve the specified
locations in the program.
c. Playback with Continuous Path Control
Continuous path control refers to a control system capable of continuous simultaneous
control of two or more axes. The following advantages are noted with this type of
playback control: greater storage capacity—the number of locations that can be stored
is greater than in point-to-point; and interpolation calculations may be used, especially
linear and circular interpolations.
CONT…….

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d. Intelligent Control
An intelligent robot exhibits behavior that makes it seems to be intelligent. For
example, it may have capacity to interact with its ambient surroundings; decision-
making capability; ability to communicate with humans; ability to carry out
computational analysis during the work cycle; and responsiveness to advanced
sensor inputs. They may also possess the playback facilities. However it requires a
high level of computer control, and an advanced programming language to input
the decision-making logic and other ‘intelligence' into the memory.
CONT…….

Introduction to robotics

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