Robotics_EC368_Module_1.pptx

Prerequisite:
Power Electronics & Instrumentation, Microprocessors & Microcontrollers
Course objectives:
• To impart knowledge about the engineering aspects of Robots and their applications
Expected outcome:
• The students will have a thorough understanding about Robots and their applications
• The students will be able to analyse and design robotic structures.
Text Books:
1. Mikell and Groover, Industrial Robotics–Technology, Programming and Applications.
2. Saeed B. Niku Introduction to Robotics. Analysis and control, applications
3. Spong and Vidyasagar, Robot Dynamics and Control
4. Ashitava Ghosal, Robotics, Fundamental concepts and analysis, OXFORD University Press, 2006
5. Fu, K.S,Gonzalez,R.C,Lee, C.S.G.,Robotics, Control, Sensing, Vision and Intelligence
1
Module 1

Module 1
Introduction-Definition and origin of robotics
Robot Anatomy, Robot specifications
Robot characteristics-accuracy, precision, and repeatability
Areas of application, classification of robots.
Robotic arm -Components and structure, Types of joints and workspace, Common kinematic
arrangements, Wrists, End effectors.
2
Module 1

3
Module 1
Introduction To Robotics
• Developed by Hong Kong based-Hanson Robotics
• October 2017, the robot became a Saudi Arabian citizen

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Robotics:
• It is the art of designing, construction, and operation of a robot.
• Robotic system consist of robots, other devices and equipments
that are used along with these robots.
• Robots were developed for doing sophisticated and dangerous
jobs by mimicking human actions.

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Generation of Robots
• First generation robots were designed
to perform factory work.
• They performed simple tasks that were
dangerous or unpleasant for people.
• Used for welding, spray painting, moving
heavy objects, handle hot materials, etc.
• Second generation were capable of doing
more complex tasks and simulate many human
functions.
• Such robots move, sense surroundings, and
respond to changes in their environment.
1961 - The first industrial robot- UNIMATE used
by General Motors

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TODAY
• Industrial Robots: Perform many factory jobs – Welding, Painting, Assembly
• Medical Robot: Robotic surgery, Transport materials, Dispense medicine, Communicate
• Assistive Robots: For helping disabled person and senior people.
• Robots for explorations: Space, Underwater and Military purposes
• Household Robots: For cleaning, surveillance,

Anatomy of Robots:
• It deals with the physical construction of the
Body, Arm and Wrist of the machine.
• E.g.: Industrial Robot
• Body is attached to the base, arm is attached
to the body and the wrist is attached to the
arm.
• Body, arm and wrist assembly together is
known
as Manipulator.
• The tool or hand attached to the wrist is known
as End effecter.
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Base
Body
Arm
Wris
t
End effecter

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Four Common Robotic Configurations:
1. Polar Configuration 3. Cylindrical Configuration
2. Cartesian Coordinate configuration 4. Jointed arm configuration
Polar Configuration
• It uses telescopic arm that can be raised or
lowered about a horizontal pivot.
• The body can be rotated along the base.
• The robot has the capability of move its arm with
in a spherical space and hence the name “spherical
coordinate” robot.
Rotatio
n
Up and down
Ref: Mikell and Groover

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Cylindrical Configuration
• It uses vertical column and a slide.
• The slide can be moved up or down along
the column.
• Arm is attached to the slide so that it can
move radially w.r.t column.
• By rotating, the robot can move in a
cylindrical workspace, hence the name
cylindrical configuration.

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Cartesian coordinate Configuration
• It uses 3 vertical slides to construct the x, y
and z axes.
• These slides can be moved up and down (
along z axis), left and right ( along x axis)
and
radial ( along y axis).
• By moving all these axes, the robot can have
a rectangular workspace, hence the name
cartesian configuration.

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Jointed arm Configuration
• These are made up of rotating joints.
• This configuration is similar to human arm, hence known as
antropomorphic.

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Advantages of different configuration:
• Cartesian configuration has the advantage of repeatability of motion.
• Polar and jointed arm robot has maximum reach from its base because these
two can extend their arm significantly.
• Lifting capacity or load bearing capacity is more for Cylindrical and Cartesian
configuration

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Robot specifications
Number of axes
• Major Axes: Use to position the wrist of the robot
• Minor Axes: Used to orient the end effectors or tool
• Redundant axes: Used for reaching different regions
Speed of the robot
• Determines the ability of the robot to accomplish a given
work.
• It is described by the word ‘cycle time’ (total time from the
beginning to the end of a process)
• speed depends on Accuracy with which the wrist moves,
weight of the load, distance to which the arm has to reach.
(Ref: Mikell and Groover or Saeed B. Niku )

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Payload
• Maximum weight of the load that can be handled by the
robot.
• Depends upon the size, configuration, construction etc.
• It is specified under the condition that the robot’s arm is in
the weakest position.
• Net weight carrying capacity is the difference between rated
payload and the weight of the end effecter.
e.g.: Rated payload = 5kg and End effecter weight= 2kg
then Net weight carrying capacity = 5-2 = 3kg

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Spatial Resolution/ Precision
• Measure of smallest increment of movement into which the
robot can divide the work volume or space.
• Depends on the resolution of position control system,
feedback measurement system and mechanical inaccuracies.
• Resolution of position control depends on the bit storage
capacity in the control memory.
E.g.: A robot with one sliding joint with full range of 1m has a control
memory of 12 bit storage. Find the control system resolution.
Using 12 bit, it is possible to have 212 = 4096 increments.
So the control resolution will be 1m/4096 = 0.244mm

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Accuracy
• Ability of the robot to position its wrist end at the desired target
point within the work volume.
• Depends on the spatial resolution.
• The worst case of accuracy is when the target is at the middle of
the two adjacent control increment points.
• So the Accuracy = one half of the control resolution

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Repeatability
• Ability of the robot to position its wrist or end effecter at the
target point repeatedly.
• repeatability error is a random variable and will be having the
shape of normal/Gaussian distribution.
• E.g.: Actual target point is denoted as ‘T’. Because of the accuracy the robot
can reach only at point ‘P’. But during work, robot is reaching only at ‘R’.

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Areas of Application
• Material Handling and machine loading and unloading
• Processing Applications: Welding, spray painting etc.
• Assembly and inspection
• Defense, House hold, research security etc.

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Classification of Robots
1. Manual handling Device: Multiple degree of freedom and is actuated by a
operator.
2. Fixed Sequence Robot: Robot that performs the successive stages of a
task according to a predetermined, unchanging method.
3. Variable sequence: Same as that of fixed sequence but modifications are
possible.

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4. Playback robot: A human operator performs the task manually by leading
the robot which records the motion for later playback. The robot repeats
the same motion according to the recorded information.
5. Numerical control robot: The operator supplies the movement program
to the robot rather than teaching it the task manually.
6. Intelligent robot: Understand its environment and the ability to complete
its task despite changes in its surroundings.

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▪ Manipulators/ Rover
▪ End effecter
▪ Actuators
▪ Power supplies & power storage system
▪ Sensors
▪ Microprocessors & controllers
▪ Softwares (higher level & lower level)
Components of Robot

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Manipulators/ Rover:
• This is the main part of the robot, which include the various links ( body,
arm and wrist), joints and other structural elements.
End Effecter:
• The tool that is connected to the wrist for doing a particular job is called
end effecter.

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Actuators:
• Actuators are the primary movers which provide both force and motion.
• The control signals are send by control system to move the robots links and
joints.
• Common types are Hydraulics, pneumatic cylinders, permanent magnet
motors, stepper motors and linear motors.
Hydraulics
pneumatic cylinders
stepper motors
servo motors

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Sensors:
• Devices which is used to get the feedback from the working
environment.
• They are also used to collect information about the internal state of
the robot.
• These sensors help the controller of the robot to understand and
estimate the location and state of each link and joint of the robot.
• vision system, tactile and touch sensors, speech synthesizers,
ultrasonic, infrared sensors are some of the common sensors.

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Microprocessors and Controllers:
• Microprocessor is the brain of the robot.
• All the calculations and decisions are made by the processor with help
of sensor inputs.
• Controller controls the motion of the actuators and thereby coordinates
the motion according to the decisions by the processor.
Software:
• Three types of softwares are used in the robots.
• One is the Operating System of the robot processor.
• Second one is used to calculate the necessary motions of each joints
and links.
• Third one is for the specific application of the robot.
Football Match
BigDog by Boston

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Robotic Arm
Degree of Freedom:
• Individual joint motion associated with the robot is known as the DOF
• This number typically refers to the number of single-axis rotational joints in
the arm.
• Higher number indicates an increased flexibility in positioning a tool
The six degrees of freedom:
Forward/back
up/down
left/right
Roll
Yaw
Pitch

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Types of Joints
•The joints helps in the movement of the robotic links.
• Depending on the type and number of joints, the DOF freedom will vary.
• The different links of the robotic arm is connected by these joints .
1. Linear Joints
2. Rotational Joints
3. Revolving Joints
4. Twisting Joint
5. Orthogonal Joints
6. Cylindrical joints
7. Spherical Joints
Ref: Mikell and Groover

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Linear Joints/ Prismatic Joints:
• A prismatic joint provides a linear sliding movement between two bodies,
and is often called a slider.
• Generally represented by letter ‘P’ or ‘L’
• It is used for forward and backward movements
• It has only one DOF and the axes of the links should be parallel to each
other.
• Achieved by either telescopic mechanism or cylinder-piston mechanism

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Rotational Joints
• Used for rotational movements
• The rotation is perpendicular to the axes of input and output links.
• It has only one DOF
• Represented by letter ‘R’

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Revolving Joints
• It also provide rotational motion, but the axis of rotation is parallel to the
axes of the links.

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Twisted Joints
• It is a type of rotational motion.
• Additionally provides a twisting motion between input and output links.
• Axis of rotation is perpendicular to the output link
• Represented by letter ‘V’

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Orthogonal Joints
• Similar to linear joint.
•Input and output links are perpendicular to each other(orthogonal)
• Represented by letter ‘O’
Cylindrical Joints
• Provides both linear and rotational motion.
•It has two DOF

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Cylindrical
Spherical Joints
• Also known as ball and socket joint.
•It has largest range of motion and has 3 DOF

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• Typically a robotic arm can have a total of 6 DOF.
• Three DOF for body and arm for robot movement, three DOF for the wrist to
align the end effector
DOF for Body and Arm
1. Vertical Traverse: Move wrist up or
down to provide vertical attitude
2. Radial Traverse: Extent or retract the
arm from vertical centre of the robot.
3. Rotational Traverse: Rotation of arm
about the vertical axis.

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Wrist
1. Wrist Roll/ Swivel: Rotate the wrist about the arm axis
2. Wrist Pitch/ Bend: Given wrist roll is in its centre position, pitch
is
for up or down rotation of the wrist.
3. Wrist yaw: Given wrist roll is in centre, yaw is for left and right
rotation.

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COMMON KINEMATIC ARRANGEMENTS OF MANIPULATORS
• Kinematics deals with the motion of objects without reference to the forces
which cause the motion.
• In many possible ways prismatic (P) and revolute (R) joints can be used to
construct kinematic chains.
1. Articulated manipulator (RRR)
• Also called a Revolute, or Anthropomorphic manipulator.
• common revolute joint design is the parallelogram linkage
• The ABB IRB1400 articulated arm is shown in Figure
(Ref: Spong and Vidyasagar )

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• In this arrangement, the joint axis z2 is parallel to z1 and both z1 and z2 are
perpendicular to z0.
•
•The revolute manipulator provides relatively large freedom of movement
in a compact space.
• Advantage of parallelogram linkage is that actuator for joint 3 is located on
link 1. Since the weight of the motor is own by link 1, links 2 and 3 can be
made more lightweight and the motors themselves can be less powerful
• Dynamics of the parallelogram manipulator are simpler.

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2. Spherical Manipulator (RRP)
• Replacing the third or elbow joint in the articulated manipulator by a prismatic
joint one obtains the spherical manipulator.
The Stanford Arm
• spherical coordinates defining the position of the end-effector with respect to
a frame whose origin lies at the intersection of the three z axes are the same as
the first three joint variables.

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3. SCARA Manipulator (RRP)
• Selective Compliant Articulated Robot for Assembly
• Developed for assembly operations.
• SCARA has z0, z1, and z2 axes which are mutually parallel to each
other

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4. Cartesian manipulator (PPP)
• A manipulator whose first three joints are prismatic
• Joint variables are the Cartesian coordinates of the end-effector with
respect to the base.
• Cartesian manipulator is the simplest of all manipulators.
• useful for table-top assembly applications, and as gantry robots for transfer
of material or cargo
Epson Cartesian
Robot

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5. Cylindrical Manipulator (RPP)
• The first joint is revolute and produces a rotation about the base, while
the second and third joints are prismatic.
• Joint variables are the cylindrical coordinates of the end-effector with
respect to the base.
The Seiko RT3300 Robot

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6. Parallel Manipulator
• A parallel manipulator has two or more independent kinematic chains
connecting the base to the end-effector.
• The closed chain kinematics of parallel robots can result in greater
structural rigidity, and hence greater accuracy, than open chain robots
ABB IRB940 Tricept Parallel Robot

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PUMA robotic arm:
• Programmable Universal Machine for Assembly
or Programmable Universal Manipulation Arm
• A total of 6 variables are required, for specifying
the position and orientation of a rigid body in
space. Therefore PUMA has 6 axis of rotation
with one DOF per axis.
• The functioning of this robot is like a human arm.
Each DOF has an actuator for motion.

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Work Volume/Space
• Refers to the space within which the robot can manipulate its
wrist end.
• End effector is not included to define the work space because
it is an additional part to the basic robotic structure.
• Work volume depends on the following factors:
• Robot’s physical configuration(types of joints, structure
of links)
• Size of the body, arm and wrist components
• Limit of robot’s joint movements
(Ref: Mikell and Groover)

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Example for workspace according to configuration

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End Effectors:
• End effectors are the end point of a robotic arm.
• End effectors are selected based on the application
• Two major type:
1. Grippers
2. Tools
Grippers:
• Used to grasp and hold objects.
• Mainly used in pick and place applications.
• Types: Mechanical Grippers, Magnets, suction cups, adhesive etc.

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• The amount of FORCE to be exerted by the gripper to hold the object
is given by an equation;
Where µ = coefficient of friction
nf= number of contacting fingers
Fg = gripper force
w = weight of the object
• Here, the force of gravity is considered parallel to the contacting
surface.
• Along with the gravitational force, if there is a force due to
acceleration of the object, then a factor called ‘ g factor is also
included in the equation’.

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µnfFg =
w.g
Modified equation is given by:
g = 3 (when acceleration force is along the direction of gravity)
= 1 (when acceleration force is opposite to the direction of gravity)
= 2 (when acceleration force horizontal to the direction of gravity)

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Tools
• Tools are used for jobs like welding, spray painting, drilling etc.
Drilling welding
Grinding

Robotics_EC368_Module_1.pptx

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