Robotic ch 1 1

Introduction to robotics
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Chapter one

Knowledge base for Robotics
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Typical knowledgebase for the design and operation of
robotics systems:
 Dynamic system modeling and analysis
 Feedback control
 Sensors and signal conditioning
 Actuators and power electronics
 Hardware/computer interfacing
 Computer programming
 Disciplines:-athematics, physics, biology, mechanical engineering, electrical engineering,
computer engineering, and computer science.

What is a Robot ?
A machine that resembles a human being and does mechanical routine tasks on command.
 A machine that looks and acts like a human being.
 An efficient but insensitive person.
 An automatic apparatus / A clever mechanical device – automaton
 Something guided by automatic controls.
E.g. remote control
 a computer whose main function is to produce motion.
A robot is an automatic, general-purpose device whose primary function is to produce motion in
order to accomplish some task.
Robotics Association of America :-An industrial robot is a re-
programmable, multifunctional manipulator designed to move
materials, parts, tools, or specialized devices through variable
programmed motions for the performance of a variety of tasks.

Definitions:-
 A robot is a system that posses a number of links attached serially to each other with
joints where each joint can be moved by some type of actuator.
 The manipulator can be moved in space and be placed in any desired location
within the work space of the robot.
 It can carry a certain amount of load, and each link is controlled be a central
controller which controls the actuators.
 … a machine able to extract information from its environment and use
knowledge about its world to act safely in a meaningful and purposeful manner.
(Ron Arkin, 1998)
 … an autonomous system which exists in the physical world, can sense its
environment and can act on it to achieve some goals.

What is Robotics?
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Robotics is the study of robots, autonomous embodied systems
interacting with the physical world.
Robotics addresses perception, interaction and action, in the physical
world.
 Robotics is the art, knowledge base, and the know-how of designing,
applying, and using robots in human endeavors.
 Robotics is an interdisciplinary subject that benefits from mechanical
engineering, electrical and electronic engineering, computer science,
biology, and many other disciplines.

Fundamental Laws of Robotics
The term robotics was then introduced by Asimov as the science
devoted to the study of robots which was based on the three
fundamental laws:
 1.A robot may not injure a human being or, through inaction,
allow a human being to come to harm.
 2. A robot must obey the orders given by human beings, except
when such orders would conflict with the first law.
 3.A robot must protect its own existence, as long as such
protection does not conflict with the first or second law.

 The first industrial robot: UNIMATE
 1954: The first programmable robot is
designed by George Devol, who coins the
term Universal Automation. He later shortens
this to Unimation, which becomes the name
of the first robot company (1962).
UNIMATE originally automated the
manufacture of TV picture tubes
History of Robotics: I
 HISTORY OF ROBOTICS
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PUMA 560 Manipulator
History of Robotics: II
 1978: The Puma (Programmable
Universal Machine for Assembly)
robot is developed by Unimation
with a General Motors design
support
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 1980s: The robot industry enters a phase of rapid growth.
Many institutions introduce programs and courses in robotics.
Robotics courses are spread across mechanical engineering, electrical
engineering, and computer science departments.
Adept's SCARA robots Barrett Technology ManipulatorCognex In-Sight Robot
History of Robotics: III
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2003: NASA’s Mars Exploration Rovers will launch
toward Mars in search of answers about the history of
water on Mars
 1995-present:
 Emerging applications in small
robotics and mobile robots drive a
second growth of start-up
companies and research
History of Robotics: IV
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 A manipulator (or an industrial robot) is composed of a
series of links connected to each other via joints. Each
joint usually has an actuator (a motor for eg.) connected to
it.
 These actuators are used to cause relative motion between
successive links. One end of the manipulator is usually
connected to a stable base and the other end is used to
deploy a tool.
Industrial Robot

Robot and Crane
 Basically, both robotic manipulator and crane are similar, their
main difference is that the crane is controlled be a human who
operates and controls the actuators, whereas the robot
manipulator is controlled by a computer that runs a program.
 The motions of the robot are controlled through a controller that
is under the supervision of the computer, which, itself is running
some type of a program.
 Thus, the robot is designed to be able to perform any task that
can be programmed simply by changing the program.

Classification of Robots
According to the Japanese Industrial Robot Association
robots are classified as:
 Manual- handling Devices:- with multiple degrees of
freedom that is actuated by an operator.
 Fixed-Sequence Robot:- performs the successive stages of
a task according to a predetermined, unchanging method
and is hard to modify.
 Variable-Sequence Robots:- same as fixed-sequence robot
in performance, but easy to modify the sequence of the
task.
 Playback Robot:- robot that repeats the same motions
according to the recorded information of human operator.

Cont…..
 Numerical Control Robot:- the operator supplies robot with
a movement program rather than teaching it the task
manually.
 Intelligent Robot:-a robot with the means to understand its
environment and the ability to successfully complete a task
despite change in the surrounding conditions under which it
is to be performed.

Advantages of Robots
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 Robots increase productivity, safety, efficiency, quality, and
consistency of products.
 Robots can work in hazardous environments without the need.
 Robots need no environmental comfort.
 Robots work continuously without experiencing fatigue(exhaust ) of
problem.
 Robots have repeatable precision at all times.
 Robots can be much more accurate than human.
 Robots replace human workers creating economic problems.
 Robots can process multiple stimuli or tasks

Disadvantages of Robots
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 Robots lack capability to respond in emergencies.
 Robots, although superior in certain senses, have limited
capabilities in Degree of freedom, Dexterity(skill),
Sensors, Vision system, real time response.
 Robots are costly, due to Initial cost of equipment,
Installation costs, Need for Peripherals, Need for training,
Need for programming.

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Why use robots?
To Perform 4A tasks in 4D environments
4A: Automation, Augmentation, Assistance,
Autonomous
4D: Dangerous, Dirty, Dull, Difficult

Robot Components
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 A robot as a system consist of the following elements
which are integrated together to perform a whole:
 Manipulator
 End effector
 Actuator
 Sensor
 Controller

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 Manipulator
 Manipulator consists of joints and links.
 Joints provide relative motion
 Links are rigid members between joints
 joint types: linear and rotary
 Each joint provides a “degree-of-freedom”
 Most robots possess five or six degrees-of-freedom
 Robot manipulator consists of two sections:-
 Body-and-arm – for positioning of objects in the robot's work
volume and
 Wrist assembly and Gripper – for orientation of objects

Cont….
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 Manipulator Configurations:
 Cartesian Coordinates
 Cylindrical Coordinates
 SCARA
 Polar Coordinates
 Jointed Arm

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Joints and Links:
 Connected to each joint are two links, one that we call the input link, the other called the
output link.
Manipulator Joints:
 Translational motion
 Linear joint (type L)
 Orthogonal joint (type O)
 Rotary motion
 Rotational joint (type R)
 Twisting joint (type T)
 Revolving joint (type V)
Joint Notation Scheme:
 Uses the joint symbols (L, O, R, T, V) to designate joint types used to construct robot
 manipulator

Controller (The brain)
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 Issues instructions to the robot.
 Controls peripheral devices.
 Interfaces with robot.
 Interfaces with humans.
Pedestal (Human waist)
 Supports the manipulator.
 Acts as a counterbalance.

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How do robots move?
Simple joints (2D)
 Prismatic -- sliding along one axis
-- square cylinder in square tube
 Revolute — rotating about one axis
Compound joints (3D)
 ball and socket = 3 revolute joints
 round cylinder in tube = 1 prismatic, 1 revolute
Degrees of freedom = Number of independent motions
 3 degrees of freedom: 2 translation, 1 rotation
 6 degrees of freedom: 3 translation, 3 rotation

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End Effectors
The end-effector is specified according to the task the robot should
execute.
For material handling tasks, the end-effector consists of a gripper of
proper shape and dimensions determined by the object to be
grasped.
To position the wrist which is then required to orient the
manipulator’s end-effector.
If arbitrary orientation in 3D space is desired, the wrist must possess
at least three DOFs provided by revolute joints.

Robots Degrees of Freedom
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Degrees of Freedom: Number of independent position variables
which would has to be specified to locate all parts of a mechanism.
In most manipulators this is usually the number of joints.
1 D.O.F. 2 D.O.F. 3 D.O.F

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 Manipulator Configurations:
 Cartesian Coordinates
 Cylindrical Coordinates
 SCARA
 Polar Coordinates
 Jointed Arm

Cont…
Body-and-Arm configurations:
 Common body-and-arm configurations are:
1) Cartesian Coordinate Body-and-Arm Assembly
 Consists of three sliding joints, two of which are orthogonal
 Other names include rectilinear robot and x-y-z robot
 straight, or linear motion along three axes:
 in and out, (x)
 back and forth, (y)
 up and down (z)
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Cont…
2) Polar Coordinate Body-and-Arm Assembly
 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)
 Also called spherical-coordinates
Rotation about the base
 Rotation about an axis in the vertical plane to raise and lower it.
 reaches in and out.
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Cont…
3)Cylindrical Body-and-Arm Assembly
 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
 Rotation about the base or shoulder. (θ)
 up and down (z)
 in and out. (R)
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Cont…
4) SCARA Robot
 SCARA stands for Selectively Compliant Assembly Robot Arm
 Similar to jointed-arm robot except that vertical axes are used for shoulder
and elbow joints to be compliant in horizontal direction for vertical insertion
tasks
 the same work area as a cylindrical-coordinates robot.
 the reach axis includes a rotational
joint in a plane parallel to the floor.
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Cont…
5) Jointed-Arm Robot
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Wrist Configurations:
 Wrist assembly is attached to end-of-arm
 End effectors is attached to wrist assembly
 Function of wrist assembly is to orient end effectors
 Body-and-arm determines global position of end effectors
 Two or three degrees of freedom:
 Roll
 Pitch
 Yaw
 Notation :RRT
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Manipulators
Robot Configuration:
Cartesian: PPP Cylindrical: RPP
Spherical: RRP
SCARA: RRP
(Selective Compliance Assembly Robot
Arm) : RRR
Hand coordinate:
n: normal vector; s: sliding vector;
a: approach vector, normal to the
tool mounting plate

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Robot Joints
 Robots may have different types of joints, such as linear, rotary, sliding, or
spherical.
 Since spherical joints are difficult to control, hence, they are not common
in robotics.
 Most robots have either a linear (prismatic) joint or a rotary (revolute)
joint.
 Prismatic joints are linear; there is no rotation involved.
 Revolute joints are rotary; there is no linear translation involved.

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Robot Characteristics
A robot can be characterized using the following
specifications:
Payload: the maximum amount of weight a robot can
carry. The payload of robots compared with their own
weight is usually very small.
Reach: The maximum distance a robot can reach
within its work envelop. It is a function of the robot’s
joint lengths and its configuration.

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Precision: how accurately a specified point can be
reached. It is a function of the actuator resolution as
well as feedback element.
Repeatability: how accurately the same position can
be reached if the motion is repeated many times.
Repeatability is much more important than precision.

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Workspace
Workspace is the collection of points in space
which a robot can reach.
The robot workspace depends on its
configuration and size of its links and
joints.
The workspace may be found either
mathematically by writing equations that
define robot’s links and joints
or empirically by moving each joint through

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Robot Application
Robots are applicable in environments where humans cannot perform task,
consistent performance and better quality. Some of the applications of robot are:
Machine loading
Pick and place operations
Welding
Painting
Sampling
Assembly operation
Manufacturing
Surveillance
Medical applications
Assisting disabled individuals
Hazardous environments
Underwater, space, and remote locations

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