Ec6003 robotics and automation notes

Robotics and Automation
EC 6003
[ELECTIVE]
Prepared By
JAI GANESH S
Asst.Professor – ECE
RMK College of Engineering and Technology

Unit 1 – Basic Concepts
• Definition and origin of robotics
• Different types of robotics
• Various generations of robots
• Degrees of freedom
• Asimov's laws of robotics
• Dynamic stabilization of robots

List of Reference
Unit # No.of
Period
Topic Text Book and
Reference Book
UNIT 1 - BASIC CONCEPTS
1 2 Definition and origin of robotics Mikell P Groover ( T1)
1 2 Different types of robotics Mikell P Groover ( T1)
1 1 Various generations of robots Deb S R ( R1)
1 1 Asimov's laws of robotics Mikell P Groover ( T1)
1 1 Degrees of freedom Mikell P Groover ( T1)
1 2 Dynamic stabilization of robots Online / Notes

Definition of a Robot:
• Word robot was coined by a Czech novelist
Karel Capek in a 1920 play titled Rossum’s
Universal Robots (RUR).
• Robota in Czech is a word for worker or
servant

• Official definition of robot was given by Robot
Industry Association (RIA), formerly known
as Robot Institute of America,
“A robot is a reprogrammable, multifunctional
manipulator designed to move material,
parts, tools or specialized devices through
variable programmed motions for the
performance of a variety of tasks”

Basic Parts of a Robot
Parts of the robot
– Manipulator
– Controller
– Teach pendant

AXES OF MANIPULATOR
6 axes
Servo motor control
Safety drives enable
Pay load of 16 kgs

INSTRUCTION FLOW - simple
TEACH
PENDANT
CONTROLLER MANIPULATOR
U
S
E
R

• Manipulator / Rover : This is the main body
of the Robot and consists of links, joints and
structural elements of the Robot.

• End Effectors : This is the part that generally handles
objects, makes connection to other machines, or
performs the required tasks. It can vary in size and
complexity according to the applications / requirements.

• Actuators : Actuators are the muscles of the
manipulators. Common types of actuators are
servomotors, stepper motors, pneumatic cylinders
etc.

• Sensors : Sensors are used to collect information about the internal
state of the robot or to communicate with the outside environment.
Robots are often equipped with external sensory devices such as a
vision system, touch and tactile sensors etc which help to
communicate with the environment

• Controller : The controller receives data from the
computer, controls the motions of the actuator
and coordinates these motions with the sensory

Origin of a Robot
• The origin of industrial robots lies way back
in 1700's and have grown tremendously
over decades

Mid 1700 – J.de vaucanson
Built several human sized mechanical dolls that plays music

1805 – h.maillardet – mechanical
doll capable of drawing
pictures

1946 – GC devol –
controller
device – records
electrical
signals
magnetically
and play them
back to operate
mechanical
machine

1954 – cw kenward – robot design

And many improvements
• 1959 – first commercial robot introduced by
planet corporation controlled by switches
• 1960 – first unimate robot introduced for
manipulator control
• 1966 – Trallfa, built and installed spray
painting robot
• 1968 – mobile robot named “shakey”
• 1971 – stanford arm, a small electrically
powered robot arm

Contd…
• 1973 – first computer type robot programming
language developed. (AL , WAVE)
• 1974 – invention of all electric drive robot
• Followed by industrial implementations for
manufacturing works
• 1979 – development of SCARA type robot
• 1982 – IBM introduced Robots for assembly using
robotic arm
• 1990’s – invention of walking robots and
rehabilitation robots, space robots, defense
applications
• 2000’s – Micro and Nano robots using smart
materials, underwater and ariel vehicles

Future robots
• Robotic engineers are designing the next
generation of robots to look, feel and act
more human, to make it easier for us to
warm up to a cold machine.
• Realistic looking hair and skin with
embedded sensors will allow robots to
react naturally in their environment.

Future robots - Personal Robots

Future robots - Professional Robots
in the field of Drug Delivery

Future robots - Rehabilitation

Classification of robots
Based on Applications
• Industrial Robots
• Tele Robots
• Explorer Robots
• Laboratory Robots
• Hobbyist Robots
• Educational Robots
• Medical Robots
Based on Configuration
• Polar Configuration
• Cylindrical Configuration
• Cartesian Coordinate
Configuration
• Jointed Arm Configuration
Entire robots can be classified in to 2 broad categories:

Classification Based on
Applications
• Industrial Robots:
– An industrial robot is a robot system used for
manufacturing. Industrial robots are automated,
programmable and capable of movement on three
or more axes.

Defining Parameters for
industrial robots
• Number of axes– two axes
are required to reach any
point in a plane;
• three axes are required to
reach any point in space.
• To fully control the
orientation of the end of
the arm(i.e. the wrist)
three more axes (yaw,
pitch, and roll) are
required.
• Some designs (e.g. the
SCARA robot) trade
limitations in motion
possibilities for cost,
speed, and accuracy.

industrial robots
• Degrees of freedom– number of
independent motions that are allowed to the
body, this is usually the same as the number
of axes.

industrial robots
• Working envelope– an envelope is the
region of space a robot can reach during its
normal range of motion.

industrial robots
• Kinematics – the actual arrangement of rigid
members and joints in the robot, which determines
the robot's possible motions.
• Classes of robot kinematics include articulated,
cartesian, parallel and SCARA.
“Kinematics” the branch of mechanics concerned with the motion of objects
without reference to the forces which cause the motion.

Kinematics – articulated robot

Kinematics – cartesian robots

Kinematics – parallel robots

industrial robots
• Carrying capacity or payload – how much weight a
robot can lift.
• Speed– how fast the robot can position the end of its
arm. This may be defined in terms of the angular or
linear speed of each axis or as a compound speed i.e.
the speed of the end of the arm when all axes are
moving.
• Acceleration – how quickly an axis can accelerate.
Since this is a limiting factor a robot may not be able
to reach its specified maximum speed for
movements over a short distance or a complex path
requiring frequent changes of direction.

industrial robots
• Accuracy – how closely a robot can reach a commanded
position. When the absolute position of the robot is measured
and compared to the commanded position the error is a
measure of accuracy. Accuracy can be improved with external
sensing, for example a vision system or Infra-Red. Accuracy can
vary with speed and position within the working envelope and
with payload.
• Repeatability – how well the robot will return to a programmed
position. This is not the same as accuracy. It may be that when
told to go to a certain X-Y-Z position that it gets only to within
1 mm of that position. This would be its accuracy which may be
improved by calibration. But if that position is taught into
controller memory and each time it is sent there it returns to
within 0.1mm of the taught position then the repeatability will
be within 0.1mm.

Applications
• Tele Robots
Tele robotics is the area of
robotics concerned with the
control of semi-autonomous
robots from a distance,
chiefly using Wireless
network (like Wi-Fi,
Bluetooth, the Deep Space
Network, and similar) or
tethered connections. It is a
combination of two major
subfields, teleoperation and
telepresence

Applications
• Explorer Robots
They are used to go where
humans cannot go and fear to
go. Eg: to explore cave, in deep
under water, to rescue people in
sunken ships. Used in Hazardous
Environments. Eg: Military
application

Applications
• Laboratory Robots
Laboratory robotics is
the act of using robots
in biology or chemistry
labs. For example,
pharmaceutical
companies employ
robots to move
biological or chemical
samples around to
synthesize novel
chemical entities or to
test

Applications
• Hobbyist Robots
This category of robots are
generally used for
entertainment purpose and
experimenting purpose. These
robots usually equipped with
speech synthesis techniques

Applications
• Educational Robots
Educational robotics is a broad term that
refers to a collection of activities,
instructional programs, physical platforms,
educational resources and pedagogical
philosophy. There are many schools which
are using the robot teacher.

Applications
• Medical Robots
A medical robot is a
robot used in the
medical sciences. They
include surgical robots.
These are in most tele
manipulators, which
use the surgeon's
actions on one side to
control the "effector"
on the other side.

Configuration
• Polar Configuration
Has one linear motion and
two rotary motions. It uses a
telescoping arm that can be raised or
lowered about a horizontal pivot.(α)
.The pivot is mounted on a rotating
base.(θ). A arm also has the capability to
move in and out to provide a linear
motion(x). The various joints provide the
robot with the capability to move its
arm within a spherical space and hence
it is also referred as Spherical coordinate
robot.

Configuration
These robots uses a vertical
column and a slide that can be
moved up or down along the
column. The robot arm is
attached to the slide so that it
can be moved radially with
respect to the column. By
rotating the column, the robot is
capable of achieving a work
space that approximates a
cylinder.
Work Envelope: Cylinder
Cylindrical Configuration

Configuration
Cartesian Coordinate Configuration
These robots uses three
perpendicular slides to
construct the x,y and z axes. Other
names are sometimes applied to
this configuration such as XYZ
robots and rectilinear robot. By
moving the three slides relative to
one another, the robot is capable
of operating within a rectangular
work envelope.
Work Envelope: Rectangular

Configuration
Jointed Arm Configuration
Jointed arm
configuration can be
classified in to 2 types:
(i) Jointed Arm Vertical
Configuration
(ii) Jointed Arm
Horizontal Configuration
(SCARA)

Work Volume or work Envelope
• The work volume is determined by the
following physical characteristics of the
robot:
– The robot's physical configuration (type of
joints, structure of links)
– The sizes of the body, arm, and wrist
components
– The limits of the robot's joint movements

Robot Configuration: (a) Polar,
(b) Cylindrical, (c) Cartesian,
(d) Jointed arm

Work Envelope: (a) Polar (b)
Cylindrical, (c) Cartesian

Various Generations of Robots
• The evolution of robotics can be illustrated
as 4 generations

First generation @
Attended Robots
• A first-generation
robot is a simple
mechanical arm.
• These machines
have the ability to
make precise
motions at high
speed, many times,
for a long time

Second generation @
Robotics Process and Automation
• A second-generation robot has
rudimentary machine
intelligence.
• Such a robot is equipped with
sensors that tell it things about
the outside world.
• These devices include pressure
sensors, proximity sensors,
tactile sensors, radar, sonar,
ladar, and vision systems.
• A controller processes the data
from these sensors and adjusts
the operation of the robot
accordingly

Third generation @
Self Service and Automation
• The concept of a third-generation robot
encompasses two major avenues of evolving smart
robot technology
– The autonomous robot
• An autonomous robot can work on its own. It contains a
controller, and it can do things largely without supervision, either
by an outside computer or by a human being
– Insect robot
• There are some situations in which autonomous robots do not
perform efficiently. In these cases, a fleet of simple insect robots,
all under the control of one central computer, can be used.
• These machines work like ants in an anthill, or like bees in a hive.

Autonomous robots and insect
robots

Fourth generation @
Cognitive Robotics
• Any robot of a sort yet to be seriously put into operation is a
fourth generation robot.
• Examples of these might be robots that reproduce and evolve, or
that incorporate biological as well as mechanical components.

Fifth Generation @
Artificial Intelligence Robotics
• Robot controller will involve complete artificial
intelligence (AI), miniature sensors, and
decision making capabilities.

Asimov's laws of robotics
• The Three Laws of Robotics or Asimov's
Laws are a set of rules devised by the science
fiction author Isaac Asimov
First Law - A robot may not injure a human being or,
through inaction, allow a human being to come to
harm.
Second Law - A robot must obey the orders given it
by human beings except where such orders would
conflict with the First Law.
Third Law - A robot must protect its own existence
as long as such protection does not conflict with the
First or Second Laws.

First Law - A robot may not injure a human being
or, through inaction, allow a human being to
come to harm
• A tool must not be unsafe to use. Hammers
have handles and screwdrivers have hilts to
help increase grip.
• It is of course possible for a person to injure
himself with one of these tools, but that injury
would only be due to his incompetence, not the
design of the tool

Second Law - A robot must obey the orders given
it by human beings except where such orders
would conflict with the First Law
• A tool must perform its function efficiently
unless this would harm the user.
• This is the entire reason ground-fault circuit
interrupters exist.
• Any running tool will have its power cut if a
circuit senses that some current is not
returning to the neutral wire, and hence
might be flowing through the user.
• The safety of the user is paramount

Third Law - A robot must protect its own
existence as long as such protection does not
conflict with the First or Second Laws
• A tool must remain intact during
its use unless its destruction is
required for its use or for safety.
• For example, Dremel disks are
designed to be as tough as
possible without breaking unless
the job requires it to be spent.
• Furthermore, they are designed to
break at a point before the
shrapnel velocity could seriously
injure someone (other than the
eyes, though safety glasses should
be worn at all times anyway).

Why this Order? Why not other orders?

Degrees of freedom
• Industrial robots are designed to perform productive
work such as pick and place, welding, assembly, etc.,
the work is accomplished by enabling the robot to
move its body, arm and wrist through a series of
motion and positions. The individual joint motions
associated with the performance of a task are referred
to by the term Degrees of Freedom (DOF)
"Degrees of freedom, in a mechanics context, are
specific, defined modes in which a mechanical
device or system can move. The number of
degrees of freedom is equal to the total number
of independent displacements or aspects of
motion."

Joints and its types
• The robot's motion are accomplished by
means of powered joints.
• Three joints are associated with the action
of body and arm.
• Another three joints are generally used to
actuate the wrist
• Joints used in the industrial robotics are of
two types,
– Prismatic Joints - Used for Linear Motions
– Revolute Joints - Used for Rotational Motions

prismatic joint
• A prismatic joint provides a linear sliding
movement between two bodies, and is often
called a slider, as in the slider-crank linkage.
A prismatic pair is also called as sliding pair.
A prismatic joint can be formed with a
polygonal cross-section to resist rotation.

revolute joint
• A revolute joint (also called pin joint or hinge joint)
is a one-degree-of-freedom kinematic pair used in
mechanisms.
• Revolute joints provide single-axis rotation function
used in many places such as door hinges, folding
mechanisms, and other uni-axial rotation devices

types of rotating joints
• (i) Rotational joint (R Joint)
• (ii) Twisting joint (T Joint)
• (iii) Revolving joint. (V Joint)

Degrees of Freedom Associated
with Arm and Body of the Robot
• Vertical Traverse: This is
the capability to move the
wrist up or down to provide
the desired vertical attitude.
• Radial Traverse: This is the
capability to move the wrist
front and back which
provides the extension and
retraction movement.
• Rotational Traverse: This is
the capability to rotate the
arm in vertical axis.

Degrees of Freedom associated
with wrist of robot
• Wrist Roll: Also called as wrist
swivel, this involves rotation of
the wrist mechanism about the
arm axis
• Wrist Pitch: Given that the
wrist roll is in the centre
position, the pitch would
involve the up and down
rotation of the wrist. this is also
sometimes called as wrist bend
• Wrist Yaw: Given that the wrist
roll is the centre position , the
Yaw would involve the right or
left rotation of the wrist.

Unit 2 – Power Sources and
Sensors

Syllabus
• Robotic Drives
– Hydraulic
– Pneumatic
– Electric
• Actuators
– Hydraulic
– Pneumatic
– Electric
• Determination of HP of motor and gearing ratio
• Variable speed arangements
• Path determination
• Micro machines in robotics
• Machine vision
• Sensors in robotics

Robotic Drives
• A robot will require a drive system for moving
their arm, wrist, and body.
• The joints are moved by actuators powered by
a particular form of drive system.
• A drive system can also be used to determine
the capacity of a robot.
• there are three different types of drive systems
available such as:
– Hydraulic drive system,
– Pneumatic drive system, and
– Electric drive system,

Hydraulic Drive Systems:
• A hydraulic drive system is a quasi-
hydrostatic drive or transmission system that
uses pressurized hydraulic fluid to
power hydraulic machinery
• A hydraulic drive system consists of three
parts:
– The generator (e.g. a hydraulic pump), driven by
an electric motor;
– valves, filters, piping etc. (to guide and control the
system);and
– The actuator (e.g. a hydraulic motor or hydraulic
cylinder) to drive the machinery.

Examples of Hydraulic Drive Systems

Pneumatic Drive System
• Pneumatic systems use air as the medium
which is abundantly available and can be
exhausted into the atmosphere after
completion of the assigned task
• The pneumatic drive systems are especially
used for the small type robots, which have
less than five degrees of freedom.

Components of Pneumatic Drive
Systems

Components of Pneumatic Drive
Systems
• Air filters: These are used to filter out the contaminants from the air.
• Compressor: Compressed air is generated by using air compressors. Air
compressors are either diesel or electrically operated. Based on the
requirement of compressed air, suitable capacity compressors may be
used.
• Air cooler: During compression operation, air temperature increases.
Therefore coolers are used to reduce the temperature of the compressed
air.
• Dryer: The water vapor or moisture in the air is separated from the air by
using a dryer.
• Control Valves: Control valves are used to regulate, control and monitor
for control of direction flow, pressure etc.
• Air Actuator: Air cylinders and motors are used to obtain the required
movements of mechanical elements of pneumatic system.
• Electric Motor: Transforms electrical energy into mechanical energy. It is
used to drive the compressor.
• Receiver tank: The compressed air coming from the compressor is stored
in the air receiver.

Electric Drive Systems
• The electric drive systems are capable of
moving robots with high power or speed.
• The actuation of this type of robot can be
done by either DC servo motors or DC
stepping motors.

Actuators
• Actuators can be categorized by the energy
source they require to generate motion. For
example:
– Hydraulic actuators use liquid to generate
motion.
– Pneumatic actuators use compressed air to
generate motion.
– Electric actuators use an external power
source, such as a battery, to generate motion.

Advantages
• Hydraulic actuators are rugged and suited for high-force
applications. They can produce forces 25 times greater
than pneumatic cylinders of equal size. They also operate
in pressures of up to 4,000 psi.
• Hydraulic motors have high horsepower-to-weight ratio by
1 to 2 hp/lb greater than a pneumatic motor.
• A hydraulic actuator can hold force and torque constant
without the pump supplying more fluid or pressure due to
the incompressibility of fluids
• Hydraulic actuators can have their pumps and motors
located a considerable distance away with minimal loss of
power.

Disadvantages
• Hydraulics will leak fluid. Like pneumatic
actuators, loss of fluid leads to less efficiency.
However, hydraulic fluid leaks lead to cleanliness
problems and potential damage to surrounding
components and areas.
• Hydraulic actuators require many companion
parts, including a fluid reservoir, motors, pumps,
release valves, and heat exchangers, along with
noise-reduction equipment. This makes for linear
motions systems that are large and difficult to
accommodate.

Pneumatic Actuator
• Pneumatic actuators are the devices used
for converting pressure energy of
compressed air into the mechanical energy
to perform useful work.

Types Of Pneumatic Actuators
• There are three types of pneumatic actuator:
they are
– Linear Actuator or Pneumatic cylinders
– Rotary Actuator or Air motors
– Limited angle Actuators

Advantages
• The benefits of pneumatic actuators come from their
simplicity.
• Pneumatic actuators generate precise linear motion
by providing accuracy, for example, within 0.1 inches
and repeatability within .001 inches.
• Pneumatic actuators typical applications involve
areas of extreme temperatures.
• In terms of safety and inspection, by using air,
pneumatic actuators avoid using hazardous
materials. They meet explosion protection and
machine safety requirements because they create no
magnetic interference due to their lack of motors.

Disadvantages
• Pressure losses and air’s compressibility make
pneumatics less efficient than other linear-motion
methods. Compressor and air delivery limitations mean
that operations at lower pressures will have lower forces
and slower speeds. A compressor must run continually
operating pressure even if nothing is moving.
• To be truly efficient, pneumatic actuators must be sized
for a specific job. Hence, they cannot be used for other
applications. Accurate control and efficiency requires
proportional regulators and valves, but this raises the
costs and complexity.
• Even though the air is easily available, it can be
contaminated by oil or lubrication, leading to downtime
and maintenance.

Electric Actuators
• Electric Actuators are devices powered by
motor that converts electrical energy to
mechanical torque
Types Of Electric Actuators
• There are three types of pneumatic actuator:
they are
– DC Motors- is an electric motor that runs on direct
current (DC) electricity.
– AC Motors - is an electric motor driven by an
alternating current.
– Stepper Motors- (or step motor) is a brushless DC
electric motor that divides a full rotation intoa
number of equal steps.

Advantages
• Electrical actuators offer the highest precision-control
positioning.
• Their setups are scalable for any purpose or force
requirement, and are quiet, smooth, and repeatable.
• Electric actuators can be networked and reprogrammed
quickly. They offer immediate feedback for diagnostics
and maintenance.
• They provide complete control of motion profiles and
can include encoders to control velocity, position, torque,
and applied force.
• In terms of noise, they are quieter than pneumatic and
hydraulic actuators
• Because there are no fluids leaks, environmental hazards
are eliminated.

Disadvantages
• The initial unit cost of an electrical actuator is
higher than that of pneumatic and hydraulic
actuators.
• Electrical actuators are not suited for all
environments, unlike pneumatic actuators,
which are safe in hazardous and flammable
areas
• A continuously running motor will overheat,
increasing wear and tear on the reduction gear.
• The motor can also be large and create
installation problems.

Horsepower
• Horsepower (hp) is a unit of
measurement of power (the rate at
which work is done). There are many different
standards and types of horsepower. Two
common definitions being used today are
the mechanical horsepower (or imperial
horsepower), which is about 745.7 watts, and
the metric horsepower, which is
approximately 735.5 watts.

Calculation of 5252
• constant tangential force of 100 pounds was applied
to the 12" handle rotating at 2000 RPM,
POWER = FORCE x DISTANCE ÷ TIME
DISTANCE per revolution = 2 x π x radius
DISTANCE per revolution. = 2 x 3.1416 x 1 ft = 6.283 ft.
Now we know how far the crank moves in one revolution. How far does the
crank move in one minute?
DISTANCE per min. = 6.283 ft .per rev. x 2000 rev. per min. = 12,566 feet per
minute
Power = 100 pounds x distance per minute
Power = 100 lb x 12,566 ft. per minute = 1,256,600 ft-lb per minute

HORSEPOWER is defined as 33000 foot-pounds of work per minute.
HP = POWER (ft-lb per min) ÷ 33,000.
HP = (1,256,600 ÷ 33,000) = 38.1 HP.
TORQUE = FORCE x RADIUS.
If we divide both sides of that equation by RADIUS, we get:
(a) FORCE = TORQUE ÷ RADIUS
Now, if DISTANCE per revolution = RADIUS x 2 x π, then
(b) DISTANCE per minute = RADIUS x 2 x π x RPM
We already know
(c) POWER = FORCE x DISTANCE per minute
So if we plug the equivalent for FORCE from equation (a) and distance per minute from
equation (b) into equation (c), we get:
POWER = (TORQUE ÷ RADIUS) x (RPM x RADIUS x 2 x π)
Dividing both sides by 33,000 to find HP,
HP = TORQUE ÷ RADIUS x RPM x RADIUS x 2 x π ÷ 33,000
By reducing, we get
HP = TORQUE x RPM x 6.28 ÷ 33,000
Since
33,000 ÷ 6.2832 = 5252
Therefore
HP = TORQUE x RPM ÷ 5252

Variable Speed Arrangements
• In most of the practical systems it is required to
operate the motor at different speed as per the
requirements
This is achieved by the implementation of Gears

Gears
• A gear or cogwheel is
a rotating machine part having cut teeth, or
in the case of a cogwheel, inserted teeth
(called cogs), which mesh with another
toothed part to transmit torque

Path determination
• Path planning for industrial robots is an
essential aspect of the overall performance of
automation systems.

• Essentially, path planning algorithms
determine how an industrial robot arm
should approach a part, how it should
process a part, and how it should orient
itself for optimal productivity and to avoid
collisions.

The Role of Proper Robot Path
Planning in Production
• Robot Accuracy: a robot’s path needs to be
meticulously planned in order for it to productively
process a part with little or no error.
• Task Repeatability: once a robot’s path is well-
defined it can repeat the same task thousands of
times without variation to help accelerate
throughput.
• Product Quality: when products are created with a
high degree of accuracy and repeatability, there are
fewer mistakes and higher consistency, leading to
higher overall quality products.

Different types of Motion
• limited sequence,
• point-to-point (PTP),
• continuous path and
• intelligent.

Limited Sequence control
• Characteristics: Each link can only stop at a
few limited positions, controlled by sensors,
mechanical stops.

point-to-point (PTP),
• Each axis or joint has many stoppable positions.
However, trajectory is not controllable at will,
although it may be roughly deterministic
– One joint at a time
• Joints can not move simultaneously. Rather, one moves after
another, in some sequence.
– Slew motion
• All joints that require motion start simultaneously at default joint
speeds
– (linear) Joint interpolation
• All joints that require movement start simultaneously and stop
simultaneously.

Continuous path Control
• Several joints can move simultaneously in
some user-specified trajectory. The most useful
ones are linear and circular interpolations.
– Linear interpolation
• Regardless of robot configuration, the robot attempts to
achieve a linear line while maintaining the tool
orientation.
– Circular interpolation
• In circular interpolation, robot will achieve a circular
motion while maintain the tool orientation.

Intelligent control
• Motions are flexible based on sensors and
intelligent to cope with various situations

Sensors
• Uses of sensors:
– Safety monitoring
– Interlocks and work cell control
– Part inspection for quality control
– Determining position and related information
about objects in robot cell

Review Questions
• Working of fiber optic sensor
• Methods of path determining
• Gearing ratio
• Types of drives and sensors
• Element of robotic vision
• Tactile sensor working
• Proximity and Range sensor working

Unit – 3
Manipulators, Actuators and End
Effectors
Prepared by
JAI GANESH S
Asst. Prof – Dept. of ECE

Syllabus
UNIT III
MANIPULATORS, ACTUATORS AND GRIPPERS
• Construction of manipulators
– manipulator dynamics and force control
– electronic and pneumatic manipulator control circuits
• End effectors
– Various types of grippers
– Design considerations.
We will discuss second half first and then first Half

End Effectors
• In robotics, an end effectors are the device or
tool that's connected to the end of a robot
arm end enables the robot arm to perform
specific task
• Usually end effectors are custom engineered
for a particular task

Types of End Effectors
• There are wide segments of end effectors
required to perform the variety of different
work functions.
• The various types can be divided into two
major categories
– Grippers
– Tools

Grippers
• They are the end effectors used to grasp and
hold objects.
• They are widely used in machine loading and
unloading
• There are various types of grippers based on
how they grasp the objects
– Mechanical Gripper
– Magnetic gripper
– Suction gripper or vacuum gripper

General classifications of gripper – No.
of Grippers
• Single gripper
– This will have only one grasping device attached to
the robot
• Double gripper
– This will have 2 grasping devices attached to the
robot

• External Gripper
• Internal Gripper
General classifications of gripper – gripping surface

Mechanical Grippers – basic definition
and operation
• A mechanical gripper is an end effectors that uses
mechanical fingers actuated by a mechanism to
grasp an object.
• Fingers are some times called as jaws.

Constraining the part in the gripper
• Physical Constriction Method
• Friction between the fingers and workpart
– In this approach the fingers must apply a force
that id sufficient for friction to retain the part
against gravity, acceleration and any other forces

Friction between the fingers and
workpart

Types of gripper mechanism
• Classification based on finger movement
– Pivoting Movement
• Linear actuation
• Gear and rack actuation
• Cam actuation
• Screw actuation
• Rope and pulley actuation
• miscellaneous
– Linear or translational movement

Pivoting Gripper Mechanisms – Linear
Actuations

Pivoting Gripper Mechanisms – Gear
and Rack method

Pivoting Gripper Mechanisms – Cam
Actuated Method

Pivoting Gripper Mechanisms – screw
Actuated Method

Pivoting Gripper Mechanisms – rope
and pulley Actuated Method

Other Types of Gripper
• In addition to mechanical gripper there are
variety of other devices that can be designed
to lift and hold the objects
– Vacuum cups
– Magnetic
– Adhesive
– Hooks scoops and other miscellaneous Devices

Magnetic Gripper
• Suitable for handling ferrous materials
• Merits:
– Pick up time is very fast
– Variation in part size can be tolerated
– They have the ability to handle the metal parts with
holes
– Requires only one surface of gripping
• Demerits:
– Residual magnetism on work part
– Limited precision
– Slipping problem

Adhesive Grippers
• Suitable for grasping fabrics and other light
weight objects

Tools as End Effectors
• Spot welding tools
• Arc welding torch
• Spray painting nozzle
• Rotating spindle for
– Drilling
– Routing
– Brushing
– Grinding
• Liquid cement applicator for assembly
• Heating torches
• Water jet cutting tool

Consideration in gripper selection and
design
• The gripper must have the ability to reach the surface of a work
part.
• The change in work part size must be accounted for providing
accurate positioning.
• During machining operations, there will be a change in the work
part size. As a result, the gripper must be designed to hold a work
part even when the size is varied.
• The gripper must not create any sort of distort and scratch in the
fragile work parts.
• The gripper must hold the larger area of a work part if it has
various dimensions, which will certainly
increase stability and control in positioning.
• The gripper can be designed with resilient pads to provide more
grasping contacts in the work part. The replaceable fingers can
also be employed for holding different work part sizes by
its interchangeability facility

Check List of Factors in the selection
and design of grippers

Frame Transformation – Translation
of frame

Frame Transformation – Rotation of
the frame

Frame – Translation and Rotation

Typical homogeneous Transformation
Matrix

Determining 3x3 Rotational Matrix

Repeating the Procedure to determine
rotation along x and y

Manipulators – Links and Joints

Manipulator control
• Position Control
– Linear control of manipulator
• Open loop and closed loop control
• Trajectory following control
• Continuous and discrete control
– Non linear control of manipulator
• Adaptive control
• Lyapunov stability analysis
• Force control
– Pneumatic control
– Electronic control

Pneumatic Force Control
Advantages
– High effectiveness
– High durability and reliability
– Simple design
– High adaptability to harsh
environment
– Safety
– Easy selection of speed and
pressure
– Environmental friendly
– Economical
Limitations
• Relatively low accuracy
• Low loading
• Processing required before
use
• Uneven moving speed
• Noise

Components of Pneumatic Control
Circuits – 2 components
• Production and transportation of compressed
air
– Compressor
– Pressure Regulating Component

• Consumption of compressed air
– Execution component
• Single acting Cylinder
Components of Pneumatic Control Circuits – 2 components

Directional control valve
2/2 Directional control valve
3/2 Directional control valve

Control Valve
• Non return Valves
• Flow Control Valves
• Shuttle Valves

Few Basic Circuits
• Flow Amplification Circuit

Few Basic Circuits
• Signal Inversion

Few Basic Circuits
• Memory Function

Single Acting Cylinder Control
• Direct and Speed Control

Double Acting Cylinder
Direct control Single control

Electronic Force Control
• Merits
– Compact in size
– Consumes less power
– Faster response
– No noise as like in pneumatic systems

Characteristics of various control systems

Force control components
• Generally force control and position control is
achieved by using Electric Motors
– DC Motors
• Working Principle
• Speed control methods
– Flux Control Method
– Armature Control Method
– Voltage Control Method
– AC Motors
– Stepper Motors

Syllabus
• Multiple robots
• Machine interface
• Robots in manufacturing and non-
manufacturing applications
• Robot cell design
• Selection of robot.

Robot cell design
• Robot work cell can be organised in to various
arrangements or layouts:
• These layouts are classified in to 3 basic types
– Robot centered cell
– Inline robot cell
– Mobile robot cell

Types of Transfers
• Intermittent transfer
– Work parts will be transferred in the conveyer and all the parts stops and
starts for processing
• Continuous transfer
– Work parts will be transferred in the conveyer and will not stop for processing(
continuous movement)
– The position and orientation of the parts are not defined. (Gets Varied time to
time)
– Can be rectified by 2 means
• A Moving Baseline tracking system
– It involves the mechanism to move the robot along the path parallel to the line of travel of work
part
– Demands for addition al degrees of freedom
– Possibility of collision during multiple robots
• A Stationary baseline tracking system
– Robot will be stationary with continuous moving conveyor.
– Special tracking systems are equipped to track the orientation of the work part
– Demands for high computation power
– Complex design
• Non synchronous transfer
– Also called as power and free system
– Deals with the irregular arrival of parts

Consideration in workcell design

Applications of Robots
• Manufacturing Applications:
– Material Transfer and Machine loading and unloading
– Processing operations
• Spot welding
• Continuous arc welding
• Spray painting
• Other applications such as drilling, grinding, polishing,
riveting, waterjet cutting, laser drilling and cutting
– Assembly and inspection
• Assembly operations
• Inspection automation

Applications of Robots
• Non Manufacturing Applications
– Education and training
– Defense operations
– Rescue operations
– Explorations (Space, Underwater and hazardous
environments)
– Locomotion

Ec6003 robotics and automation notes

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