Introduction to Robotics

Course Name: Introduction to Robotics
Course Code: MC2080
Wednesday, June 23, 2021 1
Course Instructor : Dr. Princy Randhawa
Department of Mechatronics Engg.
Manipal University Jaipur

Course Syllabus
Introduction to robotics, sensors, actuators, transmission and drives
used in robotic systems, power, torque, force calculations for robotic
systems, degrees of freedom (DOF), robot configuration, spatial
resolution, accuracy and repeatability, robot specifications, structure
of robotic system, robot motion analysis, robot dynamics and control,
trajectory planning, features of future robots, interactions of robots
with other technologies, characteristics of future robot tasks, robots
in construction trades, coal mining, utilities, military and fighting
operations, under sea robots, robots in space, service industry and
similar applications.

Course Outcome
MC2080.1 Outline the basics of robot structure, its classification, and specification
and robot drive systems.
MC2080.2 Study of type of sensors, their construction and working principle and
their application as per industrial robotic requirement.
MC2080.3 Study of robot motion analysis. To predict the position of robotic joint,
links, gripper with desired input.
MC2080.4 Study of statics and dynamics of robotic arm, and trajectory planning
using simple mathematical equations of dynamics.
MC2080.5 Learn various applications of robots in various environments.

Books/References
1. K Sun Fu, Gonzalez, Robotics- Control, Sensing, Vision, and
Intelligence, McGraw-Hill, 2nd edition, 2010.
2. Deb SR, Deb S., Robotics technology and flexible automation,
Tata McGraw-Hill Education, 1994.
Reference Books:
1. John, J. Craig, Introduction to Robotics – Mechanics and Control,
Pearson Education International, 3rd edition, 2004.
2. Yu Kozyhev, Industrial Robots Handbook, MIR Publishers, 1985.

Marks Scheme
 30 Marks –Sessional I & 2
 30 Marks Assignment- 15 Marks- Quiz
- 15 Marks- Seminar
 40 Marks –End Semester
.

Few Questions to be Answered
 What is a Robot?
 What is Robotics?
 Why do we Study Robotics?
 How can we Teach a Robot to perform a particular Task?
 What are possible applications of robots?
 Can a human being be replaced by a robot
and so on

What do you come up with first
when you think of Robotics
Mechanical Machines
Companions/Friends
Pets/Toys
Helpers
Dangerous Machines

A brief History of Robotics
Year Event and Development
1954 First patent on manipulator by
George Devot, the father of robot
1956 Joseph Engelberger started the
first robotics company: Unimation
1962 General Motors used the
manipulator: Unimate in die-casting
application
1967 General Electric Corporation made
a 4-legged vehicle.

1969  SAM was built by the NASA, USA
 Shakey an intelligent mobile robot, was built
by Stanford Research Institute (SRI)
1970  Victor Scheinman demonstrated a
manipulator known as Stanford Arm
 Lunokhod I was built and sent to the moon
by USSR
 ODEX 1 was built by Odetics
1973 Richard at CMU, USA of Chincinnati Milacron
Corporation manufactured T3 (The tomorrow
tool ) robot
1975 Raibart at CMU, USA , built a one-legged
hoping machine, the first dynamically stable
machine
1978 Unimation developed PUMA (Programmable
Universal Machine for Assembly)

1983  Odetics introduced a unique experimental
six-legged device
1986  ASV (Adaptive Suspension Vehicle ) was
developed at Ohio State University , USA
1997 Pathfinder and Sojourner was sent to the
Mars by the NASA, USA
2000 Asimo Humanoid Robot was developed by
Honda
2004 The Surface of the Mars was explored by Spirit
and Opportunity
2012 Curiosity was sent to the Mars by the NASA,
USA
2015 Sophia (Humanoid) was built by Hanson
Robotics, Hong Kong

The Robotic Market and Future
Prospects

Laws of Robotics
Asimov proposed three “Laws of Robotics”
 Law 1: A robot may not injure a human being or
through inaction, allow a human being to come to harm.
 Law 2: A robot must obey orders given to it by human
beings, except where such orders would conflict with
the first law.
 Law 3: A robot must protect its own existence as long
as such protection does not conflict with the first law.

What is the definition of Robot
 To be called a robot it should do some or all of the following
- Move Around
- Sense and Manipulate the Environment
- Display Intelligent Behaviour
Is a CNC Machine a Robot?

Definitions
The Term: Robot has come from the Czech word :
Robota, which means forced or Slave labourer.
In 1921,Karel Capek, a Czech playright, used the
term: robot first in his drama named Rosum’s
Universal Robots (R.U.R)
According to Karl Capek, a robot is a machine look-
wise similar to a human being

According to Literature, Robot has been defined in various ways
 According to Oxford English Dictionary
A machine capable of carrying out a complex series of actions automatically,
especially one programmable by a computer.
 According to International Organization for Standardization (ISO):
An automatically controlled, reprogrammable, multipurpose manipulator
programmable in tree or more axis, which can be either fixed in place or mobile
for use in industrial automation applications.
 According to Robotic Institute of America (RIA)
It is a reprogrammable multifunctional manipulator designed to move materials,
parts, tools or specialized devices through variable programmed motions for the
performance of a variety of tasks.

Robotics
It is a science, which deals with the issues related to
design, manufacturing, usages of robots.
In 1942, the term: Robotics was introduced by Issac
Asimov, in his story named Run-around.
In Robotics, we use the fundamentals of Physics,
Mathematics, Mechanical Engg, Electronics Engg.,
Electrical Engg, Computer Sciences, and others

Three generation of Robotics/ Engineering
First Generation of Robots: simple pick and place
devices wit no external sensors
Second Generation of Robots: External Sensors (vision,
tactile, etc. ) for interaction with the environment
Third Generation of Robots: Intelligence, smart
material, bio, etc.
Future Robots: bio robots, micro, nano, cybogs, aneroids
etc.

3 Hs in Robotics
3 Hs of human beings are copied into Robotics, such as
 HAND
 HEAD
 HEART

Anatomy of Robot
Anatomy Representation
Body Base
Chest Link
Shoulder Joint
Upper Arm Link
Elbow Joint
Fore-arm Link
Wrist Joint

Automation and Robotics
 Motivation
To Cope with increasing demands of a dynamic and competitive
market, modern manufacturing methods should satisfy the following
requirements:
 Reduced Production Cost
 Increased Productivity
 Improved Product Quality
 Notes
[1] Automation can help to fulfil the above requirements
[2] Automation: Either Hard or flexible automation
[3] Robotics is an example of flexible automation

Types of Robots
Robots can be classified by two types
Robots by Locomotion Robots by Application

Types of Robots
Wednesday, June 23, 2021
25
Robots
by
Locomotion
Stationary Robots
Wheeled Robots
Legged Robots
Swimming Robots
Modular Robots
Micro Robots
Rolling Robotic Balls
Snake Robots

Types of Robots
26
Robots
by
Application
Industrial Robots
Domestic Robots
Medical Robots
Military Robots
Space Robots
Hobby and Competition

Types of Robots
27
Stationary
Robots
Cartesian/Gantry Robots
Cylindrical Robots
Spherical Robots
SCARA Robots
Articulated Robots
Parallel Robots

Types of Robots
Industrial Robots
–Materials handling
–Welding
–Inspection
–Improving productivity
–Laboratory applications

Types of Robots
Mobile Robots
–Robots that move around on legs, tracks or wheels.
E.g.-
In 1979 a nuclear accident in the USA caused a leak of radioactive
material which led to production of special robot –which can handle
the radioactive materials

Types of Robots
Educational Robots
Robotic kits are used extensively in
education.
E.g.-Robolab, Lego and RoboCup
Soccer
Domestic Robots
Those designed to perform household
tasks and modern toys which are
programmed to do things like talking,
walking and dancing, etc.

Robots in Space
NASA Space Station

Micro-robot for Bypass Surgery

Robotic Arm

Interdisciplinary areas of Robotics
Mechanical Engineering
 Kinematics: Motion of the robot arm without
considering the force/and or moments
 Dynamics: Study of the force/and or moments
 Sensing: Collecting information of the environment
Computer Science
 Motion Planning: Planning the course of action
 Artificial Intelligence: To design and develop
suitable brain for the robot

Interdisciplinary areas of Robotics
Electrical/Electronics Engineering
 Control Schemes and Hardware Implementations
General Sciences
 Physics
 Mathematics

Overview of Robots
Degree of Freedom
The Reference Frames
Robot Joints
Configurations
Robot Components
Robot Specifications
Modes of Programming and Control

Reference Frames
Base Reference Frames
Joint Reference Frames
Tool Reference Frames

A Robotic system Components
 Base
 Links and Joints
 End-Effectors/
Gripper
 Wrist
 Driver/Actuators
 Sensors
 Controllers
 Software and
Hardware

Manipulator
Manipulator is a main body for the robot and consists of the joints,
links
and other structural elements of the robot.
• It is a collection of mechanical linkages (or link) connected by
joints and
included are gears, coupling devices, and so on.
• Generally, joints of a manipulator fall into two classes:
▫ revolute (rotary)
▫ prismatic (linear).
• Each of the joints of a robot defines a joint axis along which the
particular link either rotates or slides (translates).
• Every joint axis identifies a degree of freedom (DOF)
Degree of Freedom= No. of Joints

Manipulator
• Regardless of its mechanical configuration, the manipulator
defined by the joint-link structure generally contains three main
structural elements as human parts:
 the arm
 the wrist
 the end effector.
• Most robots are mounted on stationary base on the floor and its
connection to the first joint as called link 0. The output link of
joint 1 is link 1, and so on.

End Effector
• End effector is the part that is connected to the last joint (hand) of a manipulator,
which generally handles objects, makes connection to other machines, or performs
the required tasks.
• Robot manufacturers generally do not design or sell end effectors; just supply a
simple gripper.
• This is the job of a company's engineers or outside consultants to design and install
the end effector on the robot and to make it work for the given situation/task.
• In most cases, either the action of the end effector is controlled by the robot's
controller, or the controller communicates with the end effector's controlling device
such as a PLC.
• The end effectors can include a sensor to determine if a part is present.
• The addition of a simple sensor can make a gripper a relatively intelligent device.

Actuators
Actuators are used to move elements of the manipulators.
• It must have enough power to accelerate and decelerate the links and
to carry the loads, yet be light, economical, accurate, responsive, reliable,
and easy to maintain.
• Each actuator is driven by a controller.
• Common types of actuators are electric motors (servomotors and stepper
motors), pneumatic cylinders, and hydraulic cylinders.
• Electric motor especially servomotors are the most commonly used.
• Hydraulic systems were very popular for large robots in the past and
still around in many places, but are not used in new robots as often any
more.
• Pneumatic cylinders are used in robots that have on-off type joints, as
well as for insertion purposes.

Sensors
Adding sensors to an industrial robot can increase the range of
tasks the robot can perform.
• It also decreases the mechanical tolerances required of both the
robot and the robot’s environment.
• Sensors can be divided into three categories:
 Internal sensors: tell a robot the position of its various joints and
report other conditions such as fluid pressure and temperature.
 External sensors: tell the robot what is happening outside.
 Interlocks: used to protect both humans and robots. They may
possess features of both internal and external sensors.

Controller
The controller receives its data from the computer,
controls the motions of the actuators, and coordinates the
motions with the sensory feedback information.

Teach Pendant
The robot will move to various locations in
performing its tasks.
These locations can be determined by a
controller system whenever then robot’s
working environment is defined.
However, these locations are usually taught
to the robot controller and used by the
operator to move the robot to desire
locations.
 Teach pendants sometimes can also be
used to issue other commands to the robot
or to teach a relatively simple program.

Robot Joints
The Robot Joints is the important element in a robot which helps the links to travel
in different kind of movements. A joint in an industrial robot is similar to that in a
human body. It provides with a relative motion between two parts.
Different types of Joints
1. Linear- Sliding and Prismatic Joint
2. Rotary: Twisting or Revolute Joint

Robot Joints
Joints with 1 DOF
Revolute Joint (R)

Robot Joints
Joints with 1 DOF
Prismatic Joint (P)

Robot Joints
Joints with 2 DOF
Cylindrical Joint (C)

Robot Joints
Joints with 2 DOF
Hook Joint or
Universal Joint (U)

Robot Joints
Joints with 3DOF
Ball and Socket Joint/Spherical Joint (S’)

Representation of Joints
Revolute Joint (R)
Prismatic Joint (P)
Cylindrical Joint (C)

Spherical Joint (S’)
Hooke Joint (U)
Twisting Joint (T)

Joints Summary

Degree of Freedom
It is defined as the minimum no. of independent parameters,
variables, coordinates needed to describe a system completely
Note:
 A point in 2-D:2 DOF, IN 3-D space: 3DOF
 A rigid body in 3-D: 6 DOF
 Spatial Manipulator:6 DOF
 Planar Manipulator:6DOF

Redundant Manipulator
Either a spatial manipulator with more than 6 DOF or a planar
manipulator with more than 3 DOF
Under Actuated Manipulator
Either a spatial manipulator with less than 6 DOF or a planar
manipulator with less than 3 DOF

Mobility / DOF of Spatial
Manipulator
Let us consider a manipulator with n rigid moving links and m joints
Ci= Connectivity of i-th joint, i=1,2,3,…………….m
No. of Constraints put by the i-th joint=
Total no. of Constraints =
Mobility of the manipulator
It is known as Grubler’s Criterion.

Mobility / DOF of Planar
Manipulator
Let us consider a manipulator with n rigid moving links and m joints
Ci= Connectivity of i-th joint, i=1,2,3,…………….m
No. of Constraints put by the i-th joint=
Total no. of Constraints =
Mobility of the manipulator
It is known as Grubler’s Criterion.

Numerical Example
Serial Planar Manipulator

Numerical Example
Parallel Planar Manipulator

Numerical Example
Parallel Spatial Manipulator

Robot Configurations
Cartesian (3P) Robots
 Linear movement along three different axes
 Have either sliding or prismatic joint that’s
SSS or PPP
 Rigid and accurate
 Suitable for pick and place type of
operations
 Examples: IBMs RS-1, Sigma robot

Types of Robots
65
Cartesian/Gantry
Robots

Advantages
66
Cartesian/Gantry
Robots
Rigid Structure of box frame type
High Repeatability with least error
High Load carrying capability

Cylindrical (2PR) Robots
 Two Linear and one rotary movements
 Represented as TPP, TSS
 Used to handle parts/objects in
manufacturing
 Cannot reach the objects lying on the floor
 Poor dynamic performance
 Examples: Versatran 600

Advantages
68
Cylindrical
Robots
High rigidity of the manipulator
Higher Load carrying capacity
Geometrical advantage in specification

 Spherical (2RP ) or Polar Coordinate Robots
 One Linear and 2 rotary movement
 Represented as TRP, TRS
 Suitable for handling parts/objects in
manufacturing
 Can pick up objects lying on the floor
 Poor dynamic
 Performance
 Examples : Unimate 2000B

Types of Robots
70
Spherical
Robots

Advantages
71
Spherical
Robots
Higher Reach from the base
Geometric advantage in specification
Machine Loading applications need this type.

SCARA Robots

Types of Robots
73
SCARA
Robots

Articulated/ Revolute Coordinate(3 R) Robots
 Rotary Movement about three independent axes
 Represented as TRR
 Suitable for handling parts/components in
manufacturing system
 Rigidity and accuracy may not be good enough
 Examples; T3, PUMA

Advantages
75
Articulated
Robots
Higher reach from the base
Useful in continues path generation, applied to spray
painting and are welding.
Reaching the conjested small openings without
interference

Parallel or Delta Robots

Types of Robots
77
Parallel
Robots

Robot Configuration Summary
78

Resolution, Accuracy and
Repeatability
Resolution: It is defined as the smallest allowable position increment of
a robot
 Programming Resolution: Smallest allowable position increment in
robot programme
Basic Resolution Unit (BRU)= 0.01 inch/0.1 degree
 Control Resolution: Smallest Change in position that the feedback
device can measure say 0.36 degrees per pulse

Resolution, Accuracy and
Repeatability
Accuracy: It is the precision with which a computed point can be
reached
Repeatability: It is defined as the precision wit which a robot re-
position itself to a previous taught point.

Applications
In manufacturing Units
Advantages of Robots
 Robots can work in hazardous and dirty environment
 Can increase productivity after maintaining improved quality
 Direct Labour cost will be reduced
 Material cost will be reduced
 Repetitive tasks can be handled more effectively
 Arc Welding
 Spot Welding
 Spray painting
 Pick and Place operation
 Grinding
 Drilling
 Milling

Applications
Under Water Applications
Purposes
 To explore various resources
 To study under-water environment
 To carry out drilling, pipe line survey, inspection and repair of ships
Note:
 Robots are developed in the form of ROV(Remotely Operated
Vehicle) and AUV (Autonomous Under-Water Vehicle)
 Robots are equipped with sensors, propellers/thrusters, on-board
software's and others

Applications
Medical Applications
 Tele-surgery
 Micro-capsule multi-legged robots
 Prosthetic Devices
Space Applications
 For carrying out on-orbit services, assembly job and interplanetary
missions
 Spacecraft deployment and retrieval , survey of outside space
shuttle, assembly, testing, maintenance of space stations, transport
of astronauts to various locations
 Robo-nauts
 Free-Flying Robots
 Planetary exploration rovers

Applications
In Agriculture
 For Spraying pesticides
 For spraying fertilizers in liquid form
 Cleaning weeds
 Sowing seeds
 Inspection of plants
Other Applications
 Replacement of maid-servant
 Garbage Collection
 Underground Coal mining
 Sewage-line cleaning
 Fire Fighting etc.

End Effectors
An end-effector is a device attached to the wrist of a
manipulator for the purpose of holding materials, parts, tools
to perform a specific task.
Grippers: End Effector used to grasp and hold objects
Tools: End effectors designed to perform some specific
tasks
E.g. Spot Welding electrode, Spray Gun

Classification of Grippers
1. Single Gripper and Double Gripper
o Single Gripper: Only one gripping device is mounted on the wrist
o Double Gripper: Two independent gripping devices are attached to
the wrist
Example: Two separate grippers mounted on the wrist for loading and
unloading applications

2. Internal Gripper and External Gripper

3. Hard Gripper and Soft Gripper
o Hard Gripper: Point contact between the finger and the object
o Soft Gripper: Area (surface) contact between the finger and the
object

3. Active Gripper and Passive Gripper
o Active Gripper: Gripper equipped with sensor
o Passive Gripper: Gripper without sensor

A few Robot Grippers
1. Mechanical Gripper
o Use mechanical fingers (jaws) actuated by some mechanism
o Less versatile, less flexible and less costly
Example: i) Gripper with Linkage Actuation

ii ) Gripper with Rotary Actuation

ii ) Gripper with cam Actuation

2 ) Vacuum Grippers/Suction Gripper (used for thin parts)
https://www.youtube.com/watch?v=h7MpTfmNCAo

 Suction cup is made up of elastic material like rubber or soft plastic
 When the object to be handled is soft, the cup should be made of
hard substance
 Two Device can be used: Either Vacuum pump or Venturi

3. Magnetic Gripper (for magnetic materials only.
For example: various steels but not stainless steel
 Can use either electromagnets or permanent magnets
 Pick up time is less
 Can grip parts of various sizes
 Disadvantage: residual magnetism
 Stripping Device: for separating the part from the permanent
magnet
 For separating the part from the electro-magnet, reverse the
polarity

Magnetic Gripper
https://www.youtube.com/watch?v=KQHkFx49e2E

Adhesive Gripper
Grasping action using adhesive substance
To Handle light weight materials
https://www.youtube.com/watch?v=pMvdK4VifDE

Passive Gripper
Task: To insert a peg into a hole

Passive Gripper
Solution: Use Remote Centre Compliance (RCC)
 RCC is inappropriate for assembly of pegs in horizontal direction
 Insertion angle must less than 45 degrees
 Cannot be used in chamferless insertion tasks
https://www.youtube.com/watch?v=qFTUFHGGZIg

Gripper Selection and Design
Requirements
 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

Tips for Designing a Gripper
-Gripper with passive finger
-Gripper with active feedback

Gripper with passive finger
 Choose acc. to the task to be performed and the geometry and
characteristics of parts to be grasped.
 Consider the local environments, working space, conveyor
positions etc.
 Determine the no. of joint links and there config. By part
geometry and task movements
 Decide the material of construction based on type of duty,
corrosion resistance or heat geometry and task movements.
 Select proper actuators--- hydraulic for high forces, electric
motors for best control, Pneumatic for less cost and ease etc.

Gripper with active feedback
Use sensor based robots to handle heavy parts.
Use active wrist with passive fingers to handle forces
greater than 1 to 2-5 kg

Force Analysis of Gripper
Mechanism

Robot Teaching
 To provide necessary instruction to the load
Teaching Methods
Online Methods Offline Methods
Manual Teaching Lead Through Teaching
(Point to Point task)
 Control Handle/Joystick
 Push buttons
 Teach-pendant
(Continuous path task)
 Robot Simulator
Programming Language

Robot Teaching
Offline Method
VAL Programming for PUMA
Task: Pick and Place Operations
VAL Program Other VAL Commands
APPRO PART, 100 SPEED 40
MOVES PART EXECUTE
CLOSEI ABORT
DEPARTS 200 EDIT Filename
APPROS BIN, 300 LISTF
MOVE BIN STORE
OPENI DELETE
DEPART, 100 LOAD Filename

Robotic Specification
 Control Type
 Drive System
 Coordinate System
 Teaching/Programming Methods
 Accuracy/Repeatability, Resolution
 Pay-Load Capacity
 Weight of the Manipulator
 Range and Speed of arms and wrist
 Applications
 Sensor Used

Economic Analysis
Let F : Capital Investment to purchase a robot which includes
its purchasing Cost and installation Cost
B: Saving in terms of Material and Labour Cost
C: Operating and Maintenance Cost
D: Depreciation of the Robot
A: Net Savings
A=B-C-D
 G: Tax to be paid on the Net Savings
 Pay-back period, E = (Capital Investment, F)/ (B-C-G)

Economic Analysis
Let I : Modified net savings after the payment of tax
Rate of return on investment
H=(I/F)*100%
A Company decides to purchase the robot, if
Pay-back period < techno-economic life
Rate of return on investment > Rate of bank interest

Numerical Example
The cost and savings associated with the robot installation are given below:
Costs of a robot including accessories : Rs. 12, 00,000
Installation Cost: Rs. 3,00,000
Maintenance and operating cost: Rs. 20 per hour
Labour Saving: Rs. 100 per hour
Material Saving : Rs. 100 per hour
The shop runs 24 hours in a day (3 shifts) and the effective workdays in a
year are 200. The tax rate of the company is 30% and techno economic life
of the robot is expected to be equal to six years .
Determine
a) pay-back period of the robot and
b) Rate of return on investment

Solution
Capital investment F= Cost of the robot including accessories
+installation cost = Rs. 15,00,000
Total hours of the running of the robot per year =24*200= 4800
Saving per year B= Labour Saving + Material Saving
=100*4800+15*4800
=Rs. 5,52,000
Maintenance and Operating cost per year C = 20*4800 = Rs. 96,000
Techno–economic life of the robot = 6 years

Solution
Constant Depreciation per year= Rs. 15,00,000/6 =Rs. 2,00,000
Net Savings= Savings- Operating Cost- Depreciation
= 5,52,000-96,000-2,00,000
= Rs. 2, 56,000
Tax To Be Paid To The Government by the company G=30% of A
=Rs. 76,800
Pay-back period of the robot
E= (F/B-C-G)=3.9 years < techno-economic life

Solution
Net savings after the payment of the tax
I= 0.7* 2,56,000
= Rs. 1,79,200
Rate of return on investment
H= I/F*100 =11.95%> Rate of bank interest
Therefore, the purchase of the robot is justified by taking the loan
from the bank

Sensors
Human beings collect information of the surroundings
using their sensors namely, eyes, ears, nose, skin, etc. in
order to perform various tasks.
A sensor is used to take measurement of physical variable.
A sensor requires calibration
Sensors are used to build intelligent robots.

Sensor vs Transducer
Transducer = primary measuring element + secondary measuring
element
i.e. Transducer = Sensor + Signal conditioning circuit

Classification of Sensors
Sensors
Internal Sensors
(used to operate the drive units)
Example: Position sensors
Velocity Sensors
Acceleration Sensors
Force/Moment Sensors
External Sensors
(used to collect the information
Of the environment)
Example: Temperature Sensor,
Visual Sensor, Proximity
Sensor, Acoustic Sensor

Classification of Sensors
Sensors
Contact Sensors
(Physical contact between
sensor mounted on robot and
object)
Non Contact Sensors
(No Physical Contact)
Example: Visual Sensor,
Proximity Sensor, Acoustic Sensor,
Range Sensor
Touch Sensor/ Tactile
Sensor/Binary Sensor
(indicate presence or
absence of an object)
Example: Micro switch,
Limit Switch
Force Sensor/ Analog Sensor
(not only the contact is made but also the force is
measured)
Sensors using strain gauges

Characteristics of Sensors
Range: Difference between maximum and minimum values of the
input that can be measured.
Response: Should be capable of responding to the changes in
minimum time.
Accuracy: Deviation from exact quantity
Sensitivity: Changes in output/change in input
Linearity: Constant Sensitivity
Repeatability: Deviation from reading to reading , when these are
taken from a number of times under identical conditions
Resolution

Characteristics of Sensors
Touch Sensor
 Used to indicate whether contact has been made between two
objects
 Does not determine the magnitude of contact force
 Example: Micro switch, Limit switch

Sensors
Connected to Robot wrist
Micro-switches
Finger
Figure: Micro switches placed on two fingers of a robotic hand

1. Position Sensor
Potentiometer
Linear Potentiometer Angular Potentiometer
Angular Potentiometer

Angular Potentiometer
For the known values of Vin R, Vout f (r)
By measuring Vout, r can be determined and an angular displacement θ.
Demerits
Resistance of the wire is temperature dependent
Potentiometer is temperature sensitive

2. Optical Encoder
Optical Encoder
Absolute Optical Encoder Incremental Optical Encoder
Absolute Optical Encoder
It is mounted on the shaft of a
rotary device
To generate digital word
identifying actual position of
the shaft measured from zero
position

Absolute Optical Encoder

Incremental Optical Encoder
 Consists on one coded disc and two
photo detectors
 By counting the number of light and
dark zones, angular displacement can
be measured with respect to known
starting position
 It can determine the direction of
rotation also.
 It is construction-wise simpler, less
accurate and less simpler

Linear Variable Differential
Transformer (LVDT)
 It consist of two parts: fixed casing
and moving magnetic core
 In between the fixed casing and
magnetic core, there are one primary
and two secondary coils
 Produced voltage output is
proportional to the displacement of
moving part relative to the fixed base
 Ac voltage is applied to the Lp.
 Ls1 and Ls2 are connected in series
Vout=LS2-LS1

Force/Moment Sensor

Force/Moment Sensor
Strain gauge is connected to potentiometer circuit, whose
output voltage is proportional to the deflection and hence ,force
Three component of force (F) and moment (M) each are
determined by adding and subtracting the respective
components of force.
F=CMW
Readings of the strain
gauge
Forces/Moments
Calibration Matrix

Force/Moment Sensor
Precautions
 Strain gauges are to be properly mounted on the deflection bars
 Sensors should be operated within the elastic limit of its material
(deflection bars)

Range Sensor
 It measures the distance between the sensor (detector) mounted
on the robots body and the object

Proximity Sensor
Proximity Sensor
Inductive Sensor Hall Effect Sensor Capacitive Sensor
Inductive Sensor
 It consist of a permanent magnet and a
wound coil placed next to it.
 The nature of flux lines changes as the
sensor come closer to a ferro-magnetic
material
 The flux lines changes, as the ferro-
magnetic object either leave or enters the
field of magnet.
 Rate of change of magnetic flux is
proportional to induced current
(voltage)

Inductive Sensor
Voltage induced across the coil depends on the speed at which the
object either enter or leaves the magnetic field.
Polarity of the voltage depends on whether the object enters or leaves
the field.

Calibration Curve
The Figure shows the calibration curve corresponding to the
measured amplitude of voltage signal, the distance between the
sensor and the object can be determined

Hall effect Sensor
It works based on the principle of Lorentz force.
If a charge of amount q is moving with velocity in a magnetic field
strength of field , then the Lorentz force,

Inductive Sensor
Voltage across the
semiconductor will be reduced
Calibration curve for hall effect
sensor

Capacitive Sensor
When an object brought near to
the sensitive electrode , there will
be accumulation of charge and
consequently its capacitance
changes.
When the capacitance of the
sensor exceeds a predefined
threshold value, oscillation starts.
Oscillations are converted into
output voltage through PCB.
Calibration curve

Types of Robot Sensors
Light sensors.
Sound Sensor.
Temperature Sensor.
Contact Sensor.
Proximity Sensor.
Distance Sensor.
Pressure Sensors. ...
Tilt Sensors.
Voltage sensor
Current sensor
IMU Sensor
Acceleration sensor.

Light Sensor
A Light sensor is used to detect light and create a voltage difference. The two main light
sensors generally used in robots are photo resistor and Photovoltaic cells.
Types of Light Sensor
 VEX light sensor
 LEGO light sensor
 Light Sensor 1000 lux
 SCI-BOX Light Detector
 TAOS TSL235R Light to Frequency Converter
 Parallax QTI Sensor
 DFRobot Ambient Light Sensor
 Arduino LilyPad light sensor
 DFRobot BH1750 light sensor
 CdS photoconductive cell

Light Sensor
A Light sensor is used to detect light and create a voltage difference. The two main light
sensors generally used in robots are photo resistor and Photovoltaic cells.
 VEX light sensor
 LEGO light sensor
 Light Sensor 1000 lux
 SCI-BOX Light Detector
 TAOS TSL235R Light to Frequency Converter
 Parallax QTI Sensor

Light Sensor

Sound Sensor
This sensor (generally a microphone) detects sound and returns a voltage proportional
to the sound level. A simple robot can be designed to navigate based on the sound it
receives. Imagine a robot which turns right for one clap and turns left for two claps.
Complex robots can use the same microphone for speech and voice recognition.

Temperature Sensor
What if your robot has to work in a desert and transmit ambient temperature?
Simple solution is to use a temperature sensor. Tiny temperature sensor ICs
provide voltage difference for a change in temperature. Few generally used
temperature sensor IC’s are LM34, LM35, TMP35, TMP36, and TMP37.

Contact Sensor
Contact sensors are those which require physical contact against other objects
to trigger. A push button switch, limit switch or tactile bumper switch
are all examples of contact sensors.

Pressure Sensor
Pressure sensor measures pressure. Tactile pressure sensors are useful in robotics as
they are sensitive to touch, force and pressure. If you design a robot hand and need
to measure the amount of grip and pressure required to hold an object, then this is
what you would want to use.

Tilt Sensor
Tilt sensors measure tilt of an object. In a typical analog tilt sensor, a small amount of
mercury is suspended in a glass bulb. When mercury flows towards one end, it closes
a switch which suggests a tilt.

Distance (Proximity) Sensor
Most proximity sensors can also be used as distance sensors.
Type of distance sensor:
Ultrasonic Distance Sensors
Infrared Distance sensor
Laser range Sensor
Encoders
Stereo Camera

Voltage Sensor
Voltage sensors typically convert lower voltages to higher voltages,
or vice versa. One example is a general Operational- Amplifier (Op-
Amp) which accepts a low voltage, amplifies it, and generates a
higher voltage output.

Current Sensor
Current sensors are electronic circuits which monitor the current flow
in a circuit and output either a proportional voltage or a current.

IMU Sensor
Inertial Measurement Units combine properties of two or more sensors such as
Accelerometer, Gyro, Magnetometer, etc., to measure orientation, velocity and
gravitational forces.

Difference between analog and Digital Sensor
An accelerometer is a device which measures acceleration and tilt.
There are two kinds of forces which can affect an accelerometer: Static
force and Dynamic Force.

Difference between analog and
Digital Sensor
A digital sensor can only have two
values: 1 or 0, all or nothing. An example
of a digital sensor is a button, which can
either have the value of 1 when pressed
or 0 when not pressed. On a ZUM board
or a similar one, the digital sensors will
be connected on the digital pins D0-D13.
An analogue sensor can have
multiple states and is able to
transform the quantity of light,
temperature or other physical
elements into a value between 0 and
1023.
Digital Sensor Analog Sensor

7 Types of Industrial Robot Sensors
 2D Vision
 3D Vision
 Force Torque Sensor
 Collision Detection Sensor
 Safety Sensors
 Part Detection Sensors
 Others

Robot as a System
ROBOT
Working
environment
Commands Actions
Program
Task
Mechanical
Units
Actuation Units
Supervision
Units
Sensor Units

Functional units of robot

Actuator Components
Power
Supplies
Power
Amplifier
Motor
or
Servomotor
Transmission
(mechanical
gears)
Pp
Pc
Pa Pm Pu
Pda Pds Pdt
Actuator
Power Losses due to dissipation effect (friction)
Electric, Hydraulic or Pneumatic

Actuators
Electric Actuators: The Primary input power supply is the
electric energy from the electric distribution system.
Hydraulic Actuators: They transform hydraulic energy
stored in a reservoir into mechanical energy by means of
suitable pumps.
Pneumatic Actuators: They utilise pneumatic energy i.e.
compressed air, provided by a compressor and transform it
into mechanical energy by means of piston or turbines.

Electric Actuator Types
1. Servo Motor
2. DC-motors
3. Brushless DC-motors
4. Asynchronous motors
5. Synchronous motors
6. Reluctance motors
7. Stepper Motor

Electric Servomotors for robots

Electric Motor
Advantages
1. Good for all sizes of robots
2. Better control, good for high precision robots
3. Higher compliance than hydraulics
4. Reduction gears used to reduce inertia on the motor
5. Does not leak, good for clean room
6. Reliable, low maintenance
7. Can be spark free, good for explosive environments
Disadvantages
1. Low stiffness
2. Needs reduction gears, increased backlash, cost and weight
3. Motor needs braking device when not powered. Otherwise, the arm will fall

Electric Actuators
 Mainly rotating but also linear ones are available
 Linear movement with gear or with real linear motor

Pneumatic
Advantages
1. Many components are usually off the- shelf.
2. Reliable components.
3. No leaks or sparks.
4. Inexpensive and simple.
5. Low pressure compared to hydraulics.
6. Good for on-off applications and for pick and place.
7. Compliant systems.
Disadvantages
1. Noisy systems.
2. Require air pressure, filter, etc.
3. Difficult to control their linear position.
4. Deform under load constantly.
5. Very low stiffness and inaccuracy response.
6. Lowest power to weight ratio.

Hydraulic
Advantages
1 Good for large robots and heavy payload.
2. Highest power/weight ratio.
3. Stiff system, high accuracy, better response.
4. No reduction gear needed.
5. Can work in wide range of speeds without difficulty.
6. Can be left in position without any damage
Disadvantages
1. May leak and not fit for clean room applications.
2. Requires pump, reservoir, motor, hoses, etc.
3. Can be expensive, noisy and requires maintenance.
4. Viscosity of oil changes with temperature.
5. Very susceptible to dirt and other foreign material in oil.
6. Low compliance.
7. High torque, high

Stepper Motor
1. A sequence of (3 or more) poles is activated in turn, moving
the stator in small “steps”.
2. Very low speed / high angular precision is possible without
reduction gearing by using many rotor teeth.
3. Can also perform a “micro-step” by activating both coils at
once.

Stepper Motor

Robot Kinematics

Representation of an Object in 3-D space

Representation of the position

Representation of the Orientation

Frame Transformations
Frame : A set of four
vectors carrying position
and orientation information

Translation of a frame

Rotation of a frame

Translational and Rotation of frame

Translational Operator

Rotational Operator

In Matrix form

Similarly,

Properties of Rotation matrix
 Each row/column of a rotation matrix is a unit vector
 Inner(dot) product of each row of a rotation matrix with each other row
becomes equal to 0. The same is true for each column also.
 Rotation matrices are not commutative in nature.
 Inverse of a rotation matrix is nothing but its transpose.

Numerical Example

Composite Rotation Matrix

Representation of Position in other
than Cartesian Coordinate System

Cylindrical Coordinate System

Spherical Coordinate System

Representation of Orientation in other than
Cartesian Coordinate System

Roll, Pitch and Yaw angles

Numerical Example

Solution

Using Euler angles

Denavit Hartenberg notation
It is proposed in the year 1955

Link and Joint Parameters

Introduction to Robotics

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