Automation and Robotics 20ME51I WEEK 8 Theory notes.pdf

Fundamentals of Robo cs
DEPT. OF MECHANICAL ENGINEERING, SANDUR POLYTECHNIC Page: 1
FUNDAMENTALS OF ROBOTICS
1. Concepts of Industrial Robots
Robots can perform many different tasks and operations precisely. Robotic
systems consist of not just robots, but also other devices and systems that are used
together with the robots to perform the necessary tasks.
Definition:
A robot is a computer-controlled machine that is programmed to move,
manipulate objects, and accomplish work.
According to the Robot Institute of America (1979), a robot is defined as “a
reprogrammable, multifunctional manipulator designed to move material, parts, tools,
or specialized devices through various programmed motions for the performance of a
variety of tasks.”
Or
Industrial robot is defined as “a number of rigid links connected by joints of
different types that are controlled and monitored by computer.”
The advantages of robots are:
1. Increase in productivity, safety, efficiency, quality, and consistency of products.
2. Robots can work in hazardous environments.
3. Robots need no environmental comfort
4. Robots can work continuously without experiencing fatigue.
5. Robots always have repeatable precision.
Disadvantages of robots are:
1. Robots replace human workers creating economic problems,
2. Robots lack capability to respond in emergencies.
3. Safety measures are needed to ensure that they do not injure operators and
machines working with them.
4. Robots are costly due to initial cost of equipment and installation

Components of an Industrial Robot:
1. Mechanical Unit. The mechanical unit refers to the robot’s manipulative arm and
its base. Tooling such as end effectors, tool changers, and grippers are attached to
the wrist-tooling interface. The mechanical unit consists of a fabricated structural
frame with provisions for supporting mechanical linkage and joints, guides,
actuators, control valves, limiting devices, and sensors.
2. Drive. The drive system supplies the power, which enables the robot to move. Drive
for a robot may be hydraulic, pneumatic, or electric. Hydraulic drives have been
used for heavier lift systems. Pneumatic drives have been used for high speed.
Electric drive systems can provide both lift and/or precision. An AC or DC powered
motor may be used.
3. Control System. Controller is the brain of the robot. Controller is a communication
and information-processing device that initiates, terminates, and coordinates the
motions and sequences of a robot. Most industrial robots incorporate computer or
microprocessor-based controllers. These perform computational functions and
interface with sensors, grippers, tooling, and other peripheral equipment.
4. Tooling. Tooling is manipulated by the robot to perform the functions required for
the application. Depending on the application, the robot may have one functional
capability, such as making spot welds or spray-painting.

2. Applications of Robotics
Robotics has a wide range of applications across various industries and fields,
1. Manufacturing and Industrial Automation:
a. Automated Assembly Lines: Robots are used for tasks like welding, painting,
and assembling products.
b. Material Handling: Robots handle materials in factories, warehouses, and
distribution centres, improving efficiency and reducing the risk of injuries.
c. Quality Control: Robots are employed for precise inspection and testing of
products, ensuring high-quality standards.
2. Healthcare: Surgical robots assist surgeons with precision and minimally invasive
procedures.
3. Agriculture:
a. Precision Farming: Robots are used for planting, harvesting, and monitoring
crops, optimizing yields, and reducing the need for manual labour.
b. Livestock Management: Robots assist in tasks such as feeding and monitoring
livestock.
4. Logistics and Warehousing:
a. Autonomous Vehicles: Self-driving robots and drones are used for package
delivery and inventory management in warehouses.
b. Picking and Packing: Robots pick and pack items in e-commerce fulfilment
centres.
5. Space Exploration:
a. Planetary Rovers: Robots like the Mars rovers explore celestial bodies and
conduct experiments.
b. Astronaut Assistance: Robots help astronauts with tasks on the International
Space Station and in space exploration missions.

3. Configurations of robots: Articulated Robot, Polar configuration, SCARA,
Cartesian Co-ordinate Robot, cylindrical robot, Delta Robot
Articulated Robot:
Articulated robots consist of three constant parts (links) that are joined with
revolute joints and are placed on a rotating base as shown in Figure. The layout is like
a human arm. The tool (gripper) is like a palm and is adjusted to the lower part of the
arm through the wrist.
The elbow connects the lower and upper part of the arm and the shoulder
connects the upper part of the arm with the base. Many times, the shoulder joint has a
rotational motion in the horizontal plane. The articulated robot has all three axes
revolute, so the position resolution is completely dependent on the arm’s position.
Applications, these types of robots are used for:
1. Assembly operations
2. Die casting
3. Gas and Arc welding
4. Spray-painting
Advantages
1. High mechanical flexibility
2. They can move with high speed at three degrees of freedom
3. All joints can be sealed from the environment
Disadvantages
1. Extremely difficult to visualize, control, and program Restricted volume coverage
2. Low accuracy

Polar configuration:
Robots of this type consist of a rotating base, a lifting part, and a telescopic arm,
which moves inwards and outwards (refer to Figure). The 2 dimensions of spherical
robots are angles and the third is a linear distance from the point of origin. These robots
operate according to spherical coordinates and offer greater flexibility. This design is
used where a small number of vertical actions are adequate.
Applications, these types of robots are used for:
1. Handlings at die casting or fettling machines
2. Handling machine tools Arc/spot welding
Advantages
1. Large working envelope
2. Two rotary drives are easily sealed against liquids/dust
Disadvantages
1. Complex coordinates more difficult to visualize, control, and program
2. Exposed linear drive
3. Low accuracy

SCARA (Selective Compliance Articulated Robot Arm)
SCARA Robot: One style of robot that has recently become quite popular is a
combination of the articulated arm and the cylindrical robot. This robot has more than
three axes and is called a SCARA robot (refer to Figure).
The rotary axes are mounted vertically rather than horizontally. This
configuration minimizes the robot’s deflection when it carries an object while moving
at a programmed speed.
Applications
1. Pick and place work
3. Application of sealant
4. Handling machine tools
Advantages
1. High speed
2. Excellent repeatability
3. Good payload capacity
4. Large work area for floor
space
5. Moderately easy to program
Disadvantages
1. Limited applications
2. Two ways to reach point
3. Difficult to program off-line
4. Highly complex arm

Cartesian/ Rectilinear/ Gantry Robots:
The axis or dimensions of these robots are 3 intersecting straight lines (x-y-z)
as shown in Figure. The Cartesian coordinate robot is one that consists of a column and
an arm. It is sometimes called an x-y-z robot, indicating the axis of motion. The x-axis
is lateral motion, the y-axis is longitudinal motion, and the z-axis is vertical motion.
Thus, the arm can move up and down on the z-axis; the arm can slide along its base on
the x axis; and then it can telescope to move to and from the work area on the y-axis.
Applications
1. Pick and place work
2. Application of sealant
Handling machine tools
4. Arc welding
Advantages
1. Ability to do straight line insertions into furnaces
2. Easy computation and programming
3. Most rigid structure for given length
Disadvantages
1. Requires large operating volume
2. Exposed guiding surfaces require covering in corrosive or dusty environments
3. Can only reach front of itself
4. Axis hard to seal

Cylindrical Robot:
Cylindrical robots have one angular dimension and 2 linear dimensions as
shown in Figure. The rigid structure of this system offers them the capability to lift
heavy loads through a large working envelope.
The main body of such a robot consists of a horizontal arm mounted on a vertical
column. The column is mounted on a rotating base. The horizontal arm moves forward
and backward on the direction of the longitudinal axis and it also moves up and down
on the column. Column and arm are rotating on the base around the vertical axis.
Applications
2. Handling machine tools
3. Spot-welding
4. Handling die-casting machines
Advantages
1. Can reach all around itself
2. Relatively easy programming
3. Rigid enough to handle heavy loads through large working space
4. Good access into cavities and machine openings
Disadvantages
1. Cannot reach above itself
2. Will not reach around obstacles
3. Exposed drives are difficult to cover from dust and liquids

Delta Robot:
A Delta Robot is a type of parallel robot that is commonly used in applications
requiring high-speed and precise movement in a 3D space. It is often used in industries
such as manufacturing, packaging, and automation. The Delta Robot configuration is
characterized by its three arms or limbs that are connected to a common base.
1. Base: The base of the Delta Robot is usually a fixed platform that supports the entire
structure. It contains the motors and actuators responsible for controlling the robot's
movements.
2. Three Arms or Limbs: Delta Robots have three identical arms or limbs, also known
as "kinematic chains," which radiate outward from the base. These arms are
connected to the base with articulated joints. Each arm consists of multiple links
and joints, typically with three or four degrees of freedom.
3. Parallel Configuration: The key characteristic of a Delta Robot is its parallel
configuration. The three arms are connected in parallel, meaning they all originate
from a single point on the base and converge at an end effector.
4. End Effector: At the end of the three arms, there is an end effector. The end effector
is the part of the robot that interacts with the workpiece or performs a specific task.

4. Robot Wrist and its configuration
A robot wrist, also known as the robot end-effector or robot wrist assembly, is the part
of a robotic arm that connects to the end of the arm and is responsible for performing various
tasks or actions. The configuration of a robot wrist can vary depending on the type of robot and
its intended application. However, there are some common elements and configurations found
in robot wrists:
Degrees of Freedom (DOF): The number of degrees of freedom in a robot wrist
determines its ability to move in different directions. Typically, robot wrists have at least three
DOF to allow for movement in three-dimensional space. Common configurations include 3-
DOF (yaw, pitch, and roll).
These are the basic rotational movements of a robot wrist:
 Yaw (Pan): Rotation around the vertical axis.
 Pitch (Bend): Rotation around the horizontal axis.
 Roll (Swivel): Rotation around its own axis (often used for tool alignment).

5. Work Volume
The work volume or work envelope is the three-dimensional space in which the
robot can manipulate the end of its wrist. It is determined by the number and types of
joints in the manipulator, the ranges of various joints, and the physical size of the links.
Its actual shape is dependent on the robot`s configuration:
a. A polar robotic configuration tends to produce a spherical work volume;
b. A cylindrical configuration has a cylindrical work envelope and
c. A Cartesian co-ordinate robot produces a rectangular work volume.
6. Degree of Freedom
 Radial traverse
 Vertical traverse
 Rotational traverse
 Pitch (Band)
 Yaw
 Roll (Swivel)

Degree of freedom is the number of independent movements a robot can realize with
respect to its base. The number of axes is normally the same as the number of degrees of
freedom of the robot.
Each joint on the robot introduces a degree of freedom. Each degree of freedom can be
a slider, rotary, or other type of actuator. Robots typically have five or six degrees of freedom
as shown in Figure.
Three of the degrees of freedom allow positioning in 3D space, while the other two or
three are used for orientation of the end effector. Six degrees of freedom are enough to allow
the robot to reach all positions and orientations in 3D space.
 Six degrees of freedom are commonly available with articulated arm and gantry
robots.
 Four degrees of freedom are typical with the selective compliance assembly robot arm
(SCARA) configuration.
 Seven or more axes are used for some special applications.
7. Type of joints in robot
A robot joint is a mechanism that permits relative movement between parts of a
robot arm. The joints of a robot are designed to enable the robot to move its end-effector
along a path from one position to another as desired.
The basic movements required for a desired motion of most industrial robots are:
a. Rotational movement: This enables the robot to place its arm in any direction on
a horizontal plane.
b. Radial movement: This enables the robot to move its end-effector radially to reach
distant points.
c. Vertical movement: This enables the robot to take its end-effector to different
heights.
Depending on the nature of this relative motion, the joints are classified as
a. Prismatic joints b. Revolute joints

Prismatic joint (P) or Linear joint (L)
Prismatic joints are also known as sliding as well as linear joints. They are
called prismatic because the cross section of the joint is considered as a generalized
prism. They permit links to make a linear displacement along a fixed axis. In other
words, one link slides on the other along a straight line.
Orthogonal Joint (U)
The U –joint is a symbol that is denoted
for the orthogonal joint. This joint is
like the linear joint. The only difference
is that the output and input links will be
moving at the right angles.
Revolute joints
Revolute joints, where a pair of links rotates
about a fixed axis.
Rotational Joint (R Joint)
A rotational joint (R) is identified by its motion, rotation about an axis
perpendicular to the adjoining links. Here, the lengths of adjoining links do not change
but the relative position of the links with respect to one another changes as the rotation
takes place.

Twisting Joint (T Joint)
Atwisting joint (T) is also a rotational joint, where the rotation takes place about
an axis that is parallel to both adjoining links.
Revolving Joint (V Joint)
A revolving joint (V) is another
rotational joint, where the rotation takes
place about an axis that is parallel to one
of the adjoining links. Usually, the links
are aligned perpendicular to one another
at this kind of joint. The rotation
involves revolution of one link about
another.
8. End Effectors- Grippers and Types
End effectors, also known as end-of-arm tools (EOAT), are devices or tools
attached to the end of a robotic arm or manipulator. They are used to perform specific
tasks, such as gripping, manipulating, or interacting with objects in a variety of
applications, including manufacturing, assembly, material handling, and more.
Grippers are a common type of end effector, and there are various types of
grippers and tools designed for different purposes.
1. Pneumatic Grippers: Pneumatic
grippers use compressed air to
open and close, allowing them to
grip objects.

2. Electric Grippers: Electric grippers use electrical motors to open and close their
jaws. They offer more precise control over the gripping force and position.
3. Hydraulic Grippers: Hydraulic
grippers use hydraulic fluid to
generate the force required for
gripping.
4. Vacuum Grippers: Vacuum
grippers use suction to pick
up objects with flat and
smooth surfaces, such as
glass or sheet metal.
5. Magnetic Grippers: Magnetic
grippers use electromagnetic
fields to hold and manipulate
ferrous objects, like steel or iron.

End Effectors- Tools
1. Welding Torches: Welding torches are used in robotic welding applications
2. Cutting Tools: Robotic cutting tools, such as plasma cutters or water jet cutters, etc.
3. Painting Equipment: Robotic painting equipment includes spray guns and paint
applicators attached to the robot's arm.
4. Screwdrivers and Fastening Tools: Robots equipped with screwdrivers or fastening
tools can assemble products by tightening screws, bolts, or other fasteners.
5. Sensors: Some end effectors are equipped with sensors, such as cameras or
force/torque sensors.
6. Lasers: Laser-based end effectors are used for tasks like cutting, engraving,
marking, or measuring.
7. Palletizing Tools: Palletizing end effectors are designed to stack or arrange objects
on pallets, commonly used in industries like logistics and manufacturing.
8. Scanning and Inspection Tools: These end effectors are equipped with sensors or
cameras to scan and inspect objects for quality control, identifying defects or
inconsistencies.
9. Factors to be considered for Selecting a robotic gripper
Selecting the right robotic gripper for a specific application is crucial to ensure
efficient and effective robotic operations.

10. Robotic Drives- Electric Drive, Pneumatic Drive, Hydraulic Drive
Robotic drive the mechanical linkages and joints of a manipulator, which can be various
types of motors and valves. The energy for these actuators is provided by some power
source such as hydraulic, pneumatic, or electric.
There are three major types of drive systems for industrial robots:
 Hydraulic drive system
 Pneumatic drive system
 Electric drive system
Hydraulic Drive System:
Hydraulic cylinders and motors are compact and allow for high levels of force and
power, together with accurate control. These systems are driven by a fluid (Oil) that is pumped
through motors, cylinders, or other hydraulic actuator mechanisms. A hydraulic actuator
converts forces from high pressure hydraulic fluid into the mechanical shaft rotation or linear
motion.
Advantages
1. A hydraulic device can produce an enormous range of forces without the need for gears,
simply by controlling the flow of fluid Preferred for moving heavy parts
2. Preferred to be used in explosive environments
3. Self-lubrication and self-cooling
4. Smooth operation at low speeds
5. There is need for return line
Disadvantages
1. Occupy large space area
2. There is a danger of oil leak to the shop floor

Pneumatic Drive System:
These systems use compressed air to power the robots. These robots generally have
fewer axis of movement and can carry out simple pick-and place material-handling operations,
such as picking up an object at one location and placing it at another location.
Advantages
1. Less expensive than electric or hydraulic robots
2. Suitable for relatively less degrees of freedom design
3. Do not pollute work area with oils
4. No return line required Pneumatic devices are faster to respond as compared to a
hydraulic system as air is lighter than fluid
Disadvantages
1. Compressibility of air limits control and accuracy aspects, noise pollution from
exhausts and leakage of air can be of concern.
Electric Drive System:
These systems are servomotors, stepping motors, and pulse motors. These motors
convert electrical energy into mechanical energy to power the robot. Compared with a
hydraulic system, an electric system provides a robot with less speed and strength.
There are three major types of electric drive that have been used for robots:
1. Stepper Motors 2. DC/AC Servos
Advantages
1. Good for small and medium size robots
2. Better positioning accuracy and repeatability
3. Less maintenance and reliability problems
Disadvantages
1. Provides less speed and strength than hydraulic robots
2. Not all electric motors are suited for use as actuators in robots
3. Require more sophisticated electronic controls and can fail in high temperature, wet, or
dusty environments

11. Robot Control systems
 Point- to Point control Systems
 Continuous Path Control
 Intelligent control
 Controller Components
 System Control
Point-to Point control: A point-to-point robot can move from one discrete point
to another within its working envelope. During point-to-point operation the robot moves
to a position, which is numerically defined, and it stops and end effector performs the
desired task, while the robot is halted. When task is completed, the robot moves to the
next point and the cycle is repeated.
Applications:
1. Component insertion
2. Spot-welding
3. Hole drilling
4. Machine loading and unloading
Continuous Path Control: In a continuous-path robot, the tool performs its
task, while the robot (its axes) is in motion, like in the case of arc welding, where the
welding gun is driven along the programmed path. All axes of continuous path robots
move simultaneously, each with a different speed.
These are the most advanced robots and require the most sophisticated computer
controllers and software development.
Applications:
1. Spray painting
2. Finishing
3. Arc welding operations
4. Cleaning of metal articles
5. Complex assembly
processes
Intelligent Control: Intelligent control systems integrate advanced algorithms
(programs), sensors, and artificial intelligence to make robots more adaptable and
capable of handling complex and dynamic environments. These systems enable robots
to make decisions, adapt to changes in the environment, and interact with humans and
other machines intelligently.

Controlled-path robots: Controlled-Path Robot: In controlled-path robots, the
control equipment can generate paths of different geometry such as straight lines,
circles, and interpolated curves with a high degree of accuracy. Good accuracy can be
obtained at any point along the specified path. Only the start and finish points and the
path definition function must be stored in the robot's control memory. It is important to
mention that all controlled- path robots have a servo capability to correct their path.
System Control: Control systems help to control the movements and functions
of the robot. To understand the control system first we need to understand some
terminologies used in robotics.
12. Present a Robotic Coordinate system using a robot
 Joint co-ordinate system
 Rectangular co-ordinate system
 User or object coordinate system
 Tool coordinate system
Joint Coordinate System: The
joint coordinate system represents the
robot's configuration by specifying the
angles or positions of its joints. Each joint
of the robot is assigned a unique coordinate.
For example, in a robot with multiple joints,
you might have joint angles represented as
θ1, θ2, θ3, etc., for each joint.

Rectangular Coordinate System
(Cartesian Coordinate System): The
rectangular coordinate system is the most
used coordinate system in robotics. It
defines the robot's position and orientation
in three-dimensional space using X, Y, and
Z coordinates for position and roll (rotation
about the X-axis), pitch (rotation about the
Y-axis), and yaw (rotation about the Z-axis)
for orientation.
Work/ user/ Object Coordinate
System: The user or object coordinate
system allows the robot to interact with
objects in its environment from a relative
perspective. It is typically defined based
on a specific object's reference point or a
user-defined origin, orientation, and
scale.
Using this system, a robot can grasp, manipulate, or work with objects in their
local reference frame, making it easier to perform tasks like picking and placing objects
or assembly operations.
Tool Coordinate System (Tool frame): The tool coordinate system is essential
for accurately controlling the robot's end-effector (e.g., gripper, welding tool, or any
other end-of-arm tool). It defines the position and orientation of the tool relative to the
robot's end-effector. This system is crucial for tasks that require precise control over the
tool's position and orientation, such as welding, painting, or machining.

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