FUNDAMENTALS OF ROBOT
CONTENTS:
1. FUNDAMENTALS OF ROBOT
1.1 Robot Definition
1.1.1 Three Laws of Robotics
1.2 Robot Anatomy
1.3 Co-ordinate Systems
1.3.1 Polar Coordinate Body-And-Arm Assembly
1.3.2 Cylindrical Body-and-Arm Assembly
1.3.3 Cartesian Co-ordinate Body-and-Arm Assembly
1.3.4 Jointed-Arm Robot
1.3.5 Scara Robot
1.4 Work Envelope
1.5 Specifications of robots
1.5.3 Wrist Yaw.
1.5.1 Wrist Roll
1.5.2 Wrist Pitch
1.5.4 Pay Load
4.5.5 Spatial Resolution
1.6 Robot Motions
1.7 Robot Parts and their Functions
1.8 Different Applications
1.9 Different Applications
TECHNICAL TERMS:
Robot: An industrial robot is a programmable, multi-functional manipulator designed to move
materials, parts, tools, or special devices through variable programmed motions for
theperformance of a variety of tasks”
Robot Anatomy: It is concerned with the physical construction of the body, arm and wrist ofthe
machine
Actuator A power mechanism used to effect motion of the robot; a device that converts
electrical, hydraulic, or pneumatic energy into robot motion.
Cartesian-Coordinate Robot: A Cartesian-Coordinate robot is a robot whose manipulatorarm
degrees of freedom are defined by Cartesian coordinates. This describes motions that areeast-
west, north-south and up-down, as well as rotary motions to change orientation.
Closed-Loop: Control achieved by a robot manipulator by means of feed-back information.As a
manipulator is in action, it's sensors continually feed-back information to the robot'scontroller
which are used to further guide the manipulator within the given task.
Control Device Any piece of control hardware providing a means for human intervention inthe
control of a robot or robot system, such as an emergency-stop button, a start button, or aselector
switch.
Degrees of Freedom: The number of independent directions or joints of the robot
(R15.07),which would allow the robot to move its end effector through the required
sequence ofmotions.
End-Effector: An accessory device or tool specifically designed for attachment to the
robotwrist or tool mounting plate to enable the robot to perform its intended task.
Manipulator: To move, arrange, operate, or control by the hands or by mechanical
means,especially in a skillful manner: To move, arrange, operate, or control by the hands or
bymechanical means, especially in a skillful manner.
Open-loop system: Open loop controls have no feedback and require the input to return tozero
before the output will return to zero.
Wrist pitch: This involves the up or down rotation of the wrist. Wrist pitch sometimes
calledwrist bend.
Feedback: The return of information from a manipulator, or sensor to the processor of
the robot to provide self-correcting control of the manipulator. See FeedbackControl,
and Feedback Sensor.
Wrist roll: This involves rotation of the wrist mechanism about the arm axis is called wrist roll.
It is also called as wrist swivel.
Workspace: The volume of space within which the robot can perform given tasks.
Work Envelope: The set of all points which a manipulator can reach without intrusion.
Sometimes the shape of the work space, and the position of the manipulator itself can restrict
the work envelope.
Pay Load: Mass that the robot is designed to manipulate under the manufacturer’s
speciation over the entire work envelope.
Wrist yaw: Wrist yaw would involves left or right rotation of the wrist is called wrist yaw.
Accuracy: Accuracy can be defined as the ability of a robot to position its wrist end at a
desired target point within its reach.
Repeatability: It is the ability of the robot to position the end effector to the previously
positioned location.
Spatial resolution: The spatial resolution of a robot is the smallest increment of
movementinto which the robot can divide its work volume.
INTRODUCTION:
1.1 ROBOT- Definition
An Industrial Robot is a reprogrammable, Multifunctional, Manipulator designed to move
materials, parts, tools or special devices through variable programmed motion for the
performance of a variety of tasks.
1.1.1 Three Laws of Robotics
i. A robot may not injure a human being or through in action allow a human to beharmed.
ii. A robot must obey orders given by humans except when that conflicts with thefirst law.
iii. A robot must protect its own existence unless that conflicts with the first or
secondlaws.
1.2 ROBOT ANATOMY:
Robot anatomy concerned with the physical construction of the body, arm and wrist of the
machine. Most robots used in plants today are mounted on a base which is fastened to thefloor.
The body is attached to the base and the arm assembly is attached to the body. At theend of the
arm is the wrist. The wrist consists of a number of components that is to be oriented in a variety
of positions.
1.3 ROBOT BODY-AND-ARM CONFIGURATIONS
Five common body-and-arm configurations for industrial robots:
1.Polar coordinate body-and-arm assembly
2.Cylindrical body-and-arm assembly
3.Cartesian coordinate body-and-arm assembly
4.Jointed-arm body-and-arm assembly
5.Selective Compliance Assembly Robot Arm (SCARA)
1.3.1 POLAR COORDINATE BODY-AND-ARM ASSEMBLY
It uses a telescoping arm that can be raised or lowered about a horizontal pivot. The pivot
is mounted on a rotating base. These various joints provide the robot With the capability
to move its arm with in a spherical space And hence the name spherical coordinate robot.
1.3.2 CYLINDRICAL BODY-AND-ARM ASSEMBLY
It consists of a vertical column, relative to which an arm assembly is moved up or
down. The robot arm is attached to the slide so that it can be moved radially with respect tothe
column. By rotating the column, the robot is capable of achieving a work space that
approximates a cylinder.
1.3.3 CARTESIAN CO-ORDINATE BODY-AND-ARM ASSEMBLY
It uses three perpendicular slides to construct the X, Y and Z axis. Other names are
sometimes applied to this configuration are xyz robot and rectilinear robot.
By moving the three slides the robot can capable of operating with in a rectangular work
envelope.
1.3.4 JOINTED-ARM ROBOT
Its configuration is similar to that of human arm. It consists of two straight
components, corresponding to the human forearm and upper arm, mounted on a vertical
pedestal. These components are connected by two rotary joints corresponding to the
shoulderand elbow. A wrist is attached to the end of the forearm, thus providing several
additionaljoints. Several commercially available robots posses the jointed arm configuration.
1.3.5 SCARA ROBOT
A special version of the jointed arm robot is the SCARA, whose shoulder and elbow joints
rotate about vertical axes. SCARA stands for selective compliance assembly robot arm,and
this configuration provides substantial rigidity for the robot in the vertical direction,
butcompliance in the horizontal plane.
1.4 WORK ENVELOPE OR WORK VOLUME;
Work volume is defined as the space with in which the robot can manipulate its wrist end.
The work volume is determined by the following physical characteristics of the robot.
1. The robot’s physical configuration.
2. The sizes of the body, arm and wrist components.
3. The limits of the robot’s joint convention.
1.5 SPECIFICATIONS
1.5.1 Wrist Roll
This involves rotation of the wrist mechanism about the arm axis is called wrist roll. It is
also called as wrist swivel.
1.5.2 Wrist Pitch
This involves the up or down rotation of the wrist. Wrist pitch sometimes called wrist bend.
1.5.3 Wrist Yaw.
Wrist yaw would involves left or right rotation of the wrist is called wrist yaw.
1.5.4 Pay Load
Mass that the robot is designed to manipulate under the manufacturer’s spefication over
the entire work envelope.
4.5.5 Spatial Resolution
The spatial resolution of a robot is the smallest increment of movement into which the robot
can divide its work volume. Spatial resolution depends on two factors:
(i) The system’s control resolution and the robot’s mechanical inaccuracies. It is
easiest to conceptualize these factors in terms of a robot with 1 degree of freedom.
1.6 ROBOT MOTIONS:
There are six basic motions or degrees of freedom which provide the robot, with
capability to move the end effector through the required sequence of motions.
The six degree of freedom are intended to emulate the versatility of movement possessed by the
human arm. Not all robots are equipped with ability to move in six degrees .
The six basic motions consist of three arm and body motions abd three wrist motions are for
the polar type robot.
Rotational transverse – Move about a vertical axis.
Radial transverse - Extension and retraction of arm
Vertical transverse - Up and down motion
Pitch - Up and down motion of the wrist
Yaw - Side to side movement of wrist
Roll - Rotation of wrist.
1.7 JOINT NOTATIONS:
It uses the joint symbols (L, O, R, T, V) to designate joint types used to construct robot
manipulator. It Separates body-and-arm assembly from wrist assembly using a column.
1.8 NEED FOR ROBOTS:
Frequently robots are used to do jobs that could be done by humans. However there are
many reasons why robots may be better than humans in performing certain tasks.
i) Speed
ii) Hazardous Environment
iii) Repetitive Tasks
iv) Efficiency
v) Accuracy
vi) Adaptability
1.9 ROBOT APPLICATIONS
i) Material handling
ii) Machine loading/ unloading Components
iii) Spray painting
iv) Welding
v) Machining
vi) Assembly
vii) Inspection
viii) Others
QUESTION BANK
PART-A
1.Name the commonly used robot configuration system?
The commonly used robot configuration systems are
Cartesian coordinate system
Cylindrical coordinate system
Polar or spherical coordinate system
Revolute coordinate system
2.Sketch the revolving joint and show the relative joint motions?
3.Define a Robot?
RIA defines a robot as a “programmable, multifunction manipulator designed to Move
materials, parts, tools or special devices through variable programmed motions for the
performance of the variety of tasks “.
4. State the advantages of a hydraulic drive? It
gives greater speed and strength.
It gives highest power to weight ratio. It
is used for heavy payloads.
It can be used for large working envelope.
It is safe and reliable to work in wet and dirty conditions. It
can be used in hazardous environment.
5. State the disadvantages of a hydraulic drive?
It occupies more space.
Maintenance should be done regularly.
6.What is meant by workspace?
The space in which the end point of the robot arm is capable of operating is called as
workspace in other words reach ability of robot arm is known as workspace.
7. What is meant by work volume?
The volume of the space swept by the robot arm is called work volume.
8. What is meant by work envelop?
The work envelop is described by the surface of the work space.
9. What is meant by accuracy of Robot ?
The robot’s ability to reach a reference point with in the robot’s full work volume is
known as
accuracy of robot.
10.What is meant by payload capacity of Robot?
The maximum load which can be carried by the manipulator at low or normal speed .
11. What is meant by precision of Robot?
It is the smallest increment of motion for which the robot can be controlled
12.What is repeatability of Robot?
Repeatability refers to robot’s ability to return to the programmed point when it is
commanded to do so.
13.What is meant by quality of Robot?
A Robot is said to be high quality when the precision and accuracy is more .
14. Classify the motion control of Robot arm?
• Limited sequence control
• Point to Point control
• Continuous path control
• Intelligent control
15. What is automation?
It is a technology that is concerned with the use of mechanical electronic and computer based
system in the operation and control of production.
16. What are the types of automation? 1)
Fixed automation
2) Programmable automation
3) Flexible automation
17. What are the types of robot anatomy? 1)
Polar
2) Cylindrical
3) Cartesian
4) Jointed arm
18. What are the types of robot movements? 1)
Arm and body motion
2) Wrist motion
19. What are the types of wrist motions?
1) Wrist roll
2) Wrist pitch
3) Wrist yaw
20. Define speed of response?
Speed of response refers to the capability of the robot to move to the next position in a short
amount of time.
