Industrial Roboticschap01fundamentals 1312537369 Phpapp02 110805044457 Phpapp02

8/12/2019 Industrial Roboticschap01fundamentals 1312537369 Phpapp02 110805044457 Phpapp02

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Introduction to Robotics

Prof A S Rao

Robotics & CAD/CAM Laboratory

Mechanical Engineering Department

VEERMATA JIJABAI TECHNOLOGICAL INSTITUTE

MUMBAI-400019


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OutlineWhat is Robotics Robot Coordinates

Laws of Robotics Robot Reference Frames

What is a Robot Programming Modes

Classification Robot Characteristics

Robot Components Robot Workspace

Robot DOF Robot languages

Robot Joints Robot Applications


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What is Robotics:

Robotics is an interdisciplinary subject that benefitsfrom mechanical engineering, electrical andelectronic engineering, computer science, biologyand many other disciplines.

Robotics is defined as that branch of engineeringwhich deals with the study of different types ofrobots, their simulations, their designs, theirconstructions, operations, performance etc.

Robotics is a form of Industrial Automation and is atechnology with a future and a technology for thefuture


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What is a Robot :

When we compare a crane attached to a utility or towing vehicleand robot manipulator which appears to be very similar because :

Both posses a number of links attached serially to each otherwith joints

In both the systems, the hand of the manipulator can be movedin space and be placed in any desired location with in theworkspace of the system

Each one is controlled by a central controller which controls theactuators

However one is called a robot and the other a manipulator (i.e. acrane)

The fundamental difference between the two is that the crane iscontrolled by a human who operates and controls the actuators,whereas a robot manipulator is controlled by a computer thatruns a program.


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The Automatic progrmmable machines which does the required

job through various programmed motions

According to RIA: A robot is a reprogrammable multifunctional

manipulator designed to move various objects, tools, materials or

specialized devices through variable programmed motions for the

performance of variety of tasks

Law of Japan states that a robot is All purpose machine equipped

with a memory device (for handling) capable of replacing human

labour for the automatic performance of tasks

Robert Schilling defines a robot as asoftware controlled mechanical

device that uses sensors to guide one or more of its end effectors

through various programmed motions in a work space in order to

mani ulate h sical ob ects

What is a Robot : Definition :


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Classification of Robots:

I. Dr ive Techno logy

II. Work Envelope/Coord inate Geometry

III. Mot ion Con trol Methods


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I. Drive Techno logy:

Motors are part of any robot system they producespatial displacement and control axis motions of the

robot. Based on power used to drive the joints of

the robot the 3 drive technologies are :

1) Electrical drive technology

2) Hydraulic drive technology

3) Pneumatic drive technology


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1. Electrical drive technology:

Most Robotic manipulators today use electric drives inthe form of either D.C.Servomotors or D.C.Stepped

motors

D.C.Servomotors : More controllability for precision

work (neat/precise)

D.C.Stepped motors : Load carrying capacity is large

Applications :

- PCB Assembly

- IC manufacture, etc


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2. Hydraulic drive technology:

Robotic manipulator which uses oil/liquid/gel as a

drive technology. We use it for very heavy load

carrying capacity purpose.

Limitation : Cleanliness will not be maintained

Applications:

-In steel industry for carrying molten steel

-Automobile industry


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3. Pneumatic drive technology:

It is used as at the gripper for manipulating delicateobjects, e.g. used in glass industry.

The robot operates from compressed air and they are

activated tools.Limitation: Built in compliance of air, i.e. air can be

compressed, creates noise while operation.

Application:Used in pick and place operations in glass industry

II W k E l /C d i t


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II. Wo rk Envelope/Coo rd inate

Geometry :

Work Envelope is defined as locus of points in 3

Dimensional space that can be reached by the wrist of

robot.

It consists of Rotary/Revolute motion about an axis

and Translation motion along an axis (i.e.

linear/sliding/prismatic/translate)


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III. Motion Con tro l Methods :

1. Point to Point motion : The discrete points arespecified, the tool moves in a sequence of discrete

points in the workspace.

2. Continuous or Controlled path motion : The

end effector must follow a prescribed path in 3Dspace and speed of motion along the path may

vary

Examples : PTP : Spot welding, Loading &Unloading, Pick and Place, etc.

CP : Spray painting, Arc welding, Grinding, etc.


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Robot Components :

Main components are :

- Manipulator : Main body (Links, Joints etc)

- End effector : Welding Torch, Paint spray gun etc

- Actuators : servo motors,stepper motors,cylinders etc- Sensors : Vision, Touch, Speech synthesizers etc

- Controller : receives data from PC and controls the

actuators- Processor: calculates motions of joints@speeds

- Software : OS, Appliaction s/w


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Degree of Freedom (DOF) : The no. of independent movements a robot can

perform in 3D space. (or) Direction in which a robotmoves when a particular joint is activated

To fully place the object in space and alsoorientate it as desired we need to have six DOF.

A system with seven DOF does not have uniquesolution i.e Robot mounted on conveyor belt ormobile platform

In 3.5 DoF, 3 DoF are along X,Y,Z axes, and 1/2DoF for not fully controlled movement like fullyextended or retracted position of pneumaticcylinder


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Robot Joints :

Robots may have types of joints like,

Linear (Prismatic): Either hydraulic or pneumaticcylinder, used in Gantry, cylindrical or similar configurations

Rotary (Revolute) : Most such joints electrically driveneither by servomotors or stepper motors

Spherical :They posses multiple DOF ,difficult to controlthey are not commonly used except in research work.


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Robot Coordinates :

Robot configurations are specified by a succession of

Ps,Rsor Sslike 3P3R

Cartesian/Rectangular/Gantry (3P) : 3 linear joints

Cylindrical (R2P) : 2 prismatic and 1 revolute joints

Spherical (2RP) :1 prismatic and 2 revolute joints

Articulated/anthropomorphic (3R) :All revolutejoints, similar to a humansarm, common for Industrial robots

Selective Compliance Assembly RobotArm (SCARA) :2 revolute joints, 1 prismatic (vertical)they are very common in assembly operations


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Robot motions are accomplished in 3 coordinate frames like,

World Reference Frame : Defined by X,Y,Z Axes motionssimultaneously, this is universal coordinate frame.

Joint Reference Frame : Only one joint moves at a time

Tool Reference Frame : Defined by X,Y,Z Axes motionssimultaneously attached to the hand defines the motions of thehand relative to this local frame. This is very useful in robotic

programming.

Robot Reference Frames :


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Programming Modes


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Programming Modes :

Commonly used Programming Modes : Physical Setup: In this mode operator sets up switches

and hard stops along with devices like PLCs

Lead Through or Teach Mode : In this mode therobot joints are moved with a teach pendant, point to point mode

Continuously Walk -Through Mode :In this modethe robot joints are moved simultaneously with a program, itsa

continuousmode, for example painting robots


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Robot Characteristics :

Payload : It is the weight a robot can carry with out losingaccuracy, Typical values 6.6 lbs of 86 lbs Fanuc Robot LR mate.

Reach : Reach is the a maximum distance a robot can reachwith in its work envelope (reaching dexterous points)

Precision (Validity) : It is defined as how accurately aspecified point can be reached. Typical value 0.001 inch

(resolution of robot)

Repeatability (Variability) : It is defined as howaccurately the same position can be reached. Typical value

0.001 inch range for 100 runs (say)

Robot WorkSpace :


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Robot WorkSpace :

Depending on their configuration and size of

their links and joints robot can reach acollection of points called a WorkSpace

Shape of WS depends on each robot

characteristics WS may be found by moving each joint

through its range of motions

Typical WS are Cartesian,Cylindrical,

Spherical,Articulated etc


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Robot Languages :

Many robot languages are based on Cobol, Basic, C

and Fortran etc Other languages are unique and at different level

from machine level to high level languages.

High level languages are either interpreter based or

compiler based

Interpreter based languages execute one line of the

program at time such as VALand AML, so

debugging is easier

Compiler based languages execute whole program

at time such as AL and so debugging is difficult


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Robot Applications :

Machine Loading

Pick and Place operations

Welding

Painting

Inspection and testing Assembly operations

Manufacturing like drilling, deburring, cutting etc.

Surveillance

Medical applications

Hazardous environments

Underwater,space, and remote locations

T t B k


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Text Books :

Fundamentals of Robotics - T.C. Manjunath

Robotics and Control - R.K.Mittal/I J Nagrath

Introduction to Robotics - Saeed B. Niku

Introduction to Robotics - John J CRAIG

Robotics - Ashitava Ghosal

Reference Books :

Industrial Roboticschap01fundamentals 1312537369 Phpapp02 110805044457 Phpapp02

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