45894623 industrial robotics

7/27/2019 45894623 Industrial Robotics

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Industrial Robotics

Introduction

Robot configuration

Programming

End effectors

Sensors

Industrial applications


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Introduction

Brief history of development

Definition of the Robot Institute ofAmerica:

A robot is a programmable, multi-function

manipulator designed to move material, tools or

special devices through variable programmed

motions for the performance of a variety of tasks


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Robot Physical Configuration

1. Polar coordinate configuration2. Cylindrical coordinate configuration

3. Jointed arm configuration

4. Cartesian coordinate configuration


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Polar coordinate configuration

Also called Spherical Coordinate configuration

Ex: Unimate 2000 series


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Cylindrical coordinate configuration

Ex: Unimate 3000 series


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Jointed arm configuration

Cincinatti Milacron T model

Unimate PUMA model


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Cartesian coordinate configuration

Rexroth robotic system


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Robot motions: six degrees of freedom


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Cartesian Robot

Cartesian robot is formed by 3 prismatic joints, whoseaxes are coincident with the X, Y and Z planes.


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Gantry Robot

Cartesian coordinate robots with the horizontal member

supported at both ends are sometimes called Gantry robots.


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Parallel Robot

Parallel robot is a complex mechanism which is constituted

by two or more kinematics chains between, the base and theplatform where the end-effectors are located. Good

examples are the flying simulator


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Spherical Robot

It is still in the research laboratory, the Spherical robot isactually a spherical shape robot, which has an internal

driving source.


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Configuration Advantages Disadvantages

Cartesian

coordinates

3 linear axes, easy to visualize, rigid structure,

easy to program

Can only reach front of itself, requires large

floor space, axes hard to seal

Cylindrical

coordinates

2 linear axes +1 rotating, can reach all around

itself, reach and height axes rigid, rotational axis

easy to seal

Cant reach above itself, base rotation axis as

less rigid, linear axes is hard to seal, wont

reach around obstacles

SCARA coordinates 1 linear + 2 rotating axes, height axis is rigid,

large work area for floor space

2 ways to reach point, difficult to program

off-line, highly complex arm

Spherical

coordinates

1 linear + 2 rotating axes, long horizontal reach Cant reach around obstacles, short vertical

reach

Revolute

coordinates

3 rotating axes can reach above or below

obstacles, largest work area for least floor space

Difficult to program off-line, 2 or 4 ways to

reach a point, most complex manipulator


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Other Technical Features

Work volume

Precision of movement

Speed of movement Payload capacity

Type of drive system


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Accuracy and Repeatability


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Robot Programming

1. Manual method

2. Walkthrough method

3. Leadthrough method

4. Off-line programming


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Manual method

It is more like setting up the machine rather than

programming

Used for simple robots

Involves setting stops, cams, switches and relays

Uses low technology for short work cycles


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Walkthrough method

The programmer manually moves the robots arm andhand through the motion sequence of the work cycle

Each movement is recorded into memory for

subsequent playback during production

Once the motion sequence is recorded, the speed of

movement can be controlled independently

Appropriate for spray painting, arc welding, etc


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Leadthrough method

Uses a teach pendent to power drive the robotthrough its motion sequence

Each motion is recorded into memory for future

playback during the work cycle

Popular because it is easy and convenient


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Off-line programming

Uses off-line programming language

Since programming is done off-line, it means higher

utilisation of the robot and the equipment with which it

operates

Ensures integration of the robot with FMS and CIM

systems


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Robot Programming Languages

VAL

Developed by Victor Scheinman for the PUMA robot

Stands for Victors Assembly Language

Two types of statements: Monitor commands and

Programming instructions

Program instructions are written in VAL, while variouspoint locations are defined using a teach pendent


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Monitor Commands

Preparing the system for the user to write programs

Defining points in space

Commanding the robot to execute a program

Listing programs on the CRT

Examples: EDIT, EXECUTE, SPEED, HERE, etc


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Program Instructions

MOVE: Moves the robot to the location and orientation specified by the

symbol

MOVES: Moves the robot along a st.-line trajectory, to the specified

location

APPRO: Moves the end effector to the position defined, but offset along

the Z-axis by the specified distance in mm

APPROS: Similar as above, but along a st.-line trajectory

DEPART: Moves the tool the distance given along the current Z-axis of

the tool

OPENI: Opens the gripper immediately

CLOSEI: Closes the gripper immediately

EXIT: Exits from the program and transfers control to monitor mode


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VAL Programming Example

TASK:

Pick and place operation

Robot should pick up a part from one conveyor (Point A)

Place the part on another conveyor (Point B)


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VAL Programming Example

PROGRAM PICK

1. APPRO A, 50

2. MOVES A

3. CLOSEI

4. DEPART 50

5. APPRO B, 506. MOVES B

7. OPENI

8. DEPART 50

LISTL A

X/JT1 Y/JT2 Z/JT3 P/JT4 Q/JT5-105.5 87.8 119.0 -25.6 100.9

LISTL B

X/JT1 Y/JT2 Z/JT3 P/JT4 Q/JT5

-50.0 115.8 55.5 -10.7 100.2


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End Effectors

It is a device which is attached to the robots wrist toperform a specific task

It is a special purpose tooling which enables the robot

to perform a particular job

It is usually custom engineered for the job

Most robot manufacturers have engineering groups

which design and fabricate end effctors or provideadvice to their customers on end effector design

There are two types of end effectors: Grippers and tools


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Grippers

Mechanical Grippers: Friction or the physical

configuration of the gripper retains the object

Suction cups: also called vacuum cups, used for flat

fragile objects

Magnetic Grippers: for ferrous objects

Hooks: to lift parts off conveyors

Scoops/Ladles: for handling fluids, powder, pellets,

or granular substance


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Grippers

Pivot action Gripper


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Grippers

Slide action Gripper


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Grippers

Double Gripper Pivot action mechanism


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Grippers

Vacuum Gripper


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Tools as End Effectors

Spot welding gun

Arc welding tools (and wire-feed

mechanism)

Spray painting gun

Drilling head

Routers, grinders, wire brushes

Heating torches


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SENSORS IN ROBOTICS

Internal: for controlling position and veleocity of various

joints. Ex: optical encoders, potentiometers, etc

External: for workcell control.


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Types of Sensors in Robotics

Tactile and Proximity sensors

Voice sensors

Machine vision


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Tactile and Proximity sensors

Provides the robot with capability to respond to contact forces withother objects within the work volume

Two types: Touch sensors and stress sensors (tactile sensors)

touch sensors will simply indicate that a contact has been made

with an object. A simple micro switch can serve the purpose

Stress sensors measure the magnitude of the contact force.

Starin gauges are the most popular choice

Tactile sensors are useful in assembly and inspection operations.

In assembly, the robot can perform delicate part alignment and

joining operations

In inspection, touch sensing would be useful in gauging

operations and dimensional measuring activities Proximity sensors are used to sense when one object is close to

another


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Voice sensors

Used for voice programming

A speech recognition system analyses the voice inputs

and compares it with a set of stored word patterns

when a match is found between the input and the stored

vocabulary word, the robot performs some action which

corresponds to that word

It can speed up robot programming


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Machine Vision

Machine vision can be defined as the acquisition of

image data, followed by processing and interpretation

of this data by computer for some useful application

Classification: 2D and 3D vision systems


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Basic Functions of Vision system

Image acquisition and digitisation

Image processing and analysis

Interpretation


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Image Acquisition and Digitization

A camera captures the image

Image is obtained by dividing the viewing area into a

matrix of discrete picture elements(pixels)

Each pixel has a value that is proportional to the lightintensity of that portion of the scene

The intensity value for each pixel is converted into

equivalent digital value by an ADC

Selection of appropriate lighting system is important to

establish contrast between the object and the background


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Binary vision: light intensity of each pixel isultimately reduced to either of two values, white or

black, depending on whether light intensity exceeds

some threshold level

Gray scale system: capable of distinguishing and

storing different shades of gray in the image. It can

highlight the objects texture and colour.


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Each set of pixel values is referred to as a frame andstored in computer memory as frame buffer

The process of reading all the pixel values in a frame isperformed with a frequency of 25-30 times per second

Cameras used: Vidicon and Solid-state

Types of illumination: front lighting, back lighting and sidelighting



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The data for each frame must be analysed within thetime required to complete one scan (1/30 sec)

Segmentation: define and separate regions of Interestwithin the image

segmentation techniques: thresholding and edgepreparation

Feature extraction: length, width, perimeter, c.g., aspectratio, etc



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Interpretation

Object/pattern recognition

Template matching

Feature weighting



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Machine Vision Applications

1. Inspection

2. Part identification

3. Visual guidance and control

4. Safety monitoring


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Robotic Applications

Material handling: material transfer and machineloading/unloading

Processing operations: spot welding, continuous

welding, spray painting, drilling, grinding, laser cutting,riveting, etc

Assembly and inspection

45894623 industrial robotics

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