What is a Robot?

loutsyrianMechanics

Oct 30, 2013 (4 years and 13 days ago)

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1

What is a Robot?

Definition of Robot

1.
Webster:


“An automatic apparatus or device that performs
functions ordinarily ascribed to human beings or
operates with what appears to be almost human
intelligence”

2. Robot Institute of America


“A robot is a re
-
programmable, multifunctional
manipulator designed to move material, parts, tools
or specialized devices through variable programmed
motions for the performance of variety of tasks”


2


Mechanical Engineering



Design of the mechanism.Understanding of the kinematics
and


dynamics of the system.


Electronic Engineering


Design of the actuator and sensor systems.


Systems Engineering


Analysis and integration of the overall system. Signal
conditioning and Control.


Computer Science


Design of the logic, intelligence or adaptability, networking
and


interface.

Technologies that go to make up a robot

3

Robot Characteristics

1.
The following definition are used to
characterized robot specification

i.
Payload

ii.
Reach

iii.
Precession

iv.
Repeatability



4


Payload is the weight a robot can carry and still
remain within its other specifications


E.g. A robot maximum load capacity may be
much larger than its specified payload, but at
maximum level it may become less accurate, may
not follow its intended path accurately, or may
have excessive deflections


Payload

Robot Characteristics (cont)

5

Reach


Maximum distance a robot can reach within its
work envelope

Precision (validity)


Defined as how accurately a specified point
can be reached.


Most industrial robot can have precision of
0.001 inch or better

Robot Characteristics (cont)

6

Repeatability (variability)


Repeatability is how accurate the same position can be
reached of the motion repeated many times.


Repeatability is more important than precision


If a robot is not precise, it will generally show a
consistent error, which can be predicted and thus
corrected using programming.


If the error is random, it cannot be predicted and thus
cannot be eliminated.


Most industrial robots have repeatability in the 0.001
inch range

Robot Characteristics (cont)

7

Advantages & Disadvantages of Robots

Advantages


Robotics and automation can, in many situations increase
productivity, safety,efficiency, quality and consistency of
product


Robot can work in hazardous environments without the
need of life support, comfort or concern about safety


Robot needs no environmental comfort, such as lightning,
air conditioning, ventilation and noise protection


Robots work continuously without experiencing fatigue or
boredom, do not get mad, do not have hangovers and need
medical insurance or vacation

8

Advantages & Disadvantages of Robots
(cont)

Advantages


Robots have repeatable precision at all times, unless
something happens to them or unless wear out


Robots can be much more accurate than human. E.g. New
wafer handling robots have micro inch accuracies


Accessories and sensor can have capabilities beyond
humans


Can process multiple stimuli or tasks simultaneously.

9

Advantages & Disadvantages of Robots
(cont)

Disadvantages


Robots replace human workers creating economic
problems. E.g. lost salaries, social problems (dissatisfaction
and resentment among workers)


Robots lack capability to respond in emergencies, unless
the situation is predicted and the response is included in the
system. Safety measures are needed to ensure that they do
not injured operators and machine working with them

10

Advantages & Disadvantages of Robots
(cont)

Disadvantages


This includes:


Inappropriate or wring responses


A lack of decision making power


A loss of power


Damage to the robot and other devices


Human injuries


11

Advantages & Disadvantages of Robots
(cont)

Disadvantages


Robots have limited capabilities in


Degree of freedom


Dexterity


Sensors


Vision systems


Real time response

12

Advantages & Disadvantages of Robots
(cont)

Disadvantages


Robots are costly due to


Initial cost of equipment


Installation cost


Need of peripherals


Need for training


Need for programming

13

Robot Components


A Robot as a system consists of the following elements
which are integrated together to form a whole:

i.
Manipulator (or rover)

ii.
End effectors

iii.
Actuators

iv.
Sensors

v.
Controller

vi.
Processor

vii.
Software

14

Robot Components (cont)


Is the main body of the robot and consists of links, the
joints and other structural elements

Manipulator


The part that is connected to the last joint (hand) of a
manipulator.


In most cases the action of the end effector is either
controlled by the robot’s controller or the controller
communicates with the end effector’s controlling device
such as (e.g. PLC)


End Effectors

15

Robot Components (cont)


Are the “muscles” of the manipulator that move or
create mechanical action


Common types


Servomotors



power driven mechanism that help
main controller operates using low force


Stepper motors



a rotating motor in a small step
and not continuous


Pneumatic cylinders



relating to air or other gases


Hydraulic cylinders



moved by, or operated by a
fluid, especially water, under pressure.


Actuators


16

Actuators (cont)


Robot Components (cont)

17

Multiplication factor

E.g

Left piston = 2 inches in diameter (1
-
inch radius)

Right piston = 6 inches in diameter (3
-
inch radius)

Area =

r
2



Answer

Area of the left piston =

(1)
2
=
3.14

Area of the right piston = 28.26.


The piston on the right is 9 times larger than the piston on the left.
What that means is that any force applied to the left
-
hand piston
will appear 9 times greater on the right
-
hand piston. So if you
apply a 100
-
pound downward force to the left piston, a 900
-
pound
upward force will appear on the right. The only catch is that you
will have to depress the left piston 9 inches to raise the right
piston 1 inch.


Actuators (cont)


Robot Components (cont)

18

Robot Components (cont)


Sensors are used to collect information about the
internal state if the robot to communicate with outside
environment


E.g. Vision system, speech, and touch/tactile

Sensors



Similar to cerebellum (controls motions)


Receive data from computer, control actuators motions
and coordinates the motions with the sensory feedback
information


E.g. Controls angle, velocity, force

Controller


19

Robot Components (cont)


The brain


Generally a computer but dedicated to a single purpose


E.g. Calculates motions, how much/fast joint must move

Processor





Three group of software


Operating system


Robotic software


calculates necessary motions of
each joint based on kinematics equations


Collection of routines and application programs


to
use peripheral devices (e.g. vision routines, specific
task)

Software

20

Types of Robot


Function & Application


Japanese Industrial Robot Association (JIRA)


Class 1:
Manual Handling Device:

A device with
multiple DOF that is actuated by an operator


Class 2:
Fixed
-
Sequence Robot:
A device that
performs the successive stages if a task according to
predetermined, unchanging method and is hard to
modify


Class 3:
Variable

Sequence Robot:
Same as 2 but
easy to modify


Class 4:
Playback Robot:
A human operator
performs the task manually and records the motions
for later playback. The robot repeats.

Classification of Robot




21

Types of Robot


Function & Application


Japanese Industrial Robot Association (JIRA)


Class 5:
Numerical Control Robot:

The operator
supplies the robot with a movement program rather
than teaching them manually


Class 6:
Intelligent Robot:

Robot with means to
understand its environment and the ability to
successfully complete a task despite changes in the
surrounding.

Classification of Robot (cont)




22

Types of Robot


Function & Application


Robotics Institute of America (RIA)

only consider
class 3
-
6 as robots


The
Association Francaise de Robotique (AFR)


Type A: Handling devices with manual control to
telerobotics


Type B: Automatic handling devices predetermined
cycles


Type C: Programmable, servo controlled robot with
continuous point
-
to
-
point trajectories


Type D: Same as type C, but with the capability to
acquire information from its environment

Classification of Robot (cont)




23

Types of Robot


Function & Application

Robot
Application


4D Application


Dangerous


Dirty


Dull


Difficult



4A tasks


Automation


Augmentation


Assistance


Autonomous

24

Degree of Freedom (DOF)


Six degree of freedom is needed to fully place the object
in space and also oriented it as desired (move & rotate
along x
-
, y
-

and z
-
axes)


If fewer than six, the robot’s capabilities are limited


E.g.


Robot with three DOF can only move along x
-
, y
-

and z
-
axes. No orientation can be specified (only
parallel to axes)


Robot with five DOF capable of rotating about three
axes but only moving along x
-
, y
-
axes (not z
-
axes)

25

Degree of Freedom (DOF) (cont)


A system with seven degrees of freedom does not have
unique solution. There are infinite number of ways it can
position a part and orientate it at desired location. There
must be additional decision making routine (for the
controller) that allows it to pick the fastest or shortest
path to the desired destination.


Due to this which take much computing power and time
no seven DOF is used in industry


Human arms have seven DOF. (Shoulder


3 DOF,
Elbow


1 DOF, wrist
-

3 DOF)


In robot end effectors never consider as on of DOF


½ DOF
-

if movement is not fully controlled (e.g only
can fully extended or retracted, can only at 0, 30, 60 or
90 degrees)

26

Robot Coordinates


Robot configurations for positioning the hand are as
follows:


C
artesian/rectangular/gantry (3P)


Cylindrical (R2P)


Spherical (2RP)



Articulated/anthropomorphic (3R)


Selective Compliance Assembly Robot Arm
(SCARA)




P = Prismatic (linear),

R = Revolute,

S = Spherical




27

Robot Coordinates (cont)

28

Robot Workspace


Robot workspace is the ability of a robot to reach a
collection of points (workspace) which depends on the
configuration and size of their links and wrist joint.


The workspace may be found mathematically by writing
equations that define the robot’s links and joints
including their limitations, such as ranges of motions for
each joint


Alternatively can be found by subtracting all the space it
can reach with what it cannot reach.


29

Robot Workspace (cont)

30

A Point for a Cartesian
-
coordinates Robot

Arm Configuration

31

Arm Configuration (cont)

A Point for a Cylindrical
-
coordinates Robot

32

Arm Configuration (cont)

A Point for a Cylindrical
-
coordinates Robot
(cont)

33

Arm Configuration (cont)

A Point for a SCARA Robot

34

Arm Configuration (cont)

A Point for a SCARA Robot (cont)

35

Arm Configuration (cont)

A Point for a Polar
-
coordinates Robot

36

Arm Configuration (cont)

A Point for a Polar
-
coordinates Robot (cont)

37

Arm Configuration (cont)

A Point for a Jointed
-
arm Robot

38

Arm Configuration (cont)

A Point for a Jointed
-
arm Robot (cont)