Robotics

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13 Νοε 2013 (πριν από 3 χρόνια και 6 μήνες)

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ROBOTICS


1

What is robotics?


an interdisciplinary field of science that exists at the interface among the
other disciplines:


o
mechanics


o
electronics


o
informatics


o
automation



deals with the design, construction, operation, and application of robots,
as well as computer systems
.

2



Roboticists

develop man
-
made mechanical devices that can
move by themselves, whose motion must be
modelled,
planned, sensed, actuated

(
made to perform
) and
controlled
,

and whose motion behaviour can be influenced by
“programming”.



A device can only be called a “robot” if it contains a movable
mechanism, influenced by
sensing, planning, actuation
and

control

components.



3





Robots are called “intelligent” if they succeed in moving in
safe interaction with an unstructured environment, while
autonomously achieving their specified tasks.

4

Robotics



covers not just “pure” robotics or only “intelligent” robots, but
rather the broader domain of
robotics
and

automation
.



This includes “dumb” robots such as:

o
metal and woodworking machines,

o
“intelligent” washing machines, dish washers and pool
cleaning robots, etc.



The
y
all have
sensing
,
planning

and
control
, but often not in
individually separated components.



For example, the
sensing
and
planning

behaviour of the pool
cleaning robot have been integrated into the mechanical design of
the device, by the intelligence of the human developer
.

5


Robotics is, to a very large extent, all about system
integration, achieving a task by an
actuated

(
functioning
)

mechanical device, via an “intelligent” integration of
components, many of which it shares with other domains
,
e.g
.:


o
systems
&

control
;

o
computer science
;

o
character animation
;

o
machine design
;

o
computer vision
;

o
artificial intelligence
;

o
cognitive science
;

o
biomechanics, etc.


6




The boundaries of robotics cannot be clearly defined.



Its “core” ideas, concepts and algorithms are being applied in an
ever increasing number of “external” applications, and, vice versa.



Core technology from other domains (
for example
,
vision, biology,
cognitive science or biomechanics
) are becoming crucial
components in more and more modern robotic systems.


7

Components of a robotic system


The semantics of the terminology
:

sensing, planning, modelling, control
, etc.



The real robot is
a

mechanical device (“
mechanism
”) that moves around in the
environment, and, in doing so, physically interacts with this environment.



Th
e

interaction involves the exchange of physical energy, in some form or
another.



Both the robot mechanism and the environment can be the “cause” of the
physical interaction through
Actuation
, or experience the “effect” of the
interaction, which can be measured through
Sensing
.


8



Robotics
as an integrated system of control interacting with the
physical world.





Sensing

and
actuation

are the physical
ports

(
a logic circuit for the input
and output of data /
a

point of physical access or physical interface between
a circuit and a device or system at which signals are injected or extracted.
)

through which the “
Controller
” of the robot determines the interaction of
its mechanical body with the physical world.




T
he
controller can, in one extreme, consist of software only, but in the
other extreme everything can also be implemented in hardware.


9



Within the controller component, several sub
-
activities are often
identified:





Modelling
. The input
-
output relationships of all control
components can (but need not) be derived from information
that is stored in a model.





10


This model can have many forms:

o
analytical formulas,

o
empirical look
-
up tables
(an array that replaces runtime
computation with a simpler array indexing operation),


an array
data structure or simply an array is a data structure
consisting of a collection of elements values or variables ,


a data structure
is a particular way of storing and organising
data in a computer. It consists of a collection of elements (values
or variables), each identified by at least one array index or key
.



a variable
is a storage location and an associated symbolic
name which contains some known or unknown quantity or
information,


a value
is an expression which cannot be evaluated any
further
)



11



o
fuzzy
rules
(fuzzy rules are linguistic IF
-
THEN
-

constructions that
have the general form "IF A THEN B" where A and B are (collections
of) propositions containing linguistic variables. A is called the
premise and B is the consequence of the rule.),
etc.


12


The name
model

-

any information that is used to determine or
influence the input
-
output relationships of components in the
Controller
.


Other components that can all have models inside:



A “System model” can be used to tie multiple components
together, but not all robots use a System model.



The “Sensing model” and “Actuation model” contain the
information with which to transform raw physical data into task
-
dependent information for the controller, and vice versa.

13


Planning
. This is the activity that predicts the outcome of
potential actions, and selects the “best” one. Almost by definition,
planning can only be done on the basis of some sort of model.



Regulation
. This component processes the outputs of the sensing
and planning components, to generate an actuation setpoint.
T
his
regulation activity could or could not rely on some sort of
(system) model.



The term “control” is often used instead of “regulation”, but it is
impossible to clearly identify the domains that use one term or
the other.


14

Robotics technology


Sensors


A

sensor sends information, in the form of electronic signals back to the
controller.



Sensors also give the robot controller information about its
surroundings and

e.g
. ,
let

it know the exact position of the arm, or the
state of the world around it.



Sight, sound, touch, taste, and smell are the kinds of information we get
from our world.



Robots can be designed and programmed to get specific information that
is beyond what the five senses.



e.g
.
, a robot sensor might "see" in the dark, detect tiny amounts of
invisible radiation or measure movement that is too small or fast for the
human eye to see.


15


Sensors can be

o
a.
simple


o
b.
complex

-

depending on how much information needs to be stored.



A switch is a simple on/off sensor used for turning the robot on and off.



A human retina
(
the area at the back of the eye that receives light and
sends pictures of what the eye sees to the
brain
)
is a complex sensor that
uses more than a hundred million photosensitive elements
.



Sensors provide information to the robots brain, which can be treated in
various ways.



For example,
i
f
a switch is open, no current can flow; if it is closed,
current can flow and be detected

16



An
effector

is any device that affects the environment.



Robots control their effectors, which are also known as end effectors
.



Effectors include legs, wheels, arms, fingers, wings and fins.



Controllers
( the brain of the computer)
cause the effectors to produce
desired effects on the environment.


17


An
actuator
(also known as a drive)
is the actual mechanism that enables
the effector to perform an action.



Actuators typically include electric motors, hydraulic or pneumatic
cylinders, etc.



The terms
effector

and
actuator

are often used interchangeably to mean
"whatever makes the robot take an action." But actuators and effectors are
not the same thing.



Most simple actuators control a single
degree of freedom
, i.e., a single
motion (e.g., up
-
down, left
-
right, in
-
out, etc.).



sensors must be matched to the robot's task, similarly, effectors must be
well matched to the robot's task also.


18


Two basic ways of using effectors:


to move the robot around

locomotion


to move other object around

manipulation


These divide robotics into two mostly separate categories:


mobile robotics


manipulator robotics


19

Scales in a robotic system


The c
omponents

description of a robotic system is complemented by a
scale

description, i.e., the system scales have a large influence on the specific
content of the
planning, sensing, modelling
and
control
components at one
particular scale
.


Mechanical scale



The physical volume of the robot determines to a large extent the limits of
what can be done with it.


a
large
-
scale

robot (
e.g
.,
an autonomous container crane or a space shuttle)
has different capabilities and control problems than a
macro

robot (
e.g
.,
an
industrial robot arm), a
desktop

robot , or
milli
-
,

micro
-

or
nano
-
robots.


Spatial scale
.


There are large differences between robots that act in 1D, 2D, 3D, or 6D
(three positions and three orientations).

20

Time scale
.


There are large differences between robots that must react within
hours, seconds, milliseconds, or microseconds.


Power density scale
.



A robot must be actuated in order to move, but
actuators

need space
as well as energy, so the ratio between both determines some
capabilities of the robot.


System complexity scale
.


The complexity of a robot system increases with the number of
interactions between independent sub
-
systems, and the control
components must adapt to this complexity.




21

Computational complexity scale
.


Robot
controllers are inevitably running on real
-
world computing
hardware, so they are constrained by the
available
:



a.

number of
computations
;


b.
communication
bandwidth, and



c
memory
storage.



These scale parameters never apply completely independently to the
same system
.



For example, a system that must react at microseconds time scale cannot
be of macro mechanical scale or involve a high number of
communication interactions with subsystems.


22

Background sensitivity



Research in
engineering robotics
follows the bottom
-
up approach:
existing and working systems are extended and made more versatile

(
able
to change easily from one activity to another or able to be used
for many different
purposes
)
.



Research in
artificial intelligence robotics
is top
-
down: assuming that
a set of low
-
level primitives is available, how could one apply them in
order to increase the “intelligence” of a system.



The border between both approaches shifts continuously, as more
and more “intelligence” is
expressed

into algorithmic, system
-
theoretic form.


23



For example, the response of a robot to sensor input was
considered “intelligent behaviour” in the late seventies and even
early eighties
-

belonged to AI



Later it was shown that many sensor
-
based tasks such as surface
following or visual tracking could be formulated as control
problems with algorithmic solutions.



From then on, they did not belong to AI any more.




24

Features of a robot


Number of axes



Load carrying capacity



Speed of motion



Spatial resolution



Accuracy



Repeatability



Reach & stroke



Tool orientation



Operating environment


25

Types of robots


Mobile robots

o

walking
-

robots on legs are usually brought in when the
terrain is rocky and difficult to enter with wheels.

o

rolling
-

have wheels to move around.



Stationary

-

most robots perform repeating tasks without ever
moving an inch.



Autonomous

-

are self
-
supporting, they rely on their own ‘brains’.



Remote control
-

The memory and brain capacity is usually
limited.

26