<s>
A	O
servomotor	B-Algorithm
(	O
or	O
servo	B-Algorithm
motor	I-Algorithm
)	O
is	O
a	O
rotary	B-Algorithm
actuator	I-Algorithm
or	O
linear	B-Algorithm
actuator	I-Algorithm
that	O
allows	O
for	O
precise	O
control	O
of	O
angular	O
or	O
linear	O
position	O
,	O
velocity	O
,	O
and	O
acceleration	O
.	O
</s>
<s>
It	O
also	O
requires	O
a	O
relatively	O
sophisticated	O
controller	O
,	O
often	O
a	O
dedicated	O
module	O
designed	O
specifically	O
for	O
use	O
with	O
servomotors	B-Algorithm
.	O
</s>
<s>
Servomotors	B-Algorithm
are	O
not	O
a	O
specific	O
class	O
of	O
motor	O
,	O
although	O
the	O
term	O
servomotor	B-Algorithm
is	O
often	O
used	O
to	O
refer	O
to	O
a	O
motor	O
suitable	O
for	O
use	O
in	O
a	O
closed-loop	O
control	O
system	O
.	O
</s>
<s>
Servomotors	B-Algorithm
are	O
used	O
in	O
applications	O
such	O
as	O
robotics	O
,	O
CNC	O
machinery	O
,	O
and	O
automated	O
manufacturing	O
.	O
</s>
<s>
A	O
servomotor	B-Algorithm
is	O
a	O
closed-loop	O
servomechanism	O
that	O
uses	O
position	O
feedback	O
to	O
control	O
its	O
motion	O
and	O
final	O
position	O
.	O
</s>
<s>
If	O
the	O
output	O
position	O
differs	O
from	O
that	O
required	O
,	O
an	O
error	B-Algorithm
signal	I-Algorithm
is	O
generated	O
which	O
then	O
causes	O
the	O
motor	O
to	O
rotate	O
in	O
either	O
direction	O
,	O
as	O
needed	O
to	O
bring	O
the	O
output	O
shaft	O
to	O
the	O
appropriate	O
position	O
.	O
</s>
<s>
As	O
the	O
positions	O
approach	O
,	O
the	O
error	B-Algorithm
signal	I-Algorithm
reduces	O
to	O
zero	O
,	O
and	O
the	O
motor	O
stops	O
.	O
</s>
<s>
The	O
very	O
simplest	O
servomotors	B-Algorithm
use	O
position-only	O
sensing	O
via	O
a	O
potentiometer	B-Device
and	O
bang-bang	O
control	O
of	O
their	O
motor	O
;	O
the	O
motor	O
always	O
rotates	O
at	O
full	O
speed	O
(	O
or	O
is	O
stopped	O
)	O
.	O
</s>
<s>
This	O
type	O
of	O
servomotor	B-Algorithm
is	O
not	O
widely	O
used	O
in	O
industrial	O
motion	B-Algorithm
control	I-Algorithm
,	O
but	O
it	O
forms	O
the	O
basis	O
of	O
the	O
simple	O
and	O
cheap	O
servos	O
used	O
for	O
radio-controlled	O
models	O
.	O
</s>
<s>
More	O
sophisticated	O
servomotors	B-Algorithm
make	O
use	O
of	O
an	O
Absolute	O
Encoder	O
(	O
a	O
type	O
of	O
rotary	B-Algorithm
encoder	I-Algorithm
)	O
to	O
calculate	O
the	O
shafts	O
position	O
and	O
infer	O
the	O
speed	O
of	O
the	O
output	O
shaft	O
.	O
</s>
<s>
Both	O
of	O
these	O
enhancements	O
,	O
usually	O
in	O
combination	O
with	O
a	O
PID	O
control	O
algorithm	O
,	O
allow	O
the	O
servomotor	B-Algorithm
to	O
be	O
brought	O
to	O
its	O
commanded	O
position	O
more	O
quickly	O
and	O
more	O
precisely	O
,	O
with	O
less	O
overshooting	O
.	O
</s>
<s>
Servomotors	B-Algorithm
are	O
generally	O
used	O
as	O
a	O
high-performance	O
alternative	O
to	O
the	O
stepper	B-Algorithm
motor	I-Algorithm
.	O
</s>
<s>
Stepper	B-Algorithm
motors	I-Algorithm
have	O
some	O
inherent	O
ability	O
to	O
control	O
position	O
,	O
as	O
they	O
have	O
built-in	O
output	O
steps	O
.	O
</s>
<s>
This	O
often	O
allows	O
them	O
to	O
be	O
used	O
as	O
an	O
open-loop	O
position	O
control	O
,	O
without	O
any	O
feedback	O
encoder	O
,	O
as	O
their	O
drive	O
signal	O
specifies	O
the	O
number	O
of	O
steps	O
of	O
movement	O
to	O
rotate	O
,	O
but	O
for	O
this	O
,	O
the	O
controller	O
needs	O
to	O
'	O
know	O
 '	O
the	O
position	O
of	O
the	O
stepper	B-Algorithm
motor	I-Algorithm
on	O
power	O
up	O
.	O
</s>
<s>
Therefore	O
,	O
on	O
the	O
first	O
power-up	O
,	O
the	O
controller	O
will	O
have	O
to	O
activate	O
the	O
stepper	B-Algorithm
motor	I-Algorithm
and	O
turn	O
it	O
to	O
a	O
known	O
position	O
,	O
e.g.	O
</s>
<s>
A	O
servomotor	B-Algorithm
can	O
immediately	O
turn	O
to	O
whatever	O
angle	O
the	O
controller	O
instructs	O
it	O
to	O
,	O
regardless	O
of	O
the	O
initial	O
position	O
at	O
power	O
up	O
if	O
an	O
absolute	O
encoder	O
is	O
used	O
.	O
</s>
<s>
The	O
lack	O
of	O
feedback	O
of	O
a	O
stepper	B-Algorithm
motor	I-Algorithm
limits	O
its	O
performance	O
,	O
as	O
the	O
stepper	B-Algorithm
motor	I-Algorithm
can	O
only	O
drive	O
a	O
load	O
that	O
is	O
well	O
within	O
its	O
capacity	O
,	O
otherwise	O
missed	O
steps	O
under	O
load	O
may	O
lead	O
to	O
positioning	O
errors	O
and	O
the	O
system	O
may	O
have	O
to	O
be	O
restarted	O
or	O
recalibrated	O
.	O
</s>
<s>
The	O
encoder	O
and	O
controller	O
of	O
a	O
servomotor	B-Algorithm
are	O
an	O
additional	O
cost	O
,	O
but	O
they	O
optimize	O
the	O
performance	O
of	O
the	O
overall	O
system	O
(	O
for	O
all	O
of	O
speed	O
,	O
power	O
,	O
and	O
accuracy	O
)	O
relative	O
to	O
the	O
capacity	O
of	O
the	O
basic	O
motor	O
.	O
</s>
<s>
With	O
larger	O
systems	O
,	O
where	O
a	O
powerful	O
motor	O
represents	O
an	O
increasing	O
proportion	O
of	O
the	O
system	O
cost	O
,	O
servomotors	B-Algorithm
have	O
the	O
advantage	O
.	O
</s>
<s>
There	O
has	O
been	O
increasing	O
popularity	O
in	O
closed-loop	O
stepper	B-Algorithm
motors	I-Algorithm
in	O
recent	O
years	O
.	O
</s>
<s>
They	O
act	O
like	O
servomotors	B-Algorithm
but	O
have	O
some	O
differences	O
in	O
their	O
software	O
control	O
to	O
get	O
smooth	O
motion	O
.	O
</s>
<s>
The	O
main	O
benefit	O
of	O
a	O
closed-loop	O
stepper	B-Algorithm
motor	I-Algorithm
is	O
its	O
relatively	O
low	O
cost	O
.	O
</s>
<s>
Many	O
applications	O
,	O
such	O
as	O
laser	O
cutting	O
machines	O
,	O
may	O
be	O
offered	O
in	O
two	O
ranges	O
,	O
the	O
low-priced	O
range	O
using	O
stepper	B-Algorithm
motors	I-Algorithm
and	O
the	O
high-performance	O
range	O
using	O
servomotors	B-Algorithm
.	O
</s>
<s>
The	O
first	O
servomotors	B-Algorithm
were	O
developed	O
with	O
synchros	O
as	O
their	O
encoders	O
.	O
</s>
<s>
Much	O
work	O
was	O
done	O
with	O
these	O
systems	O
in	O
the	O
development	O
of	O
radar	B-Application
and	O
anti-aircraft	O
artillery	O
during	O
World	O
War	O
II	O
.	O
</s>
<s>
Simple	O
servomotors	B-Algorithm
may	O
use	O
resistive	O
potentiometers	B-Device
as	O
their	O
position	O
encoder	O
.	O
</s>
<s>
These	O
are	O
only	O
used	O
at	O
the	O
very	O
simplest	O
and	O
cheapest	O
level	O
and	O
are	O
in	O
close	O
competition	O
with	O
stepper	B-Algorithm
motors	I-Algorithm
.	O
</s>
<s>
They	O
suffer	O
from	O
wear	O
and	O
electrical	O
noise	O
in	O
the	O
potentiometer	B-Device
track	O
.	O
</s>
<s>
Modern	O
servomotors	B-Algorithm
use	O
rotary	B-Algorithm
encoders	I-Algorithm
,	O
either	O
absolute	O
or	O
incremental	B-Algorithm
.	O
</s>
<s>
Incremental	B-Algorithm
encoders	I-Algorithm
are	O
simpler	O
,	O
cheaper	O
,	O
and	O
work	O
at	O
faster	O
speeds	O
.	O
</s>
<s>
Incremental	B-Algorithm
systems	O
,	O
like	O
stepper	B-Algorithm
motors	I-Algorithm
,	O
often	O
combine	O
their	O
inherent	O
ability	O
to	O
measure	O
intervals	O
of	O
rotation	O
with	O
a	O
simple	O
zero-position	O
sensor	O
to	O
set	O
their	O
position	O
at	O
start-up	O
.	O
</s>
<s>
Instead	O
of	O
servomotors	B-Algorithm
,	O
sometimes	O
a	O
motor	O
with	O
a	O
separate	O
,	O
external	O
linear	O
encoder	O
is	O
used	O
.	O
</s>
<s>
The	O
type	O
of	O
motor	O
is	O
not	O
critical	O
to	O
a	O
servomotor	B-Algorithm
,	O
and	O
different	O
types	O
may	O
be	O
used	O
.	O
</s>
<s>
Small	O
industrial	O
servomotors	B-Algorithm
are	O
typically	O
electronically	O
commutated	O
brushless	O
motors	O
.	O
</s>
<s>
For	O
large	O
industrial	O
servomotors	B-Algorithm
,	O
AC	O
induction	O
motors	O
are	O
typically	O
used	O
,	O
often	O
with	O
variable	O
frequency	O
drives	O
to	O
allow	O
control	O
of	O
their	O
speed	O
.	O
</s>
<s>
Drive	O
modules	O
for	O
servomotors	B-Algorithm
are	O
a	O
standard	O
industrial	O
component	O
.	O
</s>
<s>
Their	O
design	O
is	O
a	O
branch	O
of	O
power	O
electronics	O
,	O
usually	O
based	O
on	O
a	O
three-phase	O
MOSFET	B-Architecture
or	O
IGBT	O
H	O
bridge	O
.	O
</s>
<s>
Most	O
modern	O
servomotors	B-Algorithm
are	O
designed	O
and	O
supplied	O
around	O
a	O
dedicated	O
controller	O
module	O
from	O
the	O
same	O
manufacturer	O
.	O
</s>
<s>
Controllers	O
may	O
also	O
be	O
developed	O
around	O
microcontrollers	B-Architecture
in	O
order	O
to	O
reduce	O
cost	O
for	O
large-volume	O
applications	O
.	O
</s>
<s>
Integrated	O
servomotors	B-Algorithm
are	O
designed	O
to	O
include	O
the	O
motor	O
,	O
driver	O
,	O
encoder	O
,	O
and	O
associated	O
electronics	O
into	O
a	O
single	O
package	O
.	O
</s>
