Jumat, 21 Mei 2010

TABLE OF COMPARISON

Comparison Data

Criterium Hydraulics Pneumatics
Energy carrier Oil
(Liquids in general)
Air
Energy transmission Pipes,hoses,
tubes,bores
Pipes,hoses,
tubes,bores
Conversion from
or into
mechanical energy
Pumps,cylinder,
hydraulics
(HY) motors
Compressors,
cylinder,
pneumatics
(HY) motors
Most important
characteristic
quantities
Pressure p
(30…400 bar),
flow Q
Pressure p
(approx.
6 bar),
flow Q
Power efficiency Excellent Compact,
reasonably priced
components due to
high operating
pressures of up to
approx. 400 bar.
Most simple linear
motor-cylinder
Good
limitations
though, due to
max operating
pressure of
only 6 bar
Accuracy
of motion
(this can be
improved
through, in
all system by
positioning
action
excellent because
oil can hardly
be compressed
Fair to good
because air
is
compressible
efficiency Fair to good,
volumetric and
frictional losses
during primary
and secondary
energy conversion,
as well as with
the open and
closed loop control
of valves
Controllability Excellent, by means
of valves and variable
displacement pumps
servo valves for closed-
loop techniques
Excellent by
means of
valves
(for small to
medium
power)
Generation of linear movement Extremely simple
by means
of cylinders
Extremely
simple by
means of
cylinders
Signal linkage
between
hydraulic
system and
other system

pneumatics
operation of
directional-
control
valves






Criterium Electrics/ electronics Mechanics
Energy carrier Electrons Shafts,
linkage,
belts,
chain,
wheels etc.
Energy
transmission
Electrically conductive
material (cables etc.)

Conversion
from or into
mechanical
energy
Generators,batteries,
Electric (E) motors,
magnets,solenoids,
linear (induction)
motor

Most important
characteristic
quantities
Voltage V, electric
current i
Force,torque,
velocity,
rotational
speed
Power efficiency Fair to good
Weight coefficient
of E-motors is
approx. 10 times
that of HY motors.
Electric switch,
though,has considerable
advantages compared to
directional control valve
Good because
energy
conversion
is not needed.
Limitations
become
apparent when
high demands
are placed
upon
controllability
Accuracy
of motion
(this can be
improved through
, in all system
by positioning
action
Differs considerably
on the one hand
hysteresis and slippage,
on the other hand
synchronous motors
and stepping motors
Excellent due
to positive
mechanical
connection
(index,
toothed
gearing,
etc)
efficiency Good. As long as
electricity is
available as primary
energy
Good. Due
to their
being no
energy
conversion,
mechanical
frictional
losses
Controllability For small power:
excellent,for larger
powers fair to good
By means of switches,relays
,semiconductors,variable speed motors and variable resistors etc.
Fair to good
Through
gearing
and lever
system etc.
Generation of
linear movement
Slightly more complicated By means of linear motors Simple by
means of
crank
mechanism
and spindle
etc.
Signal linkage
between hydraulic
system and other
system
Electromagnetic control of valves (solenoids,proportional valves),limits switches and pressure switches Drive. Or
drive take-
off,on pumps,
hydraulic
motors,
cylinders
operation of
valves through
cams and
contours

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