air muscle presentation
TRANSCRIPT
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AIR MUSCLE [PAM]
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AIR MUSCLE
An extraordinary actuatorThe Air Muscle
consists of a rubber
tube covered in
tough plastic nettingwhich shortens in
length like a human
muscle when
inflated with
compressed air at
High pressure.
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Why to go for Air Muscle?All the components are
quite expensive
A properly designed
system is more complex
than an equivalent
electromechanical system
All these componentstake up quite a bit of
valuable space within a
robot
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Brief TimelineFirst developed in the 1950 byAmerican physician,
Joseph L. McKibben
1968Rubber artificial muscle
More recently was
commercialized in the 1980's by
Bridgestone Rubber Company of
Japan.
Present working industry in this
field,
Shadow Robot Company
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Natural vs. Artificial MuscleNatural Muscle Artificial Muscle
Force applied is inversely
proportional to velocity of
actuation
Force is directly proportionalto length and size of
muscle.
Force velocity relationship isnot similar to natural muscle
Forcelength characteristicsare similar to natural muscle
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FEATURES OF ARTIFICIAL MUSCLELightweight:
Air Muscles weigh between 10g and150g
Smooth:Air Muscles have no 'stiction'
Powerful:Produce forces up to 700 N
Reproducible:Can be manufactured in identical
size.
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CONTRACTED
MOST GENERAL DIMENSIONS
30mm Air muscleEXTENDED
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Headers and FittingsThe header at each end of the
muscle consists of an Aluminum
ring, and a Delrin plastic bung,
with an M10 female thread.
This thread can be used as ameans of attachment, and to
allow air into or out of the muscle.
The muscle is supplied with
two Delrin fittings, one of which
comes with a 6mm push-fitconnector.
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Theoretical ModelF= P*(dv/dl)Vb*(dw/dl) - Ff
Where
P= Input actuation pressure
dV = The change in the actuatorsinterior volume
dl= The change in the actuators length
Vb= The volume occupied by the bladder
dw = The change in strain energy
densityFf = Friction arising from sources such
as contact between the braid and the
bladder and between the fibers of the braid
itself.
DEMONSTRATION
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MATERIALS AND PROPERTIES
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EXPERIMENTEXPERIMENT NO -1 EXPERIMENT NO -2
PAM operation at constant load PAM operation at constant pressure
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EXPRIMENT CONCLUSIONS
A PAM shortens by increasing its enclosed volume.
It will contract against a constant load if the pneumatic
pressure is increased.
This means that a PAM will shorten at a constant pressure if its
load is decreased and its contraction has an upper limit at
which it develops no force and its enclosed volume is maximal.
For each pair of pressure and load a PAM has an equilibrium
length.
This behavior is in absolute contrast to that of a pneumatic
cylinder.
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Experimental results of contraction and
elongation of the PAM
As WORKING Pressure increases,
the generated force increases and
stretched length also increases.
It follows different path when air is
injected (Blue lines) and removed
(Red lines).
As pressure increases characteristic
curve appears to be straight line. Soeasy to determine its behavior.
Ls = Reduction in length when compressed air isinjected from actual un contracted length.
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DYNAMIC CharacteristicsA 130N Air muscle takes, hardly
3 seconds (5.5-2.5)
to actuate load, one time.
The braid meshing absorbs strainenergy at starting 0.5 second
(32.5) where there is no
contraction & release energy in last
0.75 second(5.54.75)
Maximum contraction is limited to
30%.
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PAM using shape-memory polymer (SMP)Starting in state S1, the actuator is warmed
above Tg. The actuator now enters S2.
In S2 the SMP is soft and can be deformed.
When the internal bladder is pressurized, the
actuator shortens and/or produces a force if it is
coupled to a mechanical load. After the actuator
attains its desirable length, it is cooled below Tg
and the actuator enters state S3.
In S3 the SMP is fixed in its rigid state. If the
internal pressure within the bladder is released
the actuator moved to state S4.
In S4 the actuator maintains its length
indefinitely without the need for an air supply.
When the actuator is next heated above Tg, the
SMP enters state S5.
In S5 the actuator has returned to its pre-
actuation state, and has exhibited shape recovery.
Tg = Glass Transition Temperature
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WHY TO GO FOR SMP ?The actuator can be fixed more rigidly than conventional pneumatic
actuators using the phase change of the SMP material.
The actuators can achieve relatively large deformation between two rigid
states.
The actuators can maintain a continuous desirable length.
If only part of the actuator is heated, only that portion of the SMP will
transition to the rubbery state and hence, when internal air pressure is
increased only that portion of the structure will actuate.
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ADVANTAGES AND DISADVANTAGESADVANTAGES DISADVANTAGES
Lightweight
Lower Cost
Smooth
Flexible
Powerful
Compliant
Only Tensile nature Force
Efficiency is not as good
Hysteresis in the force-length characteristics
Rubber is often needed to avoid the tube
from bursting
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APPLICATIONSHUMONIDE HAND
The entire physical system is
illustrated. The physical hand and
arm comprises 4 fingers, a thumband elbow, all actuated via air
muscles. Each air muscle requires a
precisely controlled source of air
pressure to accurately position the
stroke-length of each air muscle,
positioning the hand fingers and
forearm in the required positions.
This controlled source of air is
supplied by the Valve Board
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Humanoid Robot Eye. The mechanism of the
humanoid robot eye is
imitation of the human eye,
which is modified slightly
with the assumptionsmentioned above. There is
no contact between the
pulley base (back base) and
the eyeball. With cooperativestretching or shrinking of six
EOMs, the eyeball can rotate
with 3 DOF.
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The Dexterous hand
The dexterous hand was
developed by the Shadow
robotic company. The
hands operate just like
human hands with five
fingers. It is powered by
28 Air Muscles.
LEG MOTION
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FUTURE DEVELOPMENTSPLEATED PAM
PAM would have an infinite
amount of infinitely narrow pleats,
leading to an axisymmetrical
membrane surface that would thusonly be loaded by meridional
stresses (i.e. along fold lines) and
not by parallel stresses (i.e. along
parallels, which are sections of the
surface and any planeperpendicular to the axis of
symmetry).
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COSTING & PRICES (SHADOW KIT)
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THANK YOU