Air Muscle Presentation

7/27/2019 Air Muscle Presentation

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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
http://www.humanoid.waseda.ac.jp/booklet/photo/RubberArtificialMuscle2-1968.jpghttp://www.humanoid.waseda.ac.jp/booklet/photo/RubberArtificialMuscle1-1968.jpg


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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
http://localhost/var/www/apps/conversion/tmp/scratch_6/MUSCLE%20ACTUATION%20VIDEO.FLVhttp://localhost/var/www/apps/conversion/tmp/scratch_6/MUSCLE%20ACTUATION%20VIDEO.FLVhttp://localhost/var/www/apps/conversion/tmp/scratch_6/MUSCLE%20ACTUATION%20VIDEO.FLV


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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
http://localhost/var/www/apps/conversion/tmp/scratch_6/AIRMUSCLEACTUATION.avihttp://localhost/var/www/apps/conversion/tmp/scratch_6/AIRMUSCLEACTUATION.avi


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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

Documents

Air Muscle Presentation