presentationArtificialMuscles

8/7/2019 presentationArtificialMuscles

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Artificial musclesSeminar: New artificial intelligence

(Prof. Rolf Pfeifer, Chandana Paul)

Thomas Franken [email protected]

Boris Neubert [email protected]

artificial muscles 2

Table of content

Biological basics

Pneumatic actuators Mc Kibben muscle

Series elastic actuators Shape memory alloys

EAPs

Piezoelectric effect

Contractile polymers

Nanotubes


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Biological basics

- Muscle positions

- Antagonist Agonist

- Structure of muscles

- Energy storage

- Sensors and Reflex


Muscles in a human body

Muscles are connected tothe bones with tendons


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Antagonist & Agonist


Structure of muscles


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Basic concepts

- All-Or-Nothing principal is

valid for one fibre

If impulse is strong enough,

more fibres will be excited


Energy-storage with elasticity

Energy can only be stored in elastic

materials

Example: Kangoroos store energy from

jumping in their legs, to re-use it for next

jump.


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Muscles as sensors

Spindles in muscles as sensors

- stretch of spindles without voluntary

movement causes a contraction

Reflex reaction


Reflex I Reflex as involuntary movement of muscles.


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Reflex II

Feedforward

over the

spinal cord


Functionalities of biol. muscles

Generate force

Consumption of force

Transmission of force

Storage of energy


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The autonomous Musclesystem

Tendonsystem

TendonsystemTendonsystem

Control

TendonsystemAgonist

Antagonist

Energy

SpindlesMusclefibres


Pneumatic actuators


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Pneumatic actuatorsimitate contraction

Mc Kibben muscle developed in the 1950s:

Primary objectives:

orthotic appliance for polio patients

artificial limbs for amputees




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Consists of an internal tube (shape memory polymer):

Bladder is covered by a braided mesh shell:


Pneumatic actuators

how it works

Inner tube is inflated

and the woven material expands

vertically. MOVIE MOVIE2


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Pneumatic actuatorsMc Kibben - Anthroform arm

Workgroup of Prof. Nachtigal, Uni-Saarbrcken


Pneumatic actuatorsMc Kibben - Anthroform arm


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Pneumatic actuatorsMc Kibben elbow joint


Pneumatic actuatorscomparison with biological muscle

Achievements so far:

High force to weight ratio

Lightweight

Smooth movements

Force-length properties

Elastic properties


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Pneumatic actuatorsAchievements


Pneumatic actuators


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Pneumatic actuatorsfailure


Pneumatic actuatorsfurther development

Implement a damper into the muscle to get

the right velocity force ratio

Spindle like sensors


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Series elastic actuatorimitate elasticity


Series elastic elements

Anthropomorphic Arm


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Series elastic + McKibben


Series elastic elements

Vibration damping


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Series elastic actuator

Elasticity in the actuator:

MIT - LegLab


Series elastic actuator 3

cog

cog-300[1].mov

MIT - LegLab


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Series elastic actuatorcog - sensors

Strain gauges:



PROs:

Position tolerance

Interaction with humans

Backlash free joints are not required

Damage/force tolerant


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Elasticity vs. Stiffness

Positioning problem vs. Force control


Shape Memory Alloys

Properties:

Ability to return to a predetermined shape

when heated.When an SMA is cold, it can be deformed

quiete easily.

When it is heated, it will return to the

original shape


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Shape Memory AlloysNitinol

Good electrical and mechanical properties

Forces: wire (0,020 inches diameter) lifts 16 pounds

Actuator, sensor and heater all in one material

BUT only a good solution for small applications.


Shape Memory Alloys


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Examples of SMA products

Gas flow micro valves

Non explosive release devices

Tactile feedback devices (skin simulators)


Examples of SMA products


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Examples of SMA productsSmart skin


EAP electroactive polymers


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~ Piezoelectric Matierials~

Discovery of Piezoelectric Effects

1880 Curie Brothers (existence)

1916 Langevin found piezoelectric

characteristics in quartz crystals

1925 in PVDF (PolyVinylDiFlourid)


Properties of piezo

Piezoelectric Materials can be used as Sensor

and Actuator in one

Electric impuls transformed in Sound

Sound transformed in electric impuls


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Usage of piezoelectric Mat.

Microphones

Speakers

Sensors in any area of application

Emulation of human limbs for Example

a hand .


The reinforcement of Piezo

Materials

Deflection is too low

Amplified mechanically

Artificial wing


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Gel-based Actuatorscontractile polymers


Nanotechnology using

electroactive Polymers

Excitingeffects can be realized in

electric,

chemical,thermal,

pneumatic,

optical and

magnetic ways.


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Nanotubes

Carbon atoms are arranged in honeycombpattern and join to a strong and stable sytem.


Exciting Nanotubes

Optical exciting reaches an contraction of

the tube in the activation area

Electric exciting was realized with theBucky Paper, thousends of Nanotube

groups pressed together as a sheet of paper.


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Bucky Paper Experiment

The Bucky Paper was set on a double-sided

sticky


Discussion points

For AM the energy input and the conroler

input are the same (in biol. muscles energy

is stored via ATP in the muscle itself)

presentationArtificialMuscles

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