Roger G Gilbertson
The 10 (or 11) Basic Ways
to Make Things Move
An Overview of 21st Century Actuator Technologies
Presented with Toys
RoboNexus • Santa Clara, CA
Roger G. Gilbertson
Mondo-tronics, Inc. • RobotStore.com
With thanks to John D. Busch
Roger G Gilbertson
Definition
Actuator: n. A device that transforms electrical or thermal
energy into controllable motion.
Energy
Input
Electric
+
Thermal
Actuator
Mechanism
Machine Geometry
&
Material Properties
Work
Output
Motion!
Heat
Loss
• Consumes only electricity and/or heat
• Produces only motion and waste heat
Roger G Gilbertson
Things NOT Actuators
(In the scope of this talk anyway...)
NOT stored mechanical energy:
• explosive bolts
• mouse traps
• inflated balloons
• a rock on top of a hill
NOT stored chemical energy:
• rocket engines
• internal combustion engines
• muscle power
NOT motion translated from elsewhere:
• levers
• pulleys
• pneumatics
• hydraulics
Boston’s “Big Dig”
<http://www.bigdig.com/thtml/equip08.htm>
Roger G Gilbertson
#1 Electrostatic ES
HOW
Electrostatic charge arises
from a build up or deficit of
free electrons in a material,
which can exert an
attractive force on
oppositely charged objects,
or a repulsive force on
similarly charged objects.
Electrostatic
• Force arises from build-up of free electrons
Positive
Charge
Attractive
Force
Negative
Charge
Roger G Gilbertson
#1 Electrostatic ES
Example - Silicon Micromotor
Rotor
Diameter
130 µm
Gap Charge
25-36 Volts
From Mehregany, 1990
SMALL
Microminiature
Electrostatic
Motor
Tohoku University, Sendai Japan
http://mems.mech.tohoku.ac.jp/esashilab/fsseminar/Image18.jpg
Roger G Gilbertson
#2 Electromagnetic EM
HOW
Electromagnetism
Electromagnetism arises
• Arises from motion of an electric current
from electric current
Magnetic
Field
moving through a
conducting material.
Flow
Current
nductor
Attractive or repulsive
Electric Co
forces are generated
adjacent to the conductor
and proportional to the
current flow. Structures can be built which gather and focus
electromagnetic forces, and harness them to create motion.
Typical examples of electromagnetic devices include electric
motors, solenoids, relays, speaker coils, and cathode ray tubes.
Roger G Gilbertson
#2 Electromagnetic EM
SMALL
Bulova “Accutron” Watch
www.abbeyclock.com/photos/accutron.html
Roger G Gilbertson
#3 Phase Change
HOW
Phase change systems use
the expansion and / or
contraction that occurs in
some materials as they
undergo changes between
phases (solid, liquid, gas).
• Scale invariant
• Reversible
• Observed since antiquity
Phase Change
• Dimensional changes: solid, liquid, gas
Roger G Gilbertson
#3 Phase Change
LARGE
High Output Paraffin
(HOP) Actuator
Specifications
Mass
Power/Voltage
Response time
Stroke
Output force
Operating temp.
Lifetime
Actuation temp.
35 grams
5 watts @ 28V
~200 sec. @ 24°C
0.365 cm
15.88 kgf
-120° to 80°C
500 cycles
70°C
StarSys.com
Roger G Gilbertson
#4 Thermomechanical
Material B
Material A
• Material dimensions change with temperature
Material B
Thermomechanical systems
use the physical expansion
or contraction that occurs
in materials as they
undergo temperature
changes within their phase
(solid, liquid or gas).
Thermomechanical
Material A
HOW
Structures can be built to harness the forces exerted by the
physical change in dimension. Examples include bimetallic
thermostat elements used in home temperature regulation and
toasters. These devices use the differing expansion rates of two
materials bonded together to produce a curving displacement.
Roger G Gilbertson
#4 Thermomechanical
MEDIUM
Bimetallic Thermostat
Roger G Gilbertson
#5 Piezoelectric PZ
HOW
Piezoelectric motion arises
from the dimensional
changes generated in
certain crystalline materials
when subjected to an
electric field or to an
electric charge.
Piezoelectric
• Dimensional change in crystal subjected to voltage
+
–
0
–
+
From Petrucci, 1994
Structures can be built which gather and focus the force of the
dimensional changes, and harness them to create motion
Typical piezoelectric materials include quartz (SiO2), lead
zirconate titanate (PZT), lithium niobate, and polymers such as
polyvinyledene fluoride (PVDF).
Roger G Gilbertson
#5 Piezoelectric PZ
Ultrasonic Drill
Dr. Yoseph Bar-Cohen, JPL
• Drills hard materials with little pressure
• Hollow bits create core samples
http://nctn.hq.nasa.gov/innovation/Innovation_84/sbirnasa.html
Roger G Gilbertson
#6 Shape Memory SMA
SMA materials are easily deformed at low temperature.
Shape Memory Effect (SME)
• Change in deformability at specific temperature
Heating
Deforming
Cooling
They recover the deformation at higher temp with good force.
Roger G Gilbertson
#6 Shape Memory SMA
Mars Pathfinder Sojourner Rover
Material Accumulation
Experiment (MAE)
Designed by Geoffrey Landis and Phillip Jenkins
at NASA’s Lewis (now Glenn) Research Center
Roger G Gilbertson
#6 Shape Memory SMA
AeroVironment “MicroBat” Ornithopter
Mass: 12 gr • Wing span: 23 cm • Power: 50 mAh NiCd cell • Drive: 1.8 gram “pager” motor
Rudder controlled by two opposing 25 µm diameter Flexinol Muscle Wires
Roger G Gilbertson
#6 Shape Memory SMA
Shameless Self Promotion, Part n.
Explore Muscle Wires with our
book and 3 meters total of our
most popular wires.
• 128 page Project Book
• 1 meter Flexinol 050
• 1 meter Flexinol 100
• 1 meter Flexinol 150
Enough wire to build all the
projects in the book including
Boris the motorless walking
machine. #3-168 $59.95
RobotStore.com
Roger G Gilbertson
#7 Magnetostrictive MS
HOW
Magnetostrictive
• Dimensional changes in a magnetic field
Magnetostrictive materials
exhibit very small but strong
shape changes when
High Magnetic
Field
subjected to magnetic fields. No Magnetic
Field
(>500 Oe)
The displacements exert
high forces but over small
dimensional changes,
typically less than 1 percent. Devices can harness these high
forces to create moving mechanisms.
Typical magnetostrictive materials include combinations of rare
earth elements with iron such as TbFe (“Terfenol”) and
TbDyFe (“Terfenol-D”).
Roger G Gilbertson
#7 Magnetostrictive MS
MEDIUM
Etrema
TERFENOL-D Industrial
Actuators
• Highest displacment
• High force
• Flat frequency response
• Microsecond response
• Precise control
• Wide operating temp. range
• Low voltage operation
http://etrema-usa.com/actuation/index.asp
Roger G Gilbertson
#8 Electroactive Polymers EAP
An electrical field applied across an EAP generates movement
of water and mobile positive ions in the polymer composite.
Electroactive Polymer
• Voltage causes migration of positive ions
Polymer with
metal plated
surfaces
+
–
0
Positive ions
move towards
negative
–
+
From Y. Cohen
The EAP deforms as a result of stresses generated by the ions.
Roger G Gilbertson
#8 Electroactive Polymers EAP
SMALL
EAP Starfish
Developed at JPL in cooperation with
Osaka National Research Institute
technology.jpl.nasa.gov/gallery/gl_pages/ONRI-starfish1.html
Roger G Gilbertson
#9 Magnetohydrodynamic MHD
Motion arises when the particles of a magnetic or paramagnetic fluid are
subjected to a strong magnetic field.
Magnetohydrodynamic (MHD)
• Magnetic force induces flow
Fluid Filled
Channel
Direction of
induced flow
Alternating 3-phase traveling wave
(positive, neutral, negative)
The resulting motion can be used to generate a fluid pressure, and create
flow or fluid circulation.
Roger G Gilbertson
#9 Magnetohydrodynamic MHD
YAMATO-1 World’s First
Superconducting
MHD Vessel
First voyage June 16, 1992
Hull specification
Length
30 m
Width (typ)
10.39 m
Displacement
185 ton
Planned max. speed
8 knot
Fixed capacity
10 person
Super conductive magnet specification
Coils
6 each side
Field strength each
3.5 Tesla
Cooling system: Liquid helium dipping cooling
Material: NbTi super conductive wire rod
Built by Japan’s Ship & Ocean Foundation
http://www.sdia.or.jp/mhikobe/products/etc/yamato1.html
Roger G Gilbertson
10a Curie Effect (Thermomagnetism)
Magnetic materials loose their stuff at a higher temperature.
http://www.exploratorium.edu/snacks/curie_point.html
Roger G Gilbertson
10b Electrohydrodynamics EHD
1966 electrohydrodynamics discovered by G.I. Taylor.
Example - Solid State Ethanol Pump
Out
Silicon Grids:
3 mm x 3 mm
30 µm thick
Pressure
2480 Pa
Bias: 700 V
Fluid Reservoir
Flow Rate:
14 ml/min
From Richter, 1990
Requires high operating voltage but low current. Depends greatly on the
electric properties of the working fluid.
Roger G Gilbertson
10c Meissner Effect (Diamagnetism)
• 1911 H. Kamerlingh Onnes (1853-1926)
discovers superconductivity
• 1933 F. W. Meissner and R Ochsenfeld observe
that superconductor expels external magnetic fields
and behaves as a perfect diamagnet - a magnetic
mirror (The Meissner effect)
• 1956 Bardeen, Cooper, and Schrieffer explain
superconductivity via quantum behaviors of
electrons in a vibrating lattice structure
• 1987, P. Chu., discovers Yttrium Barium Copper
Oxide (YBCO) superconducting at 90 K
http://www.superconductivecomp.com/products/kits/sc10.htm
Roger G Gilbertson
10c Meissner Effect (Diamagnetism)
http://www.exploratorium.edu/snacks/diamagnetism_www/
Roger G Gilbertson
10d Electrorheological ER
Fluids with varying viscosity when subjected to electric fields.
Electro-rheological
• Applied voltage changes fluid viscosity
0
+
–
Called the "Winslow Effect” after discovery in 1947 by researcher Willis
M. Winslow (USA).
Roger G Gilbertson
10e Magnetorheological MR
Fluids with varying viscosity when subjected to magnetic fields
Magneto-rheological Fluids
• Magnetic field changes fluid viscosity
Cool MR Project at SciToys.com
Roger G Gilbertson
11? - To the Fringe and Beyond...
Third Law:
Any sufficiently advanced technology
is indistinguishable from magic.
Second Law:
The only way of discovering the limits
of the possible is to venture a little way
past them into the impossible.
First Law:
When a distinguished but elderly*
scientist states that something is
possible he is almost certainly right.
When he states that something is
impossible, he is very probably wrong.
* Varies by field of research.
Roger G Gilbertson
11? - To the Fringe and Beyond...
Biefield-Brown Effect? Reactionless Drive?
Electrodynamic? Ionic Wind?
jlnlabs.org
Roger G Gilbertson
Conclusions
Build More Robots!
Roger G. Gilbertson
Mondo-tronics, Inc. • RobotStore.com
rgg @ Mondotronics.com
© 2004 Roger G Gilbertson
All copyrights and trademarks acknowledged, and infringements apologized for!