Transcript Lecture 8: Motors and Actuators

Lecture 8: Motors and Actuators
Working At The Boundary
Between EE/CSE/EPE,
Mechanical and Materials
Engineering
18 July 2015
Introduction to Engineering Electronics
K. A. Connor
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Magnetism
• One of the first
compasses, a fish
shaped iron leaf
was mentioned in
the Wu Ching
Tsung Yao written
in 1040
Trinity College, Dublin
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Introduction to Engineering Electronics
K. A. Connor
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Animal Magnetism
• A frog suspended in an intense magnetic field
– all of us are paramagnetic
• Much money is wasted on magnetic therapy
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Electromagnetic Revolution
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 D  
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 B  0


B
E  
t

  D
 H  J 
t
• These four equations epitomize the
electromagnetic revolution. Richard Feynman
claimed that "ten thousand years from now,
there can be little doubt that the most
significant event of the 19th century will be
judged as Maxwell's discovery of the laws of
electrodynamics"
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Magnetic Attraction
• It is possible to produce motion using
magnetic attraction and/or repulsion
• Either permanent magnets or electromagnets
or both can be used
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2 Minute Quiz
Name_____________
Sec___
• True or false, unlike magnetic poles attract and
like magnetic poles repel one another.
• Name one mechatronic device that you own or
use on a regular basis
• Which engineering majors are some interest to
you? Electrical, Computer & Systems, Electric
Power, Nuclear, Mechanical, Aeronautical,
Biomedical, Civil, Industrial & Management,
Materials, Chemical, Environmental, Engineering
Physics
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Magnetic Attraction and Repulsion
• One of the many facts we all recall from
our earliest science education
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DC Motors
• The stator is the stationary outside part of a
motor. The rotor is the inner part which
rotates. In the motor animations, red
represents a magnet or winding with a north
polarization, while green represents a magnet
or winding with a south polariztion. Opposite,
red and green, polarities attract.
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DC Motors
• Just as the rotor reaches alignment, the
brushes move across the commutator
contacts and energize the next winding. In
the animation the commutator contacts are
brown and the brushes are dark grey. A
yellow spark shows when the brushes switch
to the next winding.
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DC Motor Applications
• Automobiles
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Windshield Wipers
Door locks
Window lifts
Antenna retractor
Seat adjust
Mirror adjust
Anti-lock Braking
System
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•Cordless hand drill
•Electric lawnmower
•Fans
•Toys
•Electric toothbrush
•Servo Motor
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Beakman’s Motor
• A simple DC motor made with a battery, two
paperclips, a rubber band and about 1 meter
of enameled wire.
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Brushless DC Motors
• A brushless dc motor has a rotor with
permanent magnets and a stator with
windings. It is essentially a dc motor turned
inside out. The control electronics replace the
function of the commutator and energize the
proper winding.
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Brushless DC Motor Applictions
• Medical: centrifuges, orthoscopic
surgical tools, respirators, dental
surgical tools, and organ transport
pump systems
• Model airplanes, cars, boats,
helicopters
• Microscopes
• Tape drives and winders
• Artificial heart
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Full Stepper Motor
• This animation demonstrates the principle for a stepper motor using full
step commutation. The rotor of a permanent magnet stepper motor
consists of permanent magnets and the stator has two pairs of windings.
Just as the rotor aligns with one of the stator poles, the second phase is
energized. The two phases alternate on and off and also reverse polarity.
There are four steps. One phase lags the other phase by one step. This
is equivalent to one forth of an electrical cycle or 90°.
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Half Stepper Motor
• This animation shows the stepping pattern for a half-step stepper motor.
The commutation sequence for a half-step stepper motor has eight steps
instead of four. The main difference is that the second phase is turned on
before the first phase is turned off. Thus, sometimes both phases are
energized at the same time. During the half-steps the rotor is held in
between the two full-step positions. A half-step motor has twice the
resolution of a full step motor. It is very popular for this reason.
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Stepper Motors
• This stepper motor is very simplified. The rotor of a real stepper motor
usually has many poles. The animation has only ten poles, however a
real stepper motor might have a hundred. These are formed using a
single magnet mounted inline with the rotor axis and two pole pieces with
many teeth. The teeth are staggered to produce many poles. The stator
poles of a real stepper motor also has many teeth. The teeth are
arranged so that the two phases are still 90° out of phase. This stepper
motor uses permanent magnets. Some stepper motors do not have
magnets and instead use the basic principles of a switched reluctance
motor. The stator is similar but the rotor is composed of a iron laminates.
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More on Stepper Motors
• Note how the phases are driven so that
the rotor takes half steps
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More on Stepper Motors
• Animation shows how coils are
energized for full steps
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More on Stepper Motors
• Full step sequence
showing how binary
numbers can control
the motor
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• Half step
sequence of
binary control
numbers
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Stepper Motor Applications
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Film Drive
Optical Scanner
Printers
ATM Machines
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I. V. Pump
Blood Analyzer
FAX Machines
Thermostats
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Switched Reluctance Motor
• A switched reluctance or variable reluctance motor does not contain any
permanent magnets. The stator is similar to a brushless dc motor.
However, the rotor consists only of iron laminates. The iron rotor is
attracted to the energized stator pole. The polarity of the stator pole does
not matter. Torque is produced as a result of the attraction between the
electromagnet and the iron rotor in the same way a magnet is attracted to
a refrigerator door. An electrically quiet motor since it has no brushes.
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Switched Reluctance Motor Applications
• Motor scooters and other electric and hybrid
vehicles
• Industrial fans, blowers, pumps, mixers,
centrifuges, machine tools
• Domestic appliances
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Brushless AC Motor
• A brushless ac motor is driven with ac sine wave voltages.
The permanent magnet rotor rotates synchronous to the
rotating magnetic field. The rotating magnetic field is
illustrated using a red and green gradient. An actual
simulation of the magnetic field would show a far more
complex magnetic field.
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AC Induction Motor
• The stator windings of an ac induction motor are distributed around the
stator to produce a roughly sinusoidal distribution. When three phase
ac voltages are applied to the stator windings, a rotating magnetic field
is produced. The rotor of an induction motor also consists of windings
or more often a copper squirrel cage imbedded within iron laminates.
Only the iron laminates are shown. An electric current is induced in the
rotor bars which also produce a magnetic field.
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AC Induction Motor
• The rotating magnetic field of the stator drags the rotor around. The
rotor does not quite keep up with the the rotating magnetic field of the
stator. It falls behind or slips as the field rotates. In this animation, for
every time the magnetic field rotates, the rotor only makes three fourths
of a turn. If you follow one of the bright green or red rotor teeth with the
mouse, you will notice it change color as it falls behind the rotating
field. The slip has been greatly exaggerated to enable visualization of
this concept. A real induction motor only slips a few percent.
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Huge List of Applications from Hurst
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Aircraft Window Polarizing Drives
Antenna Positioning and Tuning Devices
Audio/Video Recording Instruments
Automated Inspection Equipment
Automated Photo Developing Equipment
Automated Photo Slide Trimming &
Mounting Equipment
Automatic Carton Marking & Dating
Machines
Automatic Dying and Textile Coloring
Equipment
Automatic Food Processing Equipment
Automatic I.V. Dispensing Equipment
Automatic Radio Station Identification
Equipment
Automotive
Automotive Engine Pollution Analyzers
Baseball Pitching Machine
Blood Agitators
Blood Cell Analyzer
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Warning Light Flashers
Railroad Signal Equipment
Remote Focusing Microscopes
Resonator Drives for Vibraphones
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Silicone Wafer Production Equipment
Solar Collector Devices
Sonar Range Recorders and Simulators
Steel Mill Process Scanners
Tape Cleaning Equipment
Tape Input for Automatic Typewriters
Telescope Drives
Ultrasonic Commercial Fish Detectors
Ultrasonic Medical Diagnostic Equipment
Voltage Regulators
Water and Sewage Treatment Controls
Weather Data Collection Machines
Welding Machines
X-Ray Equipment
XY Plotters
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Stepper Motor from Mechatronics
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Mechatronics Stepper Motor Continued
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Mechatronics
• Mechatronics is at the intersection
between several disciplinary areas, as
represented by these Venn diagrams
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What Is Mechatronics?
• Mechatronics is the synergistic
integration of mechanical engineering,
electronics, controls, and computers; all
integrated through the design process.
• EXAMPLES:
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robots
anti-lock brakes
photocopiers
consumer products (e.g., clothes dryers)
disk drives
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MEMS
• Micro-Electro-Mechanical Systems (MEMS) is the
integration of mechanical elements, sensors,
actuators, and electronics on a common silicon
substrate through the utilization of
microfabrication technology. While the electronics
are fabricated using integrated circuit (IC) process
sequences (e.g., CMOS, Bipolar, or BICMOS
processes), the micromechanical components are
fabricated using compatible "micromachining"
processes that selectively etch away parts of the
silicon wafer or add new structural layers to form
the mechanical and electromechanical devices.
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MEMS Stepper Motor
• This motor is very much like the other
stepper motors mentioned above,
except that it is 2D and very small
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MEMS
• The potential complexity of the MEMS device
increases exponentially with the number of
unique process features and individual
structural layers.
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MEMS: Steam Engine
• Water inside of three compression cylinders
is heated by electric current and vaporizes,
pushing the piston out. Capillary forces then
retract the piston once current is removed.
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Introduction to Engineering Electronics
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MEMS
• Rotary motor
• Steam Engine (single piston)
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MEMS Gear Trains
• Six gear planar train at various speeds
• Close up of six gear train
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Power MEMS
• 80 Watt gas microturbine designed and
built at MIT for MEMS power
applications
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Integrated MEMS
• This six-degrees-offreedom micro-inertial
measurement system
combines
microelectronic
circuitry [top right] with
a couple of
• micromechanical
elements: an
accelerometer [center
right] and gyroscope
[bottom right].
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Introduction to Engineering Electronics
K. A. Connor
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Integrated MEMS
• Types of micromechanical
devices that might be used
in integrated microsystems
of the future [shown
clockwise from right]
include this gear, pop-up
mirror, mirror assembly,
and hinge. The gear is part
of an assembly that has
demonstrated torque ratios
of up to 3 million to 1. The
silicon mirror is fabricated
flat on the silicon wafer,
then "popped up" to its
raised position using the
gear assembly.
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Integrated MEMS
• Sample collection regions for
concentration,
microseparation channels,
sensor arrays for detection,
and an exit region are
illustrated in schematic of the
chemical analysis section of a
micro-chemlab. Chemicals
are detected measuring the
response of surface acousticwave devices to a chemical's
presence. The photograph is
of an array of micromachined
3-µm silicon posts in a
microchannel being studied
as a tool for enhancing
electrokinetically driven liquid
separations.
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MEMS Displays
• Iridigm Display -- The iMoD element uses
interference to create color in the same way that
structural color works in nature. Microscopic
structures on butterfly wings and peacock feathers
cause light to interfere with itself, creating the
shimmering iridescent colors that we see in these
creatures. (Used in PDAs)
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Introduction to Engineering Electronics
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MEMS Displays
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The iMoD element is a simple MEMS device that is composed of two
conductive plates. One is a thin film stack on a glass substrate, the
other is a metallic membrane suspended over it. There is a gap
between the two that is filled with air. The iMoD element has two stable
states. When no voltage is applied, the plates are separated, and light
hitting the substrate is reflected as shown above. When a small voltage
is applied, the plates are pulled together by electrostatic attraction and
the light is absorbed, turning the element black.
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Introduction to Engineering Electronics
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MEMS Displays
• iMoD elements are minuscule, typically 25-60 microns on a side
(400-1,000 dots per inch). Therefore, many iMoD elements are
ganged and driven together as a pixel, or sub-pixel in a color
display. The color of the iMoD element is determined by the size
of the gap between the plates. As shown, the blue iMoD has the
smallest gap and the red has the largest. To create a flat panel
display, a large array of iMoD elements are fabricated in the
desired format (i.e. 5" full color VGA) and packaged. Finally,
driver chips are attached at the edge to complete the display.
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References
• Motor Operation Principles from
Freescale/Motorola by Ken Berringer
• Basic Stepper Motor Concepts
• MEMS Clearinghouse
• Mechatronics at Rensselaer
• Mechatronics.org
• Beakman’s Motor: Electronic
Instrumentation and Fields and Waves I
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Primary Course Goal for IEE
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Assure that each EE and CSE student has a
minimum of 20 hours of practical electronics
and instrumentation experience before they
begin taking disciplinary courses.
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For students with no experience – 20 hours
successfully completing labs
For students with some experience – 20 hours
completing labs, expanding their knowledge base
and helping those with less experience
For students outside of EE and CSE – provide a
working knowledge of electronics
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Where Will You See This Material Again?
• Mechatronics: MANE-4490 Mechatronics,
MANE-4250 Mechatronic Systems Design,
MANE 6960 Sensors & Actuators in
Mechatronics
• Motor Drives: ECSE/EPOW-4080
Semiconductor Power Electronics and
EPOW-4090 Power Electronics Lab
• Motor Control: ENGR-2350 Introduction to
Embedded Control
• Concentration in Power Electronics: EPOW4080 and MANE-4490
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