Small-Scale Maglev Train

Transcription

ECE4007 Senior Design Project
Section L01, Team Maglev
Nathan Black
Ben James
Greg Koo
Vivek Kumar
Preston Rhea
Submitted
April 30th, 2009
Contents
EXECUTIVE SUMMARY............................................................................................................1
INTRODUCTION......................................................................................................................... 2
Objective................................................................................................................................2
Motivation............................................................................................................................. 3
Background........................................................................................................................... 3
3. TECHNICAL SPECIFICATIONS.........................................................................................5
Levitation...............................................................................................................................5
Stabilization...........................................................................................................................6
Linear Motion........................................................................................................................6
Track......................................................................................................................................7
4. DESIGN APPROACH AND DETAILS.................................................................................8
AC Drive............................................................................................................................. 10
Problems with Initial LSM Design......................................................................................11
LSM Track Winding Problems............................................................................................14
5. SCHEDULE, TASKS, AND MILESTONES.......................................................................16
6. PROJECT DEMONSTRATION..........................................................................................16
7. MARKETING AND COST ANALYSIS..............................................................................17
Marketing Analysis............................................................................................................. 17
Comparison of Maglev Concept with Electric Trains................................................. 17
Comparison of Achieved Maglev Design with Other Existent Maglev Trains............ 18
Cost Analysis.......................................................................................................................18
8. SUMMARY AND CONCLUSIONS.................................................................................... 19
9. References...............................................................................................................................21
Appendix A..................................................................................................................................... 1
Electro-dynamic Suspension System for Maglev Train........................................................ 1
Description.................................................................................................................... 1
Design............................................................................................................................ 4
Appendix B..................................................................................................................................... 1
EXECUTIVE SUMMARY
Magnetically-levitating (“maglev”) train technology is a high-speed urban transportation
solution capable of contributing to pollution reduction and energy efficiency. Team Maglev’s
system is a scaled-down, proof-of-concept maglev train that traverses a three-foot long track at a
speed of up to one mile per hour. It utilizes a linear synchronous motor for propulsion and
permanent disk magnets for stabilization and levitation. The project was completed at a cost of
$523.
Conventional locomotives and the highway system create traffic congestion and
contribute heavily to smog and pollution in metropolitan areas. Maglev infrastructure can be
implemented to move trains much faster, produce no pollution from the vehicle itself, and
require easy and minimal upkeep as there are no moving parts and no friction in standard
operation. Maglev trains are a sustainable and efficient form of mass transportation for people,
commercial freight, and military applications. Team Maglev’s working prototype will show
consumers, investors, and regulators that maglev technology is a feasible, smart option for new
infrastructure development.
Further developments to our design implement an electro-magnetic suspension (EMS
configuration. The EMS configuration uses a ferromagnetic rail above a train car. Through use
of electromagnets, the train car can remain suspended above the ground by maintaining a
constant air gap between the electromagnets and the rail above. The propulsion of the proposed
EMS system can be achieved by integrating our functioning linear synchronous motor.
1.
INTRODUCTION
Maglev trains reduce pollution and increase both speed and efficiency when compared to
other modes of transportation. It is a proven technology that is becoming more feasible
technically and financially. Recent innovations in maglev technology, such as the Inductrack
system, promise “fail-proof” operation. Since maglev trains do not produce any pollutants
themselves, they can reduce pollution in transportation corridors and cities compared to their
currently-operating alternatives [3]. Team Maglev seeks to produce a small-scale proof-ofconcept maglev system in order to demonstrate to consumers, investors, and regulators that
maglev is a feasible and efficient option for new transportation infrastructure development.
Objective
The need for more sustainable and efficient mass transportation of people, commercial
freight, and military applications has led to a rethinking of rail-based transit. Team Maglev
produced a straight segment of track measuring three and one-half feet in length, capable of
levitating and accelerating a scale-model maglev train. The track was designed with ease of
construction, stability of operation, and levitation efficiency as primary constraints. The final
system provides a maximum vehicle speed of one mile per hour, passive lateral stability, passive
magnetic support with minimal friction for levitation, and user controlled speed. A
demonstration of the system provides the observer insight into how maglev technology works
and why it is a viable alternative to traditional rail transport.
Team Maglev (ECE4007 L01)
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Motivation
Transportation infrastructure around the country is less efficient, more costly to maintain, and
relatively unsafe compared to maglev technology. Conventional locomotives and the highway
system create traffic flow issues and contribute heavily to smog and pollution in metropolitan
areas. Maglev infrastructure provides lower operating costs due to no moving parts and no
friction during standard operation [1]. Given the advantages of maglev technology, investors and
developers should consider maglev as a way to increase efficiency and value for communities
and commuters.
Maglev trains can also reach higher speeds than conventional rail and provide a direct benefit
to the shipping and coast-to-coast public transportation industries. Furthermore, first-adopter
cities can claim as a part of their image the sleek, high-tech appeal of maglev technology.
Background
Maglev technology is somewhat well-known due to its Pudong-Shanghai installation in
China, where a maglev line runs from the airport to the subway line. However, the track is
infamous for its cost problems. Most of the concern is due to the line’s high cost [2]. Existing
commercial technology utilizes electromagnetic suspension (EMS), which has an extremely fine
operating requirement of maintaining a ten to fifteen millimeters gap between track and train.
The EMS system is also inherently unstable system due to its reliance on magnetic attraction
rather than repulsion.
Permanent magnets are capable of levitating huge trains due to two inventions from the
1980’s: Halbach arrays, which increase flux in one direction, and neodymium-iron-boron
magnets, which have higher intrinsic magnetic fields than other magnets. The final design for
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the small-scale system still uses permanent magnets, but it does not achieve true magnetic
levitation in all directions, as there is slight friction with the track. Levitation is achieved through
magnetic disks that interact with conventionally-magnetized magnetic strips set up in two
separate “rail” configurations. The small-scale system uses neodymium-iron-boron magnets for
all of its magnetic installations, but it does not use a Halbach array, as these were difficult to
construct effectively.
2.
PROJECT DESCRIPTION AND GOALS
The objective of the maglev project is to design and build a small-scale working model of
a maglev train. The components are divided based on their requirement in either levitating,
stabilizing or propelling the train.
The hardware components for the project include
·
A 6’’ x 8’’ x 2’’ train car
·
A track made of 3/4” x 4’ magnetic strip, propped up by wooden guides
·
Four strong neodymium disk magnets as part of the propulsion system
·
Four weak neodymium disk magnets for levitation/stabilization
·
Linear synchronous motor (three phase winding down the length of the track for
propulsion)
·
Ball bearings and rubber spaces for each of the four disk magnets used for levitation/
stabilization
·
AC Drive to provide the variable 3-phase current source
·
AC Reactor
·
Three 1 Ohm power resistors
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The underlying goals of implementing a working small-scale model of a maglev train include
Levitation at a height of 2-4 mm above the track
Propulsion up to a speed of 1 mph.
Lateral Stability while the train is levitated and being propelled forward
The most significant challenges in implementing our particular design were smoothing
out the current waveform from the AC Drive to be more sinusoidal, achieving very low friction
between the magnetic rails and disc magnets, and winding the LSM by hand evenly and precisely
enough to function properly. How these issues were overcome is explained in Section 4.
3.
TECHNICAL SPECIFICATIONS
Levitation
Table 1. Specifications for Magnetic Levitation
Criteria
Design Specification
Height (along rails)
6.5 mm
Height over LSM
2mm (optimal) - 4 mm (maximum)
Table 2. Specifications for Magnet Arrays
Criteria
Material
NdFeB Grade N52
Max B Value
14,800 Gauss ; 1.48 Tesla
Lift Magnets
4.0” x 1.0” x 0.15” [4 Thick Disc Magnet Array]
Stability Magnets
4.0” x 1.0” x 0.1” [4 Thin Disc Magnet Array]
Page |5
Stabilization
Table 3. Specifications for Magnetic Levitation
Criteria
Vertical Stability
Operating Elevation Height +/- 1 mm
Horizontal Stability
Lateral Variation +/- 0 mm
Linear Motion
A linear synchronous motor is used in the design. Approximately 15 ft of three phase
winding was placed in the center of the track as the motor primary. A specific disc magnet array
was constructed as the motor secondary. An AC Drive controls the interactions between the
primary and secondary. For braking, inherent magnetic drag force between the track and the
train decreases speed when the frequency of the AC drive is reduced. Exact electrical
propulsion specifications are shown in Table 4.
Table 4. Specifications for Linear Motor
Criteria
Class of Motor
Linear Synchronous
Primary
18 Gauge Three Phase Winding Embedded in Track
Secondary
4.0” x 1.0” x 0.1” [4 Disc Magnet Array]
Drive current
Max of 10A
Drive frequency
2.7 – 5.5 Hz
Page |6
Table 5. Specifications for Train Operation
Criteria
Initial Launch
Gentle push with hand
Operating Speed
0-1 mph
Top Speed
1 mph
Acceleration
0 mph to 1 mph in under two seconds
Track
Table 6. Specifications for Performance of LSM
Criteria
Topology
Interacting Primary (LSM) & Secondary (Train)
Wire Material
Copper
Parameters
Field Strength B = 1.2 T, Length = 0.0195m
Lorentz Force
F = I*(BxL) 1 wire: 0.051lbf
5 wires: 0.255lbf
Table 7. Specifications for Track
Criteria
Topology
Linear Track
Materials
Balsa Wood, Plexiglass
Support
Magnetic Rails glued to Wooden planks
Dimensions
¾” height, 4ft. length, 28.6mm width
Page |7
4.
DESIGN APPROACH AND DETAILS
4.1 Design Details
Train Car and Track Design
Achieving levitation is the most critical goal of the design process. The secondary goal is
propulsion. The propulsion system comprises two components—the linear synchronous motor
(LSM), which behaves like the primary, and the magnet array on the train car, which behaves
like the secondary. Four permanent magnets were arranged into an array with alternating north
and south poles as shown below in Figure 1.
Figure 1. Magnet array on bottom of train car.
These four magnets interact with the LSM that runs down the middle of the track and are crucial
for propulsion. The alternating magnetic field induced in the LSM due to the high current
flowing through the wires interacts with the magnetic field provided by these permanent
magnets. As a result, the train car is propelled down the track.
The track is responsible for stabilization and levitation of the train car. It is only
composed of two materials—magnetic strip and wooden supports. The magnetic strip is 3/4 in
tall, and was stretched 3.5 ft strips down the track. Two strips act as a single rail, so the track
contains 4 total strips. Since they are only 3 mm thick, each strip was glued to wooden planks to
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support them at a perfectly straight, 90 degree angle to the ground. The magnetic strips with
wooden supports can be seen in Figure 2a and 2b.
Figure 2. Track design—magnetic strips and wooden supports (left: initial construction of track,
right: tracks, LSM, and train car).
As shown in Figure 2, the disk magnet is levitated between the rails. Vertical levitation is
achieved since the bottom side of the disk magnet is an opposing pole to the faces of the
magnetic strips. However, the magnet slightly touches one side of the rail. This is the reason we
do not claim to have achieved “true” maglev. It was initially believed that magnet would float
stably between the rails with no contact at all, but according to Earnshaw’s Theorem, no magnet
can be levitated stably using solely permanent magnets. Thus, the edge of the disk magnet locally
re-magnetizes the weak strips to create a “ferromagnetic” attraction. As a result, the magnet rolls
along one side of the track.
To compensate, a method was needed to allow the disk magnets to spin freely as the train
car moved down the track, yet still be physically connected to the train car. To accomplish this,
ball bearings were purchased from a local skateboard shop. The bearings allow firm contact
between the car and magnet while permitting the magnet to spin with low friction. After a disk
magnets was connected to a bearing and tested on the track, there was a significant magnetic
interaction between the magnetic strips and the metal on the bearings. To compensate for this the
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distance between the bearings and magnet was increased by using rubber washers as shown in
Figure 3.
Figure 3. Separation of disk magnet and ball bearing via rubber washers.
Re-magnetization of the magnetic strips became a problem. The initial neodymium disk
magnets were very strong as they were intended to be able to carry at least a 1 lb load. Because
of the high magnetic strength of these disc magnets, every time they would roll across the
magnetic strips they would re-magnetize the strips locally. This created a stronger ferromagnetic
attraction between the disc magnet and the strip wherever it current was, which made moving it
from that position difficult. This added much more friction to these horizontal wheels, so weaker
disk magnets were sought. We used the disc magnets that were on the backside of promotional
pins given away by the Georgia Tech Women’s Resource Center. These magnets worked much
better, but also could not support the same load as the stronger ones could. This was a tradeoff,
but the weaker magnets were ultimately used because the low friction was the only way the train
was going to move under the influence of the linear synchronous motor.
AC Drive
Initially, a Lab Volt variable voltage three phase power source in room E375 of the Van
Leer building was used to test the LSM. It was capable of providing 8 amps of current to the
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track windings, and a noticeable interaction was detected between the track and a magnet array.
However, since the output frequency of the Lab Volt source was fixed at 60 Hz, linear motion of
the magnet array was unachievable. Instead of sliding down the track, the array instead moved
back and forth a small distance.
The speed at which the secondary, or magnet array, moves relative to the track windings
is given by the following formula:
Secondary Speed = 2*pole pitch*frequency of track current
(1)
The pole pitch of a single magnet is equal to its diameter, which is 0.0254 m. Therefore, when
the 60 Hz current was applied to the track, the magnet array attempted to accelerate from 0 m/s
to 3.048 m/s instantaneously. This rapid acceleration would require a large force from the track
windings in order to overcome the inertia of the stationary magnets.
In order to lessen the amount of force required from the track windings, a slow
acceleration is needed. This can be achieved by gradually ramping up the frequency of the
current supplied to the track windings. To fulfill this requirement, a Hitachi X200-022NFU was
selected as the variable frequency three phase power source for the LSM windings. It provides a
120 volt output for each phase, with a maximum current of 10A. The criteria for choosing a
drive with a maximum output current of 10A was correlated with the observation that the 60 Hz,
8 amp Lab Volt power source was able to excite the track windings strongly enough to move the
magnet array.
Problems with Initial LSM Design
The Hitachi drive was initially connected directly to the LSM track input, and the current
was increased gradually from 0 Hz to 10 Hz at various speeds between these two frequencies.
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No noticeable interaction occurred when a magnet was placed directly on the track.
Troubleshooting this technical issue was resolved by utilizing a differential voltage probe and
current probe to observe the respective waveforms at the input connection for one phase of the
track windings. The voltage waveform correctly represented the expected pulse-width
modulation (PWM) characteristics, as shown in Figure 4.
Figure 4. Voltage waveform without AC reactors.
The current waveform, which was expected to be sinusoidal, was instead very similar to
the voltage waveform. The cause of this problem was related to the relatively small µH range
inductance of the track windings. There were no reactive components of the track impedance to
filter or smooth the square wave transitions of the PWM voltage resulting in current spikes
whenever the PWM signal made voltage transitions.
To resolve this scenario, an AC reactor, which is essentially an inductor placed in series
with each phase of the AC drive’s output, was connected between the AC drive and inputs to the
track windings. Due to the fact that electric motors typically have inductance in the mH range,
the selection of an AC reactor was based upon reaching this range. Since an AC reactor was not
already available in the senior design inventory and the $100 cost to acquire one was beyond our
budget, three DC link chokes were acquired from the power electronics laboratory. Each 7 mH
link choke was connected in series with each phase from the AC drive. The current waveform
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was then observed to become more sinusoidal. However, the waveform clipped during both
positive and negative duty cycles, as shown below in Figure 5.
Figure 5. Clipping in AC waveform without resistors.
The issue was empirically resolved by placing a 1 ohm load in series with the end of the
track windings before they terminated into a wye connection. As shown in Figure 6, the clipping
is greatly reduced.
Figure 6. Final AC waveform through AC reactors and resistance.
It was deemed very important to achieve a more pure sinusoidal input current, as shown above,
since the magnetic flux relates to the current waveform as follows:
Fi = L di/dt
(2)
By having a sinusoidal current, a sinusoidal flux change is achieved, which allows the
track windings to produce a smoothly changing magnetic field that interacts with the magnet
array. Any nonlinearities or discontinues in the current waveform would cause transients in the
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magnetic field produced, causing the magnet array to slip behind the magnetic wave traveling
down the windings. Due to the requirement for the traveling wave and the speed of the magnet
array to be synchronous to maintain motion, failure to maintain synchronization would cause the
magnet array to stop and oscillate back and forth.
LSM Track Winding Problems
The initial design of the track windings consisted of one wire per phase. With the 10 amp
AC drive and the AC reactor inline, the magnetic interaction between the windings and the track
was extremely weak. By applying the theory of superposition, it was determined that adding
multiple conductors for each phase would also increase the magnetic field produced by the track.
Five 18 gauge magnet wires were connected together to form each phase. After testing the new
track design with added inductors, a much stronger magnetic interaction was detected, and a
magnet place on the track was observed to move in a linear motion down the track when the AC
drive was set to produce a 2.7 Hz input current.
During production of the five-wire track design, steel staples were implemented to hold
the wires down during the winding process. Although this initial track functioned correctly, the
magnetic field produced was observed to be weaker than a shorter five wire version held in place
by tape. A hypothesis was made that the steel in the staples served as a path of low reluctance
for flux produced in the vicinity of the staples, causing some of the flux that would have
interacted with the magnet to instead couple into the staples. There was also ferromagnetic
attraction between the staples and the magnet array. The staples were removed and held in place
by glue, instead. The revised design was also placed on Plexiglas, and the track was compressed
P a g e | 14
to make its entire length flat. This process was crucial since the LSM operation becomes more
efficient as the air gap between the track windings and the magnet array decreases.
4.2 Codes & Standards
Due to Maglev technology still be in the development stage, there are no governing codes
& standards. Once commercial implementations become more widespread, it is expected that
regulations and standards will be created regarding the design and running of Maglev systems.
4.3 Constraints, Alternative, and Tradeoffs
Inductrack I
The original design implementation modeled the Inductrack I system created by the
Lawrence Livermore National Labs. This completely passive system relied on shorted inductive
coils as the track bed and a train car with Halbach arrays beneath it to achieve levitation. When
reaching a transition speed, the magnetic field induced by the magnets moving past the coils
would overcome the magnetic drag force and produce a lift force.
After performing Matlab simulations for a small scale version of the Inductrack I, it was
realized that approximately fifty turns were needed for each shorted inductive coil. Since the
track bed is constructed by placing all the coils adjacent to one another, and the coils must be
wound to form rectangular cross sections, the resultant cost to create this design was
approximately $1000. Due to the $403 budget constraint of senior design, we were able to
pursue a small scale implementation of the Inductrack I design.
Electro-magnetic Suspension
The EMS system was initially considered, but upon review of the design requirements,
the system was decided to be too complex. The main factor was that the EDS system required a
feedback control system to regulate the current fed to an electromagnet, in order to control the air
P a g e | 15
gap between the electromagnet and a ferromagnetic rail. Since no member of the design team
had completed a systems & controls course, we deemed this design beyond our capabilities.
Permanent Magnet Design
A permanent magnet design was initially discouraged since it was not an elegant solution
to the levitation problem. Also, the scalability of a permanent magnet design is not very feasible
due to the extremely large costs that would be associated with track construction of a full scale
Maglev implementation. Only after the Inductrack I design failed, did we resort to attempting to
implement a permanent magnet design.
5.
SCHEDULE, TASKS, AND MILESTONES
See Appendix B.
6.
PROJECT DEMONSTRATION
The three main objectives of the project--levitation, propulsion and stabilization were
achieved during test runs. In order to finish construction of a working small-scale maglev train, it
was imperative to conduct an official demonstration to our Project Advisor, Dr. Steve Kenney.
Based on availability, our final project demonstration was set for Thursday, April 23rd at 11:30
AM in the Motors Lab (Room 375) of Van Leer. This was where the team had been working
throughout the semester, as it provided an ideal environment to operate the AC Drive and use the
numerous cutting machines to construct our track.
The final demonstration consisted of the following steps:
-
Powering the AC Drive to provide the variable 3-phase current
-
Setting the switch to control direction of flow of current in the LSM
-
Gently pushing the train car to provide an initial momentum
P a g e | 16
-
Controlling the frequency on the AC Drive to provide acceleration/deceleration
Important measurements were recorded, as indicated below:
-
Maximum current: 10A
-
Frequency range: 2.7 – 5.5Hz
-
Maximum load supported: 0.11 lb
-
Vertical stability: + 1mm
-
Horizontal stability: 0mm
-
Torsional stability: 0º
-
Max Speed: 1 mph
Torsional and horizontal stability were achieved as the train car traversed the track. In the
end, a working model was successfully demonstrated by simultaneously achieving the three
objectives with performance parameters in the range we proposed.
The vertical stability was measured by placing a ruler in front of one of the levitation disk
magnets and recording how much vertical variation occurred with reference to the baseboard
upon which the magnetic rails were placed. The load test was measured using quarters, which
each weight 5.67g. Quarters were added until the LSM was no longer able to pull the train car
along the track. The speed of the train car was measured by marking off a two-foot segment of
the track. A distance versus time measurement was then conducted to deduce the train car’s
speed. A stopwatch was used for timing purposes.
7.
MARKETING AND COST ANALYSIS
Marketing Analysis
Comparison of Maglev Concept with Electric Trains
P a g e | 17
A full-size working version of the proposed maglev train is a type of railway transport that
offers advantages over electric trains in the form of higher speeds, lower costs, environmental
friendliness, and lower maintenance because it has no moving parts (such as wheels) and travels
without any contact with the track, minimizing friction [9]. Maglev trains can travel over tracks
that are elevated or on ground level thereby causing less disruption to the environment, whereas
present-day electric trains require their environment to be modified in order to provide the
shortest path from point to point.
Comparison of Achieved Maglev Design with Other Existent Maglev Trains
The team’s design eliminated the need for electromagnets or cryogenically cooled
superconducting magnets, such as the ones used in the German Trans-Rapid and Japanese
Yamanashi maglev trains, respectively. The achieved design uses neodymium disc magnets, an
LSM – which produces a smoothly changing magnetic field from its 3 phases allowing the train
car to move with it - and magnetic strips for lateral stabilization and a guiding path for the train.
Team Maglev’s design also requires no control circuits to provide levitation and stabilization,
making it simpler and less expensive than other maglev designs [10].
Cost Analysis
The tables below are a representation of the total costs of designing, constructing and testing a
maglev train on a small-scale. Table 8 below includes an estimate of the number of hours
required on average per member for each segment of the whole process.
Table 8. Project Costs (in terms of hours spent) by Category
Category
Lectures
Written Documents
Hours
30
40
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Research on Concept/Design
Site Visits/Consultations
Meetings/Discussion
Construction of Model
Testing/Demonstration
Total Hours
70
30
120
40
50
380
The Site Visits/Consultations include visits to the Powder Springs American Maglev Technology
site, consultations with Dr. Greg Durgin, Dr. Ronald Harley, Dr. David Taylor, Dr. Whit Smith,
Dr. Steve Kenney, Technical Writing Coordinators and PhD students. Table 9 below includes the
costs of each segment in terms of capital input.
Table 9. Project Costs (in terms of money spent) by Category
Part
Train (Balsa wood + bearings)
Magnetic strip
18 Gauge Wire
AC Drive
Total Cost
Quantity
1
100ft
2 * 1 mile
1
Unit Price
$18
$1.8/ft
$35 /mile
$255
Total Cost
$18
$180
$70
$255
$523
It should be noted that the neodymium magnets and AC reactor were obtained free of charge.
8.
SUMMARY AND CONCLUSIONS
After going through three designs it is clear that any approach to this technology must be
taken with much attention paid to the underlying theory, mathematical justification, and all the
specifications of the materials used. The team has produced a design which uses an effective
P a g e | 19
linear synchronous motor and has mechanics and geometry which allow this to be constructed
into a full-length track, but true magnetic levitation has not yet been achieved. This is possible,
however, as an experiment with electro-dynamic suspension of a small object produced
promising results. If the magnetic strips used as rails were more strongly magnetized and more
robust against re-magnetization, they could continue to be incorporated in the design for stability
and levitation.
The current stage of the project does not allow the train to go as fast as the initially
proposed 4 - 8 mph, and it is not on a 20 ft circular track as originally proposed. However, what
exists does work and can be drawn out to a greater length, which would allow the train to
achieve a higher speed. Future development should focus on achieving electrodynamic
suspension of the train using electromagnets and reconstructing the train to be more durable and
capable of giving itself an initial acceleration without the need for slight external propulsion by
human hands. Once these are achieved, a true small-scale maglev train and track will exist.
P a g e | 20
9.
References
[1]
K. Davey, “Maglev: Transportation of the Future,” [Online Website], [cited 2009
Feb 2], Available HTTP: http://www.magneticsmagazine.com/e-prints/maglev.pdf
[2]
H. Blodget, “Mine’s Faster Than Yours,” [Online Document], [cited 2009 Feb 1],
Available HTTP: http://www.slate.com/id/2115114/
[3]
G. Rennie, “Magnetically levitated train takes flight,” [Online Document], [cited
2009 Feb 1], Available HTTP: http://www.eurekalert.org/features/doe/200411/ddoe-mlt111104.php
[9] A. Heller, “A New Approach for Magnetically Levitation Trains – and Rockets,” [Online
Website], [cited 2009 Jan 20], Available HTTP: https://www.llnl.gov/str/Post.html
[10] R. F. Post, Toward More Efficient Transport: The Inductrack Maglev System, Lawrence
Livermore National Laboratory, 2005.
P a g e | 21
Appendix A
Electro-dynamic Suspension System for Maglev Train
This part of the paper is less for ideas on where the project could go but more for a
substantial outline on what a future senior design team should pursue. First ensure that your team
composes of members who specialize in or who have heavy resources in:
·
Electromagnetics
·
Embedded Design
·
Systems & Controls (feedback systems)
This project will be difficult and the team needs to have a good backup to fall back on.
Description
For a maglev train to levitate in the simplest way as achieved by companies like
American Maglev Technologies all that is needed is electromagnets, a steel railing, sensors, a
power system to power the electromagnets, and an advanced feedback system as shown in Fig. 1.
Figure 1 – Rudimentary model of a maglev train with electromagnets, steel railings, and wires
leading to the feedback and power system in the “Black Box.”
P a g e | A-1
In another perspective simply take a simple levitation system [A-1], flip it upside down,
and elongate the electromagnet as shown in Figure 2.
Figure 2 – Flow diagram explaining how to move from basic levitation system to a maglev
levitation system. Notice the flip of the entire system and then the elongation of the
electromagnet to conform to the steel railing.
Note that this physical form is very similar to the system used in full scale levitation
systems as shown in Figure 3.
Figure 3 – Actual electromagnet used in full scale levitation system. Note the steel core wrapped
by copper wire encased in a plastic shell.
P a g e | A-2
Figure 4 shows a model of the system from the side profile with the different components
pointed out.
Hall Effect Sensors
Steel Rail
Copper Winding
Power for Electromagnet
Figure 4 – Up close diagram of system showing sensors, electromagnet, and steel rail.
The following diagram in Figure 5 in concert with the documentation referenced at the
end of this appendix should give any senior design group an idea of how to accomplish an
electro-dynamic suspension system in one semester.
P a g e | A-3
Hall Effect
Power the
PIC
Power Amp
Figure 5 – Abstract block diagram of feedback and power system for levitation.
Design
The Hall Effect Sensor used in the simple levitation system is a Honeywell SS495A
sensor. When connected to 5 V for its positive V+ and 0 V or ground for its V- input and with no
magnetic field in range it will output 2.5 Volts in the output lead. When a north pole nears it the
sensor linearly increases the output voltage until it reaches 5 V and in a similar fashion linearly
decreases until it hits 0 V on the output lead when a south pole nears it. This output could be fed
into a PIC microcontroller to regulate how much voltage is to be fed into the power amplification
circuit. This could be done in a brute force method of having a table of Hall Effect sensor outputs
and their correlating voltage outputs to go into the power amp circuit but a more elegant method
could certainly be found. This aspect of the project should be handled by the systems and
controls specialist.
P a g e | A-4
In addition to a simple lookup table or more elegant control method many levitation
circuits call for a Pulse Width Modulation (PWM) to be the input to the power amp part of the
circuit. In the referenced documentation [A-1] a fan controller IC chip with built in PWM is used
to accomplish this.
After the brains of the operation has been designed a simple power amplification circuit
should be added to bring the microcontroller output current up to an operational level for the
electromagnet to use. This can be done as simply as using a power transistor BJT but as always
consult a professor or circuits specialist to find the optimum or easiest solution.
Reference [A-2] is a video of the EDS system made using Google Sketchup.
Reference [A-3] is Team Maglev’s senior design website.
References
A-1.Guy, Marsden. "Levitation Kit." MIT. 23 Apr. 2009 <http://web.mit.edu/kumpf/www/
projects/MagLev/MagLev/Desc-Levitation.pdf>.
A-2.James, Ben. "YouTube - Future Project for Electrodynamic Suspension for a Maglev
Train." YouTube - Broadcast Yourself. 23 Apr. 2009 <http://www.youtube.com/watch?
v=mumrEE82qAw>.
A-3.Black, Nathan, Ben James, Greg Koo, Vivek Kumar, and Preston Rhea. "The Georgia
Tech Maglev Train Project." School of Electrical and Computer Engineering at the
Georgia Institute of Technology. 23 Apr. 2009 <http://www.ece.gatech.edu/academic/
courses/ece4007/09spring/ece4007l01/sk4/>.
P a g e | A-5
Appendix B
P a g e | B-1
P a g e | B-2
P a g e | B-3
*Note Page 5 was blank.
P a g e | B-4
P a g e | B-5

Small-Scale Maglev Train

Transcription

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