Small-Scale Maglev Train 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. Small-Scale Maglev Train 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) Page |2 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 Team Maglev (ECE4007 L01) Page |3 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 Team Maglev (ECE4007 L01) Page |4 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 Design Specification 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] Team Maglev (ECE4007 L01) Page |5 Stabilization Table 3. Specifications for Magnetic Levitation Criteria Design Specification 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 Design Specification 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 Team Maglev (ECE4007 L01) Page |6 Table 5. Specifications for Train Operation Criteria Design Specification 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 Design Specification 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 Design Specification Topology Linear Track Materials Balsa Wood, Plexiglass Support Magnetic Rails glued to Wooden planks Dimensions ¾” height, 4ft. length, 28.6mm width Team Maglev (ECE4007 L01) 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 Team Maglev (ECE4007 L01) Page |8 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 Team Maglev (ECE4007 L01) Page |9 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 Team Maglev (ECE4007 L01) P a g e | 10 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. Team Maglev (ECE4007 L01) P a g e | 11 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 Team Maglev (ECE4007 L01) P a g e | 12 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 Team Maglev (ECE4007 L01) P a g e | 13 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 Team Maglev (ECE4007 L01) 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 Team Maglev (ECE4007 L01) 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 Team Maglev (ECE4007 L01) 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 Team Maglev (ECE4007 L01) 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 Team Maglev (ECE4007 L01) Hours 30 40 P a g e | 18 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 Team Maglev (ECE4007 L01) 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. Team Maglev (ECE4007 L01) 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. Team Maglev (ECE4007 L01) 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.” Team Maglev (ECE4007 L01) 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. Team Maglev (ECE4007 L01) 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. Team Maglev (ECE4007 L01) 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. Team Maglev (ECE4007 L01) 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/>. Team Maglev (ECE4007 L01) P a g e | A-5 Appendix B Team Maglev (ECE4007 L01) P a g e | B-1 Team Maglev (ECE4007 L01) P a g e | B-2 Team Maglev (ECE4007 L01) P a g e | B-3 *Note Page 5 was blank. Team Maglev (ECE4007 L01) P a g e | B-4 Team Maglev (ECE4007 L01) P a g e | B-5