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MECH 4010 & 4015Design Project I

Fall 2013

CONCEPTUAL DESIGN REPORT

Magnetic Levitation Demonstration ApparatusTeam # 11

Ajay PuppalaFuyuan Lin

Marlon McCombieXiaodong Wang

Submitted: November 8, 2013

Team #11 Conceptual Design Report

Table of Contents

List of Figures.................................................................................................................................................................3

List of Tables..................................................................................................................................................................3

1. Project Information..............................................................................................................................................4

1.1. Project Title.................................................................................................................................................41.2. Project Customer(s).....................................................................................................................................41.3. Group Members..........................................................................................................................................41.4. Useful Definitions and Acronyms...............................................................................................................4

2. Conceptual Design Summary..............................................................................................................................5

3. Background and Context.....................................................................................................................................6

4. Requirements.......................................................................................................................................................7

5. Functional Overview...........................................................................................................................................8

6. Component Review.............................................................................................................................................9

6.1. Magnetic Levitation....................................................................................................................................96.2. Levitated Object........................................................................................................................................126.3. Sensors......................................................................................................................................................136.4. Microcontroller.........................................................................................................................................16

7. Overview of Conceptual Solution Alternatives.................................................................................................18

7.1. Concept 1..................................................................................................................................................187.1.1. Electromagnetic Suspension..............................................................................................................18

7.2. Concept 2..................................................................................................................................................217.2.1. Electrodynamics Repulsion...............................................................................................................21

7.3. Concept 3..................................................................................................................................................227.3.1. Vertical MagLev Track......................................................................................................................22

7.4. Concept 4..................................................................................................................................................237.4.1. Toroidal Electromagnetic Track........................................................................................................23

8. Feasibility..........................................................................................................................................................25

9. Testing and Verification....................................................................................................................................26

10. Required Engineering Expertise........................................................................................................................27

11. Resources...........................................................................................................................................................28

11.1. Facilities....................................................................................................................................................2811.2. Additional Advisors..................................................................................................................................28

12. References..........................................................................................................................................................29

Appendix A Concept Sketches..............................................................................................................................30

Appendix B Concept Evaluation Rubric...............................................................................................................34

Appendix C Sample Calculations for designing an Electromagnet.......................................................................37

Appendix D Supporting Literature........................................................................................................................38

List of Figures

MECH4010/4015 Magnetic Levitation Demonstration Apparatus of 40


Figure 1 General Schematic of demonstration device............................................................................................8Figure 2 Functional block diagram for the magnetic levitation apparatus.............................................................8Figure 3 Levitation of model car based on rotational stabilization (courtesy of futuristicnews.com).................10Figure 4 Transrapid monorail system using electromagnetic levitation (Picture courtesy

www.maglev.net)...................................................................................................................................10Figure 5 Eddy currents induced magnetic field (Diagram courtesy of www.microwavesoft.com).....................11Figure 6 Classification tree of four viable types of sensors for the magnetic levitation apparatus......................13Figure 7 Picture of Hall Effect sensor (courtesy: www.micropac.com)...............................................................14Figure 8 Inductive proximity sensor (left, courtesy of www.asi-ez.com) and capacitive displacement

sensor (right, courtesy of www.pepperl-fuchs.us).................................................................................14Figure 9 Photoelectric sensor (left, courtesy of www.directindustry.com), optical proximity sensor

(center, courtesy: www.setsensing.com), and reflective sensor (right, www.indiamart.com)...............14Figure 10 Ultrasonic sensor (courtesy of letsmakerobots.com).............................................................................15Figure 11 LEGA Mindsdtorms NXT 2.0 (left) and Arduino UNO (right).............................................................16Figure 12 Single electromagnet design with Hall Effect sensor.............................................................................19Figure 13 single electromagnet design with photoelectric sensor..........................................................................19Figure 14 Multiple electromagnet series arrangement...........................................................................................20Figure 15 Double electromagnet suspension design...............................................................................................21Figure 16 Single coil suspension design.................................................................................................................22Figure 17 Multiple coil parallel arrangement design..............................................................................................22Figure 18 Vertical Maglev design..........................................................................................................................23Figure 19 Toroidal electromagnet design...............................................................................................................24Figure 20 Magnetic Levitation Track design..........................................................................................................30Figure 21 Single electromagnetic suspension design with photoelectric sensor....................................................31Figure 22 Single electromagnetic suspension design with Hall Effect sensor.......................................................31Figure 23 Double electromagnet design with Hall Effect sensor for suspension and/or repulsion........................32Figure 24 Single multiple coil electromagnetic suspension design with Hall Effect sensor..................................32Figure 25 Vertical ring electromagnetic track design.............................................................................................33Figure 26 Toroidal electromagnet design...............................................................................................................33

List of Tables

Table 1 All options available in each category.....................................................................................................9Table 2 Comparison of sensors based on detection range and cost....................................................................15Table 3 Evaluation Matrix for Sensors................................................................................................................15Table 4 Comparison of Microcontroller cost......................................................................................................17Table 5 Highlights selected options from each category.....................................................................................18Table 6 Required engineering expertise..............................................................................................................27



1. Project Information

1.1. Project TitleMagnetic Levitation Demonstration Apparatus

1.2. Project Customer(s)Dr Robert BauerProfessorMechanical Engineering DepartmentDalhousie University

1.3. Group MembersAjay Puppala Tel: 1-902-999-4414 email: [email protected] Lin Tel: 1-902-488-6688 email: [email protected] McCombie Tel: 1-902-489-6655 email:[email protected] Wang Tel: 1-902-488-8556 email: [email protected]

1.4. Useful Definitions and AcronymsAWG - American Wire GageEOPD - Electro-Optical Proximity DetectorEM - ElectromagnetGUI - Graphical User InterfaceI/O - Input/outputMagLev - Magnetic LevitationMCU - Microcontroller UnitP - Proportional ControlPC - Personal ComputerPCB - Printed Circuit BoardPI - Proportional Integra ControlPID - Proportional Integral Derivative ControlPPE - Personal Protective EquipmentPWM - Pulse Width Modulation



2. Conceptual Design Summary

The objective of this project is to discuss the various concepts of a Magnetic Levitation Demonstration

Apparatus for MECH 4900(4905) Control Systems II course. The scope and requirements for the project are briefly

outlined and an overview of the functional components is given. There are various components in building the

device including the physical levitation, sensors, circuitry, microcontroller, and MATLAB/Simulink. Vast arrays of

options are available for each of these components; the most viable ones are considered in the document.

Consequently, several concepts were proposed and filtered down to one or two based on the degree of fulfillment of

basic requirements, cost assessment, design compatibility, and overall feasibility.

Concepts for levitation are generated based on the selected components and general design approach. These

concepts are examined for advantages and disadvantages to find better alternatives. To find the best solution for the

design and alternatives the requirement criteria is revoked and a rubric is built for comparison. Feasibility of the

design is considered and possible challenges are encapsulated. The future course of action for successful completion

of the project is enumerated in the feasibility section of the document. A method of testing the device components is

provided for validation. Additionally, the progress level of the group in the different areas related to the group is

laid out in the required expertise section. Finally, supporting calculations, literature review, and design sketches

were presented.



3. Background and Context

Demonstrations provide the opportunity for students to predict theoretical outcomes of real life

applications of course material which in turn allow them to confirm their initial understanding of those same

concepts. By making a prediction, students develop an expectation based on their initial understanding of the

concept. As they observe the demonstration they find out whether their prediction is accurate. If not, the

instructor can discuss any differences between their initial understanding and what the demonstration

actually shows.

Visual demonstrations help to bridge the gap between visual and verbal communication of course

material. Although diagrams may be a step further to having a better visual understanding of a concept, a

demonstration that produces live feedback vastly improves the delivery of course material. This concept is

similar to a salesman increasing the appeal of a product by showing its many uses through infomercials; i.e.

demonstrations of the basic use of a known concept (e.g. blending with the Magic Bullet). The only difference

for course material from this analogy is that the concepts being taught are new to students and may not be

initially understood from course lectures. Consequently, demonstrations allow students an extra chance to

try out their own theories on a subject to confirm their understanding.

Thus, the scope of our project is to design and build a portable and compact device that magnetically

levitates an object to demonstrate the different design theories presented in MECH4900 Systems II.



4. Requirements

Purpose

o Build portable demonstration device

o Levitate object magnetically

o Educational tool

o Demonstrate theories presented in MECH4900(4905) Control Systems II

Visual Requirements

o Shall be viewable from a back of the classroom and/or using cameras

o Levitate object for range of 5 cm

User Convenience & Safety

o Easy to carry; i.e. lightweight

o Easy to store

o No potential electrical risk to user

o No potential projectile risk to user

o No PPE required for operation

Power Requirements

o Conventional 120 VAC input

User Interactive Requirements

o Simulate a wide variety of control methods available in MATLAB/Simulink

o User shall interact with the device using a graphical user interface (GUI)

o Device shall be ready to operate once plugged into PC

o No additional programming shall be required

Demonstrative Requirements

o Comparison of desired, simulated, manipulated, and measured controller variables

o Nyquist plots

o Bode diagrams

o Lag, lead, lag-lead compensation techniques

o P, PI, PID control

Miscellaneous

o Shall be an active controller

o Budget $1,500



5. Functional Overview

Figure 1 below shows a general schematic of the components needed to build a functional magnetic

levitation demonstration apparatus based on the specified requirements mentioned. For magnetic levitation

to be achieved for the purpose of demonstrating various design techniques presented in Control Systems II, a

user would need to be able to vary the outcome of levitation; i.e. the levitated object must be manipulated in

some manner. The manipulation of a levitated object could only be achieved by some form of motion of the

levitated object as indicated by the very definition of levitation; “the phenomenon of a person or thing rising

into the air ...” (Wordnet Web, Princeston University). Consequently, it is anticipated that the levitating

magnetic field must be varied to achieve positional manipulation of the levitating object.

Figure 1 General Schematic of demonstration device

The next figure outlines the required functionality of the operating device. The final design should

meet this functionality.


INPUT

Control method generated in MATLAB/Simulink

Current supplied to the magnetic coil

PROCESS

Execute the control method from MATLAB/Simulink through

microcontroller

Maintain the position of the levitated object using system

feedback

Record data from sensor over specified duration of demostration

OUTPUT

Graphical display of recorded data

Position feedback of object from sensor


Figure 2 Functional block diagram for the magnetic levitation apparatus



6. Component Review

A list of component options was obtained from general research in each category. They are presented in the table below:

Table 1 All options available in each category

Levitation Technique

ObjectSensor Microcontroller

Material Shape MotionPermanent

MagnetsChrome Steel

Rectangular prism

Horizontal Hall Effect Arduino

Electromagnetic Regular Steel Circular disk Vertical ReflectiveLEGO Mindstorm

NXT 2.0Electrodynamics Neodymium Solid sphere Angled Optical Proximity BeagleBoardSuperconducting Composite Hollow sphere Photoelectric Altera DE2

DiamagneticCapacitive

DisplacementInductive ProximityUltrasonic

The following sections go through the selection process for each device. Best two or one are selected from each

category. Concepts are generated based on the selections

6.1. Magnetic LevitationThere are different to ways to levitate an object magnetically. The four major techniques consider in

the project are shown in the chart below. Quantum theory is intentionally ignored because the effect is so

small that it is certainly cannot meet the range of levitation required in the project (Lance 2005).

Pseudo levitation primarily consists of two magnets constrained vertically. They would distance

themselves apart causing levitation. This type of levitation can be immediately ruled out because it is passive.

However, it can be used in other techniques to improve the design. Also, this system can be slightly altered to

achieve stability and active control. According to Earnshaw’s theorem, permanent magnets cannot be

levitated in static configuration (Lance 2005). However, if one of them were to spin continuously with a drive

coil, levitation above a toroidal magnet arrangement is possible. The drive coil can be controlled to gain active

control. This type of levitation is employed in the Levitron toys shown below:



Figure 3 Levitation of model car based on rotational stabilization (courtesy of futuristicnews.com)

Electromagnetic levitation consists of one or more magnetic coils that are exposed to time- varying

current to create electromagnetic field to hold an object in place. This system by itself is quite unstable

because the strength of the magnetic field is high when the object is closer and low when it is further apart.

However, the field strength can be controlled through a feedback loop which is also required in the project

(Brandt 1989). The feedback loop would control the position of the levitating object based on the current that

flows through the electromagnets to adjust its field strength. This type of levitation is used in high speed

monorails.

Figure 4 Transrapid monorail system using electromagnetic levitation (Picture courtesy www.maglev.net)

Electrodynamic levitation consists of conductors that are exposed to time-varying magnetic field to

induce eddy currents in the conductive material. It creates a repulsive magnetic field around the conductor

holding the magnet coil without any support (Thompson 2000).



Figure 5 Eddy currents induced magnetic field (Diagram courtesy of www.microwavesoft.com)

This type of design puts restrictions on the type of object that can be levitated. Certainly it has to be always a

coil. Levitation can mostly be in vertical direction with the coil on top of the conductive material. This places

another major restriction on the type of motion for object to be levitated.

The stability achieved through electrodynamic levitation is considerably greater than the

electromagnetic type of levitation. This is mainly because the levitating object is pushed against gravity as

supposed to holding it. However, the levitation Is stable vertically, it may not be stable horizontally. Some sort

of support may be required to arrest the motion on the horizontal plane. Further research and advise from

the review panel member Dr. Little is needed.

Diamagnetism is a material property to repel any applied magnetic flux. A permanent magnet can be

stabilized with a di-magnet like pyrolytic graphite (Lance 2005). This technique has to be ruled out because

of the same reason for pseudo levitation, it is passive. Meissner effect which is a special case of diamagnetism

has to be ruled out due to the same reason.

The major requirements for the selection of a technique are active control of the device, stability of levitation,

ease of to build, availability of materials, and the range of levitation. These are used as the parameters for

evaluation of each technique. Table shows a comparison of the levitation techniques mentioned using the

following evaluation criteria:

1. Unacceptable2. Below Average3. Acceptable 4. Good 5. Best

Table 2 Evaluation Matrix for Levitation Techniques

Active or

Stability of Levitation

Availability of Materials

Range of Levitation

Ease to Build

Total



PassivePseudo Levitation Passive N/A N/A N/A N/A -

Rotational Stabilization Active 2 3 5 3 13

Electromagnetic Active 3 5 4 5 17

Electrodynamic Active 5 4 4 3 16

Diamagnetic Passive N/A N/A N/A N/A -

From the evaluation matrix, electromagnetic and electrodynamic types were chosen as the most suitable for

the experiment. This selection leads to a final but important factor of the project to be considered, direction of

motion. Three type of motion can be considered; vertical, horizontal, or a combination of the two. However,

for the sake of simplicity and designing an apparatus that can capture the attention of users, vertical motion

was considered to be the best option. This decision was made as vertical motion is easier to see from a

distance in comparison to horizontal motion and a combination of the two would require a more

cumbersome apparatus design that may take away from the ergonomic requirements of the project.

Additionally, it is impressive to see an object move against gravity without any visible aids.

6.2. Levitated ObjectFor magnetic levitation to be demonstrated, a suitable object must first be selected. Magnetic levitation

can only be performed on an object that can be affected by an external magnetic field. Objects that are

attracted to magnets and not able to independently sustain a magnetic field are not suitable for magnetic

levitation. These objects are attracted to magnets through magnetic induction and thus, will change magnetic

polarity in bias to magnetic attraction (CyberPhysics.co.uk). Although, magnetic attraction can be used for

levitation, these materials are still not suitable for the project as their magnetic strength varies with distance

from a magnetic source. Consequently, the most suitable object for this project is a magnet because of its

ability to maintain its magnetic poles and, most importantly, field strength in the presence of an external

magnetic field. Magnets are distinguished as strong or weak in comparison to each other based on their

permeability. Consequently, the primary criterion for selecting a suitable object material for the project is

magnetic permeability. The higher an object’s permeability the better its suitability for levitation as this also

results in an increase in sensitivity to an external magnetic field. For successful controlled levitation to occur,

the levitated objected must be able to respond to a varying magnetic field strength of an external force.

The secondary criterion of the object is its shape and size. The object should be suitably large for the

levitation to be viewable from a distance. For flat shapes, visibility may be hindered based on the objects

orientation. Consequently, the object’s shape must be one of either uniform uniaxial cross-section or visibly

well-proportioned in size. In addition, for an object with a non-uniform proportion of width and height, an

external magnetic field may cause the object to levitate horizontally away from the vertical axis of levitation.

Consequently, an object with uniform uniaxial cross-section is a better option for the levitating object. The

object can be either solid or hollow; however, a hollow sphere may require a denser material than a solid one



for the same size in order to maintain a suitable weight for levitation. Additionally, it would be difficult to

make or buy a hollow sphere as compared to a solid sphere especially for a permanent magnet. The following

table shows an evaluation matrix for object selection.

6.3. SensorsThere are various types of sensors that can measure the linear displacement of the levitating object

without touching it. It is important to determine the best type of sensor because the range and sensitivity

determines the range of the levitating object. The following diagram the categories and sensors that can be

used from each category.

Figure 6 Classification tree of four viable types of sensors for the magnetic levitation apparatus

From the diagram it is evident that there are four major categories of sensors. They are divided primarily

based on the method of operation. Magnetic sensor would measure the magnetic field strength generated

from the coil and the permanent magnet that is levitated. If the distance of the levitating magnet increased or

decreased relative to the coil, the field through the sensor would change correspondingly. Using a pre-

determined field strength and distance table, position of the object can be determined. The only type of

magnetic sensor considered for the project is the Hall Effect sensor.


Sensors

Magnetic Sensor

Hall Effect Sensor

Electric Sensor

Inductive Proximity Sensor

Capacitive Displacement

Sensor

Optical Sensor

Photoelectric Sensor

Optical Proximity Sensor

Reflective Sensor

Frequency based Sensor

Ultrasonic Sensor


Figure 7 Picture of Hall Effect sensor (courtesy: www.micropac.com)

Electric sensors works similar to a magnetic sensor, however, the magnet part is replaced either with a

capacitor or inductor that is looped around. When the object enters the sensing field, Eddy currents flow

through the object which reduces the signal amplitude and triggers a change of state in the sensor output

(DigiKey Corp.).

Figure 8 Inductive proximity sensor (left, courtesy of www.asi-ez.com) and capacitive displacement sensor (right, courtesy of www.pepperl-fuchs.us)

Optical sensors used light as a medium to detect the presence and movement of target. They are

various techniques that can be used to send and/or receive light signals from the object. Based on the

techniques optical sensors are further divided into photoelectric sensor, optical proximity sensor and

reflective sensor. EOPD is one example of the optical proximity sensor.

Figure 9 Photoelectric sensor (left, courtesy of www.directindustry.com), optical proximity sensor (center, courtesy: www.setsensing.com), and reflective sensor (right, www.indiamart.com)

Finally, the frequency based sensors are extremely powerful and useful for high detection distances.

Ultrasonic sensor is one type of frequency based sensor that can be used in the project. Basically, it emits high

frequency sound energy. Waves reflect of levitating object and are detected by the sensor. The sensor

measures the total time required for the pulse to return and calculate the distance (DigiKey Corp.).


http://www.asi-ez.com/


Figure 10 Ultrasonic sensor (courtesy of letsmakerobots.com)

The major requirements for the selection of the sensor are the range of detection of the sensor, its

compatibility with the microcontroller, and extent of effect of unwanted inputs in the measurement. Other

factors which are important to consider during the selection is the size of the sensor and ease of

configuration. Cost per unit to purchase the sensor is also important consider in the selection process. The

following table shows a list of sensors and corresponding costs based on the range of detection:

Table 2 Comparison of sensors based on detection range and cost

Type of Sensor Detection Range (cm) Price per unit (USD)

Hall effect sensor N/A 1.00

Ultrasonic sensor N/A 400+

Inductive proximity sensor 0.21.02.0

35.0050.00

115.00Capacitive displacement sensor 1.0

2.5100.00200.00

Photoelectric sensor 1.0 66.00Optical proximity sensor 15.0 7.50

*EOPD - 55.00Reflective sensor 5.0 2.50*All the prices are obtained from the Digi-Key website except for the EOPD which is taken from the Robotshop website.

Table 3 Evaluation Matrix for Sensors

SensorRange of Detectio

n

Unit Cost

Resistance to

Interference

Microcontroller Compatibility

SizeTesting

& Configuration

∑

Hall effect 4 4 4 4 4 5 25

Ultrasonic 4 1 2 3 3 3 16

Inductive proximity 1 3 2 3 3 3 15Capacitive displacement

1 2 2 3 3 3 14

Photoelectric 3 3 4 4 3 5 22

Optical proximity 4 3 3 3 3 3 22

Reflective 4 4 3 3 3 3 20The evaluation for each of the sensor type for requirements is based on the same criteria used for the levitation techniques.



From the evaluation matrix it is clearly evident that Hall Effect sensor, photoelectric sensor, and optical

proximity sensor distinguish compared to other type of sensors. If the selection has to be further narrowed

down to two sensors, definitely one of them would be Hall Effect sensor. Between the photoelectric and

optical proximity sensor is hard choose because they both have an equal score of 22. However, based on past

research, most models are build using the photoelectric sensor rather than optical proximity sensor. It is

convenient to choose photoelectric but further research and comparison is required.

6.4. MicrocontrollerA microcontroller (MCU) is a small, self-contained computer on a single integrated circuit (IC) containing

a processor core, memory, and programmable input/output peripherals. Microcontrollers are used in many

automatically controlled devices. The MCU can be described as the hub of the magnetic levitation device; it

will be responsible for controlling the power input of the electromagnet, retrieving data from the device’s

sensor, and for returning the retrieved data back to MATLAB/Simulink to be plotted and displayed on a PC.

Consequently, the MCU will be responsible for executing the function of controllers designed in

MATLAB/Simulink. There are several MCUs available from different manufacturers. However, the main

criterion to be met for the project by the MCUs is to be compatible with Matlab/Simulink via available

programming toolboxes. The MATLAB/Simulink toolboxes are separate toolkits that allow users to interface

with and command the MCU using MATLAB syntax or by uploading controllers through Simulink. The

following are some supported MCUs according to the MATLAB/Simulink website:

LEGO Mindstorms NXT 2.0

Arduino

Altera DE2

BeagleBoard

Figure 11 LEGA Mindsdtorms NXT 2.0 (left) and Arduino UNO (right)

Given that the scope and requirements of the project do not exceed the specifications of any of the

aforementioned MCUs, they were all deemed viable for the project’s application. Out of the four MCUs

mentioned, the LEGO Mindstorms NXT 2.0 and Arduino were readily available for testing, free of charge, from



the University. Consequently, there is on-campus support available from the lab technicians and graduate

students in the Mechanical Engineering department of the University. However, a decision was made to go

with the Arduino; specifically the Arduino UNO. The decision to choose the Arduino was made primarily

because it was cheaper than the NXT. Additionally, it has been the choice for most Mechanical engineering

senior year projects that required some form of controlling unit. The following is a comparison of the unit

cost of the MCUs mentioned above:

Table 4 Comparison of Microcontroller cost

MicrocontrollerUnit Cost

(CAD)

LEGO Mindstorms NXT 2.0 349.99

Arduino 28.95

Altera DE2 269.00

BeagleBoard 45.00



7. Overview of Conceptual Solution Alternatives

Based on the component selection criteria discussed in the previous section, the following table was

generated to display the selected component considerations.

Table 5 Highlights selected options from each category

Levitation Technique

ObjectMicrocontroller Sensor

Material Shape MotionPermanent

MagnetsChrome Steel

Rectangular prism

Horizontal Arduino Hall Effect

Electromagnetic Regular Steel Circular disk VerticalLEGO Mindstorm

NXT 2.0Reflective

Electrodynamics Neodymium Solid sphere Angled BeagleBoard Optical ProximitySuperconducting Composite Hollow sphere Altera DE2 Photoelectric

DiamagneticCapacitive

DisplacementInductive ProximityUltrasonic

Consequently, the following concept design solutions were generated based on selection considerations for

levitation technique, object motion, and sensor. The circuitry and microcontroller were excluded as these

components do not affect the physical design of the apparatus. The following preliminary designs were

developed from hand sketches included in Appendix A.

7.1. Concept 1

7.1.1. Electromagnetic SuspensionThe first concept that is generated based on the components that were chosen is the simple

electromagnetic suspension shown in the figure next page. The design uses an electromagnet to generate

magnetic field when power an external source. The linear position of the levitating object is determined using

a Hall Effect sensor. One sensor is enough to get the position and it is placed right under the electromagnet.

The stand to hold the device and clamp to mount the electromagnet are kept simple to avoid complications.

The major advantages with this design are simplicity of design and easiness to build. The stand and

other parts can be enhanced if this concept is chosen for reliability and portability. A major disadvantage with

this design are only small variations in position of levitating object is possible. Also, the use of Hall Effect

sensor requires a table of comparison for the field strength



Figure 12 Single electromagnet design with Hall Effect sensor

An alternative for the single electromagnet design concept is the use of photoelectric sensor. This

requires changing the design of the stand and holding method for the electromagnetic coil. This is illustrated

in figure given below:

Figure 13 single electromagnet design with photoelectric sensor

A major advantage with this type of design it is extremely accurate but the range of the sensor is quite

small. The bulbs and the sensor have to be place very close to each other. It is not very difficult to build and

appropriate level of complexity for the project. The light from the LED would help to display the object much

better than the other two designs.



The problem with the low strength of the magnetic field still persists with the design. An alternative to

the single coil design is having multiple coil electromagnets as shown in figure 14. This design might address

the problem with the range of distance for the levitating object. Presumably, adding more electromagnets

may increase the magnetic field in turn gives extra range for the levitating object. The only complication with

this design is the integration of electromagnets to produce a combined magnetic field. It requires clear

understanding of functionality of electromagnets.

Figure 14 Multiple electromagnet series arrangement

The best possible way to overcome the problem is to use two electromagnets to extend the range of

magnetic field (Please see figure 16 on the next page). There would be severe problems in terms of stability

and obtaining levitation. The levitating permanent magnet can snap to either one of electromagnet if the

current flow and direction is not properly monitored. This design might need careful attention while building

and testing for functionality.



Figure 15 Double electromagnet suspension design

7.2. Concept 2

7.2.1. Electrodynamics RepulsionThe second major concept generated from the levitation technique is the electromagnetic repulsion.

Figure 18 shows a simple arrangement based on the concept. A magnetic coil is levitated on top of a

conductor plate that is induced with eddy currents and field around it. It is easy to build and test. Attaining

vertical stability with repulsion is easier compared to electromagnetic suspension. However stability on

horizontal plane is difficult without constraining the magnetic coil. This might pose problems with the

display, may not seem free levitation. Either Hall Effect sensor or the photoelectric sensor can be used for the

measurement of distance of the magnetic coil from the conductor plate. Current has to be supplied to the

moving magnetic coil which may be difficult with the wiring and other connections.



Figure 16 Single coil suspension design

The concept of using multiple electromagnets can be extended to suspension. Figure 17 shows an

example of three coils in parallel configuration. This might cause problem of stability but increases the range

of levitation which is better for classroom display. Another problem with this design is trying to achieve the

functionality and testing the device.

Figure 17 Multiple coil parallel arrangement design

7.3. Concept 3

7.3.1. Vertical MagLev Track

The following design is consider as a different approach from the general evaluation. The idea is

motivated from the Maglev trains discussed in the levitation techniques. It gives an opportunity to

approach the design problem in a different perspective. It is uncertain whether this design may be

feasible but it was considered during evaluation. The major advantage of this model is the motion of

a levitating disk is properly constrained; thus, there is proper stability for motion. The levitation

can be seen through the gaps between the electromagnets. The major disadvantage with this



approach is that it looks like the disk is supported by the electromagnet tracks. Also, the cost to

build the physical model may be quite expensive compared to others consider primarily due to the

extra material needed to build the electromagnet tracks and the levitating disk.

Figure 18 Vertical Maglev design

7.4. Concept 4

7.4.1. Toroidal Electromagnetic TrackAnother concept consider apart from the evaluation of components is the toroidal electromagnetic track.

An object is levitated inside a torus shape core where magnetic wire coil is place around in equidistance. Few

advantages with this type of system is amount of magnetic flux that escapes outside the coke is minimum due

to symmetry. Also, it gives higher efficiency required for the sensitive circuitry. The major disadvantage is

visibility requires molding transparent plastic and also there is only limited power capacity to pass it on to

four coils.



Figure 19 Toroidal electromagnet design

All solution design alternatives are considered and briefly explained with advantages and disadvantages.

Appendix B contains the rubric for evaluation of the all the design alternatives for the 4 concepts. The basic

requirements are weighted the most compared to the parts, design, and cost assessment. The general

evaluation criterion, in page 12 is used for the assessment. This assessment does not consider the cost to

build the circuitry mainly because it is almost the same for all the concepts.

From the assessment it is evident that single electromagnet design with Hall Effect sensor is the best

solution followed by single coil suspension design. They were the top scoring concepts mainly because they

were consider a good design for the basic requirements which was weighted most in the assessment, as much

as 60%. Certainly if design assessment that evaluates for complexity and ease to build other concepts like the

single electromagnet design with photoelectric sensor and double electromagnet suspension design would be

considered. It is not surprising that their scores follow very close to the first two designs.

If other designs have to consider apart from the single electromagnet design with Hall Effect sensor for

magnetic strength it would be double electromagnet suspension design and for better design as a whole

single electromagnet design with photoelectric sensor would be considered.



8. Feasibility

The concept design, single electromagnet design with the Hall Effect sensor, was selected after

evaluating all concepts. The major components of the design include the single electromagnet levitation,

spherical permanent magnet made of Neodymium, Hall Effect sensor, and Arduino microcontroller. Almost

all of the components are available in retail stores in Halifax, N.S. except for the electromagnet which may

have to be ordered custom-made or hand built according to the magnetic field strength requirement. This

concept design has the option of conducting ether repulsion or attraction levitation depending on its

position/orientation on the apparatus. Consequently, this design provides the option of testing out both

methods of electromagnetic levitation. Testing of the device and the operating circuitry can also be a cause for

concern in the project as these components determine the feasibility of the design to meet the project’s

requirements.

In terms of availability of materials, the Hall Effect sensor and Arduino microcontroller can be

obtained from a local electronics store in Halifax called Jentronics. Permanent magnets made of Neodymium

are available at Princess Auto; however, these are disk shaped. Initial prototype and testing phase can be

carried out with the available magnet size but further research is needed to find a spherical neodymium

magnet locally; these can be purchased online. The circuit needed for the system can be built with a

prototype board, wires, and electrical components that can be bought at Jentronics. Putting them together

according to the requirement may require research into electric circuits and guidance from Electrical

advisors. Once the layout for the circuitry is determined it can be printed at a local PCB contract

manufacturer, Sunsel Systems.

There are multiple options for the electromagnet design. Calculations in Appendix C indicate the

initial approach towards building the electromagnet. There are various limitations and parameters that need

to be determined. Off the shelf electromagnets are available; however, testing is required to determine

whether this is suitable or needs to be built based on specified calculations for the apparatus (please see

Appendix D). A major challenge anticipated for the project is the integration of the components to achieve

functionality through input methods from MATLAB/Simulink. The group has so far successful interfaced the

microcontroller with MATLAB and Simulink. Other challenges include building a block diagram, executing

control methods from Control Systems II course syllabus, retrieving data from the sensor, and adhering to the

project requirements.



9. Testing and Verification

There are a variety of different shapes of magnets that can be tested to confirm the concerns of shape

on object levitation. As mentioned above in the Feasibility section, different materials and shapes of magnets

are available for purchase; thus, tests will be conducted on as many different shapes before making a final

decision. In addition, it is possible to purchase electromagnets at local hardware stores for testing, as opposed

to purchasing wires and electromagnet core materials separately without certainty of success. The

electromagnets available for purchase come in the form of pneumatic switches and igniters; these can be

taken apart to retrieve the electromagnet solenoid.

Given that the MCU must act as an input/output (I/O) hub, it is important to test out this basic

functionality in the simplest manner possible to verify its usefulness to the project. A common means of

testing out I/O applications is by toggling LEDs on and off to determine whether signal transmission is

possible. However, this may not be the most effective means of confirming data retrieval from the MCU.

Consequently, a viable alternative to testing data retrieval would be to connect a simple sensor to be powered

and read by the MCU; for example, a temperature sensor. Successful execution of basic I/O tests, as

mentioned, will prove that the necessary control of a magnetic levitating device can be achieved. Toggling the

on/off state of an LED is proof of concept that the required external supply to the electromagnet can be

regulated as needed. Retrieving data from a sensor will be proof of concept that it is possible to retrieve data

from a sensor. The next step in testing and verification would be to attempt the same test mentioned above,

but this time using the MATLAB/Simulink toolboxes. Successfully accomplishing communication or control of

the MCU using MATLAB/Simulink would prove that it is possible to control the magnetic levitation device

using the chosen MCU and MATLAB/Simulink. In other words, this would fulfill part of the necessary

functional requirements of the project.



10. Required Engineering Expertise

The following table presents a list of anticipated engineering expertise required for successful project completion.

Table 6 Required engineering expertise

Technical Area Team Member Responsible Level of Expertise RequiredTechnical Communication

Ajay PuppalaFuyuan LinXiadong WangMarlon McCombie

ExpertThis skill is important for the necessary documentation and communication required for the duration of the project

Research & Development

Ajay PuppalaFuyuan LinXiadong Wang

IntermediateDetail research must be carried out. This will help to determine the parameters necessary for levitation and component selection and testing. This expertise is important to the overall success of the project

Circuit Analysis Marlon McCombieFuyuan Lin

IntermediateA clear understanding of the function of circuit components is required for reliable and effective transfer of power and data among the components.

Microcontrollers Marlon McCombie AmateurA basic understanding of microcontrollers and programming is required to be able to test and communicate with the system components and the required GUI.

MATLAB/Simulink Controller Design

Ajay PuppalaXiadong WangMarlon McCombie

IntermediateAn intermediate level of understanding for this technical area is required for successful communication and testing between the microcontroller and the required GUI and simulation and testing of the apparatus’ ability to meet the projects main requirement for demonstration.



11. Resources

11.1. FacilitiesThe following is a list of facilities that are required for the project duration and a short description for their necessity:

Design workbencho For testing prototype apparatus and for storing materials and components to allow

easy access by team members Measurements Laboratory (C255)

o For testing EM with varying current input using an bench power supply; especially in the unlikely case that the currents needed for levitation are potentially dangerous

Machine Shop/Carpentry Shopo For fabricating a suitable chassis for the final apparatus

11.2. Additional AdvisorsName: Dr. Ya-Jun PanPosition: Professor, Mechanical Dept.Telephone: 1-902-494-6788Email: [email protected]

Name: Dr. Timothy LittlePosition: Professor, Electrical Dept. Telephone: 1-902-494-3988Email: [email protected]

Name: Jonathan MacDonaldPosition: Electrical Technician, Mechanical Dept.Telephone: 1-902-494-6557Email: [email protected]

Name: Angus MacPhersonPosition: Mechanical Technician, Mechanical Dept. Telephone: 1-902-494-3238Email: [email protected]

Name: Corey MacNeilPosition: Automation Specialist, Jentronics Ltd.Telephone: 1-902-468-7987Email: [email protected]



12. References

Brandt, E. H. "Levitation in Physics." N.p., 20 Jan. 1989. Web. 28 Oct. 2013.]\

“Definition of Levitation.” http://wordnetweb.princeton.edu/perl/webwn?s=levitation. Retrieved

November 6, 2013

“Electromagnetic Induction.” http://www.cyberphysics.co.uk/topics/magnetsm/electro/EMI.htm.

Retrieved November 7, 2013

"Electronic Components Distributor | DigiKey Corp. | CA Home Page. N.p., n.d. Sat. 03 Nov. 2013

“LEGO Mindstorms Online Store.” http://shop.lego.com/en-CA/LEGO-MINDSTORMS-NXT-2-0-8547.

Retrieved November 6, 2013

“Liquidware Online Store” http://www.liquidware.com/shop/show/ARD-UNO/. Retrieved November 6,

2013

"RobotShop : The World's Leading Robot Store." RobotShop. N.p., n.d. Sat. 03 Nov. 2013

Thompson, Marc T. "Eddy Current Magnetic Levitation: Models and Experiments." IEEE. N.p., 200. Web.

28 Oct. 2013.

Williams, Lance. "Electromagnetic Levitation Thesis." N.p., 2005. Web. 28 Oct. 2013.



Appendix A Concept Sketches

Figure 20 Magnetic Levitation Track design



Figure 21 Single electromagnetic suspension design with photoelectric sensor

Figure 22 Single electromagnetic suspension design with Hall Effect sensor



Figure 23 Double electromagnet design with Hall Effect sensor for suspension and/or repulsion

Figure 24 Single multiple coil electromagnetic suspension design with Hall Effect sensor



Figure 25 Vertical ring electromagnetic track design

Figure 26 Toroidal electromagnet design



Appendix B Concept Evaluation Rubric

Rubric for Design AssessmentSingle

electromagnet design with Hall Effect

Sensor

Single electromagnet

design with Photoelectric

sensor

Multiple electromagnet series arrang.

Basic Requirements (60% weightage)1 Viewablility & Stability of the levitating object 3 3 32 Implement control design theories 4 4 43 Portable 4 4 44 Power input: Household Outlet 4 4 45 Total weight: Easy to carry 5 4 36 Safe in class environment 4 4 47 Graphical User Interface (GUI) for interaction 4 4 48 Simulation: MATLAB 4 4 49 All plots are shown in the GUI window 4 4 4Parts Requirements (20% weightage)1 Electromagnet

Strength of the magnetic field 3 3 4Wiring 5 5 3

2 Sensor effectiveness in detection of the object 3 4 33 Microprocessor 5 5 54 Total displacement levitating object 3 2 35 Frame support 5 5 5Design Assessment (10% weightage)

1 Design complexity 3 4 42 Ease to build 4 3 23 Holistic Judgement 5 4 3Cost Assessment (10% weightage)1 Cost of wiring for electromagnet 4 4 32 Cost of sensor 4 2 43 Cost of microprocessor 4 4 44 Cost of building the frame 4 3 3Total Score 29.2 28.2 27.3

Rubric for Design Assessment



Double electromagnet

suspension design

Single coil suspension

design

Multiple coil parallel

arrangement design

Basic Requirements (60% weightage)1 View ability & Stability of the levitating object 5 4 32 Implement control design theories 4 4 43 Portable 3 4 34 Power input: Household Outlet 4 4 45 Total weight: Easy to carry 3 5 36 Safe in class environment 4 4 47 Graphical User Interface (GUI) for interaction 4 4 48 Simulation: MATLAB 4 4 49 All plots are shown in the GUI window 4 4 4Parts Requirements (20% weightage)1 Electromagnet

Strength of the magnetic field 5 4 5Wiring 3 3 3

2 Sensor effectiveness in detection of the object 3 3 33 Microprocessor 5 5 54 Total displacement levitating object 4 3 45 Frame support 5 3 4Design Assessment (10% weightage)

1 Design complexity 4 3 42 Ease to build 3 4 33 Holistic Judgment 5 4 2Cost Assessment (10% weightage)1 Cost of wiring for electromagnet 4 3 22 Cost of sensor 4 4 43 Cost of microprocessor 4 4 44 Cost of building the frame 3 4 2Total Score 28.7 29 26.7

Rubric for Design Assessment



Vertical Maglev Track

Toroidal Electromagnetic

TrackBasic Requirements (60% weightage)1 View ability & Stability of the levitating object 3 32 Implement control design theories 4 43 Portable 4 44 Power input: Household Outlet 4 45 Total weight: Easy to carry 3 36 Safe in class environment 4 37 Graphical User Interface (GUI) for interaction 4 48 Simulation: MATLAB 4 49 All plots are shown in the GUI window 4 4Parts Requirements (20% weightage)1 Electromagnet

Strength of the magnetic field 4 4Wiring 2 2

2 Sensor effectiveness in detection of the object 3 33 Microprocessor 5 54 Total displacement levitating object 4 35 Frame support 4 2Design Assessment (10% weightage)

1 Design complexity 4 52 Ease to build 2 23 Holistic Judgment 4 3Cost Assessment (10% weightage)1 Cost of wiring for electromagnet 2 32 Cost of sensor 4 43 Cost of microprocessor 4 44 Cost of building the frame 2 3Total Score 27 26



Appendix C Sample Calculations for designing an Electromagnet

Options 1.000 2.000 3.000 4.000 LimitationCore Diameter (former) (mm)

30.000 30.000 30.000 30.000 30.000

Density of object (kg/m^3) 7850.000 7850.000 7850.000 7850.000 7850.000Diameter of object (mm) 25.000 25.000 25.000 25.000 25.000Volume of ball (m^3) 0.000 0.000 0.000 0.000 0.000Mass of ball (kg) 0.064 0.064 0.064 0.064 0.064Gravity 9.810 9.810 9.810 9.810 10.810Pole area 0.001 0.001 0.001 0.001 0.001B (wb/m^2) 0.059 0.059 0.059 0.059 0.059Air gap (mm) 100.000 90.000 80.000 0.000 300.000Turns (n) 1000.000 1000.000 1000.000 1000.000 1000.000r (half diameter of core) (mm)

15.000 15.000 15.000 15.000 15.000

Length of former (mm) 100.000 100.000 100.000 100.000 100.000Cylinder (total area) (m^2) 0.011 0.011 0.011 0.011 0.011H (AT/m) 46997.891 46997.891 46997.891 46997.891 46997.891Magneto-motive force (mmf) 4699.789 4229.810 3759.831 0.000 14099.367I (A) 4.700 4.230 3.760 0.000 14.099F (N) 15.042 15.042 15.042 15.042 15.042Wire chosenAWG 19 gage() (mm) 0.912 0.912 0.912 0.912 0.912Maximum number of wires in the first layer

109.666 109.666 109.666 109.666 109.666

Stacking factor 0.900 0.900 0.900 0.900 0.900Total # of layers 10.132 10.132 10.132 10.132 10.132Total length of wire (layers) 1039.264 1039.264 1039.264 1039.264 1039.264Total length of wire (total cylinder) (mm)

102574.682 102574.682 102574.682 102574.682 102574.682

(m) 102.575 102.575 102.575 102.575 102.575The unitl Resistor of chosen wire (Ohms per 1000 ft)

8.051 8.051 8.051 8.051 8.051

Total Resistor 2.709 2.709 2.709 2.709 2.709Total Voltage 12.734 11.460 10.187 0.000 38.201Heat produced by wire 34.501 31.051 27.601 0.000 103.502



Appendix D Supporting Literature

Document source: Design, Development and Testing of an Electromagnet for magnetic levitation system by Dahiru

Sani Shuaibu and Sanusi Sani Adamu.

Note: The following equations are built based for the single electromagnet design with object levitated vertically

upwards against gravity

In the single electromagnet design, air gap between the electromagnet and levitating object plays a crucial

in determining the current that is required to follow through the electromagnet and thus the overall power required to

levitate the object. This requires analysis of force and magnetic field around the electromagnet and in between the

object. The force required to levitate an object is equal to the force of gravity ignoring air friction:

Fmagnet=Fgravity=mg

where m is the mass of the object (kg), g is the acceleration due to gravity (m/s2). From this equation the magnetic

force required can be determined. Fundamentally, electromagnets generate magnetic field when current is allowed to

pass through it. The field induces flux on ferromagnetic material that is introduced in the field. The force can be

calculated using the following equation:

Fmagnet =B2 A2μo

where F is the force (N), B is the magnetic field generated by the electromagnet (T), A is the area of the pole faces

of the electromagnet (m2), and µo is the permeability of free space for air it is always 4π x 10-7 HM-1.With this

equation the B, magnetic field generated by the electromagnet can be found. It can be used to calculate the flux

density, Ф in the air gap using the equation:

Φ=BA

This value can be used to find the magnetizing force, H in the air gap through the following equation:

H= Bμo

The magnetizing force in turn can be used to find the magneto- motive force (mmf). It primarily depends on

magnetizing force, H and air gap length, l. The value for l has to be estimated initially later altered based on the

current output. To determine current, estimation for number of turns of coil is required. Thus two variables have to

be altered to optimize the current input. The input should be feasible for the project. The following equation

correlates the variables just discussed:

I= mmfN

= H × lN

Other major aspects that need to be determined about the electromagnet include the wire type and shape of the core.

The wire selection is based on the resistance of the wire, inductance of coil and overall weight. The resistance of the

wire can be obtained from the data sheet while inductance of the coil, L has to be calculated using the formula:



L= NΦI

Higher value for inductance of coil is better for the design in terms levitation i.e., air gap. It is preferable for the wire

to be light weight because it should be easy to carry. Some options considered in the source document are for

annealed copper wires are 17, 18, & 19 AWG with diameters 0.056, 0.048, and 0.040 inch respectively. Further

research in the materials like circular mil and current of square inch density is required to determine the suitable

wire for the project.

The shape of the electromagnet is substantial in increasing the magnetic field generated by the coil.

Referring back to equation:

Fmagnet =B2 A2μo

Area of the magnetic poles can be varied to achieve greater magnetic force. Since µo is constant and B, field

strength is determined based on the current, maximizing the area would definitely improve the field strength and

ultimately the design. A possible way to improve the area is by using a U shaped or E shaped electromagnet

Selection of either depends on the ease to build and the cost involved in machining.


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