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Multidisciplinary Engineering
Senior Design
Construction of Three Dimensional
Objects and Displays Using Swarms of
Intelligent Microsystems
Team 05400
May 18, 2005
Preliminary Design Report
Brian Saghy (CE) Team Leader & Programming Lead
Alejandro Lam (EE) Integration Lead
Nathan Pendleton (EE) Electronics Lead
Brian Payant (EE) E&M Lead
Gaurav Patel (ME) Mechanical Lead
Kate Gleason College of Engineering
Rochester Institute of Technology
76 Lomb Memorial Drive
Rochester, NY 14623-5604
Page 1 of 69
Executive Summary
This preliminary design report summarizes the progress made by the Construction
of Three Dimensional Objects and Displays using Swarms of Intelligent Microsystems
Team. The goal is to design, construct, test, and debug a small, 'intelligent' robot, known
in the project as a Chunxil which is capable of navigating itself by using magnetic fields
in a one-dimensional field. This design will be part of a larger goal of being able to use a
high quantity of Chunxils in a swarm intelligence system such that they are able to form a
larger object, being useful for rapid prototyping and 3D displays. The Chunxil will be
designed with future nanotechnology in mind, keeping hardware simple, small, and
power efficient. It will also be sustainable so that future project generations can use the
Chunxils produced by this team, being able to recharge them and reprogram them as
necessary for further development and testing.
The Engineering Design Planner™ methodology was utilized by the team to do
concept development and design for the project. The portions required for the preliminary
design review have been successfully completed, with the exception of design decisions
which will be dependent on experimental data obtained from prototypes.
The first facet of the design process realizes the need for such a product that is
being discussed in this report through background research and motivations. The second
facet shows much of the concept development and brainstorming done by the team in
very early stages of the project, before many technical details were even known. From the
brainstorming, feasibility assessments are then done in the third facet in order to narrow
down which ideas are the 'best', according to the current project scope. From there, the
project scope is narrowed down enough to better define the goals, objectives, and
specifications of the project. Once the specifications are defined, the final facet of design
is done, composing the majority of the project.
By using the aforementioned design techniques, the team was able to efficiently
and intelligently define and approach the goals defined later in this paper. After this initial
design, the most challenging portion of the project – construction, testing, and debugging,
will be conducted in the summer by a few team members, and continued in the fall.
Page 2 of 69
Table of Contents
Executive Summary...............................................................................2
Index of Figures......................................................................................6
Index of Tables.......................................................................................7
Nomenclature.........................................................................................8
1 Recognize and Quantify Need............................................................9
1.1 Mission Statement.......................................................................9
1.2 Product Description.....................................................................9
1.3 Scope Limitations......................................................................10
1.4 Stakeholders .............................................................................10
1.5 Top Level Critical Financial Parameters ....................................10
1.6 Financial Analysis......................................................................11
1.7 Primary Markets ........................................................................11
1.8 Secondary Markets ...................................................................11
1.9 Innovation Opportunities...........................................................12
1.11 Background Research .............................................................12
1.12 Formal Statement of Work.......................................................14
2 Concept Development .....................................................................15
2.1 Previous Work............................................................................15
2.2 Delineation of Concepts ............................................................17
2.3 Critical Parameters................................................................18
2.4 Magnetic Fields..........................................................................19
2.4.1 Stability...............................................................................19
2.4.2 Velocity Control..................................................................22
2.5 Tank Structure...........................................................................23
2.6 Chunxil Structure.......................................................................24
2.7 Tank Electronics........................................................................25
2.8 Chunxil Electronics....................................................................26
Page 3 of 69
2.9 Software....................................................................................28
2.10 PIC Microcontroller ..................................................................29
2.11 Modularity and Sustainability..................................................30
2.12 Concepts Beyond Current Scope of Project.............................31
3 Feasibility ........................................................................................33
3.1 Magnetics Feasibility.................................................................33
3.2 Chunxil Structure Feasibility......................................................35
3.3 Micro controller Feasibility.........................................................35
3.4 Battery Feasibility......................................................................37
3.5 Feasibility Conclusion................................................................39
4 Objectives and Specifications ..........................................................39
4.1 Design Objectives......................................................................39
4.2 Magnetics/Motion Performance Specifications..........................40
4.3 Mechanical Performance Specifications ....................................41
4.4 Electrical Performance Specifications .......................................41
4.5 Software Performance Specifications .......................................42
4.6 Design Practices Used...............................................................43
4.7 Safety Issues.............................................................................44
5 Analysis and Design.........................................................................44
5.1 Magnetic Field Analysis.............................................................44
5.1.1 Introduction........................................................................44
5.1.2 Stability...............................................................................45
5.2 Mechanical Design.....................................................................51
5.3 Assembly Methods.....................................................................52
5.4 Circuit Design............................................................................54
5.5 Power Requirement Analysis.....................................................59
5.6 Software Design........................................................................62
5.7 Analysis and Design Conclusions...............................................62
6 Future Plans ....................................................................................63
6.1 Experimentation .......................................................................63
Page 4 of 69
6.2 Schedule....................................................................................63
6.3 Budget ......................................................................................65
7 Conclusion........................................................................................68
8 References.......................................................................................69
8.1 Parts Reference.........................................................................69
8.2 Other Sites Mentioned...........................................................69
Page 5 of 69
Index of Figures
Figure 1 - CMU Claytronics Project 12
Figure 2 - Cornell Self-Replicating Robots 13
Figure 3 - Impulse Driven 15
Figure 4 - Magnetic Propulsion 16
Figure 5 - Concept Focus 17
Figure 6 - Opposing Chunxil Internal Magnets 20
Figure 7- Tank Structure 23
Figure 8 - Dimension limiter placed inside tank. 24
Figure 9 - Chunxil Structure 25
Figure 10 - Capacitance Driving 28
Figure 11 - Software Timing Diagram 29
Figure 12 - Possible implementation of inductive charging 31
Figure 13 - MicroChip PIC16F88 36
Figure 14 - 16F88 Maximum IDD vs Vdd & Mhz for Internal RC 37
Figure 15 - Battery Feasibility Chart 38
Figure 16 - Tank Coil Coordinates 45
Figure 17 - Simultaneous Internal Coils 49
Figure 18 - Curved field lines with one coil 50
Figure 19 - Straightened Field Lines from two coils 50
Figure 20 - Chunxil Dimension and Axis Limiter 51
Figure 21 - Coil Holding Device 53
Figure 22 - Chunxil Assembly 53
Figure 23 - Entire Chunxil Circuit 54
Figure 24 - Re-Designed Op-Amp 57
Figure 25 - Micro-Controller w/ other circuit improvements 57
Figure 26 - Chunxil Coil Control Circuit 58
Figure 27 - Software Flow Chart from Previous Design 62
Page 6 of 69
Figure 28 - Project Plan for Senior Design I 64
Figure 29 - Project Plan for Summer Quarter 64
Figure 30 - Project Plan for Senior Design II 65
Index of Tables
Table 1 - Hybrid Coil Timing Scheme 22
Table 2 - Magnetics Feasibility Assessment 33
Table 3 - Chunxil Enclosure Feasibility 35
Table 4 - Microcontroller Feasibility Assessment 36
Table 5 - Chunxil Power Budget 60
Table 6 - Chunxil Cube Budget 66
Table 7 - Tank Modifications and Chunxil Station Budget 67
Page 7 of 69
Nomenclature
Abbreviation Meaning
SD1 Senior Design 1
SD1.5 Senior Design Summer
SD2 Senior Design II
PCB Printed Circuit Board
SMT Surface Mount Component
LED Light Emitting Diode
AWG American Wire Gauge
MEMS Micro-Electro-Mechanical Systems
Page 8 of 69
1 Recognize and Quantify Need
1.1 Mission Statement
The mission of the Construction of Three Dimensional Objects and Displays
Using Swarms of Intelligent Microsystems design project is divided into two main
objectives. The first objective is to create a control and propulsion system in which a
small, 'intelligent' robot, called a Chunxil, can navigate to a designated coordinate in a
one-dimensional free space without using motors or jets, which are infeasible for
nanotechnology. The second objective is to make such a system sustainable and easily
modifiable, allowing for future generations of the project to have a solid platform on
which to work on the controls and algorithms which can be used in three-dimensional
swarm technology, where multiple Chunxils could interact to form a three-dimensional
object.
1.2 Product Description
As nano and MEMS technology breakthroughs continue to progress, the
possibilities of build small, microscopic, intelligent robots becomes a more plausible
idea. Such robots could perform many tasks, and be produced at very low costs. With
such decreasing costs, it could be feasible to eventually create a system consisting of very
many, perhaps thousands or millions of small robots which can work together to perform
a unified task. Advancements in Swarm Intelligence algorithms and technologies also
make this concept closer to a possible reality.
Such an application of nanotechnology and swarm could be used to do rapid
prototyping and three-dimensional displays. The small Chunxils would be able to quickly
go into the desired three-dimensional formation, and 'lock' their position in space,
essentially creating a solid object. Of course, the technology to do such things is not
entirely available at this time, but the concept remains clear and unchallenged.
The distant-future goal of this product will be a complete three-dimensional object
creation system, consisting of the nano-bots, a control system, and interface to PC
software.
Page 9 of 69
1.3 Scope Limitations
The project team will consist of three electrical engineers, one computer engineer,
and one mechanical engineer. This phase of the project is to be completed over the course
of three academic quarters (9 months), and at the same time allow for future project
generations to be able to take on the project with ease. By the end of the project, it is
desired to have a small (1x1” cubed) Chunxil which can navigate itself in a one-
dimension limited field through the usage of magnetic propulsion.
1.4 Stakeholders
Stakeholders in this project include the group of students working on the project
itself, as well as RIT's Kate Gleason College of Engineering, and the inventor of the
project, Paul Stiebitz.
1.5 Top Level Critical Financial Parameters
The following describes the critical financial parameters related to this project
● The preferred size of the Chunxil cube is as small as feasibly possible, given
constraints in technologies available, mission objectives, team knowledge and
time.
● Some of the components used should be from previous design groups.
● Samples of the components, provided free of charge by the manufacturer, are to
be used in sections of the prototyping.
● Overall, individual Chunxil cubes should the cheapest possible for mass
production.
Page 10 of 69
1.6 Financial Analysis
A budget of approximately $1000 is proposed for the redesign of the Chunxil. This
budget is outlined as follows:
1. Four to eight Chunxil cubes which are fully operational; some with different
configurations (design concepts).
● One PIC microcontroller for each Chunxil
● Approximately 4 meters of 34 gauge wire for the Chunxil coils
● Two rechargeable power supplies (Coin cell lithium batteries) for each Chunxil
2. A new redesigned tank with a dimension limiter for testing purposes.
● Approximately 19 gauge wire
● Approximately sheet of polycarbonate plastic
● Twelve relays
● Power supply
1.7 Primary Markets
The primary market for the Chunxil system is for rapid prototyping. The
development of this technology enhanced with nanotechnology would benefit the design
and engineering community as an extra powerful tool in the development of consumer
products, and other macro type technologies.
1.8 Secondary Markets
Secondary markets include the entertainment industry, marketing industry and the
arts, as Chunxils could be used to create moving 3D images, which are more lifelike than
hologram projections. The functionality of the Chunxil also allows for implementation in
the in the academic and research settings as concept modeling technologies, and even in
the study of AI (neural networks technology) behavior if processing power and size are
available. There are many applications and thus many markets that can be tapped by a
Chunxil system. This is mostly due to the concept of using a Chunxil as an active,
intelligent building block.
Page 11 of 69
1.9 Innovation Opportunities
There is a myriad of applications for “Chunxil Swarm Technology”, thus many
new innovations can be implemented in the future. These innovations include:
● LED's to replicate object color
● Wireless control of the Chunxil
● Nesting, be it magnetic or geometrical
● A different shaped Chunxil
● A “rotational inertial gyro” to control orientation
● MEMS technologies
● Inductive charging and programming
1.11 Background Research
Similar projects related to this include Carnegie Mellon University's 'Claytronics'
project. The ultimate goal of the Claytronics project is also to have a group of small
robots that can form a large object. A large difference between the goals of the
Claytronics project and this is that Claytronics does not seem to be geared towards
Page 12 of 69
Figure 1 - CMU Claytronics Project
nanotechnology simplicity. The individual robots are very large and power consuming,
with a complex circuit design. A figure of the robots which work in a two-dimensional
plane is shown in Figure 1. One advantage to Claytronics' design is that it does not
require an external magnetic field to propel the robots, nor does it require a liquid to
suspend the robots. This is nice, but requires significantly more complex and power
consuming hardware.
A less similar project in existence is one which involves 'bendable' robots, which
are able to construct other robots by using
basic building blocks. This project is called
Self Replication, and is being worked on by
Cornell University. Theoretically, these robots
could not only replicate themselves, but also
build other objects out of the basic building
blocks which can represent any object.
However, this does not seem to be an objective
of the project. A photo of the robots is shown
in Figure 2.
Neither of these attempts seem suitable for nanotechnology, as they are both
complex designs involving motors and high power requirements from the robot.
The previous research done by students at RIT on this project provided much of
needed information to how the project could work, as well as recommendations to future
generations.
Page 13 of 69
Figure 2 - Cornell Self-Replicating
Robots
1.12 Formal Statement of Work
The team plans to accomplish the following during SD1:
● Facets 1-6 of the EDGE design process (complete PDR)
● A design for a prototype Chunxil and platform(circuit, software, mechanical)
Over the summer months, some members of the team plan to:
● Build a breadboard prototype of the Chunxil
● Test and verify the prototype
● Order Printed Circuit Boards and parts to be ready by SD2
Finally, by the end of SD2, the team plans to have completed:
● All of facets 1-10 of the EDGE design process (complete CDR)
● A final software and hardware design of the Chunxil and platform
● Five constructed Chunxils, and one platform to be used for testing and
debugging
● A guide for Chunxil construction and specifications for future generations
● A detailed project website
● A completed technical paper
● A working demo
Page 14 of 69
2 Concept Development
2.1 Previous Work
An ample amount of previous research and development has been done on this
project in the past.
Inertial Propulsion (Proteus 1A)
The first revision of this project attempted to use an inertial drive system,
consisting of a robot suspended in water, containing a magnetic solenoid which would
fire itself faster in one direction than the other. The concept was that the robot would
move in a similar fashion to a person scooting across a floor on a chair. The robot is
shown in Figure 3.
This design did not work well due to the lack of static friction in a fluid.
Magnetic Propulsion (Proteus 1B)
The second attempt at producing a robot which can move in a tank of fluid
consisted of a robot which had three internal magnetic coils which the robot could turn on
and off as desired. By propelling these coils against and externally induced static
magnetic field, a force was created which would move the Chunxil.
In this design:
Page 15 of 69
Figure 3 - Impulse Driven
● Tank has six high power magnetic coils on each side
● Chunxil drives itself by turning on internal coils to attract it to the desired wall
● Chunxil is able to determine location in tank by the strength of the EMF fields
induced by the external coils
● Control Problems due to magnetic field curvature and software
Though this design had control issues resulting
in the Chunxil rotating undesirably as well as
not being able to locate and stay in its
designated position, the overall design was
relatively solid, with a lot of background
research to support the physics behind it. The
team decided that this design was a good
stepping ground for this project, and that many
aspects would be re-used to save time and
effort, and further the research that has been done before, rather than simply tossing it
away.
Other Considerations
● Our main goal during this term is the control of the Chunxil, not worry about
nesting and swarm technology.
● Secondary goals include assembly ease, modularity, programmability and
charging ease.
● Start with small steps, rather than trying to tackle the whole project at once.
● Start with 1 Dimension, develop in a spiral model with the future in mind.
● Utilize improvements over the last few years in microcontrollers and batteries
Page 16 of 69
Figure 4 - Magnetic Propulsion
2.2 Delineation of Concepts
In order to assign individual research topics in a coherent fashion, the project was
broken up into four major divisions. These focus groups are shown in Figure 12. By
separating the team into smaller groups, where one or two individuals can really focus on
a given task, a higher level of productivity was expected while maintaining understanding
between different tasks, as the responsibility is shared. With a team size of five, assigning
three people to a task with different levels of responsibility helped even the workload.
Not shown in the diagram is the task of Integration, which was assigned to the
fifth person who was not given top priority in a focus group. This person is responsible
for assuring that all focus groups interact well together, and have complete understanding
of what the other focus groups are doing.
The first group, Magnetics, had the most difficult task of doing research on
magnetic fields and how they may behave with a tank setup as defined by this project.
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Figure 5 - Concept Focus
MicrocontrollerPower Management
Circuit DesignPCB Layout
Battery ChoiceSafety
Noise Reduction
Construction of Three Dimensional Objects and Displays Using Swarms of
Intelligent Microsystems (Chunxil)
ElectronicsMechanics Magnetics Controls and
Software
Chunxil Encasing
Chunxil LayoutWeight AnalysisCoil RedesignCoil WindingDim. Limiting
Field LinesField Strength
InductionCoil Size# of TurnsCoil Shape
Torque
MicrocontrollerChunxil SW
Tank SWTiming
Control System
This involves a high level understanding of physics and EMF fields which the group
seemed somewhat overwhelmed by. This focus is very critical to the overall design.
The second group, Controls and Software, had a much lighter load during Senior
Design 1, as most of the software has already been designed. It will, of course, need some
modification before being tested and debugged. This focus group was also assigned the
task of choosing the new microcontroller, for which there are many possibilities.
The electronics focus was geared to both support the microcontroller and desired
magnetic field characteristics, as well as deal with power requirements.
The mechanical focus involved choosing an appropriate Chunxil enclosure, and
designing the internal layout of the Chunxil. Also, a device which limits the Chunxil to
movement in N dimensions must be researched and designed. Furthermore, should any
structural changes be made to the tank coils, redesign would be necessary by the
mechanical group.
2.3 Critical Parameters
Critical Parameters were evaluated using the table shown in the Appendix marked
'Critical Parameters'. From this, it was possible to deduce that the Engineering
Characteristics that should be focused on most are Battery Life, External Coil Size,
Chunxil Dimensions, and the straightness of the magnetic field lines.
Page 18 of 69
2.4 Magnetic Fields
2.4.1 Stability
Although our team’s specifications are focused around 1 dimensional motion, which is
unaffected by spin, future groups will have to deal with this issue. Therefore, techniques
to alleviate rotational torque on the Chunxil were kept in mind for all physical
modifications.
Widen Tank Coils
Introduction
The field lines created by the tank coils will want to curve towards the outside and
around the operating coil. The face of the Chunxil’s coil, when activated for movement,
will align itself to face these lines. Therefore, the closer to the outside of the coil, the
more the coil will rotate.
Advantage
● Limiting the distance the Chunxil can get to the edge of the coil will lower
the amount of rotational torque.
Disadvantages
● This process will require re wrapping each tank coil which at the current
number of turns, 1000, will take a large amount of time and special machine.
● This may also require building a large external tank to hold the coils. The
smaller tank, which will contain the liquid and Chunxils, would be placed
inside.
Page 19 of 69
Simultaneously Activate 2 Coils on the Same Axis Inside the Chunxil
Introduction
The direction of current in each coil will be so that similar polarities face each other,
as shown in Figure 6.
Figure 6 - Opposing Chunxil Internal Magnets
Advantage
● The Chunxil will have resist being misaligned with the field lines stronger.
Disadvantages
● This configuration will require six coils inside the Chunxil which will be
heavier.
● More power will be required inside the Chunxil to operate two coils.
● The Chunxil further away from the pulling side of the tank will diminish the
force of the coil closer to the pulling side of the tank.
Page 20 of 69
Simultaneously Activate 2 Coils on the Same Axis on the Outside of the Tank
Introduction
The direction of current in each coil will be so that opposite polarities face each other.
Advantage
● The field lines inside the tank will be straighter.
Disadvantages
● This configuration will require the six coil design inside the Chunxil, as
previously mentioned.
● More power will be required outside of the tank to operate two coils.
● The Chunxil has a greater urge to rotate 90 degrees when located on the
opposite side of the tank as it is being pulled.
Hybrid Configurations of the Two Previously Mentioned Configurations
Summary
Combining only specific properties of the two previously mentioned configurations
can extract some of the advantages of each, while lessening their disadvantages. For
example, the tank coil on the side of the tank towards which the Chunxil is traveling
could use greater current than its opposite. This would help reduce the Chunxil’s desire
to spin.
Another method would be to divide the movement phase into two halves. In the first
half, only the pulling tank coil, that towards which the Chunxil is traveling, would be
activated. During the second half, both coils would turn on. If the Chunxil is closer to
the pulling tank coil, it could travel during both halves and obtain all the advantages from
both configurations. If the Chunxil is on the opposite side of the tank, however, it could
turn itself off for the second half of the cycle. Table 1 shows how the internal coils will be
powered in such a scenario.
Page 21 of 69
2.4.2 Velocity Control
The previous group to work on this project had difficulties controlling the velocity of
the Chunxil. The Chunxil often traveled several inches at a time, needed several seconds
until it could travel again and correct its position, and often continued to move after the
movement cycle was finished. There are many ways to lessen the force on the Chunxil.
Lower the Number of Turns on the Tank Coils
● Decreasing the number of turns in the tank coils will decrease its magnetic
field intensity.
Lower the Current In the Tank Coils
● Not only will this decrease the magnetic field intensity, but it will also decrease
the heating of the tank coils.
Modify the Size of the Tank Coils
● Changing the size of the tank coils will of affect the field intensity. It should
be noted that the change will not be uniform throughout the tank. For example,
increasing the length of the sides of the tank coils may increase the intensity at
the far end of the tank, but decrease the intensity near the activated coil.
Activate 2 Coils Inside the Chunxil on the Same Axis Simultaneously
● The two coils will slightly cancel each other out, diminishing the net force.
Page 22 of 69
Table 1 - Hybrid Coil Timing Scheme
Movement Cycle External InternalE W E W
West to East - West Side of Tank 1a + On On1b + - Off Off
West to East - East Side of Tank 1a + On On1b + - On On
Pulse the Chunxil’s Coils
● Pulsing the Chunxil’s coils, rather than continuously driving them, would
allow the force on the Chunxil to be controlled by the duty cycle.
2.5 Tank Structure
The structure of outer tank is 7x7x7 inches. The inner tank is 6x6x6 inches. The
diameter of the coil is also increased. Due to the increase of the coil diameter the
performance and visibility is better. The tank redesign is shown in Figure 7. Additional
images are in the Appendix.
Dimension Limiter
In order to limit the field of motion of the Chunxil, an axis-limiter is created that
can be moved around within the tank, allowing all of the 3D space to be tested while
removing the affects of Chunxil rotation. The dimension limiter is shown placed inside of
the tank in Figure 8.
Page 23 of 69
Figure 7- Tank Structure
2.6 Chunxil Structure
The structure of Chunxil is 1x1x1 inches. It’s a cube with five sides sealed and
one side open. Due to the structure of the Chunxil it is more water proof and has less
sides to glue on than the previous design. The wall thickness is 0.04 inches. The Chunxil
cube will have six coils, one on each side, two batteries, one PCB card and a 4x2 pin
connector for charging and reprogramming. The one open side will be glued using
ultrasonic bonding. The ultra sonic bonding is special glue, which melts the plastic and
joints together with the surface making the Chunxil cube waterproof. The dimensions
used in the drawings are in inches because it’s easy to work with, and helps to do
calculations faster.
Page 24 of 69
Figure 8 - Dimension limiter placed inside tank.
2.7 Tank Electronics
This project contains two different electronics packages, the first of which is
contained within the Chunxils. The second portion of the electronics, those electronics
used to operate the tank, will be the focus of this section. From the previous generation,
Proteus 1-B, we have an existing circuit which has been used to control power to all 6 of
the tank’s coils. However, the functional status of these electronics is not known, and
must not be assumed to be operational. Therefore our project must consider a new
electronics system which will be capable of controlling the tank’s coils.
As has been mentioned, the tank has 6 coils, one for each face of a cube. In the
previous generation these coils were approximately 5” in diameter, and made using
Page 25 of 69
Figure 9 - Chunxil Structure
copper wire, with 200 turns of 19 AWG. These coils were known to use about 2A of
current, when in operation, consuming a fair amount of power. In order to properly
handle the power of the coils, the Proteus 1-B team chose to use a configuration of 12
power relays, operated by a PIC. The overall layout and configuration of the Proteus 1-B
tank electronics is quite logical, and does not need to be entirely scrapped.
Our circuit for the tank electronics will be based on the Proteus 1-B design, as we
feel it is a good design. We will likely use the same configuration of 12 power relays to
control the coils. With each relay capable of 5A, we will ensure sufficient power
handling ability. We will also use a PIC to control the sequencing of these relays, likely a
bread-board version of the PIC 16F88. This is the same PIC that we will be using inside
the Chunxil, thus we will be comfortable with its operation and programming.
The only major difference in our plans for the tank electronics, are the appearance
of the tank electronics. We plan to organize the tank and its associated electronics, into a
cleaner, more professional, product. As such, we will house our tank’s electronics within
a removable component box, and hopefully integrate this enclosure into tank’s display.
Additionally, the tank’s coils themselves will be individually removable from the tank.
This will aid in debugging and provide for quicker repairs. At present, we plan to use
connectors to attach the coils themselves to the tank’s electronics enclosure. Again, the
principle reason to choose this configuration was to aid in debugging, repair, and provide
for future transportation / portability of the tank system.
2.8 Chunxil Electronics
The electronics contained within each Chunxil will provide a crucial role in the
success of this project. These electronics will need to provide a sufficient amount of
power to each one of the Chunxils, accurately detect the location of the Chunxil inside the
tank, and allow the Chunxils an easy connection to the outside world for charging /
programming. The Proteus 1-B team had a complicated and rather non-robust electronics
package for the Chunxils.
Page 26 of 69
Due to the robustness issue of the Proteus 1-B electronics package, it was decided
that an entirely new ‘internal’ electronics package for the Chunxils was needed.
Originally, one of the primary requirements for the new electronics package was that it be
easily removed and serviced. With this primary requirement in mind, several sketches
were made which show the entire electronics package comfortably existing on a single
board that can slide into and out of the Chunxil.
After deciding that the Chunxil’s electronics needed to be easily removed, we
began discussing some of the specific Chunxil circuits which would be needed. The first
topic which we considered was a circuit to provide the large amounts of instantaneous
power the Chunxil’s coils would require. Our reason for doing so was related to our
requirement that the entire Chunxil be rechargeable.
Upon reviewing some information regarding existing rechargeable Li-Ion
batteries, it was apparent that a single battery would not be capable of providing the high
currents needed to operate the Chunxil’s internal coils. We determined that a circuit was
required to protect the main rechargeable battery from the large current draw of the coils,
along with associated back EMF. This circuit used power transistors & capacitors to
hopefully satisfy both requirements for powering the coils and utilizing a simple
rechargeable approach to the Chunxil.
Page 27 of 69
Figure 10 - Capacitance Driving
2.9 Software
The software design in the past seemed to be well structured. It seems that using
the old software would be a wise decision, as it would take a large amount of time to re-
write the software from scratch. Of course, modifications will have to be made to the
software, including:
● Support for new microcontroller
● Controls changes for one-dimensional functionality
● Changes in constant values due to new coil designs, voltages, etc
● Changes in timings due to control decisions
The current software model has the following timing scheme shown in Figure 11.
Page 28 of 69
The smaller blocks are an AC phase in which the tank induces a current through
the Chunxil coils, allowing the Chunxil to measure the relative voltage strength induced
by each of the external coils and determine its position, using the according EMF
'coordinates'. The longer blocks are the DC phase in which the Chunxil can decide
whether or not it needs to propel itself using its internal electromagnetic coils.
Possible changes include shortening the time period between stages drastically.
Right now, there is up to 12 seconds for a complete cycle to occur. In this amount of
sampling time, the Chunxil could drift uncontrollably before the necessary corrections
can be made.
Also, if the time is shortened enough, it may be possible to have there only be one cycle
in which the Chunxil reads its coordinates, followed by all 6 drive cycles in a row. This
would shorten the time by nearly half, and could also decrease the power usage.
2.10 PIC Microcontroller
The past Chunxil and external coil circuitry used a PIC16LC716 Microcontroller,
by MicroChip. This microcontroller had one-time-programmable (OTP) memory and an
8-bit A-D converter. According to documentation, this microcontroller had enough
processing speed and IO pins for both the Chunxil and the tank. Several
recommendations were given by the previous group for possible desired features in a new
microcontroller, primarily for space-saving reasons:
● Built-in Voltage Reference
● Built-in Oscillator
● Built-in Amplifiers
Page 29 of 69
Figure 11 - Software Timing Diagram
N S EWF B N S E W F B W
N S E W F B N N S E W F B B N
S E W F B E N S E W F B S N S
E W F B F N S E W F B N N S E
Post Wake Up Delay
Sleep Timer Running
2000ms 1200ms
During team meetings, several other possible enhancements were mentioned:
● Reprogramming capabilities of Flash memory and In-Circuit Programming
would allow the Chunxil's software to be easily modified, tested, redesigned
without having to physically replace the microcontroller.
● A higher-resolution A-D converter would possibly benefit positioning accuracy
tremendously.
● Debugging capabilities would allow for better software design, testing, and
debugging.
● Lower power consumption would help battery life.
● A hardware multiplier could allow the Chunxil to do more complex
calculations for positioning.
● Data Flash memory could allow the Chunxil to save position data, even after
the batteries die. It could also allow for the Chunxil to store its coordinate
values without needing to be entirely reprogrammed.
2.11 Modularity and Sustainability
The modularity and sustainability of the Chunxil system are part of our objectives
to create a controllable Chunxil cube. It was decided through engineering analysis that the
Chunxil control debugging process would benefit from easier programmability. This is
seen from the fact that the previous Chunxil did not offer reprogramming capabilities, as
the microcontroller had one-time-programmable memory. The Chunxil also didn't offer
battery recharging capabilities. As a result, the previous Chunxil had to be disassembled
completely for a single modification to inner components, change of batteries or program
modification. This in turn affected the durability of the Chunxil cube encasement, making
it prone to leaks. Thus with the new design the need for modularity and sustainability was
taken into account. This should provide for a leak-less Chunxil cube as well as ease the
process or recharging and reprogramming. This should greatly reduce the time it takes to
test a control theory in software and debug it.
Page 30 of 69
2.12 Concepts Beyond Current Scope of Project
Some concepts discussed during the redesign of the Chunxil. Which are out of the
scope of the senior design project but that could be performed in future designs include.
● Inductive charging: use of the Chunxil cube’s coils to recharge inductively the
batteries of the Chunxil. This might also allow for an individual Chunxil cube
to be recharged in a sort of chain reaction with other Chunxil cubes, while
remaining in the tank.
● Inductive programming: Similar as the concept above, yet would probably
require individual programming through some mechanism of unique ID tags
per Chunxil.
● One method of inductive charging/programming, shown in Figure 12, could be
using an array of small coils at the bottom of the tank. Once a Chunxil is
charged and programmed, it could propel itself upward, allowing a 'dead'
Chunxil to fall to a coil and begin charging.
● Use of Gyroscope Rotational detection device: This will allow for more
accurate positioning of the Chunxil, compensating for unwanted rotation of the
Chunxil cube.
● Wireless transmission to Chunxil: due to miniaturization and processing
constraints, a system where the Chunxil position and movement is directed by
an external computer might be necessary. Thus the system might change from
Page 31 of 69
Figure 12 - Possible implementation of inductive charging
being a individual neural network type to a centralized processing type.
Wireless could also allow for communication between Chunxils in 3D space,
allowing for collision avoidance and path-choosing methods.
● Another application of wireless transmission can be the reprogramming of the
Chunxil from external means.
● Chunxil multicolor lights allowing colored object definition when combined
with miniaturization. Also neural network “mood” emission and detection can
be programmed into each Chunxil to study swarm interaction.
● Chunxil miniaturization: Currently the Chunxil is only being designed for
controllability, and thus it is 1x1x1 sized. Once the controls are complete, then
focus can be made on decreasing the size of the Chunxil.
● Swarm algorithms: Algorithms for the Chunxils to interact to form an object.
Rather than each Chunxil being programmed with a destination, the Chunxils
could act as a hive, designating tasks to other Chunxils, avoiding collision with
one another, and choosing the fastest construction method.
● Industrial Design: Making the external tank more aesthetic and marketable.
Page 32 of 69
3 Feasibility
Feasibility assessments were conducted for several of the major decisions that had
to be made for possible design decisions on the project. They are outlined below.
3.1 Magnetics Feasibility
A weighted feasibility assessment was created to compare different coil configurations
on the outside of the tank and inside the Chunxil. Each design implies the number of
turns in the coils is the same as is the current. Six factors were considered when creating
the feasibility assessment shown in Table 2.
Page 33 of 69
Coil
Configuration
Feasibility
Assessment
CurrentCurrent
DesignDesign
2 Chunxil
Coils, 1
Tank Coil,
Same Tank
Coil Radius
2 Chunxil
Coils, 1
Tank Coil,
Greater
Tank Coil
Radius
2 Chunxil
Coils, 2
Tank Coils
with
Equal
Force,
Greater
Tank Coil
Radius
2 Chunxil
Coils, 2
Tank Coils
with
Uneven
Force,
Greater
Tank Coil
Radius
RelativeRelative
WeightWeight
Desire to SpinDesire to Spin 3.0 5 5 1 2 33%Shape of FieldShape of Field
LinesLines 3.0 3 4 5 4.5 27%
Chunxil PowerChunxil Power 3.0 2 2 2 2 20%
Tank PowerTank Power 3.0 3 3 1 2 13%Ease ofEase of
ModificationModification 3.0 2 1 1 1 0%
VisibilityVisibility 3.0 3 4 4 4 7%
Weighted ScoreWeighted Score 3.0 3.5 3.8 2.5 2.8
NormalizedNormalized
ScoreScore 78.9% 91.2% 100.0% 64.9% 73.7%
Table 2 - Magnetics Feasibility Assessment
Desire to Spin
● Chunxil’s inability to stay aligned with field lines can lead to uncontrollable
spinning
● Chunxil will no longer be able to find position
● Travel will be in random directions
Shape of Field Lines
● Curvature of field lines will place rotational torque on Chunxil
● Chunxil’s positioning will be skewed
● Chunxil’s travel will no longer be at 90 degree angles
● Chunxil will no longer be able to link with flush sides
Chunxil Power
● Chunxil’s power is limited by battery output
● Difficult to dissipate heat inside Chunxil
Tank Power
● Tank Coils are current limited by wire gauge
● Excessive power draw may require additional power supplies
Ease of Modification
● Deadline (October 2005) limits complexity of modifications
● Some modification is going to be necessary for any configuration to improve
previous design
Visibility
● Possible uses are three dimensional displays and/or moving images which
would require inside of tank to be visible
Widening the tank coils’ radii, and activating a single tank coil with the two Chunxil
coils on the same axis was found to be the best design. Each configuration does have its
advantages and disadvantages, some which will not be know until a prototype is built and
tested, and therefore various arrangements may have to be tested.
Page 34 of 69
3.2 Chunxil Structure Feasibility
The Hammond pre-manufactured cube was the best pick prototype 2 from Table
3 below. The cube was five sided; it was better water proofing capabilities. The cube is
easily purchasable and inexpensive. The cost of the cube is $1.20.
3.3 Micro controller Feasibility
From the desired upgrade features of the microcontroller, the feasibility
assessment shown in Table 4 was obtained.
Page 35 of 69
Table 3 - Chunxil Enclosure Feasibility
Evaluate each additional concept against the baseline, score each attribute as: 1 = much worse than baseline concept 2 = worse than baseline 3 = same as baseline 4 = better than baseline 5= much better
than baselineCu
rren
t Ch
unxe
l Cu
be (
6 S
epar
ate
Sid
es)
Prot
otyp
e 1:
Tw
o sh
ells
put
tog
ueth
er
Prot
otyp
e 2:
Use
of
Exis
ting
Co
mm
erci
ally
A
vaila
ble
1*1*
1 in
ch
Rela
tive
Wei
ght
Chunxil Cube Size 3.0 1 5 25%
Inner Space for other components 3.0 2 4 21%
Waterproofing Capabilities 3.0 3 3 18%
Cost of Purchased Components? 3.0 4 2 4%
Ease of Assembly of a Full Chunxil Everything Inside 3.0 2 4 7%
Modularity of Physical Parameter 3.0 3 3 7%
Nesting Ability 3.0 4 2 4%
Charging and Programming Interface 3.0 5 1 14%
Weighted Score 3.0 2.6 3.4
Normalized Score 87.5% 75.0% 100.0%
Winner
From this table as well as some intelligent judgment, it was decided that the
PIC16F88 Microcontroller would be the best solution. It has low power usage as shown
in Figure 14.
Page 36 of 69
Table 4 - Microcontroller Feasibility Assessment
Curr
ent
( PIC
16C1
76)
Curr
ent
( PIC
16C1
76)
PIC
16F8
19PI
C 16
F819
Pic
16F8
8Pi
c 16
F88
Pic
18F1
320
Pic
18F1
320
TI M
SP43
0F11
3TI
MSP
430F
113
Rela
tive
Wei
ght
Rela
tive
Wei
ght
Sufficient Student Skills?Sufficient Student Skills? 3.0 3.0 3.0 3.0 1.0 2%Size/Weight/Nano-FeasibilitySize/Weight/Nano-Feasibility 3.0 3.0 3.0 2.0 1.0 13%Cost of ChipsCost of Chips 3.0 3.0 3.0 2.0 3.0 8%Cost of Programmer,Burner, and SoftwareCost of Programmer,Burner, and Software 3.0 3.0 3.0 3.0 1.0 3%Compatible ISACompatible ISA 3.0 2.0 2.0 1.0 1.0 10%Compatible Pin Layout/VoltagesCompatible Pin Layout/Voltages 3.0 2.0 2.0 2.0 1.0 5%Memory (Flash, Ram)Memory (Flash, Ram) 3.0 4.0 5.0 5.0 5.0 13%Program in-circuitProgram in-circuit 3.0 5.0 5.0 5.0 5.0 12%Sufficient bit-ADCSufficient bit-ADC 3.0 4.0 4.0 4.0 4.0 18%Power UsagePower Usage 3.0 5.0 5.0 4.0 1.0 15%Hardware MultiplierHardware Multiplier 3.0 3.0 3.0 5.0 5.0 3%Low-Power ProgrammingLow-Power Programming 3.0 5.0 5.0 3.0 5.0 5%
Weighted ScoreWeighted Score 3.3 4.1 4.2 3.7 3.1
Normalized ScoreNormalized Score 77.7% 96.8% 100.0% 88.0% 74.9%
Evaluate each additional concept against the baseline, score each attribute as: 1 =
much worse than baseline concept 2 = worse than baseline 3 = same as baseline 4 = better than baseline 5= much better
than baseline
Figure 13 - MicroChip PIC16F88
3.4 Battery Feasibility
For our project it was crucial that we were able to provide enough power to the
Chunxils. As will be discussed later in this report, our requirements specifically state that
Chunxil should be able to make 10 roundtrip journeys across the diagonal of the tank.
This is a fairly demanding requirement, considering the amount of power which will be
lost performing that work. In order to ensure that the Chunxil’s battery (or batteries)
would be right for the job, a comparison matrix needed to be generated. Below is the
resulting feasibility assessment, which clearly points out that the LIR-2032 is the
preferred choice.
Page 37 of 69
Figure 14 - 16F88 Maximum IDD vs Vdd & Mhz for Internal RC
Figure 15 - Battery Feasibility Chart
In addition to the batteries compared above, it should be noted that other batteries
should be considered, once they become more readily available. Currently, Li-Poly
(Lithium Polymer) battery technology is limited to somewhat large and bulky batteries.
These batteries are usually distributed in sizes about a few mm thick x few cm long.
Unfortunately for us, this size proved to be too large for a Chunxil, but the Li-Poly
batteries do provide higher current drains and more power capacity than the chosen Li-Ion
battery.
Also of note in the battery field is a new technology which allows certain batteries
to be fully recharged in a matter of 1 minute. This battery was very recently developed by
Toshiba, and is not yet in production. This battery might make a good candidate for
induction based charging, in future generations. However, the present prototype batteries
were all too large for the Chunxil project, at 60mm in diameter per battery.
Page 38 of 69
3.5 Feasibility Conclusion
After the feasibility assessments were conducted, many decisions were made as to
what components would be used in the new design, and what modifications would be
made to the mechanics and electrical components of the project.
4 Objectives and Specifications
In order to begin design, it was first necessary to define a strict set of requirements
and goals that should be kept in mind and adhered to during the design process. The
specifications derived are described thoroughly in this section.
4.1 Design Objectives
● A small intelligent robot, called a Chunxil, shall be designed to navigate to a
predetermined position within somewhere in a constrained 3-D space, most
likely occupied by a fluid.
● As a method of control, only 1-dimensional positioning will be required for the
scope of this project.
● If One-Dimension is attained, then multiple dimensions will be explored, given
appropriate amount of time.
● The Chunxil should be designed with nano-technology limits in mind. Extra
hardware should be avoided if possible, considering the possibility of placing
the entire Chunxil in a system-on-chip configuration for future generations.
The less things used in the Chunxil, the more feasible it would be to get them
to a very small size at a low production cost.
Page 39 of 69
4.2 Magnetics/Motion Performance Specifications
The force created by the tank and Chunxil’s coils being activated must be strong enough
to overcome the drag of water.
Force=
−32∗μ0∗N 1 N 2 I 1 I 2 A1∗A2∗z
A1z2 5
2
Where:
A1 is area of tank coil
A2 is area of Chunxil coil
N 1 is number of turns in tank coil
N 2 is number of turns in Chunxil coil
I 1 is current in tank coil
I 2 is current in Chunxil coil
z is distance from Chunxil coil’s distance from tank coil
Drag = (1/2)*CD*ρ*A*V2
Where:
CD is coefficient of drag (depends on Chunxil casing)
ρ (water) is 1000 kg/m3
A is area of Chunxil
V is velocity of Chunxil
Page 40 of 69
4.3 Mechanical Performance Specifications
The two mechanical performance specifications can be measured in weight and
size.
Weight and Density
● The density of sugar water is 1380 kg/m^3. The mass of the Chunxil cube with
total assembly is approximately 0.0568 kg. The transparency of the liquid
allows for visualization.
● The center of mass of the Chunxil shall be +- 10% of the measured physical
center.
Size and Shape
● The Tank size shall remain the same as before, a cube, 6"x6"x6" +- 0.5".
● The Chunxil's weight, height, nor depth shall exceed 1" in dimension.
● The Chunxil shall be a regular shape such that it can nest, or at least sit plush
with another Chunxil.
● The Chunxil enclosure should be designed for relatively easy replication,
allowing for multiple Chunxils to be built for testing.
4.4 Electrical Performance Specifications
The requirements for the performance of the electric system in this project have
been clearly defined. Each requirement is related to other aspects of the project, and is
quite important for the success of the project as a whole. Of course, the most crucial
aspect of electronics was that they fit comfortably inside the Chunxil; while leaving
enough room for possibly 6 coils. This will prove to be quite the challenge, as inside of a
Chunxil is less than 1”x1”x1”.
The primary requirements for the performance of the electrical system are:
Page 41 of 69
● The electronics should not take up more than 50% of the volume of a 1” cube
Chunxil.
(Leaving approximately 50% volume for the coils.)
● Chunxils will be pre-programmed to a specific route, but must be easily
reprogrammed.
● The battery must be rechargeable, & able to recharge in less than 5 hours.
● A Chunxil shall be recharged, reprogrammed & debugged without being
disassembled.
● All Chunxils must conform to a common interface standard, such that a
universal reprogramming, recharging, and debugging method can easily be
used for all Chunxils.
● A Chunxil must be able to make 10 round trip cycles across the diagonal of the
tank.
4.5 Software Performance Specifications
Software performance will be measured by the Chunxils ability to position itself
correctly within the one-dimensional axis.
● The values should be able to be programmed statically, meaning that each
Chunxil is pre-programed with a pre-determined numeric set of data
corresponding to a location in the tank.
● The Chunxil shall be able to move to and maintain a position in within 1/4th of
the measured diameter of the Chunxil from any starting position within the
given working dimension.
● Discrete positions shall be defined within the tank,with corresponding values
that should be programmed in the Chunxil to achieve such positions.
● In one dimension, tilt of axis (spinning and rotation) is not of concern.
However, in two or more dimensions the angle of the Chunxil from any wall of
the tank shall not exceed 10 degrees.
Page 42 of 69
4.6 Design Practices Used
The design practices used by the team to the redesign of the Chunxil system
include:
• Design for Systems Integration: All components are to be purchased well ahead of
schedule in order to allow for ample time to examine the interface before
integration. All components that were selected for the project were examined for
compatibility before being purchased.
• Design for scalability: The Chunxil cubes are to use technology that might be
scaled down using miniaturization technologies in the future.
• Design for modularity and sustainability: The Chunxil cubes where redesigned
with ease of programmability and recharging in mind, so as to not open the units
every time a change in code has to be made.
• Design for Manufacturability: All manufacture components (i.e. coil units,
breadboard solder components) on the Chunxil cube are to be designed and built
on equipment found on the RIT campus. Other parts of the Chunxil are bought as
independent units, like the batteries, and the Chunxil cube encasement.
• Design for Low Cost: All components were selected for both their functionality
and both their economic and power cost efficiency.
• Design for Efficiency: Since the system is largely embedded and compressed into
sealed cubes, resources are very limited on the platform. Therefore, all
components need to work efficiently without waste to ensure proper Chunxil cube
lifetime.
The actual design methodology used a combination of open team brainstorming,
individual research and feasibility for each part, engineering analysis and critical
parameters to decide the best modifications to be applied.
Page 43 of 69
4.7 Safety Issues
Because there will be many high-powered electrical components within close
vicinity of a tank full of water, extra thought must go into safety to avoid possible
electrocution:
● All external wires on the tank shall be insulated.
● Electrical components shall be isolated from the liquid medium.
● Coil current should be within reasonable specifications for the given amount of
time that they are powered.
● No component shall exceed temperature capable of burning human skin or starting
fire. If such a component can occur, it shall be properly cooled and shielded.
5 Analysis and Design
After the objectives had been clearly defined, it was possible to begin the actual
new project design and engineering analysis.
5.1 Magnetic Field Analysis
5.1.1 Introduction
No physical modifications have been done to any part of the system. Therefore, all
statements and calculations are based on knowledge of electromagnetic field concepts,
and simulation tools.
When talking about x, y, and z coordinates related to a specific coil, the coordinate
system shown in Figure 16 will be used.
Page 44 of 69
Figure 16 - Tank Coil Coordinates
5.1.2 Stability
Widen Tank Coils
Widening the tank coils will help to straighten the field lines. The magnetic field
intensity, H, will be analyzed at two points for two different coil diameters. These
diameters are not related to the actual dimensions which will be used in the tank redesign.
The current used for these calculations will be 2A and the number of turns per coil will be
1. Increasing either of these will increase the magnitude of field intensity, but not the
direction.
Using a coil side length of 4cm, the first point will be on the coils axis 4cm away from
the coil, 0,0,4.
Page 45 of 69
H total=∑k=1
4
H Sidek
H=I4 π∗R
∗cos α1cos α2 aφ
R=2242=4 . 47cm
α=tan−14 . 472
=65.90o
H Side 1=24 π∗.0447
∗cos 65.90ocos 65.90o aφ
H Side 1=2.91 aφA
m
The field intensity not in the z-direction will be cancelled out by the parallel side.
Therefore,
φ=tan−124 =26.56o
H total=4∗2.91*sin 26.56 a z
H total=5.21A
m
Next, the magnetic field intensity at the point 1,1,4 will be analyzed.
H total=∑k=1
4
H Sidek
Side 1
R=1242=4 .12 cm
α1=tan−14 .121
=76 .36o
α2=tan−14 .123
=53.94o
H Side 1=24 π∗.0412
∗cos 76.36ocos53.94o aφ
φ=tan−114=14 .0o
H Side 1=3.18 ∗ .970 a y. 2425 a z A
m
H Side 1=3.08 a y.771 a z A
m
Page 46 of 69
Side 2
R=3242=5cm
α1=tan−151=78.69o
α2=tan−153=59.03o
H Side 2=24 π∗. 05
∗cos78.69ocos59.03o aφ
φ=tan−134=36 .87o
H Side 2=2.26 ∗−.80 a x.6 a z A
m
H Side 2=−1.808a x1.356 a z A
m
Side 3
H Side 3=−1.808 a y1.356 a z A
mSide 4
H Side 4=3.08a x.771 a z A
m
Total
H Total=1. 272 a x1. 272 a y4 . 254 a z A
m
The field intensity will now be analyzed with a coil side length of 6cm.
H total=∑k=1
4
H Sidek
Side 1
R=2242=4 . 47 cm
α1=tan−14 . 472
=65.9o
α2=tan−14 . 474
=48.18o
Page 47 of 69
H Side 1=24 π∗.0447
∗cos65.9ocos 48.18o aφ
φ=tan−124=26.56o
H Side 1=3.83 ∗ .894 a y.667 a z A
m
H Side 1=3. 424 a y2.554 a z A
m
Side 2
R=4242=5.66 cm
α1=tan−15.662
=70 .54o
α2=tan−15.664
=54 .75o
H Side 2=24 π∗. 0566
∗cos70 .54ocos54.75o aφ
φ=tan−144=45o
H Side 2=2.56 ∗−.707 a x. 707 a z A
m
H Side 2=−1.81a x1.81 a z A
m
Side 3
H Side 3=−1.81 a y1.81a z A
mSide 4
H Side 4=3. 424 a x2.554 a z A
m
Total
H Total=1.61 a x1.61 a y8.728 a z A
m
Page 48 of 69
It can be seen that in this example, widening the tank coil’s side by 2cm increases the
percent of the field intensity in the z direction from 4 . 2452
4 . 24522∗1. 2722=84 .8 to
8 .7282
8.72822∗1.612=93.6 .
Simultaneously Activate 2 Coils on the Same Axis Inside the Chunxil
If the two coils inside the Chunxil are simultaneously activated in the configuration
shown in Figure 6, the resulting “North” – “South” model of the Chunxil’s faces will be
as shown in Figure 17.
Figure 17 - Simultaneous
Internal Coils
The Chunxil will only have to rotate 90 degrees to have maximum rotational torque,
the point at which it will most strongly want to realign itself correctly. In the previous
design, the Chunxil had to rotate a full 180 degrees to be at this point.
Simultaneously Activate 2 Coils on the Same Axis on the Outside of the Tank
Using the values previously derived for a point at 1,1,4 in a tank with coils of
length 6cm, the resulting magnetic field intensity will be
Page 49 of 69
H Total=1.61 a x1.61 a y8.728 a z A
m. If another 6cm coil is activated with
opposite polarity 8cm away on the opposite side of the tank, the second coil would
have a polarity of H Total=−1.61 a x−1.61 a y8.728 a z A
m. The total
resulting intensities would be H Total=17. 456 a z A
m. The field lines will only
be perfectly aligned at equal distances from each tank coil, but the will be much
straighter at other points than if only one coil was activated, as can be seen from
Figure 18 and Figure 19.
Page 50 of 69
Figure 18 - Curved field lines with one coil
Figure 19 - Straightened Field Lines
from two coils
5.2 Mechanical Design
Chunxil Axis Limiter:
The Chunxil dimension limiter is made from plexi glass. Several holes are drilled
through the plate and walls because of that there can be water flow through the channel.
The walls are adjustable so while testing it can be changed form one dimension to two or
three dimensions.
The Chunxil dimension limiter will be placed in the external tank. The Chunxil cube will
be floating between the walls, allowing for free motion but not rotation.
Page 51 of 69
Figure 20 - Chunxil Dimension and Axis Limiter
5.3 Assembly Methods
The Chunxil cube boasts a modular design, which allows for multiple ways of
placing the inner components of the cube. This modular design also allows for
partitioning of the work into work units, thus creating allowing for the use of an
“assembly line”. One of the design assembly procedures is described below.
1. First all six coils are wound up around each coil assembly according to the
number of turns calculated in our engineering analysis.
2. A PCB is prepared and components are soldered to it. The ends of the coil wires
are also soldered to their respective board locations.
3. A connector is soldered to thin wires and the connector is fused flush to the
Chunxil cube’s lid.
4. Batteries and connector wires are attached to the system.
5. Testing is performed in the system to assure proper functioning.
6. The coils are glued into place inside the Chunxil cube (Figure 21,22)
7. The PCB and Batteries are carefully inserted inside the cube.
8. The lid is placed and sealed, completing the assembly of a Chunxil cube.
Assembly of the Tank is performed, by winding lower gauge number wires around
pre-made coil structure, which are attached to the center 6x6x6 inch fluid tank separated
by standoffs. This will allow the even spread of the field on the center fluid tank.
Page 52 of 69
Page 53 of 69
Figure 21 - Coil Holding Device
Figure 22 - Chunxil Assembly
5.4 Circuit Design
The overall Chunxil circuit design has several modifications to the previous
generation’s circuit design. After reviewing the Proteus Generation 1-B circuit, we
determined that only minimal problems existed with it, thus there was no need to scrap it
entirely. As such, our Chunxil circuit shares some features with the Proteus 1-B circuit.
Figure 23 - Entire Chunxil Circuit
In the upper left hand corner of the schematic is the voltage regulation portion of
the circuit. This portion of the circuit ensures that our micro-controller is constantly
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supplied with a very clean 3 V power line, so as to ensure performance of the micro-
controller does not fade with battery life. Additionally, the input to this circuit contains a
diode, where it is to be connected with the outside world. This will prevent the Chunxil
from short-circuiting itself, when placed in the water-filled tank. Lastly, instead of using
the single battery and large capacitor system as originally planned, a two battery circuit
with smaller capacitor was determined to be sufficient.
The micro-controller, a PIC 16F88, can be seen directly below the voltage
regulation circuit, in the middle-left. The connector, for use in charging and
programming / debugging, can be seen in the lower left hand corner of the schematic.
The Coil Control Circuit is located in the upper right-hand corner of the schematic. The
Op-Amp portion of the circuit, used in location detection of the Chunxil, is located in the
bottom right-hand corner of the schematic. Lastly, the indicator LEDs are located in the
middle right of the schematic.
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The Op-Amp portion of the circuit is crucial to the operation of the Chunxil, and can be
seen above. The previous generation had a large 1M Ohm resistor between the Op-Amp
& the Analog to Digital converter line (ADA). We found this to be a slight problem with
the previous configuration. When looking at the data sheet for the micro-controller, we
noticed that a maximum input resistance to the A/D lines was listed as 10K Ohms, with a
smaller resistance being better and allowing faster data readings. In the previous circuit,
the resistor on the A/D input line was valued at 100 times the suggested maximum value.
This was probably easy to overlook, because it would have required careful
consideration of the Op-Amp's function. However, it is likely that this problem alone
could have caused serious flaws in the control of the Chunxil, as its micro-controller
probably would not have determined the correct values of many positions in a timely
manner, if it determined them at all. This could have been a source of many problems the
Proteus 1-B experiments.
The solution to this problem was we developed includes moving the low-pass
filter to the feedback portion of the amplifier. In effect, the micro-controller's A/D lines
will read close to 0 (zero) Ohms now, greatly increasing the accuracy and speed for each
Chunxil to determine its exact position. Also, our feedback loop now includes the low-
pass filter; which will remove noise from the amplifier, and make the signal cleaner.
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Figure 25 - Micro-Controller w/ other circuit improvements
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Figure 24 - Re-Designed Op-Amp
Some additional features which we added to the circuit can be seen in the figure
above. Further considerations which were made to improve the accuracy of the position
detection involved the reference voltages for the A/D converters. If you notice, we have
placed important filtering capacitors on our sensitive Vref+ and Vref- lines. These
capacitors are directly placed in front of the pins; so that noise is eliminated most
effectively.
Our circuit also includes a power indicator LED, we chose green. A second LED
is controlled by the micro-controller, for use in debugging or reprogramming. Future
revisions of the circuit, could allow for battery power monitoring with the Red LED, such
that the LED might come on when the battery is too low. Low battery voltage could
cause problems with the Chunxil’s position detection, so this will certainly be something
to consider.
In order to control the large power draw of the coils, we have a separate coil
control circuit. Our original concepts called for the Chunxils to only have 3 coils per
Chunxil. However, as was mentioned earlier, having two coils per direction will greatly
reduce the spinning problems which the previous group encountered. For future
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Figure 26 - Chunxil Coil Control Circuit
expansion & testing purposes, and to allow testing of a 6 coil Chunxil, we had to
determine a method of controlling 6 variables with a limited amount of I/O from the
micro-controller.
Our circuit is able to accomplish control of 6 coils using only 4 I/O lines. The
method used to accomplish this was individually addressing each of the coils in the X, Y,
& Z directions; or North, East and Up. Second we created a single control line for the
complimentary coils in each of those 3 directions. This allows either one or both of the
coils in a single direction to be turned on with only two bits.
Also, the Proteus 1-B team mentioned they encountered many problems with back
EMF occurring on the coils, when the current was suddenly turned off. We have
addressed this problem with a fly-back diode placed between the Vcc line, and the back
side of the coils. The fly-back diode will prevent that voltage difference from growing
past 0.6 V, from the back of the coils to the Vcc line, significantly reducing the problems
caused from coils being switched off.
5.5 Power Requirement Analysis
Our chosen Chunxil battery, the LiR-2032 is rated with the following specifications:
13.7 V nominal voltage
235mAh nominal capacity
370mA Max. drain current
4Dimensions: 20mm diameter * 3.2mm thick
5Mass: 3.0 grams
6Unit price: $1.26
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Since we are planning to use two batteries, in parallel, we should expect a 70mAh
nominal capacity of the battery package. Additionally, we should also expect a
140mA maximum drain current. By analyzing the power requirements of each main
component, we can effectively predict the runtime of a Chunxil, between charges.
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Component Expected
Power
Usage
Expected
Duty Cycle
[% of time
ON]
Quantity Net
Power
Usage
Micro-
controller
2 mA 100 % 1 2 mA
Op-Amps 2 mA 100 % 3 6 mA
Power
Transistors
2 mA 8 % 6 1 mA
Chunxil Coils 120 mA 8 % 6 60 mA
Misc.
Electronics +
Power Loss
6 mA 100 % 1 6 mA
NET POWER
CONSUMED
- 100 % 1 75 mA
Table 5 - Chunxil Power Budget
Looking at Table 5, we can see that the average drain on the batteries should be
about 75 mA. From the LiR-2032 specification, we note that the battery has a 35 mAh
capacity. By placing the two batteries in parallel, we double this capacity to 70 mAh. If
we account for a 90% margin of error for power usage, in effect doubling the estimated
power usage, we end up with about 140 mA current drain. Since the batteries are capable
of providing 70 mA for 1 hour, we would drain the batteries in approximately ½ hour, or
30 minutes. Keeping in mind, this allows for power usage to be almost twice what the
calculated value should be.
Hence, the Chunxils should be capable of running between 30 minutes - 1 hour,
on a single charge. If it takes a Chunxil 3 minutes to complete a single roundtrip cycle
across the diagonal of the tank, the Chunxil should still easily complete 10 cycles in that
30 minute period.
However, based on video of the Proteus 1-B experiment, it is fairly safe to estimate that a
Chunxil could complete a roundtrip cycle in 1 – 2 minutes. Therefore, the Chunxils
should have no problem going the required 10 cycles, or twice that, on a single charge.
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5.6 Software Design
Much of the software design will be directly taken from the previous project, and
modifications will be made during the testing and debugging phase as necessary.
Many of the parameters are dependent on experimental values of EMF fields which have
not yet been found. Once found, then they can be hard-coded into the program.
5.7 Analysis and Design Conclusions
The previous section has outlined much of the analysis that has been done, as well
as analysis that will need to be done when a working prototype is built. Unfortunately, not
all tasks can be developed in parallel, and due to time constraints, some design portions
will be delayed to the summer quarter.
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Figure 27 - Software Flow Chart from Previous Design
INITRUN
calculate target differencesreset sleep timer
record NOIZwait for int, check flags
Power On
None
go flagsleep flaginterruptturn off a-d, etc
clear flagsenable ints,a-d,etcreset sleep timer
SLEEPdisable interrupts
wait for port b sig
meas VX,VY,VZcheck alignmentcalc positon diffs
set move flagsif unaligned, set all move flags
set drive flagsstall .5 ac cycle
stall dc timeclear outputs++DCCNT
stall down time 2
re-enable interruptsclear flags
reset sleep timer
DCCNT==6?
drive flag,DCCNT==1?stall down time
drive a coilyes
no
clr DCCNT
no
set SLP flag
save state
check source of interrupt
set GO flagdisable port b int
reset sleep timer
disable sleep timer
restore state
port b int
other
sleep timeout
interrupt
GO FLGSLP FLG
6 Future Plans
6.1 Experimentation
The team is currently performing experiments on the circuitry of the Chunxil
cube, as well as creating various theoretical models to be tested to improve movement
accuracy, and power requirements. The experiments that must be conducted in the future
include:
● Performance testing to improve efficiency of components
● Testing of field strength of the Chunxil tank in order to create a simulation of
the field parameters in the tank and compare to the Chunxil cube’s reading.
● Controllability testing of the Chunxil cube on different locations in the tank
● EMF positioning detection testing.
6.2 Schedule
The Chunxil project schedule is outlined below in various Gannt charts, showing
the tasks performed in SD1 and to be performed in SD1.5 (Summer) & SD2. While the
schedule is not exact, it should give an accurate estimate of the complexity of the issues
the team will have to surmount as well as the time available to spend on each issue.
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Figure 28 - Project Plan for Senior Design I
Figure 29 - Project Plan for Summer Quarter
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Figure 30 - Project Plan for Senior Design II
6.3 Budget
The prices below reflect the current pricing of components without shipping and
handling. Since the products are being bought through RIT, tax does not apply. With the
components listed below, each Chunxil cube will have one PIC microcontroller, two
lithium cell rechargeable batteries, one PCB board, one Chunxil Cube encasement, and
some minor electrical parts.
Also, the parts to modify the tank are recorded in the second table .
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Part Name Qty
Distributor /
Manufacturer
Estimated Price
(Each)
Estimated Price
(Total)Chunxil Cube and
Lid
1 Mouser / Hammond $ 1.00 $ 1.00
Coil Encasement
plastic
6 ? $ 0.50 $ 3.00
Coil Wire AWG 35 0 ? $ 1.00 $ -Female connectors
(6 pins)
1 Digikey? $ 0.30 $ 0.30
PCB
(2 sided; quote 10
only)
1 PCB Express? $ 15.00 $ 15.00
Microcontroller
(SMT)
1 Microchip $ 2.00 $ 2.00
Coin Cell Lithium
Batteries V?
2 ? $ 1.50 $ 3.00
Sealing Glue or
Adhesive
1 ? $ 0.50 $ 1.00
Capacitors (SMT) 12 Digikey $ 0.20 $ 2.40Transistors (SMT) 7 Digikey $ 0.30 $ 2.10Resistors (SMT) 19 Digikey $ 0.05 $ 0.95Op amps 3 Digikey $ 0.50 $ 1.50Regulators 1 Digikey $ 0.75 $ 0.75Diodes 2 Digikey $ 0.30 $ 0.60LEDs 2 Digikey $ 0.30 $ 0.60
Price per Chunxil $ 34.20
Table 6 - Chunxil Cube Budget
For building 5 Chunxils, the cost will be $171
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Part Name Qty
Distributor /
Manufacturer
Estimated Price
(Each)
Estimated Price
(Total)Standoff Pins 8 ? $ 0.50 $ 4.00Transparent Plastic
Sheets
15 ? $ 2.00 $30.00
Coil Wire AWG 19 0 ? $ 1.00 $ -Relays 12 Digikey $ 0.60 $ 7.20Circuit Bread-board 2 Digikey $ 2.00 $ 2.00Screws 4 ? $ 0.10 $ 0.40Power supply 0 ? $ 10.00 $ -Serial connector
Male/Female
2 Digikey $ 3.00 $ 6.00
Male connector
(6 pins)
1 Digikey $ 0.30 $ 0.30
Battery Charger 1 ? $ 5.00 $ 5.00
Price of Tank &
Station
$15.90
Table 7 - Tank Modifications and Chunxil Station Budget
The total estimated budget of the Chunxil project for Senior Design II is thus: $186.90
This should fit well within the $2000 available funds.
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7 Conclusion
The first six facets of the MERIT design process are almost entirely complete. As
mentioned, some of the design aspects need to be acquired through experimentation
methods that are dependent on a working prototype. For this reason, much of the software
and control design will take place once more is known about the physical magnetic fields
in the tank and the actual behavior of the circuit which is constructed.
With the design mentioned, it is believed that the Chunxil will be able to
successfully navigate to its desired position and maintain that position through the use of
internal electromagnets in the Chunxil propelling against external magnets on the tank.
During the Concept Development phase, the team worked hard together to
brainstorm new ideas and modifications to previous designs. Individual research tasks
were assigned to each team member, and results were reported back during team
meetings. These concepts were later used in the feasibility assessment phase, in which the
concepts were analyzed for conceptual performance, with advantages and disadvantages.
Once the feasibility assessment was complete, and the team had a better
understanding of what parts and modifications were going to be used, the team continued
on to the design portion after designating each of the delineated tasks mentioned to
smaller sub-groups. Theses sub-groups were able to focus on their topic and be more
productive.
Over the summer quarter, more work will commence on the physical
implementation of the prototype, which will be used in further design and for PCB
manufacturing. This will prepare the team to begin testing and debugging in the fall.
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8 References
8.1 Parts Reference
www.digikey.com
www.mouser.com
www.pcbexpress.com
www.microchip.com
8.2 Other Sites Mentioned
CMU Claytronics Project - http://www-2.cs.cmu.edu/~claytronics/
Cornell Self-Replication - http://www.mae.cornell.edu/ccsl/research/selfrep/
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