3D-PRINTED MOBILE ASSISTANCE PLATFORM (MAP) FOR REHABILITATIVE
ROBOTICS
APPROVED BY SUPERVISING COMMITTEE:
________________________________________
Mo Jamshidi, Ph.D., Chair
________________________________________
Ahmad Taha, Ph.D.
________________________________________
Youngjoong Joo, Ph.D.
Accepted: _________________________________________
Dean, Graduate School
DEDICATION
I would like to dedicate this thesis to the Autonomous Control Engineering (ACE) Lab for
treating me like family and making me feel at home. I would also like to dedicate this paper to
my friends who have supported me through my Master’s degree.
3D-PRINTED MOBILE ASSISTANCE PLATFORM (MAP) FOR REHABILITATIVE
ROBOTICS
by
ERIC WINEMAN, M.S.
THESIS
Presented to the Graduate Faculty of
The University of Texas at San Antonio
in Partial Fulfillment
of the Requirements
for the Degree of
MASTER OF SCIENCE IN ELECTRICAL ENGINEERING
THE UNIVERSITY OF TEXAS AT SAN ANTONIO
College of Engineering
Department of Electrical and Computer Engineering
December 2015
iv
ACKNOWLEDGEMENTS
I would like to thank Dr. Jamshidi and Dr. Benavidez for their tutelage throughout my
master’s degree. Both individuals have challenged me to learn new topics and become a better
Electronics Engineer. I would also like to thank Jonathan Tapia and Ben Champion for their
support throughout my master’s program as well. Once again, I would like to thank the ACE Lab
for accepting me as their family. Lastly, I would like to thank the Science Mathematics And
Research for Transformation (SMART) program for sponsoring me throughout my scholastic
career.
December 2015
v
3D-PRINTED MOBILE ASSISTANCE PLATFORM (MAP) FOR REHABILITATIVE
ROBOTICS
Eric Wineman, M.S. The University of Texas at San Antonio, 2015
Supervising Professor: Mo Jamshidi, Ph.D.
This research is to conceptualize and prototype a Mobile Assistance Platform for
the rehabilitation and daily use of the elderly. Research will be conducted via a comparison with
current options and will attempt to expand upon current assistive options by transforming a
standard walker into an intelligent assistive robotics platform. The platform will be constructed
via as many open source options as available to decrease the cost of the platform and allow for a
high degree of flexibility for potential future developers. 3D-Printing will also be used to allow
for a quick construction of a semi-functional prototype by circumventing traditional design
methods and constraints. 3D-Printing will also allow for the prototype to be cost-effective to
develop, allowing the designer to focus on purchasing higher quality parts for the functional
prototype.
vi
TABLE OF CONTENTS
Acknowledgements ........................................................................................................................ iv
Abstract ............................................................................................................................................v
List of Tables .............................................................................................................................. viii
List of Figures ................................................................................................................................ ix
Chapter One: Introduction ...............................................................................................................1
Chapter Two: Features of a Robotic Walker ...................................................................................3
Chapter Three: Mechanical Design .................................................................................................7
3.1 Software Selection .........................................................................................................7
3.2 Walker Modeling ...........................................................................................................8
3.3 Wheel Assembly Design ..............................................................................................10
3.4 Tablet Arm and Mount Design ....................................................................................13
3.5 Miscellaneous Parts and Accessories...........................................................................14
Chapter Four: Mechanical Simulation ...........................................................................................15
4.1 Motivation ....................................................................................................................15
4.2 Simulation Process .......................................................................................................15
4.3 Material Choice ............................................................................................................17
4.4 Simulation Inaccuracies ...............................................................................................18
Chapter Five: 3D Printing ..............................................................................................................20
5.1 Printers and Print Process ............................................................................................20
5.2 Designing to 3D Print ..................................................................................................22
Chapter Six: Electrical Design .......................................................................................................24
vii
6.1 Component Selection ...................................................................................................24
6.2 Power System...............................................................................................................26
6.3 Robot Operating System ..............................................................................................27
6.4 Wheel Control System .................................................................................................29
Chapter Seven: Costs .....................................................................................................................31
Chapter Eight: Future Works .........................................................................................................33
Conclusion .....................................................................................................................................35
Appendices .....................................................................................................................................37
References ......................................................................................................................................58
Vita
viii
LIST OF TABLES
Table 1 Properties of ABS ..................................................................................................16
Table 2 Mobile Assistance Platform Costs .........................................................................31
ix
LIST OF FIGURES
Figure 1 Mobile Assistance Platform (MAP) Isometric View ...............................................5
Figure 2 MAP User Perspective .............................................................................................6
Figure 3 Purchased Walker (left) and Walker Assembly (right) .........................................10
Figure 4 Preliminary MAP Leg-Mount Design ...................................................................11
Figure 5 MAP Wheel Subassembly .....................................................................................12
Figure 6 Walker Wheel Assembly .......................................................................................13
Figure 7 Tablet Arm Assembly (Left) and Fixture to MAP (Right) ....................................14
Figure 8 SolidWorks Simulation Example ...........................................................................16
Figure 9 Deformation ABS (Left) and 6061 Aluminum (Right) .........................................17
Figure 10 Assembly Mass Properties .....................................................................................18
Figure 11 Up-Box (Left) Cube3 (Right) ................................................................................21
Figure 12 3D Printing Process................................................................................................22
Figure 13 Extruder Assembly UP Box (Left) Cube3 (Right) ................................................22
Figure 14 Unmodified Part (Left) and Modified Part (Right) for 3D Printing ......................23
Figure 15 Herkulex Manager Application. .............................................................................25
Figure 16 Mobile Assistance Platform Power System. ..........................................................26
Figure 17 Simple ROS Implementation. ................................................................................28
Figure 18 Simulation of MAP and Cleaning Robot in RVIZ.................................................28
Figure 19 Preliminary MAP Arm with Gripper Design. ........................................................33
.
1
CHAPTER ONE: INTRODUCTION
This thesis details the need for an intelligent walker and addresses desired features and
performance that it should have. This thesis also details the design and construction of a
functional prototype walker and its associated challenges.
Approximately three million elderly have difficulty reading according to a U.S. Census
[1], and the elderly population continues to grow larger and larger [5]. Year 2050, the amount of
seniors in the United States could be around 37 percent of the population size [6]. The increase in
elderly population and the continued need for mobility more than demonstrate the need for an
modernized intelligent walker system.
The walker could aid the elderly in obstacle detection and avoidance; this could lead to
injury reduction in the elderly and provide greater independence. The VA-PAMAID is one such
solution that aids the elderly in their daily navigation. Similar to the walker posed in this thesis, it
is also built off a common walker platform [1]. The major benefit of the VA-PAMAID is that the
user is able to modify how autonomous the walker is in terms of obstacle avoidance [1]. One
downside to the VA-PAMAID system is that the user still had to push the walker forward with
their own effort. Students from Carnegie Melon University improved on the idea by creating an
assistive walker system that was self-powered [2]. This walker used maps that had been
previously loaded in to the system along with a laser range finder to perform navigation. One
issue that this walker system faced was that (due to the walker frame design) when a user would
lean on the walker for support, they would end up engaging the breaks instead [2]. The students
note that in future work, a touch screen interface would prove to be beneficial. Another series of
students have built a prototype walker based off of the Nomad XR4000 robotic chassis [3]. The
goal of this prototype similar to the desired functionality stated above; and that is to provide
2
navigational assistance to the elderly and provide a measure of independence [3][4]. Both groups
of students used the open source Carmen package to aid with their navigation algorithms [2] [3].
This work uses the Robot Operating System as its foundation because it not only has packages
that allow navigation and path planning, but also has a wide array of packages that perform other
functions. Another area that this work explores is the used of 3D printing to enable fast, cheap,
and reliable prototyping of components for mobile assistance platforms.
Having some type of navigation on a mobile assistance platform would also prove
beneficial to support personnel because they are often required to assist the elderly with
navigation to their desired destination [3]. Not only would a robotic walker reduce the workload
of support personnel, but it could also serve as the main source of daily exercise that an elderly
person receives [5].
3
CHAPTER TWO: FEATURES OF A ROBOTIC WALKER
A walker should be able to provide some type of navigation and obstacle avoidance for
its user [1]. Navigational aid on walker platforms would also prove to be a boon to the elderly
because it could allow those with contending with cognitive impairment to accurately traverse
their surroundings should they forget where their destination may be [3]. An autonomous walker
should also be able to find a way to reach its user should it be parked in an area that is
disadvantageous for its user [2]. Students from Carnegie Melon University conducted a study
into the habits of elderly who use walkers. The students noticed that 24% of the elderly observed
placed their walkers in locations that were separate from the user [2]. This would mean that the
elderly would have to engage in the unsafe action of walking (unassisted) back to their walker.
The walker will also likely serve as the elderly’s best source of exercise [5], thus it
should be able to monitor daily activity and health conditions of its user.
Employees from Fraunhofer Institute Manufacturing Engineering and Automation
created a mobile platform called Care-O-bot II that is capable of performing many of the actions
that have been mentioned above [6]. The only issue with their system is that it is relatively large
and is not able to be easily carried by the elderly to different destinations (grocery store, doctor,
etc.) So a mobile assistance platform should be light enough for an elderly person to carry it for a
limited amount of time. One such instance where the elderly would have to carry the mobile
assistance platform is when they get in their car.
Almost all of the reviewed elderly support systems address the concern of manipulation
at an older age when muscles have grown weaker [6]. Thus a mobile assistance platform should
also aid the elderly in picking up or retrieving everyday objects.
4
The elderly will use the Mobile Assistance Platform (MAP) in conjunction with
autonomous floor cleaning robots to improve their quality of life through improved care and
quality service. The two autonomous platforms will operate over an open internet protocol link
using the robot operating system (ROS) as the backbone for the systems interface. ROS will
allow each robot to publish or subscribe to topics that are deemed necessary depending on the
scenario. The floor cleaning robot will be able to provide the user of the MAP with data about
areas of a residence that need to be cleaned and areas that have already been cleaned. The clean
and dirty areas will be displayed on a floor-map via the heads up display (HUD) that is on the
MAP. Essentially this will give the user of the MAP the freedom to direct the cleaning robots
and control how their living quarters are cleaned.
Each autonomous platform (the MAP and the floor cleaning robot) will gather
information about the surrounding environment. The floor cleaning robots will send this
information back to the MAP and the data will be processed to compose a singular floor-map of
an elderly persons living quarters. This will allow the elderly to receive an up to date feed on
their surroundings and direct each autonomous platform more efficiently should there be a spill
or incident that requires cleaning. Should an undesired object be detected on the floor, the user of
the MAP has various options on how to deal with it. The MAP and each floor cleaning robot will
have an arm affixed to their chassis. The use of the arm will be to pick up the aforementioned
objects. This will save the elderly the burden of having to strain their body to pick up an object.
The user of the MAP will have the ability to direct a floor cleaning robot to pick up an object. If
the user of the MAP decides that they want the object, the floor cleaning robot will then navigate
to the MAP and then perform a hand-off operation to transfer the object to the user. This is
beneficial because the user does not have to navigate to the object, it can be transferred to them
5
using the floor cleaning robot. Should the user of the MAP decide that they want to pick up the
object using the MAP, they will have the option to do so as well. This benefits the elderly by
indicating possible trip hazards and eliminating them using the arms affixed to each robot.
Ideally, the MAP will direct a swarm of floor cleaning robots. The swarm would be more
efficient at cleaning and could provide even more functionality to the user. The swarm of
cleaning robots will be equipped with Kinects that will allow the user of the MAP to monitor
their living quarters through the HUD on the MAP. This provides increased security and
situational awareness.
Figure 1: Mobile Assistance Platform (MAP) Isometric View
All of the aforementioned tasks will be managed by the elderly through a simplified HUD
that is displayed using an Android tablet affixed to the MAP. The tablet will also work in
conjunction with an ODROID and Arduino to control the MAP and perform all of the data
processing necessary to carry out the aforementioned tasks. The user will have at least two ways
to interface with the MAP. The first way is the traditional touch screen capability that is provided
on a basic tablet. The second way that the elderly can interface with the MAP is through a pre-
programmed series of voice commands.
6
Figure 2: MAP User Perspective
7
CHAPTER THREE: MECHANICAL DESIGN
Mechanical design was a large part of this undertaking. In order to add customized parts
to this design, a base model of the walker had to be created before the designer could create parts
that would transform it into a Mobile Assistance Platform for the elderly. The design of the
model started with the selection of the software to create and analyze the model of the walker.
After the software was selected, the designer needed analyze what type of mechanical features
the walker should have in order to assist the elderly. Finally, the parts that were necessary for the
elderly had to be designed, simulated, and 3D printed.
3.1 Software Selection
Before any design of the walker model could begin, the appropriate mechanical
engineering Computer Aided Design (CAD) software had to be selected. The designer had a
large selection of design software to choose from. The designer had to choose the software based
on a number of criteria. The mechanical engineering software would have to enable the designer
to visualize and design parts in three-dimensional space, allow some type of simulation on any
particular part or assembly to asses if it would withstand a specified amount of force. The
software also had to be affordable to the designer and needed to be able to run on an older type
of computer without delaying design time.
The software suites that were considered for this design were Ansys, SolidWorks,
Autodesk Inventor, and Google SketchUp. All software suites allowed the designer to visualize
and model physical components in three-dimensional space. All of the analyzed software also
performed simulation to some degree. Cost was not as big of a factor as originally anticipated
because the aforementioned software is offered at a great discount or free to student users. Each
software suite was also compatible with older machines and could produce models fit for 3D
8
printing. In the end, SolidWorks was subjectively selected based on prior experience and ease of
interface with each tool in the software.
3.2 Walker Modeling
The design of the MAP started with purchasing a basic assistive walker. Many different
implementations of walkers were available. There were walkers that had no wheels, two wheels,
three wheels, and four wheels. There were different walkers with and without handbrakes, cheap
and expensive, and many other different features. For the ease of design and implementation, it
was decided to use a walker that was cheap, had wheels to aid in motorized operation, and hand
brakes for added manual control.
The main goal of modeling the walker first was to have a basic platform that other
components could be used on. The model of the walker that the designer chose to use was a
Nova GetGo. The walker that was purchased for approximately $100 is a typical walker without
any special features [7]. It has 6” wheels and is crafted from hollow aluminum tubes [7]. To
begin the design of the MAP, measurements were taken on the walker using calipers and a tape
measurer since the dimensions of the walker were not available. The walker itself was composed
of sixteen separate parts. The software that was used to create a mechanical model of the walker
was SolidWorks. SolidWorks was chosen as the mechanical design software because it is used in
the designer’s current occupation and because it is compatible with the Robot Operating System
(ROS). Parts in SolidWorks are composed of two dimensional drawings called “sketches”. After
a sketch for a part is created, various options can be used to form a three dimensional part. The
application and use of sketches was used to create all parts for the MAP.
The first part that was designed was a coupling “U” shaped connector that connects the
legs of the walker together. Its primary function is to provide structural strength and support for
9
the walker. The part was made by using the swept extrusion feature in SolidWorks. Next the
front legs for the walker were measured and placed into SolidWorks using a series of swept
extrudes, extrudes, cuts, and fillets. After the front legs of the walker were created, they were
placed into an assembly along with the “U” shaped coupler. In SolidWorks, an assembly is used
to combine multiple parts into a singular functional model. These three parts formed the basic
assembly for the walker model. The designer then continued to design the rear legs of the walker.
The rear legs of the walker were simply created from a cut and a swept extrusion. It is important
to note that the angles for the bends in the legs of the walker are not exact since the designer
lacked the tools necessary to measure the angle. After the design of the rear legs were completed,
the designer created another “U” shaped coupler using the swept extrusion feature. The purpose
of this “U” shaped coupler was to connect the rear legs of the walker together. Next the designer
took the two rear legs and the coupling bar and placed them into the assembly along with the two
front legs and front coupling bar. The seat of the walker was then created using a series of cuts
and extrusions, and then placed into the assembly. The seat was used to join the front-half and
the rear-half of the walker. The final parts of the basic walker design that needed to be created
were the back rest and the associated mounts. The parts were built using the aforementioned
SolidWorks features and placed into the assembly. The walker also came with an ancillary
basket that is normally used for storage. This was also created in Solidworks and placed into the
assembly.
10
Figure 3: Purchased Walker (Left) and Walker Assembly (Right) [7]
3.3 Wheel Assembly Design
At this point, the designer had the basic assembly of the walker completed. The next
phase of the mechanical design consisted of determining how the elderly would interface with
the MAP and what features required mechanical modification. To ease the cost burden and
decrease that time that it would take to build a prototype, the designer decided to sue 3D printers
to fabricate the design instead of traditional methods. It is important to note that 3D parts are
much weaker than traditional metal parts and would not be used for structural support in a real
world application. The designer decided to create a leg adapter for the MAP first since one goal
of a robotized walker is to reduce the amount of effort that the elderly must use to move the
MAP. The designer came up with a design that would allow wheels powered via DC motors to
be affixed to the base of the MAP. The preliminary design for the MAP consisted of two support
columns and coupling devices. The designer used the Cube3 3D printer to print the parts out of
PLA for the base of the walker. The designer printed the supports for the base of the MAP,
assembled them, and then affixed them to the walker chassis.
11
Figure 4: Preliminary MAP Leg-Mount Design
Upon testing the assembly, the supports for the walker broke due to excessive stress
caused by the weight of the MAP itself. It then became apparent that the designer needed to
design stronger adapters for the MAP wheel base. At the time, the designer did not have any
other material to work with than PLA, so a fundamental design modification had to be executed.
The goal of the new base for the MAP was to increase the support provided by the 3D
printed parts and still keep the design fairly straight forward. The new design consisted of a
servo mounting plate, two supports for the wheels, two wheel mounting hubs, and a DC motor
adapter. The servo mounting plate was created via an extrude feature and multiple cuts. The two
supports for the wheel was where the strength of the design was really improved. The first
support was attached to the DC motor adapter and was made to be as close to solid plastic as
possible. The second support was similar in nature; however a hole was added to allow the wheel
hub to rotate freely. To allow the wheels of the MAP to be powered via a DC motor, holes were
added to the wheels to provide a mounting point. Each wheel hub was then connected to both
sides of the MAP wheel. The old DC motor adapters were re-used in the design of the wheel
adapters. To ensure the accuracy of the model, a new sub-assembly consisting of only the wheel
adapter parts was created. One improvement that was excluded due to the time constraint was a
12
bearing to go between the wheel hub and the mount for the wheel hub. If the designer were to
add a bearing, it would reduce the rotational friction between the wheel hub and its mount, thus
reducing the power that the DC motors would have to use in turning the wheel. After visual
verification that the parts fit together correctly in the subassembly, they were then printed and
assembled for both of the front wheels.
Figure 5: MAP Wheel Subassembly
The wheel assemblies were then mounted to the servo motors, and the servo motors to the
base of the walker. The servo motor mounts were created by taking an outside profile of the
servo motors and creating a box that enveloped them with appropriate holes for mounting
included. A shaft was added to the enclosure to enable the servo motors to mount to the long
shaft that was protruding out of the base of the walker legs. The designer then placed the MAP
on the ground to first see if the mounts could withstand the weight of the walker itself. The
mounts were able to withstand the weight of the walker and the designer moved on to designing
the next part of the map.
13
Figure 6: Walker Wheel Assembly
3.4 Tablet Arm and Mount Design
Once the walker wheel assembly was completed, the designer started work on the tablet
arms and mount for the walker. This author originally intended for the tablet arm to be controlled
via servo motors, but due to time constraints the designer decided to make the arm manually
adjustable instead. The tablet arm can be modified later or even re-printed to allow for a servo
controlled arm.
Since the arm would not be controlled via servos initially, the designer still wanted to
achieve flexibility in the positioning for the tablet. To reach this goal, a base mounting plate was
created to support the weight of the arm and the tablet. Then, a rotating fixture was designed to
allow the tablet arm to rotate 360 degrees. Two eight-inch arm links were then created to allow
for the tablet to be within visual range of the user. Finally, a tablet enclosure was made to affix
the tablet to the rotating arm. The arm was held together by tensioned screws and wing-nuts to
allow for manual adjustment. If the elderly needed the tablet to be higher in the future, more arm
links could be added to facilitate a height change.
14
Figure 7: Tablet Arm Assembly (Left) and Fixture to MAP (Right)
3.5 Miscellaneous Parts and Accessories
Once the tablet mount was finished the majority of structural work to the MAP was
complete. All that remained was to model electrical components so that they could be mounted
securely to the MAP. A miniature joystick was modeled so that it could be placed in an optimal
area near the handle bars to allow for comfortable control of the MAP. Other parts that were
made were to shield contacts of electrical components from touching the chassis of the MAP
since it is made out of conductive metal.
15
CHAPTER FOUR: MECHANICAL SIMULATION
One reason that the designer chose to use SolidWorks as the mechanical design software
was because out of all the parts designed, each part could be simulated and have stresses and/or
loads added to them. SolidWorks allows the user to do perform static, thermal, frequency,
buckling, drop test, fatigue, and pressure simulations to name a few. Static simulations were the
only type of simulations that were used in this work.
4.1 Motivation
Although not used for every part, simulations were executed to see how a part would
react under an external load. This was necessary for parts that would bear the weight of the
walker and its user because parts that were 3D printed were used to prototype some of the
structural parts for the design. This need for simulation became apparent when the first wheel
support design that was 3D printed failed. ABS and PLA filaments are both weaker than their
metal counterparts. Performing some types of simulation gave the author some insight on how
the 3D printed parts would act under a load, and whether or not they would be able to function
under a sustained load. Another benefit of the simulation suite is that it allows the user to select a
plethora of different materials to optimize the strength of the design.
4.2 Simulation Process
The first part of the simulation consisted of selecting a material for a part. For 3D printed
parts, ABS was chosen as the material since it has properties closest to PLA although it is
stronger than its counterpart [18]. ABS was used because SolidWorks 2014 Student edition does
not have any material profiles for PLA. The properties that were chosen for ABS parts were left
to the default SolidWorks profile, although the selected properties of the ABS material are
configurable through the SolidWorks interface.
16
Table 1: Properties of ABS
After the material was applied to a part, a fixture was applied to an area of the part that
would connect to the wheel assembly. Next an external load was placed on the part to simulate a
load in real life. The final part of the simulation consisted of creating a mesh of the part. A mesh
is essentially dividing a part into smaller geometric shapes that change their orientation as a load
is applied to the part. The finer the mesh of a part, the more accurate the simulation of the part is.
These simulations allowed the designer to verify the structural integrity of a part before it was
printed in reality. The figure below is shown to true scale, which allows the designer to see how
the part would ideally respond in reality.
Figure 8: SolidWorks Simulation Example
17
4.3 Material Choice
As mentioned earlier in this chapter, the material that is selected for a particular part
greatly affects its ability to support a load. To demonstrate the difference between the strength
between a 3D printed part and a metal part. The designer executed two simulations of a structural
support subassembly for the MAP. The first simulation was the part constructed out of ABS, and
the second simulation used 6061 Aluminum (aircraft grade metal). The designer calculated the
force that an average 185 lb. (approximately 84 kg) man would place on the support structure to
be 823.2 N using the equation below.
]1[* AMF
Both subassemblies were subjected to the same force and had the same fixed geometries.
The initial results showed that the ABS deformed far more than the Aluminum, but were hard for
the reader to see. To make the results more apparent, the deformation factor was scaled by 10
times for both simulations.
Figure 9: Deformation ABS (Left) and 6061 Aluminum (Right)
This result shows that although plastic parts like ABS and PLA can be used for a
prototype structure, they would not be suitable for use in a real implementation because they
deform under a lower threshold than their metal counterparts.
18
The material that is chosen to make a part can also greatly affect the weight of the final
assembly. Another benefit that SolidWorks provides to its users is the estimation of weight that a
part will have once it is produced. This allows the designer to keep the weight of the mobile
assistance platform light enough to be lifted by the elderly. If any part is going to be heavier than
desired, this function of SolidWorks allows the designer to modify the part before it is produced.
This feature also provides the designer with the center of mass of a part or assembly. This can be
useful when the designer is attempting to maximize the supporting capability of the MAP.
Figure 10: Assembly Mass Properties
4.4 Simulation Inaccuracies
One note that the designer would like the readers to be aware of is that although the
simulations were useful, they were not entirely accurate for a number of reasons. The first reason
that the simulations were not fully representative of reality was because ABS material was
assigned to the parts instead of PLA. This is because SolidWorks does not have a material profile
for PLA. The reason that this makes the simulation less accurate is because ABS is a stronger
19
type of plastic than PLA. The second reason that the simulations were not fully representative of
reality is because the parts that were 3D printed are hollow, with a certain amount of infill
percentage. The reason that the parts were printed hollow is due to the limitation of the Cube3
3D printer. It is unable to print solid parts. When SolidWorks simulates a part, it assumes that the
part is composed of a solid material. These two factors made the simulations less representative
of a part in real life. The simulations were only used a general “guide” when designing the 3D
printed parts. One useful aspect about SolidWorks is that it can publish reports on any given
simulation. An example report is shown in the appendix
.
20
CHAPTER FIVE: 3D PRINTING
3D printing is an additive manufacturing technique where a material is deposited on a
surface in thin layers until the final part is created [8]. All 3D printers use software to slice a
CAD model into small layers that they use to control how material is deposited onto a build
surface [8]. At the moment, 3D printing is used to produce relatively small quantities of
complicated parts for product design and development. In this work, 3D printers were used to
facilitate rapid prototyping for structural components of the mobile assistance platform.
The primary benefit that 3D printing provides to this work is mass customization of parts,
this allows the designer to try various part configurations without traditional “roadblocks” of
modern manufacturing [8]. Typically design and/or part customization is a process that involves
a team or group of people [8]. 3D printing eliminates the need to have a whole team to customize
a design, thus allowing complicated prototypes to be created by a single person. Of course,
another boon of using 3D printers is that they allow a user to save money on material cost [8]. If
a design is flawed or has an issue during printing, it can simply be thrown away without any
major financial impact on the user. 3D printing also has an advantage when compared with
injection molding or subtractive processes in terms of speed and waste. While injection molding
is quick once a mold for a part is made, the mold has to be tooled, which can cause a delay in
receiving a finished part. When compared to subtractive processes, 3D printing produces far less
waste, which allows the user to make more parts given the same mass of material [8].
5.1 Printers and Print Process
3D printing was used as the primary method for creating all structural components for the
MAP. Two 3D printers were utilized for the creation of the parts. The first 3D printer that was
used was the Cube3 3D printer from 3D Systems. The Cube3 is a proprietary 3D printer that
21
features a simple interface and dual extruder heads. Its build volume is 6 by 6 by 6 inches and
has a layer resolution of 70 microns. The second 3D printer that was utilized was the UP Box 3D
printer. Its build volume is approximately 10 by 8 by 8 inches and has a layer resolution of 100
microns.
Figure 11: Up-Box (Left) Cube3 (Right)
Both 3D printers can use acrylonitrile-butadiene-styrene (ABS) and Poly-lactic-acid
(PLA) filament to build their parts, and use Fused Deposition Modeling (FDM). FDM is a
process to create a three dimensional part where a material is melted and deposited on a surface
layer by layer. Both types of filament were used to create parts in order to reduce the time for
fabricating a design. The parts that were provided to the 3D printer were created in SolidWorks
and exported in a .STL file format. The models were then opened in each 3D printer’s software
and set to print after configuring parameters for a particular print. After each part was finished
printing, supports were removed from the part and it was visually inspected to make sure that
there were no errors during the print process. If an error did occur during the print process, then
the part was re-printed.
22
Start
Part Designed in SolidWorks
.STL File Produced
Printer Software Read
of .STL and print settings
Orient Part and Start Printing Process
Final Print Good?
End
Design Incorrect?
Yes
Yes
No
No
Figure 12: 3D Printing Process
The extruder structure varies from printer to printer, but most follow a typical layout.
Most 3D printers have a mechanical filament feeding system consisting of a toothed-gear and a
roller which are used to transfer filament from the spool to the extruder. The extruder element of
a 3D printer normally consists of a heating element and heat sync along with a cooling fan.
Figure 13: Extruder Assembly UP Box (Left) Cube3 (Right)
5.2 Designing to 3D Print
Although 3D printing can be a great aid to the creation of a prototype, it does have certain
setbacks that must be accounted for during the design process. When a part is designed in a CAD
23
software, the designer must take into account what kind of printer will be used and the
constraints that it will place on the part design. The first such consideration that must be made is
overall part dimensions. If the dimension of a part is greater than the size of the provided build
area, then the part will not be successfully printed. In order to print a part that is larger than the
provided build space, the designer must divide the part into smaller, easier to handle pieces. The
designer ran into such an issue when designing the cover for the tablet. To remedy this issue, the
designer decided to have the tablet cover printed in two parts.
Figure 14: Unmodified Part (Left) and Modified Part (Right) for 3D Printing
The designer also has to take into consideration the material that is used for 3D printing
and how “solid” a part is. Most 3D printers have an infill setting that allows the user to select
how much of the part volume is comprised of the print material and how much is hollow. For
example, a part that has a 10% infill would have 10% of its volume filled in with print material
and 90% would be hollow. Material is also important when it comes to selecting the wall
thickness of a 3D printed part. Normally, extra wall thickness will be necessary if the part will be
supporting a large load and is fabricated out of ABS or PLA.
24
CHAPTER 6: ELECTRICAL DESIGN
Since the Mobile Assistance Platform is a robotic platform, electrical and mechanical
design are necessary to produce a functioning prototype. This chapter details the selection of
components and the logic implementation to perform selected features from the Chapter 1.
6.1 Component Selection
For the MAP wheel control system, the designer decided to use two DC motors to drive
the front wheels for the MAP. The gear ratio of the DC motors was chosen as 131.25:1 so that
the walker would not move too fast for the elderly. The radius of each walker wheel was 0.0762
m and the maximum revolutions per minute of the selected motors were 80. Using the formulas
below, the maximum speed that the walker could move unassisted was calculated to be
approximately 0.64 meters per second to provide safety to the elderly.
]1.1[rv
]2.1[min
55.91r
s
rad
According to a report crated by Bohannon, the slowest comfortable walking speed for
elders in their 70’s was approximately 1.27 meters per second [9]. This means that while slower
than the average walking speed, the walker could not travel any faster than a comfortable pace
for the elderly.
To provide rotation to the wheels affixed to the MAP, the designer had a choice of
stepper motors or servo motors. The designer decided to use servo motors due to the fact that
they have a higher rotational speed than most stepper motors and they provide a higher torque,
although they lose out in accuracy and cost [11]. The servos that were used in this work were
Herkulex DRS-0201 servo motors. The designer chose to use this particular brand of motors
because of their easy implementation and the wide amount of features that Herkulex servo
25
motors provide. The most beneficial aspect of the selected servo motors is that their stall torque
is 24 kgf·cm [10]. This aided in the design by providing the necessary torque to rotate the load of
the DC motors, wheels, and 3D printed mounting assembly. The Herkulex servos were also
chosen because they could be quickly configured at will through the Herkulex servo manager.
Figure 15: Herkulex Manager Application [10]
The Herkulex manager application allowed the designer to assign a unique address to
each motor that was used. The manager also allowed the designer to independently configure and
test the PID controller in each servo along with various other settings. The testing of each servo
was necessary to assure that the internal PID controller was tuned correctly.
The out of the microcontrollers that the designer was familiar with, he had a choice of the
HCS12 microcontroller from Freescale or the Arduino ATmega2560. The HC9S12 had a clock
speed of 24 MHz and the ATmega2560 had a clock speed of 16 MHz; both of which are
comparable speeds for the selected application [12, 13]. The HCS12 had 43 input/output pins
while the ATmega2560 had 60 input/output pins [12, 13]. Both microcontrollers could be
programmed in C++, so language selection was not a large factor in the choice of
microcontroller. Ultimately, the designer selected the ATmega2560 and the Arduino platform
due to the large community, number of input/output pins, and support for the microcontroller.
26
The ease of using the serial interface for the ATmega2560 was also a factor in the component
selection.
6.2 Power System
The base for the power system for the MAP is a lithium polymer battery. The battery has
a capacity of 5000 mAh and a maximum discharge rate of 35C at 14.8V. This type of battery was
chosen for the large capacity that it provides and the current discharge that it provides. The
maximum safe discharge rate of the battery is between 125A for two and a half minutes and
175A for one and a half minutes, where the MAP is well below this current drawing threshold.
The entire power system for the MAP is controlled with a pushbutton switch, which can also
serve as an emergency shut-off switch in a fault scenario. From there, man power is branched
into a positive and negative bus and distributed throughout the system from there. To interface
with other components of the MAP, the power bus is broken out into three DC to DC converters
and two motor drivers. The power for the Arduino is separate from the main bus power because
the designer does not have an extra DC to DC converter.
Figure 16: Mobile Assistance Platform Power System
27
6.3 Robot Operating System
In order to make the mobile assistance platform easier for unaffiliated developers to use,
the designer decided to use the Robot Operating System (ROS) as the backbone for the software
in this design [14]. ROS is not a necessarily an operating system, it provides a structured way for
operating systems to communicate with various components [14]. Especially with modern
robotics and the large variation in hardware, the writing of software or reuse of code can prove to
be a daunting task considering the depth of knowledge that is required to interface with various
components of a robotic system; ROS is used as a means to simplify the job of the designer [14].
ROS was conceptualized to enable designers to build service robots as a facet of the STAIR
project and the Personal Robots Program (PRP), this makes ROS the ideal framework to use in
the development of an assistive robot for the elderly [14]. ROS contrasts the aforementioned
CARMEN system in that CARMEN was operated off of a server, whereas ROS can be run on a
single or multiple hosts [3,14]. For a multi-robot home assistance system, this makes ROS an
ideal vehicle to implement software design. Another boon that can be attributed to ROS is that it
is a multi-lingual framework [14]. Users of ROS have the option to program in C++, Python, and
a variety of other languages [14].
ROS implements a large variety of features using topics, messages, services, and nodes
[14]. A node is essential a software module that performs some type of operation. Nodes are able
to communicate with one another by sending items called “messages.” There are many different
kinds of messages in ROS with their own type of format. The format of a message can change
depending on the kind of data that it is sending. A node in ROS can transmit a message by
wrapping it inside of a topic. A topic is a type of information that a publisher sends and a
subscriber subscribes to. There can be many publishers, subscribers, topics, and messages on any
28
particular implementation with ROS depending on the scale of the design. A simple diagram
depicting a simple ROS implementation can be seen below.
Figure 17: Simple ROS Implementation
In this work, ROS was used to manage the output of the Xbox 360 Kinect sensor.
Specifically, ROS read the output image and depth data from the Kinect and allowed the user to
easily manipulate the data. Once the Kinect data had been obtained, a package in ROS called
RVIZ was used to display image data from the Kinect so the designer could verify functionality
and visualize that data that the Kinect receives.
Figure 18: Simulation of MAP and Cleaning Robot in RVIZ
29
Once the Kinect was verified to be in working order, the next goal was to take the image
stream from ROS and send it wirelessly to an application on a tablet using ROSJAVA. The
Kinect only puts out a raw image stream which is incompatible with the wireless link and the
Android application. To remedy this issue, the designer downloaded the
compressed_image_transport package for ROS. Essentially, this package takes an image topic
and compresses it. This was essential for the ODROID to stream the Kinect data to the tablet. To
allow ROSJAVA on the tablet to communicate with the ODROID, the ODROID was set as the
master node for the network. The application on the tablet was then made to look for a
compressed image topic. Since the names of the topics provided by the Kinect and the tablet
were different, a translator node was made to take the image topic from the Kinect and change
the name to the compressed image topic.
6.4 Wheel Control System
To control the wheel system of the walker, a miniature joystick was used to allow
motion control of the whole MAP from a single interface. It is important to note that if the
elderly have arthritis or a hand issue, the control device could be changed from a miniature
joystick to a sliding potentiometer or another alternative control system. To tie the DC motors,
servo motors and the miniature joystick together an Arduino Mega 2560 was used. The outputs
of the miniature joystick are position in the X-axis, Y-axis, and a select button in an analog
format with a voltage range from 0V to 5V. The Y-axis was used to control the speed and
direction of the DC motors that are offered to the base of the walker. The analog to digital
converter in the Arduino provides a digital output from 0 to 1023 over a 5V input range. This
means that the Arduino analog input can detect a change of approximately 4.8 mV per step. The
signal from the miniature joystick was used to control the speed of the DC motors affixed to the
30
MAP. However, before the signal could be used, the input voltage reading had to be normalized.
The input had to be normalized for two reasons. This first reason was that the neutral joystick
position provided an analog output of approximately 2.5V. The second reason was that the
digital output of the Arduino ranged between 0 to 254.
To start normalizing the control signal from the joystick, the digital reading was divided
by four and then the remainder was truncated. The input was divided by four to scale the range
from 0 to 1023 to 0 to 254. Next, half of the range was subtracted from the received value. The
subtraction was performed to take into account that the joysticks neutral position provided an
output of approximately 2.5V. A dead-band was then defined so that the walker would not move
due to erroneous reading or by mistake. The unmodified input signal was used to define the
dead-band so that there would be no loss of input accuracy. When a valid input signal was
received, the normalized signal was used to determine the desired direction for the DC motors to
rotate in. The normalized signal was also used to determine the speed that the DC motors would
move at. If the normalized signal was positive, then the output to the DC motors was scaled by a
factor of two and then had a constant value of two subtracted from the result. This is because the
motor drivers that were used cannot receive a pure DC signal as an input and still function. If the
normalized input was negative, it was scaled by a value of negative two (to account for direction)
and then underwent the same process as before. This accomplished directional and speed control
for the DC motors. The X-axis output of the miniature joystick was used to control the rotation
of the smart servos. Finally the select output was used to center the servos on their 0 degree
angle of rotation.
31
CHAPTER SEVEN: COSTS
In order for the mobile assistance platform to be viable, the cost must be cheap enough to
be affordable for the elderly or their medical providers. In this work, development costs are kept
to a minimum in accordance with Kouroupetroglou et al to demonstrate that the rapid
development of low-cost prototypes can aid in being a viable solution to elderly care [15].
Table 2: Mobile Assistance Platform Costs
Item
Unit
Cost Quantity
Total Cost
(Item)
Walker $99.00 1 $99.00
Arduino $36.98 1 $36.98
DC-DC Converter $5.99 1 $5.99
Miscellaneous Wires $29.99 1 $29.99
Male and Female Wire Headers $11.95 1 $11.95
Solder $9.49 1 $9.49
USB to TTL Adapter $7.38 1 $7.38
AA Arduino Battery Case $5.99 1 $5.99
Heat Shrink Tubing $10.49 1 $10.49
Force Sensitive Resistors $6.95 2 $13.90
DC Motor Hub $7.95 2 $15.90
DC Motor $39.95 2 $79.90
Servo Motors $132.00 2 $264.00
DC Motor Driver $12.11 1 $12.11
Miniature Analog Joystick $5.95 1 $5.95
Kinect Sensor $69.99 1 $69.99
ODROID XU3 $99.95 1 $99.95
3D Printing Filament $100.00 1 $100.00
Turnigy 5000 mAh Battery $42.06 1 $42.06
Battery Cell Checker $3.92 1 $3.92
HXT 4MM to Banana Plug Adapter $3.57 1 $3.57
Total Cost for Mobile Assistance
Platform $928.51
The PR2 robot system would cost an elderly individual between $285,000 and $400,000
[15]. Since the average medical costs for a person from 70 years old until passing is around
32
$136,000 the previous solution would be infeasible [19]. The Dynamaid robotic system is more
affordable at the price of $3,500 [15]. Table 2 demonstrates that the cost for a prototype MAP
easily meets the cost requirements for a robotic assistive care device. The only item that Table 2
omits is the cost of various kinds of nuts and bolts to affix the aforementioned components to the
MAP. In a real-world manufacturing scenario, all of the 3D printed parts for the MAP would be
constructed out of light weight and high strength aluminum or injection molded plastic. This
would mean that to produce a single MAP, there would be an associated tooling cost that would
increase the initial price baseline of the walker. Cost of the MAP would also be slightly
increased because the parts were designed for 3D printing, not for a traditional manufacturing
process so a part redesign or adaptation would be required. Essentially, parts would have to be
adapted for a particular design process [16]. Cost in this step would increase due to the
difference in design constraints between 3D printing and traditional manufacturing. It is
important to note that although cost may increase, 3D printing could still be used to limit the cost
by allowing the designer to prototype any particular part before it is sent to be manufactured.
This would reduce the likelihood of errors during the manufacturing process and therefore
potentially saving the designer cost. With reference to the following chapter, if a 6 degrees of
freedom arm were added to the walker, it would approximately increase the cost of the MAP by
the price of the servo motors used in the arm. The cost of the 3D printed parts, wires, nuts, bolts,
and all-thread would be negligible when compared to the costs of the servo motors.
33
CHAPTER EIGHT: FUTURE WORKS
In the future, many new features can be added to this design and many existing features
can be upgraded. In terms of a physical structure, all of the 3D printed components could be
replaced with metal parts or made stronger by printing each part with 100 percent infill.
Although the parts would take longer to build, this improvement would greatly increase their
strength and provide a direct safety benefit to the user. A robotic arm could be printed to allow
the elderly to pick up objects without straining themselves. Ideally, the arm would be controlled
through the Android tablet so that the elderly would only have to touch a single object on the
screen to attempt to pick it up. The arm would also increase safety by reducing the risk of the
elderly falling when they bend over to pick up an object that may be in their way.
Figure 19: Preliminary MAP Arm with Gripper Design
Although not implemented at this time, the ROS navigation package could be used in the
future to make the MAP autonomously navigate to a charging station when the elderly go to bed
for the night or recline to watch the television. This would prove to be beneficial to the elderly
by relieving them of any worry about the MAP running out of batteries because the elderly
forgot to charge it. The navigation package that ROS provides could also be used to create maps
34
of the elderly’s environment so that the Mobile Assistance Platform would recognize its location
in their living quarters. This would allow for even greater autonomy for the MAP.
35
CHAPTER 9: CONCLUSION
This work has demonstrated that producing a Mobile Assistance Platform using modern
design and prototyping techniques is feasible while remaining cost effective. The prototype MAP
greatly owes its quick development to the use of CAD software for design and 3D printing for
the quick creation and assembly of parts. If a part that has been designed is too weak or needs to
be reworked, CAD software and 3D printing greatly decrease the cost for a new part and reduce
the time needed to make a new part. Both of the aforementioned proved to be great tools for
rapid prototyping and development.
The use of the Robot Operating System allowed the designer not to focus on re-inventing
the wheel, but on practical functionality and beneficial features to add to the system. A specific
example was the use of the openni package in ROS to receive the Kinect image and depth data
and translate it into viewable image streams. The compressed_image_transport package also
allowed the designer to focus functionality of the MAP by handling the compression of the
image stream for transmission over a wireless link. ROSJAVA proved to be beneficial in the
application design space for the Android tablet. Since ROSJAVA is a relatively new offshoot
from ROS, it enabled the designer to focus mainly on the Android application design instead of
the compatibility between ROS and the Android system. One issue that may arise in the future of
using open-source software in the future is version control. As new versions or ROS are released
and as packages are modified, it is noted that changes may need to be made to support continued
compatibility with the Mobile Assistance Platform. Although version control may prove to be an
issue, since all of the software for the MAP and all of the part files are available, it will allow for
the expedient modification of parts or packages to reduce system downtime
36
(inoperability/incompatibility) and allow for the rapid adaptation and integration for new
software or hardware into the system.
Since all of the part files are electronic and the software for the MAP is public, this
allows for easy integration of many new features on the MAP such as navigation, obstacle
detection and avoidance, obstacle removal, and many more. The use of open-source design
mediums has opened the gateway to the future for robotics in rehabilitative applications.
37
APPENDIX A: SOLIDWORKS SIMULATION REPORT EXAMPLE
Simulation of
Wheel_Subassembly
Date: Thursday, October 22, 2015
Designer: Solidworks
Study name: Static 1
Analysis type: Static
Table of Contents Description ............................................................... 37
Assumptions ............................................................ 38
Model Information .................................................. 38
Study Properties ...................................................... 39
Units ......................................................................... 40
Material Properties .................................................. 40
Loads and Fixtures ................................................... 40
Connector Definitions .............................................. 41
Contact Information ................................................ 41
Mesh Information .................................................... 42
Sensor Details .......................................................... 43
Resultant Forces ...................................................... 43
Beams ...................................................................... 44
Study Results............................................................ 44
Conclusion ............................................................... 46
Description
No Data
38
Assumptions
Original Model
Model Analyzed
Model Information
Model name: Wheel_Subassembly
Current Configuration: Default
Solid Bodies
Document Name and
Reference Treated As Volumetric Properties
Document Path/Date
Modified
39
Fillet4
Solid Body
Mass:0.0921402 kg
Volume:9.03336e-005 m^3
Density:1020 kg/m^3
Weight:0.902974 N
C:\Users\Wineman\Desktop\
Walker
Model\Strong_mount.SLDPR
T
Oct 22 19:19:06 2015
Fillet1
Solid Body
Mass:0.0433537 kg
Volume:4.25036e-005 m^3
Density:1020 kg/m^3
Weight:0.424866 N
C:\Users\Wineman\Desktop\
Walker
Model\rotatormount.SLDPRT
Oct 22 19:19:06 2015
Cut-Extrude2
Solid Body
Mass:0.0156116 kg
Volume:1.53055e-005 m^3
Density:1020 kg/m^3
Weight:0.152994 N
C:\Users\Wineman\Desktop\
Walker
Model\topmount.SLDPRT
Oct 22 19:19:06 2015
Study Properties
Study name Static 1
Analysis type Static
Mesh type Solid Mesh
Thermal Effect: On
Thermal option Include temperature loads
Zero strain temperature 298 Kelvin
Include fluid pressure effects from
SolidWorks Flow Simulation
Off
Solver type FFEPlus
Inplane Effect: Off
Soft Spring: Off
Inertial Relief: Off
Incompatible bonding options Automatic
Large displacement Off
Compute free body forces On
Friction Off
Use Adaptive Method: Off
40
Result folder SolidWorks document
(C:\Users\Wineman\Desktop\Walker Model)
Units
Unit system: SI (MKS)
Length/Displacement mm
Temperature Kelvin
Angular velocity Rad/sec
Pressure/Stress N/m^2
Material Properties
Model Reference Properties Components
Name: ABS Model type: Linear Elastic Isotropic
Default failure criterion: Unknown Tensile strength: 3e+007 N/m^2 Elastic modulus: 2e+009 N/m^2
Poisson's ratio: 0.394 Mass density: 1020 kg/m^3
Shear modulus: 3.189e+008 N/m^2
SolidBody
1(Fillet4)(Strong_mount-1),
SolidBody
1(Fillet1)(rotatormount-1),
SolidBody 1(Cut-
Extrude2)(topmount-2)
Curve Data:N/A
Loads and Fixtures
Fixture name Fixture Image Fixture Details
Fixed-1
Entities: 3 face(s)
Type: Fixed Geometry
Resultant Forces
Components X Y Z Resultant
Reaction force(N) 0.000148773 0.889006 0.234329 0.91937
Reaction Moment(N.m) 0 0 0 0
41
Fixed-2
Entities: 2 face(s)
Type: Fixed Geometry
Resultant Forces
Components X Y Z Resultant
Reaction force(N) -0.000148594 0.110595 -0.234329 0.259117
Reaction Moment(N.m) 0 0 0 0
Load name Load Image Load Details
Force-1
Entities: 1 face(s)
Type: Apply normal force
Value: 1 N
Connector Definitions
No Data
Contact Information
Contact Contact Image Contact Properties
Global Contact
Type: Bonded
Components: 1 component(s)
Options: Compatible
mesh
42
Component Contact-1
Type: Node to node
Components: 2 Solid Body (s)
Component Contact-2
Type: Node to node
Components: 2 Solid Body (s)
Mesh Information
Mesh type Solid Mesh
Mesher Used: Curvature based mesh
Jacobian points 4 Points
Maximum element size 0 in
Minimum element size 0 in
Mesh Quality High
Remesh failed parts with incompatible mesh Off
Mesh Information - Details
Total Nodes 41883
Total Elements 25027
Maximum Aspect Ratio 16.453
% of elements with Aspect Ratio < 3 93.2
% of elements with Aspect Ratio > 10 0.032
% of distorted elements(Jacobian) 0
Time to complete mesh(hh;mm;ss): 00:00:04
Computer name: WINEMAN-PC
43
Mesh Control Information:
Mesh Control Name Mesh Control Image Mesh Control Details
Control-1
Entities: 1 Solid Body (s) Units: in
Size: 0.171913 Ratio: 1.5
Sensor Details
No Data
Resultant Forces
Reaction Forces
Selection set Units Sum X Sum Y Sum Z Resultant
Entire Model N 1.77533e-007 0.999601 -2.57278e-007 0.999601
44
Reaction Moments
Selection set Units Sum X Sum Y Sum Z Resultant
Entire Model N.m 0 0 0 0
Beams
No Data
Study Results
Name Type Min Max
Stress1 VON: von Mises Stress 0.813673 N/m^2
Node: 11070
9174.08 N/m^2
Node: 8353
Wheel_Subassembly-Static 1-Stress-Stress1
Name Type Min Max
Displacement1 URES: Resultant Displacement 0 mm
Node: 73
0.000281947 mm
Node: 6982
45
Wheel_Subassembly-Static 1-Displacement-Displacement1
Name Type Min Max
Strain1 ESTRN: Equivalent Strain 1.48924e-009
Element: 720
2.89175e-006
Element: 3143
46
Wheel_Subassembly-Static 1-Strain-Strain1
Name Type
Displacement1{1} Deformed Shape
Wheel_Subassembly-Static 1-Displacement-Displacement1{1}
Conclusion
47
APPENDIX B: MOBILE ASSISTANCE PLATFORM DESIGNED PARTS
Tablet Base Arm Link 1
Tablet Base Arm Link 2
48
Backrest Mount
Backrest
Basket
49
DC Motor Mount
Rotating Wheel Support
50
Strong Wheel Support
DC-DC Converter Backing
Walker Left Leg Side View (Left) and Isometric View (Right)
51
Front Legs Middle Connector
Front Legs Bottom Connector
Walker Right Leg Side View (Left) and Isometric View (Right)
52
Herkulex DRS-0201 Servo Motor
DC Motor to Wheel Hub Mount
Wheel to Support Rotating Hub
53
Hub Cap
Joystick Stand-In
LiPo Battery Mount
54
LiPo Battery Stand-In
DC Motor Shaft to Wheel Hub Adapter
55
DC Motor
Tablet Arm Rotating Mount
Servo to Walker Mount
56
Samsung Tablet Isometric View (Left) and Front View (Right)
Tablet to Walker Mounting Plate
Tablet Enclosure Left Side
57
Tablet Enclosure Right Side
Walker Wheel
58
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59
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VITA
Eric Wineman is from Sulphur, LA. He studied microcontrollers and earned a Bachelor’s
degree in Electrical Engineering from Texas A&M at Kingsville. His future plans include
attending a Ph.D. program so that he can perform research at his own lab or at AFRL while
working off a time obligation from the SMART scholarship program.
