Remote Control Vehicle Report

Final Report
ME250F2014-74
By
Valerie Chen
Andrew Lewis
Nan Li
Andrew Lin
Bo Tian
December 15, 2014
Our RMP was one of two defensive robots in our squad for the M-Ball tournament. Our RMP
needed to be able to push other objects, such as opponent RMPs and the Wolverine. The
purpose of pushing other objects was to effectively disable or at least delay the objectives of an
opponent RMP. Our design was also capable of contributing offensively, by scoring points for
pushing the Wolverine over the hole. Therefore, we needed to design an RMP with high driving
torque and a flat surface to push other objects. Our RMP had a relatively simple yet effective
design. A 1/4” thick aluminum sheet metal part supported by beams and angle stock served as
the flat surface for pushing. A double gearbox with a high (344:1) gear ratio powered to
independent axles, and each axle had three high traction wheels to minimize slipping when
pushing. A 1/16” aluminum sheet metal part was cut to the proper dimensions using the water
jet, and holes for the beam supports, angle stock, gearbox, pillow blocks, and wiring were drilled
using the drill press. This design helped our squad ultimately win the M-Ball tournament.

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TABLE OF CONTENTS
INTRODUCTION……………………………………….……………………………………….. 1
SQUAD STRATEGY……………………………………….…………………………………….2
Description of Problem……………………………………….…………………………...2
Stakeholders……………………………………….………………………………………2
Domain……………………………………….……………………………………………2
Environment……………………………………….………………………………………2
Description of Squad Strategy……………………………………….…………………… 3
Functional Decomposition…………..…………..…………..…………..…………..…….4
RMP Actions in Design Structure Matrix…………..…………..…………..……………..4
RMP Actions in Gantt Chart…………..…………..…………..…………..………………5
RMP CONCEPTUAL DESIGN…………..…………..…………..…………..…………………..6
Guardian’s Role in Squad Strategy…………..…………..…………..……………………6
Attributes and Requirements Decomposition…………..…………..……………………..6
Preliminary RMP Concept 1, Powertrain…...……..…………..…………..……………... 7
Preliminary RMP Concept 2, Chassis……….……….……….……….……….………….9
Preliminary RMP Concept 3, Blocking System……….……….……….……….……… 10
Final RMP Concept…………..…………..…………..…………..…………..…………. 11
Solid Model of Concept……….……….……….……….……….……….……………...12
Description of Concept……….……….……….……….……….……….……………… 12
How RMP Meets Assigned Role…………..…………..…………..…………..………...12
Aesthetics of RMP…………..…………..…………..…………..……..……..………….12
RMP DESIGN EMBODIMENT……….……….……….……….……….……….……….…… 14
Solid Model of Embodiment……….……….……….……….……….……….…………14
Photos of Actual RMP……….……….……….……….……….……….………………. 14
Description of Embodiment…………..…………..…………..…………..……………...15
Design Iterations…………..…………..…………..…………..…………..………….….15
How Key Dimensions Were Determined…………..…………..…………..………….... 15
Analyses and Tests…………..…………..…………..…………..…………..…………...15
Aesthetics and Craftsmanship of Embodiment…………..…………..………..…………16
RMP FABRICATION……….……….……….……….……….……….……….……….……... 17
Bill of Materials (includes material selection justification)……….……….…………….17
Material Selection Justification.…….……….……….…….……… …….……………...17
Fabrication Issues…….……….……….………….……….……….…………………….18
RMP VALIDATION AND VERIFICATION…….……….……….………….……….………..19
Alterations to Beam-Chassis and Beam-Wall Connectors…….……….……….………. 19
Alterations to Wall-Chassis Connector…….……….……….………….……….……….19
Overall RMP Validation…….……….……….………….……….……….…………...... 21
Subsystem Verification…….……….……….………….……….……….………………21
STRATEGY VALIDATION AND VERIFICATION…….……….……….…………………...24
CONCLUSION…….……….……….………….……….……….………….……….……….….25
REFERENCES…….……….……….………….……….……….………….……….……….…. 26
APPENDIX A…….……….……….………….……….……….………….……….……….…...27
APPENDIX B…….……….……….………….……….……….………….……….……………36
APPENDIX C…….……….……….………….……….……….………….……….……………37

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APPENDIX D…….……….……….………….……….……….………………………………..44
APPENDIX E…….……….……….………….……….……….………….……….…………… 47
APPENDIX F (GANTT CHARTS)…………………………………………………………….. 48

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LIST OF FIGURES
Figure 1: The North Campus arena; the only things not pictured…………………………………3
Figure 2: Sketch of Squad Strategy…………………………………………………………….. 3,6
Figure 3: Functional Tree of Squad Strategy……………………………………………………...4
Figure 4: RMP Actions of Squad Strategy in DSM……………………………………………….4
Figure 5: RMP Actions of Squad Strategy……………………………………………………….. 5
Figure 6: Three concepts for powertrain design………………………………………………….. 7
Figure 7: Three concepts for chassis design……………………………………………………… 9
Figure 8: Three concepts for blocking system design…………………………………………... 10
Figure 9: Hand sketch 1 of final RMP concept…………………………………………………..11
Figure 10: Hand sketch 2 of final RMP concept…………………………………………………11
Figure 11: Solid model of final RMP concept……….……….……….……….……….………..12
Figure 12: Solid model of embodiment……….……….……….……….……….……….……... 14
Figure 13: Solid model of embodiment……….……….……….……….……….……….……... 14
Figure 14: Side view of actual RMP……….……….……….……….……….……….…………14
Figure 15: Orthogonal view of actual RMP……….……….……….……….……….…………..14
Figure 16: Beam-Wall Connector utilizes square aluminum tube……….……….……….……..20
Figure 17: Small aluminum blocks are not used to attach pushing wall to chassis……………...20
Figure 18: Angle block connecting pushing wall and chassis provides sufficient support……... 20

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LIST OF TABLES
Table 1: Requirement decomposition and justification…………………………………………... 6
Table 2: Concept #3, with the highest score of 16, was implemented in the robot……………….8
Table 3: Concept #3, with the highest score of 18, was implemented in the robot………………. 9
Table 4: Concept #3, with the highest score of 12, was implemented in the robot……………... 10
Table 5: RMP speed exceeds system level requirement……….……….……….……….………22

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INTRODUCTION
The M-Ball game was created for the ME-250 class and is played by robotic machine players
that have been designed, built and tested by ME-250 students. There are nine squads
participating in the game and each squad consists of four teams. Each team will construct one
robotic machine player (RMP-250). Our squad, with its four RMP-250s, will compete against
other squads in the “M-Ball” competition and try to win each round of the game. To win, we
must score the most points within five minutes in the North Campus arena, which is a table with
fenced edges and a very specific layout. There are three different balls and three different scoring
locations in the arena. There is a central Ball Tower containing normal Ping-Pong balls, red
rubber balls and black rubber balls on tiers of the tower. Black balls are also located on both far
sides of the table. Each squad’s four RMP-250s will start in one corner of the table with the
opposing team starting on the opposite side. The large scoring baskets and scoring holes will be
across from the starting areas, and a smaller scoring basket will be on the corner of each starting
area. Both the types of balls and the scoring locations where the balls are placed will affect the
number of points a team scores. The Wolverine statue, which is initially in the middle of the
table, can also be used to score by moving it on top of an opponent’s scoring hole. In addition,
we receive a 75-point bonus if we manage to maneuver the Wolverine statue so that it
completely covers our opponent’s ball hole.
There are several constraints in the game. One constraint is that the materials provided for
making the RMP-250s are limited, and the squad can only spend at most an extra $200 on parts.
In addition, RMP-250s must fit in a box of dimensions 10” x 12” x 15” high, and can be a
maximum of 15 pounds. Another constraint is that the dimensions of the arena are fixed. The
RMP-250s need to be able to move on the table easily and quickly without falling off the edges
or getting stuck. Finally, none of the RMP-250s are allowed to harm the opposing robots.
Our Squad 7 strategy is composed of four RMP-250s with different roles. The first RMP, known
as R1, or the tower mover, will move the tower toward our scoring hole and drop all the plastic
Ping-Pong balls inside the tower into our scoring hole at one time. The second RMP-250, or R2,
will be the bodyguard of R1 to protect its movement, defend against the opponent, and help
move the tower if necessary. The third RMP-250, R3, will comprise our main offense, and will
get the balls from the top of the tower and then drop them into baskets. The last RMP-250, R4,
will mainly go to block the opponent’s basket as well as act as backup offense (by moving the
black balls beneath our basket into our scoring hole) if necessary.
Team 74 has been tasked with designing and building one of four RMP-250s that will be used to
help Squad 7 win the “M-Ball” competition, specifically to serve as a bodyguard (R2). The
bodyguard’s primary objective is to defend the tower mover and take care of any obstacles that
attempt to prevent the tower mover from getting the Ball Tower over our ball hole. The
bodyguard’s secondary objective is to physically block the opponent’s robots and prevent them
from acquiring balls.

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SQUAD STRATEGY
Description of Problem
Squad 7 is divided into four teams, and each team will construct one robotic machine player
(RMP-250). With its four RMPs, our squad will compete against other squads in the “M-Ball”
competition and try to score the most points within five minutes in the North Campus arena.
There are four ways to score points in the arena:
(1) Deposit balls into the rear basket
(2) Deposit balls into the front basket
(3) Deposit balls into our squad’s scoring hole
(4) Move the Wolverine statue over the opponent’s ball hole.
The squad’s final score is determined by multiplying the weight of the balls in the rear basket by
2, adding this to 1.5 times the weight of the balls in the front basket, and adding the weight of the
balls deposited into our squad’s scoring hole. In addition, we can receive a 75-point bonus if we
manage to maneuver the Wolverine statue so that it completely covers our opponent’s ball hole.
There are several constraints in the game. For instance, the materials provided for making the
RMPs are limited, and the squad can only spend an extra $200 on parts. In addition, RMPs must
fit in a box of dimensions 10” x 12” x 15” high, and can be a maximum of 15 pounds.
Stakeholders
Everyone in the squad is a stakeholder because we are all invested in winning the game.
Domain
The domain of our design is each of the four RMP-250s. They will all have different designs in
order to fulfill their required roles.
Environment
The environment is the North Campus arena, which is a table with fenced edges and a very
specific layout (see Figure 1 on the next page). Besides the starting zones of the two squads,
there are two lower, smaller “front baskets” in each corner of the arena (closest to the starting
zones) and two higher, taller “rear baskets” close to the scoring holes of the two teams. The team
that starts with its four RMP-250s in Starting Zone 1 aims to get balls into Scoring Hole 1 and
Basket 1, and the team that starts in Starting Zone 2 aims to get balls into Scoring Hole 2 and
Basket 2. In addition, there is one hollow Ball Tower filled with lightweight ping-pong balls
centered between the two baskets, with tiers on the tower holding two red balls and two black
balls. There is also a Wolverine statue centered between the two sides of the arena. Finally, there
are eight black balls at the front of the arena, four in front of each team’s Starting Zone, and
eight black balls at the rear of the arena, below each team’s basket.

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Figure 1: The North Campus arena; the only things not pictured are the two shorter baskets in the
two corners closest to the starting zones.
Description of Squad Strategy
Figure 2: Sketch of Squad Strategy
Our selected strategy is composed of four RMP-250s with different roles. The first RMP, known
as R1, will be a tower mover. By moving the tower toward our scoring hole, it will drop all the
plastic Ping-Pong balls inside the tower into our scoring hole. The second RMP, or R2, will be
the bodyguard of R1 to protect its movement, to defend against the opponent, and to help move
the tower if necessary. The third RMP, R3, will comprise our main offense, and will get the balls
from the top of the tower and then drop them into baskets. The last RMP, R4, will mainly go to
block the opponent’s basket as well as act as backup offense (by moving the black balls beneath
our basket into our scoring hole) if necessary.

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Functional Decomposition
Figure 3: Functional Tree of Squad Strategy
RMP Actions in Design Structure Matrix
1 2 3 4 5 6 7 8
R4 moves to Ball Tower and collects high balls 1
R3 blocks opponent baskets/ball hole 2
R1 moves Ball Tower over our scoring hole 3 1
R2 clears obstructions in the path of the Ball Tower 4 1
R4 deposits high balls into basket 5 1
R1 moves Wolverine over opponent’s scoring hole 6 1
R2 clears obstructions in path of Wolverine 7 1
R4 obstructs opponent robots 8 1
Figure 4: RMP Actions of Squad Strategy in DSM

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RMP Actions in Gantt Chart
Figure 5: RMP Actions of Squad Strategy
0:00 1:00 2:00 3:00 4:00 5:00
RMP #1 Move the tower
RMP #1 Adjust tower position
RMP #1 Guard tower
RMP #2 Clear the way
RMP #2 Clear the hole
RMP #2 Guard the tower
RMP #3 Proceed to the target area
RMP #3 Block the basket
RMP #4 Proceed to the target area
RMP #4 Gather first ball and score
RMP #4 Repeat the score process
Time (min:sec)

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RMP CONCEPTUAL DESIGN
Guardian’s Role in Squad Strategy
As illustrated in the arena (Figure 2) and the strategy description, our RMP’s role in the squad
strategy will be to be a bodyguard (R2). The bodyguard’s primary objective is to defend the
tower mover, and to take care of any obstacles that attempt to prevent the tower mover from
getting the Ball Tower over our ball hole. The bodyguard’s secondary objective is to physically
block the opponent’s robots and prevent them from acquiring balls.
Figure 2: Sketch of Squad Strategy
Attributes and Requirements Decomposition
To fulfill our RMP’s role, we identified and mapped the objectives, attributes, constraints, and
requirements into this chart and analyzed it.
Mission
Requirement
Create an RMP-250 capable of acting as a “bodyguard” that
1. Can push opponent robots out of the way without damaging them
2. Can defend the tower moving robot as it moves the Ball Tower over our
scoring hole.
Originating
Requirements
Powertrain
Blocking
system
Chassis Electronics
System
Requirements
1. Powerful
2. Easy to
manufacture
3. Simple to
assemble
4.
Lightweight
1. Padded and
nonlethal to
opponent robots
2. Lightweight
but sturdy
3. Large surface
area
4. Mobile
1. Smaller than 10” x
12” x 15” high
2. Large enough to
contain all
components
3. No dangerous
sharp protrusions
4. Wheels have high
traction
1. Simple controls
to drive robot
2. Easy to rapidly
manipulate
blocking system
3. Simple wiring
4. Uses available
power efficiently
Table 1: Requirement decomposition and justification

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Powertrain: First, the powertrain of the RMP must be powerful so that the robot will be able to
effectively push opponent robots out of the way. Second, the powertrain must be easy to
manufacture and simple to assemble so that we can easily fabricate it, test it, and make
alterations as needed. In addition, the powertrain needs to be lightweight so that our RMP can
move and rotate quickly.
Blocking system: First, the blocking system must also have a large surface area so that opponent
robots cannot simply drive around the blocking robot, and it must be mobile to account for a
wide range of potential opponent robots we may encounter. In addition, the blocking system
must be lightweight to move quickly, but sturdy to push opponent robots out of the way without
breaking.
Chassis: First, the chassis of the robot must be smaller than 10” x 12” x 15” high as mandated by
competition rules, but it must be large enough to contain all the needed components. In addition,
this robot cannot feature any dangerous sharp protrusions because they would interfere with its
mobility and also would create a risk of accidentally harming an opponent robot. Finally, the last
requirement of the chassis is that it must have high-traction wheels in order to effectively move
opponent robots out of the way.
Electronics: First, the electronics portion of the robot must have simple controls so that our
robot driver does not need extensive practice with it prior to competition. In addition, the
electronics system must utilize simple wiring to facilitate alterations, and it must utilize the
available power efficiently to minimize space taken up on the robot and the overall weight of the
robot.
Preliminary RMP Concept 1, Powertrain
Our RMP must be powerful enough to push obstacles out of the way, and therefore we need a
robust powertrain. We considered implementing several different powertrains and created a
design selection matrix to help us select the best option.
Figure 6: Three concepts for powertrain design; Concept #3 is the one used in the robot.

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Description: We at first designed two wheels sharing one motor (Concept #1) since it was easy
to operate and simple to build. However, we would have greater power if we added a second
motor. So our second concept (Concept #2) had one front wheel and one back wheel assembled
with two independent motors. Then we found that this concept was not able to rotate and needed
to be improved. Finally, we designed our third concept (Concept #3) to have two wheels aligned
horizontally with two independent motors. In this design, when we need to turn our robot, we
can apply a voltage across one motor while the other stays at rest.
Design Selection Matrix: In our design selection matrix (Table 2), we thought that quick
acceleration was the most important so we gave it the maximum weight of three points. The next
most important was flexible rotation (two points) and ease of operation (one point).
Attributes Weight Concept #1 Concept #2 Concept #3
Quick acceleration 3 1 3 3
Flexible rotation 2 2 1 3
Ease of operation 1 3 1 1
Sum 10 12 16
Table 2: Concept #3, with the highest score of 16, was implemented in the robot.
Quick acceleration: Both Concepts #2 and #3 have two motors and maximum acceleration, so we
gave them each three points. We gave #1 only one point because it only has one motor.
Flexible rotation: We gave three points to Concept #3 since its independently controlled wheels
allow it to easily turn and rotate. Concept #1 can turn while moving forward, but cannot rotate on
the spot, so we gave it two points. Finally, Concept #2 received one point because it does not
easily rotate.
Ease of operation: Concept #1 received three points because one motor makes it easy to operate.
We gave one point to Concepts #2 and #3 because both have two independently controlled
motors.
Overall, after analyzing the matrix, we picked Concept #3 as our final powertrain concept.

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Preliminary RMP Concept 2, Chassis
The chassis also plays an important function in our ability to perform our assigned role. The
chassis and wheel/castor placement greatly influences the stability of our RMP, and therefore we
considered several different design concepts before selecting the best one using a design
selection matrix.
Figure 7: Three concepts for chassis design; Concept #3 is the one used in the robot.
Description: We at first considered having one front roller and two rear wheels (Concept #1).
We then figured out that if we had two rollers, the front part of our RMP would be more stable.
So we created the second concept (Concept #2), which has two front rollers and two rear wheels.
Finally, we found that if we could move the two rear wheels to the middle and move one roller
from the front to the back (Concept #3), then if an opponent tries to push our RMP from the side,
we will be able to better resist the torque.
Design Selection Matrix: In our design selection matrix (Table 3), we thought that stability
should be most important, so we gave it a maximum weight of three points. The next most
important was ease of rotation (two points) and resistance to getting turned by other robots (one
point).
Stability 3 2 3 3
Ease of rotation 2 2 2 3
Resistance to getting
turned
1 1 2 3
Sum 11 15 18
Stability: Concepts #2 and #3 are more stable since they have four components supporting the
robot body. Hence, Concepts #2 and #3 received three points, while Concept #1 only received
two points.
Ease of rotation: Concept #3 is easier to rotate than Concept #2 and #1 since its two wheels are
positioned in the middle of the robot, closer to its center of mass. Thus, we gave Concept #3
three points, whereas Concepts #1 and #2 only received two points.

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Resistance to getting turned: When an opponent tries to push our RMP from the side, Concept #3
would have the greatest ability to resist rotation because the wheel positioning creates a small
moment arm for the force, and so it received three points. Concept #1 has the smallest ability to
resist rotation because it only has one roller in the front, so it received only one point. Concept
#2 received two points because its ability to resist getting turned is greater than that of Concept
#1 but less than that of Concept #3.
In summary, after analyzing the matrix, we picked Concept #3 as our final chassis concept.
Preliminary RMP Concept 3, Blocking System
Because our main role was to block opponent RMPs, we considered various blocking
mechanisms to implement our role. We created a design selection matrix to choose the best
blocking system.
Figure 8: Three concepts for blocking system design; Concept #3 is the one used in the robot.
Description: At first we designed two angled arms on the front to create a large blocking area
(Concept #1). But we then found that this concept may not be able to navigate tight spaces on the
table. Then we designed a trapezoidal body shape that had a narrow front area, which would
enable our RMP to navigate tight spaces (Concept #2). However, the narrow front part of the
trapezoidal body limited the blocking area of our RMP. Since our RMP’s role as a bodyguard
requires sufficient blocking area, we designed the third concept in the shape of a square in order
to strike a balance between a large blocking area and being able to navigate tight spaces
(Concept #3).
Design Selection Matrix: In our design selection matrix (Table 4), we thought that the wide
pushing area was the most important, so we gave it the maximum weight of three points. The
next most important attribute was resistance to rotation (two points) and ability to navigate tight
spaces (one point).
Wide pushing area 3 3 1 2
Resistance to
rotation
2 1 2 2
Ability to navigate
tight spaces
1 0 2.5 2
Sum 11 9.5 12

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Wide pushing area: It’s clear that Concept #1, with the wide blocking arms, has the largest
pushing area, so we gave it three points. Concept #3 received two points for a moderate pushing
area, and Concept #2 got one point for the smallest pushing area.
Resistance to rotation: Since Concept #1 has the longest blocking arms, it also has the longest
moment arms and is therefore the design that would most readily rotate if an opponent pushed it,
so it only received one point in the design selection matrix. Concepts #2 and #3 each received
two points because they have a similar ability to resist rotation.
Ability to navigate tight spaces: Concept #1’s large blocking arms make it almost impossible for
it to navigate tight spaces, so it received 0 points for this category. Concept #2’s trapezoidal
shape has a narrow front, so it’s relatively easier to navigate tight spaces when driving forward.
However, since the tail ends of Concepts #2 and #3 have the same design, Concept #2 does not
have that much more of an advantage over Concept #3. Therefore, Concept #2 only received a
half point more than Concept #3.
Overall, after analyzing the matrix, we selected Concept #3 as our final blocking system design.
Final RMP Concept
Figure 9: Hand sketch 1 of final RMP concept
Figure 10: Hand sketch 2 of final RMP concept

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Solid Model of Concept
Figure 11: Solid model of final RMP concept
Description of Concept
The wall at the front of the RMP is used to push obstacles in the arena. It is made out of wood to
provide rigidity and a large surface area. A piece of 1/16” thick aluminum sheet metal is placed
in front of the wood to prevent the wood from flexing during competition. The wall and sheet
metal are bolted to the chassis. Two beams made out of aluminum stock are then connected from
the top of the wall to the end of the chassis to add support to the wall. The Tamiya gearbox with
independent motors powers the two wheels independently, allowing for easy maneuvering and
controlled rotation of the RMP. The wheels have rubber treads for added traction. The drivetrain
assembly (gearbox, drive shafts, and wheels) is placed beneath the center of the chassis.
How RMP Meets Assigned Role
Our final design hinges around the RMP’s ability to push other RMPs, the Ball Tower, and the
Wolverine. The large surface area of our front pushing wall and the rigidity of the supporting
beams enables us to effectively perform this role. In addition, high-traction, rubber wheels
provide the necessary grip to withstand the forces exerted by obstacles as we push them. There
are holes in the chassis plate so that the top of the wheels can stick out of the chassis, allowing
the chassis to be lower and therefore lowering the center of gravity, which reduces the possibility
of our RMP tipping over. Finally, the two castors centered at the front and back of the RMP help
stabilize the chassis.
Aesthetics of RMP
Our RMP’s overall design, judging from the aesthetics criterion, revolves around the idea of
simplicity. In our design, we make use of the ample space the chassis plate supplies. On the top,
between the beams and wheels, we will attach the control box; much wiring in the middle of the
RMP, which we will leave the rest of the space above the chassis plate to accommodate. The
beams and connectors are also located on the far edges to provide maximum space. We
therefore have the motors, gearbox, and wheel axles below the chassis. Not only does this help
to lower the center of gravity, but it also hides many of the RMP’s components from plain sight

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to help maintain its simple look. These components are also surrounded by the wheels and
castors to shield them from possible obstacles and obstructions on the arena.
We have thus designed the RMP’s components to be well-spaced to ensure all components
function properly without any interferences. This will fortify the RMP’s reliability and help us
achieve the simplistic design. Our squad’s overall strategy may also benefit from this because
with a simple design, opponents may potentially overlook it analytically and be caught off-guard
if our RMP excels at carrying out its role.

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RMP DESIGN EMBODIMENT
Solid Model of Embodiment
Figure 12: Solid model of embodiment
Figure 13: Solid model of embodiment
Photos of Actual RMP
Figure 14: Side view of actual RMP Figure 15: Orthogonal view of actual RMP

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Description of Embodiment
A 1/4” thick aluminum sheet metal part supported by beams and an angle block serve as the flat
surface for pushing. A double gearbox with a high (344:1) gear ratio powers independent axles,
and each axle has three high traction wheels to minimize slipping when pushing. Our chassis is
made out of a 1/16” piece of aluminum sheet metal that was cut to the proper dimensions using
the water jet, and holes for the beam supports, angle stock, gearbox, pillow blocks, and wiring
were drilled using the drill press.
Design Iterations
No significant design iterations were needed as a result of our analysis, testing, or scrimmage.
Our RMP performed as expected.
How Key Dimensions Were Determined
The key dimensions of the robot were mainly determined by the size constraint in the rules,
which dictated that our robot had to be smaller than 10” x 12” x 15” high. We therefore designed
our chassis to be approximately 9” x 11” so that it would fit within these constraints. The wheels
on our RMP were custom ordered; we deliberately chose smaller diameter wheels (2-3/8”) to
increase the amount of torque. Other key dimensions were determined by the stock that was
available to us and by our overall goal of designing an RMP that was durable and stable.
Analyses and Tests
Below we have determined the necessary values of key dimensions to use for analysis of our
RMP’s final design to show that the requirements are met. Lengths are directly measured, and
forces along with the coefficient of static friction are estimated with justification for each.
r = 1.5 in = .125 ft
d1 = 3 in = .25 ft
d2 = .5 in = .0417 ft
l1 = l2 = 2.75 in = .229 ft
W = mg = 14 lb — This is a rough estimate. The control box is approximately 1 lb; the chassis
plus wheels, motor, gears, and axles are estimated to weigh approximately 3.5 lb; the front
wall is estimated to weigh 4.5 lb; the two beams are about 2 lb in total; and for added
stability and also to balance the downward moment caused by the front wall, the extra
weights on the back are about 3 lbs. The total weight makes sense as we are aiming to
create a relatively heavy RMP to act as a sturdy wall against other RMPs.
F = 2 lb — This is an approximate average force we expect other RMPs will be able to exert on
our own RMP. We predict that the majority of our opponents will be taking more offensive
types of roles, such as obtaining and scoring the balls, so they will not be mainly designed to
push others. Therefore, we assumed a relatively low value for this force.
FD = 6 lb — This is an approximate force we expect our RMP’s wheels will exert against the
objects it pushes. We took into account our gear ratio, as well as our RMP’s role compared
to other RMPs. Since we determined F to be about 2 lb (as justified before), we are
confident that our RMP will be able to push a maximum of three times that force.
µ = .5 — Looking up the static coefficients of friction for material similar to that of the Ping-
Pong table, we determined that this was the most logical value.

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See Appendix C for calculations on slipping force, tipping force, and the motor and gearbox.
From our analyses, we determined that our vehicle would slip before it tipped and that a gear
ratio of 344:1 should be used if we use the double gearbox to drive our wheels.
Aesthetics and Craftsmanship of Embodiment
The RMP’s aesthetics are almost identical to what we envisioned in our design concept. The
RMP’s design is simplistic with ample space provided by the chassis plate. The middle-back of
the plate is allotted to the control box, and the rest of the middle will be room for the wiring.
The gearbox, motors, and axles are on the underside as planned and have enough room to
function reliably.
We are satisfied with the overall craftsmanship of the RMP. All edges have the correct finishes,
burrs are all removed, and sharp edges are all filed down. The only slight issue we had was with
the tolerances of the holes while installing the beams with their connectors. These were easily
resolved as we changed the holes for the chassis plate connectors to slotted holes, and in the end,
every component installed perfectly in its correct location.

17
RMP FABRICATION
Bill of Materials
Part # Description Material Dimensions Supplier Quantity Price
1
Chassis
baseplate
1/16”
aluminum plate
9”x11”x1/16” Kit 1 -
2
Chassis-
Wall
Connector
1” aluminum
angle block
1”x1”x7” Kit 2 -
3
Metal
pushing wall
1/4” aluminum
plate
1/4”x11”x6” Kit 1 -
4 Wheels
Plastic &
Green Rubber
2-3/8” outer
diameter x 0.4”
thick, 1/2” hex
mount
BaneBots 6 $16.50
5
Tamiya
70168
Double
Gearbox Kit
- - Kit 1 -
6 Wheel shafts
3/8” aluminum
rod
0.11” diameter,
2” length
Kit 2 -
1/2" aluminum
hex
1/2" diameter,
1.5” length
McMaster 2 $1.00
7 1” ball caster - - Crib 2 -
8
Support
Beams
1/2" aluminum
square stock
1/2" x 1/2" x
12”
Kit 2 -
9
Pillow
blocks
1” aluminum
angle block
1”x1”x1.5” Kit 2 -
10
Beam-
Chassis
Connectors
3/4" aluminum
tube
3/4" x 3/4" x
3”
Kit 2 -
11
Beam-Wall
Connectors
3/4" aluminum
tube
3/4" x 3/4" x
4”
Kit 2 -
12
Fasteners
and Washers
1/4”-20 Screws
4-40 Screws
- Kit - -
Please see Appendix D for more detailed engineering drawings and manufacturing plans.
Material Selection Justification
The majority of our materials were selected directly from the provided kit because it was
cheapest and most convenient. We believed that the components in the kit would be strong
enough to withstand the forces we anticipated our RMP would experience. The wheels were the
only materials that we decided to purchase from an outside manufacturer because we wanted
more traction to be able to effectively push obstacles in the arena. We chose the wheels with the
highest coefficient of friction to be able to meet our objectives.

18
Fabrication Issues
One fabrication issue arose when we manufactured the beam connectors. While machining away
the surface of the tube that the beam was going to go through, we took too large a depth of cut.
The chips overheated, and instead of cleanly separating from the part, they became stuck in the
flutes of the end mill. Eventually, this chip build-up blocked the cutting surfaces of the end mill,
which prevented us from cutting away more material. To solve this manufacturing problem, we
cleaned out the flutes of the end mill and reduced our depth of cut.
Another manufacturing issue arose when machining the pillow blocks. We had the blocks in the
mill so we could drill and ream the hole for the bearings to go into. We wanted to clamp the part
tightly in the vice because a big drill bit was going to be drilling into a small part. However, we
did not account for how soft aluminum was and how much force the vice could put on it, and the
part deformed slightly. The free fit bolt holes that had already been drilled were deformed into an
elliptical shape, and we had to re-drill the holes so that they were circular again and the bolts
could fit through.
While we were fabricating the support system for the drivetrain, we used two bearings that were
pressed into two pillow blocks to support the shaft. However, the shafts were too big for the
bearings and we had to sand it down to a proper size so that the shafts could be pressed into the
bearings to support the whole RMP.

19
RMP VALIDATION AND VERIFICATION
The manufacturing and assembly processes generally went accordingly to plan; however, there
were a few important changes that were made.
Alterations to Beam-Chassis and Beam-Wall Connectors
Initially, to connect the beam and the chassis, we planned to drill a hole straight through the
beam and chassis and simply fasten them together with a bolt and nut. However, because the
beam sits at an angle relative to the chassis, we realized that this method would be difficult to
execute—we would either have to drill the beam while it was sitting at an angle (which could
cause the drill bit to deflect) or we could drill a hole perpendicular to the beam, in which case the
fastening nut would not sit flush with the chassis.
To eliminate these problems, we devised a fastening method that instead used the 3/4” square
aluminum tube. With this method, the beam sits inside the aluminum tube (the top part of which
has been milled away to make room for the beam) and a hole is drilled through the beam and two
walls of the tube. A fastener is placed through this hole and secured in place with a nut on the
end, thus holding the beam to the connector. A hole is then drilled through two walls of the
square-tube connector and the chassis and a fastener is placed through this hole. This secures the
connector to the chassis. A similar system was used to fasten the beam to the wall (see Figure 16
on next page).
This deviation from the manufacturing plan should improve the amount of force the pushing wall
will be able to withstand because the load is now being carried by two fasteners instead of just
one. It also made our manufacturing easier.
Alterations to Wall-Chassis Connector
Originally, we were going to attach the pushing wall to the chassis using two small aluminum
blocks (see Figure 17, on next page). However, after building the pushing wall and considering
the large reaction forces it would experience when pushing other RMPs, the tower, and the
Wolverine, the small aluminum blocks did not seem like enough support. Furthermore, the way
that they only connected to the chassis at one point created a less rigid connection between the
pushing wall and the chassis.
We thus decided to use the angle block and create one long bracket, fastened at two points to the
chassis and two points to the pushing wall, to support the base of the pushing wall (see Figure
18, on next page). The angle block’s two points of fastening to the chassis don’t allow the wall
to move as much as the aluminum blocks. The angle block provides more support than the
blocks by being taller and providing support along most of the length of the pushing wall, instead
of just two points.
Using this fastening method should increase the amount of force the pushing wall will be able to
withstand and overall make our robot more durable.

20
Figure 16: Beam-Wall Connector utilizes square aluminum tube
Figure 17: Small aluminum blocks are not used to attach pushing wall to chassis
Figure 18: Angle block connecting pushing wall and chassis provides sufficient support

21
Overall RMP Validation
The scrimmage was the validation process for our whole RMP. It is easy to lose sight of the
intent of the robot during the very detail-oriented manufacturing stage. However, the scrimmage
confirmed that we did, in fact, build the right thing. Our RMP was able to push other RMPs,
effectively getting in their way and delaying or derailing their plans. We pushed opponent RMPs
away while our teammates were busy collecting balls and moving the tower. Our RMP was also
able to push the Wolverine and push other robots into the scoring holes. Our RMP successfully
performed its role as the “Guardian.”
Subsystem Verification
Our verification methods focused on the three main subsystems of our design: the powertrain,
chassis, and blocking/pushing wall.
Powertrain
Operational Level Verification
Operational Requirement: Be able to drive forward and rotate.
Quantifiable Requirements: Rotate 360 degrees.
Drive in a straight line.
Drive forward and backward.
Operational Test: Rotate the RMP using the remote control 360 degrees ten times.
Follow a straight line on the floor ten times.
Drive backward and forward ten times.
Test Results: The RMP successfully completed all tests.
System Level Verification
System Level Requirement: Drive an average speed of at least 0.5 feet/second in order to
cross the entire arena in 20 seconds.
Operational Test: Drive the RMP 10 feet five times.
Use a stopwatch to time how long it takes the RMP to drive the
10 ft distance.
Calculate the speed of the run.
Calculate the total average speed by finding the sum of the
average speeds and dividing by 5.

22
Test Results:
Trial Time (seconds) Distance (feet) Speed (feet/second)
1 12.01 10.0 0.8326
2 12.02 10.0 0.8319
3 11.50 10.0 0.8696
4 11.56 10.0 0.8651
5 10.72 10.0 0.9328
Table 5: RMP speed exceeds system level requirement
Based on our tests, the RMP has an average speed of 0.8684
feet/second, which exceeds the system level requirement.
Component Level Verification
Component Level Requirement: The powertrain must be able to withstand approximately half
the weight of the RMP (3 lbs). The casters support the other half
of the load.
Component Level Test: Drive the RMP with all components attached.
Test Results: The powertrain can support the load created by the weight of the
RMP.
Chassis
Operational Requirement: The chassis must be able to hold all components of the RMP.
Operational Test: Measure the chassis dimensions with calipers to ensure that they
match the engineering drawing.
Test Results: The dimensions of the chassis are consistent with the
engineering drawing and the RMP.
System Level Requirement: Assemble all of the components and ensure that they fasten
easily.
Operational Test: Attach the pillow blocks, gearbox, angle block, and beams and
make sure they all easily fit through the holes without
excessively twisting/stretching/stressing any of the components.
Test Results: The RMP assembles easily.

23
Component Level Requirement: The bolts must be able to freely fit through the holes.
Component Level Test: Check that the chassis holes are not threaded.
Measure the diameters of the chassis holes to ensure that they
are free fit holes for the bolt going through them.
Make sure bolts are not too long (the part of the bolt
sticking out should not be more than 1.5 times its diameter).
Test Results: All bolts are properly installed and fit through the chassis.
Pushing/Blocking Wall
Operational Requirement: The pushing/blocking wall must able to push other RMPs.
Operational Test: Attempt to push another RMP.
Test Results: Our RMP was able to push multiple other RMPs.
System Level Requirement: Have a wall that is rigidly attached to the chassis by beams and
an angle block support.
Operational Test: Place ballast on top of the wall and make sure that there is no
play at any of the fastening points or throughout the beams and
angle block. Be sure that there is no bending in the wall.
Test Results: The wall is rigidly attached to the rest of the RMP.
Component Level Requirement: The RMP must be able to generate a driving torque of at least
𝑇𝐷 = 𝜇𝑁𝑟 = 1 ∗ 8 lb ∗
2.375 in
2
12
in
ft
= 0.79 ft ∙ lbf. The value for 𝜇,
the coefficient of friction between the wheels and the table, was
set equal to 1 because engineeringtoolbox.com listed the
coefficient of friction between rubber and plastic as 1. The value
for 𝑁, the normal force, was set equal to 8 lb because 8 lb is the
mean weight of the RMPs whose estimated weights we had
access to (RMPs from our squad and others). The value for 𝑟,
the radius of the wheels, was set equal to the diameter of the
wheels (2.375 in), divided by 2 to obtain the radius, and then
divided by 12 to convert inches into feet.
Component Level Test: Push an 8 lb RMP.
Test Results: The RMP successfully pushed an 8 lb RMP.

24
STRATEGY VALIDATION AND VERIFICATION
Our squad performed very well in both the scrimmages and the tournament. We only lost one
match in the scrimmage, and we won the tournament. All of our RMPs were functional and
capable of performing the roles originally assigned to them. In the scrimmage match that we
lost, we lost because an opponent RMP scored several black balls in the 1.5-multiplier basket at
the beginning of the game while we were focusing on implementing our tower-moving strategy.
After this loss, we made a point to not only focus on executing our own squad strategy, but also
to be mindful of the actions of our opponents.
After the scrimmage, all four teams decided to practice their driving, which paid off during
competition. The combination of the spring-loaded and non-spring-loaded joysticks on the
controller made driving the RMP tricky, so a good amount of practice was required. Our robots
were all functional after the scrimmage; the only major tweaks teams made involved eliminating
wheel slip by ensuring setscrews were tight and creating more grip by adding wheels. We knew
that all of our RMPs were capable of doing what was required of them, and if we could make
changes that would allow us to perform our tasks quicker and with more control, we would be in
good shape.
Our small changes paid off. The scrimmage allowed us to see how an M-Ball game develops,
and therefore we were able to perform better in the tournament. Our RMP prevented several
opponent RMPs from performing their goals, while the other RMPs in our squad helped push the
tower and score balls in baskets. Ironically, we won the final game the way we lost our
scrimmage game, as one of our teams scored several black balls in the 1.5-multiplier basket at
the very beginning, proving that we did study our scrimmage results and make changes.

25
CONCLUSION
The setup of the M-Ball game allows students to go in many different directions with the design
of their robot. The M-Ball game is complex, as there are multiple types of balls with different
point values, three different places to deposit balls, two large objects (the Wolverine and Ball
Tower) and eight RMPs in the arena at the same time. Therefore, each team had different ideas
on how to score the highest number of points, which led to very different designs across the
squads.
The complexity of the game required us to think like engineers and spend a large amount of time
discussing and strategizing before actually beginning to model and manufacture the RMP. It was
oftentimes hard to agree on a design concept because there were a lot of variables and unknowns
associated with the game. This required us to think critically and analyze various outcomes
without actually being able to test or experiment.
The manufacturing of the RMP made us appreciate how much work goes into manufacturing
parts and mechanisms. Making sure holes align, that shafts slide through bearings without
bending, and that the appropriate tolerances are chosen are all important steps that cannot be
neglected. It made us realize just how crucial it is to prepare properly by making good drawings
and having a good concept before actually building.
Our robot was fairly simplistic. However, because of this, we were able to build a very effective
robot that had all of its subsystems working properly. At the same time, building a more
complex robot would have perhaps allowed us to learn about more mechanical systems,
materials, and manufacturing processes. For example, we did not use a rack and pinion or
acrylic, and we never used a laser cutter, so we did not learn as much about these common
design elements. If we were to do it again, we would add another motorized function, so that we
could learn more about a different type of gearbox and transmission and gain more machining
and manufacturing experience.
We are proud and satisfied that we were able to take a concept and then use CAD and stock
materials to make a unique robot. Being able to see the entire process, from squad strategy
generation to the actual tournament, was an incredibly valuable experience, and one that we will
certainly be able to apply later as engineers.

26
REFERENCES
Lecture Slides of ME 250 Instructors Panos Papalambros and Mike Umbriac

27
APPENDIX A
The Ideation Process
We used the Classic SE Pyramid Model to aid us in generating our preliminary strategies. We
first identified our mission requirement, which was to win the game by obtaining the greatest
number of points. We then broke up this mission requirement into a series of originating
requirements, or things we could do in order to win the game. There were five of these
originating requirements:
(1) Obstruct opponent robots
(2) Cover opponent’s ball hole with Wolverine
(3) Move Ball Tower over our team’s scoring hole
(4) Deposit balls into our basket(s)
(5) Deposit balls into our scoring hole.
After we identified our originating requirements, we brainstormed the system requirements, or
the steps we would need to take to achieve each of the originating requirements, which are
organized in Figure 2 below.
Requirement decomposition of squad strategy
We utilized the system requirements to generate roles for the four RMP-250s and aimed to
complete as many of the originating requirements as possible. Two preliminary strategies that
Team 74 generated using this requirement decomposition are detailed in the following section.

28
Preliminary Strategies
Team Strategy 1
Sketch:
Sketch of Team Strategy 1
Description:
R1 in the diagram above pushes the Wolverine on top of the opponent’s scoring hole and then
proceeds to block/prevent the opposing team from obtaining balls. R2 collects the red and black
balls on the tiers of the tower and deposits them into our scoring basket. R3 retrieves the light
ping-pong balls from the bottom of the tower and pushes them into our scoring hole. R4 starts
near the metal bracket at the back of our starting zone and is in charge of depositing the black
balls under the basket and near our starting zone into our scoring hole.
Strengths:
1. We have versatile scoring. This strategy involves all RMP-250s scoring through different
methods (in the ball hole, in the basket, and with the Wolverine) and using all ball types.
2. All RMP-250s are independent. Each RMP-250 goes about its own tasks and is not
reliant on the performance (or lack thereof) of the other RMP-250s.
3. All RMP-250s are specialized. Each RMP-250 has a very specific set of tasks, and
therefore can be designed accordingly to maximize each RMP’s potential.
Weaknesses:
1. It will possibly be difficult to design or manufacture some of the mechanisms required to
achieve these tasks.
2. A lot of the scoring in this strategy relies on access to the scoring hole. If the other team
blocks or covers up the scoring hole, our team could end up missing out on a lot of
points.

29
Put Wolverine
over opponent's
scoring hole
Beat opponent to
Wolverine
Start match as
close to Wolverine
as possible
Give RMP a lot of
low end torque
Steer/control
Wolverine
Push Wolverine
from behind with
enough torque
Have an arm with
"claws" on either
side of Wolverine
to guide it
3. All RMP-250s are specialized. While this is a strength, it could also be a weakness
should a system failure occur, because the RMP-250 would be rendered nearly useless if
it cannot perform its only task.
Risks and Methods of Addressing Risks:
1. One risk is that we could design an RMP-250 that is hard or impossible to manufacture
during the building stage. This risk can be avoided by ensuring we have a thorough
knowledge of the available tools, resources, kit, and budget in order to design
appropriately.
2. Another risk is that the opposing team may block our scoring hole. If this occurs or seems
like a likely possibility, the RMP-250s in charge of scoring in the scoring hole (R3 and
R4) should work together to prevent the obstruction from being set up or removing it if it
is already in place.
3. A third risk is that any one of the RMP-250s is at risk for a system failure. To mitigate
this risk, the RMPs should have a secondary/backup mechanism in addition to the
primary features required to complete their task so that the RMP can still contribute to
scoring/blocking the opponent even if it fails in its primary duty.
Functional Trees:
RMP #1 Functional Tree
Functional Tree 1 of Team Strategy 1

30
Score black and red
balls in the basket
Retrieve black and
red balls from atop
the ball tower
Swipe balls off of
perch on ball tower
and into a
receptacle on the
RMP
Carry balls from
ball tower to basket
Carry balls in a
secure receptacle
Put balls in the
baskets
Use a projectile to
launch balls into
baskets
Position RMP in
front of basket at
appropriate angle
Lift balls out of
receptacle
Use a claw to lift
balls
Score blue and yellow
balls in the scoring hole
Collect balls out of the
bottom of the ball tower
Use a claw mechanism
that opens and closes in
order to grab balls
Transport balls from the
ball tower to the hole
Use two arms to direct
the balls towards the
scoring hole
Deposit balls into the
scoring hole
Score low placed
black balls in the
scoring hole
Retrieve black
balls from both
ends of the arena
Carry balls to
scoring hole
Use a claw to
grip the ball
Make RMP
easily
maneuverable
Deposit balls
into the scoring
hole
Release grip on
the claw to drop
the ball

31
RMP Actions:
RMP Actions of Team Strategy 1
Outcomes:
1. We successfully move the Wolverine over the opponent’s scoring hole and it remains
there for the duration of the game. All ball retrieval efforts are successful.
Squad 7’s predicted score: 450
Opponent’s predicted score: 300
Probability: Average to high
This outcome relies on the successful maneuvering of the Wolverine over the opponent’s
scoring hole. Assuming everything our squad has planned is successful and all RMPs can
continue to collect balls for the duration of the game, this score is possible.
2. One or more RMPs fails at their primary duty.
Probability: Low
If one of our RMPs fails, this would result in a large loss of points because it would be
unable to collect balls for the remainder of the game. However, if this were to occur, the
RMP could focus exclusively on defense, resulting in a low score for the opponent as
well.
3. Squad 7 operates highly efficiently; the other team experiences a failure.
Predicted score: 500
0:00 1:00 2:00 3:00 4:00 5:00
Drive towards black balls at the back of the arena
Grab a black ball
Carry the black ball to the scoring hole
Drop the ball in the scoring hole
Continue to place black balls in the scoring hole
Drive towards ball tower
Grab yellow and blue balls out from the bottom of the tower
Transport balls to scoring hole
Deposit yellow and blue balls in the scoring hole
Continue to put yellow and blue balls in the scoring hole
Drive towards ball tower
Position RMP in front of black balls on tower
Lift arm up to the height of the black ball
Swipe the black ball down and into the basket
Drive to the tall basket
Use arm to lift ball up the height of the basket
Drop the ball into the basket
Collect the remaining black balls
Lift arm up to the height of the red balls
Place the red balls in the baskets using the same process
Drive towards wolverine
Position RMP behind wolverine
Use arms to grab and guide wolverine
Drive towards oppenent's scoring hole
Position wolverine over scoring hole
Defend wolverine/obstuct opponent's paths
Time (min:sec)

32
Probability: Low
This score would only occur if our team operates very efficiently with little to no
resistance from the opposing team. In addition, if the other team experiences a failure of
one or more of their RMPs (getting stuck, falling off the table, etc.), this would allow us
to achieve a very high score by collecting more than 50% of the available balls.
Team Strategy 2
Sketch:
Sketch of Team Strategy 2
Description:
This strategy focuses on having an even balance between the offensive and the defensive. RMPs
1 and 2 (R1 and R2) will be positioned at the top left corner of the starting area as they have the
priority roles. R1 will first head over to the Wolverine statue and push it onto the opponent’s
scoring hole. It will spend the remainder of the game protecting the Wolverine and interfering
with the opponent’s potentially scoring via basket. R2 will head straight for the tower and gather
both the red balls and the ping-pong balls. It will score in either the basket or the hole (with the
basket and elevated balls being top priority), depending on the situation. Since this is the main
method of scoring, R3 will follow closely behind R2 to protect it and make sure opposing robots
do not interfere. R3 will then move into the area near the scoring hole and basket to defend both
R2 and R4. R4 will start at the bottom, close to the black balls. It will deposit the black balls into
the scoring hole and proceed to gather and score the black balls on the opposite side as well.
Strengths:
1. One strength of this strategy is its balance between scoring and defending. If one robot of
either role fails, there will be a backup for each of them to carry on the competition.
2. A second strength is that with two defensive robots instead of one, it will be more
feasible to counter interferences from the enemy team.

33
3. A third strength is that all robots are independent from one another; one robot does not
become unproductive if any other robot fails.
Weaknesses:
1. A weakness of this strategy is that R2 will be difficult to manufacture because of its need
to gather all types of balls from the tower.
2. This strategy has only two offensive robots rather than three, and therefore has less
versatile scoring than other methods like Team Strategy 1.
3. All robots are specialized, so losing any of them would mean its corresponding role
would be lost as well.
Risks and Methods of Addressing Risks:
1. A robot may get stuck in the scoring hole (R4 is at the greatest risk for this). To counter
this, we should to ensure that our robots (R4 in particular) have wheels that are large
enough to maintain traction on any side of the hole in order to escape the hole if they ever
fall in. We also need to practice driving the vehicles to acquire a good feel for the nature
of each robot’s movements.
2. R2 and R4 may fail to score properly. This can be mitigated by sufficient testing and
revisions to their designs.
3. The enemy’s team strategy will likely consist of hindering our performance, so effective
use of scrimmages is necessary to understand and take into account the possible obstacles
we will encounter.
Functional Tree:
Functional Tree of Team Strategy 2

34
RMP Actions:
RMP Actions of Team Strategy 2
Outcomes:
1. The red ball is placed in the tall basket, all eight black balls are deposited into the scoring
hole, and the Wolverine statue stays on top of the enemy’s scoring hole for the duration
of the game. Our defense has successfully interfered with the enemy.
Probability: Low
This outcome has a low probability of occurring because it predicts that the red ball is
placed in the basket and the Wolverine statue is in place over the opponent’s scoring hole
for the entire game. The Wolverine statue will most likely be a target for the opponent as
well.
2. The red ball is placed in the tall basket, all eight black balls are placed in the scoring hole,
about 15 ping-pong balls are also deposited into the scoring hole, but the Wolverine
statue is not in place. Our defense somewhat successfully interferes with the enemy.
Probability: Medium-High
This outcome has a medium/high probability of occurring because it is likely that both
teams will go after the Wolverine statue and it will end up somewhere in the middle of
the table, not covering either scoring hole.
3. The red ball is not placed in the tall basket, all eight black balls are placed in the scoring
hole, only 10 ping-pong balls are deposited into the scoring hole, and the Wolverine
statue is not in place. Our defense provides little pressure to the opponent’s offense.
Probability: Medium-Low
Assuming that we follow through with all our plans to mitigate our risks during the
competition, this outcome should have a medium to low probability of occurring.
0:00 1:00 2:00 3:00 4:00 5:00
Push the statue using a U-shaped base
Extend long arms/barrier upwards to deflect balls
Drive in the way of enemy robots
Drive to tower
Collect red ball
Drive to basket to dump ball
Collect black balls and score in basket or hole
Drive alongside Robot 2 up to the scoring area
Block approaching robots
Collect nearest black balls and score
Drive up to hole and drop balls in
Time (min:sec)

35
Diagram of final squad strategy

36
APPENDIX B
Extra Final Design Picture
Hand sketch of the pushing plate of our final RMP concept

37
APPENDIX C
Vehicle Tipping Calculations
Consider the following free body diagrams of the back wheels and front rollers of our vehicle
which we will be analyzing:
We will assume these wheels to be massless because their weight is negligible in comparison to
the weight of the other components. From the free body diagrams, we can produce the following
equation of force balance in the x-direction:
∑ 𝐹𝑥 = 0 = 𝐹𝐷 − 𝐹2 Eq. (1)
For the y-direction:
∑ 𝐹𝑦𝐴 = 0 = 𝑁2 − 𝑓2 Eq. (2)
∑ 𝐹𝑦𝐵 = 0 = 𝑁1 − 𝑓1 Eq. (3)
We can also create a moment balance equation for Figure 23:
∑ 𝑀 = 0 = 𝐹𝐷 𝑟 − 𝑇 𝐷 Eq. (4)
N2
F2
TD
f2
FD
N1
f1
r
FBD of the back wheels. FBD of the front rollers.

38
Now, consider the following free body diagram of the body of the vehicle:
We will create a force balance equation once again for the x-direction:
∑ 𝐹𝑥 = 0 = 𝐹2 − 𝐹 Eq. (5)
For the y-direction:
∑ 𝐹𝑦 = 0 = 𝑓1 + 𝑓2 − 𝑚𝑔 Eq. (6)
The moment balance around the center of gravity:
∑ 𝑀 = 0 = 𝐹𝑑1 + 𝐹2 𝑑2 + 𝑓1 𝑙1 − 𝑓2 𝑙2 Eq. (7)
Rearranging Eq. (1) and Eq. (5):
𝐹𝐷 = 𝐹2
𝐹2 = 𝐹
Thus:
𝐹 = 𝐹2 = 𝐹𝐷 Eq. (8)
From Eq. (8), we can write Eq. (7) in terms of FD and simplify:
0 = 𝐹𝐷(𝑑1 + 𝑑2) + 𝑓1 𝑙1 − 𝑓2 𝑙2 Eq. (9)
Using Eq. (6) and Eq. (9), we can find f1:
𝑓1 + 𝑓2 − 𝑚𝑔 = 0
𝑓2 = 𝑚𝑔 − 𝑓1
l2 l1
d2
d1
f2 f1
F2
F
mg
FBD of the vehicle body.

39
𝐹𝐷(𝑑1 + 𝑑2) + 𝑓1 𝑙1 − (𝑚𝑔 − 𝑓1)𝑙2 = 0
𝐹𝐷(𝑑1 + 𝑑2) + 𝑓1 𝑙1 − 𝑚𝑔𝑙2 + 𝑓1 𝑙2 = 0
𝐹𝐷(𝑑1 + 𝑑2) − 𝑚𝑔𝑙2 = −𝑓1(𝑙1 + 𝑙2)
𝑓1 =
−𝐹 𝐷(𝑑1+𝑑2)+𝑚𝑔𝑙2
𝑙1+𝑙2
Eq. (10)
From Eq. (3), Eq. (10) becomes…
𝑁1 =
𝑚𝑔𝑙2 − 𝐹𝐷(𝑑1 + 𝑑2)
𝑙1 + 𝑙2
In the same manner, we can use Eq. (2), (6), and (9) to find N2:
𝑁2 =
𝑚𝑔𝑙1 + 𝐹𝐷(𝑑1 + 𝑑2)
𝑙1 + 𝑙2
In the case of tipping, there would be no normal force on the front wheel. This means 𝑁1 < 0.
Our equation for N1 then becomes…
𝑚𝑔𝑙2 − 𝐹𝐷(𝑑1 + 𝑑2) < 0
𝐹𝐷 >
𝑚𝑔𝑙2
𝑑1 + 𝑑2
= 𝐹𝑡𝑖𝑝
This is our tipping force.
Using the values of the key dimensions we had previously determined to plug into this equation,
we obtain the following:
𝐹 𝑡𝑖𝑝 =
14 ∗ .229
. 25 + .0417
= 10.991 𝑙𝑏
Vehicle Slipping Calculations
If the vehicle slips, we can say that the driving force exceeds friction. This means 𝐹𝐷 > 𝜇𝑁2.
Our equation for N2 then becomes…
𝐹𝐷 >
𝜇𝑚𝑔𝑙1
𝑙1 + 𝑙2 − 𝜇(𝑑1 + 𝑑2)
= 𝐹𝑠𝑙𝑖𝑝
This is our slipping force.
Plugging in our values into this equation:
𝐹𝑠𝑙𝑖𝑝 =
. 5 ∗ 14 ∗ .229
. 229 + .229 − .5(.25 + .0417)
= 5.135 𝑙𝑏
Tipping vs. Slipping Conclusion
Since our Ftip > Fslip, this indicates that our vehicle would slip before it could tip over.

40
Motor/Gearbox Calculations
Consider Figure 26, in which a basic model of our robot design is subjected to a force F from a
robot we are theoretically attempting to push. TD represents the torque created by our
motor/gearbox combination acting on the rear wheel of our robot, while r represents the radius of
the front wheel. Keep in mind that this diagram represents a rough approximation of our robot,
and that it assumes the robot has four wheels, while in reality, our robot has two wheels and two
casters. The black and white circle on the robot represents its center of mass.
Basic model of robot being subjected to force F from opponent robot.
According to this diagram, in order for our robot to be able to move to the right, the driving
torque of the back wheel must equal the resistant torque created by the opponent robot, which is
equal to F*r. Therefore, we can use Equation 11 to calculate the required driving torque, TD:
𝑇𝐷 = 𝑓𝑠 𝐹𝑟 Eq. (11)
In Equation 11, fs represents the factor of safety, which is assumed to be 1.5 for this analysis. F is
estimated to be approximately 2 lbs, due to some experimental testing with a force gauge in the
lab. The radius of the wheel, r, is measured to be 1.5 in.
𝑇𝐷 = 1.5(2 lbs)(0.125 ft) = 0.375 ft ∙ lbf
Once we know the required driving torque, the next step is to select the motor that we would like
to use in our robot. The analysis that follows compares the performance of the three motor-
gearbox options: the Pololu 130-sized DC motors and double gearbox, the Mabuchi RC-260SA-
2295 and planetary gearbox, and the 99:1 Metal Gearmotor 25Dx54L mm HP.
Double Gearbox:
Because we would like to have two independently controlled wheels, the most convenient choice
would be to use the Tamiya 70168 Double Gearbox, which has a stall torque (TS0) of
0.002286 ft·lbf and a no-load speed of 11500 rpm for one motor. The dual gearbox makes use of
two motors, and therefore our true stall torque would be 0.002286*2 = 0.004572 ft·lbf.
After calculating our stall torque, the next step should be to scale the stall torque and the no-load
speed to the input voltage; however because the data sheet of the motor-gear system assumed a
nominal voltage of 6 V (which is the same as the voltage we plan to run it at), no scaling is
required.

41
Assuming the motor operates at maximum efficiency, we can calculate the required torque (Tr)
by using Equation 12:
𝑇𝑟 = 0.2𝛾𝑇𝑠0 Eq. (12)
In Equation 12, γ represents the efficiency of the gearbox, which is assumed to be 0.25 for this
analysis. This assumption is based off of the knowledge that γ is typically 5-30% for an entire
gearbox. Based on the loads we expect our gearbox to experience, we believe our gearbox will
be running near its maximum efficiency of 0.30, somewhere between 70 and 90% of its no-load
speed.
𝑇𝑟 = 0.2(0.25)(0.004572 ft · lbf) = 0.000229 ft · lbf
After calculating the required torque, we can calculate the required gear ratio (Mr) using
Equation 13:
𝑀𝑟 =
𝑇 𝐷
𝑇𝑟
Eq. (13)
𝑀𝑟 =
0.375 ft · lbf
0.000229 ft · lbf
= 1640
Unfortunately, the largest gear ratio the dual gearbox can obtain is 344, so this is what our robot
will have to use. To ensure that this lower gear ratio will still be sufficient to move our robot
though, we need to check to make sure that the stall torque of our motor-gear system (with the
344:1 gear ratio) will be greater than the required driving torque, TD. The stall torque (TS) of any
motor-gear system is calculated using Equation 14:
𝑇𝑆 = 𝛾𝑀𝑇𝑆0 Eq. (14)
𝑇𝑆 = (0.25)(344)(0.004572 ft · lbf) = 0.393 ft · lbf
This is greater than the required driving torque (TD = 0.375 ft·lbf), so a gear ratio of 344:1 should
be sufficient for our needs.
Planetary Gearbox:
If we were to use two planetary gearboxes instead of the double gearbox, we would use a similar
analysis format to determine the optimal gear ratio. The motor used with the planetary gearbox,
the Mabuchi RC-260SA-2295, has a stall torque (TS0) of 0.009588 ft·lbf and a no-load speed of
10200 rpm for one motor. We would utilize two independently controlled motors to ensure our
robot has the ability to turn, so our stall torque would actually be 0.009588*2 = 0.01918 ft·lbf.
After calculating our stall torque, the next step is to scale the stall torque and no-load speed to
the input voltage. The given values on the data sheet assume an input voltage of 4.5 V, but we
plan to run the system at 6 V. Using Equations 15 and 16, we can scale the stall torque and no-
load speed to obtain the true values:
𝑇𝑆2 =
𝑉2
𝑉1
𝑇𝑆1 Eq. (15)

42
𝑇𝑆0 =
6 V
4.5 V
(0.01918 ft · lbf) = 0.025568 ft · lbf
𝑛02 =
𝑉2
𝑉1
𝑛01 Eq. (16)
𝑛0 =
6 V
4.5 V
(10200 rpm) = 13600 rpm
Assuming the motors operate at maximum efficiency, we can calculate the required torque (Tr)
by using Equation 12, from above:
𝑇𝑟 = 0.2𝛾𝑇𝑠0 = 0.2(0.25)(0.025568 ft · lbf) = 0.001278 ft · lbf
After calculating the required torque, we can calculate the required gear ratio (Mr) using
Equation 13:
𝑀𝑟 =
𝑇𝐷
𝑇𝑟
=
0.375 ft · lbf
0.001278 ft · lbf
= 293.4
The closest available gear ratio for the planetary gearbox would be 400:1. The last step in the
gearbox analysis is to ensure that this gear ratio (400:1) will be sufficient to move our robot (the
stall torque of the motor-gear system is greater than the required driving torque). Using Equation
14, from above, we can calculate the stall torque:
𝑇𝑆 = 𝛾𝑀𝑇𝑆0 = (0.25)(400)(0.025568 ft · lbf) = 2.5568 ft · lbf
This is greater than the required driving torque (TD = 0.375 ft·lbf), so a gear ratio of 400:1 should
be sufficient for our needs.
When deciding on a motor/gearbox combination to use, we also need to be mindful of space and
resource constraints.
Testing Plans
In order to ensure that our RMP performs as optimally as possible and fulfills its roles, we have
devised three essential functions that can be quantitatively evaluated: pushing ability, speed, and
ability to resist external forces.
Pushing Ability
One of the key functions is the ability to push objects and other RMPs from the front. This is by
far its most vital task since our robot was designated by our team to act as a wall against our
opponents.
How to Test: To test how well our robot performs this function, we can measure the amount of
force it exerts when driving forward at its maximum speed. The most efficient way to measure
the amount of force exerted by our robot when driving forward is to attach a spring scale to the
back of the RMP and have it continuously drive forward until it stalls or starts slipping.

43
Testing Equipment: We will have to find a spring scale that has a measuring range specifically
encompassing the force the RMP is able to exert, and this will be the only device we will need
for the testing process.
Potential Design Changes: If we require the RMP to exert a greater force when pushing from the
front, we could adjust the gear ratio of the gearbox to exert an even greater torque if it is not
already on the highest ratio, or we could find an even stronger motor to replace the current one.
We could also attach additional parts to the bottom of the RMP that make contact with the table
surface in order to provide even more friction.
Speed
The second essential function is a combination of the RMP’s acceleration and its maximum
velocity that it can drive at. Since our role is mainly defensive, this characteristic is not as
important as the others, but still needs to be addressed as we want the RMP to be able to reach its
designated positions and catch other robots as quickly as possible.
How to Test: We will have one measured distance be equivalent to that of the length of our
RMP’s starting position to the area next to the tower. This distance will mainly be used to
observe how quickly the RMP can accelerate and get to that position; we will time it to see how
long it takes. A second measured distance will start farther ahead of the RMP to ensure that it
can reach its maximum velocity before it enters that distance. We will divide that distance by the
time it takes to run through it to find the velocity.
Testing Equipment: All we need is a stopwatch and certain measured distances.
Potential Design Changes: If we desire a greater acceleration or maximum velocity, we can
lower the gear ratio to increase the top speed, find an even stronger motor, or reduce the weight
of the RMP.
Ability to Withstand External Forces
The last function is the ability to withstand other RMPs potentially pushing our RMP from its
corners and edges. This is an important issue to address as our RMP is essentially rendered
useless in its ability to wall others if they can push through us.
How to Test: We can test this by using the same method we will use for testing the first function.
That it is, we will attach a spring scale to each corner of the RMP and tug at the spring scale
slowly until the RMP starts to shift or rotate.
Testing Equipment: We would need a spring scale that measures in the range of how much force
it would take to rotate our RMP.
Potential Design Changes: If we want the RMP to resist moments from its sides even more
effectively, we can again attach more parts to its bottom side near its front and back edges to
provide more friction, or reconfigure its wheel and roller positions.

44
APPENDIX D
Manufacturing Plan 1
Part Number: ME250-001 Revision Date: 10/22/2014
Part Name: Chassis
Team Name: Team 74, Guardian
Raw Material Stock: 1/4” Aluminum Plate from Kit
Step
#
Process Description Machine Fixtures Tools
Speed
(RPM)
1
Use height gauge to mark out
dimensions of plate (9” x 11”)
and use shear to cut plate
slightly larger than these
dimensions
Shear
Height
Gauge,
Surface Plate
2 Break edges of part by hand File
3
Clamp plate in vice, ensuring it
is adequately supported with
2+ parallels, machine both
edges that are hanging off vice
to make them parallel
Mill Vice
Parallels, 1/2
inch 2-flute
endmill,
collet
840
4
Unclamp plate, break edges,
rotate part 90°, reclamp part
and machine the other two
edges to make them parallel
Mill Vice
File,
parallels, 1/2
inch 2-flute
endmill,
collet
840
5
Remove plate from vice and
break all edges. File corners
especially well
File
6
Reclamp part, find datum lines
for X and Y.
Mill Vice
Edge finder,
drill chuck
1000
7
Center drill and drill 0.2010 in
holes
Mill Vice
Center drill,
drill chuck,
#7 drill bit
1200
8
Center drill and drill pilot holes
for large pockets
Mill Vice
Center drill,
drill chuck,
1/2” drill bit
600
9
Use endmill to machine large
pockets
Mill Vice
½ inch 2-
flute endmill,
collet
840
10
Remove part from mill; break
and deburr edges
File

45
Part Name: Wooden wall
Raw Material Stock: 1/4” Baltic Birch Plywood from Kit
Step
#
Speed
(RPM)
1
Use Vertical Band Saw
to cut off a 10.2’’ * 5’’
piece of Baltic Birch
Plywood
Band Saw Wood holder 500
2
Mill one end of part to
provide a fully
machined surface.
Mill Vice End mill 800
2
Refine the edges with
end mill and cut it down
to 4.75’’ * 10.00’’
Mill Vice End mill 800
3
Zero from one corner by
finding all the edges
Mill Vice Edge finder
4
Move to (1.50, 1.45) in
and (8.50, 1.45) in. Then
center drill and drill two
0.2010 in holes
Mill Vice
Center drill,
drill chuck,
#7 drill bit
800
5
Move to (0.25, 4.75) in
and (9.75, 4.75) in. Then
center drill and drill two
0.2010 in holes
Mill Vice
Center drill,
drill chuck,
#7 drill bit
800

46
Part Name: Beam
Raw Material Stock: 1/2” Aluminum Square Stock from Kit
Step
#
Speed
(RPM)
1
Use Vertical Band Saw
to cut off a 11.3’’ long
piece of 1/2” Aluminum
Square Stock
Band Saw Wood holder 800
2
End mill the stock to the
exact 11.28’’ length
Mill Vice
1/2 inch 2-
flute end mill
840
3
From one end A, mark
an angle of 74.5 degrees
on stock. Start from the
other side and mark the
stock at 9.34’’ away
from where the angle of
74.5 intersects the edge
Marker
4
Connect the end B with
C and remove the extra
part with end mill
Mill Vice
1/2 inch 2-
flute end mill
840
5
End mill to refine the
surfaces
Mill Vice
1/2 inch 2-
flute end mill
840
6
Measure all angles and
edges. Mill part if
necessary to make sure
they correspond to the
expected value.
Mill Vice
1/2 inch 2-
flute end mill
840

47
APPENDIX E
Component Redesign: Chassis Plate
The chassis plate of our RMP could be improved by making it out of the acrylic plate instead of
aluminum sheet metal.
Problems with Current Design
We used the 1/16” aluminum sheet metal as the chassis plate. We used the water jet to get it
down to size, to curve the corners, and create the large holes for the wheels. We then drill
pressed all free fit bolt holes to allow the angle block, beams, pillow blocks, and gearbox to
attach.
We overestimated the stiffness of the 1/16” aluminum sheet metal. Our RMP places a lot of force
on the sheet metal. The control box and beams create downward force at the back of the chassis,
and the angle block and pushing wall create downward force at the front of the chassis. These
loading conditions make the chassis bend. These downward forces are only counteracted at the
center by the weight of the gearbox, axles, and pillow blocks, which weigh significantly less and
are thus not enough to prevent the chassis from bending.
The issues created by the bending of the chassis include difficulty ensuring that the rollers and
wheels are all level, the pushing wall being closer to the ground than it should be, and less grip
being created at the rubber wheels at the center (thus causing some wheel spin/slip at high wheel
speeds). These defects amalgamate to hinder our ability to effectively control the RMP.
New Requirements and Justification
Making our chassis out of the acrylic plate instead of the aluminum sheet metal would be a
design improvement in the future. However, there would be new requirements, namely a
different manufacturing process from the one we used for producing the aluminum chassis plate.
The acrylic would have to be cut using the laser cutter, and the outer dimensions and wheel holes
would remain the same. However, the position of the bolt holes for the beams, angle block,
pillow blocks, and gearbox would have to be adjusted. Some of the holes on our chassis right
now are close (<0.25”) to the edges of the chassis. This would be a risky design with acrylic,
because it could easily crack. Therefore, all of the holes would have to be moved inward, which
would require a lot of new dimensioning. For example, the pillow blocks would have to be
smaller in order to be placed further inside the chassis, the beams would have to be more
centered as opposed to on the outer edges of the chassis, and the angle block holes would have to
be pushed further inward. However, the acrylic would not compromise the overall functionality
and goals of the RMP. It would simply call for some re-dimensioning in order to create a more
rigid chassis plate.

48
APPENDIX F (GANTT CHARTS)
Team 74 Predicted Timeline of Events as of Milestone 1
Note: All projects are worked on by all team members.
8/31 9/7 9/14 9/21 9/28 10/5 10/1210/1910/26 11/2 11/9 11/1611/2311/30 12/7 12/14
Strategy Selection
Strategy Report Due
Robot Design
Individual Member Design Brainstorm
Team 74 Meeting and Design Preliminary Finalization
Squad 7 Meeting and Design Edits
Team 74 Meeting and Design Alteration and Finalization
Design Presentations (Milestone 2 Part 1)
Generate Drawings
Design Report Due (Milestone 2 Part 2)
Robot Build
Chassis Construction
Attachments Construction
Manufacturing Plans Complete (Milestone 2.5)
Powertrain Construction
Electrical Wiring
Testing and Alterations
Validation Testing
Validation and Verification Report (Milestone 3)
Design Expo
Final Report Due

49
8/31 9/7 9/14 9/21 9/28 10/5 10/1210/1910/26 11/2 11/9 11/1611/2311/30 12/7 12/14
Strategy Selection
Strategy Report Due
Robot Design
Generate Drawings
Robot Build
Electrical Wiring
Validation Testing
Design Expo
Final Report Due

50
8/31 9/7 9/14 9/21 9/28 10/5 10/1210/1910/26 11/2 11/9 11/1611/2311/30 12/7 12/14
Strategy Selection
Strategy Report Due
Robot Design
Generate Drawings
Robot Build
Electrical Wiring
Validation Testing
Design Expo
Final Report Due

51
Team 74 Predicted Timeline of Events as of Final Report
8/31 9/7 9/14 9/21 9/28 10/5 10/1210/1910/26 11/2 11/9 11/1611/2311/30 12/7 12/14
Strategy Selection
Strategy Report Due
Robot Design
Generate Drawings
Robot Build
Electrical Wiring
Validation Testing
Design Expo
Final Report Due

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