Individual Robot Analysis Final

Individual
Robot
Analysis

Diana
Wu
Wong

A98066631

Team
4:
Jaeger

Component:
Friction
Drivetrain

MAE3
Section
A01

T.A
Howard
Tai

Wu
Wong
1

Part
I:
Description
of
Components.

Overview
of
“Gypsy
Danger”

Initial
Position
View

The
robot,
Gypsy
Danger,
fits
to
the
10x10x10
inches
constraint
and
it
is
created
to
carry
balls
from
a
10-‐
inch-‐high
elevated
platform
to
a
5-‐inch-‐high
elevated
goalie
within
a
20
inches
distance.
This
robot
was
designed

to
drive,
lift
its
upper
base,
extend
its
arm
to
reach
behind
the
balls
on
the
elevated
platform
and
retract
back
its

arm
so
that
the
ball
rests
on
the
upper
platform.
It
would,
then,
drive
back
to
the
elevated
goalie
and
release
the

ball.
The
robot
mainly
consists
of
3
components:
the
base
with
two
friction
drives
powered
by
high-‐speed

motors,
a
lift
that
elevates
the
upper
platform
up
to
5
inches
higher
than
the
limited
height
and
an
extendable

arm
that
extends
up
to
7
inches
long.
The
friction
drives
provide
great
mobility
on
high
speed.
It
allows
very

sharp
turns,
it
is
able
to
turn
360
degrees,
and
move
forwards
and
backwards
on
a
straight
line.
The
lift
allows

the
upper
platform
to
elevate
to
the
needed
height
for
the
arm
reach
the
balls
when
extended.
At
its
maximum

height,
it
can
help
the
arm
to
reach
the
yellow
ball,
which
are
often
inaccessible
for
most
robots
seen.

Fully
Extended
View

Wu
Wong
2

Component
Overview:
Friction
Drivetrain

The
robot
drives
around
using
a
classic
friction
drivetrain
attached
to
both
sides
of
the
base.
There

are
a
total
of
4
3-‐inch-‐diameter
wheels
with
O-‐Rings
in
the
back
wheels
to
help
provide
friction.
While
most

friction
drivetrains
use
rubber
bands
on
the
back
wheels,
we
decided
to
substitute
them
with
O-‐Rings

secured
with
hot
glue
since
rubber
bands
wore
out
faster.
The
drivetrain
is
powered
by
2
high-‐speed

motors
mounted
on
“mounters”
and
pressed
onto
the
back-‐wheels
with
the
force
of
springs
to
help
provide

friction
and
prevent
the
wheels
from
slipping.

The
base
also
includes
a
6x2x2.5
inches
acrylic
box
that
fits
underneath
both
motors
to
help

prevent
the
motors
from
tilting
inwards
and
slipping
away

from
the
back
wheels.
The
box
also
secures
both
motors
to
the

same
height
so
that
the
force
pressing
the
motor
to
the
wheels

is
equivalent
on
both
sides.
This
helps
the
wheels
to
spin
at
the

same
rate
and
makes
sure
that
the
robot
moves
forward
and

backwards
in
a
straight
line.

o Minimum
Set
of
Functional
Requirements:

-‐ Robot
must
be
able
to
move
back
and
forwards
straight.

-‐ Robot
must
be
able
to
support
the
weight
of
the
robot.

-‐ Robot
must
fit
within
the
10x10x10
bounded
area.

-‐ Robot
must
be
able
to
travel
20
inches
within
5
seconds.

-‐ Robot
must
be
able
to
stop
efficiently

-‐ Robot
must
be
reliable.

-‐ No
slipping.

o Design
Solutions
Considered

There
were
many
different
diameters
of
wheels
tested
to
help
achieve
the
ideal
drivetrain
that

would
provide
enough
force
to
carry
the
weight
of
the
entire
robot
and
ensure
it
travels
the
required

distance
within
a
limited
time.

Larger
wheels
provide
larger
force
and
torque
to
the
drivetrain
and

make
it
more
powerful
and
reliable,
while
smaller
wheels
help
sharper
turns
and
faster
mobility.
The

decision
came
down
between
wheels
and
wheels.
While
larger
wheels

were
more
preferable,
because
of
the
nature
of
the
design,
the
wheels
would
not
have

enough
constraints
and
they
would
start
to
wobble
eventually
slipping
the
high-‐speed
motor
off.
We

Wu
Wong
3

decided
to
use
the
wheel
and
sacrifice
power
and
torque
for
a
more
reliable
drivetrain

that
would
fulfill
our
functional
requirements.

o Summary
of
the
Component

The
drivetrain
is
moderately
reliable.
It
has
worked
80%
of
the
time
at
its
best.
Its
speed
is

extremely
high
and
it’s
turns
are
very
efficient.
The
resulting
speed,
measured
from
timing
the
robot,

was
about
20
inches
in
3
seconds,
which
outdid
the
expected
speed
(comparison
and
analysis
on
the

measurements
will
be
provided
in
the
later
sections
of
the
report).
Most
importantly,
it
was
still
able

the
weight
of
the
robot
with
a
diligent
matter,
without
affecting
much
its
speed.
The
product
did
not

only
fulfill
the
functional
requirements
set
at
the
beginning
of
the
design,
but
also
exceeded
them
from

the
result
its
performance.

Part
II:
Project
Management
Reflection-‐
Concept
Generation
and
Creativity.

On
week
4
Dr.
Delson
assigned
us
the
Individual
Concept
Generation
Assignment.

Each
person
was

to
come
up
with
4
designs
prior
to
meeting
up
with
the
team.
There
were
16
different
designs,
ranging

from
ball
shooters,
nets,
and
claws.
However,
the
most
important
and
hardest
part
of
this
project
was
to

have
4
people
to
agree
on
one
single
design
out
of
16
of
them.
The
design
must
fit
within
the
10x10x10
inch

boundary.
It
must
be
able
to
deliver
balls
from
a
10-‐inch-‐high
elevated
platform
across
a
20
inches
long

field
to
a
5-‐inch-‐high
elevated
goalie,
not
to
mention
the
15-‐inch-‐high
yellow
balls
in
the
middle
of
the

platform.
We
came
to
a
group
understanding
that
components
of
the
robot
must
be
able
to
expand
long

enough
to
be
able
to
reach
the
yellow
balls
at
most
and
mobile
to
deliver
the
balls
to
the
goalie.
We

evaluated
each
design’s
pros
and
cons
with
the
help
of
the
Pugh
Chart
and
chose
a
design
with
components

from
various
team
members’
designs.

However
the
final
design
was
a
completely
different
design
that
did
not
resemble
from
any
of
the

previous
designs.
Instead
of
using
fish
strings
and
foldable
arms,
which
were
frequently
overlapped
in
the

concept
generation
assignments,
our
team
designed
an
arm
that
would
fit
in
the
box
and
extend
vertically

through
a
gear
attached
to
a
geared-‐motor.
Although
this
design
would
extend
long
enough
to
cover
the

width
of
the
elevated
platform
and
reach
for
both
the
white
balls
and
yellow
balls,
it
wasn’t
high
enough
to

reach
the
platform.
Therefore
we
decided
to
include
a
lift
that
would
help
elevate
the
upper
platform
where

the
arm
was
placed
to
help
achieve
the
needed
height
to
reach
the
yellow
balls.
Our
original
design
also

included
a
ramp
that
would
connect
from
the
platform
to
the
goalie,
however
this
design
was
omitted
2

weeks
before
the
presentation
of
the
finalized
product
since
we
discovered
that
although
the
design
of
the

ramp
would
facilitate
delivering
the
ball
from
the
platform
straight
to
the
goalie,
it
constraint
the
robot
and

it
couldn’t
reach
some
of
the
balls.

Although
in
the
end,
we
didn’t
choose
the
design
that
the
Pugh
Chart
helped
us
narrow
down
to,
we

still
view
it
as
one
of
the
most
critical
parts
of
the
process
for
generating
our
design.
Through
this
process

we
were
able
to
learn
to
communicate
as
a
team
and
reach
a
common
understanding
of
what
our
design

emphasis
should
be:
Simplicity,
Efficiency
and
Reliable.
These
values
were
carried
on
to
the
generation
of

our
final
design
that
became
very
simplistic,
but
highly
reliable.
This
method
will
definitely
be
carried
on
to

my
future
design
projects,
as
it
was
one
of
the
most
valuable
process
that
involving
the
unification
of
the

team
and
the
product
of
an
optimal
design.

Wu
Wong
4

Part
III:
Analysis
of
the
Component

o Objective
of
Analysis

The
objective
of
this
analysis
is
to
predict
whether
the
robot
will
be
able
to
travel
in
its
expected

carrying
the
weight
of
the
robot
and
what
its
maximum
pushing
force
is.
This
analysis
can
help
predict

the
size
of
the
back
wheel
needed
to
achieve
the
time
without
slipping.
The
bigger
the
wheel
is,
the

more
reliable
the
drivetrain
is,
however
it
will
also
be
slower.
The
goal
is
to
balance
between
the

reliability
and
speed
and
also
identify
at
what
pushing
force
the
wheels
will
begin
to
slip.

o Free
Body
Diagram:
Friction
Drivetrain

FBD
for
Traction
Limiting
Case

Back
Wheel
and
Motor
Shaft
FBD
for
Motor
Stall
Analysis

o Energy
Analysis

Assumptions:

-‐ The
mass
is
concentrated
at
one
point
in
order
to
facilitate
the
calculations.

-‐ There
is
no
slipping
between
the
wheels
and
the
ground
to
assume
the
maximum
efficiency
of

the
drivetrain.

-‐ Energy
lost
due
to
friction
is
minimal
and
negligible.

-‐ The
robot
is
moving
at
constant
acceleration.

The
energy
source
of
the
drivetrain
is
two
high-‐speed
motors
mounted
on
each
side
of
the
back

wheels.
The
energy
is
transferred
to
the
wheels
by
a
spring
that
pushed
the
motors
against
the
back
wheels

and
ensure
the
friction
needed
to
keep
the
motors
from
slipping.
It
is
believed
that
the
high-‐speed
motors

will
provide
enough
torque
to
spin
the
wheels
up
to
the
expected
speed.

Linear
motion
involves
kinetic
energy
of
the
horizontal
distance
traveled
by
the
robot.
In
order
to

determine
the
needed
energy,
the
kinetic
energy
will
be
calculated
from
the
information
available.

Wu
Wong
5

𝐾𝑖𝑛𝑒𝑡𝑖𝑐 𝐸𝑛𝑒𝑟𝑔𝑦 =
1
2
𝑚 ∙ 𝑉!

The
velocity
is
found
by
the
equation

𝑉!"#$!%# =
𝐿
𝑡
=
20
5
= 4 𝑖𝑛𝑐ℎ/ sec (0.1016
𝑚
𝑠
)

The
initial
velocity
of
the
robot
will
be
at
rest.
So
ideally
the
robot
will
achieve
a
velocity
of
𝑉!"#
within
the

5
second
periods
of
acceleration
so
that
𝑉!"#$!%#
=
4
inch/sec.

𝑉!"# + 𝑉! 0
2
= 𝑉!"#

𝑉!"# = 2𝑉!"# = 8 𝑖𝑛𝑐ℎ/ sec 0.203
𝑚
𝑠

Inserting
the
newly-‐found
variables
into
the
main
equation:

𝐾𝑖𝑛𝑒𝑡𝑖𝑐 𝐸𝑛𝑒𝑟𝑔𝑦 =
1
2
𝑚 ∙ 𝑉!"#
!
=
1
2
1.347 𝑘𝑔 ∙ 0.203
𝑚
𝑠
!
= 0.0278 𝐽

Therefore
the
Kinetic
Energy
for
60s
contest
is
1.67
J.
To
ensure
the
feasibility
of
moving
the
car
for
the

distance,
the
factor
of
safety
must
be
taken
into
account.

The
maximum
amount
of
energy
for
60
seconds
for
the
high-‐speed
motor
is
77.37
J.
This
value
is
provided

by
the
MAE3
Website.
However
the
energy
is
provided
by
2
high-‐speed
motors,
therefore
the
energy

available
is
154.74
J
in
total.

𝐹. 𝑆 𝐸𝑛𝑒𝑟𝑔𝑦 = 𝐸𝑛𝑒𝑟𝑔𝑦!"!#$!%$&/𝐾. 𝐸 =

!"#.! !
!.!" !
= 92.66

The
power
needed
to
generate
the
kinetic
energy
in
60
seconds.

𝑃!"#$%!"& =
𝐾. 𝐸
𝑡
= 2.578

The
factor
of
safety
power
is
calculated
as
follows

𝐹. 𝑆 𝑃𝑜𝑤𝑒𝑟 =
𝑃!"!#$!%$&
𝑃!"#$%!"&
=
2.58
0.028
= 92.14

Although
the
Energy
Analysis
doesn’t
ensure
that
the
drivetrain
will
definitely
succeed,
it
does
provide
a

general
prediction
of
the
whether
it
is
possible
to
work.
From
the
high
values
of
Factor
of
Safety,
it
seems

that
the
drivetrain
is
highly
likely
to
perform
its
task.

o Force/Torque
Analysis:

-‐Traction
Limiting
Case:
At
what
force
the
wheels
begin
to
slip.

Assumptions:

-‐ Quasi-‐static
Analysis.
All
forces
are
treated
as
static.

-‐ Neglect
friction
of
the
wheel
bearing

-‐ Friction
between
rubber
and
cardboard,
instead
of
O-‐rings-‐plastic,
as
the
closest
value
found
on

the
internet.

Wu
Wong
6

-‐ Center
of
mass
is
off-‐centered
because
the
weight
is
mainly
distributed
at
the
back
portion
of

the
robot.

-‐ The
friction
of
the
bearing
on
the
wheels
is
small
enough
to
be
neglected.

Variables:

a
(estimated
distance
back
wheel
to
center
of
mass)
=2.5
inch=0.0635
m

b
(estimated
distance
front
wheel
to
center
of
mass)
=3.5
inch=
0.0889
m

𝜇
(coefficient
of
friction

rubber-‐cardboard)=0.65

m
(mass
of
the
entire
robot)
=
1.347
kg

Calculations:

Σ𝐹! = 0

𝐹!"#$!%&' − 𝐹!"#! = 0

Σ𝐹! = 0

𝑅!"#$ − 𝑅!"#$% = 0

Σ𝑀! = 0

𝑚 𝑔𝑏 − 𝑅!"#$(𝑎 + 𝑏) = 0

𝑅!"#$ =
!"#
!!!

Therefore
the
maximum
traction
force
happens
when

𝐹!"#$!%&',!"# = 𝜇𝑁

N=
normal
force=𝑅!"#$%

µ=
Coefficient
of
friction

Therefore
𝐹!"#$!%&',!"# = 𝜇𝑅!"#$% =
!"#$
!!!
= 5 𝑁

-‐Motor
Torque
Analysis:
At
what
Force
will
the
Motor
Stall?

Assumptions:

-‐ Traction
is
strong
enough
so
that
the
wheels
don’t
slip

-‐ Quasi-‐static
Analysis

-‐ Neglect
friction
of
the
wheel
bearing

Variables:

𝜏!
(torque
of
the
motor)=
0.012
Nm

𝑟!!!!"=
1.5
inches=
0.0381
m

Calculations:

Σ𝐹! = 0

𝐹!"#$!%&' − 𝑅!"#$ = 0

Σ𝐹! = 0

𝑅!"#$ − 𝐴! = 0

Σ𝑀! = 0

𝐹!"#$!%&' 𝑟!!!!" − 𝜏! = 0

Therefore

𝐹!"#$!%&' =
!!
!

Maximum
pushing
force
happens
at
stall
torqueà
𝜏! = 𝜏!"#$$

Wu
Wong
7

Since
there
are
motors
on
both
sides
of
the
car

𝐹!"#$!%&' =
!!!"#$$
!
=
!(!.!"#)
!.!"#$
= 6.30 𝑁

o Measurement
of
Component
Performance:

Equations
used:

𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝐸𝑟𝑟𝑜𝑟 =
𝐸𝑥𝑝𝑒𝑐𝑡𝑒𝑑 − 𝐴𝑐𝑡𝑢𝑎𝑙
𝐴𝑐𝑡𝑢𝑎𝑙
×100%

The
velocity
of
the
drivetrain
was
measured
by
timing
the
amount
of
time
the
robot
took
to
travel

10
inches.
This
method
simply
used
a
timer
to
time
the
robot
while
in
a
straight
line
for
10
inches.

The
resulting
measurements
were
10
inches
in
1.5
seconds
(0.169
m/s).
Compared
to
the
ideal

speed
from
the
functional
requirement
of
the
robot
(20
inches
in
5
seconds,
0.1016
m/s),
the
robot
was

40%
faster
than
the
expected
speed,
which
means
that
we
have
highly
underestimated
the
potential

velocity
of
this
robot.
However
the
expected
velocity
was
a
value
that
was
set
by
the
team
as
a
functional

requirement
for
the
robot,
the
fact
that
the
actual
speed
outdid
the
expected
velocity
is
highly
beneficial
for

the
robot.

0.1016 − 0.169
0.169
×100% = 39.9% = ~40%

The
pushing
force
was
measured
by
attaching
a
force
gauche
to
the
back
of
the
robot
and
holding

the
other
end
of
the
gauche
while
the
robot
drove
straight.
The
same
result
was
given
by
driving
the
robot

into
the
force
gauche
until
the
robot
couldn’t
move
further.

The
resulting
measurement
was
8
N
of
pushing
force.
Compared
to
the
estimated
result
from
the

Force
Analysis
from
the
previous
section
(6.3N
and
5N),
the
actual
pushing
force
was
underestimated
by

21.3%
and
37.5%
respectively.
There
are
several
factors
that
might
have
resulting
such
great
percentage
of

error,
however
the
most
attributed
factor
in
this
case
would
be
the
coefficient
of
friction
used.
Given
the

limited
amount
of
material
combination
for
coefficient
of
friction
provided
by
the
internet,
the
closest

material
combination
that
was
found
was
rubber-‐cardboard
coefficient
of
friction
which
ranges
from
0.4
to

0.8.
As
a
result,
a
coefficient
of
friction
of
0.65
was
chosen
to
input
in
the
calculations,
in
order
to
minimize

the
inaccuracy.
However,
the
this
value
is
still
highly
inaccurate
since
the
coefficient
of
friction
of
the
actual

material
(O-‐rings
and
Acrylic)
is
still
unknown.

6.3 − 8
8
×100% = 21.3%

5 − 8
8
×100% = 37.5%

o Conclusion:

The
Energy
Analysis
predicts
that
the
drivetrain
might
work,
however
it
does
not
ensure
that
it
will.

On
the
other
hand,
the
Force
Analysis
gave
us
a
general
idea
of
the
amount
of
pushing
force
that
will

make
the
wheels
slip
or
the
motor
stall.
From
these
analysis,
we
were
able
to
make
adjustments
to
the

component
in
order
to
increase
the
pushing
force
and
the
traction
and
maximize
the
performance
of

the
overall
machine.
For
future
reference,
I
would
keep
in
mind
the
potential
weaknesses
of
the
final

design
of
the
robot.
For
instance,
the
wheels
are
located
at
the
sides
of
the
base,
this
makes
the
robot

more
susceptible
to
attacks,
and
if
the
opponent
was
to
attack
the
wheels,
the
robot
would
be

completely
dysfunctional
and
incompetent
to
score.
Overall,
the
robot
is
very
simplistic
and
reliable,

Wu
Wong
8

however
it
is
not
most
efficient.
Because
it
mainly
relies
on
the
drivetrain
to
deliver
the
balls
from
the

platform
to
the
goalie,
it
requires
a
lot
of
control
and
maneuvering
.
Unless
the
team
members
are
very

familiar
controlling
the
robot,
it
won’t
likely
get
all
of
the
balls
(including
the
yellow
ones).

Nevertheless
it
has
been
constantly
performing
great
overall,
scoring
approximately
12
points
each

time.

Individual Robot Analysis Final

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