Download The AAA Challenge

The AAA Challenge
A First-Year Engineering Project
The Challenge
As a team, design, build, test,
demonstrate, and document an
autonomous vehicle that carries the
most mass up a ramp in the least
time using a small dc motor and using
two AAA batteries as the energy
source.
Question One
• How much power can be obtained from
two AAA batteries and for how long?
Capacity of AAA battery to deliver power determined by discharging
batteries to resistors.
Predicted power estimated by best fit line to data of multiple runs.
Watts
AAA Battery Power
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
2 ohm resistor
1 ohm resistor
0.5 ohm resistor
1 5 9 13 17 21 25 29 33 37 41 45 49 53
Time, minutes
Duracell AAA Battery Depletion
1.4
Power, watts
1.2
1.0
0.8
0.6
y = 2.68x-0.35
0.4
R2 = 0.5033
0.2
0.0
0.0
10.0
20.0
30.0
Time, minutes
40.0
50.0
60.0
Question Two
• How do we get the maximum mechanical
power out of our motor and gear system?
Lift different masses and measure velocity of ascent.
Calculate input power from product of voltage and current.
Construct performance curve from mass lifting experimental results.
Find best fit line equation to mass lifting data.
From best fit line calculate Power=torque x angular velocity.
Maximum power is target for best performance of motor/gear train.
Motor/Gears Performance
Angular Velocity, rad/s
8
7
6
5
4
3
2
y = -183.23x + 8.71
1
0
0
0.01
0.02
0.03
0.04
Torque, N-m
Mechanical Power Output
0.12
Power, Watts
0.10
0.08
0.06
0.04
0.02
0.00
0.00
0.01
0.02
0.03
Torque, N-m
0.04
0.05
Question 3
• For a ramp of a certain slope, what load
allows the system to work at its maximum
mechanical power output?
Power to Move Up Ramp
Power to move vehicle up the
ramp at constant velocity =
mvgSinq
F=mgSin
q
q
q
F=mg
• Calculate v from motor
gear train optimum power
point angular velocity,
axle angular velocity and
wheel circumference
velocity
• Calculate m such that
mvgSinq equals
optimum power of motor
gear train
• Because of system
losses, actual best m is
less than calculated m
and is determined by
testing.
Question 4
• What vehicle can the team design that will
move the most mass up the ramp the
fastest?
?
Question Five
• What principles will students learn?
– Ohm’s Law and Kirchhoff’s voltage law
– How a battery produces electrical power
– How gears work
– How a dc motor works
– Principles of force, mass, linear and angular
velocity, acceleration, torque, power, energy,
voltage, current, efficiency
Question Five
• What skills will students acquire and
practice?
– Teamwork
– Design, development, testing, and
demonstration of a complex object
– Spreadsheet solution of problems, equation
and data plotting, and curve fitting
– Oral presentations and written reports