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.

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.

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 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. q F=mg F=mgSin q Power to move vehicle up the ramp at constant velocity = mvgSinq q

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 an artifact –Spreadsheet solution of problems, equation and data plotting, and curve fitting –Oral presentations and written reports