Datasheet

Page 22· Applied Robotics with the SumoBot
√ Run the modified program.
√ Repeat the 10 second measurement and record the servo speed.
√ Keep increasing the
LowTime constant and measuring servo speed until you note
obvious speed decay.
√ Record the maximum
LowTime value you can use without slowing down your
SumoBot in your notes for future reference.
Your Turn - Wheel Rotation Speed Measurements
You can also calculate the percent speed reduction for a given pause time. Here's an
example of how to compare the percent speed reduction between programs with 20 and
40 ms pause times. Start by dividing the wheel's rotational speed (RPM) with 40 ms
pause times by its rotational speed (RPM) with 20 ms pause times. Subtract the
fractional value from 1, then multiply by 100%. If your result turns out to be a value like
12%, that means the SumoBot goes 12% slower with 40 ms low times.
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
−×=
)ms20(RPM
)ms40(RPM
1%100reductionspeedPercent
√ Calculate the percent impact of 40 ms vs. 20 ms pause times on your servo's
speed.
ACTIVITY #3: FRICTION FORCES - YOUR SUMOBOT'S ALLIES
Friction between tire treads and the sumo ring surface is another performance issue that
you will likely examine and reexamine as you customize your SumoBot. There are two
areas that you can change to improve your SumoBot's traction on the sumo ring. The
first is to increase the SumoBot's mass from 354 grams up to the maximum allowed 500
grams. The second is to experiment with tire tread materials that will grip the ring better.
This activity explains some of the physics principles behind each of these strategies and
introduces tests you can perform to measure the resulting changes in your SumoBot's
ability to push harder against its opponent.
Measurements - Force Vs. Mass
Pounds and ounces are measurements of weight. Weight is the force a planet's gravity
exerts on an object. Mass, on the other hand, is a measure of how much stuff an object is
made of - a grand total of protons, neutrons, and electrons.