PmWiki | Robots / Team3Part2

Problem: How accurate is the Wait Time command? Design a simple experiment to gain a better understanding of how the Wait Time command works and how accurate it is. Experiment 1: LEDs

Hypothesis: The Wait Time Command is an accurate way to control the amount of time an action will occur.

Procedure:

- Get stop watch ready

- Enter 128 131 then 152 10 139 0 255 250 155 50 139 10 0 250 then 153, and time the how long before the color change (it should be 5 seconds) Do multiple tests to compensate for human error.

Results: I calibrated my reaction time (a source of error) as 00:00:29 and then performed the experiment 3 times, getting the same result of 00:05:29 each time. Once my reaction time is subtracted the robot is shown to be highly accurate: getting 5 seconds, as commanded each time.

Analysis: I believe that the robot’s timer is accurate(even if my ability to use a stop watch isn’t as the difference between the actual time and my error time was the predicted time.

Experiment 2: Driving

Hypothesis: If the robot drives 250 mm/s for 10 seconds and it should have gone 2,500mm or 250cm.

Procedure:

- Mark with tape on the floor where the front bumper is.

- Enter this: 128 131 then 152 12 145 0 250 0 250 155 100 145 0 0 0 0 then 153

- Repeat 1st step and measure distance between tape lines

Results: The robot went 245 cm, instead of 250cm as I predicted.

Analysis: The difference is most likely the result of acceleration, an error in velocity, not an error of the timer itself, because it takes time for the robot to get to a certain speed when starting up from being stopped.

Conclusion:

The Wait Time command goes after the command it will control, for example if you want the robot to drive for 10 seconds you enter the drive command and then the wait 10 seconds command into your script. The Wait Time command is very accurate however when doing experiments one must factor in acceleration and human error.

-Erin Webster

Response to: Doesn't this hypothesis presume that the velocity of the Create is accurate? In my analysis, I mention that the discrepancy is most likely the result of a error in velocity. This was confirmed as the timer was accurate in the LED test, where acceleration was not a factor.