Legolab 17

Legolab 17
Date: 12-06-12
Duration: 6 hours
Group members attending: Tore, Troels & Kristian

Goal
We need  to test the robot and get rid of some bugs.

Plan   
1. Further testing of the calibration phase, the last try yesterday failed.
2. We need to correct several bugs. E.g. some strange turns, and we probably will find more during today’s testing.


Execution
1. Yesterday the robot measured several cm wrong. We need to draw the image again and do printouts to the screen to see, what the robot is doing.
The robot would sometimes oscillate between two angles when trying to face a wall. Before it would turn the difference between the two values measured by the ultrasonic sound sensors. We changed it to only turn half that value, and we put a constraint, so that it would max do 10 turns.
Half the value did not work, since the robot would try to turn 0.5 degree, and that was not possible. We instead increased the distance between the two ultrasonic sensors. This way, if the robot is turned slightly, the difference measured would be greater, and it should make the robot better at turning to the right direction. This, however, did not change anything, and we moved the ultrasonic sensors back to their original positions.
We ended up with the only change being the constraint of 10 turns.
Sometimes the right ultrasonic sensor would measure very wrong distances. We tried another sensor, but that measured a difference from the other of 3-4 cm, so we changed it back and accepted the random measurement errors.


2. The robot makes several unnecessary turns, e.g. first turn to head along the x-axis, then turn 180 degrees, then turn towards (0,0). This is done every time, the robot has finished a line and it could be combined into a single turn.
Another example is if the robot has just driven south west and the next step is northwest, it would turn 245 degrees instead of -45 degrees. We changed this to always take the shortest turn, seen in the code (*1).

Status
One of the bigger problems today is that even at full power, the robot is not able to drive straight ahead. And it was hard to find two motors, that would drive exactly the same.
We also had trouble with a dysfunctional ultrasonic sensor. It would measure strange distances, so we borrowed one from another group. Two US sensors would be tested on the same distance but the result would vary 2-3 cm.
Today was a frustrating day. Too much trouble with sensors and motors. But it mostly worked.

References
(*1) http://troelskristiantore.blogspot.dk/2012/05/legolab-code-drive.html