A line follower on an improvised strip of tape can pass one run and fail the next. Before changing the control gains, make the track reproducible. Record its dimensions, the surface, and the placement of the tape. Put a start mark where you can align the robot before each run.
Keep one variable moving
Use a fixed speed command while you compare sensor positions. Measure the sensor’s height from the track and photograph the mount from the side. Record battery voltage at the start of a run, since a change in the power source can confuse a comparison of steering changes.
Log the sensor readings beside the motor commands. A robot that leaves the line may have failed to detect the boundary, or it may have detected the boundary and lacked enough steering response. You need both signals to separate those cases.
Write the failed run
Describe the point where the robot left the track. Give the turn direction and the preceding straight length. A note such as “lost the line after the second left bend” gives you a place to begin. “Bad tuning” gives you little to check.
Use the next revision to test one proposed cause. Keep a table of changes and run identifiers. This sample log defines a test plan; replace it with your measurements and photographs once you have built the robot.
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