CHAPTER 6 ■ ROBOT LINE-FOLLOWING
Warning: A mother contacted me regarding the difficulty of removing old tape from new hardwood
flooring. She recommended the book include a warning. Now it does.
- Avoid walking on tape, because it grinds it into the floor.
- Test tape in a discreet location to ensure you can remove it without residue.
- Don’t allow tape to remain in place more than a week (or whatever the
manufacturer recommends).
An interesting aspect of blue masking tape is that it isn’t quite light and it isn’t quite dark. The upside to
this is that blue masking tape can be followed as a light line when placed on a dark background and a dark
line when placed on a light background. The downside is that the maximum contrast is less than an actual
white or black line.
There are two disadvantages to blue masking tape. First, the blue color reflects very little infrared, and
therefore is not suitable for use as a light line for robots with infrared emitters. Second, unless firmly applied,
blue tape can catch on the robot and get pulled up. Very-low-adhesion tape often suffers from this problem.
Curving and Crossing Lines
Straightaways are easy for any properly operating line follower. Sharp turns, however, can derail even a
competent robot.
With reasonable brains and an array of sensors or a vision system, you could build a line-following
robot to handle turns 45° or greater and also broken lines (see Figure 6-4). However, for the example robot,
limit turn angles to 22.5° or less. Lines should always be contiguous.
Figure 6-4. Unacceptably sharp turns: (left to right) 135°, 90°, and 45°. (far right) broken line
Figure 6-5. Acceptable 180° turn made gradually from 22.5° segments
Given a series of smaller turns over a longer distance, you can guide the robot in any direction
(see Figure 6-5).