Tuesday, February 02, 2010

Arduino Robot 2 - Part 1 - Forward Scanner

Work has been coming along well on the development of the second version of Arduino Robot. There have been multiple set backs; the biggest of which is my purchase of a continuous rotation servo instead of a normal one. Otherwise the bot is constructed and mostly works in tests.

The goals for Robot 2 were a step up from Robot 1:
  • Ability to continually scan in front of itself.
  • Ability to back and turn to avoid obstacles.
  • Smoother movement.
Basically Robot 2 is a wandering avoidance robot; called Arduino Robot 2 - Wandering Tank. For this to work, I needed some type of affordable sensor to place at the front of the robot; and from there the ability to look around with it. My solution was to mount a sensor on a servo. The servo would be used to sweep across a selected field of vision looking for possible collisions. So Wandering Tank has to do the following:
  • Move Forward
  • Scan left to right
  • Move backwards while object detected
  • Turn after object no longer detected 
  • Repeat 
Because only a continuous rotation servo was available without spending more money; the design was changed so that instead of targeting a degree; the servo would have some way to trigger moving back and forth. The eventual solution was to mount a light sensor just behind the servo. A disk was then cut with a slot cut out defining the open degrees of movement. The scanner would scan back and forth, reversing direction each time the light sensor met darkness. It didn't work out this simple, and I'm still perfecting the code. It does perfectly scan back and forth in normal light conditions however.

To fix the problem, a led will be added with the purpose of providing a continually known light source. The problem being that when moved from the work bench to any other area, the relative light/dark changes and the servo starts to just spin and rip wires asunder.

Until part 2, where the complete Wandering Tank project will be shared, here is the scanning servo. Any ideas on doing this better are welcome!

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