This small robot was designed to demonstrate
      precise odometry with Mindstorms technology. Thus the name "ODObot.
      I also wanted to see the issues with a drive belt system, since
      my current project - VacBot uses belts to drive it. To achieve
      repeatable precise increments in movement, a cam was used to
      push a switch in every 1/5 rotation of the wheel. Thus by counting
      the clicks, you can tell how far you've gone and thus navigate
      to a goal destination within reason and tolerances of the system.
      The goal was to start at one point in a maze that had been modeled
      after dozens of competition mazes to include sharp turns and
      long distances to travel straight.

      
Problems solved.

      
My first issue
      was the fact that the robot did not go straight because of speed
      differences and wheel alignment with such a crude construction
      method. This was solved by putting a friction coupling element
      between both drive motors so the speeds were averaged out.

      
Second was resolution.
      With only 1/5 wheel positional clicks, the turning was not exactly
      90d. By holding one wheel stationary during a turn, the outer
      wheel had twice the clicks it had to go to turn, and thus doubled
      my resolution on turns to an acceptable level.

      
This was the first
      robot programmed in Robolab, a superior interface to the bricks
      processor, allowing you to do just about anything most of the
      C based programs will do.

 Click on the image for a larger view
 

      
Side view
      showing the pulley drive system to the small gear train on the
      wheels.
 

      
Top View.
      Both sides were built as separate identical parts that were mirror
      images then combined later.
 

      
A standard
      caster wheel on the rear.
 

      
The back
      view, showing the extensive use of locking struts to keep the
      robot connected very rigidly. It easily passed the "throw
      it on the carpet test" and didn't fall apart.
 

      
Ok, so
      here's the maze made from formica topped particle board bought
      at Home Depot, and black and red tape. It was designed for a
      much smaller robot, so was tight fitting in some areas!
 

      
Movie Clip  (1.4MB)
This
      fairly long movie shows the typical and very repeatable performance
      ODObot1 in the maze, and thus proves that precise navigation
      with even crude Lego technology is possible. (with sound!)

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