Updated 8/21/05

 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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