My mechanics are basic. Mice are constructed from any materials to hand
- wood, aluminium section from suspended ceiling, etc. The situation has
improved since I mastered the design and manufacture of printed circuit boards
at home!
The position of the wheels in a tricycle is a compromise between stability, turning circle, etc. The Bug has drive wheels spaced 9.5 cms with the nosewheel positioned to form an equilateral triangle. When turning the nosewheel is set at 90 degrees to a line from the stationary wheel. Reversing is more difficult because changing the direction of one of the drive wheels results in the mouse turning on point centred between the drive wheels and the nosewheel collides with the wall. To avoid this, the nosewheel angle is offset as shown in the diagrams, causing the mouse to move away from the wall during the first half turn and then recovering centre position during the second half.
The overall weight is about 12 ozs with particular care to keep the sensor bar as light as possible to reduce turning moment. The battery pack is sited over the drive wheels. The position of the front sensor must be far enough forward to have sensed the presence of a front wall before the mouse enters the next square and makes a decision (19 cms from driving wheels). On turning, the side sensors look for the next corner post before turn is initiated and are positioned 15 cms from driving wheels.