Design

Basic design
The sweeper is built with Lego Mindstorms set. It uses two servo motors, one on each side. The NXT intelligent brick is located in the middle of the vehicle and is placed very low to ease the attachment of a rag. The brick is the brain of the vehicle, it uses measurements from sensors to decide next movement steps. Figure 1 to 3 show the sweeper without a rag, from different views.

Figure 1. Top view of the sweeper

Figure 2. Front view of the sweeper

Figure 3. Bottom view of the sweeper

Sensors
The sweeper has two touch sensors in front of the chassis, used to detect obstacles. When any touch sensor is pressed, the sweeper stops, move backwards for a short distance, and then chooses another direction randomly to go forward. On top of the sweeper, there is a compass sensor, used to detect if the sweeper is stuck in a corner or a dead-end street. The compass measures the direction (0-360) of the movement of the sweeper. If the direction has little changes during a period (measures as the number of wheel rotations),

Attachment of cleaning rag
To conduct cleanning job, a rag is attached to the sweeper. Figure 4 to 6 show the sweeper with a rag attached.

Figure 4. Sweeper with rag, top view

Figure 5. Sweeper with rag, front view

Figure 6. Sweeper with rag, bottom view

The following figure shows after cleanning, dust is accumulated on the rag.

Figure 7. Dusty rag

The video below shows how the sweeper runs. Notice how the sweeper gets stuck and then gets out of a dead-end street at 1:47 and 3:25.