This is the hardware I designed for our final project for SFU's ENSC-182 robotics class. My partner wrote the sonar-based maze-solving software in RobotC; I wrote the code that plots and updates the maze on the display as the robot explores it.
About this creation
(Note: the robot will draw solid walls as the sonar detects them, and plot X's in the dead ends, but this image doesn't show it.) It also makes frusrated R2-D2 style beeps when it encounters a dead-end.
Note that there is a hollow space between the motors and the NXT microcontroller; this space is used for the rechargeable battery pack that our class uses, but there is no part in Lego Digital Designer to represent it.