Robots I have built:

Quadratic: This 4 wheel drive wall follower and maze solver was built using a PCB from Peter Harrison but with my own motors and sensors.

The processor is an STM32F405 Arm device which is programmed in C

It uses Faulhaber motors driving modified Scalexrtix Pro wheels, and visible light LEds for wall sensing. An on board Gyro can help with the turns but is quite noisy and drifts a bit.

The 4 wheel drive gives it good traction but can make turning less precise than a 2 wheel mouse as the centre of turning can move around somewhere between the two wheels on each side.

It is a good and quick non contact wall follower but I have still to sort out the accuracy of turning to make it a reliable maze solver

It took second place in the Seniors non contact wall following competition at the 2014 Techfest