Searching and mapping a micromouse maze is a relatively complex task. It involves many tasks. The most basic of these is the ability to have the robot drive around the maze in a controlled manner without crashing into the walls.
Since every maze solving micromouse has to be able to do that basic navigation, a great way to get going is to build a wall follower robot. It will run in a standard maze (classic or half-size) and be able to find the maze goal by following one wall. There is guaranteed to be a route to the goal following a left hand wall.
The aim is for the robot to get to the centre as fast as possible but it should not rely on bouncing off the posts and walls to do so. Occasional contact is to be expected but the robot should not do that as a means of navigation or correction.
Some of these robots are very simple indeed. Just one or two sensors, a couple of motors and a battery are nearly enough to get the job done. Indeed, some of the simplest robots turn out to be very quick. For the aspiring maze solver though, the robot will typically have a full set of wall sensors and an on-board computer to control everything. While most of these ‘smarter wall followers do not properly keep track of their location in the maze, it is not too hard to do and would form an excellent basis for building a full maze solver. In fact, if you want to build a maze solver, start with a wall follower because solving the maze is, literally, almost the last thing you need to do.
UKMARS maintains the rules for the UK Wall Follower Contest.