UK Micromouse Wall Follower Rules October 2021


The wall follower classes have been introduced to create a simpler contest than the maze solver competition. Wall following mice are divided into two classes

  1. those mice that sense the position of the walls by making contact with them and
  2. those mice that sense the position of the walls without making contact with them.

The maze is of the same general specification in the Maze Solver and Wall follower classes but the arrangement of the walls is different. In the wall following classes the walls are arranged so that a mouse following the left hand wall will eventually reach the goal area of the maze.

The Wall Follower Maze

  • The wall follower maze shall comprise 16 x 16 multiples of an 18cm x 18cm unit square. The walls constituting the wall follower maze shall be 5cm high and 1.2cm thick. Passageways between the walls shall be l6.8cm wide. The outside wall shall enclose the entire wall follower maze.
  • The side of the wall follower maze walls shall be white, and the top of the walls shall normally be red. The floor of the wall follower maze shall be black and finished with a matt variety of paint or varnish. The coating on the top and side of the wall shall be selected to reflect, and the coating on the floor shall be selected to absorb, visible and infra-red light.
  • The start of the wall follower maze shall be located at one of the four corners. The starting square shall have walls on three sides. The starting square orientation shall be such that when the open wall is to the ‘north’, outside wall follower maze walls are on the ‘west’, and ‘south’. The goal area of the wall follower maze shall be a single square designated by the judges.
  • Square posts, each 1.2cm x l.2cm x 5cm high, shall be placed at the four comers of each unit square (the lattice points). The wall follower maze shall be constituted such that there is at least one wall touching each lattice point.
  • The dimensions of the wall follower maze shall be accurate to within 5% or 2cm, whichever is less. Assembly joints on the wall follower maze floor shall not involve steps or gaps of greater than 1mm. The change of slope at an assembly joint shall not be greater than 5 degrees. Gaps between the walls and posts shall not be greater than 1mm.
  • A start sensor may be placed at the boundary between the starting unit square and the next unit square. A destination sensor may be placed at the entrance to the destination square. The light beam from each sensor will be horizontal and positioned 1 cm above the floor.

The Wall Follower

  • A wall follower is subject to the following size constraints –maximum width 25cm, maximum length 25cm. There is no height limit. A wall follower must be completely self contained and must receive no outside assistance.
  • The method of wall sensing is at the discretion of the builder; however, the wall follower must not exert a force on any wall likely to cause damage.
  • The power source will normally be batteries and electric motors, however alternative power sources will be permitted at the discretion of the judges.
  • If the judges consider that a wall follower has a high risk of damaging the maze it will be disqualified from the competition.
  • The wall follower must negotiate the wall follower maze; it must not climb or jump over the walls of the wall follower maze.
  • Nothing may be deposited in the wall follower maze.

The Competition

  • The wall follower is allowed an amount of time allocated by the judges, typically 2 minutes. During this time it may make repeated runs from the exit of the start square to the entrance of the destination square. Each of these run times will be noted. Any run started within the allocated time will be allowed a grace period, typically 30 seconds, beyond the allocated time in which to complete that run. The run will score if completed within the grace period.
  • The judges have the discretion to request a wall follower to retire in the event that it seems unlikely to reach the destination in the allocated time.
  • The time taken to negotiate the wall follower maze shall be measured either by the contest officials using a stop watch, or by sensors fixed at the start and the finish squares.
  • Touches: A robot that becomes stuck in the maze and is clearly unable to continue may be allowed manual intervention from the handler. The robot may be removed completely from the maze and the run restarted. Alternatively, the robot may be given minor manual assistance in the form of a nudge or it may be re-aligned within the current cell. Every such assistance is counted as a touch and will be given a touch penalty. The handler may return the mouse to the start square at any time during its allocated time. This disqualifies that run and starts a new one.
  • Scores: Scoring for the wall follower event is based on a combination of run time and touch penalties. For each robot, the shortest run time and the number of touches for that run will be recorded. Scores will be grouped by the number of touches and ordered by run time. A run with fewer touches will always rank higher than a robot with more touch penalties.
  • If any part of a wall follower is replaced during its performance – such as batteries or EPROMs -or if any significant adjustment is made, then any memory of the maze within the wall follower must be erased before re-starting. Slight manipulations of sensors will probably be condoned, but operation of speed or strategy controls is expressly forbidden without a memory erasure. The mice may have software stored in EPROMs. However, at the judges’ discretion, but not in normal circumstances, mice with battery backed up RAM may be allowed to download control software if the memory is erased accidentally during a run. The handler, in this instance, must convince the judges that the original software has been reloaded.
  • If no successful run has been made, the judge will make a qualitative assessment of the wall follower’s performance, based on the distance achieved, ‘purposefulness’ versus random behaviour and quality of control.
  • If a handler elects to retire a wall follower because of technical problems, the judges may, at their discretion, permit it to perform again later in the contest.
  • The judges reserve the right to make changes to any of the above in the interest of fair play and sportsmanship, and to ensure that all competitors have an enjoyable competition. In the event of ambiguity, the judges’ interpretation of any clauses of the rules shall prevail.