UK Micromouse Rules

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UK Micromouse Maze Solver Rules

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  1. The Micromouse Maze
    1. The micromouse maze shall comprise 16 x 16 multiples of an 18cm x 18cm unit square. The walls constituting the micromouse maze shall be 5cm high and 1.2cm thick. Passageways between the walls shall be 16.8cm wide. The outside wall shall enclose the entire micromouse maze.
    2. The side of the micromouse maze walls shall be white, and the top of the walls shall normally be red. The floor of the micromouse maze shall be made of MDF and[1] finished with a matt variety of black paint (blackboard paint). 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.
    3. The start of the micromouse 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 micromouse maze walls are on the 'west', and 'south'. At the centre of the micromouse maze shall be an opening composed of 4 unit squares. This central square shall be the destination.
    4. Square posts, each 1.2cm x 1.2cm x 5cm high, shall be placed at the four comers of each unit square (the lattice points). The micromouse maze shall be constituted such that there is at least one wall touching each lattice point, except for the destination square.
    5. The dimensions of the micromouse maze shall be accurate to within 5% or 2cm, whichever is less. Assembly joints on the micromouse 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.
    6. 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.
    7. Multiple paths to the destination square are allowed and are to be expected.
  2. The Micromouse
    1. A micromouse is subject to the following size constraints –maximum width 25cm, maximum length 25cm. There is no height limit. A micromouse must be completely self contained and must receive no outside assistance.
    2. The method of wall sensing is at the discretion of the builder; however, the micromouse must not exert a force on any wall likely to cause damage.
    3. The power source will normally be batteries and electric motors, however alternative power sources will be permitted at the discretion of the judges.
    4. If the judges consider that a micromouse has a high risk of damaging the maze it will be disqualified from the competition.
    5. The micromouse must negotiate the micromouse maze; it must not climb or jump over the walls of the micromouse maze.
    6. Nothing may be deposited in the micromouse maze.
    7. Each micromouse should be fitted with a suitable hook or loop, for lifting the micromouse out from the centre of the maze, should this prove necessary. Contestants may not be allowed to climb over the micromouse maze.[2]
  3. The Competition
    1. The time taken to travel from the start square to the destination square is called the "run" time. Travelling from the destination square back to the start square is not considered a run. The total time taken from the first activation of the micromouse until the start of each run is also measured. This is called the ‘maze’ or ‘search’ time. If the micromouse requires any manual assistance at any time during the contest, it is considered ‘touched’. Scoring is based on these three parameters.
    2. Each micromouse is allowed a maximum of 10 minutes to perform. This may be reduced if time is limited. The judges have the discretion to request a micromouse to retire in the event that it seems unlikely to reach the destination in the allocated time.
    3. The scoring of a micromouse shall be obtained by computing a handicapped time for each run as follows:
      • Score Time = Run Time + Search Penalty + Touch Penalty.
      • Search Penalty = 1/30 1/100 [3] of the maze or search time, in seconds, associated with that run.
      • Touch Penalty = 3 seconds plus 1/10 of the run time, in seconds, [4] if the micromouse has been touched at any time prior to the run.
      For example, if a micromouse, after being in the micromouse maze for 4 minutes without being touched, starts a run which takes 20 seconds, the run will have a handicapped time score of 20 + 1/30100 (4 x 60) = 28 seconds.
      However, if the micromouse has been touched prior to the run, an additional touch penalty of (3 + (1/10 x 20)) 3 seconds is added giving a handicapped time score of 33 seconds.
    4. When the micromouse reaches the destination square, it may stop and remain at the micromouse maze centre, or it may continue to explore other parts of the micromouse maze, or make its own way back to the start. If the micromouse stops at the centre, it may be lifted out, manually, and restarted by the handler. Manually lifting it out shall be considered touching the micromouse and will cause a touch penalty to be added on all subsequent runs. If the micromouse does not remain in the destination square at the end of a run, it may not be stopped manually and restarted.
    5. The time for each run (run time) shall be measured from the moment the micromouse leaves the start square until it enters the destination square. The total time on the micromouse maze (maze or search time) shall be measured from the time the micromouse is first activated.
    6. The time taken to negotiate the micromouse maze shall be measured either manually by the contest officials, or by sensors set at the start and destination. If sensors are used, the start sensor shall be positioned at the boundary between the start square and the next unit square.
    7. The mouse handler is permitted to pick up the mouse for the purpose of minor maintenance such as the cleaning of tyres when, and only when, the mouse is in the start square. Such maintenance will not incur a touch penalty.[5]
    8. The starting procedure of the micromouse shall be simple and must not offer a choice of strategies to the handler. For example, a decision to make a fast run to the centre as time runs out must be made by the micromouse itself. The starting procedure shall be submitted to the judges when the micromouse is registered on the day of the contest.
    9. The micromouse handler is given 1 minute, from the moment the micromouse is required to start, to make adjustments to the micromouse sensors (calibration). However, no selection of strategies must be made and no information on the micromouse maze configuration may be entered or captured in the memory.
    10. The maze or search time clock will commence after the expiry of the 1 minute time limit even if the handler is still making adjustments to the sensors.
    11. If a micromouse "gets into trouble" the handlers can ask the judge for permission to abandon the run and restart the micromouse at the start square. A micromouse may not be re-started merely because it has taken a wrong turning. The judges may add a time penalty for a restart. The judges' decision is final.
    12. Modification of the control strategy of the micromouse is not permitted at any time once the mouse has entered the maze.
    13. If a micromouse elects to retire because of technical problems, the judges may, at their discretion, permit it to perform again later in the contest. The micromouse will then be deemed to have taken an extra three minutes search time (i.e. if a micromouse retires after four minutes, then when re-starting it will be counted as having taken seven minutes and will have only three more minutes to run). This permission is likely to be withdrawn, if time is limited.
    14. The judges will use their discretion to award the prizes, which in addition to the major prizes may include prizes for specific classes of micromouse -e.g. lowest cost, most ingenious, best presented, most entertaining etc.
    15. Before the micromouse maze is unveiled, the mice must be accepted and kept in view of the contest officials. The handlers will place the mice at the start under the officials' instructions.
    16. 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.


  1. Seems like an unnecessary restriction - PJH
  2. This is almost never used. A more accessible maze would remove the requirement. PJH
  3. We would like to change the maze time divider up from 30 to 100. This makes it less of a penalty for subsequent runs after the first one and keeps the encouragement for efficient searching. DH+IB
  4. We should simplify the touch penalty to be just a straight 3 seconds - I.e. remove the current one tenth of the run time. DH+IB
  5. We think that if a mouse comes back to the start cell and is stationary, the owner should be able to pick it up and clean the tyres etc without incurring a touch penalty. DH+IB