Petit Slalom for Lego MindStorm

Petit Slalom

Teams of 1or 2 (or more) students will program a LEGO® Mindstorm Robot to travel through a slalom course made on the rough side of a half-sheet of tempered hardboard.

In a slalom course, competitors travel from the starting gate to the finish line while maneuvering through a series of gates.

Teams may desire to change or modify their robot program before, during, or between rounds of the competition.


    Tracks and Gates

  1. The track consists of a 3 ft. by 6 ft. piece of tempered hardboard as shown in figure 1. Robots will run on the rough side. The track is unadorned with sides and the spacing dots are done in marker. Tape or paint is not used on the track to ensure that the surface provides consistent traction.
  2. A gate consists of a pair of 9 ounce party cups (gate markers) placed upside down 12 inches apart (on centers). One cup will be green (or a plain cup marked with an “L”) and the other cup will be red (or a plain cup marked with an “R”).
  3. Robots must pass forward through the gate with the green cup on the robot’s own left and the red cup on the robot’s own right.
  4. One special (optional) gate consists of a green cup with a horizontal band of masking tape (or a plain cup marked “LB”) and a red cup with a horizontal band of masking tape (or a plain cup marked with an “RB”). The robot must pass backwards through this gate with the green striped cup on the robot’s own left and the red striped cup on the robot’s own right.
  5. Dots in the drawing (figure1) indicate possible positions for gate markers. The dots are 12 inches apart. The lower left dot in the figure is at (x, y) coordinate (1/2 ft, 1 foot) the upper right hand dot is at coordinate (2 1/2 ft, 5 ft).
  6. The location of the starting line is shown in figure 1. The robot may start with the axle of the drive wheels on the starting line to achieve a consistent start. The starting line is not a gate.
  7. The finish line will consist of a paving brick placed at one of four locations abutting the edge of the track. These positions are marked as A, B, C, and D on the figure 1.

    Conduct of Each Round

  8. At the beginning of each round, the judges will place the finish line and up to four gates on the track. A brick (in addition to the finish line) may be placed on the track to encourage robots to go through the established gates. The arrangement of gates and the finish line will then be revealed.
  9. Each team will then program their robot to travel the course.
  10. When each team completes their programming, they will place their robot into the line (queue). Part of the score will be based on the position of the robot in the line (order of testing). The run will start when all robots are in line.
  11. A robot removed from the line (queue) except to travel the course can only be placed back at the end of the line.
  12. A maximum time of 15 minutes will be allowed for programming. No robot will be allowed into the line (queue) after that time.
  13. After a run, robots may be placed back into the line for a second attempt using the same programming.
  14. If time allows, the track will be rearranged and a second or third round will be performed. If additional rounds are completed, the team’s best score from each round will be added to determine the team’s overall score and the winners for the challenge.


  15. Scoring will be based on time and deductions. The time will be the time required to travel from the starting line to the finish line. Time starts on first movement. A maximum of 20.0 seconds will be recorded. Times will be deducted from that score as follows.
    • 4 seconds/(place in line +1). This means that the team first in line has a deduction of 2 seconds, second place has a deduction of 1.33 seconds, third place has a deduction of 1 second, forth place has a deduction of 0.8 seconds etc.
    • 3 seconds for each gate that the robot travels through cleanly (in the correct direction without touching a gate marker).
    • 2 seconds for each gate that the robot passes completely through in the correct direction but touches a gate marker (the gate marker moves but the robot stays between the dots on the track).
    • 1 second for each gate that a portion (but not all) of the of the robot passes through (the gate marker moves and the robot travels over a dot), or that the robot passes through in the wrong direction.
    • 2 seconds for touching the finish line.
    • 1 second for moving backward at least 1 inch and doing a victory dance after touching the finish line.
    • 1 second for having the best victory dance.
  16. There will be a 10-second penalty for passing through a gate out of order. This penalty is incurred when the robot passes through a gate (or touches the finish line) without having at least attempted to pass through the previous gate in the correct direction. This penalty may not be used to make a score worse than 20.0 seconds for any round.
  17. Each round ends when robots have had at most two opportunities to run.
  18. The team with the shortest time (including deductions) to run the petite slalom will be declared the winner of that round.
    • Example 1: The robot first in line passes completely through one gate in the proper direction, clips a marker on the next gate, and then falls off of the track. The score will be 13 seconds (20 – 2 – 3 – 2 = 13).
    • Example 2: The robot third in line starts, then passes cleanly through one gate, bypasses the next gate completely (not programmed to go through), touches the third and final gate, touches the finish line in 16 seconds and then moves backwards 1 inch. The score will be 17 seconds (16 –1 – 3 + 10 – 2 – 2 – 1 = 17).
Last updated 13 June 2015
© P. A. Wiedorn 2007