Figure 8

Here is a simple idea that I often use when I need a quick challenge for speedier teams to work on while they are waiting for the rest of the class. For example, when I’ve asked all teams to make a standard build such as the Robot Educator Model.

Figure 8 challenge

The challenge

Program a robot to drive around four chair legs in a “figure 8” pattern.

Equipment required

A four-legged chair or equivalent.

As can be seen in the photo, I usually use a few pieces of tape to mark the starting line and the position of the chair legs.

Teacher notes

Although this is of course a fairly straight-forward challenge, I find it useful for exploring different ways of making a two-wheeled robot turn, including:

  • turning on the spot (with both wheels turning in opposite directions),
  • one wheel fixed, or
  • both wheels moving forward but at different power levels.

Having successfully completed a single “figure 8”, I like to challenge teams to see how many times their robot can perform the circuit without intervention. This raises questions of reliability and repeatability, and leads nicely into a discussion around the limitations of dead reckoning. For more on this topic, see Why Doesn’t My Robot Drive Straight?

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Rob Torok

I'm a teacher in Tasmania, Australia, and have been using LEGO MINDSTORMS with my students since 2001. I'm the editor in chief for LEGO Engineering (this site) as well as the content editor for LEGO Education Australia (

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