The Plan and the Reality 5: Relay Race

This is one of a series of posts documenting my approach to teaching robotics in a year 11/12 Engineering Design class. The students are 16- to 19-year olds and we typically have three ~90 minute classes per week.

As a result of my students having the Robotics Educator Model built for the Wave Challenge, I like to follow on from this with a few more challenges that make use of the Robot Educator Model. I generally prefer challenges that don’t reinforce the notion that all robots are robot cars, but given that we’ve already got them built, it makes sense to use them.

The first of these challenges provides another opportunity for teams to work together, this time in pairs of teams.

Relay Race – Initial Setup

Relay Race

The challenge (short version): Pairs of robots run a relay race.

The challenge (long version):

  • Each side of the relay race track will be marked by a line of tape, about 2 metres apart.
  • You will need to pair up with another team.
  • One robot from each pair will start lined up on one side of the track (marked with tape), with the other robot from each pair lined up on the other side.
  • On “Go!”, the first drives forward.
  • When it reaches the other side of the track, the second robot starts and drives back to the first side.
  • The first one back is the winner.

Obviously the biggest challenge with this task is working out how to make the robots signal each other. It’s always very interesting to see how teams solve this problem. Over the years I’ve seen students try all the sensors available in the EV3 sets, with varying levels of success. As always, I encourage a diversity of solutions. For example, even though it’s typically quite difficult to solve this challenge using the touch sensor, I don’t discourage its use – after all, it provides a great lesson about the value of reliability and repeatability in robotic systems.

This year, my students tended to gravitate towards solutions that involved using the ultrasonic sensor to trigger the second robot.

I used the following approach to score the the teams’ performance.

  • First robot
    • Starts on a touch sensor press (1 point)
    • Stops after crossing tape on opposite side (1 point)
  • Second robot
    • Starts autonomously when the first robot crosses the line (1 point)
    • Stops after crossing tape on opposite side (1 point)
  • Stretch goals
    • Your robots are reliable – or you win the race! (1 point)
    • Your robots complete the race having passed a “baton” (1 point)
Safe following distance

Safe Following Distance

Challenge: Program a robot that slows to a gentle stop when it sees an obstacle and follows at a safe distance.

We finished the week with the first part of a series of challenges that builds towards an understanding of proportional controls.

I’ve expanded on this approach in more detail in this post: Line Following and Proportional Controls.

Also in The Plan and the Reality

This series documents my approach to teaching robotics in a year 11/12 Engineering Design class.

  1. The Plan and the Reality 3: Wave to the Distance
  2. The Plan and the Reality 4: Research Task and Tallest Tower
  3. The Plan and the Reality 5: Relay Race

View the entire series

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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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