Assessment: EV3 - Captain's Buried Treasure Challenge

Assessment Type: 

This Challenge is borrowed from the NXT version of the course. The Captain's Buried Treasure, Part I (see attached pdf file) Students are required to use precision swing turns to end up where "X" marks the stop. The combination of two obtuse angle turns and three straight stretches provides a good lesson on odometry navigation (using time or rotations to control movement - no sensors). Some key learning to watch for:

  • Have students begin to break large tasks into smaller individual behaviors to make them more manageable
    • Lay the ground work for the future Flow Chart lesson
  • Reinforce the importance of adding comments to their programs as an organization tool
  • Ensure students are using the prescribed swing turn and understand is implementation details
  • Repeatability is a struggle with plastic robots.
    • Factors which effect repeatability include:
      • Initial orientation of tribot - x,y position and rotation
      • Slack in drive train (motors, gears wheels)
      • Wheel alignment Wheel balance (wobble)
      • Structural rigidity
      • Uneven friction
      • Mismatched motors
      • Battery level
      • Motor control (Move & Motor Blocks)
  • Probe how students developed the parameters for their Move Blocks
  • Guess-and-check
    • Proportions (figure out distance of one rotation and scale for others, etc.)
    • Rotation sensor feedback (use Port View app while physically move the tribot the desired distance,without wheels slipping, and recording the reading for use as the Move Block Duration parameter)

Discuss why this challenge was so difficult (tedious) and introduce the idea of odometry for navigation versus using sensors to help determine position during navigation. With odometry, you only know your position at the very beginning and each error or variation compounds on the previous errors or variations.

Attached Resource: 
Education Level: 
Middle School
High School
Focus Subject: 
Robotics Hardware
Robotics Software