The SNATCH3R: line following and obstacles removal

This is the SNATCH3R, a small mechanical wonder. This model appears in the book of Laurens Valks “The Lego Mindstorms Ev3 Discovery Book” and you can build it using the Lego Mindstorms Ev3 Retail Set.

From the Small Robots repository on GitHub you can download the C# code for a program linked with the Monobrick firmware library that features three different functionalities: 

  1. Line following and obstacles removal. This is the most enjoyable! The robot will follow a black line on the floor and if it detects an obstacle, it removes the obstacle. Have a look at the video below to see it in action!
  2. Remote control of the robot using the Ev3 IR Remote. This second functionality is pretty standard: you can use the Ev3 IR Remote to control the robot,
  3. Nearest obstacle pick, and place in close proximity of the Ev3 Beacon.  The goal is to detect a number of targets on the floor using the Ev3 IR Sensor in proximity mode; then the robot has to reach each target and move it in close proximity of the Ev3 Beacon. Unfortunately, this one doesn’t work very well: once the robot snatches the target, the Ev3 IR Sensor has great difficulties in finding the beacon because its line of sight is obstructed by the target itself.

SNATCH3R main components

The main active components of the SNATCH3R are:

  • Two Ev3 Large Motor drives the left and the right caterpillar to move the robot forward, backward, and to let it turn.
  • One Ev3 Large Motor drives the gripper. Due to the interesting mechanics of this robot, just one motor is enough to close the gripper and lift the gripper arm in a pretty nice sequence. Have a look at the video below to see how it works.
  • One Ev3 Color Sensor in reflection mode detects the line to follow.
  • One Ev3 IR Sensor in proximity mode senses the obstacle along the course if any. However the Ev3 IR Sensor can be also used in remote mode to command the robot with the Ev3 Remote.
  • One Ev3 Touch Sensor.

Video and gallery

The video below shows the SNATCH3R performing a simple task: the robot must follow the black line on the floor, and if it detects an obstacle, it must remove the obstacle by placing it once on the right of the track and once on the left of the track.


The SNATCH3R: line following and obstacles removal
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2 thoughts on “The SNATCH3R: line following and obstacles removal

    • January 3, 2019 at 9:19 pm

      Hello Novian,

      Thank you for your question.
      The building instructions for the SNATCH3R are described in the The Lego Mindstorms Ev3 Discovery Book written by Laurens Valk. In this blog you can find the C# code to program it.
      If you’re interested in building instructions, maybe you can have a look at the Ev3 Tracked Explorer Mark II.



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