Find the LEGO Mindstorms motors that work best for you Pro Preview

The LEGO Mindstorms EV3 set comes with two LARGE motors. But even though these motors look almost the same they are not quite the same. There are always some differences in their behaviour. If you have more than two motors, because you bought them or you won them somewhere at a competition, it is worth doing an experiment to find which pair of motors works best. 

  • #668
  • 09 Jan 2018
  • 2:38

Experiment to find Compatible Motors

Take two of the motors and make the robot move forward ten times. Measure and record the difference. Then take another pair of the motors and repeat the above experiment. At the end, you should find the pair of motors that work best. 

All the motors are compatible with each other, but by finding the once that are most compatible you will have the robot move in a straighter line.


When trying to move forward with the robot it might slightly move to the left or to the right. And this might be because of the motors. Although the motors look very similar they are not exactly similar and there are always some differences between the motors. So, you should try to find the best pair of motors that works for you. How do we do this? Let's discuss. When you buy the LEGO Mindstorms EV3 set it comes with 2 large motors and 1 medium motor. And that's fine for most of the cases but if you have additional motors probably because you won them in a competition or you've bought additional motors you should try to experiment with the motors. And to find the pair of motors that works best for your robot. Why? Because if you see on some of the videos that when the robot moves forward, it could make a slight mistake and turn to the left or turn to the right. And you can then just switch the motors and switch the ports and you'll see that the reverse will happen. So, it is not a problem of the construction, it's not a problem of the program it is sometimes just a problem of the motors because the motors are not perfectly similar and equal. There are some differences and the PID algorithm is trying to keep the robot moving in a straight line but there are some differences. So, the way you experiment: First, you take the robot and you move forward with the robot like 10 times and you record the different values of what is the error at the end. Then you change one of the motors for example, this motor here with another motor for example, this motor you change it and you test again. Move forward and record. Then you take the one that you have, put it on the other side and you do all kinds of combinations with the motors and at the end you have the recordings for each pair of motors and how the pair behaves and how precise the robot is at the end. And this is how you find the best pair of motors and you should try to use this pair from now on for this specific robot.

Courses and lessons with this Tutorial

This Tutorial is used in the following courses and lessons

Image for Moving Straight with LEGO Mindstorms EV3 robots
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