Imagine the setup in this image: enter image description here

We have a platform resting on a fulcrum. On both sides, at the same distance from the fulcrum, we have 2 motors which control the height on either side of the platform by rotating.

If the left hand motor were rotated by +500 encoder counts, can we assume that right hand motor would need to rotate by -500 encoder counts to compensate for the change in height?

If not, how could I calculate the required change in encoder counts?

  • $\begingroup$ How is the platform connected to the motors? What happens when the motors rotate? Please edit your question accordingly. $\endgroup$
    – Robin
    Commented Jan 22, 2016 at 8:45
  • $\begingroup$ Is the platform rigid? $\endgroup$
    – Karlo
    Commented Jan 22, 2016 at 9:25
  • $\begingroup$ Do the motors have an eccentric weight on them? $\endgroup$
    – Ethan48
    Commented Jan 22, 2016 at 14:09

1 Answer 1


If the two motor systems are identical other than being mirror images of each other, then yes, each motor will rotate the same amount.

This is not true if the angles are a little out of phase, the lengths of the rods are different, or the positions relative to the fulcrum are different.

  • $\begingroup$ While this is true, the naivete of the OP's wording suggests he could benefit from some basic trigonometry discussion about similar triangles. $\endgroup$ Commented Jan 22, 2016 at 12:37
  • $\begingroup$ @CarlWitthoft I'd be happy to have that discussion...:) $\endgroup$
    – M-R
    Commented Jan 23, 2016 at 13:17

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