How do I synchronise 3 NXT motors?

[Carsten Svendsen]

I am completely out of ideas. The fact that the NXt display isn't working doesn't make it easier to see what's going on.

I've tried using the rotation sensor block (A) and output it directly to the duration of a motor block (B); The motor (B) starts spinning constantly as soon as motor (A) has changed it's rotation value, which is not what I want obviously.

I outputted the rotation sensor value (A) to the tone frequency of a sound block and it was working fine.

I can synchronise 2 motors with the move block, but I need to synchronise all 3. Any ideas?

[vl_cn]

When I want to synchronize motors, I use loops to control them.

Say there is an target position (sampled from A for example).

Now create a loop, and in it calculate the difference between the target position and current position (sampled from B).

Multiply that amount by 4 or something, then set it as power for B.

Repeat loop until necessary.

[Carsten Svendsen]

Thank you. I was thinking today after the I posted this, if a PID controller would be too complicated, but you just reminded me that I only need the P portion of it which makes it significantly easier.

Initial tests prove successful, so I am very happy