Pseudoposition control with FR A800 E Series + Beijer XP 340 PLC + Incremental encoder

[pedrovg 1]

Hi everyone, 

First of all, thank you all for the help so far. We are coming to the end of the project I've been working on and the help of this forum has been incredible!

We want to have pseudoposition control with a FR A 800 E Series VFD, a Beijer PLC XP 340 and an incremental encoder (0-4096) in the motor. We are using this for a telescope, and one motor revolution corresponds to the telescope moving by 0.5 degrees.

The idea would be to change the speed according to the position of the mount. We can read any parameter from the VFD into the PLC (including the encoder pulse), but I cannot get my head around how to be able to determine, at every time, the position of the mount in degrees. We can read the encoder, but this will inform us of where the mount is in a range of 0-0.5 degrees. 

Does anyone have an idea on how to do this? It would be great if the VFD had something that allowed us to keep counting encoder counts until we had a full revolution of the telescope mount, but I cannot find a way of having this.

Thanks!

 

[Goran Vuckovic 15]

I think that easiest method would be by using PLC inside function of A800, and adding one inductive proximity sensor for 0 degrees. After that everything would be more or less simple math.