S120 Speed control-> Determine Motor Position

I am facing this problem. I have an asynchronous motor with an incremental encoder of 1024/revolution. I want to implement speed control with encoder (control type) but I would also like to extract somehow from the Drive the position of the motor. I would like to calculate in the PLC program the actual motor position (in OB35 for example) by integrating some kind of encoder signal that I could receive from the drive.

I understand that with "speed control" the S120 does not (?) provide the position to the PLC directly, or does it somehow?With control scheme "basic positioner" you work with positions, but I want to provide directly via an analog value the speed setpoint, so I want to stick to speed control with encoder.

The only thing I found is parameter p479, which is some kind of encoder signal, but this signal has a very strange behaviour. In the expert list this value starts from 0..32767 and after the first overflow, it changes somehow its variable type and continiues adding till a very big value that is not provided to the PLC. If I put parameter p479 at a telegram to the PLC, then I receive a Byte which overflows after 32767 and starts from the beginning while the parameter in S120 continues to grow unlimited... I don't get that..

Is there any better way to get the position of the motor via some kind of other parameter? The only idea that I have with this way, is to read the Delta_X (subtract the current encoder signal from the value I had at the previous OB35 call) covered between two OB35 calls and somehow extract the distance covered and then convert it to some real number, which will be added/subtracted from a total sum.. Is there something better than this?

Thank you!

You can activate the functionmodule positioncontroller by a right mouse click on the drive. Them set p2550 =0 and set p1160 =1 (? Activate setpointenable again ) 

On the mechanic mask you can configure your mechanic and you will get the position in r2521.

Hello Zako,

how can I activate the position controller function module? Through the DDS configuration you mean? Where do I have to 'right click'? Thank you

Anyway, I did find some kind of solution: I send p479[0] (current motor encoder[1] signal) via a free 999 Telegram to PLC. From there I made a function that reads every 10ms the encoder signal and it integrates the current Delta_X traveled from the encoder during those 10ms.

Am I doing something wrong in starter?

Thank you!

I wonder though how we can reference the axis position. Is there some kind of parameter, which is resetting the total distance travelled from the motor?   [Edit]: Im looking at function diagram 4010 in List Manual, could it be p2515 or maybe p2514?

Thanks!

... yes p2514, p2515 for homing of incremental Encoders,

oder p2507 (?) for absolute Encoders (I am not in the Office now ).