Hello,

Currently we are trying to ramp an analog output as smoothly as possible within 1 or 2 seconds for use with a hydraulic proportional valve, currently were using this ramp FB, however this ramp block is not smooth enough as you can see the handles on the valve stutter whilst moving because the steps the ramp block sends out are too big.

The ideal situation would be that we the analog output simply ramps up and down consistantly with no steps.

Is there some kind of output module or serparate component after the output that could do this for us?

Our preference would be 0..10V for easy of measuring, but other solutions are always welcome.

Were currently using a 6AG1510-1SJ01-2AB0, ET200SP with a 6AG1510-1SJ01-2AB0 analog output.

Many thanks,

Rik.

AutoGen_1367594

currently were using this ramp FB, however this ramp block is not smooth enough as you can see the handles on the valve stutter whilst moving because the steps the ramp block sends out are too big

I can't see anything, sorry.

Where do you call the FB (which OB)?

What is the scan time of this OB?

BTW, the output card's product code is invalid. 

Well, Rik, I’m not sure if one of the experts can give you a better answer than this, but all I can say is that it seems extremely unlikely to me that you need an external device to turn a low-resolution output from the PLC into a finer resolution output. I suppose what I am saying to you is that I strongly doubt that is what your actual problem is. Of course, I don’t really understand your setup properly, but my experience would lead me to read a jerky motion as more likely to be a symptom of a badly tuned loop, rather than a low-resolution signal. It could, of course, also be a symptom of an under sized actuator or what is sometimes called ‘mechanical stiction’ – unanticipated frictional additions to the load.

If the jerkiness really is caused by a low-resolution signal, then I would have to ask questions of the ramp function that you are using. Ramp functions that give a finer resolution result should not be difficult to find. There is one written by Siemens included in the Library of General Functions. I have never had cause to use it myself, but I would expect it to be a high excellence ramp function if it is written by Siemens themselves.

The last suggestion I could make is to consider if there is any setup you need to do with the hydraulic proportional valve itself. In terms of identifying your actual problem, technical support from the hydraulic valve manufacturer might be the best place to start.

Hello,

there is more then one solution.

1. you write a own "ramp"-function with a lower stepwide and call tehm at a cyclic interrupt, e.g.100 ms.

Otherwise can you use a PID-control where you use only the PI without the D, e.g. can you use the CONT_C

Call them at a cyclic interrupt (e.g 200 ms) and it should work smoothly.

regards
CaOd