Sync RMC's

Just an idea.

I did a test gearing an axis accross Profibus. I took my RMC70 sent axis 0 position out on Profibus. Read this in my PLC sent it back to the RMC. Took this address and set gearing to axis 1. It worked however at 1:1 it was a little ruff. At 2:1 it was smooth enough for some applications. The PLC had a scan time of 10ms. I was thinking of doing the test again with a 5ms scan time.

If you could send a message from one RMC to another on the network without using the PLC I think this could be a good option.

Your thoughts?

Great fourm. Good job guys.


Glad you like the forum!

Yes, syncing RMCs over the network would be cool. The issue is that then we have to become a master for the communications, which would require a lot of work and redesign. Another issue is that the position data would not be updated as fast as the feedback, which cause jumpiness, but that could probably be filtered out fairly well. Perhaps if we used Ethernet/IP I/O, it might be fast enough and consistent enough, and may not even be that much work. Notice that “not much work” is a very relative term - we have lots of features that we always want to put in, but only so many resources.

However, you can just use an RMC150E and sync up to 8 axes. Do you really need more than that, or are you just working on an academic exercise? Do you need to do it over PROFIBUS?

Jacob Paso

I thought it was a good first post. What I need is a good way to use my Siemens PLC with an RMC150E. I think the best way would be an RMC150P I just didn’t want to ask for it again.

I don’t know much about Ethernet/IP I/O but that is what I was thinking. Just food for thought.

What’s your time frame for needing the RMC150E to communicate with the Siemens?

Well I just went from an RMC100 to 2 RMC70’s so any time would be great. I know you are working on it. Unless I got a big job that I just could not do with the two 70’s. I would just wait until you have Profibus on the RMC150.

There are a couple of ways to synchronize axes over mulitple RMC. The best way is to use an output from the PLC that is wired into all the RMCs. This input would be a start execution. The PLC would download the commands the all the RMCs and the start execution bit is set high by the PLC. All the RMCs will start at the same time. I see this as the easiest.

If there is a run/stop input one can stop the axes and restart the command. This would provide an ‘inching’ or jogging feature.

I have an application I’m working on right now to sync 14 axes. Thanks for the start command note Peter, my question is stopping on error from axes on different RMC’s. It is a fairly slow application, but is a large mass and it is critical not to get this load out of sync. In other words if I have a fault on one controller (axis) I need all to stop.

You could use a discrete output on each RMC and wire it to an input on the other RMC(s), then program the RMCs to halt the axes when the input turns on. This would be the fastest method. If you are using a host controller, such as a PLC, it could do something similar, but it would be slower.

The RMC15x and RMC10x have two digital outputs and two inputs. The outputs are SSR relays. The can be used to sink or source. In this case we want the RMC outputs to source current for the RMC inputs. An output from each RMC can be connected in series to a 24 volt supply. The other side is connected to one input each of the two RMC. This way if either output gets a fault it will open its relay and the inputs will not be energized by the 24 volts. If power fails the RMC will also fault if the 24 volts is not also powering the RMCs.