motion control: S7 vs. ControlLogix

i know a lot about ControlLogix motion control and practically nothing about S7 motion control. for those who have worked with both, how does motion control with the S7 platform compare to what is offered in the ControlLogix platform?

we have had some german based machine builders supply machines with S7 PLC's but they did not use any Siemens motion control products. i found that a little odd.

hagar,

Your first post on this forum kicked off the latest round of the AB vs S7 'debate' (I put this in inverted commas as it invariably ends in just a slanging match)

Your second post looks to continue the general theme although probably won't be quite so contentious.

Here are a couple of suggestions for future threads...

- What is better for control, PLC or PC based systems?
- Why should I pay for PLC programming software?

krk said:

hagar,

Your first post on this forum kicked off the latest round of the AB vs S7 'debate' (I put this in inverted commas as it invariably ends in just a slanging match)

Your second post looks to continue the general theme although probably won't be quite so contentious.

Here are a couple of suggestions for future threads...

- What is better for control, PLC or PC based systems?
- Why should I pay for PLC programming software?

Click to expand...

you forgot " how do I copy license diskettes?"

hagar said:

we have had some german based machine builders supply machines with S7 PLC's but they did not use any Siemens motion control products. i found that a little odd.

Click to expand...

What motion platform did they use? I would bet it was another German company that starts with an E.

One of the issue with Simotion is that it just hasn't been around as long as the Controllogix motion, and wasn't as easy to integrate.

Siemens is big into motion in many ways that AB is not. As far as I know AB does not do any CNC stuff anymore. Siemens has a lot of CNC stuff. I have looked at some of the Simotion stuff and it looks ok but the cost was high.

I think the key to motion control is about the same as the key to plc's. It depends on what you want to do. Some controls are good for somethings and others are better at others.

I love the Delta RMC for what I am working on now. The new stuff Peter has is great. However I used Delta Tau for 6-7 years before I changed jobs and started with the RMC. Delta Tau is great for what it does. Its very flexible and you can do a lot that you can't do with the RMC. Even when i was using the Delta Tau I did not use it for everything. For a lot of simple machines we used Fagor CNC controllers. They worked well and we did not have to make a CNC interface. We even used some AD plc's for stepper control and Baldor Mint drives for some simple servo applications. I guess what i am saying is everything has its place. I think a good control guy will use the best product for the application. Sometimes the best product is AB sometimes its Siemens and sometimes its someone else.

CharlesM said:

I love the Delta RMC for what I am working on now. The new stuff Peter has is great.

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I second Charles recommendation in general, but we would need a who lot more information to make a recommendation. I haven't got the chance to used one of their controllers yet but I've been looking into them hard. Delta's RMC75 is probably the most well thought out controller I've seen. What I like is that they have designed in many tools to help you diagnose what is wrong and dial them in.

Hagar - I don't like the hit and run tactics you have used in your first two post. In fact I find them down right rude. Involve yourself in the conversation or at least come back and tell us you appreciate our input or it did no good.

Let me know what is on your wish list!

CharlesM said:

Its very flexible and you can do a lot that you can't do with the RMC.

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If you have a wish list like the one for the Red Lion I would love to see it. I bet most manufacturers that monitor this site would love to see constructive ideas like the one about making the Red Lion displays better. I know I would.

You should also know that the RMC150, the new stuff, isn't officially released yet and isn't done yet. CharlesM is one of the first to see a RMC150. We can make commands that do exactly what you want to if you just let us know. Have you looked at the time the CPU takes per loop? You can see we have plenty of time left to add the features you may need.

If the feature you want isn't there then tell us

Even negative feedback keeps us from oscillating

Now back to Rockwell vs Siemens motion control. I am biased toward the Rockwell motion control since we make the 1756-HYD02 and 1756-MO2AS for Rockwell.

The Rockwell motion control has motion blocks that allows one to easily move axes from ladder. It is also possible to coordinate many axes from the PLC but since the PLC does all the coordination one needs to add more processors as more motion modules are added. The back plane has a Sercos like interface where position are downloaded at fixed intervals and the motion modules do fine interpolation from point to point.

The M02AE,HYD02 and M02AS, and maybe more, share the same code and are different only in the inputs or feedback. This means that you can mix and match these modules and they will all work pretty much the same. If you know one module then you know the others. If you need to mix and match feed back then this is an important feature. I insisted on this. This is a feature that we have had on the RMC100 since the beginning and now on the RMC150. Previously, the SLC500 had many motion motion modules made by many different companies. We made the 1746-QS. The problem was tech support. Each SLC500 motion module was completely different. This is not the case with the Control Logix motion modules. This makes supporting the motion module much easier since there is a unified interface. It also makes it much easier for the end user because learning one module provides 97% of what you need to know to use the other modules. I know I am sounding like a Rockwell advertisement. Just know that our motion controllers work with either Siemens or Rockwell PLCs.

first of all, i am sorry if i offended anybody. i have very little experience with the S7 platform and lots with the ControlLogix platform, but in the near future i believe that i will be using the S7 platform a lot. i wanted to hear from the grunts on what i will be getting into. i am excited to hear so many good things about S7 platform from my first post but i am interested in comparing the two more specifically in the motion control category.

in general our machines use small servo motors. product cycle times are ~2 seconds.

the machines from germany that i mentioned before came in with lenze and berger motion control.

i had no idea that this was such a sensitive issue to compare the two, but thanks for all the comments and feedback. it has been helpful.

If you have a wish list like the one for the Red Lion I would love to see it. I bet most manufacturers that monitor this site would love to see constructive ideas like the one about making the Red Lion displays better. I know I would.

Click to expand...

I to like the Red Lion post. I don't use their HMI's but I do use some of their other products. My question for starting improvement list on RMC's would be how many people here use them. That sounds like a good question for a poll. If I get time tonight I will start one.

You should also know that the RMC150, the new stuff, isn't officially released yet and isn't done yet. CharlesM is one of the first to see a RMC150. We can make commands that do exactly what you want to if you just let us know. Have you looked at the time the CPU takes per loop? You can see we have plenty of time left to add the features you may need.

Click to expand...

The RMC70 & the RMC150 are great. I like being able to do math easy. The RMC100 could do math but the new controllers do it a lot easier.

The features you have are covering everything I need to do for now. The one thing I was needing was more axis and the 150 should cover that. At my last job I did a lot of CNC type work. I know you have talked about doing some work with G code but I don't think you have anything as of yet. The PMAC handles G code very well.

/me throws his hat in the ring!
I am currently working my way through our first hydraulic motion application using a ContolLogix+M02AS card.
The learning process hasn't been too painful having made quite a few systems using S7-Technology projects. Configuration of feedback devices was painless (although the SSI rates seems a little low) and tuning is moving forward as expected (trace, fiddle, trace, fiddle... rinse and repeat). The Motion blocks in the ladder code are straightforward enough to understand and use. Fault handling could be a little more descriptive at times but is generally adequate.
All in all the motion seems pretty mature and the ControlLogix backplane/rack arrangement is good. No complaints.

Siemens motion.
We've built both hydraulic and Masterdrive MC Compact Plus systems. We've used either normal S7-319 PLCS (all tuning done at the drive level) with the MC_Open motion control blocks for the ladder code or the 315T/317T Technology PLC's.
The Masterdrives are long in the tooth now and Sinamics is where you will be pushed for new electric servo drive projects. I can't comment on these as we've not used them but the Masterdrive systems have performed well.

Step 7 Technology CPU's have two controllers in the same physical package - the PLC CPU (315 or 317) for handling all ladder logic, standard IO, communications and a dedicated Technology motion controller CPU. The two are kept very seperate with all motion functions being handled on the Tech CPU means that PLC CPU scan time does not affect Motion and vice versa. This means you can load up the PLC with large programs/IO operations without fear of impacting Motion performance. The Tech CPU has its own profibus port to attach the motion equipment to (required motion components muut run in Isochronos mode for deterministic control), onboard highspeed inputs for limit sensors etc.
The Technology configuration software is fully integrated with Step 7 manager - motion control blocks (a few more than the ControlLogix but almost identical names) are as simple to use in the ladder logic. The axis appears as a DB in the PLC with the same kind of information as the Controler_Axis_Tag in RS5000 - the only difference is that all information is available without the use of GSV's on an 8ms update rate. Fault handling is a little more descriptive with a SFB available to publish the Technology messages onto the PLC CPU for HMI's to pickup.
Tuning of the two systems looks the same although the "Expert List" parameter access in the Technology configurator lets you tinker with 100's of parameters. This may be available on the Control Logix but I haven't found it yet.
The S7-Technology is a standard S7-300 rack item so all the usual IO options are there and the PLC CPU has a profibus port of it's own for standard comms. etc.

The relative merits of Profibus/Step 7/EthernetIP/RS5000 will be argued forever in a million different forums, not here please!
They both do the same work in deffering ways. They both have quirks that must be found and stumbled over. Neither is perfect.
I enjoy using both systems as they are not crippled by major flaws and both give good performance.

I am more familiar with Siemens but am trying to be inpartial:
1) I can build a S7-Technology based system with more axis for less money than the equivalent Rockwell system.
2) The S7-Technology processor seems (and this may still be familiarity) to be more powerful at gearing/caming/synchronising multiple axis.
3) Actual performance of single axis (as this is all I've done in Rockwell) control is very good from both manufacturers
4) Control Logix networks with other Control Logix more easily than S7 ever will.

A lot comes down to familiarity - if you've only got a couple of axis and no taxing synchronisation then go with what you're most familiar with.
If you're looking at more than 2 or 4 axis or some more complicated Caming/Gearing S7-Technology may have the upper hand.

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