Comparing Allen Bradley and Siemens

  • Thread starter Douglas E. Weaver
  • Start date
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Thread Starter

Douglas E. Weaver

Does anyone have any information or experience between Allen Bradley and Siemens for Motion Control. I am looking at a new application and trying to decide if there is a clear advantage of one versus the other.
 
Motion control is a big word.
Can you supply more info!
How many axis of control?
What type of communication protocol you would like to use i.e. sercos, analog, profibus, RIO....
Do you need motion and PLC logic all in on package?
Is the project complex that it needs camming profiles or just gearing functions?
M.P.
 
Dennis,

I cannot speak for Siemens, but if you are attempting to do ANY kind of coordinated motion control (like you want to draw a straight or curved line in space with two axes) or you want a flexible method with which to coordinate two or more axes . . . using MotionLogix can be shall we say - cumbersome?

It is a decent controller for material handling applications that involve point to point moves - but is incredibly lousy at coordinated motion without jumping through a myriad of soft cam setups that are not intuitive. Also, tuning tools and PID loop performance is substandard. While they have a very fast servo update rate, they deal only with integer feedback data with no sub-count interpolation. As a result, low resolution feedback systems exhibit poor low speed servo control (derivative gain terms are fidgety as they are forced to work within the 200 usec fixed servo update rate and are prone to give you quantization errors.) Also, this low resolution kills the effectiveness of feedforward terms as well - when you differentiate a low res command, you get garbage.

So . . . from a trajectory generation standpoint it is not well suited to coordinated motion and from a PID Loop performance standard - it has some inherent design flaws that create poor servo performance and lacks data gathering / tuning tools to be able to really see what is going on with sufficient enough bandwidth to be of real value.

I know of some fairly complex coordinated motion applications that have been done using the MotionLogix product - but the effort to develop and ongoing effort to support them is not something I would wish on anybody who wants to be able to have a life outside of the plants where these are located.

Of course - I am sure there are a few Rockwell salesmen who would differ with these comments . . . I wouldn't expect any less :)

Tell us a little more about the application and it will be easier to make a judgment on the suitability of either of these controllers to your task.

Ken Brown
Applied Motion Systems, Inc. http://www.kinemation.com
 
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Marc Sinclair

What sort of motion control, Servo? stepper, Inverter drive how complex and what sort of HMI is needed?
 
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Douglas E. Weaver

The system will have 8 axis control. There will also be general machine control done with a PLC. So an integrated system would be nice. The type of communication depends on if I use Allen Bradley or Siemens. If I go AB, I will use sercos. The machine control will involve gearing, camming, and dancer feedback to control tension.
DEW
 
J

James Ingraham

Rockwell bad. Siemens worse.

Ask someone else, you will get the exact reverse.

Occaissionally, you might meet someone who actually LIKES the products from one or the other. The will have noticable masochistic tendencies.

Nothing is easy, and the motion control world is especially difficult. Nothing on the market has a "clear advantage."

You do not want to jump into this alone. For that reason, I recommend you base your decision on the support available to you internally and from vendors, and not on technical merits. There won't be any real technical differences: an inch-pound is an inch-pound whether it's from A-B or Siemens. I think you'll find pricing similar. So now what counts is what do you know, and who can help you know more?

-James Ingraham
Sage Automation, Inc.
 
The machine is an 8 axis system. The protocol for the system will depend on what Supplier is used. If Allen Bradley is used, I would use the sercos communication protocol with Kinetics servo system and a 5563 processor.
The applictaion will involve other machine funcitions that will be programmed using a PLC, so coordination and integration between machine control and motion control is very important. The servo system will need to do gearing, camming, and dancer controlled tension. The system will also feedback measured product information to adjust the position control system and the camming.
 
Douglas, (sorry for calling you Dennis on my last post)

Any reason you are not considering a "traditional" motion controller that is well suited to this type of application? We have done numerous applications in paper, film and building paper converting that range from 5 - 24 axes using a Delta Tau UMAC interfacing to both Siemens (via. Profibus) and Allen Bradley (via. Rockwell Ethernet or DeviceNet).

8-Axes of control are easily managed by a single controller and this allows the PLC to manage state logic in an efficient manner and the motion controller to manage motion. The other benefit to this approach is that troubleshooting of the motion is much easier with a product that is designed from the ground up to do motion.

Ken
 
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Davis Gentry

I strongly suggest that you not use either A-B or Siemens for this type of application - in my experience you will find it difficult to make it work with either one. There are a number of other motion controllers on the market which will handle this, including:

Delta Tau Data Systems Berkeley Controls MEI Galil

naturally, I think ours will do it best, but any of the above (and I'm sure a number of others) will do better than A-B or Siemens.

One interesting point - if you use a PLC for the main machine control, we have Data Highway and Profibus communications capabilities.

You already got your best advice in a previous posting - get help from someone who has done this before. While this sounds like a common application (I've certainly done it a few times, and most other motion control types out there probably have as well) it is a nontrivial task to keep all of these axes properly registered and keep the dancer off of its endpoints.

Davis Gentry Applications Engineer Delta Tau Data Systems
 
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ScienceOfficer

Douglas---

With other partisan posts noted, here's the Allen-Bradley partisan position:

This sounds like a great application for ControlLogix and the 1756-M08SE SERCOS interface. With today's Version 11 software and firmware, you will have one integrated environment within which to do commissioning, tuning, interlocking, ladder logic, motion programming, and external communication. In a comparison with only Siemens, the Integrated Architecture is the strongest reason to choose A-B. (A-Listers that have used earlier A-B motion architectures for multi-axis systems should take another look.)

Having said that, I'll now join the chorus that's telling you to get an experienced integrator involved early in the project. There's a lot of great hardware out there, with an infinite number of ways to put it together. A motion integrator will know what's available today, and can work with you to make sure you get a system that fits well in your plant.

I'd rather have you happy with someone else's stuff than unhappy with my stuff.

Hope this helps!

Larry Lawver Rexel / Central Florida
 
J
You should also consider Schneider Electric's Sercos offer. It is very well integrated into the PLC with either the Quantum or Tele Platforms using the MMS or CSY motion controllers respectively. They both coordinate 8 axes motion and can facilitate dancer control. Unlike AB's Sercos offer, Schneider's motion controllers coordinate the motion control, not the PLC! With AB and 8 axes, you will definitely need a second PLC dedicated to the motion control portion.
 
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ScienceOfficer

I have no clue about the performance of Schneider motion control systems, and Mr. Manelas has no clue about Allen-Bradley's ControlLogix. I'll therefore make no estimate of the performance of a Schneider system in this application while rejecting his estimate of A-B's performance.

To clarify Mr. Manelas' description, I'll note that ControlLogix CPUs address motion interface modules across the backplane (including the SERCOS modules) while calculating motion solutions in the CPU that owns the motion module. The system supports, among many other configurations, multiple 8- and 16-axis SERCOS modules. If you happen to have a system so big that multiple CPUs are required, that is one of the expansion options available on the ControlLogix backplane, but nothing mentioned so far in this thread indicates that is necessary for this application.

It is definitely not true that "you will definitely need a second PLC" to do this job, and my local Schneider rep seems to compete against me quite well without imagining limitations in my products.

Hope this helps!

Larry Lawver Rexel / Central Florida
 
Douglas,

Have your local Siemens distributor or Siemens application engineer give you a demo. I assure you that the 6SE70 MC drive and an S7300 or 400 PLC will do the job. The 6SE70MC drives can do all the camming, gearing and your dancer control internal to the drive. Use the PLC for logic and sending gear ratio's etc to the drive. You do not need a separate motion controller for this project.

Give this a look.

http://www.sea.siemens.com/prodmach/product/pk/pmpkov.html
 
S
Check out MachineMate before you decide. It can handle 8 SERCOS axes or 4 analog, 48in/ 32out, IEC 1131 PLC built-in, Win2K OS out of the box.
 
6

6SE70 MC experienced... VERY

Yeah, the 6SE70 MC might be able to do the job... if you have about a year to figure out how to get it to do it... without tripping over the limitations.

Been there. Done that... Won't do it again.

Yeah, get the demo, but don't take the "canned demo" at face value... get them to show you the block diagrams and make them change the functionality there using Simovis... while you watch. Then ask about F01 functionality and what it takes to get F01 activated (ask about PIN numbers and FID numbers and phone calls)

Time for some truth out there.

As for your specific question, it really depends upon your application. PLC's can be used to solve many motion applications quite easily... and can be impossible to use for solving other applications.
 
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