Difference B/W PLC and Motion controllers

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Thread Starter

Denson

What all are the main difference between PLC and motion controllers?
Which one is good for machine manufactures? What all are the reasons?
 
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James Ingraham

> What all are the main difference between PLC and motion controllers? <

Well, the line is pretty blurred these days. Traditionally, PLCs didn't do motion, period. That changed about 10 years ago, and now motion in the PLC, in ladder logic, is commonplace.

Motion controllers focus on controlling servos (or steppers). They typically DON'T use ladder logic, and don't have the same breadth of I/O and communications options.

> Which one is good for machine manufactures? What all are the reasons? <

Sorry; those questions are too vague. If I had to pick just one, I'd pick a PLC because it has more options. But there are lots of applications where a motion controller would be a better fit.

-James Ingraham
Sage Automation, Inc.
 
This is like opening a can of worms. My opinion is those who were historically Motion Control vendors and who migrated to adding logic to their motion control generally have an extremely flexible motion controller to handle very advanced applications. Those who were historically PLC vendors and migrated to adding Motion to their logic controllers generally have very good logic control but their motion control is limited, somewhat constrained to what you see is what you get.

Do motion controllers do logic? yes. do the PLC's now known as PAC's do motion? yes. But from my experience if you really need good motion control stick with somebody who has done only motion for the majority of their existence, and same for logic...
 
Modern motion controllers are closer to PAC vs PLC because except possibility to perform complex coordinated motion task for up 16 (for some controllers even up 32) servo axes, allow to perform logic task with build-in I/O or with one of field bus controlled networks as CAN, Modbus, DeviceNet,etc.
 
K

Ken Emmons Jr.

I second this logic.

I've worked with high end motion (Delta Tau PMAC), intelligent drive motion (Copley, Elmo), and PLC motion (Mitsubishi Q motion controller). While I've gotten all of them to do the job, the PMAC is the most flexible, highest performing, and cleaner in implementation(once you get it set up). I'll kind of extend what DriveGuy said and mention that if your application fits into one of the basic types any of the simple motion devices will usually work. If you need performance and/or flexibility beyond that you are screwed because the workarounds may not exist.

A colleague of mine an I believe that the revolution in machine programming will stem from motion and/or robot controllers extending their reach into general control and not from PLCs extending their reach into motion control.

KEJR
 
Ken is right, sometimes the work arounds don't exist (and you sit there frustrated wishing you had product xyz to work with)... BTW Ken, I do like Delta Tau, but there have been a few times they didn't have what I needed. It really depends on what you are trying to get done.
 
K

Ken Emmons Jr.

Hello,

Driveguy, we've had our fair share of issues with Delta Tau, but we have also used a lot of older PMACs to great success, so it is a mix. I'm looking forward to using their new Power PMAC which is in Beta testing now. From what I understand they have real function calls with parameter passing and don't require you to use their cryptic "I" variables anymore. It should make for a much more powerful system from a controls software standpoint.

Just curious, what kinds of things didn't work out with Delta Tau?

~KEJR
 
W

William Sturm

Back to the original question. A key difference between a PLC and a motion controller is the type of programming. PLC's can update a large amount of logic in a parallel or (nearly) continuous fashion. Motion controllers tend to be programmed in steps or blocks that get executed one at a time, like a state machine. Some controllers do both.

Bill Sturm
 
Yes, the Power PMAC looks pretty slick. Glad to see they have plans for PowerLink EtherCat etc. It really opens the door to use a lot of different amplifiers. I want to see a demo of the new software and hardware. It would be nice for them to have some graphical software like others, but still have all the low level hooks.

My issues I've had with DT is that I needed some larger amplifiers than they (or anyone) had at the time for use with the PWM Acc. Had an app where I couldn't get a resonating freq. filtered/programmed out (not saying that anyone else could get it done, I just couldn't get it quite 100% with DT). and you know just overall lack of patience sometimes on very diffcult apps that couldn't be accomplished with anything else...

We'll let Bill back on topic it appears he wants to discuss the difference between motion controllers and PLC's :)
 
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