Motion Control

Hi guys. I need to drive about 15 servo motors on one PLC. Can anybody give me an idea on how to do this.

Your preferences for logic controllers and preferences for servo controllers are largely going to dictate your combination of the two.

Tell use more about your application !

Do some or all of these axes of motion have to be co-ordinated, or are they all standalone ?

I wouldlike to use an Omron PLC. The motors are independently acting, if thats what you mean by stand alone. they are not necessarily coordinated.. thanx, hope you can help me on this..

Look out for the new CJ1 module to use with the CJ PLC.....
Namely the CJ1W-NCF71 - this is their brand new Position Contol Unit. It is compatiable with MECHATROLINK-II High speed Field Network. Basically u can daisy chain upto 16 W-Series servo drives. U might also need the motion software to go with (CX-Motion-NCF), i am unsure of the pricing and have never used one. Contact your loacl rep for more details or Jay might be able to shead more light....

I would strongly suggest that you sit down with your Omron rep. You are about to lay out some serious coin, and it is inumbent on you to be sure both you and they fully understand what you want to accomplish.

You can get some guidance and ideas, but don't base your decisions soley upon what you read here.

I normally use Siemens PLCs with SEW servos and a Profibus communications link.
The most I've done is 11 Servos on one PLC, but there is plenty of room left over, and I am confident that I could double or triple that number. All these servos are independently acting (Single Axis), I haven't set up one requiring similtaneous two axis control, but it looks like I will get my hands on one soon.

If you want to use Omron, then you could probably use SEW servos with the Device Net card, or you could try out the new Ethernet card.

Other brands of servos have similar communications options.

There are other methods of doing this, but this is the option I normally use.

Hi All

Just like to know what people would think of A.B and Control logix
5000 as we will have a job soon with about 8 servos and I would
just like to hear the good and the bad wiyh CLX motion


Donnchadh K.

Omron does DeviceNet well, so you could distribute that many position controllers on a network.

My personal favorite is the Ultra 3000i indexing drive, but there are handfuls of other positioners that work on that network too. I have only used SEW's Profibus interface, not their DeviceNet one.

If the servocontrollers are all meant to be in the same control cabinet, you might save money and space using a multi-axis controller. If they are distributed around a system or machine, then networked single-axis controllers are ideal.

Omron's CJ1W-NCF71 is a powerful unit. Unfortunately, it is still not available in North America (beats me why). It is a child of joint developement between Omron and Yaskawa and, in essence, is Yaskawa's motion controller (Mechatrolink II is Yaskawa's propreitary high-speed communications bus).

I would suggest using Yaskawa proper, but the learning curve may be quite steep.

I was using CLX few years ago (ca 4 years ago I think) to control
two custom pick and place robots driven by AB servos 1394.
My experience might be out of date and not nececarily reflect
current situation.
this was in time when RSL5000 was in version 2.5x. By the time
we got all parts, RSL5k grew a bit and it was called v6.x to
match firmware numbers. I didn't use motion on CLX since and
I hope they made improvements in both hardware and software.

CLX is very powerfull system but in those days half of motion
instructions didn't work or didn't work correctly.
another problem was very shaky axis tune-up and
feedback monitoring for example. we had two spectacular
crashes because of loose connection on +5V power supply
(feedback power supply).
feedback devices (resolvers) ware connected to servo system
unit which then converted this signal to pulses which was
then sent to 1756-M02E motion controllers. Normally loss
of feedback should generate alarm and disable affected axis
and stop system but this wasn't the case - motion controller
would loose position (position value would change randomly)
but continue to run like nothing happened.
The M02E motion controllers could control up to 2 axis but
nowdays they have SERCOS motion controllers that can control
up to 8 phisical axis (not sure about the number, I think it was up to 8).
It would be nice if it could also have virtual axis (or two)
even if all phisical axis are connected (M02E couldn't do that).
One colegue (very sharp and experienced guy) was struggling
to get acceptable performance out of single axis which was the only
node on DeviceNet network configured to run at max speed.
If you have just few fixed positions that servo is supposed to use
with predefined parameteres (pos, accel, decel, etc.)
and with low dmeand on curent position data, DeviceNet is ok.
Anything more will be no fun...

If you're serious

If you're really serious about this many axes of motion,
you really should be looking at something with a high
speed link.

SERCOS comes to mind,
and,
if you're thinking SERCOS, and, if you're serious, then
you can only look at BOSCH/REXROTH/INDRAMAT.

IMHO, OC

I guess I missed this at the time

panic mode said:

I was using CLX few years ago (ca 4 years ago I think) to control
two custom pick and place robots driven by AB servos 1394.
My experience might be out of date and not nececarily reflect
current situation.
this was in time when RSL5000 was in version 2.5x. By the time
we got all parts, RSL5k grew a bit and it was called v6.x to
match firmware numbers. I didn't use motion on CLX since and
I hope they made improvements in both hardware and software.

CLX is very powerfull system but in those days half of motion
instructions didn't work or didn't work correctly.
another problem was very shaky axis tune-up and
feedback monitoring .

Click to expand...

I've been doing motion control with ControlLogix since ver 2.25 and I have no idea what you're talking about. Never experienced any instructions not working correctly. That is not to say that I never misunderstood how they should work. The auto-tune procedure in my experience always comes up with gains that are way too high, but that's nothing new - same thing happened with the IMC S-class.

panic mode said:

we had two spectacular
crashes because of loose connection on +5V power supply
(feedback power supply).
feedback devices (resolvers) ware connected to servo system
unit which then converted this signal to pulses which was
then sent to 1756-M02E motion controllers. Normally loss
of feedback should generate alarm and disable affected axis
and stop system but this wasn't the case - motion controller
would loose position (position value would change randomly)
but continue to run like nothing happened.

Click to expand...

You can't blame loose connections on software.
You need to configure what action to take on loss of feedback or feedback noise - status only, stop motion, disable drive.

panic mode said:

It would be nice if it could also have virtual axis (or two)
even if all phisical axis are connected (M02E couldn't do that).

Click to expand...

You can create lots of virtual axes (I don't know if there's a limit) and you don't need a motion control card installed to do it. Apart from their real-world application, they are very useful for simulation in conjunction with the trending features built in to RSLogix5000.