precise motor controlling through PLC

[muds]

hi all,,

how precise movement of servo motor can be control through PLC(delta), any suggestion ??

and which is more Suitable...using servo motor with PLC or using ac motor with encoder feedback to plc??


thanks in advance,,

 

[widelto]

I would say, do not waste your time, efforts and money. Right tools for the right project, only use a motion controller a normal PLC will drive you crazy. Maybe Delta PLC has a motion controller go to their web page.

 

[Peter Nachtwey]

I agree with widelto. There is a lot more to motion control than you think. PLC cards are not fast and deterministic enough for starters.

 

[RussB]

All true unless you have a dedicated Motion control modual like the GE-IP PAC Motion module IC695PMM335, which is used in the RX3i system. Search at support.ge-ip.com for details.

 

[MikeMinHTown]

you will need a bridge between the PLC and the motor. The PLC is designed around discrete input/output, and for anything other than a fan or belt on/off, the PLC will not have the response or accuracy. For positioning, one option is to have a servo/controller system that can send inputs to the PLC such as HOME. in cycle, Position0....PositionX, READY, FAULT... In this way the PLC handles the program steps of position command but the controller handles the detailed work of faults, and feedback.

 

[muds]

thnks for ur reply,,!

still confuse which way to go,,

not experience of motion controller and its locally easily availability,,
using ac or dc motor with encoder feedback to plc ..can PLC read its count and instantaneous stop command?? and one more thing that position is not fixed, position depend on work requirement (through HMI).

 

[NevisGroup]

Define: 'precise'
I have run across many versions of 'percise'.
If you mean fractions of a motor revolution in fractions of a second then go with a proper servo controller.
If you mean a couple of gear teeth over a few seconds then you can probably use a PLC. (Now you have to weigh development time VS servo module).

I have done many applications of both. It is quite simple to count teeth on a sprocket over a few seconds and plug a DC motor to a stop. I have done a cutting press that holds tenths of thousandths this way (very precise).

 

[jraef]

thnks for ur reply,,!

still confuse which way to go,,

not experience of motion controller and its locally easily availability,,
using ac or dc motor with encoder feedback to plc ..can PLC read its count and instantaneous stop command?? and one more thing that position is not fixed, position depend on work requirement (through HMI).

As was said, a simplistic PLC, such as many built by Delta, is not going to give you any reasonable precision. But we actually don't know what you mean by "precise" either.

A PLC executes a routine in a linear fashion, "Begin here, end there, repeat". The more instructions you have, the more time it takes to go from "here" to "there". If in the middle f that, you tell a motor to go to a position, and try to watch that process while executing other commands, by the time the PLC finishes its scan and comes back to the motion command, it's too late.

A Motion Controller operates differently. It is always watching ONLY the motion aspects of the task and feedbacks from the servos, then fine tuning the commands to the servo drivers on the fly if the dynamics of the load change. A motion control "card" in a PLC rack will be essentially a parallel processor to the PLC CPU, offloading the motion control aspects of the task, and just updating the status to the PLC as necessary.

If your PLC does not have that available, then your definition of "precise" had better be very loose. If you do want precision and you have already invested in a PLC that is not motion compatible, you can get stand-alone servo controllers that are capable of one or two axes of motion, if that's all you need. Delta makes those too by the way.

 

[muds]

Define: 'precise'
I have run across many versions of 'percise'.
If you mean fractions of a motor revolution in fractions of a second then go with a proper servo controller.
If you mean a couple of gear teeth over a few seconds then you can probably use a PLC. (Now you have to weigh development time VS servo module).

I have done many applications of both. It is quite simple to count teeth on a sprocket over a few seconds and plug a DC motor to a stop. I have done a cutting press that holds tenths of thousandths this way (very precise).

precise means accurate stop on desired position. in application of bottle filling ,, i want to operate motor according to its need, 500ml,,or 1L etc,,
and thanks ur quote that weigh alot,,so servo controller can do filling accurately in desired quantity,,
and one more thing can PLC communicate with servo controller to changes revolutions?

 

[muds]

jraef ,, thanks,, thats clear confusions,,

do u suggest any Motion Controller?

thanks God! Not invested in any thing yet,,

 

[MikeMinHTown]

I will just throw it out there: IAI robo cylinder. from my experience IAI is simple, precise, and robust. I have seen a FESTO system that works just like IAI, but it is too flashy and likes to fault out all the time from a bad program. At the other end of the spectrum is yaskawa motoman with ultimate control, great precision....and steep cost and learning curve.... what kind of work are you trying to do?

 

[muds]

I will just throw it out there: IAI robo cylinder. from my experience IAI is simple, precise, and robust. I have seen a FESTO system that works just like IAI, but it is too flashy and likes to fault out all the time from a bad program. At the other end of the spectrum is yaskawa motoman with ultimate control, great precision....and steep cost and learning curve.... what kind of work are you trying to do?

i want to operate pump for bottle filling purpose,, (per rotation say X-m.litter), so i am trying to control rotations as per desired filling quantity,,

 

[BlueAltezza]

Doesn't Delta offer a Servo with the (motion)controller built into it?

You can program all of the motion in the drive without needing a PLC.

I know for sure Emerson (EP-P drives) and Yaskawa (MP2600iec) have the motion built into the drive, thought Delta did as well but don't know the series off the top of my head.

 

[MikeMinHTown]

("...I have seen a FESTO system that works just like IAI, but it is too flashy and likes to fault out all the time from a bad program..." I just want to clarify that the Festo units are great, the bugs are in the PLC program...)

You might not actually need a servo. For rotary indexing, say to place a container under a filler, you could go with a Camco-Ferguson type that uses a DC motor, drive, and a dwell switch.

http://www.destaco.com/rotary-index-drives.html

I have several of these running in the plant they are robust and will save you a lot of programming trouble, but I see that Camco Ferguson does have an indexer designed for servo motor use.

For my applications, we use indexers with a mechanically built in number of degrees per index, seems as though the servo unit would provide the accuracy through the servo motor's positioning...

 

[widelto]

i want to operate pump for bottle filling purpose,, (per rotation say X-m.litter), so i am trying to control rotations as per desired filling quantity,,

My suggestion is to use a flowmeter instead of a servo. There are several companies that can handle valves for filling together with flowmeters. Also with flowmeter you can have inventory.

Some other companies use weight scales for filling:
http://www.hardysolutions.com/solut...ispensing-dosing-pack/grossnet-weight-filling