I am a newbie to plc's who needs to implement a 2 axis motion control project. 10 yrs ago I built a pc based machine which worked fine, all done in asssembler. The trouble was as I was learning as I went it all took so long! I now need to do something similar for my business and I suspect it will all be a lot easier to use a plc for the rotary encoder inputs, and the ac motor drive outputs, with some sort of link to a pc based user interface. Are there plc's that are suitable for this application?
Motion control
- Thread starter worsel
- Start date
randylud
Member
Well, yes, and no!
By your own admission, you are taking on a fairly complex project with little or no background. You might look at a servo drive system that is capable of interfacing to your PC. The PLC route is ok, except it can be a little daunting for a newbee. You will find that PLCs in general do not support servo apps without a fair amount of programming. Now, before all the ControlLogix and others jump all over that statement, I know they will work and do the job a little easier than their predecessors. However, you will still need the servo drives to run the motors, PLC outputs are not meant to do that. So, others will doubtless give you other options, but you should check out the servo drive systems first. They are first rate for your application and might be a better fit to your background in the old assembler days.
rsdoran
Lifetime Supporting Member
Just about any brand could. I think "down under" the main 2 brands are AB and OMRON.
AB offers options for motion control:
http://www.ab.com/motion/
OMRON probably has something similar but I am not familiar with them. I am sure BOB, Jay or someone will tell.
Its possible to get stand alone motion control from many sources.
AB offers options for motion control:
http://www.ab.com/motion/
OMRON probably has something similar but I am not familiar with them. I am sure BOB, Jay or someone will tell.
Its possible to get stand alone motion control from many sources.
guest
Guest
G
control
Last summer we did a motion control job on
an edger with the help of these people and you
may end up not even needing a plc.
http://www.deltacompsys.com/
:site:
Last summer we did a motion control job on
an edger with the help of these people and you
may end up not even needing a plc.
http://www.deltacompsys.com/
:site:
SNK
Member
AB Contrologix is Really Nice.
Problem is, the Software/Hardware will bankrupt you. The Drives are good, use SERCOS interface. The interfacing is all done through the SERVO CARD. Not the PLC I/O like the above posted. This is the ultimate closed loop control. The most expensive, too. If you are OK with Ladder logic, you will learn very quickly with the commands in RSlogix5000. I wouldn't say it is easy, but is do-able by a intermediate techie,
There are however lots of cheap Servo systems out there that will communicate over a host of comms. RS232, DH485...etc all for cheap. Under $500.00US for the drive, 2-500$ for smaller motors....depends on your app.
Good Luck
Problem is, the Software/Hardware will bankrupt you. The Drives are good, use SERCOS interface. The interfacing is all done through the SERVO CARD. Not the PLC I/O like the above posted. This is the ultimate closed loop control. The most expensive, too. If you are OK with Ladder logic, you will learn very quickly with the commands in RSlogix5000. I wouldn't say it is easy, but is do-able by a intermediate techie,
There are however lots of cheap Servo systems out there that will communicate over a host of comms. RS232, DH485...etc all for cheap. Under $500.00US for the drive, 2-500$ for smaller motors....depends on your app.
Good Luck
If you would like to have a backup pool of resources in NZ, you should look seriously at AB's ControlLogix systems. The motion control programming is totally integrated with the regular ladder programming.
As I've said numerous times in the past, the first step in any motion control project should be a detailed mechanical analysis of the axes to determine load inertia and friction, which, combined with worst case move profiles and cycle times will enable selection of a suitably sized motor, transmission, and drive combination.
Then you can start to think about the programming.
As I've said numerous times in the past, the first step in any motion control project should be a detailed mechanical analysis of the axes to determine load inertia and friction, which, combined with worst case move profiles and cycle times will enable selection of a suitably sized motor, transmission, and drive combination.
Then you can start to think about the programming.
Yes, Omron also have a large range of servo/stepper solutions available. The CJ1 is abot the most inexpensive and CX-Programmer and CX-Motion would be required and make life fairly easy for an intermediate programmer.
I do not generally do motion but if you require help post and let me know. There are guys here in Sydney that do this stuff all the time. I could put you in touch with someone, if you wish.
I do not generally do motion but if you require help post and let me know. There are guys here in Sydney that do this stuff all the time. I could put you in touch with someone, if you wish.
LadderLogic
Member
I am afraid the problem was stated too vaguely for anything but very vague advice. Two axes - what motor size? What's the torque requirements? Coordinated or independent motions? What kind of motion profiles - max distances, move times, etc? What are the demands for accuracy and repeatability? Will there be a number of pre-programmed moves that hardly ever change or are you looking for complete flexibility? Will the application be mostly motion or you would need to fit some machine sequencing, valve-clicking and data crunching as well?
Et cetera, et cetera. All the PLC mentioned above would be able to solve most of these tasks, as well as dedicated motion controllers, but in absense of these guidelines you may end up with the system on your hands that either would not perform or would be too costly and overblown for your app.
Et cetera, et cetera. All the PLC mentioned above would be able to solve most of these tasks, as well as dedicated motion controllers, but in absense of these guidelines you may end up with the system on your hands that either would not perform or would be too costly and overblown for your app.
Peter Nachtwey
Member
Finally!! Good show LadderLogic.
My first question would be, "what is the application?" Knowing the application would answer many of the specific questions LadderLogic asked. LadderLogic doesn't want to guess. That is the sign of a professional.
My first question would be, "what is the application?" Knowing the application would answer many of the specific questions LadderLogic asked. LadderLogic doesn't want to guess. That is the sign of a professional.
That is why I suggested getting in touch with a guy in Sydney that knows what he is doing with motion.
The other option would be contact the local Omron distributor. They can work through the solution and can supply ALL gear requiered for the job including servo/stepper motors, controllers, PLCs, CX-programmer, CX-Motion (really makes life easy), etc etc.
Application is a piece of sawmilling equipment. 2 independant axis each with a 2kw braked ac motor drive. No ramp up/down is needed, accuracy 0.5 mm. It just needs to keep track of position information from rotary encoder, in either an incremental or absolute fashion, receive a byte or 2 from a pc indicating the new position required, and then turn the motor on & then off accordingly. I know things wont be perfect with a barebones system like this but I cant afford to bite off more than I can chew. Each axis is incrementing in one direction only against a load before reseting against limit switches ready for the next cycle so that simplifies things.
Steve Bailey
Lifetime Supporting Member + Moderator
You've still left out some necessary information. The most important is how long can you take to execute the motion.
Let's say your PLC has a 10 millisecond scan time. That means it can only recalculate the position error and adjust the speed command to the drive (or tell it to stop) once every 10 milliseconds. If you're going to have any chance of hitting your target position, the axis has to be moving considerably less than 0.5 mm in those 10 milliseconds.
Motion controllers, whether stand-alone or PLC modules, are capable of much faster response times.
Let's say your PLC has a 10 millisecond scan time. That means it can only recalculate the position error and adjust the speed command to the drive (or tell it to stop) once every 10 milliseconds. If you're going to have any chance of hitting your target position, the axis has to be moving considerably less than 0.5 mm in those 10 milliseconds.
Motion controllers, whether stand-alone or PLC modules, are capable of much faster response times.
mgvol
Member
Whatever you decide to do, just STAY AWAY FROM PARKER COMPUMOTOR (or Compumtoker, as we had renamed it). Unless you want to spend hours of writing a ton of code just to service the I/O and to overcome the shortcomings of their product. I am one of four who now have many gray hairs because of their products buil-in "features". And did I mention the uncontrolled, max-velocity runaways....?
pushing it up hill with pointed stick
Sounds like your "drive" consists of a reversing contactor. Also sounds like you're hoping that the motor brake will give consistent stopping time/distance. If I'm correct, you're wasting your time.worsel said:
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