Hi opto masters,
I would like to ask if anyone of you had tried using servo drives with PAC?
If yes, what brand of servo drive? A little bit of info would be much appreciated.
I would just like to know if this works before purchasing a servo drive for a test.
Thanks,
JJ
I’m wondering if either @philip or @Barrett have done any work with servo drives in PAC Control…
Not sure if this is going to be applicable, but I’ve integrated Teknic Clearpath servo motors on a project. I used their Clearcore device as an intermediary. The Clearcore device is basically an industrial Arduino with an ethernet port and Teknic has various C libraries and example code for it - but you need to be able to program in C and have a good understanding of asynchronous programming if needed. I rolled my own simple command response protocol over ethernet to the Clearcore from an EPIC.
I found the Opto22 high frequency modules to be too slow to control these directly.
This sounds to be complicated you reckon? Is it better to buy a PLC to control the servo drive? then I will just connect our opto22 to the PLC and control the servo drive.
Yes, but the client already had the parts so I made it work - it ended up working well, but I have a software engineering background so it wasn’t a big deal.
Probably, let the PLC do the PWM and Opto command via modbus would be a reasonable approach.
JJ,
Yes I have done 4 jobs using Opto22 to a servo drive. If you want a real servo drive and motor, use Kollmorgen. A bit expensive, but they do exactly what you ask them to do, not close but right on the money.
The problem with most servo drives is they tend to be oriented around using fieldbus like Profinet, Ethernet IP, and so on. There are some that do Modbus TCP which is actually not too bad and I found I could do <10ms response times in talking to the automation direct drive. This is not considered real fast in servo systems, however, this is more than sufficient to give motion task commands and or get feedback.
The newest series of Kollmorgen now natively talk Modbus for control.
What you have to understand about servo drives is, they are designed to do pre-assigned motions on their own, without your controller telling it to make each move and or more incremental decisions. This means that you can tell the drive to do a whole series of moves and speed changes and so on with one simple command. You preprogram these entire moves or “motion tasks” in a table on the drive. In addition, they also have the capability of reacting to any position in the travel. This means that I can set a series of positions registers, “AND” or “OR” them together, and attach them to the drives outputs or attach them to a register that I am monitoring in Modbus. This means that instead of a trigger happening way past where the event occurred, it can happen in less than 1 ms of the event.
On the Kollmorgen job I just did, we were using A 14 HP Kollmorgen Goldline series motor (virtually indestructible) with an older series of drive (for reasons that defy logic…) so I had to use the Opto22 Profibus module to talk to the drive. This did work ok, but I would have much rather used the new 2g drive and talk ModbusTCP. This drive and motor, only using a resolver not an encoder, stops on and holds <1 micron position. IE; when it stops, it doesn’t even waffle, it’s on zero when home.
So, to answer your question, yes, and it works just great. The key is getting to know your drive and the way it works. Know that telling your drive what to do every step of the way is in my opinion, the wrong way to use a drive. These drive are very specific purpose driven, their internal timings are on the nanosecond scale, nothing in the way of a controller is going to be able to react and talk fast enough to handle that.
There are some controllers out there that are more specifically designed to talk to drives, Beckhoff and Mitsubishi come to mind. Beckhoff uses EtherCat and Mitsubishi probably does too. Ethercat is essentially the goto fieldbus for drives, it is very fast. Which is why Opto should and could make a Ethercat driver for Pac Control. As I understand it, they already have one in Controlsys. On the other hand, a fieldbus like Ethercat and Profinet are very efficient in using the bandwidth, they are also complicated and difficult to use in many respects, especially when compared to ModbusTCP.
Another company that makes pretty good stuff at a pretty reasonable price is Applied Motion. They make a really wide range of both steppers and servos and drives with a wide range of protocols. I used one of their steppers to make a coil winder follower with a 1/2hp stepper that is still in use today after 12 years of 3 shift operations. Their limitation is HP, I don’t think they exceed 1 hp.
Hope this helps, feel free to message me as well.