Synchronizing 2 motors in phase and speed

Hi guys!!! I`m new here and asking for some help.
I have 2 motors to be synchronized in phase (have 2 encoders too) and in speed.
The only information i have from the first of them is that an output is set during 0º-90º and from 180º to 270º.
I have 720º to synchronize them.
I was thinking of using the PID block, but not sure how it works
Im using a ML1400
Any ideas would be great, thanx in advance

Damian

This is interesting, I would use a powerful PLC like delta or Controllogix and motion instructions.

What type motors? What drives? What motion control method?
What speeds? What precision for synchronization?
What means "output is set during 0º-90º and from 180º to 270º"?
Are the motors and the encoders similar?
Is ML1400 a firm requirement?

Sergei, I have no info about the motors, the drive is an ATV312 (TLMQ).
The speed is given by the first of the motors, that I have no access to it. Only thing I have in my ML1400 (must be this one)as a feedback is that other PLC sends me a digital output that is set to 1 during 0º to 90º, 0 from 90º to 180º, 1 from 180º to 270º and 0 from 270º to 360º(this is done with an encoder), that is to say, I can calculate the time this output is set to 1 in the 1/4 of loop of the motor, work with it, and then send to the ATV312 the correction calculated to synchronize in speed both motors.

Can you just double the size of the ATV312 and connect both motors to the output in parallel? Use separate overloads to protect each motor from overcurrent. I have used this setup on multi-motor conveyors in the past. Maybe this is not precise enough for your application.

This would normally be an app for a motion controller or a more powerful PLC with motion control capabilities - plus either servo or variable-frequency drives. I don't think something like ML1400 is up to the task here.

More Questions

Are the encoders connected directly to the motors or to the driven equipment? What is the speed of the encoders?

This should be easy but not in a PLC

A PID block is the least of your worries. The target or motion profile generator is the challenge. That requires some complex math that isn't practical to do in a PLC let alone a Micro Logix

It would be best if you were more precise about the motion. I could simulate the motion profile then.

Are the motors and the encoders similar?

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It shouldn't make any difference.

damianr said:

Hi guys!!! I`m new here and asking for some help.
I have 2 motors to be synchronized in phase (have 2 encoders too) and in speed.
The only information i have from the first of them is that an output is set during 0º-90º and from 180º to 270º.
I have 720º to synchronize them.
I was thinking of using the PID block, but not sure how it works
Im using a ML1400
Any ideas would be great, thanx in advance Damian

Click to expand...

I know you already said you have no info on motors but that could be useful.

Uhh what kind of machine is this for? Do both loads have to be in synch and if so what tolerance? Is synch both rotational speed and position??

More description would be most helpful.

Would it be possible to use a clutch that engages to lock them together when they are aligned within your 2 revolution and within 30 degree tolerances.

Dan Bentler

leitmotif said:

I know you already said you have no info on motors but that could be useful.

Click to expand...

Eventually but it isn't necessary to do the motion profile synchronizing.

More description would be most helpful.

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Yes, a chart or graph should be made that shows the position of the two motors in degrees as a function of time.

Would it be possible to use a clutch that engages to lock them together when they are aligned within your 2 revolution and within 30 degree tolerances.

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There is an IEC motion command called Clutch-By-Distance that we support that will make this easy. The two motors can be synchronized within a revolution and even faster. The limitation is the ability of the motors to accelerate.

I believe the ATV312 is a vector drive. You're only chance of success is to connect them in master slave with a frequency signal and monitor and control the modes with digital I/O. There should be a way to configure an output that represents your tolerance for "synchronization". That word especially when you throw in phase suggests a tolerance for precision way beyond your hardware, but it would be cheap to try a frequency or pulse train between the two drives (cost of shielded cable and research time).

OkiePC said:

I believe the ATV312 is a vector drive. You're only chance of success is to connect them in master slave with a frequency signal and monitor and control the modes with digital I/O.

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??? How does the slave make a smooth ramp to be in phase with the master?

There should be a way to configure an output that represents your tolerance for "synchronization".

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When doing applications like flying shears it is as small as 0.010 inches at 30 to 50 inches per second. The target motion profiles are exact. The error are only due to the mechanical design and tuning.

That word especially when you throw in phase suggests a tolerance for precision way beyond your hardware, but it would be cheap to try a frequency or pulse train between the two drives (cost of shielded cable and research time).

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Phase means that the slave must be going at the same speed but the position could be ahead or behind the master. The IEC motion specifcation has a phase command too. It makes it easy to adjust phase.

Peter Nachtwey said:

??? How does the slave make a smooth ramp to be in phase with the master?

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He didn't ask for that did he?

damianr said:

I have 720º to synchronize them.

Click to expand...

damianr said:

...I have no info about the motors, the drive is an ATV312 [Schneider Telemechanique Altivar 312].
The speed is given by the first of the motors, that I have no access to it. Only thing I have in my ML1400 (must be this one)

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"we the willing, led by the unknowing, are doing the impossible for the ungrateful. We have done so much, with so little, we are starting to get the crazy idea we can do anything with nothing!"

Or is 720 degrees his tolerance for syncronization?

If he only has 720 degrees in which to ramp from zero to syncronized at full speed and full load, he has no chance without a motion controller.

Peter said:

When doing applications like flying shears it is as small as 0.010 inches at 30 to 50 inches per second. The target motion profiles are exact. The error are only due to the mechanical design and tuning.

Click to expand...

Yes, we know what is possible with motion control, but what is the tolerance required by damianr's application?

Peter said:

Phase means that the slave must be going at the same speed but the position could be ahead or behind the master. The IEC motion specifcation has a phase command too. It makes it easy to adjust phase.

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And, reading his post without assuming he meant something different, you are right.

He can't get it done with his list of hardware.

The fact that he is thinking of doing this with a PID in a Micrologix suggests his innocence, which leads me to suspect that his opening paragraph using the word phase and synchronized, might (small maybe) mean that his definition of the words are inaccurate or just different than ours.

If I were given the same task and restrictions, I would tell the "boss" that the best I could do without a motion controller would be a master/slave follower arrangement, and he'd either say "try it" (which would be fun as long as I knew nothing would blow up) or chitcan the idea and give me something feasible to do.

But this is easy to do if you know how and have the right tools

If one has only a ML1400 and no clue then it isn't feasible.

He didn't ask for that did he?

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No, but this really isn't an option if you want to keep the torque within limits is it? A motor doesn't simply accelerate instantly to match speed with the master.

I agree that damianr is "innocent".

Typically we are asked to get things in phase as soon/quickly as possible. This typically would be much shorter than a revolution.