shaunzer

Synchronising 1S servos

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Hi I have 2 servos. One drives on the X and the other on the Y axis. I want both to reach the target position at the same time. The servos are driving a worm gear.

Is there an easy way to do this or am I going to set up time delays or something along those lines.

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Not familiar with the actual motion commands in Omron.  The equivalent, I would consider (in Rockwell terms) is the MAG (Motion Axis Gearing) where the X would be the master and the y would be the slave.  This also ties their encoders together and allow for them to move in a coordinated fashion.

I'm sure the Omron experts on here can give you a better pointers.

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Yes, it would be a gearing function as pcmccartney1 has pointed out. Look up the MC_GearIn, MC_GearInPos, and MC_GearOut functions.

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I would create 3 axes.  One for each of your real servos and one virtual axis.  I would gear both to the virtual axis using the MC_GearIn Function block and then command the virtual axis.  

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Just now, Michael Walsh said:

I would create 3 axes.  One for each of your real servos and one virtual axis.  I would gear both to the virtual axis using the MC_GearIn Function block and then command the virtual axis.  

That's an interesting approach. May I ask why you would recommend this rather than gear in the 2 physical axis?

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I just like the clarity of it, I think. This way both physical axes are treated equally and programmed the same.  Neither is the master.  Also, with the _mcLatestCommand option, the servos have to be in the proper order (node number-wise) on EtherCAT.  The master would need to be a lower EtherCAT node number.  Doing it this way just removes any chance of getting that wrong.  

It used to be that the performance would be better with this option due to the fact that if both servos were tuned the same, the following error to the master axis would be the same and the axes would achieve closer synchronization.  However with the _mcLatestCommand option, both servos would get the exact same command if you geared them together without a virtual axis.  

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That's great information. Thanks Michael!

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Thank goodness the experts stepped in!

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Thanks for the info, clears some stuff up. I'll give that a go

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Which PLC you use? If it is allow motion control axis then you can create an axis group. With a group you can move syncronized the axises.

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If the end goal is an interpolated move where the axes both reach the target at the same time, why are you not using the group motion and interpolated control function blocks?  Why are we talking about virtual axes for that?

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3 hours ago, Crossbow said:

Why are we talking about virtual axes for that?

For the reasons that he answered me. I like the virtual axis idea for a unison or a true geared type motion.

The original poster did mention an X and Y axis so I would agree with you, this does sound like an interpolated move. I've never used them. He's got a lot of options, which is better than having limitations. :-2

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4 hours ago, Crossbow said:

If the end goal is an interpolated move where the axes both reach the target at the same time, why are you not using the group motion and interpolated control function blocks?  Why are we talking about virtual axes for that?

I took his original post to be two servos driving two sides of the a single device.  I may have misread it, but he says they are driving a worm gear (singular).  Of course if this is driving two worm gears in an X-Y Cartesian arrangement, then linear interpolation is the correct course of action.  

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