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Author Topic: Need Help! DSPMC Setup  (Read 26030 times)

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Re: Need Help! DSPMC Setup
« Reply #30 on: April 25, 2013, 04:28:41 PM »
Still get the Z Axis drop.  Some one out there has to have experienced this before, anybody?!?!

Rufi, the servo drive usually has a setting to advance or delay the on/off of the brake output with respect to the servo being on or off.  On these deltas the offset can be as much as 1 sec.  Is there any way that there can be an output selected to be a "brake" or otherwise special output that turns off with a set advance of the pid loop.  Or add an option to have the PID loop shut off a bit late compared to the outputs in an estop/reset/error event?  This would solve the issues.  It could even be only on one axis, doesn't have to be all 8, or a selectable number of axes.  I don't know what this would entail in the plugin/firmware, I'm sure its not as easy as it sounds, but I'd think would make for a better solution.

Should I not have the servos in torque mode as was suggested earlier?  I had a much harder time getting any motion in speed mode, but I wonder if that would work better as the Z shouldn't drop as it would be trying to maintain zero speed rather than zero torque.  Thoughts/experiences on this?
Re: Need Help! DSPMC Setup
« Reply #31 on: April 25, 2013, 04:30:12 PM »
are you using output 44 or 43 for the brake?

this will turn the brake on when PID is OFF:

while(1)
     SetDSPData(44, NOT(GetDSPData(35)) )
wend


This version will turn the brake on when PID is ON:

while(1)
     SetDSPData(44, GetDSPData(35) )
wend

dont know what polarity is needed in your setup.

thanks



Re: Need Help! DSPMC Setup
« Reply #32 on: April 25, 2013, 04:32:51 PM »
Output energized is brake off.  So the second one is what I did.  43 is actually the brake, I was using 44 to test the macros as nothing is attached to it, less risk :)
Re: Need Help! DSPMC Setup
« Reply #33 on: April 25, 2013, 04:36:20 PM »
so this one then:

while(1)
     SetDSPData(44, GetDSPData(35) )
wend


this is going to energize and de-energize the output within couple of milliseconds at most.  is that not fast enough?  may be there is delay in your brake mechanism.  the controller I believe is doing it right.

rgds
Rufi
Re: Need Help! DSPMC Setup
« Reply #34 on: April 25, 2013, 05:01:02 PM »
Right.

And I don't think the controller is doing it wrong, just not the way I need it to.  The drive electronics allow for an adjustment of overlap time to compensate for latency in the relay and the brake itself.  With the current setup there is no overlap, which allows the z axis to drop.
Re: Need Help! DSPMC Setup
« Reply #35 on: April 25, 2013, 05:57:01 PM »
When setting up the brake it would be nice if the brake would stay on just a little after the drive enable comes on and if the brake would come on instantly the moment the drive enable goes off/estop/limit switchkicks in.

The question I have is when an e-stop condition is detected, is there a time lag between the PID drop out and the drive enable drop out?

Mike
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.
Re: Need Help! DSPMC Setup
« Reply #36 on: April 25, 2013, 07:15:05 PM »
When setting up the brake it would be nice if the brake would stay on just a little after the drive enable comes on and if the brake would come on instantly the moment the drive enable goes off/estop/limit switchkicks in.

The question I have is when an e-stop condition is detected, is there a time lag between the PID drop out and the drive enable drop out?

Mike

It seems that it is nearly instantaneous off and on.  On doesn't seem to be an issue, I need a bit of time from output off to pid off.  Would be nice to have either option as I can see both being needed.  Hopefully it's something doable in the firmware, otherwise I'll have to find another way.
Re: Need Help! DSPMC Setup
« Reply #37 on: April 25, 2013, 08:37:15 PM »
ideally you need a time parameter to say how long to keep PID active when axis enable is dropped by mach3.   may be per axis parameter setup.   I will check if we can add this.  can't promise right now but I see it may be doable.

rgds
Rufi

Re: Need Help! DSPMC Setup
« Reply #38 on: April 25, 2013, 09:52:28 PM »
If it's doable that would be perfect!!
Re: Need Help! DSPMC Setup
« Reply #39 on: April 26, 2013, 11:34:50 AM »
Update:

Moved the brake control back to the servo drive.  Switched the servo drives over to speed control vs torque control.  I'm actually getting much better motion now, I can have less following error at higher accelerations and velocities, very good!  And because the servo is in speed control mode a zero signal means zero speed, so the drive will essentially maintain position without input from the dspmc.  This also provides some overlap with the brake and servo power so the z axis doesn't drop 2 inches when Reset is hit.  The only issue now is why when estopped the servo drive holds the brake output on (which means brake is off) cause the z to descend in an estop condition.  For now I just won't estop the drive, the servo enable signal from mach/dspmc kills the servo in that state anyways.  I have an email into delta on that one.

So, with that hurdle hopefully tackled, onto getting this tool changer program working!

I still think that being able to delay the PID loop in the dspmc is a great option to have tho, if it's capable of it.