Estop and single axis configuratoin

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21 Sep 2019 20:24 #145788 by Scot
Hello all,

So I finished wiring my amps and servos up with Pico-systems boards and brushless drives and I loaded my PC with LinuxCNC. Jon over at Pico-systems was unbelievably helpful over these past weeks of me prepping and wiring, BTW. He's the support MASTER. But when I got everything connected, I ran into a snag that I was hoping to figure out using more eyes.

I managed to edit the OUTPUT_SCALE of the 2 axis's of my system in the univpwm.ini file with what I'm about 99% sure are the numbers to drive the servos so I can tune them, next. Then I went to check the encoders and found one that just dithered between .0003" and 0. The other worked flawlessly. So I checked the wiring, which was solid. But when I installed these encoders, one gave me a bit of trouble and slid onto the motor shaft with a bit more difficulty than I'll bet was optimum. And when it bottomed on the motor housing, it came in at a bit of an angle with a snap at the end. So I opened it and sure enough, it was bent. So my guess is that the reader was damaged or the wheel was scraping. It's kind of hard to see that stuff when it's inside of a black housing with no peep holes! So I'm just putting two and two together. Also, when I went to turn the motors to check the encoders, Linux CNC wouldn't come out of Estop for me to turn on the amps. Could that be because of the encoder? Or is it likely because of something I missed in the wiring?

Needless to say, I'm out an encoder, not just because it was bent, but because when I went to give the wheel a check to see if it was spinning true, it slid on the shaft like the wrong key in a keyhole. Then without the set screw even being tightened, it locked on to the shaft! So yeah. That wheel is now shot. Getting it off was TOTALLY destructive to it. Another is on the way, along with a spare, though. Unfortunately, my manic nature doesn't like the idea of having to wait nearly a week to get that part. And I know I can get more done if I have a clear path to do what I can.

What I really want to know, though, is can I, without rewiring much in the control box, set it up so I can tune just one axis in, then move the motor to the other physical axis and then tune the motor with the single amp and write down all the PID data to plug into the INPUT_SCALE for the other axis? I know it won't be using the other amp, since I'll be disconnecting it. But since this is a gangtool lathe, the two axis's will have slightly different characteristics, physically, and the motors are all but identical. So I figured if I could do this, all I would have to do, sans a few tweeks in the tuning would be to mount the encoder and then the motor and it would save me a ton of time once the encoders arrive. It will also give me much needed experience in tuning these motors. This is my first closed loop system. I need all the hands-on time I can get. Has anyone done this before using Pico products? And if so what would be a good approach?

Any help would be greatly appreciated.

Thanks in advance,

Scot

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21 Sep 2019 22:00 #145794 by tommylight
forum.linuxcnc.org/10-advanced-configura...ning-detailed-how-to

Have a read through that as it contains a lot of info on the proper procedure of wiring and testing closed loop servo systems.
It does pertain to Mesa 7i77 though, but the theory is valid for any type of control/drive system.
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22 Sep 2019 07:17 #145823 by Scot
That's a great synopsis. The photos really helped. I also got some input from Jon. Apparently the board and amps are not powering up properly. So unfortunately, Until I track the issue of getting the hardware powered correctly, I'm kind of dead in the water.

No matter what, though, that's a great set of information. I'll be referring to it often, I'm sure.
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