- LinuxCNC
- General LinuxCNC Questions
- Intermittent Z Axis Spike with Yaskawa Servos, 5i25/6i25 and 7i77
Intermittent Z Axis Spike with Yaskawa Servos, 5i25/6i25 and 7i77
I have an issue on a 5 axis, 6 joint machine that I’m finishing up. The machine is an XYYZAB configuration that is taking advantage of the new joints/axes capabilities in master. The X, Y1, Y2, A, and B axes all work just fine and all axes have been tuned and work smoothly. The problem I’m having is that the Z axis occasionally experiences a motion spike, even at standstill. When I say occasionally, it is something that may happen every few minutes or it can go an hour or more between events.
At first, I thought it was an encoder noise issue. A differential capture with a 4 channel scope showed some high frequency noise on the encoder lines, but not enough that I would expect it to be a problem with differential signals. Nonetheless, I’ve gone back over things and taken steps to filter any common mode noise and installed ferrite chokes on all low speed and analog signals. I even went so far as to purchase and install the galvanic isolator for between the host card and the 7i77. I’ve tried 3ft and even 18 inch cables between the host card and the 7i77. This thing really has me stumped.
The real kicker is that halscope shows the f-error of the joint and corresponding PID counter-response in sync, presumably as a result of the 5i25 read/write, PID calcs, and scope all running in the same thread. Anyone have any ideas on how to proceed? I have swapped out the servo drive and motor as well just to make sure it wasn’t In the hardware and I still see the same occasional glitch.
Also pertinent, I have done extensive load / latency testing in the computer and latency never goes above 7000. I have, however seen an occasional serial DOIT error stating that it didn’t complete, but these don’t correspond to the spikes that I’m seeing on the Z axis. I’ll also add that if I use SigmaWin to interface the drive directly, it never exhibits the issues. That leaves me with only the loop facing linuxcnc that is in play.
Any thoughts on where to go from here? The halscope traces I’ve captures so far don’t really tell me whether a spike in f-error or a spike in PID output is happening first.
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That would check if this is specific to a 7I77 channel or external hardware
Encoder noise seems unlikely to cause such a repeatable glitch and should be possible to eliminate
with encoder input filtering
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I think its time for a whiskey and coke... I'm having a hard time accepting what just turned up whiel testing this.
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This is expected ( Axis 5 is normally used for spindle control so has a independent enable (axis 0..4 have a common enable ) )I then moved the analog out over to 5 and the drive didn't enable. A quick check with the meter showed that the enable component (I'm assuming a FET) isn't activating to enable the drive.
The homing in the wrong direction error Is much more likely a hal or setup error than software of firmware
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As for homing, I generally would agree with you, but here's the catch. I'm not touching the INI file at all and the only thing I'm changing int the HAL are the encoder and analog numbers, Z jogs and homes fine on encoder4/analog4 as well as encoder5/analog5 now that i tied in spinena. I'm going to set up halscope and let it sit for a while to see if I get the same spiking.
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- LinuxCNC
- General LinuxCNC Questions
- Intermittent Z Axis Spike with Yaskawa Servos, 5i25/6i25 and 7i77