Hi, A PID loop has been added to the Xylotex HAL file in the ARM/BeagleBone/Xylotex configs section. Take a look there for a way to set up the axes with a PID loop that gets rid of the hunting problem.
Jeff On Wednesday, May 10, 2017 at 7:15:44 AM UTC-7, Alexander Rössler wrote: > > This phenomena is known as PRU pin hunting and a result of the internal > PRU stepper feedback loop being too "tight" (so the DIR pin toggles all > the time). You can fix it by adding a PID loop before the stepper and > adding a minimum threshold. Just search for PRU pin hunting in the > mailing list. > > Another solution would be to adapt the PRU HAL driver code. However, the > PID loop has the additional advantage that it smoothes out RT jitter. > > The solution is also present in the Machinekit fdm Python libraries: > > https://github.com/machinekit/machinekit/blob/master/lib/python/fdm/config/base.py#L61-L75 > > > [email protected] <javascript:> writes: > > > Hello Nick, > > If i am correct this is some form of "hunting" mode which is being done > by > > the feedback loop in the PRU. I have seen the same behavior on our > > machines, but I have no clue what this actually does internally in > > machinekit. > > > > Op woensdag 10 mei 2017 11:14:45 UTC+2 schreef Nick Collier: > >> > >> I am running Machinekit on a BBB. > >> > >> When tasting the physical step and direction output pins with an > >> oscilloscope, I noticed that there are various rectangle/pulse type > waves > >> on the direction pins when the respective axis are not moving. Is this > >> normal? > >> > >> As soon I make the axis move, the direction pin goes to either high or > low > >> depending on the direction. > >> > >> When the axis are moving, everything looks fine. But I would expect no > >> signal when there is no movement. The step outputs produce no signal > when > >> there is no movement, so I guess the signal from the direction outputs > are > >> not going to do any harm. > >> > >> > > > -- > Alexander > -- website: http://www.machinekit.io blog: http://blog.machinekit.io github: https://github.com/machinekit --- You received this message because you are subscribed to the Google Groups "Machinekit" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. Visit this group at https://groups.google.com/group/machinekit. For more options, visit https://groups.google.com/d/optout.
