Gene,
Just picking a nit here.
Your claim of "A machine with stepper/servo's needs no PID's" is directly
countered by your previous statement "by the PID in the controller"
therefore the machine does have a PID somewhere.
I (and everyone else) know(s) what you meant. I just had to smile and then
I had to comment.
regards
Stuart
On Thu, Jul 4, 2024 at 5:21 AM gene heskett <ghesk...@shentel.net> wrote:
> On 7/4/24 05:10, andy pugh wrote:
> > On Wed, 3 Jul 2024 at 20:32, Viesturs Lācis <viesturs.la...@gmail.com>
> wrote:
> >
> >> I believe that I need to specify encoder-offset parameter, but I do
> >> not understand how exactly encoder-offset value for BLDC component is
> >> calculated.
> >
> > I think that the motor "zero" angle for the 8i20 is defined as where
> > the motor sits with V+ connected to U and V- to V and W. If this is
> > where the index pulse is, then your encoder offset is zero.
> >
> > You could do this with a bench PSU, but it's mayeb easier (and closer
> > to the real setup) to do it in a command-line hal session reset the
> > encoder to the index, then setp the angle to zero and setp the current
> > to a couple of amps (or enough to move the rotor) in each direction
> > and the encoder offset is the midpoint. (it's in counts)
> >
> > Things are slightly complicated by the 8i20 built-in lead-angle
> > calculation. (ie, you give it _rotor_ angle and it calculates _phase_
> > angle)
> >
> > eg:
> > halrun
> > loadrt hostmot2
> > loadrt hm2_eth board_ip=10.10.10.10
> > show pin
> > loadrt threads
> > addf hm2_....read thread1
> > addf hm2.....write thread1
> > start
> >
> > loadusr halshow
> > {setup a watch of the encoder index-enable and counts)
> > setp encoder.0.index-enable 1
> > {rotate motor by hand until the index-enable resets)
> > setp hm2...8i20...current 0.5
> > {note the encoder counts}
> > setp hm2....8i20...current -0.5
> > {note the encoder counts)
> > {maybe repeat to get good statistics)
> >
> >
> > There may be enables to set, it's been a long time. You might need
> > more, or less, current. Depending on the pole count there will be
> > several zeros, one is likely to align very closely with the index.
> >
> > If the encoder offset turns out to be zero, or close to zero, at this
> > point you should be able to scale the encoder to give a zero-to-one
> > output per _electrical_ revolution and connect the encoder angle to
> > the 8i20 commutation angle and spin the motor with current commands.
>
> Thank you for a very educational post, Andy.
>
> I personally have not used any BLDC motors as I've found the
> stepper/servo to be an amazingly better control for me. They do exactly
> what the stepper driver tells them to do as the motor is locked to the
> stepper drivers output by the PID in the controller, which LCNC is not
> aware of. A machine with stepper/servo's needs no PID's.
>
> But I've pinned the above post and others should too as it seems to be
> the best BLDC setup instructions we have seen here.
>
> Take care & stay well Andy.
>
> Cheers, Gene Heskett, CET.
> --
> "There are four boxes to be used in defense of liberty:
> soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author, 1940)
> If we desire respect for the law, we must first make the law respectable.
> - Louis D. Brandeis
>
>
>
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