Cannot get working 5i25 + 7i76 + 8i20

PCW wrote:

That is a 10 pole motor

Ok, I will make correction.


Also is not clear what NVMAXCURRENT should I set, according to motor datasheet:
Rated current A (rms) 8.2
Instantaneous max. current A (rms) 35


Minimum or max or on the middle?

All the way to 30A would be the correct setting, however
I would not do that until everything is running and ready to tune

PCW wrote:

That is a 10 pole motor

It fixed bldc problem, now it works as expected.
Also I closed loop with pid component and now it works as real servo in velocity mode.

It looks like 8i20 is designed to run in position mode, it really lacks some velocity
mode and requires much faster servo-thread because of it.

PCW wrote:

also there is a improved version of BLDC in master that doubles the commutation timing accuracy
I would suggest using that as well

Could you give some instructions on how to install an improved version of BLDC form master?

The 8I20 works in torque (current) mode
This requires LinuxCNC to close the velocity loop (Via the D term)
Typically this requires a 4KHz or so servo thread for axis use
(note a bare motor without load will be hard to tune in any case)

Some advantages of torque mode are:

1. You can sense the motor load (the PID output)
2. You can limit the torque (say when homing)
3. All tuned in one place
4. Simpler hardware (drive needs no direct encoder connection)

And some disadvantages:

1. Since host runs velocity loop, it needs a higher thread rate
2. A little tricker to tune

Do you have the linuxcnc development environment set up?
a git pull and rebuild of master will do if that's the case

otherwise maybe a buildbot binary can be installed