2013.07.10 13:10, Anders Wallin rašė:
> This sounds doable as long as there is space on the fpga for a lookup-table
> and you can get the commutation tuned correctly (I guess the
> tuning/alignment process is already required and works ok for the current
> bldc implementation).
I use "qi" mode with bldc.n.init. It works ok, I just need to find right 
encoder-offset value, which I did manually experimenting.
>
> Could you somehow verify that the non-optimal behavior or problems you are
> seeing actually are because of commutation?
> OR, would it be possible that simple PWM ("voltage"?) control with a
> PID-loop that gets feedback from the encoder is quite hard and doesn't work
> well at high RPM even with a 250us servo-thread?
I compared two boards: 7i43-P and 5i23 with the same setup with 7i39-H, 
config, PC, except for necessary things to adapt to different boards.
On 5i23 I am running servo thread at 200us successfully. With 7i43 I 
reached 280us without hangs and realtime delays. While servo thread 
usual period was about 230us and max period was 420us. All this test 
actually was made on one working axis only, but three identical axes 
where configured.

Results: with 7i43 motors could not go so fast as with 5i23. Besides 
this they made more noise running at higher speeds than on 5i23.

I could compare two tests with 5i23, just with different servo period (I 
tested this already, but don't remember exact results, so can't be 
precise here).

>
> I once tried using current-sensing chips from IRF that produce PWM-output -
> this could be one option if you want to try a current-loop.
Could you please specify which chips you tried? What do they take as an 
input - PWM, analog ref, ..?

>
> Anders

Marius


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