Commutating brushless servo with Hall sensors

[wlewis]

Is it possible to commutate a brushless servo using only the Hall sensors on a GeoBrick LV?

 

Or is it essential to have an encoder to measure the motor position?

[Richard Naddaf]

Yes, you can. I had posted a reply with an example for Power. Then I realized that it was Turbo.

 

There is a note in the Users Manual on page 56. So, this is typically for velocity control due to the low resolution (6 counts per electrical cycle). And the halls must be wired into the A, B, and C inputs.

 

- The encoder conversion table is the same as quadrature.

- I7mn0 = 11

 

For commutation purposes, and for smoother control, it is best to commutate off of the encoder conversion table, using the 1/T extended count:

- Ixx83 = (e.g. $3501)

- Ixx01 = 1

- Ixx70 = 1

- Ixx71 = 6 * 32

[wlewis]

Thanks Richard.

 

I'm finally now testing out this application.

 

A couple of questions:

- given that the Hall sensors are single-ended, should I be connecting the A-, B- and C- encoder pins to 2.5V?

- the Turbo PMAC Software Reference Manual documentation for I7mn0 says that the 6x decode option is only available on Version B or later of the DSPGATE1 chips. Is there a way of finding out if my GeoBrick LV has the correct version? Or when did Version B of the DSPGATE1 start shipping?

 

Thanks,

Wayne