Kanalog Interfacing with a drive that takes "dual phase" input

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boss4
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Joined: Sun Apr 29, 2018 9:36 pm

Kanalog Interfacing with a drive that takes "dual phase" input

Post by boss4 » Sat Mar 16, 2019 11:33 pm

I have a servo drive (aerotech BA30) that has an option for "dual phase" control. Wherein you provide external commutation in the form of +/- 10 volt commands on 2 separate inputs. The manual for the drive describes dual phase as:

"This mode is used with a brushless motor only. In this configuration, the differential input, pre-amplifier, and self-commutation circuits are bypassed. The dual-phase inputs are sinusoidal and are 120° out of phase from each other. The third phase is generated by the amplifier. "

Would I be able to use 2 kanalog DAC outputs to generate the dual phase commands described above? The position input to the kanalog would be a quadrature encoder wherein I can sync the Z signal with a specific phase of the motor.

If you look at the drive datasheet you will see that it also supports other control types that would be easier to setup. I have an issue however the issue is that the motor I am using has no hall sensors. Moreover its a 14 pole motor so external commutation encoders don't appear to be an option as the common ones from US digital and AMT don't support motors with more than 12 poles.

Admittedly I am trying to piece together a bunch of parts from the scrap pile.

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TomKerekes
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Re: Kanalog Interfacing with a drive that takes "dual phase" input

Post by TomKerekes » Sun Mar 17, 2019 4:50 pm

Hi boss4,

The example DualDACPhaseFindAndCommutateV2.c should work for you.

See also DualDACRotateForever.c and AutoPhaseFindDualDACs.c
Regards,

Tom Kerekes
Dynomotion, Inc.

boss4
Posts: 4
Joined: Sun Apr 29, 2018 9:36 pm

Re: Kanalog Interfacing with a drive that takes "dual phase" input

Post by boss4 » Tue Mar 19, 2019 5:36 am

Hi Tom,

Thanks for the reply.

I am a little confused on determining invDistPerCycle. This is a 14 pole 3 phase motor that will have a 2048 PPR encoder. Is that then 7 cycles per revolution so that invDistPerCycle = 7/2048.

Second in the example the DualDACPhaseFindAndCommutateV2.c output is set to NO_OUTPUT_MODE so do the params for velocity acceleration, jerk etc. still effect the axis? Also do the OutputChan0/OutputChan1 settings do anything other than store the DACS being used in this example.

Final question, if I sync the index pulse to phase A then the CommutationOffset should be zero right?

thanks!!

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TomKerekes
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Re: Kanalog Interfacing with a drive that takes "dual phase" input

Post by TomKerekes » Tue Mar 19, 2019 4:19 pm

Hi boss4,
I am a little confused on determining invDistPerCycle. This is a 14 pole 3 phase motor that will have a 2048 PPR encoder. Is that then 7 cycles per revolution so that invDistPerCycle = 7/2048.
That sounds correct, but the AutoPhaseFindDualDACs.c should figure all that out for you automatically. Configure that, run it, and post the reported results.
Second in the example the DualDACPhaseFindAndCommutateV2.c output is set to NO_OUTPUT_MODE so do the params for velocity acceleration, jerk etc. still effect the axis?
Yes they do. The motion profile trajectory is completely independent of what type of motor you have or how it is being driven.
Also do the OutputChan0/OutputChan1 settings do anything other than store the DACS being used in this example.
No. They are only used by your Commutation Program. With NO_OUTPUT_MODE KFLOP doesn't output anything.
Final question, if I sync the index pulse to phase A then the CommutationOffset should be zero right?
Possibly. But it depends on how things are defined. That might be where phase A has zero torque rather than maximum torque. So you might need a shift of 1/4 cycle one way or the other. But again it is simplest to allow AutoPhaseFindDualDACs.c to figure that all out for you by it observing how the motor actually responds to phase currents.

BTW you might see the other current Thread on this same topic.
Regards,

Tom Kerekes
Dynomotion, Inc.

turbothis
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Joined: Fri Mar 15, 2019 4:07 pm

Re: Kanalog Interfacing with a drive that takes "dual phase" input

Post by turbothis » Tue Mar 19, 2019 10:39 pm

hey boss, we are very much in the same boat!
i have some experience in this and tom is still helping a ton

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