InstaSpin-BLDC Code Samples and Tutorial

The BOOSTXL-DRV8301 does NOT support BLDC control. The inverter only has low-side current shunt sensing, NO total current shunt sensing required for closed loop BLDC.  However, you COULD do something like InstaSPIN-BLDC control just for commutation using the Vph sensing but

1. the Vph filters on the inverter are quite low (for our FAST algorithm) when for Bemf BLDC zero cross / integration you would like them quite high, higher than any motor frequency

2. We have no SW examples

Unfortunately, if you want to work directly with something like InstaSPIN-BLDC it would be easiest to try the DRV8312-C2-KIT or DRV8301-HC-C2-KIT.  BTW - both these kits have the same issue with #1.  If you have a high speed motor you would be best served in updating the pole of the Vph filter for IS-BLDC.

So If I wanted to do simple BEMF based 'closed loop' commutation similar to the standard ESC's available for Hobby Airplane motors using either Piccolo or MSP, what resources / tools / code / samples can I refer to ?

Since - InstaSpin-BLDC is one of the three (BLDC, FOC, Motion) shouldn't there be more reference code / samples / guidance available? Am I missing something completely here?

Mohammed,

InstaSPIN-BLDC is supported on two kits, DRV8312-C2-KIT and DRV8301-HC-C2-KIT.  As noted, the phase voltage feedback is not ideal for high speed motors, so if you want to use a high speed motor I would suggest changing these filters to a much higher pole (larger than your max frequency).

the SW for these kits is included in www.ti.com/controlsuite

Yes, the BOOSTXL-DRV8301 is a better inverter for a hobby style ESC. It has a larger current than DRV8312 EVM but smaller (better resolution) than DRV8301 EVM.  It also has a better voltage resolution for small motors in the 6-24V range.  Unfortunately we don't support InstaSPIN-BLDC on this inverter hence we don't support the SW on the LAUNCHXL-F28027F.

We introduced InstaSPIN-BLDC first three years ago. We now focus only on -FOC and -MOTION for new solutions. It is significantly better.

What qualifies as 'high speed' ? Would 15000 - 20000 RPM be considered as high speed ?

we need to speak in electrical Hz, not mechanical RPM, so that depends on your # of poles.  With 4 poles, 20 KRPM is 667 Hz, which would be fine for InstaSPIN-BLDC and the DRV8312 kit (pole is ~715 Hz) and you probably wouldn't see too many issues with the DRV8301 EVM/BOOST (pole <400 Hz).

If using InstaSPIN-BLDC and the DRV8301 boards and your motor is > 800 Hz you should change the phase voltage filter pole.

Okay, then it means we do have a problem! Our motors are 9 poles which translates to 1500Hz.

Can you provide any details or reference to what changes need to be done in more detail please.

Does this mean even the FOC logic will not work or only BLDC has a problem?

1500 Hz for IS-FOC on the DRV8301 EVM/BOOST is typically fine. The EVM has some issue with current sampling at highest duty cycle, and the voltage and current scaling typically aren't ideal for low voltage / medium current motors.

For best InstaSPIN-BLDC results, to change the voltage filter pole you need to update the circuit described in SPRUHJ1 chapter 5.2.4 to be > 1500 Hz.  This HW will then NOT work well for InstaSPIN-FOC (the drift in the C for the filter can cause  more error at higher pole frequencies which causes issues with IS-FOC estimations).

This is good! Thanks a lot for bringing this to our notice. Can you point me to a UserGuide for IS-BLDC similar to the one for FOC/Motion you just referenced.

the UG for InstaSPIN-BLDC is not nearly as thorough (the solution is much simpler though).

you can read the project guide from

C:\ti\controlSUITE\development_kits\DRV830x-HC-C2-KIT_v105\InstaSPIN_BLDC\~Doc

there is a lab that can be found from this page

http://www.ti.com/ww/en/mcu/instaspin/instaspin-bldc.shtml

and there are several videos on IS-BLDC that can be found at the bottom of the video player at this page

http://www.ti.com/ww/en/mcu/instaspin/support_community.shtml

Hello Chris,

We have given up on BLDC for now. So in the context of IS-FOC, one more question. Is there any estimate on how many electrical Hz the  TMS320F28027F can handle comfortably? We are trying to chose a motor and trying to balance RPM & torque etc. You mentioned earlier that 1500Hz should not be a problem for the Booster EVM but now I want to know in the context of the MCU. Thanks!

Mohammed,

With the 60 MHz device, you are going to need to limit your current & estimator frequencies to about 15 KHz (and even this doesn't leave you much headroom for other things).  That 15 KHz could allow electrical frequencies of 1500-2200 Hz for your rotor speed.

With the 90 MHz device we are able to run 30 KHz frequencies (very little headroom remaining) and 4000 Hz+

Thanks Chris,

Our max should not exceed 1400 Hz. We need some headroom too else we will have to add one more MCU! How low can we go on the estimation frequencies without affecting torque too much? Is there any guideline / documentation on this as well. Thanks again for your valuable and precise answers.

Keep your est and CTRL rates at 8x your max frequency.

So I'd recommend 12 KHz minimum for both. This will use ~40+ MIPS of 60, so ok headroom on 27F.