ESC Sensored to Sensorless - Possible or Not?

[S.B.D]

Hi,

I had an idea for testing methods of BEMF detection using a sensored BLDC ESC.
I would like to use an off the shelf sensored ESC as the power stage but connect an MCU to its hall sensor inputs.
The external MCU will manage all the sensorless algorithm given by the throttle and BEMF detection circuitry and translate the data for
the off the shelf ESC's hall inputs to modulate the motor with correct timing.

Is this possible or am I missing something...

Thanks,
S.B.D

 

[amberwolf]

IIUC you're basically using the MCU to emulate hall sensor position signals; there's no reason this shouldn't work. Burtie's Timing Adjuster 2 does exactly this, though it is using hall sensors as it's input signals, instead of BEMF/etc. There have also been analog boards based on op-amps or comparators that convert BEMF into hall signals.

You could actually take a TA2, build the hardware on the front end for converting BEMF into suitably-shaped lower-voltage pulses to input into the TA2's hall inputs, and then use the TA2 to adjust timing. I have considered taking one of those analog boards I describe above to do the hardware part into the TA2, just to see how well it would work.

But I expect you want to use the analog inputs of the MCU to read the BEMF so you can filter and adjust it all thru software rather than hardware, which means coming up with all of it from scratch.

 

[S.B.D]

Hi Amberwolf,
Thanks for the confidence builder. Just wanted to know if anyone finds a problem with this "multi-core" approach ...
My plan is to have the main ESC MCU deal with the current liming, PWM generation & voltage cutoff.
Secondary (external) MCU will read the 3 halls and 3 BEMF waveforms and translate this into the original hall signals.

If I understand correctly I need to tap into the throttle input in order for the secondary MCU to know when when to start the sensorless start sequence.
Is my assumption correct?

Thanks!

S.B.D

 

[lutach]

I helped HobbyWing with a few ideas for a car ESC and this was one of them. They came up with the source code though, all I did was offer the idea.