Sensorless ESC starting and control strategies

[GordonFreeman]

I can't find the site (industrial or EV site), but I was reading that there are two main strategies for sensorless control.

1. The unused phase produces a back EMF signal that flips (reverses sign)and the timing can be estimated from that and the motor speed.

2. Some sort of "ping" signal is sent to the the windings (even while running)and can calculate rotor position and timings from that.

It was explained that strategy #2 is far superior to strategy #1. It also said starting studders are reduced or eliminated.

Which sensorless ESCs use which control strategy (probably only Company reps can answer this). Shawn? Frank?

[Shawn Palmer]

Touchy subject here. :-)

I've had the pleasure of meeting Frank at the 18th Nats, and it was a pleasure. Nice guy, and a HECK of a lot better driver than I'll ever be!

Anyway, from what I remember, neither Frank nor I are engineers. Even if we were, I doubt we'd be able (or willing) to explain detection secrets (said with a smile).

In Castle's case, we have patents pending for several of the hardware and software solutions the Mamba Max uses that broke new ground in sensorless operation.

Patrick (owner and lead engineer at Castle) has been to this board before, so maybe he can better answer your question without letting too many cats out of the bag :-)

Shawn

[TheSteve]

You can always search for patents, and then have fun trying to read them.
What Castle is doing for motor startup is amazing, I will say that.

[Shawn Palmer]

Found this from Patrick in another thread:

"Well, without getting too deep into the technical details, we use both fast A/D sampling of the back-EMF, and A/D phase to phase delta sampling, as well as direct comparators (phase / phase and phase / neutral) to determine the rotor position in real time.

Patrick"