Something that bothers me for quite a while now: why is there no small / cheap hardware emulator for BLDC motors? I've seen contraptions where two motors are coupled and one is actively driven whereas the other just has a resistive load hooked up to it or a rectifier at best.
There's really nothing wrong with connecting BLDC driver chips back-to-back with inductors in between. Here it's being done to benchmark a large 3 phase inverter but the principle is pretty much the same.
Allegro makes an array of sensorless BLDC chips with sinusoidal and trapezoidal output modes and different options to set torque and nominal rotation speed.
All that's missing is a way to scale the sensed average current to e.g. a VCO control voltage and fudge around with loop stability to match the host BLDC controller.
At the end of the day I assume noone ever bothered to look into it because... I mean... why would you?
Unless you need to emulate a BLDC motor for arbitrary controller chips of a host device (DLP beamer :D) to be hacked...
ps. candidates for sensorless BLDC controllers:
Texas Instruments DRV10983
Allegro A4942, A4964 to name a few
ON Semi LB11683H
Owo JY02A ... just joking