sensored vs sensorles hub motor (fact check)

[jimmyhackers]

friends conjecture: running a hub motor sensorless will accelerate faster/provide more power.

my conjecture: i always thought it was the other way round. i.e. a sensorless motor may use more power....but doesnt actually put more power down on the tarmac.

just wondering whats the actual deal?

 

[E-HP]

friends conjecture: running a hub motor sensorless will accelerate faster/provide more power.

my conjecture: i always thought it was the other way round. i.e. a sensorless motor may use more power....but doesnt actually put more power down on the tarmac.

just wondering whats the actual deal?

Based on reading the stuff on the forum, seems like it would depend on which part of the band, since it's mainly a timing thing. From a dead stop or down low, sensored has the advantage, then sensorless for higher speeds. A controller that switches from sensored to sensorless would be better, and FOC would be ideal for timing.

 

[larsb]

True :thumb:

BEMF voltage is normally what is used in sensorless control to detect position. At low rpm the BEMF is low and therefore measurement is affected by noise and error.

Hall sensors detect position through the rotor magnetic field (which is constant) and therefore give a better position estimation at low RPM. They suffer from some limitations though: the position is only updated every 60 electrical degrees, physical positioning of sensors always have some error and the sensor signal suffers from a certain delay which causes an rpm-dependent offset in the detected position. Therefore sensorless is normally better at higher rpm.