Hacker News new | ask | show | jobs
by numpad0 595 days ago
Sorry if it sounded dismissive, but, I mean, modern motor control formulae[1][2] don't have a term for RPM. Motor controller derives new output state from just torque and instantaneous state of the motor, RPM is somewhat externally controlled unless that version of formula is in use. Hence the capsule analogy: F=ma for constant F means a > 0 and (rotational)velocity monotonically increases.

It doesn't make instinctive sense to me too that motor people haven't been thinking RPM-first for some time, but apparently they're not.

1: https://en.wikipedia.org/wiki/Vector_control_(motor)

2: https://en.wikipedia.org/wiki/Direct_torque_control

1 comments

> Motor controller derives new output state from just torque and instantaneous state of the motor

And the way it makes the motor state advance causes acceleration. It doesn't matter what variable goes into the formula, especially since you can convert freely. I'm pointing at the output and what I find scary about it. What comes first doesn't matter, I'd have the same issue even if I'm looking at the control formula from a jerk-first perspective.

And I don't really see the value of the "against nothing" analogy because the reason it's increasing torque is because it thinks there's resistance.