microstep clarification

[stirling]

Not really a gecko question I suppose but...

Given everything I've read about the purpose and caveats of microstepping - why do some manufacturer's drives have settings for 128 microsteps etc. I'm particularly thinking of things like - more than 10 is empty resolution which seems to make perfect sense (thanks for the excellent explanation Mariss) and clumping etc. etc.

[Mariss Freimanis]

Only 2 reasons I can think of:

1) Need to turn smoothly at very low speeds. Microsteps become individual steps (step, stop, step, stop) when the speed drops below about 100 steps per second. At microsteps/step, this is about 3 RPM. At 128 microsteps/step, this speed is 12.8 times lower or about a 1/4 RPM.

2) The motor is being run closed-loop. The motor microstep resolution must then exceed the encoder resolution by a significant amount to give stable operation.

Mariss

[stirling]

Hmmmmm - Do I detect an undertone that you're not quite convinced Marris?

1) Given the "clumping" problem - would even this be reliable I wonder?

2) Again - given the "clumping" problem - I can see the poor old PID going crazy. Not to mention the (in my view) slightly dodgy idea of trying to turn a stepper into a servo.

But - thanks for your reply - I thought maybe there was some VERY good reason that I'd missed - I'm guessing maybe not.

Cheers

Ian

[stirling]

I just read this elsewhere

Also higher microstepping resolutions will also help to eliminate the zero position glitch that is very prominent with drivers that are limited to lower resolutions or morph to a full step driver after a certain speed.

I have no idea what a "zero position glitch is" - anyone?

[Mariss Freimanis]

I have no idea what a "zero position glitch" is either. It's not a technical term, that's for sure.

Mariss