Re: Geckodrive

Man, you're preaching to The Preacher.

Mariss: I'm standing in line, anxiously, to re-fit my big, albeit
slow, easily stalled, machine. Thanks for the early indication that
the Gecko SP100 (Stall-Proof) will become a reality.

JohnC


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Jack Hudler" <yahoo@...>
wrote:

>
> Unless I'm missing something in your post (you said "step motor").
>
> A stepper motor by its very nature is stallable via load, inertia,

and

> resonance. Unless you're suppressing mid range instability caused

by parametric

> oscillations then you're always in danger of stalling regardless of

loading.

> These suppression or damping features are usually found on high end
> micro-stepper drivers.
> You can fix this some what by having a stepper with extra torque

than needed but

> that's a wasteful and expensive route and all you've really done is

changed the

> rotor inertia.
>
> Once a stepper stalls it enters a very chaotic state and at this

point the

> pulses from the incremental encoder are all invalid. You always

have to re-index

> after a stall to remove the chaotic error. Still the end effect is;

you're part

> is screwed.
>
> At any rate an incremental encoder is not going to give you advance

warning of a

> stall in order to avoid it. You might try putting a tachometer on

it and

> programming a DSP to sense the instability but that's not a cheap

route either.

>
> This technique might be useful on a servo motor using current and

tach/encoder

> feedback. This is also something you find on some high end servo

drivers.

>