Re: Geckodrive

Mariss, this isn't making any sense, but I think it has to do with
what you call a stall and what I call a stall.

To me, a motor is stalled when it no longer rotates. Are you saying
that your GREX device will keep that motor moving no matter what?

Now unless you have magic powers, this isn't possible. Which makes
me think that your interpretation of stall is different than mine.

Based on your description below, it appears as though the drive will
slow down the velocity in hopes that the greater torque at low speed
will overcome the load and allow the motor to rotate again.
However, at some point, there will be a load in excess of what the
drive/motor can overcome - resulting in a stalled (Stopped) motor.
Does the GREX then fault or what is planned for this condition?

Thanks

Chris





--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis"
<mariss92705@...> wrote:

>
> No, the motor does not stall. It is prevented from doing that by
> monitoring the lag angle and decelerating the rotating magnetic

field

> to prevent it from getting more than 1.8 degrees ahead of the

rotor.

>
> The net effect is the motor slows down under heavy load. As it

does,

> more torque is available as speed drops until a "balance point" is
> found where available torque equals load torque.
>
> Relieve the load torque and the motor accelerates until a new

balance

> point is found.
>
> The lead/lag angle register is analogous to the position error

summing

> node in a classic servo. A step pulse increments this register,

the

> encoder count decrements it. The contents of this register is

input to

> a PID algorithm; the PID algorithm output then modifies the step

pulse

> rate to keep the summing node at a desired constant value.
>
> The lead/lag register also is used to increase the

motor's "stiffness".

>
> An open-loop step motor has +/- 1.8 degrees of stiffness. In fact,

a

> step motor only delivers its rated holding torque when its shaft

is

> displaced 1.8 degrees from its no-load position. The servoed

response

> is to "step into" the load, canceling this error. A 500-line

encoder

> gives a 10-fold increase in stiffness over an open-loop step motor.
>
>
> Mariss
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "lcdpublishing"
> <lcdpublishing@> wrote:
> >
> > Okay, so the motor still stalls like any other stepper system.
> > However, it tolerates the stall and provides feedback to the
> > controlling software which would allow for a recovery if in fact

the

> > problem causing the stall is self-correcting?
> >
> > It sounds neat, yet impossible at the same time. Either way, it
> > sounds like it has the potential of allowing higher speed

performance

> > from stepper systems. Perhaps I should look at this as if it

were in

> > an adaptive control system and it would make more sense.
> >
> > Sounds cool guys.
> >
>