Re: Re: DC motor as replacement for Stepper motor

Mariss

As usual, you make a great deal of sense within the constraints that you
impose on your steppers and servos mind experiments. Given the primary
constraint of commanded position and not exactly how to get to it, (velocity)
or what happens if there is a deviation between commanded and actual
(torque), you are right on.

I believe that it would be possible under most circumstances, given g-code in
on one end and shaft out on the other to still tell the difference. Simply
put a pair of pump pliers and a stethoscope on the shaft. If it goes bump
bump bump when you turn it against stopped command, or when you hold it
steady against commanded motion, it's a stepper. If it ramps quickly up to a
plateau with nice steady torque, hangs in there for a while, and then
suddenly free-wheels it's one of your wonderful 3?0 drives and a servo motor
with encoder.

Perhaps we should blind fold me and run this test at NAMES this year. We can
all watch Ray make an a-- of himself yet again! Watch 'em build these
things with 5HP motors. I'll bring my big pliers! <g>

RayH

>    From: "mariss92705" <mariss92705@...>

> Hi,
>
> Let's try to clear some of the fog surrounding this subject. What I
> would suggest is "stepper or servo" is in fact two sides of the same
> coin.
>
> To show that, the "black box" concept is a useful thought construct
> here.
>
> Let's assume that you have two black boxes. Unknown to you is one box
> contains a step motor while the other contains a servomotor. Each box
> also contains the drive electronics; a full step drive for the
> stepper and a 200 count encoder and servodrive for the other. Both
> boxes also contain a PC (they are big boxes).

<s>