Re: Doubling up servo's...

--- In CAD_CAM_EDM_DRO@yahoogroups.com, stan <stan.distortion@...> wrote:

>
> Sorry if I'm way off the mark with this, new to the thread and

throwing in an

> idea.
> I was thinking of something along these lines for eliminating backlash.
> Basically 2 motors (reduction etc.) sharing the same controller with

diodes

> and power resistors between them arranged so motor A is getting more

power

> than motor B in fwd and B more than A in rev, one motor would always

pull the

> other. I'm guessing it would only work as the current gets high

enough for

> the resistors to have an effect though.
> cheers
>

Backlash is typically not in the motor so having a breaking motor on
the same axis will either just make motor A work harder or actually
make the backlash worse. Best method to deal with backlash (like
loose steering on a car) is to fix it at the component that is causing it.

There are methods with rack and pinion where you have a rack wide
enough for two pinions (on the same shaft) and you preload each pinion
in the opposite direction. Two more narrow racks with a pinion running
on each one and on the same shaft works even better. Then there is
the one wide pinion with two racks offset approach.....

In leadscrews the backlash needs to be addressed at the nut some form
of anti backlash nut a dual nut design for conventional leadscrews works.

Since the drive to servos is PWM, putting in series resistors can have
effects that may cause other problems. Diodes would do really nasty
things if in series. At best the motor would spin only one direction.

Once again sharing two motors on a servo or stepper drive is
problematic at best.