Re: These servo motors worth a darn?

stratton@... wrote:

> Well it should be possible to somehow design a servo system that would
> look at two encoders, one on the screw (or a linear) and one on the
> motor. Or put an encoder on the screw and the tachometer (which is
> often seperate rather than numerically dervied from the encoder) on
> the motor.

Arrgh! No, you really don't want to do that. There is absolutely no
reason to put another encoder on the motor, but you might want to have
a tachometer either on the motor or the leadscrew. But, the system just
has to be set up so that the springiness of the motor to screw coupling
is not significant. If it IS significant, it will cause problems in the servo
loop. But, fixing it with additional sensors is a bad approach. A much
better approach is to solve the flex with a different coupling method or
material.

But, for machine tool drives, the toothed belt should be fine.

Jon