Gday Aidan
Quote:
|
i can't help but thinking that the next big step will be a move to direct drive.
|
Direct drive is essentially just a big stepper, and will have a minimal gain ( at arcsec resolution ) without high quality encoders as well.
The big advances will be gained as absolute encoder technology matures and becomes cheaper/simpler to setup and use.
Quote:
|
you eliminate any mechanical PE
|
Again,
at the arcsec level, you can reduce, but not eliminate errors ( both periodoc and non periodic ), as all mechanical devices are built to tolerances.
Errors in fabrication of the poles of the motor, will affect its use without encoders and errors in the etching of the encoders themselves will result in errors in the final position.
Just do the math to see what 1 arcsecond of error is on say
a 5" dia encoder disk, and then factor in thermal stability,
eccentricity in mounting, flexure etc etc. Its not trivial.
There sure are ways to get the errors down low, but in the end, it gets down to a cost benefit equation as the tolerances drop and the costs skyrocket.
Andrew