Earlier quoted context omitted.
Those motors are just closed-loop steppers. I'd say they're inappropriate for robot arms because they can only apply their specified torque when the angle happens to be in proximity to a full step [0]. Proper AC servo motors like the A3 series from Delta are - as far as I understand - able to apply their specified torque with "infinite" resolution, in practice limited primarily by the encoder. In robotics though, BLD…
Thank you for your reply. Proper servos with high torque are quite expensive. I wanted to keep the project under a certain amount to scale it. With the springs to compensate the static loads (gravity) I can use weaker servos but I didn’t yet completed the “sensitivity table” of the generated angular momentums. Yes indeed, the ~10arcmin should represent something like 5mm at about 1m distance. Plus the ~30mm of the 1.…
But steppers won't necessarily save you either, because that torque specification only applies to full steps.
Harmonic drives are great but unfortunately quite expensive.
What you might want to do is go cheap on most of the components and add a decent-ish encoder and use software to compensate for the imprecision. CUI's AMT series of encoders is widely available and comes with up to 14-bit resolution. I believe this can be a pain in the arse to get right but it sounds like you're comfortable with maths so it might work well for you.