I'm not an expert but the video is very comprehensive. There is closed loop control that is extremely precise in a relative way. In this domain it's all relative anyway because there's no GPS so to speak. It's all reference frames and 3-2-1 locality. [edit: ahhh at 21:47 in the video he says (paraphrasing) "there is offset due to thermal drift of the plastic parts as they get warmed by the motors". ]

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Joel_Mckay 3 hours ago | parent [-]

In general, platforms are placed in a temperature-controlled/heated draft-guard chamber, on a vibration isolation table, and use uniform materials that do not deform much in the narrow operating temperature range (+-0.5'C).

The stage is not the primary design constraint, but rather it is the position sensors that still cost. At a certain point, some realize the pi-usa stages lofty price was actually fairly reasonable in retrospect.

Best regards, =3

	▲	bahmboo 2 hours ago \| parent [-]
		Interesting. I researched what you referenced. This is a fantastic "hobby project" level of engineering but if one is truly tasked with this level of metrology there are still many aspects that need to be addressed and corrected for. Usually that means there is a lot of money on the line and one can't mess it up. Hence the high price tag of established industry accepted solutions. -whew- I wrote that myself.