To my knowledge, the "robot" subtype is a subtype of construct, which uses Knowledge Arcana. Going through the robot subtype notes now... doesn't say anything that would make it different.
Actually, the PFSRD has it already although from Inner Sea Bestiary.
Also, this is not a PFS specific questions so probably best served over at the rules forum.
The details for this are also featured in the Iron Gods Player's Guide.
Researching Technology
A character can use the following skills to research technological subjects. Other skills may have research applications as well, subject to GM approval.
Heal: Used to identify and understand pharmaceuticals.
Knowledge (arcana): Although robots are constructs, Knowledge (arcana) cannot be used to identify robots or their abilities and weaknesses.
Knowledge (engineering): This is the most important skill with regard to technological subjects. Knowledge (engineering) can be used to identify a robot’s abilities and weaknesses. Knowledge (engineering) is also used to identify and understand unknown technological objects in a similar manner to how Spellcraft is used to identify the properties of a magic item. The DC to correctly identify and understand an unknown technological object is equal to the object’s Craft DC. An object with a Craft DC of 15 or less can be automatically identified and understood by someone trained in Knowledge (engineering) who also has the Technologist feat.
Knowledge (geography): Used for astronomy.
I've heard the Technology guide is being added to the PRD, which is unprecedented for campaign setting books, due to its importance in the Iron Gods AP. That won't happen until after Gencon, of course.