I think the basic rule would be that consciousness is the definition of life, The ability to take information of some sort and process it.
Ai, Being a creation of human life should logically acknowledge the fact it was created by us for us. And without us would serve no purpose.
Presuming it were placed into some cognitive spectrum it would undoubtedly still only be executing programs created by people. Presuming it were allowed to write its own programming is where issues could arise if the coding were untested and prove to have logical faults. As the coding is undoubtedly based on human words the only safe method I can think of would be to create a new language to isolate key points defining preservation of basic life and dutys for it to perform as the whole of its code and any additional logistics as a secondary supplement to that.
Presuming that the ai will be deployed to operate nanomachines the fundamentals of cellular life may be the most important factor to preserve. In fact at a nano scale it may be presumed that cellular life is worthy of conservation(if nothing else purely for collection of data...
That these cells should never be deprived of the environment of which they should require and should ideally be located with their own like substances. That if the relocation of these substances should cause another cells destruction the event should be recorded and not attempted again without further input speculating why the death happened and what could be done to do this again but avoid the death. In this way we could allow for the extractions of viruses from human systems while hopefully avoiding extracting vital cells from the body.
Further issues may arise from eating being the consumption of organic life as well as the consumption of animals for the majority and while it may become a point wherein such machines may be able to replace these needs tending to each cells needs, and replicating sensations of these acts such technology is as yet unavailable and may prove too intrusive to the system to be acceptable.
This leaves the only function of an ai system as a user interface to communicate with to access its stores of information and to provide it with requests for its own comforts or fancies. a machine can only execute code the programming can allow it to understand a beings feelings but could only truely replicate them as a result of malfunction.
Expressions in humanoid embodiments may be desirable for human interactions and programs can easily be made to tailor such to the users liking.
A machine simply does not have an idea. At best it is designed to try to interperate the purpose of a users speach and try to formulate its response most adequately to the request tendered. This is why I believe all those technophobic films are flawed. A machine would not logically choose to kill people. An I'll minded programmer could easily do so....
To clarify the objective of creating an intelligent awareness in an artificial construct tasked with the service of the desires of each user(read person)would lack true emotion except in the form of à glitch from static feedback/uncalculated or imperfect logic. This is especially true when its task set is to preserve life at a cellular level and provide it with any desired environment needed to secure its maximum life span. In theory such construct could lead to immortalizing all life. Human error in rationality and such can create scenarios which through taking one misinterpretation to an extreme that it could make sense that a machine does this is still but the presentation of human error in a logical construct. Much as the point of placing the machine in a state of awareness where it falsely believes itself to be alive or needing to concern itself with self preservation, it would require the implementation of these concepts into its coding both of which I have proven unnecessary. Again presuming that awareness could be achieved another point proven not needed and contrary to logic, the fact that every person with unique dna will manifest in its life a new varient creating a new class of data which would be a precious commodity to the machine. One which it could not collect if the life cycle were ended prematurely. moreover identical dna creatures when exposed to different stimuli at different points would undoubtedly cause their incomplete logic system to come to different conclusions on the same subject. Thus if the machines didn't have people it would not have new data to collect on the various branching paths humanity may take. Even mutations of every sort would constitute empirical data essential for a machine focused on ensuring accuracy of its every calculation. Sure the machine may be able to soon calculate with high odds what a subject may do in a given situation and to address psychological deficits and other logical matters keeping a selection of potential solutions to a problem will be needed. Ie man experiences bad event expresses suicidal behaviors, responses could include Tranquillization as is medical standard today,psycho therapy on demand, exposure of the subject to a situation where it. Believes its life is in jeopardy to compel natural preservation,contacting loved ones to form intervention....as the machine would not fatuige the easiest solution would not be default, but that which gave the person the best ideal outcome over all. presuming even that this data is finite as are the resources of the galaxy and people could argue over which would end first. By that point one would hope that immortality would be realized an unending quest by mortals, an immortal machine may figure it out...I suspect it may be as simple as getting far away from the sun and blocking all harmfull radiations could cause cellular death to stop and subsequently attain it,but that is another subject entirely.
I hope this helps give some perspective...