How to define unmanned drone

[Wahazar]

Is it possible, using existing rulesets format, to define drone unit, which doesn't make unhappy citizens when going out from the city?
There would be nice to have weak unit, which can be used for patrolling duty without all these revolts.

[Corbeau]

units.ruleset

For the particular unit:

uk_happy = 0

For military units it's usually 1, for Diplomats, Settlers etc. it's 0.

[Wahazar]

Thank you for answer, I was fooled by this parameter name, though that it is for martial law (I expected something like uk_unhappy)