I take it this is distinguished between "periodic control" (it should be that way round, not "control periodic", carried out in accordance with a known and established schedule, and "surprise" control, where the controlling authority just turns up unannounced, so those subject to control have no opportunity to tidy things up and the controlling authority finds out how things really are on a regular basis. I think such visits would normally be referred to as "unannounced" or "unscheduled" rather than "unexpected", though the latter is not wrong. I would also say that rather than "control" may not be the best word here; these would more commonly be called "inspections" or even "visits", in my opinion.

--------------------------------------------------
Note added at 12 mins (2013-08-31 10:43:49 GMT)
--------------------------------------------------

Oh dear, my typing! I meant "this is distinguishing" (line 1), not "this is distinguished". And the last sentence should read "I would also say that "control" may not be the best word".

--------------------------------------------------
Note added at 15 mins (2013-08-31 10:46:08 GMT)
--------------------------------------------------

And another thing: ignore what I said about "control periodic"; I see now that this is obviously the Romanian expression. Sorry about all this!