The Martian Centurions are a fictonal robotic race who serve under the Martian Imperial Army. Their name is actually a corruption of the Koshallic Sthentlhiurwio'nai, which roughly translates as 'Metal Hive-Soldier'. This is a fairly good description of the Centurions, who as well as being metal can be very like-minded on occasions, albeit very cowardly as a result. However, the one under the employ of Z-9 are more competent. They appear to be sentient, and make up a large portion of the Imperial Army, while the organic Martians act as officers.
The Centurions have a rather pleasant voice, provided by Michael Dorn, who incidentally also did the voice of Worf in Star Trek.