Bedford’s iRobot Corp. will buy Evolution Robotics Inc. for $74 million, adding a new line of floor-cleaning robots to its suite of consumer and military robots. Evolution’s Mint cleans wood floors and costs about $200. CEO Colin Angle said iRobot plans to focus on growing the overseas market for Mint. The deal also bring new technical talent to iRobot, Angle said. It also comes as iRobot faces some uncertainty on the defense side of business with the Pentagon trimming its budget.