Methods and systems are provided for an engine crankshaft including an un-balanced mass coupled to a planetary gear set driven by the engine crankshaft. In one example, a system may include an engine crankshaft as a sun gear for a planetary gear set, with a single un-balanced mass coupled to an outer ring of the planetary gear set. In another example, a method may include driving an engine crankshaft in a first direction and driving an un-balanced mass coupled to an outer ring of a planetary gear set in a second direction opposite to the first direction, with rotation of the outer ring being driven by the engine crankshaft.