A combine harvester is described, comprising a cleaning system (100, 200) for receiving a flow of harvested and threshed crop, the cleaning system comprising at least one cleaner assembly (105, 110, 210) for cleaning the harvested and threshed crop and a drive assembly connected to the cleaning system, the drive assembly being configured to drive the cleaning system, thereby driving the at least one cleaner assembly to perform a reciprocating cleaner movement. The drive assembly comprises a variable speed drive assembly with a rotary drive comprising a rotatable output shaft (175) for driving the cleaning system, a transmission (176, 177, 178) configured to connect the rotatable output shaft (175) to the at least one cleaner assembly of the cleaning system (100, 200), the transmission being configured to convert an angular movement of the rotatable output shaft (175) to the reciprocating cleaner movement, and a control unit (190) configured to control an angular velocity of the rotatable output shaft (175) based on an input signal (192) received at an input (194) of the control unit (190).
