Combine Harvester Control System

A method of controlling a flow of crop material through a grain cleaning unit incorporating a precleaning sieve having adjustable louvres adjustable by a first actuator, an upper sieve having adjustable louvres adjustable by a second actuator and a lower sieve having adjustable louvres adjustable by a third actuator, comprises the steps of

• generating a first cleaning airstream is directed through the upper and lower sieves and a second cleaning airstream is directed through the precleaning sieve,
• measuring an air pressure determined by air pressure sensors at a plurality of locations within the grain cleaning unit,
• determining by a controller, coupled to the air pressure sensors and the first, second and third actuators and operable to control operation of the first, second and third actuators, any desired variation to a position of the louvres of the precleaning sieve, and
• generating a signal from the controller to the first actuator to adjust the position of the louvres of the precleaning sieve accordingly.