Abstract: An automatic control varies the ground speed of a combine due to changing field conditions, based on engine speed and combine feeder conveyor load variables.

Abstract: The threshing cylinder and feeder conveyor of a combine with electrohydraulic elements are controlled by a digital computer. The computer generates a proportional voltage which is input to a linear amplifier. The amplifier provides control of the spool of an electrohydraulic servovalve. The servovalve controls the speed and direction of the threshing cylinder and feeder conveyor hydraulic motor drive. Tachometer sensors provide feedback measurement of the actual speed of the hydraulic motor output shaft. Analog-to-digital converters (A/D's) interface the computer with the sensors. Control algorithms employ velocity feedback and compensation for pressure rises due to increases in the torque on the cylinder caused by the material to be threshed entering the threshing cylinder-concave region. Easy reversal of the direction of the threshing cylinder and feeder conveyor, eliminating some of the problems associated with plugging, is available with this type of speed control equipment.