Abstract: The method for automatically controlling the height of a header used with a farm implement comprises the steps of: sensing the height of the header above ground; selecting a desired height of the header above ground; determining any difference error between the selected height and the sensed height; determining the direction of the difference error, up or down; generating an electrical correction pulse having a duty cycle directly related to the amount of the difference error; supplying the electrical correction pulse to solenoid operated valving means to cause same to supply and/or relieve a pulse of pressurized fluid to a mechanism for raising or lowering the header; and repeating the above steps automatically and continuously to move the header in intermittent pulses toward the selected height, thereby automatically to control the height of the header above ground.

Abstract: A self propelled combine having forward main drive wheels and rear steerable wheels. A hydrostatic drive including a variable displacement motor is arranged to drive the main drive wheels. An electronic-hydraulic control system is automatically operable to drive the rear steerable wheels in response to sensing preselected pressure and combine attitude values while automatically varying the displacement of the hydrostatic drive motor to minimize combine speed changes and to provide torque as required under varying loads imposed by hilly terrain or increasing amounts of grain collected in the grain tank of the combine.