Agricultural harvester with closed loop header control

Abstract

A method and apparatus for controlling an agricultural harvester having a cut crop receiving header coupled to a hydraulic cylinder. The header applies a force against the ground that is adjusted by applying pressure to the cylinder. A first proportional valve is fluidly coupled to the cylinder, and responds to a first input signal by increasing pressure in the cylinder to a setpoint value, when the pressure is less than the setpoint. A second proportional valve is also fluidly coupled to the cylinder, and responds to a second input signal by reducing pressure in the cylinder to the setpoint pressure value, when the pressure is greater than the setpoint. A pressure signal representing cylinder pressure is received. The difference between the measured pressure and the setpoint is used to compute the first and second input signals, which are transmitted to the valves. Cylinder pressure is maintained substantially at the setpoint, maintaining the force applied against the ground by the header substantially constant. Alternatively, header height may be measured and the valves controlled to maintain header position substantially constant relative to the ground or the harvester frame. Header lateral tilt is controlled while controlling either cylinder pressure or header height. A resume function returns the header from a raised position to a cutting position at the beginning of a new row.