Agricultural harvester ground tracking control system and method using fuzzy logic

A method and control system for an agricultural harvester having a frame and a cut crop receiving header coupled to a hydraulic cylinder. The header has a cutter pivotably mounted on its bottom. The header has a height relative to the frame that is adjusted by applying fluid under pressure to the cylinder. A first control valve is fluidly coupled to the cylinder and responsive to a first input signal for increasing fluid pressure in the cylinder to raise the header. A second control valve is fluidly coupled to the cylinder and responsive to a second input signal for reducing fluid pressure in the cylinder to lower the header. An electrical flex angle signal is produced, representing a flex angle between the bottom of the header and the cutter. A plurality of local maximum and minimum values of the flex angle signal are measured as the cutter passes over respective maxima and minima of a height of the ground relative to the frame. The local maximum and minimum values are identified and stored. A fuzzy inferring device determines the first and second input signals by fuzzy inference based on the plurality of local maximum and minimum values.