Two degrees of freedom control for combine harvester header height control

This paper presents a two degree of freedom (DOF) controller for combine harvester header height control (HHC). Previous work [1] identified fundamental limitations to the tracking and disturbance rejection bandwidths for feedback control designs. In this work, we utilize H∞ optimal control design to ensure closed loop stability and robust performance, and augment a feedback loop with a feedforward control structure based on readily available Global Positioning System (GPS) information. The GPS provides anticipatory information of the field map elevation, which become disturbances to the header height control problem, to the feedforward controller thereby increasing the overall disturbance rejection bandwidth. Simulation results illustrate the performance improvements resulting from the two DOF design over the stand alone feedback controller. Additionally, an error analysis examines the effect of uncertainties from system modeling and field map measurements on the system performance.