This paper discusses the development of a method for on-the-fly, self-calibration of a mass-flow sensing system on a harvest combine in order to enable accurate mass-flow sensing and, consequently, yield mapping, under varying input conditions, for example due to changes in the moisture content of harvested grains or the aging of elevator paddles. The proposed method relies on a known or estimated physics-based relationship between the grain dynamics through the grain elevator and a measured force imparted on an impact plate through collisions with the grains. The paper provides a summary description of the modeled relationship between the rate of mass flow and impact-plate sensor readout and conceptualizes the self-calibration scheme through the introduction of an additional, controllable, degree of freedom of the plate. The validity of the self-calibration technique is illustrated through off-line application to bench-top and full-scale experimental test data.

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