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It would be desirable to produce a precision yield map using smaller area for mass measurements. However, when the reaping distance decreases for each measurement, disturbance effects become prominent. Since tractors or trailers have rather larger masses compared to harvested crop mass, disturbance effects of ground undulation through the vehicle dynamics overwhelm the harvested mass of a unit area. Therefore, it is inevitable to provide a method to remove the error components from the yield data.

In this study, an indirect method of crop flow measurement is suggested to show robustness to the disturbance. The proposed method is counting the number of interrupted light transmission in arrays of LED and phototransistor sets, and then mass data can be obtained through a predetermined relationship between crop flow and photosensor output. Since the number of interrupted light transmission is counted without any contact, vehicle vibration has no effects on the measurements.

The experiments were conducted for the small scale flows of beans, rice, and bamboo strips under extreme vibration. Converted mass from the photosensor output show no effects on vibration, even though the mass obtained by load cells have much greater magnitudes of noises than the mass itself.