Design and modeling of grain impact sensor utilizing two crossed polyvinylidene fluoride films

Abstract. In order to reduce the unavoidable grain losses during harvesting, the combine harvester‘s operational parameters should be adjusted accordingly. So, it is important to develop a real-time sensor which can monitor the grain losses. A grain impact sensor utilizing crossed piezoelectric polyvinylidene fluoride (PVDF) films as sensitive material is described.

This sensor is composed of two crossed layers of sensor unit arrays, a damping layer and a support plate. The two layers are insulated from each other but can detect the impact simultaneously. The sensor unit arrays of those two layers are perpendicular and the sensor units in each layer are independent and parallel. Each sensor unit has its independent signal processing circuit, which is composed of charge amplifier, band-pass filter, envelope detector and voltage comparator. Two signals from two layers presented a two-dimensional impact position information through multi-sensor fusion technology. The sensor can obtain the spatial distribution of grain loss accurately to reduce the error-recognition ratio. Moreover, the grain impact sensor was simulated by finite element method to obtain the best number and size of the sensor units for higher sensitivity, detection speed, stress transfer efficiency, deformation transfer efficiency.