Optimum design of grain sieve losses monitoring sensor utilizing partial constrained viscoelastic layer damping (PCLD) treatment

Grain sieve losses has been an important dominant factor for automatic adjustment of the major working parameters of combine harvesters such as cylinder speed, concave clearance, fan speed and vehicle forward speed. To monitor grain sieve losses real-timely in the working processing of combine harvester, a grain sieve losses monitoring sensor, which utilizing YT-5 type piezoelectric ceramic as sensing material developed. To accelerate grain sieve losses monitoring sensor's detecting speed, theoretical analysis was performed from view of structural vibration and a partial constrained viscoelastic layer damping (PCLD) treatment was carried out on the surface of the grain sieve losses monitoring sensor. On the basis of analyzing the mechanical relationships among each layer of the sandwich in depth, an optimal position to past the viscoelastic layer was found. Grain collision experiment results found that grain collision signal attenuate time was shortened to about 2-3 ms after treated with PCLD in places with relative larger modal deformation, namely, the developed sensor could identify more than 300-500 grains within 1s in theory, which verified that the sensor's detecting speed was significantly improved. To test the performance of the developed sensor, calibration experiments carried out in the laboratory, and analysed the influence of moisture content (MC), sensor mounts height and angle on measurement accuracy. At last, installed grain sieve losses monitoring sensor on a combine harvester field experiments took place; experimental results showed that the largest measurement relative error was 4.48% when harvesting rice.