Design And Test Of Monitoring Device Of Cleaning-loss For Combine Harvester

A kind of half-feed grain combine harvester was developed by Xihua university together with a corporation.This kind of combine harvester functioned well during harvesting in the field and finally accomplished the expected harvesting task with good cleanliness.But the main problems of this combine harvester were high loss rate and instability during grain cleaning.In terms of the instability during grain cleaning under terrible condition,a cleaning-loss monitoring and sensing device was used to monitor the real-time loss rate,by means of which the operator is reminded in time,thus the loss rate could be decreased and the instability could be improved.The main tasks are as follows:(1)The cleaning-loss of the harvester in the harvesting process was analyzed,the mathematical model of monitoring the loss rate was set up according to the judgment criterion of the cleaning rate.Based on the principle of cleaning loss and the model,the monitoring device was wholly designed.(2)304 stainless steel sheet was selected for the sensitive sheet by consulting literature.and the thickness of the sensitive sheet was calculated and selected according to the material properties.The boundary condition of the sensitive plate was analyzed and calculated by means of sheet and shell theory,which provided theoretical support for the selection of the aspect ratio of the sensitive sheet and the fixed boundary condition.It ensured that the signal peak voltage could be monitored and the attenuation time of the vibration signal was shortened,which was helpful to reduce the mutual interference probability.(3)The signal to be detected and the noise signal were analyzed by using the measurement data of the vibration signal.The signal processing circuit was designed by taking the difference between the signal of grains' impact on sensitive sheet and the noise signal,then the above processing units were manually welded together to get signal processing.(4)Based on the theory of vibration isolation,the mechanical model of the vibration isolation structure was simplified.The stiffness of vibration isolation system was mathematically calculated on the simplified mechanical model,and the design model of vibration isolation structure was established.According to the random vibration at the rack where monitoring device of cleaning-loss was mounted,intrinsic frequency of rubber was determined,and dynamic stiffness was determined by the theoretical calculation.By thecombination of frequency and amplitude of vibration,preload of rubber isolator and shore hardness,temperature and coordination conditions,the ratio n of dynamic stiffness and static stiffness was selected,and static stiffness was obtained,geometrical parameters of vibration isolator were determined by the longitudinal static stiffness.After the design of vibration isolator,test was carried out in the laboratory,and testing results were compared with the one without vibration isolator.Finally it showed that monitoring device of cleaning-loss with vibration isolator was relatively better at vibration isolation effects.(5)Accuracy of the monitoring device of cleaning-loss was studied.The installation parameters of the device were optimized through the test,and the monitoring accuracy of the whole device was verified.It was proved that the device basically satisfied the expectation and could meet the purpose and requirements of monitoring cleaning-loss rate.