| The yield monitor system can provide decision for agricultural yield and operation by acquiring the yield information of field.Existing yield monitor system can realize the measurement of crop yield by acquiring the grain flow information and position information of combine harvester for the field operation.Grain flow is measured by impulse method to measure the grain mass flow rate of the pneumatic conveying device.the volumetric method is used to measure grain volume of the scraper conveyor.In order to reduce the measurement error of the grain flow,improve the accuracy of the BeiDou Navigation Satellite System(BDS)and obtain the reliable yield data,the following work was carried out.1.To obtain the grain flow and location information.The impulse type flow sensor was designed for the auger type grain conveying structure.The design of laser sensor array for scraper type grain conveying structure.the elevator scraper is arranged on the side of multiple laser,the measured grain is divided into a plurality of measurement area,reduce the measurement error caused by the change of grain distribution.The position data is obtained by the BDS and the position error of system is corrected by position and pseudo range differential position technology.2.Aiming at the problem that combine harvester could not obtain reliable grain flow information in complex noise background.Wavelet Decomposition(WD)is proposed to denoise the output signal of grain flow sensor.The method is as follows:using the LabVIEW to acquire the output signal of the grain flow sensor and analyzing the amplitude-frequency characteristics of signal.the energy-dominant frequency band is set as the grain effective signal,the chaotic and the amplitude change flat frequency band are set as the noise signal.According to the spectrum of original signal and noise to determine how to choose the wavelet function and decomposition scale.The Mallat algorithm is applicated to decompose and remove the noise components of grain flow signal.3.Using the MCU to design the yield monitor system,which acquiring the flow,position and speed information,the yield information was stored in SD card.Computer read the SD storage information.The calculated yield data was transfered into the Origin software worksheet,by the Origin software to generate the flow map and yield map of field.4.Through the experiment of grain conveying platform,the db4 wavelet is chosen as the wavelet function and the decomposition scale is 6.The effective data of grain flow are reconstructed by wavelet and calibrated by MCU.The maximum relative error of the grain mass is 1.68% under different grain flow.The yield monitor system was installed on the combine harvester to simulate the rice harvest experiment.The quantitative rice are transported to the grain tank output at a different rate per unit time.The speed of driving wheel of grain-conveying auger is gradually increased to the grain flow experiment.After the WD for the output signal of flow sensor,reconstructing the base frequency of grain flow information can be removed by the vibration noise.The average relative error of grain flow measurement is 4.60%.The yield data recorded in the yield monitor system was imported into PC to plot yield map.According to the comparison of the yield map and the actual yield measurement,the relative error of yield is no more than 7.14%,the accuracy of the yield map is verified.This method can provide a reference for the study of yield measurement in combine harvester. |
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