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Investigation of a Measurement System on Seed-metering Performance Based on Capacitive Sensors

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Tutor: SunYuJing
School: Jilin University
Course: Agricultural Mechanization Engineering
Keywords: seeding performance,capacitive sensor,LabVIEW,motoring system
CLC: S223.2
Type: Master's thesis
Year:  2013
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With the development of agriculture mechanization, precision seeder has been widelyused in the agricultural production. The seed-metering device is the key part of precision seeder,and its performance plays a crucial role in the seeding quality. In order to ensure the seedingquality, it is necessary to achieve the real-time monitoring of the seed-metering device forworking conditions. Therefore, the study on the monitoring system of the seed-metering deviceperformance is of much significance. Nowadays, the seed-metering device performance islargely detected by photoelectric detection method. The principle of the method is that whenthe seed passing through the detection zone of seed-transportation tube, the pulse signal isgenerated by the seed intercepting the beam, and then the seeding performance is obtained byprocessing the signal. Therefore, it is available to achieve the monitoring of the seeding process.However, the photoelectric sensor is more likely susceptible to the field dust, and it is not easyto identify seeds falling simultaneously. Therefore, the accuracy of the sensor detection isinfluenced by the aspects above.In this paper, we present a new method to monitor the performance of seed-meteringdevice based on capacitive sensor due to the one using photoelectric method being susceptibleto the filed dust as well as being difficult to identify the seeds falling simultaneously. The maincontents of the study include the following:£¨1£©The overall design of the seed-metering device performance motoring system basedon capacitive sensor. The scheme design of the seed-metering device performance motoringsystem is presented by analyzing the performance indicator of the seed-metering device. Thecapacitive sensor, the hardware and the software of the seed-metering device performancemotoring system as well as the interface of the system have been designed.£¨2£©The structural design of the capacitive sensor and the experimental study of a singleseed. According to the requirements of the seed-metering device structure, three kinds ofcapacitive sensors including the Crossed E-shaped plate type, the Paralleled plate type and theDifferential tri-plates type have been designed. The experiment of a single seed is carried out totest the performance of the three sensors. The results of the experiment indicated that when theseed velocity reaches the range of0.272-0.664m/s, the average changes of the capacitance inthe differential tri-plates type sensor and the Crossed E-shape plate type sensor is0.1245pF and0.1115pF, respectively. And they meet the requirements of the seed-metering performancemotoring. While the Paralleled plate type sensor cannot detect the seed at the range of thetesting velocity. This paper selects the Crossed E-shape plate type sensor as the one of theseed-metering performance motoring system for its easy installment.£¨3£©The hardware design of the seed-metering performance motoring system. The capacitance-to-digital converter AD7747is used to collect the capacitance from the sensor andconvert them into digital data. The single-chip microcomputer CY7C68013is selected as thecontroller of the hardware system. The external storage circuit, the communication interfacecircuit and the power circuit have been designed. Therefore, it is available to implement thefunction of data acquisition, data conversion and data communication.£¨4£©The control software design of the seed-metering performance motoring system. Thecontrol program of the slave computer including the main program of the controller, thefirmware program of the single-chip microcomputer CY7C68013and the collection programof AD7747is designed using C language. The software of the host computer is designed byVirtual Instruments LabVIEW. The functions of information processing and display of seedingperformance, USB interface communication and seeding exception reporting have beenachieved. Though the comprehensive tests of the seed-metering device performance motoringsystem, the percent of pass detection accuracy, the re-seeding detection accuracy and themiss-seeding detection accuracy is95.3%,97.4%and90.9%, respectively. Therefore, it isavailable to achieve the real-time motoring of the seeding process, and the performanceindicators of the seed-metering device are displayed on the LabVIEW interface. Finally, thealarm signal is sent out in time when the exception, such as no seed falling and seeding-tubeblocking, is detected.
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