Design and experiment on variable reseeding system for rapeseed precision metering device

Precision seeding plays an important role in intelligent agricultural machinery development because of its advantages of saving seeds, reducing labor intensity, improving operation efficiency and increasing farmers' income. Loss sowing caused by complex field environment and mechanical faults such as clogged seeding holes, pressure fluctuation and faster rotation speed of seeding plate is inevitable for rapeseed pneumatic precision metering device. Artificial reseeding or transplanting in the later stage not only increases manpower and material resources consumption but also delays farming season, reduces crop yield. Thus, loss sowing detection and automatic reseeding system has become one of the development trends in intelligent precision seeding. In recent years, domestic and foreign scholars carried out many related studies on loss sowing detection and reseeding system, mainly for potato, corn, wheat and other large and medium seeds. Few studies have focused on loss sowing detection and reseeding system for rapeseed and other small seeds because of its small size, light weight and high frequency seeding. Ding Youchun put forward a loss sowing detection algorithm to evaluate seeding performance for rapeseed precision device and designed a spiral-tube reseeding device. However, a relatively complete system of loss sowing detection and reseeding system was not proposed. In this study, a variable reseeding system for rapeseed precision metering device was designed and tested. The system was composed of loss sowing detection device, rotation speed measuring device of seeding plate, variable reseeding device and reseeding monitoring display device. The commands and data between components of this system were orderly transmitted for real-time businesses by nRF24L01 wireless transceiver module. Discs with magnetic steel array (which magnetic steel numbers weres proportional to seeding holes) synchronously rotated with seeding plate, and rotation speed measuring device of seeding plate sensed magnetic steel with hall sensor to acquire theoretical seeding frequency. Loss sowing detection device installed under the metering device sensed rapeseed flow sequence, acquired seeding time intervals sequence and seeding numbers within one detection cycle sequence utilizing time capture interrupt function of MSP430 single-chip. Theoretical seeding frequency was updated by receiving the rotation datas which transmitted (timing 1s) from rotation speed measuring device of seeding plate. Loss sowing and reseeding state parameters (including miss coefficient, detection cycle, seeding numbers within one detection cycle, max seeding time interval and rotation speed of reseeding device) were calculated with the method of loss sowing detection in real time by time-varying window, and wireless transmitted to variable reseeding device and reseeding monitoring display device. The variable reseeding device integrated direct current speed reduction motor, single-chip microcomputer control system, motor drive system, wireless transceiver module and separate power into a whole. It received the reseeding command and variably reseeded in real-time utilizing the relational model of rotation speed and duty cycle. Reseeding monitoring display device, equipped with 7-inch color LED display screen, scrolling refresh displayed the status parameters of loss sowing and reseeding in recent 10 detection cycles. Bench test of variable reseeding system was carried out on the JPS-12 test-bed of pneumatic rapeseed precision metering device. During the test, variable reseeding device was lagged behind rapeseed precision metering device by 800 mm with 20 holes as a detection cycle. The theoretical loss sowing coefficient was set as 0.30, 0.50, 0.72, 0.90 and 1.00, and tests were carried out respectively at different rotation speed of 15, 20, 25, 30 and 35 r/min. The test results showed that, when precision metering device was within the range of normal seeding rate, the detection result of loss sowing was consistent with the actual value. Variable reseeding device could adjust its rotation speed to realize variable reseeding, and the ratio of reseeding amount to loss sowing amount was stable in a range of 1.2-1.4. In addition, field test indicated that the system avoided loss sowing on the basis of weak multiples sowing and improved seeding quality. The variable reseeding system presented may provide an effective technical support for loss sowing and auto-reseeding of rapeseed and other small seeds. © 2018, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.