Technique And Device Of Rapeseed Flow Sensor And Variable Reseeding For Loss Sowing

Mechanized precision seeding plays an important role in intelligent agricultural machinery development due to its advantages of saving seeds,reducing labor intensity,improving operation efficiency and increasing farmers' income.Sowing monitoring and loss sowing detection and reseeding are the development trends of intelligent precision seeding.Rapeseed is the largest oil crop planted in China,the sowing quantity of precision metering device is indirectly obtained through seed changes in seed box or rotation speed of metering device with number of hole in seed plate for rapeseed and other small seeds because of its small size,light weight,high frequency seeding and closed seeding process.Complex field environment and mechanical faults will inevitably cause loss sowing and crop yield reduction.So it is necessary to design a sensing device for real-time detection of rapeseeds and other small seeds flow,and design a set of loss sowing detection and reseeding system on this sensing base.Finally it can be used for sowing quantity monitoring,loss sowing detection and automatic reseeding in the process of rapeseed precision sowing,and improves sowing quality and efficiency.Based on the analysis of current situation on seed sensing and loss sowing detection and reseeding for precision metering device at home and abroad,a seed flow sensing device for rapeseed precision metering device with principle of piezoelectric induction.And on the basis of the sensing device,a set of loss sowing detection and variable reseeding system for rapeseed precision metering device was designed and tested.The main research contents were conducted as follows:(1)A seed flow sensing device for rapeseed precision metering device was designed,which realized inducing and counting for rapeseed and other small seeds.Specifically,based on the analysis of impact signal characteristics between rapeseed and piezoelectric film,piezoelectric sensing detection method for rapeseed flow was explored,and sensing structure of sinking groove substrate and piezoelectric film which improved time resolution for high frequency seed flow detection and effectively eliminated mechanical vibration interference was designed.Collision trajectory between rapeseed and PVDF(polyvinylidene fluoride)piezoelectric film was recorded and analyzed using high-speed photography and collision dynamics.These data provided a quantitative reference for the design of key structures in terms of the diameter of catheter,sloping angle of piezoelectric film,position of seed-output,length of catheter,etc.The signal acquisition system turned weak signal into single pulse signal by signal conditioning(including signal amplification,half wave rectification,voltage comparison,and mono-stable triggering).Then,the real-time detection of seeding frequency and seeding quantity of rapeseed flow was obtained through the timing and counting function of the MCU(micro-controller unit).Finally,these data were transmitted at a fixed time interval by wireless transmission module to the monitoring display terminal,and the real-time display and storage of detection data were realized.Bench experiment and field experiment results indicated that the sensing device could detect the seed flow seeding frequency and seeding quantity,and detection accuracy was not less than 98% under normal seeding.(2)Integrated variable reseeding device for loss sowing of rapeseed precision metering device was designed,and it provided technical support for automatic reseeding for loss sowing.The variable reseeding device integrated spiral-tube reseeding device,direct current speed reduction motor,single-chip microcomputer control system,motor drive system,wireless transceiver module and separate power into a whole body,leading to compact structure in size with relatively independent function.With the experimental verification,height of inner screw,number of spiral-tube,size of seeding export hole in seed box and other structures were optimized.Direct current motor was driven through fixing the frequency of PWM and adjusting its pulse width to control rotation speed of reseeding device.And then variable seeding rate could be obtained by this way.Metering characteristics tests showed that when rotation speed of the reseeding device was 23-228 r/min,seed number collected in one minute increased linearly with the rotation speed increasing,seeding number from each solenoid in every rotation period of reseeding device was 1.2-1.4.Function relationship between PWM duty cycle and rotation speed was got using the curve fitting method.(3)Loss sowing detection and variable reseeding system for rapeseed precision metering device was designed and performance test was carried out.The system was made up of loss sowing detection sensing device,rotation speed measuring device of seeding plate,variable reseeding device for loss sowing and monitoring display device for loss sowing and reseeding.The commands and data between components of system were orderly transmitted for real-time businesses by nRF wireless transceiver module.Loss sowing detection sensing device detected seeding time intervals sequence and seeding number within a detection cycle sequence.Theoretical seeding frequency was updated by receiving the rotation data which being transmitted(timing 1s)from rotation speed measuring device of seeding plate.Reseeding rotation speed was obtained by reseeding strategy for loss sowing.Loss sowing and reseeding state parameters were calculated with the method of loss sowing detection in real time by time-varying window,and transmitted to variable reseeding device for loss sowing and monitoring display device for loss sowing and reseeding.Reseeding device received the reseeding command and variable reseeded in real-time utilizing corresponding duty cycle.Monitoring display device for loss sowing and reseeding refreshed and scrolling displayed the status parameters of loss sowing and reseeding in recent 10 detection cycles.Test of loss sowing detection and variable reseeding system showed that when precision metering device was within normal range,detection result of loss sowing was consistent with the actual value and variable reseeding device could adjust its rotation speed to realize variable reseeding.Thus the system effectively reduced miss index and improved seeding quality.