| The precision seeding system is the core component of the planter,which has an important impact on the planting and production of crops.The traditional seeding system is propelled by land wheel,which affects the uniformity of speed when sliding.The negative pressure fan is driven by the power output shaft or hydraulic motor,and the negative pressure fluctuation of the ground turning is large.If the high negative pressure is maintained at all times,the power loss increases.The guide tube is fixed,and the change of working speed causes the collision variation between the seed and the guide tube wall to increase,which affects the consistency of plant spacing.The intelligent level of seeding system is low,and it is difficult for operators to obtain seeding information accurately.Aiming at a series of shortcomings in the existing seeding system,so as to improve the intelligence and precision of the seeding system,a multi-objective electric drive intelligent variable precision seeding system is developed.The system is based on CANopen communication protocol,with STM32 microcontroller as the main station,electric drive seeding speed variable control system,electric drive negative pressure variable supply system,intelligent control seeding guide system and seeding performance detection system as slave stations,to realize the functions of accurate driving of seeding speed,negative pressure variable supply,precise seed delivery and correct detection of seeding performance.The main contents of this paper are as follows:（1）Accurate drive of seeding speed:The air suction seed metering device is selected as the research object.The seed metering plate has gears,and the motor drives the seed metering plate from the circumference to make the seed metering device work.The torque measurement test bench of the metering device was built,and the torque of the circular drive metering device was less than or equal to 0.4N·m.The integrated stepping servo motor is selected as the seeding drive motor and the STM32 microcontroller is chosen as the master station controller.The operating speed was measured by the GPS sensor,and the actual speed was fed back by the motor itself.The incremental PI algorithm was used to realize the closed-loop control of the motor speed.The Kmpand Kmi were 450 and 2.25,respectively.In the constant speed and variable speed tests at 2～12km·h-1,the average settling time,steady state error and overshoot were 514.17ms,2r·min-1 and 1.9%;450.42ms,1.98r·min-1 and 1.49%respectively.（2）The negative pressure variable supply of the fan:By the bench test,the relationship between the duty cycle-negative pressure-speed-current of the fan was explored,and then the high-speed camera was used to analyze the single-grain adsorption rate of the seeds at different operating speeds.The ICAN7404 module is used to communicate with STM32,and the Kalman filter algorithm was used to improve the accuracy of fan speed measurement,and then the piecewise incremental PI algorithm was used to realize the feedback control of fan speed.The three groups of Kfp and Kfi were 0.33,0.04;0.35,0.04;0.37,0.05 respectively.In the constant speed and variable speed tests at 2～12km·h-1,the average settling time,steady state error and overshoot were 1106.5ms,108.37r·min-1 and 1.28%;1123.58ms,95.69r·min-1 and 0.53%respectively.（3）Precise delivery of seeds:A deformable seed guide tube with electric push rod as the power source is designed.The theoretical and EDEM simulation analysis of the movement process of seeds in the deformable seed guide tube is carried out.The mathematical model of working speed-electric push rod displacement is established,and the communication with STM32 is realized by ICAN3402 module.Using high-speed camera shooting analysis,at 2～12 km·h-1,the seed trajectory and secondary collision rate of the seed in the fixed and deformable seed tube were analyzed.The average secondary collision rate of the fixed and deformable seed tube was 27.53%and 7.66%.Compared with the fixed seed tube,the secondary collision rate of the variable seed tube decreased by 19.87%.At2～12km·h-1,when the negative pressure fan maintains the maximum speed,the coefficient of variation of seeding spacing is reduced by 22.32 percentage points on average compared with the fixed seed tube.In the 15,30,45 seconds variable speed test,the average qualified rate is 6.15%higher than the fixed seed tube.（4）Correct detection of seeding performance:The detection of seeding performance is realized by using the opposite optical fiber sensor and amplifier,and the communication with STM32 is also realized by ICAN7404 module.The experimental results showed that the average value of seeding accuracy was 98.84%and the coefficient of variation was 0.38%at 2～12km·h-1,and it still reached 98.53%at 12km·h-1.Compared with the high-speed camera shooting,the performance of the sensor seeding detection is analyzed.The difference between the average qualified rate of the seeding spacing and the missing seeding rate is less than 1%.At the same time,the serial port screen is used as the human-computer interaction module to realize the seeding detection parameter display,seeding data input and control system start and stop.Relevant bench tests were designed to verify the performance of the multi-objective electric drive seeding system.The results showed that the average qualified rate of the multi-objective electric drive seeding system was 95.26%at 2～12km·h-1,and the power consumption of the optimal speed of the fan was reduced by 39.08W compared with the maximum speed.At 8～12km·h-1,the average values of qualified rate,multiple rate,missing rate and coefficient of variation of multi-objective electric drive seeding system were increased by 4.29%and dropped by 2.64%,1.65%and 26.54 percentage points respectively compared with traditional seeding system.At 2～12km·h-1,the detection average values of the qualified rate,multiple rate,missing rate and coefficient of variation of the fiber optic sensor differ by 1.25%,0.97%,0.28%and 0.76%from those of the JPS-12 test bench.In the15,30,45 seconds variable speed test,the average qualified rate of the multi-objective electric drive seeding system and the optical fiber sensor was 95.68%and 96.81%,respectively,which was 6.67%and 1.13%higher than that of the traditional seeding system and the JPS-12 test bench.The multi-objective electric drive intelligent variable precision seeding system studied in this paper can realize accurate driving of seeding speed,negative pressure variable supply,accurate seed delivery and accurate detection of seeding performance,moreover,part and the overall working performance meet the requirements of precision seeding operation.The research scheme and content of the system can provide some new ideas for the intelligent development of precision seeding system. |
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