To improve the accuracy of the parameters used in the discrete element simulation test, this study calibrated the simulation parameters of cotton seeds by combining a physical test and simulation test. Based on the intrinsic parameters used for the physical test of cotton seed, according to the freefall collision method, inclined plane sliding method, and inclined plane rolling method, the contact parameters of cotton seeds and cotton seeds, stainless steel, and nylon were measured, respectively. The physical test of the accumulation angle and angle of repose of the cotton seeds was conducted. It was obtained to process the image of the seed pile with Matrix Laboratory software. The Plackett–Burman test was used to screen the significance of the simulation parameters. The optimal value range of the significant parameters was determined according to the steepest climbing test. The second-order regression model of the significant parameters, the stacking-angle error, and the angle-of-repose error were obtained according to the Box–Behnken design test. Taking the minimum stacking-angle error and angle-of-repose error as the optimization target values, the following optimal parameter combination was obtained: the interspecies collision recovery coefficient was 0.413, the interspecies static friction coefficient was 0.695, and the interspecies rolling friction coefficient was 0.214. Three repetitive simulation experiments were conducted to prove the reliability of the calibration results. The research results can be used for discrete element simulation experiments for cotton precision seed metering.

HighlightsThis study designed an air-suction jujube picking and conveying device to address the problems of low transport efficiency and high damage rate.Theoretical analysis, Fluent software simulation, and prototype testing determined the diameter of the conveying pipe, the inlet and outlet diameters of the suction chamber, and the fan type and speed.A Box-Behnken center combination design in Design-Expert software was used to perform response surface orthogonal tests to optimize the device.This study provides a reference for further optimization of the air-suction jujube picking and conveying device.Abstract. To address the problems of low transport efficiency and high damage rate, an air-suction jujube picking and conveying device was designed. The main components of the device include the fan, suction chamber, and conveying pipe. Simulation of the conveying pipe and suction chamber was performed using Fluent software, and the airflow rate and pressure were analyzed for conveying pipes of five different diameters and suction chambers with different inlet and outlet diameters. In the simulation results, the diameter of the conveying pipe was 105 to 165 mm, and the outlet diameter of the suction chamber was 150 to 210 mm. The Box-Behnken center combination design method in Design-Expert software was used to perform response surface orthogonal tests with the conveying pipe diameter, suction chamber outlet diameter, and fan speed as the test factors, and the jujube conveying rate and breakage rate as the target values. The results show that the order of the test factors on the jujube conveying rate is: fan speed = conveying pipe diameter > suction chamber outlet diameter, and the order of the test factors on the jujube breakage rate is: fan speed > suction chamber outlet diameter > conveying pipe diameter. The experimental results were verified in field tests with the optimized parameters. When the conveying pipe diameter was 165 mm, the suction chamber outlet diameter was 200 mm, and the fan speed was 3254 rpm, the average jujube conveying rate in the verification test was 238.68 kg h-1. The relative error between the experimental verification value and the theoretical optimized value was 1.44%, which is less than 5%. The average value of the jujube breakage rate in the verification test was 2.18%. The relative error between the experimental verification value and the theoretical optimized value was 3.81%, which is also less than 5%. This study provides a reference for subsequent research and optimization of the air-suction jujube picking and conveying device. Keywords: Air suction, Conveying device, Conveying pipe, Jujube, Suction chamber.

In order to solve the problems such as the inability to automatically mix a variety of solid fertilizers and the unreasonable fertilizer amount, improve fertilizer utilization, and reduce production costs, this study designs a variable formula fertilization control system based on a prescription diagram, including pressure sensor, speed sensor, servo motor, fertilizer discharge actuator, Programmable Logic Controller (PLC controller), vehicle control terminal, etc. Based on pre-loaded soil prescription diagram and combining fertilizer pressure and ground wheel speed detection information, the system obtained a formula fertilization control strategy through calculation to realize the function of fast and automatic formula of nitrogen, phosphorus, and potassium fertilizers and precise variable fertilization. The experimental study on the performance of the variable formula fertilization control system showed the following: the measurement error range of the pressure sensor was 0.005~0.03%; the relationship between the motor speed and the amount of nitrogen, phosphorus, and potassium fertilizer discharged was calibrated. Three gears were established for the motor speed: low (10 r/min), medium (30 r/min), and high (50 r/min); the measurement accuracy of the speed sensor was above 98%. The test verified that the control accuracy of the variable formula fertilization system reached more than 95%, which met the requirements of fast automatic formula and precise variable fertilization and had good practicability and economy.

To realize the real-time monitoring of the cotton precision seeding operation process and improve the intelligence level of cotton precision planters, based on automatic color matching detection technology and visualization technology, this study designs a monitoring system for the sowing quality of cotton precision planters. The monitoring system is based on the double-silo turntable type cotton vertical disc hole seed metering device as the research carrier, and is composed of a missed seeding monitoring module and a visualization module. Among them, the missed seeding monitoring module includes an incremental rotary encoder, color code electric eye color fiber optic sensor, color code sensor amplifier, etc.; the visualization module includes data acquisition module, industrial computer, and so on. The missing seeding monitoring module is installed on the seed spacer of the cotton precision seed metering device. It uses Labview software for graphical programming and is equipped with a multi-functional industrial computer. It realizes the monitoring of parameters such as the number of sowings, the number of missed sowings, the speed of the hole seeder, the forward speed of the machine, and the sowing area. The results of the bench test and field test of the sowing monitoring system showed that the accuracy rate of the system’s broadcast monitoring was over 93%, and the accuracy rate of missed broadcast monitoring was over 91%. The system solved the technical problem that cotton film-laying and sowing were not easy to detect. It could accurately detect the quality of cotton sowing in real time and meet the actual requirements of sowing monitoring.