Precision Fertilization Control System Research for Solid Fertilizers Based on Incremental PID Control Algorithm

Aiming to realize the real-time automatic proportioning of various solid fertilizers in the process of variable rate fertilization and improve the accuracy of the fertilization control system, a variable solid-fertilizer closed-loop fertilization control system and corresponding fertilizer apparatus based on the prescription map was designed for nitrogen (N), phosphorus (P) and potassium (K) fertilizers by using increment PID control algorithm. The system mainly included master-slave controllers, prescription map, Beidou positioning module, speed measuring module, human-machinery interface, electric fertilization motors and fertilization monitoring modules. The function of master controller was as follows: receiving the instructions from human-machinery interface, positioning data acquiring from Beidou module, measuring vehicle speed by Hall sensor module, reading theoretical fertilization amount from prescription map, monitoring the working status of electric fertilization motors, and sending the fertilization instructions to slave controller. Human-machinery interface was used to set or read the operation parameters between master controller and mobile APP. The slave controller received and delivered fertilization motors instructions. According to the fact that small and medium-sized seeders were widely used in field production in China, the laboratory experiments were carried out with the speeds of fertilization applicator setting in the range of 3.5 km/h to 6.5 km/h, and the maximum and the mean response time of the control system was obtained of 1.85 s and 1.45 s, respectively. When the fertilization rates were set as 50 kg/hm2, 100 kg/hm2, 200 kg/hm2 and 300 kg/hm2 at vehicle speeds of 4 km/h, 5 km/h, and 6 km/h, the accuracy of control and monitoring were more than 97.16% and 98.56%, respectively. In the field experiment in Donghai Village, Shuangcheng District, Harbin, China, with vehicle speeds of 4 km/h, 5 km/h, 6 km/h, the application accuracy of urea, diammonium phosphate and potassium chloride based on a soil prescription map were more than 97.22%, 98.60% and 97.73%, respectively, which met the requirement of precision fertilization system. © 2021, Chinese Society of Agricultural Machinery. All right reserved.