Study On Control System Of Bivariate Fertilization Seeder

Precision agriculture is widely recognized as sustainable agriculture, and has been achieving significant economic and social benefits in developed countries. Variable rate fertilizer(VRF) technology is an important part of precision agriculture system, and is an effective way to stop the irrational use of fertilizer in our country. Most domestic VRF applicators currently used MCU or PLC as their core controller, so they could not provide a friendly user interface. Meanwhile, with their limited computing power, they could not use GPS/GPRS messages to control several motors in real time. It's also hard to extend their functions.In order to solve those problems, a real-time control system based on ARM and DSP dual-CPU architecture was developed. With considerations on PCB reliability and signal integrity, we divided the system into four parts:ARM-based upper control system, DSP-based main control system, CAN-based speed measurement system and GPS/GPRS communication system. And, we developed the corresponding software and hardware: ARM-based upper control system was installed WINCE5.0 system, and it had a 7-inch LCD touch screen which could provide a friendly user interface. The tasks of the ARM-based upper control system were: real-time control by providing GUI and touch operation; drew the electronic map and generated prescription in different ways; fertilization and seeding control with the help of DSP-based main control system; GPRS communication with the remote server to download the prescription or to upload the operating status in real time.DSP-based main control system used DSP/BIOS to schedule fertilization and seeding in real-time. The tasks of the system were: controlled the DGPS module, and interpreted the GPS information; fertilization control; seeding control; communicated with CAN-based speed measurement system and ARM-based upper control system.CAN-based speed measurement system was used to measure the speed of the tractor. CAN bus has high speed and high reliability . The system used CAN bus to transfer the speed information to DSP-based main control system which used the speed information for real-time control.GPS/GPRS communication system was used for DGPS information collection and GPRS communication with the remote server. GPS module and GPRS module used different serial ports to communicate with DSP and ARM system respectively.In order to overcome shortcomings of the original control algorithm, this paper presented a control strategy based on fuzzy inference system(FIS). The method took into account the relationship between the approaching three fertilization-seeding rate, and output near-optimum opening length and rotational speed sequence in real time. It could eliminate the occurrence of big opening length with small rotational speed when fertilization rate was small, and reduced the impact of pulsation of the outer genera mechanism.At last, we had done calibration experiment, DGPS positioning accuracy measurement experiment and control algorithm verification experiment. The result of these experiments showed that, the control system was reasonable and feasible. It's easy to control, and had a high control accuracy. The control system of VRF applicator met the need of design requirement and has passed the inspection.