Research Of Sowing Depth Control System For Precision Seeder Unit Based On PLC

On the basis of analyzing the seeding process of precision planter, this paper designed a sowing depth control system for precision seeder unit based on PLC.The core of the system is Siemens S7-200PLC, using PID algorithm, achieving control of the operating speed of the hydraulic cylinder.According to the control system design proposal, electrical components were selected reasonably and the control system’s relative circuit and electrical control cabinet were designed and installed. Meanwhile, the paper completed the compilation of PLC control program through analysis and research of the control processes. Touch screen was chosen as the human-computer interaction interface of the control system to achieve the related parameter settings and signals centralized display, and the collected data could be observed and recorded timely.Through analyzing the electro-hydraulic servo system’s characteristics and working principle, according to the basic equations of the dynamic characteristics of the each link, the paper derived the transfer function of each power element of hydraulic control system, and mathematical model of electro-hydraulic control system was established. MATLAB/Simulink software was applied to establish simulation model of the control system, and critical proportional band method was adopted to tuning and optimized PID parameters of the control system. Also, experimental verification of different parameters was performed under the simulation model. Verification results showed that the mathematical model was accurate, method of tuning parameters was reasonable.Through the static and dynamic response test, the system performance was verified and analyzed. The test results showed that operating performance and theoretical analysis of the system was consistent, and the performance can fully meet the design requirements of the control system. Finally,the practical application showed that the advantages of system included stable operation, high reliability, convenient to operate and maintenance, and it has a higher value of use and promotion.