基于CAN总线的变量施肥控制器设计

Design of Variable Rate Fertilization Controller Based on CAN Bus

阐述了基于CAN总线的变量施肥作业系统的组成及电液比例阀控液压马达排肥驱动系统,设计了变量施肥控制器和基于电液比例阀的闭环PID控制算法。利用阶跃响应对PID参数进行整定并分析了闭环控制系统的性能,同时制定了基于CAN总线的通讯协议;推导了施肥量控制公式,并对尿素、磷酸二铵和复合肥3种常用颗粒肥料的控制曲线进行了标定,田间常量和变量施肥试验表明,所设计的变量施肥控制器能满足变量作业的要求。

A variable rate fertilization controller based on CAN bus was presented. Firstly, variable rate fertilization control system and electro-hydraulic proportional valve-controlled motor rotation speed control system were introduced. Secondly, design of variable rate fertilization controller was described in detail including closed-loop PID control algorithm and communication protocol based on CAN bus. PID control parameters were determined through step response experiments and performance of closed- loop control system was analyzed. Variable rate fertilization control formula was deduced. Three kinds of fertilizers, urea ammonium phosphate and compound fertilizer, were used to test at different rotation speeds. Relationship equations between application rate of the three kinds of fertilizers and rotation speeds were calibrated. Finally, field experiments of fixed-rate and variable-rate fertilizations were conducted. Results show that the developed controller is suitable for variable rate application.