基于PLC的变量施肥控制系统设计与试验

[摘要l提出了一个以PLC为主机，集成光学传感器和控制装置的变量施肥控制系统。根据实时监测的作物
光谱信息和施肥机具的实际前进速度调节施肥量。系统采用无损测试技术和模糊控制算法，通过归一化植被差异
指数测量仪实时获取归一化植被差异指数，结合施肥机具行进速度调节执行机构中的电磁阀，实现实时变量施肥。
关钮词:变量施肥
中图分类号:S03;
可编程控制器
S126; S224.2
归一化植被差异指数

Design and Experiment on PLC Control System of Variable Rate Fertilizer
          Shao Limin' Wang Xiu2 Niu Xiaoying' Qian Dongping'
                      (1. Agriculture University of Hebei
2. National Engineering Research Center for Information Technology in Agriculture)
Abstract
    A real-time control system of the automatic variable rate fertilizer applicator was presented.
The control system takes PLC as the mainframe，and integrates with the optical sensor and
automatic control equipment. The quantity of fertilizer was adjusted with the tractor speed and
the crop spectrum data by real-time measuring. The technology of non-destructive test and the
fuzzy control algorithm was adopted in the system. According to the speed of the tractor and the
real-time value of NDVI (normalized difference vegetative index) from NDVI equipment，the real
time variable rate fertilizer was realized via opening or closing the electromagnetic valves of the
system.
        Key words Variable rate fertilizer，PLC
    引言
    化肥过量使用将导致种植成本提高，造成经济
效益下降，甚至导致土壤养分积累过多而出现环境
污染等问题，不利于农业的可持续发展。因此研制一
种集成光学传感器和施肥控制装置的变量施肥控制
系统，施肥对象为冬小麦，所施肥料为液体氮肥。
1系统施肥盘的确定
1. 1归一化植被差异指数
    归一化植被差异指数(NDVI)是通过对红外线
    收稿日期:2006-04一18
Normalized difference vegetative index
和近红外线的入射和反射光进行数学运算而得出的
一个植被指数。这一指标被普遍用来衡量作物的健
康状况和长势好坏[[1-2]，其值越高说明长势越好，其
运算公式为