水肥一体机肥液电导率远程模糊PID控制策略

为检测水肥一体机肥液电导率(EC),并将其控制在合理范围内,基于物联网技术,设计了远程水肥灌溉控制系统,将自整定模糊PID控制算法引入远程开发者服务终端中,通过模糊PID控制算法调控本地端变频注肥泵的频率进而精准控制EC,并对本地端PID和远程端模糊PID控制算法进行了对比试验验证。结果表明:目标EC越大,稳态EC越精确,但稳态时间和超调量均增大;与传统本地端PID控制相比,该系统响应速度快、EC波动幅度小、稳定,当目标EC为2.5 mS/cm时,稳态时间和超调量分别达到120 s和20.8%,混肥时间和实测EC均能满足水肥控制实际需求。该研究实现了EC的远程模糊PID控制,以及灌溉施肥系统的计算机、手机微信多终端灌溉数据监测和开关量控制。

Strategy on Remote Fuzzy PID Control for Fertilizer Liquid Conductivity of Water Fertilizer Integrated Machine

Precision control of the concentration of fertilizer is an important part of the integrated control system of water and fertilizer. It is the foundation to realize precision fertilization by detecting the electric conductivity (EC) value of fertilizer and controlling it in a reasonable range. Based on Internet of things technology, the remote control system was designed and developed, self-tuning fuzzy PID control algorithm was introduced into the equipment in the terminal, and the fuzzy PID control algorithm was used to control the local end frequency of variable frequency pump, and in turn to realize the precise control of EC value, and the local end PID and remote end fuzzy PID control algorithm were validated through the contrast test. The results showed that the larger the target EC value was, the more accurate the steady-state EC value was, but the steady-state time and overshoot were increased. Compared with the traditional local PID control, the response speed of the system was fast, the EC fluctuation range was small and stable. When the target EC value was 2.5mS/cm, the steady-state time and overshoot reached the maximum, which were 120s and 20.8%, respectively. The mixing time and measured EC value could meet the actual demand of water and fertilizer control. The research not only realized the remote fuzzy PID control of EC value, but also realized the irrigation data monitoring and switching control of the computer, mobile phone and WeChat multi-terminal of the irrigation and fertilization system.