马铃薯水肥一体化脉冲控制浓度自调整系统设计——基于PLC控制

Design of Pulse Control Concentration Self-adjusting System for Potato Water and Fertilizer Integration Based on PLC Control

结合当前我国马铃薯水肥一体化灌溉的发展趋势及发展需求,设计了一款基于西门子PLC精确控制的水肥一体化系统,相比于单片机控制,系统在运行稳定性、混肥均匀性、系统响应时间、水肥利用率均得到了显著的提升。系统由水源工程、首部控制系统、输水网管组成。控制枢纽系统以西门子PLC为核心,配合远传压力表和电导率、酸碱度传感器可以实时检测输水网管中的水压及水肥浓度。在水肥一体化系统中独立设置了浓度自调节的小循环管路,相比直接向主管道中注混合液,小循环浓度子调节管路可以明显地减小水肥浓度的误差,传感器读取当前的水肥浓度,会与预设值做差值比较,再经过比例积分微分计算进行调整。在施肥过程中,PID闭环控制系统可以保证系统运行的流畅性。使用McgsPro触摸屏编辑软件编写人机交互界面,可以直观显示灌溉时间、时长、EC值、pH值及历史数据。试验结果表明:恒压变频控制系统以调节频率的方式改变电动机的转速,输水网管中的水压在较小的范围内波动,采用调节脉冲时间周期的方式进行水肥浓度的调整,能够实现施肥频率的自动调整和流速的稳定输出,表现出了良好的吸肥特性,提高了水肥的利用率。

According to the development trend and demand of integrated irrigation of water and fertilizer for potato in China, an integrated system of water and fertilizer based on Siemens PLC is designed, the stability of the system, the uniformity of the mixed fertilizer, the response time of the system and the utilization ratio of water and fertilizer were improved significantly. The system is composed of water source engineering, head control system and water conveyance network. Siemens PLC is the core of the control hub system, together with the remote pressure gauge and the conductivity and Ph sensors, the water pressure and the concentration of water and fertilizer in the water distribution network can be measured in real time, in this integrated water and fertilizer system, a small circulation pipe with self-regulation of water and fertilizer concentration is set independently. Compared with injecting mixed liquid directly into the main pipe, the sub-regulation pipe with small circulation concentration can obviously reduce the error of water and fertilizer concentration, the sensor reads the current concentration of water and fertilizer, compares it with the preset value, and then adjusts it by means of proportional, integral and differential calculations. In the process of fertilization, Pid closed-loop control system can ensure the smooth operation of the system. Using McgsPro touch screen editing software, the man-machine interface can display the irrigation time, duration, EC value, Ph value and historical data directly. The experimental results show that the constant voltage variable frequency control system changes the speed of the motor by adjusting the frequency, the water pressure in the pipe fluctuates in a small range, and the concentration of water and fertilizer is adjusted by adjusting the pulse time cycle, the integrated water and fertilizer system can realize the automatic adjustment of fertilizer application frequency and the stable output of flow velocity.